The efficient removal of dolomite from phosphate ores using a novel collector: Flotation selectivity and collecting mechanism

The removal of magnesium-contained minerals from phosphate ores poses significant challenges because of the resembling surface characteristics and inferior selectivity of conventional fatty acid and its derivatives. However, litter attention has been paid to develop highly selective collector to upgrade magnesium-contained phosphate ores. In this work, an attempt was made to explore a novel and efficient dolomite collector to remove dolomite from phosphate ores by means of reverse flotation, and multiple analytical techniques including Zeta potential, wettability, adsorption amount, microcalorimetry and X-ray photoelectron spectroscopy (XPS) were employed to elucidate the collecting mechanism of Nonylphenol ether phosphate-10 (TXP-10) in reverse flotation. TXP-10 showed good selective collecting ability toward dolomite at pH of 5–10 without depressant. The addition of sulfuric acid (H₂SO₄) prior to TXP-10 further improved the selectivity of TXP-10. Zeta potential and adsorption amount results indicated that TXP-10 preferentially adsorbed on dolomite in contrast to apatite. Microcalorimetry results indicated that the adsorption heat and rate between TXP-10 and dolomite was much bigger and faster compared with apatite. XPS and simulation results revealed that the −OPO₃ groups of TXP-10 chemically bonded with Ca and Mg sites on dolomite, while physically adsorbed on apatite due to scarce Ca distribution density and the steric hindrance effect. In addition, H₂SO₄ barely reacted with Ca and Mg sites on dolomite but strongly interacted Ca sites on apatite, further expanding the adsorption difference of TXP-10 on apatite and dolomite. The study might provide some new insights into the development of novel reverse collector for the efficient beneficiation of magnesium-contained phosphate ores.