Some theoretical and experimental limitations in the determination of surface free energy of siliceous solids

The components of surface free energy of silica gel were calculated according to various theoretical approaches, and based on the data from different experimental methods (i.e., gas chromatography and thin column wicking). The results are compared, and widely discussed in terms of theoretical imperfections, accuracy of the liquid surface tension components data, as well as specific conditions (affecting the surface properties) implied by the used experimental method. Special attention was paid to adsorbed water layers. The differences in the results (especially those, dealing with donor-acceptor interactions) are discussed in terms of the mechanism of water vapour adsorption. The adsorbed water may provide an increase of electron-donor interactions of the surface. (C) 1999 Elsevier Science S.A. All rights reserved.