Modification of chitosan with carboxyl-functionalized ionic liquid for anion adsorption

We report a novel chitosan derivative, chitosan-ionic liquid (CS-IL) conjugation for anion adsorption. Specifically, CS-IL conjugation was synthesized through the reaction of amino groups of chitosan with carboxylic groups of 1-carboxybutyl-3-methylimidazolium chloride. Due to the amphiphilic structure, CS-IL conjugation could self-assemble into nanoparticles in distilled water. This novel chitosan derivative revealed good anion adsorption performance, and the adsorption capacity of Cr2O72- and PF6- was 0.422 mmol/g and 0.840 mmol/g, respectively. The adsorption of Cr2O72- and PF6- could be improved at low pH, which was ascribed to the adsorption of protonated -NH2 on chitosan. Importantly, the chitosan derivative would aggregate in the water after the adsorption and could be easily separated. The properties enable CS-IL conjugation to be used as a novel anion adsorbent for wastewater treatment. (C) 2013 Elsevier B.V. All rights reserved.