Metal Oxides - Shodhgangashodhganga.inflibnet.ac.in/bitstream/10603/19192/6/06... · 2018-07-09 ·...

CHAPTER 1 INTRODUCTION AND LITERATURE SURVEY

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Metal Oxides: Metal oxides play a very important role in many areas of chemistry, physical and materials

science [1-6]. Metal oxides are formed as a consequence of co-ordination tendency of metal

ions so that oxide ions form co-ordination sphere around metal ions and give rise to close

packed structure. The different physical, magnetic, optical and chemical properties of metal

oxides are of great interest to chemists because these are extremely sensitive to change in

composition and structure. Extensive studies of this relationship leads to a better

understanding of the chemical bond in crystal. The metal oxides are attracting special

attention of scientists due to their easy mode of formation and multifunctional behaviour.

The transition metals and their compounds are used as catalysts is chemical industry and in

battery industries. Besides, these compounds can be used in formation of interstitial

compounds and alloy formation. The transition metals have the special properties of

formation of coloured compounds and show magnetic properties. Metals of d-block elements

are used for many industrial applications. They behave as catalysts, super conducting

materials, sensors, ceramics, phosphors, crystalline lasers etc. Besides these they are excellent

photoactive materials and work as photosensitizer. Mixed metal oxide (MMO) electrodes are

devices with useful properties for chemical electrolysis. The term refers to electrodes in

which the surface contains two kinds of metal oxides- one kind usually RuO2 and IrO2 desired

reaction such as production of chlorine gas. The other metal oxides is typically titanium

dioxide which does not conduct or catalyze the reaction, but is cheaper and prevents

corrosion of the interior. The interior of the electrode is typically made of titanium. The

amount of precious metal (that is other than titanium) can be around 10 to 12 grams per

square meter. Applications include electrolytic cells for producing free chlorine from salt

water in swimming pools and cathodic protection of buried submerged structures.

The World of Oxide Nanomaterials

The metal elements are able to form a large diversity of oxide compounds [7]. These can

adopt a vast number of structural geometries with an electronic structure that can exhibit

metallic, semiconductor or insulator character. In technological applications, oxides are used

in the fabrication of microelectronic circuits, sensors, piezoelectric devices, fuel cells,

coatings for the passivation of surfaces against corrosion, and as catalysts. In the emerging

field of nanotechnology, a goal is to make nanostructures or nano arrays with special

properties with respect to those of bulk or single practice species [8-12]. Oxide nanoparticles


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can exhibit unique physical and chemical properties due to their limited size and a high

density of corner of edge surface sites. Particle size is expected to influence three important

groups of basic properties in any material. This comprises the structural characteristics and

lattice symmetry and cell parameters [13]. Bulk oxides are usually stable systems with well-

defined crystallographic structures. In order to display mechanical or structural stability, a

nanoparticle must have a low surface free energy. As a consequence of this requirement,

phases that have a low stability in bulk materials can become very stable in nanostructures.

This structural phenomenon has been detected in TiO2, VOx, Al2O3 or MoOx oxides [14-16].

Size-included structural distortions associated with changes in cell parameters have been

observed, for example, in nanoparticles of NiO, Fe2O3, ZrO2, MoO3, CeO2 and Y2O3. As the

particle size decreases, the increasing number of surface and interface atoms generates stress/

strain and concomitant structural perturbations [17-21].The second important effect of size is

related to the electronic properties of the oxide. In any material, the nanostructure produces

the so-called quantum size or confinement effects which essentially arise from the presence

of discrete, atom-like electronic states. From a solid-state point of view, these states can be

considered as being a superposition of bulk-like states with a concomitant increase in

oscillator strength [22]. Additional general electronic effects of quantum confinement

experimentally probed on oxides are related to the energy shift of execition levels and optical

bandgap [23-24].Structural and electronic properties drive the physical and chemical

properties of the solid, the third group of properties influenced by size in a simple

classification. In their bulk state, many oxides have wide band gaps and a low reactivity [25].

A decrease in the averages size of an oxide particle do in fact change the magnitude of the

band gap [26-27], with strong influence in the conductivity and chemical reactivity [28-29].

Surface properties are a somewhat particular group included in this subject has great

importance in chemistry. Solid-gas or solid-liquid chemical reactions can be mostly confined

to the surface and/or sub-surface regions of the solid.

SYNTHESIS OF NANOPARTICULARATED OXIDES:

The first requirement of any novel study of nanoparticulated oxides is the synthesis of the

material. The development of systematic studies for the synthesis of oxide nanoparticles is a

current challenge and, essentially, the corresponding preparation methods may be grouped in

two main streams based upon the liquid-solid [30] and gas solid [31] nature of the

transformations.Liquid-solid transformations are possibly the most broadly used in order to

control morphological characteristics with certain “chemical” versatility and usually follow a


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“bottom-up” approach. A number of specific methods have been developed among which

those broadly in use are:

1) Co-precipitation methods:

This involves dissolving a salt precursor (acetates, nitrate, etc.) in water (or other

solvent) to precipitate the oxo-hydroxide form with the help of a base. Very often,

control of size and chemical homogeneity in the case of mixed-metal oxides are difficult

to achieve. However, the use of surfactants, sonochemical methods, and high-gravity

reactive precipitation appear as novel and viable alternatives to optimize the resulting

solid morphological characteristics [32-33].

2) Sol-gel processing:

The method prepares metal oxides via hydrolysis of precursors, usually alcoxides in

alcoholic solution, resulting in the corresponding oxo-hydroxide. Condensation of

molecules by giving off water leads to the formation of a network of the metal

hydroxide; Hydroxyl-species undergo polymerization by condensation and form a dense

porous gel. Appropriate drying and calcinations lead to ultrafine porous oxides [34].

3) Microemulsion technique:

Micromusion or direct/ inverse micelles represent an approach based on the formation of

micro nano-reaction vessels under a ternary mixture containing water, a surfactant and

oil. Metal precursors on water will proceed precipitation as oxo-hydroxides within the

aqueous droplets, typically leading to monodisperesed materials with size limited by the

surfactant- hydroxide contact [35].

4) Solvothermal methods:

In this case, metal complexes are decomposed thermically either by boiling in an inert

atmosphere or using an autoclave with the help of pressure. A suitable surfactant agent is

usually added to the reaction media to control particle size growth and limit

agglomeration.

5) Template / Surface derivatized methods:

Template techniques are common to some of the previous mentioned methods and use

two types of tools; soft-templates (surfactants) and hard-templates (porous solids as

carbon or silica). Template and surface mediated nanoparticles precursors have been

used to synthesize self-assembly system.

6) Chemical vapor deposition (CVD) :

There are a number of CVD processes used for the formation of nanoparticles among

which we can highlight the classical (thermally activated/pydrolytic), metalorganic,


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plasma-assisted, and photo CVD methodologies [36]. The advantages of this

methodology consist of producing uniform, pure and reproduce nanoparticles and films

although requires a careful initial setting up of the experimental parameters.

7) Pulsed laser deposition (PLD) :

Multiple pulsed laser deposition heats a target sample (4000 K) and leads to instantaneous

evaporation, ionization and decomposition, with subsequent mixing of desired atoms. The

gaseous entities formed absorb radiation energy from subsequent pulses and acquire

kinetic energy perpendicularly to the target to be deposited in a substrate generally heated

to allow crystalline growth [37].Irrespective of the preparation method use to obtain

ultrafine nano-oxides, the studies of nanoparticle preparation yielded compelling evidence

concerning the fact that crystallization does not follow a traditional nucleation and growth

mechanism. Although subjected to further assessment, it appears that the simple idea that

a small primary size would prime nucleation as the key step of crystallization seems

essentially correct and holds certain general validity, at least in solid-solid crystallization

mechanisms (e.g. heating of oxo-hydroxides to form oxides). When additional liquid/gas

phase crystallization steps are involved in the final formation of the nanoparticle (e.g. as

in solvothermal methods), other steps like ostwald ripening may be also of prime

importance. In any case, a lot of novel insights have been recently uncover in solid-solid

transformations and two main theories describe crystallization to proceed either by

surface (single particle) and/or interface (two or multiple particle) nucleation [38-39]. The

primacy of one of them has been postulated to be a function of the oxide chemical nature

and temperature, being presumably surface effects always predominant at higher

temperatures. Both theories mostly received support from kinetic approaches but very

recent analyzes sensitive to structural order in the amorphous precursor materials have

demonstrated by key role of intraparticle local order (below 1 nm) in driving the

nucleation temperature onset in a broad interval of ca. 200 K , showing that the whole

crystallization mechanism of oxide nanoparticles appears only compatible with some kind

of intraparticle, dimensional – restricted (“surface”) mechanisms [40]. This invokes for

the crucial structural characterization of the initial, XRD- amorphous materials in order to

further progress in the understanding the nanostructure influence in morphological

properties of oxides.


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PROPERTIES OF NANOPARTICULATED OXIDES:

The current knowledge on oxide materials allows affirming that most of their phsycio-

chemical properties display acute size dependence. Physico-chemical properties of special

relevance in chemistry are mostly related to the industrial use of oxides as sensors, ceramics,

absorbents and/or catalysts. A bunch of novel application within these fields rely on the size-

dependence of the optical transport, mechanical, and surface/ chemical properties of oxide

nanomaterials. Size effects in oxide chemistry have frequently two interrelated faces,

structural/electronic quantum-size and size-defect or non-stiochiometry effects. Hence, here

we will describe the influence of these two phenomena in the main physico-chemical

properties of oxides.

Optical properties:

The optical conductivity is one of the fundamental properties of metal oxides and can be

experimentally obtained from reflectivity and absorption measurements. While reflectivity is

clearly size-dependent as scattering can display drastic changes when the oxide characteristic

size (primary/secondary particle size) is in/out the range of photon wavelength [41],

absorption features typically command main absorption behavior of solids. Due to quantum-

size confinement, absorption of light becomes both discrete – like and size-dependent. For

nano-crystalline semiconductors, both linear (one exciton per particle) and non-linear optical

(multiple excitons) properties arise as a result of transitions between electron and hole

discrete or quantized electronic levels.

Transport Properties:

Oxide materials can present ionic or mixed ionic/ electronic conductivity and it is

experimentally well established than both can be influenced by the nanostructure of the solid.

The number of electronic charge carriers in a metal oxide is a function of the band gap energy

according to the Boltzmann statistics. The electronic conduction is referred to as n- or p-

hopping – type depending on whether the principal charge carrier are, respectively electrons

or holes. The number of “free” electron/ holes of an oxide can be enhanced by introducing

non-stiochiometry and, in such case, are balanced by the much less mobile oxygen/ cation

vacancies. In an analogous manner of hoping –type conduction takes place when ions can

hop from site to site within a crystal lattice as a result of thermal activation [42].

Mechanical properties:

Main mechanical properties concerns low (yield stress and hardness) and high

(superpasticity) temperature observables. Information on oxide nanomaterials is scarce and

mainly devoted to analyze sinterability, ductibility, and superpasticity [43].


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Chemical properties:

Metal oxides are used for both their redox and acid/ base properties in the context of

absorption and catalysis. The three key features essential for their application as absorbents or

catalysts are (i) the coordination environment of surface atoms (ii) the redox properties and

(iii) the oxidation state at surface layers. Both redox and acid/ base properties are interrelated

and many attempts can be found in the literature to establish correlations of both properties

[44-45]. In a simple classification, oxides having only s or p electrons in their valence orbitals

tend to be more effective for acid/base catalysis, while those having d or f outer electrons find

a wider range of uses. The solid in a given reaction conditions that undergoes reduction and

reoxidation simultaneously by giving out surface lattice oxygen anions and taking oxygen

from the gas phase is called a redox catalyst. The commonly accepted mechanism was

devoted by Mars Van Krevelen and essentially implies that redox systems require high-

electronic conduction cations to manage electrons and high oxygen-lattice mobility. Based on

modern isotopic exchange experiments, the redox mechanisms of chemical reactions can be

more specifically divided in (i) extrafacial oxygen in which absorbed (oxygen) species react

(electrophillic reaction) and (ii) interfacial oxygen where lattice oxygen vacancies are created

(nucleophilic reaction). There are enormous evidence that nucleophilic oxygen is capable of

carrying out selective oxidations while it seems that electrophilic species seems to

exclusively work on non-selective ones. Latter, it was shown that hydrocarbon selective

oxidation starts with H-abstraction steps and that the filling of oxygen vacancies require the

cooperation of a significant number of cations. So, typically, an oxidation reaction demands

to optimize three important steps; the activation of the C-H bond and molecular oxygen, and

the desorption of products (to limit over-oxidation). The effect of size of these key steps is

unknown but can be speculated to be related to the oxidation state of surface cations and their

ability to manage electrons and the influence of non-stoichiometry on the gas-phase oxygen

species handling and activation. Many oxides also display acid/ base properties. Oxide

materials can contain Bronsted and Lewis acid/base sites. Bronsted acid (A) and base (B)

interactions consists of an the exchange of protons as HA+B = A + HB+. Lewis acidity is

characteristic of ionic oxides and practically absent in covalent oxides. The strongest Lewis

and oxides are Al2O3 and Ga2O3. As a general rule, the stronger the Lewis acid, the few

available sites (amount) due to the higher level of surface hydroxylation. As mentioned,

because Lewis acidity is mostly associated to oxides with ionic character, Lewis basicity is

mostly associated to oxides with ionic character; Lewis basicity is mostly associated with

them. This means that the stronger the Lewis acid sites, the weaker the basic sites and vice


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versa. On the contrary, most of the ionic metal oxides do not carry sufficiently strong

Bronsted acidity to protonate pyridine or ammonia at room temperature although the more

acid of them can do it higher temperatures. In spite of this, the surface OH groups of most

ionic oxides have a basic more than acid character. Covalent low-valent nonmetal oxides

(SiO2, GeOx, Box) also show quite weak Bronsted acid and properties. Finally, strong

Bronsted acidity appears in oxides of elements with formal valence five or higher (WO3,

MoO3, N2O5, V2O5 and S-containing oxides). Zinc oxide presents the wurtzite structure and

displays a high covalent Zn-O bond [46]. ZnO is a wide band gap semiconductor extensively

studied due to its intrinsic properties but with a limited industrial use as a UV-blocker in sun

lotions [47], as a component in mixed oxide varistors [48], as a catalyst/ photcatalyst [49].

Additionally, forthcoming applications are envisaged as a gas sensor, solar cell and or / non-

linear optical systems [50]. Of particular interest is the fact that ZnO can display novel

nanostructures (nanorings, nanosprings, nanohelices, and nanobows), not typically observed

in other oxides, due to the polar characteristics of their surface [51]. Surface and quantum

size effects have been described as responsible of compressive strain and band gap blue shift

in nanostructured ZnO nanoparticles. However, surface effects and particularly, non-

stiochiometry and the presence of hydrogen (forming part ort no of hydroxyls) seem

persistent phenomena with larger influence in the oxide properties when comparing with

quantum – alone. Although acoustic phonons are dominated by quantum confinement, optical

phonons and visible (yellow/green) luminescence display properties mostly related to the

presence of defects and/or hydrogen impurities without significant chemical/ physical

sensibility to confinement [52]. Chemical properties seem also enhanced by the nanostructure

but again a critical role of oxygen vacancies and hydroxyl radicals is noticed [53]. There also

been also a lot of work concerning ZnO-based mixed oxides mostly by doping with Mg, Mn

and Cd in order to modulate the band gap of the oxide [54]. Fe and O form a number of

phases, e.g., FeO (wustite); Fe3O4 (magnetite), Fe2O3 (hematite), Fe2O3 (maghemite). The

latter phase is synthetic while remaining oxides occur in nature. The Fe-O phase diagram

shows the predominance of the Fe2O3 stiochiometry for most temperature and pressure

preparation conditions [55]. The magnetic properties of the Fe oxides have been extensively

studied; in particular, the enhancing magnetic recording properties of magnetic and

maghemite for nanostructure materials, or the use of the latter in Fe2O3-SiO2 composite

materials having magneto- optical properties. Most physico-chemical studies are centered in

the alpha (corundum structure with a distorted hexagonal anion closed – packed) and gamma

(cubic inverse spinel) phases. Size stability of the polymorphs has been studied but there is


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still a lack of consensus in a significant number of issues; particularly related to the existence

of nano-particles with alpha structure.

1.2 REVIEW OF IMPORTANT APPLICATIONS OF METAL OXIDES

1.2.1 Catalyst:

Metal/Mixed metal oxides have wide applications as catalyst some of them are described

here. Morales et al.[56] synthesized manganese iron or nickel mixed oxide catalysts (MnFe

or MnNi, respectively).A detailed description of the bulk and surface structure of each system

was achieved by means of measurements of specific surface area, XRD, XPS, FT-IR, and

Mo¨ssbauer spectroscopies. The characterisation results show that MnNi catalysts are formed

as NiMnO3 and Ni6MnO8 mixed oxides besides a little amount of Mn2O3. In contrast, MnFe

catalysts consist of an oxide mixture (Fe2O3, Mn2O3 and Mn5O8) forming incipiently a solid

solution. The catalytic activity was evaluated in the combustion of propane and ethanol,

selected as model volatile organic compounds. Luca and coworkers [57 ] used the tar

reforming catalytic activity of iron and nickel based catalyst supported on alkaline-earth

oxides CaO, MgO and calcined dolomite [a (CaMg)O solid solution] investigated in a fixed

bed reactor operating at temperatures ranging from 650 to 850 °C; Toluene and 1-methyl

naphthalene were used as model compounds for tar generated during

biomassgasification.Mostafa et al. [58] synthesized the iron nickel oxide catalysts were

prepared using co-precipitation procedure and studied for the conversion of synthesis gas to

light olefins. In particular, the effects of a range of preparation variables such as [Fe]/[Ni]

molar ratios of the precipitation solution, precipitate aging times, calcination conditions,

different supports and loading of optimum support on the structure of catalysts and their

catalytic performance for the tested reaction were investigated.It was found that the catalyst

containing 40%Fe/60%Ni/40wt%Al2O3, which was aged for 180 min and calcined at 600 °C

for 6 h was the optimum modified catalyst. Guan et al. [59] prepared the calcined scallop

shell (CS) applied for the adsorption and decomposition of biomass -derived tar. In this study,

steam reforming of tar derived from pruned apple branch over CS was investigated in a fixed

bed at 650 °C. It was found that CS had good activity for the steam reforming of tar to

produce synthesis gas (syngas), and was able to be recycled. To promote the gas production

efficiency, iron or nickel was supported on the CS, and used for the reforming of tar. The

effect of heating rate on the gas production rate was investigated, and it was found that

reduced iron or nickel supported CS showed better activities under the condition of rapid

heating. Iron or nickel based catalyst in its oxide state was also investigated for the reforming

of tar. Huang et al. [60] showed the iron-doped nickel oxide films application as oxygen


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evolution catalysts in the photoelectrochemical production of hydrogen from solar energy.

The effects of processing parameters on the film properties, such as overpotential,

composition, surface morphology and preferred orientation, were investigated. The

electrochemical experiment, structural and compositional measurements indicate that the

relative lower substrate temperature, higher RF power, higher working pressure and oxygen

content are necessary to gain lower overpotential. Rahman and cowokers [61] carried out

nickel oxide on alumina aerogel catalysts convert propylene into acrylonitrile through the

interaction with nitric oxide (nitroxidation). For a NiO/Al2O3 aerogel catalyst, with Ni:Al

ratio 1:1, the activity decreases by about 20% over a 3-h run. Simultaneously, a carbon

deposit is observed on the catalyst which results from the cracking of hydrocarbons and from

the boudouard reaction of generated carbon monoxide. Addition of water vapor into the feed

slows down the deactivation process by promoting the water-gas shift reaction without

affecting the activity. Addition of a basic component like magnesia (0.2 Mg : 0.8 Ni) to the

NiO/Al 2O3 aerogel catalyst also enhances the stability by retarding the cracking reactions.

Huang et al. [62] studied iron-doped LaNiO3 catalysts with a perovskite structure prepared

via self-combustion and tested in auto-thermal reforming (ATR) of ethanol.Characterizations

of temperature-programmed surface reaction (TPSR), X-ray diffraction (XRD), physical N2

adsorption, and temperature-programmed reduction (TPR) were carried out. The results

indicate that LaNiO3 perovskite structure was successfully formed via self-combustion.With

iron-doping in LaNiO3, the perovskite structure still remains, in the form of solid solution

La(Ni, Fe)O3, where iron is reducible and the nickel-iron alloy forms after the reduction. In

addition, the surface area of the iron-doped samples increased. Morozova et al. [63]

discovered the NiO and α-Fe2O3 samples from various backgrounds and used as precursors of

the catalysts for CO hydrogenation. The effect of the initial microstructure of oxides on the

morphological peculiarities and catalytic properties of the newly formed catalysts was studied

using transmission electron microscopy and in situ XRD combined on-line with gas-

chromatographic analysis. Tsoncheva and coworkers [64] found that several SBA-15 type

mesoporous silicas, where different means of surfactant removal have been used, have been

modified by copper and iron oxide, and tested as catalyst for methanol decomposition. The

materials were thoroughly characterized by nitrogen physisorption, X-ray diffraction,

Moessbauer spectroscopy and temperature programmed reduction with hydrogen. The

different means of template removal results in SBA-15 materials different in mesopore size

and degree of microporosity. These parameters have a strong influence on the reductive and

catalytic properties of the obtained composite materials. Natter et al. [65] studied cluster


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models for sites on the {1 1 1} surface of Fe3O4 and used to study the strength of bonding of

water-gas shift intermediates using density functional theory. Three site models were used,

representing an unpromoted catalyst, a catalyst where copper cations substitute for iron

cations below the surface and a catalyst where copper cations substitute in the surface. The

strengths of bonding of oxygen, carbon dioxide, dissociated water and dissociated formic acid

were all observed to decrease by less than 20 kJ mol−1 when copper substituted below the

surface, but they decreased by 60–80 kJ mol−1 when copper substituted in the surface of the

catalyst. Tsoncheva and coworkers [66] examined mixed copper and iron modified MCM-41

mesoporous silica with various Cu/Fe ratio characterized by N2 physisorption, X-ray

diffraction (XRD), transmission electron micrographs (TEM), X-ray photoelectron

spectroscopy (XPS), moessbauer spectroscopy and temperature programmed reduction with

hydrogen. Their catalytic properties in methanol decomposition to CO and H2 are

investigated and compared with that of the corresponding mono-component materials. The

catalytic behaviour of bi-component materials are discussed based on the nature of the

catalytic active sites. Kustov et al. [67] worked on vanadia, copper and iron oxide catalysts

supported on conventional TiO2, ZrO2 and sulphated – TiO2 and ZrO2. These catalysts were

characterized by elemental analysis, N2-BET, XRD, and NH3-TPD methods. The influence of

potassium oxide additives on the acidity and activity in NO selective catalytic reduction

(SCR) with ammonia was studied. The absolute activity of the samples does not vary

significantly depending on the nature of the active metal and the acidic properties of the

support used, seem to be influenced mainly by the concentration of active metal. Zhang et al.

[68] produced the metal–silica interaction and catalytic behavior of Cu-promoted Fe–Mn–

K/SiO2 catalysts investigated by temperature-programmed reduction/desorption (TPR/TPD),

differential thermogravimetric analysis, in situ diffuse reflectance infrared Fourier transform

analysis, and mössbauer spectroscopy. The Fischer–Tropsch synthesis (FTS) performance of

the catalysts with or without copper was studied in a slurry-phase continuously stirred tank

reactor. The characterization results indicate that several kinds of metal oxide–silica

interactions are present on Fe–Mn–K/SiO2 catalysts with or without copper, which include

iron–silica, copper–silica, and potassium–silica interactions.Simona and coworkers et al. [69]

utilized the properties of copper-based pillared clays (Cu-PILC) studied and compared with

those of the analogous iron-based clays (Fe-PILC) in the wet hydrogen peroxide catalytic

oxidation (WHPCO) of model phenolic compounds (p-coumaric and p-hydroxybenzoic

acids) and real olive oil milling wastewater (OMW). These two catalysts show comparable

performances in all these reactions, although they show some differences in the rates of the


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various steps of reaction. In particular, Cu-PILC shows a lower formation of oxalic acid

(main reaction intermediate) with respect to Fe-PILC.K. Eguchi et al. [70] chacterized the

reduction process of copper–iron spinel oxide, which is active for steam reforming of

dimethyl ether after mixing with alumina and investigated by a transmission electron

microscope (TEM), scanning TEM (STEM), and energy dispersive X-ray (EDX) analyzer.

The catalyst preparation was started from formation of well-sintered CuFe2O4 by calcination

in air at 900 °C. After reduction of CuFe2O4 with hydrogen at 250 °C, metallic copper grains

were developed on reduced spinel surface by the phase separation from the oxide. Strong

chemical interaction between deposited Cu and reduced spinel oxide was expected from their

intimate interfacial contact and lattice matching. Han et al. [71] evaluated a series of Cu-Fe

bimetal amidoximated polyacrylonitrile (PAN) fiber complexes with different molar ratios of

Cu2+ to Fe3+ ions prepared using a simple exhaustion method, and characterized using FTIR,

DRS and XPS, respectively. They were tested as the heterogeneous fenton catalysts for

rhodamine B degradation with H2O2 in the dark and under visible light irradiation. The

results indicated that Cu-Fe bimetal amidoximated PAN fiber complexes could more

effectively catalyze the dye degradation in water than Fe amidoximated PAN fiber complex,

especially in the dark. Riz et al. [72] checked the oxidative dehydrogenation of n-butane to

butenes over iron-zinc oxide catalysts. X- ray diffraction (XRD), temperature-programmed

reduction (TPR) and mossbauer spectroscopy were used to try to identify the catalytically

active phase. It was found that the presence of a zinc ferrite (ZnFe2O4) phase with a spinel

structure yields high selectivity to butenes. Nam and coworkers [73] analysed the

hydrogenation of carbondioxide to hydrocarbon sover iron oxide catalysts studies were

carried out in a fixed bed reactor under pressure of 10 atm and temperature of 573 K. Iron

oxide catalysts promoted with V, Cr, Mn and Zn prepared by precipitation method were

adopted in the present study. The catalysts were characterized by XRD, carbondioxide

chemisorption and mössbauer spectroscopy. The hydrocarbons were formed directly from

carbondioxide over iron catalysts. Rethwisch et al. [74] studied supported iron oxide and zinc

oxide samples as water-gas shift catalysts at temperatures from 620 to 720 K. The supports

studied were SiO2, Al2O3, TiO2, MgO, ZnO and Na-mordenite. The catalytic activity of all

supported iron samples was significantly lower than that of magnetite (Fe3O4). It is suggested

that whereas magnetite functions as a catalyst via an oxidation-reduction pathway, all

supported iron and zinc oxide samples operate via an associative mechanism for the water-

gas shift. The catalytic activities of the supported samples decreased as the acidity of the

support or the electronegativity of the support cations increased. Mirzaei and coworkers [75]


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find out the effect of a range of preparation variables such as the precipitate ageing time and

[Fe]/[Co] molar ratio of precipitation solution on the composition and morphology of iron-

cobalt oxide catalysts prepared using a co-precipitation method and the optimum preparation

conditions were identified with respect to the catalyst activity for the Fisher–Tropsch

reaction. The effect of different promoters along with loadings of optimum support and

promoter on the activity and selectivity of the 40%Fe/60%Co as an optimum molar ratio are

studied and it was found that the catalyst containing 40%Fe/60%Co/15 wt%SiO2/1.5 wt%K

which aged for 2 h, is an optimum modified catalyst for the conversion of synthesis gas to

ethylene and propylene. Mizaei and coworkers [76] synthesized iron cobalt oxides and

studied for the conversion of synthesis gas to light olefins. In particular, the effect of a range

of preparation variables such as the precipitate ageing time and [Fe]/[Co] molar ratio of the

precipitation solution were investigated in detail. The preparation procedure and also the

optimum preparation conditions were identified with respect to the catalyst activity for the

hydrogenation of carbon monoxide. The results are interpreted in terms of the structure of the

active catalyst and it has been concluded that the catalyst containing 40% Fe/60% Co – on

molar basis – and aged for 2 h, is the most active catalyst for the conversion of synthesis gas

to ethylene and propylene. Weiqing et al. [77] investigated a new heterogeneous catalyst,

lead–zinc double oxide. It had been prepared for the synthesis of diphenyl carbonate (DPC)

by transesterification of dimethyl carbonate (DMC) and phenol. The effects of preparation

method, calcination temperature, precursor and molar ratio of Pb/Zn on the catalytic activity

have been investigated. XRD, TPR and atomic absorption spectroscopy were employed for

the catalyst characterization. The results show that Pb3O4 is the main active species, and that

amorphous ZnO plays a role as the promoter. Wang et al. [78] studied nanoparticle zinc-

titanium oxide materials prepared by the aerogel approach. Their structure, surface state and

reactivity were investigated. Zinc titanate powders formed at higher zinc loadings possessed a

higher surface area and smaller particle size. X-ray photoelectron spectroscopy (XPS)

revealed a stronger electronic interaction between Zn and Ti atoms in the mixed oxide

structure and showed the formation of oxygen vacancy due to zinc doping into titania or zinc

titanate matrices. The 8–45 nm aerogel particles were evaluated as catalysts for methanol

oxidation in an ambient flow reactor. Carbon dioxide was favorably produced on the oxides

with anion defects. Machado et al. [79] described the immobilization of anionic iron (III)

porphyrin (FePor) family on zinc hydroxide chloride (ZHC). The FePor immobilization was

performed at room temperature under magnetic stirring, under air atmosphere, of each

complex ethanol solution and the ZHC solid support suspension. Pollard et al. [80]


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synthesized georgeite basic copper carbonate mineral synthesised in aqueous solutions from

copper salts. It has now been shown that a zincian georgeite (i.e. georgeite with some

substitution of copper by zinc) is formed by precipitation with sodium carbonate in copper-

zinc systems. Conversion of zincian georgeite to a malachite phase in an aqueous medium

occurs more slowly than the equivalent conversion of pure copper georgeite. The possibility

of georgeite formation as a precursor to malachite in the manufacture of copper/zinc catalysts

is discussed It is suggested that the blue/green colour transition seen during the ageing of

precipitated copper/zinc catalyst precursors can be attributed to the conversion of georgeite to

malachite. Pollard et al. [81] studied four new bimetallic model precursors of copper-zinc

oxide catalysts for methanolization.The new compounds were characterized by elemental

analysis, IR spectroscopy, and thermal analysis under dynamic conditions. Li and coworkers

[82] discovered the doping effect of potassium permanganate on the performance of a

copper/zinc oxide/alumina catalyst for methanol synthesis. It was found that doping with

potassium permanganate appreciably enhanced the activity of the catalyst. The optimum

nominal dosage of potassium permanganate was found to be 6.0 mol.%. The precursors and

the calcined, reduced and syngas-treated catalysts undoped and doped with potassium

permanganate were characterized by X-ray photoelectron spectroscopy and X-ray-induced

auger transition, powder X-ray diffraction, atomic absorption spectroscopy and temperature

programmed oxidation. Sengupta et al. [83] developed mixed oxides of copper and zinc by

thermal decomposition of the coprecipitates obtained from mixed metal nitrate solutions by

addition of ammonium bicarbonate (series ABn and hydroxide series AMn). These were

characterised by diffuse reflectance spectroscopy and electron spinesonance spectroscopy. It

was found that in series ABn appreciable dissolution of Cu2+ ions in the zinc oxide matrix had

occurred and in this solid solution the Cu2+ ions occupied distorted octahedral sites. Inui and

coworkers [84] investigated the effect of ultrasonic treatment on methanol synthesis activity

of a copper/zinc/aluminum oxide catalyst. It has been found that insonation of the suspension

during co-precipitation and aging steps appreciably enhanced the activity of the catalyst and

along with the increase of the frequency of the ultrasound, the enhancement grew stronger. It

has also been revealed that this enhancement is due to the promotion of the ultrasound for the

formation of the hydrotalcite – like phase in the precursor of the catalyst. Saito et al. [85]

developed the role of metal oxides such as Ga2O3, Al2O3, ZrO2 and Cr2O3 contained in

Cu/ZnO-based ternary catalysts for methanol synthesis from CO2 and H2 classified into two

categories: to improve the Cu dispersion and to increase the specific activity. Huang et al.

[86] found that hydrogen production resulting from the partial oxidation of methanol (POM)


14

was investigated using copper-zinc-supported gold catalysts. The influence of oxygen

concentration on activity and initiation temperature (Ti) over Au4.3CZ (ca. 4.3 wt.% Au,

32.3 wt.% Cu and 63.4 wt.% Zn) catalysts was compared with CZ (ca. 31.7 wt.% Cu and

68.3 wt.% Zn) catalysts. The Au4.3CZ catalyst was able to react at temperatures lower than

195 °C, while CZ catalyst could not be initiated without pre-activation. Astier et al. [87]

examined the new vanadium-copper-zinc and vanadium-copper or copper-zinc complex

compounds prepared with variable Cu/ (Cu+Zn) atomic ratios with a theoretical (Cu+Zn)/V

ratio of 1 by the reaction of ammonium vanadate with mixtures of copper and/or zinc

ammonia complexes. The catalysts obtained from the reduction of these new compounds

were systematically analyzed by the B.E.T. method and the surface copper concentration was

determined by titration with nitrous oxide decomposition. Ethanol was dehydrogenated into

ethanol only (selectivity of 100%) at 190°C under both dynamic and differential

conditions.Suarez et al. [88] worked on the influence of ammonia and nitric oxide oxidation

on the selective catalytic reduction (SCR) of NO by ammonia with copper/nickel and

vanadium oxide catalysts, supported on titania or alumina. In the SCR reaction, the VTi

catalyst had a higher activity than VAI at low temperatures, while the CuNiAl catalyst had a

higher activity that CuNiTi. A linear relationship between the reaction rate of ammonia

oxidation and the initial reduction temperature of the catalysts obtained by H2TPR showed

that the formation rate of NH3 species in copper/ nickel catalysts would be higher than in

vanadia catalysts. Bianco et al. [89] discovered the selective reduction of NOx, with ammonia

on alumina-supported copper catalysts . It is shown to be effective when O2 or NO2 are

present in the feed. Under steady state conditions, the presence of NO2 in the feed stream

increases the overall rate of reduction of NOx and simultaneously reduces its dependence on

the oxygen concentration. A maximum in activity is found for a molar inlet ratio NO2/NO ≈

1. It has also been observed that the stoichiometry of the process is a function of the reaction

temperature, with a secondary NH3 oxidation reaction appearing at temperatures above 500

K.Orsini and coworkers [90] utilized the reduction of NO with H2 on copper nickel and

chromium – nickel catalysts. Both CuNi and CrNi catalysts were prepared by impregnation

on Al2O3 pellets. Dry-pressed catalysts, CrNi with Al2O3 powder were formed with several

catalysts containing the NiCr2O4 spinel. A pressed nickel oxide catalyst was highly active for

the reduction of NO while impregnated nickel oxide was much less active. Copper oxide and

chromium oxide were relatively inactive. Addition of small amounts of copper to

impregnated nickel oxide improved the activity of the latter catalysts, but above about 24

atmoic percent copper, activity decreased with increase in copper content. The activity of the


15

pressed chromium – nickel catalysts increased with increase in nickel content. Chakrabarti et

al. [91] studied catalytic reduction of nitric oxide with ammonia by use of Girdler's G-22

(barium promoted copper chromite) and T-312 (nickel oxide and copper oxide on gamma

alumina) catalysts inside a carberry type stirred tank reactor. Helium was used as the carrier

gas. The nitric oxide and ammonia concentrations in the feed varied from 550 to 1400 ppm

and 700 to 7900 ppm, respectively. Temperature levels were from 177 to 316°C.Gas flow

rates ranged from 200 to 300 lh−1. Empirical kinetic expressions for both catalysts were

developed which adequately represent the experimental results. Fuentes et al. [92] evaluated

nickel or copper-based catalysts obtained from hydrotalcite-like precursors in order to find

catalysts able to work at intermediates temperatures (200–350°C) in water gas shift reaction

(WGSR). Samples based on nickel (or copper), aluminum and zinc were obtained by co-

precipitation, characterized by several techniques and evaluated in WGSR. Zinc caused

changes in the cell parameters of hydrotalcite-type structure, which determined the structural

and textural properties of calcined samples. For all catalysts, zinc oxide was detected. In the

case of nickel-based hydrotalcites, aluminum cations were incorporated into nickel oxide

lattice, hindering reduction; however, the addition of zinc decreased this effect. For copper-

based samples, aluminum entered into copper oxide lattice and the copper reduction

decreased with the increase of zinc amount in solids. After calcination, copper catalysts

showed lower specific surface areas than nickel ones. Khadiri and Astier [93] checked a

series of well-defined nickel, copper and nickel copper molybdenum complex compounds

isomorphous of the ammonium triammine tetranickel pentamolybdate . The characterization

of the catalysts obtained by reduction in hydrogen of these precursors is difficult but the use

of the chemisoprtive decomposition of nitrous oxide together with the reactions of benzene

hydrogeneation and propanol decomposition make possible an estimation of the surfaces

atomic copper nickel ratio.Youn et al. [94] analysed metal oxide-stabilized mesoporous

zirconia supports (M–ZrO2) with different metal oxide stabilizer (M = Zr, Y, La, Ca, and Mg)

prepared by a templating sol–gel method. 20 wt% Ni catalysts supported on M–ZrO2

(M = Zr, Y, La, Ca, and Mg) were then prepared by an incipient wetness impregnation

method for use in hydrogen production by auto-thermal reforming of ethanol.The effect of

metal oxide stabilizer (M = Zr, Y, La, Ca, and Mg) on the catalytic performance of supported

nickel catalysts was investigated. Ni/M–ZrO2 (M = Y, La, Ca, and Mg) catalysts exhibited a

higher catalytic performance than Ni/Zr–ZrO2, because surface oxygen vacancy of M–ZrO2

(M = Y, La, Ca, and Mg) and reducibility of Ni/M–ZrO2 (M = Y, La, Ca, and Mg) were

enhanced by the addition of lower valent metal cation. Hydrogen yield over Ni/M–ZrO2


16

(M = Zr, Y, La, Ca, and Mg) catalyst was monotonically increased with increasing both

surface oxygen vacancy of M–ZrO2 support and reducibility of Ni/M–ZrO2 catalyst. Among

the catalysts tested, Ni catalyst supported on yttria-stabilized mesoporous zirconia (Ni/Y–

ZrO2) showed the best catalytic performance. Narcis et al.[95] discussed ZnO-supported Ni

and Cu as well as bimetallic Co-Ni and Co-Cu catalysts containing 0.7 wt% sodium promoter

in the ethanol steam-reforming reaction at low temperature (523–723 K), using a bioethanol-

like mixture diluted in Ar. Monometallic ZnO-supported Cu or Ni samples do not exhibit

good catalytic performance in the steam-reforming of ethanol for hydrogen production.

Copper catalyst mainly dehydrogenates ethanol to acetaldehyde, whereas nickel catalyst

favours ethanol decomposition. Komatsu and coworkers [96] find out the catalytic activity of

pure, doped nickel oxide, and mixtures of nickel oxides with different dopents were

investigated by the reaction of carbon monoxide oxidation. The incorporation of lithium ions

in the oxide enhanced the activity and the addition of indium lowered the activity. The

activity of mixtures increased to several times greater than would be predicted by simple

additive effect of single doped catalysts. Deraz et al. [97] synthesized alumina-supported NiO

catalysts, promoted with 0.14-3 wt.% ZnO prepared by impregnation and then calcined at

400, 600, and 800 °C for 4 and 40 h. The phase analysis, surface and catalytic properties were

investigatedby using XRD technique, nitrogen adsorption at -196 °C, and oxidation of CO by

O2 at 200-300 °C ,respectively. The results obtained reveal that ZnO doping of Ni/Al mixed

oxides followed by calcination at 400 or 600 °C for 4 h brought about slight increase in their

specific surface area, which decreased progressively by increasing the calcination

temperature of doped solids to 800 °C for 4 and 40 h. CO oxidation activity over NiO/Al2O3

mixed solids increased by treatment with ZnO followed by heating at 400 or 600°C for 4 h,

and then decreased by increasing the calcination temperature to 800 °C for 4 and 40 h.

Zhuang and coworkers [98] used by a thermal gravimetric balance reactor and a temperature-

programmed reaction technique, it was found that carbon deposition on cerium oxide-

containing nickel catalysts was decreased in both the induction and the constant carbon

growth periods. Mean while the catalysts maintained activity for the steam reforming

reaction. Based on this and our previous research a model for the promoting effect of cerium

oxide is proposed. Aai et al. [99] followed the results of a leaching kinetics study of spent

nickel oxide catalyst with sulfuric acid. The effects of spent catalyst particle size, sulfuric

acid concentration, and reaction temperature on Ni extraction rate were determined. The

results obtained show that extraction of about 94% is achieved using −200+270 mesh spent

catalyst particle size at a reaction temperature of 85 °C for 150 min reaction time with 50%


17

sulfuric acid concentration. The solid/liquid ratio was maintained constant at 1:20 g/ml. The

leaching kinetics indicate that chemical reaction at the surface of the particles is the rate-

controlling process during the reaction. The activation energy was determined as about 9.8

kcal/mol, which is characteristic for a surface-controlled process. Zoo et al. [100] studied the

pre-reforming of commercial liquefied petroleum gas (LPG) over Ni–CeO2 catalysts at low

steam to carbon (S/C) molar ratios less than 1.0. It was found that the catalytic activity and

selectivity depends strongly on the nature of the support and the interaction between Ni and

CeO2. The Ni–CeO2/Al 2O3 catalysts, which were prepared by impregnating boehmite

(AlOOH) with an aqueous solution of cerium and nickel nitrates, exhibited the optimal

catalytic activity and remarkable stability for the steam reforming of LPG in the temperature

range of 275–375 °C. The effects of CeO2 loading, reaction temperature and S/C ratio on the

catalytic behavior of the Ni–CeO2/Al 2O3 catalysts were discussed in detail. Mucka et al. [101]

showed the catalytic activities and some physico-chemical properties of NiO-ZnO catalysts

prepared by precipitation of mixtures of carbonates and nitrates of both metals and

subsequent calcination have been tested before and after irradiation, using the decomposition

of hydrogen peroxide as a test reaction. A mutual influence of both oxides and their

sensitivities to ionizing radiation has been proved. Busca et al. [102] carried out the urea

hydrolysis method to prepare well-crystallized Ni-Co-Zn-Al layered double hydroxides to be

used as precursors of mixed oxide catalysts for the ethanol steam reforming (ESR) reaction.

The calcination of the layered precursors gives rise to high surface area mixed oxides, being

actually a mixture of a rock salt phase (NiO), a wurtzite phase (ZnO) and a spinel phase. The

steam reforming of ethanol has been investigated over these catalysts after calcination at 973

K in flow reactor experiments. All these catalysts are active for ESR. At 820 K the selectivity

to hydrogen increases with cobalt content. The most selective catalyst is the Ni-free Co-Zn-

Al mixed oxide essentially constituted by a single spinel type phase Zn 0.55Co 0.45[Al 0.45Co

0.55]2O4.Yang et al. [103] reported the application of an inexpensive and easily-prepared lead

oxide-manganese oxide catalyst combined with nafion (designated as Nf/PbMnOx) as a

highly efficient air-cathode for a zinc-air battery. Mechanistic study of the reduction of O2 for

Nf/PbMnOx in alkaline aqueous solution using rotating ring/disk electrode voltammetry, and

also an electrochemical approach using a wall-jet screen-printed ring disk electrode has been

verified. Hubicki and Wojcik [104] synthesized that platinum has been widely applied in

catalytic industry and the recovery of noble metals from industrial wastes becomes an

economic issue. The laboratory studies of platinum (IV) microquantities removal from 1 M

alumnium, copper, iron, nickel and zinc chloride solutions in 0.1 M hydrochloric acid


18

solutions on the anion exchanger Duolite S 37 of the functional secondary and tertiary amine

groups were carried out. For this anion exchanger the fraction extracted values (%E, Pt(IV))

as well as the sorption isotherms were determined depending on the king of aqueous phase

and phase contact time. Majumdar et al. [105] used the thermal decomposition of the oxalates

of zinc; nickel and iron (II) have been re examined from a fresh experimental approach.

Differential thermal analysis (DTA) and thermogravimetry (TG) of the individual oxalates

and of mixtures of zinc oxalate with either nickel/iron oxalate or products of decomposition

of the latter two, were carried out in air in sample cells made of different materials (Pt, Al,

Al 2O3, Ni). The information gathered from thermo analytical experiments, together with

information derived from specific chemical tests for the evolution of carbon monoxide during

decomposition, chemical analyses, XRD and stoichiometric and thermochemical

considerations helped to specify some of the inadequately explained features of the courses

and kinetics of decomposition of the metal oxalates. Yadav and Kharkara [106] followed

liquid phase hydrogenation of a series of nitriles, namely, benzonitrile, butyrotirle,

cinnamonitrile and crotonontrile over and has been investigated and the activities of the

catalysts have been correlated with the structure of the catalysts on the basis of frontier

orbital energy levels. Bridier et al. [107] studied the partial hydrogenation of propyne over

copper-based catalysts derived from Cu–Al hydrotalcite and malachite precursors and

compared with supported systems (Cu/Al2O3 and Cu/SiO2). The as-synthesized samples and

the materials derived from calcination and reduction were characterized by XRF, XRD, TGA,

TEM, N2 adsorption, H2-TPR, XPS, and N2O pulse chemisorption. Catalytic tests were

carried out in a continuous flow-reactor at ambient pressure and 423–523K using H2:C3H4

ratios of 1–12 and were complemented by operando DRIFTS experiments. The propyne

conversion and propene selectivity correlated with the copper dispersion, which varied with

the type of precursor or support and the calcination and reduction temperatures. Kazi et al.

[108] showed the pathogenesis of some heart diseases has been associated with changes in

the balance of certain trace elements. We examined the association of iron, copper and zinc

between biological samples (scalp hair, whole blood and urine) and mortality from

myocardial infraction (MI) patients of (first, second and third heart attack).Kozlowski et al.

[109] discoverd metal ions, especially with high chemical activity (e.g. redox-active Cu and

Fe) must be carefully managed in biological systems. The “uncontrolled” activity, e.g.

catalysis of Fenton-like reactions by ions like Cu(I) or Fe(II), is so damaging for the

biological milieu that right from their entry, metal ions need to be strictly controlled until

they arrive at their storage site. Ferraris and Rossi et al.[110] developed the behaviour of Cu-


19

ZnO catalysts in propene hydrogenation at 323 K has been investigated in order to gain

information as to whether or not a synergic effect due to ZnO on the activity of copper is

present. With this aim, two different series of catalysts were prepared by coprecipitation at

(A) variable or (B) constant (≈ 8) pH. The whole composition range from CuO/ZnO 100:0 to

0:100 was covered in preparation A, while only copper-rich samples (CuO/ZnO≥67:33) were

prepared from method B. Chemisorption experiments of hydrogen and propene on samples

reduced with hydrogen at 473 K point to the presence of adsorption sites in binary samples

different from those existing in single components, that are influenced by the outgassing

temperature. Shimomura et al. [111] investigated copper oxide-zinc oxide-alumina catalysts

for methanol synthesis and kneading methods for comparison of catalytic activity, physical

properties, and estimation of the effective surface area by carbon monoxide chemisorption.

The coprecipitated catalysts, which are already industrially employed, have higher catalytic

activities than the kneaded ones, the optimum chemical composition being around Cu:Zn:Al

= 60:35:5 (atom%) in both cases. The total pore volume, the mean pore radius, and the

porosity of the coprecipitated catalysts were three to four times larger than those of the

kneaded ones. The pore-size distribution ranges from 50 to 5000 Å for the coprecipitated

catalysts and from 40 to 10,000 Å for the kneaded ones. The former is equivalent to the

copper and zinc oxide values in an individual state, while in the latter the values change in the

composite form, with 80- and 20-Å mean particle sizes, respectively. The crystallite size of

the composition with a higher catalytic activity after reduction was about 100 Å both for zinc

oxide and copper in the coprecipitated catalysts and 170–180 Å for copper and 270–280 Å

for zinc oxide in the kneaded ones. From these facts it was proposed that a finely mixed state

in the oxidized precursor has its origin during the coprecipitation process. T.Tsoncheva et al.

[112] worked on nanosized copper ferrites were prepared by thermal method from the

corresponding hydroxide carbonate precursors varying the temperature of synthesis. The

phase composition of the obtained materials was characterized by XRD, Mössbauer

spectroscopy, DSC and TPR analysis. Their catalytic properties were tested in total oxidation

of toluene and methanol decomposition to CO and hydrogen. K.Faungnawaki et al. [113]

discussed dimethyl ether steam reforming (DME SR) was performed over composite

catalysts of copper ferrite spinel (CuFe2O4) and alumina for hydrogen production, applicable

to fuel cell. The composite catalysts both with and without pre-reduction were active for

DME SR when the pre-reduced catalyst exhibited higher initial activity, but longer activation

process was observed for the composite catalyst without pre-reduction. DME conversion and

hydrogen production significantly depended on gas hourly space velocity (GHSV) and


20

reforming temperatures (Tr). DMEconversion (>95%), H2 production rate

(∼50 mol kgcat−1 h−1), and H2 concentration (ca. 73%) were achieved at Tr of 350 °C and

GHSV of 1500 h−1. Yen –Chun Liu et al. [114] worked on copper ferrite nanopowders were

successfully synthesized by a microwave-induced combustion process using copper nitrate,

iron nitrate, and urea. The process only took a few minutes to obtain CuFe2O4nanopowders.

The CuFe2O4 powders specific surface area was 5.60 m2/g. Moreover, these copper ferrite

magnetic nanopowders also acted as a catalyst for the oxidation of 2,3,6-trimethylphenol to

synthesize 2,3,5-trimethylhydrogenquinone and 2,3,5-trimethyl-1,4-benzoquinone for the

first time. On the basis of experimental evidence, a rational reaction mechanism is proposed

to explain the results satisfactorily.M.M.Rashad et al. [115] discussed cubic copper ferrite

CuFe2O4 nanopowders have been synthesized via a hydrothermal route using industrial

wastes. The synthesis conditions were systematically studied using statistical design (Box–

Behnken Program) and the optimum conditions were determined. The results revealed that

single phase of cubic copper ferrite powders can be obtained at different temperatures from

100 to 200 °C for times from 12 to 36 h with pH values 8–12. The crystallite size of the

produced powders was in the range between 24.6 and 51.5 nm. The produced copper ferrite

powders were appeared as a homogeneous pseudo-cubic-like structure. A high saturation

magnetization (Ms 83.7 emu/g) was achieved at hydrothermal temperature 200 °C for 24 h

and pH 8. Photocatalytic degradation of the methylene blue dye using copper ferrite powders

produced at different conditions was investigated. A good catalytic efficiency was 95.9% at

hydrothermal temperature 200 °C for hydrothermal time 24 h at pH 12 due to high surface

area (118.4 m2/g).Shou-Quing Liu et al. [116] worked on a magnetic species was

synthesized in a 100 mL Teflon-lined stainless steel autoclave at 180 °C for 10 h. The

synthesized species was characterized by powder X-ray diffraction, transmission electron

microscopy, scanning electronic microscopy, Fourier-transform infrared spectroscopy, X-ray

photoelectron spectroscopy and vibrating sample magnetometry at room temperature. The

results showed that the synthesized species was nickel ferrite nanoparticles with diameters of

approximately 10 nm. The nanoparticles exhibited a photo-Fenton catalytic feature for the

degradation of rhodamine B in the presence of oxalic acid. The effects of pH, oxalic acid

concentration, and dosage of the catalyst, on the degradation rates of the dyes were examined.

Niyaz Mohammad Mahmoodi et al. [117] discussed photocatalytic ozonation of dyes with

copper ferrite (CuFe2O4) nanoparticle (CF nanoparticle) prepared by co-precipitation method

was investigated. Reactive Red 198 (RR198) and Reactive Red 120 (RR120) were used as


21

dye models. The characteristics of CF nanoparticle were studied using Fourier transform

infrared (FTIR) and scanning electron microscopy (SEM). UV–Vis and ion chromatography

(IC) analyses were employed to study of dye degradation. The effect of operational

parameters on dye degradation such as CF nanoparticle dosage, pH, dye concentration and

salt (inorganic anions) was studied. Formate, acetate and oxalate anions were detected as

dominant aliphatic intermediates.Wichaid Ponhan et al. [118] worked on tetragonal copper

ferrite (CuFe2O4) nanofibers were fabricated by electrospinning method using a solution that

contained poly(vinyl pyrrolidone) (PVP) and Cu and Fe nitrates as alternative metal sources.

The as-spun and calcined CuFe2O4/PVP composite samples were characterized by TG-DTA,

X-ray diffraction, FT-IR, and SEM, respectively. After calcination of the as-spun

CuFe2O4/PVP composite nanofibers (fiber size of 89 ± 12 nm in diameter) at 500 °C in air for

2 h, CuFe2O4 nanofibers of 66 ± 13 nm in diameter having well-developed tetragonal

structure were successfully obtained. The crystal structure and morphology of the nanofibers

were influenced by the calcination temperature. Tsubokawa et al. [119] worked on the

oxidations of alcohols with copper(II) salts mediated by 2,2,6,6-tetramethylpiperidinyloxy

radical (TEMPO) moieties immobilized on ultrafine silica and ferrite surface were

investigated. Based on the above results, the oxidations of alcohols were considered to

proceed as follows: alcohols are oxidized with oxoaminium moieties on silica and ferrite

surface, which were formed by the reaction of surface TEMPO moieties with copper(II) salts,

and oxoaminium moieties on the surface itself are reduced to the corresponding

hydroxylamine moieties after the oxidation. Then the hydroxylamine moieties are oxidized

with copper(II) salts to regenerate TEMPO moieties on the surface. For example, in the case

of the oxidation of benzyl alcohol, Silica-TEMPO was recycled about 45 times. Silica-

TEMPO and Ferrite-TEMPO were readily recovered from reaction mixture by centrifugation.

1.2.2Photocatalyst:

Metal / Mixed metal oxides have wide application as photocatalyst. Luminita et al. [120]

synthesized copper sulphide powder. Thin films were developed by doctor blade deposition

of CuxS and CuxS/TiO2 composites with photocatalytic properties. The powder and thin film

properties were characterized in terms of: the Fourier transform infra-red (FTIR), the X-ray

diffraction (XRD), UV–vis spectroscopy, atomic force microscopy (AFM).The

secmiconductors association and the films homogeneity limit the electron- hole

recombination, resulting in good efficiency in dyes photo degradation even under vsisible

light irradiation. Aman and coworkers [121] studied waste water of copper mines and copper

processing plant. Simultaneous photoreductive removal of copper (II) and selenium (IV) is


22

studied for the first time using spherical binary oxide photocatalysts under visible light from

a single contaminant, EDTA is found to be the best for Cu(II) reduction whereas formic acid

is the best for Se(IV) reduction. In a mixed solution both EDTA and formic acid perform

very well under visible light irradiation. Photodeposited material is found to be copper

selenide rather than pure copper and selenium metal. This indicates that the waste water

containing copper and selenium ions can be efficiently treated under visible or solar light.

Yoong et al. [122] followed the advantage of copper doping into TiO2 semiconductor

photocatalyst for enhanced hydrogen generation under irradiation at the visible range of the

electromagnetic spectrum. Two methods of preparation for the copper-doped catalyst were

selected – complex precipitation and wet impregnation methods – using copper nitrate

trihydrate as the starting material. The dopant loading varied from 2 to 15%. Characterization

of the photocatalysts was done by thermogravimetric analysis (TGA), temperature

programmed reduction (TPR), diffuse reflectance UV-Vis (DR-UV-Vis), scanning electron

microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction

(XRD). Photocatalytic activity towards hydrogen generation from water was investigated

using a multiport photocatalytic reactor under visible light illumination with methanol. Three

calcination temperatures were selected – 300, 400 and 500 °C. It was found that 10 wt.%

Cu/TiO2 calcined at 300 °C for 30 min yielded the maximum quantity of hydrogen. Xia and

coworkers [123] prepared the novel CuO-SnO2 nanocomposite oxide photocatalysts . The

maximum photocatalytic activity of the CuO-SnO2 photocatalyst was observed to be calcined

at 500 °C for 3 h (the molar ratio of Cu to Sn was 1:1) due to the sample with good

crystallization and high surface area. Xu et al . [124] showed 1-D mesoporous TiO2 nanotube

(TNT) with large BET surface area and employed for simultaneous photocatalytic H2

production and Cu2+ removal from water. Cu2+, across a wide concentration range of 8–

800 ppm, was removed rapidly from water under irradiation. The removed Cu2+ then

combined with TNT to produce efficient Cu incorporated TNT (Cu-TNT) photocatalyst for

H2 production. Average H2 generation rate recorded across a 4 h reaction was between 15.7

and 40.2 mmol h−1 g−1 depending on initial Cu2+/Ti ratio in solution, which was optimized at

10 atmosphere. In addition, reduction process of Cu2+ was also a critical factor in governing

H2 evolution. In comparison with P25, its large surface area and 1-D tubular structure

endowed TNT with higher photocatalytic activity in both Cu2+ removal and H2 production.

Neppolian et al. [125] carried out an ultrasound – assisted method for synthesizing

nationalized Pt-graphene oxide (GO) – TiO2 photocatalyst. The Pt-GO-TiO2 nanoparticles

were characterized by diffused reflectance spectroscopy, X-Ray diffraction, N2 BET


23

adsorption – desorption measurements, atomic force microscopy and transmission electron

microscopy. The intermediate products formed during the degradation of DBS were

monitored using electrospray mass spectrometry. The ability of GO to serve as a solid

support to anchor platinum particles on GO-TiO2 is useful in developing new photocatalysts.

Xu et al. [126] studied efficient Cu incorproated TiO2 (Cu–TiO2) photocatalysts for

hydrogen generation fabricated by four methods: in situ sol–gel, wet impregnation, chemical

reduction of Cu salt, and in situ photo-deposition. Among the four photocatalysts, the sample

that was synthesized by in situ sol–gel method exhibited the highest stability. High

efficiency, low cost, good stability are some of the merits that underline the promising

potential of Cu–TiO2 in photocatalytic hydrogen generation Magalhaes et al.[127] discovered

floating photocatalysts based on composites of low density polyethylene (LDPE) containing

30, 68 and 82 wt.% of TiO2 P25. The floating photocatalyst can be reused for at least three

consecutive times without any significant decrease on the discoloration and total organic

carbon removal after each reuse.Hu and coworkers [128] investigated different p-type Cu2O

powders prepared from electrodeposition and subjected to analysis of their photocatalytic

activity in water reduction. The electrodeposited Cu2O powders were obtained by scraping

the deposited films off the substrate. The coupling was made to avoid back reactions of the

photo-induced charges. Appropriate crystalline-texture tuning, as well as charge

delocalization promotion, is looked to as the key issue for efficient H2 generation from water

reduction over p-type Cu2O photocatalysts. Xu et al. [129] found that highly dispersed CuO

was introduced into TiO2 nanotube (TNT) made by hydrothermal method via adsorption–

calcination process or wet impregnation process to fabricate CuO incorporated TNT

photocatalysts (CuO-TNT) for hydrogen production. This high photocatalytic activity of CuO

-TNT was mainly attributed to the unique 1-D tubular structure, large BET surface area and

high dispersion of copper component. Compared to wet impregnation, adsorption–calcination

process was superior to produce active photocatalyst, since it was prone to produce

photocatalyst with more highly dispersed CuO. Anandan et al. [130] reported efficient ZnO

based visible-light photocatalysts, Cu(II) modified CdxZn1−xO were developed by adopting a

hybrid approach, consisting of band engineering by formation of a solid solution and surface

modification of co-catalyst. The visible-light activity of CdxZn1−xO photocatalysts was

greatly improved by the surface modification of Cu2+ ions. The strategy in the present study

is a promising approach for applying ZnO – based photocatalysts for indoor

applications.Mahapure and coworkers [131] demonstrated the synthesis of novel

photocatalyst, zinc indium vanadate (ZIV) by solid – solid state route using respective oxides


24

of zinc, indium and vanadium. Optical study showed the band gap around 2.8 eV, i.e. in

visible region, Photocatalalytic acvivity of phenol degradation under visible light irradiation

was performed using the photocatalyst. Kansal et al.[132] worked on a flower like ZnO

nanostructure .The phase structure and morphology of the synthesized ZnO was characterized

by XRD, SEM and TEM. Experiments were also performed to investigate the reusability and

stability of the synthesis ZnO. Liao et al. [133] produced a novel binary oxide photocatalyst

ZnO/TiO2 prepared by solgel method using citric acid as a complex reagent and its

photocatalytic activity was investigated. It was showed that the addition of ZnO could

enhance the activity significantly, and sulfating ZnO/TiO2 with sulfuric acid resulted to

dramatic enhancement, the degradation ratio of methyl orange could be up to 71.9%

compared with 55% of degradation of ZnO/TiO2 catalyst. Shifu et al. [134] utilized p-type

ZnO powder by decomposition of zinc nitrate at 3500 °C for 1 h. p-n junction photocatalyst

p-ZnO/TiO2 was prepared by ball milling of TiO2 in H2O solution doped with p-ZnO. The p-

n junction photocatalyst p-ZnO/TiO2 was characterized by UV-Vis diffuse reflection

spectrum, scanning electron microscopy (SEM). Namely, the p-n junction photocatalyst p-

ZnO/TiO2 has higher photocatalytic reduction activity. The mechanisms of influence on the

photocatalytic activity were also discussed by the p-n junction principle. Yang et al. [135]

characterised nitrogen-doped titanium oxide (TiO2−xNx) films prepared by ion-assisted

electron-beam evaporation, using rutile powder as source material. The films deposited with

nitrogen ion bombardment at various nitrogen partial pressures (PPN2) were investigated by

X-ray diffraction patterns, Raman, UV–Vis absorption and X-ray photoelectron spectra. The

series of films exhibit a consistent relationship among structures, red-shift in visible light

absorption, and visible light-induced the hydrophilicity and photocatalysis. Khan and

coworkers [136] evaluated well-crystalline ZnO nanoparticles (NPs) synthesized in large-

quantity via simple hydrothermal process using the aqueous mixtures of zinc chloride and

ammonium hydroxide. The NPs are almost spherical shape with the average diameters of

∼50 ± 10 nm. The quality and composition of the synthesized NPs were obtained using

Fourier transform infrared (FTIR) and electron dispersed spectroscopy (EDS) which

confirmed that the obtained NPs are pure ZnO and made with almost 1:1 stoichiometry of

zinc and oxygen, respectively. Yu et al. [137] checked a series of WO3/ZnO composite

photocatalysts with different WO3 concentrations prepared by a precipitation-grinding

method followed by calcination at different temperatures The photocatalytic activity of the


25

samples was evaluated by photocatalytic degradation of acid orange II under UV light (λ =

365 nm) irradiation. The increase in the photocatalytic activity could be attributed to the

coupling of WO3, which suppressed the growth of ZnO particles, increase of the surface area

and increased amount of surface OH groups of the sample. The presence of WO3 also

restrained the recombination rate of e−/h+ pairs. Li et al. [138] analysed nano-crystalline

ZnO particles synthesized via an ion exchange method and used in a methyl-orange

photocatalytic degradation process. An ion exchange resin mixed bed system was used in the

suspension for separation of nano-ZnO and methyl-orange after photocatalysis reaction.

Byproducts and other inorganic ions were transfered into resin phase. Nano-ZnO

photocatalyst can be regenerated and reused.Aman et al. [139] discussed waste water of

copper mines and copper processing plant contains both copper and selenium ions with other

contaminants. Beydoun et al. [140] prepared magnetic iron oxide-titania photocatalysts

(Fe3O4-TiO2) using a coating technique in which the photoactive titanium dioxide was

deposited onto the surface of a magnetic iron oxide core. A decrease in surface area due to

sintering, along with the diffusion of Fe ions into the titanium dioxide coating are seen as

contributing factors to the decline in photoactivity which accompanied an increase in the heat

treatment. This is an indication of changing surface properties as heat treatment in applied.

For single – phase TiO2 powders, this is postulated to be due to a decrease in the surface

hydroxyl (OH) groups and/or residual organics (OR) groups. The reducing duration of the

heat treatment revealed that a heat treatment duration of 20 min at 4500 C was sufficient to

transform amorphous titanium dioxide into a photoactive crystalline phase. Koorman and

coworkers [141] synthesised and studied the photocatalyic activity of α-Fe2O3 colloids. It is

compared to the activities of colloids and suspensions of ZnO and TiO2. The formation of

H2O2 is investigated and the oxidation of organic molecules is studied with high sensitivity.

While ZnO and TiO2 are found to be quite active photocatalysts in the formation of hydrogen

peroxide and in the degradation of chlorinated hydrocarbon molecules. Yu et al. [142]

investigated in order to more easily separate TiO2 photocatalyst from the treated wastewater,

TiO2 photocatalyst is immobilized on coal fly ash by a precipitation method. The titanium

hydroxide precipitated on coal fly ash by neutralization of titanium chloride is transformed

into titanium dioxide by heat treatment in the temperature range of 300–700 °C. The major

iron oxide, existing in coal fly ash as an impurity, is magnetite (Fe3O4). The phase

transformation into hematite (Fe2O3) by heat treatment improves the removal rate of NO gas


26

for TiO2-coated coal fly ash. Wu et al. [143] synthesized the nanoparticles of TiO2 modified

with carbon and iron by sol–gel followed solvothermal method at low temperature. Its

chemical composition and optical absorption were investigated by X-ray diffraction (XRD),

X-ray photoelectron spectroscopy (XPS), photoluminescence emission spectroscopy (PL),

UV–vis absorption spectroscopy, and electron paramagnetic resonance (EPR). The

synergistic effects of carbon and iron in modified TiO2 nanoparticles were responsible for

improving visible light photocatalytic activity. Maretti et al. [144] prepared dioxo iron

phthalocyanine tetrasulphonate (FeO2Pc) incorporated inside the integrality space of a

layered double oxide (LDH). Evidence for the inclusion of the FeO2Pc inside the intercalary

spaces of LDH was obtained from the expansion the basal layer distance of the host. The

solid is able to act as an effective photocatalyst for the degradation of aqueous phenol.

Pradhan et al. [145] carried out the iron incorporated mesoporous Al2O3-MCM-41

nanocomposites, synthesized by sol-gel and followed by wetness impregnation method. They

were found to be active photocatalysts for evolution of hydrogen energy from water in the

presence of sacrificial agent under visible light illumination. The textual properties (high

surface area, narrow pore size, large pore volume and mesoprosity), visible light active band

gap energy 1.90 eV and small practical size (47.95nm) collectively contribute for high

hydrogen production ability.Aman et al. [146] studied waste water of copper mines and

copper processing plant contains both copper and selenium ions with other contaminants. In

this paper simultaneous photoreductive removal of copper (II) and selenium (IV) is studied

for the first time using spherical binary oxide pohotocatalyst under visible light. Their study

shows that 100 ppm of mixed solution can be removed under visible light in 40 min of

reaction using TiZr-10 as catalyst. Photodeposited material is found to be copper selenide

rather than pure copper and selenium metal. This indicates that the waste water containing

copper and selenium ions can be efficiently treated under visible or solar light.Akhavan et al.

[147] discovered the effect of thickness of TiO2 coating on synergistic photocatalytic activity

of TiO2 (anatase)/α-Fe2O3/glass thin films as photocatalysts for degradation of Escherichia

coli bacteria in a low-concentration H2O2 solution and under visible light irradiation was

investigated. The improvement in the photoinactivation of bacteria on surface of TiO2/α-

Fe2O3 was assigned to formation of TiO–Fe bond at the interface. Chen–Shifu and coworkers

[148] developed p-n junction photocatalyst p-CaFe2O4/n-ZnO prepared by ball milling of

ZnO in H2O doped with p-type CaFe2O4. The Structural and optical properties of the p-n

junction photocatalyst p-CaFe2O4/n-ZnO were characterized by X-ray powder diffraction

(XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-


27

Vis diffuse reflection spectrum (DRS) and fluorescence emission spectra [149] . The

mechanism of influence on the photocatalyst activity were also discussed by the p-n junction

principle. Smith et al. [150] developed sulfated Fe2O3-TiO2 (SFT) synthesized by treatment

of immenite ore with sulfuric acid. The presence of sulfated Fe2O3-TiO2 and mixed phase of

Fe2O3- TiO2 was confirmed by DRIFT spectra and XRD. The dispersion of sulfate displayed

thermal stability up to 5000°C. The photocatalytic activity was evaluated by the oxidation of

4- chlorophenol (4-CP) in aqueous medium under UV-vis and visible light irritation. Zhang

et al. [151] induced Bi2WO6 photocatalyst synthesized via a facile low-temperature

combustion synthesis method, using glycine as the fuel. The photocatalytic activities of the

as-synthesized samples were evaluated by the photo degradation of rhodamine B (RhB) and

phenol under visible – light irradiation. The photocatalyst showed much enhanced visible

photocatalytic efficiency, up to 94.2% in 4 h, than the bulk Bi2WO6 powder (SSR) in the

degradation of phenol. Seup et al. [152] examined a magnetically separable photocatalyst

prepared by a continuous multi step spray pyrolysis process. In the first step, nickel ferrite

core particles were prepared by an ultrasonic spray pyrolysis. In the second step, tetraethyl

orthosilicate (TEOS) and titanium isopropoxide (TTIP) were sequentially injected and coated

on the surface of the core particles coated layers were decomposed to form silica and tinania

layers in a final furnace reactor. The titania- silica layered particles displayed higher photo

activity. The strong adhesion between the coated layer and the nickel ferrite core is attributed

to the features of the multi-step process, where in the core particles are exposed to high

temperature in the second reactor for only a few seconds and transformation of the core

particles into non-magnetic particles is prohibited. Liu and coworkers [153] worked on the

commonly used photocatalyst, TiO2 (anatase) immobilized on porous nickel using 3 wt%

polyvinyl alcohol (PVA) as the binder. The observance of photocatalytic degradation of Sal

under pH values and initial concentrations was explained by the adsorption behavior of Sal.

The parameters of the Langmuir Hinshelwood expression have been determined by different

experimental ways. Zhang et al. [154] utilized titanium isopropoxide, ammonium carbonate

and nickelous nitrate as the sources of titanium, nitrogen, and nickel to prepare titania

photocatalyst co-doped with nitrogen and nickel by means of the modified sol–gel method

[155]. The effects of annealing temperature and component on the phase composition and

photocatalytic activity were investigated. Nickel atoms existed in the form of Ni2O3,

dispersed on the surface of TiO2, suppressed the recombination of photo-induced electron-

hole pairs, raised the photo quantum efficiency, and led to the enhancement of photocatalytic

performance.Shifu and coworkers [156] chacterized p-n Junction photocatalyst NiO/TiO2


28

was prepared by sol-gel method using Ni(NO3)2.6H2O and tetrabutyl titanate [Ti(OC4H9)4] as

the raw materials. The results show that, for photocatalytic reduction of Cr2O7, the optimum

percentage of doped-NiO is 0.5% (mole ratio of Ni/Ti). The photocatalytic activity of the p-n

junction NiO/TiO2 is much higher than that of TiO2 on the photocatalytic reduction of Cr2O7.

The mechanisms of influence on the photocatalytic activity were also discussed by the p-n

junction principle. Sreethwaong et al. [157] evaluated photocatalytic activity of mesoporous

titania supported nickel oxide photocatalyst synthesized by single – step sol-gel (SSSG)

process combined with surfactant assisted template method investigated for hydrogen

evolution from an aqueous methanol solution, in comparison with one prepared by

conventional incipient wetness impregnation (IWI) method. Characterization results

demonstrated the significant modification of physical characteristics of the single-step sol-gel

photocatalyst, anticipated to relating to the observation of higher photo catalytic hydrogen

evolution activity. Xu et al. [158] checked a magnetically separable photo catalyst

TiO2/SiO2/NiFe2O4 (TSN) with a typical ferromagnetic hysteresis prepared by a liquid

catalytic phase transfer method. When the intensity of applied magnetic field weakened to

zero, the remnant magnetism of the prepared photocatalyst faded to zero. The magnetic

composite showed high photocatalytic activity for the degradation of methyl orange in water.

A thin SiO2 layer between NiFe2O and TiO2 shell prevented effectively the leakage of

charges from TiO2 particles to NiFe2O4, which gave rise to the increase in photocalytic

activity. Kudo et al. [159] analyzed the structure of nickel-loaded K4Nb6O17 pholocatalyst in

an overall water splitting reaction by means of XPS, EXAFS, TEM, and XRD. K4Nb6O17 has

an ion-exchangeable layered structure which possesses two different kinds of alternating

interlayer spaces, i.e. interlayers I and II, where K+ ions are located. Therefore, each niobate

macroanion sheet is regarded as a “two-dimensional” photocatalyst where H2 and O2 evolve

at different sides of the layer. Neppolian et al. [160] discussed an ultrasound-assisted method

for synthesizing nanosized Pt-graphene oxide (GO)-TiO2 photocatalyst. The Pt-GO-TiO2

nanoparticles were characterized by diffused reflectance spectroscopy, X-ray diffraction, N2

BET adsorption-desorption measurements, atomic force microscopy and transmission

electron microscopy. The mineralization of DBS was enhanced by a factor of 3 using Pt-GO-

TiO2 compared to the P-25 (TiO2). In the presence of GO, an enhanced rate of DBS oxidation

was observed and when doped with platinum, mineralization of DBS was further enhanced.

The initial solution pH had an effect on the rate of photocatalytic oxidation of DBS, whereas

no such effect of initial pH was observed in the sonochemical or sonophotocatalytic oxidation

of DBS. Hayat et al. [161] find out photcatalytic oxidation of phenol using nickel oxide


29

(NiO) nanoparticles synthesized by sol-gel method. The morphology of synthesized catalyst

was studied by using field emission scanning electron microscopy (FESEM), energy

dispersive X-ray spectroscopy (EDX) and high resolution transmission electron microscopy

(HRTEM) and X-ray diffraction (XRD). The photocatalyic activity of NiO was evaluated by

degradation of phenol under irridation of unique source like UV laser. The degradation of the

phenol followed a pseudo first-order rate kinetics. Yoong and coworkers [162] discussed the

advantage of copper doping onto TiO2 semiconductor photocatalyst for enhanced hydrogen

generation under irradation at the visible range of the electromagnetic spectrum . Three

calcination temperatures were selected – 300, 400 and 5000°C . It was found that 10 wt%

Cu/TiO2 calcined at 300°C for 30 min yielded the maximum quantity of hydrogen. The

reduction of band gap as a result of doping was estimated and the influence of the process

parameters on catalytic activity was explained. Biswal et al. [163] synthesized a novel

composite CdS-Zns/ Zirconium – titanium phosphate (ZTP) photocatalyst working under

visible light. N2 adsorption – desoprtion, diffuse reflectance UV-vis spectroscopy (DRUV-

vis), photoluminescence. Results towards hydrogen production with an apparent quantum

efficiency of 9.6% under visible light illumination. Nakhate et al. [164] used an

environmental friendly nanocrystalline NixTiO2 (x=5 and 7%) synthesized by hydrothermal

method. The requisite quantity of commercial TiO2 and Ni(NO3)2 6H2O was leached in

alkaline medium using hydrothermal recator at 120°C. The reported method is effective for

the synthesis of visible light driven photocatalyst and easy to scale up. XRD results showed

that nickel was doped in the form of NiO. SEM picture shows spherical morphology to Ni-

Doped TiO2 and nanofibred particle to hydrothermally treated TiO2 samples. Reza and

coworkers [165] followed Zn 1-X Cu XS and Zn 1-xNixS nanocomposites were synthesized

by using a controlled co-precipitation. The nanocomposite materials were characterized by

the use of UV – Vis spectra, atomic absorption spectroscopy, X-ray, diffraction patterns,

transmission electron microscopy image and Brunauer- Emmet Teller method. The maximum

degradation of dye was obtained at pH 5-7. The Zn 0.94 Ni 0.06S and Zn 0.90Cu 0.10 S

nanocomposites show the highest photoactivity. The influence of hydrogen perodixe and

several anions were studied on the photoactivtiy of proposed catalysts. Lee et al. [166]

prepared collodial solutions containing nano-sized TiO2 particles successfully obtained by

adding a small amount of water and employing solvothermal method.A thin film obtained

from this colloidal solution exhibited much better properties than another film obtained via a

sol–gel method. Wang et al. [167] showed homogeneous mixed Cr-doped Ba4In2O7/In2O3

nanocomposite (Cr-BIO) synthesized by a simple sol-gel method. The Cr-BIO powder was


30

characterized by thermogravimetric (TG), X-ray diffractions (XRD) scanning electron

microscopy (SEM) and UV-vis diffuse reflectance spectrometry. The electrode exhibited

obvious photo-assisted chargeable properties in KOH aqueous solution as the discharge time

increased remarkably under the xenon light irradiation. The photo-assisted chargeability of

HSA/Cr-BIO electrode was then discussed. Nicolas Keller et al. [168] was carried out to

reduce the drawbacks related to the use of provides or immobilized catalysis in gas – and

liquid – phase applications, a new material for the use as photocatalyst support was obtained

by chemical vapor decomposition at 7000C of an ethane – hydrogen mixture over a woven

glass microfiber supported nickel catalyst. The presence of hydrophilic oxygenated groups

located at the outer surface of the carbon nanofibres allowed the sol-gel preparation of a

woven glass microfiber – carbon nanofiber supported TiO2 (20 wt %. Catalyst using

tetraisopropoxide as precursor. This new photocatalyst was totally stable under UV

irradiation.Nukajima et al. [169] synthesized thermally stable mesoporous Ta2O5 by a sol-gel

technique using a material having a BET surface area of 145 m2 g-1, mesopore diameter of

3.5nm, and mesopore volume of 0.20 mlg-1. The formation of thicker walls results in higher

thermal stability than tantalum oxides prepared by a ligand – assisted templating method.

1.2.3Sensors:

Metal / Mixed metal oxides have wide application as sensors some of them have been

described here. Komilla et al. [170] synthesized gas and humidity sensors based on iron

oxide polypyrole nanocomposites Iron – oxide sensor nanocomposites of iron oxide and

polypyrrole were prepared by simultaneous gelation and polymerization process. The

composites in the pellet from were used for humidity and gas sensing investigations. Gas

sensing was performed for CO2 N2 and CH4 gases at varying pressures. The sensors showed a

linear relationship between sensitivity and pressures for all the gases studied. The sensors

showed highest sensitivity to CO2 gas. Tongpool et al. [171] synthesized sol gel processed

iron oxide silica nanocomposite films as room temperature humidity sensors. Iron oxide-

silica nanocomposite films have been fabricated using sol-gel process and spin coating

technique. Iron oxide and silica were segregated. As Si content in the films increase, the films

were more compact. The iron oxide films calcined at 4000C were hematite but in the presence

of silica, iron oxide is composed of hematite and magnetite. Neri et al. [172] studied role of

the Au oxidation state in the Co sensing mechanism of Au/iron oxide based gas sensors. A

study on the CO sensing mechanism of sensors based on Au-doped/ iron oxide thick films is

reported. Thick films were prepared from coprecipitated powders of Au/Fe2O3 calcined at

temperatures between 100 and 4000C.A detailed micro structural characterization by XRD,


31

TEM and XPS has shown that nanometer sized gold particles with gold in a positive

oxidation state are predominant after calcination of the powders at 1000C. The anomalous

response observed over the film annealed at the lowest temperature has been related to the

participation of Au (III) ions in the CO sensing mechanism. Jorge et al. [173] studied novel

optical NO2- Selective sensor based on Phthalocyaninato – iron (H) incorporated into a

nanostructured matrix.A novel highly optical NO2-selective complexing agent. In order to

solubilize the iron phthalocyanine and to obtain the monomer species, a N-donor ligand was

used as a solvent. The effect of the type and concentration of the N-donor ligand, and the

influence of the iron phthalocyanine concentration were investigated as well as the effect of

the composition and the morphological characteristics of the nanostructured material.

P.Althainz et al. [174] The influence of the response of iron oxide gas sensors.

Microgranular layers of iron oxide have been prepared by the deposition of dried aerosol

droplets of iron oxalate and subsequent decomposition to investigate the gas sensing

properties of this special morphology. For comparison, compact iron-oxide films have been

prepared by sputtering of iron and successive oxidation. Several different granular gas

detectors have been produced consisting of spherical particles with sizes between 0.2 and 1.2

µm in narrow size distributions. The compact films exhibit a pronounced sensitivity increase

with molecular weight of the vapour. In contrast, the granular layers detect all gases with

similar sensitivities and react faster than the compact layers. Neri et al. [175 ] studied of

wake influence in co response on gold – doped iron oxide sensors. A temperature

programmed desorption (TPD) study of the water and CO- interaction with the surface of

gold doped iron oxide sensors is presented. TPD data has shown that CO does not adsorb in

the absence of water. The adsorption of CO occurs when water is present as coadsorbate,

through the formation of a surface formate intermediate. TP reaction of CO with oxygen in

both dry and wet air has shown that water also promotes CO oxidation, likely via the same

formate intermediate. The effect of water on the CO sensing of Au/Fe2O3 sensors was also

investment. Chakraborty et al. [176] selective detection of methane and butane by

temperature modulation in iron doped tin oxide sensors. In the present study it is possible to

develop sensors based on iron doped tin dioxide, which can detect both methane and butane

(present in CNG and LPG, respectively) at a temperature at 3500C. However, the same

sensors can selectively detect butane at a temperature of 4250C. The incorporation of

palladium as a catalyst in Fe-doped SnO2 sensors removes the typical selectivity, and the

temperature of the maximum response coincide for methane and butane. Neri et al. [177]


32

studied humidity sensing properties of Li-iron oxide based thin films. Li-doped iron oxide

thin films deposited on a porous ceramic substrate by a liquid-phase method (LPD) were

investigated as humidity sensors. Large variations in the resistance, up to about 4-5 order of

magnitude, were observed by changing the relative humidity (RH) between 10 and 90%. The

role of Li on the response to water vapour of iron oxide thin films is discussed. Retting et al.

[178] studied α-Iron oxide an intrinsically semiconducting oxide material for direct

thermoelectric oxygen sensors. Intrinsically semiconducting oxide materials offer the

possibility for highly sensitive direct thermoelectric gas sensors. Intrinsic α-Fe2O3 has been

chosen as a well suited candidate for direct thermoelectric gas sensors. The used temperature

modulation technique combined with a regression analysis allowed a determination of the

measured thermopower within 6.4 s and the possibility for self-diagonstics. These presented

results shows a possible realization of fast, accurate, highly sensitive direct thermoelectric gas

sensors. Comini et al. [179] studied influence of Iron addition on ethanol and CO sensing

properties of tin oxide prepared with the RGTO technique. Effects of iron introduction in

RGTO prepared tin oxide gas sensors are presented. The films were deposited by sputtering

from a tin target with the introduction of an adjustable number or iron inset. Iron content was

varied in the range 0-7%. The thin films are investigated by the volt-amperometric technique

for electrical and gas-sensing properties. The response of the sensors is stable and

reproducible at all operating temperatures tested (200-5000C) during 3 months of operation.

Cantalini et al. [180] worked on niobium – doped αFe2O3 semiconductor ceramics sensors

for the measurement of nitric oxide gases. The NO, NO2 and NOx gas-sensitivity properties

of Nb-doped α-Fe2O3 sintered compacts have been studied in the 0–100 ppm gas

concentration and 150–300 °C temperature ranges, by d.c. and a.c. techniques. Sensors have

been prepared by suspending a 130 m2 g−1 α-Fe2O3 powder in a standard Nb solution in order

to yield Nb/Fe atomic percentages between 0.5 and 20 at.%. Sintering has been performed at

800 °C for 2 h. The 20% doped material shows a gas sensitivity (S), defined as RG/RA,

where RA and RG are the electrical resistances in air and in the sample gas, respectively, as

high as 36 at 100 ppm NO2 and 200 °C working temperature. An electrical equivalent circuit

including a constant phase element (CPE), which can simulate the electrical response of the

sensor in the 0–100 ppm NO2 gas concentration range, is also presented. Baratto et al. [181]

studied iron doped indium oxide by modified RGTO deposition for ozone sensing

nanostructured thin films based on indium oxide have been prepared by a modified rheotaxial

growth and thermal oxidation (RGTO) deposition technique. The layers were additivated


33

with 8–30% iron in order to stabilize the microstructure and to enhance the sensing properties

toward ozone. The electrical test of the sensing layers indicated high sensitivity to ozone

together with a relatively low cross-sensitivity to interfering gases. Belle et al. [182] studied

the size dependent gas sensing properties of Spinel iron oxide nanoparticles. Spinel iron

oxide nanoparticles of sizes from 12 to 60nm have been prepared via a hydrothermal

synthesizes. The electrical and gas sensing properties were characterized by impedance

spectroscopy using multielectrode substrates. The materials exhibit good sensor responses

towards NH3 with low cross sensitivities towards H2 and NO at 2500C. A linearly increasing

sensor response towards NH3 and H2 with decreasing particle size was found. Tesfamichael et

al. [183] worked on thin film deposition and characterization of pure and iron doped electron

beam evaporated tungsten oxide gas sensors. Pure tungsten oxide (WO3) and iron-doped

(10 at.%) tungsten oxide (WO3:Fe) nanostructured thin films were prepared using a dual

crucible electron beam evaporation (EBE) technique. The films were deposited at room

temperature under high vacuum onto glass as well as alumina substrates and post-heat treated

at 300 °C for 1 h. The heat treated films were investigated for gas sensing applications using

noise spectroscopy. It was found that doping of Fe to WO3 produced gas selectivity but

reduced gas sensitivity as compared to the WO3 sensor. Wang et al. [184].Synthesized iron-

doped vanadium tin oxide nanocrystallites for CO gas sensing Iron-doped vanadium–tin

oxide nanoparticles have been synthesized by a hydrolysis and co-precipitation method from

iron(II) acetate, vanadium(III) acetylacetonate and tin tetrachloride. Based on sensitivity

measurements in a semiconductor CO gas sensor, the iron doping resulted in a shift of the

maximum sensitivity toward the lower temperature side. A correlation between the surface

state and sensor performance is proposed. Brezoi et al. [185] studied phase evolution

included by polypyrrole in iron oxide- polypyrrole nanocomposite. Nanocomposite of

polypyrrole and iron oxide were prepared using simultaneous gelation and polymerization

processes. Varied amounts of pyrrole were added to a solution containing in Fe (III) salt as

precursor and 2-metoxy ethanol as solvent. The properties of nano composities formed by

combining conducting polymers and oxides nano particles are strongly dependent on

concentration of polymer and have brought out more fields of applications such as smart

windows, toners in photocopying, conductive paints, drug delivery, recharge able batteries.

These nanocomposites were used for humidity and gas sensors. Biswal et al. [186] studied

pure and Pt-loaded gamma iron oxide as sensor for detection of sub ppm level of acetone. In

this study, pure and Pt-loaded nanocrystalline γ-Fe2O3 have been prepared by precipitation

using ultrasonic irradiation. The synthesized powders were characterized by X-ray diffraction


34

(XRD), thermo-gravimetric analysis (TGA), differential thermal analysis (DTA),

transmission electron micrograph (TEM), selected area electron diffraction (SAED), scanning

electron microscope (SEM) and energy dispersive X-ray (EDX). Gunjakar et al. [187]

studied chemical deposition of nano crystalline nickel oxide from urea containing bath and its

use in liquefied petroleum gas sensor. Nanocrystalline nickel oxide (NiO) was deposited onto

glass substrates using a chemical deposition method from a bath containing nickel (Ni2+) ions

and urea at 363 K. The chemically deposited nickel oxide films were effectively used as a

liquefied petroleum gas (LPG) sensor and the maximum response of 36.5% was recorded on

exposure to 0.3 vol% of LPG at 698. Banno et al. [188] worked on selective nitrogen dioxide

sensor based on nickel copper oxide mixed with rare earths scandium – doped nickel copper

oxide bulk, which consists of Ni0.8Cu0.2O, CuO, Sc2O3, and Sc2Cu2O5, responds only to NO2

(50 – 500 ppm) among NOx gases. Thin films of the oxide are prepared by a magnetron

sputtering method, and their NOx- sensing characteristics are studied. The disappearance of

crystalline Sc2Cu2O5 in the film might affect the sensing performance for NOx. Hotovy et al.

[189] studied on preparation of nickel oxide thin films for gas sensors applications. Nickel

oxide (NiO) thin films were prepared by dc reactive magnetron sputtering from a nickel metal

target in an ArO2 mixed atmosphere in two sputtering modes. The oxygen content in the gas

mixture varied from 15% to 45%. The films prepared in the oxide-sputtering mode were

amorphous while the films in metal-sputtering mode exhibited polycrystalline (fcc) NiO

phase, found that good NiO stoichiometric films are obtainable with a polycrystalline (fee)

structure at 40% oxygen content in the metal-sputtering mode. Jan Hrfac et al. [190] Nitric

oxide sensor based on carbon fiber covered with nickel porphyrin layer deposited using

optimized electro polymerization procedure.Electropolymerization regime of meso-tetrakis

(3-methoxy-4-hydroxyphenyl) porphyrin is optimized to yield films possessing both

electrocatalytical and permselective properties towards nitric oxide oxidation.The sensor

composed of electrochemically oxideized carbon fiber, covered solely with nickel porphyrin

derivative layer electropolymerized. Nafion coating can further enhance selectivity propeteis

as well as aids to the stability of the sensors responses.Fei, Cao, et al. [191] Highly sensitive

non enzymatic glucose sensor, based on electrosum copper oxide doped nickel oxide

composite micro fibers. An improved non enzymatic glucose sensor based on copper oxide-

doped nickel oxide composite microfibers (CuO-NiO-MFs) modified flurone tin oxide (FTO)

electrode was prepared by electrospinning and calcination technologies without using any

immobilization. Its application for detecting glucose concentration of human serum sample

showed good agreement with the results obtained from automatic biochemical analyzer.Cao


35

et al. [192] studied nickel oxide micro fibers immobilized onto electrode by electrospining

and calcination for non enzymatic glucose sensor and effect of calcinations temperature on

the performance. Nickel oxide microfibers (NiO-MFs) were directly immobilized into the

surface of fluorine tin oxide (FTO) electrode by electrospinning and calcinations without

using any immobilization matrix for nonenzymatic glucose sensor which is among the best

values reported in literature. Additionally, excellent selectivity and stability have also been

obtained. Pontie et al. [193] Improvement in the performance of a nickel complex – based

electro chemically sensor for the detection of nitric oxide in solution.The electroformation of

the tetrasulfonated nickel phthaolocyanine (NiTSPc) film in alkaline solution onto carbon

fiber microelectrode is investigated in order to improve the electrochemical detection of nitric

oxide (NO) in solution. The phthalocyanine film formed by cyclic voltammetry gives a

modified microelectrode with a good sensitivity to NO, higher than the obtained one with

nickel phthalocyanine and/or prophyrin deposited by controlled potential electrolysis.

Bedioui et al. [194] Elaboration and use of nickel planar macrocyclic complex based sensors

for the direct electrochemical measurement of nitric oxide in biological media. We described

here the electrochemical detection of nitric oxide, NO, in biological systems by using

chemically modified ultramicro carbon electrodes. In the first part of the paper, the different

steps involved in the electrochemical preparation and characterization of the nickel – based

sensor are described. Cao et al. [195] Highly sensitive nonenzymatic glucose sensor based on

electrospun copper oxide doped nickel oxide composite microfibers. An improved

nonenzymatic glucose sensor based on copper oxide- doped nickel oxide composite

microfibers (CuO-NiO-MFs) modified fluorine tin oxide (FTO) electrode was prepared by

electrospinning and calcination technologies without using any immobilization. The

nonenzymatic glucose sensors that have been reported in the literature. Additionally, its

application for detecting glucose concentration of human serum sample showed good

agreement with the results obtained from automatic biochemical analyzer. Ho et al. [196]

Chemiresistor type No gas sensor based on nickel phthalocyanine thin films .The sensing

characteristics of nickel phthalocyanine (NiPc) thin films for use in a chemiresistor type nitric

oxide gas sensor are discussed. The gas- sensing properties, including current transient,

sensitivity, response time, and aging, are studied. A kinetic model proposed in the literature

for sensing NO2 with lead phthalocyanine (PbPc) thin films, in which adsorption involves

displacement of surface adsorbed O2 from a range of heterogeneous sites, can be used to

explain our experimental results. For a lower concentration range, between 5 and 50 ppm

NO, the sensitivity lies between 0.41 and 0.42, while for a higher concentration range,


36

between 50 and 500 ppm, the sensitivity decreases to about 0.17 to 0.19.C.V. Reddy et al.

[197] studied semiconducting gas sensor for chlorine based on inverse spinel nickel ferrite.

Nickle ferrite, a p-type semi conducting oxide with an inverse spinel structure has been used

as a gas sensor to selectively detect chlorine in air. This compound was prepared by two

different routes namely, the citrate and co-precipitation method and sensor properties of the

resulting compounds from both the methods were compared. X-ray diffraction was used to

confirm the structure. The sensitivity to chlorine has been compared with that of other

inferring gases. A probable explanation has been proposed to explain the selective sensitivity

to oxidizing gases like chlorine. Noh et al. [198] studied electrical properties of nickel oxide

thin films for flow sensor application In this work, NiO thin films, with thermal sensitivity

superior to Pt and Ni thin films, were formed thorough annealing of Ni films deposited by a

r.f. magnetron sputtering. The annealing was carried out in the temperature range of 300-

5000C under atmospheric condition because of their high resistively and very linear TCR, Ni

oxide thin films are superior to pure NI and Pt thin films for flow and temperature sensor

applications. Salini et al. [199]sttudied highly sensitive sensor for picomolar detection of

insulin at physiological PH, using GC electrode modified with guanine and electro deposited

nickel oxide nano particles. The electro chemical behavior of insulin at glassy carbon (GC)

electrode. The modified electrode was applied for insulin detection using cyclic voltammetry

of hydrodynamic amperometry techniques. It is promising for for the monitoring of insulin in

chromatographic effluents. Mu et al. [200] studied nano nickel Oxide modified non –

enzymatic glucose sensors with enhanced sensitivity through an electro chemical process

strategy at high potential. Development of fast and sensitive sensors for glucose

determination is important in food industry, clinic diagnostics, biotechnology and many other

areas. in these years, considerable attention has been paid to develop non-enzymatic

electrodes to solve the disadvantages of the enzyme modified electrodes, such as instability,

high cost, complicated immobilization procedure and critical operating situation et.al. The

non-enzymatic sensors response quickly to glucose and the response time is less than 5’s,

demonstrating excellent electroatlytical activity and assay performance the proposed non-

enzymatic sensors can be used for the assay of glucose in real sample.Scandium – doped

nickel copper oxide bulk, which consists of Ni0.8Cuo.2O, CuO, Sc2O3, and Sc2Cu2O5, responds

only to NO2 (50-500ppm) among NOx gases. Thin films of the oxide are prepared by an r.f.

magnetron sputtering method, and their NOx- sensing characteristics are studied. The

disappearance of crystalline Sc2Cu2O5 in the film might affect the sensing performance for

NOx. D. Barreca et al. [201] worked on supported copper oxide nano systems synthesized by


37

chemical vapor deposition (CVD) on Al2O3 substrates and characterized by means of

glancing incidence X-ray diffraction (GIXRD), secondary ion mass spectrometry (SIMS) and

field emission scanning electron microscopy (FESEM). The obtained results revealed good

responses even at moderate operating temperatures, with characteristics directly dependent on

the system composition and nano – organization. Yang et al. [202]worked on copper oxide

nano particles sensors for hydrogen cyanide detection.Uprecedented selectivity and

sensitivity. CuO nano particles were synthesized in a facile way, and characterized by

scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray

photo electron spectroscopy, and thermo gravimetry. Using these CuO nano particles, CuO

functionalized QCM resonators were fabricated and explored for HCN sensing. The current

results would provide an exciting alternative to fast, sensitive and selective detection of trace

HCN, which would be of particular benefit in the area of public security and environmental

application. Wei et al. [203] a novel hydrogen sulfide room temperature sensor based on

copper nanoluster functionalized tin oxide thin films. A novel room temperature solid state

senor for the detection of hydrogen sulfide is described. The sensor was fabricated by first

depositing a thin film of tin oxide on to a glass substrate followed by surface functionalizing

with monolayer protected copper nano clusters (MPCs) capped with different capping agents

prepared as per the brust synthesis. The response time for all the samples is smaller than 2

min. Wang et al. [204] studied low temperature H2O sensor based on copper oxide/ tin

dioxide thick film. nano structured tin dioxide (SnO2) powders were prepared by a sol-gel

dialytic process and the doping of CuO on it was completed by a deposition precipitation

method. The thick film sensors were fabricated from the CuO/ SnO2 polycrystalline powders.

Sensing behavior of the sensor was investigated with various gases including CO, H2, NH3

hexane, acetone, ethanol, methanol and H2S in air. It might have promising applications in

the future.Saumya et al. [205] studied flectropun pallodium (IV) doped copper oxide

composite Nanofibers for non emetic glucose sensor. Pd (IV) doped CO oxide composite

nanofibers (PCNFs) have been successfully fabricated via electrospinning and then employed

to construct an amperometric non-enzymatic glucose sensor. These results indicate that

PCNFs are promising candidates for amperometric non enzymatic glucose

detection.Tudorache et al. [206] prepared humidity sensor applicative material based on

copper-zinc-tungsten spinel ferrite the effect of partially substitution of iron with tungsten on

the properties of copper-zinc spinel ferrite for humidity sensors application was presented.

The electric properties of the Cu0.5Zn0.5W0.3Fe1.7O4 spinel ferrites heat-treated at different

temperatures and humidity conditions were characterized and analyzed. As an application of


38

the material the characteristics of a resistive and capacitive humidity sensors were analyzed

using Cu0.5Zn 0.50.3Fe1.7O4 ferrite as active material.Mukherjee et al. [207] Synthesised and

studied process induced improvement on the gas sensing characteristics of nano-crystalline

magnesium zinc ferrite particles. The gas sensing performances of the ferrite based sensors

can be improved by modifying their surfaces to volume ratio, grain size, morphology and

meso-porous nature. Synthesis of phase pure ferrites with desired micro-structural features at

lower calcinations temperature remains a challenging task. In order to improve their gas

sensing performance, they have investigated the (synthesis) process induced modifications of

the phase and micro-structural features of wet chemical synthesized ferrite sensing elements.

These structural and micro-structural features are found to have significant influence on the

gas sensing performances of Mg0.5Zn0.5Fe2O4 particles prepared using two different wet

chemical routes.Mukherjee et al. [208] studied promising methane-sensing characteristics of

hydrothermal synthesized magnesium zinc ferrite hollow sphere. The promising methane-

sensing characteristics (i.e. per cent response, response and recovery time) identified for Mg

0.5Zn0.5F2O4 hollow sphere-based sensing elements are attractive for developing

chemoresistive-type non-conventional complex oxide-based combustible gas

sensors.Mukherjee et al. [209] studied Reducing gas sensing behavior of nano-crystalline

magnesium–zinc ferrite powders as an effective alternative of simple binary oxides, cubic

spinel oxides are considered to be attractive to make sensitive and stable gas sensor, selective

to a specific gas and on the investigation of the gas sensing characteristics of cubic spinel

based nano-crystalline magnesium zinc ferrite powders. The conductance transients during

response and recovery processes have been modeled using Langmuir adsorption isotherm and

activation energies for gas adsorption and desorption processes have been estimated from the

respective thermally activated kinetic processes.Sutka et al. [210] studied on gas sensing

properties of Zn-doped p-type nickel ferrite. For characterization of gas sensor material,

synthesized by sol–gel auto combustion method, X-ray diffraction (XRD), scanning electron

microscopy (SEM), DC resistance and impedance spectroscopy (IS) measurements were

employed. The response change of Zn doped nickel ferrite is related to the interruption of

hole hopping between nickel ions. This was improved by change of conductivity type with

temperature and gas exposure. Rezlescu et al. [211] studied semiconducting gas sensor for

acetone based on the fine grained nickel ferrite .The sensitivity to some reducing gases

(acetone, ethanol, methane and liquefied petroleum gas—LPG) of calcia doped nickel ferrite

(NiFe2O4 + 1%CaO) and cobalt and manganese doped nickel ferrite, Ni 0.99Co0.01MnxFe

2−xO 4−δ (x = 0.01 and 0.02), was investigated. The samples were prepared by self


39

combustion method. The gas sensitivity largely depends on the composition, temperature and

the test gas species. The ferrite compounds doped with Co and Mn are selective to detect

reducing gases at low operating temperature. The mixed ferrite with Ni0.99Co0.01Mn0.02Fe

1.98O4−δ composition is sensitive and selective to acetone gas. Reddy et al. [212] studied on

semiconducting gas sensor for chlorine based on inverse spinel nickel ferrite is a p-type

semiconducting oxide with an inverse spinel structure has been used as a gas sensor to

selectively detect chlorine in air. The sensitivity to chlorine has been compared with that of

other interfering gases. A probable explanation has been proposed to explain the selective

sensitivity to oxidising gases like chlorine.Darshane et al. [213] studied on nanostructured

nickel ferrite a liquid petroleum gas sensor. The present investigation deal with the synthesis

of nanostructured nickel ferrite (NiFe2O4) and their liquid petroleum gas-sensing

characteristics. The results suggest possibility of utilization of the nanostructured nickel

ferrite, without addition of any precious metal ion, as the LPG detector. Galindo et al. [214]

studied catalytic properties of nickel ferrites for oxidation of glucose, β-nicotiamide adenine

dinucleotide (NADH) and nickel ferrite nanoparticles (NiFe2O4) were synthesized by

electrochemical method and used as catalyst for direct oxidation of glucose, NADH and

methanol. Characterization of these nanoparticles was carried out by X-ray diffraction,

Mössbauer spectroscopy, and colloidal properties such as hydrodynamic radius and Zeta

potential.Lokhande et al. [215] worked on magnetic studies on one-step chemically

synthesized nickel ferrite thin films. Nickel ferrite thin films were synthesized at room

temperature using one-step electrodeposition solution processing. Reaction kinetics was also

proposed. An effect of air baking on the structural, surface morphological and magnetic

properties was investigated. Petrila [216] studied on humidity sensor applicative material

based on copper-zinc-tungsten spinel ferrite .The effect of partially substitution of iron with

tungsten on the properties of copper-zinc spinel ferrite for humidity sensors application was

presented.The electric properties of the Cu0.5Zn0.5W0.3Fe1.7O4 spinel ferrites heat-treated at

different temperatures and humidity conditions were characterized and analyzed. As an

application of the material the characteristics of a resistive and capacitive humidity sensors

were analyzed using Cu0.5Zn0.5W0.3Fe1.7O4 ferrite as active material. Satyendra Singh et al.

[217] worked on synthesis of nanorods and mixed shaped copper ferrite and their applications

as liquefied petroleum gas sensor .The preparation and characterization of nanorods and

mixed shaped (nanospheres/nanocubes) copper ferrite for liquefied petroleum gas (LPG)

sensing at room temperature. The structural, surface morphological, optical, electrical as well

as LPG sensing properties of the copper ferrite were investigated. Single phase spinel


40

structure of the CuFe2O4 was confirmed by XRD data. The role of PEG in the synthesis for

obtaining nanospheres/nanocubes has also been demonstrated. Khandekar et al. [218] worked

on liquefied petroleum gas sensing performance of cerium doped copper ferrite.The gas

sensing properties of sintered samples were studied towards different reducing gases such as

liquefied petroleum gas (LPG), acetone, ethanol and ammonia. The sample with 4% cerium

doped CuFe2O4(Ce4) showed the maximum gas sensitivity (86%) towards LPG with fast

response time of 5 s and good recovery time of 68 s. Singh et al.[219] Investigated the effects

of surface morphologies on response of LPG sensor based on nanostructured copper ferrite

system. Gas sensing properties shows the spinel CuFe2O4 synthesized in 1:1 molar ratio

exhibit best response to LPG adsorption/resistance measurement. Thus resistance based LPG

sensor is found robust, cheap and may be applied for kitchens and industrial applications.

1.2.4 Superconductors:

Metal / Mixed metal oxides have wide application as superconductors some of them are

described here. Takahama et al. [220] synthesized fialmentary Y123 superconductors by

solution spinning and partial – meltprocess. The fiber axis of the filament is normal to the c-

axis of the orthorhombic phase. For the direction to the fiber diameter, the JC value of the

sample with random orientation was higher than that the sample with c-axis orientation

texture. The sample with random orientation has J of 104A/cm2 at 77K and O T. Although

the JC value (103/Acm2 at 4 T) of the sample slightly decreased with the applied field, the Jc

value of than 102/A cm2 was maintained at 10T. Manasiev et al. [221] used chemical

methods of synthesis of materials play a crucial role in the design and discovery of new

material’s, and also provide better and less cumbersome methods for preparing known

materials. The reaction mechanisms of transition metal salts and their mixtures in molten

nitrates are given. Then, the preparation of dispersed simple oxides, multicomponent system,

layered intercalation hosts and supported catalysts are described. Several examples of this

molten salt synthesis approach are given with the described. Several examples of this molten

salt synthesis approach are given with the objective of optimizing textural properties for

catalytic applications. Management of the reaction can be obtained by modifications of the

molten bath by using some dopant such as a nitrite or a carbonate. Josef Novak et al. [222]

followed this method is based on the oxidation of a known amount of iron (II) ions with

oxide superconductors YBaCuO and BiSrCaCuO in a 2-5 mol-1 solution of hydrobromic acid.

This procedure allows the dissolution of samples even at elevated temperature. The reliability

interval is 5%. Retoux et al. [223] prepared a new bismuth iron oxide, isostructural with the

2233 superconductor. The electron diffraction study showed the existence of satellites,


41

similar to those observed in the superconducting bismuth cuprates. A preliminary mossbauer

study was performed. Hosono et al. [224] discovered two new classes of superconductors in

the course of materials exploration for electronic active oxides. One is 12CaO.7Al2O3 crystal

in which electrons accordance in the crystallographic sub-nanometer sized cavities. The other

is iron oxypnicitides with a layered structure. The high Tc is emerged by doping carriers to

the metallic parent phases which undergo crystallographic transition (tetra to ortho) and

Pauli para to antiferromagnetic transition at 150K. Boeck et al. [225] discovered that oxygen

deficiency in the iron based – HTSC GdFeAsO seems to create a parallelogram shaped Fe2+

ion/oxygen deficiency pattern in the Fe2O2 plane in c- direction. The doping distance in

direction of the super-current shows a strong correlation to the transition temperature. Nohara

et al. [226] developed an overview of the crystal structures and physical properties of the

recently discovered iron-platinum – arsenide superconductors Ca10(PtnAs8) (Fe 2-x Pt xAs2)5

(n=3 and 4), which have a superconducting transition temperature up to 38 K, is provided.

The upper critical field Hc2, hydrostatic pressure dependence of superconducting transition

temperature Tc and normal-state magnetic susceptibility are reported. Yoshizawa et al. [227]

investigated the elastic properties of the iron – based superconductor Ba(Fe 1-xCo x)2As2 with

various Co concentrations. The elastic constant shows remarkable anomalies associated with

the structural phase transition and the superconducting transition. These results shows the

strong electron – lattice coupling in this system, and support the prevailing scenario on the

relevant role of structural fluctuation coupling to orbital’s to understand a whole picture of

iron- based superconductor. Shein et al. [228] found that the atomic models of nanotubes for

layered FeSe, LiFeAs, SrFe2As2, and LnFeAsO- the parent phases of so – called 11, 111, 122

and 1111 groups of newly discovered family of iron-based high temperature superconductors

are proposed. Shirage et al. [229] reported we have utilized a high-pressure (HP) technique

to synthesize a series of newly – discovered iron (nickel) – based superconductors. For the

LnFeAsO-based superconductors (Ln=lanthanide), This showed that the introduction of

oxygen (O)- deficiency in the LnO layers, which is achievable only through HP process, The

effect of O-deficiency, variation of Ln ions, and the external pressure on T are examine.

Upper critical field measurement on single crystalline sample of PrFeAsO 1-y shows the

superconducting antistrophe of 5, which is smaller than cuprates. Gomez et al. [230]

examined the substitution of a small fraction of Cu atoms by Fe atoms in the copper oxide

superconductors proven to be useful in sensing, with mossbauer spectroscopy the local

surroundings of the Cu sites of their structures. In this work they reported the results of such

substitution in the Nd1.85Co0.15Cu2O4-s system. Whangbo et al.[231] reviews examination of


42

superconducting temperature Tc and the in plane Cu-O bond lengths of the TI-and Bi – based

copper – oxide superconductors with characteristics similar to those found for La 2-xSrxCuO4.

The correlations are grouped into three major classes according to the size of the cations

occupying the 9-coordination sites. The observations and their implications are examined in

terms of the overlap populations of the in-plane Cu-O bonds calculated as a function of the

number of electrons in the x2-y2 bands of the CuO2 layers. Ihara et al. [232] worked empirical

rules on high-Tc superconductors with cubic lattice structure . High entropy state of lattice,

high degeneracy of energy levels and high possibility of electronic and lattice instability are

key factors for cubic superconductors with high Tc. The basis of the rules, some cubic-

structured copper-oxides with inversion symmetry were proposed as high Tc

superconductors. Bushida et al.[233] produced the new cubic Cu6O8MX compounds (M=

In, Sc, Cu, Y and Pb, and X=NO3 and CI) for High-Tc superconductors. They have high

structure symmetry (Fm3m) and CuO4 clusters as structural units which play an important

role to the mechanisms of superconductivity. Ohta and coworkers [234] utilized a clear

correlation between superconducting transition temperature, Tc, and the energy level of

apical oxygen relative to that of the CuO2 plane, VA, is found to exist throughout all the

known hole-doped superconductors. Pressure dependence of Tc is explained in terms of this

Tc-VA correlation. Crabtree et al. [235] characterized resistive and magnetic measurements

of the superconducting transition in good quality single crystals of YBa2Cu3O7-s and La 2-xSr

xCuO4 and in good polycrystalline samples of Ba 1-xK xBiO3 used to derive the temperature

dependence and anisotropy of the upper critical field. The definition of Tc from resistance

curves and the origin of the upward curvature in the upper critical field are discussed.

Manthiram et al. [236] evaluated thallium cuprates chemically characterized by adopting

simple wet-chemical procedures for the determination of Tl and oxygen contents. The

oxidation of the CuO2 sheets in the Tl 2-yBa2Ca n-1CunO 2n+4-x family is primarily due to (i) an

overlap of the Tl-6s band with the conduction bond of the CuO2 sheets for smaller y=0.0 and

(ii) Tl vacancies for larger y=0.5. Thallium cuprates have an oxygen deficiency in the Tl2O2

layers unlike the analogous bismuth cuprates, which have excess oxygen in the Bi2O2+x layer.

The origin of the orthorhombicity, which appears after low-temperature. Marashima and

coworkers [237] checked the effect of Zn substitution in La-Sr-Cu-O and Y-Ba-Cu-O

systems. Close similarities in their behaviour suggest that the mechanism of

superconductivity for the two systems is unlikely to be different. Beales et al. [238] analyzed

a new series of layered copper oxides with the elements lead and cadmium in the rock – salt

dopant layer is reported. Materials with the nominal composition (Pb0.5Cd0.5) (Sr 1+xLa 1-


43

xCuO5 from as the (Pb, Cd)-1201 phase when x=0 and are superconducting with a maximum

Tc of 40 K as measured by the onset of diamagnetism. These data and additional

measurements on the previously reported (Pb, Cd)-1212 phase demonstrate the improved

properties arising from the lead and cadmium mixture in comparison to either lead and zinc

or lead and copper mixtures in the rock-salt dopant layer for samples with the same

stoichiometry prepared under the same condition. Kuhberger and Gritzner [239] discussed the

influence of Zn doping on the physical and electrical properties of the TI-1223 phase for

samples with the composition (TI0.5Pb0.5) (Sr0.9Ba0.1)2 Ca2 (Cu1-xZnx) 3 O8+s (x=0,

0.01, 0.05 and0.1) Sr. –Ba-Ca-Cu-Zn containing precursor materials were prepared the

addition of Zn increased the content of the Tl-1212 phase, changed the microstructure,

decreased the transition temperature slightly and reduced the critical current density at 77K.

Li et al. [240] studied zinc oxide powder prepared by decomposition of zinc peroxide and

zinc nitrate show evidence of acceptor states from iodometric titrations. Chemical analysis

also shows the presence of nitrogen in the samples by nitrate decomposition. As zinc oxide

particles become small there is an increase in unit cell dimensions and a red shift of the

absorption edge. Ozawa et al. [241] synthesized for chemical vapor deposition, in which

vapors or metallic organic compounds are introduced and decomposed over a substrate to

form thin films, data on the volatility of the compounds are of essential importance as basic

data. Thermal analysis is a useful tool for observing volatility . Khan and Rahim et al. [242]

synthesized cadium doped Cu0.5 Tl0.5 Ba2Ca3Cu4-y cd y0 12-s (y=0, 0.25, 0.5, 0.75, 1.0)

samples and their superconducting properties are studied using X-ray diffraction (XRD),

resistively, ac-susceptibility and Fourier Transform Infrared (FTIR) absorption

measurements. The FTIR absorption measurements of these samples have shown hardening

of apical oxygen modes of type. Kasperczyk et al.[243] followed unusual properties of high

temperature superconductors of the YBa2CU3O7-y type and its modifications are not to

understand within the standard phonon-mediated mechanisms. Crystal field effects are also

discussed in connection with substitutions of copper with other transition metals. Boeck et

al.[244] showed samples with Bi 2-0.5 Sr 1.9Ca 1.05 (Cu 1-x Fex)2 O8+ (0≤ x ≤ 0.15) compositions

synthesized by a liquid mix process able to give single phase compounds. The EDX results

are more consistent with a Bi2Sr2CuO6-Bi2Sr2CaCu2O8 intergrowth metal in which Fe is

accommodated in the Bi2Sr2CuO6 microdomains than with the model of substitution in a

Bi2Sr2CaCu2O8 single phase. Jirsa et al. [245] carried out pinning homogeneity and the

content fluctuation of light rare earth ions in a (Nd0.33Eu0.38Gd0.28) Ba2Cu3Oy melt textured


44

(MT) pellet 16 mm in diameter, doped by 0.035 mol% ZnO. The strip-like structure observed

on the crystal surface was evidently of another origin than the lamellar substructure in the

MT samples and did not significantly contribute to vortex pinning. The secondary peak in

Jc(B) of the single crystal was quite strong, showing a well set point-like disorder. Tiginyanu

et al. [246] focused on the description of nanostructured metal oxides representing the most

common, diverse and richest class of materials in terms of electronic structure and structural,

chemical, and physical properties. These nanomaterials with controlled composition surface

terminations, and crystalline structures are important for future applications in novel devices.

Santoro et al. [247] discovered the layered structures of the known superconducting copper

oxides described in terms of alternating slices having the rock salt and perovskite structure.

Each slice is made up of a number of layers and each layer can be represented by specifying

its chemical composition and its atomic configuration. This layer by layer representation of

the crystal structures of oxide superconductors offers a convenient method for classifying and

comparing to one another these important materials, and for predicting new compounds

which may exhibit interesting electronic properties. Shirage et al. [248] developed a high

pressure (HP) technique to synthesize a series of newly-discovered iron (nickel)- based

superconductors. For the LnFeAsO-based superconductors (Ln = lanthanide). The effect of

O-deficiency, variation of Ln ions, and the external pressure on Tc are examined. Upper

critical field measurement on single crystalline sample of PrFeAsO1−y shows the

superconducting anisotropy of 5. Shein and coworkers [249] investigated based on first

principle FLAPW-GGA calculations, we have investigated structural and electronic

properties of the recently synthesized tetragonal (space group P4/nmm) nickel – based

pnictide oxide superconductors 3.3k (Ni2P2) (Sr4Sc2O6) and 2.7k (Ni2As2) (Sr4Sc2O6).

Optimized structural data, electronic bands, total the partial densities of states, and Fermi

surface topology have been obtained and discussed. Hsu and Gokcen [250] found that the

superconductivity transition temperature Tc of Bi2Sr2CaCu2O8 (designated as 2212)

decreased from 90 to 75 K at 4000C under 176 bar of oxygen pressure, P (O2). Above 5000C,

this cuprate dissociated to 2201 and other nonsupercondcuting oxides. The standard Gibbs

change for the dissolution of oxygen pas determined as G0 (J/mol of O) = 86,500-67.5 T (in

K) and compared pith G0 for other types of cuprate superconductors in phich Tc increases

pith P (O2). Doverspike et al. [251] reported the 1:2:4 yttrium barium copper oxide

superconductor prepared and sintered to high density by high pressure techniques. This

material is phase pure and shows a sharp transition temperature of 80 K. High temperature X-


45

ray powder diffraction of the 1:2:4 material shows a small anisotropy in thermal expansion.

The result in less microcracking in polycrystalline materials due to thermal expansion

anisotropy in devices based on 1:2:4. Watanabe et al. [252] examined rietveld analysis of the

powder X-ray diffraction of a new layered oxyarsenide, LaNiOAs, which was synthesized by

solid-state reactions, revealed that LaNiOAs which was synthesized by solid – state reactions,

revealed is compared of alternating stacks of La-O and Ni-As layers. The diamagnetic

susceptibility measured at 1.8K corresponded to 20% of perfect diamagnetic susceptibility,

substantiating that LaNiOAs is a bulk superconductor. Gyuov et al. [253] reviewed a small

calcium – substituted YBa2Cu4O8 (1-2-4) high temperature superconductor synthesized from

a precursor obtained by spray-drying of a nitrate solution containing the corresponding metals

in a stoichiometric ratio. The transition in Ca-substituted YBa2Cu4O8 occurs at a temperature

by about 8 K higher than Tc of the Ca-free phase. Raman spectra suggest that during the

substitution calcium doesnot occupy barium positions in the YBa2Cu4O8 lattice.Shoji et al.

[254] worked on position lifetime spectra measured on YBa2 (Cu1-x Mx)3 O7-y (M=-Fe, Ni) as

a function of temperature between 20K and room temperature. The positron lifetime and its

thermal behavior strongly depend on the iron concentration while are less affected with the

nickel substitution. Lynn et al. [255] produced a brief review on both the rare earth and Cu

magnetism in the Ba2Cu3O6+x, Ba2Cu4O8, (La-Sr)2 CuO4 and (Nd-Ce)2 CuO4 systems. The Cu

magnetism is dominated by the strong in plane exchange interactions. The rare earth ions, on

the other hand, order at low temperatures irrespective of the presence or absence of

superconductivity. Eickemeyer and coworkers [256] utilized cube textured substrate tapes

prepared by cold forming and annealing from nickel and microlloayed nickel in order to

manufacture long flexible superconductors of the YBCO (YBa2Cu3O7-) type . Perrin et al.

[257] characterized a systematic study of the influence of annealing under various

atmosphere (vacuum, nitrogen, oxygen and NF3), on the superconducting properties of the

Bi1, Sr1, Ca1 Cu2 Ox compositions. The 110 K Tc onset progressively decreases to about 90 K

as a function of annealing time and/or temperature when the samples are treated under

vacuum or under nitrogen gas, and increases again after further thermal treatments under

oxygen even at a temperature as a low as 1000C, reaching 110 K when annealed at 250-

3000C. In contrast, the 85 K transition is slightly modified under the same conditions.

Erdogan et al. [258] evaluated the present paper reports on a systematic study of the

influence of Zn alloying on the structural and optical characteristics of CuZnO thin films.

Nanocrystalline CuZnO thin films were prepared on p-type Si (1 0 0) substrates by spin

coating from a CuO solution mixed with Zn of 0.8.0 at %. When the Zn doping concentration


46

was above 4.0 at % the crystalline quality and preferential orientation of the thin film

weakened in turn. The XRD and FT-IR results showed single phase CuZnO for the lower (at

% ≤ 6.0) Zn Concentration. The works showed that the structural and optical properties of

CuO films doped with Zn can be improved and the 4.0 at % Zn-doped CuO thin films have

the best crystallization quality and the strongest emission ability. Nenartaviciene et al. [259]

checked superconducting YBa2 (CU1-xCrx)4O8 (x=0.01; 0.03; 0.05; 0.01; 0.20) oxides

synthesized by the aqueous sol-gel method. Effects of chromium substitutions on the

properties of compounds were studied by resistively measurements, X-ray powder

diffraction, infrared spectroscopy, electron microscopy and elemental analysis. The point

defect chemistry approach, which explains the change of Tc by substituting chromium for

copper in theYBa2Cu4O8 superconductor, is presented. Sagsoz et al. [260] analyzed in the

diffusion mechanism of iron impurities in bulk YBa2Cu3O7 (YBaCuO) superconductor

prepared by standart solid state reaction method and its effect on lattice structure under

different magnetic field have been examined. The effects of different magnetic field

intensities on crystal structure of iron diffused samples have been investigated by quantitative

Energy Dispersive X-Ray Fluorescence (EDXRF) and X-Ray Diffraction (XRD) techniques.

Katase et al. [261] discussed the epitaxial growth of Fe-based superconductors such as CO-

doped SrFe2As2 (SrFe2As2: Co) still has insufficient properties for a device application

because they have rough surfaces and are decomposed by reactions with water vapor in an

ambient atmosphere. These films also have atomically – flat surfaces with step-and – terrace

structures and exhibit chemical stability against exposure to water vapor. Hamada et al. [262]

found that the pressure of superconducting transition temperature (Tc ) FeSr2YCu2O8 samples

were synthesized by solid-state reaction with multiple annealing process. Ekino et al. [263]

synthesized tunnel break junction method adopted to study polycrystalline samples of iron

oxypnictide superconductor NdFeAs (O0.9 F0.1) with Tc=48K. Measurements were carried out

at 4.2K. Break –junction (BJ) conductance versus voltage curves showed gap-edge peaks

with the peak to peak distances at 4.2 K where the superconducting energy gap e>0 is the

elementary change. This ratio implies strong – coupling superconductivity in the framework

of Bardeen- Copper – Schrieffer theory, being, however, much, smaller than that for high Tc

copper oxides. Raj et al. [264] used the chemical reactivity between superconducting ceramic

materials (YBa2Cu3O7-x, Bi2Sr2CaCu2O8+x and Bi2SrCuO6+x) and the cathode material of solid

oxide fuel cells (La0.65Sr0.3MnO3) was investigated by long-term annealing experiments of

pressed powder mixtures lasting two weeks at 8500C. The formation of undesirable products,


47

especially SrCrO4, due to diffusion processes across the interface was confirmed by

investigations of metallographic cross-sections. Janaki and coworkers [265] followed

tetragonal iron selenide and telluride superconductors through solid state reaction at 4500C

and 5500C, respectively. These synthesis temperatures have been established by optimization.

The partial substitution of Se by Te leads to an enhancement of Tc to 13K. The non-

superconducting telluride Fe1.09Te exhibits a metal-insulator phase transition at 82K.

Substitution studies of this telluride system by S and Si have in addition been carried out to

investigate if chemical pressure induces superconductivity. Ren et al. [266] reported detailed

measurements of the temperature dependence of the lower critical field Hc1 of the FeAs –

based superconductor SmFeAsO0.9F0.1 (Sm-1111) andBa0.6 K0.4Fe2As2 (Bak-122) by global

and local magnetization measurements. Excellent fitting to the data can be reached with two

s-wave superconducting gaps. Comparison of the absolute values of Hc1(0) between Sm-1111

and Bak-122 shows a relatively large superfluid density for the latter.Jiao et al. [267] showed

the upper critical fields (Hc2) of the single crystals (Sr, Na) Fe2As2 and Ba0.55K0.45Fe2As2

determined by means of measuring the electrical resistivity, using the facilities of pulsed

magnetic field at Los Alamos such a difference mainly results from the multi-band effect,

which might be modified via doping. Mukuda et al. [268] carried out novel superconducting

characteristics and unusual normal state properties in iron based prictide superconductors by

mean of studies in REFeAsO1-y (RE=La, Pr, Nd) and Ba0.6 K0.4 57Fe NMR and 75AsN

NQR/NMR. Fe2As2 [269]. Katsuyamaet et al. [270] discovered the magnetic hysterisis loops

of YBa2Cu3Oy, Ln1+xBa2-xCu3Oy (Ln=Sm, Nd) and YBa2 (Cu 1-xFex)3 Oy systems measured

by a superconducting quantum interference device (SQUID), magnetometer, and the

relationship between the microscopic structure and effectiveness of pinning centres for the

flux lines.

1.2.5 Adsorbents:

Metal / Mixed metal oxides have wide application as Adsorbents. Some of them are

described here. Quan et al. [271] synthesized removal of Copper from aqueous solution

using iron-containing adsorbents derived from methane fermentation sludge. Iron-containing

adsorbents prepared from methane fermentation sludge (MFS) were characterized by N2

adsorption, XRD, SEM, EDX, pH determination and elemental analysis. The desorption

studies were also performed and the mechanisms of Cu(II) adsorption was proposed.the

results indicated that the adsorbent obtained at 7000C for 1 h in a steam atmosphere possessed

the highest capability for Cu (II) adsorption. The invisibility of copper adsorption on the iron

containing adsorbents is attributed to the formation of strong bonds between Cu (II) and the


48

iron (hydr) oxides. The adsorbent can be applied to remove copper from water or soil by

fixation onto the surface. Wang et al. [272] used removal of impurities from copper

electrolyte with adsorbent containing antimony. A new adsorbent was synthesized possesses

not only the properties of common adsorbents, but also special merits of its own. The paper

presents the results of adsorbent synthesis, characterization, regeneration, and metal ion

separation. The feasibility of utilizing this adsorbent for copper electrolyte purification has

been examined. Garces et al. [273] followed a new method for study of the adsorption

function of an adsorbent applied to the study of the adsorption, applied to the study of the

adsorption function of isopropyl alcohol on a zinc oxide catalyst 11.The sorbent’s sorption

capacity at breakthrough increased with the sulfidation temperature reaching 87% of the

theoretical value for desulphurization at 4000C. A deactivation model that considers the

activity of the solid reactant was used to fit the experimental data. Good agreement between

the experimental breakthrough curves and the model predictions was obtained. Stein Kolfe

[274] prepared characterization and studied properties of iron oxide coated zeolite as

adsorbent for removal of copper (II) from solution in fixed bed column. Thermodesorption

curves of isopropyl alcohol from a zinc oxide catalyst have been analyzed under the

assumption that the Langmuir isotherm for a heterogeneous surface is a valid model. From

visual inspection of the deosption curves five sets of adsorption sites were assumed. Asare

and Fuerstenav [275] discovered adsorption phenomena in hydrometallurgy, the uptake of

copper nickel and cobalt by oxide adosrbents in aqueous ammoruacal solutions. The uptake

or adsorption of copper, nickel and cobalt by finely divided oxide solids in aqueous

ammoniacal medium has been investigated experimentally in order to determine how

adsorption on leach residues can affect the recovery of leachable metals. Adsorption behavior

was found to have maxima and minima as a function of pH, the magnitude of which depends

on ammonia concentration, the metal cation, and the adsorbent.Osseo- Asare and D.W.

Fuerstenav [276] developed Adsorption phenomena in hydrometallurgy 3 Model for coprq,

nickel and cabalt uptake. The uptake of hydrolysable ions by oxide absorbents in aqueous

ammoniacal solutions has been interpreted in terms of a mechanism involving the

competitive adsorption of all the aqueous species. An adsorption model is presented which

combines double layer theory with properties of the substrate (pzc, dielectric constant), the

solvent medium (dielectric constant) and the aqueous ionic species (stability constants). Ning

et al. [277] investigate effect of zinc and cerium addition on property of Copper based

adsorbents for phosphine adsorption. A series of copper based activated carbon (AC)

adsorbents were prepared in order to investigate the effect of Zn, Ce addition on Cu-based


49

AC adsorbents for phosphine (PH3) adsorption removal from yellow phosphorous tail gas. N2

adsorption isotherm and X-ray diffraction (XRD) results suggested that the addition of Zn

could increase the adsorbent ultramicropores, decrease the adsorbent supermicropores and the

adsorbent average pore diameter. Therefore it enhanced the PH3 adsorption capacity.

Appropriate amount of Ce addition could promote the reducibility of copper oxide, increase

the thermal stability of adsorbent, and therefore enhance the PH3 adsorption capacity. The

present study indicated that the Cu-based adsorbents might be one of candidates for PH3

removal from yellow phosphorous tail gas. Bose et al. [278] found that critical evaluation of

treatment strategies involving adsorption and chelation for wastewater containing Copper,

Zinc and Cyanide industrial wastewater containing heavy metals and cyanide requires

treatment for removal of both metals and cyanide before disposal. Conventional methods for

treatment of such wastewater involve alkaline – chlorination for cyanide destruction,

followed for pH adjustment for metal precipitation, and subsequent removal of precipitate by

solid-liquid separation processes. The objective of the study described in this paper is to

critically evaluate treatment strategies involving some indigenous adsorbents and a low-cost

chelating agent for treatment of a simulated wastewater. The evaluation procedure involved

comparison of the performance of these treatment strategies with that of conventional

treatment. Cheng Pan et al. [279] reported reusing sewage sludge ash as adsorbent for copper

removal from wastewater. The sewage sludge ash (SSA) can potentially be used for removal

of heavy metals from wastewater due to its similar chemical composition to that of fly ash

and blast-furnace silage. The adsorption test of applying SSA into synthetic wastewater

revealed that the adsorption isotherm of SSA for copper ions generally followed the

Langmuir model. The primary mechanisms of copper removal by SSA included electrostatic

attraction, surface complex formation, and cation exchange. Arias et al. [280 ] examined

competitive adsorption and adsorption of copper and zinc in acid soils As an aid to evaluating

the environmental threat posed by Cu and Zn when both are present in acid soils competitive

and noncompetitive adsorption of Cu and Zn onto samples of the surface horizon of eight

such soils was measured in batch experiments carried out at pH 5 with 0.01 M NaNO3 as

background electrolyte. The Langmuir–Freundlich equation was not appropriate for these

data: it could not be fitted to the Zn data, and when fitted to the Cu data the uncertainty in the

values of its parameters was too large for them to be useful. Desorption of Cu into NaNO3

solution from previously Cu-loaded Soils in no case exceeded 11% of the Cu previously

adsorbed, whereas analogous desorption of Zn was in all cases greater and ranged from 9% to


50

32%.Wayne Tubrbeville and Nora Yap [281] reviews the chemistry of Copper containing

sulphur adsorbents in the presences of mere tans. A brief review of the chemistry of copper

and thiols is given and a contrast is made to the behavior of copper-containing adorbents used

for the desulfurization of liquid hydrocarbon streams that are routinely treated in refinery

processes. At a temperature of approximately 1500C very well formed lamellar crystals of

copper (I) thiolate are formed, which indicates that the copper migreates from the surface of

the catalyst to expose bulk copper for further reaction.Turan et al. [282] worked Adsorption

of copper and zinc tons. Determination of the optimal conditions by the statistical design of

experiments. In their study, a full factorial experimental design was utilized to access the

effect of three factors on the adsorption of copper (II) and zinc (II) ions are an aqueous

leachate of an industrial waste with little as adsorbent. The adsorption kinetics models, the

second order model best described the data. Illite was a reasonably effective adsorbent for

Cu2+ and Zn2+ from aqueous leachates of industrial waste. Xiaomin Li et al. [283] produced

Preparation and evaluation of orange peel cellulose adsorbents for effective removal of

cadmium, zinc, cobalt and nickel. The preparation of chemically modified orange peel

cellulose adsorbents and its biosorption behaviors of Co(II), Ni(II), Zn(II) and Cd(II) have

been studied. Effects of different chemical modifications on the adsorbent properties

including different alkalis saponification The maximum adsorption capacities of Ni(II),

Co(II), Zn(II) and Cd(II) for SPA, SPA, SCA and SOA were obtained as 1.28, 1.23, 1.21 and

1.13 mol/kg and have increased by 95, 178, 60 and 130% The Langmuir and Freundlich

adsorption isotherms models fitted the experimental data best with regression

coefficient R2 > 0.95 for all the metal ions. Elution efficiencies with different concentrations

of HCl were evaluated. Poly chronopoulou et al. [284] utilized novel Fe-Mn-Zn-Ti-O mixed

metal oxides for the low temperature removal of H2S from gas steams in the presence of H2,

CO2 and H2O. The efficiency of Fe–Mn–Zn–Ti–O mixed-metal oxides of varying

composition prepared by sol–gel methods toward removal of H2S from a gas mixture

containing 0.06 vol% H2S, 25 vol% H2, 7.5 vol% CO2, and 1–3 vol% H2O was studied in the

25–100 °C range. In particular, a three times greaer H2S uptake at 250C compared with that

on the commercial adsorbent was found. The work provides new fundamental knowledge that

could trigger further research efforts toward the development of alternative mixed metal

oxide not based on toxic. Qian et al. [285] characterized removal of copper from aqueous

solution using iron containing adsorbents derined from methane fermentation sludge. Iron-

containing adsorbents prepared from methane fermentation sludge (MFS) were characterized


51

by N2 adsorption, NRD, SEM, EDX, pH determination and elemental analysis. The results

indicated that the adsorbent obtained at 70000C for 1 h in a steam atmosphere possessed the

highest capability for Cu (II) adsorption. The Cu (II) adsorption onto the composite

adsorbents in via ion-exchange with H, Ca and K ions, surface precipitation and binding with

active sites on the surface of iron hydro oxides at various pH values. The adsorbents can be

applied to remove copper from water or soil by fixation onto the surface. Han et al. [286]

evaluated characterization and properties of iron oxide coated zeolute as adsorbent for

removal of copper (II) from solution in fixed bed column. A new composite adsorbent, iron,

oxide coated zeolite (IOCZ), was characterized and employed for the removal of Cu (II) from

aqueous solution using fixed bed column. The Thomas model was found suitable for the

description of break through curve at all experimental conditions, while Adams- Bohart

model was only for an initial part of dynamic behavior of the IOCZ column. The theoretical

breakthrough curve was compared with experimental breakthrough curve profile in the

dynamic process. Chen et al. [287] checked preparation and characterization of porus

granular ceramic containing dispersed aluminium and iron oxide as adsorbents for fluoride

removal from aqueous solution. Porous granular ceramic adsorbents containing dispersed

aluminum and iron oxides were synthesized by impregnating with salt solutions followed by

precipitation at 60000C. Characterization studies on the adsorbent by SEM, XRD, EDS, and

BET analysis were carried out to clarify the adsorption mechanism. The adsorbents were

sphere in shape, 2-3 mm in particle size, highly porous and showed specific surface area of

50.69 sq m/g. The experimental data were well explained with pseudo- second- order kinetic

model. Results from this study demonstrated potential utility of Al/Fe dispersed in porous

granular ceramics that could be developed into a viable technology for fluoride removal from

aqueous solution. Dellyanni et al.[288] analyzed modelling the sorption of metal ions from

aquous solution by iron based adsorbents. The possibility of using iron-based adsorbents (i.e.

akaganeite or goethite) to remove heavy metal ions from aqueous solutions was the aim of

the present review paper. Synthesized material was used in two forms, i.e. in fine powder of

nanocrystals and in the from of grains (as granular). Typical adsorption models were

discussed and the bed depth – service time equation has been applied to the sorption results in

order to model the column operation. Wang et al. [289] discussed micro wane – assisted

preparation of bamboo charcoal based iron – containing adosrbents for Cr (VI) removal.

Bamboo charcoal – based, iron containing adsorbents (Fe-BC) was developed by using

bamboo charcoal (BC) as a supporting medium for ferric iron that was impregnated by Fe2

(SO4)3 H2SO4 simultaneous treatment, followed by microwave heating. The results showed


52

that the BET specific surface area, total pore volume. The adsorption of Cr (VI) onto Fe-BC

was spontaneous and exothermic under the studied conditions. Column adsorption

experiment with Fe-BC showed that Cr (VI) could be removed to below 0.05 mg/L within

360 bed volumes at empty bed contact time 2 min when the groundwater containing

approximately 0.12 mg/L of Cr (VI) was treated. Tseng et al. [290] synthesized kinetics and

equilibrium of adsorption removal of copper from magnetic polymer adsorbent. This study

examined the desorption of copper ions, which were adsorbed on the magnetic polymer

adsorbent (MPA) of polyvinyl acetate- iminodiacetic acid (M-PVAC-IDA), by ethylenedian

intertraacetic acid (EDTA). Stage – wide desorptions were applied to remove the Cu(II) ions

from the Cu (II) adsorbed M-PVAC-IDA (A-M-PVAC-IDA). Two simple kinetic models, the

pseudo- first- order equation and pseudo- second – order equation, were employed to

stimulate the kinetic behaviors of adsorption and desorption. The adsorption capacities (qe)

estimated by the pseudo – first – order equation are more accurate in comparison with those

simulated by the pseudo – second – order equation. The values of qe after CADOs are

consistent with the predicted results via the previous work, evidencing that the adsorption

behavior and the characteristics of the regenerated adsorbent of altered. Yiaomin Li et al.

[291] prepared preparation and evaluation of orange peel cellulose adsorbents for effective

removed or cadmium zinc, cobalt and nickel. The preparation of chemically modified orange

peel cellulose adsorbents and its biosorption behaviors of Co (II), Ni(II), Zn (II) and Cd (II)

have been studied. Effects of different chemical modifications on the adsorbed properties

including different alkalis saponification (NaOH, NH4OH and Ca(OH)2) and different acids

(C6H6O.7H2O, H2C2O4, and H3PO4) modification after sponification with NaOH were

investigated. Effects of initial pH, initial metal ions concentrations, shaking time and solid/

liquid ratio on metal ions biosorption were also investigated. Biosorption equilibriums were

rapidly established in about 60 min and the adsorption kinetics model. It enhanced the PH3

adsorption capacity. Appropriate amount of Ce addition could promote the reducibility of

copper oxide, increase the thermal stability of adsorbent, and therefore enhance the PH3

adsorption capacity. Ning et al. [292] showed Effect of zinc and cerium addition on property

of copper based adsorbents for phorphine adsorption. A series of copper – based activated

carbon (AC) adsorbents were prepared in order to investigate the effect of Zn, Ce addition on

Cu-based AC adsorbents for phosphine (PH3) adsorption removal from yellow phosphorous

tail gas. N2 adsorption isotherm and X-ray diffraction (XRD) results suggested that the

addition of Zn could increase the adsorbents ultracropores, decrease the adsorbent

supermicropores and the adsorbents average pore diameter. S. Vellaichamy and K. Palanivelu

CHAPTER 1

[293] was carried out Preconcentration and separation of copper, nickel and zinc in aqueous

samples by flame atomic absorption spectrometry after column solid phase extraction on to

MWCNTS impregnated with D

been developed for the determination of copper, nickel and zinc ions in natural water

samples. This method is based on the adsorption of copper, nickel and zinc on multiwalled

carbon nanotubes (MWCNTs) impregnate

(D2EHPA) and tri-n-octyl phosphine oxide (TOPO). The developed method was applied for

the determination of copper, nickel and zinc in electroplating wastewater and real water

sample with satisfactory results (R.S.D

oxidation of carbon monoxide on non

Alumina-supported NiO catalysts, promoted with 0.14

impregnation and then calcined at 400,

surface and catalytic properties were investigated by using XRD technique, nitrogen

adsorption at −196 °C, and oxidation of CO by O

maximum increase in the catalytic reac

250 °C ( ) due to doping with 3 wt.% ZnO attained 78 and 217% for the catalysts

calcined at 400 and 600 °C for 4 h, respectively

study of adsorption properties of Turkish fly ashes 1. The case of nickel (ii), copper (ii) and

zinc (ii). The objective of this study was to compare two different Turkish fly ashes (Afsin

Elbistan and Seyitomer) for their ability to

[Zn(II)] from an aqueous solution. The effect of contact time, pH, initial metal concentration

and fly ash origin on the adsorption process at 20±2

ash as an adsorbent improved with increasing calcium (CaO) content. Adsorption data in the

range of pH values (3.0–8.0) using Ni(II) and Cu(II) concentrations of 25±2

concentration of 30±2 mg/l in solution were correlated using the linear forms of the Lang

and Freundlich equations. Han

adsorbents for removal of copper (II) from solution in fixed bed column. A new composite

adsorbent, iron oxide coated zeolite (IOCZ), was characterized and e

of Cu (II) from aqueous solution using fixed bed column. The effects of various experimental

conditions, such as the flow rate, initial metal concentration and bed depth, were studied. The

dynamics of the adsorption process were fit

model. The bed depth service time (BDST) model was applied to predict the service times

with other flow rate and initial concentration.

INTRODUCTION AND LITERATURE SURVEY

53

was carried out Preconcentration and separation of copper, nickel and zinc in aqueous


MWCNTS impregnated with D2EHPA- Topo mixture A solid phase extraction method has



carbon nanotubes (MWCNTs) impregnated with di-(2-ethyl hexyl phosphoric acid)

octyl phosphine oxide (TOPO). The developed method was applied for


sample with satisfactory results (R.S.D.'s <10%).Allah M. Deraz [294]

oxidation of carbon monoxide on non-doped and zinc oxide doped nickel alumina catalyst

supported NiO catalysts, promoted with 0.14–3 wt.% ZnO, were prepared by

impregnation and then calcined at 400, 600, and 800 °C for 4 and 40 h. The phase analysis,


°C, and oxidation of CO by O2 at 200–300 °C, respectively. The

maximum increase in the catalytic reaction rate constant per unit surface area measured at

) due to doping with 3 wt.% ZnO attained 78 and 217% for the catalysts

°C for 4 h, respectively.Beigin Bayat [295] discovered Comparative


zinc (ii). The objective of this study was to compare two different Turkish fly ashes (Afsin

Elbistan and Seyitomer) for their ability to remove nickel [Ni(II)], copper [Cu(II)] and zinc


and fly ash origin on the adsorption process at 20±2 °C were studied. The effectiveness of fly

ent improved with increasing calcium (CaO) content. Adsorption data in the

8.0) using Ni(II) and Cu(II) concentrations of 25±2

mg/l in solution were correlated using the linear forms of the Lang

Han et al. [296] studied properties of iron oxide coated zeolite as


adsorbent, iron oxide coated zeolite (IOCZ), was characterized and employed for the removal



dynamics of the adsorption process were fitted by Adams – Bohart model and Thomas


with other flow rate and initial concentration.Ariass et al. [297] investigate Competitive

INTRODUCTION AND LITERATURE SURVEY

was carried out Preconcentration and separation of copper, nickel and zinc in aqueous


A solid phase extraction method has



ethyl hexyl phosphoric acid)

octyl phosphine oxide (TOPO). The developed method was applied for


] studied Catalytic

doped and zinc oxide doped nickel alumina catalyst

3 wt.% ZnO, were prepared by

°C for 4 and 40 h. The phase analysis,


°C, respectively. The

tion rate constant per unit surface area measured at

) due to doping with 3 wt.% ZnO attained 78 and 217% for the catalysts

discovered Comparative


zinc (ii). The objective of this study was to compare two different Turkish fly ashes (Afsin-

remove nickel [Ni(II)], copper [Cu(II)] and zinc


°C were studied. The effectiveness of fly

ent improved with increasing calcium (CaO) content. Adsorption data in the

8.0) using Ni(II) and Cu(II) concentrations of 25±2 mg/l and Zn(II)

mg/l in solution were correlated using the linear forms of the Langmuir

properties of iron oxide coated zeolite as


mployed for the removal



Bohart model and Thomas


investigate Competitive


54

adsorption and disorption of copper and zinc in acid soils As an aid to evaluating the

environmental threat passed by Cu and Zn when both are present in acids soils, competitive

and noncompetitive adsorption of Cu and Zn onto samples of the surface horizon of eight

such soils was measured in batch experiments carried out at pH. These data were better fitted

by the Freundlich equation than by he Langmuir equation.Qian et al. [298] found that

Removal of Copper from aqueous solution using iron containing adosrbents derived from

methane fermentation sludge. Iron-containing adsorbents prepared from methane

fermentation sludge (MFS) were characterized by N2adsorption, XRD, SEM, EDX, pH

determination and elemental analysis. The results indicated that the adsorbent obtained at

700 °C for 1 h in a steam atmosphere possessed the highest capability for Cu(II) adsorption.

The high copper removal ability of the MFS-derived materials is attributed to their

intermediate surface area, strong surface basicity and the presence of iron (hydro) oxides on

their surface. The adsorbent can be applied to remove copper from water or soil by fixation

onto the surface. Characterization and properties of iron oxide coated zeolite as adsorbent

[299] for removal of copper (II) from solution in fixed bed column. A new composite

adsorbent, iron oxide coated zeolite (IOCZ), was characterized and employed for the removal

of Cu (II) from aqueous solution using fixed bed column the Thomas model was found

suitable for the description of breakthrough curve at all experimental conditions, while

Adams – Bohart model was only for an initial part of dynamic behavior of the IOCZ column.

The theoretical breakthrough curve was compared with experimental breakthrough curve

profile in the dynamic process. The saturated column was regenerated by 1 mol-1 hydrogen

chloride solution and IOCZ could be reused in Cu (II) removal. Han et al. [300] examined

reuse of waste silica as adsorbent for metal removal by iron oxide modification. Silica gel is

widely used in research laboratories, especially for the purification of organic compounds.

Consequently, waste silica gel is generated in increasing amounts. In the preparation of the

adsorbent, the optimal pretreatment temperature and iron concentration were investigated.

The coated waste silica was characterized for BET surface area, pore size, specific pore

volume and iron content. Iron oxide- coated waste silica was tested for the adsorption of

Pb(II), Cu((II) and Ni(II) from solutions in a batch system. The presence of salt reduced the

adsorption efficiency of the adsorbent. The adsorption behavior followed both Langmuir and

Freundlich isotherms (250C). Tseng et al. [301] reviewed kinetics and equilibrium of

disorder removal of copper from magnetic polymer adsorbent. Their study examined the

desorption of copper ions, which were adsorbed on the magnetic polymer adsorbent (MPA)

of polyvinyl acetate- iminodiacetic acid (M-PVAC, IDA), by ethylenediaminetetraacetic acid


55

(EDTA). Stage-wise desorptions were applied to remove the Cu (II) ions from the Cu(II)

adsorbed M-PVAC-IDA (A-M PVAC- IDA). Two simple kinetic models, the pseudo – first –

order equation and pseudo – second – order equation, were employed to simulate the kinetic

behaviors of adsorption and desorption. With respect to the kinetics of adsorption behavior,

the simulated results by both kinetic models exhibit good agreement with the experimental

data. The values of qe after CADOs are consistent with the predicted results via the previous

work, evidencing that the adsorption behavior and the characteristics of the regenerated

adsorbent of D-M-PVAC-IDA were not altered. In the experiments of desorbing copper ions.

Zhang et al. [302] worked Preparation and evaluation of a novel Fe-Mn binary oxide

adsorbent for effective arsenite removal. Arsenite As(III) is more toxic and more difficult to

remove from water than arsenate As(V)). As there is no simple treatment for the efficient

removal of As(III), an oxidation step is always necessary to achieve higher removal. The

adsorbent was characterized by BET surface areas measurement, powder XRD, SEM, and

XPS. The results showed that prepared Fe–Mn binary oxide with a high surface area was

amorphous. The results compare favorably with those obtained using other adsorbent. The

effects of anions such as humic acid (HA), which possibly exist in natural water, on As(III)

removal were also investigated. The high uptake capability of the Fe–Mn binary oxide makes

it potentially attractive adsorbent for the removal of As (III) from aqueous solution.

Mahmoud et al. [303] produced removal and preconcentrators of lead (II), Copper (II),

Chromium (III) and iron (III) from waste waters by surface developed alumina adsorbents

with immobilized 1-nitroso-2-naphthol. The potential removal and preconcentration of lead

(II), copper (II), chromium (III) and iron (III) from wastewaters were investigated and

explored. Three new alumina adsorbent of acidic, neutral and basic nature (I-III) were

synthesized via physical adsorption and surface loading of 1-nitroso-2-naphthol as a possible

chelating ion-exchanger. The outlined results from the distribution coefficient and separation

factor evaluations (low metal ion concentration levels) were found to denote to a different

selectivity order: Pb (II)> Cu (II) > Cr (III)) due to the strong contribution of alumina matrix

in the metal binding processes. Ren et al. [304] utilized Adsorptive removal of arsenic from

water by an iron – zirconium binary oxide adsorbent Arsenate and arsenite may exist

simultaneously in groundwater and have led to a greater risk to human health. In this study,

an iron-zirconium (Fe-Zr) binary oxide adsorbent for both arsenate and arsenite removal was

prepared by a coprecipitation method. The ionic strength effect experiment, measurement of

zeta potential, and FTIR study indicate that As(V) forms inner-sphere surface complexes,

while As(III) forms both inner- and outer-sphere surface complexes at the water/Fe-Zr binary


56

oxide interface. Han et al. [305] characterized characterization and properties of iron oxide

coated zeolite as adsorbent for removal of copper (II) from solution in fixed bed column. A

new composite adsorbent, iron oxide coated zeolite (IOCZ), was characterized and employed

for the removal of Cu(II) from aqueous solution using fixed bed column. The effects of

various experimental conditions, such as the flow rate, initial metal concentration and bed

depth, were studied. The dynamics of the adsorption process were fitted by Adams–Bohart

model and Thomas model. The theoretical breakthrough curve was compared with

experimental breakthrough curve profile in the dynamic process. The saturated column was

regenerated by 1 mol l−1hydrogen chloride solution and IOCZ could be reused in Cu(II)

removal. Chen et al. [306] evaluated Characterization of cartonated tricalcium silicate and its

sorption capacity for heavy metals: A miron scale composite adsorbent of active silicate gel

and calcite. Adsorption- based processes are widely used in the treatment of dilute metal –

bearing wastewaters. The development of versatile, low-cost adsorbents is the subject of

continuing interest. The effects of metal ion concentration, pH and contact time on binding

ability was investigated by kinetic and equilibrium adsorption isotherm studies. The

adsorption capacity for Pb (II), Cr (III), Zn (II) and Cu (II) was found to be 94.4 mg/g, 83.0

mg/g, 52.1 mg/g and 31.4 mg/g, respectively.Wayne Turbeville and Nora Yap checked [307]

the chemistry of copper containing sulphur adsorbents in the presence of mercaptans. A brief

review of the chemistry of copper and thiols is given and a contrast is made of the behavior of

copper – containing adsorbents used for the desulfurizatoin of liquid hydrocarbon streams

that are routinely treated in refinery processes. In addition, it is shown that bulk copper is

involved in the adsorption of mercaptans, as there is significantly more sulfur than there is

copper on the surface. Reaction mechanisms are proposed for the process of desulfurization

of liquid hydrocarbon streams containing mercaptans when using a copper – containing

adsorbent.Mahmoud et al. [308] analyzed the removal and preconcentration of Pb (II) from

drinking tap water and wastewater samples via applications of newly modified three alumina

physically loaded – dithizone adsorbents. Selective removal of Pb (II) from wastewater

samples was accomplished with percentage recovery values of 94-99 + 1-2%, while the

results collected from the selective preconcentration of Pb (II) from drinking tap water

proved excellent percentage recovery values of 96-99+2-3% and 94-95 + 2-4% for the two

studied concentration values 1.212 ng ml-1 and 4.800 g ml-1, respectively. Mei Sun et al.

[309] discussed characterization of adsorbent composition in co-removal of hexavalent

chromium with copper precipitation. Mechanisms of hexavalent chromium co-removal with

copper precipitation by dosing Na2CO3 were studied with a series of well-designed batch


57

tests using solutions containing 150 mg l-1 Cu (II) and 60 mg l-1 Cr (VI). solubility products,

neither copper-carbonate nor copper-hydroxide precipitates can be produced at pH around 5.0

for a pure 150 mg l-1 copper precipitation, characterization of copper-carbonate precipitates

(adsorbent) was carried out through developing pC-pH curves of the systems by both

equilibrium calculations and MINEQL+ 4.5 (a chemical equilibrium modeling software). Li

et al. [310] synthesized preparation of macroporous bead adsorbents based on poly (Vinyl

alcohol) Chitosan and their adsorption properties for heavy metals from aqueous solution. A

novel macroporous bead adsorbents based on poly(vinyl alcohol)/chitosan (PVA/CS beads)

were prepared, characterized and were used for the adsorption of heavy metal ions from

aqueous solution. The resulting PVA/CS beads were perfectly spherical in shape and

exhibited good mechanical strength and chemical stability. The presence of NaNO3 (0–

0.137 mol/L) had little effect on Cu2+ adsorption, but the adsorption of Pb2+, Zn2+ and

Cd2+ decreased significantly in the same conditions. Various thermodynamic parameters were

calculated and the results showed that the adsorption of all metal ions onto PVA/CS beads

was feasible and endothermic in nature. The results from the sequential adsorption–

desorption cycles showed that PVA/CS bead adsorbents held good desorption and reusability,

which would be a potential application in the fixed-bed continuous-flow column for the

removal of heavy metals.Wei et al. [311] used selective adsorption and separation of

Chromium (VI) on the magnetic iron – nickel oxide form waste nickel liquid. A new

composite adsorbent, iron oxide coated zeolite (IOCZ), was characterized and employed for

the removal of Cu (II) from aqueous solution using fixed bed column. Scanning electron

microscope (SEM), FTIR, X-ray diffraction spectrum (XRD) and BET analyses were used to

study the surface properties of the coated layer. The Thomas model was found suitable for the

description of breakthrough curve at all experimental conditions, while Adams- Bohart model

was only for an initial part of dynamic behavior of the IOCZ column. The theoretical

breakthrough curve profile in the dynamic process. The saturated column was regenerated by

1 mol -1 hydrogen chloride solution and IOCZ could be reused in Cu (II) removal. Deliyanni

et al. [312] studied modeling the sorption of metal ions from aqueous solution by iron based

adsorbents. The possibility of using iron-based adsorbents (i.e. akaganéite or goethite) to

remove heavy metal ions from aqueous solutions . The removal efficiency of the packed-bed

column was examined and compared.Typical adsorption models were discussed and the bed

depth-service time equation has been applied to the sorption results in order to model the

column operation.Dinesh. Mohan and Charies V. Pi Hman Jr. showed activated carbons and

low cost adsorbents for remediation of tri-and hexavalent chromium from water. Hexavalent


58

chromium is a well – known highly toxic metal, considered a priority pollutant. Industrial

sources of Cr (VI) include leather training, cooling tower blowdown, plating, electroplating,

anodizing baths, rinse waters, etc. The most common method applied for chromate control is

reduction of Cr (VI) to its trivalent from in sold (pH) and subsequent hydroxide precipitation

of Cr (III) by increasing the pH to 9.0-10-0 using lime.After an overview of chromium

contamination is provided, more than 300 papers on chromium remediation using adsorption

are discussed to provide recent information about the most widely used adsorbents applied

for chromium remediation. Wu et al. [313] carried out chromium removal by confining the

magnetic properties of iron oxide with adsorbents properties of carbon nanotubes. The

adsorption behaviors of lanthanum (III) from an aqueous chloride medium, using iron oxide

loaded calcium alginate beads were studied using equilibrium batch and column flow

techniques. The effect of pH, contents of loaded iron oxide, ionic strength, adsorbent dose,

contact time, and temperature on adsorption capacity of the magnetic beads was investigated.

The Langmuir adsorption isotherm models were used for the description of the adsorption

process. Furthermore, column breakthrough curves were obtained and the La (III) loaded

magnetic beads were regenerated using 0.05 mol/L CaCl2 solution. Gupta et al. [314] studied

lanthanum adsorption using iron oxide loaded calcium alginate beds .The adsorption features

of multiwall carbon nanotubes (MWCNTs) with the magnetic properties of iron oxides have

been combined in a composite to produce a magnetic adsorbent. Composites of

MWCNT/nano-iron oxide were prepared, and were characterized by X-ray diffraction

(XRD), field emission scanning electron microscope (FESEM) and Fourier transform

infrared spectroscopy (FTIR). The composites have demonstrated a superior adsorption

capability to that of activated carbon. The results also show that the adsorptions of Cr (III) on

the composites is strongly dependent on contact time. Streat et al. [315] discovered hydrous

ferric oxide as an adsorbent in water treatment. Freshly prepared granular ferric hydroxide

using both a freeze/thaw and ambient temperature synthesis route are compared with a

commercially available product for the adsorption of trace arsenic from water. The effect of

interfering anions is discussed in relation to the adsorption isotherms in the pH range 4–9.

Also, breakthrough curves are examined to show the effect of anionic interference in packed

column operation. Bayat et al.[316] developed Comparative study of adsorption properties of

Turkishesin fly ashes. The case of nickel (ii), copper (ii) and zinc (ii) The objective of this

study was to compare two different Turkish fly ashes (Afsin-Elbistan and Seyitomer) for their

ability to remove nickel [Ni(II)], copper [Cu(II)] and zinc [Zn(II)] from an aqueous solution.

The effectiveness of fly ash as an adsorbent improved with increasing calcium (CaO) content.


59

Adsorption data in the range of pH values (3.0-8.0) using Ni (II) and Cu(II) concentrations of

25+2 mg/l and Zn (II) concentration of 30+2 mg/l in solution were correlated using the linear

forms of the Langmuir and Freudlich equations. S. Vellaichamy and K. Palanivelu [317]

Investigated Preconcentration and separation of copper, nickel and zinc in aqueous samples

by flame atomic absorption spectrometry after column solid phase extraction onto MWCNTs

impregnated with D2EHPA- Topo mixture. A solid phase extraction method has been

developed for the determination of copper nickel and zinc ions in natural water samples. This

method is based on the adsorption of copper, nickel and zinc on multiwalled carbon

nanotubes (MWCNTs) impregnated with di(2-ethyl hexyl phosphoric acid) (D2EHPA) and

tri-n-octyl phosphine oxide (TOPO). The developed method was applied for the

determination of copper, nickel and zinc in electroplating wastewater and real water sample

with satisfactory results (R.S.D.’s <10%).Mahmoodi et al. [318] worked on magnetic ferrite

nanoparticle–alginate composite.Magnetic ferrite nanoparticle (nickle–zinc ferrite) (MFN)–

alginate composite was synthesized and characterized. Dye removal ability of MFN–alginate

from single and binary systems was studied. The effect of MFN–alginate dosage and pH on

dye removal was elucidated. The dye adsorption isotherm and kinetics were studied. It was

found that BB9, BB41 and BR18 followed the Tempkin, Langmuir, and Langmuir isotherms,

respectively. Wang et al. [319] studied adsorption capability for congo red on nanocrystalline

MFe2O4 (M = Mn, Fe, Co, Ni) spinel ferrites. It is the first time to give a comprehensive

comparison and analysis of the adsorption capacity of ferrite nanocrystals with spinel

structure for CR has been studied. Research indicates that the cations distribution of

MFe2O4 ferrites is the most important factor to decide their adsorption capacity. Electrostatic

absorption was conceived as the main adsorption mechanism.Meanwhile, the

MFe2O4 nanoparticles exhibited a clearly ferromagnetic behavior under applied magnetic

field, which allowed their high-efficient magnetic separation from wastewater. Aziz et al.

[320] enhanced magnetic separation and photocatalytic activity of nitrogen doped titania

photocatalyst supported on strontium ferrite. The synthesized catalysts were further

characterized with X-ray diffraction (XRD), transmission electron microscope (TEM), energy

dispersive X-ray spectroscopy (EDS), BET surface area analysis, vibrating sample

magnetometer (VSM), X-ray photon spectroscopy (XPS) and visible light spectroscopy

analysis for their respective properties. It also resulted in reduced band gap (2.8 eV) and

better visible light absorption between 400 and 800 nm compared to N-doped TiO2. The

photocatalytic activity was investigated with a recalcitrant phenolic compound namely 2,4-

dichlorophenol (2,4-DCP) as a model pollutant under direct bright and diffuse sunlight


60

exposure. A complete degradation of 2, 4-DCP was achieved with an initial concentration of

50 mg/L for both photocatalysts in 180 min and 270 min respectively under bright sunlight.

Similarly the diffuse sunlight study resulted in complete degradation for supported N–

TiO2 and >85% degradation N–TiO2, respectively.Safarik [321] Magnetically modified

microbial cells is a new type of magnetic adsorbents.Microbial cells, either in free or

immobilized form, can be used for the preconcentration or removal of metal ions, organic and

inorganic xenobiotics or biologically active compounds. Magnetic modification of these cells

enables to prepare magnetic adsorbents that can be easily manipulated in difficult-to-handle

samples, such as suspensions, in the presence of external magnetic field.

1.2.6 Ceramics:

Metal / Mixed metal oxides have wide application as Ceramics some of them are described

here. Hamid et al. [322] synthesized copper – cobalt heterofimetallic ceramic oxide this film

deposition. Thin films of halide free Cu–Co mixed metal oxide have been prepared at 390 °C

from the heterobimetallic complex Co4(THF)4(TFA)8(µ-OH)2Cu2(dmae)2 · 0.5C7H8 (1)

[dmae = N,N-dimethylaminoethanol(CH3)2NCH2CH2O−), TFA = triflouroacetate (CF3COO−),

THF = tetrahydrofurane (C4H8O)] which was prepared by the reaction of [Cu(dmae)Cl]4 and

Co(TFA)2 · 4H2O. Pasaribu et al. [323] used friction reduction by adding copper oxide into

alumina and zirconia ceramics. The friction and wear of alumina and zirconia ceramics doped

with various weight percentages (0.5, 1 and 5 wt. %) of CuO was studied. Dry sliding tests by

using a pin-on-disc tribotester were conducted on these materials against commercially

available Al2O3, ZrO2, SiC, and Si3N4 ceramic balls. The coefficient of friction of CuO doped

in alumina sliding against Al2O3 balls reduces from 0.7 to 0.4 and hardly depends on the

normal load and the velocity. These smooth patchy layers, which carry the normal load, are

responsible in reducing the coefficient of friction. Whatmore et al. [324] prepared high Tc

yttrium barium copper oxide ceramics and thin films. Yttrium barium copper oxide ceramics

with transition temperatures of up to 98K and small transition widths have been produced by

conventional mixed oxide and solution routes. The compositions of these films are discussed

as a function of sputtering conditions. Low temperature sintering and microwave dielectric

properties of 0.5 LaAlO 3-0.5 SrTiO3 ceramics using copper oxide additions [325]. The

microwave dielectric properties and the microstructures of 0.5LaAlO3–0.5SrTiO3 ceramics

with CuO addition prepared with conventional solid-state route have been investigated. The

dielectric constant as well as the Q×f value decreases with increasing CuO content. At

1460 °C, 0.5LaAlO3–0.5SrTiO3 ceramics with 0.25 wt.% CuO addition possess a dielectric

constant (εr) of 35.2, a Q×f value of 24 000 (at 8 GHz) and a temperature coefficient of


61

resonant frequency (τf) of −13.5 ppm/°C. Alkoy and Papila [326] showed microstructural

features and electrical properties of copper oxide added potassium sodium niobate ceramics

efects of 0.5, 1.0 and 1.5 mole% CuO addition on the properties of potassium sodium niobate

(K0.5Na0.5)NbO3-KNN ceramics were investigated. Pure KNN and CuO added KNN pellet

samples were sintered at 1100 and 10900C for 4th, respectively. Curie temperature has shifted

from 480 to 4350C with increasing CuO ratio. Shahid et al. [327] was carried out copper

cobalt oxide ceramic thin films from single source precursors two heterobimetallic

coordination complexes [Co(acac) Cu2 (bdmap)2 Cl3].C7H8 (1) and [Co(acac)Cu2(bdmap)2

synthesized by simple chemical technique and characterized by their melting points. The

scanning electron microscopy of copper – cobalt oxide films grown from both the precursors

describe highly compact and smooth morphology with homogenously dispersed spherical

particles with excellent adhesion properties to the substrates. Huang et al. [328] studied

dielectric properties of copper oxide doped 0.95 Ba(Zn1/3 Ta2/3)- 0.05 BaZa03 ceramics at

microwave frequency. The microwave dielectric properties of conventional solid state route

prepared 0.95Ba (Zn1/3Ta2/3)O3-0.05BaZrO3 ceramics with CuO addition have been

investigated. Ordering structure was not observed at sintering temperatures 1280-14300C.

Copper oxide, as a sintering aid, was found to effectively lower the sinering temperature of

0.95 Ba (Zn1/3Ta2/3)O3-0.05BaZrO3 ceramics. For application of high selective microwave

ceramic resonator and filter, 0.95Ba (Zn1/3Ta2/3)O3-0.05BaZrO3 is proposed as a suitable

material candidate. Pasaribu et al. [329] discovered environmental effects on friction and

wear of dry slidig zirconia and alumina ceramics doped with copper oxide. The influence of

the addition of copper oxide on the friction and wear characteristics of dry sliding zirconia

and alumina at various humidities and elevated temperatures is outlined in this article. At

various humidities, it is found that the addition of CuO give a significant contribution in

reducing the coefficient of friction of dry sliding zirconia against alumina. Hodkin [330]

developed the wetting of irridated ceramics by liquid metals to provide guidance about the

possible differences between the surface energy, SV of used and unused uranium dioxide

fuel. The invariant contact angles measured for copper drops at 11000C in argon, resting on

UO2 fuel samples with burn-up levels of up to 1.2% suggests that little change in SV had

occurred during irridation 10. Ezhilvalanvan et al. [331] studied the effect of antimony oxide

stoichiometry on the nonlinerity of zinc oxide var star ceramics. The effect of antimony oxide

at higher concentration (>2 mol%) and variable valence states of Sb on the nonlinearity of

ZnO varistor ceramics has been investigated. Simplified compositions containing

92.5ZnO+3Bi2O3+ 2.5Co3O4

+ 2Sb2O5 (mol%) show nonlinearity coefficient (α) upto 65.


62

Ceramic formulations derived from Sb2O5 bring about higher α than those with Sb2O3 or

Sb2O4, provided the concentration of Sb2O5 is ≥ 2 mol. The method of formulation of the

ceramics by way of higher oxygen content of the additives is critical in attaining high

nonlinearity. This can be explained on the basis of formation of the depletion layer at the

profiteering stage itself, because of the surface states arising out of the chemisorbed oxygen

form the incipient liquid phase. Bachili et al. [332] reported rare-earth doped poly crystalline

zinc oxide electroluminescent ceramics. Trivalent rare earth ions (Eu3+, Tm3+, Er3+) doped

zinc oxide ceramics have been prepared. They were found to be luminescent when submitted

to electric fields and the luminescence spectra are those of the trivalent rare earth ions.

Compared to varistors which have the same structure (a polycrystalline semi conducting zinc

oxide pellet sandwiched between two metallic solders). The variation of the luminescence

intensity with the applied voltage allows an estimation of the size of the zinc oxide grains

which has been compared to that measured from the scanning electron micrographs.

lvanchenko et al. [333] examined desorption thermal degradation model of zinc oxide

ceramics. The deosrption degradation model of nonlinear zinc oxide ceramics with

intercrystalline potential barriers is developed. It allows to connect the decreasing of surface

electronic states concentration with desorption of oxygen at heating up of the grain boundary

by electrical current in process of degradation. Masai et al. [334] reviewed precipitation of

ZnO in Al2O3 – doped zinc borate glass ceramics. Crystallization behavior of the oxide

semiconductor ZnO in zinc borate glass was investigated. The precipitated crystalline phase

of glass ceramics containing a small amount of Al2O3 was α-Zn3B2O6 whereas that of the

glass ceramics containing a large amount of was ZnO. The present results suggest that

crystallization of ZnO from multi component glass is dominated by the local coordination

state of the mother glass. Sharma et al. [335] worked on preparation and study of magnetic

properties of silico phosphate glass and glass – ceramics having iron and zinc oxide. The

magnetic properties of 25SiO2.50CaO.15P2O5-(10-x) Fe2O3-xZnO (where x=0, 2, 5 mol%)

glass and glass – ceramics have been studied. The glasses are prepared by melt quench

technique and heat treated at 8000C for 6h. electron spectroscopy for chemical analysis

(ESCA) revealed that the fraction of non-bridging oxygen decreases with the increase in zinc

oxide content. Effect of controlled heat treatment on magnetic properties was studied by

means of a Superconducting Quantum Interference Device (SQUID) magnetometer.

Mossbauer Spectroscopy at room temperature was also carried out to determined the state of

iron ions in glasses and glass-ceramics. Isomer shift values of the glasses suggest that Fe3+


63

and Fe2+ are in tetrahedral coordination. Hirota et al. [336] produced zinc oxide ceramics

with a sustainable antibacterial activity under dark conditions. Fabrication of ZnO ceramics

with a sustainable antibacterial activity even in the dark has been conducted. Fine ZnO

powders were hydrothermally treated in 0.5-3 mol ml-1 Zn(NO3)2 aqueous solutions at 110-

1800C for 3-20h. After an uniaxial pressing of the ZnO powders thus prepared, they were

sintered at 400-6000C for 1 h in air. ESR and chemical photoluminescence analyses have

cleared that radical oxygen of super oxide (O2) originated from the surface of ZnO might

exhibit an antibacterial activity even under the dark condition. Nahm [337] utilized

microstructure and electrical properties of T6-doped zinc oxide based ceramics. The

microstructure and electrical properties of Zn-Pr-Co-Cr-Tb oxide based ceramics were

investigated for different Tb4O7 amounts. The increase of Tb4O7 amount led to more

densified ceramics, increasing from 5.73 to 5.85 g/cm3 in sintered density. Carek et.al. [ 338]

find out BaBiO2.77 as a promoter of the varistor property in zinc oxide ceramics. Metal oxide

varistors typically are made by bulk ceramic technology. The homogeneity of ceramics and

the grain interface profile are of primary concern in varistor design and processing. The

nonohmic property in the ZnO varistor is attributed to the Bi enrichment at ZnO grain

boundaries and Bi-rich intergranular layer. The Bi phase distribution in the ceramics is

homogenous. Also, the volume of not contributing with break-down voltage intergranular

phase is restrained. Kutty and Ezhilvalavan characterized [339] zinc oxide ceramic varistors

formulated with barium orthosilicate for operation in the 3-15 V battery range. Varistors

working in the 3-15 V battery voltage range can be obtained from ZnO ceramics formulated

with Ba2SiO4 as the extra aditive. The presence of a large surface state density and a

changing pattern of trap states at the grain boundary interfaces are more significant than large

grani size in attaining lower breakdown voltages. Demidenko et al. [340] evaluated

Scintillation properties of ceramics based on zinc oxide. Ceramic tight- ultrafilitration (UF)

membrances were coated with iron oxide layers to investigate the removals of phenol and/or

natural organic matter (NOM) from waters. The effects of iron oxide coating on NOM

rejections were dependent on NOM characteristics in waters aluminum oxide or iron oxide

surfaces of the ceramic membrances were not affected by each other. Compared with the

uncoated membrane, membrane coating did not change membrane permeability. Coated iron

oxides were stable and iron leaking was not observed. Coating tight UF ceramic membranes

with iron oxide layers may improve NOM rejections. Sabbatini et al. [341] analyzed

fabrication and characterization of iron oxide ceramic membranes for arsenic removal.

Nanoscale iron oxide particles were synthesized and deposited on porous alumina tubes to


64

develop tubular ceramic adsorbers for the removal of arsenic, which is an extremely toxic

contaminant even in very low concentrations. Its natural presence affects rural and low

income populations in developing countries in Latin America and around the world Arsenic

concentrations were determined by inductively coupled plasma – optical emission

spectroscopy (ICP-OES). Due to its low cost and simple operation the system can be applied

as a point of use device for the treatment or arsenic contaminated ground waters in

developing countries. Shama and Dixit discussed [342] a comparison of dry and air-coled

turning of grey cast iron with mixed oxide ceramic tool. They compare the performance of a

mixed oxide ceramic tool in dry and air cooled turning of grey cast iron. First, the study was

done in the range of process parameters where dry turning provided satisfactory performance.

The contours of surface roughness and tool life were generated with the help of trained neural

networks. It was observed that air-cooling significantly reduces the tool wear at high cutting

speed. At higher cutting speeds, where the dry turning performs very poorly, the air cooled

turning provides an improed surface finish also apart from the reduction in tool wear.

Zaspalis et al. [343] synthesized arsenic removal from contaminated water by iron- oxide

sorbents and porous ceramic membranes. An adsorption – filtration process using porous

ceramic membranes is proposed for the purification of water from arsenic As (V) ions. Iron

oxide in nano particle and micro particle form is used as adsorbent in combination with

ultrafiltration and micro filtration asymmetric multilayer ceramic membranes, respectively.

The subsequent ultra filtration process shows complete nano particle rejection producing

therefore purified water with arsenic content lower. Bantsis et al. [344] used synthesis of

porous iron oxide ceramics using Greek wooden templates and mill scale waste for EMI

applications. The scope of this study is the synthesis of low cost iron oxideceramics with the

porous structure for light weight Electro magnetic interference (EMI) shielding applications,

using mill scale waste as the initial material, utilizing Greek wood templates. Also

demonstrated that the structures of the iron oxide were hierarchically porous developed

according to the wood templates. Moreover, the pore shape and size distribution showed a

dependence on the cancilation temperature and wood template. Specifically, the temperature

increase from 10000C to 12000C created larger but less pores in µm scale. Finally these low

cost iron oxideceramics exhibited electrical (mainly) and magnetic properties suitable for

electro magnetic shielding applications. Sharma et al. [345] followed preparation and study

of magnetic properties of silico phosphate glass and glass – ceramics having iron and zinc

oxide. The magnetic properties of 25SiO2.50CaO.15P2O5.(10-x) Fe2O3-xZnO (where x=0, 2,


65

5 mol%) glass and glass – ceramics have been studied. These glasses are prepared by melt

quench technique and heat treated at 8000C for 6 h. Electron spectroscopy for chemical

Analysis (ESCA) revealed that the fraction of non-bridging oxygen decreases with the

increase in zinc oxide content. The micro structure as seen by scanning electron microscopy

(SEM) exhibits formation of nano size particles. The analysis of the glass without ZnO shows

about 58 wt% of total iron ions is in the Fe3+ state. Chen et al. [346] prepared and studied

magnetic properties of silico phosphate glass and glass ceramics having iron and zinc oxide.

Porous granular ceramic adsorbents containing dispersed aluminum and iron oxides were

synthesized by impregnating with salt solutions followed by precipitation at 6000C,

Characterization studies on the adsorbent by SEM, XRD, EDS and BET analysis were carried

out to clarify the adsorption mechanism. The experimental data were well explained with

pseudo – second- order kinetic model. Results from this study demonstrated potential utility

of Al/Fe dispersed in porous granular ceramics that could be developed into a viable

technology for fluoride removal from aqueous solution. Sharma et al. [347] showed effect of

ZnO on phase emergence, microstructure and surface modifications of calcium

phosphosticated glass/ glass ceramics having iron oxide. The effect of ZnO on phase

emergence and micro structure properties of glass and glass – ceramics with composition –

25SiO2.50CaO.15P2O5. (10-x) Fe2O3-xZnO (where x = 0, 2, 5, 7 mol%) has been studied.

Surface modifications of glass – ceramics in simulated body fluid have been studied using

Fourier transform infrared reflection spectroscopy (FTIR), XPS and SEM. The microstructure

of the glass – ceramics heat treated at 8000C exhibits the formation of nano-size (50-60mm)

grains. On heat treatment at 10000C crystallites grow to above 50 mm size and more than one

phase are observed in the microstructure.Vilarinho and Baptista [348 ] studied out effect of

excess of iron oxide and lead oxide on the microstructure and dielectric properties of lead

iron tungstate ceramics. Lead – iron tungstate Pb (Fe2/3W1/3)O3; PFW) perovskite ceramics

were prepared by the conventional mixed oxides method. Additional amounts of Fe2O3 and

PbO were used to examine the role of excess oxides on the phase development, densification

behavior and dielectric properties. The densification behavior and the microstructures

obtained after firing were very dependent on the starting stoichiometry. Thomas et al. [349 ]

studied advanced ceramic interconnect material for solid oxide fuel cells: Electrical and

thermal properties of calcium and nickel Yttrium chromites. For more than 30 years

aluminium oxide (Al2O3) ceramics have been used for implants in maxillofacial and

orthopeadic surgery. Up to now there are no reports and also no investigations on

hypersensitivity reactions by additional presence/ absence of Al2O3 disk as well as the


66

proliferative response of PBMC of non- allergic individuals. Yoon et al. [350] discovered

Micronoar determination of sulfur oxoanions and sulfide at a renewable sol-gel carbon

ceramic electrode modified with nickel powder. The structural, thermal and electrical

characteristics of calcium- and nickel doped yttrium chromites were studied for potential use

as the interconnect material in high temperature solid oxide fuel cells (SOFCs) and other high

temperature electrochemical and thermoelectric devices. Nickel doping remarkably enhanced

sintering behavior of otherwise refractory chromites, and densities 94% of theoretical density

were obtained after sintering at 14000C in air with 15 at%. Ni. Undesirable oxygen ion

“leakage” current was insignificant in dual atmosphere conditions. No interfacial interactions

with YSZ were detected after firing at 14000C. Salimi et al. [351] developed preparation

conditions of pure and stoichiometric NiX Fe3-x O4 d bulk ceramics The sol-gel technique was

used to fabricate nickel powder carbon composite electrode (CCE). The nickel powder

successfully used to deposit NiOx thin film on conductive carbon ceramic electrode for large

surface area catalytic application. The hydrodynamic amperometry at rotation modified CCE

at constant potential versus reference electrode was used for detection of sulfur derivatives.

Less expense, simplicity of preparation, good chemical and mechanical stability, and

especially good surface renew ability by simple mechanical polishing and repetitive potential

cycling. Corso et al. [352] investigated NixFe3-xO4 (0<x<1) phases are spinels which are

difficult to obtain under pure, dense and conductive ceramics forms. Treatment under inert

atmosphere leads to a biphasic system of spinel and NiO monoxide. At first, a treatment

under air is carried out to synthesize dense and pure spinel ceramics. This treatment is

followed by an annealing under inert atmosphere to reduce a part of Fe3+ and to form

stiochiometric ferrites with semiconducting properties. Chen et.al. [353] found that Leaching

behavior of nickel from waste multi layer ceramic capacitor. The leaching behavior of nickel

present in waste multi layer ceramic capacitors (MLCC) was studied using different acidic

leaching regents in a stirred batch reactor. The fraction of Ni leached was found to be 97%

for a pulp density of 5 g/L and temperature 900C in an agitation time of 90 min. The leaching

rate of nickel was limited by the diffusion of HNO3 solution throughout thin channels that

were formed between BaTiO3 layers during the leaching of nickel. Sharma and Dixit [354]

compress the performance of a mixed oxide ceramic tool in dry and air – cooled turning of

grey cast iron. First, the study was done in the range of process parameters where dry turning

provided satisfactory performance. The study was extended to the range in which dry turning

performed poorly in terms of tool life. Tool wear, surface roughness of the machined job and

forces and vibration during the cutting were studied. At higher cutting speeds, where the dry


67

performs very poorly the air-cooled turning provides an improved surface finish also apart

from the reduction in tool wear.Ezugrwu and Tang [355] find out Surface abuse when

machining cast iron (G-17) and nickel base superalloy (in conel 718) with ceramic tools.

Single- point continuous – turning tests were carried out on a G-17 cast iron and a nickel

base, Inconel 718, study using round and rhomboid – shape pure oxide (Al2O3+ZrO2) and

mixed oxide (AleO3+TiC) ceramic tools to study the extent of damage on the machined

surfaces under optimum cutting conditions. Hardness, values of the outer layer of the

machine surfaces (upto 0.20 mm deep) show that the cutting conditions chosen produced

significant variation and values well above the average hardness of the work materials

because of the high rate of work hardening, increased compressive stresses and plastic

deformation, particularly for the nickel base, Inconel 718, alloy. Jain et al. [356] reviewed

effect of the A/B ration on the microstructures and electrical properties of (Ba0.95 + Ca0.05)

(Ti0.8) for multilayer ceramics capacitors with Nickel electrodes. The microstructures and

electrical properties of the pervoskite – type oxides with various A/B ratios were studied

using X-ray diffraction (XRD) and transmission electron microscopy (TEM) with an energy

dispersive X-ray spectrometer (EDS). The oxides electrical performances in multilayer

ceramic capacitors (MLCCs) with nickel electrodes were closely related to the A/B ratio of

the powder. It was found that with decreasing A/B ratio, the maximum permittivity was

increased due to a larger grain size, and the Curie point shifted to a higher temperature.

Zhang et al. [357] worked on the electrical failure behaviors and mechanism of current

limiting BaTiO3-based positive – temperature coefficient (PTC) ceramic, thermistors coated

with electroless nickel – phosphorous electrode. The failure behaviors, by the action of

electric field, of commercial BaTiO3-based positive temperature coefficient (PTC) current –

limiting ceramic thermisistors coated with electroless Ni electrodes were investigated. In

addition, the shock characteristics of BaTiO3-based PTCR ceramic were related to the content

of phosphorus in the electroless nickel – phosphorus content, 4 wt% in the alloy. Gao et al.

[358] studied electrical properties of copper – nickel ceramic magnetic desired from mixed

oxalate. Cu0.3Ni0.66Mn2.04O4 negative temperature coefficient (NTC) ceramic was prepared

using mixed oxalate – derived oxide powder. The mixed oxalate was synthesized by milling a

mixture of copper acetate, nickel acetate, manganese acetate and oxalic acid at room

temperature. The difference in the electrical property of the as- prepared ceramic is attributed

to the fine – grained microstructure and the lower sintering temperature used in the present

study. Azam et al. [359] utilized study of electrical properties of nickel doped SnO2 ceramic

nanoparticles. Nickel doped tin oxide (Sn1-xNixO2, where x= 0, 05, 0.05 and 0.09) nano


68

particles with sub- 5 nm size were synthesized using sol-gel method. The structural and

compositional analyses were carried out using XRD, FESEM and EDAX. The particle size

was observed to vary from 5 nm to 2 nm as the nickel content was increased. Complex

impedance analysis which was used to separate the grain and grain boundary contributions to

the system suggests the dominance of grain boundary resistance in the doped samples.

Bulasara et al. [360] characterize performance characteristics of hydrothermal and sonication

assisted electroless plating baths for nickel ceramic composite membrane fabrication. This

paper addresses the performance characteristics of nickel – ceramic composite membranes

fabricated with hydro thermal mass transfer coupled elcetroless plating baths. Parametric

investigations were carried out for wide range of initial nickel sulfate concentration (0.04 –

0.16 mol/L) in the solution at a higher loading ratio (393cm2/L). The microfiltration study on

oil – in – water emulsions inferred that the membrane fabricated with HTSO coupling and

Ci=0.04 mol/L gave a rejection of 90.13% and membrane permeability of 0.11 x 10-10 m3.m-

2s-1Pa-1. Salimi et al. [361] check amperometric detection of insulin at renewable sol gel

desired carbon ceramic electrode modified with nickel powder and potassium octa

cyanomoloybdativ (IV). A renewable three- dimensional chemically modified carbon ceramic

electrode (CCE) containing nickel powder and K4[Mo(CN)8] was constructed by sol-gel

technique. The electro chemical properties and stability of modified electrode was evaluated

by cyclic voltammetry in pH range 4-10. The apparent electron transfer rate constant (Ks) and

transfer coefficient (α) were determined by cyclic voltammetry and they were about 17.1 and

0.57 s-1, respectively. The catalytic activity of the modified CCE toward insuling oxidation

was investigated at pH range of 3-8 by cyclic votammetry. Flow injection amperometric

determination of insulin at pH 7.4, at this modified electrode yielded a sensitivity 8.1 nA/ nM

and detection limit 40 pM (based on S/N = 3). Jiang et al. [362] discussed Enhancement of

the analytical properties and catalytic activity of a nickel hexacaynoferrate modified carbon

ceramic electrode prepared by two step sol –gel technique. Because of the high economic,

environment, and safety costs associated with pure oxygen as a process feedstock, oxygen –

conducting ceramic membranes have been explored as an alternative oxygen source for

hydrocarbon conversion reactors. The materials of interest for membrane reactor applications

are mixed ionic – electronic conducting (MIEC) ceramic materials that conduct electrons as

well as oxygen ions. This describes general attributes of oxygen – MIEC membrances,

followed by an overview of published work with oxygen – MIEC ceramic membranes.

Specific topics include membrane composition, membrane modification strategies, and


69

application of oxygen – MIEC membranes for synthesis gas production. Goswami et al. [363]

find out crystallization behavior of Li2O-ZnO-SiO2 glass ceramics system.They studied the

crystallization behavior in two types of lithium zinc silicate (LZS) glasses: (a) LZSL

composition (wt%) Li2O, 12.65; ZnO, 1.85; SiO2, 74.4; Al2O3 3.; K2O, 2.95;P2O5, 3.15;

B2O3, 1.2 (low ZnO); and (b) LZSH composition (wt%); Li2O, 8.9; ZnO, 24.03; SiO2, 53.7;

Na2O, 5.42; P2O5, 2.95; B2O3, 5 (high ZnO carried). Significant differences in the formation

of crystalline phases and their relative ratios were observed between heating and cooling

schedules. For LZSL, formation of Li2SiO3 phase along with small fraction of cristobalite

phase was seen when CS was followed. However, in the case of LZSH, formation of lithium

zinc silicate as major crystalline phase along with cristobalite phase is seen when HS was

followed. For LZSI, the average thermal expansion coefficient (TEC) values were found to

be around 178 x 10-7 and 114 x 10-70C-1, for CS and HS, respectively.Baruzzo et al. [364]

synthesizes possible production of ceramic tiles from marine dredging spoils alone and mixed

with other waste materials. Dredging spoils, due to their composition could be considered a

new potential source for the production of monolithic ceramics. Nevertheless, abundance of

coloured oxides in these materials preclude the possibility of obtaining white products, but

not that of producing ceramics with a good mechanical behavior. As goal of the present

research we have produced and studied samples using not only dredging spoils alone, but also

mixtures with other waste materials such as bottom ashes from an incinerator of municipal

solid waste water absorption, density, strength, hardness, fracture toughness, thermal

expansion coefficient of the fired bodies were measured; XRD and SEM images were also

examined. The fired samples were finally tested in acidic environment in order to evaluate

their elution behavior and consequently their environmental compatibility. Hiramatsu et al.

[365] used Layered mixed anion compounds; Epitaxial growth, active function exploration,

and device application. Optoelectronic properties and device applications of layered mixed –

anion compounds such as oxychalcogenide LaCuOCh (Ch=chalcogen) and oxyupincitde

LaTMOPn (TM=3rd transition metal, Pn=pnicogen) are reviewed. Several distinctive

functions have been found in these materials based on our original material exploration. By

extending the material system from the copper based oxychalcogenides to isostructural

compounds, transition metal – based LaTMOP (TM=Fe, Ni), we have found novel

superconductors, LaFeOP and LaNiOP. Sharma et al. [366] followed Preparation and study

of magnetic properties of Silico phosphate glass and glass – ceramic having iron and zinc

oxide. The magnetic properties of 25SiO2.50CaO.15P2O5.(10-x)Fe2O3-xZnO (where x=0, 2, 5

mol%) glass and glass – ceramics have been studied. These glasses are prepared by melt


70

quench technique and heat treated at 8000C for 6 h. Electron Spectroscopy for Chemical

Analysis (ESCA) revealed that the fraction of non – bridging oxygen decreases with the

increase in zincoxide content. The analysis of the glass without ZnO shows about 58 wt% of

total iron ions is in the state. The samples on heat treatment show improved magnetic

properties due to the formation of magnetic nonparties.Liusar et al. [367] showed Solid

solutions of mixed metal Mn3-x MgxFe4 orthophosphates: colouring performance within a

double firing ceramic glaze. Solid solutions of mixed metal Mn3-xMgxFe4(PO4)6

orthophosphates (x=0, 0.5, 1, 1.5, 2, 2.5 and 3) were prepared for the first time (from

coprecipitate powders calcined upto 10000C) and characterized by thermal analysis XRD,

SEM/EDX, UV-VI, NIR, spectroscopy and colour measurement. The obtained solid solutions

with a minimized Mn content (especially Mg3Fe4(PO4)6 composition, without Mn) could

serve as low – toxicity Fe reservoirs to stabilize hematite in double – firing glazes and

produce an interesting dark – brown colouration, being an alternative to other brown ceramic

pigments containing hazardous metals (i.e., Cr., Ni, Zn, or Sb). Baruzzo et al. [368] was

carried out Possible production of ceramic tiles from marine dredging spoils alone and mixed

with other waste materials. Dredging spoils, due to their composition could be considered a

new potential source for the production of monolithic ceramics. Nevertheless, abundance of

coloured oxides in these materials preclude the possibility of obtaining while products, but

not that of producing ceramics with a good mechanical behavior. Water absorption, density,

strength, hardness, fracture toughness thermal expansion coefficient of the fired bodes were

measured. The fired samples were finally tested in acidic environment in order to evaluate

their elution behavior and consequently their environmentally compatibility.The

electrochemical reduction of several metal and mixed – metal sulfate aqueous solutions [369]

at a palladium electrode has been studied. For magnesium, lanthanum, yttrium and scandium

sulfates, metal (oxy) hydroxide films are produced by catholically induced precipitation of

the metal cations, following to the local generation of hydroxide ions at the hydrogen sorbing

cathode No films are accessible from the sulfate solutions of electropositive metals such as

sodium and potassium, where the corresponding metal oxides and hydroxides are highly

soluble. Metals are electrodeposited from separate sulfate solutions of zinc nickel and indium,

in presence of the catholically induced precipitation of the metal (oxy)- hydroxide. Zhidong

Li et al. [370] worked on performance of NiCu ferrite fine particles and ceramics synthesized

using egg white. The results of X-ray diffraction showed that the main phase, NiCu ferrite

with fine particles were obtained from the nitrates-egg white or nitrates-citrate acid mixture

calcined at 400°C for 3 hs. Vibrating Sample Magnetometer (VSM) measurements indicated


71

the NiCu material with fine particles were typical soft magnetic materials. Combined results

of magnetization curves, saturation magnetization (Ms), residual magnetization (Mr),

coercitive force (Hc), it has been found that the NiCu ferrite material synthesized from

nitrates - egg white has better magnetic performance than that from nitrates -citrate acid. Cu

doping can increase the Ni-ferrite's permeability. Tu et al. [371] worked on treatment of

complex heavy metal wastewater using a multi-staged ferrite process. Complete removal of

heavy metal from complex heavy-metal wastewater (CHMW) requires advanced technology.

This study investigated the feasibility of a multi-staged ferrite process (MSFP) for treating

CHMW, containing Cd, Cu, Pb, Cr, Zn, Ag, Hg, Ni, Sn and Mn. The performance of MSFP

in removing heavy metals from wastewater was subsequently investigated and the parameters

of three treating steps in MSFP were optimized under 70 °C and 90 °C at pH 9, and 80 °C at

pH 10. After the three-staged procedures, all heavy metals in supernatant and sludge could

fulfill the contamination levels regulated by law. In addition, the sludge generated from the

MSFP was examined by XRD and forms a stable spinel structure, which could be effectively

separated by external magnetic field.Ahmed et al. [372] Nano-crystalline copper ferrites from

secondary iron oxide (mill scale) . Meanwhile, the types of phase formed and the magnetic

properties of the produced samples were investigated using X-ray diffraction, scanning

electron microscope and vibrating sample magnetometer. The results indicated that with a

firing temperature of 1100 °C, the compact possesses higher compressive (832 kg/cm2)

strength and higher bulk density (3.93 g/cm3), whereas higher saturation magnetization

(45.2 emu/g) and lower coercivity (6.13 Oe) were achieved for compacts fired at 1200 °C.

The effect of firing time at optimum firing temperature on physical and magnetic properties

of the produced compacts seems to be insignificant. The crystal structure of the copper ferrite

was transformed from its tetragonal into a cubic structure accompanying the dissociation of a

part of the copper ferrite into delafossite at high firing temperature.

1.2.7 Fuels:

Metal / Mixed metal oxides have wide application as fuels some of them are described here.

Coffey et al. [373] synthesized copper doped lanthanum strontium ferrite for reduced

temperature solid oxide fuel cells.Copper doped lanthanum strontium ferrite showed superior

kinetics for the electro-reduction of oxygen. The improvement was confirmed with cyclic

voltametric studies on half cells and on full fuel cell tests. Copper doped materials have

unusual electrochemical characteristics and copper apparently undergoes a one electron

reduction at overpontentials less than -0.1.V. This occurred only in air but not in oxygen.

Zhan et al. [374] used thin film solid oxidefuel cells (SOFCs) composed of thin coatings of 8


72

mol% Y2O3-stabilized ZrO2 (YSZ) and thick substrates of (La0.8Sr0.2)0.98MnO3 (LSM)- YSZ

cathodes, are fabricated using the conventional tape casting and tape lamination

techniques.Maximum power densities for hydrogen and propane at 8000C are 0.26W cm-2 for

CuO-YSZ ceria anodes and 0.35 Wcm-2 and 0.22W cm-2 for CuO-SDC- ceria anodes,

respectively. Electrochemical impedance analysis suggests that CuO-SDC ceria exhibits a

much lower anodic polarization resistance than CuO-YSZ-ceria, which could be explained by

the intrinsic mixed oxygen ionic and electronic conductivities for SDC in the reducing

atmosphere. Ai et al. [375] followed vaccum assisted elecleless Cu incorporated by vacuum

assisted electroless plating into porous Ni/Sm0.2Ce0.8O1.9 (Ni/SDC) anodes as the active

anodes for the oxidation reaction of hydrogen and methane of intermediate temperature solid

oxidefuel cells (IT-SOFCs). The increase in the performance of the cell with the Cu

electroless plated Ni/SDC anodes is most likely attributed to the enlarged effective three

phase boundaries (TPBs) by interconnecting the isolated Ni and/or SDC particles with the

electroless plated Cu network and the formation of TPBs at the Cu/SDC interface due to the

activation of SDC surface by the Cu deposition. The stability test shows that cell degradation

in dry methane due to carbon deposition is significantly reduced by the electroless copper

plating. Zhao et al. [376] prepared high performance cathode supported solid oxide fuel cells

with copper anodes. Thin film solid oxide fuel cells, composed of thin coatings of 8 mol%

Y2-O3 stabilized ZrO2 (YSZ), thick substrates of infiltrated La0.8S0.2FeO3 (LSF)-YSZ

cathodes and CuO- SDC (Ce0.85Sm10.15O1.925) – ceria anodes, are fabricated using the

conventional tape casting and infiltration methods. Ferki et al. [377] showed synthesis,

structural analysis and electrochemical performance of solid oxide-fuel cells (SOFCs),

La2Ni1-xCuO4+5 (x=0, 0.01, 0.02, 0.05 and 0.1) doped with copper in percentages, varying

between 1% and 10% were prepared following the modified Pechini method. In contrast,

doping with higher amounts of copper (2%, 5% and 10%), led, after heating at 10000C for 48

h, to the formation of another phase resulting from the diffusion of copper into the YSZ

electrolyte, limiting the interest of these materials as SOFC cathodes. Wang et al. [378]

physically mixed LiLaNi-Al2O3 and copper as conductive anode catalysts in a solid oxide fuel

cell for methane internal reforming and partial oxidation. copper are added to LiLaNi-Al2O3

to improve the electronic conductivity property for application as the materials of the anode

catalyst layer for solid oxidefuel cells operating on methane. The surface conductivity tests

demonstrate it is extremely improved for LiLaNi-Al2O3/Cu catalyst due to the addition of 50

wt% copper. A cell with LiLaNi-Al2O3/Cu (50:50) catalyst layer is operated on mixtures of

methane O2, methane – H2O and methane – CO2, and peak power densities of 1081, 1036 and


73

988 mW cm-2 are obtained at 8500C, respectively, comparable to the cell with LiLaNi-Al 2O3

catalyst layer. In summary, the results of the present study indicate that LiLaNi-Al2O3/Cu

(50:50) catalysts are highly coking resistant and conductive catalyst layers for solid oxide

fuel cells. Tavares et al. [379] developed a novel copper based anode for low-temperature

solid oxide fuel cells prepared through the conventional ceramic technology and using CuO

and SDC (Ce0.8Sm0.2O1.9) powders with controlled, particle size. Solid oxide fuel cells having

the new anode were tested for both humid hydrogen and methane. Power densities of ca. 250

mW cm-2 were achieved in H2 at 6000C and in CH4 7000C even if the SDC- electrolyte

supporting membrane was 250 m thick. Short term stability tests (maximum 64h) showed an

initial impairment, but not dramatic, of the new anode performance and the formation of

carbon deposits. Senguttuvan et al. investigate. Lee et al. [380] determine whether a copper

oxide modified Pt cathode (PtCuOm) improves a performance of direct methanol fuel cells

(DMFC), we performed structural and morphological analysis of the cathode and measured

current – potential prole and impedance spectroscopy. These results may play a role in better

long – term stability of DMFC systems.Senguttuvan et al. [381] investigate solid oxide fuel

cells (SOFC) are emerging as an alternate source of energy. Anodes form one of the

components of the fuel cells. Ni/Yttrium stabilized zirconia is a classic anode material for

SOFC when hydrogen is used as the fuel source, but it is not that effective when methane is

used as fuel source due to carbon deposition on the anode. Scanning and back scattered

electron micrographs reveal a clear two – phase structure only in the samples with greater

than 20 mol% of CuO loading. Atomic force microscopy carried out on 33 mol% loaded

zirconia shows a three-phase structure with flattened seven – fold – coordination of Zr4+ with

oxygen. Sapkota et al. [382] found that a zinc air fuel cell (ZAFC) of taper – end structure

was designed with a polyamide – base plastic. An air cathode with multiply layers of blended

inexpensive metal oxide. MnO2 and CeO2 showed a remarkably stable electricity –

generating performance even at high current density. A cheap thin nylon filter was found as a

potential candidate for the separator in ZAFC because of its high stability and durability in

the alkali electrolyte and proper pore size. Visinescu et al. [383] reported a suitable fuel in

new low temperature combustion based synthesis of zinc aluminate oxide.Starch has been

tested as single- fuel and in a two – fuel mixture, together with N-methylurea, in a new

combustion and equivalence ratios φe (φe= fuel/oxidant). Crystal structures were refined by

Rietveld method. UV-Vis spectroscopic analysis have confirmed the intrinsic properties of

the resulted mixed metal oxide, but also shows the presence of a certain disorder degree for


74

all the other samples. The superior values of the band gap (4.2-4.7 eV) for the obtained

oxides relative to the bulk case (3.8 eV) are the result of the nanometric dimensions o the

particles. Jungdeok et al. [384] examined zinc-doped barium strontium – cobalt ferrite

(Ba0.5Sr0.5CO0.2,ZnxFe0.8O3-5 (BSCZF); x=0, 0.05, 0.1, 0.15, 0.2) powders with various

proportions of zinc-were prepared using the ethylenediamine tetraacetic acid (EDTA) citrate

method with repeated ball-milling and calcining. The resistance decreased further by about

30% when Sm0.2Ce0.8O2-5 (SDC) electrolyte particles were incorporated and the sintering

temperature was increased to 10000C. Compared to BSCF without zinc. BSCZF experienced

the lowest decreased in electrochemical properties when the sintering temperature was

increased from 9500C to 10000C. Using a composite cathode of BSCZF 05 and 30 wt% of

SDC button cells composed of an Ni – SDC support with a 30 µm dense SDC membrane

exhibited a maximum power density of 605 mW cm-2 at 7000C. Lee et al. [385] in

preliminary comparatively studies of zinc and zinc oxide electrode on corrosion reaction and

reversible reaction for Zn/air energy system is considered to be a promising power energy

source. While both the zinc oxide and the modified zinc oxide electrodes are reversible.

However, as far as dendrite formation is concerned there is no marked improved in case of

the zinc oxide and the modified zinc oxide electrodes. Kwon et al. [386] investigated the

sensing properties Al2O3-doped ZnO for combustion control in lean- burn conditions. Planar

– type sensing elements made of heater, electrode and sensing layer were formed on an

alumina substrate using a screen printing technique. Our exhaust gas sensor exhibits

significant resistance changes even under lean conditions, apparently due to the

simultaneously functioning of bulk and surface conduction mechanisms. Utilizing the sensor

for the feedback control of a domestic boiler. Shie et al. [387] examined the effects of

additives of potassium carbonate (K2CO3) and zinc oxide (ZnO) on the pyrolysis of waste

sunflower – oil cake using a 60 kW pilot – scale plasma torch reactor. In order to match the

appeal of resource reutilization, one can use the waste K2CO3 resulted from the sorption of

CO2 with KOH in greenhouse gas control and the waste ZnO obtained from the melting

process as additives for the co-pyrolysis of sunflower oil – cake, yielding fuels rich in CO

and H2, respectively utilize effect of additives on the electrochemical behavior of zinc anode

due to its low cost and high power density, the Zn/air energy system is considered to be a

promising power energy source. Similarly, hydrogen over potential plays a major role. Their

study attempts to reduce dendrite formation and raise hydrogen overpotential through the

addition of cellulose and lead oxide, respectively. It is concluded that cellulose reduce


75

dendrite formation to some extent. It also works well to raise the hydrogen overpotential even

in the absence of lead oxide. Sapkota et al.[388] characterized zinc air fuel cell (ZAFC),

which generates electricity by the reaction between oxygen and zinc pallets in a liquid

alkaline electrolyte is a potential candidate for an alternative energy generator. It is applicable

to portable mobile, stationary, and military purposes. In spite of its high potential as an

alternative power source, it is yet in a preliminary stage of commercialization because of a

few uncertainties remained. Zhang et al. [389] worked on a series of gold zinc oxide catalysts

prepared using a coprecipitation procedure, and their performance for catalytic oxidation

removal of CO from H2 rich gas was investigated in a fixed bed – reactor. when the content

of platinum in Au (1.5)/ZnO300 was lowered with increasing content of Pt. The ideal

composition for Au (1.5) – Pt/ZnO300 was 1.0 wt% Pt. (Au (1.5) – P (1.0)/ ZnO300. Guo et al.

[390] checked the effects of zinc modification methods on membrane sintering, electrical

conductivity of BaZro.4Ceo.4Y0.3O3-5 (BZCY4) and the thermo – mechanical match of the

BZCY4 electrotype with anode. An anode-supported thin film BZCY4-3 electrolyte solid

oxide fuel cell (SOPC) was successfully fabricated, and the fuel cell delivered an attractive

performance with a peak power density of 307 mW cm-2 at 7000C. Rasouli et al. [391]

prepared cobalt – doped ZnO nanoparticles were synthesized by combustion method. Mixture

of citric acid and glycine were used as fuel. Citric acid combustion alone led to amorphous

powder. Scherrer’s equation demonstrated that the crystallite size increases with citric acid/

glycine (C/G) radio (38-61nm). SEM and TEM images illustrated that the morphology of the

powder depends on the C/G ratio and changes from rod – like to spongy hexagonal particles.

Reflectance spectra showed that by higher C/G ratios, deeper green colors are obtained. Guo

et al. [392] discussed proton – conducting solid oxide fuel cells with a dual – layer

electrolyte, constructed of a highly protonic conductive BaCe0.8Y0.2O3-δ (BZCY4) electrolyte,

was easily fabricated by dry pressing the electrolyte powders onto an NiO+BZCY4 anode

substrate, followed by co-sintering at a high temperature. The performance of the as

fabricated cell with the BCY and BZCY4 dual – layer electrolyte was studied. Peak power

densities of 249 and 101 mW cm-2 were achieved at 700 and 5000C, respectively. Tsukada et

al. [393] studied composite sorbents, for the simultaneous removal of sulfur compounds and

alkali and heavy metals from coal gasifier products in the integrated qualification fuel cell

(IGFC) system, were prepared. Iron oxide and zinc – ferrite were selected as desulphurization

sorbents and they were synthesized by precipitation from either ferric chloride, ferric nitride

or ferric and zinc nitride solution in these solution fine oxide particles such as kaolinite,


76

sepiolite, and activated clay, which have the capability of alkali and heavy metal absorption,

were dispersed. Chockalingam et al. [394] discussed gadolinium – doped ceria has

demonstrated as high –ionic conductivity at moderate temperatures and is a potential

candidate as electrolyte in solid oxide fuel cell (SOFC) devices. This design is principally

similar to the grain boundary design in zincoxide varistors. In order to not overload the

entire composition with insulating particles (and thus reducing the ionic conductivity

substantially due to volumetric dilution) the insulating grains have to be small (nanometer

sized) and uniformly distributed throughout the matrix (cenium oxide). Moreover, the

insulating grains should not dissolve or otherwise alter the cerium oxide matrix. Small sizes

for the alumina particles prevent the overall composition from being overloaded with non-

conducting particles and the coating process enhance a very uniform distribution of the

alumina particles in be (microwave) sintered. Characterized by SEM, TEM, XRD, density

and conductivity measurement are prescribed to evaluate properties of the proposed nano-

composite electrolyte. Wu et al. [395] studied the characteristics of a novel method for Hg

removal using H2S and sorbents containing iron oxide . The following results were obtained

(1) the presence of H2S was indispensable for the removal of Hg from coal derived fuel gas;

(2) Hg was removed effectively by the sorbents containing iron oxide in the temperature

range of 60-1000C (3) the presence of oxygen may play very important role in the Hg

removal and formation of elemental sulfur was observed upon heating of the used sample. a

process for the removal of Hg using H2S over iron oxides sorbents, which will be located just

before the wet desulfurization unit and catalytic COS converter of a coal gasification system.

it is necessary to undertand the reactions between the iron oxide sorbent and other

components of the fuel gas such as H2S, CO, H2, H2O, etc. Bhaskar et al. [396] developed

the recycling of waste lubricant oil from automobile industry found to be best alternative to

incineration. Silica (SiO2), alumina (Al2O3), silica – alumina (SiO2-Al 2O3) supported iron

oxide (10 wt% Fe) catalysts were prepared by wet impregnation method and used for the

desulphurization of waste lubricant oil into fuel oil. The extent of sulphur removal increases

in the sequence of Fe/SiO2- Al2O3<Fe/Al2O3<Fe/SiO2 and this might be due to the presence

of smaller crystalline size (7.4nm) of Fe2O3 in Fe/SiO2 catalyst. X-ray diffraction results

suggest the presence of iron sulphide in the used catalyst. Gas chromatography with thermal

conductivity detector analysis confirms the presence of H2S in gaseous products. In addition,

Fe/SiO2 catalyst facilitated the formation of lower hydrocarbons by cracking higher

hydrocarbons (C40) present in waste lubricant oil. Cheng et al. [397] developed acid mine

drainage (AMD) as an important contributor to surface water pollution due to the release of


77

acid and metals. Fe (II) in AMD reacts with dissolved oxygen to produce iron oxide

precipitates, resulting in further acidification, discoloration of stream beds, and sludge

deposits in receiving waters. It has recently been shown that new fuel cell technologies, based

on microbial fuel cells, can be used to treat AMD and generate electricity. Here we show that

this approach can also be used as a technique to generate spherical nano-particles of iron

oxide that, upon drying, are transformed to goethite. fuel cell technologies can not only be

used for simultaneously AMD treatment and power generation, but that can generate useful

products such as iron oxide particles having sizes appropriate for used as pigments and other

applications. Halmann and Steinfold [398] studied fuel gases from coal, gas, or oil –fired

power stations, as well as from several heavy industries, such as the production of iron, lime

and cement, are major ethnographic sources of global CO2 emissions. The thermodynamic

constraints are determined for the production of syngas suitable for methanol, hydrogen, or

ammonia synthesis. The environmental and economic consequences are assessed for large –

scale commercial production of these chemical commodities. The production of ammonia in

the above processes seems particularly attractive, as it consumes the nitrogen in the fuel

gases. Leion et al. [399] studied chemical – looping combustion (CLC) is a novel technology

that can be used to meet demands on energy production without CO2 emissions. The

experiments were carried out in a laboratory fluidized – bed reactor that was operating

cyclically with alternating oxidation and reduction phases. The exhaust gases were led to an

analyzer where the contents of CO2, CO, CH4 and O2 were measured. Gas samples collector

in bags were used to analyze the content of hydrogen in a gas chromatograph. The results

showed that both the iron one and the oxide scale worked well as oxygen carrier and both

oxygen carriers increased their reactivity with time. Otsuka et al. [400] investigated pseudo –

storage of hydrogen and its recovery by redox of iron oxide have been proposed as a new

method of the storage and supply of hydrogen for PEFC vehicles. Among the additives to

iron oxide tested, Al, Cr, Zr, Ga and V were the effective elements enhancing both the

reduction with H2 (storage of H2) and reoxidation with water (recovery of H2) of the iron

oxide (3Fe+4H2O=Fe3O4+4H2) at low temperatures (<4000C). The additives moderated the

sintering of iron oxide markedly with repeated redox cycles. It is suggested that another

important role of additivities is to activate H2 and H2O at the surface of iron oxide or to

enhance the diffusion of O2- as a result of the formation of compound oxides between the

additive and iron oxide. Lorente et al. [401] discussed the steam – ron process, based on the

redox reaction of iron oxides (Fe3O4+4H2 → 3F2+4H2O), as an interesting alternative to other


78

methods of storing and generating pure hydrogen to a solid oxide fuel cell (SOFC), a

mathematical mode for the oxidation process in a fixed bed reactor has been developed and is

used to estimate the behaviour of the reactor under various operating conditions (e.g. amount

of iron, steam flow rate; temperature). Huang et al. [402] found the oxidation kinetics and

electrical properties of oxide scales thermally grown on the surface of a commercial ferrite

alloy have been investigated on the un oxidized and pre-oxidized alloys as functions of

temperature and time under oxidizing atmospheres with four different electrodes. Oxidation

kinetic studies with the an-oxidized alloys show a nearly parabolic dependence on time of

oxide-scale growth rate, but a significantly increased growth rate with a coating of LSCo

compared to those without and with the coatings of LSM and platinum. It mechanism

associated with the formation of Cr2O3. SEM observations show that oxidation of the un-

oxidized alloy in the presence of an oxide electrode results in considerable inter diffusion of

Cr and the electrode cations especially Co across the interfaces. The FeOx- based catalyst

was applied to the decomposition of extra heavy oils such as vacuum distilled residuai oil and

Orimulsion. These extra heavy oils were effectively decomposed over the ZrO2-Al 2O3-FeOx

catalyst with steam, and the yields of lighter hydrocarbon reached to above 60%. Ozaki et al.

[403] studied development of an elemental mercury (Hg0) removal process for coal derived

fuel gas is an important issue in the development of a clean and highly efficient coal power

generation system. Iron – based sorbents such as iron oxide (Fe2O3), supported iron oxide on

TiO2, and iron disulfide have been proposed as active mercury sorbents. Temperature

programmed decomposition desorption (TPDD) experiments revealed that the decomposition

characteristics of mercury species captured on the sorbent was similar to that of HgS reagents

(meta cinnabar). Furthermore, it was observed that the characteristics of the decomposition of

mercury species depended on the sorbent type of sorbents and reaction conditions. Yang et al.

[404] discussed perovskite – oxide Ba1.0CO0.7Fe0.2Nb0.1O3-δ as oxygen transport membrane

and cathode material for solid oxide fuel cells (SOFCs). No obvious variation can be

observed in TEC by A – site deficiency. The electrical conductivity and TEC of

Ba1.0CO0.7Fe0.2Nb0.1O3-δ decrease while the cathode polarization resistance increases with the

increase in iron doping concentration. The highest conductivity of 13.9 S cm-1 and the lowest

cathode polarization resistance of 0.07. Wang et al. [405] produced Ni-Al2O3 composites

with varying contents of nickel synthesized via a glycine nitrate process (GNP) and an

impregnation process (IMP). Their potential application as an anode functional layer for

internal methane CO2 reforming in a solid oxide fuel cell is investigated. H2-TPR results


79

show that the chemical interaction between NiO and Al 2O3 decreases as the nickel content

increases. Catalytic tests demonstrate that 15 wt % Ni-Al 2O3 catalysts exhibit the best

catalytic activity for methane CO2 reforming. However, the carbon formation rates over Ni-

Al 2O3 prepared via GNP are lower than those over Ni-Al2O3 prepared via IMP using the

same amounts of nickel, with the exception of the 1 wt % Ni-Al2O3 catalyst. Raman

spectroscopy and O2-TPO results indicate that the degree of graphitization and the amount of

carbon deposited on the 15 wt % Ni-Al2O3 catalyst synthesized via GNP are lower than those

of the catalyst prepared via IMP following a 60 h stability test. A cell with a 15 wt% Ni-

Al 2O3 catalyst layer prepared via GNP is fabricated that delivers a peak power density of

1006 mW cm-2 at 850 °C when operating on methane – CO2 gas mixtures, which is

comparable to that observed when operating in hydrogen fuel. Pratihar et al. [406]

characterized nickel – yttria stabilized zirconia (Ni-YSZ) cermet, widely used as an anode

material for solid oxide fuel cells (SOFCs). While the nickel to nickel chain maintains the

electrical conductivity path, the YSZ contributes to lowering the thermal expansion and in

habits nickel coarsening during high temperature 10000C operation. An electroless technique

is employed to prepare a uniform nickel coating on the YSZ powder the process parameters

for this technique are optimized. Notably, the cermet thus prepared shows percolation at a

much lower nickel content (10-20 vol%) compared with those reported in the literature.

Halzer et al. [407] studied the effects of compositional and environmental parameters on the

kinetics of micro structural degradation and investigated for porous Ni/CGO anodes in solid

oxide fuel cells (SOFC). Improved methodologies of SEM-imaging, segmentation and object

recognition are described which enable precise qualification of nickel grain growth over time.

Due to these methodological improvements the grain growth can be described precisely with

a standard devotion of only 5-15 nm for each time step. Coffey et al. [408] discussed copper

doped lanthanum strontium ferrite for reduced temperature solid oxide fuel cells. Copper

doped lanthanum strontium ferrite showed superior kinetics for the electro-reduction of

oxygen. The generic formulation was La1−xSrxCu1−yFeyO3 (LSCuF) where x ranged from 0.2

to 0.3 and y varied from 0 to 0.4. Doping with copper improved the electrocatalytic activity

compared with undoped material. In oxygen, the La0.7Sr0.3Cu0.2Fe0.8O3 sample showed

current densities approximately 2–3 times that of La0.7Sr0.3FeO3 and 10 times that of

La0.8Sr0.2FeO3. Faungnawaki et al. [409] studied hydrogen production from dimethyl ether

steam reforming over composite catalysts of copper ferrite spinel and alumina. Dimethyl

ether steam reforming (DME SR) was performed over composite catalysts of copper ferrite

spinel (CuFe2O4) and alumina for hydrogen production, applicable to fuel cell. A highly


80

active composite was achieved when the calcination temperature of the Cu spinel was at

900 °C and that of the alumina was at or below 700 °C.. Mixing state of the copper spinel and

the alumina was also investigated. After mixing with alumina, the present CuFe2O4 markedly

exhibited excellent activity for DME SR in comparison to the commercial CuFe2O4 and

Cu/ZnO/Al2O3. Tsoncheva [410] thermally synthesized nanosized copper ferrites as catalysts

for environment protection. Nanosized copper ferrites were prepared by thermal method from

the corresponding hydroxide carbonate precursors varying the temperature of synthesis. The

phase composition of the obtained materials was characterized by XRD, Mössbauer

spectroscopy, DSC and TPR analysis. Their catalytic properties were tested in total oxidation

of toluene and methanol decomposition to CO and hydrogen. The relation between the

synthesis parameters, phase composition of the samples and their transformation under the

oxidation or reduction reaction medium was investigated in turns to understand the catalytic

behavior of the obtained materials.Chun Lieu [411] discussed magnetic and catalytic

properties of copper ferrite nanopowders prepared by a microwave-induced combustion

process. Copper ferrite nanopowders were successfully synthesized by a microwave-induced

combustion process using copper nitrate, iron nitrate, and urea. The process only took a few

minutes to obtain CuFe2O4nanopowders. The CuFe2O4 powders specific surface area was

5.60 m2/g. Moreover, these copper ferrite magnetic nanopowders also acted as a catalyst for

the oxidation of 2,3,6-trimethylphenol to synthesize 2,3,5-trimethylhydrogenquinone and

2,3,5-trimethyl-1,4-benzoquinone for the first time. On the basis of experimental evidence, a

rational reaction mechanism is proposed to explain the results satisfactorily. Kamble et al.

[412] discussed synthesis of Mg 0.48Cu 0.12Zn 0.40Fe2O4 ferrite and its aptness for multilayer

chip component application. As-synthesized ferrite samples were then subjected to

crystallographic, structural and magnetic investigations by techniques viz. X-ray diffraction,

IR spectroscopy and B–H measurements. Purity and phase formation were confirmed by

XRD examinations. Cation redistribution was also suggested by XRD analyses which

supplement the variation of magnetic properties. IR absorption bands were found to be in the

expected high frequency range (574.95 cm−1 and 582.39 cm−1) and low frequency range

(≈431 cm−1) which fortifies the spinel phase formation. Boost in magnetic performance of

sucrose methods' yield was observed owing to reduced porosity and increased surface area.

Fresno et al. [413] discussed comparative study of the activity of nickel ferrites for solar

hydrogen production by two-step thermochemical cycles.The samples leading to higher

hydrogen yields, averaged over three cycles, are those calcined at 700 °C in each group

(supported and unsupported) of materials. The comparison of the two groups shows that


81

higher chemical yields are obtained with the supported ferrites due to better utilisation of the

active material. Therefore, the highest activity is obtained with ZrO2-supported

NiFe2O4 calcined at 700 °C. Sora et al.[414] discussed crystal structures and magnetic

properties of strontium and copper doped lanthanum ferrites.The average bond distance

(Fe/Cu)–O and the pseudo-cubic unit cell volume decrease with increasing Cu content in

accordance with the presence of higher valence states of the transition metals. The magnetic

structure was modeled for the monophasic samples (x=0.05 and 0.10) assuming an

antiferromagnetic interaction between Fe/Cu neighboring cations (G-type): the magnetic

moments order antiferromagnetically along the b-axis, with the spin direction along a-axis.

The magnetic moments of the Fe/Cu atoms areµx=2.66(3)µB and 2.43(3)µB for the

compositions x=0.05 and 0.10, respectively. By measuring the first magnetization curve and

the hysteresis loops, coexisting antiferromagnetic and weak ferromagnetic interactions were

observed for all samples. Lee et al. [415] worked on inter-diffusion between NiCuZn-ferrite

and LTCC and its influence on magnetic performance. The magnesium (Mg) and aluminum

(Al) ions from LTCC also diffuse into ferrite for a shorter distance. Several new phases form

through such inter-diffusion. For example, the inter-diffusion between alumina and ferrite

induces the formation of hematite whose presence is detrimental to the saturation

magnetization and permeability of ferrite. Additionally, inter-diffusion also induces changes

in the lattice parameters of ferrite. A linear relationship between the lattice constant of ferrite

and saturation magnetization is noked, which demonstrates that magnetic properties are

strongly tied to the crystalline structure of ferrite. Singh et al. [416] investigated on effects of

surface morphologies on response of LPG sensor based on nanostructured copper ferrite

system.Synthesis of a copper ferrite system (CuFe2O4) via chemical co-precipitation method

is characterized by X-ray diffraction, surface morphology (scanning electron microscope) and

optical absorption spectroscopy. Study of gas sensing properties shows spinel

CuFe2O4 synthesized in 1:1 molar ratio exhibit best response to LPG adsorption/resistance

measurement. Thus resistance based LPG sensor is found robust, cheap and may be applied

for kitchens and industrial applications. Abbaspour et al. [417] worked on electrocatalytic

hydrogen evolution reaction on carbon paste electrode modified with Ni ferrite

nanoparticles.Nanoparticles of mixed oxides of Fe and Ni are prepared by a low temperature

coprecipitation method. The effects of Ni content in synthesized nanoparticles on the

electrocatalysts performance for hydrogen evolution reaction are investigated by

electrochemical techniques. Scanning electron microscopy and X-ray diffraction

spectroscopy are used for studying the morphology and structure of Ni-ferrite nanoparticles


82

(NPs). The tafel slopes for the hydrogen evolution reaction are found to be between

97.75 mV dec−1 and 122.19 mV dec−1 on carbon paste electrodes modified with ferrite NPs

and kinetic parameters show that the volmer step must control the hydrogen evolution

reaction. The electrodes are resistive to passivation and they can be renewed easily. Hagary et

al. [418] studied the influence of Cd doping on the microstructure and optical properties of

nanocrystalline copper ferrite thin films. Nanocrystalline thin films of mixed Cu–Cd ferrites,

Cu1−xCdxFe2O4 (x = 0, 0.2, 0.3, 0.5, 0.7, 0.8, 0.9 and 1), were deposited by electron beam

evaporation technique. The films were annealed at 450 °C for 1 h. The effect of Cd doping on

the structural and optical properties of the deposited films has been investigated by using X-

ray diffraction (XRD) and optical spectrophotometry. XRD patterns of the annealed films

show spinal cubic structure. The refractive index dispersion of the films was found to

increase with Cd content and discussed in terms of the Wemple–Di Domenico single

oscillator model. Kuo [419] assessment of redox behavior of nickel ferrite as oxygen carriers

for chemical looping process. After five successive cycles, NiFe2O4 powder with a single

phase of spinel structure demonstrated higher redox cycling behavior and better stability than

standard NiO and Fe2O3 has been addressed the mechanism underlying the redox cycling by

NiFe2O4 spinel powder. Results demonstrate the feasibility of using the proposed preparation

of NiFe2O4 as an oxygen carrier in a reversible chemical looping process (CLP). Pattanaik

[420] worked on growth of nanoscale nickel ferrite on carbonaceous matrix- A novel method

of turning harmful particulates into a functional nanocomposite. The nickel ferrite content in

the composite varies with the Fe/Ni ratio in particulate, fuel type, and combustion condition.

Such variation may lead to the composite exhibiting diverse physical behaviors. Detailed

structure and cation distribution in dispersed ferrite have been studied using Fe and Ni K-

edges XAFS spectroscopy. Peaks are identified in the radial structure function with specific

atom pair correlations within the spinel ferrite from which the relative occupancy of the

cations in the octahedral and tetrahedral sites can be discerned. The results show that Ni(II)

has strong preference for the octahedral site, while Fe(III) prefers both sites which is

consistent with that of an inverted spinel ferrite. Kuo et al. [421] carried out assessment of

redox behavior of nickel ferrite as oxygen carriers for chemical looping process.

NiFe2O4 powder with a single phase of spinel structure demonstrated higher redox cycling

behavior and better stability than standard NiO and Fe2O3. We also addressed the mechanism

underlying the redox cycling by NiFe2O4 spinel powder. Our results demonstrate the

feasibility of using the proposed preparation of NiFe2O4 as an oxygen carrier in a reversible

chemical looping process (CLP). Lin et al. [422] worked on synthesis and characterization of


83

nickel ferrite nanocatalysts for CO2 decomposition. The complete decomposition of CO2 was

possible because of higher degree of oxygen deficiency and surface-to-volume ratio of NFNs.

The pre-edge XANES spectra of Fe atom in NFNs exhibits an absorbance feature at 7115 eV

for the 1s to 3d transition which is forbidden by the selection rule in case of perfect

octahedral symmetry. The EXAFS data showed that the NFNs had two central Fe atoms

coordinated by primarily Fe–O and Fe–Fe with bond distances of 1.87 and 3.05 Å,

respectively. Methane gas was produced during the reactivation of NFNs by flowing H2.

Decomposition of CO2, moreover, recovery of valuable CH4 using heat energy of offgas

produced from power generation plant or steel industry is an appealing alternative for energy

recovery.

Problem Statement and organization of work

Extensive literature survey reveals that the metal oxides have wide applications as catalyst,

sensors, superconductors, adsorbents; ceramics etc. Metal oxides play a very important role

in many areas of chemistry, physical and materials science [1-6]. Metal oxides are formed as

a consequence of co-ordination tendency of metal ions so that oxide ions form co-ordination

sphere around metal ions and give rise to close packed structure. The different physical,

magnetic, optical and chemical properties of metal oxides are of great interest to chemists

because these are extremely sensitive to change in composition and structure. Extensive

studies of this relationship leads to a better understanding of the chemical bond in crystal.

The metal oxides are attracting special attention of scientists due to their easy mode of

formation and multifunctional behavior.

Problam statement and organization of the work

Precipitation method is widely used in the synthesis of nanomaterials. Shape and size

of nanoparticles depends on the chemical used in the synthesis To observe the role of

different chemicals in the synthesis procedure, nanosized metal/mixed metal oxides such as

iron oxide, zinc oxide, copper oxide, nickel ferrite, zinc ferrite, copper ferrite, nickel copper

ferrite, nickel zinc ferrite, zinc copper ferrites have been synthesized taking different starting

materials not reported earlier and using ammonia as precipitating agent. Synthesized

nanosized metal/mixed metal oxides have been characterized using TGA/ DTA, X – ray

diffraction method (XRD), Scanning Electron Microscopy (SEM), Transmission Electron

Microscopy (TEM) and Magnetic measurements (VSM) studies. The detailed studies

involved in this problem were carried out under the following steps.

1. Synthesis of nanosized metal oxides

(a) Synthesis and characterization of nanosized iron oxide.


84

(b) Synthesis and characterization of nanosized copper oxide.

(c) Synthesis and characterization of nanosized nickel oxide.

(d) Synthesis and characterization of nanosized zinc oxide.

2. Synthesis of nanosized mixed metal oxides

(a) Synthesis and characterization of nanosized zinc ferrite.

(b) Synthesis and characterization of nanosized copper ferrite.

(c) Synthesis and characterization of nanosized nickel ferrite.

3. Synthesis of nanosized mixed metal oxides

(a) Synthesis and characterization of nanosized nickel zinc ferrite.

(b) Synthesis and characterization of nanosized copper zinc ferrite.

(c) Synthesis and characterization of nanosized nickel copper ferrite.


85

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