Composite Fiber Membranes Research Articles

Covalently immobilized cobalt Phthalocyanine@MWCNT PDMS hollow fiber membrane for highly selective, reversible and bio-inspired oxygen transport

Facilitated oxygen transport is an effective strategy for the oxygen transport that may enhance the oxygen permeance and its selectivity, which may provide oxygen rich permeate that can be used in medical applications as in the present COVID-19 pandemic situation for providing the sufficient oxygen to the patients. This study presents the bio-inspired oxygen transport by covalently bonded Cobalt Phthalocyanine complex anchored on multi walled carbon nanotube (MWCNT) via axial ligand, incorporated in PDMS hollow fiber membranes with 0.05, 0.1, 0.5 and 1.0 wt % loadings. Successful functionalization of MWCNT was confirmed by Raman spectroscopy and X-ray photoelectron spectroscopy. The membranes were thoroughly characterized by using FE-SEM with elemental mapping, ATR-IR, DSC and TGA analysis. It demonstrated facilitated oxygen transport through the covalently immobilized Cobalt complex of the membrane with high oxygen permeance of 49 GPU as well as exceptional oxygen selectivity of 17 at 0.5 wt % Cobalt Phthalocyanine@ MWCNT loading. These values are highest among the known Cobalt complex based hollow fiber composite membranes in the literature suggesting its best utility in selective oxygen concentration for practical applications.

Electrospun egg white/polyvinyl alcohol fiber dressing to accelerate wound healing

The purpose of this experiment was to prepare a new biological dressing for skin defect healing by electrospinning. Membranes consisting of egg white (EW) with 12% polyvinyl alcohol (PVA) solution (v/v, 60EW/40PVA, 50EW/50PVA, 40EW/60PVA) were obtained by electrospinning. The biological properties of the resulting fibrous membranes were tested in vitro and in vivo. Scanning electron microscopy (SEM) showed that the EW/PVA nanofiber membranes had a uniformly porous and smooth fibrous structure. The fiber thickened with increasing EW proportion. X-ray diffraction (XRD) showed that crosslinking improved the crystallinity of the composite fiber films. Fourier transform infrared (FT-IR) spectroscopy showed that PVA and EW existed independently in the composite fiber membranes after crosslinking. Mechanical tests showed that the tensile modulus and tensile strength of the fibrous membranes increased significantly after crosslinking. In vitro degradation experiments showed that crosslinking improved the stability of the EW/PVA nanofiber membranes in water. Cytotoxicity and cell proliferation tests proved the good biocompatibility of the fibrous membranes, with 60EW/40PVA significantly promoting cell proliferation. A full-thickness skin defect rat model confirmed that 60EW/40PVA significantly enhanced full-thickness skin wound healing and regeneration. This experiment verified the feasibility of using the EW/PVA composite material to prepare electrospun fiber dressings and promote skin defect repair and regeneration.

Evaluation of dynamic mechanical and cytotoxic properties of electrospun poly (lactic acid)/cellulose nanocrystalline composite membranes

In this paper, polylactic acid (PLA)/cellulose nanocrystalline (CNC) composite fiber membranes were prepared by electrospinning technique. The microstructure of the fiber membranes produced was all transformed from a smooth surface to a nanoporous surface by varying the CNC loading level. The influence of CNC content on the morphology, thermal dynamic properties, and cytotoxic properties of PLA/CNC composite nanofiber membranes was characterized. The results show that water molecules can enhance the hydrogen bonding networks between PLA and CNC. when the cellulose nanocrystal content is less than 10%, the composite membranes have good dynamic mechanical properties and no significant cytotoxic effect.

Degradable ultrathin high-performance photocatalytic hydrogen generator from porous electrospun composite fiber membrane with enhanced light absorption ability

A photocatalytic hydrogen energy generator was assembled with electrospun membrane. The unique internal structure enhances the light absorption ability and ensures the dispersion of photocatalysts, endowing the generator with excellent performance.

Electrospinning preparation and near-infrared absorption properties of a silica/cesium tungsten bronze micro-nano fiber membrane.

Silica/cesium tungsten bronze (SiO2/CsxWO3) composite micro–nano fiber membranes were prepared by the co-precursor electrostatic spinning method using cesium chloride, tungsten powder and tetraethyl orthosilicate as raw materials. TGA, XRD, FT-IR, XPS, SEM and ultraviolet-visible-near red spectrophotometry were used to analyze the thermal decomposition process, phase composition, microscopic morphology and near-infrared absorption properties of the product. Studies have shown that as the ratio of Cs/W of raw materials increases, the crystallinity of CsxWO3 in the product increases first and then decreases. When n(Cs)/n(W) reaches 0.5, its crystallinity is the most complete; similarly, calcination also contributes to the crystallization of Cs0.33WO3, but high temperatures above 800 °C will also destroy its crystal structure. The study found that after calcination at 700 °C, the fiber membrane with a Cs/W atomic ratio of 0.5 has the best infrared absorption performance. The average absorbance of near-infrared light at 780–2500 nm is 1.5, which is 5.56 times that of the pure SiO2 fiber membrane. The tensile strength reaches 2.4 MPa, which can meet practical requirements. This research provides a basis for the development of flexible solar shading materials under complex outdoor conditions.

Improved CO2/CH4 separation performance of mixed‐matrix membrane by adding ZIF‐7‐NH2 nanocrystals

AbstractMembrane‐based technology is an attractive alternative in terms of CO2 separation. Pebax‐based membranes are regarded as potential candidates for CO2 separation due to the favorable interaction between its poly (ethylene oxide) chains with CO2 molecules and inorganic fillers. However, the separation performance for CO2/CH4 mixture is still suffered from the moderate gas permeability and selectivity. To overcome this problem, in this work, amino‐functionalized zeolite imidazolate framework (ZIF‐7‐NH2) nanocrystals were used as fillers to blend with Pebax 1657 for fabricating mixed‐matrix membranes (MMMs). XRD, Brunauer–Emmett–Teller (BET), scanning electron microscope, and 1H nuclear magnetic resonance characterization indicated that ZIF‐7‐NH2 with the highest crystallinity was synthesized. Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), and Young's modulus showed that it has good interfacial interaction. Gas separation test results showed that both the CO2 permeability and CO2/CH4 selectivity of the 31 wt% ZIF‐7‐NH2/Pebax MMMs increased by 80 and 170%, respectively. The improved performance is attributed to the addition of ZIF‐7‐NH2 nanocrystals and the favorable interfacial interactions between the polymer and ZIF‐7‐NH2 nanocrystals. Furthermore, the polyvinylidene fluoride supported hollow fiber composite membranes also exhibit the long‐term stability for CO2/CH4 separation.

Electrospun stereocomplex polylactide porous fibers toward highly efficient oil/water separation

The urgent needs for water protection are not only developing the highly efficient wastewater treatment technologies but also designing the eco-friendly materials. In this work, the eco-friendly composite fibers composed of poly(L-lactide) (PLLA), poly(D-lactide) (PDLA) and maghemite nanoparticles γ-Fe2O3 nanoparticles were fabricated through electrospinning technology. Through regulating the processing parameters and introducing additional annealing treatment, nanoscale porous structure and the stereocomplex crystallites (SCs) are simultaneously constructed in the composite electrospun fibers. Physicochemical performances measurements exhibited that the fiber membranes had excellent lipophilicity, good mechanical performances, and high hydrolysis resistance, and all of which endowed the fiber membranes with high oil adsorption capacities, and the maximum oil adsorption capacities achieved 148.9 g/g at 23 °C and 114.8 g/g at 60 °C. Further results showed that the fiber membranes had good oil/water separation ability. The gravity-driven oil flux was 6824.4 L/m2h2, and the water rejection ratio was nearly 100% during separating oil/water mixture. Specifically, the fiber membranes showed good stability during the cycling measurements. It is evidently confirmed that the composite PLLA-based fiber membranes with porous structure and SCs can be used in wastewater treatment, especially in some rigorous circumstances.

Stabilized Lithium Anode via a Uniform Li-Ions Distribution Enabled by a Robust LLZTO/Polysulfone Electrospun Membrane

Lithium metal batteries (LMBs) using lithium metal as the anode is a promising technical route for the next battery. lithium metal anode delivers the highest energy density. Therefore, it has been extensively studied by scientists. Unfortunately, Li-metal anode is incapable to practical applications due to the dendritic propagation during the repeated charging/discharging process leading to short-circuit and severe safety issues. we loaded the fast Li-ions conductor LLZTO ceramic particles on the polysulfone (PSU) fiber. The LLZTO/PSU composite fiber membrane networks inherited both lithiophilic properties and strong rigidity from LLZTO particles, which could suppress the local electric field and exert influence of adjusting the distribution and deposition behavior of Li-ions while the improved mechanical properties against lithium dendrites. Therefore, the lithium metal anode with modified surface of composite fiber can effectively inhibit the formation of lithium dendrites with a prolong life-span.

Composite zeolite hollow fiber membrane for the removal of nickel using forward osmosis

This work discusses the preparation, characterization, and feasibility test of composite zeolite hollow fiber membranes, with UV-curable resin as a secondary coating material, in removing Ni (II) using FO process. The preparation of the membrane started by depositing zeolite membrane onto alumina hollow fiber, followed by photopolymerization process once the outer layer was fully covered. Various characterization techniques were used on the composite membrane, namely field emission-scanning electron microscopy (FESEM), X-ray diffraction analysis, Fourier transform infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET) analysis, contact angle measurement, and performance tests using FO. The results show that the membranes enabled a reduction of reverse solute once incorporated with UV-curable resin. The lowest reverse solute flux obtained was 0.008 kg m−2 h−1, when pure water was flowed in the outer surface and 100,000 mg L−1 sodium chloride (NaCl) was used in the lumen. The UV-curable resin was unstable in the presence of Ni (II), which later formed complex ions. Adsorption of Ni (II) ions caused agglomeration of zeolite particles, causing membrane defects.

Nafion-PTFE hollow fiber composite membranes for improvement of anti-fouling and anti-wetting properties in vacuum membrane distillation

Nafion-PTFE hollow fiber composite membranes were fabricated and applied in vacuum membrane distillation (VMD) process to improve the anti-fouling and anti-wetting performance in the presence of oil and surfactant. The composite membrane exhibited an underwater super-oilphobic property according to the contact angle test. The VMD performance when treating saline feed containing 3.5 wt% NaCl and 1000 ppm mineral oil for the composite membrane behaved a stable flux for 40 h. In construct, an immediate and sharply-declined flux was observed for the pristine PTFE, indicating the significant improvement in the anti-fouling property. Meanwhile, the composite membrane also alleviated the wetting phenomena caused by the surfactant comparing with the pristine PTFE membrane, and the Nafion-PTFE composite membrane behaves a stable flux and high salt rejection higher than 99.99% for 60 h treating saline feed containing O/W emulsions. The pressure depression effect of the Nafion layer on the mass transfer was analyzed. It was found that the depression could be reduced with the increasing of the feed temperature and the enhancement of the corresponding effective pore diameter of the Nafion layer, that the pressure depression factor decreased from 0.23 to 0.04 with the feed temperature increasing from 60 °C to 75 °C.

Removal of high concentration Congo red by hydrophobic PVDF hollow fiber composite membrane coated with a loose and porous ZIF-71PVDF layer through vacuum membrane distillation

Although membrane distillation (MD) technology has the outstanding advantages of almost 100% solute retention and mild operation conditions, its further development is limited by low permeate flux. In order to solve the problem, the improvement of membrane hydrophobicity becomes one of the effective solutions. In this study, a loose and porous hydrophobic zeolitic imidazolate frameworks-71 (ZIF-71)/polyvinylidene fluoride (PVDF) coating layer was composited on the outside surface of PVDF hollow fiber support membrane by the dilute solution coating to enhance membrane hydrophobicity. The prepared hollow fiber composite (HFC) membranes were employed to remove high concentration Congo red (CR) through VMD. The effects of different operation conditions including the dye concentration, feed temperature, vacuum pressure and feed flow rate on CR rejection and permeate water flux were investigated. In the variation range of operating conditions, all the CR rejection of the PVDF HFC membranes shows a slight change and remains above 99.9%. Under the optimal operation conditions including dye concentration 600 mg·L−1, vacuum pressure 31.325 kPa, feed temperature 60°C and feed flow rate 50 L·h−1, HFC membrane exhibit a permeate water flux of 13.15 kg·m−2·h−1. HFC membrane suffers dye fouling during the continuous dye filtration for 100 h. The fouling mechanism was proposed and a combined cleaning way including forward washing, back flushing and chemical desorption has been proved to be effective in recovering membrane water flux.

Highly efficient separation membrane based on cellulose acetate/chitosan fibrous composite substrate with activated carbon functional adsorption layer

AbstractBACKGROUNDFor improving the permeability and selectivity of adsorption separation membranes, membrane materials, structural morphology and separation technology must continue to be investigated. Development of a membrane that is environmentally friendly, cost‐effective and with high filter precision is an important direction in current research.RESULTSThe air pressure spraying method was used to prepare an activated carbon (AC)–cellulose acetate/chitosan (CA/CS) composite membrane. The CA/CS fiber composite membrane was prepared as substrate layer, and AC was loaded on the surface of the CA/CS composite membrane as a functional adsorption layer. When the spraying pressure was 0.01 MPa and the mass ratio of AC/CS was 2:1, a composite membrane with even and compact morphology could be obtained. Both the compact AC functional layer and complete CA/CS substrate layer endowed the AC–CA/CS composite membrane with an excellent water filtration property. At low feeding pressure, the permeate flux and rejection rate of bisphenol A (BPA) could reach 9.27 × 103 L m−2 h−1 and 98.31%, respectively. Meanwhile, the adsorption capacities of the membrane were investigated. It tended to equilibrate quickly in 2 min for dyes and BPA. The equilibrium adsorption capacities of the membrane for acid blue, acid yellow and BPA were 175.80, 164.0815 and 79.58 mg g−1, respectively. The adsorption process conformed to pseudo‐second‐order kinetics and the Langmuir monolayer adsorption model.CONCLUSIONSThis work could provide a practical and effective feasibility for membrane separation technology. © 2020 Society of Chemical Industry (SCI)

A novel polyethersulfone/modified activated carbon fiber composite membrane: potential for removal micropollutants from water under the electric field.

This study aimed to develop a novel composite membrane based on polyethersulfone (PES) and modified activated carbon fibers (ACFs) to remove of sulfamethoxazole (SMZ) from water. The modification of ACFs was conducted by using acid, Fe, and Mn and was confirmed by Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray spectroscopy (EDS), and water contact angle measurement. Later on, the composite membranes were prepared using PES (9 wt%), N-N-dimethylacetamide (DMAc) (75 wt%), polyethylene pyrrolidone (PVP) (5 wt%), anhydrous lithium chloride (LiCl) (1 wt%), and various types of modified ACFs (0.8 wt%) as additives. It was found that the contact angle of the membrane decreased by more than 20°, and the zeta potential decreased by more than 10 mV. ACF modified by Fe was used as an admixture, membrane obtained the high comprehensive performance. Especially bovine serum albumin (BSA) rejection rate and flux recovery ratio (FRR) reached 98.8% and 98.4%, respectively. And the removal rates of SMZ increased by 24.6% under the electric field. The degradation products were detected by high-performance liquid chromatography/mass spectrometry (HPLC/MS). Based on this result, the possible degradation pathways of SMZ are proposed.

초저압용 나노중공사 복합막의 제조

폴리설폰 한외여과 중공사막 표면에 염석법을 이용하여 폴리비닐아민(poly(vinyl amine), PVAm)을 코팅시간, 이온세기, 건조온도, 가교농도 등을 변경하여 나노여과 중공사 복합막(NF hollow fiber composite membranes)을 제조하였으며 이를 염화나트륨(NaCl) 100 ppm과 황산칼슘(CaSO₄) 100 ppm 용액에 대하여 투과도와 배제율을 측정였다. 모든 조건에서 염화나트륨보다 황산칼슘의 배제율이 더 컸는데 이는 크기 및 도난 배제효과에 기인한 것으로 생각된다. 반면에, 투과도에서는 오히려 황산칼슘의 경우가 염화나트륨의 경우보다 높았는데 이는 아미노기(-NH₂)로인한 막의 팽윤으로 인하여 분자크기가 큰 2가 이온이 자유로이 투과할 수 있는 통로를 제공하는 것으로 사료된다. 대표적으로 이온세기 0.2, 가교제농도 0.7%, 코팅시간 30초, 건조온도 및 시간 80℃, 20분 조건에서 염화나트륨에 대하여 투과도 22 LMH(L/m²/hr)와 배제율 74% 그리고 황산칼슘에 대하여 투과도 29 LMH와 배제율 92%를 각각 나타내었다.

Effect of Additives on the Performance of PPBES Composite Forward Osmosis Hollow Fiber Membranes.

A polyamide composite forward osmosis (FO) hollow fiber membrane was successfully prepared with a novel copoly(phthalazinone biphenyl ether sulfone) (PPBES) polymer. Effects of different additives including ethylene glycol methyl ether (EGME) and lithium chloride anhydrous (LiCl) in the dope solution on the morphologies and properties of PPBES support membranes and composite FO hollow fiber membranes were investigated. With the increase of EGME content in the dope solution, the water flux of PPBES support membranes and FO hollow fiber membranes decreased. When LiCl was added into the dope solution, the water flux of FO hollow fiber membranes improved significantly with the increase of LiCl content. Additionally, the FO performance of the PPBES membrane was further optimized by adding triethylamine (TEA) in the interfacial polymerization (IP) process. In comparison with other FO membranes, the novel PPBES composite FO hollow fiber membrane displayed a remarkably high water flux of 45.3 L/m2 h and a low specific reverse salt flux of 0.15 g/L.

Trimetallic composite nanofibers for antibacterial and photocatalytic dye degradation of mixed dye water.

Membrane technology is an advanced approach to making a healthier and cleaner environment. Using such catalytic membrane technology to get clean, usable water by removal of dye impurities as well as pathogenic microbes is the main goal behind the research work. Here, we present the synthesis and efficacy study of polymethyl methacrylate (PMMA)-based Ag/ZnO/TiO2 trimetallic bifunctional nanofibers with antibacterial and photocatalytic activity. The nanofibers have been proven to be effective for the degradation of methylene blue (MB 93.4%), rhodamine B (Rh 34.6%), auramine-O (Au 65.0%) and fuchsin basic (FB 69.8%) dyes individually within 90 min in daylight. The study is further extended in abating a mixture of these dyes from contaminated water using composite nanofibers. Also, in the case of a mixture of these dyes (3 ppm each), nanofibers show dye degradation efficiency (DDE) of 90.9% (MB), 62.4% (Au) and 90.3% (FB and Rh) in 60 min. The role of Ag nanoparticles with a synergic photocatalytic effect on ZnO and TiO2 is also demonstrated. Also, PMMA/ZnO/TiO2 composite fiber membrane in synergy with silver particles shows better antibacterial activity against Gram-negative bacteria E. coli, making PMMA/Ag/ZnO/TiO2 fibers a promising candidate in water purification.Electronic supplementary materialThe online version of this article (10.1007/s13204-020-01540-6) contains supplementary material, which is available to authorized users.

Preparation and Properties of an Alginate-Based Fiber Separator for Lithium-Ion Batteries

The membrane is one of the key inner parts of lithium-ion batteries, which determines the interfacial structure and internal resistance, ultimately affecting the capacity, cycling, and safety performance of the cell. In this article, an alginate-based fiber composite membrane was successfully fabricated from cellulose and calcium alginate with flame-retardant properties via a traditional papermaking process. In the membrane, the calcium alginate plays a bridging role and the cellulose acts as a filler. After 100 cycles, lithium-ion batteries by the alginate-based fiber separator exhibited better capacity retention ratios (approximately 90%) compared with those of commercial PP separators. Furthermore, the alginate-based fiber separator demonstrated fine thermal stability and electrochemical properties, showing a stable charge-discharge capability and no hot melt shrinkage at higher temperatures, which is a breakthrough in improving the safety of the cell. This research affords a new way for the large-scale fabrication of safe lithium-ion battery separators.

Reduced Graphene Oxide/Carbon Fiber Composite Membrane for Self-floating Solar-thermal Steam Production

Solar-thermal water evaporation has attracted increasing attention owing to the promising potential to solve the global clean water and energy crisis. But, the development of this strategy is limited by the lack of materials with high solar-thermal conversion efficiency, local heating of superficial water, easy preparation and low cost. Herein, we proposed a facile strategy to prepare a reduced graphene oxide/carbon fiber composite membrane, denoted as RGO/CF membrane. The surface of the RGO/CF membrane was highly hydrophobic, endowing the composite membrane with the self-floating ability on the water without any assistance. The light absorbance ability achieved as high as ca. 98% in the wavelength range of 300–1200 nm. The steam evaporation efficiency under the illumination of 3-sun was 97%, generating water steam at a rate of 4.54 kg·m−2·h−1. Moreover, the solar-thermal steam production rate showed high stability during successive 30 cycle tests.

High thermal stability multilayered electrolyte complexes via layer-by-layer for long-life lithium-sulfur battery

In this work, polyacrylonitrile/sulfonated poly(ether ether ketone) (PAN/SPEEK) composite fiber membrane as separator for lithium-sulfur battery was first prepared by electrospinning. In order to reduce the shuttle effect, multilayered polyelectrolyte complexes (CS/CNTs)n as surface modification agents were prepared by alternating deposition of oppositely charged hydroxylated multi-walled carbon nanotubes (MWCNTs-COOH) and chitosan (CS) via the layer-by-layer method. The as-prepared fiber multilayered complex separator (FMCS) was finally treated by heating at 120 °C to form cross-linked network for better thermal stability. FMCS possessed much higher porosity than that of the commercial PP separator (44%). As expected, the assembled membranes remained intact even at 150 °C, while PP separator shrunk severely. Compared with PP, PAN/SPEEK/(CS/MWNTs-COOH)10 showed the discharge capacity of 956.9 mAh/g at 0.1 C and maintained 463 mAh/g after 100 cycles with the capacity retention rate of 48.4% which is higher than that of the commercial PP separator. Thus, this work can provide a simple method for modifying separator for long-life lithium-sulfur battery.

A food-grade continuous electrospun fiber of hordein/chitosan with water resistance

Hordein electrospun ultra-thin fibers are unstable in an aqueous environment. Chitosan was added to improve their water resistance. With increasing chitosan concentration, the viscosity and conductivity of the biopolymer blends increased, and the surface tensions remained almost constant. The structure and morphology of composite biopolymer fiber membranes showed that the average fiber diameter varied with chitosan concentration. ATR-FTIR spectra showed that the C–H stretching band changed or disappeared with increased chitosan. X-ray diffraction showed that chitosan was distributed in hordein fibers without crystallites. Compared with the hordein nanofibers, thermogravimetric analysis and derivative thermogravimetry curves showed that hordein/chitosan electrospun fibers had slightly decreased thermal stability. In conclusion, a low chitosan content improved the water resistance and other properties of hordein fibers, without changing their morphology or structure.