Peroxodisulfate assisted leaching of chalcopyrite

This research investigated the effectiveness of peroxodisulfate (S ₂O ₈ ^2-) for enhancing copper leaching rates from chalcopyrite. Batch and column experiments were performed using sulfuric acid leach solutions at pH = 2, with and without Na ₂S ₂O ₈. The presence of peroxodisulfate greatly increased copper leaching rates. Tafel analysis and electrochemical impedance spectroscopy experiments performed using chalcopyrite powder electrodes indicated that peroxodisulfate increased the corrosion rate by decreasing the charge transfer resistance for chalcopyrite oxidation. In contrast to the preferential leaching of iron that has been observed for other oxidants added to chalcopyrite leach solutions, peroxodisulfate assisted leaching resulted in the release 1 mol of Cu per mole of Fe, which is identical to their stoichiometric ratio in chalcopyrite. Rates of Cu leaching from chalcopyrite followed a surface reaction rate limited, shrinking-core model with an apparent activation energy of 41 kJ/mol.