DFT insights into the sulfidation mechanism of Fe-impurity smithsonite

The sulfidation-flotation of Fe-bearing smithsonite is still a challenge in practice. Currently, theoretical understandings on reagents adsorption on impurity-bearing mineral surface are still lacking. Here we first systematically investigated the adsorption of HS on perfect and Fe-impurity smithsonite (101) surfaces in the absence and presence of H2O by density-functional theory (DFT). We found Fe-impurity dramatically changed the structure and electronic properties of smithsonite surface. In the absence and presence of H2O, the adsorption energies of HS on Fe-bearing smithsonite surface were all lower than those of perfect surface. The Mulliken bond populations and DOS analysis results showed that the formed Fe-S bonds on Fe-impurity smithsonite surface were less stable than the Zn-S bonds formed on the perfect surface. Meanwhile, the competitive adsorption capacity of H2O and HS on perfect and Fe-impurity surfaces was different. The interaction of H2O and HS to TZn site on perfect surface was in the order of HS > H2O while that to TFe site on TFe-impurity surface was H2O > HS, and the adsorption of HS was depressed. Furthermore, S-OH was contained in the sulfidation product of BFe-impurity surface, and the hydrophobicity of the formed sulfidation film greatly decreased, which was also not conducive to the sulfidation-flotation.

Automated summary

The presence of Fe impurities significantly altered the structure and electronic properties of smithsonite surfaces, affecting the sulfidation-flotation process. The adsorption energy of HS on Fe-bearing smithsonite surfaces was lower than on perfect surfaces, and the presence of S-OH in the sulfidation product decreased the hydrophobicity of the sulfidation film, which was not conducive to sulfidation-flotation.