Column bio-oxidation of low-grade refractory gold ore containing high-arsenic and high-sulfur: Insight on change in microbial community structure and sulfide surface corrosion

Currently, there is a lack of research on column bio-oxidation for low-grade refractory gold ore with high arsenic and sulfur content. Therefore, it is essential and significative to investigate column bio-oxidation for this type of gold ore. The column bio-oxidation process of refractory gold ore was characterized by a variety of analytical methods, including X-ray diffraction, 16S rRNA gene analysis, scanning electron microscope coupled with energy-dispersive X-ray spectroscopy and 3D confocal laser scanning microscopy. The evolution of the microbial community structure was analyzed. Simultaneously, the process of passive film formation and the behavior of the dynamic corrosion on the sulfide surfaces were described in detail. The results showed that the cyanidation of gold yielded 81 +/- 2% after column bio-oxidation. The oxidation extent for As, Fe and S were 57 +/- 1%, 38 +/- 1% and 44 +/- 1%, respectively. The community structure of attached and planktonic microorganisms was different and changed with the oxidation time. Importantly, the Sulfur film was observed on the arsenopyrite surface under scanning electron microscope, yet it was not found on the pyrite surface. This finding revealed that the inhibitory effect generated by the passive film of arsenopyrite was significantly higher than that of pyrite. Furthermore, the average corrosion pit volume per unit area of pyrite and arsenopyrite were 161 +/- 6 mu m(3)/mu m(2) and 65 +/- 3 mu m(3)/mu m(2). This indicated that arsenopyrite was more easily oxidized during the column bio-oxidation.