Method and Mechanism of Selective Separation of Fluorite from Calcite Using a Ternary-Coordination Complex Collector

Due to their similar active sites, fluorite and calcite cannot be separated well using the traditional sodium silicate depressant and fatty acid collector in industry. Therefore, a ternary-coordination complex of Pb-BHA-NaOL with high selectivity and strong collecting ability was developed as a novel fluorite collector based on the principle of interfacial assembly by making full use of the respective properties of lead nitrate (Pb), benzohydroxamic acid (BHA), and natrium oleate (NaOL). The flotation tests confirmed that the Pb-BHA-NaOL collector at a molar ratio of 8:8:1 could separate fluorite from calcite well at pH 9.0. The contact angle results indicated that the difference in contact angle between the surfaces of fluorite and calcite was bigger after Pb-BHA-NaOL collector treatment. Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations further proved that the Pb(OH)-BHA-OL− complex of the collector had stronger interaction with fluorite. Moreover, the O 2s orbitals of the N-O and C-O groups of the collector could hybridize with the fluorite Ca 3p orbitals to generate the O-Ca covalent bonds. Therefore, the new collector proposed in this work has potential application prospects in fluorite flotation.