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Transcript of organo clay studies
ADVANCES IN FRACTIONATION AND CHARACTERIZATION OF NATURALLY OCCURING
ORGANO-CLAY COMPLEXES
Sankhadip DasRoll No -10538
Division of Soil Science and Agricultural Chemistry
Indian Agricultural Research InstituteNew Delhi-110012
1.Introduction
2.Nature of organo-clay complexes
3.Fractionation of organo-clay complexes
4.Characterization of organo-clay complexes
5.Research Findings
6.Conclusion
7.Path ahead
Contents
IntroductionThe soil clay-humus complex plays an important role in forming the structure and fertility of agricultural soils Stevenson (1982)
“Clay-associated organic matter as all organic matter present in the clay-sized fraction, both free organic particles and organic matter bound to minerals
Wattel-Koekkoek & Buurman (2004)
‘Primary structure of soils as defined by the soil texture resulting from the association of organic matter (OM) with primary mineral particles, and as complexes that are isolated ‘after complete dispersion of soils’
Christensen (1996)
Secondary organo-clay complexes were defined as the aggregation of several primary organo-mineral complexes
Nature of Organo Clay Complexes
Clay-organic complexes enriched in top soils are the main reservoirs of plant nutrients.
Organo-clay complexes are the adsorption products between the organic cations anions or molecules transfered from solutions , liquid or gaseous states to clay surfaces generally due to the physical or chemical bonds ( long or short range respectively).
Organo-clay complexes are conglomerate soil colloid in which clay, oxides/hydroxides (including sesquioxides and allophanes) and humic material remain associated.
The types and amount of layer silicates, intercalation of OM, content of pedogenic oxides, soil properties, vegeatation , etc are decisive in the formation of clay-organic bonds.
Fractionation of Naturally Occurring Organo - clay
complexes
Physical Fractionation Techniques
Density Fractionation
Aggregate fractionation
Particle size fractionation
Centrifugation
Gravity sedimentation
High-gradient magnetic separation (HGMS)
Size exclusion chromatography
Physical fractionation methods in the strict sense include size and density separation of primary organo–mineral complexes in whole soil, which means that aggregates are not considered (Christensen, 1992).
Chemical fractionation techniques
Extraction of Soil Organic Matter in aqueous solutions with and without electrolytes
By use of organic solvents
By hydrolysis of organic matter
By oxidation of organic matter
Characterization of Organo- clay complexes
13C nuclear magnetic resonance spectrocopy (13C-
NMR) X ray diffraction analysis
Transmission electron microscopy analysis
Scanning electron microscopy analysis Near -edge X ray absorption fine structure spectroscopy
Fourier transform infrared spectroscopy (FTIR)
Thermal analysis .
Nuclear magnetic resonance spectroscopy
The first attempt to use nuclear magnetic resonance (NMR) spectroscopy for structural characterization of soil humic substances was reported by Barton and Schnitzer (1963) and Neyroud and Schnitzer (1972).
13C-NMR can used to determine the number of non-equivalent carbons and to identify the types of carbon atoms(methyl, methylene, aromatic, carbonyl….) which may present in compound.
When energy in the form of radiofrequency is applied
When applied frequency is equal to precessional frequency
Absorption of energy occurs
Nucleus is in resonance
NMR signal is recorded
Principle of NMR
Thermal Analysis
Thermal method of analysis are group of techniques in which changes in physical and /or chemical properties of a substance are measured as a function of temperature, while substance is
subjected to controlled temperature programmed
Mass
ΔT ΔH
Deformation
Gas decompose
Thermal diffusivity
Volume
PhysicalPropertie
s
Differential Scanning Analysis
Differential Thermal Analysis
Dynamic Mechanical
Analysis
Laser Flash Analysis
Dilatometry
Evolved Gas Analysis
Thermo Gravimetric Analysis
Techniques most commonly used :
1. Thermo-microscopy2. Differential thermal
analysis
3. Differential scanning calorimetry 4. Thermo-gravimetry
Thermo gravimetric analysis (TGA)
It is an analysis, the mass of sample is recorded continuously as its temperature is increased linearly from ambient to high temperature.
Mass of material a functions of temperature.
Processes occurring without change in mass (e.g.- Physical transitions ) cannot be studied by TG
Differential Thermal Analysis(DTA)
Heat absorbed or emitted by sample is observed by measuring the temperature difference between that sample and reference compound as temperature of both are increased.
ΔT =TS -Tr as function of Temperature.
Temperature of furnace
The technique was developed by E.S. Watson and M.J. O'Neill in 1960, and introduced commercially at the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy in 1963
Differential scanning calorimetry
X-ray diffraction is based on constructive interference of monochromatic x-rays and a crystalline sample.
The interaction of incident rays with the sample produces constructive interference when conditions satisfy Bragg’s law.
X ray Diffraction
nλ=2dsinθ
Fourier Transformed Infra-Red Spectroscopy
FTIR collects all wavelengths
simultaneously and scans at once. FTIR works based on Michelson
Interferometer which having Beam splitter Fixed mirror Movable mirror
Transmission electron microscopy
Transmission electron microscopy (TEM) has seldom been used in soil organic matter research, although it showed the variety of OM morphology found in the clay-sized fraction of soils (Feller et al., 1991; Chotte et al., 1993)
The first TEM was built by Max Knoll and Ernst Ruska in 1931, with this group developing the first TEM with resolution greater than that of light in 1933 and the first commercial TEM in 1939.
Scanning electron microscopy
The first scanning electron microscope (SEM) debuted in 1938 ( Von Ardenne) with the first commercial instruments around 1965. Its late development was due to the electronics involved in "scanning" the beam of electrons across the sample
SEMs use an electron beam instead of a beam of light, which is directed towards the specimen under examination
RESEARCH FINDINGS
Study on Differential thermal analysis of Humic acids, clay and clay humus complexes from various soils
hbkk
(Ahmed et al., 2002)
DTA curves of a) Humic acids, b) clay, and c)clay –humus complexes from various soils.
Effect of rhizosphere on Organo-clay complexation
(Mandal & Datta ,2005)
DRXD analysis of vertisols and Alfisols of Rhizosphere and Non-rhizosphere
(Ahmed et al., 2002)
Study on the comparision of X-ray diffraction patterns of clay fractions and clay-humus complexes of different soils
Entisol clay
Entisol clay-humus complex
Mollisol ΙΙ clay-humus complex
Molliso ll clay
Mollisol Ι clay-humus complex
Mollisol Ι clay
Alfisol clay
Vertisol clay
Vertisol clay-humus complex
Alfisol clay-humus complex
XRD patterns of different soils
Impact of tillage and puddling operations on the stability and physico-chemical properties of clay-humus complexes
Effect of thermal activation (35oC) on changes in organic carbon content of clay –humus complexes of surface(0-15 cm) and subsurface soil(15-30 cm ) as affected by long term NT and T treatments
(Vennila and Datta .,2008)
Contd….
Effect of thermal activation (35oC)on changes in organic carbon content of clay–humus complexes of surface(0-15 cm) and subsurface soil(15-30 cm ) as affected by long term NP and P treatments.
Solid state 13C NMR spectra of the source HA (SHA) and the unadsorbed HA (humic acid) fractions after coatingon kaolinites (HAKs), montmorillonites (HAMs) and goethites (HAGs). (Ghosh et al ., 2009)
Study of fractionation behavior of Humic Acid upon sorption on mineral surfaces with varying surface properties.
Study of organo clay complexes obtained from various soils by Transmission electron microscopy
(Ahmed et al., 2002)
TEM images of clays and clay-humus complexes of Entisol (a,b,c) & Mollisol Ι (d,e,f) respectively
Contd…
TEM images of clays and clay-humus complexes of Alfisol(g,h), Vertisol (i,j) & Mollisol ΙΙ (k,l) respectively
Scanning electron microscopy (SEM) images of (a) natural bentonite and (b) HDTMA-bentonite.
Effect on natural bentonite on modification with Hexadecyltrimethylammonium(HDTMA) bromide
(Ikhtiyarova et al., 2012)
Study on the structural arrangement of Humic acids isolated from different soils of China
SEM images of the HAs samples.(Xu et al., 2006)
ConclusionDXRD analysis helped in the better study of stability of the organo-clay
complexes not possible by conventional XRD techniques
The NMR results show a semi quantitative distribution of different carbon
moieties in the original HA and HA fractions obtained after coating.
SEM micrographs was able to show the surface changes of natural
bentonite on application of surfactant resulting in rough appearance of
surface
TEM micrographs helped in the identification of clay minerals of various
nature in different typesof soils
Stability of organo-clays was seen to be increased with depth in both
puddling and tillage conditions.
Path AheadMore studies on the nature of natural organo -clay complexes are to be conducted in comparision to synthetic ones
Surfactant studies of humic acids fractions of organo-clay complexes have to be carried out on a large scale
Studies regarding the influence of soil micro-organisms on the complexity mechanism between organic matter and clay minerals will help in greater understanding of the nature of organo-clay complexes
Modern techniques are to be used by replacing the conventional and traditional techniques in order to get a good understanding on the characteristics of organo-clay complexes