Kinetics studies on heavy metal ions extraction by Amberlite XAD2 impregnated resins containing a bifunctional organophosphorous extractant

Kinetics measurements on the extraction of divalent metal ions (Zn, Cu and Cd) with impregnated resins, prepared by adsorption of a bifunctional extra ctant, O-methyl-dihexyl-phosphine-oxide O'-hexyl-2-ethyl phosphoric acid (I -IL) into polymeric macroporous supports of Amberlite XAD2 (XAD2-HL), were made. The extraction process is accompanied by fast chemical reaction and i s characterized by a sharp moving boundary between the reacted shell and th e shrinking unreacted core within the impregnated resin. Analyses of the re spective rate data in accordance with two theoretical models used to explai n the metal extraction kinetics showed that process is controlled by the ra te of diffusion of the ions penetrating the reacted layer at high metal ion concentration (1 x 10(-2) mol l(-1)) and controlled by the rate of diffusi on of the ions across the liquid film surrounding the resin particle at low metal ion concentration (1x10(-4) mol l(-1)). Particle diffusion coefficie nts and mass transfer constants across the liquid film were determined from the graphical representation of the proposed models. (C) 1998 Elsevier Sci ence BN. All rights reserved.