Abstract
Bio-oxidation of refractory sulfidic gold minerals has been applied at the commercial scale as a pre-treatment to improve gold yields and reduce chemical consumption during gold cyanidation. In this study, the effect of initial cell concentration on the oxidation of pyritic gold ore was evaluated with four aerated bioreactors at 30 °C with 10% pulp density and pH maintained at 1.4 with NaOH. Results of NaOH consumption and changes in soluble Fe and S concentrations indicated that increasing the initial cell concentration from 2.3 × 107 to 2.3 × 1010 cells mL−1 enhanced pyrite oxidation during the first week. However, by day 18 the reactor with the lowest initial cell concentration showed profound performance enhancement based on soluble Fe and S concentrations, sulfide-S and pyrite contents in the residues, and subsequent gold leaching of the bio-oxidation residues by cyanidation. Overall, the results showed that the cell concentration was clearly beneficial during the initial stages of oxidation (first 7–8 days).
Highlights
Pyrite is one of the most widely distributed sulfides in the earth and is commonly found as a gangue mineral in association with valuable minerals [1]
◦ C used for the pyrite oxidation experiments was not the optimum temperature for all species in the mixed culture, it was in the temperature range of all species and in the optimal range for L. ferriphilum, which is a key iron oxidiser that operates at high redox potentials required for pyrite oxidation
During the first week of the pyrite oxidation experiment, NaOH consumption and soluble Fe and S concentrations indicated that the increasing initial cell concentration enhanced pyrite oxidation in the range of initial cell concentrations of 2.3 × 107 –2.3 × 1010 cells mL−1
Summary
Pyrite is one of the most widely distributed sulfides in the earth and is commonly found as a gangue mineral in association with valuable minerals [1]. Many gold deposits are sulfidic in nature and contain pyrite, arsenopyrite, and pyrrhotite. Refractory gold ores harbour finely disseminated gold particles encapsulated by a sulfide matrix that makes the gold inaccessible to lixiviants. Pre-treatment of the sulfide matrix is required to improve gold yields and reduce chemical consumption during gold leaching [2]. Conventional pre-treatment for refractory sulfidic gold ores include ultrafine grinding, roasting, and pressure oxidation. These methods are associated with several disadvantages such as high investment costs, low gold recovery, and environmental risks [3]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
