Fungal-Transformation of Surrogate Sulphides and Carbonaceous Matter in Refractory Gold Ores: Revisited

In the recovery of gold from refractory gold ores, pretreatment is required to decompose sulphides and liberate occluded gold before cyanidation, and to deactivate carbonaceous matter and prevent it from adsorbing dissolved gold. Until the past three decades, most commercial pretreatment processes had been by abiotic means. Biological pretreatment methods on a commercial basis are therefore a recent phenomenon, and several researches are underway to assess the ability of different biological agents in the breakdown of sulphur and carbonaceous matter in gold ores. This paper, which revisits an earlier study, presents an overview of ongoing research aimed at assessing the capability of the fungus, Phanerochaete chrysosporium, to degrade sulphides and carbonaceous matter. Surrogate carbonaceous materials (lignite, bituminous and anthracite coals) and pure sulphides (pyrite and arsenopyrite) were used to model the behavior of carbonaceous matter and sulphides in refractory gold ores. The results indicate that the fungus biotransforms through destruction of the ordered structure, followed by introduction of oxygen groups, which inhibits the uptake of aurocyanide ions by carbonaceous matter, while enhancing the affinity of cyanide for the oxidized sulphide material in subsequent cyanidation treatment. The findings contribute to knowledge on novel and technically viable alternative methods for oxidative pretreatment of refractory gold ores.