Nonideal adsorption equilibria described by pure component isotherms and virial mixture coefficients

A novel method is used to describe adsorption equilibria of nonideal mixtures. The two-dimensional virial equation of state is reorganized so that contributions of single components are separated from those of mixed components. Existing single component adsorption isotherm equations, which describe pure component data better and with fewer parameters than a truncated virial series, are substituted for the pure component terms. The remaining equation of state then contains terms corresponding to the pure component isotherms and terms with virial cross-coefficients for the mixture. The method is applied first to a mixture of Langmuirian adsorbates to demonstrate a sound thermodynamic and mathematical basis. We then consider nonideal binary and ternary mixtures of carbon dioxide, hydrogen sulfide, and propane on H-mordenite and a highly nonideal mixture of n-hexane and water on activated carbon.