The dissolution of chalcopyrite in chloride solutions: Part 1. the effect of solution potential

A study of the dissolution of several copper concentrates under controlled potential conditions in chloride solutions has demonstrated that the rate of dissolution of chalcopyrite is strongly dependent on the potential of the solution. Linear rates were obtained for the dissolution of chalcopyrite in solutions containing 0.2 M HCl and 0.5 g L^{- 1} Cu(II) at 35 °C. The rate is enhanced within a range of potentials of 550 to 620 mV (versus SHE) and the presence of dissolved oxygen is essential for enhanced rates within this potential window. Even though dissolved oxygen is important in order to achieve acceptable rates of dissolution, excessive oxidation can increase the potential into a region in which passivation is possible. Reduction of the potential into the optimum region results in restoration of enhanced rates of dissolution. On the other hand, dissolution at low potentials (< 540 mV) results in reduced rates of copper dissolution which increase significantly when the potential is subsequently increased to above 580 mV. Mineralogical studies have shown that chalcopyrite remains un-leached and small amounts of covellite appear to be formed on the surface of the chalcopyrite at low potentials. All concentrates appear to dissolve at roughly the same rate under the same conditions, despite differences in the composition and mineralogy of the samples.