Adsorptive interactions of glucose and carbon dioxide with basic sites over alumina

Abstract

Two kinds of alumina (Al₂O₃-1, Al₂O₃-2) have been examined for glucose adsorption from dimethyl sulphoxide solutions. The Al₂O₃-1 adsorbent is found to adsorb considerable amounts of glucose while the Al₂O₃-2 adsorbent is found to adsorb little glucose.

IR spectroscopy of the adsorbents and adsorbed CO₂ species has revealed that Al₂O₃-1 carries significant amounts of basic OH groups on its surface whereas Al₂O₃-2 carries few basic sites. This indicates that Al₂O₃-1 provides acidic glucose molecules with good adsorption sites (basic), which results in a larger degree of adsorption.

XP spectroscopy of the adsorbents with and without adsorbed glucose has revealed that only the C 1s spectra for the Al₂O₃-1–glucose system exhibit measurable changes upon glucose absorption.

From the analysis of the C 1s difference spectra, the molecular structure of glucose is found to be almost unchanged by the interaction with the basic site. This suggests that the acidic C₁—OH group located at the periphery of the glucose molecule is responsible for the adsorptive interaction with the basic site. This view has been supported by a small adsorption capacity of Al₂O₃-1 for the methyl-α-D-glucoside adsorbate.