Mechanism of HCA and CEPPA in flotation separation of cassiterite and fluorite

Abstract

As an essential raw material for the tin industry, cassiterite ore needs to be effectively separated and purified, and the removal of impurities such as fluorite becomes the key to cassiterite flotation. In this study, the flotation separation of cassiterite (SnO2) and fluorite (CaF2) was enhanced by using hydroxylcitric acid (HCA) as fluorite inhibitor and 2-carboxyphenyl phosphonic acid (CEPPA) as collector. With a reagent scheme of 120 mg/L CEPPA and 4.5 mg/L HCA at pH 10.0, the flotation recovery of cassiterite and fluorite was 92.80% and 13.57%, respectively. Under the same experimental conditions of artificially mixed mineral flotation, the flotation index of cassiterite concentrate grade 78.19% and recovery 90.29% was obtained. The selective adsorption mechanism of CEPPA and HCA on minerals was investigated by Zeta potential, Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The results showed that CEPPA anions had chemically adsorbed on cassiterite and fluorite, and the adsorption of HCA on fluorite surface was stronger than that on cassiterite surface. XPS analyses further confirmed that Ca sites exposed on fluorite had a stronger affinity for HCA than cassiterite. Furthermore, the addition of HCA had little effect on the adsorption of CEPPA on cassiterite, while the strong chemisorption of HCA on fluorite surface prevented the adsorption of CEPPA on fluorite. These results provide a theoretical basis and promising new strategy for the flotation separation of cassiterite and fluorite.