The role and use of hydrogen peroxide as an oxidant in the leaching of minerals. 1. acid solutions

The results of an electrochemical study of the use of hydrogen peroxide in the dissolution of selected sulphide minerals in acidic sulfate solutions in the absence and presence of iron(III) are described. The behaviour of peroxide on platinum and gold electrodes has been studied in parallel. The focus has been on the effect of peroxide on the equilibrium and mixed potentials under various conditions. It has been confirmed that the measured potentials of peroxide solutions on platinum and gold electrodes are not true equilibrium potentials but mixed potentials established by simultaneous oxidation of peroxide to oxygen and reduction to water. The effect of added iron(III) ions on such potentials have been further studied. This approach has been extended to the potentials of pyrite, chalcopyrite and covellite under similar conditions. Linear sweep voltammetry has been used to elucidate and confirm the mechanisms proposed for the potential measurements. Synergism in the simultaneous reduction of peroxide and iron(III) on both metal and mineral electrodes has been observed and characterized. Implications of these results to previously published leaching studies and to possible practical application of peroxide as an oxidant are discussed.