The influence of different forms of mineral processing on the bio-oxidation of sulphide minerals bearing gold

The presence of sulphide minerals, such as pyrite, chalcopyrite etc., can pose major challenges in the gold extraction processes, regardless of the downstream extraction route used, including cyanidation and the use of thiosulphate. These sulphides consume the reagents used in this above-mentioned extraction processes, leading to operational problems due to the ever-increasing ionic strength during the extraction processes, which impacts the solubility of the oxidizing agent, specifically dissolved oxygen, which is of paramount importance for extracting gold. This bio-oxidation process aims at solubilizing the aforementioned sulphide minerals, using indigenous autotrophic microorganisms, such as Acidithiobacillus thiooxidans, Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans, subsequently reducing the consumption of leaching agents used in gold extraction turning this process more efficient and cost-effective. In this study, different crushing operations were used, such as the use of jaw crusher, high pressure grinding rolls (HPGR) and high voltage pulse fragmentation (HVPF), aiming at determining the influence of these unit operations on the bio-oxidative process of the aforementioned sulphide minerals, as prior steps to the extraction of gold particles encapsulated in the matrices of the aforementioned sulphides, substantially reducing the consumption of gold leaching agents, thus avoiding the milling operation, which is the most expensive in extractive metallurgy.