LIQUID ADSORPTION AND IMMERSIONAL WETTING ON HYDROPHILIC HYDROPHOBIC SOLID-SURFACES

The preferential adsorption on adsorbents with different surface hydrophobicity (hydrophobic layer silicates) can be properly described by the thermodynamic data of the adsorbed layer. When the components in a binary liquid mixture are very different in polarity, as they are in methanol-benzene mixtures, the polarity of the surface can be characterized through the shape of the excess isotherms and the azeotropic composition. The free energy DELTA21G = f(x1) calculated from the excess isotherms, gives information about the decrease in free energy due to the displacement. The displacement enthalpy isotherms DELTA21H = f(x1) can be determined with flow microcalorimetry and the thermodynamic description of the adsorption layer is complete. The combination of displacement free energy and enthalpy with adsorption excess amounts gives a new way to determine the volume of the adsorbed layer. The combination also gives data to determination of the molar (DELTA21g, DELTA21h) thermodynamic data, which describe the polarity of a surface in a certain liquid mixture.