Biooxidation of arsenopyrite to improve

Cyanide leaching is the traditional process for the extraction of gold from primary raw materials. However, when the gold host rock contains high concentrations of sulphides, an oxidative pretreatment is often needed. This study investigates the potential of biooxidative leaching as an environmentally friendly alternative compared to conventional pretreatment processes. Using Thiobacillus ferrooxidans and Thiobacillus thiooxidans, bioleaching was conducted at bench scale on refractory gold-bearing arsenopyrite ore from the Gölcük mine in Turkey. A factorial plan of experiments tested various factors influencing the biooxidative pretreatment to enhance gold recovery during cyanidation. Results showed that direct cyanide leaching without bioleaching resulted in no gold dissolution. However, with fine grinding, a recovery of 55.3% was achieved after 48 hours of cyanidation. Notably, cyanidation of bioleached arsenopyrite allowed for dissolution of 84.3% of gold in just 2 hours under optimized conditions (20% pulp density, pH 2, 200 rpm stirring, 30°C). Furthermore, preliminary tests indicated that a 3-day bioleaching facilitated the solubilization of 95.2% Au after 48 hours cyanidation, increasing to 96.8% with a 7-day bioleaching duration. This study demonstrates the efficiency of biooxidation in improving gold cyanidation.