Phenomenological Kinetics of Real Gas-Adsorption-Systems: Isothermal Adsorption

Since Langmuir published the derivation of his famous adsorption isotherm equation in 1918, hundreds of papers on the kinetics of gas adsorption on solid surfaces have appeared in the world literature. Until the early fifties of the 20th century, these were mainly papers reporting on experimental studies of the kinetics of adsorption in various adsorption systems. Surprisingly, although the Langmuir isotherm described the adsorption equilibria fairly well, the related kinetic expressions generally failed to describe the adsorption kinetics. So, beginning in the early fifties, vigorous attempts were made to improve that kinetic approach based on ideas of the Absolute Rate Theory (ART). Since then, one has been able to see more progress on the theoretical side than in the related experimental studies. However, the vast majority of these papers treated hypothetical adsorption kinetics in virtual adsorption systems with well-defined surfaces. This was especially true in the case of the theoretical studies of isothermal adsorption kinetics. Certain progress was made in theoretical studies of the kinetics of thermodesorption, where the energetic heterogeneity of the real solid surfaces was demonstrated in an impressive way. Here, almost all the attempts to take energetic surface heterogeneity into account were based on a further generalization of the ART approach.