Technology of autoclave oxidation of refractory gold-bearing concentrates with preliminary oxidation of sulfide minerals under atmospheric conditions

The laboratory studies results of the atmospheric oxidation of two samples of Russian gold-bearing sulfide concentrates are presented. The results of the concentrates oxidation under atmospheric conditions (up to 100 оC) in sulfuric acid (pH < 1) and close to neutral (pH 5) media are presented. The influence of the main parameters of the atmospheric process (concentrate size, duration, solid content in the pulp, pH of the pulp) on the degree of sulfide sulfur oxidation has been established. The conditions have been chosen to ensure the oxidation of up to 15–20% sulfide sulfur in the initial concentrates at this stage in a limited time (no more than 6–8 hours) without additional costs for their preliminary ultrafine grinding. The results of autoclave oxidation (225 оC) of residues after atmospheric oxidation are presented. The possibility of intensive and deep oxidation of the remaining sulfide minerals and elemental sulfur (the degree of oxidation of sulfide and elemental sulfur is more than 98–99%) formed under atmospheric conditions is shown. The positive effect of preliminary atmospheric oxidation of sulfide concentrates in sulfuric acid media on the main indicators of subsequent autoclave oxidation (gold extraction, cake yield) has been established. A basic technological scheme for autoclave processing of refractory goldcontaining concentrates is proposed, including their preliminary atmospheric oxidation with the addition of industrial products and technological waste (autoclave solution containing Fe3+ ions and H2SO4, and waste gas from autoclave containing 80–90% (vol.) of oxygen), which can increase the efficiency and productivity of autoclave enterprises by 10–20% without the cost of the key reagent which is oxygen.