Adhesion properties of and factors influencing Leptospirillum ferriphilum in the biooxidation of refractory gold-bearing pyrite

Leptospirillum ferriphilum (L. ferriphilum) is a widely used microorganism in the commercial biooxidation process. Its ability to adhere to sulfide ores when grown in sulfide mineral substrates is very important for the entire biooxidation process. However, few studies have investigated the ore adhesion properties of L. ferriphilum. In this paper, the effects of temperature, pH and the passive layer of the sulfide ore surface on the ore adherence properties and biooxidation capacities of L. ferriphilum LJ02, which was screened by our laboratory, were investigated. The results of these experiments showed that both the contact and non-contact leaching mechanism were evident during the sulfide biooxidation process. L. ferriphilum LJ02 preferred the contact leaching mechanism to the non-contact leaching mechanism. Within the experimental range of temperatures from 36 °C to 46 °C, the OAR (ore adhesion ratio) of L. ferriphilum LJ02 increased initially and then decreased with the temperature. The optimum OAR was 0.84 at 41 °C. Within the experimental pH range of 1.1 to 2.0, the OAR of L. ferriphilum LJ02 decreased with pH. The optimum OAR was 0.87 at pH 1.1. It was also found that the OAR of L. ferriphilum LJ02 could be reduced by the passive layer on the surface of the sulfide ore, which was generated during the biooxidation process. Moreover, it seems that the OAR of L. ferriphilum LJ02 was proportional to the sulfide biooxidation efficiency.