Comparative kinetic study of the silver-catalyzed chalcopyrite leaching at 35 and 68 °C

The influence of silver and iron concentration and the presence or absence of oxygen was investigated in the silver-catalyzed chalcopyrite leaching. The leaching tests were performed at two different temperatures (35 and 68 °C) in stirred flasks (180 rpm) containing 0.5 g of mineral and 100 mL of Fe3+/Fe2+ sulphate solutions at pH 1.8 and at an initial redox potential of 500 mV vs. Ag/AgCl. The addition of a great excess of silver favoured the transformation of chalcopyrite into copper-rich sulphides, such as: covellite, CuS, and geerite, Cu8S5. These sulphides prevented the formation of CuFeS2/Ag2S galvanic couple and, thus, the regeneration of silver. In addition, oxygen in solution plays a key role in the regeneration of silver ions acting as the main oxidizing agent for Ag2S.