M soleimani - Department of Chemical and Petroleum Engineering Sharif Univerisity of Technology, Tehran, Iran.
S Hosseini - Department of Chemical and Petroleum Engineering Sharif Univerisity of Technology, Tehran, Iran
R Roostaazad - Department of Chemical and Petroleum Engineering Sharif Univerisity of Technology, Tehran, Iran.
S.M Mousavi - Department of Chemical and Petroleum Engineering Sharif Univerisity of Technology, Tehran, Iran-Department of Chemical Technology, Lappeenranta University of Technology, Lappeenranta, Finland

A thermophilic iron oxidizing bacterium, Sulfobacillus, has been isolated (60  C) from the Kooshk lead and zinc mine near the city of Yazd in central Iran. In addition, a mesophilic iron oxidizing bacterium, Acidithiobacillus ferrooxidans, has been adapted (33  C) to high amounts of zinc. Effects of some variable parameters such as solid concentration, temperature, pH and Eh on the bioleaching of sphalerite low-grade mineral ore from Kooshk lead and zinc mine were investigated. Bioleaching experiments were carried out in two batch airlift bioreactor with a recycling stream. The results indicate that the efficiency of zinc extraction is dependent on all the variables studied for both microorganisms. Maximum zinc recovery was achieved using a thermophilic culture. Zinc dissolution reached 91.4% with Sulfobacillus and 87% with Acidithiobacillus ferrooxidans at 10% w/v pulp density , after 9 days.

Bioleaching; Acidithiobacillus ferrooxidans; Sulfobacillus; Airlift bioreactor; Sphalerite; Low-grade mineral ore; Zinc extraction