Bioleaching of pyrite by extreme thermophilic ThiobaciUus

In order to investigate the feasibility of biodesulfurization by an extreme thermophile in high iron concentration, high acidity and elevated temperature environment, four groups of pyrite column bioleaching experiments at variable initial pH values were carried out by using a novel strain of extreme thermophilic Thiobacillus which was isolated from Rehai acidic hot spring in Tengchong in southwestern China. It is found that the new strain is resistant to high acid and high iron environment in which the pH value is 0.58 and the soluble iron concentration is 38.9 g·L^-1, while the redox potential maintains at a low level from 580 to 640 mV. The highest value of iron recovery can reach up to 17.8% after leaching for 28 d when the initial pH value is 2. The bacterial growth evidently represents a lag phase, a logarithmic phase and a stationary phase sequentiMly in the traditional bioleaching route, while reducing the initial pH value can prolong the time of reaching the steady periodical. In addition, precipitation formation of jarosite and a little sulfur is promoted in the high iron system of which the total iron concentration is 38.9 g·L^-1 and the temperature is 70℃. The novel strain can oxidize the majority of S^O to SO₄^2- even when the pH value is lower than 0.9.