Significantly Improved Separation Efficiency of Refractory Weakly Magnetic Minerals by Pulsating High-Gradient Magnetic Separation Coupling with Magnetic Fluid

High-gradient magnetic separation (HGMS) is indispensably applied in the rougher separation stage of refractory weakly magnetic minerals. The most difficult problem while processing refractory weakly magnetic minerals is the low selectivity of HGMS caused by the competing capture of magnetic valuable and gangue minerals. In this study, a paramagnetic fluid is introduced into HGMS and an innovative method, termed high gradient magnetic separation coupling with magnetic fluid (HGMSCMF), with a significantly high selectivity is proposed. A new competing force (magnetic repulsive force) generated by the magnetic fluid will enlarge the force difference of valuable and gangue minerals and improve selectivity. The relative magnetic force acting on the magnetic valuable and gangue minerals can be adjusted by varying the fluid volume susceptibility, with the optimal fluid susceptibility approaching that of gangue minerals. HGMSCMF experiments on an ilmenite ore using paramagnetic MnCl2 solutions showed that the selectivity was remarkably improved by increasing MnCl2 concentrations (fluid susceptibility). The TiO2 grade and mass of magnetic products could be simultaneously improved by increasing the applied induction in HGMSCMF, whereas in conventional HGMS, the TiO2 grade and recovery decreased and increased, respectively. HGMSCMF is applicable to various matrices (or separators), and a significantly improved TiO2 grade (close to that of industrial concentrates) could be obtained with only one-stage HGMSCMF. The recycling of magnetic fluid and cost economy of HGMSCMF are also discussed and analyzed. HGMSCMF presents several advantages over conventional HGMS and has great application prospects for realizing the clean and efficient utilization of refractory weakly magnetic minerals or materials.