Enhanced adsorption of sulfide and xanthate on smithsonite surfaces by lead activation and implications for flotation intensification

In the flotation of zinc oxide minerals, unavoidable lead ions (Pb2+) in the pulp interact with the mineral surface, sulfidizing reagents, and collectors. This interaction affects the sulfidization characteristics and xanthate adsorption on the surfaces of zinc oxide minerals. In this study, the mechanism of the interaction between Pb2+ and smithsonite surfaces, its effect on the surface sulfidization of smithsonite, and its response to xanthate adsorption were investigated. The flotation results showed that the addition of 5 × 10−4 mol/L Pb2+ in the pulp greatly increased the smithsonite flotation recovery. Pb2+ can interact with smithsonite surfaces to form a significant layer of lead-containing species. The amount of sulfide species on the smithsonite surface significantly increased after Pb2+ pretreatment and sulfidization. This shows that Pb2+ pretreatment promoted the reaction between the mineral surface and sodium sulfide because of the newly generated lead-containing species on the smithsonite surface. Infrared spectroscopy showed that the amount of xanthate adsorbed on the smithsonite surface in the Pb2+–sulfidization–xanthate system was larger than that in the sulfidization–xanthate system. An appropriate concentration of Pb2+ in the pulp before sulfidization could therefore promote sulfidization of smithsonite surfaces and improve xanthate adsorption. This would enhance the hydrophobicity of the smithsonite surfaces and increase the smithsonite flotation recovery.