A NEW ADSORPTION-ISOTHERM FOR HETEROGENEOUS ADSORBENT BASED ON THE ISOSTERIC HEAT AS A FUNCTION OF LOADING

A new adsorption isotherm model is proposed in this paper for a hetero geneous solid. The basis of this isotherm equation is that the degree of heterogeneity is reflected through the variation of the isosteric h eat of adsorption with respect to loading. This degree as well as the pattern of heterogeneity is assumed to be independent of adsorbate use d. The influence of the adsorbate on the isotherm will be through the interaction energy at zero loading as well as parameters which reflect the way in which the adsorbate fits into the adsorption sites. The re sulting isotherm equation is very general, and under certain condition s it reduces to many isotherms commonly used in the literature, such a s the Langmuir, Langmuir-Freundlich, Toth, Fowler-Guggenheim and Nitta et al. equations. The new isotherm is tested with adsorption isotherm data of many adsorbates on various samples of activated carbon and ze olite, and the parameters extracted for these adsorbates shed some lig ht on the system heterogeneity. Implications of this new isotherm are discussed in this paper. Copyright (C) 1996 Elsevier Science Ltd.