Relatedness of Cu and Fe speciation to chalcopyrite bioleaching by Acidithiobacillus ferrooxidans

The relatedness of copper and iron speciation to chalcopyrite bioleaching by acidophilic Acidithiobacillus ferrooxidans was analyzed by synchrotron radiation-based X-ray diffraction (SR-XRD) and Cu, Fe K-edge X-ray absorption near edge structure (XANES) spectroscopy, accompanying with the determination of leaching parameters and the observation of chalcopyrite surface modification by scanning electron microscopy. The results showed that chalcopyrite was leached gradually by A. ferrooxidans, with similar to 70.58% of Cu2+ dissolution after 30 days of bioleaching when the mineral surface was evidently attacked. During the bioleaching, bomite and chalcocite were detected at day 3 and day 9 when the redox potential was less than 500 mV, but they disappeared at day 18 and day 30 when covellite was detected and the redox potential was about 550 mV. The linear fitting of Cu and Fe}CANES spectra quantitatively demonstrated the composition of leaching residue: the copper species comprised similar to 84.8% of chalcopyrite, similar to 10.2% of bornite and similar to 5.0% of chalcocite at day 3, then changed to similar to 90.1% of chalcopyrite, similar to 6.5% of bomite and similar to 3.4% of chalcocite at day 9; the composition became similar to 89.8% of chalcopyrite and similar to 10.2% of covellite at day 18, and similar to 80.3% of chalcopyrite and similar to 19.7% of covellite at day 30. The iron species comprised similar to 26% of chalcopyrite and similar to 74% of jarosite at day 30. Elemental sulfur and jarosite were detected from day 3 but without evident negative effect on the copper extraction. (C) 2015 Elsevier B.V. All rights reserved.