Discussion. Comparison of models

The application of Langmuir and lAST/RAST to adsorption from liquid solutions is limited, thus we concentrate our comparative evaluation on the adsorption of gas mixtures on solids. 

In one of the few comparative studies in the literature, Chen, Ritter and Yang (1990) compared LAST to the multicomponent Langmuir equation for the adsorption of gases at elevated pressures (15-25 bar). 

Due to the high pressures, Langmuir is used with fugacities determined from the virial equation of state. It was found that the predictions with the multi-component Langmuir model were better than with lAST for two binary gas mixtures (H2-CO and CO-CH4) at various temperatures, but lAST proved to be superior when modelling the systems CO-CO2 and CH4-CO2 and for aU the ternary and quaternary systems. However, overall both models proved to adequately predict the mixed gas data and the predictions from the two models were very similar. From a mathematical and computational point of view, the explicit Langmuir model is simpler, while lAST needs an iterative solution method  

First of all, it should be mentioned that sevCTal experimental data for multicomponent adsorption show some scatter and inconsistencies which should be accounted for when evaluating the performance of the models. 

As can be seen both from Table 14.1 and the detailed results presented by Bartholdy (2012) and Bartholdy et al. (2013), none of the approaches perform very satisfactorily in all cases and acmally overall lAST and multicomponent Langmuir perform similarly, with lAST being overall a bit better. Even though the differences on percentage deviations are similar in some systems, lAST performs more robustly and acmally the multicomponent Langmuir is completely erroneous for some systems, e.g. adsorption on molecular sieves. 

---