JOURNALOFENVIRONMENTALSCIENCESISSN1001-0742CN11-2629/Xwww.jesc.ac.cnAvailableonlineatwww.sciencedirect.comJournalofEnvironmentalSciences2013,25(6)1098–1106Effectsofenvironmentalfactorsonsulfamethoxazolephotodegradationundersimulatedsunlightirradiation:KineticsandmechanismJunfengNiu∗,LilanZhang,YangLi,JinboZhao,SidanLv,KeqingXiaoStateKeyLaboratoryofWaterEnvironmentSimulation,SchoolofEnvironment,BeijingNormalUniversity,Beijing100875,ChinaReceived11September2012;revised04November2012;accepted19November2012AbstractToadvancetheknowledgeoftheenvironmentalfateofsulfamethoxazole(SMX),wesystematicallyinvestigatedtheeffectsofnaturalwaterconstituentsandsyntheticsubstances(i.e.,TiO2nanoparticles(nTiO2)andTi-dopedβ-Bi2O3(NTB))onthephotodegradationkineticsofSMXunderxenonlampirradiation.ThephotolysisofSMXinaqueoussolutionfollowedfirst-orderkinetics.OurresultsshowedthathigherconcentrationsofSMX,fulvicacid,suspendedsediments,NTBandhigherpHvaluedecreasedthephotodegradationratesofSMX,whereasH2O2improvedtheSMXphotodegradation.TiO2nanoparticleshadadualeffectonphotodegradationduetotheirphotocatalyticactivityandphotoabsorptionofphotons.NointermediatesmoretoxictowardVibriofischerithanSMXwereproducedafterdirectphotolysisandphotocatalyticdegradationfor3hr.ThephotolysisofSMXinvolvedthreepathways:hydroxylation,cleavageofthesulfonamidebond,andfragmentationoftheisoxazolering.ThisstudylaysthegroundworkforabetterunderstandingoftheenvironmentalfateofSMX.Keywords:photodegradation;sulfamethoxazole;environmentalfactors;toxicityDOI:10.1016/S1001-0742(12)60167-3IntroductionSulfamethoxazole(SMX)belongstothesulfonamideclassofantibacterialcompoundsandisextensivelyusedinhumanandveterinarymedicine(Mookherjeeetal.,2012).Ina1999–2000USGSreconnaissanceofUSstreams,SMXwasfoundathigherconcentrationsthanothersulfon-amidesandthenwascategorizedasapersistentantibiotic(Kolpinetal.,2002).Recently,theconcentrationofSMXinsurfacewatershasbeendetectedatlevelsfrom30to480ng/L(Hebereretal.,2008;Luoetal.,2010)andashighas2000ng/Linmanymunicipalsewagetreatmentplants(Andreozzietal.,2003;Buenoetal.,2007).ThehighfrequencyofdetectionandrelativepersistenceofSMXinthewatersystemindicatedthatthiscompoundwasapotentialrisktotheecosystembalance(Xuetal.,2011).EventhoughSMXhasnodirecteffectonhumanhealth,itexhibitsbiotoxicityforsomefishandalgaegrowth(Sandersonetal.,2004).Inaddition,SMXwasalsoreportedtoinducegeneticmutationsandchroniceffectseveninlowconcentration(Zhangetal.,2010).Inspiteofitsintensiveuseinmodernmedicineandubiquitouspresenceinsurfacewaters,knowledgeonthe*Correspondingauthor.E-mail:junfengn@bnu.edu.cntransportationandtransformationofSMXintheaquaticenvironmentisstilllimited.Inrecentyears,manypublishedreportsareavailableonvariouschemical,physical,andbiologicaltreatmenttechniquestoremoveSMXfromwastewater,suchashydrolysis,sorption,andbiodegradation(Andreozzietal.,2003;Boreenetal.,2003;Buenoetal.,2007).However,itwasdemonstratedthatabioticprocesseslikehydrolysisorsorptiontosedimentswereofminorimportancefortheeliminationofSMX(Radkeetal.,2009).Inaddition,theeliminationofSMXthroughsewagetreatmentisincom-plete,thusresidualSMXvaryingfrom0.01to2.0µg/Lhasbeendetectedinmunicipalsewagetreatmentplanteffluents(Andreozzietal.,2003;Buenoetal.,2007).Apartfromhydrolysis,sorption,andbiodegradation,photolysismaybemoreeffectivefortheeliminationofantibi...
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