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

Abstract

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 absorption near-edge structure (XANES). Solution studies show that elevated temperatures promoted chalcopyrite dissolution. A final copper recovery of 41% was achieved at 48°C, while only 15% at 30°C. Cu K-edge XANES analyses indicated more iron than copper dissolved, leaving on the particle surface CuSn-like species in the early stages of leaching. In the late stages of leaching, copper in CuSn-like species was leached, leaving behind Sn-like species. The slowness of leaching of Sn-like species may be the reason why no CuSn-like species were formed in the late stages, and thus why chalcopyrite passivated. In addition, Fe K-edge XANES indicates no significant amount of jarosite formed at 30°C; however, at 48°C, jarosite precipitation was profoundly accelerated, which accounted for 51% of the iron species in the residue at day 35.