Abstract
In this work, density functional theory (DFT) calculations, X-ray photoelectron spectroscopy (XPS) and electrochemistry analysis were combined to analyze the electrochemical dissolution process of bornite during bioleaching. DFT calculations showed that bornite was a conductor with metallic conductivity. The formula of bornite may be (Cu+)5Fe3+(S2−)4 and the surface reconstruction of (111)-S surface was discussed. Electrochemistry and XPS analysis showed that bornite tended to be directly oxidized with high conductivity when the potential was higher than 0.3 V vs. Ag/AgCl. Elemental sulfur (S0), FeOOH and CuS were the main intermediate species on the bornite surface during the oxidation process. The production of S0 and FeOOH on bornite surface can be significantly accelerated with increased redox potential, but no insoluble sulfate (SO42−) formed on bornite surface in 0.3–0.65 V vs. Ag/AgCl. The oxidative dissolution of bornite was significantly accelerated with increasing redox potential, which was one important reason why mixed culture was more effective than single strains of A. caldus and L. ferriphilum in bornite bioleaching. The insoluble SO42− was formed mainly through the chemical reactions in solution and then covered the bornite surface in bioleaching. Based on the obtained results, a model for interpreting the dissolution process of bornite in bioleaching was proposed.
Highlights
IntroductionBio-hydrometallurgy (bioleaching) is considered an economically promising technology for clean extraction of sulfide minerals such as chalcopyrite (CuFeS2 ), pyrite (FeS2 ) and chalcocite (Cu2 S) [1]
Bornite (Cu5 FeS4 ) is a kind of copper resource that is relatively widespread on Earth.Bio-hydrometallurgy is considered an economically promising technology for clean extraction of sulfide minerals such as chalcopyrite (CuFeS2 ), pyrite (FeS2 ) and chalcocite (Cu2 S) [1].bioleaching of bornite is an important research topic and the dissolution mechanisms of bornite during bioleaching should be firstly studied to enhance its bioleaching efficiency
Bornite is considered as an intermediate species in chalcopyrite bioleaching, and chalcopyrite was reported as the intermediate species during bornite bioleaching [2,3,4,5]
Summary
Bio-hydrometallurgy (bioleaching) is considered an economically promising technology for clean extraction of sulfide minerals such as chalcopyrite (CuFeS2 ), pyrite (FeS2 ) and chalcocite (Cu2 S) [1]. Bioleaching of bornite is an important research topic and the dissolution mechanisms of bornite during bioleaching should be firstly studied to enhance its bioleaching efficiency. Bornite is considered as an intermediate species in chalcopyrite bioleaching, and chalcopyrite was reported as the intermediate species during bornite bioleaching [2,3,4,5]. The study of dissolution mechanisms of bornite during bioleaching is essential for interpreting the dissolution mechanisms of chalcopyrite bioleaching. Some publications have reported that bornite has non-ignorable effects on chalcopyrite dissolution [6,7,8]. The dissolution of sulfides during bioleaching sometimes can be Minerals 2018, 8, 173; doi:10.3390/min8040173 www.mdpi.com/journal/minerals
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