Abstract:Pilot experiments to extract gold from refractory gold concentrates by continuous bio-pre-oxidation and cyaniding were investigated. Effects of parameters on gold cyanide leaching were studied. Bio-oxidation mechanisms of gold bearing pyrite were analyzed by electrochemical techniques. The results show that in single slot oxidation, removal rate of S, Fe and As rises with increase of bio-oxidation time in linear relationship with no obvious oxidation effect after 9 days. It is reasonable to calculate oxidation slag rate, sulfur removal rate, gold leaching rate, and oxidation effect with SiO2 content in oxidizing slag. In continuous pre-oxidation experiment, oxidation rate of sulfide is 79.13% and gold cyanidation extraction rate is 92.94% under the conditions including oxidation time of 7 d, pulp density of 15%, temperature of 42 ℃, and agitation speed of 60 r/min. Electrochemical experiment results show that addition of bacterium promotes anodic oxidation reaction and reduces corrosion potential and reaction resistance without change anodic oxidation mechanisms of gold bearing pyrite.