Experimental and DFT study of the sulfidation of smithsonite: Impact of water and oxygen

Water and oxygen have a significant effect on the sulfidation of smithsonite. However, few studies considered the water and oxygen effects, and the roles of water and oxygen in the sulfidation process remain ambiguous. In this work, the impact of water and oxygen in the sulfidation of smithsonite was creatively investigated by flotation tests, XPS measurements, and DFT calculations. The flotation test results showed that the sulfidation level of smithsonite by directly adding Na2S was not good enough to get a high recovery. The XPS measurement results showed that the sulfidation product of ZnSOn can be formed on smithsonite surface apart from Zn-S under oxygenated aqueous conditions. The DFT simulation results showed that mixed molecular and dissociated adsorption of H2O was observed on smithsonite surface, which prevented the HS adsorption. Besides, it further illustrated the formation of sulfidation products of zinc sulfur oxides in the presence of H2O and O2. Moreover, the sulfidation product of Zn-S can be oxidized by the O2. Thus, it was unstable. In summary, oxygen can be involved in the sulfidation process by dissociated adsorption. This work is crucial and helpful for understanding the sulfidation flotation of smithsonite.