Investigation of three-liquid-phase extraction systems for t

SeparationandPuri cationTechnology76 (2010) 191–197

ContentslistsavailableatScienceDirect

SeparationandPuri cation

Technology

journalhomepage:/locate/seppu

r

Investigationofthree-liquid-phaseextractionsystemsfortheseparationofTi(IV),Fe(III)andMg(II)

KengXiea,b,c,JunmeiZhaoa,LiangrongYanga,c,PinhuaYua,c,HuizhouLiua,

a

KeyLaboratoryofGreenProcessandEngineering,InstituteofProcessEngineering,ChineseAcademyofSciences,Beijing100190,ChinaNationalEngineeringLaboratoryforHydrometallurgicalCleanerProductionTechnology,Beijing100190,Chinac

GraduateUniversityoftheChineseAcademyofSciences,Beijing100039,China

b

articleinfoabstract

Three-liquid-phaseextractionsystem(TES)composedofanorganicsolvent-richtopphase,apolymer-richmiddlephaseandasalt-richbottomphasehasbeenconsideredtobeapromisingmethodofisolationandseparationofmulti-component.Inthispaper,wetriedtouseTEStotreatmulti-metalsolutionsincludingTi(IV),Fe(III)andMg(II)forthe rsttime.Differentcombinationsoforganicextractant–polymer–inorganicsaltwereevaluated.Andtheeffectsofsolutionacidity,complexingagentsandadditivesonthemetalionspartitioningwereinvestigated.TheresultsindicatedthatMg(II)wascon-centratedinthesalt-richbottomphase,whereasTi(IV)andFe(III)werequantitativelyextractedintothetrialkylphosphineoxide(TRPO)(ordi-2-ethyl-hexylphosphoricacid(D2EHPA))-richtopphase.Andtheadditionofethylenediaminetetraaceticacid(EDTA)enabledFe(III)todistributeintothepolyethyleneglycolwithmolecularmass2000(PEG2000)-richmiddlephase.ThetransferofFe(III)greatlyimprovedtheselectivityofthetopphaseforTi(IV)andmadeasigni cantimpactontheseparationofTi(IV),Fe(III)andMg(II).

© 2010 Elsevier B.V. All rights reserved.

Articlehistory:

Received31January2010

Receivedinrevisedform8October2010Accepted14October2010

Keywords:

Three-liquid-phaseextractionsystemSeparationTi(IV)Fe(III)Mg(II)

1.Introduction

Avastmajorityofindustrialef uentsandwastewater,suchasetchingorpickingbaths,electroplatingrinseliquors,leachingsolutiongeneratedduringhydrometallurgyminingwater,spentphotographicsolutionsandsoforthmaycarryiron,manganese,chromiumandahostofnon-ferrousmetalssuchascopper,nickel,zinc,titanium,magnesium,aluminum[1].Discardoftheseef u-entsmaycauseenvironmentalproblemsandeconomicloss.Thusitisnecessaryto ndoutsuitabletechniqueforextraction,sep-aration,andrecoveryofthesemetalsinconsiderationofwastetreatment,ualtechniquesfortheseparationandrecoveryofmetalsare,forexample,precipitation,liquid–liquidextraction,electroly-sisandionexchange.Amongthesetechniques,theliquid–liquidextractiontechniqueexhibitsasuperiorseparationperformancethanothers.Throughtheapplicationofdifferentdiluents,extrac-tants,andaqueousphaseconditions,thetechniquemaybeadaptedtohandleawidevarietyofsolutes.Extractionkineticsisoftenrapid,enablinghighthroughput,andthetechnologymaybeengineeredforselectivityandef ciencythroughtheuseofmultistagecontac-

Correspondingauthorat:No.1,BeiErTiao,ZhongGuanCun,HaidianDistrict,Beijing100190,China.Tel.:+861062554264;fax:+861062554264.

E-mailaddress:hzliu@(H.Liu).1383-5866/$–seefrontmatter© 2010 Elsevier B.V. All rights reserved.doi:10.1016/j.seppur.2010.10.007

tors.However,itiscon nedtopurifyonemetalinonestepduetothemasstransferbetweenthetwophases.

Three-liquid-phaseextractionsystem(TES)composedofanorganicsolvent-richtopphase,apolymer-richmiddlephaseandasalt-richbottomphaseshowspossiblemuchhigherselectivitythantheusualwater–oilliquid–liquidsystemandaqueous-two-phasesystem(ATPS),providingphaseswithawiderangeofpolaritiesandchemicalpropertiestosuitdifferentpurposes[2].Inourlabo-ratory,Chenetal.[3]andShenetal.[4]havedevelopedsomeTESscontainingpolyethyleneglycol(PEG)orethyleneoxide–propyleneoxide(EOPO)randomcopolymersandusedthemforseparat-ingofglycyrrhizicacidandliquiritinfromglycyrrhizauralensis schextractaswellastreatingsimulatedwastewatercontainingp-nitrophenol(p-NP)andphenol.ResultsshowedthatTEScon-tainingethyleneoxide–propyleneoxiderandompolymers,butylacetateand(NH4)2SO4couldachievesatisfyingseparationyieldsatpH=9.3withabout80%phenolinthesolvent-richtopphaseand95%p-NPinthepolymer-richmiddlephase,respectively[5].Yuetal.[6]continuedtheresearchandselectedTESscontain-inghexanetotreatthemodelwastewatercontainingisomersofp-NPando-NP.About85wt.%o-NPand90wt.%p-NPcouldbesimultaneouslyextractedintothetopandmiddlephaseatpH=4.0,respectively.TESoffersapotentiallyattractivealternativetotreatmulti-componentef uentsinthatitcombinestheprocessofextractionandpuri cationofleasttwocomponentsinasingleunitoperation.