Blend Membranes Research Articles

(Invited, Digital Presentation) Polybenzimidazole and Its Use in Energy Storage and Conversion

Polybenzimidazole (PBI) is a unique polymer. It has high mechanical strength and stability, and is not conductive. However, in contact with acids, the imidazole rings are protonated, and PBI becomes proton conductive. In contact with alkaline solutions, the amine groups are deprotonated, and PBI becomes hydroxide conductive. Control of the doping process allows to adjust the uptake and hence allows to control conductivity and permeability of PBI membranes. Therefore, PBI can be used in various ways for several applications. Phosphoric acid doped PBI blends were tested in the HT PEMFC, and showed more than >2000 hours stable, high performance operation at very challenging high current density of 800 mA/cm2 (one of world-best results).[1] Sulfuric acid doped PBI membranes were developed for use in the vanadium redox flow battery. We show that stable performances with an energy efficiency >91% and coulomb efficiency >99% @ 80 mA/cm2 can be achieved, which is one of the highest reported performances.[2, 3] By using a newly developed membrane fabrication process, hydroxide conducting membranes with a conductivity of > 310 mS/cm2 were be obtained. Porous supports enhanced the mechanical stability of these membranes, and PEM-water electrolyser-like performance was achieved in an alkaline water electrolyser, which was successfully operated for 1000 hours without failure.[4] A common way to increase the mechanical stability of membranes is reinforcement with a porous support. The drawback is that different swelling ratios of matrix and support can form voids, which results in unacceptably high gas crossover in electrolyzers and fuel cells. To tackle this issue, we pore filled an electrospun PBI fiber mat with a bomoalkylated polymer and reacted it with the imidazole groups available on the PBI fiber surface, thus forming a covalently bonded interface. In a final step, the remaining bromoalkyl groups were quaternized. The membrane was tested for 200 hours in an electrolyzer, and showed no signs of degradation. [5] [1] N. Nambi Krishnan, N.M.H. Duong, A. Konovalova, J.H. Jang, H.S. Park, H.J. Kim, A. Roznowska, A. Michalak, D. Henkensmeier, Polybenzimidazole / tetrazole-modified poly(arylene ether) blend membranes for high temperature proton exchange membrane fuel cells, J. Membr. Sci., 2020, 614, 118494. https://doi.org/10.1016/j.memsci.2020.118494[2] C. Noh, D. Serhiichuk, M. Najibah, Y. Kwon, D. Henkensmeier, Optimizing the performance of meta-polybenzimidazole membranes in vanadium redox flow batteries by adding an alkaline pre-swelling step, Chem. Eng, J., 405 (2021) 126574. https://doi.org/10.1016/j.cej.2020.126574[3] unpublished results[4] under review[5] Malikah Najibah, E. Tsoy, H. Khalid, Y. Chen, Q. Li, C. Bae, J. Hnát, M. Plevová, K. Bouzek, J.H. Jang, H.S. Park, Dirk Henkensmeier, PBI nanofiber mat-reinforced anion exchange membranes with covalently linked interfaces for use in water electrolysers, J. Membr. Sci., 2021, 640, 119832. https://doi.org/10.1016/j.memsci.2021.119832

Tuning the Intermolecular Interactions of Sulfonated Ionomer Via Polymer Blending

Morphology of proton exchange membranes defines the proton conductivity and the durability of the membranes. One cost-effective approach to manipulate the morphology of the sulfonated ionomers is via polymer blends. In this study, varying compositions of Penta Block Copolymers (PBC) with two different ion-exchange capacity (IEC) of 1.0 and 2.0 were blended with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) to create 2wt% homogenous solution-cast membranes in chloroform. Unmodified PPO membrane possessed higher thermal decomposition temperatures of 427.41°C, and unmodified PBC(1.0) and PBC(2.0) decomposed at 399.85 °C and 400.805 °C, respectively. Both PBC(1.0)-PPO and PBC(2.0)-PPO blend membranes exhibited a similar trend for the changes in decomposition temperature with composition. As the PPO blend ratio increased, the decomposition temperature of PBC(1.0)-PPO and PBC(2.0)-PPO increased by 6.5% and 6.6%, respectively. These changes may be attributed to the increase in thermal stabilities due to PPO’s inherently high glass transition temperature. Water Uptake (WU) studies revealed that PBC(1.0) and PBC(2.0) membranes blended with PPO have reduced WU% as the PPO blend ratio increases. Unmodified PPO is highly hydrophobic and has a WU of 1.52%, while unmodified PBC(1.0) and PBC(2.0) portrayed WU of 14.44% and 74.5%, respectively. When hydrophobic PPO blends with the hydrophilic sulfonated ionomers, the ionic channels are hindered, lowering the WU%. For instance, WU of PBC (1.0)-PPO blend in the ratio of 50:50 is halved compared to PBC (1.0)-PPO blend of 90:10 ratio. Similarly, WU of PBC (2.0)-PPO blend in the ratio of 50:50 is lowered by 72.25% compared to PBC (2.0)-PPO blend of 90:10 ratio. In conclusion, the study shows that polymer blending significantly alters the membrane’s intermolecular interactions and changes the membrane’s durability and water uptake. The impact is more evident as the IEC of the sulfonated ionomers is increased. Proton conductivity studies and morphological transitions will be incorporated in future investigations. Figure 1

Novel Anion-Exchange Blend Membranes Comprised of a Commercially Available & Water-Soluble Ionomer for All-Vanadium Redox Flow Batteries

The All-Vanadium Redox Flow Battery is a promising technology for solving the problem of cost-efficient and safe large-scale storage of renewable energies [1]. One key component of the batteries, which alters the performance and long-term stability of those systems, is the membrane. For this purpose, Nafion based membranes are often used. However, these membranes are high in cost and show a significant capacity fading and reduction of coulombic efficiency mainly due to crossover of vanadium species [2]. One way around this is to use commercially available, low-cost materials with positively charged ammonium groups, which can effectively repel positively charged vanadium species due to the Donnan exclusion effect [3, 4].In this work we present novel anion-exchange blend membranes comprised of a commercially available and water-soluble ionomer and a PBI blend matrix, which can be used in All-Vanadium Redox Flow batteries. For this approach the water-soluble ionomer was modified to achieve solubility in organic solvents and miscibility with the matrix polymer. The resulting membranes show good mechanical properties even at high IECs and can be modified in a wide range of properties by adjusting the amounts of ionomer and matrix polymer and/or by the addition of crosslinking agents.The above-mentioned membranes were characterised ex-situ by using EIS, NMR spectroscopy, IR spectroscopy, DMA, TGA, tensile tests and permeability tests. In addition, first promising in-situ characterisations were performed in a VRFB single-cell test station.Literature[1] Fan, X; Liu, B; Liu, J; Ding, J; Han, X; Deng, Y; Lv, X; Xie, Y; Chen, B; Hu, W; Zhong, C.: Battery Technologies for Grid-Level Large-Scale Electrical Energy Storage. Trans. Tianjin Univ. 2020, 92 – 103.[2] Düerkop, D; Widdecke, H; Schilde, C; Kunz, U; Schmiemann, A.: Polymer Membranes for All-Vanadium Redox Flow Batteries: A Review. Membranes 2021.[3] Xi, J; Wu, Z; Teng, X; Zhao, Y; Chen, L; Qiu, X.: Self-assembled polyelectrolyte multilayer modified Nafion membrane with suppressed vanadium ion crossover for vanadium redox flow batteries. J. Mater. Chem. 2008, 1232.[4] Mohammadi, T; Kazacos, M.: Modification of anion-exchange membranes for vanadium redox flow battery applications. Journal of Power Sources 1996, 179 – 186.

Molecular sieving through 'layer-by-layer' self-assembly of polyelectrolytes and highly crosslinked graphene oxide

Lack of access to potable water and abating levels of ground water level demands the reuse of unconventional water sources after remediating it in a sustainable way. In this context, purifying brackish, land and sea water seems a feasible solution to the ever-growing population.In this work, a novel composite membrane was fabricated by 'layer-by-layer' self-assembly of poly-dopamine (PDA) and polystyrene sulfonate (PSS) supported on a highly crosslinked graphene oxide (GO) membrane to sieve ions to purify contaminated water as well as enhance the resistance towards chlorine. This GO membrane was sandwiched between layers of various nanoporous polyvinylidene difluoride (PVDF) membranes obtained by selectively etching out the PMMA component from the demixed blends. The blend membranes were designed following the melt-extrusion process and subsequent quenching to facilitate confined crystallization of PVDF and selective etching of PMMA. The membranes with different pore sizes were tuned on varying the composition in blends and a gradient in microstructure was achieved by stitching the membranes. Pure water flux, salt rejection, dye removal, and antibacterial activity were performed to study the membrane's efficiency. The GO membrane was chemically crosslinked with methylenediamine to impart dimensional stability and to enhance rejection efficiency through the nanoslits that GO offers. Besides effective rejection, the sandwiched membrane was modified with ‘layer-by-layer’ self-assembly of polyelectrolytes on the surface to improve the chlorine tolerance performance. This strategy resulted in an excellent salt (about 95% and 97% for monovalent and divalent ion, respectively) and dye rejection (100% for both cationic and anionic dye), besides facilitating excellent chlorine tolerance performance. Moreover, this modified membrane showed superior antifouling properties (flux recovery ratio is more than 90%) and excellent antibacterial performance (near about 3 log reduction).Thus the concept of using layer-by-layer self-assembly of polycations (PDA) and polyanions (PSS) onto a hierarchical chemically modified GO sandwiched PVDF membrane proved to be a productive strategy to purify contaminated water. Thus the membrane can be a potential candidate for domestic as well as industrial application.

Fabrication of Rechargeable Photoactive Silk Fibroin/Polyvinyl Alcohol Blend Nanofibrous Membranes for Killing Bacteria.

Antibacterial materials that prevent bacterial infections and mitigate bacterial virulence have attracted great scientific interest. In recent decades, bactericidal polymers have been presented as promising candidates to combat bacterial pathogens. However, the preparation of such materials has proven to be extremely challenging. Herein, photoactive silk fibroin/polyvinyl alcohol blended nanofibrous membranes grafted with 3,3’,4,4’-benzophenone tetracarboxylic dianhydride (G-SF/PVA BNM) were fabricated by an electrospinning technique. The premise of this work is that the G-SF/PVA BNM can store photoactive activity under light irradiation and release reactive oxygen species for killing bacteria under dark conditions. The results showed that the resultant G-SF/PVA BNM exhibited the integrated properties of an ultrathin fiber diameter (298 nm), good mechanical properties, robust photoactive activity and photo-store capacity, and great photoinduced antibacterial activity against E. coli and S. aureus (99.999% bacterial reduction with 120 min). The successful construction of blended nanofibrous membranes gives a new possibility to the design of highly efficient antibacterial materials for public health protection.

Polyphenylsulfone/polyethylene glycol hexadecyl ether blend membranes with enhanced surface hydrophilicity for high-performance nanofiltration of dye solution

Polyphenylsulfone/polyethylene glycol hexadecyl ether blend membranes with enhanced surface hydrophilicity for high-performance nanofiltration of dye solution

Experimental Investigation of boron phosphate Incorporated speek/pvdf blend membrane for proton exchange membrane fuel cells

The recent studies focused on the blend membranes to a great extent due to their capability of gathering some important polymer characteristic features. In this survey, boron phosphate (BP) doped sulfonated poly (ether ether ketone)/Poly (vinylidene fluoride) (SPEEK/PVDF) blend membrane having high ionic conduction capability was synthesized. The boron phosphate doping to the membrane matrix enhanced the membrane properties in terms of proton exchange membrane conditions. The sol-gel and casting method was used to synthesise the SPEEK/PVDF blend membrane. The characterization tests to observe the structure of the membrane, such as X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), FT-IR and mechanical/thermal stability tests were conducted. The membrane ionic transportation and water retention were improved directly by the addition of boron phosphate. The highest power density (242 mW cm−2) and current density (400 mA cm−2) at 0.6 V were obtained by SPEEK/PVDF/10BP, respectively. Additionally, the proton conductivity value of 39 mS cm−1 was obtained for SPEEK/PVDF/10BP sample at 80 °C. The authors concluded that both boron phosphate additive and SPEEK/PVDF blend membrane have promising results for fuel cell future operations.

Ionomer Membranes Produced from Hexaarylbenzene-Based Partially Fluorinated Poly(arylene ether) Blends for Proton Exchange Membrane Fuel Cells.

In this study, a series of high molecular weight ionomers of hexaarylbenzene- and fluorene-based poly(arylene ether)s were synthesized conveniently through condensation and post-sulfonation modification. The use a of blending method might increase the stacking density of chains and affect the formation both of interchain and intrachain proton transfer clusters. Multiscale phase separation caused by the dissolution and compatibility differences of blend ionomer in high-boiling-point solvents was examined through analysis and simulations. The blend membranes produced in this study exhibited a high proton conductivity of 206.4 mS cm−1 at 80 °C (increased from 182.6 mS cm−1 for precursor membranes), excellent thermal resistance (decomposition temperature > 200 °C), and suitable mechanical properties with a tensile strength of 73.8–77.4 MPa. As a proton exchange membrane for fuel cell applications, it exhibits an excellent power efficiency of approximately 1.3 W cm−2. Thus, the ionomer membranes have strong potential for use in proton exchange membrane fuel cells and other electrochemical applications.

MPEG-b-PES-b-mPEG-based candidate hemodialysis membrane with enhanced performance in sieving, flux, and hemocompatibility

The efficiency of the hemodialysis membrane has been widely improved by blending small molecular additives and modifying the membrane surface for patients with chronic or acute kidney disease. However, a qualified sieving property, flux, and hemocompatibility are intractable to give consideration simultaneously, while the elution of small-molecular additives and modifiers easily cause coagulation, complement activation, etc. Fortunately, the BCP methoxy polyethylene glycol-polyethersulfone-block-methoxy polyethylene glycol (mPEG-b-PES-b-mPEG) based membranes exhibiting great potential for sieving in middle molecular toxin and compatibility between mPEG-b-PES-b-mPEG and PES, is nearly unfeasible elution during hemodialysis, by reason of including bounded hydrophilic segments by chemical bonds. Here, the mPEG-b-PES-b-mPEG is synthesized to fabricate the membranes, including blend membranes and BCP membrane. As a result, the blend membranes have shown an increasing flux, hemocompatibility, and sieving of lysozyme with the increasing cooperation of mPEG-b-PES-b-mPEG, the block copolymer (BCP) mPEG-b-PES-b-mPEG membrane has shown better balance than the blend membranes in flux, sieving, and hemocompatibility. Besides, for exploring further possibilities, the typical blend membrane M4 (mPEG-b-PES-b-mPEG: 20%, PES: 5%) and BCP membrane M5 (mPEG-b-PES-b-mPEG: 25%) are post tailored by ethanol at 50 °C for 2 h. This process leading the typical membranes to an efficient flux (M5-P: 442.22 L m−2 h−1) and sieving performances (M5-P: the urea and lysozyme sieving of 96.43% and 74.97%) due to the effect of ethanol at the micro-molecular chain movements and microspheres transfer. Our work presents BCP mPEG-b-PES-b-mPEG a promising future in hemodialysis membranes according to the superior performances of flux and sieving.

Prediction on the compatibility of chitosan/polyvinyl alcohol blend based on Schneier mixing enthalpy

A polymer blend system was established with chitosan (CS) and polyvinyl alcohol (PVA). The compatibility of CS/PVA blend was predicted via Schneier mixing enthalpy, and the effects of deacetylation on the blend compatibility were further investigated. In addition, CS/PVA blend membranes were prepared via solvent evaporation. Results showed that CS/PVA blends were completely compatible systems when the deacetylation was 50%-82.89%, while the blends turned into partially compatible ones when the deacetylation was more than 82.89%. Herein, CS was revealed to be partially miscible with PVA, and the blend became compatible as CS content was less than 32% or more than 76%. Moreover, the morphology evolution of the blend membranes verified that CS was miscible with PVA as the mass ratio reached 4:6. It was basically consistent with the prediction results derived from Schneier mixing enthalpy.

Poly(ionic liquid) copolymer blended polyvinyl chloride ultrafiltration membranes with simultaneously improved persistent hydrophilicity and pore uniformity

Persistent hydrophilicity and uniform pore structure are key features of antifouling ultrafiltration membranes. Here, a poly(ionic liquid) copolymer, poly(methyl methacrylate)-b-poly(1-butyl-3-vinylimidazolium tetrafluoro-borate) (PMMA-b-PBVImBF4), was designed and synthesized by a simple free radical polymerization method and was employed to manipulate the hydrophilicity and pore structure of polyvinyl chloride (PVC) ultrafiltration membranes through the classic non-solvent induced phase separation. The hydrophobic PMMA segment, which has a carbonyl group, could be twined with the PVC chain, thus ensuring that the copolymer was stably anchored in the PVC skeleton, while the hydrophilic PBVImBF4 segment was segregated on the membrane surface. Membrane hydrophilicity and pore size uniformity were simultaneously enhanced. A 100 % increase in pure water flux, 45.8 % increase in mechanical strength, and 80 % increase in flux recovery rate were achieved when 3.85 wt% PMMA-b-PBVImBF4 was added. After 3 cycles of BSA filtration, the pure water flux of the copolymer-modified membrane was 267.0 L·m−2·h−1, approximately 4 times that of the pristine PVC membrane. Due to the stable existence of PMMA-b-PBVImBF4 in the membrane, the improved membrane hydrophilicity was maintained after 30 days of continuous washing.

Fabrication of polyethersulfone/polyacrylonitrile electrospun nanofiber membrane for food industry wastewater treatment

In the present work, polyethersulfone/polyacrylonitrile (PES/PAN) blended electrospun nanofiber-based membrane was fabricated and applied for an environmentally friendly protocol for removing methylene blue (MB) from aqueous solutions. The structural integrity of the newly synthesized membrane was investigated by SEM, FTIR, TGA and XRD, demonstrating the successful integration of the PES/PAN blended nanofibers membrane. SEM results exhibited a smooth surface of the blended PES/PAN nanofiber membrane with an ultrathin diameter of 151.5 nm, much better than the pristine PES nanofiber membrane (261.5 nm). Besides, the blended PES/PAN nanofiber membrane showed a good mechanical stability and hydrophilicity nature, which are vital for adsorption study. Experimental adsorption kinetic data obeyed by the pseudo-second-order (R2 = 0.9970) and consistent with the Langmuir isotherm model (R2 = 0.9983) by showing the maximum adsorption capacity of 1010 mgMB/g at neutral pH and room temperature, indicating that that the adsorption process occurred in a monolayer form of the membrane surface. Meanwhile, selective inorganic ions were used to simulate the real wastewater scenario and found that PO43− positively influences MB adsorption. The novel membrane resulted in optimally recyclable up to 5 times. In addition, the adsorption mechanism revealed that electrostatic attraction was the dominant factor in the generation of the adsorption capacity of the membrane. Based on these results, it could be concluded that this novel PES/PAN blend nanofibers membrane could be a potential candidate for future wastewater treatment application with increased efficiency.

Materials selection for choosing the best composite blend polymeric membrane for hydrogen/oxygen proton exchange membrane fuel cell

Aromatic sulfonated polymers as a suitable candidate for Nafion membrane in proton exchange membrane fuel cells are the subject of many research activities. It has proved that these polymers need higher ion exchange capacities to reach the same proton conductivities compared to the Nafion membrane, which is a result of their different microstructures. Accordingly, to compensate different microstructures in the Nafion and sulfonated aromatic substitutions, several composite blend membranes of poly(ether sulfone) (PES) and poly(ether ether ketone) (PEEK), including electrospun fibers of highly-sulfonated/non-sulfonated PEEK and PES polymers have prepared. For comparison, two membranes with a routine solution-casting technique also have been made. The membrane-electrode assemblies are tested in H2/O2 single-cell. Before that, characterization measurements have performed for all membranes. To select the best sample between prepared membranes, multi-criteria decision-making (MCDM) have used, and to achieve more reliable results, four techniques of Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE), COmplex PRoportional ASsessment of alternatives (COPRAS), and VIekriterijumsko KOmpromisno Rangiranje (VIKOR) have applied. According to the experiments and MCDM methods, composite blend membrane containing sulfonated electrospun fibers of PEEK in non-sulfonated PES matrix gains the best rank among all membranes.

A hybrid batch distillation/membrane process for high purification part 2: Removing of heavy impurities from xenon extracted from natural gas

High-purity xenon of 6 N purity grade and higher is widely used in electronics, space, and medicine. A hybrid distillation/membrane process for the purification of xenon extracted from natural gas by gas hydrate crystallization is studied experimentally and via simulations. Membrane gas separation data for xenon-containing mixtures is measured for polysulfone membrane and polyetherimide/polyimide blend membrane. Parametric analysis and process optimization are performed in Aspen Plus Dynamics™ for a middle-vessel batch distillation column with an integrated hollow fiber membrane unit implemented via Aspen Custom Modeler™. Removal of higher- and lower-boiling impurities such as ethane, carbon dioxide, propane, methane, and krypton is considered to achieve 6 N and 9 N target purity grades. Hybrid distillation/membrane process flowsheets built with a multi-stream passive heat exchanger with either retentate or permeate being returned to the column are analysed. It is shown that the operating conditions and the configuration of the hybrid process with a membrane separation treatment of heavy impurities fraction can be tailored to achieve up to 30% increase in batch productivity for the considered case studies and improve xenon recovery reaching above 99.8% as compared to standalone batch distillation, which is especially critical for higher purity grades.

Effect of thermal crosslinking process on membrane structure and PEM fuel cell applications performed with SPEEK-PVA blend membranes

One of the promising options in the pursuit of clean and sustainable energy is fuel cell technology. PEM fuel cell stands out among fuel cell technologies due to its high efficiency, compactness, and ability to be used in portable applications. SPEEK (with different sulfonation degrees) and PVA blend membranes, which are thought to create a good synergy for PEM fuel cell, were prepared by using the solution casting method. As a result of the weight loss experiments, it was understood that the membranes dissolve in water regardless of the degree of sulfonation. Thermal crosslinking was carried out to prevent the membrane dissolution in water, which is in continuous contact with water in the fuel cell. Dissolution was mostly prevented by means of the thermal crosslinking process. Changes in the physical, chemical, and mechanical structure of the membrane after thermal crosslinking were comparatively determined by fourier transform infrared (FTIR), thermogravimetric analysis – differential thermal analysis (TGA-DTA), differential scanning calorimetry (DSC), water uptake capacity, swelling property, ion exchange capacity (IEC), dynamic mechanical analysis (DMA), electrochemical impedance analysis and oxidative stability. In addition, single-cell performance tests were performed with the membrane that gave the best results in the characterization analyses. Analysis results showed that thermal crosslinking prevented the dissolution of membranes in water ingreat extent. In addition, it was determined that the thermally crosslinked membranes had a more stable structure.

Highly antifouling porous EVAL/F127 blend membranes with hierarchical surface structures

Membrane fouling is widely acknowledged as the major hindrance to the efficient separation of oil-water emulsions. Superhydrophilic EVAL/F127 porous membranes with micron-submicron hierarchical structure were prepared via micro-molding assisted immersion precipitation (PSμm process). The micron-scale concave-convex structure was constructed by the micro-molding process with 1000 mesh sandpaper, and then the sub-micron structure of the surface was modulated by F127. With the combination of optimized hierarchical structure and F127 hydrophilic modifier, EVAL/F127 porous membrane is superhydrophilic (water contact angle less than 10°) and strongly anti-fouling. ATR-FTIR, SEM, AFM, water contact angle (WCA), pure water flux, porosity and equilibrium water content were used to characterize the textural and properties of EVAL porous membranes. The separation performance and antifouling properties of the membranes were evaluated using oil-in-water emulsions as fouling agents. When the F127 content was 10%, the EVAL/F127 blended porous membrane not only performed well in retention performance (95.3% retention), but also had high flux recovery (91.6%) after hydrodynamic cleaning. Thus, the combined strategy based on hierarchical structure and hydrophilic modification provides a facile solution for the preparation of antifouling membranes.

Dual-Structure PVDF/SDS Nanofibrous Membranes for Highly Efficient Personal Protection in Mines.

Pneumoconiosis in miners is considered a global problem. Improving the performance of individual protective materials can effectively reduce the incidence of pneumoconiosis. In this study, the blend membrane of sodium dodecyl sulfate and polyvinylidene fluoride with a dual structure was prepared using electrospinning techniques, and the morphological structure, fiber diameter, and filtration performance of the nanofiber membranes were optimized by adjusting the PVDF concentration and SDS content. The results show that the incorporation of SDS enabled the nanofiber membranes to show tree-like and beaded fibers. Compared with the original PVDF membrane, the small content of tree-like fibers and beaded fibers can improve the filtration efficiency and reduce the resistance of the fiber membrane. The prepared nanofiber membrane has excellent comprehensive filtration performance, and the quality factor is 0.042 pa−1 when the concentration of PVDF is 10 wt% and the addition of SDS is 0.1 wt%. Furthermore, after high-temperature treatment, the membrane could still maintain good filtration performance. The PVDF/SDS blend nanofiber membrane has outstanding filtration efficiency and good thermal stability and can fully meet the personal protection of miners in underground high-temperature operation environments.

Effects of Medium Cut-Off Polyarylethersulfone and Polyvinylpyrrolidone Blend Membrane Dialyzers in Hemodialysis Patients: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

The use of medium cut-off (MCO) polyarylethersulfone and polyvinylpyrrolidone blend membrane is an emerging mode in hemodialysis. Recent studies have shown that MCO membranes exhibit a middle high molecular weight uremic toxin clearance superior to standard high flux hemodialysis. We conducted a systematic literature review and meta-analysis of randomized controlled trials to investigate whether MCO membranes efficiently increase the reduction ratio of middle molecules, and to explore the potential clinical applications of MCO membranes. We selected articles that compared beta 2-microglobulin (β2M), kappa free light chain (κFLC), lambda free light chain (λFLC), interleukin-6 (IL-6), and albumin levels among patients undergoing hemodialysis. Five randomized studies with 328 patients were included. The meta-analysis demonstrated a significantly higher reduction ratio of serum β2M (p < 0.0001), κFLC (p < 0.0001), and λFLC (p = 0.02) in the MCO group. No significant difference was found in serum IL-6 levels after hemodialysis. Albumin loss was observed in the MCO group (p = 0.04). In conclusion, this meta-analysis study demonstrated the MCO membranes’ superior ability to clear β2M, κFLC, and λFLC. Serum albumin loss is an issue and should be monitored. Further studies are expected to identify whether MCO membranes could significantly improve clinical outcomes and overall survival.

Hydrophilic and Positively Charged Polyvinylidene Fluoride Membranes for Water Treatment with Excellent Anti-Oil and Anti-Biocontamination Properties.

Membrane fouling limits the rapid development of membrane separations. In this study, a blend membrane containing polycationic liquid (P(BVImBr1-co-PEGMA1)) is presented that can improve the antifouling performance of polyvinylidene fluoride (PVDF) membranes. By mixing the polycationic liquid into PVDF, an improved membrane-surface hydrophilicity and enlarged membrane porosity were detected. The water contact angle decreased from 82° to 67°, the porosity enlarged from 7.22% to 89.74%, and the pure water flux improved from 0 to 631.68 L m−2 h−1. The blend membrane surfaces were found to be always positively charged at pH 3~10. By applying the membranes to the filtration of oil/water emulsion and bovine serum albumin (BSA) solution, they showed a very high rejection rate to pollutants in wastewater (99.4% to oil droplets and 85.6% to BSA). The positive membrane surface charge and the increased membrane hydrophilicity resulted in excellent antifouling performance, with the flux recovery rates of the dynamic filtration tests reaching 97.3% and 95.5%, respectively. Moreover, the blend membranes demonstrated very low BSA adhesion and could even kill S. aureus, showing excellent antifouling properties.

Tröger's base polymer blended with poly(ether ketone cardo) for high temperature proton exchange membrane fuel cell applications

Developing membrane electrolyte materials with high performance and low cost is a key factor in promoting the application and commercialization of the high temperature proton exchange membrane fuel cell (HT-PEMFC). In this work, a Tröger's base (TB) polymer is synthesized from commercially available and low-cost 4,4′-diamine-3,3′-dimethyl-biphenyl (DMBP) and dimethoxy methane in trifluoroacetic acid via a one-pot TB polymerization reaction under mild conditions. The obtained polymer is composited by TB unit and DMBP moiety (named as DMBP-TB), which occupies a good organic solubility, high thermal stability and excellent chemical resistance. Due to the built-in bicyclic amine rings and intrinsic microporous structure, the pure DMBP-TB membrane exhibits a remarkable phosphoric acid (PA) doping content as high as 1077% in 85 wt% PA solution at room temperature. However, the excessive swelling and poor mechanical integrity hinder the PA doped DMBP-TB membrane as the HT-PEM. Thus, the commercial and low-cost engineering thermoplastic of poly(ether ketone cardo) (PEKC) is employed as the enhanced material to prepare DMBP-TB blend membranes. The DMBP-TB/50%PEKC/149%PA membrane displays an anhydrous conductivity of 0.061 S cm−1 at 180 °C and a tensile strength of 8.7 MPa at room temperature, which enables H2–O2 fuel cell with a peak power density of 536 mW cm−2 at 180 °C without backpressure, suggesting the utility for HT-PEMFCs.