Gold Extraction from Refractory Sulfide Gold Concentrates: A Comparison of Bio-oxidation and Neutral Atmospheric Pre-treatment and Economic Implications

摘要

The effect of bio-oxidation and neutral atmospheric oxidation pre-treatment of refractory gold concentrates on gold and silver extraction during cyanidation was investigated. A series of pre-treatment experiments was conducted on three high sulfur (> 9%) refractory concentrates with 0.92-1.25 g/t gold and 64-90 g/t silver. Cyanidation of the pre-treated concentrates using both methods was compared with respect to gold and silver leaching efficiency and reagent consumption. Bio-oxidation experiments were carried out using a mixed culture of Acidithiobacillus ferroxidans, Acidithiobacillus thiooxidans, and Leptospirillum ferrooxidans. The experimental results showed that both neutral atmospheric oxidation and bio-oxidation processes led to improvements in gold and silver extractions. The best result was achieved using neutral atmospheric oxidation at 20% pulp density, increasing gold and silver extraction to 78 and 73%, respectively. This corresponds to increases of 47 and 37% over direct cyanidation of the untreated concentrate. For bio-oxidation pre-treatment, increasing the duration had a negative effect on silver leaching efficiency due to jarosite formation. Cyanide consumption was reduced after neutral atmospheric oxidation and increased after bio-oxidation pre-treatment. Lime consumption increased while thiocyanate production was decreased after both pre-treatment methods. In terms of economic efficiency, neutral atmospheric oxidation pre-treatment was superior to bio-oxidation pre-treatment.