Fabrication of high-performance composite membranes based on hierarchically structured electrospun nanofiber substrates for pervaporation desalination

A review on green materials: Exploring the potential of poly(vinyl alcohol) (PVA) and nanocellulose composites

Polyvinyl alcohol (PVA) and nanocellulose (NC) composite systems are promising candidates with exciting implications for sustainability, adaptability, and future uses. This research investigates the synergistic features of PVA and nanocellulose, focusing on their renewable and biodegradable nature as important contributors to sustainable material development. An overview of various processing techniques of PVA/NC composites, and their morphological, thermo-mechanical, barrier and biodegradable properties is examined, revealing its enhanced performance attributes compared to conventional materials. This review also discusses the numerous applications of PVA and nanocellulose composites in packaging, biomedical engineering, and environmental remediation. Furthermore, the discussion expands on the potential future applications of these composites, emphasizing their importance in tackling critical global concerns such as pollution reduction, resource conservation, and healthcare breakthroughs. With ongoing research focusing on functionalisation strategies and scalable production methods, PVA and nanocellulose composites are poised to revolutionize multiple sectors, offering sustainable solutions that align with the principles of circular economy and environmental stewardship. Finally, this review emphasises the enormous contributions of PVA and nanocellulose composites to sustainable material innovation, their broad applicability across industries, and their promise to shape a more resilient and environmentally friendly future.

The Efficiency of Polyester-Polysulfone Membranes, Coated with Crosslinked PVA Layers, in the Water Desalination by Pervaporation

Composite polymer membranes were obtained using the so-called dry phase inversion and were used for desalination of diluted saline water solutions by pervaporation (PV) method. The tests used a two-layer backing, porous, ultrafiltration commercial membrane (PS20), which consisted of a supporting polyester layer and an active polysulfone layer. The active layer of PV membranes was obtained in an aqueous environment, in the presence of a surfactant, by cross-linking a 5 wt.% aqueous solution of polyvinyl alcohol (PVA)-using various amounts of cross-linking substances: 50 wt.% aqueous solutions of glutaraldehyde (GA) or citric acid (CA) or a 40 wt.% aqueous solution of glyoxal. An ethylene glycol oligomer (PEG 200) was also used to prepare active layers on PV membranes. Witch its help a chemically cross-linked hydrogel with PVA and cross-linking reagents (CA or GA) was formed and used as an active layer. The manufactured PV membranes (PVA/PSf/PES) were used in the desalination of water with a salinity of 35‱, which corresponds to the average salinity of oceans. The pervaporation method was used to examine the efficiency (productivity and selectivity) of the desalination process. The PV was carried at a temperature of 60 °C and a feed flow rate of 60 dm3/h while the membrane area was 0.005 m2. The following characteristic parameters of the membranes were determined: thickness, hydrophilicity (based on contact angle measurements), density, degree of swelling and cross-linking density and compared with the analogous properties of the initial PS20 backing membrane. The physical microstructure of the cross-section of the membranes was analyzed using scanning electron microscopy (SEM) method.

Spontaneous thermal energy transfer and anti-gravitational water pumping using Al2O3 fiber-enhanced flexible nonwoven material as a high-performance and self-floating solar evaporator

Solar-driven evaporation is promising to address water scarcity. However, preserving the heat inside evaporators instead of allowing run-off, and synergistically utilizing it to wick water from the bulk, is still underexplored. Herein, a dual-functional bridge of longitudinal orientated channels of Al2O3 fibers (AOFs) embedded in a multi-layered nonwoven evaporator was proposed to create a buffer for spontaneous thermal conduction and anti-gravitational water pumping. As a self-floating system with high porosity and flexibility, benefiting from the strong water transporting ability and high thermal conductivity of the AOFs, a superhigh evaporation rate (2.79 kg m-2 h-1 under 1 sun) can be achieved with great stability and durability. This work highlights the potential of promoting thermal management using a large-scale vapour chamber and mass-producible nonwoven technology to prepare a high-performance evaporator for practical applications.

Biomass-based materials for solar-powered seawater evaporation

Clean and safe water is crucial to maintaining human life on earth. Solar-powered seawater desalination (SSD) is a promising and feasible way to use solar energy resources to overcome water scarcity. Among all the candidate materials for solar seawater evaporators, biomass-based materials stand out thanks to their excellent inherent natural structure, ease of preparation, low cost, and abundant resources. In this article, we review biomass-based materials, from angiosperms, algae, and fungi to animal materials and other atypical biomass materials, proposed for solar-powered seawater evaporation in the shape of the nanofluid, membrane, gels, composite sponge structures, composites Janus structures and other composites. The approaches for improving biomass-based solar seawater evaporators (BSSE) performance are emphasized, including optical absorption regulation, system thermal management optimization, adequate water supply, salt resistance, and effective steam condensate recovery. In the end, the opportunities and challenges of biomass-based materials for SSD are illustrated.

Electrospun nanofibrous membrane with antibacterial and antiviral properties decorated with Myoporum bontioides extract and silver-doped carbon nitride nanoparticles for medical masks application

Public health safety issues have been plaguing the world since the pandemic outbreak of coronavirus disease (COVID-19). However, most personal protective equipments (PPE) do not have antibacterial and anti- toxicity effects. In this work, we designed and prepared a reusable, antibacterial and anti-toxicity Polyacrylonitrile (PAN) based nanofibrous membrane cooperated with Ag/g-C₃N₄ (Ag-CN), Myoporum.bontioides (M. bontioides) plant extracts and Ag nanoparticles (NPs) by an electrospinning-process. The SEM and TEM characterization revealed the formation of raised, creased or wrinkled areas on the fiber surface caused by the Ag nanoparticles, the rough surface prevented the aerosol particles on the fiber surface from sliding and stagnating, thus providing excellent filtration performance. The PAN/M. bontioides/Ag-CN/Ag nanofibrous membrane could be employed as a photocatalytic bactericidal material, which not only degraded 96.37% of methylene blue within 150 min, but also exhibited the superior bactericidal effect of 98.65 ± 1.49% and 97.8 ± 1.27% against E. coli and S. aureus, respectively, under 3 hs of light exposure. After 3 cycles of sterilization experiments, the PAN/M. bontioides/Ag-CN/Ag nanofibrous membrane maintained an efficient sterilization effect. Molecular docking revealed that the compounds in M. bontioides extracts interacted with neo-coronavirus targets mainly on Mpro and RdRp proteins, and these compounds had the strongest docking energy with Mpro protein, the shortest docking radius, and more binding sites for key amino acids around the viral protein targets, which influenced the replication and transcription process of neo-coronavirus. The PAN/M.bontioides/Ag-CN/Ag nanofibrous membrane also performed significant inhibition of influenza A virus H3N2. The novel nanofiber membrane is expected to be applied to medical masks, which will improve human isolation and protection against viruses.

Electrospun Nanofiber-Based Membranes for Water Treatment

Water purification and water desalination via membrane technology are generally deemed as reliable supplementaries for abundant potable water. Electrospun nanofiber-based membranes (ENMs), benefitting from characteristics such as a higher specific surface area, higher porosity, lower thickness, and possession of attracted broad attention, has allowed it to evolve into a promising candidate rapidly. Here, great attention is placed on the current status of ENMs with two categories according to the roles of electrospun nanofiber layers: (i) nanofiber layer serving as a selective layer, (ii) nanofiber layer serving as supporting substrate. For the nanofiber layer's role as a selective layer, this work presents the structures and properties of conventional ENMs and mixed matrix ENMs. Fabricating parameters and adjusting approaches such as polymer and cosolvent, inorganic and organic incorporation and surface modification are demonstrated in detail. It is crucial to have a matched selective layer for nanofiber layers acting as a supporting layer. The various selective layers fabricated on the nanofiber layer are put forward in this paper. The fabrication approaches include inorganic deposition, polymer coating, and interfacial polymerization. Lastly, future perspectives and the main challenges in the field concerning the use of ENMs for water treatment are discussed. It is expected that the progress of ENMs will promote the prosperity and utilization of various industries such as water treatment, environmental protection, healthcare, and energy storage.

Pervaporation as a Successful Tool in the Treatment of Industrial Liquid Mixtures

Pervaporation is one of the most active topics in membrane research, and it has time and again proven to be an essential component for chemical separation. It has been employed in the removal of impurities from raw materials, separation of products and by-products after reaction, and separation of pollutants from water. Given the global problem of water pollution, this approach is efficient in removing hazardous substances from water bodies. Conventional processes are based on thermodynamic equilibria involving a phase transition such as distillation and liquid-liquid extraction. These techniques have a relatively low efficacy and nowadays they are not recommended because it is not sustainable in terms of energy consumption and/or waste generation. Pervaporation emerged in the 1980s and is now becoming a popular membrane separation technology because of its intrinsic features such as low energy requirements, cheap separation costs, and good quality product output. The focus of this review is on current developments in pervaporation, mass transport in membranes, material selection, fabrication and characterization techniques, and applications of various membranes in the separation of chemicals from water.