Oxidative dissolution of bornite by Acidithiobacillus ferrooxidans

The oxidation of finely ground (−200 μm) bornite (Cu5FeS4) by Acidithiobacillus ferrooxidans was evaluated in oxygen uptake and shake flasks experiments. The oxidation was a net acid-consuming reaction. Residual bornite was not detected by X-fray diffraction in solids after 2 days of contact in acid leach solution, indicating that the chemical and biological oxidation of bornite was relatively fast. Virtually 100% of copper solubilization was achieved in A. ferrooxidans cultures with or without ferrous iron, while in abiotic controls the copper extraction was around 30%. Bornite was not oxidized by Acidithiobacillus thiooxidans in respirometric or shake flasks experiments. Covellite (CuS) was detected as a secondary phase under all experimental conditions. Sulfur and jarosite were formed only in the presence of A. ferrooxidans.