Nanostructured anion exchange membranes based on poly(arylene piperidinium) with bis-cation strings for diffusion dialysis in acid recovery

Abstract

• The prepared AEMs demonstrated excellent microphase separation structures and were used for acid recovery by diffusion dialysis. • The ion transport channels can be controlled by regulating the content of ionic groups within the AEM. • These membranes displayed superior ionic conductivity, thermal stability and mechanical properties. • Under ambient conditions, AEMs exhibited significant acid fluxes U H + (10 × 10 -3 − 65 × 10 -3 m/h) and separation factor (16–25). A series of anion exchange membranes (AEMs) based on poly(arylene piperidinium) with bis -cation strings were prepared by a simple synthetic method for diffusion dialysis (DD). Through Menshutkin reaction, 1-(6-bromohexyl)-1-methylpiperidinium bromide was grafted onto the hydrophobic poly(arylene piperidine) backbone to produce side-chain-type AEMs with bis- piperidinium strings (QPBPipXAc). The self-assembled nanostructure of these AEMs was verified by SAXS and AFM images. The properties and DD performance of QPBPipXAc AEMs with different contents of bis- piperidinium ionic groups were systematically studied, including mechanical properties, ionic conductivity, thermal stability. The prepared AEMs demonstrated favorable overall properties due to the formation of self-assembled nanostructured hydrophilic-hydrophobic phase separation morphology. The hydrophilic domains provide more efficient ion transport channels for high acid flux, whereas the hydrophobic domains restrict the AEMs swelling and Fe 2+ ion transport. The prepared QPBPipXAc AEMs displayed high H + dialysis coefficients (U H + , 10 × 10 -3 − 65 × 10 -3 m/h) and separation coefficients (S, 15.67–25.38). Compared with the commercial membrane DF-120 (U H + = 9 × 10 -3 m/h, S = 18.5), the prepared AEMs have better diffusion dialysis performance, indicating that they could be the potential candidates for application for acid recovery.