KINETIC-STUDIES ON HEAVY-METAL IONS REMOVAL BY IMPREGNATED RESINS CONTAINING DI-(2,4,4-TRIMETHYLPENTYL) PHOSPHINIC ACID

Kinetics measurements on the extraction of divalent metal ions (Zn, Cu and Cd) with impregnated resins prepared by adsorption of di(2,4,4-tr imethylpentyl)phosphinic acid (DTMPPA=HL) onto a macroporous polymeric support of Amberlite XAD2 were made. The extraction process is accomp anied by fast chemical reaction and is characterized by a sharp moving boundary between the reacted shell and the shrinking unreacted core w ithin the impregnated resin. Analyses of the respective rate data in a ccordance with two theoretical models used to explain the metal extrac tion kinetics showed that process is controlled by the rate of diffusi on of the ions penetrating the reacted layer at high metal ion concent ration (1x10(-2) mol.L-1) and controlled by the rate of diffusion of t he ions across the liquid film surrounding the resin particle at low m etal ion concentration (1x10(-4) mol.L-1). Particle diffusion coeffici ents and mass transfer constants across the liquid film were determine d from the graphical representation of the proposed models.