Adsorption equilibrium of solvent vapors on activated carbons

Adsorption amounts of solvent vapors such as n-hexane, toluene, and MEK on two commercial activated carbons (SLG-2PS and X-7000) were measured experimentally using a quartz spring balance connected with a high vacuum system. Single-species equilibrium data show typical type II isotherms, which are most frequently encountered in separation processes. Equilibrium data obtained at relative vapor pressures less than 0.3 were fitted to four well-known isotherms such as Langmuir, Freundlich, Sips, and Dubinin-Astakov (D-A) equations. All isotherm equations were found to describe experimental equilibrium data satisfactorily. Only the Langmuir equation was not proper to fit the equilibrium data of solvent vapors on SLG-2PS. In order to evaluate the adsorption energy distribution of the solvent vapors on activated carbons, a simple model based on the condensation approximation (CA) approach was applied. According to the result, it was proven that two carbons have energetically heterogeneous surfaces.