Modélisation et simulation, outils d’accélération du design des microsystèmes d'extraction liquide-liquide

National audienceIl s'agit de présenter l'apport de la modélisation au prototypage de microsystèmes séparatifs dédiés. les limites de certains outils de modélisation seront discutées

Sustainable Solvent Extraction Process for Fe Analysis in Radioactive Samples Based on Microfluidic Tools

International 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

Luminescence of uranium(VI) after liquid-liquid extraction from HCl by Aliquat® 336 in nn-dodecane:1-decanol by time-resolved laser-induced luminescence spectroscopy

International audienceTo investigate the extraction of uranium(VI) in HCl media by Aliquat® 336 in 1:99 (v:v) 1-decanol:$n$-dodecane mixture, our objective is to identify the complexe(s) in the organic phase by time-resolved laser-induced luminescence spectroscopy (TRLS). The extraction mechanism is supposed to involve the formation of [UO$_2$Cl$_4^{2-}$⋅(R$_4$N$^+$)$_2$] in the organic phase. The occurrence of such a species leads to the presence of the UO$_2$Cl$_4^{2-}$ species in the organic solution, which luminescence shows particular features. The luminescence spectra and decay time evolutions are obtained in the organic phase as a function of HCl concentration in the aqueous phase (0.5–6 M). The extraction of UO$_2$Cl$_4^{2-}$ is confirmed by the particular spectrum of uranium(VI) in the organic phase, and the typical splitting of the luminescence bands, due to the crystal field effect, is clearly evidenced. The stoichiometry is verified using luminescence intensity variation as a function of the activity of Cl$^−$, and extraction constants are calculated both using the specific interaction theory and Pitzer model. A decomposition of the spectrum of the extracted complex in the organic phase is also proposed. The decay time variation as a function of temperature allows estimating the activation energy of the luminescence process of the extracted complex

Mise en place de l'extraction liquide-liquide en microsystèmes : Etablir des écoulements segmentés à façon pour optimiser le transfert de masse

L'une des techniques séparatives les plus importantes à ce jour pour les analyses radiochimiques est l'extraction liquide-liquide. Alors que la fabrication de microsystèmes s'est considérablement perfectionnée, l'extraction liquide-liquide en microsystèmes est en plein essor. Dans ce format elle peut bénéficier des avantages liés à la miniaturisation qui sont la possibilité de réaliser des couplages, le contrôle précis de l'aire interfaciale entre les phases aqueuse et organique en présence, et des temps de contact. Une première étude, dédiée à l'extraction liquide-liquide en flux parallèles d'uranium en milieu chloré agressif par l'Aliquat® 336 (système rapide) et d'europium en milieu nitrique par le N,N'-dimethyl N,N'-dibutyl tetradecylmalonamide (système lent) [1, 2], a permis de mettre en évidence les limitations des flux parallèles pour ce type d'étude. Ainsi, si une valeur optimale de rendement d'extraction a pu être obtenue pour un système chimique rapide, cela n'a pas été possible dans le cas du système chimique lent. Une façon d'optimiser les rendements d'extraction des systèmes cinétiquement lents est de mettre en ?uvre des écoulements permettant d'augmenter l'aire interfaciale spécifique. C'est pourquoi nous étudions la possibilité de former des écoulements segmentés à façon. En s'appuyant d'une part principalement sur les modèles hydrodynamiques décrits par Xu [3] et Cubaud [4], et d'autre part sur une méthodologie permettant de déterminer les grandeurs caractéristiques des écoulements observés expérimentalement dans des jonctions en T et en croix (tailles, fréquence et vitesse des gouttes), nous avons développé un modèle capable de prédire la valeur de l'aire interfaciale spécifique pour les deux systèmes chimiques de l'étude. L'étude du transfert de masse est réalisée en mesurant les concentrations des analytes après séparation des phases grâce à un séparateur membranaire de façon à déterminer les rendements d'extractions en fonction des valeurs d'aires interfaciales spécifiques et des rapports de volumes engagés. Ces rendements d'extraction sont comparés aux rendements en batch. Ces résultats seront exploités par la mise en place d'un modèle de transfert de masse réalisé avec le logiciel COMSOL Multiphysics®. [1] Hellé G., Robertson S., Cavadias S., Mariet C., Cote G., Microfluidics and Nanofluidics 19(5) 1245-1257, 2015 [2] Hellé G., Mariet C., Cote G., Microfluidics and Nanofluidics 17(6), 1113-1128, 2014 [3] Xu J.H., Li S.W., Tan J., Luo G.S., Microfluidics and Nanofluidics 5, 711-717, 2008 [4] Cubaud T., Mason T.G., Physics of Fluids 20(5), 053302, 200

Les microsystèmes au service de la chimie analytique verte pour le nucléaire

International audienceMiniaturization of analytical devices provides new perspectives for safety improvement, optimisation, anddiversification of processes (reduction of matter shipment, reduction of stored materials, energy savings,reaction conditions that are inaccessible with macroscopic reactors…). This reduced scale satisfies most ofthe criteria of green analytical chemistry as well as the principle of minimization of hazards associated toradioactive samples, thanks to a major reduction of sample quantities, reactants, wastes, and analysis time,and to automation. An increasing number of specific microsystems or “labs-on-a-chip” have been developedwith this ambition, particularly for radionuclides purification and separation steps, and for their analysesin complex and hard-to-handle samples. This article illustrates the development of analytical microsystemsfor isotopic, elemental and speciation analysis as met in nuclear-related activities, and underlines the mainchallenges to take up.La miniaturisation des dispositifs analytiques offre, pour le domaine nucléaire, des perspectives nouvellespour la sécurisation, l’optimisation et la diversification des procédés (réduction des transports de matière,réduction des quantités stockées, énergétique, conditions réactionnelles inaccessibles aux réacteursmacroscopiques…). Cette échelle réduite satisfait la plupart des critères de la chimie analytique verte, ainsique le principe de minimisation des risques et nuisances associés aux échantillons radioactifs, par uneréduction très importante des quantités d’échantillons, des réactifs, des déchets générés par les installations,du temps d’analyse et par l’automatisation. Un nombre croissant de développements de microsystèmesou « laboratoires sur puce » spécifiques sont réalisés dans ce sens, en particulier pour les étapes depurification et séparation de radionucléides, et pour leurs mesures dans des échantillons complexes etdifficiles à manipuler. Cet article propose d’illustrer le développement de microsystèmes analytiquesappliqués à des problématiques d’analyse isotopique, élémentaire et de spéciation rencontrées dans lenucléaire, et de souligner les principaux défis qui restent à relever

Intérêt de la microfluidique pour l'analyse des radioéléments

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Improved chromatographic performances of glycidyl methacrylate anion-exchange monolith for fast nano-ion exchange chromatography

International audienceAn efficient and reproducible photopolymerized poly(glycidyl methacrylate-co-ethylene dimethacrylate) was synthesized in Teflon-coated fused-silica capillaries (100 mu m id) and functionalized by reaction of triethylamine with reactive epoxy groups. We report here the successful transfer of a standard polymerization mixture optimized for the thermally initiated synthesis of glycidyl-based monolith to photo-induced polymerization. The monolith obtained after optimization of the photo-initiation conditions was characterized in reverse-phase chromatography evaluating its suitability in terms of efficiency, retention and hydrodynamic permeability. Reproducibility of the photo-induced procedure was satisfactory with RSD below 6% for retention and efficiency and slightly higher for hydrodynamic permeability (12%). The functionalized generic support was then used in nano-ion-exchange chromatography. Efficiencies up to 75 000 plates/m, ion-exchange capacity of 8 nano-equivalents/cm of monolithic column, with a combination of a satisfactory hydrodynamic permeability allowed to perform fast separations of five inorganic anions in <3 min maintaining baseline resolution. The efficiency of the monolith was not retention-dependent, demonstrating its wide range of possible applications for highly retained anions

Design of experiments as tools to tailor impregnated polymers specific for radionuclides separation in microsystems

An experimental design is described for optimization of the microscopic morphology of a methacrylate monolith that was elaborated for chromatographic separation of radionuclides in nitric acid media. This paper presents a systematic study of the synthesis of the polymeric porous monolith poly(ethylene glycol dimethacrylate-co-allyl methacrylate) used as solid-phase support and a post-functionalization of the monolith in microsystem with tributyl phosphate extractant. Polymerization time and chemical composition of the polymerizable mixture that comprises water, 1,4-butanediol, 1-propanol, monomers were chosen as the most relevant experimental factors of the photochemical process. Using the globules area as a significant response of an experimental design, the monolith morphology can be predicted. A new versatile and robust impregnation process was developed in microsystem. The designed micro chromatographic system showed a good resistance in concentrated nitric acid and a great loading capacity compared to commercially available solution (150 mg U versus 75 mgU/g resin)

Potential of ion imprinted polymers synthesized by trapping approach for selective solid phase extraction of lanthanides

International 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