Poly Vinyl Alcohol Membranes Research Articles

Cellulose nanofiber and halloysite nanotubes embedded polyvinyl alcohol membranes for pervaporation dehydration of epichlorohydrin–isopropanol–water ternary feed mixture

AbstractThe dehydration of epichlorohydrin (ECH)–isopropanol (IPA)–water mixtures was conducted by using pervaporation separation process. Two types of crosslinked polyvinyl alcohol (PVA) membranes, PVA‐Glu and PVA‐TEOS, were prepared using glutaraldehyde (Glu) and tetraethyl ortho silicate (TEOS), then mixed with cellulose nanofiber (CNF) and halloysite nanotube (HNT) fillers, respectively. They characterized using field emission scanning electron microscopy to observe surface morphology, Fourier‐transform infrared spectroscopy to study the filler–polymer interactions and chemistries of membranes, and X‐ray diffraction experiment for the analysis of membrane crystallinity. Finally, a pervaporation test was carried out to dehydrate the ECH–IPA–water feed solution at the azeotropic feed composition. From the result, the membrane of PVA‐Glu, including 4% w/w CNF filler, showed a flux of 0.17 kg (m2h)−1 and a separation factor of 456. However, the membrane of PVA‐TEOS with 5% w/w HNTs filler indicated a flux of 0.15 kg (m2h)−1 and a separation factor of 4158. The higher pervaporation performance of the HNTs‐added PVA‐TEOS membrane is attributed to the smaller size and more porous nature of HNTs than CNFs.

A novel integrated circular economy approach in green synthesis of copper oxide nanoparticles from waste printed circuit boards and utilization of its residue for preparation of carbon engulfed nano polymer membrane

Electronic waste is a major threat to our environment. Handling and recycling of electronic waste towards the circular economy is a tedious process. Researchers are trying to enhance the existing recycling techniques to improvise the process for better efficiency and also to result in lower by-products. Pre-treatment of Waste Printed Circuit Board (WPCB) using sodium hydroxide solution as solvent under autoclaving conditions results in 100% of epoxy removal efficiency. Further, the selective leaching process of WPCB utilizing ammonium chloride solution and ammonia buffer solution, reduced with the help of Cathantharaus roseus plant leaf extract, clears the way for the generation of copper oxide nanoparticles. Synthesized nanoparticles are separated by repeated centrifugation at 10000 rpm for 30 min using sterile distilled water, then drying it in a hot air oven for 2 h. Samples are characterized using HRTEM and FESEM-EDX. The residual thermoset of WPCB is muffle treated at 550 °C for 3 h to get desired carbon forms and is characterized using Raman spectroscopy, FESEM-EDX. Grounded carbon forms are utilized for synthesizing carbon-engulfed polyvinyl alcohol (PVA) membrane using electro-spinning, which finds its application in dye removal. Synthesized nano-sized polymer membrane is characterized using TGA, FESEM-EDX, FTIR and tensile strength through Universal Testing Machine.

Preparation and characterisation of tough and porous polyvinyl alcohol/POC membrane for biomedical applications

Polyvinyl alcohol (PVA) is a synthetic polymer that has been extensively studied for fabricating porous membranes via electrospinning for diverse biomedical applications. However, the poor mechanical properties of electrostatically spun PVA nanofiber membranes severely limit their application in the biomedical field. Therefore, porous, tough hybrid PVA-based fibrous membranes were prepared by introducing poly (1,8-octanediol citrate) (POC) into PVA fibrous membranes followed by sodium citrate treatment. The tensile modulus, fracture strength, and fracture toughness of the sodium citrate-treated PVA/POC (CPP) membranes achieve 119.81 ± 5.32 MPa, 10.34 ± 1.57 MPa and 401.51 ± 11.67 MJ m−2, respectively, which were ∼60, ∼10, and ∼4 times higher than those achieved by the pristine PVA membrane. Moreover, the novel CPP membranes exhibited suitable biodegradation ratios and high cell/issue affinities, suggesting their potential biomedical applications in soft or hard tissue repair. This strategy, which provides porous structures, high mechanical properties and excellent biocompatibility, demonstrates a facile but effective approach for the development of advanced biomaterials.

A molecular level based parametric study of transport behavior in different polymer composite membranes for water vapor separation

The membrane dehumidification technology has great energy-saving potential compared to traditional methods. However, the design of composite membrane depends mostly on trial tests. To understand the mechanisms dominating material properties and quantitatively predict the air dehumidification performance of the composite membranes in practical applications, various models combined with different polymeric materials and porous support membranes were developed and investigated by using grand canonical Monte Carlo (GCMC) and Molecular dynamics (MD) simulation methods. The interfacial interactions between the selective layer and the support membrane were analyzed in detail to explore the interface stability and compatibility of various composite membranes. The physical characteristics (density, fractional free volume, solubility parameter and cohesive energy density) and transport properties (solubility, diffusivity, permeability and selectivity) of various composite membranes were parametrically evaluated. The polydimethylsiloxane (PDMS) composite membranes exhibited stronger interfacial interaction in comparison to the PVA composite membranes. The hydrophilicity and polarity of polyvinyl alcohol (PVA) polymer resulted in a stronger interaction between the gas molecules and the PVA membrane. According to the solution–diffusion mechanism, the PVA-PVDF membrane presented the optimal H2O permeability of 3121.38 Barrer among all composite membranes. Generally, polyvinylidene fluoride (PVDF) or polyacrylonitrile (PAN) as the materials of support membrane had good fiber forming characteristics and low gas diffusion resistance, which significantly affects the performance of selective layers. The microscopic mechanisms revealed in this work would lay a solid theoretical foundation for the design of high performance composite membrane for air dehumidification.

Surface molecular imprinted membranes as a “gate” for selective transdermal release of chiral drug amlodipine

Amlodipine is a commonly used and effective drug for the treatment of hypertension. This work investigates imprinted membranes with functional molecular recognition properties prepared via the surface molecular imprinted technology. The surface molecular imprinted membrane are synthesized by taking (S)-amlodipine (S-ADP) as the template molecule, methacrylic acid (MAA) as the functional monomer, and N, N′-methylenebisacrylamide (MBA) as the cross-linker in the present of a surface-initiating system of –OH/Ce4+ constituted by the hydroxyl on the surface of basilemma polyvinyl alcohol (PVA) and ammonium cerium sulfate dissolved in solvent.The imprinted layer is grafted onto the PVA membranes followed by the removal of the S-ADP template molecule, obtaining the S-ADP surface molecular imprinted membranes (S-ADP-SMIMs). The membrane is characterized by Fourier transform infrared reflection (FTIR), and scanning electron microscopy (SEM),13C Nuclear Magnetic Resonance spectroscopy (13C NMR) and X-ray photoelectron spectroscopy (XPS). The ability of enantioseparation and selective permeability of S-ADP-SMIMs is studies. As a result, the selectivity coefficient is 4.6 and the optical purity of adsorption liquid gets up to 80% for S-ADP-SMIMs. However, the non-surface molecular imprinted membrane (NSMIM) shows no selectivity. And the results of in vitro release experiments reveal that the cumulative amounts released of S-ADP and R-amlodipine (R-ADP) is 1459.01 μg cm−2 and 106.21 μg cm−2, respectively. In the skin permeation experiments, the optimal drug concentration is 4.0 mg/mL, Carbopol is determined 0.9% and 1% oleic acid is acted as excellent permeation enhancer. The cumulative amount transported reaches 1719.68 μg cm−2 for S-ADP, while a lower value of 228.17 μg cm−2 is measured for R-ADP. These results strongly suggest the formation of imprinted cavities, which offer selectivity for the transport of S-ADP. So, the imprinted membrane is universal for other chiral drugs. It makes it possible to selectively delivery dominant isomers exactly and efficiently.

Polyvinyl alcohol membrane incorporated with amine-modified silica nanoparticles and ionic liquid for facilitated transport of CO2

The application of polymeric membranes in post-combustion carbon capture is limited by solution-diffusion. In this work, polyvinyl alcohol (PVA) membranes with facilitated transport of carbon dioxide (CO2) were improved by incorporating the fixed carrier, amine-modified silica nanoparticles (SiO2) and the mobile carrier [bmim][Tf2N] ionic liquid. The BET surface area of diethanolamine (DEA)-modified SiO2 nanoparticles decreased from 150.14 m2/g to 22.68 m2/g, but they improved the surface hydrophilicity of PVA membranes more significantly than the unmodified SiO2 nanoparticles due to the existence of secondary amine groups. Fourier transform infrared spectra confirmed the incorporation of secondary amine and anion of IL that can facilitate CO2 permeation. The thermogravimetric analysis also revealed that the thermal stability of PVA membranes was improved by incorporating inorganic nanoparticles and ionic liquid. The thickness of the dense PVA layer coated on polyethersulfone support increased by incorporating SiO2 and DEA-modified SiO2 nanoparticles, as shown by scanning electron microscope images. The positive effects of SiO2 nanoparticles on the CO2 separation performance of PVA membranes were enhanced by reducing the particle size and increasing particle loading. DEA elevated the enhancement through the Zwitterion mechanism. [bmim][Tf2N] IL also improved the CO2 separation performance of PVA membranes. Hence, the PVA membrane containing 2 wt% of DEA-modified SiO2 nanoparticles (15-20 nm) and 0.4 M of [bmim][Tf2N] IL in ethanol attained a CO2 permeance of 3016 GPU and CO2/N2 selectivity of 62.08.

Pervaporation Polyvinyl Alcohol Membranes Modified with Zr-Based Metal Organic Frameworks for Isopropanol Dehydration.

Metal-organic frameworks (MOFs) are perceptive modifiers for the creation of mixed matrix membranes to improve the pervaporation performance of polymeric membranes. In this study, novel membranes based on polyvinyl alcohol (PVA) modified with Zr-MOFs (MIL-140A, MIL-140A-AcOH, and MIL-140A-AcOH-EDTA) particles were developed for enhanced pervaporation dehydration of isopropanol. Two membrane types (substrateless–freestanding; and formed on polyacrylonitrile support-composite) were prepared. The additional cross-linking of membranes with glutaraldehyde was carried out to circumvent membrane stability in pervaporation dehydration of diluted solutions. The synthesized Zr-MOFs were characterized by scanning electron microscopy, X-ray powder diffraction analysis, and specific surface area measurement. The structure and physicochemical properties of the developed membranes were investigated by Fourier-transform infrared spectroscopy, scanning electron and atomic force microscopies, thermogravimetric analysis, swelling experiments, and contact angle measurements. The PVA and PVA/Zr-MOFs membranes were evaluated in pervaporation dehydration of isopropanol in a wide concentration range. It was found that the composite cross-linked PVA membrane with 10 wt% MIL-140A had optimal pervaporation performance in the isopropanol dehydration (12–100 wt% water) at 22 °C: 0.15–1.33 kg/(m2h) permeation flux, 99.9 wt% water in the permeate, and is promising for the use in the industrial dehydration of alcohols.

Polyvinyl alcohol and sodium alginate hydrogel coating with different crosslinking procedures on a PSf support for fabricating high-flux NF membranes

Polyvinyl alcohol (PVA) and sodium alginate (SA) hydrogel-coated nanofiltration (NF) membranes with high-flux and permselectivity were prepared. The coating of PVA and SA hydrogel selective layer on a porous polysulfone (PSf)/non-woven fabric ultrafiltration substrate membrane was conducted through different three procedures including pre-crosslinking, in-situ crosslinking, and immersing crosslinking and the use of glutaraldehyde as a crosslinking agent. The properties and performances of all types of the prepared membranes were evaluated through ATR-FTIR spectroscopy, AFM, SEM, zeta potential, contact angle, and cross-flow permeation tests. The immersing technique resulted in the formation of TFC membranes with higher hydrophilicity, smoother surface layer, higher negative charge, higher permeation flux, higher salt rejection and better anti-fouling performance. Also, the higher negative surface charge of the immersing coated TFC membranes due to dissociation of hydrophilic functional groups of the PVA and SA hydrogel selective layer resulted in higher As(III) rejection. SA coated NF membrane through immersing method exhibited a higher pure water permeability of 11.2 L m−2 h−1 bar−1, NaCl, MgSO4, and Na2SO4 rejection of 38.2%, 55.1%, and 70.4%, respectively with As(III) rejection of 60.6%. All types of the PVA and SA hydrogel-coated PSf membranes possessed improved fouling resistance to BSA aqueous solution, superior anti-fouling performance was obtained with SA hydrogel coating through immersing method. Such optimum membranes indicated high stability in the long-term experiments. This study showed that the coating of the SA hydrogel layer on a PSf support through immersing method could be a promising candidate for fabricating high-flux NF membranes.

Boric acid-loosened polyvinyl alcohol/glutaraldehyde membrane with high flux and selectivity for monovalent/divalent salt separation

Polyvinyl alcohol (PVA) has the advantages of excellent hydrophilicity, good film-forming properties and competitive prices, thus it is an ideal membrane material. However, rare reports about PVA membrane for monovalent/divalent salt separation, which is widespread in chemical industry can be found. Herein, we developed a novel boric acid (BA)-loosened PVA/glutaraldehyde (GA) membrane with high flux and selectivity for monovalent/divalent salt separation. Our idea is based on the fact that BA and PVA can form a complex due to some special interactions (including chemical bonding and H-bonding). In general, PVA membrane needs to crosslink with GA for obtaining a high salt rejection. However, PVA/GA membrane is usually too compact, leading to a low membrane water flux. The formation of PVA/BA complex reduced PVA/GA membrane crystallinity and increased its pore size, thereby improving the membrane flux obviously (by 16 times). PVA/GA/BA membrane flux is high: under 7.5 bar, its pure water flux was 20.20 L/m2·h. Besides, a high monovalent/divalent salt selectivity (64.21) was also achieved since the rejection of monovalent salt (NaCl) declined sharply and meanwhile the high rejection of divalent salt (Na2SO4) was maintained. Moreover, the developed PVA/GA/BA membrane exhibited a good alkali resistance, antifouling performance and stability of permselectivity, which has a bright application prospect. This work may pave a novel avenue to develop high-performance PVA monovalent/divalent salt separation membranes.

The Influence of Anion-Stripped MIL-101(Cr) Dispersed in Thin-Film Polyvinyl Alcohol Membrane Matrix on the Methylene Blue Dye Separation

This study investigates the production and performance of a novel nanofiltration membrane for removal of cationic dye (Methylene blue) and multivalent cations. These positively charged membranes are made by dispersing a modified cationic metal–organic framework, Cl-MIL-101(Cr), into the polyvinyl alcohol matrix as a membrane skin layer. To this end, the mobile anion (Cl−) embedded in the MIL-101(Cr) structure plays a role to create a positive partial charge on the membrane. In this study, the effects of MOF content and their types on the membrane structure were considered by FTIR, XRD, FESEM, Zeta potential and water contact angle. The results have shown that membranes filled with Cl-MIL-101(Cr) attained higher permeate flux and rejection than those of MIL-101(Cr). Particularly, this study indicates that the low irreversible resistance (19.49%) and high flux return ratio (80.50%) have been related to the membrane containing 15% cationic Cl-MIL-101(Cr). However, this membrane rejected more than 30.41% of AlCl3 salt and 99.08% of methylene blue with approximate permeate flux of 20 L/m2·h. It is recommended that the fabricated membrane be placed in the flow path process of cationic dyes purification.

Robust and water-selective natural-cellulose-nanofiber-reinforced polyvinyl alcohol composite membranes for pervaporation of isopropanol/water mixtures

High-strength polyvinyl alcohol (PVA)–6-cellulose nanofiber (CNF) composite membranes for pervaporation separation of isopropanol (IPA)/water mixtures were produced using a solution casting method. Their morphological and physicochemical properties were evaluated using field emission scanning electron microscopy, atomic force microscopy, attenuated total reflection–Fourier-transform infrared spectroscopy, and X-ray diffraction. Upon the addition of various concentrations of CNF to PVA membranes, the tensile strengths of the PVA–CNF composite membranes increased with increasing CNF loading from 35.01 MPa for the pristine PVA membrane to 80.98 MPa for the membrane with an CNF loading of 10 wt% owing to the interactions between PVA and CNF. The effect of CNF loading was examined using pervaporation experiments, and the results indicated that the flux values of the membranes increased and their separation factors decreased with increasing CNF loading. The optimized membrane (PC-6 with a CNF loading of 6 wt%) presented stable pervaporation performance with a flux of 20-21 g/(m2h) and water content in the permeate of 20-21 g/m2h and 99.90±0.10 % after 120 h of operation at 40°C for a IPA/water feed of 85/15 (w/w). In summary, the high-strength water-selective PVA–CNF membranes fabricated in this study are promising for pervaporation separation of IPA/water mixtures.

Poly (Vinyl Alcohol) Composite Membrane with Polyamidoamine Dendrimers for Efficient Separation of CO2/H2 and CO2/N2

Although polyvinyl alcohol (PVA) membranes are commonly used for CO2 separation, there is still large development space in mechanical properties and high selectivity of the gas separation process. In this study, the gas separation performance and mechanical properties of the (PVA/Cu2+) substrate membranes were improved by introducing polyamidoamine (PAMAM). PAMAM had an important effect on the gas adsorption and separation performance of the membrane. In addition, the gas adsorption and separation properties of the PVA/Cu2+/PAMAM membrane (PPCm) were analyzed and studied when the inlet gas pressure and the species of mixed gases were variable. The results showed that the crystallinity and mechanical properties of the membrane with the PAMAM had been significantly improved. Young’s modulus of PPCm with 30% PAMAM was 132% higher than that of the PVA/Cu2+ composite membrane without PAMAM. In addition, efficient separation efficiency and high selectivity of the gas separation process were observed. The separation factors of the PPCm for CO2/H2 and CO2/N2 were about three times higher than that of the PVA/Cu2+ substrate membranes. These results suggested that the introduction of PAMAM was promising for CO2 separation and permeance.

Performance Research of PVA (Polyvinyl alcohol) Based on HKUST-1 as Additive

We report a 98.8% UV light barrier, water resistant and better mechanical performance PVA membrane based on 5% HKUST-1 as UV protection additive, and compared with ZnO and UV 531. X-ray photoelectron spectroscopy (XPS) revealed binding energy decrease of Cu 2p3/2 and Cu 2p1/2, to be 1.2 eV and 1.4 eV, respectively, which indicates Cu2+ partially converted to Cu+ in the presence of residual C in PVA during UV irradiating, very different from that of ZnO which can be ascribed to diffused reflection.

Preparation and pervaporation performance of PVA membrane with biomimetic modified silica nanoparticles as coating

Polyvinyl alcohol (PVA) has been widely used in pervaporation dehydration due to its low price and good stability. However, the inherent “trade-off” effect of polymer membrane makes the pervaporation performance relatively limited. In this work, the rough and super-hydrophilic surface were constructed by biomimetic modification of silica (SiO2) coating on the PVA membrane, which achieved simultaneous growth of total flux and separation factor compared with the control, and overcame the “trade-off” effect. The morphology, structure and hydrophilicity of membranes were characterized. Results demonstrated that PVA/polydopamine (PDA)/SiO2 composite membranes had strong hydrophilicity and high surface roughness. In addition, the effects of SiO2 loading amount, operating temperature, feed ethanol concentration and long-term stability on the ethanol dehydration performance were investigated. For the PVA/PDA/SiO2-6 composite membrane, total flux was 1388 g m−2 h−1, and the separation factor was 150(69 °C,90 wt% ethanol concentration), which was 1.8 times and 1.4 times that of the pristine PVA membrane, respectively.

Microwave-induced ultrafast crosslinking of Poly (vinyl alcohol) blended with nanoparticles as wave absorber for pervaporation desalination

Although pervaporation (PV) membranes based on crosslinked polyvinyl alcohol (PVA) exhibit high desalination performance, the thermal crosslinking process often takes several hours. Here, we report a microwave assisted method to reduce the crosslinking duration. Moreover, to the PVA crosslinking system, a MOF particle, UIO-66, was added to increase the microwave absorbing efficiency and improve the desalination property. As a result, the PVA crosslinking time decreased to 2 min and the water flux increased by 67% compared with the plain crosslinked PVA membrane.

Solvent-resistant polyvinyl alcohol nanofilm with nanopores for high-flux degumming

Vegetable oil degumming is the first step of edible oil processing industry. Achieving highly efficient degumming by the polymeric membrane requires specific separation of phospholipid with endurance in organic solvent. Here, we show a method to fabricate solvent resistant polyvinyl alcohol (PVA) membranes from a colloidal aqueous system of nanoparticles made up of maleic acid (MA) molecules and PVA chains. The MA molecules associated physically over the PVA chains by electrostatic interaction in liquid phase, which in turn control cross-linking density of the final solid PVA membrane. The system produces a membrane layer of nanometer-scale thickness having mean pore radius of 1.55 nm with functional hydrophilic groups and exhibited membrane flux of 14 L m−2 h−1 bar−1 with phospholipid rejection selectivity of 92% for potential degumming of crude vegetable oil.

Swelling-Resistant, Crosslinked Polyvinyl Alcohol Membranes with High ZIF-8 Nanofiller Loadings as Effective Solid Electrolytes for Alkaline Fuel Cells.

The present work investigates the direct mixing of aqueous zeolitic imidazolate framework-8 (ZIF-8) suspension into a polyvinyl alcohol (PVA) and crosslinked with glutaraldehyde (GA) to form swelling-resistant, mechanically robust and conductivity retentive composite membranes. This drying-free nanofiller incorporation method enhances the homogeneous ZIF-8 distributions in the PVA/ZIF-8/GA composites to overcome the nanofiller aggregation problem in the mixed matrix membranes. Various ZIF-8 concentrations (25.4, 40.5 and 45.4 wt.%) are used to study the suitability of the resulting GA-crosslinked composites for direct alkaline methanol fuel cell (DAMFC). Surface morphological analysis confirmed homogeneous ZIF-8 particle distribution in the GA-crosslinked composites with a defect- and crack-free structure. The increased ionic conductivity (21% higher than the ZIF-free base material) and suppressed alcohol permeability (94% lower from the base material) of PVA/40.5%ZIF-8/GA resulted in the highest selectivity among the prepared composites. In addition, the GA-crosslinked composites’ selectivity increased to 1.5–2 times that of those without crosslink. Moreover, the ZIF-8 nanofillers improved the mechanical strength and alkaline stability of the composites. This was due to the negligible volume swelling ratio (<1.4%) of high (>40%) ZIF-8-loaded composites. After 168 h of alkaline treatment, the PVA/40.5%ZIF-8/GA composite had almost negligible ionic conductivity loss (0.19%) compared with the initial material. The maximum power density (Pmax) of PVA/40.5%ZIF-8/GA composite was 190.5 mW cm−2 at 60 °C, an increase of 181% from the PVA/GA membrane. Moreover, the Pmax of PVA/40.5%ZIF-8/GA was 10% higher than that without GA crosslinking. These swelling-resistant and stable solid electrolytes are promising in alkaline fuel cell applications.

The combination of a new PERVAPTM membrane and molecular sieves enhances the ethanol drying process

A new commercial polyvinyl alcohol (PVA) membrane (PERVAP™ 4100HF) was characterized by scanning electron microscopy (SEM), Fourier-transform infrared (FTIR), and contact angle (CA) goniometer. The separation performance of the membrane for drying ethanol by pervaporation was also investigated and compared with a standard membrane (PERVAP™ 4100) under same operating conditions. The results show that the new membrane is thinner and less cross-linked than the standard one. The water permeance in PERVAP™ 4100HF (∼800 GPU) is four-time higher than that in PERVAP™ 4100 (200 GPU) at 70 °C and for <5 wt.% of water concentration in the feed. The water/ethanol selectivity of the new membrane under this operating condition is very high (∼7000). The effect of feed water concentration on the Arrhenius activation energy was also investigated to evaluate the mass transfer through the membrane under other operating conditions, like higher temperatures and lower feed water concentrations. Simulation results confirmed that optimizing the operating temperature, the new membrane exhibits outstanding separation performance for drying ethanol below 500 ppm of water. Lastly, the ethanol drying process using the PERVAP™ membranes is compared with a molecular sieve system. Although the new membrane can easily dry ethanol below 500 ppm of water, a hybrid system consisting of pervaporation followed by molecular sieves leads to an interesting process solution, e.g., for a feed flow of 1000 kg/h, the required membrane area and the quantity of molecular sieves can be reduced from 650 m2 to 250 m2 (2.6 times less), and from 2252 kg to 204 kg (11 times less), respectively. Therefore, the ethanol drying process can be greatly optimized in terms of capital costs and energy when using a hybrid system instead of using pervaporation or molecular sieve system alone.

Modified PVA membrane for separation of micro-emulsion

Release of liquefied hydrocarbons in domestic and industrial effluents, along with oil spills cause significant adverse effects on the soil, water, aquatic ecosystem, and humans. Thus, selective and cost-effective technology to address this challenge is highly desirable. Here, we report the fabrication of electrospun polyvinyl alcohol (PVA) membrane, modified with glutaraldehyde (GA) and a device thereof, for treatment of oil emulsions and recovery of precious fossil fuel. The modified PVA membranes are super-oleophobic with a high static underwater oil contact angle of 163 ± 3° for motor oil. Investigation of wetting properties suggests that the membrane can efficiently separate different oils such as sesame oil, motor oil, mustard oil, and sunflower oil from their emulsions. The motor oil emulsion with separation efficiency of >99% at an excellent permeate flux of 5128 L/m2·h·bar has been achieved. Thus, the prepared modified PVA membrane construes an easy solution for not only effective treatment of oily wastewater but also for oil recovery with high flux.

Optimizing Effective Parameters to Enhance the Sensitivity of Vertical Flow Assay for Detection of Escherichia coli.

Vertical flow immunoassays (VFIAs) are considered potential point-of-care testing (POCT) devices compared to lateral flow assays due to their ability to analyze a comparatively large sample volume and ease of multiplexing. However, VFIA devices are limited by low analytical sensitivity when coupled with a visual colorimetric signal. Herein, we carefully analyzed key parameters that accounted for the proper functionality of VFIA that can be modified to enhance the overall sensitivity of VFIA. In particular, we focused on improving the stability of conjugate pads impregnated with capture antibodies, maintaining a controlled flow rate to ensure higher analyte reactivity with capture antibodies, and enhancing the absorption efficiency. The results showed that air-drying of conjugate pads in the presence of 5% (w/v) lactose significantly improved the stability of antibodies during long-term storage. Integration of dissolvable polyvinyl alcohol (PVA) membrane of optimal concentration as a time-barrier film into the sensor delayed the flow of samples, thereby increasing the biorecognition interaction time between immunoreagents for the formation of immuno-complexes, which in turn led to higher sensitivity of the assay. Furthermore, the employment of an absorbent pad with higher water holding capacity significantly reduced the non-specific binding of immunocomplexes, thereby reducing the possibility of false-negative results.