Supramolecular receptors in solid phase: developing sensors for anionic radionuclides

Abstract

New solid-phases for the binding, separation and extraction of perrhenate and pertechnetate (ReO₄⁻ and TcO₄⁻) from water solutions have been developed from a selective molecular receptor. Host compounds being capable of encapsulating these oxoanions are of great interest. The azacryptand, containing two tripodal tetra-amine subunits covalently linked by p-xylyl spacers, is known to display high affinity for ReO₄⁻ and TcO₄⁻ in water. The syntheses of new solid phases, obtained by fixing the receptor on mesoporous silica MCM-41 and Amberlite CG50 supports, are here described. FT-IR, micro-Raman, elemental analysis (CHN), sorption isotherms, ²⁹Si MAS NMR, and SEM/EDS were employed for solids characterisation. Promising performances were found for silica derivatives, for which the amount of the receptor fixed on silica ranged from 0.2 to 0.3 mmol g⁻¹. The perrhenate sorption mechanism was investigated with the aim to select the conditions for application in batch and fixed bed column systems.