Biological Pretreatment of Arsenopyrite Tailings and its effect on cyanide Leaching of Gole

Gold embedded in pyrite and arsenopyrite is difficult to recover by cyanidalion. Roasting of such ores releases sulphur dioxide and arsenic trioxide, which cause atmospheric pollution. Biological leaching has been widely studied as a pretreatment method to enhance gold recovery. Thiobacillus ferrooxidans carry out oxidation of iron, sulphur, and arsenic, thereby liberates the particles of gold for recovery. At Kolar Gold Field, Karnataka there is an accumulation of tailings containing 2-3 g/t gold. Bioleaching of these tailings with Thiobacillus thiooxidans and T. ferrooxidans has been carried out to remove pyrite and arsenopyrite. The tailings were basic in nature. Treatment with T. thiooxidans minimized the requirement of sulphuric acid to maintain the optimum bioleaching medium. A 90% gold recovery could be achieved by subjecting the pretreated residue to cyanidalion