Use of dielectric relaxation for measurements of surface energy variations during adsorption of water on mordenite

This paper tries to assess simply and quantitatively the link between classical adsorption theories and dielectric spectroscopy, in order to demonstrate that dielectric spectroscopy can be used as a tool of determination of surface energy variations due to movements of charge carriers at the surface of solids. A simple theory is developed to analyze hops of cations at the surface of mordenite, which are detected by complex impedance spectroscopy during adsorption of water. An energy of extraction of the cation can be determined from measurements and its dependence on the quantity of water molecules adsorbed is shown and qualitatively and quantitatively explained, using relationships developed in order to interpret adsorption phenomena generally. The agreement with other determinations of the adsorption energies and solid surface energy is correct.

The energy of extraction of a Na cation from the internal surface of a Na-mordenite, in the presence of adsorbed water, is deduced from complex impedance spectroscopy using a simple physical model. The influence of the adsorbed water quantity is interpreted using well-known relationships describing adsorption. Data are in good agreement with enthalpies of adsorption and estimates of solid surface energy, showing that the CIS could be a valuable tool for studying adsorption of polar molecules at the surfaces of complex solids.Figure optionsDownload as PowerPoint slide