Bio-oxidation of a high-sulfur refractory gold concentrate with a two-stage chemical-biological approach

Abstract

A two-stage chemical-biological oxidation approach, which applied a high temperature chemical oxidation stage prior to the bio-oxidation stage, was employed to accelerate the bio-oxidation rate of Axi gold concentrate with pyrite as the main sulfide phase. The extraction levels of Fe and S were 67.0% and 72.9% in the traditional one-stage bio-oxidation approach, while the values were elevated respectively to 78.0% and 79.6% with the two-stage approach. Accordingly, the extraction rate of gold was increased from 83.6% to 90.3% when subjected to the two-stage approach. The intensification mechanism of the two-stage approach was carried out by using Scanning Electron Microscope-Energy Dispersive X-ray Spectroscopy (SEM- EDX), X-ray photoelectron spectroscopy (XPS) and particle size analysis. The results indicated that pyrite on the surface of the concentrate was partly oxidized and particle size of the concentrate diminished after the first stage (chemical oxidation), which would facilitate the subsequent bio-oxidation process.