Enthalpic Determination of the Interaction of Modified Activated Carbons with Benzene and Hexane as Pure Solvents and Binary Mixtures

Abstract

Three activated carbons with different physicochemical characteristics are prepared and their N2 isotherms at 77 K and CO2 isotherms at 273 K are determined. The energetic interaction between three activated carbons with different physicochemical properties, and two hydrocarbons as pure liquids and as binary mixtures at different concentrations, was characterized by determining the enthalpy of immersion, in order to evaluate the effect of adsorbents and adsorbates, as well as that of the addition of another adsorbate to the system. For the pure solvents, the enthalpy of immersion (ΔHi) is higher for the aromatic compound (−94.98 to −128.80 J g−1) than for the aliphatic compound (−16.36 to −53.35 J g−1); for the mixtures, the values are between −36.39 and −98.37 J g−1, where the interaction increases with the solid that was subjected to thermal treatment and presented the lowest content of surface oxygenated groups, while the energetic parameter decreases with the solid that presents chemical modification with nitric acid, behavior that is evident in the pure solvents and in the mixtures. Activated carbons have a CO2 adsorption between 3.43 and 3.79 mmol g−1.