A facile approach to fabricate composite anion exchange membranes with enhanced ionic conductivity and dimensional stability for electrodialysis

Abstract

It is significant to develop anion exchange membranes (AEMs) with efficient ionic transport and desirable stabilities (mechanical and dimensional) for various applications, including electrodialysis (ED). In this paper, three types of composite AEMs based on quaternized polysulfone (QPSU) and polyvinyl alcohol (PVA) blends: QPSU/PVA composite AEM (M0), potassium thioacetate (PT) modified QPSU blending with PVA (M1) and QPSU blending with 4-formylbenzoic acid (FBA) modified PVA (M2-X, X = mass ratio of the FBA with the values of 0.05 and 0.20), have been investigated. Our investigation demonstrates that the swelling ratios of M1 and M2-0.05 were significantly reduced to 10.9% and 4.7% at 20 °C, much lower than M0 (16.9%). This can be due to the formed hydrogen-bonding network viaOH from PVA and >CO from PT structure on PSU within M1 or the ionic crosslinking interactions between COO– from FBA and >N+– on QPSU within M2. Though the free volume inside AEM matrix is reduced, the chloride ion conductivities of M1 and M2-0.05 reach 20.5 mS cm−1 and 23.5 mS cm−1 at 20 °C. In ED application, the optimized M2-0.05 has the highest NaCl removal ratio of 74.6% within 120 min (vs. 61.06% of the commercial AEM-Type II), and exhibits better desalination performance with high current efficiency (98.0% vs.92.8%) and lower energy consumption (2.2 kWh kg−1 NaCl vs. 2.4 kWh kg−1). The simple preparation process and good ED performance of M2-0.05 are indicative of its potential ED application.