Recovery of rare earth metals from NdFeB magnets using antisolvent crystallization: scale up and life cycle assessment

Recycling of rare earth elements (REEs) has become of paramount importance for permanent magnets used in electric vehicles, wind turbines and motors. There is an imbalance in supply and demand of this commodity and the REE has been identified as critical raw materials by the European Union. This study focuses on the recovery of REEs (La, Pr, Nd, Dy, Y) from sulfuric acid leach solutions using antisolvent crystallization, scaling up the process by hybrid process modelling, and performing environmental impact assessment. Ethanol is used as an antisolvent to crystallize REE2(SO4)3∙8H2O. The impact of inorganic impurities including Cu(II), Co(II), Al(III), B(III), Fe(II) and Fe(III) on the quality of the crystal product, in terms of purity and morphology, has been investigated. Higher purity (above 99%) is obtained for seeded experiments, and the purity is higher for higher seed loading and lower antisolvent dosing rate. Furthermore, the REEs have a tendency to be precipitate as a mixed phase, i.e. REE2(SO4)3∙8H2O. By balancing the addition of antisolvent and seed loading the optimum conditions in terms of high purity and productivity can be found. Scale-up of the process to 100 kg/batch, with solvent recovery of ethanol and H2SO4 (aq.), waste heat reutilization and trade-off analysis, potentially reduces the global warming potential from 40 kg CO2 eq to 0.96 kg CO2 eq /kg REE2(SO4)3∙8H2O. The results can provide valuable insights to understand and optimize the recovery of REEs from sulfate media as a pure concentrate from impure leach liquors. The potential for scaling up the process is also demonstrated resulting in relatively low impacts on global warming.