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The galvanic interaction between pyrite and galena surface has been investigated using density functional theory (DFT) method. The calculated results show that galvanic interactions between pyrite and galena surface are decreased with the increase of contact distance. The galvanic interactions still occurs even the distance larger than the sum of two atoms radius (≈2.8 Å), and the limit distance of galvanic interaction between galena and pyrite surface is about 10 Å, which is consistent with the quantum tunneling effect. Through Mulliken charge population calculation, it is found that electrons transfer from galena to pyrite. For galena surface, Pb 6s and 6p states lose electrons and S 3p state loses a small amount of electrons, which causes the electron loss of galena. For pyrite surface, Fe 4p state obtains large numbers of electrons, resulting in the decrease of positive charge of Fe atom. However, the 3p state of S atom loses a small numbers of electrons. The reactivity of mineral surface has also been studied by calculating the frontier orbitals of minerals. Results suggest that the highest occupied molecular orbital (HOMO) coefficients of galena are increased whereas those of pyrite are decreased with the enhancing galvanic interaction, indicating that the oxidation of galena surface would be enhanced due to the galvanic interaction. The Fukui indices and dual descriptor values of surface atoms suggest that the nucleophilicity of the galena surface increases, meanwhile, the electrophilicity of pyrite surface increases with the decrease of the contact distance. In addition, the density of states (DOS) of atoms results show that the activity of electrons in Pb 6s and 6p orbitals enhances while the activity of electrons in Fe 3d orbitals weaken due to the galvanic contact between minerals. [ABSTRACT FROM AUTHOR]

[Display omitted] • Galvanic interaction between chalcopyrite and galena has been studied by DFT method. • Galvanic interaction weakens the bonding DOS of O-Fe bonds, S-Cu bonds and S-Fe bonds. • Oxidation peak of electrode with a mix of chalcopyrite and galena is weaker than pure. Chalcopyrite is often associated with galena in nature, which brings great difficulties to the flotation recovery of chalcopyrite. One of the main reasons for these difficulties is that galvanic interaction between chalcopyrite and galena has a significant effect on the oxidation and flotation behavior of chalcopyrite. In this paper, density functional theory and cyclic voltammetry measurement were used to study galvanic interaction between chalcopyrite and galena and its effect on the adsorption of oxygen and xanthate molecules on chalcopyrite (0 0 1) surface. The results show that the galvanic interaction inhibits the dissociation of oxygen molecules on the surface of chalcopyrite (0 0 1), and it also weakens the bonding DOS of O-Fe bonds, S-Cu bonds and S-Fe bonds, which may be detrimental to the adsorption of xanthate and oxygen molecules on the surface of chalcopyrite (0 0 1). The cyclic voltammetry measurements results show that compared with pure chalcopyrite and pure galena electrode, the oxidation peak intensity of the electrode with a mass ratio of chalcopyrite and galena of 1:1 near 0.4 V is weaker at pH 9.18 and a butyl xanthate concentration of 0.001 mol/L, which is consistent with the results of DFT studies. [ABSTRACT FROM AUTHOR]

We investigate the galvanic interaction between galena and eight different grinding media including low carbon steel (carbon content 0.1 wt%), medium carbon steel (carbon content 0.3 wt%), high carbon steel (carbon content 0.9 wt%), and grinding medium containing 0.1 wt% Ce, 0.1 wt% La, 0.1 wt% Y, 4.6 wt% Cr, or 1.5 wt% Mn, and the effects of those galvanic interactions on the surface structure, surface activity and adsorption of oxygen and xanthate molecules on galena surface have also been investigated. [Display omitted] • The galvanic effect between galena and grinding media was studied using DFT method. • Medium carbon steel can enhance the oxidation of galena surface by galvanic effect. • Grinding medium containing La enhance the adsorption of xanthate on galena surface. Galena has different electrostatic potentials from grinding medium. Collision and friction occur between them in the grinding process, which lead to electron transfer and charge redistribution on galena surface, affecting surface oxidation and galena recovery. In this paper, the galvanic interaction between galena and eight different grinding media including low carbon steel (carbon content 0.1 wt%), medium carbon steel (carbon content 0.3 wt%), high carbon steel (carbon content 0.9 wt%), and grinding medium containing 0.1 wt% Ce, 0.1 wt% La, 0.1 wt% Y, 4.6 wt% Cr, or 1.5 wt% Mn has been studied using DFT method. The effects of those galvanic interactions on the surface structure, surface activity and adsorption of oxygen and xanthate molecules on galena surface have been investigated. The results show that the adsorption of oxygen and xanthate molecules on the surface of galena is the strongest with medium carbon steel (carbon content is 0.3 wt%), followed by low carbon steel and high carbon steel. In addition, compared with the grinding media containing chromium, cerium, yttrium and manganese, the grinding medium containing lanthanum (lanthanum content is 0.1 wt%) is more conducive to the adsorption of oxygen and xanthate molecules on the surface of galena. [ABSTRACT FROM AUTHOR]

Pyrite is a mineral often associated with coal in coal seams and is a major source of sulfur in coal. Coal–pyrite is widely distributed, easily available, low-cost, and non-toxic, and has high light absorption coefficient. So, it shows potential for various applications. In this paper, the density-functional theory (DFT + U) is used to construct coal–pyrite with carbon doped in the sulfur and iron vacancies of pyrite. The effects of different carbon defects, different carbon doping concentrations, and different doping distributions in the same concentration on the electronic structure and optical properties of coal–pyrite were studied. The results show that the absorption coefficient and reflectivity of coal–pyrite, when its carbon atom substitutes the iron and sulfur atoms in the sulfur and iron vacancies, are significantly higher than those of the perfect pyrite, indicating that coal–pyrite has potential for application in the field of photovoltaic materials. When carbon is doped in the sulfur vacancy, this impurity state reduces the width of the forbidden band; with the increase in the doping concentration, the width of the forbidden band decreases and the visible-light absorption coefficient increases. The distribution of carbon impurities impacts the band gap but has almost no effect on the light absorption coefficient, complex dielectric function, and reflectivity, indicating that the application of coal–pyrite to photovoltaic materials should mainly consider the carbon doping concentration instead of the distribution of carbon impurities. The research results provide a theoretical reference for the application of coal–pyrite in the field of photoelectric materials. [ABSTRACT FROM AUTHOR]