Rationally designed mineral phase reconstruction for selective extraction and full-component recovery of Nd-Fe-B magnet scraps

Abstract

The strong bonding between atoms in Nd-Fe-B magnets makes the high-efficiency and near-zero-waste recovery of all components become a challenge. In this work, a new method combined mineral phase reconstruction with physical separation is proposed to recycle REEs (rare earth elements) and non-REEs from the magnet scraps. Metal Bi as a key initiator is designed to reconstruct the Nd₂Fe₁₄B and Nd-rich original phases in the magnet. It indicates that the two original phases were constructed into non-bonding Fe-rich phase (containing non-REEs) and Bi-rich phase (containing REEs), respectively. Subsequently, the Bi-rich substance magnetically separated from the reconstructed scrap powders were distilled to extract the RE metals. The volatile metal Bi and Fe-rich substance are reusable. The recovery rates of REEs and non-REEs reach 97.3% and 97.6%, respectively. The phase evolution during the phase reconstruction was discussed, and a comparative assessment of the energy consumption and CO₂ emissions was conducted. This work provides a low-consumption and environmental-friendly shortcut for full-component recovery of the Nd-Fe-B magnet scraps.