Preparation and characterization of chitosan-poly (vinyl alcohol)/polyvinylidene fluoride hollow fiber composite membranes for pervaporation dehydration of isopropanol

Fabrication of PVA-PVC composite membrane for enhanced TDS removal from tannery effluent: sustainable water treatment approach

The environmental burden of tannery wastewater, characterized by high levels of total dissolved solids (TDS) and other contaminants, presents a significant challenge for sustainable water management. This study addresses this issue by developing a novel polyvinyl alcohol (PVA) and polyvinyl chloride (PVC) composite membrane optimized for efficient TDS removal from tannery effluent. The membrane was fabricated using a solution casting technique, with glutaraldehyde employed as a crosslinking agent to enhance mechanical properties and stability. Characterization techniques, including Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), zeta potential analysis, and contact angle measurements, were used to evaluate the membrane's surface chemistry, morphology, and hydrophilicity, which are crucial for pollutant separation. Performance testing demonstrated that the membrane achieved a TDS removal efficiency of 91.73% at an optimal pH of 8 and a transmembrane pressure of 3.5 bar, with a permeability of 194 Lm-2 h-1 bar-1. Additionally, substantial reductions in turbidity (94.51%), chemical oxygen demand (COD, 91.91%), biological oxygen demand (BOD, 89.70%), salinity (80.57%), and total suspended solids (TSS, 96.45%) were observed. The membrane exhibited impressive mechanical properties, with a tensile strength of 44 ± 0.43 MPa, 150 ± 0.67% elongation at break, Young's modulus of 750 ± 0.47 MPa, and flexibility of 23 ± 0.53%, indicating its flexibility and durability. Its partial biodegradability and potential for scalable production contribute to its environmental sustainability. This work establishes the PVA-PVC composite membrane as a promising and cost-effective solution for industrial wastewater treatment, offering a sustainable approach to mitigating water pollution in the leather industry.

State-of-the-Art Organic- and Inorganic-Based Hollow Fiber Membranes in Liquid and Gas Applications: Looking Back and Beyond

The aggravation of environmental problems such as water scarcity and air pollution has called upon the need for a sustainable solution globally. Membrane technology, owing to its simplicity, sustainability, and cost-effectiveness, has emerged as one of the favorable technologies for water and air purification. Among all of the membrane configurations, hollow fiber membranes hold promise due to their outstanding packing density and ease of module assembly. Herein, this review systematically outlines the fundamentals of hollow fiber membranes, which comprise the structural analyses and phase inversion mechanism. Furthermore, illustrations of the latest advances in the fabrication of organic, inorganic, and composite hollow fiber membranes are presented. Key findings on the utilization of hollow fiber membranes in microfiltration (MF), nanofiltration (NF), reverse osmosis (RO), forward osmosis (FO), pervaporation, gas and vapor separation, membrane distillation, and membrane contactor are also reported. Moreover, the applications in nuclear waste treatment and biomedical fields such as hemodialysis and drug delivery are emphasized. Subsequently, the emerging R&D areas, precisely on green fabrication and modification techniques as well as sustainable materials for hollow fiber membranes, are highlighted. Last but not least, this review offers invigorating perspectives on the future directions for the design of next-generation hollow fiber membranes for various applications. As such, the comprehensive and critical insights gained in this review are anticipated to provide a new research doorway to stimulate the future development and optimization of hollow fiber membranes.

Vacuum-Assisted Interfacial Polymerization Technique for Enhanced Pervaporation Separation Performance of Thin-Film Composite Membranes

In this work, thin-film composite polyamide membranes were fabricated using triethylenetetramine (TETA) and trimesoyl chloride (TMC) following the vacuum-assisted interfacial polymerization (VAIP) method for the pervaporation (PV) dehydration of aqueous isopropanol (IPA) solution. The physical and chemical properties as well as separation performance of the TFCVAIP membranes were compared with the membrane prepared using the traditional interfacial polymerization (TIP) technique (TFCTIP). Characterization results showed that the TFCVAIP membrane had a higher crosslinking degree, higher surface roughness, and denser structure than the TFCTIP membrane. As a result, the TFCVAIP membrane exhibited a higher separation performance in 70 wt.% aqueous IPA solution at 25 °C with permeation flux of 1504 ± 169 g∙m-2∙h-1, water concentration in permeate of 99.26 ± 0.53 wt%, and separation factor of 314 (five times higher than TFCTIP). Moreover, the optimization of IP parameters, such as variation of TETA and TMC concentrations as well as polymerization time for the TFCVAIP membrane, was carried out. The optimum condition in fabricating the TFCVAIP membrane was 0.05 wt.% TETA, 0.1 wt% TMC, and 60 s polymerization time.

Development of Novel Membranes Based on Polyvinyl Alcohol Modified by Pluronic F127 for Pervaporation Dehydration of Isopropanol

Membrane methods are environmentally friendly and can significantly improve the design and development of new energy consumption processes that are very important nowadays. However, their effective use requires advanced membrane materials. This study aims to improve the performance of pervaporation polyvinyl alcohol (PVA)-based membrane for isopropanol dehydration. To achieve this goal, two methods were applied: (1) bulk modification of PVA by Pluronic F127 and (2) development of supported PVA-based membrane using polyphenylene isophthalamide (PA) as a substrate with a various porosity. Developed membranes were characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy (SEM), contact angle measurement, and swelling experiments. The concentration influence of PA casting solution (12–20 wt.%) on the performance of porous PA membranes (substrates) was investigated in ultrafiltration of pure water and bovine serum albumin (BSA) solution as well as by microscopic methods (SEM and atomic force microscopy). The developed dense and supported PVA-based membranes were tested in the pervaporation dehydration of isopropanol. Optimal transport characteristics were obtained for a supported membrane with a PVA-based selective layer containing 3 wt.% Pluronic F127 onto an ultrafiltration PA (17 wt.%) substrate: improved permeation flux 0.100–1.164 kg/(m2 h) and 98.8–84.6 wt.% water content in the permeate in pervaporation dehydration of isopropanol (12–80 wt.% water).

How Can the Desert Beetle and Biowaste Inspire Hybrid Separation Materials for Water Desalination?

Highly effective, hybrid separation materials for water purification were generated following a bioinspired system available in nature. The desert beetle was the inspiration for the generation of separation materials. Using the hydrophobic poly(vinylidene fluoride) (PVDF) membrane as the basis, the membrane was first activated and then furnished with silane-based linkers, and the covalent anchoring of chitosan was successfully accomplished. The obtained surface architecture was a copy of the desert beetle's armor possessing a hydrophobic matrix with hydrophilic domains. The modification was done in the presence or the lack of catalyst (N,N-diisopropylethylamine) that made it possible to tune easily wettability, roughness, and material as well as adhesive features. The membrane morphology and surface chemistry were studied by applying a series of analytical techniques. As a result of chitosan attachment, substantial improvement in transport and separation was reported. Pristine PVDF was characterized by a water flux of 5.28 kg m^-2 h^-1 and an activation energy of 48.16 kJ mol^-1. The water flux and activation energy for a hybrid membrane with chitosan were equal to 15.55 kg m^-2 h^-1 and 33.98 kJ mol^-1, respectively. The hybrid materials possessed enhanced stability and water resistance that were maintained after 10 cycles of membrane distillation tests.

Development of zeolite-A incorporated PVA/CS nanofibrous composite membranes using the electrospinning technique for pervaporation dehydration of water/tert-butanol

Using the electrospinning technique, composite nanofibrous membranes were developed on a dense PVA layer from a solution of poly(vinyl alcohol) (PVA)/chitosan (CS)/zeolite-A.

Sustained Release of Linezolid from Prepared Hydrogels with Polyvinyl Alcohol and Aliphatic Dicarboxylic Acids of Variable Chain Lengths

A series of hydrogels with a specific release profile of linezolid was successfully synthesized. The hydrogels were synthesized by cross-linking polyvinyl alcohol (PVA) and aliphatic dicarboxylic acids, which include succinic acid (SA), glutaric acid (GA), and adipic acid (AA). The three crosslinked hydrogels were prepared by esterification and characterized by equilibrium swelling ratio, infrared spectroscopy, thermogravimetric analysis, mechanical properties, and scanning electron microscopy. The release kinetics studies of the linezolid from prepared hydrogels were investigated by cumulative drug release and quantified by chromatographic techniques. Mathematical models were carried out to understand the behavior of the linezolid release. These data revealed that the sustained release of linezolid depends on the aliphatic dicarboxylic acid chain length, their polarity, as well as the hydrogel crosslinking degree and mechanical properties. The in vitro antibacterial assay of hydrogel formulations was assessed in an Enterococcus faecium bacterial strain, showing a significant activity over time. The antibacterial results were consistent with cumulative release assays. Thus, these results demonstrated that the aliphatic dicarboxylic acids used as crosslinkers in the PVA hydrogels were a determining factor in the antibiotic release profile.

Development and Characterization of New Pervaporation PVA Membranes for the Dehydration Using Bulk and Surface Modifications

In the present work, the novel dense and supported membranes based on polyvinyl alcohol (PVA) with improved transport properties were developed by bulk and surface modifications. Bulk modification included the blending of PVA with chitosan (CS) and the creation of a mixed-matrix membrane by introduction of fullerenol. This significantly altered the internal structure of PVA membrane, which led to an increase in permeability with high selectivity to water. Surface modification of the developed modified dense membranes, based on composites PVA-CS and PVA-fullerenol-CS, was performed through (i) making of a supported membrane with a thin selective composite layer and (ii) applying of the layer-by-layer assembly (LbL) method for coating of nano-sized polyelectrolyte (PEL) layers to increase the membrane productivity. The nature of polyelectrolyte type-(poly(allylamine hydrochloride) (PAH), poly(sodium 4-styrenesulfonate) (PSS), poly(acrylic acid) (PAA), CS), and number of PEL bilayers (2⁻10)-were studied. The structure of the composite membranes was investigated by FTIR, X-ray diffraction, and SEM. Transport properties were studied during the pervaporation separation of 80% isopropanol⁻20% water mixture. It was shown that supported membrane consisting of hybrid layer of PVA-fullerenol (5%)⁻chitosan (20%) with five polyelectrolyte bilayers (PSS, CS) deposited on it had the best transport properties.