A copper and iron K-edge XANES study on chalcopyrite leached by mesophiles and moderate thermophiles

摘要

To reveal the mechanism of chalcopyrite biooxidation at different temperatures, pure chalcopyrite leached by mesophiles (30°C) and moderate thermophiles (48°C) was characterized by synchrotron X-ray apbsorption near-edge structure (XANES). Solution study shows that elevated temperature significantly promoted the chalcopyrite dissolution. A copper concentration of 1.32g/l was finally achieved in 48°C leaching, while only 0.49g/l copper was released in 30°C bioleaching. Cu AT-edge XANES study shows the formation of a CuSn-like solid phase at early leaching stage and a decrease of this phase at late stage. This result suggests the preferential release of iron, which is followed by the successive dissolution of copper resulting in a metal-deficient sulfur-rich layer (S_n~(2-)) left on the chalcopyrite surface which further hinders chalcopyrite dissolution. In addition, Fe K-edge XANES indicates that no significant amount of jarosite was formed in 30°C bioleaching; however, in 48°C bioleaching jarosite precipitation was profoundly accelerated, which reached a contribution of 50.5% at day 35.