Magnetic-separation-of-ferrihydrite-from

Magneticseparationofferrihydritefromwastewaterbymagneticseedingandhigh-gradientmagneticseparationNurayKarapinar*TechnologyDepartment,GeneralDirectorateofMineralResearchandExploration,06520Ankara,TurkeyReceived22May2002;receivedinrevisedform5March2003;accepted6March2003AbstractFerrihydrite,amemberofironoxidesfamily,hasbeenusedasanadsorbentfortheremovalofheavymetalionsfromindustrialwastewater.Thesuccessoftheoperationdependsmainlyontheefficientremovalofferrihydritefromtheaqueousphase.Hence,theemphasisofthisstudywasgivenontheseparationofferrihydritebyhigh-gradientmagneticseparator(HGMS)toovercomesolid/liquidseparationdifficultiesofferrihydrite.ThispaperclarifiestheseedingofferrihydritewithmagnetitemineralanditseffectsontheoperationparametersinHGMS.Magneticseedingtechniquewasusedtomakemagneticseparationavailablefortheremovalofferrihydrite,andthemagnetitemineralwaschosenasaseedingmaterial.Themethodclearlyinvolvestheattachmentofferrihydritetoamagneticseedmaterialandsubsequentmagneticseparationofferrihydrite–magnetitecoagulates.Inseedingprocess,finelydividedmagnetiteparticleswereentrappedinferrihydriteprecipitateevolvingbyincreasingpHofsolution.InrelationwiththehydrolysispropertiesofFe(III)ion,thereisapHrangewheretheseedingperformanceisoptimal.Iron/magnetiteratiohadamarkedeffectontheseparationofseededferrihydriteprecipitatebyHGMS.ThisratiodeterminestheoperationparameterssuchasmagneticfieldstrengthandflowrateonwhichthecostandperformanceofHGMSdepend.Testresultsshowedthatwhenusedwithmagneticseedingtechnique,HGMShasthepotentialtoovercomeseparationdifficultiesassociatedwithadsorption-basedtreatmenttechniqueswithitsadvantagesofhigh-performance,high-capacityandlow-spacerequirements.D2003ElsevierScienceB.V.Allrightsreserved.Keywords:ironoxides;ferrihydrite;magneticseeding;solid/liquidseparation;magneticseparation0301-7516/03/$-seefrontmatterD2003ElsevierScienceB.V.Allrightsreserved.doi:10.1016/S0301-7516(03)00029-2*Tel.:+90-312-2873430/2116;fax:+90-312-2875409.E-mailaddress:karapin