Time distribution of surface energy on heterogeneous surfaces by inverse gas chromatography

The time separation of experimental surface energy on silica gel and calcium oxide together with the time independent rate constants for adsorption and desorption of pentane, hexane and heptane is described, applying the reversed-flow version of inverse gas chromatography. The dependence of surface energy on the time of measurement is attributed to the heterogeneity of the solid surface. The results obtained agree with Fowkes formalism only for the last Gaussian bands of the London component of the total surface free energy, plotted against experimental time and taking into account their distribution function, found experimentally. This corresponds to adsorbate molecules bound on the second layer of the solid surfaces. (C) 2003 Elsevier B.V. All rights reserved.