Copper Recovery from Chalcopyrite Concentrate by Indigenous Mesophilic and Thermophilic Bacteria

A mesophilic iron oxidizing bacterium, Acidithiobacillus ferrooxidans, has been isolated (33°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°C) from the Kooshk Lead and Zinc Mine near the city of Yazd in the center point of Iran. Variation of pH, ferrous and ferric concentration and cell growth on time and effects of some factors such as temperature, initial ferrous concentration and pH on bioleaching of chalcopyrite concentrate obtained from Sarcheshmeh Copper Mine near the city of Kerman in the south of Iran were investigated. Bioleaching experiments were carried out in 500 ml shake flask containing 250 ml of the medium, 5% (v/v) inoculum and 2% (w/v) of concentrate. Control bioleaching tests were carried out with concentrate sterilized 250 ml of the medium without inoculum by the addition of 5 ml of 0.5% (v/v) formaline in ethanol. The results indicate that the efficiency of copper extraction is dependent on all of the mentioned variables; especially temperature and initial ferrous concentration have more effect than other factors for this microorganism. In addition, results show that the maximum copper recovery was achieved using a thermophilic culture. Copper dissolution reached 80% with Sulfobacillus while it was 72% with Acidithiobacillus ferrooxidans at pH=1.5, initial Fe2+ concentration=7000 and 9000 mg/lit for mesophilic and thermophilic strains respectively, after 30 days.

Keywords:

bioleaching , Acidithiobacillus ferrooxidans , Solfobacillus , sulfide mineral , chalcopyrite concentrate , copper recovery