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TreatmentofWastewaterContainingRDXbyFenton'sReagentXUHang(徐航)1,ZHANGDong-xiang(张东翔)2,XUWen-guo(徐文国)11.SchoolofScience,BeijingInstituteofTechnology,Beijing100081,China;2.SchoolofChemicalEngineeringandEnvironment,BeijingInstituteofTechnology,Beijing100081,ChinaAbstract:Fenton'sreagentwasemployedtotreatthewastewatercontainingRDX.TheeffectsofFeSO4concentration,H2O2concentration,pHvalue,reactiontime,temperatureandinitialCODofwastewateronresidualCODofwastewaterwereinvestigated.TheresultsshowthattheoptimumFeSO4concentrationandpHare700mg/Land2.5,respectively,andtheresidualCODofwastewaterdecreaseswiththeriseinH2O2concentration,butincreaseswiththeriseintempera-ture.AfterFenton'sreagenttreatment,theinitialCODoflessthan874mg/Lwastewatercanmeeteffluentstandard.Underconditionsof100mg/LH2O2,437mg/LinitialCODand15℃temperature,thelowestresidualCODisobtainedat83.80mg/Lin5min.KeyWords:advancedoxidationprocessing;Fenton'sreagent;RDX;wastewaterCLCNumber:X703DocumentCode:AArticleID:1673-002X(2008)01-0018-04Received2007-08-09SponsoredbyNationalNatureScienceFoundationofChina(20476010)BiographiesXUHang(1982—),doctoralstudent;ZHANGDong-xiang(1965—),associateprofessor,boris@bit.edu.cnIntroductionThehexahydro-1,3,5-trinitro-1,3,5-triazine(RDX)isoneofthemostcommonhighlyenergeticexplosives.ThewastewatercontainingalotofRDXandorganiccontaminantisproducedduringindustrialprocessingofcoatingandrecyclingRDX.Thecharac-teristicsoftheorganicwastewaterarestrongchro-maticity,non-transparent,highchemicaloxygende-mand(COD)andlowbiochemicaloxygendemand(BOD)/CODratio.ThepreviousreportsonRDXshowedthatitisclassifiedasapossiblehumancar-cinogen[1].Nowadays,therearemanyapproachestodealwithexplosivewastewater,suchasbiodegrada-tion[2],chemicalcoagulation,photocatalytic[3]andchemicaloxidation[4].Fenton'sreagentisatypicaladvancedoxidationtechnologytodealwithorganicwastewater.AmixtureofFe(Ⅱ)catalystandH2O2canformfreeradicals(·OH)tooxidizecontaminantsinacidaqueous[5].ThereactionmechanismforFen-ton'sreagentinacidaqueousisshowninFig.1.Ifthe·OHisnottrappedbyaspecies,anotherFe(Ⅱ)andH2O2willreactwithit.Therefore,Fe(Ⅱ)dosageandH2O2dosagehavethepropervaluesinFentonoxidationprocessing.Fig.1 MechanismofFenton'sreagentinacidaqueousInthispaper,Fenton'sreagentisusedtotreattheorganicwastewatercontainingRDX.TheeffectsofinitialFe(Ⅱ)concentration,initialH2O2concen-tration,pHvalue,reactiontime,temperatureandinitialconcentrationoforganicwastewaterareinvesti-gatedindetail.1 Experiment1.1 WastewaterThewastewatercontainingRDXusedinthisstudywasobtainedfromanexplosivemill(China).Itwasanalyzedthatthesamplewastewatercontained—18—JOURNALOFCHINAORDNANCEsometoxicorcoloredorganiccontaminants,suchasRDX,azocompounds,andfattygroupcompounds,inwhichCODcontentwasabout45-50g/L,andthechromaticitywas30000-35000.Andtheex-perimentalwastewaterwastakenfromthesamplewastewater,inwhichCODwasdilutedto437mg/L.1.2 ReagentsFeSO4·7H2O,H2SO4,K2Cr2O7,Ag2SO4,(NH4)2Fe(SO4)2·7H2O,NaOH,H2O2(30%inH2O)wereofanalyticalgradeandpurchasedfromBeijingChemicalReagentCompany(China).1.3 ProceduresandAnalysisFentonoxidationwasprocessedusinga100mLwastewatersolutioncontainingRDXinabeaker.Thewastewaterwasstirredinamagneticstirrer.ThepHofwastewaterwasadjustedusingH2SO4.Thequan-titativeFeSO4andH2O2wereaddedtothewastewa-ter.ItspHwasraisedto10byusingNaOHsolutiontoquenchtheoxidationbytheendofreaction.CODofwastewaterwastestedbyGB1914—89(K2Cr2O7method).2 ResultsandDiscussion2.1 EffectofInitialFeSO4DosageFig.2 EffectofadditionofFeSO4dosageTheamountofferrousionisoneofthemainpa-rametersinfluencingtheFentonoxidationprocessing.Fig.2showstherelationshipbetweenresidualCODofwastewaterandtheinitialFeSO4dosageduringFen-tonprocessing.TheresultsindicatethatadditionofFeSO4from300to700mg/LcanincreaseCODre-movalanddecreaseresidualCODofwastewaterfrom362.1to58.9mg/LduringtheFentonprocessing.However,theresidualCODofwastewatercanin-creaseto83.7mg/LifFeSO4dosageisaddedto1100mg/L.Thus,whenH2O2dosageis1000mg/L,700mg/LofinitialFeSO4canbeusedasanopti-mumdosageforFenton'sreagenttodealwithwastewatercontainingRDX.Theexperimentalphe-nomenasuggestthatFe(Ⅱ)isoxidizedbyH2O2togenerate·OH(Eq.(1)),andhighactive·OHat-tacksanddestroysorganiccontaminantsinacidaque-ous[6].ButexcessiveFe(Ⅱ)canconsumesome·OH(Eq.(2))anddecreaseeffectofFenton'sreagent[7].Fe2++H2O2Fe3++·OH+OH-,(1)Fe2++·OHFe3++OH-.(2)Fig.3 EffectofpHvalue2.2 EffectofInitialpHValuepHofthesolutionisanotherimportantparame-terforFentonoxidationprocessing[8].TheeffectofpHonthedecompositionofwastewatercontainingRDXbyFentonoxidationprocessingisshowninFig.3.ItcanbeseenclearlyfromFig.3thattheadditionofpHfrom1.5to2.5isabletoincreasetheCODre-movalofwastewateranddecreasetheresidualCODofwastewaterfrom120to58.9mg/L.ButthefurtheradditionofpHfrom2.5to6.0cansharplydecreasetheCODremovalandincreaseresidualCODofwastewaterfrom58.9to152.4mg/L.Therefore,pHof2.5isconsideredastheoptimumvalueinFen-tonoxidationprocessing,whichissupportedbysomepreviousRefs[8-9].AtlowpH(pH2.5),theCODremovalislimitedbecausethefreeradicalsareconsumedbytheexcess