The application of 3-phosphopropionic acid in the flotation separation of fluorite from calcite and its selective depression mechanism

Fluorite often coexists with calcite naturally and the efficient separation of these two minerals has been a long-troubled problem. In this study, the inhibitory action of 3-phosphopropionic acid (3-PPA) in the flotation separation of fluorite from calcite was investigated and its depression mechanism was detailly explored. In single mineral flotation experiments, when the dosage of sodium oleate (NaOL) was 60 mg/L and the dosage of 3-PPA was 90 mg/L at a pH of 7.5, the recovery rates of fluorite and calcite were 92.52 % and 20.51 %, respectively. At this point, in the concentrate obtained from the mixed ore flotation test, the grade and recovery rate of CaF 2 were 76.24 % and 77.78 %, respectively, demonstrating a selective inhibitory effect on calcite. Zeta potential results confirmed that 3-PPA selectively interacted with calcite, impeding the subsequent adsorption of NaOL. Adsorption capacity tests, Fourier transform infrared spectroscopy (FTIR) and atomic force microscope (AFM) tests showed that 3-PPA powerfully and abundantly adsorbed on the calcite through its phosphate and carboxyl groups, while physically adsorbed on the fluorite surface with relatively small adsorption amount. Molecular dynamics (MD) simulations revealed that 3-PPA aggregated on the calcite surface and formed strong chemical and hydrogen bonding interactions with the calcite (1 0 4) surface through its phosphate groups. In contrast, on the (1 1 1) surface of fluorite, 3-PPA was dispersed and the interaction was weak. Therefore, 3-PPA exhibited a selective inhibitory effect on calcite, enabling the separation of fluorite and calcite.