Selective flotation separation of smithsonite from dolomite by using sodium hexametaphosphate as a depressant

Abstract

In this study, a depressant sodium hexametaphosphate (SHMP) was introduced for the flotation separation of smithsonite from dolomite using mixed benzohydroxamic acid (BHA) and sodium oleate (NaOL) as the collectors. Micro-flotation experiments were conducted to investigate the flotation behavior of smithsonite and dolomite in the absence and presence of SHMP. Furthermore, the depression mechanism of the SHMP was unraveled by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) analysis, and flotation solution chemistry. The flotation results showed that the recovery of dolomite decreased from 26.63% to 2.25% when the addition of SHMP in the flotation system increased from 0 to 50 g/t, while the smithsonite recovery exhibited a slight increase from 91.05% to 93.10%, which improved the separation effect greatly. FTIR measurements and XPS analysis revealed that the SHMP was chemically adsorbed on the dolomite surface in the form of hydrophilic complexes with Ca2+ and Mg2+, thus depressing adsorption of the mixed BHA/NaOL. Flotation solution chemistry analysis suggested that Zn2+ could form ZnCO3 on the surface of the dolomite leading to the transformation of the dolomite surface to the smithsonite surface. And SHMP could form hydrophilic complexes with Ca and Mg sites on the dolomite surface, thus depressing the adsorption of BHA/NaOL on the transformed dolomite surface.