Galvanic Interaction Between Galena And Manganese Dioxide In Hydrochloric Acid Medium Part I - Electrode Kinetics Studies

Abstract

Galvanic interaction between galena and manganese dioxide in hydrochloric acid medium was studied through polarization measurements conducted on compact disc electrodes of the minerals under different [H+] (0.025-0.2M) and [Pb++] (0.003 to 0.1 M). The two minerals formed a galvanic couple where galena dissolved as anode and MnO2 as cathode associated with a strong galvanic interaction that predominated over the self-corrosion rates of the individual minerals. Polarization diagrams of the mineral couple indicated that the overall reaction was under the control of the anodic half reaction which itself was limited by boundary layer diffusion of lead ions. Electrochemical parameters such as the self- and galvanic corrosion current densities and galvanic potential, obtained through polarization studies, were helpful in predicting the leaching behavior of the two minerals in presence of each other. Applying the Butler-Volmer equation and Nernst-Brunner equations to describe the cathodic and the anodic processes, a rate equation for the overall dissolution reaction was derived, which described well the experimentally determined parameters.