Bioleaching of Fe and Cu from pyrite stone and ore concentrate by iron and sulphur-oxidizing bacteria

In this research for screening of iron and sulphur- oxidizing bacteria, the samples were collected from more than 60 sites in different areas of iran (northern, sounthren, eastern, western and centeral areas) and we succeeded to isolate 4, 8 and 3 bacterial strains identical to Thiobacillus ferooxidans, Leptospirlum ferooxidans and Thiobacillus thiooxidans, respectively. These strains were capable of oxidation of iron(ferrous to ferric) and sulphur(acid production). The pH reduction rang was 0.7-0.9 and acid production level in 15 and 24 days was reached to 13.2-16-43 and 26.16-44.15 g/l, respectively.The results of the investigation on relation of cell numbers to reduction at pH revealed that when the pH decreased from 4 to 2, the number of bacterial cells was promoted 2–3 times.The study on Fe and Cu bioleaching capacity of these bacteria from pyrite and a kind of copper ore concentrate, shows that the used bacteria not only can tolerate physicochemical condition of these ores and so grow and be active in their environment but are also able to leaching of ferric and copper from pyrite stone and ore concentrate.Consequently produced ferric iron amount from SF medium was 2g/l and when mixed culture (Fe and S-oxidizing bacteria)was used the leached iron amount from pyrite stone and ore concentrate by L2+R10 and Larz8 + R9 was 3.5 and 1.33 g/l, respectively. On the other hand, leached copper by mixed Larz8 + R9 was 1330 ppm.