Polymeric ionic liquid gels composed of hydrophilic and hydrophobic units for high adsorption selectivity of perrhenate.

The removal of TcO from aqueous solutions has attracted more and more attention recently, and ReO has been widely used as its natural analog. In this work, polymeric ionic liquid gel adsorbents, PC-CvimBr, with high adsorption capacity and selectivity towards ReO were synthesized by radiation-induced polymerization and crosslinking. PC-CvimBr was composed of two monomers: a hydrophobic unit, 1-vinyl-3-dodecylimidazolium bromide for high selectivity, and a hydrophilic unit, 1-vinyl-3-ethylimidazolium bromide for improved kinetics. A gel fraction up to 90% could be achieved under 40 kGy with varied monomer ratios. The adsorption of PC-CvimBr gels for ReO was evaluated by batch adsorption. The PC-CvimBr gel containing 20 mol% hydrophilic unit (named PC-CvimBr-A) could significantly improve the adsorption kinetics, which had an equilibrium time of 24 h. The adsorption capacity obtained from the Langmuir model was 559 mg g (Re/gel). The selective factor against NO was 33.4 ± 1.9, which was more than 10 times higher than that of PCvimBr, and it could maintain ReO uptake as high as 100 mg g in 0.5 mol kg HNO. The ΔH and ΔS of the NO /ReO ion-exchange reaction of PC-CvimNO-A were -16.9 kJ mol and 29 J mol K, respectively, indicating physical adsorption. The adsorption mechanism of ReO onto PC-CvimBr-A gel was ion-exchange, and it could be recovered using 5.4 mol kg HNO.