Nanofiber Filter Research Articles

Large scale poly(vinyl alcohol-co-ethylene)/TiO2hybrid nanofibrous filters with efficient fine particle filtration and repetitive-use performance

A high-yielding nanofiber-based filtration material with excellent performance was developed and provides a promising way to control the severe air pollution at present.

Magnetic BaFe12O19 nanofiber filter for effective separation of Fe3O4 nanoparticles and removal of arsenic

Magnetic nanoparticles are promising in applications where magnetic separation is intended, although material losses via leaching mechanisms are often inevitable. Magnetic separations with widely available permanent magnets can effectively trap particles, leading to a complete removal of used or waste particles. In this report, we first demonstrate the synthesis of the thinnest (112.7 ± 16.4 nm) and most magnetic (71.96 emu g−1) barium hexaferrite (BaFe12O19, BHF—fridge magnet) via an organic solvent-free electrospinning procedure. When the fibers are then packed into a column, they clearly remove 12 nm magnetite (Fe3O4) nanoparticles quantitatively. The same BHF cartridge also removes more than 99.9 % As-treated magnetite nanoparticles at capacities up to 70 times of its weight. As a result, one liter of 150 μg L−1 As-contaminated water can be purified rapidly at a material cost of less than 2 US cents.

Fabrication of electrospun polyamide-66 nanofiber layer for high-performance nanofiltration in clean room applications

Clean room is an environment in which the concentration of ambient particles is controlled in order to keep the number of particles in the room at a minimum level. Clean room garments should be capable of preventing the transmission of particles from a person to the ambience. Filtration properties, along with favorable breathability and elasticity, provide a strong reason for using these structures for clothing purposes in the clean room environment. In the present study, the polyamide-66 nanofiber layer was electrospun on Spunbond–Meltblown–Spunbond nonwoven substrate as coating in several time intervals. Consequently, the filtration test was conducted on two groups of particles. Dioctyl phthalate as uniform particles and atmospheric particles as nonuniform particles were used to evaluate the filtration efficiency of the nanofibrous filter. The statistical analysis showed that the filtration efficiency for dioctyl phthalate particles was less than atmospheric particles. Also, at longer coating time, the difference between efficiencies was at the lowest level. Air permeability and water vapor permeability were studied as components of garment thermal comfort specifications. Results of this study show that air permeability decreased and overall filtration efficiency of the produced layer was improved by increasing of coating time.

Bacterial filtration efficiency of green soy protein based nanofiber air filter.

High bacterial filtration efficiency (BFE) filters, based on nanofibers derived from blends of grain proteins and poly-ethylene-oxide (PEO), were produced by an electrospinning process. Specifically, polymer blends consisting of purified soy flour/PEO with a ratio of 7/3 were spun into nanofibers and characterized. A new laboratory based experimental apparatus for testing BFE was designed and used to test BFE of bacterial aerosols consisting of Escherichia coli (E. coli). Performances of soy protein based nanofiber filters with nanofiber mass varying from 1 to 5 g/m2 as well as a nanofiber filters prepared from pure PEO were compared. The results showed that BFE values for filters containing 5 g/m2 protein based nanofibers and PEO nanofiber filter were 100 and 81.5%, respectively. The results also indicated that the BFE increased as the protein content in the nanofiber filter increased. These novel protein based nanofiber filters have demonstrated a clear potential for effective removal and retention of E. coli bacteria during air-filtration. These filters can be effectively deployed in environments such as hospitals and senior residential areas to reduce bacterial infections.

Preparation and Characterization of Fibrillated Nanofibrous Filter Material

The nanofiber, which diameter less than 1000 nm, has been discovered as advanced fiber material for high efficiency filtration. Tencel fiber is a new kind of regenerated fiber which can be easily fibrillated by a mechanical beating process to form nanofiber morphology. The present study shows the nanofiber morphology of Tencel fiber and investigates how the structure and properties of filter material change with the impact of fibrillated nanofiber. The results show a mass of nanofibril appeared after the Tencel fiber is intensively beat. At the same time, the air permeability and pore size of filter material is decreased with the decrease of fibrillated nanofiber content while the strength gets an opposite trend. Whats more, the filtration efficiency of the filter material is significantly enhanced by fibrillated nanofiber which filtration rate achieves 6.3 for particles bigger than 4 μm at 20 wt%. This paper has shed some light on the application of fibrillated fibrillated nanofiber to enhance the efficiency of filter material effectively.

Filtration and Length Determination of Airborne Carbon Nanotubes in the Submicrometer Range Using Nanofiber Filters

The growing usage of carbon nanotubes (CNTs) in different applications increases concern of negative influence of CNTs on human health. Therefore the control of CNTs is significant and filtration is an effective method to control airborne CNTs. We investigated penetration of airborne CNTs through nanofiber filters composed of micro and nanometer fiber. The theoretical model for nanofiber filter media was also investigated and the experimental results agreed with the model. The penetrations of CNTs through the nanofiber filters were compared with the penetration through a screen type filter made of stainless steel. Moreover, the geometrical lengths of CNTs were calculated by the filtration method using the nanofiber filter. The calculated lengths showed a good agreement with the measured lengths by scanning electron microscopy analysis. The developed method for the length measurement of CNTs provides the possibility of online measurement for elongated particles such as CNTs.

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.

Filtration performance of cigarette filter tip containing electrospun nanofibrous filter

Nanofibrous filters made of electrospun nanofibers are used in different types of filtration. In this study, nanofibrous filters comprising of electrospun filter media between two nonwoven layers were placed in cigarette filter tip and the performance of the new filter was assessed. Electrospinning conditions were varied to achieve ultrafine cellulose acetate nanofibers for this purpose. Nanofibers of different diameters and different layer thickness (based on unit area weight) were used. Tar removal efficiency increased by increasing the unit area weight of filter media. Nanofibrous filter containing nanofibers with a mean diameter of 280 nm increased efficiency from 47.7 to 71.6% for filter tip and efficiency sharply decreased by increasing the diameter of nanofibers. Double layer electrospun filter media showed higher efficiency and lower pressure drop than those of single one with the same unit area weight. Tar removal efficiency increased significantly by using nanofibrous filters, whereas the pressure drop was not affected severely. On the other hand, tar/nicotine ratio reduced.

Edible oil mill effluent; a low-cost source for economizing biodiesel production: Electrospun nanofibrous coalescing filtration approach

Article history: Biofuels have increased in popularity because of rising oil prices and the need for energy security. However, finding new raw sources for biodiesel production is still challenging. The oil which comes from wastewater effluent generated in edible oil mills (EOM) can be considered a low-cost, widely available, emerging and interesting source for biodiesel production. This study tries to improve the coalescing filtration by using electrospun nanofibrous filters for oil recovery from the EOM effluent. In order to improve the separation efficiency of the filters, thermal treatments (90oC to 150oC) were used. Results indicate that oil recovery using coalescing filtration is a promising method for providing a new source for making biodiesel production more economical.

Properties of Hydrophilic Chitosan/Polysulfone Nanofibrous Filtration Membrane

Electrospun nanofibrous membranes are useful water filtration materials due to their high interconnected porosity and tunable pore sizes, which cause very high permeability and selectivity. However, poor mechanical properties and easy fouling due to their extremely high surface area limit their applications. Therefore, it is desirable to enhance the mechanical properties and the hydrophilicity of such electrospun nanofibrous membranes. In this paper, electrospun polysulfone (PSF) nanofibrous membranes were treated with plasma. Crosslinked chitosan solution was then employed to pad the membranes. We studied the influence of the chitosan concentration and the volume of glutaraldehyde on the morphology, porosity structure, mechanical properties and hydrophilicity of electrospun polysulfone nanofibrous membranes. The results showed that the average pore size decreased from 4.5 μm to 2.68 μm, the breaking stress increased from 6.01±0.44 MPa to 9.25±0.45 MPa, and the water contact angle decreased from 130.8° to 0° in 30 s when chitosan was applied to the membranes. These changes occurred by padding due to the crosslinked chitosan solution. The results indicate that a significant improvement occurred in the mechanical properties; the highly hydrophobic PSF membrane was changed to a superhydrophilic one and the pore size was reduced. These results encouraged us to propose this material as a water filtration membrane with longer life span, lower fouling and higher rejection efficiency.

Filtration and Length Determination of Airborne Carbon Nanotubes in the Submicrometer Range Using Nanofiber Filters

Filtration and Length Determination of Airborne Carbon Nanotubes in the Submicrometer Range Using Nanofiber Filters

Fabrication of Electrospun Polyamide-6/Chitosan Nanofibrous Membrane toward Anionic Dyes Removal

Nanofibrous filter media of polyamide-6/chitosan were fabricated by electrospinning onto a satin fabric substrate and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and water contact angle (WCA). Anionic dye removal capability of the filter was investigated for Solophenyl Red 3BL and Polar Yellow GN, respectively, as acidic and direct dyes were investigated with respect to solution parameters (pH and initial dye concentration) and membrane parameters (electrospinning time and chitosan ratio) through filtration system. Experiments were designed using response surface methodology (RSM) based on five-level central composite design (CCD) with four parameters to maximize removal efficiency of the filter media. Moreover, the effect of parameters and their likely interactions on dye removal were investigated by mathematically developed models. The optimum values for solution pH, initial dye concentration, electrospinning time, and chitosan ratio were predicted to be 5, 50 mg/L, 4 hr, 30% and 5, 100 mg/L, 4 hr, 10%, respectively, for achieving 96% and 95% removal of Solophenyl Red 3BL and Polar Yellow GN. Evaluation of the estimation capability of applied models revealed that the models have a good agreement with experimental values. This study demonstrated that polyamide-6/chitosan nanofibrous membrane has an enormous applicable potential in dye removal from aqueous solutions.

Design and Characterization of Electrospun Polyamide Nanofiber Media for Air Filtration Applications

Electrospun polyamide 6 (PA 6) and polyamide 6/6 (PA 6/6) nanofibers were produced in order to investigate their experimental characteristics with the goal of obtaining filtration relevant fiber media. The experimental design model of each PA nanofibers contained the following variables: polymer concentration, ratio of solvents, nanofiber media collection time, tip‐to‐collector distance, and the deposition voltage. The average diameter of the fibers, their morphology, basis weight, thickness, and resulting media solidity were investigated. Effects of each variable on the essential characteristics of PA 6/6 and PA 6 nanofiber media were studied. The comparative analysis of the obtained PA 6/6 and PA 6 nanofiber characteristics revealed that PA 6/6 had higher potential to be used in filtration applications. Based on the experimental results, the graphical representation—response surfaces—for obtaining nanofiber media with the desirable fiber diameter and basis weight characteristics were derived. Based on the modelling results the nanofiber filter media (mats) were fabricated. Filtration results revealed that nanofiber filter media electrospun from PA6/6 8% (w/vol) solutions with the smallest fiber diameters (62–66 nm) had the highest filtration efficiency (PA6/6_30 = 84.9–90.9%) and the highest quality factor (PA6/6_10 = 0.0486–0.0749 Pa−1).

Preparation of electrospun polyurethane filter media and their collection mechanisms for ultrafine particles

Electrospinning is a simple and versatile process to produce polymer nanofibers, which are useful for ultrafine particle filtration. In this study, a polyurethane filter with an average fiber diameter of 150–250 nm was prepared through the electrospinning process and its filtration characteristics were investigated. We found that the electrospun fiber diameter was highly dependent on the polyurethane concentration, electric field, and tip-to-collector distance. As the polyurethane concentration, electric field, and tip-to-collector distance under the same electric field increased, the fiber diameter increased. We also found that the produced filter media had a minimum collection efficiency at particles sizes from 80 to 100 nm, which implies an electrostatic attraction between the filter and the test particles. Furthermore, we observed that interception was a predominant collection mechanism at Peclet numbers higher than 10 in nanofiber filtration for ultrafine particles. Implications: A polyurethane nanofiber filter with excellent mechanical properties was prepared, and the effect of operating conditions on fiber morphology was examined. The filter fabricated by an electrospinning process is charged and has high filtration efficiency due to electrostatic force. Therefore, it can be a good alternative to control hazardous ultrafine particles.

Coalescing filtration of oily wastewaters: characterization and application of thermal treated, electrospun polystyrene filters

ABSTRACT In this study, a number of electrospun nanofibrous polystyrene (PS) filters were developed and applied for coalescing filtration of an oily wastewater stream at pilot scale. The effect of thermal treating on the morphology and performance of electrospun nanofibrous filters was studied. The initial effect of thermal treating started after 130°C and the maximum allowable thermal treating temperature observed was 150°C. The results obtained indicated that thermal treating led to the formation of uniform pore structure and pore size distribution, lower pore size, lower pore tortuosity, as well as higher coalescing filtration efficiency. Moreover, the surface roughness and surface energy decreased after thermal treating. To the best of our knowledge, this was the first attempt to use thermal treated electrospun nanofibrous PS filters at pilot-scale liquid–liquid coalescing filtration of oily wastewaters.

Nanofabric nonwoven mat for filtration smoke and nanoparticles

The process of production of filtration mats of various thickness from PVC and PVDF polymers by the electrospinning method is presented in the paper. Filtration of nanoparticles and submicron particles is an important problem in industry and health protection systems, in particular in air-conditioning and ventilation appliances. This problem can be effectively solved by application of non-woven fibrous filtration mats. The experimental investigations of mechanical properties of nanofibrous filtration mats produced by electrospinning and the measurements of removal efficiency of submicron particles from flowing gas have indicated potential usefulness of these nanomats for gas cleaning of air-conditioning systems and/or ventilation ducts. The experimental results obtained for cigarette smoke of a mass median diameter of about 1 μm, used as test particles, have shown that nonwoven nanofibrous filtration mats produced by electrospinning have a good filtration efficiency for nano- and submicron particles, owing to a pressure drop similar to HEPA filters. Particles of this size are particularly difficult to be removed from the flow by a conventional method, for example, by a cyclone or electrostatic precipitator.

Meltblown nanofiber media for enhanced quality factor

Nanofibers definitely hold great advantage and promise in filtration as they have very high specific surface area, which ensures greater probability of capturing the particles and hence, the filtration efficiency of the nanofiber filter media is high. Electrospun nanofibers are prohibitively expensive due to extremely low production rate. With recent advances in melt blowing technology, nanofibers could be produced at production rate few orders of magnitude higher than that of conventional single syringe electrospinning and hence, quite cost effective. Influence of air pressure and die to collector distance (DCD) were studied on the number average fiber diameter for the nanofibers as well as the performance properties of the nonwoven webs, each factor at three discrete levels. The nanofibers were as fine as 260 nm. A very encouraging observation of the study is very high values of quality factor observed for nanofiber nonwoven filter media. In order to compare the filtration efficiency of different nanofiber nonwoven media samples with different basis weight, a novel term of specific filtration efficiency is proposed and was found that the specific filtration efficiency with the increase in DCD or air pressure.

Further improvement of air filtration efficiency of cellulose filters coated with nanofibers via inclusion of electrostatically active nanoparticles

Air filtration efficiency and pressure drop of nanofibrous filter media based on polyacrylonitrile (PAN) nanofibers with and without TiO2 nanoparticles were evaluated. The nanofibrous filter media were fabricated by covering a cellulose substrate with varying masses of PAN fiber or PAN/TiO2 hybrid nanofiber. Capillary flow porometry tests revealed that the hybrid nanofibrous filter media showed larger pore size and broader pore size distribution than their counterpart pure PAN nanofibrous filter media. The pressure drop of the filter media covered with the PAN/TiO2 hybrid nanofibers (0.5 g/ft2) was 4 times less than that of the counterpart filter media at an air velocity of 80 cm/s. Despite less fiber coverage density on the cellulose substrate and a greatly reduced pressure drop, the filtration efficiency of the nanofibrous filter media made with PAN/TiO2 hybrid fibers was found to be much greater than that of those made with just pure PAN fibers, especially for smaller particles in the range 0.1–0.5 μm. These results might be influenced by the added electric charge caused by the insertion of TiO2 nanoparticles in the fibers. Therefore, the improvement of two important features, enhanced filtration efficiency and reduced pressure drop can be simultaneously achieved through the use of polymer/TiO2 hybrid nanofibrous filter media. This holds promise for facile development of energy-saving, high performance filters.

Water–diesel secondary dispersion separation using superhydrophobic tubes of nanofibers

Water-in-oil dispersion separation in the petrochemical industries is important due to safety, ecological and economic reasons. In this work, nanofiber mat filters are fabricated in flat sheet and cylindrical geometries and tested for separation of water dispersions in diesel fuel. The nanofiber mats are formed by electrospinning. Due to the fiber size, pore size, and material composition, the nanofiber mat surfaces are superhydrophobic which aids in the separation of the dispersion. The superhydrophobic surfaces are oleophilic due to their low surface energy. The surface roughness of the nanofiber membranes enhance the hydrophobicity while the oleophilicity allows the non-aqueous phase to easily flow through the nanofiber membrane. The cylindrical nanofiber filters performed with separation efficiency as high as 98% on a total mass basis for water drops in the range of 7–50μm in ultra low sulfur diesel fuel (ULSD) with a face velocity of 1.55cm/min. The flat filter geometry performed at about 92% separation efficiency at a similar face velocity. This work shows practical water–diesel separation filters can be constructed in tubular geometries.

Visualization of water flow during filtration using flat filtration materials

Filtration materials are very important elements of some industrial appliances. Water filtration is a separation of solid materials from fluid. Solid particles are captured on the frontal area of the filtration textile and only liquid passes through it. It is important to know the filtration process in a detailed way to be able to develop filtration materials. Visualization of filtration process enables a better view of the filtration. This method also enables to determine efficiency and homogeneity of filtration using image analysis. For this purpose, a new waterfiltration measuring setup was proposed and constructed. Filtration material is mounted into the optically transparent place in the setup. Laser sheet is directed into this place as in the case of Particle Image Velocimetry measuring method. Monochrome and sensitive camera records the light scattered by seeding particles in water. The seeding particles passing through the filter serve for measuring filtration efficiency, and also for visualization of filtration process. Filtration setup enables to measure also the pressure drop and a flow. The signals are processed by National Instruments compactDAQ system and UMA software. Microfibrous and nanofibrous filtration materials are tested by this measuring method. In the case of nanofibrous filtration, appropriate size of seeding particles is needed to be used to perform a process of filtration.