Effect of pyrite with different semiconducting properties on bornite bioleaching in the presence of Leptospirillum ferriphilum

Synergetic effect of pyrite on strengthening bornite bioleaching has been confirmed in our former work. However, the effect of pyrite with different semiconducting properties on bornite bioleaching has not been investigated yet. In order to fill this important knowledge gap, hall effect tests, electrochemical tests, X-ray diffraction (XRD) tests and X-ray photoelectron spectroscopy (XPS) tests combined with bioleaching experiments were performed to investigate the effect of pyrite with different semiconducting properties on the bioleaching of mixed ore (pyrite and bornite mixed at mass ratio of 3:1). It was found that the copper extraction of mixed ore containing the n-type pyrite was 10% higher than that of the p-type pyrite in sulfuric media. The difference however could be narrowed and eliminated in the presence of Leptospirillum ferriphilum (L. ferriphilum), and the leaching rate of copper could eventually both reach 85%. Results of XRD and XPS of leached residues confirmed that pyrite with different semiconducting properties could not change the dissolution mechanism of bornite, and a large amount of jarosite and elemental sulfur formed at the latter stage of bioleaching may be responsible for bornite passivation. The result of electrochemical measurements further proved the conclusion drew from XRD tests and indicated that n-type pyrite had better performance on increasing corrosion kinetics of bornite than p-type pyrite.