Gibbsian surface excess for gas adsorption - Revisited

The Gibbsian surface excess (GSE) represents the true experimental variable for measuring pure and multicomponent gas adsorption equilibria and kineti cs by all conventional adsorption methods (volumetric, gravimetric, chromat ographic, column dynamic, total desorption, isotope exchange, etc). The GSE can be used as primary variables to formulate the general thermodynamic an d kinetic models for adsorption on energetically homogeneous and heterogene ous adsorbents. Thus, practical thermodynamic properties like surface poten tials, isosteric heats of adsorption of components, and heat capacities of adsorption systems can be estimated using GSE. Several thermodynamic consis tency tests (differential and integral) for binary adsorption systems can a lso be formulated using GSE. A mathematical framework describing the isothe rmal and nonisothermal column dynamics for adsorption of multicomponent gas mixtures can be developed using GSE. It can be used to simulate practical process design models (pressure and thermal swing adsorption) for gas mixtu re separation and purification. There is no need to estimate actual amounts adsorbed from the measured GSE variables by making ambiguous assumptions a bout the size of the adsorbed phase. The experimental GSE can be used to co mpletely describe all practical thermodynamic, kinetic, column dynamic, and process design aspects of gas adsorption technology.