Blend Membranes Research Articles

Development of MoS2/O-MWCNTs/PES blended membrane for efficient removal of dyes, antibiotic, and protein

In this work, a nanocomposite of MoS2 nanosheets and oxidized multi-walled carbon nanotubes (O-MWCNTs) was prepared using the hydrothermal method. The successful synthesis of the MoS2/O-MWCNTs nanocomposite was further confirmed using a scanning electron microscope (SEM), energy dispersive X-Ray dot mapping, and X-ray diffraction analysis. The synthesized nanocomposite was used as a nanoadditive for the improvement of polyethersulfone (PES) polymeric membrane. The phase inversion route was used to prepare MoS2/O-MWCNTs blended membranes containing different amounts of nanocomposite (0–1 wt%). The morphology of the prepared membranes was studied using SEM and atomic force microscopy techniques. Asymmetric structure with small pores at the top layer and well-developed large finger-like pores and macro voids at the sublayer can be observed in fabricated membranes. The hydrophilicity enhancement of the PES membrane in the existence of nanocomposite was verified by the contact angle test. The modified membrane containing 0.75 wt% of MoS2/O-MWCNTs exhibited improved permeability of 64.1 L/m2 h bar, and high pollutants removal of 93.5% for reactive blue 19, 97.5% for rifampicin, 98.4% for reactive red 195, and 99% for bovine serum albumin, with enhanced flux recovery ratio of 60.8%. Moreover, the stability of the blended membrane in the long-time operation makes it a promising candidate to be applied in the treatment of textile and industrial wastewaters.

Effect of Polyphenylsulfone and Polysulfone Incompatibility on the Structure and Performance of Blend Membranes for Ultrafiltration.

This study deals with the modification of polyphenylsulfone ultrafiltration membranes by introduction of an incompatible polymer polysulfone to the polyphenylsulfone casting solution to improve the permeability. The correlation between properties of the blend polyphenylsulfone/polysulfone solutions and porous anisotropic membranes for ultrafiltration prepared from these solutions was revealed. The blend polyphenylsulfone/polysulfone solutions were investigated using a turbidity spectrum method, optical microscopy and measurements of dynamic viscosity and turbidity. The structure of the prepared blend flat sheet membranes was studied using scanning electron microscopy. Membrane separation performance was investigated in the process of ultrafiltration of human serum albumin buffered solutions. It was found that with the introduction of polysulfone to the polyphenylsulfone casting solution in N-methyl-2-pyrrolidone the size of supramolecular particles significantly increases with the maximum at (40–60):(60:40) polyphenylsulfone:polysulfone blend ratio from 76 nm to 196–354 nm. It was shown that polyphenylsulfone/polysulfone blend solutions, unlike the solutions of pristine polymers, are two-phase systems (emulsions) with the maximum droplet size and highest degree of polydispersity at polyphenylsulfone/polysulfone blend ratios (30–60):(70–40). Pure water flux of the blend membranes passes through a maximum in the region of the most heterogeneous structure of the casting solution, which is associated with the imposition of a polymer-polymer phase separation on the non-solvent induced phase separation upon membrane preparation. The application of polyphenylsulfone/polysulfone blends as membrane-forming polymers and polyethylene glycol (Mn = 400 g·mol−1) as a pore-forming agent to the casting solutions yields the formation of ultrafiltration membranes with high membrane pure water flux (270 L·m−2·h−1 at 0.1MPa) and human serum albumin rejection of 85%.

Influence of chemistry and fiber diameter of electrospun PLA, PCL and their blend membranes, intended as cell supports, on their biological behavior

The prevalence of osteoarthritis, a degenerative cartilage disease that causes joint surface erosion and loss of mobility, emphasizes the need of producing a functional articular cartilage replacement. Tissue engineering has been the focus of recent research as a possible strategy for cartilage regeneration and repair. The most widely used technique for the manufacture of nanofibers is polymer electrospinning. Polylactic acid (PLA) and polycaprolactone (PCL) have been proved particularly suitable for nanofiber preparation, with many biomedical applications. The main aim of this work was to evaluate the behavior of adipose tissue-derived mesenchymal stem cells (ASCs) cultured on biomaterials of PLA, PCL and a combination of both (PLA/PCL), manufactured by electrospinning. We analyzed the bioactive properties of these cells in cultures on them, in terms of proliferation, adhesion, morphology, viability and differentiation. In addition, the influence of the thickness of the fibers in each biomaterial on these cellular characteristics was evaluated for their use in Cartilage Regenerative Medicine applications to promote chondrogenic differentiation. Depending on the parameter assessed, different results were obtained on each biomaterial. Using both polymers successful results on cellular viability were obtained, although in the case of PCL the cellular response in all the experiments was significantly better. As for the blends, positive outcomes were obtained, but they did not overtake the characteristics of PCL. Interestingly, ASCs were able to differentiate into chondrocytes without adding specific chondrogenic media in the three biomaterials tested. Moreover, a marked cell differentiation on PCL with 1.8 μm-fiber diameter and PLA/PCL blends was observed. These findings may play a key role in cartilage Regenerative Medicine and Tissue Engineering.

Effect of pore-forming/hydrophilic additive anchorage on the mesoporous structure and sieving performance of a blended ultrafiltration (UF) membrane

Pore forming agent or hydrophilic additives are necessary for the optimization of membrane pore structure and surface physicochemical properties. Although it has been demonstrated that the blending additives tends to locate around membrane pore walls due to segregation and this would further leach out in practical operations, the impact of additives fate on membrane pore structure as well as sieving performance is almost overlooked in literatures. In this study, five kinds of Pluronic copolymers with different molecular architectures were employed for casting PSF UF membranes, and the fate of these copolymers in membrane matrix was explored by combing FTIR and XPS spectra with TG analysis. More importantly, the evolutions of membrane mean pore radius (r*) and radius distribution (σ) after additive leaching were quantitatively investigated based on the modified Steric Pore Model (SPM). In passive solute sieving experiments, the increment of r* and σ possessed positive correlation with the degree of polymerization (DP) of EO segments within the corresponding additive. The results of thermoporosimetry and saline filtration experiments further evidenced that such a correlation should be attributed not only to the steric hindrance of EO segment, but also to its hydration ability. Moreover, the intrinsic polymer geometry (rST) was also a crucial factor for understanding the evolutions of membrane pore structure during additive leaching. Especially for membranes having small rST, both the isopropanol (IPA) treatment and poly-dopamine (PDA) decoration experiments suggested that pore enlargement and the generation of new small cavities would occur simultaneously during additive leaching, making the prediction complicated. Finally, we proposed that the relative synthetic aperture (RSA) could serve as a complementary indicator for understanding and describing the pore enlargement behavior of a blended UF membrane. In an industrial point of view, it also offers a new way to evaluate and predict the long-term performance and stability of a blending modified porous membrane.

High Performance of Anion Exchange Blend Membranes Based on Novel Phosphonium Cation Polymers for All-Vanadium Redox Flow Battery Applications.

The deployment of alkaline anion exchange membranes (AEMs) in flow battery applications has the advantage of a low cationic species crossover rate. However, the alkaline stability conjugated to the low conductivity of hydroxide ions of anion exchange membranes (AEMs) still represents a major drawback for the large deployment of such technology. In this study, three types of tetraarylpolyphosphonium (pTAP)-based copolymers (namely, CP1, CP2, and CP3) are synthesized and blended with chitosan and polyvinylidene fluoride (PVDF) for the fabrication of AEMs. Chitosan, a green biopolymer, was employed as a blend to enhance the water uptake of the base ionomer matrix. It is proposed that the abundancy of hydroxyl groups in chitosan improves considerably the ionic conductivity, water transport, and ion selectivity of the membrane, together with facilitating the dispersion of the chitosan in the pTAP copolymer matrix. The purpose of blending PVDF is instead to provide stable mechanical strength to the composite blend. The chemical, mechanical, and thermal stabilities of the three fabricated composite-blend membranes (i.e., CM1, CM2, and CM3) were characterized. All the membranes exhibited a high water retaining capacity of up to 36.26% (recorded for CM2) along with a hydroxyl ion conductivity of 17.39 mS cm-1. Due to the strong interactions between pTAP copolymers, chitosan, and PVDF polymers (confirmed also by Fourier transform infrared spectroscopy), the studied anion exchange membranes are able to retain up to 97% of the original OH conductivity after 1 M KOH treatment at room temperature for 100 h. The three membranes, namely, CM1, CM2, and CM3, have vanadium ion permeabilities measured at 20 °C of 1.775 × 10-8, 1.718 × 10-8, and 1.648 × 10-8 cm2/s, respectively, which are lower than that for the commercially available Nafion. The good stability and remarkable cell performance of the composite-blend membranes reported here make them definitely excellent candidates for the future generation of vanadium redox flow batteries.

Fungal-derived carboxymethyl chitosan blended with polyvinyl alcohol as membranes for wound dressings

Multifunctional blend membranes composed of poly (vinyl alcohol) (PVA) and fungal mushroom-derived carboxymethyl chitosan (F-CMCS) were produced using a simple solution casting technique for wound dressing applications. The structural interactions between PVA and F-CMCS were confirmed by Fourier infrared spectroscopy. The crystallinity of the membranes was examined by X-ray diffraction. Field emission scanning electron microscopy confirmed the homogeneity and coarser texture with a porous-like network in the internal structure of the membranes. The hydrophilicity, swelling, and degradation of the fabricated membranes were examined according to the F-CMCS content. The PVA/F-CMCS membrane displayed potential antibacterial activity against Escherichia coli (gram-negative) and Staphylococcus (gram-positive) bacteria. An in vitro cell study of skin fibroblasts and keratinocytes on the PVA/F-CMCS membranes confirmed the biocompatibility. The hemolysis assay demonstrated the hemocompatibility of the developed membranes. The antibacterial, biocompatibility, and good hemolysis in the PVA membrane were influenced by the F-CMCS composition ratio up to 40%. The all-inclusive properties of the PVA/F-CMCS membranes highlight its potential use in wound dressing applications.

Effects of additive dosage and coagulation bath pH on amphoteric fluorocarbon special surfactant (FS-50) blend PVDF membranes

Amphiphilic copolymers containing hydrophilic and hydrophobic blocks represented by surfactants have proven to be more effective for modifying membranes than hydrophilic copolymers. However, studies on the effects of additive and coagulation bath pH on the morphology and properties of surfactant-modified membranes have rarely been reported. Hence, this study aims to investigate the effects of the additive dosage and the coagulation bath pH on the mechanisms of phase inversion and performance improvement of amphoteric fluorocarbon special surfactant (FS-50) blended PVDF membranes. It was observed that the pure water flux increased from 114.68 LMH/bar of the original membrane M0 to 205.02 LMH/bar of the blend membrane M1, and then to 615.88 LMH/bar of the coagulation-bath-regulated membrane MPH9 with a high BSA rejection rate of 90.86%, showing a two-stage jump. The addition of FS-50 promoted the instantaneous phase inversion of the membrane, allowing the blend membrane to exhibit a higher proportion of pore characteristics and stronger permeability. After that, the mechanisms of the membrane phase inversion process affected by the coagulation bath pH were interpreted according to the pH-response characteristics of FS-50 in terms of charge repulsion effect and compressed double-electron layer effect. Furthermore, the cross-sectional morphology and the surface structure of the membrane prepared in acidic and alkaline coagulation baths were significantly affected by the pH of the coagulation bath, exhibiting different features. For one, the porosity of the membranes gradually decreased as the acidity and alkalinity of the coagulation bath increased, and the membrane MPH9 exhibited both maximum surface and overall porosity. For another, the coagulation bath pH did not negatively affect the contact angle, surface roughness and tensile strength of the membranes. Overall, adjusting the dosage of FS-50 and the pH of the coagulation bath is a promising approach to greatly enhance membrane performance.

Efficient Fenton-Like Catalysis Boosting the Antifouling Performance of the Heterostructured Membranes Fabricated via Vapor-Induced Phase Separation and In Situ Mineralization.

A photocatalytic membrane with significant degradation and antifouling performance has become an important part in wastewater treatment. However, the low catalyst loading on the polymer membrane limits its performance improvement. Herein, we fabricated poly(vinylidene fluoride) (PVDF) and poly(acrylic acid) (PAA) blend membranes with a rough surface via a vapor-induced phase separation (VIPS) process. Then Fe3+ was cross-linked with the carboxyl groups on the membrane surface and further in situ mineralized into β-FeOOH nanorods. The resultant membranes exhibit not only hydrophilicity and underwater superoleophobicity but also favorable separation efficiency and high water flux in oil-in-water emulsions separation. Under visible light irradiation, the membrane can degrade methylene blue (MB) to 95.2% in 180 min. More importantly, the membrane has a significant photocatalytic self-cleaning ability for crude oil with a flux recovery ratio (FRR) as high as 94.1%. This work brings a new strategy to fabricate the rough and porous surface for high loading of the hydrophilic photo-Fenton catalyst, improving the oil/water emulsion separation and antifouling performance of the membranes.

Permselectivity improvement of PEBAX® 2533 membrane by addition of glassy polymers (Matrimid® and polystyrene) for CO2/N2 separation

AbstractTwo series of novel blend membranes based on poly(ether‐block‐amide) (PEBAX® 2533) and 5 and 10 wt% of two glassy polymers (Matrimid® and polystyrene [PS]) were prepared using a new mixed solvent with a low boiling point for CO2/N2 separation. Fourier‐transform infrared spectroscopy, field emission scanning electron microscopy, and X‐ray diffraction analyses were used to characterize the samples. A decrease in membrane crystallinity was observed by the addition of glassy polymers. The gas permeability measurements were performed to obtain CO2/N2 permselectivity of membranes. The maximum performance was found for the membrane with 5 wt% Matrimid content, for which CO2 permeability and CO2/N2 selectivity increased by 21% and 76%, respectively. Three permeation models were used to predict the CO2 permeability of blend membranes. The Maxwell model showed acceptable coincidence with the experimental data at 5 wt% content of the glassy polymer. For 10 wt% content of glassy polymer, the Lewis‐Neilson model showed the most accurate predictions for CO2 permeability. A method for quantitative comparison of membrane performance was also proposed by defining the geometric closeness to the Robson upper bound limit. Finally, it was found that an increase in the feed pressure improved the membrane performance at high pressures.

Novel Cellulose Triacetate (CTA)/Cellulose Diacetate (CDA) Blend Membranes Enhanced by Amine Functionalized ZIF-8 for CO2 Separation.

Currently, cellulose acetate (CA) membranes dominate membrane-based CO2 separation for natural gas purification due to their economical and green nature. However, their lower CO2 permeability and ease of plasticization are the drawbacks. To overcome these weaknesses, we have developed high-performance mixed matrix membranes (MMMs) consisting of cellulose triacetate (CTA), cellulose diacetate (CDA), and amine functionalized zeolitic imidazolate frameworks (NH2-ZIF-8) for CO2 separation. The NH2-ZIF-8 was chosen as a filler because (1) its pore size is between the kinetic diameters of CO2 and CH4 and (2) the NH2 groups attached on the surface of NH2-ZIF-8 have good affinity with CO2 molecules. The incorporation of NH2-ZIF-8 in the CTA/CDA blend matrix improved both the gas separation performance and plasticization resistance. The optimized membrane containing 15 wt.% of NH2-ZIF-8 had a CO2 permeability of 11.33 Barrer at 35 °C under the trans-membrane pressure of 5 bar. This is 2-fold higher than the pristine membrane, while showing a superior CO2/CH4 selectivity of 33. In addition, the former had 106% higher CO2 plasticization resistance of up to about 21 bar and an impressive mixed gas CO2/CH4 selectivity of about 40. Therefore, the newly fabricated MMMs based on the CTA/CDA blend may have great potential for CO2 separation in the natural gas industry.

Potential Evaluation of PVDF/PAN Membranes for Separation of Oil from Industrial Waste

Aim: The aim of the experiment is to characterize the Modified Membrane from PVDF/PAN and its application in removing the Emulsified oil waste from the Industry. Objective: To get the maximum separation of the emulsified oil from the waste water, composite (PVDF/PAN) membrane was prepared in the laboratory. Methods: New PVDF/PAN blend based ultrafiltration membranes were synthesized by phase inversion method. The blend membrane was treated at room temperature with aqueous sodium hydroxide solutions. Results: The facile eco-friendly preparation of PVDF/PAN blended membrane has a wide potential for practical applications in emulsified wastewater remediation. The chemical functionality of the modified membranes was confirmed by IR spectra. Conclusion: For the separation of emulsified oily wastewater, the as-prepared composite (PVDF/PAN) membrane could effectively separate oil/ water emulsions with separation efficiency of above 99.8%. Unmodified membranes (A and B) showed 95.4-99.8% rejection. However, in the case of membranes C and D, oil rejection was higher for the modified membranes as compared to the unmodified membranes.

Design and fabrication of high performance membrane for carbon dioxide separation via blending poly(ethylene oxide-b-amid 6) with dense, glassy and highly CO2-philic amidoximated polymers

Blend membranes based on the poly(ethylene oxide-b-amid 6) (Pebax 1657) block copolymer and carbon dioxide (CO2)-philic glassy polymers including polyacrylonitrile (PAN), acrylonitrile/ vinylimidazole copolymer (P(AN-co-VIm)) or corresponding amidoximated derivatives, i.e. P(AO-AN) and P(AO-AN-co-VIm), as additive were prepared using solution casting method. To increase CO2-philic groups, acrylonitrile- based polymers were amidoximated via reacting with hydroxyl ammonium chloride (NH2OH.HCl) reagent where amidoximation process was evaluated by FTIR and 1H NMR. Compatibility and morphology of components in the blend membranes and blend density were examined by ATR-IR and DSC, FE-SEM and densitometry tests, respectively. Shifting of the peaks in the ATR-IR spectra showed that the Pebax 1657 chains establish a hydrogen bonding with the homo- or copolymer chains. The crystallinity and melting temperature (Tm) of polyamide (PA) domains in the Pebax 1657 decreased by increasing the amount of acrylonitrile- based polymers and their amidoximated derivatives. Also, the glass transition temperature (Tg) of the polyethylene oxide (PEO) domains increased due to the glassy nature of the additives. FE-SEM results indicated that all membranes are dense and there is a good interaction between the Pebax and the additives. The dense structure and free volume reduction in the membranes were confirmed by increasing membrane density resulting from increase in the amount of acrylonitrile- based polymer and amidoximated derivatives. The permeability of CO2, nitrogen (N2) and methane (CH4) gases from pure and blend membranes was measured by constant pressure/ variable volume method at 3 bar and ambient temperature. By increasing the amount of acrylonitrile- based polymers, i.e. PAN and P(AN-co-VIm), up to 20 wt%, the permeability of CH4, N2 and CO2 increased and then decreased with further increasing of the additive content. In blend membranes containing amidoximated polymers, i.e. (P(AO-AN) and P(AO-AN-co-VIm)), CO2 permeability and of CO2/N2 and CO2/CH4 selectivity showed an increased trend up to 60%wt additive due to increased number and type of nitrogen atoms in the membrane structure. Compared to the pure Pebax 1657, CO2 permeability and CO2/N2 and CO2/CH4 selectivity in blend membrane containing 40 wt% of P(AO-AN-co-VIm) copolymer increased by 193%, 497% and 495%, respectively.

Synthesis and characterization of tailor‐made N‐vinylpyrrolidone copolymers and their blend membranes with polyvinyl alcohol for bioethanol dehydration by pervaporation

AbstractTailor‐made poly(N‐vinylpyrrolidone‐co‐(2‐[dimethylamino]ethyl methacrylate)) P(NVP‐co‐DMAEMA) and poly(N‐vinylpyrrolidone‐co‐N‐vinylimidazole) P(NVP‐co‐PNVIm) with defined monomer molar ratio are synthesized via free radical polymerization. The random copolymers are fully characterized and then blended with polyvinyl alcohol (PVA) to investigate their chemical and thermal properties as membrane materials. Composite membranes are further prepared from the PVA/copolymer blends on a porous support, which are evaluated in terms of separation performance for the dehydration of ethanol by pervaporation. The membranes prepared from the blends exhibit up to four times higher water permeances than pristine PVA membrane, albeit the selectivity is slightly lower. Nevertheless, the membranes from blends with a ratio of 95:5 (PVA/copolymer) show improved selectivity and higher permeance values compared to the commercial PERVAP™ 4155–80, especially the blends composed by the copolymers of coPDMAEMA60 and coPDMAEMA20. The membrane prepared from the blend containing the homopolymer coPDMAEMA100 exhibits the highest water/ethanol selectivity and shows stable separation performance throughout the whole long‐term stability test. Thus, this study demonstrated that by synthesizing tailored copolymers (rather using the commercial ones) and blending with PVA, the separation performance of membranes can be significantly improved and tuned for specific dehydration processes.

Development and Characterization of Biocompatible Membranes from Natural Chitosan and Gelatin for Pervaporative Separation of Water-Isopropanol Mixture.

Natural polymers have attracted a lot of interest in researchers of late as they are environmentally friendly, biocompatible, and possess excellent characters. Membranes forming natural polymers have provided a whole new dimension to the separation technology. In this work, chitosan-gelatin blend membranes were fabricated using chitosan as the base and varying the amount of gelatin. Transport, mechanical, and surface characteristics of the fabricated membranes were examined in detail by means of the characterizing techniques such as Fourier transform infrared spectroscopy, differential scanning colorimetry, wide angle X-ray diffraction, scanning electron microscope, and thermogravimetric analysis. In order to analyze the water affinity of the developed blend chitosan-gelatin membranes, the percentage degree of swelling was examined. Out of the fabricated membranes, the membrane loaded with 15 mass% of gelatin exhibited the better pervaporation performance with a pervaporation separation index value of 266 at 30 °C for the solution containing 10% in terms of the mass of water, which is the highest among the contemporary membranes. All the fabricated membranes were stable during the pervaporation experiments, and permeation flux of water for the fabricated membranes was dominant in the overall total permeation flux, signifying that the developed membranes could be chosen for efficient separation of water–isopropanol mixture on a larger scale.

Blended Anion Exchange Membranes for Vanadium Redox Flow Batteries.

In this study, blended anion exchange membranes were prepared using polyphenylene oxide containing quaternary ammonium groups and polyvinylidene fluoride. A polyvinylidene fluoride with high hydrophobicity was blended in to lower the vanadium ion permeability, which increased when the hydrophilicity increased. At the same time, the dimensional stability also improved due to the excellent physical properties of polyvinylidene fluoride. Subsequently, permeation of the vanadium ions was prevented due to the positive charge of the anion exchange membrane, and thus the permeability was relatively lower than that of a commercial proton exchange membrane. Due to the above properties, the self-discharge of the blended anion exchange membrane (30.1 h for QA–PPO/PVDF(2/8)) was also lower than that of the commercial proton exchange membrane (27.9 h for Nafion), and it was confirmed that it was an applicable candidate for vanadium redox flow batteries.

Molecular design and fabrication of PIM-1/polyphosphazene blend membranes with high performance for CO2/N2 separation

New polymeric blend membranes for CO2 separation were synthesized based on insights from molecular dynamics simulation. A molecular-level structure-property relationship in polymers of intrinsic microporosity (PIM) based blend membranes was investigated in detail computationally. Calculated local density profiles and energy of interaction of the blend membranes, composed of PIM-1 and various polyphosphazenes, showed that using the polyphosphazene with a higher concentration of ether side chains can improve the compatibility with PIM-1. Based on the findings of computational studies, blend membranes were experimentally fabricated from PIM-1 and polyphosphazenes with various polyether side chain concentrations. Polyether concentration in polyphosphazenes was correlated with the film properties and gas transport performance of the blend membranes. Blend membranes showed very high CO2 permeability (3100-5300barrer) and improved CO2/N2 selectivity (24–28), outperforming all other PIM-based blend membranes reported to date. Moreover, the CO2 permeability performance of the blend membranes was tested 566 h under real post-combustion flue gas from a coal-fired power plant, including CO2, N2, H2O, O2, SOx and NOx.

Highly Conductive Polyelectrolyte Membranes Poly(vinyl alcohol)/Poly(2-acrylamido-2-methyl propane sulfonic acid) (PVA/PAMPS) for Fuel Cell Application.

In this study, chemically cross-linked PVA/PAMPS membranes have been prepared to be used in direct methanol fuel cells (DMFCs). The structural properties of the resultant membrane were characterized by use FTIR and SEM. Additionally, their thermal stability was assessed using TGA. Moreover, the mechanical properties and methanol and water uptake of membrane was studied. The obtained FTIR of PVA/PAMPS membranes revealed a noticeable increase in the intensity of adsorption peaks appearing at 1062 and 1220 cm−1, which correspond to sulfonic groups with the increasing proportion of PAMPS. The thermograms of these polyelectrolyte membranes showed that their thermal stability was lower than that of PVA membrane, and total weight loss gradually decreased with increasing the PAMPS. Additionally, the functional properties and efficiency of these polyelectrolyte membranes were significantly improved with increasing PAMPS proportion in these blends. The IEC of polymer blend membrane prepared using PVA/PAMPS ratio of 1:1 was 2.64 meq/g. The same membrane recorded also a methanol permeability coefficient of 2.5 × 10−8 cm2/s and thus, its efficiency factor was 4 × 105 greater than that previously reported for the commercial polyelectrolyte membrane, Nafion® (2.6 × 105). No significant increase in this efficiency factor was observed with a further amount of PAMPS. These results proved that the PVA:PAMPS ratio of 1:1 represents the optimum mass ratio to develop the cost-effective and efficient PVA/PAMPS blend membranes for DMFCs applications.

Effect of alumina nanoparticles on the antifouling properties of polycarbonate‐polyurethane blend ultrafiltration membrane for water treatment

AbstractIn this work, the flexibility of polycarbonate (PC) membrane was improved by using polyurethane (PU) additive. However, due to the hydrophobic nature of the PU polymer, alumina (Al2O3) nanoparticles were incorporated to PC‐PU blend membrane. The prepared membranes have been used in a submerged membrane system to eliminate humic acid molecules from polluted water in both the presence and absence of coagulant (polyaluminum chloride). The obtained results showed that introduction of PU into PC membrane diminished hydrophilicity and enhanced porosity. Moreover, the flexibility of the PC membrane remarkably improved. Introduction of 1.5 wt% Al2O3 to the PC‐PU blend membrane led to enhancement in both porosity and hydrophilicity. Results of morphological studies showed that in the presence of Al2O3 nanostructures, finger‐shaped voids seemed to elongate across the entire thickness of the prepared membrane. Atomic force microscopy images showed that incorporation of PU and Al2O3 to the PC membrane resulted in a smoother surface. The antifouling performance of membranes revealed that the PC‐PU/Al2O3 nanocomposite membrane possessed the most favorable antifouling features owing to its lowest surface roughness as well as highest hydrophilicity. For all membranes utilizing coagulant (PAC), the irreversible fouling ratio and the flux recovery ratio significantly diminished and increased, respectively.

Synthesis and Characterization of Proton Conducting Polymer Electrolytes based on Poly (N-vinyl pyrrolidone) and Polyvinylchloride

Poly (N-vinyl pyrrolidone) (PVP), Polyvinylchloride (PVC) blend membrane doped with different molar weight percentage of NH4Br has been prepared by solution casting technique using dimethyleformamide (DMF) as solvent and characterized for electrical properties. The prepared polymer electrolyte has been studied by XRD, FT-IR, Dielectric and Capacitance measurements. The XRD results show that the amorphous nature of PVP has increased in 70%PVP: 30%PVC. It is also observed that the amorphous nature of 70%PVP: 30%PVC is further increased by the addition of different concentration of NH4Br. A complex formation of PVP: PVC, PVP: PVC: NH4Br have been confirmed by FT-IR studies. Proton conductivity for the above film has been measured using impedance spectroscopy. The polymer blends 70%PVP: 30%PVC shows an ionic conductivity of 8.46X10-8 Scm-1. The conductivity of the blend film increases as concentration of NH4Br increases. The maximum proton conductivity 2.78X10-3 Scm-1 has been observed for 70%PVP: 30%PVC: 0.6 Molar weights (MWt) NH4Br. The primary proton battery with configuration of Zn + ZnSO4.7H2O/70PVP:30PVC: 0.6 Mwt% NH4Br/PbO2 + V2O5 are fabricated and tested.

Preparation of butadiene-bridged polymethylsiloxane (BBPMS)/ethyl cellulose (EC) hybrid membranes for gas separation

Hybrid membranes containing different loadings of butadiene-bridged polymethylsiloxane (BBPMS) in ethyl cellulose (EC) were prepared by an one-pot blending method from a non-isolated solution of polymethylhydrosiloxane (PMHS) reaction with butadiene, and a solution of EC in THF. The semi-crosslinked BBPMS and the BBPMS/EC hybrid membranes having good compatibility were characterized by Fourier transfer infrared (FTIR) and Scanning electron microscopy (SEM). The BBPMS/EC hybrid membranes exhibited good membrane forming ability, heat resistance and mechanical properties. It was worth mentioning that the BBPMS/EC blended membranes exhibit good selectivity for CO2/N2 and O2/N2. Specifically, the blended membrane (BBPMS/EC-5:5) showed the highest ideal selectivities for CO2/N2 and O2/N2 were 25.5 (at a CO2 permeability of 175 Barrer) and 4.85 (at a O2 permeability of 33.2 Barrer), respectively. Compared to the pure EC membrane, the ideal CO2/N4 selectivity and the ideal O2/N2 selectivity of the blended membrane (BBPMS/EC-5:5) were increased by 41.8% and 53.0%, respectively. The modification strategy using semi-crosslinked polysiloxanes to enhance gas transfer of EC is promising for fabrication of high performance CO2 and O2 separation membranes.