A model for the adsorption of gold from I-2/I- 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 AuI2- ions replace the Cl- ions at the active sites of the polyaniline matrix. The model incorporates the external mass transfer of AuI2- from the bulk solution to the membrane surface, followed by the pore diffusion of AuI2- 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 AuI2- within the membrane is about 8.3 x 10(-6) cm(2)/s. The potential applications of the present formulation are discussed. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012