Unveiling the role of Ca ion in the sulfidation of smithsonite: A density functional theory study

In this paper, density functional theory calculations were innovatively used to study the experimentally observed depression of Ca ion and its mechanism on the sulfidation of smithsonite. The calculation results indicated that the reactivity of smithsonite surface after Ca ion adsorption was remarkably decreased, and the adsorption energies for HS on smithsonite surface in the presence of Ca ion were far larger than those in the absence of Ca ion. For one thing, the analysis results of Mulliken bond population, electron density, and partial density of states showed that the generated Ca-S bonds for HS adsorption on smithsonite surface after Ca ion adsorption were weaker and more unstable compared with Zn-S bonds for HS adsorption on the surface before Ca ion adsorption. For another, the hydration shell on smithsonite surface after Ca ion adsorption was found to be more difficult to be broken through by HS. These two factors lead to the inhibition of Ca ion on the adsorption of HS on the surface of smithsonite. This work reveals inhibition of Ca ion and its atomic-level mechanism on the sulfidation of smithsonite, which is helpful to the understanding of the negative effect of Ca ion on the sulfidation of smithsonite. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

In this study, density functional theory calculations were used to investigate the inhibition effect and mechanism of calcium ion on the sulfidation of smithsonite. The results showed that the reactivity of the smithsonite surface was significantly decreased after the adsorption of calcium ion, and the adsorption energies of HS on the smithsonite surface in the presence of calcium ion were much higher than those in the absence of calcium ion. The analysis of bond population, electron density, and partial density of states revealed that the calcium-sulfur bonds formed after calcium ion adsorption were weaker and less stable compared to the zinc-sulfur bonds formed before calcium ion adsorption. Moreover, the hydration shell on the smithsonite surface became more resistant to penetration by HS after calcium ion adsorption. These factors jointly contributed to the inhibition effect of calcium ion on the adsorption of HS on the smithsonite surface. This study provides important insights into the negative impact of calcium ion on the sulfidation of smithsonite.