Synthesis of a novel ionic liquid modified copolymer hydrogel and its rapid removal of Cr (VI) from aqueous solution

A novel ionic liquid modified copolymer hydrogel (PAMDA) was successfully synthesized by a simple water solution copolymerization using acrylamide (AM), dimethyldiallylammonium chloride (DADMAC) and ionic liquid (1-ally1-3-methylimidazolium chloride; [Amim]Cl) as copolymerization monomers. The structure and morphology of as-prepared copolymer hydrogel PAMDA were confirmed by Fourier transform infrared (FT-IR), field-emission scanning electron microscope (FE-SEM) and thermogravimetric analysis (TG). The copolymer hydrogel was applied as a novel adsorbent for the rapid removal of Cr (VI) from aqueous solution. The effects of several parameters such as the content of ionic liquid [Amim]Cl, solution pH, contact time, adsorbent dosage and initial Cr (VI) concentration on the adsorption were also investigated. The modification of [Amirn]Cl significantly enhanced Cr (VI) adsorption. The adsorption equilibrium data fitted with Langmuir isotherm model better than Freundlich isotherm model. The maximum adsorption capacity for Cr (VI) ions was 74.5 mg L-1 at 323 K based on Langmuir isotherm model. The removal rate could reach 95.9% within 10 min at 323 K and the adsorption process of Cr (VI) on PAMDA was well described by the pseudo-second-order kinetic model. The activation energy of adsorption was further investigated and found to be 1.094 kJ mol(-1), indicating the adsorption of Cr (VI) onto PAMDA was physisorption. (C) 2015 Elsevier Inc. All rights reserved.