Dissolution kinetics of copper sulphide anodes

Constant current and voltammetric experiments were carried out with synthetic and natural chalcocite and synthetic digenite anodes in a variety of electrolytes. Rapid dissolution of copper occurred at low potentials until limited by the rate at which copper could be transported from the reaction zone by diffusion through electrolyte held within the porous product layer. At this point, the potential rose sharply (galvanostatic) or the current began to fall (voltammetric) corresponding to the formation of elemental sulphur. Quantitative support for this mechanism was obtained using a simplified model of the pore diffusion process. The complexity of the solid-state reactions occurring in the anode product was revealed by a novel technique which enabled direct observation of the product profile during electrolysis.