Abstract
Hydrometallurgical processing of chalcopyrite is hindered predominantly due to the passivation layers formed on the chalcopyrite surface. However, the effects of impurity cations released from the gangue are not yet well understood. Density functional theory (DFT) calculations were carried out to investigate monovalent cations of Na+ and K+ on chalcopyrite (001)-S surface using Materials Studio. The results show that the 3d orbital of Fe and 3p orbital of S predominantly contribute to their activities during chalcopyrite oxidation and dissolution processes. In addition, SO42− is more likely to be adsorbed on one Fe site in the presence of Na+, while it is preferentially adsorbed on two Fe sites in the presence of K+. However, the adsorption of both Na2SO4 and K2SO4 on the chalcopyrite (001)-S surface contributes to the breakage of S–S bonds, indicating that the impurity cations of Na+ and K+ are beneficial to chalcopyrite leaching in a sulfuric environment. The adsorption energy and partial density of states (PDOS) analyses further indicate that the adsorption of Na2SO4 on chalcopyrite (001)-S surface is favored in both -BB (bidentate binuclear ) and -BM (bidentate mononuclear) modes, compared to the adsorption of K2SO4.
Highlights
Chalcopyrite (CuFeS2 ), as one of the most abundant copper-bearing sulfide minerals, accounts for approximately 70% of the copper reserve on Earth [1]
Most studies show that the slow kinetics of chalcopyrite are due to its crystal structure requiring high energy to be broken, and due to the passivation layers formed on the chalcopyrite surface during the leaching process, with the latter being considered to be rate controlling [2,6,7,8,9,10,11,12,13,14]
The reconstructed chalcopyrite (001)-S surface shows the formation of disulfide based on both the bond length and electron density
Summary
Chalcopyrite (CuFeS2 ), as one of the most abundant copper-bearing sulfide minerals, accounts for approximately 70% of the copper reserve on Earth [1]. Chalcopyrite is an economic mineral for copper production in both pyrometallurgical and hydrometallurgical processes, but is related to many environmental problems such as acid mine drainage (AMD) [2]. Hydrometallurgical strategy has been realized to be more promising, industrial implementation is still limited to date, predominantly due to slow leaching kinetics [3,4,5]. Most studies show that the slow kinetics of chalcopyrite are due to its crystal structure requiring high energy to be broken, and due to the passivation layers formed on the chalcopyrite surface during the leaching process, with the latter being considered to be rate controlling [2,6,7,8,9,10,11,12,13,14]. In order to develop proper alternatives to avoid surface passivation and enhance the hydrometallurgical efficiency, various strategies, including surface-sensitive X-ray photoelectron spectroscopy (XPS)
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