EnhancedRemovalofUranium(VI)byNanoscaleZerovalentIron

EnhancedRemovalofUranium(VI)byNanoscaleZerovalentIron
SupportedonNa−BentoniteandanInvestigationofMechanism
GudongSheng,
†
XiaoyuShao,
†
YiminLi,
†,
* JianfaLi,
†
HuapingDong,
†
WeiCheng,
†
XingGao,
‡
andYuyingHuang
‡
†
CollegeofChemistryandChemicalEngineering,ShaoxingUniversity,HuanchengWestRoad508,Shaoxing,Zhejiang312000,P.R.
China
‡
ShanghaiSynchrotronRadiationFacility(SSRF),ShanghaiInstituteofAppliedPhysics,ChineseAcademyofSciences,Zhangheng
Road239,Shanghai201204,P.R.China

1.INTRODUCTION
Uranium(U)isacommoncontaminantfoundinwaternear
manynuclearpowerplants,weapon-relatedwastesitesand
uraniummininglocations.ItcanexistasU(0)orinseveral
oxidationstatessuchasU(III),U(IV),andU(VI),among
whichU(VI)andU(IV)arethemajorstatesinthe
environment.
1
Itiswell-knownthatU(VI)ofhightoxicity
andmobilitydominatesunderoxidizingconditions,andexists
mainlyascomplexed,adsorbedorprecipitateduranyl(UO2
2+
)
species,whileU(IV)existscommonlyaslesssolublespeciesof
lowtoxicityunderreducingconditions.
1,2
Manystudieshave
shownthatthefateandtransportofuraniuminthenatural
environmentisgreatlyaffectedbytheredoxtransformation
betweenU(VI)andU(IV),andthusreductionofsoluble
U(VI)tolesssolubleU(IV)hasbeenproposedasanimportant
methodtoremediateU-contaminatedsites.
1−3
SincethereportofCantrelletal.,
4
zerovalentiron(ZVI)has
beenconsideredasoneofthemostpromisingapproachesto
remediateU(VI)andothermetalsfromcontaminated
groundwaterbecauseZVIisinexpensiveandreadilyavailable.
5
Subsequently,numerousstudieshavefocusedonthereaction
kineticsandmechanismsbetweenZVIandU(VI).
6,7
Recently,
nanoscalezerovalentiron(NZVI)hasreceivedmuchattention
forthetreatmentofU(VI)duetoitshigherreactivitythanZVI
ofordinarysizes.
2,8,9
However,freshlypreparedNZVIisaptto
aggregateintolargeclusters,leadingtothedecreased