Extraction of rare earth elements from neodymium (NdFeB) magnet scrap using magnesium halides

초록

The demand for neodymium (NdFeB) permanent magnets for electric vehicles and eco-friendly generators is increasing. However, NdFeB magnets contain rare earth elements (REEs), which are limited in supply. In this study, we performed an exchange reaction between magnesium halides (fluoride and chloride) and waste NdFeB scrap and then compared the characteristics of the extracted halides salts. The compositions of the ternary Mg fluoride (LiF:NaF:MgF2 = 50:40:10 in mole ratio) and chloride (LiCl:NaCl:MgCl2 = 10:50:40 in mole ratio) salts were thermodynamically determined for achieving low eutectic temperatures. The reactions between the NdFeB scrap powder (1-2 mm) and Mg halide salts were carried out at 1073 and 873 K for the fluoride and chloride systems, respectively, in an argon atmosphere. After the reaction, we separated Nd halide from the residual salt and evaluated the Ndextraction rate. The phase formation of the salt was analyzed using X-ray diffraction (XRD), and the extraction rate of Nd was analyzed using inductively coupled plasma optical emission spectroscopy (ICPOES). Nd was extracted in the form of Nd halide (NdF3 or NdCl3), and the extraction rates in the fluoride and chloride systems are 98.64% and 84.59%, respectively. Thus, the fluoride system is more effective than the chloride system for Nd extraction. Our study provides a comprehensive comparative analysis of the effectiveness of fluoride and chloride systems in extracting REEs from NdFeB magnet scrap. Our study findings can be used to develop an effective method for recycling magnet scraps. (c) 2024 Published by Elsevier B.V. on behalf of Chinese Society of Rare Earths.

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