Polyacrylonitrile/poly(acrylic acid) layer-by-layer superimposed composite nanofiber membrane with low iron ion leaching-out and stable methylene blue-removing performance

Advanced nanofibers for water treatment: Unveiling the potential of electrospun polyacrylonitrile membranes

The challenges pertaining to the potable water scarcity and pollution motivates us to envision innovative strategies. Industrial wastewater containing hazardous heavy metals, synthetic dyes, and oil exacerbates the pursuit of clean drinking water. Among the array of available technologies, electrospun nanofiber membranes have garnered attention due to their efficiency, high surface-to-volume ratio, cost-effectiveness, scalability, and multifunctionality. These membranes possess distinct physical and chemical attributes that position them as ideal solutions to water purification challenges. Their versatility enables effective contaminant removal through filtration, adsorption, and chemical interactions. Polyacrylonitrile (PAN) emerges as a frontrunner among electrospun polymers due to its affordability, remarkable physical and chemical characteristics, and the ease of production. Research efforts have been dedicated to the study of electrospun PAN membranes, exploring modifications in terms of the functionalization of PAN molecular chain, incorporation of appropriate nanoparticles, and composition with other functional polymers. Parameters such as functional groups, hydrophilicity, mechanical properties, porosity, pore structure, reusability, sustainability, zeta potential, and operational conditions significantly influence the performance of electrospun PAN membranes in treating the contaminated water. Despite progress, challenges surrounding fouling, toxicity, scalability, selectivity, and production costs ought to be addressed strategically to enhance their practicality and real-world viability. This review comprehensively scrutinizes the current landscape of available electrospun PAN membranes in water treatment encompassing diverse range of synthesized entities and experimental outcomes. Additionally, the review delves into various approaches undertaken to optimize the performance of electrospun PAN membranes while proposing potential strategies to overcome the existing hindrances. By carefully analyzing the parameters that impact the performance of these membranes, this overview offers invaluable guidelines for researchers and engineers, thus empowering them to design tailored electrospun nanofiber membranes for specific water purification applications. As the innovative research continues and strategic efforts address the current challenges, these membranes can play a pivotal role in enhancing water quality, mitigating water scarcity, and contributing to environmental sustainability. The widespread application of electrospun nanofiber membranes in water treatment has the potential to create a lasting positive impact on global water resources and the environment. A dedicated effort towards their implementation will undoubtedly mark a crucial step towards a more sustainable and water-secure future.

Enhanced wound healing with a bilayered multifunctional quaternized chitosan-dextran-curcumin construct

This study introduces a novel bilayer wound dressing that integrates a quaternized chitosan-polyacrylic acid (QCs-PAA) sponge as the top layer with electrospun nanofibers containing curcumin as the bottom layer. For the first time, QCs and PAA were combined in an 80:20 ratio through freeze-drying to form a porous sponge layer with ideal structural properties, including 83 ± 6 % porosity and pore diameters of 290 ± 12.5 μm. For the bottom layer, five groups of nanofibers containing PAA, dextran, and curcumin were electrospun onto the porous sponge. All wound dressings were non-toxic and exhibited exceptional antibacterial activity against S. aureus and E. coli. All groups, particularly the QP/PD0.25Cur bilayer dressing, showed significant HaCaT cell adhesion. Angiogenesis assays confirmed a remarkable increase in blood vessel number and thickness in samples containing 0.25 w/w% curcumin, with vascular density increasing from 0.32 in the single-layer sponge to 0.54 in the QP/PD0.25Cur sample, representing a 68 % enhancement. In vivo studies demonstrated that within 14 days, wound healing was accelerated with the QP/PD0.25Cur bilayer dressing, achieving 96 % closure compared to other groups. The findings revealed that all fabricated bilayer sponge-nanofiber wound dressings, particularly the 0.25 w/w% curcumin sample, can be a suitable candidate for wound management.

Construction of a Fluorescence/Phase-Change Dual-Mode Sensor Based on Carbon Dots/Poly(acrylic acid) for Highly Selective and Sensitive Detection of Ferric Ions

Fe3+ is one of the crucial metal ions in biological systems, and its excess or deficiency in the body can trigger various diseases, posing a serious threat to human health. Moreover, improper handling or disposal of Fe3+ can lead to water pollution, thereby harming the environment. Therefore, the development of highly selective and sensitive Fe3+ detection probes is particularly urgent. In this paper, a dual-mode sensor based on sol-gel and fluorescence signal responses was developed for the visual detection of Fe3+. The visual sensing method based on the simultaneous response of Fe3+-triggered dual signals can minimize the interference from false-positive signals and enhance detection accuracy. The dual-mode sensor, denoted as PAA@CDs, was constructed by incorporating high-brightness (high fluorescence emission intensity) green-yellow carbon dots (CDs) into poly(acrylic acid) (PAA), which possesses a large number of carboxyl functional groups. Based on the interaction of Fe3+ with the surface functional groups of CDs, nonfluorescent complexes are formed, leading to nonradiative electron transfer, which induces fluorescence quenching and produces a fluorescence signal visible to the naked eye. Additionally, the interaction of Fe3+ with the carboxyl groups of PAA triggers the cross-linking of PAA, causing a sol-gel phase change signal. Consequently, the PAA@CDs exhibit a dual-response signal in Fe3+ detection. Based on the fluorescence method, the linear detection range of PAA@CDs for Fe3+ is 0.05-2.60 mM with a limit of detection (LOD) of 5.14 μM. Meanwhile, using the sol-gel method, the linear detection range is 0.02-2.20 mM, and the LOD is 42.5 μM. Furthermore, the PAA@CDs probes can be successfully applied to the detection of Fe3+ in real water samples, demonstrating their potential value in the analysis of real samples containing multiple ions.

Membrane-catalysis integrated system for contaminants degradation and membrane fouling mitigation: A review

The integration of catalytic degradation and membrane separation processes not only enables continuous degradation of contaminants but also effectively alleviates inevitable membrane fouling, demonstrating fascinating practical value for efficient water purification. Such membrane-catalysis integrated system (MCIS) has attracted tremendous research interest from scientists in chemical engineering and environmental science recently. In this review, the advantages of MCIS are discussed, including the membrane structure regulation, stable catalyst loading, nano-confinement effect, and efficient natural organic matter (NOM) exclusion, highlighting the synergistic effect between membrane separation and catalytic process. Subsequently, the design considerations for the fabrication of catalytic membranes, including substrate membrane, catalytic material, and fabrication method, are comprehensively summarized. Afterward, the mechanisms and performance of MCIS based on different catalytic types, including liquid-phase oxidants/reductants involved MCIS, gas involved MCIS, photocatalysis involved MCIS, and electrocatalysis involved MCIS are reviewed in detail. Finally, the research direction and future perspectives of catalytic membranes for water purification are proposed. The current review provides an in-depth understanding of the design of catalytic membranes and facilitates their further development for practical applications in efficient water purification.

Magnetic‐controllable Janus fibrous membranes with wind‐resistant floatability for airflow‐enhanced solar evaporation

Interfacial solar evaporation has been widely regarded as a promising pathway to desalinate seawater without secondary pollution and additional carbon emission. However, one of the challenges rarely considered is the floating stability and remote controllability of the evaporator in the face of wind and waves at the seawater surface. Herein, we demonstrate magnetic Janus membranes (MJMs) with remotely magnetic controllability and wind‐resistant floatation for enhanced interfacial solar evaporation in airflow condition. These membranes are fabricated by sequential electrospinning of a hydrophobic Fe3O4‐embedded polyvinylidene fluoride (PVDF) layer and a hydrophilic polyacrylonitrile (PAN) layer. Due to the superparamagnetism of Fe3O4, our MJMs can be remotely manipulated by a magnet and can float in situ with the aid of a magnetic field, even facing the blast of airflow with a speed of 1.75 m/s. Moreover, the MJMs realize an enhanced vapor diffusion under airflow (v = 0.5 m/s) and show a water evaporation rate of 1.39 ± 0.06 kg∙m−2∙h−1 under one sun, which is 40.4% higher than that in windless condition. This work provides a promising material solution with magnetic design for the practical offshore application of Janus membranes in interfacial solar evaporation.