ENERGETIC AND STRUCTURAL HETEROGENEITY OF ACTIVATED CARBONS DETERMINED USING DUBININ ISOTHERMS AND AN ADSORPTION POTENTIAL IN MODEL MICROPORES

Adsorption on microporous carbons is investigated in terms of their micropore structure and their adsorption energy heterogeneity. The pore size heterogeneity is proposed to be a controlling factor for the adsorption energy heterogeneity. The relationship between adsorption energy and pore sizes is based on the dependence of the molecule-pore interaction potential well depth as a function of the pore width. The adsorption integral equation is used to analyze data generated from the DR and DA isotherms using typical experimental conditions. It is observed that the adsorption systems described by these isotherms are strongly heterogeneous from the standpoint of their adsorption energetics which are characterized by asymmetrical energy distributions with a broadening toward high energies. It is also shown that these distributions correspond to relatively narrow and symmetrical peaks characterizing the distribution of pore sizes. The strong asymmetrical relationship between adsorption energy and pore width magnifies the energetic heterogeneity even though pore size distributions show only modest dispersion. It is demonstrated that the Henry's law region appears as a natural consequence of the assumed model. © 1992.