Description du sujet de thèse

A certain 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 being able to process these wastes in such a way as to concentrate these metals for recycling. It so happens that natural hydrothermal systems are capable of selectively sorting chemical elements that are diluted in the Earth's crust. In a geo-inspired approach, we propose to develop a hydrothermal process for treating NdFeB permanent magnet powders in order to obtain a product enriched in rare earth elements, mainly Nd, Dy, and Pr, all of which are considered critical elements.

The idea here is to develop a hydrothermal process that allows the separation of these phases under mild chemical conditions starting from magnet powders. The scientific strategy will consist of conducting laboratory experiments, including calorimetric measurements, to achieve a thermodynamic description of the system. This will be implemented in a thermodynamic and hydrodynamic code (COMSOL interface) to guide the optimization strategy for the separation process and to carry out an initial scale-up (from 1g to 1kg) towards an industrial process with a low environmental footprint. The results of this work could then be applied to the recycling of other elements.

The ideal candidate has a background in physical chemistry with a particular interest in modeling (thermodynamics & hydrodynamics) as well as experimentation (hydrothermal and solvothermal chemistry). Knowledge of geochemistry can be acquired during the PhD.

Contexte de travail

The PhD student will join a team comprising an Earth Sciences laboratory (ISTerre, Grenoble - https://www.isterre.fr/) and an industrial partner (Cristal Innov – Saint-Hélène du Lac - https://www.cristal-innov.com/fr/), specialized in crystal growth under hydrothermal conditions. The candidate's activity will be shared between the two sites, mainly at ISTerre-Grenoble initially (experimentation/modeling) and then progressively at Cristal Innov for the final scale-up phase. This project is funded by the ANR and also involves the Multi-Materials and Interfaces Laboratory of UCLB1 (LMI, Lyon, France).

Contraintes et risques

The experimental component of the thesis will involve working in a chemistry lab and handling high-pressure equipment. The PhD student will therefore receive appropriate training. A short training course in the use of COMSOL will also be provided.