Enhanced chalcopyrite leaching by mechanical activation: New insights from microstructure

Bioleaching is an effective technique for treating low-grade copper sulfide ore, but low leaching rate limit its industrial application of chalcopyrite bioleaching. Many passivation film compositions have been hypothesized to explain the difficulty of chalcopyrite leaching, but the essential reason remain unclear. Mechanical activation can not only reduce the solid particle size, but also result in lattice defects and induce redox reactions, and even affect the electronic structure of the solid. Therefore, the mechanical activation enhanced chalcopyrite leaching and its influence mechanism was investigated. The main conclusions are as follows: mechanical activation can significantly reduce chalcopyrite particle size, simultaneously, microscopic strain and cell volume increased; the mechanical activation changed the energy band structure of chalcopyrite—the positions of the conduction band and the valence band were positively shifted, implying that Fe3+ could more easily capture electrons from the chalcopyrite surface to be reduced, thus the leaching rate of chalcopyrite increased significantly in in Fe3+ solution. The results show that the passivation film may affect the leaching of chalcopyrite, but the structural characteristics of chalcopyrite is the essential reason for the difficulty of chalcopyrite leaching.