Abstract
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 Fe 3+/Fe 2+ 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, Cu 8S 5. These sulphides prevented the formation of CuFeS 2/Ag 2S 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 Ag 2S.
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