9 research outputs found

    Développement d'un microsystÚme séparatif sur monolithe organique pour l'analyse des radionucléides en milieu acide nitrique

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    Radionuclides analysis is a key point for nuclear waste management and nuclear material control. Several steps of sample modification have to be carried out before measurements in order to avoid any interferences and improve measurement precision. However those different steps are long, irradiant and difficult to achieve in gloveboxes. Moreover they produce liquid and solid waste. The goal of the study is to offer a new alternative to the use of solid phase extraction column for radionuclides separation in hard nitric acid medium. The system will decrease the amount of nuclear waste due to the analysis and automatize the different steps of the analysis. A plastic device made of COC containing a micro solid phase extraction column is first designed. Stationary phase is a poly(AMA-co-EDMA) monolith synthetized in situ. Its structure is adjustable and its functionalization versatile with a high resistance to nitric acid medium. Exchange capacity is 150 mg/g of monolith for TBP and TBP/CMPO column and up to 280 mg/g of monolith in case of DAAP. Exchange coefficients are determined for U(VI), Th(IV), Eu(III) and Nd(III) for 3 different extractants (and Pu(IV) in case of TBP column). Monolith synthesis is transferred in centrifugal device and hydrodynamic behavior studied. U,Th/Eu separation was finally carried out in both classic and centrifugal microsystem on TBP column.L’analyse des radionuclĂ©ides est une nĂ©cessitĂ© pour la gestion des matiĂšres et dĂ©chets radioactifs liĂ©e Ă  l’industrie nuclĂ©aire. Pour Ă©viter les interfĂ©rences et amĂ©liorer la prĂ©cision des mesures, les Ă©tapes de traitement de l’échantillon et de sĂ©parations restent aujourd’hui incontournables. Elles sont cependant longues, irradiantes, difficiles Ă  mettre en Ɠuvre en boite Ă  gants et produisent un volume de dĂ©chets liquides et solides significatif. L’objectif de cette thĂšse est de proposer une alternative innovante Ă  l’utilisation des colonnes d’extraction sur phase solide dans les protocoles de sĂ©paration des radionuclĂ©ides en milieu nitrique concentrĂ© permettant de rĂ©duire ces dĂ©chets en fin de cycle analytique et d’automatiser ces Ă©tapes. Un premier microsystĂšme jetable en plastique (COC) intĂ©grant une micro-colonne sĂ©parative de chromatographie d’extraction a Ă©tĂ© conçu. La phase stationnaire est un monolithe poly(AMA-co-EDMA) synthĂ©tisĂ© par photopolymĂ©risation in situ Ă  structure ajustable, fonctionnalisable Ă  façon, rĂ©sistant au milieu nitrique concentrĂ©. Les capacitĂ©s d’échange obtenues sont de l’ordre de 150 mgU/g de monolithe pour le TBP et le mĂ©lange TBP/CMPO et 280 mgU/g de monolithe pour le DAAP. Les valeurs des coefficients de partage des monolithes imprĂ©gnĂ©s ont Ă©tĂ© dĂ©terminĂ©es pour U(VI), Th(IV), Eu(III) et Nd(III) pour les 3 extractants (ainsi que pour Pu(IV) dans le cas de monolithes imprĂ©gnĂ©s par le TBP). La synthĂšse du monolithe a Ă©tĂ© transfĂ©rĂ©e en microsystĂšme centrifuge et aprĂšs Ă©tude hydrodynamique, la sĂ©paration U,Th/Eu en milieu nitrique a Ă©tĂ© rĂ©alisĂ©e sur colonne imprĂ©gnĂ©e TBP en microsystĂšme classique puis transfĂ©rĂ©e en microsystĂšme centrifuge

    Development of a separatif microsystem for radionuclides analysis in nitric acid media

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    L’analyse des radionuclĂ©ides est une nĂ©cessitĂ© pour la gestion des matiĂšres et dĂ©chets radioactifs liĂ©e Ă  l’industrie nuclĂ©aire. Pour Ă©viter les interfĂ©rences et amĂ©liorer la prĂ©cision des mesures, les Ă©tapes de traitement de l’échantillon et de sĂ©parations restent aujourd’hui incontournables. Elles sont cependant longues, irradiantes, difficiles Ă  mettre en Ɠuvre en boite Ă  gants et produisent un volume de dĂ©chets liquides et solides significatif. L’objectif de cette thĂšse est de proposer une alternative innovante Ă  l’utilisation des colonnes d’extraction sur phase solide dans les protocoles de sĂ©paration des radionuclĂ©ides en milieu nitrique concentrĂ© permettant de rĂ©duire ces dĂ©chets en fin de cycle analytique et d’automatiser ces Ă©tapes. Un premier microsystĂšme jetable en plastique (COC) intĂ©grant une micro-colonne sĂ©parative de chromatographie d’extraction a Ă©tĂ© conçu. La phase stationnaire est un monolithe poly(AMA-co-EDMA) synthĂ©tisĂ© par photopolymĂ©risation in situ Ă  structure ajustable, fonctionnalisable Ă  façon, rĂ©sistant au milieu nitrique concentrĂ©. Les capacitĂ©s d’échange obtenues sont de l’ordre de 150 mgU/g de monolithe pour le TBP et le mĂ©lange TBP/CMPO et 280 mgU/g de monolithe pour le DAAP. Les valeurs des coefficients de partage des monolithes imprĂ©gnĂ©s ont Ă©tĂ© dĂ©terminĂ©es pour U(VI), Th(IV), Eu(III) et Nd(III) pour les 3 extractants (ainsi que pour Pu(IV) dans le cas de monolithes imprĂ©gnĂ©s par le TBP). La synthĂšse du monolithe a Ă©tĂ© transfĂ©rĂ©e en microsystĂšme centrifuge et aprĂšs Ă©tude hydrodynamique, la sĂ©paration U,Th/Eu en milieu nitrique a Ă©tĂ© rĂ©alisĂ©e sur colonne imprĂ©gnĂ©e TBP en microsystĂšme classique puis transfĂ©rĂ©e en microsystĂšme centrifuge.Radionuclides analysis is a key point for nuclear waste management and nuclear material control. Several steps of sample modification have to be carried out before measurements in order to avoid any interferences and improve measurement precision. However those different steps are long, irradiant and difficult to achieve in gloveboxes. Moreover they produce liquid and solid waste. The goal of the study is to offer a new alternative to the use of solid phase extraction column for radionuclides separation in hard nitric acid medium. The system will decrease the amount of nuclear waste due to the analysis and automatize the different steps of the analysis. A plastic device made of COC containing a micro solid phase extraction column is first designed. Stationary phase is a poly(AMA-co-EDMA) monolith synthetized in situ. Its structure is adjustable and its functionalization versatile with a high resistance to nitric acid medium. Exchange capacity is 150 mg/g of monolith for TBP and TBP/CMPO column and up to 280 mg/g of monolith in case of DAAP. Exchange coefficients are determined for U(VI), Th(IV), Eu(III) and Nd(III) for 3 different extractants (and Pu(IV) in case of TBP column). Monolith synthesis is transferred in centrifugal device and hydrodynamic behavior studied. U,Th/Eu separation was finally carried out in both classic and centrifugal microsystem on TBP column

    Microsysteme separatif sur monolithe organique pour l'analyse des radionucleides (U, Pu, Produits de fission) en milieu acide nitrique

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    International audienceL'analyse des radionucleides presents dans les dechets de haute ou moyenne activite s'effectue selon des protocoles operatoires incluant l'enchainement de plusieurs operations de separation/purification. Il s'agit donc d'un processus analytique long, complexe et difficile a mettre en place dans un environnement hostile. L'utilisation de microsystemes automatises pourrait conduire a une reduction du temps d'analyse, a de meilleures performances analytiques ainsi qu'a une cadence d'analyses elevee grace notamment au multiplexage. La presentation portera sur la synthese photochimique d'un monolithe methacrylate fonctionnalise par un ammonium quaternaire par chimie-clic

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

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    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)

    Microfluidics devices applied to radionuclides separation in acidic media for the nuclear fuel cycle

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    International audienceMiniaturization of analytical devices provides new perspectives for safety improvement, intensification, and diversification 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 of the criteria of green analytical chemistry as well as the principle of minimization of hazards associated to radioactive 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 developed with this ambition, particularly for radionuclides purification and separation steps, and for their analyses in complex and hard-to-handle samples. This article illustrates the development of microsystems for elemental separations in acidic media prior to isotopic or elemental measurements by mass spectrometry or a radiometric analysis method for nuclear-related activities, and underlines the main challenges to take up

    Photochemical Synthesis and Versatile Functionalization Method of a Robust Porous Poly(ethylene glycol methacrylate-co-allyl methacrylate) Monolith Dedicated to Radiochemical Separation in a Centrifugal Microfluidic Platform

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    International audienceThe use of a centrifugal microfluidic platform is an alternative to classical chromatographic procedures for radiochemistry. An ion-exchange support with respect to the in situ light-addressable process of elaboration is specifically designed to be incorporated as a radiochemical sample preparation module in centrifugal microsystem devices. This paper presents a systematic study of the synthesis of the polymeric porous monolith poly(ethylene glycol methacrylate-co-allyl methacrylate) used as a solid-phase support and the versatile and robust photografting process of the monolith based on thiol-ene click chemistry. The polymerization reaction is investigated, varying the formulation of the polymerisable mixture. The robustness of the stationary phase was tested in concentrated nitric acid. Thanks to their unique " easy-to-use " features, centrifugal microfluidic platforms are potential successful candidates for the downscaling of chromatographic separation of radioactive samples (automation, multiplexing, easy integration in glove-boxes environment, and low cost of maintenance)

    Vertical export flux of metals in the Mediterranean Sea

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    We examined metal (Al, V, Cr, Mn, Fe, Ni, Cu, Zn, Cd and Pb) and particulate organic carbon (OC) concentrations of the marine vertical export flux at the DYFAMED time-series station in the Northwestern Mediterranean Sea. We present here the first data set of natural and anthropogenic metals from sediment trap moorings deployed at 1000 m-depth between 2003 and 2007 at the DYFAMED site. A highly significant correlation was observed between most metal concentrations, whatever the nature and emission source of the metal. Cu, Zn and Cd exhibit different behaviors, presumably due to their very high solubility and complexation with organic ligands. The observed difference of atmospheric and marine fluxes in terms of temporal variability and elemental concentration suggests that dense water convection and primary production and not atmospheric deposition control the marine vertical export flux. This argument is strengthened by the fact that significant Saharan dust events did not result in concomitant marine vertical export fluxes nor did they generate significant changes in metal concentrations of trapped particles

    Control of the anisotropic shape of cobalt nanorods in the liquid phase: from experiment to theory
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    International audienceThe polyol process is one of the few methods allowing the preparation of metal nanoparticles in solution. Hexagonal close packed monocrystalline Co nanorods are easily obtained in basic 1,2-butanediol at 448 K after a few minutes using a Co(II) dicarboxylate precursor. By using a combined experimental and theoretical approach, this study aims at a better understanding of the growth of anisotropic cobalt ferromagnetic nanoparticles by the polyol process. The growth of Co nanorods along the c axis of the hexagonal system was clearly evidenced by transmission electron microscopy, while the mean diameter was found to be almost constant at about 15 nm. Powder X-ray diffraction data showed that metallic cobalt was generated at the expense of a non-reduced solid lamellar intermediate phase which can be considered as a carboxylate ligand reservoir. Density functional theory calculations combined with a thermodynamic approach unambiguously showed that the main parameter governing the shape of the objects is the chemical potential of the carboxylate ligand: the crystal habit was deeply modified from rods to platelets when increasing the concentration of the ligand, i.e. its chemical potential. The approach presented in this study could be extended to a large number of particle types and growth conditions, where ligands play a key role in determining the particle shape.Graphical abstract: Control of the anisotropic shape of cobalt nanorods in the liquid phase: from experiment to theory
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