Poly(aryl piperidine) anion exchange membrane with self-assembled siloxane crosslinked networks for efficient ion separation in alkaline waste treatment via electrodialysis

Abstract

In electrodialysis technology applications, anion-exchange membranes (AEMs) have great potential in recovering alkali from industrial wastes and are expected to recover alkali from industrial wastes. In this study, a series of AEMs based on polyarylpiperidines crosslinked with varying ratios of siloxanes were synthesized. Compared to the uncrosslinked PBP AEM and commercial Neosepta AHA, biphenylpiperidine-based AEMs (PBP-CPMTS₄₀ and PBP-CPMTS₆₀) demonstrated superior ion flux, alkali separation performance, and economic efficiency due to their optimized water uptake (WU) and ion exchange capacity (IEC). Notably, PBP-CPMTS₆₀ AEM exhibited optimal water swelling, low membrane resistance (1.98 Ω·cm²), and the highest OH⁻ conductivity (14.1 mS·cm⁻¹) at room temperature. It also demonstrated excellent alkali stability, retaining 89.71 % of its IEC and 85.07 % of its OH⁻ conductivity after 1200 h of exposure to 2 M NaOH at 80 °C. During Cl⁻ and OH⁻ ion separation via electrodialysis, the dilution compartment concentration decreased from 0.40 M to 0.12 M within 180 min, achieving a high current efficiency of 87.21 % and an energy consumption of 2.32 kW·h·kg⁻¹. This study presents a rational siloxane crosslinking strategy to mitigate AEM degradation in alkaline environments, offering significant potential for electrodialysis-based alkali concentration application.