Hydrothermal separation of Rare-Earth elements: Application to NdFeB magnets – SYDERANT

A number of industrial and household wastes contain metals of economic or even geostrategic interest, in low to very low concentrations. There is a real socio-economic challenge in treating these wastes in such a way as to concentrate the metals for recycling. Natural hydrothermal systems are capable of selectively sorting the chemical elements that are diluted in the Earth's crust. In a geoinspired approach, we propose to develop a hydrothermal process for treating NdFeB permanent magnet powders to obtain a product enriched in Rare Earth Elements, mainly Nd, Dy and Pr, all of which are considered critical elements. To achieve this goal, we set up a team comprising an Earth Sciences laboratory (ISTerre) and an industrial company (Cristal Innov) specialized in crystal growth under hydrothermal conditions. Hydrothermal treatment (200 – 300°C) of permanent magnets has been shown to produce magnetite (Fe3O4), neodymium hydroxides and borates, as well as significant quantities of valuable H2. The idea here is to develop a hydrothermal process enabling these phases to be separated under mild chemical conditions from magnet powders supplied by a producer (Daimantel and MagReeSource). This eco-efficient process is a breakthrough compared to current technologies. The scientific strategy followed will consist in conducting laboratory experiments, including calorimetric measurements, to derive a thermodynamic description of the system. This will be implemented in a thermodynamic and hydrodynamic code (COMSOL interface) to guide the separation optimization strategy and achieve an initial change of scale (1g to 1kg) towards an industrial process with a low ecological footprint. Results from this project could be then implemented for recycling other species.