环境污染物的光催化降解活性物种与反应机理许宜铭

　　:200810　＊(No.20525724)、(No.20477038,20873124)(973)(No.2009CB825300)＊＊　e-mail:[e-mail]环境污染物的光催化降解:活性物种与反应机理＊许宜铭＊＊(浙江大学化学系　杭州310027)　　以二氧化钛为代表的光催化能使许多有毒的有机污染物发生降解或矿化,产生易被生物降解的小分子和二氧化碳,过程涉及羟基自由基等活性物种。本文在作者小组的工作基础上,试图总结近年来二氧化钛、(羟基)氧化铁、杂多酸和金属酞菁光催化或光敏化在水处理方面所取得的研究进展。综述的重点是二氧化钛半导体光催化,讨论的内容包括:(1)超氧自由基、羟基自由基和单线态氧的检测和各种生成机理;(2)金属离子、杂多酸和氟离子修饰催化剂表面对活性物种产生的影响和可能机理;(3)离子交换树脂和有机膨润土负载金属酞菁对吸附和可见光敏化降解水中有机物的影响。　光催化　活性物种　反应机理　污染物　二氧化钛　氧化铁　杂多酸　金属酞菁:O643.3　:A　:1005-281X(2009)023-0524-10PhotocatalyticDegradationofEnvironmentalPollutants:TheActiveSpeciesandReactionMechanismXuYiming＊＊(DepartmentofChemistry,ZhejiangUniversity,Hangzhou310027,China)Abstract　Photocatalysisasrepresentedbytitaniumdioxidecanmakemanytoxicorganicpollutantsdegradedormineralizedintobiogradablesmallmoleculesorcarbondioxide,theprocessinvolvingactivespeciessuchashydroxylradicals.Thisarticle,basedontheauthor'sgroupwork,attemptstooutlinetherecentdevelopmentinphotocatalysisorphotosenstiztationoftitaniumdioxide,iron(hydr)oxides,polyoxometalates(POM)andmetalphthalocyanines(MPc)forwatertreatment.Theemphasisisputonthesemiconductorphotocatalysisbytitaniumdioxide.Thediscussionincludes:(1)detectionofsingletoxygen,hydroxylandsuperoxideradicals,andvariousmechanismsproposedfortheirformation,(2)surfacemodificationofcatalystwithmetalions,POMandfluorideions,andpossiblemechansimsfortheireffectsontheproductionofreactivespecies,and(3)immobilizationofMPcontoionicexchangeresinandorganoclay,andtheinfluenceonsorptionandvisiblelightinduceddegradationoforganicpollutantsinaqueousmedium.Keywords　photocatalysis;reactivespecies;reactionmechanism;pollutants;titaniumdioxide;iron(hydr)oxides;polyoxometalates;metallophthalocyaninesContents1　PhotocatalysisofTiO2semiconductor1.1　Superoxideradicals1.2　Hydroxylradicals1.3　Singletoxyen1.4　Separationofphotogeneratedchargecarriers2　Organicphotodegaradtionmediatedbyferricoxide212320093化　学　进　展PROGRESSINCHEMISTRYVol.21No.23　Mar.,20093　Organicphotodegradationmediatedbypolyoxometalate4　Metalphthalocyaninesensitizedorganicdegradationundervisiblelight5　Conclusionremarks,、[1—6]。,、,、,、CO2。、、,、、,。(320—400nm)(400—800nm),,[1,7—9],,。,[10]:,O2、H2O;,。,TiO2,。,。,,。,Ohtani[11],。,()。,、、,。30[1—6],,,TiO2[12],。,。,,[13];、,,[14,15];,,[16]。,、、。,,、。,。1　1976,CareyTiO2,[17]。,[1—6,8—23]。,TiO2,CO2,。TiO2、、、、pH。,,[24,29],TiO2。TiO2,[5,6]。,TiO2,(h+)(e-)(1)。,;。,。TiO23.2eV,388nm。TiO2+hνTiO2(e-,h+)(1)　　,e-h+Ti3+O-·[2,5,6]。,。,TiO20.87eV,8e-[5]。,e-、h+、(O2-·)、(·OH)(1O2)。,,。,TiO2·525·23　:,。e-+O2O-·2(2a)e-+O-·2+2H+H2O2(2b)1.1　,TiO2O2e-O-·2(2a)[1—6]。,NakatoFTIR,[30]。,Hoffmann[2]Nakato[30],H2O22。,(1)。,TiO2,e-。,TiO2Cr2O72-Cr3+[19,20]。LitterEPR,Cr(Ⅴ),[21]。1　[6]Table1　Redoxpotentialsofsomeactivespecies[6]SpeciesorhalfreactionE°(V,NHE)TiO2(e-)-0.12TiO2(h+)+3.08O2+H++e-HO2-0.05HO2+H++e-H2O2+1.5H2O2+H++e-OH+H2O+0.72OH+H++e-H2O+2.72O2+4H++4e-2H2O+1.231O2+4H++4e-2H2O～2.211.2　TiO2(3.08—0.059pH)V。,h+,()(R+·ads,3)[6,10]。,,h+,(·OHsurf,4)。,·OHsurf。1991,Serpone,TiO2·OH1.5—1.7V[6,31]。,·OHads·OHsurf。,,·OHsurf1.5V2.7V。h++RadsR+·ads(3)h++Ti—OH(H2O)Ti…·OH(H+)(4)　　1979,BardDMPOEPR,TiO2·OH[32]。,。,2003,Nosaka:DMPO-EPRTiO2·OH,DMPOh+,DMPO·OH[33]。,MurakamiNosaka(LIF)[34,35],·OH。,·OHH2O,0—8mm。,FittschenLIF,Nosaka,5H2O2(6)[36]。[34—36],。,·OHH2Oh+。2·OHsurfH2O2(5)H2O2+hν2·OH(6)e-+H2O2·OH+OH-(7)　　,1999,Tatsuma,TiO212.5—500μm,[37]。,,H2O2(6)。,,H2O2O2e-(2)[38]。2004,Nakato[39—41],TiO2h+(4)。TiO2(100),O-2pTiO20.7eV。FTIR,,TiO2O2H2O。,Nakato,H2Oh+Lewis(8),[Ti—O·HO—Ti]s。[Ti—O—Ti]s+h++H2O　　　[Ti—O·HO—Ti]s+H+　(8)　　,SalvadorTiO2(110),8[42]。Salvador,h+,OH-H2O,·526·化　学　进　展21TiO2。Salvador,·OH2H2O2(6)e-(7)[42]。,MurakamiNosaka[34,35],H2O29[Ti—OOHHO—Ti]s,H2O2e-·OH(7)。[Ti—O·HO—Ti]s+h++H2O　　　[Ti—OOHHO—Ti]s+H+　　(9)1.3　O2-··OH,TiO21O2。2004,Nosaka,TiO21O2,O2-·h+1O2[43]。,TiO21O2,1O2(0.12—0.38)TiO2[44]。,Macyk,1O2O2TiO2,TiO2,[45]。1.4　1,。,、,。O2TiO2,[25,29]。,TiO2。,,,e--h+,。,TiO2Fe3+,X3B[46]。,Fe3+O2E°(+0.77V-0.05V),TiO2e-,。,Fe2+O2。,Fe3+Fe2+,[47]。,TiO2Cr(Ⅵ),Fe3+Fe2+[20]。CrⅥ-CrⅤE°(+0.6V[21]),Fe3+CrⅥTiO2e-Fe2+,Fe2+CrⅥFe3+。,Fe3+Cr(Ⅵ)[20]。TiO2H3PW12O40(POM),[48—51]。Ferry,POMTiO2e-,[48]。Choi,POMO2TiO2。POMTiO2e-,O2POM[49]。ZhaoGC-MS、DMPO-EPRTOC,POMTiO2,O2-·。,O2,O2-·[50]。XuX3B,POMTiO2X3B。,POMX3BTiO2。·OH,,POMe-,h+·OHsurf(4)。POM[50]。,X3Bh+,·OHsurfh+。,POM,X3B,X3B[51]。,POM-TiO2DCP。,TiO2h+。2000,Minero[52],TiO210mMNaF,3。·OH,,TiO290%·OHsurf,F-TiO2·OHfree[53]。F-F-E°(+3.52V),h+。,,TiO2,h+·OHfree。·OHfree·OHsurf,[52]。,·OH。SelliDMPO-EPR,F-TiO2·OHTiO210[54]。XuPOM,X3B·527·23　:,X3B。,·OH·OHfree[51]。ChoiTiO2,NaF。,,·OHH2O2UV(6),·OH[55]。Choi[56],,TiO2,。,UV,Minero[56]。UV,TiO2TiⅢ,TiⅣ,TiⅢ-OH。,,,TiⅢ-F,TiⅣ-F。,Minero。TiO2TiⅣ-OHTiⅣ-F,h+·OHsurf。,·OHsurf,。,。,MineroTiO2。,,,[52]。,。Choi[55]。,XuTiO2[57]。,。TiO2,,1mM15。TiO2,TiO2,。,,F-TiO2TiO2。,Xu(1)[57]。TiO2,·OHsurf,·OHsurf·OHfree。。[52]pH[52,56],,1　TiO2[57]Fig.1　Fluoride-promoteddesorptionof·OHfromTiO2[57]。,TiⅣⅢ,·OHsurf,。,TiO2TiO2[57]。F-TiO2,Xu[57],TiO2,TiO2。,TiO2Ag+,TiO2。,TiO2,TiO2,O2,。e-,TiO2,TiO2[57]。,[20,58,59]。Ag+F-,TiO2O2F-[57]。Ag+O2e-,,·OHfreeh+。(4),Lewis(8)。·OH(9)[35]。O2,Durrant,TiO24h+,,h+·OH[60]。2　,、。,(),[13]。·528·化　学　进　展21Fe