The separation of chemical elements is at the heart of the mining, the recycling of nuclear and electronic waste and water decontamination. However, hydrometallurgical processes such as liquid-liquid extraction and leaching use considerable volumes of solvents and organic compounds that are often polluting and volatile. Today, the environmental challenges of reducing the use of volatile organic compounds represent a key challenge for hydrometallurgy.
Hydrophobic eutectic solvents have recently been considered for liquid-liquid extraction[1], offering a number of advantages such as lower volatility and higher flash point, as well as improved extraction performance in some cases associated with different extraction mechanisms compared with the diluents conventionally used in liquid-liquid extraction. [2,3] Our laboratory has also carried out promising preliminary tests to apply these hydrophobic eutectic solvents to the leaching of metallic powders. Although very promising, eutectic solvents are still not widely applied in hydrometallurgy because they need to be optimised and better understood.
The aim of this thesis will therefore be to prepare and test hydrophobic eutectic solvents (HES) based on conventional extractant molecules known in the laboratory and to study their liquid-liquid extraction and leaching properties with respect to various metals of interest such as lanthanides and actinides. The mechanisms of extractions in these unconventional solvents will be addressed by closely observing the effects of complexation and structuring, in order to optimise performance. The extraction properties of various metals will be evaluated by ICP-OES and compared with the physico-chemical and structural properties of the systems (density and viscosity measurements, acid-base and Karl Fisher titration, NMR and IR spectroscopies, tensiometry, X-ray and small-angle neutron scattering (SAXS, SANS), etc.).