Synthesis of high-performance anion exchange membranes based on poly(aryl ether nitrile ketone)s bearing piperidinium moieties for cost-effective high-salinity water electrodialysis

The development of a facile approach to fabricate anion exchange membranes (AEMs) with efficient ionic transport and their ideal performance in application environments is of great significance. This study aimed to prepare a novel type of anion exchange membrane for electrodialysis desalination. In this work, we synthesized a series of high-performance AEMs via direct aromatic nucleophilic substitution polycondensation using poly(aryl ether nitrile ketone) backbones functionalized with piperidinium groups. By systematically adjusting the molar ratio of the piperidinium-containing monomer to 4,4′-dihydroxybenzophenone (DODPK), a range of AEMs with tunable compositions were obtained. This approach was designed to optimize the balance between ionic conductivity and mechanical stability, thereby improving the desalination performance of the membranes. The prepared AEMs were integrated into an electrodialysis (ED) system to evaluate their performance in the desalination of a concentration cell. The optimized AEM exhibited a high desalination rate (96.1 %), high current efficiency (>99 %), and low energy consumption (2.27 kwh/kg) within 180 min of operation, and sustained a > 90 % desalination efficiency over five consecutive 180-min ED cycles. Notably, the desalination rate > 90 % with an initial salt concentration of 14.0 g/L, while maintaining low energy consumption (2.55 kwh/kg). The membrane also demonstrated robust anti-fouling performance against organic foulants, retaining high desalination rates (>92.5 %) and low energy consumption with methyl sulfonate (MS) and benzene sulfonate (BS). In contrast, sodium dodecyl sulfate (SDS) led to a noticeable performance decline due to micelle-induced fouling. These findings establish a scalable, cost-effective approach for industrial-scale ED applications, particularly for high-salinity water treatment where energy efficiency is paramount. The membrane's superior performance-to-cost ratio positions it as a promising solution for addressing global water scarcity challenges through advanced desalination technologies.