简介：Amovingboundarymodelunderconsideringthevolumechangeofsphericalresinbeadsduringionexchangeprocesseswasemployedtorecognizethemechanismsofreecoveringuraniumfromcarbonatesolutionsusingstronglybasicanionexchanger.Twoimportantfactors,swellingandionexchange,whichdirectlyaffecttheviolumeofionexchangersweretakenintoaccount.AnionexchangemechanismhasbeenfoundfortheforwardreactionPCl/[UO2(CO3)3]^4-,andisparticaldiffusiongoverningathighconcentrationofthecomplexanion.ThemechanismofRCl/U(VI)atpH5.5-7.5isachemicalreactiontakingplaceatthemovingboundaryoftheunreactednucleus.ForthereversereactionRnU/NaCl,theuranyltricarbonatecomplexanionintheresinphaseisreplacedbyCl^-ionswithanionexchangemechanismalwaydeterminedbyparticlediffusion.TheotherformsofuraniuminthesolidphaseloadedontheresinatpH5.5-7.5shouldbelongtonon-exchangeableuranium.ThemechanismofthereversereactionRnU/HClisalwayschemicalreactionwhichisnotrestrictedtothemovingboundaryoftheunreactedcore.

简介：Apracticalandeconmicalprocessforeffectivelyrecoveringuraniumfromcarbonatesolutionsispresented.TheuraniumcomplexesaremadeunstablebyadjustingthepHofmixedsolutionsofNa2CO3andNaHCO3toabout7-8byHCland/orNaOH.WithinthisrangeofpHvalue,thesuper-equivalentuptakeofuraniumcomparedwithexchangeofCl^-andUO2(CO3)3^4-canbeworkedout,thetotalfreeeenergychangetakesontheminimumvalue,thepredominantspeciesofuraniuminresinphasemaybeU2O7^2-exceptforalittleamountofUO2^2+.