Effect of hydrogen sulfide on reductive leaching of chalcopyrite by copper

A series of leaching and electrochemical experiments were conducted to elucidate the critical role of hydrogen sulfide (H 2 S) in copper-driven reduction of chalcopyrite. Results demonstrate that in the absence of H 2 S, metallic copper converts chalcopyrite into bornite (Cu 5 FeS 4 ). However, the introduction of H 2 S promotes the formation of chalcocite (Cu 2 S) by altering the oxidation pathway of copper. Electrochemical analysis demonstrates that the presence of H 2 S significantly reduces the corrosion potential of copper from 0.251 to -0.223 V (vs SHE), reaching the threshold necessary for the formation of Cu 2 S. Nevertheless, excessive H 2 S triggers sulfate reduction via the reaction of 8Cu+H 2 SO 4 +3H 2 S=4Cu 2 S+4H 2 O (Δ G =-519.429 kJ/mol at 50 °C), leading to inefficient copper utilization.