Polymer inclusion membrane (PIM) containing ionic liquid as a proton blocker to improve waste acid recovery efficiency in electrodialysis process

Industrial activities generate large amounts of low-concentration waste acids. This is not only a waste of resources, but also a hazard to the environment. Waste acid recovery and concentration by electrodialysis (ED) has received more and more attention. However, proton leakage through anion exchange membrane reduces the ED efficiency for acid concentration, thus it limits the application of ED. The present work evaluates for the first time the potential use of polymer inclusion membranes (PIMs) based on affordable ionic liquids as proton blocker in ED. Results showed that the fabricated PIMs exhibited sufficient ion exchange capacity (0.84–1.23 mmoL/g) as an anion exchange membrane. Furthermore, the PIMs performed a similar proton blocking performance (H+ transport number 0.14) and lower membrane area resistance (PIM: 13 Ω cm2, ACM: 38 Ω cm2), when compared with a commercial proton blocking membrane (ACM from ASTOM). Therefore, this membrane fabrication method successfully solved the trade-off effect between proton blocking efficiency and membrane electrical resistance. The acid concentration by using PIM in ED was 1.37 times higher than that of using ACM. What's more, PIMs showed good stability in electrodialysis experiments. Therefore, the ionic liquid based PIMs are proved as promising acid blocker for acid recovery applications.