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.