Purification of fluorite concentrate via stepwise magnetic separation: An experimental and simulation study

The fluorite concentrate from the Bayan Obo ore exhibits low grade with significant impurities including iron, rare earth minerals, and calcium-bearing gangue minerals. This study developed a magnetic purification process by combining high-gradient magnetic separation (HGMS) and superconducting magnetic separation (SCMS) technologies, leveraging magnetic susceptibility differences between fluorite and gangue minerals. The optimized process achieved high-quality fluorite concentrate with 97.20 % grade and 82.14 % recovery. Modern analytical techniques, including Automated Mineral Identification and Characterization System (AMICS), Vibrating Sample Magnetometry (VSM), X-ray Diffraction (XRD), and computational simulations, were employed to investigate the separation mechanisms between fluorite and associated iron, rare earth, and calcium-bearing minerals. Results demonstrate that conventional HGMS effectively removes strongly iron minerals but exhibits limited effectiveness in separating fluorite from weakly magnetic rare earth minerals and calcium- bearing gangue. Under superconducting high-intensity magnetic fields of 5 T, optimized parameters with 0.12 mm magnetic matrix wires and slurry flow rate of 0.09 m/s enabled efficient capture of residual weakly magnetic iron mineral hematite, rare earth minerals bastnaesite and monazite, carbonate minerals dolomite, and phosphate minerals apatite while minimizing fluorite entrainment. This selective magnetic adsorption, attributed to the differential magnetic susceptibility of fluorite and gangue minerals, constitutes the critical mechanism for advanced fluorite purification.