Development of a new process for the selective rare earth recovery from used permanent magnets

International audienceAlbeit being considered today as the most critical raw materials group with the highest supply risk, the recycling of rare earth elements (REE) from permanent NdFeB magnets is almost inexistent. Therefore, a large research effort is needed for over-coming the current scientific and technological barriers and improving the recycling efficiency. Innovative, profitable and eco-designed processes have to be developed, which require extensive R&D effort from basic research to technological developments. The CEA has gained a world-class expertise in the field of separation processes by hydrometallurgy and pyrometallurgy, several solvent extraction processes being developed and industrially implemented for the nuclear fuel cycle. In this communication, an efficient combined hydro- and pyrometallurgical process aimed at REE recovery and separation from used or refurbished NdFeB permanent magnets will be presented. The process integrates the mechanical and physico-chemical treatment of NdFeB magnets, followed by a solvent extraction step for the recovery and intra-separation of REE using a selective extracting molecule with excellent affinity for heavy REE (Dysprosium) which are today the most critical REE. A solvent extraction flow sheet was calculated and tested in laboratory-scale mixer-settlers from a genuine solution of permanent magnets leached in nitric acid. More than 99.9% of dysprosium and neodymium were recovered in two different streams with purities higher than 99.99%. A subsequent pyrometallurgical treatment via molten chloride salt electrolysis allowed the isolation of pure Dy metal with excellent faradic yields. Based on these results, a first techno-economic analysis was made to scale-up the process at an industrial scale and will be presented in the paper. This is one of the first examples of an effective, closed-loop REE recovery and separation process, starting from magnet scrap down to individual pure REE as metals, which paves the way for future developments in the field