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-trimethylpentyl)phosphinic acid (DTMPPA=HL) onto a macroporous polymeric support of Amberlite XAD2 were made. The extraction process is accompanied by fast chemical reaction and is characterized by a sharp moving boundary between the reacted shell and the shrinking unreacted core within the impregnated resin. Analyses of the respective rate data in accordance with two theoretical models used to explain the metal extraction kinetics showed that process is controlled by the rate of diffusion of the ions penetrating the reacted layer at high metal ion concentration (1x10(-2) mol.L-1) and controlled by the rate of diffusion of the ions across the liquid film surrounding the resin particle at low metal ion concentration (1x10(-4) mol.L-1). Particle diffusion coefficients and mass transfer constants across the liquid film were determined from the graphical representation of the proposed models.