Bioleaching of Chalcopyrite by Pure and Mixed Cultures of Acidithiobacillus and Leptospirillum

摘要

Bioleaching is an economical method for the recovery of metals, which requires low investment and operation cost. Furthermore, it is generally more environmentally friendly than many physicochemical metal extraction processes. The bioleaching of chalcopyrite in shake flasks was investigated with pure cultures of Acidithiobadllus ferrooxidans, Acidithiobacillus thiooxidans, Acidithiobacillus caldus and Leptospirillium ferriphilum and mixed cultures. The mixed cultures containing both iron- and sulfur-oxidizing bacteria were more efficient than the pure culture alone. The presence of sulfur-oxidizing bacteria positively increased the dissolution rate and percentage recovery of copper from chalcopyrite. Mixed cultures consisting of moderately thermophilic Leptospirillium ferriphilum and Acidithiobacillus caldus leached chalcopyrite more effectively than mesophilic Acidithiobacillus ferrooxidans pure and mixed cultures. The decrease of chalcopyrite dissolution rate in leaching systems containing Acidithiobacillus ferrooxidans after 12-16 days coincided with the formation of jarosite precipitation on the mineral surface during the bioleaching as a passivation layer. Low pH reduces significantly jarosite formation in the leaching systems of L. ferriphilum pure culture and mixed cultures.