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

• Cu, Fe speciation during chalcopyrite bioleaching was analyzed by SR-XRD and XANES.
• The intermediates S0, jarosite and metal-deficiency sulfides were identified.
• Bornite and chalcocite were detected when Eh was less than 500 mV.
• Covellite formed when Eh was about 550 mV.
• No evident inhibition effect on copper extraction by S0 and jarosite precipitation.

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 ~ 70.58% of Cu2 + dissolution after 30 days of bioleaching when the mineral surface was evidently attacked. During the bioleaching, bornite 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 XANES spectra quantitatively demonstrated the composition of leaching residue: the copper species comprised ~ 84.8% of chalcopyrite, ~ 10.2% of bornite and ~ 5.0% of chalcocite at day 3, then changed to ~ 90.1% of chalcopyrite, ~ 6.5% of bornite and ~ 3.4% of chalcocite at day 9; the composition became ~ 89.8% of chalcopyrite and ~ 10.2% of covellite at day 18, and ~ 80.3% of chalcopyrite and ~ 19.7% of covellite at day 30. The iron species comprised ~ 26% of chalcopyrite and ~ 74% of jarosite at day 30. Elemental sulfur and jarosite were detected from day 3 but without evident negative effect on the copper extraction.

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