Influence of metallic ions in the bioleaching of chalcopyrite by Sulfolobus BC: Experiments using pneumatically stirred reactors and massive samples

The influence of several metal ions on the bioleaching of a copper concentrate by Sulfolobus BC was studied using pneumatically stirred columns. Ag, As, Bi, Co, Hg, Mo and Ru were tested, and 10 g metal/kg concentrate were added, except in the case of Mo and Ag where 4 g Mo/kg concentrate and 1 g Ag/kg concentrate were used. Bismuth was the only metal to enhance the initial dissolution rate of copper, and bring about a greater final extraction than was obtained in the culture with no cation added. In addition, experiments were carried out with massive samples of two types of chalcopyrite in order to study the interaction of silver and bismuth with the mineral. The mechanism of action of each cation was different: silver reacted with the surface of the chalcopyrite to form a layer of Ag 2S. This layer caused the passivation of the mineral in places with a deposit and promoted the anodic behavior of the surface not covered. On the other hand, bismuth acted in solution and prevented the formation of phosphate complexes of Fe 3+ by precipitating as bismuth phosphate so increasing the oxidizing potential of the Fe 3+/Fe 2+couple.