The improved NRTL adsorption isotherm for the case of energetically heterogeneous solid surfaces

In this work the modification of isotherm equation originally derived by Haghtalab and Farzad (Fluid Phase Equilib. 292, 36, 2010) is presented. By applying the Vacancy Solution Theory (VST) and NRTL activity coefficient model a new adsorption isotherm is developed. Besides the non-ideality resulting from interaction effects the energetic heterogeneity of adsorption system is taken into account. The rigorous treatment of the adjustment of new adsorption isotherm to minimize correlations between the best-fit parameters is proposed. Thus, some of the quantities in the theoretical isotherm are common for all isotherms and characterize the adsorption system. The obtained agreement between the theory and experiment is very satisfactory.