Effect and mechanism of Cu(II) on flotation separation of cassiterite from fluorite

Abstract

The effect and mechanism of Cu(II) on the flotation separation of cassiterite from fluorite using styrene phosphonic acid (SPA) as a collector were investigated by flotation tests, zeta potential measurements, X-ray photoelectron spectroscopy (XPS) analysis and density function theory (DFT) calculations. SPA showed good collecting ability for both cassiterite and fluorite, and Cu(II) could intensively and selectively depress fluorite. At pH 4.0, using 100 mg/L SPA as the collector and 5 × 10−4 mol/L Cu(II) as the inhibitor, a tin concentrate with a grade of 92.3% SnO2 and a recovery of 85.6% was obtained for an artificially mixed sample which contained 47.86% SnO2. Zeta potential and XPS analyses indicated that Cu(II) was anchored on cassiterite surface but not on fluorite surface, and Cu(II) hindered the adsorption of SPA on fluorite but had negligible influence on the adsorption of SPA cassiterite. DFT calculations confirmed that the affinity between Cu(II) and SPA is much stronger than that between Cu(II) and fluorite surface, and the adsorption of SPA on cassiterite surface was not weakened by the presence of Cu(II). Consequently, it was inferred that Cu(II) consumed the collector SPA in the pulp, and the flotation of cassiterite was unaffected but fluorite was depressed by Cu(II). Therefore, Cu(II) is an effective inhibitor for the flotation separation of cassiterite from fluorite.