Catalytic Effect of Magnetite on Chalcopyrite Bioleaching: Insights from Primary Adsorption, Electrochemistry, and EPS Production

Bioleaching is an environmental and economical approach to recover metals from low-grade ores and refractory resources. However, chalcopyrite bioleaching is often hindered by its high lattice energy and the formation of passivating layers. This study investigates the influence of magnetite on the bioleaching mechanism of chalcopyrite by Sulfobacillus thermosulfidooxidans , with focus on bacterial adhesion, electrochemical experiments, and extracellular polymeric substances (EPS) production. The results showed that the presence of magnetite enhanced chalcopyrite dissolution, raising the copper extraction efficiency from 12.3% to 15.1%. Moreover, the presence of magnetite inhibited the primary adhesion of cells to chalcopyrite surfaces, and increased EPS and extracellular proteins production of free cells, which promoted the indirect non-contact mechanism, so it improved the oxidation of Fe 2+ to Fe 3+ . Also, it decreased the EPS of attached cells, and hindered the diffusion of ions on the mineral surface. Therefore, the magnetite-promoted bioleaching of chalcopyrite was mainly related to galvanic interaction and the enhanced indirect non-contact mechanism, but independent of the bacterial adhesion to mineral surfaces. This work can provide an innovative method and essential theoretical support for strengthening the chalcopyrite bioleaching process.