Abstract
Most studies conducted have focused on the pulp density, Fe3+ concentration and sulfuric acid concentration, etc., of bio-oxidation, and few have reported on the influence of different bio-oxidation methods on kinetics. In this study, a comparative investigation on refractory gold concentrate by batch and continuous bio-oxidation was conducted, with the purpose of revealing the kinetics influence. The results showed that improving the removal rates of the gold-bearing pyrite (FeS2) and arsenopyrite (FeAsS) yielded the best results for increasing gold recovery. The removal rates of S, Fe and relative gold recovery linearly increased when compared to the second-order equation increase of the As removal rate in both batch and continuous bio-oxidation processes. The removal kinetics of S and Fe by continuous bio-oxidation was 12.02% and 12.17% per 24 h day, approximately 86.64% and 51.18% higher than batch bio-oxidation, respectively. The higher removal kinetics of continuous bio-oxidation resulted from a stepwise increase in microbe growth, a larger population and higher dissolved Fe3+ and H2SO4 concentration compared to a linear increase by batch bio-oxidation. The cyanidation gold recovery was as high as 94.71% after seven days of continuous bio-oxidation, with the gold concentrate sulfur removal rates of 83.83%; similar results will be achieved after 13 days by batch bio-oxidation. The 16sRNA sequencing showed seven more microbe cultures in the initial residue than Acid Mine Drainage (AMD) at genus level. The quantitative real-time Polymerase Chain Reaction (PCR) test showed the four main functional average microbe populations of Acidithiobacillus, Leptospirillum, Ferroplasma and Sulfobacillus in continuous bio-oxidation residue as 1.08 × 103 higher than in solution. The multi-microbes used in this study have higher bio-oxidation activity and performance in a highly acidic environment since some archaea co-exist and co-contribute.
Highlights
Hansford [23] investigated the kinetics of refractory gold concentrate by batch and continuous bio-oxidation, but the results showed that the pyrite bio-oxidation rate by batch bio-oxidation was close to those obtained from continuous bio-oxidation
The results of the relationship of S, Fe and As removal with gold recovery by different bio-oxidation methods showed that gold recovery from batch and continuous bio-oxidation linearly increased as the sulfur removal rate increased, and in terms of the formula were RAu = 0.37Rs + 63.76 (R2 = 0.97) and R* Au = 0.41R* s + 59.76 (R2 = 0.99), respectively
The removal rates of S, Fe and relative gold recovery linearly increased when compared to the second-order equation increase of the As removal rate in both batch and continuous bio-oxidation processes
Summary
Roasting [3], pressure oxygen oxidation [4], bio-oxidation [5] and chemical oxidation [6,7]. Are the commercial pretreatment technologies normally used to improve gold recovery before cyanidation from refractory gold ores. The roasting oxidation process is accomplished with heavy pollution and limited gold recovery, with 30% sulfide sulfur as the standard maximum content requirement in refractory gold concentrate. Pressure oxidation gold recovery usually yields higher outputs than any other oxidation techniques; only a few process plants are operational globally because of its high investment cost, and complex operating process. Pressure oxygen oxidation requires a maximum of 20% sulfide sulfur in concentrate. The first refractory gold concentrate pressure oxygen oxidation plant was not established in China until 2016 by Shuiyindong Gold Mine, a wholly subsidiary company of Zijin Mining Group
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