Flotation separation of fine smithsonite from calcite using sodium hexametaphosphate as the depressant in the Na2S-Pb(Ⅱ)-KIAX system

Abstract

In this study, the effects of sodium hexametaphosphate (SHMP) on the flotation of fine smithsonite and calcite in the Na2S-Pb(Ⅱ)-KIAX system were investigated. The micro-flotation results demonstrated that the fine smithsonite and calcite exhibited similar floatability in the Na2S-Pb(Ⅱ)-KIAX flotation system. After adding 20 mg/L SHMP, the flotation recovery of calcite was reduced by 43.52%, while smithsonite was hardly affected. Furthermore, the mechanism of the selective separation was systemically investigated via ultraviolet–visible spectroscopy analysis, zeta potential measurements, Fourier transform infrared spectroscopy (FTIR) analysis, and X-ray photoelectron spectroscopy (XPS) analysis. These results demonstrate that SHMP played a dual role in the flotation process. The SHMP acted as a depressant by promoting the formation of CaHPO4 and Ca(H2PO4)2 on the calcite surfaces. In addition, it acted as a dispersant and significantly decreased the mineral zeta potential to improve the repulsive force between the mineral particles and to fully disperse the fine smithsonite and calcite. Therefore, the addition of SHMP was favorable to the separation of fine smithsonite and calcite via sulfidization–xanthate flotation.