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

Abstract

In a study of the electrochemistry of peroxide in the leaching of metals and minerals it has been confirmed that the measured potentials of solutions (hydroxide, carbonate, bicarbonate and ammonia) containing peroxide on platinum and mineral electrodes are not true equilibrium potentials but mixed potentials established by simultaneous oxidation of peroxide to oxygen and reduction to water. The potentials are dependent only on the solution pH and not on the nature of the surface or the solution. A mixed-potential model has been derived that is consistent with the potential measurements.Linear sweep voltammetry has been used to establish that the rate of the anodic oxidation of the various minerals is small compared to the rates of reduction and oxidation of peroxide at the mixed potentials and can therefore be ignored in the model.A limited study has been made of the rate of disproportionation of peroxide in the above solutions and the results compare well with previously published data.The implications of these results to previously published leaching studies and to the practical direct application of peroxide as an oxidant have been discussed.It is unlikely that peroxide will find direct application as an oxidant (or reductant) in the large scale leaching of minerals given its instability, relatively poor reactivity except at high concentrations and its cost.