Modelling of Single-Gas Adsorption Isotherms

Abstract

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.

Adsorption isotherm model of Hg2+ with biochar from young coconut waste

“…It indicates the relative distribution of energy and the heterogeneity of adsorbate sites. Adsorption is favorable when 1/n is greater than zero (0 < 1/n < 1); unfavorable when 1/n is more than one; and irreversible when 1/n = 1 [29]. The value of 1/n in Hg adsorption was determined to be 1.04.…”

“…Hg adsorption was investigated using isotherm models to estimate the optimal adsorption process based on high R 2 values [29]. The adsorption of Hg with B-YCW, the R 2 of the linear Henry, Freundlich, and Langmuir model isotherms can be used.…”

“…The Langmuir model also explains the separation factor (R L ) which can be related to the K L constant as a dimensionless constant expressed as a variation of the area and porosity of the relevant adsorbent, indicating that higher surface area and pore volume can increase the adsorption capacity. The splitting factor determines whether adsorption is linear (R L = 1), irreversible (R L = 0), unfavorable (R L > 1), or favorable (0 < R L < 1) [29]. The RL value for Hg adsorption with B-YCW is 0.0054.…”

Equilibrium study for mercury removal using sub-bituminous coal and its application on ex-gold mining soil contaminated with mercury

“…Based on the high R 2 values, isotherm models were used in Hg adsorption to evaluate the best adsorption procedure (Chilev et al, 2022). Adsorption of Hg with SC showed that the R 2 values of the linear isotherm models, Langmuir > Freundlich > Henry (R 2 = 1>0.9999>0.9998), can be used.…”

Effect of Modified Surface of Cotton Straw Nanocellulose and Their Application for Removal of Lead from Aqueous Solution

“…The Toth isotherm becomes the standard Langmuir equation when n = 1. As with the Sips equation, the parameter n is therefore stated to describe the heterogeneity of the system (Chilev et al, 2022). According to the Elovich model, the chemical processes that cause adsorption form the basis of the adsorption mechanism (Dada et al, 2021).…”