Selective liquid sorption and wetting of pillared montmorillonites

Pillared montmorillonite was used as an adsorbent for binary mixtures of hydrocarbons and alcohols (benzene/n-heptane; ethanol/cyclohexane; ethanol/toluene; propanol/ toluene). The adsorbent was prepared from the Na-form of a bentonite from Milos by reaction with polyhydroxoaluminium solutions. The adsorption behaviour of the pillared montmorillonite was characterized by the adsorption excess isotherms and the heats of immersion. Sorption capacities and wetting properties differed significantly from those of the Na-montmorillonite. Benzene was adsorbed preferentially from mixtures with n-heptane. Ethanol and propanol were also preferentially adsorbed from mixtures with cyclohexane and toluene but the curves showed azeotropic points at molar fractions of alcohols of 0.7-0.9. The calorimetric data revealed the partially hydrophobic character of the pillared montmorillonite. The heat of wetting of benzene or toluene on the pillared samples was distinctly higher than that of ethanol whereas ethanol gave the highest wetting enthalpies on Na-montmorillonite.

Polar Interactions at Carbon Surfaces Described by the Dubinin Equations and by an XPS-Based Model

The interaction of polar molecules at carbon surfaces is briefly reviewed within the framework of the Dubinin theory. A linear relationship is observed between the term a0 of the Dubinin-Serpinski equation and heats of immersion calculated from equilibrium isotherms for water vapour adsorption by a series of microporous carbons with increasing polarities. A quantitative relationship is proposed between surface polarity, characterised by the spectroscopically measured surface oxygen concentration [O]T and calorimetric heat of immersion in water for a series of non-porous carbon blacks.