The effect of dissolved calcite species on the flotation of bastnaesite using sodium oleate

The flotation behavior of bastnaesite, a major mineral source of rare earth elements, is strongly affected by the dissolved species of gangue minerals that change the solution chemistry and mineral surface properties. In this work, the effect of dissolved calcite species on the flotation of bastnaesite was investigated by conducting micro-flotation experiments, zeta potential measurements, Fourier-transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS) analysis. Micro-flotation experiments confirmed that calcium and carbonate ions in calcite supernatant significantly reduced the flotation of bastnaesite in strongly alkaline condition. Zeta potential measurements showed that the IEP of higher bastnaesite was obtained after the addition of calcite supernatant species. Species distribution diagram demonstrated that the adsorption of sodium oleate on the surface species of bastnaesite was inhibited by the generation of calcium-containing hydroxy complexes and precipitates. FT-IR analysis suggested that the decrease the sodium oleate concentration in solution and the generation of calcium oleate precipitate on the mineral surface are possible reasons for the reduced recovery. XPS analysis further revealed that the metal carbonates and hydroxy complexes of calcium adsorbed on the bastnaesite surface in the presence of calcite supernatant, which concealed the surface active sites, caused the decrease in bastnaesite flotation recovery.