Adsorption isotherms for microporous adsorbents

Abstract

Adsorption equilibria in slit pores are calculated using an analytic solution of the classical Ono-Kondo equation with modified boundary conditions. A new equation is developed for isotherms of gas adsorption on microporous adsorbents. This equation describes isotherms of Type I in the IUPAC classification scheme for temperatures below the critical point and also describes the unusual adsorption of supercritical fluids. This new equation predicts an isotherm that follows the behavior of the Dubinin-Radushkevich (DR) isotherm for relative pressures pps, between 10−1 and 10−5. However, while the DR equation does not give correct behavior either for very low pressures or for moderate to high pressures, this new equation is valid over the whole range of relative pressures. Results obtained are compared with experimental data for adsorption of nitrogen, carbon dioxide, hydrogen sulfide, propane, carbon tetrachloride, ethanol, benzene, iso-octane, n-butane, and methane on activated carbon.