Acidic sulphate leaching of chalcopyrite concentrates in presence of pyrite

Chalcopyrite leaching by ferric ions (a) without pyrite (b) in presence of pyrite. [Display omitted] ► 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 410–440mV vs Ag, AgCl. ► High redox potentials and iron concentrations above 5g/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. Copper concentrates with mineralogy dominated by chalcopyrite have slow leaching kinetics at atmospheric pressure in sulphate media because of the formation of passivation layer on its surface during the leaching. To enhance the leaching rate of the copper concentrate, pyrite was added to act as a catalyst. Pyrite and copper sulphide minerals then form a galvanic cell which increases both the copper leaching rate and yield. Effect of parameters such as solution redox potential, temperature, initial acid concentration, solids content, total initial iron concentration and pyrite to copper sulphide minerals mass ratio were investigated. Mineralogical analyses by XRD were performed on selected leach residues and the feed materials. A copper recovery higher than 80% in 24h was achieved at a redox potential of 410mV vs Ag, AgCl, a temperature of 85°C, 15g/L of initial acid concentration, a solid content of 7.8% (w/v), a total initial iron concentration 5g/L and pyrite to copper sulphide minerals mass ratio 2:1. XRD patterns on leach residues showed that candidates for surface passivation, i.e. jarosite and elemental sulphur, were formed at high total initial iron concentrations.