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Concept of Ideal Adsorbed Solution using Gibbsian Surface Excess Framework

Sircar, Shivaji
Industrial & Engineering Chemistry Research 2016 v.55 no.46 pp. 12119-12122
adsorption, engineering, mixing, sorption isotherms, temperature
A concept of creating an ideal multicomponent- gas adsorbed phase by mixing pure gas adsorbed phases of the components at constant surface potential and temperature using the Gibbsian Surface Excess (GSE) framework of adsorption is proposed. The GSE provides the only unambiguously measured experimental quantity to describe the extent of adsorption. The actual amounts adsorbed can be estimated from the GSE only by making extraordinary assumptions about the volume and structure of the adsorbed phase. The correlations between the multicomponent and pure gas GSE isotherms generated by the proposed concept closely resemble those for the classic Ideal Adsorbed Solution Theory (IAST), which was developed by using the actual amounts adsorbed as the primary variables. The proposed correlations can be obtained by simply substituting the actual amount adsorbed of components in the corresponding IAST correlations by the GSE of the components. All pure and multicomponent gas adsorption data published in the literature are GSE, and they are directly used in the IAST by loosely assuming that they are actual amounts adsorbed. Thus, it appears that the proposed concept of this work has been inadvertently used in all past works which use IAST to estimate multicomponent adsorption isotherms from pure component isotherm data.