Comparison of bioleaching ability of two native mesophilic and thermophilic bacteria on copper recovery from chalcopyrite concentrate in an airlift bioreactor

A mesophilic iron oxidizing bacterium, Acidithiobacillus ferrooxidans, has been isolated (33 degrees C) from a typical chalcopyrite copper concentrate of the Sarcheshmeh copper mine in the region of Kerman located in the south of Iran. In addition, a thermophilic iron oxidizing bacterium, Sulfobacillus, has been isolated (60 degrees C) from the Kooshk lead and zinc mine near the city of Yazd in central Iran. Effects of some variable parameters such as solids concentration, temperature and pH on the bioleaching of chalcopyrite obtained from Sarcheshmeh copper mine were investigated. Bioleaching experiments were carried out in two batch airlift bioreactors with a recycling stream. The results indicate that the efficiency of copper extraction is dependent on all the variables studied for both microorganisms. Maximum copper recovery was achieved using a thermophilic culture. Copper dissolution reached 85% with Sulfobacillus and 70% with Acidithiobacillus ferrooxidans at 10% w/v pulp density, after 10 days. (c) 2005 Elsevier B.V. All rights reserved.