Flotation response of cerussite after hydrothermal treatment with sulfur and the sulfidation mechanism

Abstract

Hydrothermal sulfidation followed by flotation is well known as a promising technology for recovery of valuable metals from refractory non-ferrous ores. Cerussite (PbCO3), as one of the most representative lead oxide minerals, was selected as the research object in this paper. Hydrothermal sulfidation performances were directly characterized by flotation tests and the sulfidation mechanism was further revealed by XRD, XPS and EPMA–EDS. Flotation tests results showed that flotation recovery of cerussite reached approximately 80% at a suitable S/PbCO3 mole ratio and pH. XRD analyses results confirmed that the cerussite was transformed into mainly PbS and PbSO4 after hydrothermal sulfidation. XPS analyses results indicated that more lead-bearing species including PbSn and PbO·PbSO4, besides mainly PbS and PbSO4, were generated at the surface. EPMA–EDS results showed that the core part of particle remained lead carbonate, but the out layer of particle was completely converted into sulfur-bearing compounds. A reaction model of hydrothermal sulfidation of cerussite with sulfur was designed and the sulfidation process can be divided into five steps: disproportionation of sulfur, adsorption of disproportionation products, dissolution of carbonate ion, formation of lead sulfide precipitate and diffusion of carbonate ion. These findings can lay a good theoretical foundation for optimizing the hydrothermal sulfidation process to recover cerussite and even other non-ferrous metals oxide materials by using the hydrothermal sulfidation–flotation processes.