Measurement of adsorption energies on heterogeneous surfaces by inverse gas chromatography

Inverse gas chromatography methods, like the reversed-flow gas chromatograp hy technique, offer a new pathway to the determination of adsorption energi es of gaseous substances on heterogeneous solid adsorbents, as a function o f time. The theoretical development was based on the local isotherm model o f Jovanovic, and the experimental arrangement was a simple gas chromatograp h, slightly modified. The method was applied to four gas-solid systems, at 323.2 K, namely, gaseous C2H4 and ZnO, PbO, TiO2, Fe2O3, the solids also be ing gamma-irradiated with 8.2 Mrad before adsorption experiments. The resul ts obtained point to the conclusion that a time transition period with resp ect to the adsorption energy exists, consisting of maxims and minima in the values of energy with time. It ends by levelling off at long times. The ki netic physicochemical quantities of adsorption have also been measured. (C) 1999 Elsevier Science B.V. All rights reserved.