Abstract:The composition of passive layer of chalcopyrite was investigated by X-ray photoelectron spectroscopy (XPS), accompanied with cyclic voltammetry (CV). The leaching experiment shows that the extraction rates of Cu with leaching for 30 d by sterile control and microorganisms are 4.0% and 21.5%, respectively. In comparison, 3.8% and 10.5% Fe are leached by sterile control and microorganisms, respectively. The results of XPS studies suggest that Fe atoms dissolve preferentially from the chalcopyrite lattice, and disulfide (S₂^2-), polysulfide (S_n^2-) and elemental sulfur (S⁰) are identified on the chalcopyrite surfaces leached by sterile control and microorganisms. Additionally, sulfate (SO₄^2-) is detected on the chalcopyrite surfaces leached by microorganisms, and most of it probably originates from jarosite. The analysis of CV results reveals that metal-deficient sulfide (Cu_1-xFe_1-yS_2-z, y>x) and elemental sulfur (S⁰) passivate the surface of chalcopyrite electrode. The elemental sulfur and/or jarosite coating on the chalcopyrite surface may have impact on the leaching process; however, the disulfide, polysulfide or metal-deficient sulfide plays a more key role in the chalcopyrite leaching.

Key words: bioleaching; chalcopyrite; passive layer; electrochemistry