Conditions for bioleaching a covellite-bearing ore

This paper reports evaluation of a composite sample from Newmont Mining Corporation's Kupfertal deposit located at the Peruvian Minera Yanacocha mining operation to amenability for use of bioleaching to extract the copper occurring primarily as the mineral covellite (CuS). Column testing was performed to compare bioleaching at ambient mesophilic temperature (20-23 °C) using Acidithiobacillus/Leptospirillum/Sulfobacillus species and at elevated thermophilic temperature (60-65 °C) conditions with archaea Acidianus and Metallospheara. Over a period of 346 days, bioleaching copper extraction by mesophilic bacteria ranged from 12 to 20%, determined by residue assays. Increasing the temperature of bioleaching to 60-65 °C increased copper extraction to 62-65%. Copper extraction was continuing to increase at termination of the column tests. The advantage of use of thermophilic archaea for bioleaching covellite is consistent with their use for bioleaching the highly refractory chalcopyrite (CuFeS2). This paper discusses the comparative conditions and results for bioleaching of covellite.