Air Filtration Materials Research Articles

Electrospun PS/PAN Nanofiber Membranes Formed from Doped Carbon Nanotubes with a Fluffy and Multi-scale Construction for Air-Filtration Materials

Electrospun PS/PAN Nanofiber Membranes Formed from Doped Carbon Nanotubes with a Fluffy and Multi-scale Construction for Air-Filtration Materials

Indoor air dust removal system based on high-voltage direct current triboelectric nanogenerator

Indoor air pollution has become the "invisible killer" of human health, which may cause respiratory diseases, chronic lung diseases, bronchitis, lung cancer, and other diseases. Here, we propose and demonstrate an indoor dust removal system that utilizes high-voltage electrostatic adsorption without assistance of any air filter material. The triboelectric nanogenerator (TENG) is based on contact electrification and air breakdown effects, with a maximum output open-circuit voltage (Voc) of 27 kV. This indoor dust removal system consists of a rotation mode high voltage TENG with direct current (RH-DC-TENG) and dedusting glass (DG), which can achieve rapid reduction of PM2.5 from 954 μg/m3 to 50 μg/m3 in an 8000 cm3 air chamber in 199 s under TENG rotation speed of 120 rpm. This indoor dust removal system is concise, safe, and effective, providing a potential self-driven and sustainable avenue to contributing to a cleaner indoor air environment and improving human health.

Polyphenylene sulfide fabric with enhanced oxidation resistance and hydrophobicity through polybenzoxazine surface coating for emission control in harsh environment

Emissions from power generation and municipal waste incineration sources are primarily at high temperatures and contain corrosive gases, particulate pollutants and are enormously challenging on the performance of the filtration systems in use. Here, polyphenylene sulfide (PPS) nonwoven fabric, a primary material used commercially in such settings, is modified with a polybenzoxazine precursor as a coating to deliver improved thermal and oxidation resistance to the fibrous substrate. The polybenzoxazine precursor undergoes chain propagation and crosslinking upon the treatment process to provide a protective layer over the PPS fibers such that enhanced structural stability in a harsh environment was demonstrated. We have shown the improved overall tensile strength (+15%), Young’s modulus (+26%), and more hydrophobic nature of the modified PPS fabric, while the superior environmental stability and better filtration performance could be achieved. Such methodology may lead to higher service temperature and extended service time of the PPS filtration bags in harsh fire exhaustion airstreams encountered in power plants or municipal garbage incineration facilities. The crosslinkable benzoxazine could also be the most cost-effective high temperature coating layer on fibers, enabling future high-performance air filtration materials.

Multi-functional air filters with excellent flame retardancy and fire-warning capability

High fire-safe air filters are indispensable for indoor environments, such as vehicle interior, fresh air filtration system, and window screens. However, it is still challenging to afford both excellent flame retardancy and rapid fire-warning capability in air filters. In this study, we fabricate a type of high-efficient fiber filters with combined flame-retardant and fire-warning performance. Nanofibers with a specific tri-layer structure are designed to incorporate Polyacrylonitrile (PAN) matrix and two functional components, flame retardant ammonium polyphosphate (APP) and amino-functionalized carbon nanotube (A-CNTs). The resultant PAN/CNTs/APP fiber filters have high PM2.5-10 capture efficiency of > 99.99%. The filters can not be burnt in vertical burning test and exhibit high limiting oxygen index value of 30.9%. Moreover, the resultant PAN/CNTs/APP fiber filters achieve short fire-warning response time (∼5s) when encounters fire. This work offers a facile and cost-effective approach to fabricate multifunctional air filters, and shows promising applications in vehicle interior, firefighting, fresh air filtration and building materials.

Characteristics of Basepaper Blended with Bamboo Organosolv Pulps and Wood Kraft Pulps for Air Filter Application

Air pollution is a major environmental issue; thus, air purification apparatus fitted with various types of filter have become popular to remove suspended particulate matter, dirts and toxic materials to create a clean environment. Polypropylene is the most popular types of filter materials; however, is not easily reusable, which can lead environmental pollution during incineration process. In this regards, applications of cellulosic fibers to air filter materials could be an alternative way to alleviate these issues. In this study, sheets of paper blended with bamboo pulps from an organosolv pulping and kraft pulps were produced in a pilot-scale papermachine and investigated as a base paper to fabricate a potential air filter architecture. The air resistance of the blended paper was less than one second regardless of the grammage and mixing ratios of bamboo and kraft pulps, indicating the resulting base paper could be used an air filter material.

Theory and technology of air filtration: review

The development of modern science and technology, improving the level of industrialization, increase people's awareness of environmental protection were leaded to the world's demand for filter materials to purify the air. This review presented an overview of air pollutants classification, history of fiber materials, theory of air filtration technology, and traditional air filtration (materials, characteristics, advantages, disadvantages, and standards). In addition, the paper reviewed the mechanisms of filtration, which include diffusion, interception, intermolecular interaction, straining, inertial impaction, gravitation, and electrostatic interaction of particles on the filter surface. Different studies have revealed the possibilities for the utilization of activated carbon fiber in the removal of VOC or odor from gaseous emissions in the air.

Needle-punched electret air filters (NEAFs) with high filtration efficiency, low filtration resistance, and superior dust holding capacity

• N eedle-punched E lectret A ir F ilters ( NEAFs ) with a 3D fluffy structure are designed and successfully fabricated. • NEAFs exhibit high filtration efficiency, low filtration resistance, and large dust holding capacity at the same time. • NEAFs also show superior charge and filtration stability due to the employment of MgSt charge enhancing additive. Air purification can effectively capture particulate matter and reduce the health risk from indoor air pollution. However, it remains a challenge to fabricate filtration materials with high filtration efficiency, low filtration resistance, and large dust holding capacity at the same time. Herein, we report N eedle-punched E lectret A ir F ilters ( NEAF s) not only exhibiting the abovementioned performance, but also owning superior charge and filtration stability. By employing corona charging and MgSt charge enhancing additives, NEAFs exhibited high filtration efficiency (99.2%) and ultralow filtration resistance (13.93 Pa). Importantly, NEAFs only had 0.6% decline in filtration efficiency after heat treatment, which was much better than commercial meltblown materials. In addition, the needle-punching technique generated a unique 3D fluffy structure, resulting in a large dust holding capacity of 23.6 g m −2 . Our design of NEAFs may provide new guidelines for next-generation high-performance air filtration materials.

Study on static adsorption characteristics of a new reduced graphene oxide air filter material for volatile formaldehyde from glue

Formaldehyde is one of the main indoor pollutants, and living in an environment with formaldehyde for a long time can cause serious damage to the human body. In this paper, non-woven fabrics and new reduced graphene oxide air filter materials were used to perform static adsorption tests on formaldehyde volatilized from glue. The results show that the new reduced graphene oxide air filter material has good formaldehyde adsorption performance, and the adsorption saturation of this material is as long as 4 hours, which is twice that of F6 non-woven fabric. Within 4 hours, the formaldehyde removal efficiency of the new reduced graphene oxide air filter material and F6 non-woven fabric were 15.4% and 2.9%, respectively, and the formaldehyde adsorption was 0.81·10-3mg and 4.32·10-3mg, respectively, and the removal efficiency was improved5.9 times. This paper provides reference and reference value for the adsorption performance of new composite air filter materials on harmful gas pollutants.

Filtration performance of new reduced graphene oxide air filter material against bacteria in the atmosphere during the initial stage of heating

With the large-scale outbreak of the COVID-19, people have gradually realized the importance of bioaerosols in the environment, and how to efficiently filter out microbial aerosols in the air, so as to create a safe and healthy air environment is urgent. The non-bacteriostatic F6 non-woven filter material and the synthesized new reduced graphene oxide air filter were tested and analyzed in this paper, and the filtration performance of the material against bacterial aerosols in the atmosphere at the initial stage of heating. The results showed that during the initial stage of heating, the particle size distributions of aerosols in the atmosphere during working days were stageⅠ(>7.0μm)4.34%, stageⅡ(4.7~7.0μm)4.62%, stageⅢ(3.3~4.7μm)13.30%, stageⅣ(2.1~3.3μm)21.11%, stageⅤ(1.1~2.1μm)38.70%, stageⅥ(0.65~1.1μm)17.92%. The particle size distributions of aerosols in the atmosphere on non-working days were stageⅠ(>7.0μm)4.52%, stageⅡ(4.7~7.0μm)13.66%, stageⅢ(3.3~4.7μm)23.04%, stageⅣ(2.1~3.3μm)31.82%, stageⅤ(1.1~2.1μm)15.18%, stageⅥ (0.65~1.1μm)11.78%. The new reduced graphene oxide filter material had a 10% increase in the filtration efficiency of the total bacterial aerosol compared with the ordinary non-woven filter material. Among them, the filtration efficiency of the respirable bacterial aerosol (particle size <4.7μm) was significantly improved by 40%. The results of this study could provide a certain reference for building a safe interior in the post-epidemic era, and also provided reference value for the research and development of functional air filters.

Zeolite imidazole framework-8(ZIF-8) decorated keratin-based air filters with formaldehyde removal and photocatalytic disinfection performance

Air pollution, consisting of particles of broad sizes, bioaerosols, and gaseous toxic chemicals, has become a serious hazard to public health. However, conventional fibrous filters have the disadvantages of high air resistance and limited ability to remove toxic gaseous and inhibit harmful microorganisms. Herein, we report a bilayer multifunctional air filter material based on applying electrospinning and needle-punching methods to generate hierarchically structure. Specifically, the air filter consists of keratin-based nanofibers as an upper layer and ZIF-8-modified polyethylene terephthalate/polyethylene needle-punched materials as the substrate. Green, facile, and controllable sonication process involved in thermally-assisted coating method was used to incorporate ZIF-8 onto the substate. The exposed functional groups of keratin and porous ZIF-8 nanocrystals with a high surface area promote the capture capability for small particulate pollutants and toxic gaseous molecules. Meanwhile, the needle-punched substrate with large pores significantly reduces the pressure drop and imparts photocatalytic disinfection performance to the air filter by the excellent photocatalytic characteristic of ZIF-8. This study proposes a novel strategy to fabricate hierarchical multifunctional air filters by combining electrospinning and needle-punching and plays a guidance role in designing and developing keratin-based hybrid materials.

Ag/Zn Galvanic Couple Cotton Nonwovens with Breath-Activated Electroactivity: A Possible Antibacterial Layer for Personal Protective Face Masks.

The water vapor exhaled by the human body can severely accelerate the charge dissipation of commercial face masks, thereby reducing the electrostatic adsorption efficiency and increasing the bacterial invasion risk. This study developed an electroactive antibacterial cotton nonwoven (Ag/cotton/Zn) using eco-friendly magnetron sputtering technology. The Ag/Zn electrode constructed on the surface of cotton nonwovens could produce a microelectric field in the moist environment of human respiration, which endowed Ag/cotton/Zn with excellent electroactivity. When Ag/cotton/Zn was used as an additional layer of polypropylene melt-blown nonwovens or polylactic acid nanofibers, the prepared personal protective air filter had a filtration efficiency of up to 96.8% and an appropriate pressure drop and air permeability. The antibacterial results based on bacterial aerosols showed that the antibacterial efficiency against Escherichia coli and Staphylococcus aureus in 20 min was 99.74 and 99.79%, respectively, indicating an excellent electroactive killing efficiency against airborne bacteria. In addition, Ag/cotton/Zn showed excellent biological security. These results shed some light on the design and fabrication of next generation of personal protective air filter materials driven by human breathing.

Bio-based electrospun nanofiber as building blocks for a novel eco-friendly air filtration membrane: A review

• Basic principle of electrospun nanofiber membranes for air filtration is demonstrated. • Characteristics and advantages of electrospun natural bio-based nanofiber membranes are analysed. • Comprehensive performance of electrospun natural polymer nanofiber membranes in air filtration is discussed. • Limitations, modification strategies and future perspectives are presented. Currently, air pollution as a thorny issue has been affecting the atmospheric environment and human health for a long time. Air filtration is a crucial and effective method to improve the air quality. The nanofiber membranes fabricated by electrospinning technology have play a prospective role in the field of air filtration due to their porous structure, high specific surface area, controllable morphology and multi-functional fiber surface. The excessive utilization of traditional air filter materials prepared from non-degradable polymers or glass fibers poses huge challenges to environmental protection. Supported by the advantages of wide availability, environmental sustainability, biocompatibility and biodegradability, natural polymers have become good candidates to substitute traditional synthetic polymers for manufacturing air filtration media. In this review, the necessity and mechanism of air filtration are firstly introduced. On this basis, it is proposed to evaluate the performance parameters of nanofiber membranes prepared by electrospinning technology in air filtration. In addition, in view of the restrictions of traditional air filtration materials, the valuable prospects of eco-friendly and sustainable natural bio-based materials are introduced in detail, as well as the diverse categories and comprehensive performance of their nanofiber membranes prepared by electrospinning technology in removing air pollutants. Given that the research summary of this review, we finally deliberate the remaining problems and future challenges.

ZIF-67 grown on a fibrous substrate via a sacrificial template method for efficient PM2.5 capture and enhanced antibacterial performance

In the design air filtration materials, surface modification and porosity control are appealing strategies to achieve a higher quality factor. In this study, a sacrificial template method was introduced to obtain hierarchically metal–organic framework (MOF)-loaded micro/nano-backbone fibrous filters. Cobalt carbonate hydroxide hydrate nanoneedle arrays were first grown on polyester fabric as a sacrificial template that provide Co2+ source for constructing a ZIF-67 on micro/nano fibrous backbone substrate, which resulted in a combination of enokitake-like and bead-on-string-like structure simultaneously. This unique structure effectively reduced the pore size of the fabric and provided a modified surface with a maximum exposure of MOFs. As a consequence, the composite fabric filter exhibited excellent PM2.5 removal efficiency of 97.5 ± 1.2%, while with only a small increase in pressure drop (∼14 Pa). Particularly, the PM2.5 filtration quality factor was up to 0.051, which is 200% higher than that of pristine PET. Furthermore, the composite fabric filter showed excellent antibacterial activity against both S. aureus and E. coli. This study facilitated the design of hierarchically MOF-loaded fibrous filter materials with excellent comprehensive filtration performance.

Tailoring Nanonets‐Engineered Superflexible Nanofibrous Aerogels with Hierarchical Cage‐Like Architecture Enables Renewable Antimicrobial Air Filtration

AbstractPurification of pathogenic air has become an essential part of infection prevention and control. Most present air filters can hardly achieve excellent air filtration performance and the effective inactivation of the airborne pathogens at the same time. Herein, a bottom‐up approach is reported upon to construct cage‐like structured superflexible nanofibrous aerogels (CSAs) with renewable antimicrobial properties by combining electrospun silica nanofibers, bacterial cellulose nanofibers, and the hydrophobic SiOSi elastic binder. The following efficient grafting of N‐halamine compounds endows the CSAs with biocidal function. The resultant aerogels exhibit intriguing features of high porosity, hydrophobicity, superelasticity, foldability, renewable chlorination ability (>5400 ppm), high filtration performance toward PM0.3 (>99.97%, 189 Pa), and excellent antibacterial and antiviral activity (6 logs reduction within 5 min contact), enabling the aerogels to intercept and inactivate the pathogenic contaminants in air. The successful synthesis of CSAs provides a new possibility to design high‐performance air filtration materials for public health protection.

Ultrafine PVDF Nanofibers for Filtration of Air-Borne Particulate Matters: A Comprehensive Review.

The ongoing global pandemic has bestowed high priority uponthe separation of air-borne particulate matters (PMs), aerosols, etc. using nonwoven fibrous materials, especially for face masks as a means of personal protection. Although spunbond or meltblown nonwoven materials are amongst the forerunners for polymer microfiber-based face mask or air filter development in mass scale, relatively new process of nonwoven manufacturing such as electrospinning is gaining a lot of momentum amongst the filter membrane manufacturers for its scalability of nanofiber-based filter membrane fabrication. There are several nanofiber-based face masks developing industries, which claim a very high efficiency in filtration of particulate matters (PM0.1–10) as well as other aerosols for their products. Polyvinylidene fluoride (PVDF), which is commonly known for its use of tactile sensors and energy harvesters, due to its piezoelectric property, is slowly gaining popularity among researchers and developers as an air filter material. Electrospun PVDF nanofibers can be as fine as 50 nm in mass scale, which allows the membrane to have large surface area compared to its volume, enhancing nanofiber–PM interaction. At the same time, the breathability index can be improved through these PVDF nanofiber membranes due to their architectural uniqueness that promotes slip flow around the fibers. The conductive nature of PVDF makes it advantageous as a promising electret filter allowing better capturing of ultrafine particles. This review aims to provide a comprehensive overview of such PVDF nanofiber-based filter membranes and their roles in air filtration, especially its application in filtrate of air-borne PMs.

Preparation of high-temperature resistant poly (m-phenylene isophthalamide)/polyacrylonitrile composite nanofibers membrane for air filtration

Nowadays, many industrial factories usually emit a large amount of dusty waste gas with high temperature in daily production, which will bring huge threat to the environment and human health if they are not disposed properly. However, the existing removal technology for high-temperature dusty gas have some shortcomings in practice, especially for the low efficiency on extremely small particles of filtration. Electrospinning is a technique commonly used to produce ultrafine nanofibrous filter. By combining high-temperature resistant materials with electrospinning technology can give high-temperature resistant materials the small size effect of nanofibers. It is expected to prepare a new kind of air filter material which performs high-precision filtration, excellent mechanical property and high-temperature resistance. This study focuses on polyacrylonitrile (PAN) with high spinnability and high-performance poly (m-phenylene isophthalamide) (PMIA) fiber to prepares PMIA/PAN composite nanofiber membranes. By adjusting the combination of mass fraction and mass ratio of the two organic solutions, PMIA/PAN composite nanofiber membranes were prepared to own the excellent mechanical properties, stable filtration performance and better high-temperature resistance. The experiments show that the breaking strength and elongation at break of PMIA/PAN composite nanofiber membrane with a combination of mass fraction of 11–12 and a mass ratio of 9:1 are 2.683 MPa and 37.36% respectively. Furthermore, the filtration efficiency of PMIA/PAN composite nanofiber membranes can maintain over 99% after a series of heat treatment. • By blending the solutions to prepare PMIA/PAN nanofiber membranes integrated the advantages between the two components. • The PMIA/PAN composite nanofibers membrane not only maintains a filtration efficiency above 99% after a series of heat treatments but owns great mechanical property. • Using the self-made needleless electrospinning machine to prepare PMIA/PAN composite nanofibers membrane, which can realize the mass production.

Multistructured Electrospun Nanofibers for Air Filtration: A Review.

Air filtration materials (AFMs) have gradually become a research hotspot on account of the increasing attention paid to the global air quality problem. However, most AFMs cannot balance the contradiction between high filtration efficiency and low pressure drop. Electrospinning nanofibers have a large surface area to volume ratio, an adjustable porous structure, and a simple preparation process that make them an appropriate candidate for filtration materials. Therefore, electrospun nanofibers have attracted increased attention in air filtration applications. In this paper, first, the preparation methods of high-performance electrospun air filtration membranes (EAFMs) and the typical surface structures and filtration principles of electrospun fibers for air filtration are reviewed. Second, the research progress of EAFMs with multistructures, including nanoprotrusion, wrinkled, porous, branched, hollow, core-shell, ribbon, beaded, nets structure, and the application of these nanofibers in air filtration are summarized. Finally, challenges with the fabrication of EAFMs, limitations of their use, and trends for future developments are presented.

Electrospun Nanofiber Mats for Filtering Applications-Technology, Structure and Materials.

Air pollution is one of the biggest health and environmental problems in the world and a huge threat to human health on a global scale. Due to the great impact of respiratory viral infections, chronic obstructive pulmonary disease, lung cancer, asthma, bronchitis, emphysema, lung disease, and heart disease, respiratory allergies are increasing significantly every year. Because of the special properties of electrospun nanofiber mats, e.g., large surface-to-volume ratio and low basis weight, uniform size, and nanoporous structure, nanofiber mats are the preferred choice for use in large-scale air filtration applications. In this review, we summarize the significant studies on electrospun nanofiber mats for filtration applications, present the electrospinning technology, show the structure and mechanism of air filtration. In addition, an overview of current air filtration materials derived from bio- and synthetic polymers and blends is provided. Apart from this, the use of biopolymers in filtration applications is still relatively new and this field is still under-researched. The application areas of air filtration materials are discussed here and future prospects are summarized in conclusion. In order to develop new effective filtration materials, it is necessary to understand the interaction between technology, materials, and filtration mechanisms, and this study was intended to contribute to this effort.

Material Properties Analysis with Addition of Nanofibres for Air Intake Filtration in Internal Combustion Engines

The aim of this study is to provide an experimental properties evaluation of a standard filter material (cellulose) and materials with fiber layer addition with small diameters (nanofibers). Filter media, including cellulose, used in the internal combustion engine inlet air filtration are made of high diameter fibres, approx. 15 µm. Significantly higher separation and filtration efficiency performance are obtained for materials with lower fibre diameters (nanofibres), however, at the expense of a significantly higher pressure drop, affecting the engine performance. Filter media manufacturers mainly specify the structure parameters (pore size, air permeability and thickness), without giving any information on the dust filtration performance and rate. The literature includes test results for models of different filter media structures. Filtration process modelling using polydisperse dust with particles of different shape and density and irregular filter media structure is possible using advanced computer techniques, however, the process is complex and requires many simplifications. Test results can be applied directly in the automotive industry. The data can be obtained by experimental tests on filter medium specimens, complete filter elements or air filters which are costly and time-consuming tests, however, those test methods are the most reliable. Conditions and testing methodology for intake air filter materials used in internal combustion engines were developed. Filtration and flow resistance efficiency and accuracy were done depending on test dust mass stopped per unit area. Tested materials filtration efficiency was assessed by a filtration quality factor, which includes experimentally determined efficiency and accuracy as well as flow resistance values. Much higher efficiency and filtration accuracy of dust grains below 5 µm in filtration materials with nanofibers addition compared to standard filtration material (filter paper) were demonstrated. For the same flow resistance values, filter materials with nanofibers addition accumulate smaller dust mass than standard filter paper. Usage of materials with nanofibers addition used in motor vehicles intake air filtration ensures their high efficiency and accuracy. It minimises its components wear, but at the expense of faster flow resistance increase, which shortens filter life and increases filter replacement frequency. Results obtained during the experimental research partly fill the gap when it comes to the basic material properties used in internal combustion engines intake air filter partitions production.

Hierarchically Structured Nanocellulose-Implanted Air Filters for High-Efficiency Particulate Matter Removal

Fine particulate matter (PM) air pollution has increasingly become a global problem; thus, high-performance air filtration materials are in great demand. Herein, we first prepared a biodegradable hierarchically structured nanocellulose-implanted air filter with a high filtration capacity using a freeze-drying technique. In this hierarchically structured air filter, porous structures of corrugated paper and cellulose nanofibrils (CNFs) were used as a frame and functional fillers, respectively. The self-assembled structure of the CNF fillers could be controlled by changing the freezing temperature, CNF sizes, concentrations, and base weights. Only the CNFs with a smaller size and concentration of 0.05 wt % were able to self-assemble to well-dispersed fibril networks. With constant optimization of conditions, when the base weight went up to only 0.25 g/m2, the coverage of the corrugated paper fibers with CNF networks became perfect, and a high efficiency of 94.6% for PM0.3 removal was achieved, while maintaining a relatively low pressure drop of 174.2 Pa. All of the raw materials we used are biodegradable, nonpetroleum-based materials, contributing to sustainable development. We believe that such excellent biodegradable high-performance cellulose-based air filtration materials will provide a new direction for the application of nanocellulose in air filtration.