Visual MINTEQ model, ToF-SIMS, and XPS study of smithsonite surface sulfidation behavior: Zinc sulfide precipitation adsorption

In this study, we investigate the smithsonite surface sulfidation by zinc sulfide precipitation adsorption. Smithsonite solubility experiments indicated that the C-ZnT in Na2S solution (1.0 x 10(-3) mol/L) was 1-2 orders of magnitude lower compared with the corresponding experiment results in deionized water. Na2S addition benefited the dissolution rate of smithsonite in deionized water. Visual MINTEQ model results confirmed that the zinc sulfide precipitation formed after the main sulfidation reaction between Zn(OH)(2(aq)) and HS- ions at pH 10, compared with the conversion from ZnS(aq), Zn2S32- ions, and Zn4S64- ions to sphalerite. Moreover, X-ray diffraction and X-ray photo-electron spectroscopy (XPS) analysis showed that the average crystallite sizes of zinc sulfide precipitation particle obtained by co-precipitation technique were approximately 2.32 nm in size. These particles were composed of zinc monosulfide and zinc polysulfide. Time-of-flight secondary ion mass spectrometry and XPS analysis provided strong evidence for zinc sulfide precipitation adsorption on the smithsonite surfaces. Furthermore, more mass signals of S-, ZnS-, S-2(-), and Zn2S- were observed from the zinc sulfide precipitation than from natural sphalerite, and the monosulfide in the zinc sulfide precipitation was easily adsorbed on the smithsonite surfaces. Results elucidate the smithsonite surface sulfidation behavior during zinc sulfide precipitation adsorption. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.