68 research outputs found
Sustainable Solvent Extraction Process for Fe Analysis in Radioactive Samples Based on Microfluidic Tools
No full textInternational audienceThe decommissioning and dismantling of nuclear plants, and the subsequent management of the wastes require a large number of radiochemical analyses in the timeline of the operations. Validated analytical methods for radionuclides measurements are employed to ensure reliable sample characterizations. The radioactivity of the samples, which induces handling and shipment constraints, and the use of harmful chemical reactants in some analytical procedures, are among the motivations to use miniaturized techniques that would considerably lower the amounts of samples and chemicals. Moreover the decrease of the analytical time is a major concern considering the increasing demand for radiochemical analyses. The purpose of this work is to develop a microsystem-based protocol for the recovery of 55Fe from samples. Analytical solvent extraction protocols adapted to co-flow glass microsystems, were developed and tested on iron extraction into ethyl acetate. A first extraction protocol consists of the partitioning of the Fe(cupferrate)3 chelate, from the aqueous phase to the organic phase. A second extraction protocol is based on the reactive transfer of iron using the cupferron in the organic phase. The two protocols were tested on a single Y-junction and a double stage Y-junction glass microsystems. After optimization of the liquid flow rates, the iron extraction was achieved within about 2 s or less. While the best extraction yield of (60.3 ± 4.9) % was obtained with the former protocol in the double stage Y-junction, higher values of (83.1 ± 5.2) % and (81.7 ± 2.0) % were obtained with the single and double stage microsystems, respectively, with the second protocol. These last results compare well with the yield of (93.0 ± 2.3) % measured in batch, and could even be optimized by using slightly longer microchannels. Such microsystem-based extractions will be further applied to the analysis of 55Fe by liquid scintillation
Complexes aqueux de lanthanides (III) et actinides (III) avec les ions carbonate et sulfate. Etude thermodynamique par spectrofluorimétrie laser résolue en temps et spectrométrie de masse à ionisation électrospray
No full textLa prévision de l'impact sur l'environnement d'un éventuel stockage géologique de déchets radioactifs, s'appuie sur la modélisation thermodynamique du comportement de radionucléides dans des eaux souterraines. Dans ce cadre, l'analogie entre lanthanides et actinides(III) est bien confirmée par analyse critique de la littérature et comparaison aux résultats expérimentaux obtenus. Le complexe limite, Eu(CO3)33 , est identifié par mesures de solubilité en solutions de Na2CO3. Puis les constantes de formation des complexes Eu(CO3)i3 2i (i = 1-3) et Eu(SO4)i3 2i (i = 1-2) sont mesurées par SLRT. L'étude de la formation de LaSO4+ en solution par ESI-MS montre un bon accord avec la spéciation attendue. L'enthalpie et l'entropie de la réaction Cm(CO3)2 +CO32 =Cm(CO3)33 sont déduites de mesures de la constante d'équilibre par SLRT entre 10 et 70C. L'effet de la force ionique est calculée par la formule TIS.The prediction of the environmental impact of a possible geological disposal of radioactive wastes is supported by the thermodynamic modelling of the radionuclides behaviour in the groundwater. In this framework, the analogy between lanthanides and actinides(III) is confirmed by a critical analysis of the literature and the comparison with experimental results obtained here. The limiting complex, Eu(CO3)33 , is identified by solubility measurements in Na2CO3 solutions. Then the formation constants of the complexes Eu(CO3)i3 2i (i = 1-3) and Eu(SO4)i3 2i (i = 1-2) are measured by TRLFS. The formation of aqueous LaSO4+ is studied by ESI-MS and is in good agreement with the expected speciation. The enthalpy and entropy of the reaction Cm(CO3)2 +CO32 =Cm(CO3)33 are deduced from TRLFS measurements of the equilibrium constant between 10 and 70C. The ionic strength effect is calculated using the SIT formula.EVRY-BU (912282101) / SudocSudocFranceF
Spectroluminescence measurements of the stability constants of CaUO(CO) complexes in NaClO medium and the investigation of interaction effects
No full textInternational audienc
Analysis of radionuclides in microsystem: application to the selective recovery of
No full textThe minimization of the sample quantities required by analytical laboratories, as well as the increase of the fastness of the analytical operations are emerging axes for improved radiochemical analyses related to D&D issues. Two microsystem-based protocols were developed for the selective recovery of 55Fe from radioactive samples by solvent extraction. Both protocols were tested on iron solutions in two different microchips. The yields of Fe extraction were compared with macroscale batch experiments. Better performances with more than 80% of iron extracted were obtained with the second protocol, which is based on a reactive transfer of the iron cation, and more suited to the use of microchannels and very low contact times. This study already demonstrate the high potential of microfluidic technology to improve analytical operations on D&D samples. This method will further be validated with radioactive samples
Formation of MSeO<sub>4</sub>(aq) complexes (M<sup>2+</sup> = Mg<sup>2+</sup>, Co<sup>2+</sup>, Ni<sup>2+</sup>, Cu<sup>2+</sup>, Cd<sup>2+</sup>) studied as a function of temperature by affinity capillary electrophoresis
No full textInternational audienceComplexation of divalent cations (Mg2+, Co2+, Ni2+, Cu2+, Cd2+) by selenate ligand was studied by ACE (UV indirect detection) in 0.1 mol/L NaNO3 ionic strength solutions at various temperatures (15, 25, 35, 45 and 55°C). For each solution, a unique peak was observed as a result of a fast equilibrium between the free ion and the complex (labile systems). The migration time corresponding to this peak changed as a function of the solution composition, namely the free and complexed metal concentrations, according to the complexation reactions. The results confirmed the formation of a unique 1:1 complex for each cation. The thermodynamic parameters were fitted to the experimental data at 0.1 mol/L ionic strength: (25°C) = −(6.5 ± 0.3), −(7.5 ± 0.3), −(7.7 ± 0.3), −(7.7 ± 0.3), and –(8.1 ± 0.3) kJ/mol and = 2.5 ± 0.2, 4.7 ± 0.4, 4.5 ± 0.6, 8.4 ± 1.1, and 7.2 ± 0.6 kJ/mol for M2+ = Mg2+, Co2+, Ni2+, Cu2+, and Cd2+, respectively. Complexes with alkaline earth and transition metal cations could be distinguished by their relative stabilities. The effect of the ionic medium was treated using the specific ion interaction theory and the thermodynamic parameters at infinite dilution were compared to previously published data on metal–selenate, metal–sulfate, and metal–chromate complexes
Investigation of the Luminescence of [UO<sub>2</sub>X<sub>4</sub>]<sup>2–</sup> (X = Cl, Br) Complexes in the Organic Phase Using Time-Resolved Laser-Induced Fluorescence Spectroscopy and Quantum Chemical Simulations
No full textThe luminescence
properties of the [UO2Cl4]2– complex in an organic phase, especially the influence of large organic
countercations, have been studied by time-resolved laser-induced fluorescence
spectroscopy (TRLFS) and ab initio modeling. The experimental spectrum
was assigned by vibronic Franck–Condon calculations on quantum
chemical methods on the basis of a combination of relativistic density
functional approaches. The shape of the luminescence spectrum of the
uranyl tetrachloride complex is determined by symmetrical vibrations
and geometrical change upon emission. The possible change in the luminescence
properties depending on the first and second uranyl coordination spheres
was predicted theoretically for the [UO2Br4]2– and [R4N]2[UO2Cl4] ([R4N] = [Bu4N], [A336]) systems.
The computations reveal that, for U(VI), the second coordination sphere
has little influence on the spectrum shape, making speciation of uranyl
complexes with identical first-coordination-sphere ligands tedious
to discriminate. The computed structural changes agreed well with
experimental trends; theoretical spectra and peak attributions are
in good accordance with TRLFS and magnetic circular dichroism (MCD)
data, respectively
A combined ab initio and time-resolved laser-induced fluorescence study of uranium-ligand interactions
No full textInternational audienc
Potential of ion imprinted polymers synthesized by trapping approach for selective solid phase extraction of lanthanides
No full textInternational audienceIon imprinted polymers (IIPs) specific to lanthanides were synthesized using neodymium ions (Nd3+) as template ions. Nd3+ ions form binary complex ions with 5,7-dichloroquinoline-8-ol (DCQ) or vinylpyridine (VP), or ternary complex ions with both DCQ and VP in 2-methoxyethanol, before copolymerization in the presence of styrene and divinylbenzene as monomer and cross-linker, respectively. DCQ was expected to be trapped in the synthesized polymers pores. The template ion removal was then optimized. For the first time, the DCQ leakage was determined by HPLC-UV during the template removal and the sedimentation steps before solid-phase extraction (SPE) packing. It was observed that the trapped DCQ was unfortunately lost in significant amounts, up to 51%, and that this amount varied from one synthesis to another. The grinded and sieved polymers were next packed in SPE cartridges. The study of the SPE profiles obtained with the IIPs synthesized either with the binary or the ternary complex confirmed the prominent role of DCQ on the selectivity of an IIP by comparison with a non-imprinted polymer (NIP), i.e. a polymer synthesized under the same conditions as those of the IIP but without template ions. The influence of the porogenic solvent on the selectivity was also investigated by replacing 2-methoxyethanol by acetonitrile or dimethylsulfoxyde (DMSO). The polymers synthesized in DMSO led to the most repeatable results when elution solutions with a gradual decrease in pH were percolated through the cartridge. This is why DMSO was used to optimize the SPE protocol in order to maximize the difference of extraction yield between the IIP and the NIP, i.e. promoting a selective retention on the IIP. A value of about 30% was obtained for La3+, Ce3+, Nd3+, and Sm3+. Nevertheless, with the optimized SPE protocol, IIPs from different syntheses did not have the same SPE behavior, which may result from different random leakages of DCQ. This demonstrates for the first time the main limitation of the IIPs synthesized in bulk with the trapping approach for their use in SPE
Investigation of the luminescence of (X=Cl, Br) complexes in organic phase using time-resolved laser-induced fluorescence spectroscopy and quantum chemical simulations
No full textThe luminescence properties of the complex in an organic phase, especially the influence of large organic counter cations, have been studied by time-resolved laser-induced fluorescence spectroscopy (TRLFS) and ab initio modeling. The experimental spectrum was assigned by vibronic Franck-Condon calculations on quantum chemical models based on relativistic density functional approaches. The shape of the luminescence spectrum of the uranyl tetrachloride complex is determined by symmetrical vibrations and geometrical change upon emission. The possible change of the luminescence properties depending on the first and second uranyl coordination sphere was predicted theoretically for and ( = , ) model systems. The computations reveal that for U(VI), the second coordination sphere has little influence on the spectrum shape, making speciation of uranyl complexes with identical first coordination-sphere ligands tedious to discriminate. The computed structural changes agreed well with experimental trends; theoretical spectra and peaks attribution are in a good accordance with TRLFS and MCD data respectively
Exploring excited state potential energy profile and luminescence properties of uranyl complexes by TRLFS and ab initio methods
No full textInternational audienc
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