二段式鸟粪石结晶法处理铜氨络合废水英文柴立元

Trans.NonferrousMet.Soc.China27(2017)457−466Two-sectionalstruviteformationprocessforenhancedtreatmentofcopper−ammoniacomplexwastewaterLi-yuanCHAI1,2,CongPENG1,2,Xiao-boMIN1,2,Chong-jianTANG1,2,Yu-xiaSONG1,2,YangZHANG1,2,JingZHANG1,2,MohammadALI1,21.SchoolofMetallurgyandEnvironment,CentralSouthUniversity,Changsha410083,China;2.ChineseNationalEngineeringResearchCentreforControlandTreatmentofHeavyMetalPollution,CentralSouthUniversity,Changsha410083,ChinaReceived30May2016;accepted6January2017Abstract:Mg2+andPO43+wereaddedintothesyntheticwastewater,leadingtothedissociationofthecomplexionsinthewastewater,andresultinginremovalofcopperandammoniatherein.Theeffectsofagentsadditionamount,pH,andreactiontimeontheremovalefficiencyofcopperandammoniawereinvestigated.Inparticular,two-sectionalstruviteformation(TSSF)processwasestablishedforcopperandammoniaremoval.MgCl2andNa2HPO4wereaddedbyfollowing90%additioninthefirstsectionandremained10%inthesecondduringtheTSSFprocess.Comparedwithonesectionalstruviteformation,TSSFpossessedmuchbetterperformance.Underconditionofn(NH3-N):n(Mg):n(P)=1:1.2:1.5(molarratio),pH=9,andreactiontimeof30min,theremovalefficienciesofcopperandammoniawere98.9%and99.96%,respectively.TheenhancedperformanceofTSSFisexplainedbythecompetitionofammoniabycopper−ammoniacomplexesandstruvite.Thedissociationofcopper−ammoniacomplexesisfurtherdemonstratedbythermodynamicequilibriumanalysis,onthebasisofcalculationsandestablishmentofpredominancephasesdiagram.Moreover,XRDandEDSanalysesfurtherconfirmedtheformationofstruviteandprecipitationofcopper,whichprovethetransmissionofcopperandammoniafromliquidphaseintosolidphase.Keywords:struvite;copper−ammoniacomplex;ammoniaremoval;heavymetalwastewater;precipitation1IntroductionAmmoniaisoneessentialnutrientthatcanleadtowatereutrophicationwhenitispresentinexcess[1−4].Meanwhile,ammoniaisaversatileligandcapableofformingcomplexcompoundswithmanymetalionssuchas234Cu(NH),234Co(NH)and234Pd(NH)[5,6].Forexample,thewastewaterfrommineralextractionindustriescontainsheavymetalsandammonia[7−9].Copperandammoniaarefrequentlyfoundintheeffluentsoftannery,explosives,andtimberindustries[10,11],withammoniapresentatconcentrationrangingfrom0.4to380mg/L[12].Spentetchingsolutionwithahighconcentrationofbothammonia(500−2000mg/L)andcopper(100−3000mg/L)isformedafterprintedcircuitboard(PCB)etching[13,14].Thechelatedmetal−ammoniaionsarequitestableinsolutionandthusaredifficulttodecompose,whichimposesagreatchallengeforefficientaswellassimultaneousremovalofmetalandammoniafromthecomplexwastewater.Previousstudiesmainlyfocusedonremovalofeitherheavymetals[15−17]orammonia[18].Onlyafewresearchesinvestigatedsimultaneousremovalofheavymetalandammoniafromtheirchelatedsolution.Forexample,SUNetal[19]studiedthesimultaneousremovalofberylliumandammonianitrogenbybiologicalaeratedfilter.PRESSMANetal[20]usednitrifyingbiofilmtoremoveammoniaandcoppersimultaneously.ZHANGetal[21]usedadualchambermicrobialfuelcelltorecoverammonia−coppercomplexfromwastewater.However,thesebiologicalmethodseitherhadnosatisfactoryefficiency,orhadlongtreatmentperiodarisenfromthemicrobialactivityinhibitioncausedbyheavymetals.StruviteformationmethodisakindofchemicalFoundationitem:Project(51674305)supportedbytheNationalNaturalScienceFoundationofChina;Project(2013WK2007)supportedbytheKeyProjectofScienceandTechnologyofHunanProvince,China;Project(2015CX001)supportedbytheInnovationStimulatingProgramofCentralSouthUniversity,China;KeyProject(1602FKDC007)supportedbyScienceandTechnologyProgramofGansuProvince,ChinaCorrespondingauthor:Chong-jianTANG;Tel:[phone];Fax:[phone];E-mail:[e-mail]:10.1016/S1003-6326(17)60052-9Li-yuanCHAI,etal/Trans.NonferrousMet.Soc.China27(2017)457−466458precipitationmethodtoremoveammoniafromwastewater,whichistypicallyrealizedbyprecipitationofmagnesiumammoniaphosphatehexahydrate(MgNH4PO4·6H2O,alsodenotedasMAP)byaddingmagnesiumsaltsandphosphatestowastewater[22−24].Generally,thechemicalstruviteformationmethodcouldefficientlyavoidtheinhibitioncausedbyheavymetals.However,thereisseldomreportaboutthesimultaneousremovalofammoniaandheavymetalsbystruviteformationmethod,whichmightbeduetothecostofextraadditionofmagnesiumandphosphate.Nonetheless,thestruviteisnotsothermostablethusitcouldbethermalized,sothemagnesiumandphosphatecouldberecycledforfurtherprecipitationofammonia,whichwasconfirmedbymanyresearchers[25,26].Fromthisperspective,struviteformationmethodcanactuallybeaneconomicalmethodforheavymetalandammoniaremovalfromwastewater.So,itisquitemeaningfultostudythestruviteformationmethodasapromisingwaytoremoveheavymetalandammoniafromwastewater.Theobjectivesofthisstudyaretoestablishthestruviteformationmethodfortreatmentofcopper−ammoniacomplexwastewaterandtodissolvethetrickyproblemindissociatingcopper−ammoniacomplex.Firstly,theeffectsoftheinfluentialfactorsincludingpH,agentdosage,andreactiontimeonremovalefficiencywereinvestigated.Secondly,thethermodynamicanalysistowardthestruviteformationprocesswasconductedbasedonthedetectionofthepre