The recycling of rare earths elements (REE) from conventional and unconventional sources is of economic and strategic importance for industrial sovereignty in the face of the challenges posed by the energy transition. The dissolution of phosphate and sulphate minerals results in the production of acidic effluents rich in metal ions, which must then be selectively separated in order to be valorised. To this end, the Laboratory for Laboratory of Recycling and Valorization Processes for Energy (LRVE) is interested in the development of extracting systems allowing the separation of REE from each other according to their atomic weight.
In this context, this PhD research topic aims to evaluate the applicability of extractants in a sulfuric or phosphoric acid medium. These may include phosphoric, phosphonic or phosphinic acids, or solvating molecules such as diglycolamide-type moieties. The main objectives will be, firstly, to understand the coordination mechanisms involved during the extraction stages for the separation of rare earth elements into groups (e.g. light and heavy elements) and to assess the impact of the presence and nature of counter-ions. This will be achieved by conducting dynamic sorption/desorption tests using a liquid-liquid extraction process, and by evaluating parameters such as capacity, selectivity and separation factors (ICP-AES, ICP-MS) of commercial or custom-synthesised molecules (NMR, IR, LC-UV, GC). Subsequently, the ideally selective stripping step will be investigated to ensure the reversibility of the extraction step and to prepare the technological building blocks not addressed in this study (conversion, resin capture, etc.). These results will enable an assessment of the ability of the extractant molecules to separate rare earth elements into several fractions within complexing media.
This project will be carried out at the CEA Marcoule site and is aimed at students in their second year of a Master’s degree or third year of an engineering programme specialising in organic chemistry or separative chemistry, with an interest in organic synthesis, analysis and the development of separation processes. Rigorous thinking, an analytical mind and scientific writing skills are required. This project will enable students to acquire skills in synthetic chemistry and separative chemistry within the context of a topic of significant strategic importance.