Thesis presented October 24, 2017

Abstract:
The supply of uranium-based nuclear fuel is a key issue of the electricity production strategy in France, especially as demand for natural uranium will continue to increase in the near future. Rare earths are also considered as strategic metals due to their remarkable properties which make them essential in many applications related to new technologies.
There is therefore an interest in developing new, more efficient processes for the extraction of uranium and rare earths than those currently used. The aim is to respond to a permanent increase in demand for raw materials, against the backdrop of the development of new recycling processes, especially for rare earths.
Through a multi-scale approach, this PhD thesis sets to develop novel organic ligands with a strong extractant ability for uranyl (UO₂²⁺) or for rare earths (TR³⁺), as well as a high selectivity with respect to various impurities, in particular iron (Fe³⁺). Thus, many ligands have been designed, synthesized and tested by liquid- liquid extraction in several acidic synthetic media. Bifunctional bi-, tri- and pentadentate molecules have been developed and their complexing properties and their speciation in organic medium have been evaluated in the presence of UO₂²⁺ and Fe³⁺ by different approaches (DFT, UV-visible, IR, ESI-MS, EXAFS). Furthermore, several new ligands have been evaluated for the selective extraction of rare earths and the results obtained are remarkable. Overall, these studies have led in some cases to the development of novel molecular designs with excellent extractant properties. Their optimization, coupled with different analytical techniques, fulfilled the objectives of this thesis and will serve in the future to the development of new efficient and selective extractants.

Keywords:
Synthesis, ligands, selective extraction, coordination chemistry, uranium, rare earths

On-line thesis. ​