Induced crystallization of Pb2+ on smithsonite surface during sulfidation-xanthate flotation

Abstract

Smithsonite is a common oxidized zinc ore, and its recovery has gained increasing attention to meet the high demand for zinc. Current methods to concentrate oxidized zinc ores are through sulfidation flotation or “sulfidation + metal + xanthate” flotation. However, such techniques are not sufficiently efficient for treating smithsonite. In this study, Pb(NO3)2 was used to pre-treat smithsonite as a crystallization inducer, and the mechanism of lead modification was studied through micro-flotation tests, adsorption measurements, contact angle measurements, X-ray diffraction (XRD), scanning electronic microscopy (SEM), and TOF-SIMS analysis. The micro-flotation test results showed that the recovery of smithsonite after Pb2+ pre-treatment increased from 80.3% to 85.3%. The comprehensive results of adsorption experiments, contact angle measurements, XRD and SEM analysis indicated that Pb2+ adsorbed on the smithsonite surface and transformed portion of smithsonite into cerussite, increasing the active sites on the mineral surface for adsorption of S ions. The newly formed PbS after sulfidation had an effect of induced crystallization on subsequently formed PbS, increasing PbS species and making the surface more effective for xanthate flotation. ToF-SIMS was used to visualize the 3D distribution of Pb2+ and S2- adsorption, and it further proved that pre-treatment with Pb(NO3)2 enhanced the sulfidation process of smithsonite.