Microscopic perspective of the combined collector CTAB/SPA on the flotation separation of fluorite and calcite: Adsorption morphology and interaction force

It is difficult to separate fluorite and calcite due to their similar surface properties. This article applied combined collector cetyltrimethylammonium bromide (CTAB)/styrene phosphonic acid (SPA) to separate fluorite from calcite and explored the adsorption morphology and interaction force. Flotation results indicated that effective separation between fluorite and calcite with CTAB/SPA at a molar ratio of 1:1, at the concentration of 1x10-4 mol/L and pH 11.0. Surface tension measurements indicated a synergistic effect of CTAB/SPA in solution. The combined collector increased the hydrophobicity difference between fluorite and calcite surfaces. Zeta potential measurements illustrated that both CTAB and SPA adsorbed on fluorite and calcite surfaces, with CTAB as the main collector. Atomic force microscope (AFM) analysis further demonstrated that more CTAB/SPA adsorbed on fluorite surface than that on the calcite surface, resulting in a stronger hydrophobic force between fluorite particles. It was concluded that CTAB, as the main collector in the combined collector, adsorbed on the fluorite surface, while SPA interspersed between the CTAB molecules, with an adsorption model proposed. These macroscopic and microscopic points provide a possibility for the flotation separation between fluorite and calcite.