Chlorination-driven phase control for selective REE-Fe separation from NdFeB waste

Securing reliable supplies of rare-earth elements (REEs) increasingly depends on efficient recycling, as primary production remains geopolitically concentrated while demand from advanced technologies continues to grow. However, recycling of NdFeB waste continues to rely on conventional hydrometallurgical and pyrometallurgical processes, which are waste generating due to the intrinsic challenge of separating REEs from iron-rich phases. Here, we demonstrate a ZnCl₂-assisted chlorination strategy that selectively converts Nd into an acid-soluble NdOCl, while stabilizing Fe as insoluble oxides (ZnFe₂O₄ and Fe₂O₃), thereby suppressing co-dissolution and facilitating efficient REEs-Fe separation. Thermodynamic analysis identifies atmosphere and temperature as critical parameters governing phase evolution. Experimental validation confirms that, under optimized conditions (air, 700 °C), REEs recoveries reach 99.31% (Nd), 93.85% (Dy), and 98.82% (Pr), while Fe dissolution is limited to 2.30%. In contrast, inert atmospheres promote Fe dissolution, and temperatures ≥800 °C induce NdFeO₃ formation, both of which compromise selective recovery. Kinetic analysis further reveals a nucleation-and-growth controlled mechanism consistent with the Avrami-Erofeev model. This route thus offers a streamlined and reagent-efficient process for REEs recovery from waste NdFeB, offering a scalable route toward closing the REEs supply loop.