Bio-oxidation of refractory gold ores containing stibnite and gudmundite

Arsenic and antimony are environmental pollutants associated with several diseases, including skin cancer. One of the main sources of both elements is the oxidation of sulphide minerals, particularly arsenopyrite and therefore any of both elements is a concern in gold mining operations because arsenic- and antimony-bearing sulphides may contain significant gold contents. Bioleaching is considered more environmentally-friendly than chemical processes to recovery gold, particularly from low-grade ores and residues bearing such sulphides. Thus, the current work has investigated the bio-oxidation of both a gold-bearing sulphide concentrate and a flotation tailing by Acidithiobacillus ferrooxidans, at 32 °C, focusing on the behaviour of both arsenic and antimony. Fe2＋ supplementations were required in order to increase the oxidation efficiency and the optimum pH value was 1.75. The cyanidation tests confirmed the refractory nature of the samples under study (21%). The solid products of the bio-oxidation stage showed gold extractions four times as large (85%) as that of the initial sample. The dissolution of antimony was low with no evidence of the formation antimony precipitates. Unlike arsenic, the latter reported mostly to the solid product of the bioleaching step as inert sulphide particles.