Adsorption with activated carbons (ACs) has been recently reported as an affordable environmental application to remove and recover ionic liquids (ILs) from water streams. In this work, an extensive analysis of the separation of imidazolium-based ILs from aqueous solution, based on adsorption equilibrium experiments at 308 K, has been performed. The study includes five commercial and four modified ACs, with a wide variety of structural and chemical properties, a carbon black and also two inorganic adsorbents. The materials tested were characterized by several techniques in order to establish the role of the porous structure and chemical surface on their adsorption capacities. We found that the microporous ACs with low concentration of polar groups in their surface are the best candidates for adsorption of hydrophobic ILs, reaching uptakes of up to 1 g of IL per gram of adsorbent. The influence of both cation and anion on the adsorption process was analyzed from the adsorption isotherms of 27 different ILs. The dependence of the adsorption uptake with the chemical structure of the Its was explained by mean of the quantum-chemical COSMO-RS model, which provides information of the intermolecular interactions between the IL adsorbate and the AC adsorbent. As a result, some insight into the adsorbent modifications needed for improving of the adsorption of specific ILs were achieved and successfully applied to the adsorption of hydrophilic ILs by oxidized ACs. In addition, a procedure for regenerating the exhausted adsorbent and recovering the IL by acetone extraction was validated upon successive adsorption-desorption cycles with two commercial ACs. Finally, the acetone was separated by atmospheric distillation, being the IL recovered without structural modification. (C) 2012 Elsevier B.V. All rights reserved.