Effects of heating-sulfidation on the formation of zinc sulfide species on smithsonite surfaces and its response to flotation

Smithsonite is a carbonate mineral that is hard to be recovered using sulfidation-xanthates flotation due to its poor sulfidation effect at ambient temperature. In this paper, the interaction between sulfur ions and smithsonite surfaces at various temperatures and its response to flotation were investigated. The micro-flotation tests showed that heating-sulfidation significantly improved the floatability of smithsonite, and the maximum flotation recovery increased by similar to 30% from 20 degrees C to 60 degrees C. Zeta potential, FESEM-EDS and ToF-SIMS studies demonstrated that the sulfidation behavior of smithsonite proceeds through a chemical reaction. This process is not a mere surface reaction, but rather involves the inner layers of the solid to form the zinc sulfide film. Heating promotes the formation of a thicker sulfide film on the smithsonite surface. XPS analysis results revealed that zinc sulfide species formed on the sulfurized smithsonite surface were composed of monosulfide and polysulfide, and the S distribution ratio in polysulfide exhibits an increased trend with increasing the sulfidation temperature. This may be another important reason for the improved floatability of smithsonite via heating-sulfidation.