Membrane Technology & Research (United States)

We investigated the Cl–/SO42−permselectivity and antibacterial properties of polyvinylidene fluoride-g-poly[2-(dimethylamino) ethyl methacrylate] (PVDF-g-PDMAEMA)-based anion-exchange membranes (AEMs) prepared by a nonsolvent induced phase inversion process. In this work, we assessed the contribution of the chain length of the quaternizing agent using two distinct alkyl spacers: methyl (C1) and decyl (C10) groups, followed by dual cross-linking. The dual-step cross-linking process included in situ cross-linking achieved individually with xylene dichloride (XDC) or poly(methyl methacrylate)-co-poly(chloromethylstyrene) (PMMA-co-PCMSt), followed by surface cross-linking using N,N,N′,N′-tetramethyl-1,6-hexanediamine (TMHDA). Thus, the impact of a small molecular cross-linker (XDC) and a polymeric cross-linker (PMMA-co-PCMSt) on the selectivity of the membranes was studied. Among the four dual-cross-linking network-architected robust membranes, the representative PDC membrane, featuring a C10 side chain and dual cross-linking with PMMA-co-PCMSt and TMHDA, achieved a remarkable Cl–/SO42− permselectivity value of 28.25 using a 0.05 M NaCl + 0.05 M Na2SO4 mixture. Additionally, this membrane demonstrated outstanding antibacterial efficacy against E. coli and B. subtilis, with 99.9% bacterial inhibition (BI) in each case. Dynamic biofouling studies showed that the PDC membrane retained better performance, with only a 55% decline in desalination efficiency after five continuous cycles, compared to 67.9% for the commercial Ionsep AEM, highlighting its superior antibiofouling properties.

Nitrogen, a prevalent water pollutant, is a major cause of eutrophication and the formation of black, odorous water bodies, posing significant threats to both ecological security and human health. Effectively controlling nitrogen pollution in wastewater is therefore essential for preserving aquatic ecosystems. The membrane bioreactor (MBR), which integrates the advantages of biological and membrane technologies, has attracted considerable attention for its application potential in wastewater nitrogen removal. This article elucidates the mechanisms and characteristics of nitrogen removal in MBR systems based on the latest research advancements. It provides an in-depth analysis of the key environmental factors affecting nitrogen removal efficiency and comprehensively summarizes enhanced processes centered on MBR technology. Furthermore, the article addresses corresponding strategies for mitigating MBR membrane fouling and offers suggestions and prospects for future research directions.

Abstract Manganese‐based oxides are promising cathode materials for aqueous zinc ion batteries (AZIBs) due to their high energy density and low cost. However, the cycling stability is severely limited by the sluggish reaction kinetics as well as the manganese dissolution. In this work, two pyridinium ionic porous organic polymers (iPOPs) composite ɛ‐MnO 2 cathode materials, CN‐POP@MnO 2 and PN‐POP@MnO 2 , are prepared by an in situ composite method. The stable skeleton of iPOPs effectively prevents the structural collapse of the cathode. Its ionic sites and rigid network framework work together to disrupt the coordination environment of hydrated zinc ions, accelerating reaction kinetics and reducing cathode polarization. Therefore, the resultant batteries based on CN‐POP@MnO 2 and PN‐POP@MnO 2 cathodes exhibit excellent electrochemical performance. Especially for PN‐POP‐based batteries, the specific capacity is maintained at ≈96 mAh g −1 after 1500 cycles at 1 C, and the capacity attenuation rate is 0.017% per cycle.

Nanofiltration (NF) membrane technology has emerged as a promising part of desalination techniques due to its high rejection to divalent ions with a low requirement of energy. Polyamide (PA) membranes, as widely used NF membranes, still suffer from critical limitations. One limitation is the dense polymeric network, which imposes a significant mass transfer resistance. Another limitation is its insufficient hydrophilicity, which causes foulant adsorption through hydrophobic interactions, leading to low water permeance and fouling. Herein, the hydrophilic graphene oxide (hGO) nanosheets functionalized with Fe(III)–phytate complexes were integrated into PA membranes during interfacial polymerization, resulting in the formation of a composite membrane with enhanced hydrophilicity and a relatively loose structure, thereby improving both separation efficiency and antifouling performance. Moreover, the enlarged interlayer channels between hGO nanosheets provide additional fast-transport pathways, which contributes conjointly to the improvement of water permeance. The optimized PA-hGO membrane displayed about 1.5-fold higher water permeance compared to the pristine PA membrane while successfully holding a Na2SO4 rejection of over 98%.