Modelling of Single-Gas Adsorption Isotherms

The present paper reviews and analyses different models that could be used to describe the adsorption equilibrium of pure gases. The adsorption equilibrium of hydrogen, nitrogen and methane is characterised and modelled. Several thermodynamic conceptions have been selected and tested for the calculation of physico-chemical parameters. The model of Dubinin has been selected to estimate the pseudo-saturation vapour pressure. The best results for the molar volume of the adsorbate have been obtained by using Do’s equation. Eight models, namely Langmuir, Freundlich, Sips, Toth, Jovanovic, UNILAN, OBMR and Potential Theory, describing the adsorption equilibrium of pure gases, have been tested and compared with experimental data obtained from the literature at three different temperatures (283 K, 298 K and 313 K). In order to determine the best fit, the correlation coefficient and the standard errors for each parameter have been used to evaluate the data. All the models used in this study, except for Freundlich’s equation in the case of nitrogen or methane adsorption, are in good agreement between experiment and modelling for the adsorption isotherms.