Adsorption d'eau sur la kaolinite: Influence de la nature des sites actifs

Abstract

Water adsorption on kaolinite is a specific cooperative adsorption which does not satisfy the fundamental hypothesis of the BET theory. The adsorption isotherms on different homoionic samples show the effect of the hydration energy of the active sites (exchangeable cations) on quantitative adsorption data. The corresponding calorimetric curves present a maximum which characterizes interactions in the adsorbed phase. A relationship is apparent between these interactions and the electric field or the polarizability of the fixed cation, these factors determining the nature of the bond between the surface and cation. From the experimental data, we may propose an approximative value for the number of molecules which compose the primary hydration sheath of the active sites.