Acidic sulphate leaching of chalcopyrite concentrates in presence of pyrite

► Pyrite addition has a major catalytic effect on chalcopyrite leaching in acidic ferric sulphate media. ► High copper recoveries were obtained in a small redox potential window around 410-440 mV vs Ag, AgCl. ► High redox potentials and iron concentrations above 5 g/L resulted in passivation of the chalcopyrite surfaces. ► Acidity had minor importance on copper recoveries provided stoichiometric amounts were added to avoid precipitation of ferric iron.