research article facile preparation of phosphotungstic

Hindawi Publishing CorporationInternational Journal of PhotoenergyVolume 2013 Article ID 406158 9 pageshttpdxdoiorg1011552013406158

Research ArticleFacile Preparation of Phosphotungstic Acid-Impregnated YeastHybrid Microspheres and Their Photocatalytic Performance forDecolorization of Azo Dye

Lan Chen and Bo Bai

College of Environmental Science and Engineering Changrsquoan University Xirsquoan 710054 China

Correspondence should be addressed to Bo Bai baibochdeducn

Received 16 January 2013 Revised 9 April 2013 Accepted 9 April 2013

Academic Editor Elias Stathatos

Copyright copy 2013 L Chen and B Bai 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

Phosphotungstic acid (HPW)-impregnated yeast hybrid microspheres were prepared by impregnation-adsorption techniquethrough tuning pH of the aqueous yeast suspensionsThe obtained products were characterized by field emission scanning electronmicroscopy (FE-SEM) energy dispersive spectrometry (EDS) X-ray diffraction (XRD) thermogravimetry-differential scanningcalorimetry (TG-DSC) and ultraviolet-visible spectrophotometry (UV-Vis) respectively FE-SEMandEDS ascertain that theHPWhas been effectively introduced onto the surface of yeast and the resulting samples retain ellipsoid shape with the uniform size(length 45 plusmn 02120583m width 30 plusmn 03120583m) and good monodispersion XRD pattern indicates that the main crystal structure of as-synthesized HPWyeast microsphere is Keggin structure TG-DTA states that the HPW in composites has better thermal stabilitythan pureHPW Fourier transform infrared spectroscopy (FT-IR) elucidates that the functional groups or chemical bonds inheritedfrom the pristine yeast cell were critical to the assembling of the composites UV-Vis shows that the obtained samples have a goodresponding to UV lightThe settling ability indicates that the hybrid microspheres possess an excellent suspension performance Inthe test of catalytic activity the HPWyeast microsphere exhibits a high photocatalytic activity for the decoloration of Methyleneblue and Congo red dye aqueous solutions and there are a few activity losses after four cycles of uses

1 Introduction

Solid heteropoly acids (HPAs) a kind of environmental-friendly catalysts could replace liquid acids to minimize thepollution damage to the environment [1ndash3] Among variousHPAs structural classes Keggin-typeHPAs especiallyKegginphosphotungstic acid (H

3PW12O40 HPW) have strong acid-

ity and high conductivity [4] By thismeans a few of previousresearch studies have focused on the application of HPW forthe photodecomposition of various kinds of environmentalproblems through fully making use of its strong Broslashnstedacidity character redox properties and the quasiliquid prop-erties [5ndash9] Till now utilizing homogeneous HPA as pho-tocatalysts in the polluted aqueous solution is very common[10 11] However from a practical point of view it may notbe possible to employ this HPW as homogeneous reactionin photoreactor because of its easy solubility in polar solventwhich inevitably leads to an expensive and time-consuming

separation and recovery of photocatalysts from solvent [12]In addition the low specific surface area or low thermostabil-ity of HPA particles makes it difficult to improve its catalyticactivity effectively [13] To solve these problems a fewalternative strategies have been proposed to support HPWcatalysts on the surface of adsorbent substance For instanceGao et al [14] obtained carbonized resin-12-phosphotungsticacid (HPW) catalyst by employing carbonized resin as sup-port Wen et al [15] fabricated HPWSiO

2successfully by

using a series of SiO2as supports and further demonstrated

that the catalytic performance of HPWSiO2in alkylation

reactions remarkably depended on the properties of the silicasupport Obalı and Dogu [16] described the fabrication ofactivated carbon-tungstophosphoric acid catalysts via uti-lization of activated carbon as supports and the compositescatalysts have a better catalytic activity than pure HPW forthe synthesis of tert-amyl ethyl ether (TAEE) Yang et al [17]prepared H

3PW12O40MCM-48 composite photocatalyst by

2 International Journal of Photoenergy

loading phosphotungstic acid on the mesoporous MCM-48and the test of catalytic activity shows that the degradation ofmethyl orange aqueous solution could reach 8453

Recently yeasts as biotemplates or supports to synthesizecatalysts have attracted considerable attention For exampleHe et al [18] synthesized Cu

2O hollow spheres by employing

yeasts as biotemplates Weinziel et al [19] prepared SiO2

hollow particles using yeasts as biotemplates Our groups [20]obtained the raspberry-like TiO

2yeast composite photo-

catalysts successfully by exploiting yeasts as supports Tosum up a serial of excellent merits have been brought alongfor the obtained composite catalysts [21] Typical benefitsinclude the following (1) The tunable and uniform shape ofsupports can be easily achieved from the abundant microbialcells resources in nature (2) Additional surface modificationcan be left out due to the preexistence of functional groupsinherited from the hydrophilic cell wall of microbial cells(3) The composites using yeasts as supports have integratedproperties originating from their hybrid components whichrepresent a new style of economical and environmental-friendly catalysts [20]

Thus in the present work the phosphotungstic acid(HPW)-impregnated yeast (HPWyeast) hybrid micro-spheres were prepared by impregnation-adsorption tech-nique through tuning pH of the aqueous yeast suspensionsfirstly Then the obtained hybrid microspheres were charac-terized by SEM EDS XRD FT-IR and UV-Vis respectivelyA possible mechanism for the formation of the compositemicrospheres was proposed Moreover the photocatalyticactivities of HPWyeasts microspheres were evaluated byexamining the decolorization of Methylene blue and Congored The reusability of HPWyeast as catalyst was estimatedfurther

2 Experimental

21 Materials Yeast powder was purchased fromAngel YeastCo Analytical grade phosphotungstic acid (HPW) sulphuricacid (H

2SO4) was provided by Xirsquoan Chemical Agent Corp

and used without further purification Double distilled waterand absolute ethanol were used throughout the experimentalprocedures

22 Synthesis of HPWyeast HybridMicrosphere In a typicalsynthesis procedure 1000 g yeast powder was washed withdistilled water and ethanol for three times respectively Thewashed yeast was dispersed in 50mL of distilled water ThepH was adjusted to approximately 2-3 by adding dropwisesulphuric acid The suspension was magnetically stirred for30min to facilitate the dispersion of the yeast particles300mg HPW dissolved in 40mL ethanol was added tothe previously mentioned suspensions with constant stir-ring The mixture was continuously magnetically stirredfor 10 h at room temperature and then left for 3 h with-out further stirring or shaking to ensure the formation ofHPWyeast heterocoagulated particles Then the mixturewas collected by centrifugation followed by three cycles of

distilled water and ethanol rinsing to get filtrate precipita-tion and finally dried in drying oven at 60sim80∘C for 40minAfter that the HPWyeast composite microspheres wereobtained

23 Characterization of Samples X-ray diffraction (XRD)patterns of the samples were carried out on a RegakuDMAX-3C diffractometer operated at a voltage of 40 kVand a current of 20mA at a 002∘ scan rate with Cu K120572radiation Field-emission scanning electromicroscope (FE-SEM) images were taken on a JEOL-6300F field-emissionscanning electromicroscope with an accelerating voltageof 15 kV Fourier-transform infrared (FT-IR) spectroscopymeasurements were recorded with a Bruker TENSOR 27FT-IR spectrometer Thermal gravimetric analysis (TG) anddifferential scanning calorimetry (DSC) were performed ona HCT-2 apparatus at a heating rate of 10∘Cmin

24 The Setting Performance 0050 g HPWyeast micro-spheres were dispersed into 50mL of distilled water in avertical cylindrical burette at room temperature At regularintervals the falling height was determined The sedimenta-tion ratio (119877) was measured by

119877 =119886

119886 + 119887

times 100 (1)

where 119886 is the length of the clear fluid and 119887 is the length ofthe turbid fluid respectively

25 Catalytic Activity The photocatalytic activity of theprepared samples was evaluated by the photocatalytic decol-orization of anion dye Congo Red and cationic dyes Methy-lene Blue (MB) at room temperature The experimentalprocedure was as follows 100mg of the prepared powderswas dispersed in 100mL of MB aqueous solution with aconcentration of 12mgL in a beaker (with a capacity of150mL) and the suspensions were magnetically stirred inthe dark for 30min prior to irradiation with UV light TheUV-light lamp placed 7 cm above the beaker was used as alight source The concentration of MB aqueous solution wasdetermined by a UV-visible spectrophotometer (TU-4100)Before and after irradiation samples (6mL) were collectedat regular intervals Each sample was centrifuged to separatethe catalyst from the liquid and the supernatant was analyzedThe samples were returned into the reactor immediately aftereach analysis

In order to evaluate the reusability of the obtainedmicro-spheres in the photocatalytic processes the measurement ofthe lifetime of the HPWyeast was assessedThe experimen-tal procedure was the same as the photocatalytic activity testaforementioned The only difference is that the experimentwas operated four times In each experiment the catalystswere centrifuged and recovered from the photocatalyticsystem without other treatments that would be as catalyst forthe other photodegradation experiments

International Journal of Photoenergy 3

(a) (b)

(c) (d)

(e)

Figure 1 FE-SEM images of (a) yeast and (b c d and e) HPWyeast microspheres observed under different magnifications

3 Results and Discussion

31 FE-SEM and EDS The morphologies of yeast andHPWyeast particles under the different magnificationsare showed in Figure 1 Figure 1(a) displays that the mor-phology of the naked yeast washed with distilled waterand ethanol is approximately spherical with the diameterranging from 31 120583m to 41 120583m In Figures 1(b) and 1(c)the HPWyeast microspheres maintain shape of the prim-itive yeast with relatively good monodispersity From thehigh-magnification images in Figure 1(d) it is clearly seen

that each of microspheres has ordered elliptic shapes ofuniform size with the length of 45 plusmn 02 120583m and widthof 30 plusmn 02 120583m Compared with the naked yeast thediameter of the HPWyeast microspheres has increasedonly by a small amount which arises from the attach-ment of HPW particles onto the surface of yeast core Thehigher resolution picture of a single HPWyeast micro-sphere (Figure 1(e)) indicates that the surface of species hassmooth and continuous textural taints although part ofareas on the surface of the species still remains rough andunsmooth


Weight concentration ()

SamplesC

CO

O

P

P

S

0 1 2 3(keV)

S

W

Pure yeast 6512 3446 024 018 0HPWyeast 5207 3598 042 017 1136

(a)

C

O

PW

W

W P

0 1 2 3(keV)

S

(b)

Figure 2 EDS spectra of (a) bare yeast and (b) HPWyeast samples

10 20 30 40 50 60 70

2000

4000

6000

8000

Inte

nsity

(au

)

2120579 (deg)

(a)

10 20 30 40 50 60 70500055006000650070007500

Inte

nsity

(au

)

2120579 (deg)

(b)

10 20 30 40 50 60 70

05000

100001500020000

lowast

lowastlowast

lowastlowast

lowastlowast

lowastlowast

lowast

lowast

lowastlowast

lowast

lowastlowast

lowastlowast

lowast

660554651543

541442532521

431332

300400

222

310220

211200

110

110

Inte

nsity

(au

)

2120579 (deg)

0ndash11

H3PW12O40

H3PW12O40middot 6H2O

(c)

Figure 3 XRD patterns of (a) yeast (b) HPWyeast and (c) HPW

In order to ascertain the detailed structures of HPWyeast composites EDS was used to characterize the changeof elemental concentration on the yeast cores and finalHPWyeast composites respectively The results are shownin Figure 2 For the yeast core the peaks correspondingto C O P and S are observed in Figure 2(a) After thecoverage of HPW on the yeast surface new peaks attributedto W elements (from HPW molecular) begin to appear inFigure 2(b) A decline of the C signal intensity is observedin comparison with pure yeast cores Also these changeshave been further ascertained by quantitative evaluationof the surface atom concentration of the primitive yeastand the HPWyeast composites From the inset table inFigure 2 we can see that the W element on the surface ofHPWyeast microspheres is 1136 Compared with bareyeast core a decrease in the atomic concentration of the C

and S elements and an increase in the P and O elementsare detected due to the coverage of HPW onto surface ofthe yeast The previously mentioned results provide assertiveevidence that our synthesis method is effective in embeddingHPW uniformly onto the yeast surface without disorderingthe structure of yeast cells

32 XRD XRD patterns of yeast HPW and HPWyeastcomposite are recorded in Figure 3The typical XRD patternof yeast is recorded in Figure 3(a) The broad peak around2120579 = 20

∘ indicates that the yeast supports can be assignedto amorphous species In Figure 3(c) the positions of thesharp peaks below 2120579 = 10∘ could be ascribed to cubicphase H

3PW12O40sdot6H2O (Hydrogen Tungsten Phosphate

Hydrate) and were indexed to the reported data (JCPDS


100 200 300 400 500 600 7000

20

40

60

80

100

100 200 300 400 500 600 700

0

1

2

3

4

Wei

ght (

)

yeast yeastHPW

119879 (∘C)

Δ119879

Figure 4 TG and DTA curves of yeast and HPWyeast samples

50-0304) The other remaining diffraction peaks match wellwith the standard diffraction data (JCPDS 50-0657) of thecubic structure H

3PW12O40

(12-tungstophosphoric acid)The XRD analysis coincides with the Keggin structure ofHPW In Figure 3(b) the HPWyeast samples show that anobvious diffraction peak around 2120579 = 20∘ arose from theamorphous structure of yeast and some inconspicuous peaksof HPW crystal suggest that the attached HPWmolecule hasmonolayer dispersion on the surface of yeast core

33 TG-DTA TGDTA curves of yeast and HPWyeastsamples are recorded in Figure 4 It is noted that the weightloss of as-obtained HPWyeast particles can be divided intothree stages in the TG curve The weight loss of ca 6 wasobserved below 100∘C because of the release of less stablephysically absorbed water in HPW and the evaporation ofadsorbed moisture remaining in the yeast cells which isaccompanied by a broad endothermic peakThe rapid weightloss of about 40 at the temperature range of 250ndash500∘Cmay contribute to the desorption of crystal water in HPWand the thermal decomposition of yeast biomass which isaccompanied by two exothermic peaks below 500∘C A littlereduction in weight was observed above 500∘C which couldbe associated with the loss of frame water in HPW and thedestruction of its structure This result was supported bythe DTA curve which shows an exothermic peak at about704∘C Furthermore compared with the related literatureof the temperature of complete decomposition [22] theattachments of HPW onto the surface of yeast have evidentlyenhanced the thermal stability of the HPWmolecule

34 FT-IR In order to confirm the chemical structure of theHPWyeast composites FT-IR spectra of yeast cells pureHPW and HPWyeast composites and their intermediatein the synthesis stages are recorded respectively The resultsare shown in Figure 5 The characteristic adsorption peaksof bare yeast in Figure 5(a) at 342361 292791 164140 and107626 cmminus1 are ascribed to the OndashH stretching vibration

4000 3500 3000 2500 2000 1500 1000 5000

01

02

03

04

05

06

07

08

09

Amide II

Amide IndashOH

Tran

smiss

ion

(au

)

yeast HPWyeast HPW

ndashCH2 ndashP = O

(a)

(b)

(c)

(d)

yeastH+

Wavenumber (cmminus1)

(a)

Tran

smiss

ion

(au

)

1100 1050 1000 950 900 850 800

04

05

06

07

08

PndashOaWndashOcndashW

WndashObndashWW = Od

81973

89688

97789

8023788917

98175108012

(d)

(c)


(b)

Figure 5 FT-IR spectra of (a) pristine yeast (b) yeast treated byH2SO4solution (c) HPWyeast microspheres and (d) HPW

CH2asymmetric stretching vibration amide group and Cndash

O stretching vibration separately [23ndash27] In the case of pureHPW in Figure 5(d) the presences of the finger print bandsbelow 1100 cmminus1 are characteristic of the PW

12O4

3minus ion withthe Keggin structuresThe PW

12O4

3minus Keggin anion structureconsists of a PO

4tetrahedron surrounded by four W

3O9

groups formed by edge-sharing octahedral These groups areconnected to each other by corner-sharing oxygen [28 29]This structure generates different types of oxygen atomswhich are responsible for the signature of FT-IR bands for theKeggin anions below 1100 cmminus1 [30 31]Themain adsorptionpeak at 108012 cmminus1 is ascribed to PndashOa stretching andthe peak at 98175 cmminus1 derives from W=Od stretchingThe other peaks at 88917 cmminus1 and 80237 cmminus1 are due tothe WndashObndashW and WndashOcndashW bridges respectively [32ndash34]


COOH

COOR

NH

OH+ + +

++++

++++++++

++++++++++++++++++++++++++++

pH2-3

Yeast

HPW

+

HPWyeastDye

HPW

h

Dye

+

HPWlowast

OH2

+

NH2

+

H+yeast

O2minus

HO2

O2

HPWminus

Scheme 1The formationmechanismof theHPWyeast composite particles and their synergetic effect on the decoloration of azo dye aqueoussolution

From Figure 5(c) the simultaneous existence of typicalinfrared bands of Keggin unit and yeast cells implies that theHPW has been loaded onto the surface of yeast cells andthe Keggin structure has been preserved Moreover it canbe found that the W=Od mode shifts from 98175 cmminus1 to97789 cmminus1 the WndashObndashW mode moves from 88917 cmminus1to 89618 cmminus1 and the absorption band of WndashOcndashW shiftsfrom 80237 cmminus1 to 81973 cmminus1 All the characteristic bandsof OndashH CH

2 amide group and CndashO in HPWyeast shift

at different degrees in comparison with pure yeast Theseconcurrent shifts can be attributed to the interaction betweenthe Keggin anions in HPW and the functional groups on thesurface of yeast cells such as carboxyls hydroxyls and amideThe possible mechanism for the formation of HPWyeast isillustrated in Scheme 1

35 UV-Vis UV-visible diffuse reflectance spectra (DRS) ofyeast HPW and HPWyeast are showed in Figure 6 InFigure 6(a) the HPW shows an adsorption peak at 267 nmwhich is attributed to the charge transfer transition of WndashOndashW bridge bond in Keggin anions [35] From Figure 6(b)the absorption wavelength of HPWyeast at around 300 nmcan be assigned to HPWmolecules embedded on the surfaceof yeast Because of the interaction between HPW and yeastthe UV absorption of two peaks is shifted from 267 nm and300 nm to 268 nm and 305 nm respectively Additionallythe band edge of the HPWyeast UV-Vis DRS is alsored shifted (460 nm) The red shift mentioned-above madeHPWyeast possible for photochemical catalysis through avisible light excitation A similar observation was made byYuan et al [36]These results indicate that the primaryKegginstructure has been introduced on the surface of yeast Thisis also in agreement with the FT-IR analysis Moreover thephotographs of HPWyeast microspheres and pure yeastsare taken respectively in the insert images of Figure 6We can see the color of the obtained HPWyeast speciesexhibiting a slighter grey than the pure yeast which was inaccordance with its absorption spectrum

36 The Settling Tests In principle using yeast as sup-port in HPWyeast products can encourage the compos-ite microspheres exhibiting unique suspension ability The

300 375 450 525 600 675 7500

015

03

045

06

075

09

Abso

rptio

n

(b)

(b)(c)(a)

(a)

120582 (cmminus1)

Figure 6 UV-Vis DRS spectra of (a) HPW (b) HPWyeast and (c)pure yeast samples

sedimentation performance of HPWyeast microspheres inaqueous solutions is showed in Figure 7 In each experimentall the particles were dispersed in water without any addi-tional additive It is clearly observed that the HPWyeastspecies have excellent suspension ability as that of the yeastTo be more specific the setting ratios of pure yeast andthe HPWyeast samples only went down about 100 and200 separately after 280min The scattered capacity ofHPWyeast is a bit worse than that of yeast due to theattachment of HPW onto the surface of yeast The realisticsedimentation photographs at different time are recorded asthe insert images in Figure 7 The outstanding suspensionstability of HPWyeast samples is ascribed to the apparentdensity of composite As a kind of aquatic microorganismsthe wet density of yeast (109 plusmn 0008 gsdotcmminus3) is almost equalto that of water According to Stokes equation (2) lowerapparent density of HPWyeast particles will cause lowsedimentation velocity [37]

1198810=

2 sdot (120588 minus 120590) sdot 119892 sdot 1199032

9 sdot 120578

(2)


0 50 100 150 200 25020

40

60

80

100

(b)(a)

(a)

(b)

0 min 120 min 280 min

t (min)

R(

)

Figure 7 The settling curves of (a) pure yeast and (b) HPWyeastmicrospheres

In (2) 1198810is sedimentation velocity of the particles in

carrier fluid 119903 and 120588 are the radius and apparent density of theparticles respectively 120590 and 120578 are the density and viscosityof the carrier fluid respectively and 119892 is the gravitationalconstant In the slurry reactor it is well known that the goodsuspension ability of HPWyeast microspheres could ensurethat the catalysts maintain dispersed state for a long time inaqueous solutionThat is not only beneficial to the adsorptionof dye molecules but also made it possible for HPW to getthe utmost out of light source to realize oxidizing organicpollutants by photocatalytic degradation In addition owingto the micrometer size of the yeast support the HPWyeastcomposite microspheres could recover and recycle from thereaction system rapidly accomplished by common filtration

37 Catalytic Performance In order to examine the appli-cation taints of HPWyeast microspheres for the removalof water contaminants the aqueous solutions of cationicdyes Methylene Blue were taken as an example The decol-orization by H+yeast (the yeast was treated with H

2SO4)

and HPWyeast microsphere was carried out respectivelyFrom Figure 8(a) it is shown that the MB aqueous solution isbarely photolyzed by UV irradiation only From Figure 8(c)it can be seen that only 89 decolorization of MB dye canbe achieved by combination of yeast and UV irradiationduring the 150min reaction time The causes of decoloriza-tion of MB dye aqueous solution can be attributed to theabsorption capacity of yeast For the HPWyeast compositecatalyst 981 of the MB was decomposed after 150min ofirradiation and the gradual fading of aqueous MB solutionwas observed It is obvious that the decolorization functionof HPWyeast was effective By contrast it can also beconcluded that the Keggin structure of HPW plays a key rolein the decolorization of the MB The reaction mechanismfor the decolorization of aqueous MB by the yeastHPW isproposed as follows [38 39]

HPWyeast ℎV997888997888rarr HPWlowastyeast (3)

HPWlowastyeast +H2O 997888rarr HPWminusyeast + ∙OH (4)

HPWminusyeast +O2997888rarr HPWyeast +O

2

minus (5)

O2

minus+H+ 997888rarr HO

2(6)

When a photon of UV light shines on the HPW surfacethe O(2p) minus gtW(5d) charge transfer in the Keggin structureleads to the formation of excited-state species (HPW)lowast (3)The excited-state species (HPW)lowast have higher oxidationcapacity through forming electron-hole pairs In liquid-phasereaction the photoholes react with the water molecules and∙OH radicals are generated (4) ∙OH radicals are strongand unselective oxidant species in favor of totally oxidativedegradation and mineralization for organic substrates Theactive ∙OH radicals lead to the degradation of the MBAlternatively in the presence of dioxygen the reducedcatalyst (HPWminus) undergoes an easy reoxidation through thetransfer of electron from reduced species to dioxygen (5)Thus the activated oxygen species HO

2radical formed (6)

However it is documented that surface-bound and solvated∙OH radicals are amain oxidant to attack dye [38 39] Duringthe regeneration of catalysis the positive charged surface ofyeast could be an efficient electron acceptor to make HPWkeep the photocatalytic cycle persisting As we all knowthere are diverse functional groups which are contained inchemical substances in the yeast cell wall such as carboxylamine hydroxyl and phosphoryl These functional groupscould make yeast have different zeta potential the surfacecharges of the particles in the same solvent at diverse acid-base intense The isoelectric point of yeast is around pH 33[40 41] When the pH of the solution is under 33 the zetapotential of yeast is above zero displaying surface positivecharge (Scheme 1) The surface positive charge catalyzes theoxidation of O

2

minus into the activated oxygen species HO2

which accelerates the catalytic reaction rates of HPWyeastas the result In order to prove our conjecture of the yeastrsquosrole in catalysis the decolorization of anionic dye Cong Redwas also tested It could be seen from Figure 6 that thedegradation rate for Cong red decreases much than that ofMB at the same initial mole concentration One reason fordecrease of the reaction ratewould be assigned to the decreaseof the concentration of the positive charge of yeast becauseCong Red as an anionic dye neutralizes the positive chargeon the surface of yeast It is just another proof of our thoughtthat the positive charge in the surface of yeast can speed upthe discoloration rate of dye The further details mechanismis currently under investigation

One of the advantages of using heterogeneous catalystsis the possibility of their reusability [42] The lifetime of theHPWyeast composite catalyst has been studied by runningthe reaction successively with the same catalyst which wasseparated by simple centrifugation without other treatmentFrom Figure 9 it can be seen that the catalytic activity ofHPWyeast had no significant decrease after four runs Itonce again demonstrated that the HPWyeast compositescould simply recycle and recover from the reaction systemThe excellent reusability of the HPWyeast catalyst indicatesthat product has better stability and negligible loss of theKeggin units


0 20 40 60 80 100 120 140100

80

60

40

20

0

On

(a)(c)

(d)

(e)

(f)

(b)

Off

Light

Dec

olor

izat

ion

rate

()

Congo redMB Congo red + HPWyeast

MB + HPWyeastMB + H+yeast

Congo red + H+yeast

t (min)

Figure 8 Discolorations reaction of MB and Congo red

1 2 3 40

20

40

60

80

100

Deg

rada

tion

rate

()

Reaction cycle

Congo red Methylene blue

Figure 9 The recycle use of HPWyeast in decoloring of MB andCong red

4 Conclusion

In summary we have successfully prepared the HPWyeastcomposite microspheres through impregnation-adsorptiontechnique by tuning pH of the aqueous yeast suspensionsPhysical-chemical characterization results suggest that HPWis monodisperse on the surface of yeast and the main struc-ture belongs to Keggin unit The composites have uniformsize and good thermal stability The obtained samples haveoutstanding suspension property and are easy to be sepa-rated under the conventional centrifugation The catalyticperformance indicates that the HPWyeast microsphereshave potential applications for the removal of a range ofanionic and cationic dyes fromwastewaterMore importantly

the composite catalysts can be used repeatedly without signif-icant decrease of activity It seems that the yeast support playsan important role in regeneration of catalyst The presentmethod can be extended to the synthesis of other hybridmicrosphere of different sizes and shapes by preselectingsuitable biosupport

Acknowledgments

This work was financially supported by China PostdoctoralScience Special Foundation National Natural Science Foun-dation of China (Grant no 21176031) and Natural ScienceFoundation of Shaanxi Province (no 2011JM2011)

References

[1] NMizuno andMMisono ldquoHeterogeneous catalysisrdquoChemicalReviews vol 98 no 1 pp 199ndash217 1998

[2] Y H Guo C W Hu X L Wang et al ldquoMicroporousdecatungstates synthesis and photochemical behaviorrdquo Chem-istry of Materials vol 13 no 11 pp 4058ndash4064 2001

[3] L Li Q Y Wu Y H Guo and C W Hu ldquoEffect of thermaltreatment on surface and bulk properties of FeZSM-5 zeolitesprepared by different methodsrdquo Microporous and MesoporousMaterials vol 87 no 2 pp 93ndash102 2005

[4] M M Heravi F Derikvand and F F Bamoharram ldquoHighlyefficient four-component one-pot synthesis of tetrasubstitutedimidazoles using Keggin-type heteropolyacids as green andreusable catalystsrdquo Journal ofMolecular Catalysis A vol 263 no1-2 pp 112ndash114 2007

[5] A Heydaria S Khaksara M Sheykhana and M TajbakhshldquoH3PMo12O40

as a new and reusable catalyst for Mukaiyamaand Mannich reactions in heterogeneous mediardquo Journal ofMolecular Catalysis A vol 287 no 1-2 pp 5ndash8 2008

[6] A Kumar P Singh S Kumar R Chandra and SMozumdar ldquoAfacile one-pot synthesis of thioethers using heteropoly acidsrdquoJournal of Molecular Catalysis A vol 276 no 1-2 pp 95ndash1012007

[7] X M Yan J H Lei D Liu Y CWu andW Liu ldquoSynthesis andcatalytic properties of mesoporous phosphotungstic acidSiO

2

in a self-generated acidic environment by evaporation-inducedself-assemblyrdquo Materials Research Bulletin vol 42 no 11 pp1905ndash1913 2007

[8] S T Li C D Wu Y S Yan X M Lu and P W HuoldquoPhotodegradation of organic contaminant by heteropoly acidrdquoProgress in Chemistry vol 20 no 5 pp 690ndash697 2008

[9] P Kormali D Dimoticali D Tsipi A Hiskia and E Papa-constantinou ldquoPhotolytic and photocatalytic decompositionof fenitrothion by PW

12O3minus40

and TiO2 a comparative studyrdquo

Applied Catalysis B vol 48 no 3 pp 175ndash183 2004[10] H Hori E Hayakawa K Koike H Einaga and T Ibusuki

ldquoDecomposition of nonafluoropentanoic acid by heteropoly-acid photocatalyst H

3PW12O40in aqueous solutionrdquo Journal of

Molecular Catalysis A vol 211 no 1-2 pp 35ndash41 2004[11] X Yang G Yu L R Kong and L S Wang ldquoKinetic Study

on Photodegradation of Acid Red 3B Catalyzed by HeteropolyAcidrdquo Environmental Science vol 23 no 3 pp 40ndash43 2002

[12] K Su Z Li B Cheng L Zhang M Zhang and J Ming ldquoThestudies on the Friedel-Crafts acylation of toluene with aceticanhydride over HPWTiO

2rdquo Fuel Processing Technology vol 92

no 10 pp 2011ndash2015 2011


[13] Y J Zeng H J Yu and L Shi ldquoStructure and Catalytic Activityof Phosphotungstic Acid Supported on Y-Zeoliterdquo ChemicalReaction Engineering and Technology vol 23 no 6 pp 542ndash5472007

[14] F Gao J W Sun and S H Zhong ldquoSynthesis and characteriza-tion of heteropoly acid catalyst supported on carbonized resinrdquoChinese Journal of Catalysis vol 19 no 2 pp 187ndash190 1999

[15] L Y Wen S K Shen and E Z Min ldquoPhysicochemical andCatalytic Properties of 12-Phosphotungstic Acid Supported onDifferent Silicardquo Chinese Journal of Catalysis vol 21 no 6 pp524ndash528 2000

[16] Z Obalı and T Dogu ldquoActivated carbon-tungstophosphoricacid catalysts for the synthesis of tert-amyl ethyl ether (TAEE)rdquoChemical Engineering Journal vol 138 no 1ndash3 pp 548ndash5552008

[17] S J Yang Y J Zhang and H L Zhang ldquoDegradation ofMethyl Orange Solution over H

3PW12O40MCM-48rdquoChemical

Reaction Engineering and Technology vol 27 no 6 pp 562ndash5662011

[18] WHe X Tian YDu et al ldquoBiologically formed hollow cuprousoxide microspheresrdquo Materials Science and Engineering C vol30 no 5 pp 758ndash762 2010

[19] DWeinzierl A Lind andWKunz ldquoHollow SiO2microspheres

produced by coating yeast cellsrdquoCrystal Growth andDesign vol9 no 5 pp 2318ndash2323 2009

[20] B Bai N Quici Z Y Li and G L Puma ldquoNovel one stepfabrication of raspberry-like TiO

2yeast hybrid microspheres

via electrostatic-interaction-driven self-assembled heterocoag-ulation for environmental applicationsrdquo Chemical EngineeringJournal vol 170 no 2-3 pp 451ndash456 2001

[21] B BaiW S Guan Z Y Li and G L Puma ldquoBio-template routefor facile fabrication of Cd(OH)


and their subsequent conversion to mesoporous CdO hollowmicrospheresrdquoMaterials Research Bulletin vol 46 no 1 pp 26ndash31 2011

[22] B S Li Z X Liu C Y Han W Ma and S J Zhao ldquoInsitu synthesis characterization and catalytic performance oftungstophosphoric acid encapsulated into the framework ofmesoporous silica pillared clayrdquo Journal of Colloid and InterfaceScience vol 377 no 1 pp 334ndash341 2012

[23] S J Joris and C H Amberg ldquoNature of deficiency in non-stoichiometric hydroxyapatites II Spectroscopic studies ofcalcium and strontium hydroxyapatitesrdquoThe Journal of PhysicalChemistry vol 75 no 20 pp 3172ndash3178 1971

[24] M Beekes P Lasch and D Naumann ldquoAnalytical applicationsof Fourier transform-infrared (FT-IR) spectroscopy in micro-biology and prion researchrdquo Veterinary Microbiology vol 123no 4 pp 305ndash319 2007

[25] K C Blakeslee and R A Condrate ldquoVibrational spectraof hydrothermally prepared hydroxyapatitesrdquo Journal of theAmerican Ceramic Society vol 54 no 11 pp 559ndash563 1971

[26] K J Rothschild and N A Clark ldquoAnomalous amide I infraredabsorption of purplemembranerdquo Science vol 204 no 4390 pp311ndash312 1979

[27] R A Nyquist and R O Kagel Infrared Spectra of InorganicCompounds Academic Press New York NY USA 1971

[28] J Yang M J Janik D Ma et al ldquoLocation acid strengthand mobility of the acidic protons in Keggin 12-H

3PW12O40

a combined solid-state NMR spectroscopy and DFT quantumchemical calculation studyrdquo Journal of the American ChemicalSociety vol 127 no 51 pp 18274ndash18280 2005

[29] A E R S Khdera H M A Hassana and M S El-Shall ldquoAcidcatalyzed organic transformations by heteropoly tungstophos-phoric acid supported on MCM-41rdquo Applied Catalysis A vol411-412 pp 77ndash86 2012

[30] Y S Kim F Wang M Hickner T A Zawodzinski and J EMcGrath ldquoFabrication and characterization of heteropolyacid(H3PW12O40)directly polymerized sulfonated poly(arylene

ether sulfone) copolymer composite membranes for highertemperature fuel cell applicationsrdquo Journal of Membrane Sci-ence vol 212 no 1-2 pp 263ndash282 2003

[31] L Zhang H Q He R Kamal SO Abdul Rasheed et alldquoFabrication of novel phosphotungstic acid functionalizedmesoporous silica composite membrane by alternative gel-casting techniquerdquo Journal of Power Sources vol 221 pp 318ndash327 2013

[32] L Zhang Q Jin L Shan Y Liu X Wang and J HuangldquoH3PW12O40

immobilized on silylated palygorskite and cat-alytic activity in esterification reactionsrdquo Applied Clay Sciencevol 47 no 3-4 pp 229ndash234 2010

[33] P Staiti S Freni and S Hocevar ldquoSynthesis and charac-terization of proton-conducting materials containing dode-catungstophosphoric and dodecatungstosilic acid supported onsilicardquo Journal of Power Sources vol 79 no 2 pp 250ndash255 1999

[34] X L Sheng Y M Zhou Y W Zhang M W Xue and YZ Duan ldquoImmobilization of 12-tungstophosphoric acid onLaSBA-15 and its catalytic activity for alkylation of o-xylenewith styrenerdquo Chemical Engineering Journal vol 179 pp 295ndash301 2012

[35] P M Rao A Wolfson S Kababya S Vega and M V LandauldquoImmobilization of molecular H

3PW12O40heteropolyacid cat-

alyst in alumina-grafted silica-gel and mesostructured SBA-15silica matricesrdquo Journal of Catalysis vol 232 no 1 pp 210ndash2252005

[36] J Yuan P Yue and L Wang ldquoA study on the magnetically sup-ported heteropolyacid nanophase catalystsrdquoPowder Technologyvol 202 no 1ndash3 pp 190ndash193 2010

[37] H T Pu F J Jiang and Z L Yang ldquoPreparation and prop-erties of soft magnetic particles based on Fe

3O4and hollow

polystyrene microsphere compositerdquo Materials Chemistry andPhysics vol 100 no 1 pp 10ndash14 2006

[38] Y H Guo Y H Wang C W Hu et al ldquoMicroporous poly-oxometalates pomsSiO

2 synthesis and photocatalytic degra-

dation of aqueous organocholorine pesticidesrdquo Chemistry ofMaterials vol 12 no 11 pp 3501ndash3508 2000

[39] Y Bin Y Zhou Y X Jing et al ldquoPhotocatalytic degradationof aqueous 4-chlorophenol by silica-immobilized polyoxomet-alatesrdquo Environmental Science amp Technology vol 36 no 6 pp1325ndash1329 2002

[40] M Mercier-Bonin K Ouazzani P Schmitz and S LorthoisldquoStudy of bioadhesion on a flat plate with a yeastglass modelsystemrdquo Journal of Colloid and Interface Science vol 271 no 2pp 342ndash350 2004

[41] A Bingol H Ucun Y K Bayhan A Karagunduz A Cakiciand B Keskinler ldquoRemoval of chromate anions from aqueousstream by a cationic surfactant-modified yeastrdquo BioresourceTechnology vol 94 no 3 pp 245ndash249 2004

[42] E Rafiee and S Shahebrahimi ldquoNano silica with high surfacearea from rice husk as a support for 12-tungstophosphoric acidan efficient nano catalyst in some organic reactionsrdquo ChineseJournal of Catalysis vol 33 no 8 pp 1326ndash1333 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Carbohydrate Chemistry

International Journal of


Journal of

Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


Chromatography Research International


Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of


loading phosphotungstic acid on the mesoporous MCM-48and the test of catalytic activity shows that the degradation ofmethyl orange aqueous solution could reach 8453

Recently yeasts as biotemplates or supports to synthesizecatalysts have attracted considerable attention For exampleHe et al [18] synthesized Cu

2O hollow spheres by employing

yeasts as biotemplates Weinziel et al [19] prepared SiO2

hollow particles using yeasts as biotemplates Our groups [20]obtained the raspberry-like TiO

2yeast composite photo-

catalysts successfully by exploiting yeasts as supports Tosum up a serial of excellent merits have been brought alongfor the obtained composite catalysts [21] Typical benefitsinclude the following (1) The tunable and uniform shape ofsupports can be easily achieved from the abundant microbialcells resources in nature (2) Additional surface modificationcan be left out due to the preexistence of functional groupsinherited from the hydrophilic cell wall of microbial cells(3) The composites using yeasts as supports have integratedproperties originating from their hybrid components whichrepresent a new style of economical and environmental-friendly catalysts [20]

Thus in the present work the phosphotungstic acid(HPW)-impregnated yeast (HPWyeast) hybrid micro-spheres were prepared by impregnation-adsorption tech-nique through tuning pH of the aqueous yeast suspensionsfirstly Then the obtained hybrid microspheres were charac-terized by SEM EDS XRD FT-IR and UV-Vis respectivelyA possible mechanism for the formation of the compositemicrospheres was proposed Moreover the photocatalyticactivities of HPWyeasts microspheres were evaluated byexamining the decolorization of Methylene blue and Congored The reusability of HPWyeast as catalyst was estimatedfurther

2 Experimental

21 Materials Yeast powder was purchased fromAngel YeastCo Analytical grade phosphotungstic acid (HPW) sulphuricacid (H

2SO4) was provided by Xirsquoan Chemical Agent Corp

and used without further purification Double distilled waterand absolute ethanol were used throughout the experimentalprocedures

22 Synthesis of HPWyeast HybridMicrosphere In a typicalsynthesis procedure 1000 g yeast powder was washed withdistilled water and ethanol for three times respectively Thewashed yeast was dispersed in 50mL of distilled water ThepH was adjusted to approximately 2-3 by adding dropwisesulphuric acid The suspension was magnetically stirred for30min to facilitate the dispersion of the yeast particles300mg HPW dissolved in 40mL ethanol was added tothe previously mentioned suspensions with constant stir-ring The mixture was continuously magnetically stirredfor 10 h at room temperature and then left for 3 h with-out further stirring or shaking to ensure the formation ofHPWyeast heterocoagulated particles Then the mixturewas collected by centrifugation followed by three cycles of

distilled water and ethanol rinsing to get filtrate precipita-tion and finally dried in drying oven at 60sim80∘C for 40minAfter that the HPWyeast composite microspheres wereobtained

23 Characterization of Samples X-ray diffraction (XRD)patterns of the samples were carried out on a RegakuDMAX-3C diffractometer operated at a voltage of 40 kVand a current of 20mA at a 002∘ scan rate with Cu K120572radiation Field-emission scanning electromicroscope (FE-SEM) images were taken on a JEOL-6300F field-emissionscanning electromicroscope with an accelerating voltageof 15 kV Fourier-transform infrared (FT-IR) spectroscopymeasurements were recorded with a Bruker TENSOR 27FT-IR spectrometer Thermal gravimetric analysis (TG) anddifferential scanning calorimetry (DSC) were performed ona HCT-2 apparatus at a heating rate of 10∘Cmin

24 The Setting Performance 0050 g HPWyeast micro-spheres were dispersed into 50mL of distilled water in avertical cylindrical burette at room temperature At regularintervals the falling height was determined The sedimenta-tion ratio (119877) was measured by

119877 =119886

119886 + 119887

times 100 (1)

where 119886 is the length of the clear fluid and 119887 is the length ofthe turbid fluid respectively

25 Catalytic Activity The photocatalytic activity of theprepared samples was evaluated by the photocatalytic decol-orization of anion dye Congo Red and cationic dyes Methy-lene Blue (MB) at room temperature The experimentalprocedure was as follows 100mg of the prepared powderswas dispersed in 100mL of MB aqueous solution with aconcentration of 12mgL in a beaker (with a capacity of150mL) and the suspensions were magnetically stirred inthe dark for 30min prior to irradiation with UV light TheUV-light lamp placed 7 cm above the beaker was used as alight source The concentration of MB aqueous solution wasdetermined by a UV-visible spectrophotometer (TU-4100)Before and after irradiation samples (6mL) were collectedat regular intervals Each sample was centrifuged to separatethe catalyst from the liquid and the supernatant was analyzedThe samples were returned into the reactor immediately aftereach analysis

In order to evaluate the reusability of the obtainedmicro-spheres in the photocatalytic processes the measurement ofthe lifetime of the HPWyeast was assessedThe experimen-tal procedure was the same as the photocatalytic activity testaforementioned The only difference is that the experimentwas operated four times In each experiment the catalystswere centrifuged and recovered from the photocatalyticsystem without other treatments that would be as catalyst forthe other photodegradation experiments


(a) (b)

(c) (d)

(e)







SamplesC

CO

O

P

P

S

0 1 2 3(keV)

S

W


(a)

C

O

PW

W

W P

0 1 2 3(keV)

S

(b)


10 20 30 40 50 60 70

2000

4000

6000

8000

Inte

nsity

(au

)

2120579 (deg)

(a)

10 20 30 40 50 60 70500055006000650070007500

Inte

nsity

(au

)

2120579 (deg)

(b)

10 20 30 40 50 60 70

05000

100001500020000

lowast

lowastlowast

lowastlowast

lowastlowast

lowastlowast

lowast

lowast

lowastlowast

lowast

lowastlowast

lowastlowast

lowast

660554651543

541442532521

431332

300400

222

310220

211200

110

110

Inte

nsity

(au

)

2120579 (deg)

0ndash11

H3PW12O40


(c)









100 200 300 400 500 600 7000

20

40

60

80

100

100 200 300 400 500 600 700

0

1

2

3

4

Wei

ght (

)

yeast yeastHPW

119879 (∘C)

Δ119879



3PW12O40




4000 3500 3000 2500 2000 1500 1000 5000

01

02

03

04

05

06

07

08

09

Amide II

Amide IndashOH

Tran

smiss

ion

(au

)

yeast HPWyeast HPW

ndashCH2 ndashP = O

(a)

(b)

(c)

(d)

yeastH+


(a)

Tran

smiss

ion

(au

)

1100 1050 1000 950 900 850 800

04

05

06

07

08



81973

89688

97789

8023788917

98175108012

(d)

(c)


(b)




12O4


12O4



3O9



COOH

COOR

NH

OH+ + +

++++

++++++++

++++++++++++++++++++++++++++

pH2-3

Yeast

HPW

+

HPWyeastDye

HPW

h

Dye

+

HPWlowast

OH2

+

NH2

+

H+yeast

O2minus

HO2

O2

HPWminus







300 375 450 525 600 675 7500

015

03

045

06

075

09

Abso

rptio

n

(b)

(b)(c)(a)

(a)

120582 (cmminus1)



1198810=


9 sdot 120578

(2)


0 50 100 150 200 25020

40

60

80

100

(b)(a)

(a)

(b)


t (min)

R(

)





2SO4)





2

minus (5)

O2


2(6)


2radical formed (6)


2





0 20 40 60 80 100 120 140100

80

60

40

20

0

On

(a)(c)

(d)

(e)

(f)

(b)

Off

Light

Dec

olor

izat

ion

rate

()



Congo red + H+yeast

t (min)


1 2 3 40

20

40

60

80

100

Deg

rada

tion

rate

()

Reaction cycle



4 Conclusion



Acknowledgments


References









2




12O3minus40









no 10 pp 2011ndash2015 2011

























3PW12O40















3O4and hollow


















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


(a) (b)

(c) (d)

(e)







SamplesC

CO

O

P

P

S

0 1 2 3(keV)

S

W


(a)

C

O

PW

W

W P

0 1 2 3(keV)

S

(b)


10 20 30 40 50 60 70

2000

4000

6000

8000

Inte

nsity

(au

)

2120579 (deg)

(a)

10 20 30 40 50 60 70500055006000650070007500

Inte

nsity

(au

)

2120579 (deg)

(b)

10 20 30 40 50 60 70

05000

100001500020000

lowast

lowastlowast

lowastlowast

lowastlowast

lowastlowast

lowast

lowast

lowastlowast

lowast

lowastlowast

lowastlowast

lowast

660554651543

541442532521

431332

300400

222

310220

211200

110

110

Inte

nsity

(au

)

2120579 (deg)

0ndash11

H3PW12O40


(c)









100 200 300 400 500 600 7000

20

40

60

80

100

100 200 300 400 500 600 700

0

1

2

3

4

Wei

ght (

)

yeast yeastHPW

119879 (∘C)

Δ119879



3PW12O40




4000 3500 3000 2500 2000 1500 1000 5000

01

02

03

04

05

06

07

08

09

Amide II

Amide IndashOH

Tran

smiss

ion

(au

)

yeast HPWyeast HPW

ndashCH2 ndashP = O

(a)

(b)

(c)

(d)

yeastH+


(a)

Tran

smiss

ion

(au

)

1100 1050 1000 950 900 850 800

04

05

06

07

08



81973

89688

97789

8023788917

98175108012

(d)

(c)


(b)




12O4


12O4



3O9



COOH

COOR

NH

OH+ + +

++++

++++++++

++++++++++++++++++++++++++++

pH2-3

Yeast

HPW

+

HPWyeastDye

HPW

h

Dye

+

HPWlowast

OH2

+

NH2

+

H+yeast

O2minus

HO2

O2

HPWminus







300 375 450 525 600 675 7500

015

03

045

06

075

09

Abso

rptio

n

(b)

(b)(c)(a)

(a)

120582 (cmminus1)



1198810=


9 sdot 120578

(2)


0 50 100 150 200 25020

40

60

80

100

(b)(a)

(a)

(b)


t (min)

R(

)





2SO4)





2

minus (5)

O2


2(6)


2radical formed (6)


2





0 20 40 60 80 100 120 140100

80

60

40

20

0

On

(a)(c)

(d)

(e)

(f)

(b)

Off

Light

Dec

olor

izat

ion

rate

()



Congo red + H+yeast

t (min)


1 2 3 40

20

40

60

80

100

Deg

rada

tion

rate

()

Reaction cycle



4 Conclusion



Acknowledgments


References









2




12O3minus40









no 10 pp 2011ndash2015 2011

























3PW12O40















3O4and hollow


















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



SamplesC

CO

O

P

P

S

0 1 2 3(keV)

S

W


(a)

C

O

PW

W

W P

0 1 2 3(keV)

S

(b)


10 20 30 40 50 60 70

2000

4000

6000

8000

Inte

nsity

(au

)

2120579 (deg)

(a)

10 20 30 40 50 60 70500055006000650070007500

Inte

nsity

(au

)

2120579 (deg)

(b)

10 20 30 40 50 60 70

05000

100001500020000

lowast

lowastlowast

lowastlowast

lowastlowast

lowastlowast

lowast

lowast

lowastlowast

lowast

lowastlowast

lowastlowast

lowast

660554651543

541442532521

431332

300400

222

310220

211200

110

110

Inte

nsity

(au

)

2120579 (deg)

0ndash11

H3PW12O40


(c)









100 200 300 400 500 600 7000

20

40

60

80

100

100 200 300 400 500 600 700

0

1

2

3

4

Wei

ght (

)

yeast yeastHPW

119879 (∘C)

Δ119879



3PW12O40




4000 3500 3000 2500 2000 1500 1000 5000

01

02

03

04

05

06

07

08

09

Amide II

Amide IndashOH

Tran

smiss

ion

(au

)

yeast HPWyeast HPW

ndashCH2 ndashP = O

(a)

(b)

(c)

(d)

yeastH+


(a)

Tran

smiss

ion

(au

)

1100 1050 1000 950 900 850 800

04

05

06

07

08



81973

89688

97789

8023788917

98175108012

(d)

(c)


(b)




12O4


12O4



3O9



COOH

COOR

NH

OH+ + +

++++

++++++++

++++++++++++++++++++++++++++

pH2-3

Yeast

HPW

+

HPWyeastDye

HPW

h

Dye

+

HPWlowast

OH2

+

NH2

+

H+yeast

O2minus

HO2

O2

HPWminus







300 375 450 525 600 675 7500

015

03

045

06

075

09

Abso

rptio

n

(b)

(b)(c)(a)

(a)

120582 (cmminus1)



1198810=


9 sdot 120578

(2)


0 50 100 150 200 25020

40

60

80

100

(b)(a)

(a)

(b)


t (min)

R(

)





2SO4)





2

minus (5)

O2


2(6)


2radical formed (6)


2





0 20 40 60 80 100 120 140100

80

60

40

20

0

On

(a)(c)

(d)

(e)

(f)

(b)

Off

Light

Dec

olor

izat

ion

rate

()



Congo red + H+yeast

t (min)


1 2 3 40

20

40

60

80

100

Deg

rada

tion

rate

()

Reaction cycle



4 Conclusion



Acknowledgments


References









2




12O3minus40









no 10 pp 2011ndash2015 2011

























3PW12O40















3O4and hollow


















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


100 200 300 400 500 600 7000

20

40

60

80

100

100 200 300 400 500 600 700

0

1

2

3

4

Wei

ght (

)

yeast yeastHPW

119879 (∘C)

Δ119879



3PW12O40




4000 3500 3000 2500 2000 1500 1000 5000

01

02

03

04

05

06

07

08

09

Amide II

Amide IndashOH

Tran

smiss

ion

(au

)

yeast HPWyeast HPW

ndashCH2 ndashP = O

(a)

(b)

(c)

(d)

yeastH+


(a)

Tran

smiss

ion

(au

)

1100 1050 1000 950 900 850 800

04

05

06

07

08



81973

89688

97789

8023788917

98175108012

(d)

(c)


(b)




12O4


12O4



3O9



COOH

COOR

NH

OH+ + +

++++

++++++++

++++++++++++++++++++++++++++

pH2-3

Yeast

HPW

+

HPWyeastDye

HPW

h

Dye

+

HPWlowast

OH2

+

NH2

+

H+yeast

O2minus

HO2

O2

HPWminus







300 375 450 525 600 675 7500

015

03

045

06

075

09

Abso

rptio

n

(b)

(b)(c)(a)

(a)

120582 (cmminus1)



1198810=


9 sdot 120578

(2)


0 50 100 150 200 25020

40

60

80

100

(b)(a)

(a)

(b)


t (min)

R(

)





2SO4)





2

minus (5)

O2


2(6)


2radical formed (6)


2





0 20 40 60 80 100 120 140100

80

60

40

20

0

On

(a)(c)

(d)

(e)

(f)

(b)

Off

Light

Dec

olor

izat

ion

rate

()



Congo red + H+yeast

t (min)


1 2 3 40

20

40

60

80

100

Deg

rada

tion

rate

()

Reaction cycle



4 Conclusion



Acknowledgments


References









2




12O3minus40









no 10 pp 2011ndash2015 2011

























3PW12O40















3O4and hollow


















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


COOH

COOR

NH

OH+ + +

++++

++++++++

++++++++++++++++++++++++++++

pH2-3

Yeast

HPW

+

HPWyeastDye

HPW

h

Dye

+

HPWlowast

OH2

+

NH2

+

H+yeast

O2minus

HO2

O2

HPWminus







300 375 450 525 600 675 7500

015

03

045

06

075

09

Abso

rptio

n

(b)

(b)(c)(a)

(a)

120582 (cmminus1)



1198810=


9 sdot 120578

(2)


0 50 100 150 200 25020

40

60

80

100

(b)(a)

(a)

(b)


t (min)

R(

)





2SO4)





2

minus (5)

O2


2(6)


2radical formed (6)


2





0 20 40 60 80 100 120 140100

80

60

40

20

0

On

(a)(c)

(d)

(e)

(f)

(b)

Off

Light

Dec

olor

izat

ion

rate

()



Congo red + H+yeast

t (min)


1 2 3 40

20

40

60

80

100

Deg

rada

tion

rate

()

Reaction cycle



4 Conclusion



Acknowledgments


References









2




12O3minus40









no 10 pp 2011ndash2015 2011

























3PW12O40















3O4and hollow


















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0 50 100 150 200 25020

40

60

80

100

(b)(a)

(a)

(b)


t (min)

R(

)





2SO4)





2

minus (5)

O2


2(6)


2radical formed (6)


2





0 20 40 60 80 100 120 140100

80

60

40

20

0

On

(a)(c)

(d)

(e)

(f)

(b)

Off

Light

Dec

olor

izat

ion

rate

()



Congo red + H+yeast

t (min)


1 2 3 40

20

40

60

80

100

Deg

rada

tion

rate

()

Reaction cycle



4 Conclusion



Acknowledgments


References









2




12O3minus40









no 10 pp 2011ndash2015 2011

























3PW12O40















3O4and hollow


















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0 20 40 60 80 100 120 140100

80

60

40

20

0

On

(a)(c)

(d)

(e)

(f)

(b)

Off

Light

Dec

olor

izat

ion

rate

()



Congo red + H+yeast

t (min)


1 2 3 40

20

40

60

80

100

Deg

rada

tion

rate

()

Reaction cycle



4 Conclusion



Acknowledgments


References









2




12O3minus40









no 10 pp 2011ndash2015 2011

























3PW12O40















3O4and hollow


















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

























3PW12O40















3O4and hollow


















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

research article facile preparation of phosphotungstic

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