Research Article Photocatalytic Removal of Microcystin-LR...

Research ArticlePhotocatalytic Removal of Microcystin-LR by AdvancedWO3-Based Nanoparticles under Simulated Solar Light

Chao Zhao12 Dawei Li1 Yonggang Liu3 Chuanping Feng2 Zhenya Zhang1

Norio Sugiura1 and Yingnan Yang1

1Graduate School of Life and Environmental Sciences University of Tsukuba Tsukuba 305-8572 Japan2School of Water Resources and Environment China University of Geosciences Beijing 100083 China3Institute of Environmental Sciences Zhengzhou University Zhengzhou 450001 China

Correspondence should be addressed to Yingnan Yang yangjiayangjpyahoocojp

Received 1 July 2014 Revised 1 September 2014 Accepted 1 September 2014

Academic Editor Xiao-Feng Zhao

Copyright copy 2015 Chao Zhao et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

A series of advanced WO3-based photocatalysts including CuOWO

3 PdWO

3 and PtWO

3were synthesized for the

photocatalytic removal of microcystin-LR (MC-LR) under simulated solar light In the present study PtWO3exhibited the best

performance for the photocatalytic degradation ofMC-LRTheMC-LR degradation can be described by pseudo-first-order kineticmodel Chloride ion (Clminus) with proper concentration could enhance the MC-LR degradation The presence of metal cations (Cu2+and Fe3+) improved the photocatalytic degradation of MC-LR This study suggests that PtWO

3photocatalytic oxidation under

solar light is a promising option for the purification of water containing MC-LR

1 Introduction

Eutrophication in superficial freshwater bodies induced fre-quent cyanobacteria blooms worldwide The occurrence oftoxic cyanobacterial blooms in eutrophic lakes reservoirsand other recreational water has been identified as an increas-ingly serious problem in many countries [1] The toxinsreleased into freshwater by cyanobacteria are well docu-mented [2]

Microcystins (MCs) are the most commonly occurr-ing toxins released by cyanobacteria MCs are cyclic hepta-peptides containing the unique C

20amino acid 3-amino-

9-methoxy-268-trimethyl-10-phenyldeca-46-dienoic acid(ADDA) MCs are strongly hepatotoxic because they inhibitserinethreonine protein phosphatases 1 and 2A [3] Acuteexposure may result in hepatic injury promote primary livercancer and even cause the death of animals and humansOne of the most common occurring MCs is the highlytoxic microcystin-LR (MC-LR) which has leucine (L) andarginine (R) in the variable positions The World Health

Organization (WHO) has determined a provisional guidelinevalue of 10 120583g Lminus1 for MC-LR in drinking water Variouswater treatment processes have been evaluated to determinetheir performance in decomposing these toxins HoweverMCs are chemically stable across a range of pH values andtemperatures due to their cyclic structure Consequentlytraditional water treatment processes are not reliable for theremoval of MCs [4ndash6]

Photocatalytic oxidation as an advanced oxidation tech-nology has been considered an environment-friendly watertreatment method [7ndash11] When the photocatalyst exposureto a light with appropriate wavelength happens electron (eminus)and hole (h+) pairs are generated on the catalyst surface Thephotogenerated electrons and holes react with oxygen andwater molecules or hydroxyl groups adsorbed on photocata-lyst surface to formhighly reactive species such as superoxideradicals (∙O

2

minus) and hydroxyl radicals (∙OH) [12] Theseradicals can oxidize a number of organic pollutants includingdyes pesticides and herbicides [7ndash11 13] Previous researchproved that photocatalytic oxidation with TiO

2photocatalyst

Hindawi Publishing Corporatione Scientific World JournalVolume 2015 Article ID 720706 9 pageshttpdxdoiorg1011552015720706

2 The Scientific World Journal

could effectively destroy MCs even at extremely high toxinconcentrations [14 15] However TiO

2has a large band gap

energy (119864119892) of 32 eV that restricts the wide use of this

photocatalyst because it can only absorb UV light whichaccounts for 5 of the solar light [16] Many efforts have beenmade to enhance the photocatalytic performance of TiO

2

under solar light For example Ag-modified TiO2thin film

was developed for bacteria disinfection under solar light [1718] TiO

2-filmCuO microgrid heterojunction and P-doped

TiO2nanoparticles were synthesized for the decomposition

of organic dye [19 20] By contrast tungsten trioxide (WO3)

can utilize solar light more effectively than TiO2 because it

has an 119864119892between 24 and 28 eV [10] In addition WO

3

is inexpensive to prepare and stable inlsquoacidic and oxidativeconditions whichmakes it a promisingmaterial for photocat-alytic applications Previous research showed that photocat-alytic degradation of organic pollutants such as organic dyesusingWO

3under solar lightwas intensified by the presence of

suitable dopants such as Pt Pd and CuO [21ndash23] Howeverthere is little research on the photocatalytic degradation ofMCs using WO

3-based photocatalysts under solar light

In the present study three types of WO3-based photo-

catalysts including CuOWO3 PdWO

3 and PtWO

3were

synthesized for photocatalytic degradation of MC-LR undersimulated solar light The characteristics of developed WO

3-

based photocatalysts were analyzed by BET surface area X-ray diffraction (XRD) and scanning electron microscopy(SEM) A series of batch experiments were carried out toevaluate the photocatalytic performance of the developedphotocatalysts forMC-LR degradation under simulated solarlight On the other hand chlorides and metal cations arecommon in water and they are important in many treatmenttechnologies such as breakpoint chlorination and electro-chemical oxidation methods [24] Therefore in this studythe effects of chloride ions (Clminus) and metal cations (Cu2+and Fe3+) on the photocatalytic degradation ofMC-LR undersolar light were also investigated

2 Experimental

21 Reagents WO3powder microcystin-LR (MC-LR) stan-

dard (ge95 purity FW 9952 gmolminus1) terephthalic acid99 and Cu(NO

3)2sdot3H2O (999 purity) were purchased

from Wako (Wako Pure Chemical Industries Ltd Japan)Hexachloroplatinic acid (H

2PtCl6sdot6H2O) and Pd powder

with a surface area of 40ndash60m2 gminus1 were supplied by Sigma-Aldrich (Sigma-Aldrich Co LLC USA)

22 Photocatalyst Preparation TheWO3loaded with 01 wt

CuO (marked as CuOWO3) was synthetized by an impreg-

nation method [21] Cu(NO3)2aqueous solution was mixed

with WO3powder and the mixture was dried on hot plate

and then calcined at 300∘C for 30min in airThe Pd doped WO

3photocatalyst (PdWO

3) was pre-

pared by themechanical mixing of Pd (wt versusWO3) and

WO3in a ceramic mortar [25]

The Pt modified WO3sample (PtWO

3) was developed

using a photodeposition method [21] from H2PtCl6sdot6H2O

on the fine particulate WO3under visible light irradiation

in pure water and subsequently in an aqueous methanol(10 vol) solution

23 Photocatalyst Characterization The crystalline phases ofthe prepared photocatalysts were determined using a powderX-ray diffraction (XRD) (Rigaku RINT2200 Japan) Themorphology of the prepared photocatalysts was analyzed bya scanning electron microscopy (SEM) (JEOL JSM-5600Japan)The specific surface area of the prepared photocatalystwas measured using a BET surface area analyzer (CoulterSA3100 USA)

24 Photocatalytic Removal of MC-LR The photocatalyticdegradation of MC-LR by prepared WO

3-based photocat-

alyst was performed in a 6mL glass vessel placed on amagnetic stirrer A simulated solar lamp (XC-100B SERICLtd Japan) equipped axially at the center region above theglass vessel was employed as the irradiation source In thepresent experiments pure WO

3and the developed three

types of WO3-based photocatalysts (CuOWO

3 PdWO

3

and PtWO3) were previously dispersed in water using an

ultrasonic bath sonicator for 30minThen the photocatalystsdispersed solutions were transferred to the glass vesselscontaining MC-LR to obtain a final volume of 5mL TheinitialMC-LR concentration in each glass vessel was 1mg Lminus1Before irradiation the suspension was magnetically stirredfor 60min in the dark to achieve adsorption equilibriumAfter that the lamp was switched on to initiate the photo-catalytic reaction Temperature of the whole laboratory wascontrolled at 25 plusmn 1∘C by an air conditioner In addition amini-air-circulator was also employed near to the reactor tomake sure constant local temperature during the photocat-alytic reaction exists During irradiation 025mL of samplewas withdrawn at a time interval of 30min centrifuged at10000 rpm for 10min and filtered through a 022 120583m filtermembrane before the HPLC analysis

The concentration of MC-LR was measured using ahigh performance liquid chromatography (HPLC) (Jasco-1500 Jasco Japan) equipped with a high-resolution diodearray detector (Jasco UV-1570) set at 238 nm Samples wereseparated on a C18 column (46 times 250mm 5 120583m) using amixture of acetonitrile and 005M phosphate buffer (pH 6832 68 vv) as the mobile phase at a flow rate of 1mLminminus1All the experiments were replicated three times under thesame conditions and the average value was used for analyses

25 Detection of Hydroxyl Radicals (∙119874119867) The detectionof hydroxyl radicals generated by the prepared WO

3-based

photocatalysts was carried out according to Ishibashi et al[26] Terephthalic acid was used as a probe molecule todetect the photogenerated ∙OH radicals in the photocatalyticreaction system A sample of 4mg developed WO

3-based

photocatalyst powderwas dispersed in a 20mL solutionmadeof terephthalic acid at 5 times 10minus4M dissolved in a 2 times 10minus3MNaOH aqueous solution The simulated solar light was usedas an irradiation source During the irradiation samples werewithdrawn and centrifuged at a 20min time interval Then

The Scientific World Journal 3

10 20 30 40 50 60 70

Inte

nsity

2120579 (deg)

(a)

(b)

(c)

(d)

Figure 1 XRD patterns of WO3and modified WO

3samples (a)

PdWO3 (b) PtWO

3 (c) CuOWO

3 and (d) pure WO

3

the centrifuged solution was transferred in a quartz cell andthe photoluminescence spectra of 2-hydroxyterephthalic acidgenerated by the reaction of terephthalic acid with ∙OHweremeasured on aHitachi F-4500 fluorescence spectrophotome-terThe spectrawere recorded between 350 and 550 nmunderan excitation at 315 nm

3 Results and Discussion

31 Characterization of WO3-Based Photocatalysts The crys-

talline phases of the developed WO3-based photocatalysts

were measured by a powder X-ray diffraction (XRD) (RigakuRINT2200 Japan) Characteristic peaks are observed forall diffraction patterns which are indexed to the standardcard (JCPDS 43-1035) As shown in Figure 1 all sampleshave monoclinic WO

3structure and the metal doping does

not influence the crystal structures of WO3 No extra peaks

except for monoclinic WO3are observed (Figure 1) This

phenomenon can be explained by the small amount ofCuO Pd and Pt species content and high dispersion in thesamples

The morphology and microstructure of the developedphotocatalysts were analyzed by scanning electron micros-copy (SEM) (Figure 2)The SEM images of pure andmodifiedWO3photocatalysts showed that they are composed of

particles with size ranging from 100 to 200 nm The specificsurface area of the pure WO

3was about 5m2 gminus1 which is in

agreement with other reports [22] The specific surface areaof modified WO

3photocatalysts (CuOWO

3 PdWO

3 and

PtWO3) was slightly increased to 60 65 and 70m2 gminus1

respectively due to the metals loading and a grind of WO3

powders in the preparation process

32 Photocatalytic Removal of MC-LR Using Various WO3-

Based Photocatalysts As shown in Figure 3 the concentra-tion of MC-LR was virtually unchanged after 180min solarlight irradiation when there was no photocatalyst in the solu-tionThis result indicated that MC-LR was stable under solar

light irradiation After 180min photocatalysis approximately248 of MC-LR was removed from the aqueous solution inwhich only pure WO

3was added The modified WO

3-based

photocatalysts (CuOWO3and PdWO

3) achieved 314 and

429 MC-LR removal respectively The PtWO3composite

achieved a 100 degradation of MC-LR after 180min solarlight irradiationThemodifiedWO

3-based photocatalysts are

supported by many previous researches Arai et al reportedthat the photocatalytic activity of PdWO

3was 2 times higher

than that of CuOWO3in the degradation of acetaldehyde

and the performance of PtWO3was better than that of

CuOWO3for decomposing formaldehyde [22 23] In this

present study PtWO3exhibits the best photocatalytic per-

formance for the degradation of MC-LR under solar lightirradiation

33 The Mechanism of MC-LR Degradation by WO3-Based

Photocatalysts The relative more positive conduction bandlevel of WO

3(+05 V versus NHE) compared to potential for

the single-electron reduction of oxygen (O2O2

minus= minus056V

versus NHE O2HO2= minus013 V versus NHE) was the main

reason for the relative slow reaction rate of WO3-induced

photocatalytic reactions In the presence of CuO Pd and Ptthe reduction of O

2molecules can be promoted effectively

by a multielectron process (O2H2O2= +068V versus NHE

O2H2O = +123V versus NHE) [22 27] In a photocatalytic

reaction the following chain reactions have been postu-lated

Catalyst + ℎV 997888rarr eminus + h+ (1)

O2+ 2eminus + 2H+ 997888rarr H

2O2

(2)

H2O2997888rarr 2 ∙OH (3)

H2O + h+ 997888rarr ∙OH +H+ (4)

Photocatalytic degradation ofMC-LRwas initiated by theattack of hydroxyl radical (∙OH) on the conjugated dienestructure of ADDA [28] indicating the primary reactivespecies inMC-LR degradation is ∙OH radicalThe photogen-erated ∙OH radicals can be detected by photoluminescencespectra analysis Figure 4 shows the photoluminescent spec-tral changes of PtWO

3during 60min solar light irradiation

At the wavelength of 425 nm the photoluminescence inten-sity gradually increased from 25 to 438 au with increasingthe irradiation time to 60min indicating that ∙OH radicalswere generated on the photocatalyst-water interface viaphotocatalytic reactions [26 27]

Figure 5 presents the photoluminescence intensity of pureWO3and modified WO

3-based photocatalysts at 425 nm

as a function of irradiation time The photoluminescenceintensity induced by simulated solar light in terephthalicacid solution was linearly related to the irradiation time Thenumber of ∙OH radicals generated on the surface of thesephotocatalysts was proportional to the irradiation time andfollowed zero-order kinetic model [26 28] Furthermore theslopes of the regression lines represent the generation rateof ∙OH radicals (Figure 5) Without a dopant WO

3could


CuO

(a)

Pd

(b)

Pt

(c) (d)

Figure 2 SEM images of WO3and modified WO

3samples (a) CuOWO

3 (b) PdWO

3 (c) PtWO

3 and (d) pure WO

3

Control

0

10

20

30

40

50

60

70

80

90

100

0 15 30 45 60 75 90 105 120 135 150 165 180Irradiation time (min)

WO3

CuOWO3

PdWO3PtWO3

MC-

LR re

mov

ed(

)

Figure 3 The effect of catalysts on the efficiency of photocatalyticdegradation of MC-LR (Experimental conditions MC-LR concen-tration of 1mg Lminus1 catalyst concentration of 100mg Lminus1 and simu-lated solar light intensity of 04mWcmminus2)

only generate a small number of ∙OH radicals under solarlight irradiation The generation rate of ∙OH radicals on thesurface of pure WO

3is merely 004 auminminus1 When doped

with CuO Pd and Pt the generation rate of ∙OH radicalson WO

3surface was obviously enhanced During 60min

solar light irradiation PtWO3achieved the highest gener-

ation rate (072 auminminus1) of ∙OH radicals which was muchhigher than those byCuOWO

3(017 auminminus1) andPdWO

3

(042 auminminus1) Since the photocatalytic degradation ofMC-LR was initiated by the attack of ∙OH radical PtWO

3

seems to be the most promising photocatalyst for MC-LRremoval due to its higher generation rate of ∙OH radicalsTherefore in the following part PtWO

3was selected as the

photocatalyst forMC-LR removal under simulated solar lightirradiation

34 Kinetic Analysis in a Range of Light Intensities The kinet-ics of photocatalytic oxidation for MC-LR were analyzedusing Langmuir-Hinshelwood (L-H) model expressed as fol-lows

119903 =119889119862

119889119905=119896119870119862

(1 + 119870119862) (5)


0

5

10

15

20

25

30

35

40

45

50

350 375 400 425 450 475 500 525 550

Fluo

resc

ence

inte

nsity

(au

)

Wavelength (nm)

min20

40min60min

min0

Figure 4 Photoluminescence spectral changes observed duringirradiation of the PtWO

3sample (Experimental conditions NaOH

concentration of 2 times 10minus3M terephthalic acid concentration of 5 times10minus4M PtWO

3concentration of 200mg Lminus1 and simulated solar

light intensity of 04mWcmminus2)

Since119870119862 is much less than 1 if neglecting the term of119870119862 theL-H model can be simplified to a pseudo-first-order kineticequation

ln(1198620

119862) = 119896119870119905 = 119896app119905 (6)

where 119903 is the reaction rate (mg Lminus1minminus1) 1198620is the initial

concentration of MC-LR after dark adsorption (mg Lminus1) 119862is the concentration of MC-LR at time 119905 (mg Lminus1) 119905 is theirradiation time (min) 119896 is the reaction rate constant (minminus1)119870 is the adsorption coefficient of MC-LR on a photocatalystparticle (Lmgminus1) and 119896app is the apparent rate constant forthe photocatalytic degradation of MC-LR

The kinetic curves for the degradation of MC-LR byPtWO

3under various intensities of solar light irradiation

are shown in Figure 6 The correlation coefficient (1198772) valuesof linear regression in all the cases are greater than 099which confirms the photocatalytic degradation of MC-LR byPtWO

3under simulated solar light well follows the pseudo-

first-order kinetic equation The corresponding 119896app valuesof MC-LR degradation were 0148 0196 and 0241minminus1under 02 04 and 08mWcmminus2 solar light irradiationrespectively At higher intensity of solar irradiation moreelectron-hole pairs were expected to generate on photo-catalyst surface resulting in the enhancement of MC-LRdegradation According to Ohko et al [29] if photocatalyticreaction proceeded under purely light-limited conditionsthe degradation rate would depend on adsorbed photonnumbers (light intensity) linearly In this present study anonlinear relationship of photodegradation rate with lightintensity was observed (figure was not shown) that seemingly

Fluo

resc

ence

inte

nsity

(au

)

0

5

10

15

25

20

30

35

40

45

50

0 10 20 30 40 50 60Irradiation time (min)

WO3

CuOWO3PdWO3PtWO3

y = 0041x + 168 R2 = 0993

y = 0165x + 148 R2 = 0989y = 0417x + 128 R2 = 0998

y = 0720x + 175 R2 = 0996

Figure 5 Photoluminescence intensity of pure WO3and modified

WO3-based photocatalysts as a function of irradiation time (Exper-

imental conditions NaOH concentration of 2 times 10minus3M tereph-thalic acid concentration of 5 times 10minus4M catalyst concentration of200mg Lminus1 and simulated solar light intensity of 04mWcmminus2)

00

05

10

15

20

25

30

35

40

0 15 30 45 60 75 90 105 120 135 150Irradiation time (min)

Ln(C

0C

)

y = 0015x + 0013 R2 = 0999

y = 0020x + 0057 R2 = 0999

y = 0024x + 0149 R2 = 0994

02mW cmminus2

04mW cmminus2

08mW cmminus2

Figure 6 Efficiency of photocatalytic degradation of MC-LR as afunction of light intensity (Experimental conditions MC-LR con-centration of 1mg Lminus1 and PtWO

3concentration of 100mg Lminus1)

implies the photocatalytic reaction proceeded under a light-rich condition In that case the surface adsorptive property ofphotocatalyst has a major influence on the photodegradationrate Although MC-LR concentration showed a very slightdecrease during 60min dark adsorption (removal rate wasless than 5) a systematic study on the effects of initial


Control

0

10

20

30

40

50

60

70

80

90

100

0 15 30 45 60 75 90 105 120Irradiation time (min)

MC-

LR re

mov

ed(

)

[Clminus] = 002mM[Clminus] = 01mM[Clminus] = 02mM

Figure 7 Efficiency of photocatalytic degradation of MC-LR as afunction of Clminus concentration (Experimental conditions MC-LRconcentration of 1mg Lminus1 PtWO

3concentration of 100mg Lminus1 and

simulated solar light intensity of 04mWcmminus2)

MC-LR concentration should be carried out in the futureresearch That is helpful to understand clearly that the pho-todegradation proceeds under light-rich or light-limitedcondition Since the average intensity of natural solar light isgenerally 08mWcmminus2 PtWO

3appears to be a promising

photocatalyst for the degradation of MC-LR in practicalwater

35 Effect of Chloride Ion (Clminus) on the Photocatalytic Degrada-tion of MC-LR Sodium chloride (NaCl) was introduced intothe reaction solution at different concentrations to investigatethe effect of Clminus on the photocatalytic degradation ofMC-LRAs shown in Figure 7 withoutClminus addition about 886MC-LR was removed after 120min solar light irradiation WithClminus addition at the concentration of 002mM the percentageremoval of MC-LR increased to 948 whereas the percent-age removal of MC-LR decreased to 798 and 742 whenthe Clminus concentrations were 01mM and 02mM respec-tively The results indicate that Clminus at proper concentrationcould enhance the photocatalytic degradation of MC-LRwhereas excessive Clminus could inhibit the degradation Thisphenomenon can be ascribed to the formation of Cl radicals(∙Cl) in the photocatalytic reaction systemWithClminus additionat an appropriate concentration the photogenerated holes onthe catalyst surface were scavenged by the Clminus ions to form∙Cl radicals [30 31] The ∙Cl radical is also a kind of highreactive species that can oxidize many organic substancesGuo et al reported that Clminus ions adsorbed on TiO

2surface

promoted the photocatalytic oxidation of propylene [32]However excessiveClminus ions can also scavenge ∙OHradicals toformCl

2molecules very quickly and the reactivity of Cl

2was

lower than that of ∙OH [33] Consequently when adding Clminus


Control

0

10

20

30

40

50

60

70

80

90

100

MC-

LR re

mov

ed(

)

Fe3+

Cu2+

Figure 8The effect of 02mMofmetal ions on the efficiency of pho-tocatalytic degradation of MC-LR (Experimental conditions MC-LR concentration of 1mg Lminus1 PtWO

3concentration of 100mg Lminus1

and simulated solar light intensity of 04mWcmminus2)

at an excessive concentration the Clminus ions began to scavenge∙OH radicals preferentially that decreased the photocatalyticdegradation of MC-LR

36 Effect of Metal Cations (Cu2+ and Fe3+) on the Photocat-alytic Degradation ofMC-LR The fast recombination of pho-togenerated electrons and holes on the catalyst surface is animportant factor that limits the photocatalytic degradationof organic substances Consequently to enhance the pho-tocatalytic activity of catalysts improving the separation ofphotogenerated electron-hole pairs is very essential Metalcations can be used as the scavengers of photogeneratedelectrons and seem to be an effect additive for suppressing therecombination of photogenerated electrons and holes Theenhanced photocatalytic activity of WO

3by addition of Cu2+

and Fe3+ in the reaction solution has been reported for thedegradation of various organic substances such as phenol andsucrose [34 35]

In order to investigate the effects of metal cations on pho-tocatalytic degradation of MC-LR Cu(NO

3)2and Fe(NO

3)3

were introduced into the reaction solutions at a concentrationof 02mM As shown in Figure 8 without metal cationsaddition about 876 MC-LR was removed after 120minsolar light irradiation In the presence of 02mM Cu2+ andFe3+ the percentage removal of MC-LR increased to 100and 947 respectively The addition of Cu2+ and Fe3+obviously enhanced the photocatalytic degradation of MC-LR under solar light irradiation

The possible mechanism for the enhanced photocata-lytic activity of PtWO

3by Cu2+ and Fe3+ addition can be

described as follows (1) The consumption of photogeneratedelectrons by the reduction of Cu2+ and Fe3+ ions suppressed


the recombination of electrons and holes that increased thenumber of ∙OH radicals in the reaction system (7) and (8)[36] In addition (2) the Cu2+ and Fe3+ can react with H

2O2

generated in a photo-Fenton reaction to produce additional∙OH radicals in the reaction system (9) and (10) Consider

Cu2+ + eminus 997888rarr Cu+ (7)

Fe3+ + eminus 997888rarr Fe2+ (8)

Cu+ +H2O2+H+ 997888rarr Cu2+ + ∙OH +HOminus (9)

Fe2+ +H2O2+H+ 997888rarr Fe3+ + ∙OH +HOminus (10)

Then the increased number of ∙OH radicals in the reactionsolution promoted the photocatalytic degradation of MC-LR [37 38] According to Irie et al [39] and Liu et al [40]electrons in the surface grafted Fe3+ and Cu2+ ions efficientlycause multielectron reduction of adsorbed O

2molecules to

achieve high quantum efficiency value Therefore the H2O2

produced during themultielectron reduction ofO2molecules

also promoted the photodegradation of MC-LR in aqueoussolution

37 Photocatalytic Degradation Pathway of MC-LR The deg-radation pathway of MC-LR through photocatalytic reactionhas been in detail reported by Su et al [41] As shown inFigure 9 MC-LR is a relatively large molecule with a cyclo-structure which consists of a usual 20-carbon amino acid(ADDA) that expresses biological toxicity and an amino acidN-methyldehydroalanine (MDHA) The MC-LR moleculeis more readily attacked by ∙OH radicals at four sites ofthe toxin three on the ADDA chain ((A) aromatic ring(B) methoxy group and (C) conjugated double bonds) andone on the cyclic structure ((D) MDHA amino acid) [28]Among these the conjugated double bond (site (C)) at theADDA moiety of MC-LR molecule has been reported to besusceptible to photocatalytic attack [42 43] The destructionof MC-LR molecule by the attack of ∙OH radicals on thesesensitive sites leads to production of many kinds of interme-diate products which can be degraded to final products byfurther reaction with ∙OH radicals

In this present study although the complete removal ofMC-LR was obtained after 180min solar irradiation whenusing PtWO

3as photocatalyst less than 50of the totalMC-

LR was mineralizedThis can be attributed to the productionof many kinds of intermediates which are stable againstphotocatalytic destruction and do not undergo complete oxi-dation Since MC-LR was not completely mineralized itis important to confirm that the intermediate products arenontoxic Lawton et al [14] assessed the toxicity of intermedi-ates produced in photocatalytic degradation of MC-LR usingbrine shrimp bioassay method and they could not detect anymeasureable toxicity

4 Conclusions

A series of advanced WO3-based photocatalysts includ-

ing CuOWO3 PdWO

3 and PtWO

3were developed for

(A) (B)(C)

(D)

MeO

OO O

O

O

OO

HN

HN

HN

N

NH

NH

COOH

COOH

HN

HN

NH2

NH

Figure 9 The molecular structure of microcystin-LR and the mainattack sites ((A) benzene ring (B) methoxy group (C) conjugateddouble bond (D) unsaturated double bond of MDHA) of hydroxylradicals during photocatalytic reaction ADDA 3-amino-methoxy-10-phenyl-268-trimethyl-deca-46-dienoic acid

the photocatalytic removal of microcystin-LR (MC-LR)under simulated solar light irradiation In this present studywhen doped with CuO Pd and Pt the generation rateof ∙OH radicals on WO

3surface was obviously enhanced

PtWO3achieved the highest generation rate of ∙OH radicals

and exhibited the best photocatalytic performance for thedegradation of MC-LR under solar light irradiation Thephotocatalytic degradation ofMC-LR by PtWO

3under solar

light well followed the pseudo-first-order kinetic equationClminus addition at an appropriate concentration could enhancethe photocatalytic degradation of MC-LR by PtWO

3under

solar light irradiation The addition of Cu2+ and Fe3+ obvi-ously enhanced the photocatalytic degradation of MC-LRunder solar light irradiation The developed PtWO

3is a

promising photocatalyst for enhancing the photocatalyticremoval of recalcitrant organic compounds like MC-LR inwater under solar light irradiation

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

This work was supported in part by Grant-in-Aid forExploratory Research 26670901 and Scientific Research (A)22248075 from Japan Society for the Promotion of Science(JSPS)

References

[1] WW Carmichael ldquoCyanobacteria secondary metabolitesmdashthecyanotoxinsrdquo Journal of Applied Bacteriology vol 72 no 6 pp445ndash459 1992

[2] F Al Momani D W Smith and M Gamal El-Din ldquoDegrada-tion of cyanobacteria toxin by advanced oxidation processesrdquoJournal of Hazardous Materials vol 150 no 2 pp 238ndash2492008

[3] R E Honkanen J Zwiller R E Moore et al ldquoCharacterizationof microcystin-LR a potent inhibitor of type 1 and type 2A


protein phosphatasesrdquoThe Journal of Biological Chemistry vol265 no 32 pp 19401ndash19404 1990

[4] V M Vasconcelos and E Pereira ldquoCyanobacteria diversityand toxicity in a wastewater treatment plant (Portugal)rdquoWaterResearch vol 35 no 5 pp 1354ndash1357 2001

[5] KHimbergA-MKeijola LHiisvirtaH Pyysalo andK Sivo-nen ldquoThe effect of water treatment processes on the removal ofhepatotoxins fromMicrocystis andOscillatoria cyanobacteria alaboratory studyrdquo Water Research vol 23 no 8 pp 979ndash9841989

[6] S Takenaka and Y Tanaka ldquoBehavior of microcystins and itsdecomposition product in water treatment processrdquo Chemo-sphere vol 31 no 7 pp 3635ndash3641 1995

[7] C Shifu andC Gengyu ldquoPhotocatalytic degradation of organo-phosphorus pesticides using floating photocatalyst TiO

2sdot SiO2

beads by sunlightrdquo Solar Energy vol 79 no 1 pp 1ndash9 2005[8] M Sharon B Pal and D V Kamat ldquoPhotocatalytic killing

of pathogenic bacterial cells using nanosize Fe2O3and carbon

nanotubesrdquo Journal of Biomedical Nanotechnology vol 1 no 4pp 365ndash368 2005

[9] M C Lopez M I Fernandez S Rodrıguez J A SantaballaS Steenken and E Vulliet ldquoMechanisms of direct and TiO

2-

photocatalysed UV degradation of phenylurea herbicidesrdquoChemPhysChem vol 6 no 10 pp 2064ndash2074 2005

[10] T Arai M Yanagida Y Konishi Y Iwasaki H Sugihara and KSayama ldquoEfficient complete oxidation of acetaldehyde into CO

2

over CuBi2O4WO

3composite photocatalyst under visible and

UV light irradiationrdquo The Journal of Physical Chemistry C vol111 no 21 pp 7574ndash7577 2007

[11] M Miyauchi ldquoPhotocatalysis and photoinduced hydrophilicityof WO

3thin films with underlying Pt nanoparticlesrdquo Physical

Chemistry Chemical Physics vol 10 no 41 pp 6258ndash6265 2008[12] U I Gaya and A H Abdullah ldquoHeterogeneous photocatalytic

degradation of organic contaminants over titanium dioxide areview of fundamentals progress and problemsrdquo Journal of Pho-tochemistry and Photobiology C Photochemistry Reviews vol 9no 1 pp 1ndash12 2008

[13] N Genc ldquoPhotocatalytic oxidation of a reactive azo dye andevaluation of the biodegradability of photocatalytically treatedand untreated dyerdquoWater SA vol 30 no 3 pp 399ndash405 2004

[14] L A Lawton P K J Robertson B J P A Cornish and MJaspars ldquoDetoxification of microcystins (cyanobacterial hepa-totoxins) using TiO

2photocatalytic oxidationrdquo Environmental

Science and Technology vol 33 no 5 pp 771ndash775 1999[15] I Liu L A Lawton D W Bahnemann and P K J Robertson

ldquoThe photocatalytic destruction of the cyanotoxin nodularinusing TiO

2rdquoApplied Catalysis B Environmental vol 60 no 3-4

pp 245ndash252 2005[16] Z-G Zhao and M Miyauchi ldquoNanoporous-walled tungsten

oxide nanotubes as highly active visible-light-driven photocat-alystsrdquo Angewandte Chemie vol 47 no 37 pp 7051ndash7055 2008

[17] O Akhavan and E Ghaderi ldquoSelf-accumulated Ag nanoparti-cles on mesoporous TiO

2thin film with high bactericidal activ-

itiesrdquo Surface and Coatings Technology vol 204 no 21-22 pp3676ndash3683 2010

[18] O Akhavan ldquoLasting antibacterial activities of Ag-TiO2Aga-

TiO2nanocomposite thin film photocatalysts under solar light

irradiationrdquo Journal of Colloid and Interface Science vol 336 no1 pp 117ndash124 2009

[19] J Zhang H Zhu S Zheng F Pan and T Wang ldquoTiO2Film

Cu2O microgrid heterojunction with photocatalytic activity

under solar light irradiationrdquo Applied Materials and Interfacesvol 1 no 10 pp 2111ndash2114 2009

[20] Y Lv L Yu H Huang H Liu and Y Feng ldquoPreparationcharacterization of P-doped TiO

2nanoparticles and their excel-

lent photocatalystic properties under the solar light irradiationrdquoJournal of Alloys and Compounds vol 488 no 1 pp 314ndash3192009

[21] R Abe H Takami N Murakami and B Ohtani ldquoPristine sim-ple oxides as visible light driven photocatalysts highly efficientdecomposition of organic compounds over platinum-loadedtungsten oxiderdquo Journal of the American Chemical Society vol130 no 25 pp 7780ndash7781 2008

[22] T Arai M Horiguchi M Yanagida T Gunji H Sugihara andK Sayama ldquoComplete oxidation of acetaldehyde and tolueneover a PdWO

3photocatalyst under fluorescent- or visible-light

irradiationrdquo Chemical Communications no 43 pp 5565ndash55672008

[23] T Arai M Yanagida Y Konishi Y Iwasaki H Sugihara andK Sayama ldquoPromotion effect of CuO co-catalyst on WO

3-

catalyzed photodegradation of organic substancesrdquo CatalysisCommunications vol 9 no 6 pp 1254ndash1258 2008

[24] L Li and Y Liu ldquoAmmonia removal in electrochemical oxi-dation mechanism and pseudo-kineticsrdquo Journal of HazardousMaterials vol 161 no 2-3 pp 1010ndash1016 2009

[25] Y Liu Y Ohko R Zhang Y Yang and Z Zhang ldquoDegradationof malachite green on PdWO

3photocatalysts under simulated

solar lightrdquo Journal of Hazardous Materials vol 184 no 1ndash3 pp386ndash391 2010

[26] K-I Ishibashi A Fujishima T Watanabe and K HashimotoldquoDetection of active oxidative species in TiO

2photocatalysis

using the fluorescence techniquerdquo Electrochemistry Communi-cations vol 2 no 3 pp 207ndash210 2000

[27] Q Xiao Z Si J Zhang C Xiao and X Tan ldquoPhotoinducedhydroxyl radical andphotocatalytic activity of samarium-dopedTiO2nanocrystallinerdquo Journal of Hazardous Materials vol 150

no 1 pp 62ndash67 2008[28] I Liu L A Lawton and P K J Robertson ldquoMechanistic studies

of the photocatalytic oxidation of microcystin-LR an investiga-tion of byproducts of the decomposition processrdquo Environmen-tal Science and Technology vol 37 no 14 pp 3214ndash3219 2003

[29] Y Ohko K Hashimoto and A Fujishima ldquoKinetics of pho-tocatalytic reactions under extremely low-intensity UV illumi-nation on titanium dioxide thin filmsrdquo The Journal of PhysicalChemistry A vol 101 no 43 pp 8057ndash8062 1997

[30] G Munuera A Navio J Soria and A R Gonzalez-elipeldquoPhoto-adsorption of oxygen on chlorinated TiO

2surfaces a

possible way to photo-oxy-chlorinationsrdquo in Studies in SurfaceScience and Catalysis T Seiyama and K Tanabe Eds vol 7 pp1185ndash1197 1981

[31] S Kutsuna Y Ebihara K Nakamura and T Ibusuki ldquoHetero-geneous photochemical reactions between volatile chlorinatedhydrocarbons (trichloroethene and tetrachloroethene) and tita-nium dioxiderdquoAtmospheric Environment A General Topics vol27 no 4 pp 599ndash604 1993

[32] J Guo L Mao J Zhang and C Feng ldquoRole of Clminus ions inphotooxidation of propylene on TiO

2surfacerdquo Applied Surface

Science vol 256 no 7 pp 2132ndash2137 2010[33] H-C Liang X-Z Li Y-H Yang and K-H Sze ldquoEffects of

dissolved oxygen pH and anions on the 23-dichlorophenoldegradation by photocatalytic reaction with anodic TiO

2nan-

otube filmsrdquo Chemosphere vol 73 no 5 pp 805ndash812 2008


[34] T Arai M Yanagida Y Konishi H Sugihara and K SayamaldquoUtilization of Fe3+Fe2+ redox for the photodegradation oforganic substances overWO

3photocatalyst and for H

2produc-

tion from the electrolysis of waterrdquo Electrochemistry vol 76 no2 pp 128ndash131 2008

[35] D Beydoun H Tse R Amal G Low and S McEvoy ldquoEffectof copper(II) on the photocatalytic degradation of sucroserdquoJournal of Molecular Catalysis A Chemical vol 177 no 2 pp265ndash272 2002

[36] M D Ward and A J Bard ldquoPhotocurrent enhancement viatrapping of photogenerated electrons of TiO

2particlesrdquo Journal

of Physical Chemistry vol 86 no 18 pp 3599ndash3605 1982[37] K Okamoto Y Yamamoto H Tanaka M Tanaka and A Itaya

ldquoHeterogeneous photocatalytic decomposition of phenol overTiO2powderrdquo Bulletin of the Chemical Society of Japan vol 58

no 7 pp 2015ndash2022 1985[38] T Y Wei and C C Wan ldquoKinetics of photocatalytic oxidation

of phenol on TiO2surfacerdquo Journal of Photochemistry and Pho-

tobiology A Chemistry vol 69 no 2 pp 241ndash249 1992[39] H Irie S Miura K Kamiya and K Hashimoto ldquoEfficient

visible light-sensitive photocatalysts Grafting Cu(II) ions ontoTiO2and WO

3photocatalystsrdquo Chemical Physics Letters vol

457 no 1ndash3 pp 202ndash205 2008[40] M Liu X Qiu M Miyauchi and K Hashimoto ldquoEnergy-level

matching of Fe(III) ions grafted at surface and doped in bulkfor efficient visible-light photocatalystsrdquo Journal of theAmericanChemical Society vol 135 no 27 pp 10064ndash10072 2013

[41] Y Su Y Deng and Y Du ldquoAlternative pathways for photo-catalytic degradation of microcystin-LR revealed by TiO

2nan-

otubesrdquo Journal of Molecular Catalysis A Chemical vol 373 pp18ndash24 2013

[42] M Welker and C Steinberg ldquoRates of humic substance pho-tosensitized degradation of microcystin-LR in natural watersrdquoEnvironmental Science and Technology vol 34 no 16 pp 3415ndash3419 2000

[43] P Chen L Zhu S Fang CWang and G Shan ldquoPhotocatalyticdegradation efficiency and mechanism of microcystin-RR bymesoporous Bi

2WO6under near ultraviolet lightrdquo Environmen-

tal Science amp Technology vol 46 no 4 pp 2345ndash2351 2012

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


could effectively destroy MCs even at extremely high toxinconcentrations [14 15] However TiO

2has a large band gap

energy (119864119892) of 32 eV that restricts the wide use of this

photocatalyst because it can only absorb UV light whichaccounts for 5 of the solar light [16] Many efforts have beenmade to enhance the photocatalytic performance of TiO

2

under solar light For example Ag-modified TiO2thin film

was developed for bacteria disinfection under solar light [1718] TiO

2-filmCuO microgrid heterojunction and P-doped

TiO2nanoparticles were synthesized for the decomposition

of organic dye [19 20] By contrast tungsten trioxide (WO3)

can utilize solar light more effectively than TiO2 because it

has an 119864119892between 24 and 28 eV [10] In addition WO

3

is inexpensive to prepare and stable inlsquoacidic and oxidativeconditions whichmakes it a promisingmaterial for photocat-alytic applications Previous research showed that photocat-alytic degradation of organic pollutants such as organic dyesusingWO

3under solar lightwas intensified by the presence of

suitable dopants such as Pt Pd and CuO [21ndash23] Howeverthere is little research on the photocatalytic degradation ofMCs using WO

3-based photocatalysts under solar light

In the present study three types of WO3-based photo-

catalysts including CuOWO3 PdWO

3 and PtWO

3were

synthesized for photocatalytic degradation of MC-LR undersimulated solar light The characteristics of developed WO

3-

based photocatalysts were analyzed by BET surface area X-ray diffraction (XRD) and scanning electron microscopy(SEM) A series of batch experiments were carried out toevaluate the photocatalytic performance of the developedphotocatalysts forMC-LR degradation under simulated solarlight On the other hand chlorides and metal cations arecommon in water and they are important in many treatmenttechnologies such as breakpoint chlorination and electro-chemical oxidation methods [24] Therefore in this studythe effects of chloride ions (Clminus) and metal cations (Cu2+and Fe3+) on the photocatalytic degradation ofMC-LR undersolar light were also investigated

2 Experimental

21 Reagents WO3powder microcystin-LR (MC-LR) stan-

dard (ge95 purity FW 9952 gmolminus1) terephthalic acid99 and Cu(NO

3)2sdot3H2O (999 purity) were purchased

from Wako (Wako Pure Chemical Industries Ltd Japan)Hexachloroplatinic acid (H

2PtCl6sdot6H2O) and Pd powder

with a surface area of 40ndash60m2 gminus1 were supplied by Sigma-Aldrich (Sigma-Aldrich Co LLC USA)

22 Photocatalyst Preparation TheWO3loaded with 01 wt

CuO (marked as CuOWO3) was synthetized by an impreg-

nation method [21] Cu(NO3)2aqueous solution was mixed

with WO3powder and the mixture was dried on hot plate

and then calcined at 300∘C for 30min in airThe Pd doped WO

3photocatalyst (PdWO

3) was pre-

pared by themechanical mixing of Pd (wt versusWO3) and

WO3in a ceramic mortar [25]

The Pt modified WO3sample (PtWO

3) was developed

using a photodeposition method [21] from H2PtCl6sdot6H2O

on the fine particulate WO3under visible light irradiation

in pure water and subsequently in an aqueous methanol(10 vol) solution

23 Photocatalyst Characterization The crystalline phases ofthe prepared photocatalysts were determined using a powderX-ray diffraction (XRD) (Rigaku RINT2200 Japan) Themorphology of the prepared photocatalysts was analyzed bya scanning electron microscopy (SEM) (JEOL JSM-5600Japan)The specific surface area of the prepared photocatalystwas measured using a BET surface area analyzer (CoulterSA3100 USA)

24 Photocatalytic Removal of MC-LR The photocatalyticdegradation of MC-LR by prepared WO

3-based photocat-

alyst was performed in a 6mL glass vessel placed on amagnetic stirrer A simulated solar lamp (XC-100B SERICLtd Japan) equipped axially at the center region above theglass vessel was employed as the irradiation source In thepresent experiments pure WO

3and the developed three

types of WO3-based photocatalysts (CuOWO

3 PdWO

3

and PtWO3) were previously dispersed in water using an

ultrasonic bath sonicator for 30minThen the photocatalystsdispersed solutions were transferred to the glass vesselscontaining MC-LR to obtain a final volume of 5mL TheinitialMC-LR concentration in each glass vessel was 1mg Lminus1Before irradiation the suspension was magnetically stirredfor 60min in the dark to achieve adsorption equilibriumAfter that the lamp was switched on to initiate the photo-catalytic reaction Temperature of the whole laboratory wascontrolled at 25 plusmn 1∘C by an air conditioner In addition amini-air-circulator was also employed near to the reactor tomake sure constant local temperature during the photocat-alytic reaction exists During irradiation 025mL of samplewas withdrawn at a time interval of 30min centrifuged at10000 rpm for 10min and filtered through a 022 120583m filtermembrane before the HPLC analysis

The concentration of MC-LR was measured using ahigh performance liquid chromatography (HPLC) (Jasco-1500 Jasco Japan) equipped with a high-resolution diodearray detector (Jasco UV-1570) set at 238 nm Samples wereseparated on a C18 column (46 times 250mm 5 120583m) using amixture of acetonitrile and 005M phosphate buffer (pH 6832 68 vv) as the mobile phase at a flow rate of 1mLminminus1All the experiments were replicated three times under thesame conditions and the average value was used for analyses

25 Detection of Hydroxyl Radicals (∙119874119867) The detectionof hydroxyl radicals generated by the prepared WO

3-based

photocatalysts was carried out according to Ishibashi et al[26] Terephthalic acid was used as a probe molecule todetect the photogenerated ∙OH radicals in the photocatalyticreaction system A sample of 4mg developed WO

3-based

photocatalyst powderwas dispersed in a 20mL solutionmadeof terephthalic acid at 5 times 10minus4M dissolved in a 2 times 10minus3MNaOH aqueous solution The simulated solar light was usedas an irradiation source During the irradiation samples werewithdrawn and centrifuged at a 20min time interval Then


10 20 30 40 50 60 70

Inte

nsity

2120579 (deg)

(a)

(b)

(c)

(d)


3samples (a)

PdWO3 (b) PtWO

3 (c) CuOWO

3 and (d) pure WO

3















3 PdWO

3 and








3-based


3) achieved 314 and





3was 2 times higher










minus= minus056V










2O2

(2)

H2O2997888rarr 2 ∙OH (3)

H2O + h+ 997888rarr ∙OH +H+ (4)







3could


CuO

(a)

Pd

(b)

Pt

(c) (d)


3samples (a) CuOWO

3 (b) PdWO

3 (c) PtWO

3 and (d) pure WO

3

Control

0

10

20

30

40

50

60

70

80

90

100


WO3

CuOWO3

PdWO3PtWO3

MC-

LR re

mov

ed(

)









3


3





119903 =119889119862

119889119905=119896119870119862

(1 + 119870119862) (5)


0

5

10

15

20

25

30

35

40

45

50

350 375 400 425 450 475 500 525 550

Fluo

resc

ence

inte

nsity

(au

)

Wavelength (nm)

min20

40min60min

min0







ln(1198620

119862) = 119896119870119905 = 119896app119905 (6)








Fluo

resc

ence

inte

nsity

(au

)

0

5

10

15

25

20

30

35

40

45

50


WO3

CuOWO3PdWO3PtWO3

y = 0041x + 168 R2 = 0993

y = 0165x + 148 R2 = 0989y = 0417x + 128 R2 = 0998

y = 0720x + 175 R2 = 0996




00

05

10

15

20

25

30

35

40


Ln(C

0C

)

y = 0015x + 0013 R2 = 0999

y = 0020x + 0057 R2 = 0999

y = 0024x + 0149 R2 = 0994

02mW cmminus2

04mW cmminus2

08mW cmminus2





Control

0

10

20

30

40

50

60

70

80

90

100


MC-

LR re

mov

ed(

)









2surface



2was



Control

0

10

20

30

40

50

60

70

80

90

100

MC-

LR re

mov

ed(

)

Fe3+

Cu2+









3)2and Fe(NO

3)3







2O2







2molecules to








4 Conclusions


ing CuOWO3 PdWO

3 and PtWO

3were developed for

(A) (B)(C)

(D)

MeO

OO O

O

O

OO

HN

HN

HN

N

NH

NH

COOH

COOH

HN

HN

NH2

NH






3under solar


3under


3is a




Acknowledgment


References










2sdot SiO2





2-



2

over CuBi2O4WO
































3-







2photocatalysis







2surfaces a







2nan-





2produc-















2nan-













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




10 20 30 40 50 60 70

Inte

nsity

2120579 (deg)

(a)

(b)

(c)

(d)


3samples (a)

PdWO3 (b) PtWO

3 (c) CuOWO

3 and (d) pure WO

3















3 PdWO

3 and








3-based


3) achieved 314 and





3was 2 times higher










minus= minus056V










2O2

(2)

H2O2997888rarr 2 ∙OH (3)

H2O + h+ 997888rarr ∙OH +H+ (4)







3could


CuO

(a)

Pd

(b)

Pt

(c) (d)


3samples (a) CuOWO

3 (b) PdWO

3 (c) PtWO

3 and (d) pure WO

3

Control

0

10

20

30

40

50

60

70

80

90

100


WO3

CuOWO3

PdWO3PtWO3

MC-

LR re

mov

ed(

)









3


3





119903 =119889119862

119889119905=119896119870119862

(1 + 119870119862) (5)


0

5

10

15

20

25

30

35

40

45

50

350 375 400 425 450 475 500 525 550

Fluo

resc

ence

inte

nsity

(au

)

Wavelength (nm)

min20

40min60min

min0







ln(1198620

119862) = 119896119870119905 = 119896app119905 (6)








Fluo

resc

ence

inte

nsity

(au

)

0

5

10

15

25

20

30

35

40

45

50


WO3

CuOWO3PdWO3PtWO3

y = 0041x + 168 R2 = 0993

y = 0165x + 148 R2 = 0989y = 0417x + 128 R2 = 0998

y = 0720x + 175 R2 = 0996




00

05

10

15

20

25

30

35

40


Ln(C

0C

)

y = 0015x + 0013 R2 = 0999

y = 0020x + 0057 R2 = 0999

y = 0024x + 0149 R2 = 0994

02mW cmminus2

04mW cmminus2

08mW cmminus2





Control

0

10

20

30

40

50

60

70

80

90

100


MC-

LR re

mov

ed(

)









2surface



2was



Control

0

10

20

30

40

50

60

70

80

90

100

MC-

LR re

mov

ed(

)

Fe3+

Cu2+









3)2and Fe(NO

3)3







2O2







2molecules to








4 Conclusions


ing CuOWO3 PdWO

3 and PtWO

3were developed for

(A) (B)(C)

(D)

MeO

OO O

O

O

OO

HN

HN

HN

N

NH

NH

COOH

COOH

HN

HN

NH2

NH






3under solar


3under


3is a




Acknowledgment


References










2sdot SiO2





2-



2

over CuBi2O4WO
































3-







2photocatalysis







2surfaces a







2nan-





2produc-















2nan-













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




CuO

(a)

Pd

(b)

Pt

(c) (d)


3samples (a) CuOWO

3 (b) PdWO

3 (c) PtWO

3 and (d) pure WO

3

Control

0

10

20

30

40

50

60

70

80

90

100


WO3

CuOWO3

PdWO3PtWO3

MC-

LR re

mov

ed(

)









3


3





119903 =119889119862

119889119905=119896119870119862

(1 + 119870119862) (5)


0

5

10

15

20

25

30

35

40

45

50

350 375 400 425 450 475 500 525 550

Fluo

resc

ence

inte

nsity

(au

)

Wavelength (nm)

min20

40min60min

min0







ln(1198620

119862) = 119896119870119905 = 119896app119905 (6)








Fluo

resc

ence

inte

nsity

(au

)

0

5

10

15

25

20

30

35

40

45

50


WO3

CuOWO3PdWO3PtWO3

y = 0041x + 168 R2 = 0993

y = 0165x + 148 R2 = 0989y = 0417x + 128 R2 = 0998

y = 0720x + 175 R2 = 0996




00

05

10

15

20

25

30

35

40


Ln(C

0C

)

y = 0015x + 0013 R2 = 0999

y = 0020x + 0057 R2 = 0999

y = 0024x + 0149 R2 = 0994

02mW cmminus2

04mW cmminus2

08mW cmminus2





Control

0

10

20

30

40

50

60

70

80

90

100


MC-

LR re

mov

ed(

)









2surface



2was



Control

0

10

20

30

40

50

60

70

80

90

100

MC-

LR re

mov

ed(

)

Fe3+

Cu2+









3)2and Fe(NO

3)3







2O2







2molecules to








4 Conclusions


ing CuOWO3 PdWO

3 and PtWO

3were developed for

(A) (B)(C)

(D)

MeO

OO O

O

O

OO

HN

HN

HN

N

NH

NH

COOH

COOH

HN

HN

NH2

NH






3under solar


3under


3is a




Acknowledgment


References










2sdot SiO2





2-



2

over CuBi2O4WO
































3-







2photocatalysis







2surfaces a







2nan-





2produc-















2nan-













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

5

10

15

20

25

30

35

40

45

50

350 375 400 425 450 475 500 525 550

Fluo

resc

ence

inte

nsity

(au

)

Wavelength (nm)

min20

40min60min

min0







ln(1198620

119862) = 119896119870119905 = 119896app119905 (6)








Fluo

resc

ence

inte

nsity

(au

)

0

5

10

15

25

20

30

35

40

45

50


WO3

CuOWO3PdWO3PtWO3

y = 0041x + 168 R2 = 0993

y = 0165x + 148 R2 = 0989y = 0417x + 128 R2 = 0998

y = 0720x + 175 R2 = 0996




00

05

10

15

20

25

30

35

40


Ln(C

0C

)

y = 0015x + 0013 R2 = 0999

y = 0020x + 0057 R2 = 0999

y = 0024x + 0149 R2 = 0994

02mW cmminus2

04mW cmminus2

08mW cmminus2





Control

0

10

20

30

40

50

60

70

80

90

100


MC-

LR re

mov

ed(

)









2surface



2was



Control

0

10

20

30

40

50

60

70

80

90

100

MC-

LR re

mov

ed(

)

Fe3+

Cu2+









3)2and Fe(NO

3)3







2O2







2molecules to








4 Conclusions


ing CuOWO3 PdWO

3 and PtWO

3were developed for

(A) (B)(C)

(D)

MeO

OO O

O

O

OO

HN

HN

HN

N

NH

NH

COOH

COOH

HN

HN

NH2

NH






3under solar


3under


3is a




Acknowledgment


References










2sdot SiO2





2-



2

over CuBi2O4WO
































3-







2photocatalysis







2surfaces a







2nan-





2produc-















2nan-













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Control

0

10

20

30

40

50

60

70

80

90

100


MC-

LR re

mov

ed(

)









2surface



2was



Control

0

10

20

30

40

50

60

70

80

90

100

MC-

LR re

mov

ed(

)

Fe3+

Cu2+









3)2and Fe(NO

3)3







2O2







2molecules to








4 Conclusions


ing CuOWO3 PdWO

3 and PtWO

3were developed for

(A) (B)(C)

(D)

MeO

OO O

O

O

OO

HN

HN

HN

N

NH

NH

COOH

COOH

HN

HN

NH2

NH






3under solar


3under


3is a




Acknowledgment


References










2sdot SiO2





2-



2

over CuBi2O4WO
































3-







2photocatalysis







2surfaces a







2nan-





2produc-















2nan-













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





2O2







2molecules to








4 Conclusions


ing CuOWO3 PdWO

3 and PtWO

3were developed for

(A) (B)(C)

(D)

MeO

OO O

O

O

OO

HN

HN

HN

N

NH

NH

COOH

COOH

HN

HN

NH2

NH






3under solar


3under


3is a




Acknowledgment


References










2sdot SiO2





2-



2

over CuBi2O4WO
































3-







2photocatalysis







2surfaces a







2nan-





2produc-















2nan-













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials









2sdot SiO2





2-



2

over CuBi2O4WO
































3-







2photocatalysis







2surfaces a







2nan-





2produc-















2nan-













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






2produc-















2nan-













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



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