Hybrid Silica Based Materials as New Solid Phase Extractants.
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HYBRID SILICA BASED MATERIALS AS NEW SOLID PHASE EXTRACTANTS. Stéphane Bourg(1), Jean-Charles Broudic(1), Olivier Conocar(1), Joël J.E. Moreau(2), Daniel Meyer(1) and Michel Wong Chi Man(2). (1) CEA Valrho, DCC/DRRV/SPHA, Atalante, BP 171 30207 Bagnols sur Cèze Cedex, France (2) Laboratoire de Chimie Organométallique, CNRS UMR 5076, ENSCM, 8 Rue de l'Ecole Normale, 34296, Montpellier Cedex 5, France ABSTRACT Organic-inorganic hybrids exhibiting specific properties are easily prepared by incorporation of organic fragments in an inorganic network. Increasing attention is being paid to hybrid silsesquioxane gels, which are prepared by sol-gel hydrolysis condensation of organic molecules containing two or more trialkoxysilyl substituents. These hybrids consist of a mixed three-dimensional network, where the organic fragment, cross-linking siloxane chains, is part of the framework. Owing to the presence of a strong Si-C bond between the organic and the inorganic fragments, highly stable hybrid network are produced in this way. A variety of materials can be produced according to the intrinsic properties of the organic. We report here the preparation of hybrid materials with complexing properties upon hydrolysis-condensation of ligands functionalized by Si(OR)3 groups. New hybrid silica based materials containing malonamide ligands have been prepared by sol-gel hydrolysis condensation of functionalized precursors and have been used as solid phase extractants for the complexation of actinides. This approach is quite different from the classical immobilization procedure of complexing agents. The sol-gel approach allows one to adjust the ligand loading and to achieve some control and some tuning of the ligand environment since the oxide matrix is built around the complexing moieties. These hybrids proved to be highly efficient extracting solids. INTRODUCTION The R&D on spent nuclear fuel produces high-level-liquid-waste (HLLW) containing radionuclides (fission products and actinides). This diversity requires drastic polyvalent processes to treat them and the extraction chromatography on modular functionalized silicas seems to be a relevant technique either for a separation or a subsequent confinement of the elements. For a few years, sol-gel chemistry[1] is the most important and versatile route for the synthesis of organically modified materials.[2, 3] Hybrid silicas, prepared by sol-gel hydrolysis condensation of alkoxy-silylated organic molecules, constitute an interesting class of amorphous materials.[4-8] It consists in mixed three-dimensional networks with an homogeneous distribution of the organic fragment in the inorganic matrix. A variety of amorphous silica-based hybrids can be produced upon hydrolysis of silicon alkoxides with different structures (Figure 1). The mild reaction conditions of this process allow a tailoring of the materials properties.[9-14]
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