Liquid-liquid extraction of uranium using monoamides can be limited by complex phenomena, such as third-phase formation or precipitation. This third phase contains a very high concentration of uranium complexes, strongly reducing extraction efficiency and hindering extractant reuse.
The aim of the present PhD is to investigate whether ultrasound (US) can limit third-phase formation and improve uranium extraction. Sonication generates micrometric cavitation bubbles that oscillate and collapse violently, producing intense mixing and shear forces. Cavitation is known to enhance mass transfer and, in many systems, reaction kinetics. However, to the best of our knowledge, it has not yet been applied to uranium liquid-liquid extraction.
The influence of US parameters (frequency, power, irradiation time, etc.) will be investigated using a two-scale approach:
- Nanoscale: effect of US on the size and interactions of organic-phase aggregates and their relationship with extraction and third-phase formation;
- Macroscale: effect of US on mixing, viscosity, extraction kinetics, and phase separation.
Complementary characterization techniques will be used to assess the effect of US on uranium extraction. ICP-OES will quantify uranium concentrations and determine extraction yields and distribution ratios. SAXS/SANS will characterize organic-phase aggregates, while rheology will probe changes in viscosity and flow properties. NMR, IR, and UV–vis spectroscopy will provide complementary information on molecular interactions, uranium speciation, and the chemical environment of the extracting species. Together, these techniques will correlate molecular-scale organization, macroscopic properties, and uranium extraction performance.
The work will also include an instrumentation component, involving the design and development of an experimental cell suitable for in situ studies under US irradiation.