A kinetic model for the adsorption of gold from I₂/I⁻ solutions onto a porous polymer membrane

Abstract

A model for the adsorption of gold from I 2 /I À aqueous solutions onto a cellulose acetate (CA)-polyaniline (PANI) porous membrane is presented. The adsorption of gold is represented by an ion-exchange overall reaction in which AuI 2 À ions replace the Cl À ions at the active sites of the polyaniline matrix. The model incorporates the external mass transfer of AuI 2 À from the bulk solution to the membrane surface, followed by the pore diffusion of AuI 2 À to reach the active sites in the membrane. The overall ion-exchange reaction was assumed to achieve local instantaneous equilibrium. Verification of the kinetic model with the experimental data showed that the effective diffusivity of AuI 2 À within the membrane is about 8.3 Â 10 À6 cm 2 /s. The potential applications of the present formulation are discussed.