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Effect_1

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Effect_1

    Effect

,LnWenying(吕文英),LIXiaoxia(黎晓霞).,YULin(ag),

    ;LIDaguang(李大光)

    ;“.DepartmentofResourceandEnvironment,FoshanUniversity,Foshan528000,China;2.FacultyofEnvironmentalScienceandEngineering,Guangzhou510006

    ;China;iFacultyofChemicalEngineeringandLightIndustry,GuangdongUniversityofTechnology,Guangzhou510006,China)

    ;Received27October2006;revised5January2007

    ;Abstract:HodopedTi02nanoparticleswithhigherphotocatalyticactivitywerepreparedbyanacidcatalyzedsolgelmethod.Thephoto

    ;catalyticdecompositionofmethylorangeinaqueoussolutionwasusedasaprobereactiontoevaluatetheirphotocatalyticactivities.Theef- ;fectsofHodopingonthecrystallitesizes,crystalpattern,surfacecomposition,andopticalpropertyofthecatalystswereinvestigatedby

    ;meansoftechniquessuchasXRayDiffraction(XRD1.TransmissionElect

    ronMicroscopy(TEM),DiffuseReflectanceUVVisSpectros.

    ;copY(UVvisDRS).FourierTransformInfrared(FrIR),andPhotoLu

    miniscence(PL)spectra.Moreover,themodificationmechanismof ;Hodopingwasalsodiscussed.TheresultsshowedthatHod0pingcouldinhibit

    phasetransformationfromanatasetomtile,suppressthe ;growthofTiO,grains,causeblueshiftoftheabsorptionspectrumedge,acceleratesurfacehydroxylation,andenhancetheseparationeffi

    ;ciencyofphotoinducedelectron.holepairs.whichresultedinasignificantimp

    dopedTiOz.Among rovementinthephotoreactivityofHo

    ;them,theHodopedTiO,calcinedat500.Cachievedthehighestphotocatalyticactivity.

    ;Keywords:titaniumdioxide;Hodoping;characterization;photocatalysis;methylorange;rareearths

    ;Photocatalyticdestructionoforganicpollutantsinthe ;presenceofTiO2appearstobeaviabledecontamination1Experimental ;processofwidespreadapplication,nomatterthestate(gas ;orliquid)orchemicalnatureoftheprocesstargetlJ_How

    1.1Preparationofrio.dopedTiO2catalysts

    ;Ver,tressnuadetect,me.I.02photocatalyncefficencYT ;opralreHodopedTiO2nanopartic1es,twokindsof

    ;lsnotgn.

    ;.

    ;asmerecomb1nationofphotogenemtedelec

    ;solutions(solutionAandB)werepraredfirst.SolutionA

    ;n_no

    ;.

;1epairsresults1nlowphotoquaI1mme~ciencyH‟was

    ;madefrombutyltitanateandisopmpaI1o1inaI1appm

    ;„here

    ;.

    ;fore,man

    ;.

    ;y

    ;.

    ;medsnaveeenundemnmproVepriateproportionanditspHwasaajustedtoabout3.0with

    ;cnehytlcacnot.riUd

    meanhHC1.SolutionBwasmadefromHo(NO3)3,whichwasdis.?nsm1 ;.

    ;2haveproVedbe

    ;.

    ;af1c1entmutetoaJterthesolvedwithdeionizedwater.Then,SolutionBwasadded

    ;photoacntyo.f

    nan.osize,dnm‟Am?ngmen1press1.y.edropwiseintoSolutionAundervigomusstirring,andtheunmeIoIpublican0ns,nowever,t ;.

    ;ewreference

;,.

    ;sdeal,v1m

    ;molarratioofbutyltitanate,isopropaI1o1,deionizedwater,

    ;tne

    ;,

    ;srlhcespecumpropertyofnania,modifiedbYrare ;andHo3+was1:22:4:0.005.conseqIently,alightyellowish ;Inthepresentstudy,theHodopednaI1osizedTiO2:tl伽叻伽d

    dmn.gezedforafew

    ;phocaJywereparedbya

    1acd—cata1yedo‟gelge1wasagedforfivedaysunderobtuon,.

    ;aI1

    ;vl~

    ;d

    ;-

    ;thendried

    ;method.Withtheobjectivetounderstandtheeffectsof.,…….,,n

    ..:………

    ;Ho.d:plng0nthephycoche衄浏properneS,pho

    gener.calcinedinairatdifferenttemperateventually

    ;1

    ;ated

;.

    ;argec

    ;,

    ;arriers,an

    ;.

    ;dsurfa

    ;.

    ;ceh

    ;.

    ;ydroxylofTi02

    ;.

    ;,thecataHo—do.edTiO2catalystsweree… ;d

    ;

    ;ina---r

    ;

    ;c

    ;ysspIeparedwerecharacenzedbymeansofVousspecd

    ;opinglevelof0.5,abbreviatedas0.5%HoTiO2.Inthet

    ;ralanalysistechniques.Meanwhile,themodification…. ;.

    ;,,

;

    ;,

    ;

    ;mechanism.fHo-dopingwasa.discussedinthisarti.‟wasal

    ;B

    ;so

    ;Foundationitem:ProjectsupportedbytheNationa1Natura1ScienceFoundationofChina(20677012)

    ;,

    ;FoundadonofNaturalScienceofGuangd.ngPr0vince ;(04205301)andFoundationofScienceandTechnologyofGuangdongProvi

    nce(2006A36701003)

    ;Correspondingauthor:CAIHeshanfE.mail:caiheshanl5@yahoo.com.cn;T

    e1.:+86.757.82400596)

    ;

    ;

    ;stitutedbydeionizedwater.Allthechemicalsusedinthe ;experimentswereofanalyticalgrade.

    ;1.2CharacterizationofH0.dopedTi02catalysts ;Thecrystallinephaseofthepreparedphotocatalystswas

    ;analyzedbyXRD(RigakuD/MAX2200vPC,Japan)with

    ;aCuKaradiation=0.154056nm)at36kVwithagraphJte

    ;monochromatorandscansat8o)/min.Thecrystallitesize ;couldbedeterminedfromthebroadeningofthecorre

    rayspectralpeaksbytheScherrerformula,and ;spondingX

    ;thelatticeparameterscouldalsobederivedfromtheXRD ;data.Theparticulatemorphologyofthephotocatalystswas

    ;observedonTeM(JEM100CXII.Japan)at190kV.Tbin

    ;vestigatethechangesinthelocalstructureoftheTiO, ;photocatalysts.FT.spectraweremonitoredbytherlTlO ;nicolet380spectrometer(USA).UVVisiblediffusereflec

    ;tancespectraofthephotocatalystsweremeasuredona ;UVVisspectrophotometer(uv3150,Shimadazu,Japan)

    ;withareflectanceunit.Thephotoluminescence(PL1emis

    ;sionspectraoftheTiO,samplesweremeasuredusingafluo

    ;rescencespectrophotometerRF-5301,Shimadazu,Japan). ;1.3Measurementsofphotocatalyticactivityofphoto

    ;catalysts

    ;Al1thephotocatalysisexperimentswereperformedonthe ;equipmentthathada250mlhollowcylindricalphotoreactor ;(SGY1,NanjingSTOCo.Ltd.)equippedwithaquartzwa

    ;terjacket.ThesetupisdisplayedinFig.1.A300W

    ;high--pressuremercurylampwithpfimarywavelengthdis-- ;tributionatapproximately365nmwaspositionedinthein

    ;nerpartofthephotoreactorandcoolwatercirculated ;throughthequartzjacketsurroundingthelamp.Batchex

    ;perimentswereconductedat(25?2).C.

    oxidation,theexperimentalsolutionwas ;Priortophoto

    ;preparedasfollows:250mlmethylorangesolutionwitha ;concentrationof20mg/Lwaspipedintoabrownflask,and ;RefreshingwaterRefreshingwater

    ;Fig.1Schemeofphotoreactor

    ;JOURNALOFRAREEARTHS,VoL26,No.1.Feb.2008

    ;0.25gphotocatalystwasaddedintoitundershaking.inan ;ultrasonicator,for15min.Thesuspensionwastransferredto ;thephotoreactorandmagneticallystirredinadarkcondition. ;for30min,toestablishanabsorption/desorptionequilibrium ;condition.Theairwasaeratedtothesolutionatarateof200 ;ml/minandthenthefightwasturnedon.Theparallelali

    ;quotsof10mlweretakenfromthesampleportatdifferent ;timeintervals,foranalysis,afterremovalofthecatalystby ;centrifugation,twice,at40OHDr/min.for10mineach.The ;absorblanceofresidualmethylorangewasdetectedbya ;UVVissFectrometer(722N,Shanghai),andthedegradation ;rateofmethylorangewascalculated.

    ;2Resultsanddiscussion

;2.1XRDanalysis

    ;TheXRDpatternsofthephOtOcata1Vstsareshownin ;Fig.2.ItcanbeseenthattheXRDpattemsofpureTiO,and

    dopedTiO2nanoparticlescalcinedat500.Caresimilar, ;Ho

    ;inwhichTiO,existsasasingleanatasephase.Although ;pureTiO2andHodopedTiO2samplescalcinedat650.C

    ;existasthecoexistenceofanataseandrutile.therelativein

    ;tensityofthe110Deakdecreasesgreatlybecauseof

    doping.ItcanbededucedthatHodopinghasasignifi ;Ho

    ;cantinhibitoryeffectonthephasetransformationofTi02 ;andthenleadstohigherthermalstability.Physicalproper. ;tiesdeterminedfromXRDdatawiththeScherrerformulaof ;thesamplesarelistedinTab1e1.Itmayindicarethat ;Hodopingcouldalsohindertheincreaseofcrystallitesize ;duringcalcination.Infact.itseemsimpossibleforHo”to

    ;reallycooperatewiththematrixofTiO2becauseofthe ;mismatchoftheionicradiiofTiandHo”.Itisexpected

    ;thatthesurroundinglanthanideionswillinhibitthephase ;transitionofARthroughtheformationofaTiOLnbond.

    ;Ontheotherhand,theLn20latticelockstheTiOspecies

    ;attheinterfacewithTiO,domains,preventingthenuclea- ;tionthatisnecessaryforthetransformationofanataseto

;20,f.)

    ;Fig.2XRDpatternsofpureTiO2andHodopedTiO2

    ;

    ;CAIHSetaL,EffectofHo.dopingonphotocatalyticacKvityofnanos~edTi02

    catalyst

    ;A:Anatase)R:Ruffle

    ;(a)

    ;O

    ;Fig.3TEMmicrographsofsamplespureTiO2(a)andHodopedTiO2(b)cal

    cinedat500.C

    ;mille,andresultsinthedecreaseofthecrystallitesizeof ;TiO27J.

    ;2.2TEManalysis

    ;Fig.3showstheTEMmicrographsofpureTiO2and ;HodopedTiO2samplescalcinedat500.C.Theaverage ;particlesizeofpureTiO2rangesfrom15to20nm,whereas, ;thatofHodopedTiO2isaround10L_15nm.Incomparison ;withthepureTiO2sample,theHodopedonehasrelatively

    ;uniformsphericalgrains,narrowsizedistribution,andgood ;dispersivity,indicatingthatHodopingCanimprovethepar

    ;ticlemorphology,andretardthegraingrowthofTi02on ;heat-treating.

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