Nonwoven Membrane Research Articles

Enhancement of anammox performance in a novel non-woven fabric membrane bioreactor (nMBR)

As well as a membrane separator, a non-woven fabric module could be employed as a biomass carrier to enhance microorganism proliferation and nitrogen removal.

Effect of pore size on gas resistance of nanofiber membrane by the bubble electrospinning

This paper explores the influence of pore size on gas resistance by comparing micron non-woven and nanofiber membrane. The result shows that membrane with a higher filtration and lower gas resistance can be received by controlling the pore size of nanofiber membrane.

An electrospun lignin/polyacrylonitrile nonwoven composite separator with high porosity and thermal stability for lithium-ion batteries

In this work, lignin/polyacrylonitrile composite fiber-based nonwoven membranes (L–PANs) were prepared by electrospinning with dispersing different amounts of lignin in the polyacrylonitrile (PAN) solutions.

Comparison of tetracycline rejection in reclaimed water by three kinds of forward osmosis membranes

Comparison of the rejection of trace tetracycline (TC) in the secondary effluent of an anoxic–oxic (AO) system by forward osmosis (FO) was investigated at the mini-lab scale. The effects of different operating conditions including membrane orientation, flow velocity, and draw solution concentration and solute on TC rejection were also explored. The results revealed that TC rejection increased with increasing water flux, but high reverse salt flux may reduce TC rejection through enhanced solution ionic strength. Membranes with a nonwoven structure could reduce TC rejection via increased flow velocity. In the pressure retarded osmosis (PRO) mode, rejection of charged TC was higher than in the FO mode because of enhanced electrostatic repulsion. In addition, the reverse draw solute could hinder the forward diffusion of TC, thus leading to a decline in TC rejection. The cellulose triacetate with embedded polyester screen (CTA-ES) membrane displayed consistently higher TC rejection than that of the cellulose triacetate with a cast nonwoven (CTA-NW) membrane, and the rejection of TC by a thin-film composite with embedded polyester screen (TFC-ES) membrane was relatively lower compared to CTA membranes. These findings provide further insight into TC rejection mechanisms and potentially can be useful for FO process operation in wastewater reclamation.

Dynamic fouling behavior and cake layer structure changes in nonwoven membrane bioreactor for bath wastewater treatment

A nonwoven fabric module was used as a solid–liquid medium in a membrane bioreactor for bath wastewater treatment. The flux-step method was performed to define the maximum allowable flux and then was verified over a long period operation under six different imposed fluxes ranging from 8L/(m2h) to 18L/(m2h). During the long-term tests, the treatment performance and filtration characteristics of the nonwoven membrane bioreactor (NWMBR) were investigated. The membrane fouling mechanisms under the different operating phases of the NWMBR were also discussed. Results show that the NWMBR operated in two stages during the six tests. In the early stage, the filling up of the internal structure of the membrane caused the rapid formation of a dense cake layer. In the late stage, the increasing imposed flux changed the morphology of the cake layer and affected the membrane fouling differently. When the flux exceeded the critical flux of 15L/(m2h), a thin but dense cake layer formed rapidly and decreased the membrane permeability. When the flux was lower than the critical flux, a loose filamentous biomass layer formed on the nonwoven membrane surface, which acted as a secondary membrane that prevented the adsorption of extracellular polymeric substances, soluble microbial products, and particles onto the membrane surfaces.

Synthesis and characterization of Y2Ti2O7 and ErxY2−xTi2O7 nanofibers

1-D nanostructures are deemed to be important building blocks for future optical and optoelectronic nanodevices. We have used electrospinning methods to synthesize nanofibers and freestanding, non-woven nanofibers membranes of single phase yttrium titanate and ErxY2−xTi2O7 (x = 0–12 %) with diameters less than 150 nm and have characterized the physical, thermal and optical properties. We have demonstrated that such fibers can be synthesized at a relatively low cost and high production volume with a narrow diameter range. No clear phases are observed up to a calcination temperature of 700 °C and pyrochlore phase appear at 725 °C which are also confirmed by the TGA. Single pyrochlore phase is observed at temperatures greater than 900 °C. No other oxide phases are present.

Diatomite- and polyvinyl alcohol-modified nonwoven fabric in membrane bioreactor for wastewater reclamation

In the current study, diatomite- and polyvinyl alcohol (PVA)-modified nonwoven fabric was applied in membrane bioreactor (MBR) for wastewater reclamation. The characteristics of the modified nonwoven were elaborated via water contact angle, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy measurements. It showed that the hydrophilicity of nonwoven was enhanced, and water contact angle was decreased from 112.71° to 53.83°. SEM images show that the nonwoven fibers are uniformly covered with PVA, and diatomite deposited on nonwoven fabrics is glued by PVA polymer. The performance of modified nonwoven was evaluated in MBR system at a flux of 6.2–16.5 L/m2 h. Results showed that the anti-fouling property of modified nonwoven membrane was enhanced, and the effluent qualities could meet the requirements for water reclamation.

Water filtration properties of novel composite membranes combining solution electrospinning and needleless melt electrospinning methods

ABSTRACTNew composite polyvinyl alcohol (PVA)/polypropylene (PP) membranes were prepared by combining both solution electrospinning and melt electrospinning methods. Self‐designed and made needleless melt electrospinning device was used to fabricate PP membranes which acted as the support layer. PVA membrane on the surface was fabricated via solution electrospinning. The electrospun PVA/PP composite membranes were characterized by the pore size distribution, pure water flux, and rejection ratio, then compared with general composite membranes. Characterizations revealed that the fiber diameter of solution electrospun PVA membrane and melt electrospun PP membrane were 0.171 ± 0.027 and 2.24 ± 0.33 μm, respectively, and the average pore size was 0.832 μm and 27.29 μm, which was much smaller than the nonwoven membrane. The rejection ratio to the 500 nm particles of the PVA/PP composite membrane could reach more than 96%, which was much larger than that of the PVA/non‐woven substrate of 90%, and the melt electrospun PP membrane of 80%, and still maintained high permeate flux of 32,346 L/m2h under the pressure of 0.24 bar. This approach of compositing the solution electrospun membranes and melt electrospun membranes could be useful in designing novel microfiltration membrane owning both higher flux and higher rejection ratio. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41601.

Elucidating membrane surface properties for preventing fouling of bioreactor membranes by surfactin

ABSTRACTThe large scale production of bacterial surfactin‐an anionic lipopeptide is restricted by its high cost of production. Surface sorption of surfactin causes membrane fouling, decreasing air permeation, or filtration efficiency of membranes used in bioreactors. The aim of this study was to elucidate surface properties leading to reduction or even the prevention of surfactin sorption on fibrous membranes. Surface modification of fibrous polyethylene terephthalate (PET) nonwoven membranes using cationic and/or anionic biopolymers, or an antiadhesive fluorinated polymer, with or without a prior air plasma treatment, resulted in membranes with varying surface properties. Membranes with superhydrophilic to superhydrophobic behavior with varying surface charges (positive, nul, and negative) were produced. Water contact angle (WCA), capillary uptake, as well as Zeta potential of each modified membrane, were quantified. Sorption tests using surfactin, were carried during 5, 24, and 48 h, at pH 7. The amphiphilic anionic lipopeptide sorbed on positively charged membranes as well as on negatively charged hydrophobic, hydrophilic, or superhydrophobic membranes. PET membrane functionalized with alternate deposition of chitosan and alginate presented surface properties (zeta potential of −20 mV and WCA = 80°), which was effective in rejecting 100% of the anionic surfactin both at an initial stage and at a late stage (after 48 h). Discussion is proposed to explain possible interactions between the anionic lipopeptide and the functionalized nonwovens. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41622.

A specially structured conductive nickel-deposited poly(ethylene terephthalate) nonwoven membrane intertwined with microbial pili-like poly(vinyl alcohol-co-ethylene) nanofibers and its application as an alcohol sensor

The trend in development of portable and wearable sensors in healthcare-related applications promotes an expanding demand for flexible, stretchable and electrically conductive fabrics. A novel structured conductive nickel-deposited poly(ethylene terephthalate) (PET) membrane intertwined with microbial pili-like poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibers has been prepared. FTIR and XRD analysis indicated that the deposited metallic nickel was semi-crystalline with a FCC structure. SEM observations showed that nickel was compactly deposited on the surfaces of the nanofibers and PET substrate in the Ni@nanofibers/PET membranes. The coated nanofibers acted as conductive bridges among the randomly entangled PET fibers, leading to a significant increase in the conductivity of Ni@PVA-co-PE nanofibers/PET membranes. Abrasion tests suggested that Ni@PVA-co-PE nanofibers/PET membranes have superior stability in electrical conductivity compared to that of the native Ni@PET membrane. The membrane with high conductivity and good stability was employed as an electrode to construct a capacitive alcohol sensor. The sensor demonstrated good sensitivity and high efficiency.

Electrospun poly(butylene carbonate) membranes for guided bone regeneration: In vitro and in vivo studies

A nonwoven membrane for guided bone regeneration, constituting of poly(butylene carbonate), with a backbone that is similar to poly(ϵ-caprolactone), was prepared by electrospinning. The as-fabricated poly(butylene carbonate) membranes were to be used as guided bone regeneration membranes with efficacies equal to or better than poly(ϵ-caprolactone) membranes. The contact angles of electrospun poly(butylene carbonate) membranes (fPBC) (101.90 ± 4.19°) were lower than those for electrospun poly(ϵ-caprolactone) membranes (fPCL) (117.79 ± 3.38°) ( p < 0.01). To examine the biocompatibility, we investigated cell morphology, proliferation, and differentiation in vitro. The bone regenerative efficacy was evaluated in rat calvarial defect. The cell numbers were increased in accordance with culture period. Cells had a stellate shape and broad cytoplasmic extensions on the membrane. Alkaline phosphatase activity was significantly higher on fPBC than on fPCL ( p < 0.05). Defects covered by fPBC and fPCL achieved a similar degree of regeneration at 4 weeks in vivo and were significantly better than uncovered samples ( p < 0.01).Based on the results of this study, the potential for using electrospun poly(butylene carbonate) membranes in guided bone regeneration is highly significant . In addition, poly(butylene carbonate) could be a promising alternative to poly(ϵ-caprolactone) for biomedical applications.

Performance of diatomite/iron oxide modified nonwoven membrane used in membrane bioreactor process for wastewater reclamation.

This study describes an approach for surface modification of a nonwoven membrane by diatomite/iron oxide to examine its filterability. Analysis results showed that nonwoven hydrophilicity is enhanced. Static contact angle decreases dramatically from 122.66° to 39.33°. Scanning electron micrograph images show that diatomite/iron oxide is attached on nonwoven fiber. X-ray diffraction analysis further proves that the compound is mostly magnetite. Fourier transformed infrared spectra results reveal that two new absorption peaks might be attributed to Si-O and Fe-O, respectively. Modified and original membranes were used in double nonwoven membrane bioreactors (MBRs) for synthetic wastewater treatment. High critical flux, long filtration time, slow trans-membrane pressure rise and stable sludge volume index confirmed the advantages of modified nonwoven. Comparing with original nonwoven, similar effluent qualities are achieved, meeting the requirements for wastewater reclamation.

Use of airflow to improve the nanofibrous structure and quality of nanofibers from needleless electrospinning

Mass production of nanofibers from needleless electrospinning shows great potential in research and development of nanofibers. However, how to improve the electrospinning performance so as to achieve high quality nanofibers is still of great challenge. In this study, airflow has been applied to optimize upward needleless electrospinning from ring spinneret. Effects of airflow speed and the position of airflow on the nanofiber quality and production rate have been investigated. It has been found that thinner and more uniform nanofibers were produced when airflow was applied to needleless electrospinning system. It also improved the collected nonwoven membrane, resulting in better nanofibrous structure of the as-spun nanofibers. Application of airflow on needleless electrospinning would further benefit the development of mass production of nanofibers from needleless electrospinning.

Electrospun nanofiber membranes for electrically activated shape memory nanocomposites

A novel shape memory nanocomposite system, consisting of a thermoplastic Nafion polymer and ultrathin electrospun polyacrylonitrile (PAN)-based carbonization nanofiber membranes, is successfully synthesized. PAN-based carbonization nanofiber networks that offer responses to deformations are considered to be an excellent actuation source. Significant improvement in the electrical conductivity of carbon nanofiber membranes is found by adjusting the applied voltage power in the electrospinning PAN process varying from 7.85 to 12.30 S cm−1. The porous structure of the carbon nanofiber membranes provides a large specific surface area and interfacial contact area when combined with the polymer matrix. Shape memory Nafion nanocomposites filled with interpenetrating non-woven electrospun PAN carbonization membranes can be actuated by applying 14 V electrical voltage within 5 s. The results, as demonstrated through morphology, electrical and thermal measurements and a shape recovery test, suggest a valuable route to producing soft nanocomposites.

The enhanced alcohol sensing response of multiwalled carbon nanotube networks induced by alkyl diamine treatment

The vapor sensing properties of multiwalled carbon nanotube networks (MWCNT-Ns) of randomly entangled pristine nanotubes and the nanotubes treated by KMnO4–H2SO4, ethylenediamine and hexamethylenediamine deposited on polyurethane supporting non-woven membrane to vapors of linear alcohols (methanol, ethanol, 1-propanol, 1-butanol and 1-pentanol) are measured by monitoring of electrical resistance of the networks. The substantial increase is observed in the sensor response of the networks to vapors of the alcohols induced by the alkyl diamine treatments of nanotubes in comparison with those of pristine and the KMnO4 treated MWCNT-Ns. Analysis of the enhanced linear alcohol sensing properties of the MWCNT-Ns is concentrated on the interactions between the network and the alcohols and the amount of adsorbed alcohols on the networks by using the Fourier transform infrared (FTIR) spectroscopy analysis and the gravimetric measurements. The scanning electron microscopy, Brunauer–Emmett–Teller surface area and thermal gravimetric analyses are used for the characterization of the networks as well as FTIR. The result shows that the enhanced vapor sensor response can be attributed to the extent of the interaction area between the carbon nanotubes and the alcohols.

Electrospun polyimide-based fiber membranes as polymer electrolytes for lithium-ion batteries

Polymer electrolytes based on electrospun polyimide (PI) membranes are incorporated with electrolyte solution containing 1molL−1 LiPF6/ethylene carbonate/ethylmethyl carbonate/dimethyl carbonate to examine their potential application for lithium ion batteries. The as-electrospun non-woven membranes demonstrate a uniformly interconnected structure with an average fiber diameter of 800nm. The membranes, showing superior thermal stability and flame retardant property compared to the commercial Celgard® membranes, exhibit high porosity and high uptake when activated with the liquid electrolyte. The resulting PI electrolytes (PIs) have a high ionic conductivity up to 2.0×10−3 S cm−1 at 25°C, and exhibit a high electrochemical stability potential more than 5.0V (vs. Li/Li+). They also possess excellent charge/discharge performance and capacity retention. The initial discharge capacities of the Li/PIs/Li4Ti5O12 cells are 178.4, 167.4, 160.3, 148.3 and 135.9 mAh g−1 at the charge/discharge rates of 0.2C, 1C, 2C, 5C and 10C, respectively. After 200 cycles at 5C, a capacity around ∼146.8 mAh g−1 can be still achieved. The PI-based polymer electrolytes with strong mechanical properties and good electrochemical performance are proved to be promising electrolytes for lithium ion batteries.

Effect of Nylon-6 Concentration on Morphology and Efficiency of Nanofibrous Media

Electrospinning is a method of nanofiber filter media production. By this method, it is possibleto produce media with nanofiber in the range of nanometer to micrometer. Nanofibrous media provide a large specific surface area in a finite volume thus they are suitable for filtration applications. In this study, nanofiber non-woven membranes production of Nylon-6 by electrospinning method is investigated. It is demonstrated that the total filter efficiency and pressure drop increases by increasing the thickness of filer media. The objective of this experimental study was to find out the effect nylon concentration and thickness of nanofilter media.Samples by different Nylon-6 concentrations and time of electrospinning were made. The filtration characterizations of these media were investigated in different laboratory conditions. The SEM micrographs of specimens treated by ImageJ software reveal that the porosity passes by a minimum at 10% concentration. The diameter of nanofiber varied in the range of 47 to 89 nm when the nylon concentration varied from 7.5% to 15% respectively. The efficiency was improved more than three times by electrospinning operation for all three concentration samples. Our results showed that the highest efficiency obtained in this study was 99.96% belonging to 10% Nylon-6 concentration for 45 minutes electrospinning time.

Polyimide matrix-enhanced cross-linked gel separator with three-dimensional heat-resistance skeleton for high-safety and high-power lithium ion batteries

To develop a kind of gel polymer electrolyte with high ion conductivity and good mechanical strength and thermal stability, a polyimide (PI) matrix-enhanced cross-linked gel separator is designed and fabricated by a simple dip-coating and heat treatment method. The PI nonwoven substrate provides high-temperature thermal stability for the gel separator and the crosslinked gel part yields enhanced affinity with the liquid electrolyte. Besides, the cross-linked polymer network could solve the issue of long-term durability of the composite separator in batteries. The gel separator shows better cyclability and rate capability than the traditional PP separator, implying a promising potential application in high-power, high-safety lithium ion batteries. The preparation process is compatible with the traditional manufacturing process of nonwoven membranes, and can be easily converted into continuous production on the industrial scale.

Electrospun polycaprolactone/ZnO nanocomposite membranes as biomaterials with antibacterial and cell adhesion properties

In the present study we have investigated the effect of zinc oxide (ZnO) nanoparticles on the fiber diameter, fiber morphology, antibacterial activity, and enhanced cell prolifer- ation of the electrospun polycaprolactone (PCL) non-woven membrane. The effect of the ZnO nanoparticle concentration on the fiber diameter and fiber morphology was investigated using a scanning electron microscope (SEM). Fourier trans- form infraredspectroscopy(FT-IR)analysis was carried out to determine the nature of the interaction between the PCL and the ZnO nanoparticles. We also investigated the mechanical stability and antibacterial activity of the fabricated material. Interestingly, the membranes with ZnO nanoparticles showed enhanced mechanical stability, antibacterial properties, fibro- blast proliferation, and improved metabolic activity of the cells. Further, this is the first report regarding the ability of a biomaterial containing ZnO nanoparticles to enhance cell proliferation.

Improved mechanical properties and hydrophilicity of electrospun nanofiber membranes for filtration applications by dopamine modification

Electrospun nanofiber membranes (ENMs) are an emerging platform for membrane filtration; however, widespread applications of ENMs are hindered by poor mechanical strength attributed to their high porosity, intrinsically low, random fiber orientations and weak interactions between fiber junctions. In addition to suitable mechanical properties, most water-based filtration processes require membranes to be hydrophilic in order to resist fouling and enhance water flow. In this study, we demonstrate a simple chemical modification capable of improving the mechanical properties of polyacylonitrile (PAN) and polysulfone (PSu) ENMs. The chemical modification involves the polydopamine (PDA), a hydrophilic polymer. PDA has the dual benefit of hydrophilization and strengthening of ENMs to improve their wettability and tolerance to operational and handling conditions. When deposited onto the fibers, PDA promotes bonding between fibers by coating junction points throughout the nonwoven. The coated nonwoven membranes showed a 100 to 300% increases in tensile strength and Young׳s Modulus with no decrease in flexibility while retaining their porous structure and high water permeability. For hydrophobic PSu ENMs, the hydrophilicity was also significantly improved after coating.