[en] Ionic liquids have many favorable properties over conventional diluents in solvent extraction. They provide an environmentally benign feature, adjustable polarity and, in some cases, higher extraction performances that remain however not predictable. As it may have a major role in extraction mechanisms, we evidence the supramolecular aggregation of HDEHP/TOPO extractant molecules in the [OMim][NTf₂] ionic liquid. (authors)

[en] Full text of publication follows. When new uranium ores are about to be exploited in Mongolia as in Kazakhstan, it arouses big interest among industrials who look more than ever for optimized and highly efficient extraction systems. In this context, solvent extraction processes are commonly applied at the purification step, without being always fully satisfying. Design of optimized processes is therefore crucial. For this, the mechanisms at the basis of the good extraction properties need to be fully understood. It is now established that the mechanisms underlying solvent extraction processes are based not only on the molecular chelation properties of the extracting agents, but also on their ability to form supra-molecular aggregates due to their amphiphilic nature [1]. A recent and promising challenge in solvent extraction is to replace the conventional organic solvents (often toxic and volatile), with ionic liquids (IL) [2]. Depending on the extraction systems tested, these new solvents show better efficiency than the conventional ones [3]. Although some assumptions based on ions exchanges have been proposed in the literature [2,3], the involved mechanisms are still poorly understood. So far, no study was conducted to evaluate the IL effect on the aggregation properties of the extracting agents, even though ILs are known to modify the curvature radii of surfactant microemulsions [4]. Our aim is therefore to evaluate the influence of IL structure and polarity on solvent extraction mechanisms, by looking at their influence on the aggregation of the extracting agents. We present the case if an extractant system we have already well characterized in common solvents: the HDEHP/TOPO system. The combination of these two molecules is known to allow a synergistic extraction of uranium in a ratio 4:1[5]. We showed that these synergistic properties are related to a favored aggregation [1], and combined SAXS and SANS measurements pointed out the solvent polarity influence on this system. We therefore focus here on the influence of IL structure on extraction and aggregation properties of this system. It appears that the global uranium extraction is still efficient, but with a synergism peak, shifted to a different TOPO ratio. This interesting feature could also be related to smaller Critical aggregation concentrations. Despite the strong structuration peaks of this kind of solvent, SAXS experiments allowed moreover observing a signal characteristic of the presence of aggregates at small angles. As the solvent peaks of IL makes a proper solvent subtraction difficult, SANS experiments were also conducted to bring a contrast complementary to SAXS measurements, and to make possible a complete analysis of the aggregates microstructure. References: [1] S. Dourdain, I. Hofmeister, O. Pecheur, J-F. Dufreche, R. Turgis, A. Leydier, J. Jestin, F. Testard, S. Pellet-Rostaing,and T. Zemb, Langmuir 2012, 28, 11319-11328. [2] M.L. Dietz, D.C. Stepinski, Talanta, 75, 2 (2008) 598. [3] L. Liu, P. Bauduin, T. Zemb, J. Eastoe, J. Hao, Langmuir, 25 (2009) 2055. [4] O. Zech. S. Thomaier, P. Bauduin, T. Ruck, D.Touraud, W. Kunz, J. Phys. Chem. B, 113 (2009) 465. [5] A. Harrar, O. Zech, A. Klaus, P. Bauduin, W. Kunz, J. Coll. Interf. Sc., 362 (2011). (authors)

[en] Abstracts are provided for the different contributions. They address: The UDEPO database of the IAEA; The availability on the long term of world uranium resources; Interpreting U-Th distribution in the continental crust for radiometric data (NEEDS GeoMac project); The U cycle and the growth-remobilization of continents (NEEDS URCO project); The petrographic and geochemical characterisation of bituminous, sandstone and mud-stone shales in Morocco (analogy with the confinement and storage of radioactive wastes); Recent developments in radiometry (from well logging to measurement in laboratory); Multi-scale approach for the characterisation of emanometry anomalies noticed in the Zoovch Ovoo deposit, Mongolia; A new investigation tool for mining applications (the underground muon tomography, NEEDS ToMuFor project); Contribution of VIS-PIR spectrometry to the study of coffinite in the mining context; Isotopic fractioning of oxygen during processes of precipitation, calcination and reduction of uranium oxides; H₂ production and mobility in uranium deposits associated with a discrepancy; Lixiviation of the hydrogen-bearer Cigar Lake ore; New molecules extracting the uranium present in industrial phosphoric acid; Mechanisms of uranium extraction in ionic liquid media (NEEDS MINION project); Uranium recovery from acid media by using silica-type functionalized solid supports; Damage zone of reactivated Hudsonian faults, a major fluid pathway for large and deep brine percolation in basement rocks of the Athabasca basin (Cigar Lake U deposit, Canada); Is a fertile basement complex a necessary prerequisite to the genesis of high grade U/C-type uranium deposits: source rock clues from the Eastern Athabasca Basin?; Structural analysis of the ductile-brittle fault network in the basement below the Athabasca Basin (Martin Lake, Saskatchewan) - Implications on the controls of uranium-related hydrothermal alteration; Integrated targeting for fault-related basement-hosted uranium deposits: lessons from geologically-constrained 3D gravity inversion modelling and lead isotope geochemistry at the Contact prospect (Kiggavik area, Thelon Basin, Canada); Geology and structural controls in the Contact prospect, Kiggavik uranium project (NE Thelon area, Canada); Synthesis and characterisation of UTi₂O₆ brannerite; Physico-chemical characterisation of natural brannerite samples by scanning electronic microscopy and electronic probe; Assessment of the atmospheric impact of a uranium mine on the recording of radionuclides and metallic trace elements in a mire; Contribution of thermodynamics to UF₆ industrial production; Effects of irradiation on the evolution of mineralogical properties of apatites (NEEDS IrrPO4 project); Prospection guides in searches for uranium mineralizations in the Tim Mersoii Basin; Metallogenic model of uranium deposits associated with the Arlit fault (Tim Mersoii Basin, Niger); Molybdenum valorisation from effluents of a uranium ore treatment plant; Characterisation of the host layer of uranium mineralizations of Mikouloungou (High Ogooue Province, Gabon) - Part 1: Sedimentology, stratigraphy, diagenesis. Geo-dynamic implication on the Francevillian. Part 2: Petrography, dating. Geodynamic implications on the Francevillian