Biooxidation of Refractory Gold Sulfide Concentrate of Olympiada Deposit

Abstract

Results of research on technological processes for treatment of refractory gold-arsenic ores using bioleaching of concentrates are presented. In October 2001 the first line of bioreactors on Mill-2 began operation with projected throughput of 3 million tons a year. In July 2007 Mill-3 began operation with projected throughput of 5 million tons a year. At present the closed joint stock company Gold Mining Company «Polyus» occupies a leading position in gold extraction from hard rocks in the Russian Federation. Processing of refractory gold-arsenic ores is conducted on Mill-2 and Mill-3 by a flotation-cyanide scheme using a unique biooxidation technology, BIONORD®, designed to process concentrates in the extreme climatic conditions of the North, . The achieved productivity of the Olympiada Mining Combine, from the processing of both oxidized and refractory ores of the Olympiada deposit, is 26.7 tons of gold a year. The gold is mostly present as finely dispersed and submicroscopic particles in close association with sulfide minerals, usually pyrite, pyrrhotite, arsenopyrite and antimonite. The average productivity of the lines is 1000 t/day. The process time is 100-150 h. The pulp density is 150-200 g/l. The working temperature is 39-40oC. The microbial association is represented by three species of chemolithotrophs: “Sulfobacillus olympiadicus”, Leptospirillum ferrooxidans, and Ferroplasma acidiphilum present in proportions 60-80%, 10-20%, and 10-17%, respectively. During the process 87% of sulfide minerals are oxidized. Thus, 98% of the pyrrhotite, 95.4% of the arsenopyrite, 70% of the antimony sulfides and 60% of the pyrite is oxidised. Biooxidation enables 97% of the gold to be released.