A scaled-up continuous process for biooxidation as pre-treatment of refractory pyrite-arsenopyrite gold-bearing concentrates

This study describes using biooxidation as pre-treatment for refractory pyrite-arsenopyrite gold-bearing concentrates in both batch and continuous tests. The removal rates of the elemental constituents of arsenopyrite and pyrite were examined during a biooxidation pre-treatment of gold concentrate. Batch tests were performed in a 20-L reactor for 16 days. The continuous biooxidation experiments were conducted in six 300-L reactors configured as 3 primary and 3 secondary reactors, giving a 7-day cumulative retention time at the design feed rate. Real-time PCR was used to monitor the dynamic succession of the acidophilic bacterial population. Compared to the maximum removal rate of the batch tests (in the initial 10 days), the arithmetic average release rate in the continuous tests is nearly twice as high, because it can maintain the active microbial community composition and slow the ion accumulation in the slurry. Therefore, the residence time to attain a certain oxidation degree could be significantly reduced for the continuous scale-up operation. The biooxidation of refractory pyrite-arsenopyrite gold-bearing concentrates was reinforced efficiently in the continuous pilot experiments.