Bio-oxidation of Arsenopyritic and Pyritic Containing Gold Ore from Tianli Gold Mine and Process

Abstract

Being the most common sulfide minerals, Arsenopyrite and pyrite under oxidizing conditions breaks down to release acids of As and S into the environment, leading to acid mine drainage with high concentrations of dissolved As. In this research, the dissolution of gold ore (with FeS2 and FeAsS as the main sulfides) from Tianli gold mine, Liaoning province, China was investigated. The experiments were conducted in 500mL conical flasks containing 200mL of three different media, 3% pulp density and 1.6 initial pH. The results indicated that treatment with mix culture medium resulted in the dissolution of 99% of Arsenic and 99% of iron, which was higher as compared with when treated in the same culture medium after centrifugation for 20 minutes which in turn higher in comparison with when treated in acidic and pure sterile system. The oxidation potential, Eh of the mix culture medium reached 680mV (vs.SCE) within the first three days of the experiment where as that of centrifuged, acidic and sterile media reached 580, 450 and 445mV (vs.SCE) respectively. The pH tends to increase within the first three days which eventually decreased to nearly one toward ending, courtesy of pyrite which is believed to be net acid releasing sulfide. The dissolution is suggested to be a combined effect of enzymes, ferric iron ions and organic acids. It was observed that enzymes and ferric ions played an essential role in the dissolution process.