Preprocessing and Leaching Methods for Extraction of REE from Permanent Magnets: A Scoping Review

The demand for REEs is continuously increasing in the European Union due to the rapid development of high-tech applications that contain REEs, mainly those based on electrification. However, the REE supply in Europe is limited because of the exclusive production of these metals by third-world countries. The European supply/demand gap for REEs can be covered with the development of recycling technologies from secondary resources, such as REE permanent magnets. NdFeB and SmCo magnets are the two main categories of REE-containing permanent magnets. In the following work, studies focusing on the preprocessing and leaching methods in order to extract REEs were identified and discussed. Although preprocessing includes controversial steps, i.e., milling and demagnetizing, numerous studies have focused on the leaching of REEs from NdFeB magnets using either inorganic or organic solvents. Meanwhile, the literature based on Sm recovery methods from SmCo magnets has been limited.