Air Filtration Materials Research Articles

Study of Graphene Oxide/Polymer Composite Membranes in Air Filtration of PM2.5

pollution, particularly the issue of fine particulate matter (PM2.5), which has emerged as a significant environmental and public health concern globally. It is particularly important to develop efficient, economical and sustainable air filtration materials to reduce the concentration of PM2.5. In this study, we investigated the potential application of some polymers such as polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN) and polyaniline (PANI) composites with graphene oxide (GO) for efficient PM2.5 filtration. These composites were found to have excellent filtration performance, thermal stability. PVDF/ GO/PI nanofiber membranes maintained stable performance under repetitive filtration cycles and high temperature conditions. PAN/GO/PI nanofiber membranes exhibited good mechanical properties and stable cycling performance.PANI/GO composites took advantage of the unique properties of the conductive polymers, and in TGA experiments, they showed minimal mass loss. Their durability and efficiency remain high even after multiple wash cycles, highlighting their potential for practical applications.

Research on the process of preparing fiber filtration membrane by centrifugal blowing electrospinning technology

AbstractCurrently, the problem of air pollution is getting more and more serious, especially the pollution of tiny solid particles (PM, particulate matter) in the air, which poses a great challenge to the environment and human health. Therefore, it is particularly important to develop air filtration materials with high filtration efficiency and low resistance to meet this challenge. In this study, we propose to prepare air filtration membranes by centrifugal jet electrospinning technology, design multifactorial orthogonal coupling experiments, and investigate the effects of key process parameters of centrifugal jet electrostatic spinning, including solution concentration, airflow rate, rotational speed, and voltage, on the fiber diameter and uniformity by applying the polar analysis of variance and analysis of variance. PAN‐BaTiO3 electret nanofiber filtration membranes with high efficiency and low resistance were prepared by combining the optimized process of centrifugal blowing electrospinning. Various characterization methods (tensile test, water contact angle test, surface charge test, filtration test) were used to evaluate the effect of different BaTiO3 electret contents (0%, 0.1%, 0.5%, 1%) on the comprehensive performance of the filtration membranes, and the electret filtration efficiency of the electret filtration membranes prepared by the present process reached as high as 96.56% with a pressure drop of 29 Pa.

Construction of highly efficient flame retardant cellulose nanofibrils/bamboo activated charcoal based composite aerogel sheet for excellent PM2.5 removal

Developing biomass air filter materials with efficient filtration for particulate matter 2.5 (PM2.5) and low pressure drop is a great challenge. Targeting this issue, cellulose nanofibrils (CNF) were employed as the skeleton materials mixing with bamboo activated charcoal (BAC), polyethyleneimine (PEI), and ammonium polyphosphate (APP) as the functional fillers, followed by freeze-drying and hydrophobic modification to prepare CNF/BAC based composite aerogel sheet for capture for PM2.5. The resulting aerogel sheet showed good filtration efficiency for PM2.5 (98.64 %), which benefited from the three-dimensional network structure from CNFs and PEI and electrostatic adsorption of both BAC and APP with negative charge. After reusing for 5 times, the filtration efficiency of the system could still maintain at 95.88 %. In addition, the introduced both APP and PEI made the system have excellent flame retardant through the synergistic effect of nitrogen and phosphorus. In view of excellent properties and simple preparation, this work supplies a promising way to prepare multifunctional biomass air filter.

Effect of multifunctional cationic polymer coatings on mitigation of broad microbial pathogens.

Infection control is critical for maintaining a healthy home, work, and hospital environment. We test a cationic polymer capable of capturing and eradicating viral and bacterial pathogens by applying the polymer to the air filtration material and textiles. The data suggest that the simple addition of cationic material can result in the improvement of an infectious resilient environment against viral and bacterial pathogens.

Deep trapped bipolar heterocharges enable electret nanofibrous membranes for high-efficiency PM0.3 filtration

Recently frequent global pandemic outbreak triggers the demand of high-efficiency aerosol filtration materials. Most of traditional electret air filters can hardly achieve high efficiency (>99.99 %) due to limited charge density and inappropriate charge distribution. The influence mechanism of nanofibers bipolar heterocharge configuration on electrostatic capture of airborne particles is still confusing. Herein, a novel strategy to create high-efficiency air filters based on electret nanofibrous membranes with deep trapped heterocharge is reported. Space charges and dipole charges with opposite polarity are formed in electrospun membranes composed of different polymers under in-situ charge injection and electric poling during electrospinning. Nanoscale spatial surface potential mapping on individual nanofiber characterized by Kelvin probe force microscopy demonstrates bipolar heterocharge distribution. Numerical simulation shows that fiber heterocharge distribution endows the electret membrane with greater electrostatic field intensity gradient, resulting in stronger electrostatic force between nanofibers and airborne particles. With bipolar heterocharge configuration and bimodal fiber diameter distribution, the nanofibrous membranes exhibit high-efficiency low-resistance filtration property against 0.3 μm NaCl particles (99.994 %, 97.4 Pa) at 5.3 cm s−1. Furthermore, benefiting from charges with deep trap energy of 1.12 eV, the membranes still maintain 99.972 % filtration efficiency after 40 h exposure in 95 % relatively humidity. The prepared membranes brings new insight in the design of high-efficiency and long-term stability air filtration materials for public health precaution. This study not only reveals influence mechanism of nanofibers heterocharge distribution on electrostatic attraction, but also provides useful guidance for fiber charge configuration design to improve aerosol filtration performance of electret filters.

Two-Dimensional Piezoelectric Nanofibrous Webs by Self-Polarized Assembly for High-Performance PM0.3 Filtration.

Particulate matter (PM) pollution has posed a serious threat to public health, especially the global spread of infectious diseases. Most existing air filtration materials are still subjected to a compromise between removal efficiency and air permeability on account of their stacking bulk structures. Here, we proposed a self-polarized assembly technique to create two-dimensional piezoelectric nanofibrous webs (PNWs) directly from polymer solutions. The strategy involves droplets deforming into ultrathin liquid films by inertial flow, liquid films evolving into web-like architectures by instantaneous phase inversion, and enhanced dipole alignment by cluster electrostatics. The assembled continuous webs exhibit integrated structural superiorities of nanoscale diameters (∼20 nm) of the internal fibers and through pores (∼100 nm). Combined with the wind-driven electrostatic property derived from the enhanced piezoelectricity, the PNW filter shows high efficiency (99.48%) and low air resistance (34 Pa) against PM0.3 as well as high transparency (84%), superlight weight (0.7 g m-2), and long-term stable service life. This creation of such versatile nanomaterials may offer insight into the design and upgrading of high-performance filters.

Novel multi-hierarchical nanofiber aerogel for high efficient filtration of high-temperature flue gas

Fibrous air filtration materials are highly effective at capturing particulate matter (PM) from emissions. Yet, many commercially available filters are difficult to achieve high filtration efficiency for PM while maintaining low filtration resistance. Furthermore, the elevated temperatures (ranging from 100.0 to 250.0 °C) commonly associated with pollution sources necessitate stringent thermal resistance requirements for filtration materials. Here, a new strategy for the preparation of aerogels for high-temperature gas filtration is reported. Firstly, a unique “grooved and secondary pore” structure polyaryl thioether sulfone (GPASS) nanofibers are initially fabricated using a combination of “wet” electrostatic spinning and aqueous etching. And then, the oxidized GPPASS aerogel (O-GPPASS) can be obtained through simple acid and freeze-dried treatment. It is found that the as-prepared aerogel exhibits high filtration efficiency of 99.7 % for PM0.3, accompanied by low pressure drop of 17.2 Pa, and high quality factor (QF) of 0.362 Pa−1. Remarkably, after enduring high-temperature conditions of 330.0 °C for 4.0 h, the O-GPPASS aerogel still maintains an impressive filtration performance, with a 99.6 % efficiency and a pressure drop of 17.6 Pa for PM0.3 particles. It will well meet the needs of filter materials used in high temperature environments. This innovation is poised to supersede traditional high-temperature air filtration materials, paving the way for sustainable advancements in industrial applications.

Preparation of modified halloysite nanotubes@Ag3PO4/polyacrylonitrile electrospinning membranes for highly efficient air filtration and disinfection

Particulate matters (PMs) and airborne bacteria are among the most severe indoor air issues due to their substantial implications for human health. Therefore, it was imperative to conduct a comprehensive investigation on air filtration materials with superior filtration performance and antibacterial properties. Here, the m-Hal@Ag3PO4 composite particles were prepared by using modified halloysite nanotubes (m-Hal) as the support of Ag3PO4 nano-photocatalysts. These composite antibacterial particles were uniformly dispersed within a polyacrylonitrile (PAN) solution and were subsequently electrospun into m-Hal@Ag3PO4/PAN composite nanofiber membranes (CNMs) possessing excellent antibacterial properties. The incorporation of 30 wt% m-Hal@Ag3PO4 additionally enhanced the filtration efficiency of PM0.3 to 99.9%, at an airflow rate of 32 L/min, while concurrently reducing the pressure drop by 36.7%. The photocatalytic degradation efficiency of CNMs towards ciprofloxacin reached 99%. The antibacterial experiments demonstrated that CNMs exhibited potent antibacterial activity against both Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli)under dark and light conditions. Under visible light irradiation, the average diameter of the inhibition zone for the composite membrane surpassed that observed under dark conditions, indicating a predominant enhancement in its antibacterial efficacy through photocatalysis. The enhanced photocatalytic performance and excellent stability can be attributed to the incorporation of Ag3PO4 with m-Hal, which enhanced the dispersibility and facilitated efficient carrier separation of Ag3PO4. The present type of CNMs exhibited the advantages of high efficiency and low resistance air filtration, photodegradation ability, and recyclability, thereby enhancing the efficacy and lifespan of PMs filtration, bacteria disinfection, and antibiotic degradation. This offered a novel concept and viable approach for indoor air and water purification based on electrospinning technology.

In-situ polarized coaxial PVDF/PL nanofiber filtration membrane with high efficiency, low resistance and antimicrobial properties

Aerosols are prone to breed bacteria on air filtration materials so as to cause secondary air pollution, especially carrying bacteria and viruses. This paper utilized coaxial electrospinning technology with traditional Chinese medicine Physalis alkekengi Linn as the core layer antibacterial material and polyvinylidene fluoride/polyacrylonitrile mixed solution as the shell layer material. Nonsolvent phase separation technology was employed to prepare the porous shell layer, achieving sustained slow-release and long-lasting antibacterial effects from the core P. alkekengi Linn. In addition, an in-situ polarization technology from high voltage in electrospinning process was adopted to achieve permanent polarization of polyvinylidene fluoride, which changed from α-crystal to β-crystal. Using the electrostatic charge adsorption effect and the ultra-fine pore size screening of the nanofiber membrane, high-efficiency and low-resistance filtration of aerosols above 0.3 μm was achieved (99.98% filtration efficiency and filtration resistance less than 25 Pa). It can be widely used in the field of air filtration and protection in high-risk environments such as stations, schools, and hospitals, achieving long-lasting antibacterial, high-efficiency, and low-resistance air filtration and protection.

Electrospun 3D Curly Electret Nanofiber Air Filters for Particulate Pollutants

Amidst rapid industrialization and urbanization, air pollution has emerged as a global environmental challenge. Traditional air filtration materials face challenges in effectively filtering PM0.3 and often result in discomfort due to high air resistance when used for personal protection, as well as excessive energy consumption in industrial air purification applications. This study initially utilized extremely high environmental humidity to induce fiber formation, resulting in the preparation of a fluffy fiber membrane with a three-dimensional curly morphology, which increased the porosity to 96.93%, significantly reducing air resistance during filtration. Subsequently, rutile TiO2 with a high dielectric constant was introduced, exploiting the low pressure drop characteristic of the fluffy 3D curly fiber membrane combined with the electret effect of TiO2 nanoparticles to notably improve the issue of excessive pressure drops while maintaining filtration efficiency. The microstructure, morphology, and element distribution of the fibers were analyzed using FESEM and EDS. FTIR and XRD were employed to examine the functional groups and crystal structure within the fibers. The electret effect and filtration performance of the fiber membrane were investigated using an electrostatic tester and a particulate filtration efficiency tester. The results demonstrated that inducing fiber formation under high-humidity conditions could produce fibers with a 3D curly structure. The fiber membrane was highly fluffy, significantly reducing the pressure drop. Introducing an appropriate amount of titanium dioxide markedly improved the electrostatic effect of the fiber membrane, enhancing the filtration performance of the 3D curly PVDF/TiO2 composite fiber membrane. With a 0.5% addition of TiO2 nanoparticles, the filtration efficiency of the fiber membrane reached approximately 99.197%, with a pressure drop of about 49.83 Pa. This study offers a new approach to developing efficient, low-resistance air filtration materials, showcasing the potential of material innovation in addressing air quality challenges within the sustainable development framework.

Trap-induced hydro-charging polylactic acid nonwovens with high charge storage capability for stable and efficient air filtration

Under the background of carbon neutrality, eco-friendly biodegradable polylactic acid (PLA) melt-blown nonwovens have been developed in air filtration. Nevertheless, the filtration performance of existing PLA melt-blown nonwovens is in an embarrassing situation and fails to meet the requirement of high efficiency air filters. Here, with controllable doping of N, N′-ethylene bis-stearamide (EBS), and barium titanate (BaTiO3) into PLA, through the melt-blown process, the charge-storage capacity of PLA nonwovens enhanced significantly. By utilizing the hydro-charging technology thereafter, we have prepared hydro-charged PLA/EBS/BaTiO3 nonwovens (HCP-EB) with excellent filtration performances. The doped EBS and BaTiO3 could improve the crystallization and charge storage capacity of PLA during the melt-blown process, thus constructing a large number of interfacial traps between crystalline and amorphous regions, leading to more electric charges captured during the hydro-charging process. The HCP-EB exhibited a high filtration efficiency (99.69 %) for PM0.3, a low pressure drop (27.44 Pa), and superior charge storage stability. Furthermore, the HCP-EB, remained at 99.18 % filtration efficiency after 48 h of treatment at 90 % relative humidity. After 3 months of storage, it still possessed an excellent filtration efficiency (99.02 %). Our work will contribute to the practical application of PLA melt-blown nonwovens in air filters and masks, and inspire the research of next-generation biodegradable electret air filtration materials.

Multi-functional nanofibrous membrane with antibacterial property for highly effective capture of PM0.3 and hydrogen sulfide

In order to reduce the possible harm caused by air pollution, including particulate matters (PM), harmful gases and airborne pathogens, high-efficiency air filtration materials are attracting more and more attention. Therefore, multifunctional materials that can filter these pollutants and kill pathogenic bacteria simultaneously are urgently desired. Herein, a copper-coordinated nanofibrous membrane, named PAN-P-Cu, was successfully prepared based on polyacrylonitrile (PAN) nanofibers grafted polyethyleneimine (PEI) by electrospinning and coordination assembly method. The PAN-P-Cu showed high filtration efficiency (99.9%) towards PM0.3 under an airflow velocity of 5.3 cm s−1 and high filtration efficiency (99.94%) towards PM10, respectively. Importantly, used membrane could be regenerated by a simple washing process. Moreover, PAN-P-Cu possessed removal property of 60 mg g−1 for hydrogen sulfide through the occurrence of chemical reactions. Furthermore, the PAN-P-Cu also exhibited excellent antibacterial activities against Escherichia coli and Staphylococcus aureus (>99.99%). This work may provide new insights on designing high-performance and multi-functional air filtration materials for public health protection in complicated environments.

Hybrid 3D printing and electrospinning technique for the production of air filter materials and the effect of different infill patterns on air permeability

Hybrid 3D printing and electrospinning technique for the production of air filter materials and the effect of different infill patterns on air permeability

Developing cellulose nanofibrils/Na-montmorillonite composite air filter with efficient filtration ability for PM2.5 and adsorption of formaldehyde

Indoor and outdoor air treatment is one of the key issues that people focus on. However, developinggreen air filtration materials withhigh filtration efficiency (FE), low pressure drops (ΔP) and good mechanical propertiesis still intractable challenges. In this study, we designed a green compositeaerogel air filter with double filtration mechanism, where Na-montmorillonite (NMMT) was exploited in the adsorption ability for PM2.5 due to its unique layered structure, high specific surface area, and negative charge. In the system, cellulose nanofibrils (CNF) as the structure materials were mixed with HCl acidified modified Na-montmorillonite (HMMT) as the functional particles, followed by freeze-drying to obtainCNF/HMMT compositeaerogel air filter. The resultingaerogel air filter showed excellent capture ability to PM2.5 (up to 96.5 %) and adsorption performance for formaldehyde (81.97 mg/g). This was mainly due to both the mechanical interception of the three-dimensional network constructed by CNF and the surface electrostatic adsorption of HMMT.After hydrophobic modification with methyltrimethoxysilane (MTMS), the samples displayed good water resistance, recycling performance and mechanical properties. In view of its features of environment-friendly, wide source and low cost, the aerogel air filter has the possibility of wide application.

Hyperbranched Polymer Induced Antibacterial Tree-Like Nanofibrous Membrane for High Effective Air Filtration.

The air filtration materials with high efficiency, low resistance, and extra antibacterial property are crucial for personal health protection. Herein, a tree-like polyvinylidene fluoride (PVDF) nanofibrous membrane with hierarchical structure (trunk fiber of 447nm, branched fiber of 24.7nm) and high filtration capacity is demonstrated. Specifically, 2-hydroxypropyl trimethyl ammonium chloride terminated hyperbranched polymer (HBP-HTC) with near-spherical three-dimensional molecular structure and adjustable terminal positive groups is synthesized as an additive for PVDF electrospinning to enhance the jet splitting and promote the formation of branched ultrafine nanofibers, achieving a coverage rate of branched nanofibers over 90% that is superior than small molecular quaternary ammonium salts. The branched nanofibers network enhances mechanical properties and filtration efficiency (99.995% for 0.26µm sodium chloride particles) of the PVDF/HBP-HTC membrane, which demonstrates reduced pressure drop (122.4Pa) and a quality factor up to 0.083 Pa-1 on a 40µm-thick sample. More importantly, the numerous quaternary ammonium salt groups of HBP-HTC deliver excellent antibacterial properties to the PVDF membranes. Bacterial inhibitive rate of 99.9% against both S. aureus and E. coli is demonstrated in a membrane with 3.0 wt% HBP-HTC. This work provides a new strategy for development of high-efficiency and antibacterial protection products.

Light stabilizer-modified hydrocharging melt-blown nonwovens with superior charge stability for air filtration

Particulate matter poses substantial risks to human health, air visibility, climate, and ecological equilibrium. Electret materials are instrumental in air purification and personal protection, as they significantly enhance filtration efficiency without increasing pressure drop. Despite these advantages, developing electret filters with both high filtration efficiency and stable performance under thermal conditions and prolonged storage has proven challenging. In this study, we introduce a novel electret melt-blown filter fabricated through hydrocharging technology supplemented with the light stabilizer UV3346. The interaction of water and air molecules with melt-blown fibers generated abundant positive and negative charges, thereby amplifying the electrostatic attraction effect. Concurrently, UV3346 mitigated the formation of reactive free radicals and minimized charge exchanges, thus enhancing charge storage stability. Owing to the incorporation of UV3346, the UV3346/PP-0.8 melt-blown nonwovens, having a basis weight of 22 g/m2, demonstrated a filtration efficiency of 99.55 %, a low pressure drop of 59.45 Pa, and marginal decrease in filtration efficiency after heat treatment at 130 °C. Notably, the filtration efficiency experienced only a 0.30 % reduction after a two-year storage period, markedly outperforming commercial alternatives. This study is expected to inform future work on high-performance air filtration materials suitable for both air purification and personal protection equipment.

Highly Efficient Fabrication of Biomimetic Nanoscaled Tendrils for High-Performance PM0.3 Air Filters.

Particulate matter pollution has become a serious public health issue, especially with the outbreak of new infectious diseases. However, most existing air filtration materials face challenges such as being too bulky, having high resistance, and a trade-off between filtration efficiency and air permeability. Here, a unique electro-blown spinning technique is used to prepare an air filter made of biomimetic nanoscaled tendril nonwovens (Nano-TN). The introduction of an airflow field significantly increases the whipping frequency and the strain mismatch of composite jets, achieving large-scale and highly efficient preparation of Nano-TN. The resultant Nano-TN has an ultrahigh porosity (97%) and a small pore size (2.9 μm). At the same filtration level, its air resistance is 37% lower than that of traditional straight nanofibrous nonwovens and has a higher dust-holding capacity. Moreover, compared with traditional three-dimensional air filters, the Nano-TN filter is thinner, offering tremendous application prospects in various environmental purification and personal protection fields.

Influence of Electrospinning Parameters on the Morphology of Electrospun Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Fibrous Membranes and Their Application as Potential Air Filtration Materials.

A large number of non-degradable materials have severely damaged the ecological environment. Now, people are increasingly pursuing the use of environmentally friendly materials to replace traditional chemical materials. Polyhydroxyalkonates (PHAs) are receiving increasing attention because of the unique biodegradability and biocompatibility they offer. However, the applications of PHAs are still limited due to high production costs and insufficient study. This project examines the optimal electrospinning parameters for the production of PHA-based fibrous membranes for air filtration. A common biodegradable polyester, Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), was electrospun into a nanofibrous membrane with a well-controlled surface microstructure. In order to produce smooth, bead-free fibers with micron-scale diameters, the effect of the process parameters (applied electric field, solution flow rate, inner diameter of hollow needle, and polymer concentration) on the electrospun fiber microstructure was optimized. The well-defined fibrous structure was optimized at an applied electric field of 20 kV, flow rate of 0.5 mL/h, solution concentration of 12 wt.%, and needle inner diameter of 0.21 mm. The morphology of the electrospun PHBV fibrous membrane was observed by scanning electron microscopy (SEM). Fourier transform infrared (FTIR) and Raman spectroscopy were used to explore the chemical signatures and phases of the electrospun PHBV nanofiber. The ball burst strength (BBS) was measured to assess the mechanical strength of the membrane. The small pore size of the nanofiber membranes ensured they had good application prospects in the field of air filtration. The particle filtration efficiency (PFE) of the optimized electrospun PHBV fibrous membrane was above 98% at standard atmospheric pressure.

Preparation, characterization and antibacterial properties of hydro-charged melt-blown nonwovens coated with an N-halamine

Air filtration materials can protect humans from the invasion of airborne pathogens. However, pathogens intercepted by air filters can survive in fibrous materials and pose a threat to human health...

Engineering self-assembled 2D nano-network membranes through hierarchical phase separation for efficient air filtration

Air pollution has garnered significant worldwide attention; however, the existing air filtration materials still suffer from issues related to monotonous structure and the inherent trade-off between PM rejection and air permeability. Herein, a spider web-inspired composite membrane with continuous monolayer structured 2D nano-networks tightly welded on nanofibers in the electrospun membrane scaffold is designed via a hierarchical phase separation strategy. The resultant biomimetic hierarchical-structured membranes possess the integrated features of hierarchical multiscale structures of 2D ultrafine networks composed of nanowires with a diameter of 31 nm self-assembled by nanoparticles, exceptional characteristics involving small average aperture, extremely low network thickness, high porosity and promising pore channel connectivity, combined with rich surface polar functional groups (3.02D dipole moment). Consequently, the composite membrane exhibits a high PM0.3 capture efficiency of 99.6 % and low pressure drop of 58.8 Pa, less than 0.06 % of atmosphere pressure, with outstanding long-term PM2.5 recycling filtration performance. The hierarchical phase separation–driven 2D nano-networks construction strategy, by virtue of their feasibility and tunability, holds great promise for widespread application across diverse membrane-related domains for air filtration.