Increasing rare earth extraction kinetics by tailored magnetic fields

Abstract The separation of the chemically similar rare-earth (RE) elements is difficult, consumes large amounts of chemicals, energy, water and emits environmentally harmful substances. To enhance the efficiency of RE separation, we develop and validate a magnetic-assisted solvent extraction method. For that purpose, we use a Hele-Shaw configuration and investigate the Dysprosium (Dy) cation exchange across a water-oil interface in the presence of a millimeter-sized NdFeB magnet. The tailored magnetic field introduces a Kelvin force that drives solutomagnetic convection if the modified Rayleigh number, Ra * , exceeds the critical value Ra * ~ 5 × 10 6 . This convection continuously replenishes Dy(III)-depletion at the interface with fresh solution from bulk. The resulting enhancement in extraction kinetics, expressed by the Sherwood number, scales nearly quadratically with Ra * . This magnetic field-driven intensification enables more efficient bulk separation of heavy RE and could potentially provide a greener separation route with superior selectivity.