Comparing various multicomponent adsorption equilibrium models

The effects of energy distribution function and load multicomponent isotherm on predictions of multicomponent adsorption equilibria were studied. The effect of the single-component isotherm equation on the ideal adsorbed solution theory (IAST) predictions was also investigated. Five predictable multicomponent adsorption equilibrium models were evaluated using binary and ternary experimental data in the literature. Two of the models apply the IAST at a patch of sites having uniform energy to yield a local adsorption isotherm, and then the local isotherm is integrated over the full energy distribution assumed to take either uniform or binomial functional form. The third model uses a local extended Langmuir equation and the integration is done over a uniform energy distribution. The last two methods assume the global IAST with the single-component isotherm described by either the Unilan or Toth equation. The prediction results depend on the choice of energy distribution function and the single-component isotherm equation. In general, the heterogeneous IAST seems to be a better approach than a global IAST.