Measurement and modeling of adsorption equilibria of imidazolium-based ionic liquids on activated carbon from aqueous solutions

Adsorption equilibria of imidazolium-based ionic liquids (ILs), [Omim]Cl, [Hmim]Cl and [Bmim]Cl, onto activated carbon from aqueous solutions were measured using a dynamic fixed-bed method at temperatures from 303 to 323 K. The measured amount of adsorbed IL increased with an increase in alkyl chain length of cation as [Omim]Cl > [Hmim]Cl > [Bmim]Cl, and this trend can be explained by hydrophobicity of the IL. The amount of adsorbed ILs decreased with an increase in temperature and ranged from 0.70 to 0.61 mmol/g-adsorbent at a concentration of 1.2 mol/m(3) for the case of [Omim]Cl. Fitting parameters in the Dubinin-Astakhov (DA) equation determined with correlation of the experimental data, E (interaction energy between IL and adsorbent) and q(0) (saturated adsorption amount of IL), increased with an increase in the alkyl chain length of cation, and that could be clearly related to the physicochemical properties of the IL such as hydrophobicity and molecular size. Analysis of adsorption equilibrium data with the DA equation allows design of adsorption processes for ILs. (C) 2017 Elsevier B.V. All rights reserved.