Zhang, Yan, Li, Qian, Liu, Xiaoliang, Yin, Huaqun, Yang, Yongbin, Xu, Bin, Jiang, Tao, and He, Yinghe (2020) The catalytic effect of copper ion in the bioleaching of arsenopyrite by Acidithiobacillus ferrooxidans in 9K culture medium. Journal of Cleaner Production, 256. 120391.

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Abstract

Bioleaching pre-treatment of arsenopyrite (FeAsS), a common mineral occurring in deposits of gold ore that makes the extraction of gold difficult, has attracted significant attention recently due to its simple operation and environmental friendliness. A critical impedance of bioleaching to its large scale industrial application is the slow leaching kinetics. Several metal cations have previously been found to accelerate the leaching process. This paper reports results from an in-depth investigation into the bioleaching of arsenopyrite including leaching experiments, thermodynamic analysis of the leaching system and physicochemical analyses of the materials. The results suggest that a passivating film consisting mainly of As2S2, As2S3 and S-0 formed on the arsenopyrite surface in the initial bioleaching of 36 h in the 9K culture containing Acidithiobacillus ferrooxidans. This film disappeared when Cu2+ was added to the system. The bioleaching of arsenopyrite was efficiently improved at the Cu2+ level of 0.05 g/L with its leaching period significantly shortened from 19 d to 13 d. Based on the results, the paper also proposes possible leaching mechanisms and the role of Cu2+ in improving the rate of the leaching process. Specifically, Cu2+ is found to facilitate the oxidative dissolution of the passivating species of As2S2, As2S3 and S-0 by forming Cu2S/CuS that can be rapidly oxidised by Fe3+ back to Cu2+. A catalytic cycle of Cu2+/(Cu2S/CuS) is thus likely established on the Fe3+/Fe2+ catalytic cycle, resulting in the elimination of the passivating film. The bacteria utilised the two synergistic cycles to catalyse the leaching of arsenopyrite.

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