Abstract
Cu2+ exhibited a good activation effect on specularite. However, its microscopic activation mechanism needs further study. Additionally, Cu2+ was mainly present in the flotation solution as Cu2+, Cu(OH)+, and Cu(OH)2 at pH = 7. Therefore, density functional theory (DFT) calculations were used to investigate the effect of Cu species such as Cu2+, Cu(OH)+, and Cu(OH)2 adsorbed on the crystal structure and properties of the specularite (0 0 1) surface. The adsorption mechanism of different Cu components on the surface was also further clarified by the analyses of the adsorption model, adsorption energy, partial density of states (PDOS), charge transfer, and bond properties. In addition, the obtained results are discussed. Based on the obtained results, it can be concluded that the geometric structure and electronic properties on the surface changed after adsorbing Cu components and that the O3–Fe1–O1 structure was more susceptible to the adsorbates. The adsorption engines results show that Cu components could be spontaneously adsorbed onto the specularite (0 0 1) surface with adsorption energies of −0.76, −0.85, and −1.78 eV, corresponding to Cu2+, CuOH+, and Cu(OH)2, respectively. Therefore, the adsorption stability of the Cu species on the specularite surface increased in the order of Cu2+ < Cu(OH)+ < Cu(OH)2. Additionally, the adsorption sites for Cu species on the surface were different. Cu2+ interacted mainly with O atoms on the surface, forming Cu–O complexes, while Cu(OH)+ and Cu(OH)2 acted mainly through the O atom of –OH, interacting with Fe atoms to form Cu–O–Fe complexes. The formation of Cu–O and Cu–O–Fe complexes increased the adsorption sites for sodium oleate, with more hydrophobic species being generated to improve the floatability of specularite.
Highlights
Copper ions are often used as an activating ion in flotation to increase the floatability of minerals, and there were many studies on the activation mechanisms of copper ions on metallic sulfide minerals and nonmetallic oxidized ore [1,2,3]
The Effect of Cu Species Adsorbed on the Structure of the Specularite (0 0 1) Surface
The results indicate that the structure of O–Fe–O and Fe–O–Fe on the specularite surface was influenced by the Cu species adsorbed
Summary
Copper ions are often used as an activating ion in flotation to increase the floatability of minerals, and there were many studies on the activation mechanisms of copper ions on metallic sulfide minerals (e.g., sphalerite and pyrite) and nonmetallic oxidized ore (e.g., chlorite and quartz) [1,2,3]. The previous studies did not comprehensively discuss the influence of Cu2+ adsorption on the crystal structure and properties of specularite or its activation mechanism. DFT calculations can be used for the influencing mechanism of activators, inhibitors, and dispersants on the target minerals in flotation systems. Han et al [25] used DFT calculations to study the crystal structure and surface properties of clay minerals, such as kaolin and smectite, which have a serious impact on the flotation process from a microscopic point of view, and their interactions with commonly used dispersants and inhibitors mechanism were studied. The current study used DFT simulation to construct adsorption models of Cu2+ , Cu(OH)+ , and Cu(OH) on a specularite (0 0 1) surface and to optimize the structures, as well as to explore the influence of Cu species on the crystal structure and properties of specularite (0 0 1) surface. The microscopic activation mechanism of Cu2+ absorbed on specularite is illustrated at atomic scale
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