The role of EH measurements in the interpretation of the kinetics and mechanisms of the oxidation and leaching of sulphide minerals

Measurements have been made of the potentials of pyrite, arsenopyrite and chalcopyrite rotating disk electrodes in acid sulfate solutions containing iron(III) and iron(II). These potentials have been compared with those of a stationary platinum wire and glassy carbon (pyrite) and platinum (arsenopyrite and chalcopyrite) ring electrodes. It has been demonstrated that the potential measured in the bulk of the solution can only be approximated to that at the surface of the minerals under conditions of relatively high concentrations of iron(II). A theoretical treatment of the mixed potential model has enabled the difference between the bulk solution potential and the mineral potentials to be calculated from the electrochemical characteristics of the reactions involved. These calculated differences have been compared with the experimental values.