Chloride leaching of chalcopyrite

Two new process flowsheets have been developed which combine chloride leaching of copper from chalcopyrite with solvent extraction, to selectively transfer copper to a conventional sulfate electrowinning circuit. Chloride leaching with copper(II) as oxidant offers significant advantages for copper including increased solubility and increased rates of leaching. Both process flowsheets were similarly designed with a two stage counter-current leach but differ with respect to iron deportment. The goethite model flowsheet includes sparging of air or oxygen to the second leach stage to aid precipitation of iron as goethite (FeOOH). The hematite model flowsheet precipitates iron as hematite (Fe2O3) downstream from the leach in a dedicated autoclave. A mass balance has been completed for both process flowsheets and this determined the concentrations of copper and iron species in feed liquor returning to the leach following copper solvent extraction.The optimum leach extraction conditions were determined by varying grind size, temperature and residence time for both leach model scenarios. Leach tests were conducted using a chalcopyrite concentrate from Antamina in northern Peru, which contains a low to moderate amount of gangue material. The hematite model was also examined using a Rosario concentrate from Chile which contained chalcocite in addition to chalcopyrite and significant pyrite. Leach tests based on the hematite model were successful in achieving copper extractions > 95% in 4–6 h at 95 °C after fine grinding the concentrate (P90 = 41 μm). However, copper extraction exceeded 99% from the finely ground Rosario concentrate (P90 = 37 μm). In the goethite model leach tests, 89% copper extraction was achieved under optimum conditions in the atmospheric conditions tested.