Ionic liquid-based pore-filling anion-exchange membranes enable fast large-sized metallic anion migration in electrodialysis

The development of low-resistance ion-exchange membranes enabling fast transport of large-sized metallic anions is extremely desirable for the treatment of metal containing effluents using electrodialysis (ED). Herein, mechanically stable ionic liquid-based pore-filling anion-exchange membranes (PFAEMs) with excellent transport performance for large-sized metallic anions were fabricated by impregnating porous polytetrafluoroethylene with ionic liquid (IL) tricapryl(methyl) ammonium chloride, poly(ethylene glycol) dimethacrylate and poly(vinylidene fluoride-co-hexafluoropropylene). The superior compatibility between the ILs and polymeric chains ensured the stable existence of quaternary ammonium groups, thus enabling fast metallic anion migration along the continuous pathway in the membrane matrix at a low current density. The prepared PFAEM exhibited a dramatically greater flux of HCrO 4 − (90.7 μmol m −2  s −1 ), which was 9.5 and 4.4 times higher than the flagship commercial Neosepta@ASE and Neosepta@AMX membranes, respectively. The area resistance of PFAEM (3.4 Ω cm 2 ) was found to be 3.4 and 2.0 times lower than those of the Neosepta@ASE and Neosepta@AMX membranes, respectively. Besides, the preeminent transport performance of PFAEM to other metal coordination anions revealed the universality of the prepared membrane. Moreover, the extremely high limiting current density and satisfactory long-term stability of PFAEM manifested bright prospects for realizing efficient metal separation in industrial-scale applications.