Interaction between Hydrocarbons C₆ and Modified Activated Carbons: Correlation between Adsorption Isotherms and...

Adsorption isotherms of benzene, cyclohexane, and hexane were determined from the gas phase on microporous activated carbons with Brunauer-Emmett-Teller areas between 816 and 996 m² g^-1. The Dubinin-Radushkevich equation was used to calculate the parameters of characteristic energy E _o and micropore volume W _o. Also, immersion enthalpies of activated carbons in solvents were obtained (benzene: -95.0 to -145.1 J g^-1; cyclohexane: -21.2 to -91.7 J g^-1; and hexane: -16.4 to -66.1 J g^-1), and they were used to calculate the product E _o W _o with the Stoeckli and Kraehenbuehl equations. Subsequently, values of E _o W _o from the two techniques (between 512 and 2223 J cm³ mol^-1 g^-1 for the adsorption isotherms; between 1204 and 12008 J cm³ mol^-1 g^-1 for immersion enthalpies) were correlated with some characteristics of the adsorbate such as molecular size, the molar volume, and the dielectric constant. It was found that modifying the activated carbon affected the adsorption process, being favored by temperature changes and restricted by oxidation processes. The adsorbate, which showed the highest values for E _o W _o, was benzene, because it had a smaller molecular size and a higher dielectric constant.