Comparative study of S, Fe and Cu speciation transformation during chalcopyrite bioleaching by mixed mesophiles and mixed thermophiles

- Bioleaching of chalcopyrite by mixed mesophiles and mixed thermophiles was analyzed.
- S, Fe and Cu speciation transformation was detected by SR-based technologies.
- The intermediates S0, jarosite, chalcocite, bornite and covellite were identified.
- The formation of bornite, chalcocite and covellite was related with redox potential.
- The formation of bornite could accelerate chalcopyrite dissolution.

The bioleaching experiments of chalcopyrite were conducted with mixed mesophilic culture (30 °C), moderately thermophilic culture (45 °C) and extremely thermophilic culture (65 °C), respectively. During bioleaching, the S/Fe/Cu speciation was analyzed by synchrotron radiation (SR) based X-ray diffraction (XRD) and S, Fe and Cu K-edge X-ray absorption near edge structure (XANES) spectroscopy. The results showed that the chalcopyrite dissolution could be significantly promoted by these mixed cultures, and the promotion effects were enhanced with the increase of bioleaching temperature. For all bioleaching tests, the formation of intermediates S0, jarosite and secondary minerals (chalcocite, bornite and covellite) was detected, in which the formation of bornite, chalcocite and covellite was just related with redox potential. The formation of bornite could accelerate chalcopyrite dissolution, while the decrease of bioleaching microorganisms could reduce chalcopyrite dissolution.