Clean Recovery Rare Earth Elements from NdFeB Magnets Waste by Using AlCl3 Solution - a Closed-loop Process

Abstract

NdFeB permanent magnets are crucial for the new energy and electronic information industries, and NdFeB magnets waste is also most significant rare earth secondary resources. The current mainstream recycling process is based on HCl leaching solvent extraction, which consumes a large amount of HCl and chemical reagents, inevitably, generates wastewater and organic waste, causing serious environmental pollution. This work developed an alternative green process for selectively recovering rare earth elements from NdFeB permanent magnets using AlCl₃ solution, which can selectively dissolve Nd₂O₃ of roasted NdFeB, and the separation factor between Nd and Fe can reach 6617. Molecular dynamics calculations indicate that as the concentration increases, Al³⁺ tends to form polymers. This is mainly due to the polarization effect of Al³⁺, which affects the hydrogen bonding structure between water molecules, leading to more water molecules coordinating with them. Simultaneously, due to the solvation effect, agglomeration phenomena also occurred between Al³⁺. In addition, the polarization effect of Al³⁺ weakens the strength of hydroxyl bonds in H₂O molecules. Consequently, more active protons were ionized in the solution and selective dissolution of Nd₂O₃ was achieved. After 10 leaching cycles, the solution still maintains excellent separation performance of selectively dissolve rare earth elements of NdFeB magnets waste. The chemical reagent investment in this process is about one-third of the existing industry process, providing a promising approach for the green and acid free recovery of rare earth elements secondary resources.