A Simple General Relationship between the Dielectric Losses Measured on Divided Solids and Adsorption Thermodynamic

Abstract

Dielectric losses measured on a zeolite sample have been investigated to correlate these measurements with surface thermodynamic. The polarization conductivity measurement allows the determination of variables which are linked to the adsorption enthalpies and entropies but also to the system dynamic. To quantitatively interpret the results, it is necessary to know the energetic heterogeneity of the solid sample. The thermally stimulated current measurement (TSDC) appears as a possible tool. Therefore this new method of studying adsorption by combining two techniques seems promising. This paper is an introduction to the work under development.

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

“…For many years, we have focused our interest on dielectric relaxation phenomena occurring in bulk and on surfaces [6]. Solids studied contain cations, which are able to move when an electric field is applied.…”

“…Afterward, we will show that it is possible to assess the enthalpies corresponding to movements of cations and the modifications of these enthalpies due to adsorption of water. The study of the adsorption of water onto an Na-mordenite presented here is considered as an example of a possible general approach, which will be applied in the near future to other ionic systems still being experimentally studied [3][4][5][6]12]. …”

Analysis of Thermally Stimulated Depolarization Currents (TSDC) Measured on Exchanged Clays

“…Information obtained by these techniques allows some understanding of the behavior of the solid surface at a macroscopic level, but these techniques do not provide information about the microscopic mechanisms of adsorption. However, it is well known that the energy of individual adsorption sites is a key factor in order to theoretically predict the adsorption properties of a solid surface, like the quantity of molecules adsorbed or 1 To whom all correspondence should be addressed. E-mail: jmd@univ-montp2.fr.…”

Behavioural Change according to the Si/Al Ratio of Successive Na-Mordenites Observed through Their Dielectric Relaxation during Water Vapour Adsorption Process

“…In actual fact, the method consists in measuring, as accurately as possible, the variations of a parameter related to the surface structure and depending on the vapour pressure imposed on the system, at constant temperature. The work we did previously on the zeolites [9][10][11][12] moved us to examine a Na-mordenite…”