Studies on adsorption of amino acids on β-cyclodextrin bonded to silica particles

The adsorption properties of certain amino acids from aqueous solution onto β-cyclodextrin-bonded silica particles (CDS) has been investigated with the aim of in-depth understanding of the host–guest interaction. Adsorption equilibrium data are correlated with the Langmuir, Freundlich and Redlich–Peterson isotherm, the Langmuir model being found to provide the best fit of the experimental data. The adsorption rate curves for almost all the solutes appear to be typical of the first-order kinetics. However, more precise kinetics will require inclusion of the external mass transfer effect initially and particle diffusion effect at the later stage. IR studies show significant changes in the adsorption of amino acids onto CDS. The stretching vibration frequencies of the O–H and N–H bonds on the guest molecules are changed with the formation of the complexes. The porous structure of CDS as revealed by scanning electron micrograph thus shown to be promising materials for enantioselective separation of amino acids.