Development of an Organic Acid-Based Process for Rare Earth Recovery from NdFeB Magnets

The recovery of rare earth elements (REEs) from NdFeB magnets is essential for securing sustainable supply chains for critical materials. In this study, the leaching behavior of Nd, Pr, and Dy was comparatively evaluated using five organic acids (citric, malic, tartaric, oxalic, and acetic acids) under identical experimental conditions. Citric acid demonstrated the highest leaching efficiency and was selected for further process optimization. A design of experiments (DoE) approach was applied to assess the combined effects of solid-to-liquid ratio, temperature, and time at a fixed citric acid concentration of 1.5 mol L −1 , revealing a multidimensional operational window capable of achieving high REE solubilization rather than a single optimum condition. Two purification strategies were subsequently investigated: solvent extraction using di(2-ethylhexyl)phosphoric acid (D2EHPA), yielding a 99.3% pure REE product, and an oxidative precipitation route based on in situ oxalic acid formation, achieving 95.7% purity with reduced process complexity.