52 research outputs found

    Environmental changes and radioactive tracers

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    Template effect in caesium selective phenolic resins

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    Two new phenolic resins have been synthesised by alkaline polycondensation of resorcinol and acetaldehyde using template polymerisation. The extraction properties of the resins have been evaluated in competitive extraction and show a selectivity in favour of Cs+. This selectivity is enhanced for the template resins. Structural data of the resins are discussed on the basis of C-13-NMR CPMAS spectra. In particular, for caesium template resins, a structure similar to resorcinarene has been evidenced

    Polymeric and immobilized crown compounds, material for ion separation

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    We describe the synthesis of ionoselective polymers bearing different pendant crown ethers. The synthesis was applied to various macrocycles. We discuss the influence of macrocyclic cavity Size and rigidity of the polymers on the extraction behavior. Accessibility of active sites can be achievied with immobilized functionalized polyurethanes chemically bound to an inorganic solid support, with no change of ionoselective properties

    Design of ion-exchange resins selective of caesium. Synergistic effect of macrocycle in phenolic resins

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    The extraction of caesium by resorcinol based resins was investigated. At high hydroxide concentration ([OH-] = 0.15 M), the alkali-metal cations' sorption selectivity (determined in competitive extraction system) for resorcinol resins was found to be Cs+ gt Li+ gt Rb+ gt K+ gt Na+, whereas at pH 7 this selectivity was found to be Cs+ gt Rb+ gt K+ gt gt Na+ approximate to Li+. Different mechanisms of ion exchange occurring in these phenolic resins can explain this selectivity series. Then different macrocycles were incorporated in the resins. The ionoselective properties of these new ion-exchange resins are strongly influenced by the nature of the crosslinker. The presence of macrocycles lead to an improvement of selectivity towards caesium in relation with the size of the macrocycles introduced

    Synthesis and evaluation of resorcinol-based ion-exchange resins for the selective removal of cesium

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    Control of the reaction conditions during the alkaline polycondensation of resorcinol with formaldehyde leads to polymeric resins with improved capacity toward caesium. The resins obtained are characterized by determining their moisture regain and ion-exchange capacity. The distribution coefficient (D) for alkali-metal cations are determined in a competitive extraction system at different pH. The alkali-metal cation sorption selectivity series is strongly influenced by the pH of the solution. Two kinds of mechanism can explain these selectivity series. Extraction of caesium from simulated radioactive waste was studied at different pH in the presence of a large excess of sodium. The study also includes the kinetic and the ion-exchange capacity for caesium of the sodium form of the resins

    Extraction of cesium from an alkaline leaching solution of spent catalysts using an ion-exchange column

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    The selective extraction of cesium from an alkaline leaching solution of spent catalysts using phenolic resins was studied. The resins were synthesized by alkaline polycondensation of formaldehyde by phenol, resorcinol, catechol, and phloroglucinol. Their ionoselectivities for five alkali metals were evaluated with a solid-liquid extraction, and their ion-exchange capacities were compared. The resin with the best selectivity for cesium was tested with a real solution at different pH values. An on-column extraction is proposed to obtain cesium with high purity

    Elimination of vanadium and arsenic from VKCs catalysts

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    Vanadium and arsenic eliminations from an alkaline leaching solution of spent VKCs catalysts were studied. To this end, several commercial resins or polymers synthesized in the laboratory were evaluated in a solid-liquid batch extraction. Conditions for an effective extraction of vanadium and arsenic were determined. An extraction process, using a glass column, is described for the recovery of the vanadium. The elimination of arsenic by precipitation is proposed

    Polyaminocarboxylic acids rejection by charged nanofiltration membrane

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