Copper precipitation during leaching of various copper sulfide concentrates with cupric chloride in acidic solutions

The leaching behavior of copper sulfides in concentrated cupric chloride solution at 95 °C and at ambient pressure was studied in order to scrutinize the leaching behavior of a single bornite and four different chalcopyrite concentrates obtained from various mines around the world. The highest chalcopyrite oxidation was achieved with the highest pyrite content in the concentrate, suggesting galvanic effect on chalcopyrite dissolution. It was found that iron and copper from chalcopyrite did not dissolve into the solution in an equal ratio, as expected. A significant amount of copper precipitated at pH ≤ 1.4. This study showed that chalcopyrite chloride leaching, in the absence of oxygen purging, leads to covellite precipitation. The mineralogical studies on a leach residue established that the precipitated copper was a secondary covellite (CuS). Leaching of bornite rich concentrate did not increase acidity and no equally strong copper precipitation was observed at pH = 2.1.