Pilot-scale tank biooxidation of gold bearing arsenopyrite concentrates

This article presents the results of experimental tests regarding the bacterial oxidation of arsenopyrite gold concentrate, containing gold (60 g/t), sulfides (23 %), iron (26 %), and arsenic (11 %). The primary objective was to assess the efficiency of a microbial consortium comprising Acidithiobacillus ferrooxidans AF-2 and Sulfobacillus thermosulfidooxidans strains in gold extraction. The methodology involved pilot-scale tests conducted in six reactors, each with a volume of 1.5 m3, where the solids concentration was maintained at 20 % (w/w) and the retention time of the concentrate was optimized from 12 to 6 days. The results demonstrated a sulfide destruction rate exceeding 90 %, leading to gold recovery from biooxidation products by cyanide leaching of over 94 %. Additionally, an average gold recovery rate of 95 % was achieved. The removal of arsenic was successfully performed through two-stage neutralization with calcium carbonate, resulting in an insignificant final concentration of arsenic (0.14 mg/L) in TCLP tests, indicating no special disposal requirements for the precipitate. The findings suggest that the method provided effective conditions for arsenic precipitation and enhanced gold extraction from refractory ores.