Facile synthesis of a novel polymeric ionic liquid gel and its excellent performance for hexavalent chromium removal.

A novel polymeric ionic liquid gel (PIL gel) was simply synthesized by γ-radiation-induced polymerization of ionic liquid monomer 1-allyl-3-vinylimidazolium chloride and crosslinking at ambient temperature without any additives. By changing the radiation dose, the properties of the resulting gel including the gel fraction, crosslinking density and equilibrium degree of swelling were optimized. The resulting PIL gel exhibited a superior adsorption ability toward Cr(vi) in aqueous solutions with a broad pH range (1-7) through anion exchange. It was found that the adsorption kinetics followed the pseudo-second-order model. The adsorption of Cr(vi) by the PIL gel obeyed the Langmuir isotherm equation with a theoretical maximum adsorption capacity of 283 mg g(-1), twice the highest value for ionic liquid-based adsorbents that have been reported. In addition, the PIL gel could be recovered using a NaCl solution or a NaOH solution without much decreasing the adsorption capacity. This work paves the way for the scale-up production of PIL gels using the radiation technique for potential application in heavy metal removal.