Enhanced chalcopyrite bioleaching with mechanical activation and redox potential regulation

Abstract

The bioleaching of chalcopyrite is limited by its slow leaching rate. To improve dissolution kinetics, the effects of Fe²⁺ and Fe³⁺ on mechanical activation-pretreatment chalcopyrite leaching by Acidithiobacillus caldus (A. caldus) and Sulfobacillus thermosulfidooxidans (S. thermosulfidooxidans) were studied. Mechanical activation reduces particle size and causes lattice defects in chalcopyrite, leading to significantly increased chemical leaching. In bioleaching experiments, A. caldus enhanced the leaching efficiency of mechanically activated chalcopyrite in the Fe³⁺ system, reaching a leaching rate of 95.3%. Increasing the number of sulfur-oxidizing microorganisms and reducing the number of iron-oxidizing microorganisms in the leaching system can keep Redox Potential (ORP) within an appropriate range, thereby improving the bioleaching efficiency. Chalcopyrite chemical leaching and bioleaching with S. thermosulfidooxidans are controlled by surface chemical reactions and internal diffusion, respectively, while chalcopyrite bioleaching with A. caldus contains both mechanisms. The main residues during bioleaching are elemental sulfur and chalcopyrite; therefore, controlling the solution potential and ferrous/sulfur oxidation activity of microorganisms can enhance the bioleaching of chalcopyrite.