Malachite sulfidation flotation mechanism: Sulfidation anisotropy insights

Abstract

Malachite, being highly hydrophilic and difficult to be floated conventionally, is usually beneficiated by sulfidation flotation in industry. However, the complex crystal structure of malachite leads to the formation of various fracture surfaces with distinct properties during crushing and grinding, resulting in surface anisotropy. In this study, we explored the surface anisotropy of malachite and further investigated its sulfidation mechanism from the coordination chemistry perspective, considering the influence of the Jahn-Teller effect on malachite sulfidation. Computational results reveal that the penta-coordinated Cu ions on the malachite (201) and (010) surfaces exhibit stronger activity compared to those on the malachite ($\bar{2}01$) surface. Additionally, the tetra-coordinated structure formed by HS⁻ adsorption on the malachite (010) and (201) surfaces is more stable, with more negative adsorption energy, compared to the hexacoordinated structure formed by HS⁻ adsorption on the ($\bar{2}01$) surface. The sulfidized malachite surface has an additional pair of π electron and smaller HOMO (highest occupied molecular orbital)-LUMO (lowest unoccupied molecular orbital) gap with xanthate molecules, causing stronger π backbonding with xanthate. This study provides new insights into the surface sulfidation mechanism of malachite and offers a theoretical reference for the design of targeted flotation reagents.

Keywords

malachite / sulfidation flotation / surface anisotropy / coordination chemistry / Jahn-Teller effect / density functional theory

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Central South University