Abstract:During bornite (bio)leaching, the relationship between the production of intermediate products and redox potential is unknown. In this study, a series of electrochemical tests and surface analytical methods were adopted to investigate the electrochemical dissolution of natural bornite and the formation of the sulfur species on the bornite surface. Electrochemical tests demonstrated that the surface of bornite experienced three distinct variations over a broad anodic potential (300-800 mV (vs Ag/AgCl)): “activation” (< 400 mV (vs Ag/AgCl)), “passivation” (400-700 mV (vs Ag/AgCl)), and “transpassivation” (> 700 mV (vs Ag/AgCl)). XPS results indicated that covellite-like species, S_n^2-/S⁰, and insoluble SO₄^2- were considered as intermediate products during bornite electrochemical dissolution. Furthermore, AFM results proved that the accumulation of S_n^2-/S⁰ made bornite surface suffer severe passivation when applied potentials were 600 and 700 mV (vs Ag/AgCl), respectively. The most advantageous potential for bornite (bio)leaching was shown to be 400 mV (vs Ag/AgCl).

Key words: bornite; bioleaching; electrochemical dissolution; surface species; atomic force microscope