Alkaline enrichment via electrodialysis with alkaline stable side-chain-type polysulfone-based anion exchange membranes

Abstract

• Two series of side-chain-type polysulfone-based AEMs were prepared via menshutkin reaction. • The optimized AEM exhibits the low area resistance, and good alkaline stability in ED process. • The optimized AEM show the better NaOH enrichment performance than commercial AEM. • The investigation on AEM of this type suggests its potential ED application for alkali enrichment. To meet the need of efficient resource utilization, developing stable and efficient anion exchange membranes (AEMs) for alkaline enrichment application is of significance. In this work, we designed four polysulfone-based side-chain-type AEMs with several cations and different length of spacers per chain, to explore the structure-property relationship and obtained AEMs with high performance for alkaline enrichment via electrodialysis (ED). Our investigation demonstrates that, the optimized AEM (CM-TQ6Q6Q-1, 1.38 mmol·g −1 ) exhibits low swelling ratio of 8.9%, low area resistance of 2.48 Ω·cm 2 , acceptable OH – conductivity of 13.7 mS·cm −1 . In addition, this AEM also shows relatively good alkaline stability with the IEC retention of 96.7% relative to the original IEC, suggesting the potential application of alkaline enrichment via electrodialysis (ED). After 5-times NaOH enrichment tests in ED, CM-TQ6Q6Q-1 AEM shows an efficient ED performance with alkaline concentration times of ~1.8 (current efficiency: ~90.0%; energy consumption: 8.47 kWh·kg −1 ), and maintains 96.4% of its original IEC, which are even comparable to those from commercial AEM (Neosepta AHA). The results demonstrate that the as-prepared AEM shows the promising potential ED application for alkali enrichment from the alkaline waste water.