Nanofiber Filter Research Articles

Development of SPI/AC/PVA nano-composite for air-filtration and purification

PurposeDevelopment of high efficiency nanofibrous air filter membrane by electrospinning process, to address the air pollution (both the particulate matter and the gaseous components) problem, which has become a major environmental concern.Design/methodology/approachBy exploiting the advantage of active sites on soy protein isolate (SPI), the very high surface area of micro-pore rich activated carbon (AC) and the biocompatibility and biodegradable nature of polyvinyl alcohol (PVA). The authors have developed a SPI/AC/PVA hybrid membrane. Spun-bond nonwoven substrate was used as the support material to enhance the mechanical properties and also the filter handling properties. The properties of nanofibrous membrane including morphology, air permeability, filtration efficiency and formaldehyde absorption test were carried out as per standard test methods.FindingsSPI-based membrane offers a great potential in air filtration/purification applications. Its potential to capture glancing pollutants at the molecular level is because of the presence of numerous functional groups on the soy protein surface, which enhances the adsorption of particulate matter and toxic gases, even bacteria and viruses to its surface.Originality/valueThe results are anticipated to provide a potential method to promote the development of a nanofibrous membrane, which can act as a high performance, dual function and eco-friendly air filter/purifier.

3D structure design and simulation for efficient particles capture: The influence of nanofiber diameter and distribution

Software simulation is a convenient and efficient way to design and check different air filter structures with high efficiency and low pressure drop. In this work, nanofiber filters of different diameters ranging from 100 to 900 nm were designed to check their influence on filtration efficiency, pressure drop and quality factor (QF). Slip-flow effect of air molecules was considered on the surface of single fiber. Then, filters with different diameter distributions were constructed to study the filtration efficiency discrepancy when the filter thickness and porosity were kept equal. With a rotation of the filters composed of nanofibers of 500 nm in diameter in the computational domain, the filtration efficiency and QF increased steadily. The simulation results were partially verified by electrospun cellulose acetate nanofiber filter, and meanwhile provide with new insights into the filter structure design of high filtration efficiency with low pressure drop.

Nanofiber Filter Performance Improvement: Nanofiber Layer Uniformity and Branched Nanofiber

ABSTRACT We developed two types of high performance nanofiber filters by increasing the uniformity of the fiber layer’s deposition on the substrate media and by fabricating nanofiber with a branched morphology, in which additional fibers were spun to radiate from the main fibers. We subsequently compared them with conventional and beaded nanofiber filters in terms of particle removal efficiency, filter pressure drop, and particle loading capacity. First, the uniformity of the nanofiber’s deposition, which was visually evaluated using optical and electron microscopes, was increased by removing the substrate surface charge during electrospinning. The uniform nanofiber filters demonstrated a higher filtration efficiency with a lower pressure drop than their conventionally electrospun counterparts, which exhibited irregular fiber layers. Second, branched nanofiber was fabricated by adjusting the viscosity of the polymer solution. The performance of the nanofiber filters was dramatically improved by the decrease in air flow resistance, which resulted from (1) a longer distance streamwise between the fibers and (2) a smaller diameter for the fibers. The enhanced efficiency was also due to (3) the additional fibers branching out from the main fibers.

Continuous production and properties of mutil-level nanofiber air filters by blow spinning.

Nanofibers are gradually being widely used in air filtration due to their unique characteristics. However, the mass production of nanofiber filter material faces several problems. Blow spinning is an emerging technology, which have great potential for mass production of nanofibers. In this work, we have successfully realized the continuous production of 500 mm wide nanofiber membranes by blow spinning, which enables continuous preparation of multi-level nanofiber filter materials: PAN60 (filtration efficiency is 63.2%, pressure drop is 18 Pa), PAN80 (filtration efficiency is 80.7%, pressure drop is 38 Pa), PAN90 (filtration efficiency is 92.9%, pressure drop is 58 Pa) and PAN99 (filtration efficiency is 99.5%, pressure drop is 123 Pa). In order to improve the stability performance of melt-blown filters, we provide a strategy that combines nanofibers with a melt-blown filter. PAN nanofibers were sprayed directly on the melt-blown filter by blow spinning. The composite filters have more stable filtration performance and higher efficiency when intercepting particles with a diameter below 100 nm than melt-blown filters.

Influence of fiber diameter, filter thickness, and packing density on PM2.5 removal efficiency of electrospun nanofiber air filters for indoor applications

Electrospinning is a versatile technique to fabricate nanofiber filters with high PM2.5 removal efficiency and relatively low pressure drop. The eletrospun nanofiber filters may therefore be applied in buildings to reduce indoor exposure to PM2.5 and the associated adverse health effects. This study investigated the influence of various filter parameters, including fiber diameter, filter thickness, and packing density, on the PM2.5 removal efficiency. In this work, 25 nylon electrospun nanofiber filters with different filter parameters were prepared, and the PM2.5 removal efficiency of each sample was measured at five different face velocities. In total, 125 sets of measured data were obtained. The results show that the PM2.5 removal efficiency of nylon electrospun nanofiber filters was negatively associated with the fiber diameter, and positively associated with the thickness of the filter. However, there was no clear correlation between PM2.5 removal efficiency and packing density. This investigation further developed a semi-empirical model for predicting the PM2.5 removal efficiency of nylon nanofiber filters. The accuracy of the model was satisfactory with a median relative error of 7.9%.

Electrospun nanofiber from various source of expanded polystyrene (EPS) waste and their characterization as potential air filter media

This paper reported on the fabrication of nanofibrous membranes from various sources of expanded polystyrene (EPS) waste using electrospinning technique and their application as air filter media. The filter membranes were made from four EPS waste sources, i.e. food packaging, EPS craft, instant noodle cup, and electronic packaging. The properties of the membranes fabricated from those sources were compared to obtain the best EPS waste source for air filter application. To make the precursor solutions, those samples were dissolved in d-limonene:DMF with the concentration of 15, 20, and 25 wt%. The solid EPS density, solution viscosity, and surface tension were measured. The fiber diameter and morphology of nanofibers were characterized by scanning electron microscopy (SEM) for each EPS variation. The fabricated membrane properties (crystallinity, wettability, and mechanical strength) and filtration properties (pressure drop, PM2.5 filtration efficiency, and quality factor) were fully characterized and analyzed. Homogeneous fiber diameter with various morphologies (beaded, wrinkled, and smooth fiber) were obtained from all samples with hydrophobic to super-hydrophobic surface (water contact angle ranging from 106 to 153°). Also, the EPS solid density affected the solution viscosity with the expression of η = 0.132 ρ0.29, which then affected the fabricated membrane packing density, porosity, and mechanical properties. Overall, the experimental results showed that all EPS nanofiber filters had great potential as an air filter media. The EPS filter made from food packaging waste with the solution concentration of 15 wt% exhibited the highest efficiency and quality factor of 99.99% and 0.15 Pa−1, respectively.

Fabrication of durable superhydrophobic nanofibrous filters for oil‐water separation using three novel modified nanoparticles (ZnO‐NSPO, AlOO‐NSPO, and TiO2‐NSPO)

Three reusable and durable superhydrophobic nanofibrous filters were prepared by dip coating the nanofibrous fabric in the three different dispersed solutions of the newly modified nanoparticles (ZnO‐NSPO, AlOO‐NSPO, and titanium dioxide [TiO2]‐NSPO). The contact angle results proved that the TiO2‐NSPO coated nanofibrous polyacrylonitrile (PAN) filter was hydrophobic with the water contact angle (WCA) of 141° while the ZnO‐NSPO and AlOO‐NSPO coated nanofibrous PAN filters were superhydrophobic with the WCA of 168° and 152°, respectively. The as‐prepared filters can be utilized as an effective martial for oil‐water separation with separation efficiency of over 98%.

Fabrication of bead-on-string polyacrylonitrile nanofibrous air filters with superior filtration efficiency and ultralow pressure drop

The presence of ultrafine particle matter (PM) in air is one of the most hazardous environmental issues because of their severe threat to human health. Design and development of cost-effective and energy-efficient air filters to remove the PM by facile methods are highly demanded. Electrospun nanofibrous membranes have been explored for PM filtrations as they can achieve high removal efficiencies due to their ultrafine nanofibers. However, their enhanced particle removal efficiencies are at the cost of high pressure drops. In this work, porous bead-on-string filters with nanobeads along the nanofiber axis have been successfully fabricated by optimizing the polyacrylonitrile (PAN) concentration of electrospun dopes and ambient humidity condition during the electrospinning process. The combined effects of polymer concentration and humidity condition could achieve an unbalanced status between the repulsive and constrictive forces along the jets from the spinneret in the electrospinning process, which generated a filter with a desirable bead-on-string morphology. The nanobeads are able to reduce the packing density and alleviate the pressure drop through the filter while the ultrafine nanofibers guarantee the PM removal efficiency. Besides, the effects of nanofiber diameter, airflow rate and nanobead density on the filtration efficiency and pressure drop of NaCl solid and Paraffin oil aerosols with an average diameter of 300 nm have been investigated systematically. With the assistance of bead-on-string construction, the pristine PAN filter can easily achieve an excellent efficiency above 99% with a low pressure drop of 27 Pa at an airflow rate of 4.2 cm/s. This work suggests that transformation of electrospun filters from a nanofibrous structure to a bead-on-string morphology via the adjustments of polymer concentration and ambient humidity is sufficient to generate filter mediums with excellent efficiency and low airflow resistance for air filtration applications, which is also facile to be scaled up as no special equipment and costly chemicals are required.

A Strip Biosensor with Guinea Green B and Fuchsin Basic Color Indicators on a Glass Nanofiber Carrier for the Cholinesterase Detection of Nerve Agents.

This paper deals with the innovation of the Czech colorimetric biosensor Detehit designed for the simple, fast, and sensitive detection of nerve agents. The innovation is based on the use of an indicator consisting of a mixture of two triphenylmethane dyes, Guinea green B and a basic fuchsin, on a glass nanofiber filter paper carrier. The advantage of this solution is the blue–red color transition, which is much more visible than the white–yellow transition of other Detehit biosensors. The newly designed biosensor allows the users to visually detect (with the naked eye) the presence of the most significant paralytic substances (sarin, soman, cyclosarin, tabun, VX) in water at concentrations of at least 0.001 μg/mL. This biosensor design also enables one to detect these substances in air or on contaminated surfaces.

Preparation of nanofibrous metal-organic framework filter for rapid adsorption and selective separation of cationic dye from aqueous solution

A nanofibrous metal-organic framework (MOF) filter was successfully fabricated via co-electrospinning of anionic bio-MOF-1 (Zn8(Ad)4(BPDC)6O·2(NH2(CH3)2)+, 8DMF, 11H2O) and polyacrylonitrile (PAN) for adsorption and selective separation of cationic dyes from aqueous solution. Characterization with FT-IR, EDS and PXRD confirmed that bio-MOF-1 crystals were effectively encapsulated into PAN nanofibrous matrix and their crystallinity maintained well. Due to the free NH2 (CH3)2+ cations in the channel of bio-MOF-1 and nucleophilic group CN in PAN, both bio-MOF-1 crystals and PAN nanofibers were only capable of adsorbing cationic dyes and could not adsorb neutral and anionic dyes. Benefiting from the synergistic effect of bio-MOF-1 and PAN, the bio-MOF/PAN filter exhibited rapid adsorption rate towards positively charged dye methylene blue (MB+), and realized the fast selective separation of MB+ from mixed dyes solution. More importantly, the bio-MOF/PAN filter can be effectively regenerated through ion-exchange process. The adsorption capacities of the filter towards MB+ kept relatively stable values within the five cycles of filtration-regeneration, indicating that bio-MOF/PAN filter can meet the requirement of long service life. This work may provide a new insight into the development of electrospun MOF nanofibrous membrane as a filter for rapid separation and purification of organic dyes from practical wastewater.

Green electrospun nanofiber membranes filter prepared from novel biomass thermoplastic copolyester: Morphologies and filtration properties

Abstract High-performance and eco-friendly nonwoven-nanofiber filters comprising renewably sourced bio-based polyesters were fabricated by electrospinning (ES). Typical commercial nonwoven filters are thick, with uneven fiber distributions and low recovery. Bio-based polymers made of raw plant materials have soft textures. Over 75% of the polyester used herein was sourced renewable. We observed variations in its morphology under different operating conditions in scanning electron microscope images by tuning the operating parameters of ES and using different DMF/CHCl3 solvent ratios. We produced various types of ES nanofibers with uniform fiber diameters ranging from 400 to 2000 nm, which increased filter efficiency and helped overcome existing shortcomings in filter applications. A scanning mobility particle sizer and NaCl aerosol particles of sizes 30–300 nm were used to test the prepared nanofiber filters. Owing to their high specific surface areas/volume ratios and small-fiber diameters, the nanofiber filters with fiber diameters smaller than 500 nm forcefully resisted the majority of suspended particles. The averaged penetration ability of ES fiber was decreased from 30% to 4%, with increasing heating temperature and annealing time. Thicker ES fibers with beaded morphologies exhibited average penetration

Solution blown nanofibrous air filters modified with glass microparticles

High-pressure drop and lower dust holding capacity reduce the performance of nanofibrous air filters. For that reason, this study was carried out to form filters with high-quality factor and high dust holding capacity, thanks to the glass particle additives. In this study, as an approach to such modifications, fluffy nanofiber webs were produced via solution blowing. Polyamide 6 (PA6) was chosen as the base for the nanofibrous mats, where glass microparticles were embedded as an additive to reduce web solidity. The effects of glass microparticle embedding on the filtration performance and pressure drop of the mats were investigated. SEM analysis was performed to analyze nanofiber diameter and morphology. Also, the barrier properties of samples were examined by air filtration and air permeability tests. Findings showed that the addition of glass particles did not alter fiber morphology significantly. However, lowering the pressure drop resulted in higher air permeability and better filtration performance in terms of the quality factor. Glass particles embedded composite samples exhibited a higher quality factor compared to the neat PA6 sample, and the PA6 + 5%GP sample has the highest quality factor value around 0.43. The filtration efficiency of this sample was 99.97% at an expense of 187.3 Pa pressure drop. The obtained enhancement was conducted to the lower solidity of composite webs which was 36% lower for the PA6 + 5%GP sample.

Hierarchical Porous Poly(l-lactic acid) Nanofibrous Membrane for Ultrafine Particulate Aerosol Filtration.

Ultrafine particulate aerosols less than 100 nm diffuse randomly in the air and are hazardous to the environment and human health. However, no technical standards or commercial products are available for filtering particle sizes under 100 nm yet. Here, we report the development of a porous poly(l-lactic acid) (PLLA) nanofibrous membrane filter with an ultra-high specific surface area via electrospinning and a post-treatment process. After PLLA fibres were electrospun and collected, they were treated by acetone to generate a blossoming porous structure throughout each individual fibre. Characterizations of morphology, crystallinity, and mechanical and thermal properties demonstrated that the porous structure can be attributed to the nonsolvent-induced spinodal phase separation during electrospinning and solvent-induced recrystallization during post treatment. The blossoming porous structure with high specific surface area contributed to excellent filtration efficiency (99.99%) for sodium chloride (NaCl) ultrafine aerosol particles (30-100 nm) with a low pressure drop (110-230 Pa). Notably, under 7.8 cm/s air flow rate, the membrane samples performed better for filtering smaller-sized aerosol particles than the larger ones when evaluated by the quality factor (0.07). Finally, this finding demonstrates that the electrospun membrane with a hierarchical pore structure and high specific surface area hold great potential in applications as air-filtering materials.

Electrospun meta-aramid/polysulfone-amide nanocomposite membranes for the filtration of industrial PM2.5 particles

Filtering of industrial PM2.5 is a major challenge for global environmental and animal protection. Filtering of materials with excellent thermal stability and other comprehensive performances is required for the removal of fine particles in high-temperature operating industries such as steel, cement, metallurgy, incineration, etc. In this study, a meta-aramid/polysulfone-amide (PMIA/PSA) composite nanofibrous filtration membrane is prepared via solution electrospinning for the development of high-temperature-resistant filtering products. To maximize the merits of each component, PMIA/PSA composite nanofibrous membranes with different mass blending ratios are prepared to determine the optimal balance. It is found that the PMIA/PSA composite nanofibrous membranes show excellent thermal stability and thermal shrinkage performance. They also maintain superb mechanical retention ratios after 200 h treatment at 200 °C. In addition, they exhibit excellent removal efficiency of polystyrene aerosol (PSL) particles of various sizes. It is found that the removal efficiency of PMIA/PSA (3/7) is 96.7% for 0.1 μm, 98.3% for 0.2 μm and 99.6% for 0.3 μm particles and it possesses optimal filtration resistance (79 Pa), while other composite membranes can reach a removal efficiency of over 99.7%. Our experimental results illustrate that the filtration efficiency for PM2.5 of PMIA/PSA (7/3), (5/5) composite nanofibrous membranes is still kept as high as 99.9% even after being treated at 200 °C for 120 h. It indicates that the prepared composite nanofibrous membranes have potential for applications where high-efficiency filtration is desired, such as bag dust filters for use under high temperatures.

Electrospun nanofiber filters for highly efficient PM2.5 capture

With the recent increase of concern on the health impact of air pollution, there has been growing interest in filtration technologies that can effectively remove fine inhalable particles (PM2.5) in the air with diameters that are generally 2.5 µm or smaller. Among various technologies presented, nanofiber-based filters provide A simple, but effective route to rapidly capture these fine particulate matters. In this review, we briefly introduce the health hazards associated with PM2.5 and highlight the importance of air filtration technology with particular emphasis on nanofiber-based filters prepared via electrospinning. Then, we summarize various fiber materials and additives utilized in electrospun nanofibers to enhance the filtration efficacy. Furthermore, we highlight some of the recent advances in the materials design of electrospun nanofiber filters for PM2.5 removal and discuss the current issues and future perspectives.

Development of nanofiber filter to capture one blood circulating tumor cell in one drop of blood

Development of nanofiber filter to capture one blood circulating tumor cell in one drop of blood

Submicron aerosol filtration performance of centrifugally spun nanofibrous polyvinylpyrrolidone media

In this study, polyvinylpyrrolidone-based nanofibrous air filter media were produced via centrifugal spinning and subsequently stabilized by thermal cross-linking process. Samples were produced using solutions with three different polymer concentrations (5, 10 and 20 wt.%) and three different rotational speeds (4000, 6000 and 8000 r/min). After obtaining the optimum web structure with the lowest average fiber diameter and the most uniform distribution, the webs were later thermally cross-linked in order to stabilize polyvinylpyrrolidone against the degradative effects of water. In addition, the webs were subjected to dissolvability tests to see the efficacy of cross-linking treatment. Morphological, structural and chemical characterizations of the polyvinylpyrrolidone webs were performed by SEM, XRD and FTIR, respectively. Finally, filter efficiency and pressure drop were measured to assess filter performance. The results have shown that the lowest average fiber diameter is obtained at the highest rotational speeds. Subsequent thermal cross-linking treatment has been found to prevent fibers from dissolving in water. The produced water-resistant, environmentally friendly polyvinylpyrrolidone nanofibrous filter media has had a satisfactory filtration performance with a high filter efficiency of 99.995% and a high quality factor of 0.39 mm H2O−1.

The Effect of Nonwoven Microfiber Substrate Polypropylene Thickness to Air Filtration Performance of Polyacrilonitrille Nanofiber

Since a nanofiber medium on itself is soft and fragile and cannot be used alone as air filters. Coating nanofiber on a rigid substrate to form a composite that can be handled readily is necessary. Beside can improve the filtration efficiency, adding the substrate will also save the use of nanofibers mat itself. The aim of this study is to evaluate the effect of substrate thickness on the performance of nanofibers mat in aerosol filtration in order to find the optimum thickness of substrate that can increase the quality of nanofiber filter. The substrate used was a low cost microfiber non-woven fabric made from polypropylene (PP). The nanofibers mat was composed of electrospun polyacrylonitrile (PAN) with concentration of 9 wt.% which dissolved at N,N dimethylformamide (DMF). Five variations of PP different in thickness was used as substrate. From the SEM image, it was found that there is increasing fiber diameter of PAN after electrospun into PP substrate. From the porosity estimation of each nanofiber, it was found that the porosity decreased with increasing the substrate thickness. For test the performance of nanofiber filter, the particles of polystyrene latex (PSL) which generated by atomizer was used as the aerosol particle. In addition, to evaluate the performance filter in PM2.5 filtration, the experiment was carried out with generate the smoke from burning incense. Air filtration performance of all variations is obtained by comparison the results of measurement including: pressure drop, efficiency and quality factor. From the results, there is limitation on the substrates thickness based on the value of the quality factor obtained. Overall, PP nonwoven as the substrates gives the great contribution on the efficiency of PAN nanofiber. Keywords: substrate, polypropylene, thickness, nanofiber, air filtration.

Multifunctional TiO2/polyacrylonitrile nanofibers for high efficiency PM2.5 capture, UV filter, and anti-bacteria activity

In this work we present a multifunctional filter having polyacrylonitrile (PAN) nanofibers with embedded commercial P25 and/or TiO2 bead filler. The composite nanofibers were synthesized through a green method of electrospinning. The properties of the filters having single- and/or binary-filler composite fibers were investigated. It was found that TiO2 beads have higher electrostatic attraction to capture PM2.5 than P25. Binary-filler nanofiber filter having a higher beads/P25 ratio shows an excellent filtration efficiency of 96.75% with a low pressure drop of 88 Pa. As a result, a high quality factor of 0.039 has been obtained. This is 177% enhancement as compared to the PAN-only filter. Furthermore, the composite filters also exhibit antibacterial activity of 5.5 under 30 min UV irradiation, which is 9 times higher than that of the PAN-only filter. These results indicate that PAN-based composite filter with commercial P25 and/or TiO2 beads fillers is excellent material for making facial mask.

Self-assembly of positively charged SiO2/Y2O3 composite nanofiber membranes with plum-flower-like structures for the removal of water contaminants

Abstract Water contaminants, especially bacterial and viral contaminants, have substantially negative impacts on human health because of their wide variety and incredibly small sizes. To develop a nanofiber filter with a high adsorption capacity, a positively charged SiO2/Y2O3 composite membrane with a plum-flower-like structure was prepared by self-assembly and heat treatment. The effects of the hydrothermal temperature and reaction time on the morphology of the composite nanofiber membrane (NFM) were investigated. In the composite NFM, the Y2O3 nanoflowers were tightly bound to the SiO2 nanofiber support. The possible formation mechanism of the composite NFM with a plum-flower-like structure is discussed. The results indicated that the Y2O3 nanoparticles were attached to the SiO2 nanofiber support via a Y-Si-O chemical bond. The surface charge of the composite NFM and its adsorption properties toward water contaminants were characterized. The isoelectric points (IEP) of the composite NFM calcinated under a N2(96%)/H2(4%) atmosphere was 9.23. The maximum bacterial retention was close to 100% and the log reduction values (LRV) of the bacteria were 6. Viral contaminants were simulated using a small molecule with two negative charges, titan yellow, with a maximum saturated adsorption capacity and removal rate of the plum-flower-like NFM for titan yellow were 87.96 mg/cm3 and 99.999%, respectively. After reusing a membrane five times, the composite NFM retained a removal rate of 95.641%. This positively charged SiO2/Y2O3 composite NFM with a plum-flower-like structure has broad application prospects in the fields of contaminant removal and virus filtration.