电镀废水处理的新工艺

中南民族大学硕士学位论文电镀废水处理的新工艺姓名：李岩申请学位级别：硕士专业：分析化学指导教师：杜冬云20090602INiCl2NiFA/HA[Cr(III)][Cr(VI)][As(III)][As(V)](FZ)(FZ)20%XFZ[Cr(VI)][Cr(III)]FZCr(VI)FZCr(VI)Cr(III)FZCr(III)FZCr(III)pHpHpH1.660%4.0g/L170r·min-1t=90min533.1mg·L-1Cr(III)530.0mg·L-1Cr(VI)42.9mg·L-10.01mg·L-1Cr(III)FZCr2O329.5%TCr0.94mg·L-1IIpHFZ(V)(T)pH=6.0FZV1=6.0mLT1=20minpH=9.0FZV2=24.0mLT2=21h100.61mg·L-1100.83mg·L-10.70mg·L-10.53mg·L-10.2mg·L-1IIIAbstractElectroplatingisoneofthemostpollutingindustriesworldwide.Intheelectroplatingprocess,alargeamountoftoxicandpollutingwastewaterwasproduced.Thesewastewaterscontainlargequantitiesofheavymetals(gold,silver,chromium,cadmium,nickel,leadetc),cyanideandotherorganiccompounds,whichareharmfultoorganismandhumanbeingsifuntreatedortreatedineffectivelynotmeetingtheeffluentstandard.SomemetalssuchasCraremobileandcanpenetrateintotheundergroundwateraquifers.Therefore,monitoringthelevelsoftoxicmetalsanddeterminationoftheirphysico-chemicalformsareimportant.Itisnowwellknownthatthetoxicity,bioavailability,mobility,andotherimportantpropertiesoftheseheavymetalsdependontheirspeciationaswellastheirtotalconcentrations.Thetermspeciationmeanstheoccurrenceofdifferentchemicaland/orphysicalformsor‘species’ofanelementinasample.Withreferencetometalsitisoftenusefultomakeadistinctionbetweenphysicalspeciation(distributionamongdissolved,colloidalorparticulateforms)andchemicalspeciation(distributionamongvariousdistinctchemicalspeciesinsolutionincluding‘uncomplexed’and‘complexed’formssuchasNiCl2andNi–FA/HAcomplexes).Chemicalspeciationalsoincludesthedistinctionbetweendifferentoxidationstatesofanelement,e.g.Cr(III)andCr(VI)orAs(III)andAs(V).Themosttoxicformsarethefreemetalionsandthelabilecomplexes,whiletheleasttoxicformsarethestronglyboundmetalcomplexesaswellasmetalsadsorbedoncolloidalparticles.Therefore,itisessentialtounderstandthespeciationwhenelectroplatingwastewateristreatedbychemicalprecipitation.Thethesisdiscussestreatmentofwastewatercontainingdifferentspeciesofchromium,nickelandcyanide,utilizingsodiumsulfide,heavymetalchelatingagent(FZ),ferricsaltsetc.FZisananioniccompound,containing20%effectivecomponentinaqueoussolution.Thisnewcompoundhasthepropertiesofpolymercoagulantandcomplexionabilityofdithicarbamate.Inaddition,theflockgeneratedfromFZandheavymetalsisfeaturedbylargevolume,rapidprecipitationandeasydewateringofthesludge.ThemechanismofremovingCr(VI)andCr(III)wasobtainedbyX-rayphotoelectronspectroscopy(XPS)andFouriertransforminfrared(FT-IR).Theresultsindicatedthat,firstly,FZandhexavalentchromiumCr(VI)redoxreactionoccurredIVunderacidicconditions.Secondly,FZreducedCr(VI)totrivalentchromiumCr(III).Andthen,theresidualFZchelatedCr(III),achievingtheremovalofchromium.TheoptimalconditionsofremovingCr(III)wereobtainedbyorthogonalexperimentaldesign.AndthekeyfactorswerepHanddosages.Fortherecoveryofchromiumfromwastewaterproducedinelectroplatingplants,theprocessofsodiumsulfide-reductionprecipitationwasinvestigated.Theinfluencingfactors(pHvalue,dosage,reactiontimeandstirringrate)ofchromiumrecoverywerediscussed.TheoptimalpHvalueof1.6,thedosageofsodiumsulfideforindustrialuse(60%)of4.0g·L-1ofwastewater,reactiontimeof90minandstirringrateof170r·min-1,theinitialconcentrationsoftrivalentchromiumCr(III)533.1mg·L-1andhexavalentchromiumCr(VI)530.0mg·L-1decreasedto42.9mg·L-1and0.01mg·L-1,respectively.Meanwhile,thecontentofCr2O3inchromiumslagis29.5%,meetingtherequirementforreusing.Then,forremovingresidualtrivalentchromiumCr(III)furtherwithheavymetalchelatingagent(FZ).TheconcentrationoftotalchromiumTCrintheeffluentwas0.94mg·L-1.Freenickelandnickelcyanidecomplexaretwoformsinelectroplatingwastewater.TheirRemovalefficienciesfromsimulatedelectroplatingwastewaterweredoneinbatchexperimentswithaheavymetalchelatingagent(FZ).ResultsshowedthatpH,dosagesofFZandstirringtimeaffectedtheefficiencyofnickelremovals.Theoptimalconditionsofremovingfreenickelwere:pH6.0,dosageofFZof6.0mLandstirringtimeof20min.Whiletheoptimalconditionsofremovingnickelcyanidecomplexwere:pH9.0,dosageofFZof24mLandstirringtimeof21h.Undertheconditions,theinitialconcentrationofthetwoformsofnickel,100.6mg·L-1and100.8mg·L-1,werereducedto0.70mg·L-1and0.53mg·L-1,respectively.Finally,thecombinationofironsaltsandaerationprocesscanreducecyanidecomplexto0.2mg·L-1.Theprocessissimple,safeandefficient,withlittlesecondarypollution.Thismethodcouldbeusedtoreplacethetraditionalalkalinechlorinationforcyanidecomplexremoval,whichhaslowefficiencyandresultsinchlorinepollution.KeyWords:electroplatingwastewater;speciation;heavymetalchelatingagent;chromiumwastewater;nickelwastewater;cyanidewastewater;recovery11______211.11.1.110%[1-2][3]1.1.21.1[4-5]21.1Fig1.1theprocessofelectroplating1.1.3[6][7][8][9][10][11][12][Cr(VI)][13-14][Cr(VI)][Cr(III)][15]Cr(VI)[16-18]WHO2µmolL-1[19]Cr(VI)CrO42-Cr2O72-(HCrO4-)pHCr(VI)[20]Cr(III)5.0mgL-1[21]ABCD3[22-24][Ni(II)][24][11]100250mg0.3mL•L-10.11mL•L-11h1.21.2.1[25](1)(2)(3)(4)(5)Petruzellietal.[26]Chmielewskietal.[27]LinKiang[28]Yalcinetal.[29]Cr(VI)Cr(III)pH4[30,31]SofiaA.Cavacoetal.[32