Assessment of Hydrophobic-Hydrophilic Properties of Microporous Materials from Water Adsorption Isotherms

The characterization of the hydrophobic-hydrophilic properties of different types of microporous materials, namely activated carbons, pillared clays and zeolites, was made by the determination of water adsorption isotherms. The data were analysed by the Dubinin and Astakhov (D-A) equation. The use of the E parameter of the D-A equation as a measure of the hydrophobic-hydrophilic character is proposed. When the information obtained from the E parameter is compared with the information that can be obtained from other parameters used in the literature to characterize the hydrophobicity of materials, it is found that the former is more sensitive and is more directly related with the shape of the adsorption isotherms which, ultimately, is the more direct manifestation of the hydrophobic-hydrophilic properties of a given material.