Kinetics of goldcyanide extraction using ion-exchange resins containing piperazine functionality

The search for suitable resins for goldcyanide recovery from cyanide solutions prompted the synthesis of resins incorporating new functionalities that solve many of the existing problems. A new type of ion-exchange resin (PS-PIP) incorporating a piperazine group, linked onto a styrene-divinylbenzene macroporous network, was developed for goldcyanide solutions. Kinetics measurements were made on the extraction of goldcyanide (Au(CN)(2)(-)) with the ion-exchange resin (PS-PIP). The extraction process is accompanied by fast ion-exchange reaction and is characterised by a sharp moving boundary between the reacted shell and the shrinking unreacted core within the resin. Analyses of the respective rate data in accordance with two theoretical models used to explain the metal extraction kinetics showed that the process is controlled by the rate of diffusion of the ions penetrating the reacted layer at goldcyanide concentrations in the range 10-40 mg 1(-1) and controlled by the rate of diffusion of the ions across the liquid film surrounding the resin particle at goldcyanide concentrations lower than < 2 mg 1(-1). Particle diffusion coefficients and mass transfer constants across the liquid film were determined from the graphical representation of the proposed models. (C) 2002 Elsevier Science B.V. All rights reserved.