Leaching Behavior of Rare Earth Elements from Waste NdFeB Magnets Utilizing Deep Eutectic Solvents

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The leaching behavior of a rare earth element, neodymium, from waste NdFeB magnets using deep eutectic solvents (DESs) was investigated. Eight different DESs were prepared for leaching tests. The basic tests were conducted on Nd and Fe compounds, Nd2O3, Fe, and Fe2O3. Using GUC-LAC, ChCl-LAC, and EG-MA, Nd2O3 was leached by 64–100%. With the three DESs, Fe exhibited a leaching efficiency of over 94% in all DESs, while that of Fe2O3 remained low at <7%. Based on the results, leaching tests were conducted on NdFeB magnets with and without oxidative roasting. The leaching efficiencies of Nd and Fe significantly decreased after the roasting, at 27% and 4.7%, respectively. This was attributed to the formation of NdFeO3 during the roasting. Therefore, to selectively recover Nd from NdFeB magnets, the application of the appropriate pre-treatment method is necessary, prioritizing the separation of individual oxides to Nd2O3 and Fe2O3.