| Abstract
| - To numerically classify solution adsorption isotherms, a difference or deviation measure, DSmc (therelative difference between two sums of the adsorption maximum's characteristics of selectivity isotherms× 100), is derived. The measure is applicable to completely miscible binary solutions on solids. This quantityevaluates the difference between an adsorption system and the ideal adsorption system (ideal adsorbedand bulk phases, homogeneous surface, and equal molar area solution components) at the point of maximumadsorption. For model systems, DSmcs are calculated at several levels of surface heterogeneity (Gaussiandistribution of surface energy) and for different signs of phase nonideality (regular solution phases) on ahomogeneous surface and on a simple two-site-type heterogeneous surface. All heterogeneous surfaceshave negative DSmc values, but nonideal phases have DSmcs with signs opposite to the sign of deviationfrom Raoult's law. DSmcs from both U- and S-shape isotherms are reported for 16 experimental systemsconsisting of hydrocarbon mixtures and both alcohol + hydrocarbon and alcohol + water solutions oracetone + carbon tetrachloride on several silica gels and a variety of carbons.
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