Synthesis and application of a quaternary ammonium ionic liquid collector for flotation separation of fluorite and bastnaesite

The efficient flotation separation of rare earth elements (REEs) from gangue minerals is crucial in mineral processing. This study synthesized a quaternary ammonium salt ionic liquid collector, tetrabutylammonium salicylhydroxamate (T-S), and investigated its performance in separating bastnaesite and fluorite. T-S was synthesized from salicylhydroxamic acid (SHA) and tetrabutylammonium chloride (TBAC), and its molecular structure was characterized using Fourier transform infrared (FTIR) spectroscopy. Microflotation tests indicate that T-S outperforms SHA and TBAC in both collecting ability and selectivity for bastnaesite. Adsorption, zeta potential, and infrared spectroscopy measurements reveal that T-S exhibits stronger adsorption on bastnaesite compared to SHA and TBAC. X-ray photoelectron spectroscopy (XPS) and molecular dynamics simulations (MDS) results confirm that chemical adsorption occurs between Ce on the bastnaesite surface and the –C(=O)NHOH groups of T-S. Moreover, the interaction between T-S and the bastnaesite surface is stronger than that with the fluorite surface. This work provides valuable insights for designing ionic liquid collectors for the flotation separation of bastnaesite and fluorite.