A facile approach to prepare crosslinked polysulfone-based anion exchange membranes with enhanced alkali resistance and dimensional stability

Abstract

Novel anion exchange membranes with enhanced ion exchange capacity, dimensional stability and alkali stability were prepared by a facile synthesis method. Internal crosslinking networks in the resulting membranes were achieved by reacting chloromethylated polysulfone with 4,4 0 -trimethylene bis(1methylpiperidine) (BMP), where BMP was used as both a quaternization reagent and crosslinker without requirement of post-functionalization. In order to evaluate the alkali resistance and dimension stability performance of the resulting membranes, the molar ratio of BMP in the resulting membranes was fixed at four different contents: 40%, 60%, 80% and 100%. The obtained membranes were accordingly denoted as CAPSF-N, in which N ¼ 40, 60, 80 and 100, respectively. Due to the dense internal network structure and spatial conformation of the six-membered rings, the resulting CAPSF-N AEMs showed enhanced dimensional structures (at 60 C, the water uptakes and swelling ratios of CAPSF-N were 8.42% to 14.84% and 2.32% to 5.93%, respectively, whereas those for the commercial AEM Neosepta AMX were 44.23% and 4.22%, respectively). In addition, after soaking in 1 M KOH solution at 60 C for 15 days, the modified membranes exhibited excellent alkaline stability. The CAPSF-100 membrane showed the highest alkali stability (retained 85% of its original ion exchange capacity and 84% of its original OH À conduction after the alkaline stability test), whereas the non-crosslinked APSF broke into pieces.Additionally, compared to the commercial Neosepta AMX membrane under the same test conditions, the desalination efficiency of CAPSF-100 was enhanced, and the energy consumption was lower.Polysulfone (M w $ 35 000 g mol À1 ) and 4,4 0 -trimethylene bis(1methylpiperidine) (99%) were bought from Sigma-Aldrich, China. PSF was dried at 80 C in vacuum before use. This journal isScheme 1 Preparation of cross-linked CAPSF and APSF membranes.This journal is Fig. 6 In ED process: (a) limited current density test: C-V curves of CAPSF-100, CAPSF-80, APSF, and commercial AEMs; (b) change of potential over stack with different AEMs; (c) conductivity change in concentrate/dilute chamber.Fig. 7 (a) NaCl removal ratio, (b) current efficiency and energy consumption after 2.5 h in ED.36382 | RSC Adv., 2019,9,[36374][36375][36376][36377][36378][36379][36380][36381][36382][36383][36384][36385] This journal is

Series-Connected Tetracation Partially Cross-Linked Anion Exchange Membranes: Insight towards Consequences of Alkyl Spacer Length

“…Results shows that the synthesized membranes are endowed with anion selectivity. The t m – value of AEM-Q5-C X membranes is higher than the AEM-Q1 membrane due to their high fixed cationic charge densities and more aggregate architecture . According to the electric double-layer theory and the Donnan equilibrium theory, counterion transport number or membrane permselectivity is highly dependent on concentration of fixed charges in the membrane matrix and aggregate structure of the membrane when external conditions are kept constant.…”

“…TWEDA 1: NaCl concentration-0.1 M; ED time-150 min; number of cell pairs-not mentioned; effective area of each membrane-20.25 cm 2 . CAPSF-100: NaCl concentration-0.5 M; ED time-150 min; number of cell pairs-1; effective area of each membrane-19.62 cm 2 . PAEK-60-im: NaCl concentration-0.5 M; ED time-160 min; number of cell pairs-1; effective area of each membrane-19.62 cm 2 .…”

“…Additionally, RO is intensive in capital and operational costs and also considered a non-energy-efficient technology. , Electrodialysis (ED), “an ion exchange membrane (IEM)-based separation technique”, is a fascinating well-established technique applied to seawater/brackish desalination with high water recovery with balanced pH. Moreover, environmental friendliness, simple design, low maintenance cost, efficient separation, low energy consumption (EC), and convenient operation make ED process a reasonable choice for desalination. , Additionally, electrodialysis has acted to be leading choice for wastewater treatment, selective ion separation, acid/alkali recovery, food processing, organic recycling, and production of high-purity fertilizers. − …”

“…Thus, it is highly desirable to design AEMs with excellent ionic conductivity and good mechanical strength, and great efforts have been made to tackle the trade-off between membrane conductivity and mechanical strength. In this regard, cross-linking strategy has been extensively considered with the aim to address the same. ,− Particularly, cross-linked AEMs reveal high mechanical strength and impart lower swelling. It is important to mention that some studies realized significant conductivity decline for cross-linked AEMs with respect to their uncross-linked counterparts. , In this context, inclusion of a cross-link with multi (di-, tri-, or tetra-) quaternary or tertiary ammonium groups is an effective strategy to achieve a balance between ionic conductivity and membrane stability. ,, Cross-linked AEMs with multications show an aptitude for desirable ionic conductivity without sacrificing mechanical stability.…”

“…Moreover, environmental friendliness, simple design, low maintenance cost, efficient separation, low energy consumption (EC), and convenient operation make ED process a reasonable choice for desalination. 12,13 Additionally, electrodialysis has acted to be leading choice for wastewater treatment, selective ion separation, acid/alkali recovery, food processing, organic recycling, and production of high-purity fertilizers. 14−18 As the crucial component of electrodialysis, the performance of ion exchange membranes has garnered considerable attention in deciding stable electrodialysis operation.…”