Synthesis, characterization and sorption properties of silica modified with some derivatives of β-cyclodextrin.

Nanoporous β-cyclodextrin-containing silicas which differ by functional substituents of wide edge of attached cyclic oligosaccharide molecules (alcohol, bromoacetyl, thiosemicarbazidoacetyl groups) have been synthesized. The structure and chemical composition of the surface, porosity of obtained materials, their chemical and thermal stability have been characterized by scanning electron microscopy, IR spectroscopy, thermogravimetry, nitrogen ad-desorption, elemental and chemical analyses of solid surface. Sorption of trace amounts of cadmium (II) in the presence of ten- and hundred-fold excess of hardness salts by synthesized organosilicas has been studied. It has been demonstrated that the sorption equilibrium is reached after 30 min. The sorption of trace amounts of cadmium (II) from multi-component solutions does not decrease, but even increases in the presence of hardness salts, simulating soft and hard water. Coefficients of distribution and selectivity as well as the sorption parameters of Langmuir and Freundlich equations have been calculated. It was found that the driving force of cadmium (II) sorption on the surface of functional β-cyclodextrin-containing silicas is the formation of inclusion complexes "β-cyclodextrin-nitrate-anion". It has been proved the formation of supramolecular structures on the surface of synthesized organosilicas as a result of cadmium (II) sorption. Chemical composition of supermolecules depends on the structure of surface active centers.