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A series of gentamicin‐modified anion exchange membranes (AEMs) immobilized by mussel‐inspired dopamine coating is prepared in this work. The purpose is to improve antibacterial activity and fouling resistance of the commercial AEMs (AEM Type I, Fujifilm Co.). As a result of the applied modification, the hydrophilicity of membrane surface improved significantly. Thus, the as‐prepared modified AEMs exhibit the good antifouling property, in electrodialysis (ED) experiments by using the sodium dodecylbenzenesulfonate and albumin from bovine serum as model foulants. Furthermore, taking into account the results of the antibacterial test, the resulting modified AEMs exhibit improved antibacterial property for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). After a brief contact with bacteria, the antibacterial rates of modified AEMs coating with gentamicin‐based polymer are 80.11% for E. coli and 90.66% for S. aureus, which are much higher than pristine AEM (6.28% and 9.07%), respectively. In addition, the modified membrane has good operational stability during ED process and recovery ability after contamination, and also maintains satisfactory electrochemical properties. This investigation highlights a design of simple strategy for the preparation of antimicrobial and antifouling AEM, which can be used for ED. [ABSTRACT FROM AUTHOR]

• Two series of side-chain-type polysulfone-based AEMs were prepared via menshutkin reaction. • The optimized AEM exhibits the low area resistance, and good alkaline stability in ED process. • The optimized AEM show the better NaOH enrichment performance than commercial AEM. • The investigation on AEM of this type suggests its potential ED application for alkali enrichment. To meet the need of efficient resource utilization, developing stable and efficient anion exchange membranes (AEMs) for alkaline enrichment application is of significance. In this work, we designed four polysulfone-based side-chain-type AEMs with several cations and different length of spacers per chain, to explore the structure-property relationship and obtained AEMs with high performance for alkaline enrichment via electrodialysis (ED). Our investigation demonstrates that, the optimized AEM (CM-TQ6Q6Q-1, 1.38 mmol·g−1) exhibits low swelling ratio of 8.9%, low area resistance of 2.48 Ω·cm2, acceptable OH– conductivity of 13.7 mS·cm−1. In addition, this AEM also shows relatively good alkaline stability with the IEC retention of 96.7% relative to the original IEC, suggesting the potential application of alkaline enrichment via electrodialysis (ED). After 5-times NaOH enrichment tests in ED, CM-TQ6Q6Q-1 AEM shows an efficient ED performance with alkaline concentration times of ~1.8 (current efficiency: ~90.0%; energy consumption: 8.47 kWh·kg−1), and maintains 96.4% of its original IEC, which are even comparable to those from commercial AEM (Neosepta AHA). The results demonstrate that the as-prepared AEM shows the promising potential ED application for alkali enrichment from the alkaline waste water. [ABSTRACT FROM AUTHOR]

• A new type of monovalent anion-selective amphoteric membrane was fabricated. • The blend AIEMs show the good miscibility between the two polymer components. • The swelling ratio of the optimized blending AIEM is as low as 10.9% at 25 °C. • The Cl–/SO 4 2– selectivity of the most optimized AIEM in ED is 21.8 at 2.5 mA cm−2. It is of significant importance to develop highly monovalent anion-selective membranes (MASM) having stable structure for a wide range of applications. To realize the efficient monovalent/bivalent anion separation, in this work, three amphoteric ion-exchange membranes (AIEMs) through blending were fabricated for use in electrodialysis (ED). The three membranes were prepared by blending amino-containing poly(arylene ether sulfone) (PAES-NH 2) with 10, 15, and 20 wt% of sulfonated polysulfone (SPSf), respectively, followed by grafting imidazolium salt-terminated side alkyl chains on PAES backbone. Our investigations demonstrate that each transparent AIEM shows good miscibility between the two components, which has been verified by a homogeneous structure via SEM observation and by an even distribution of N element via EDX mapping. In the ED process at a current density of 2.5 mA cm−2, AIEM with 15 wt% of SPSf shows the superior perm-selectivity (Cl–/SO 4 2–) of 21.8, relative to many reported MASMs having modified surfaces (<6.0), which is synergistically contributed by (i) electrostatic repulsion difference from the negatively-charged sulfonate groups against monovalent Cl– ions and bivalent SO 4 2– ions and (ii) hydrated energy difference of hydrated Cl–/SO 4 2– ions. This work thus presents a strategy to guide the architectural design of advanced MASMs. [ABSTRACT FROM AUTHOR]

Ion-conductive polymers having highly ordered and well-defined phase-separated structures are potential materials for use as monovalent anion-selective membranes (MASMs). In this work, to investigate the effect of hydrophobic spacers, four side-chain-type imidazolium salt-tethered poly(arylene ether sulfone) anion-exchange membranes (AEMs) with different alkyl spacer lengths (–CH 2 – number: 3, 6, 9, and 12) were fabricated for use in electrodialysis (ED). Our investigations using atomic force microscopy, small angle X-ray scattering and X-ray diffraction demonstrate that the extended alkyl spacers change the nano-phase-separated structures, with an increased ion cluster space ranging from 3.29 nm to 7.76 nm, resulting from increased immiscibility between the additional hydrophobic alkyl spacers and (i) the hydrophobic aromatic backbones and (ii) the hydrophilic ion-conductive groups. In addition, with the extension of the alkyl spacer, chloride (Cl−) ion conductivity at 25 °C decreases from 16.4 mS cm−1 to 11.4 mS cm−1 and water uptake is reduced to 12.8% (20 °C). It is found that the as-prepared AEM with a hexyl alkyl spacer shows the superior perm-selectivity (Cl−/SO 4 2−) of 7.10 (separation efficiency: 70.3%), as compared with three others (3.48, 6.81, and 4.26). This work thus presents an efficient strategy to guide the architectural design of novel MASMs. Image 1 • Four side-chain-type AEMs with different alkyl spacer lengths were fabricated. • Pronounced phase-separated morphologies verified by AFM and SAXS are obtained. • Extended alkyl spacer decreases the ion conductivity and lowers the water uptake. • Perm-selectivity of PAES-6C-IM AEM attains a maximum of 7.10 at 5.0 mA cm−2. [ABSTRACT FROM AUTHOR]

Ion selective separations play crucial roles in the fields of energy storage, pollution management, and industrial processes, etc. Ion exchange membranes (IEMs) offer promise for these separations but often lacking the required selectivity. In this work, we have developed a kind of IEM based on metal-organic frameworks (MOFs) to enhance membrane separation performance for electrodialysis (ED). Specifically, for poly(arylene ether sulfone)-based anion exchange membranes (AEMs), we introduced the modified MOFs through doping to create a transport pathway for target ions, leveraging their precise size-based separation effects. This approach significantly improves ion selectivity. Remarkably, at a current density of 2.5 mA·cm−2, the monovalent ion selectivity (Cl−/SO 4 2−) of PAES-UIO-66-Pyr could reach 54.26, while the monovalent ion selectivity (NO 3 −/SO 4 2−) could reach 55.90. These enhancements may stem from the incorporation of MOF particles, which facilitate the formation of fixed-size channel structures within membrane matrix. These fixed-size channels, coupled with the hydrophobic differences between the original poly(arylene ether sulfone) polymer, created a composite channel system that significantly improved the separation performance for monovalent ions, including Cl−/SO 4 2− and NO 3 −/SO 4 2−. [Display omitted] • A kind of MOF-modified cross-linked poly(arylene ether sulfone) AEM has been prepared. • The introduced cross-linked structure increases the density of AIEM. • The perm-selectivities of Cl−/SO 4 2− and NO 3 −/SO 4 2− reached 54.26 and 55.90, respectively. • The incorporation of MOFs could facilitate the formation of fixed-size channel structures. [ABSTRACT FROM AUTHOR]

[Display omitted] Ion exchange membranes (IEMs) with high monovalent-ion selectivity show promising application in ion resource recovery. In this work, we report a kind of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)-based on amphoteric ion exchange membranes (AIEMs) having cross-linked structure. Therein, four imidazolium-terminated aliphatic chains (2IM-nC, n = 3, 6, 9, and 12) with varied number of −CH 2 − were used as crosslinker for cross-linking membrane matrix. Small-angle X-ray scattering tests indicate that the ion cluster sizes of the four AIEMs are evaluated with values of 0.378, 0.384, 0.388 to 0.408 nm, which possibly render the enhanced mono-valent anion selectivity of as-prepared AIEMs. Tested in the electrodialysis (ED) filled with a mixture solution of 0.05 M NaCl + 0.05 M Na 2 SO 4 , at current densities of 2.5 mA·cm−2 and 5.0 mA·cm−2, the P SO 4 2 - Cl - values of cross-linked AIEM having longer alkyl chains are 20.41 and 22.51, respectively, which are higher than AIEM with shorter cross-linker alkyl chain under the same conditions (3.5). Due to the hydrophilic surface and hydrophilic/negatively charged zwitterionic surface of AIEM, act as useful barriers via physical blocking and electrostatic repulsion, respectively, the anti-fouling performance of IEMs is improved simultaneously. In view of the superior performance, it is believed that the structure–property relationship of AIEM developed here can serve as a guideline for advanced IEMs. [ABSTRACT FROM AUTHOR]

Amphoteric polyelectrolytes have been used as the materials for the high-performance ion-exchange membranes applied in redox flow battery and electrodialysis (ED) etc. In this work, four amphoteric ion-exchange membranes (AIEMs) based on sodium 1-propanesulfonate-3-methylimidazole (MIm-PS) and 1-butylimidazole (BIm) decorated poly(2,6-dimethyl-1,4-phenylene oxide) have been prepared for mono-/bi-valent anion separation by using the electrodialyzer. The optimized AIEM has a low surface area resistance of 5.79 Ω⋅cm2. During the ED testing, at 2.5 mA⋅cm−2, the perm-selectivity (P S O 4 2 − C l − ) tested in a binary mixture of 0.05 M NaCl and 0.05 M Na 2 SO 4 , achieves the value of 16.12 at 30th min, which is significantly higher than that of anion-exchange membrane (1.68) as the reference. This superior separation performance has been further verified by the perm-selectivity of 55.5, tested in a single solution of 0.05 M NaCl or 0.05 M Na 2 SO 4. The high perm-selectivity results from the electrostatic repulsion difference of mono-/bi-valent ions against the negatively-charged –SO 3 – groups, accompanying with pore-size sieving effect resulting from the smaller ion cluster space of 0.261 nm. It is interesting to find that AIEMs show the increased ion flux values of Cl−/SO 4 2−, though the presence of the negatively-charged –SO 3 − groups, which is possibly related to the convex particle-like surface that increasing the effective surface area for ions passing. This work may provide a reference to guide the architectural design of advanced monovalent anion-selective IEMs. [Display omitted] • A series of amphoteric IEMs based on decorated PPO has been prepared. • The optimized amphoteric IEMs has the low surface area resistance of 5.79 Ω cm2. • Introduction of amphoteric structures increases the surface roughness of IEMs. • The perm-selectivity (Cl−/SO 4 2−) of as-prepared AIEM outperforms the commercial AEM. • The perm-selectivity of the AIEM tested in binary mixture solution achieves 16.12. [ABSTRACT FROM AUTHOR]

• A strategy for the preparation of crosslinked AEMs with 3D network structure was reported. • The ultraviolet cross-linking method makes the reaction simpler and more controllable. • The as-prepared AEMs with 3D structure show the enhanced mechanical and thermal stabilities. • The optimized AEM shows NaCl removal rate of 75.0% and current efficiency of 92.7%. A series of trimethylamine quaternized crosslinked anion-exchange membranes (AEMs) based on polysulfone has been prepared by using an ultraviolet cross-linking method, which avoids the uneven reaction and undesirable aggregation of the basic functional groups (trimethylamine) by heterogeneous quaternization. The ultraviolet cross-linking method makes the reaction simpler and more controllable, compared with traditional method. By crosslinking, at 40 °C, the water uptakes of as-prepared AEMs decrease from 62.6% to 36.9%, while the linear expansion ratios reducing from 26.3% to 13.4% without significantly sacrificing the surface area resistance (increased 2.32 Ω cm2 to 2.98 Ω cm2). In addition, the introduced crosslinking yields the more robust AEMs with increased tensile strength from 4.32 to 11.89 MPa and increased elongation at break in a range of 13.8–30.9%. The significantly reduced water absorption, enhanced (dimensional and mechanical) stabilities suggest crosslinkers with more acrylate groups could promote high crosslinking within AEMs. For electrodialysis (ED) application, the optimized AEM exhibits an enhanced NaCl removal ratio of 75.0%, current efficiency of 92.7% and energy consumption of 6.06 kWh Kg−1, compared with AEM without cross-linking (61.4%; 75.9%; 6.20 kWh Kg−1). This investigation demonstrates that the as-proposed strategy has certain guiding significance for the development of advanced AEMs. [ABSTRACT FROM AUTHOR]

• Three composite AEMs from QPSU and PVA blends have been fabricated for ED. • The swelling ratio of optimized M 2 -0.05 AEM was significantly reduced to 4.7% at 20 °C. • The chloride ion conductivity of M 2 -0.05 reaches 23.5 mS cm−1 at 20 °C. • M 2 -0.05 has the superior NaCl removal ratio of 74.6% within 120 min (vs. 61.06% of AEM-Type II). 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 (M 0), potassium thioacetate (PT) modified QPSU blending with PVA (M 1) and QPSU blending with 4-formylbenzoic acid (FBA) modified PVA (M 2 -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 M 1 and M 2 -0.05 were significantly reduced to 10.9% and 4.7% at 20 °C, much lower than M 0 (16.9%). This can be due to the formed hydrogen-bonding network via OH from PVA and >C O from PT structure on PSU within M 1 or the ionic crosslinking interactions between COO– from FBA and >N+– on QPSU within M 2. Though the free volume inside AEM matrix is reduced, the chloride ion conductivities of M 1 and M 2 -0.05 reach 20.5 mS cm−1 and 23.5 mS cm−1 at 20 °C. In ED application, the optimized M 2 -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 M 2 -0.05 are indicative of its potential ED application. [ABSTRACT FROM AUTHOR]