Surface properties of metal ions modified silicas

Abstract

The surface properties of metal (alkali and alkaline earth) modified silica beads were investigated by the inverse gas chromatography method. Silica beads, obtained from silica sol, were characterized by their specific surface areas, crystal structure and amount of sorbed cations. Retentions of several n-alkanes were measured in the temperature range from 340 to 480 K. The standard free energy of vapour (a mole) transfer from the gas phase to the standard state on the surface, that is, adsorption energy, was calculated from the net retention volume. For n-alkanes, the free energy of adsorption is equal to its dispersive component that varies in the range from 22 to 65 mJ m(-2). The metal modification of silica leads to a decrease in the free energy of adsorption enhancing the homogeneity of the silica bead surface. (C) 1999 Elsevier Science B.V. All rights reserved.