Synthesis and characterization of organic-inorganic hybrid mesoporous anion-exchange resins for perrhenate (ReO₄^-) anion adsorption

Organic-inorganic hybrid mesoporous anion-exchange resins based on either pure silica or organosilica support materials were prepared and tested for the adsorption of perrhenate (ReO₄^-) anions in aqueous solutions. The prepared samples were characterized using nitrogen adsorption-desorption measurements, Fourier transform infrared spectroscopy, Raman spectroscopy, small-angle X-ray scattering, ²⁹Si cross-polarization/magic-angle-spinning nuclear magnetic resonance, and scanning transmission electron microscopy. Among the prepared samples, the hybrid mesoporous anion-exchange resins functionalized with N-((trimethoxysilyl)propyl)-N,N,N-tri-n-butylammonium ions showed higher affinities for perrhenate ions than did the resins functionalized with N-((trimethoxysilyl)propyl)-N,N,N-trimethylammonium ions. The enhancement by the bulky ammonium functional ligand is consistent with Hofmeister selectivity.