Pretreatment with acidic ferric sulfate leaching promotes the bioleaching of bornite

According to previous studies on bornite leaching, we found that the acidic ferric sulfate leaching was more efficient than the bioleaching in the early stage. This paper investigated the leaching of bornite by pretreatment with acidic ferric sulfate leaching for different times following bioleaching. The bioleaching culture consisted of Leptospirillum ferriphilum and Acidithiobacillus caldus. The leaching results showed that adding bacteria after acidic ferric sulfate leaching for 2 h enabled to extract 89% of copper during a period of 6 days. In contrast, a lower extraction efficiency was achieved with acidic ferric sulfate leaching (34%) and bioleaching (27%) alone. After pretreatment, more Fe2+ was produced in the solution, which enabled the bacteria to maintain higher oxidation activity and thus promoted the dissolution of bornite. Phase and surface species analysis of leaching residues revealed that almost all copper in bornite was dissolved under these conditions, and a large amount of jarosite and elemental sulfur were formed. Jarosite occurred as a passivation layer.