Maintaining parallel flows in microsystem during solvent extraction of concentrated Uranium(VI) solutions a solution for the screening of extractive molecules
Résumé
Future nuclear fuel reprocessing will require new extracting molecules exhibiting better performances (higher affinity, selectivity and stability under irradiation). Batch liquid-liquid extraction screening trials are carried out to identify an extracting molecule of interest . These molecules are often expensive to synthesize and purify, consequently, screening processes involving low volumes show attractiveness. Miniaturized liquid-liquid extraction allows to reduce the quantities of both radionuclides and extractant used for the screening. Therefore, generated waste, chemical and radiological risks are reduced [1]. Furthermore, microsystems provide many advantages such as large interfacial areas, short diffusion distance [2], high surface / volume ratio [3] and process intensification [4]. In this communication, the use of a commercial microsystem as a tool for the screening of new extractants will be exhibited. The chemical reference system [HNO$_3$] = 3M / 30% TBP in n-dodecane was chosen as model to validate the applicability of liquid-liquid extraction microsystem for the screening at high U(VI) concentrations. The implementation of parallel flows is a suitable way to easily get a good phase separation. Flow patterns depend on the compositions of the two phases and particularly on their viscosities [5]. High-grade concentrations implicate variations of the viscosities of the two phases along the extraction process. This affects the stability of laminar flows and the quality of the phase separation at the outlet of the microsystem [5]. Then, the influence of high U(VI) concentrations (0-140 g.L$^{-1}$) on flow patterns was studied in order to succeed in maintaining parallel flows during the extraction process despite the evolution of the viscosities. Finally, U(VI) extraction performance was evaluated with optimized experimental conditions to demonstrate the potential application of such microdevice for the screening of alternative extracting molecules.
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