Decoupling the effects of solid and liquid phases in a Pb-water glass mixture on the selective flotation separation of scheelite from calcite

Abstract

In this study, lead ion was combined with water glass to separate scheelite from calcite using flotation. The effects and underlying mechanisms of the liquid and solid phases generated in this combined depressant (Pb-water glass, a mixture of lead ion and water glass) on the flotation performance of scheelite and calcite were investigated through micro-flotation experiments, X-ray diffraction (XRD) measurements, ultraviolet–visible (UV–Vis) spectrophotometer measurements, fourier transform infrared spectrometer (FTIR) analysis, zeta potential measurements, and X-ray photoelectron spectroscopy (XPS) tests. The flotation results indicate that the selective flotation separation of scheelite from calcite results from the liquid phase, not the solid phase. The XRD and FTIR results indicate that under different mass ratios of lead ion to water glass, the solid phases are the lead-silicate with amorphous structures, while the UV–Vis results reveal significant absorption differences in the liquid phases under different mass ratios of lead ion to water glass. The zeta potential and XPS results indicate that less metal silicate polymers are adsorbed on the scheelite surface than on the calcite surface, allowing NaOL to be adsorbed on the scheelite surface, but not on the calcite surface, and selective flotation separation of scheelite from calcite is therefore achieved. XPS results further reveal that the metal silicate polymers in the liquid phase are adsorbed on both mineral surfaces by firstly breaking the Ca-O group and then reacting with the Ca active sites.