KINETIC ASPECTS OF GALVANIC INTERACTIONS BETWEEN MINERALS DURING DISSOLUTION

A quantitative description of galvanic interactions between sulphide m inerals based on thermodynamic and kinetic parameters has been develop ed. A voltage balance over the galvanic couple provides the basis for a mathematical description of the magnitude of the galvanic interactio n. The contributions to the voltage balance include the cell emf of th e galvanic couple, kinetic descriptions of the anodic and cathodic hal f-reactions, the voltage characteristics of mineral-mineral contacts a nd the voltage losses across the solution. The rates of the anodic and cathodic half-reactions were modelled by the Butler-Volmer equation a nd the diffusion equation. The galvanic couples were constructed as ro tating ring-disc electrodes so that solution voltage losses were negli gible. Two galvanic couples, copper-pyrite and galena-pyrite, were cha racterised by initially determining the thermodynamic and kinetic para meters associated with the anodic and cathodic half-reactions under di fferent conditions of ferric concentration, electrode rotation rate an d temperature. A potentiostat was used to vary the voltages losses acr oss mineral-mineral contacts. The effect that semiconducting propertie s of minerals have on the magnitude of the galvanic interaction was de scribed by examining the anodic dissolution of galena under illuminati on. The thermodynamic and kinetic parameters were used in the mathemat ical model to obtain a prediction of the magnitude of the galvanic int eraction. The mathematical model is observed to be in good agreement w ith the experimentally measured galvanic currents.