Thermochemical modification for the surface of smithsonite with sulfur and its flotation response

Thermochemical modification for the surface of smithsonite with sulfur and its flotation response were investigated by micro-flotation tests, X-ray powder diffractometer (XRD) combining with thermodynamic calculations, X-ray photoelectron spectroscopy (XPS) and electron probe microanalysis (EPMA). Micro-flotation tests results showed that the addition of the sulfur at a small S/ZnCO3 mole ratio (0.05) during the thermochemical modification process facilitated flotation of the smithsonite and improved the flotation recovery by approximately 65%. The results of XRD analyses and thermodynamic calculations verified that the smithsonite was decomposed into zincite and then interacted with sulfur, forming sphalerite at the surface, after the thermochemical modification in the presence of sulfur. XPS analyses results revealed that both ZnS and ZnS2 were formed at the surface of the obtained zincite. EPMA analyses confirmed that the sulfides were unevenly distributed at the out layer of the zincite. The average concentration of S at the surface of the obtained zincite increased with the increase in the sulfur dosage. This study gave a deep insight into the interaction between the smithsonite and sulfur at high temperatures and further enriched the surface sulfidation mechanism of the smithsonite.