Air Filtration Membranes Research Articles

Fluorine-Free Amphiphobic SBS/PAN Micro/Nanofiber Membrane by Integrating Click Reaction with Electrospinning for Efficient and Recyclable Air Filtration.

The membrane fouling derived from the accumulated dust pollutants and highly viscous oily particles causes irreversible damage to the filtration performance of air filters and results in a significant reduction in their service life. However, it is still challenging to construct high-efficiency and antifouling air filtration membranes with recyclable regeneration. Herein, the fluorine-free amphiphobic micro/nanofiber composite membrane was controllably constructed by integrating click chemistry reaction and electrospinning technique. Low-surface-energy fibers were constructed by a thiol-ene click chemical reaction between mercaptosilane and vinyl groups of polystyrene-butadiene-styrene (SBS), combined with hydroxyl-terminated poly(dimethylsiloxane) during the electrospinning process. The functional air filter is then prepared by the two-layer composite strategy. Because of the advantages of liquid-like fibrous surface and micro/nanofibrous porous structure, SBS/PAN composite membrane simultaneously shows superior antifouling performances of pollutants and filtration efficiency of over 97% PM0.3 removal. More importantly, the antifouling fibrous membrane still presents a stable and efficient filtration efficiency after multiple washes. Its service life in dust filtration environments is approximately 1.7 times longer than that of the substrate membrane. This work may provide a significant reference for the design of antifouling fiber membranes and high-efficiency air filters with long life spans and reusability.

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.

Electrospun porous polyacrylonitrile/polyvinylpyrrolidone nanofiber membrane with ultra-hydrophilic and high moisture-permeability for dust personal protection

The serious dust pollution in coal mine working environment can cause occupational lung diseases and other diseases, affecting the life and health of miners. Therefore, the prospect of developing an air filtration membrane with high filtration performance is of remarkable significance. This study prepared a porous Polyacrylonitrile (PAN) /Polyvinylpyrrolidone (PVP) nanofiber membrane based on Electrospinning and post-treatment technology used for downhole personal protection. The prepared porous nanofiber membrane increased the specific surface area by 133.63 % and the porosity by 391.02 % (compared with the pure PAN nanofiber membrane), and was able to achieve a high filtration efficiency of 98.76 % and a low pressure drop of 165 Pa at an air flow rate of 85 L/min. Meanwhile, this study conducted contact angle and moisture permeability tests on the prepared composite fiber membrane. After 1 second of water droplets falling on the fiber membrane, it had a 14° contact angle (strong hydrophilicity), and the moisture permeability reached 4256.677 cm3/m2·d·Pa, which could discharge the water vapor generated by respiration in time. In addition, given the complex and irregular pore distribution of electrospun nanofibers, the fractal correlation dimension of nanofiber membrane pores was studied through fractal theory, and the relationship between the fractal dimension of fiber pores and respiratory resistance was discussed. Based on this, the nanofiber membrane prepared in this study can be widely used in individual protection in mines.

Preparation of ethyl cellulose bimodal nanofibrous membrane by green electrospinning based on molecular weight regulation for high-performance air filtration

Preparing bio-based air filtration membrane through green electrospinning strategy is a vital approach to alleviating environmental and energy crises. However, the development of related biomaterials and method for regulating membrane structure are still lacking. In this study, ethyl cellulose (EC) bimodal nanofibrous membrane was prepared by electrospinning using ethanol and water as solvents to achieve high-performance air filtration. A new strategy for bimodal fiber molding based on molecular weight modulation was proposed. The EC polymer chains with medium molecular weights were subject to the highest degree of inhomogeneity of solvent intrusion, and there were significant differences in viscous forces “microscopically”, leading to the formation of bimodal structure by inhomogeneous stretching of the jet. The well-defined bimodal structure endowed EC membrane with excellent air filtration performance. The filtration efficiency for PM0.3, pressure drop, quality factor were 99.11 %, 42.2 Pa, and 0.112 Pa−1, respectively. Compared to the commonly used zein, EC cost just 12.77 %, and its solution had a 50 % longer shelf life, making it a more desirable biomaterial. This work will facilitate the application of more biomaterials in air filtration, promote the green fabrication of high-performance air filtration membranes, and realize sustainable development.

Constructing Stable Polyvinyl Alcohol/Gelatin/Cellulose Nanocrystals Composite Electrospun Membrane with Excellent Filtration Efficiency for PM2.5.

Considering the high demand for air quality, the development of biomass-based air filtration membranes with high air filtration efficiency and good stability is an urgent task. In this work, polyvinyl alcohol (PVA), gelatin (GA), and cellulose nanocrystals (CNC) were mixed and prepared into a membrane through an electrospinning method for air filtration. After a hydrophobic modification, the modified PVA/GA/CNC composite membrane showed excellent filtration efficiency for PM2.5 (97.65%) through the internal three-dimensional structure barrier and the electrostatic capture effect of the CNC with a negative charge, as well as a low-pressure drop (only 50 Pa). In addition, the modified PVA/GA/CNC composite membrane had good mechanical properties (maximum tensile fracture rate of 78.3%) and high stability (air filtration efficiency of above 90% after five wash-filter cycles and a high-temperature treatment at 200 °C). It is worth noting that the whole preparation process is completed without organic solvents, putting forward a new strategy for the construction of green air filtration membranes.

Gel-confined fabrication of fully bio-based filtration membrane for green capture and rapid detection of airborne microbes

Air filtration has become a desirable route for collecting airborne microbes. However, the potential biotoxicity and sterilization of current air filtration membranes often lead to undesired inactivation of captured microbes, which greatly limits microbial non-traumatic transfer and recovery. Herein, we report a gel-confined phase separation strategy to rationally fabricate a fully bio-based filtration membrane (SGFM) using soluble soybean polysaccharide and gelatin. The versatile SGFM features fascinating honeycomb micro-nano architecture and hierarchical interconnected porous structures for microbial capture, and achieves a lower pressure drop, higher interception efficiency (99.3%), and superior microbial survivability than commercial gelatin filtration membranes. Particularly, the water-dissolvable SGFM can greatly simplify the elution and extraction process after bioaerosol sampling, thereby bringing about maximum sample transfer and vigorous recovery of collected microbes. Meanwhile, green capture coupled with ATP bioluminescence endows the SGFM with rapid and quantitative detection capability for airborne microbes. This work may pave the way for designing green protocols for the detection of bioaerosols.

Enhancing antibacterial activity and air filtration performance in electrospun hybrid air filters of chitosan (CS)/AgNPs/PVA/cellulose acetate: Effect of CS/AgNPs ratio

The increase in particulate matter (PM), especially PM2.5, has become a global threat to human health. To get rid of this severe pollutant, air filtration is forecasted as a promising, cost-effective, and effective method. This study utilized dual-spinneret electrospinning to fabricate the electrospun hybrid nanofibrous membranes (EHMs) of chitosan (CS)/silver nanoparticles (AgNPs)/polyvinyl alcohol (PVA)/cellulose acetate (CA). The effect of CS/AgNPs ratios was also investigated to obtain high-efficient air filtration membranes with outstanding antibacterial activity. Results disclosed that EHMs containing high AgNPs content improved the filtration performance and antibacterial properties while decreasing the wettability and tensile strength of EHM membranes. In addition, the EHM1 was found to be the most effective air filter membrane due to its high filtration efficiency of 99.78 % (PM2.5), low-pressure drop of 61.15 Pa, high-quality factor of 0.09 Pa−1, and enhanced inhibition zone of 100–141 %. Thus, this study suggests that the EHMs of CS/AgNPs/PVA/CA with a high AgNPs/CS ratio fabricated via a dual-electrospinning technique are expected to be a promising material choice for an air filter with efficient filtration performance and excellent antibacterial activity, resulting in a more sustainable and healthier future.

Graphene and its derivatives for air purification: A mini review

Acceleration of industrialization causes an increase in concentration of greenhouse gases (GHGs), particularly CO2, as well as particulate matter in the air. Therefore, it is necessary to develop strategies for the elimination of GHGs. Graphene and its derivatives were reported to be excellent candidates for CO2 adsorption and also for the removal of particulate matter by air filtration. For the fabrication of air filtration membranes, by using graphene/graphene derivatives, they were incorporated with certain polymers such as polyacrylonitrile and made into nanofibrous membranes. Electrospun nanofibrous membranes are characterised by high porosity, small pore size and excellent connectivity, have been found to be a promising candidate for air filtration. The review article focuses on two aspects of air purification, first part discuss the use of graphene/graphene derivatives for CO2 adsorption and the second part discuss the use of graphene based electrospun nanofibrous membranes for particulate matter removal. The factors influencing the efficiency of filtration has been discussed in detail.

Effective preparation of environmentally friendly polyglycolic acid (PGA) nanofibrous membrane with antibacterial property for high-efficiency and low-resistance air filtration

In recent years, the antibacterial air filters have been crucial for protecting human health. However, most commercial filters are made of non-biodegradable petroleum polymers, which poses a great challenge for environment protection of recycling after large-scale use. Hence, the air filtration membrane, biodegradable polyglycolic acid loaded with antibacterial ε-polylysine-dialdehyde microcrystalline celluloses (PGA@EPL-DAMCs), was prepared by electrospinning. The incorporation of EPL-DAMCs varied the morphology of the resultant PGA@EPL-DAMCs and endowed them with good antibacterial activity. In addition, it was found that the PGA/EPL-DAMC-24% exhibited the best filtration efficiency (99.83%) and bacterial rate (up to 99.97% and 99.99% for E.coli and S.aureus, respectively). Finally, the degradation performance of the PGA electrospun membrane was also investigated, indicating that PGA@EPL-DAMCs composite nanofiber membranes had broad prospects in biodegradable filtration material, can be applied to develop biodegradable and environmentally friendly medical protective materials with highly efficient air filtration and significant antimicrobial effects.

Enhancing Adhesion between Polyphenylene Sulfide Fabric and Polytetrafluoroethylene Film for Thermally Stable Air Filtration Membrane

Enhancing Adhesion between Polyphenylene Sulfide Fabric and Polytetrafluoroethylene Film for Thermally Stable Air Filtration Membrane

Preparation of PVA/PEI/CNC/ZnO composite membrane with good mechanical properties and water resistance by electrostatic spinning using for efficient filtration of PM2.5

AbstractIt is still a serious challenge to construct a water‐soluble polymer‐based air filtration membrane with high efficiency and good mechanical properties by electrospinning. In the study, using polyvinyl alcohol (PVA) and polyacetylimide (PEI) as the main materials, both nanocellulosic crystal (CNC) and zinc oxide (ZnO) as the synergistic reinforcers and methyltrimethoxysilane (MTMS) as the hydrophobic modifier, the electrospun PVA/PEI/CNC/ZnO composite nanofibrous membrane with dual air filtration mechanisms was established. One of the mechanisms was the interception of the three‐dimensional network structure built by the composite nanofibrous membrane, the other was the electrostatic adsorption provided by CNC. Based on the dual air filtration mechanisms, the filtration efficiency of particulate matter 2.5 (PM2.5) reached 98.20%. Moreover, the composite nanofibrous membrane displayed a good thermal stability and could still maintain more than the filtration efficiency of 83% and low‐pressure drop after treatment at 200 °C for 1 h. Moreover, the composite nanofibrous membrane could still maintain the filtration efficiency (97.3%) and low‐pressure drop (110.7 Pa) after five washing cycles after filtration, reflecting good reusability. Interestingly, the PVA/PEI/CNC/ZnO composite nanofibrous membrane was simple to produce and demonstrated excellent filtration efficiency, as well as excellent thermal stability, which could be an effective barrier against PM2.5 invasion.

Preparation of electrospun PVA@Ls@BAC@PDMS composite nanofibrous air filtration membrane with high efficiency removal for PM2.5 and excellent heat resistance

AbstractDevelopment of water‐soluble polymer air filtration materials attracts considerable attentions due to their environmentally friendly performance and high efficiency, but the balance of mechanical strength, efficiency and pressure drop still is a severe challenge. Focusing on this issue, polyvinyl alcohol (PVA), bamboo activated carbon (BAC) and sodium lignosulfonate (Ls) were combined to construct an electrospinning system with two filtration functions. In the PVA@Ls@BAC system, the 3D network constructed by the electrospun PVA based nanofibrous could effectively intercept PM2.5, and the introduced Ls enhanced the mechanical strength of PVA nanofibrous due to its good rigidity. In addition, the added negatively charged BAC facilitated the electrostatic adsorption of PM2.5 while also improved the heat resistance of the system. Moreover, polydimethylsiloxane (PDMS) was introduced to enhance the water resistance of the system. The resulting electrospun PVA@Ls@BAC@PDMS composite nanofibrous air filtration membrane exhibited excellent air filtration performance (98.67%), water repellency (123.7° of WCA), and reusable performance, as well as having good mechanical property and the tensile fracture strain reaching 112%. Because of its good performance and simple preparation process, the electrospun PVA@Ls@BAC@PDMS composite nanofibrous air filtration membrane has great application space.

Zr doped flexible TiO2 nanofibrous membranes for high-efficiency oily particulate matter removal from high temperature flue gas

The filtration of high-temperature flue gases containing complex gas composition and oily particulate matter (PM) poses great challenges to the design of air filtration membranes. Ceramic nanofibers are potential membrane materials that possess the thermal resistance necessary for high-temperature filtration but the inherit poor brittleness limits their use. Herein, we report the fabrication of a flexible and porous Zr-doped TiO2 nanofibrous membrane (Zr–TiO2 NFM) for oily PM removal from high-temperature flue gas. The doping of Zr4+ ions not only improved the mechanical strength, leading to an outstanding tensile strength as high as 1.78 MPa, but also endowed a high specific area (68.34 m2 g−1). The prepared Zr–TiO2 NFMs possessed a high filtration efficiency of 99.98% with low pressure drop of 96 Pa (industrial gas velocity of 1 m∙min−1) and excellent long-term stability after 5 cycles of filtration at 350 °C. Significantly, different capture and evolution behaviors of PM at 25–350 °C were discovered. Below 200 °C, the oily particles would adhere, coalesce, spread out and form oil film on fibers. Different from oily particles, the non-oily particles would attach and accumulate on the fibers when temperatures are higher than 200 °C. This study brings a new insight to deeply understanding the capture process of PM at different temperatures and designing next-generation membranes for high temperature flue gas filtration.

A novel multi-gradient PASS nanofibrous membranes with outstanding particulate matter removal efficiency and excellent antimicrobial property

Air pollution, especially tiny pollutant particles and harmful microorganisms, has become a serious environmental issue, bringing great damage to human body. Air filtration has been a widely used and effective method for air purification. However, the addition of antimicrobial agents usually leads to the agglomeration and the toxicity of the filter material. Here, a versatile poly (aryl sulfide sulfone)/graphene oxide@silver (PASS/GO@Ag) air filtration membrane was fabricated by in-situ reduction and electrospinning approach, resulting in high filtration efficiency and excellent biocompatibility. The results showed that GO@Ag antimicrobial agent was successfully synthetized. The Ag nanoparticles (NPs) on the GO surface not only increased the antimicrobial property but also reduced the agglomeration of the antimicrobial agent. Meanwhile, GO@Ag was wrapped on the surface of the PASS nanofibers by ultrasonication to form a rough surface to further improve the filtration efficiency. The as-prepared PASS/GO@Ag membrane exhibited high air filtration performance (99.63 ± 0.34 %, 79.17 ± 1.07 Pa). Besides, it also showed excellent antimicrobial properties and good biocompatibility. The antibacterial rates of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were 99.57 ± 1.04 % and 97.93 ± 1.31 %, respectively. More importantly, the PASS/GO@Ag membrane could endow long-term use for one month, with the antibacterial rates of E. coli and S. aureus of 96.52 ± 1.20 % and 94.48 ± 1.13 %, respectively. Therefore, the developed membrane will have great potential for personal air filtration.

Study on Filtration Performance of PVDF/PUL Composite Air Filtration Membrane Based on Far-Field Electrospinning.

At present, the situation of air pollution is still serious, and research on air filtration is still crucial. For the nanofiber air filtration membrane, the diameter, porosity, tensile strength, and hydrophilicity of the nanofiber will affect the filtration performance and stability. In this paper, based on the far-field electrospinning process and the performance effect mechanism of the stacked structure fiber membrane, nanofiber membrane was prepared by selecting the environmental protection, degradable and pollution-free natural polysaccharide biopolymer pullulan, and polyvinylidene fluoride polymer with strong hydrophobicity and high impact strength. By combining two kinds of fiber membranes with different fiber diameter and porosity, a three-layer composite nanofiber membrane with better hydrophobicity, higher tensile strength, smaller fiber diameter, and better filtration performance was prepared. Performance characterization showed that this three-layer composite nanofiber membrane had excellent air permeability and filtration efficiency, and the filtration efficiency of particles above PM 2.5 reached 99.9%. This study also provides important reference values for the preparation of high-efficiency composite nanofiber filtration membrane.

Biodegradable trilayered micro/nano-fibrous membranes with efficient filtration, directional moisture transport and antibacterial properties

Particulate matters (PMs) pollution and bacteria severely affect human health. Fibrous filters have shown great potential in intercepting PMs and bacteria. However, developing a novel respirator material endowed with multi-functions, such as efficient filtration, antibacterial activity, directional moisture transport and biodegradability is still challenging. Herein, a multifunctional air filtration membrane with hierarchical structure was fabricated by sequentially electrospinning poly (ε-caprolactone) (PCL) fibrous membrane, PCL/gelatin fibrous membrane and PCL/gelatin/ε-poly (L-lysine) (ε-PL) fibrous membrane. The fabricated trilayered fibrous membrane exhibited high PM filtration efficiency and a low pressure drop. Moreover, the fibrous membrane possessed excellent antibacterial activity due to the incorporation of ε-PL. In addition, the trilayered fibrous membrane provided directional water transport performance by the combination of hydrophobic fibrous layer and hydrophilic fibrous layer, thus improving the comfort of the wearer. Importantly, benefiting from the biodegradability property of PCL, gelatin and ε-PL, the fibrous membrane was biodegradable, which could decrease the burden on the environment. The fabricated trilayered fibrous membrane not only shows promising potential as a highly efficient, antibacterial, moisture-wicking and biodegradable air filtration membrane, but also offers a versatile strategy to design a multifunctional face mask.

Multistage-Split Ultrafine Fluffy Nanofibrous Membrane for High-Efficiency Antibacterial Air Filtration.

Antibacterial air filtration membranes are essential for personal protection during the pandemic of coronavirus disease 2019 (COVID-19). However, high-efficiency filtration with low pressure drop and effective antibiosis is difficult to achieve. To solve this problem, an innovative electrospinning system with low binding energy and high conductivity was built to enhance the jet splitting, and a fluffy nanofibrous membrane containing numerous ultrafine nanofibers and large quantities of antibacterial agents was achieved, which was fabricated by electrospinning polyamide 6 (PA6), poly(vinyl pyrrolidone) (PVP), chitosan (CS), and curcumin (Cur). The filtration efficiency for 0.3 μm NaCl particles was 99.83%, the pressure drop was 54 Pa, and the quality factor (QF) was up to 0.118 Pa-1. CS and Cur synergistically enhanced the antibacterial performance; the bacteriostatic rates against Escherichia coli and Staphylococcus aureus were 99.5 and 98.9%, respectively. This work will largely promote the application of natural antibacterial agents in the development of high-efficiency, low-resistance air filters for personal protection by manufacturing ultrafine nanofibers with enhanced antibiosis.

Piezoelectric Nanofiber Membrane for Reusable, Stable, and Highly Functional Face Mask Filter with Long‐Term Biodegradability

AbstractThe emergence of the SARS‐CoV‐2 pandemic and airborne particulate matter (PM) pollution has led to remarkably high demand for face masks. However, conventional respirators are intended for single use and made from nondegradable materials, causing serious concern for a plastic‐waste environmental crisis. Furthermore, these facemasks are weakened in humid conditions and difficult to decontaminate. Herein, a reusable, self‐sustaining, highly effective, and humidity‐resistant air filtration membrane with excellent particle‐removal efficiency is reported, based on highly controllable and stable piezoelectric electrospun poly (l‐lactic acid) (PLLA) nanofibers. The PLLA filter possesses a high filtration efficiency (>99% for PM 2.5 and >91% for PM 1.0) while providing a favorable pressure drop (≈91 Pa at normal breathing rate) for human breathing due to the piezoelectric charge naturally activated by respiration through the mask. The filter has a long, stable filtration performance and good humidity resistance, demonstrated by a minimal declination in the filtration performance of the nanofiber membrane after moisture exposure. The PLLA filter is reusable via common sterilization tools (i.e., an ultrasonic cleaning bath, autoclave, or microwave). Moreover, a prototype of a completely biodegradable PLLA nanofiber‐based facemask is fabricated and shown to decompose within 5 weeks in an accelerated degradation environment.

Construction of ultra-stable polypropylene membrane by in-situ growth of nano-metal–organic frameworks for air filtration

• MOFs were grown on the polypropylene fibers by the in-situ growth method. • Nano-sized MOFs have been synthesized to enhance the capture of PM particles. • Under the sonication of 600W, 80% of the MOFs were still loaded on the fibers. Air pollution, especially solid particulate pollution, seriously endangers people’s physical and mental health. As a result, the performance and stability of air filtration membranes are increasingly required. In this work, the nano-sized (sizes < 100 nm) polypropylene@zeolitic imidazolate framework-8 (PP@ZIF-8) membranes and polypropylene@copper(II) benzene-1,3,5-tricarboxylate (PP@Cu-BTC) membranes were designed in an in-situ growth method. These membranes can achieve efficient and stable filtration of PM2.5 particles in a practical environment. The PM1.0 quality factor and filtration efficiency of PP@Cu-BTC increased by 49.28% and 58.04%, respectively, compared to the PP membrane. In addition, more than 87% of metal–organic frameworks (MOFs) particles are still fixed on the fiber after ultrasonic treatment with ultrasonic power of 600 W for 30 min. Moreover, the membranes are recyclable and have excellent water resistance (>74.5% against PM1.0 after five washing cycles) and outstanding long-term storage performance (>94.9% against PM1.0 after storage for one month). This PP@MOFs membrane provides another idea for building stable and efficient air filtration membranes.

Ferroelectric PVDF nanofiber membrane for high-efficiency PM0.3 air filtration with low air flow resistance

The significant public health concerns related to particulate matter (PM) air pollutants and the airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have led to considerable interest in high-performance air filtration membranes. Highly ferroelectric polyvinylidene fluoride (PVDF) nanofiber (NF) filter membranes are successfully fabricated via electrospinning for high-performance low-cost air filtration. Spectroscopic and ferro-/piezoelectric analyses of PVDF NF show that a thinner PVDF NF typically forms a ferroelectric β phase with a confinement effect. A 70-nm PVDF NF membrane exhibits the highest fraction of β phase (87%) and the largest polarization behavior from piezoresponse force microscopy. An ultrathin 70-nm PVDF NF membrane exhibits a high PM0.3 filtration efficiency of 97.40% with a low pressure drop of 51 Pa at an air flow of 5.3 cm/s owing to the synergetic combination of the slip effect and ferroelectric dipole interaction. Additionally, the 70-nm PVDF NF membrane shows excellent thermal and chemical stabilities with negligible filtration performance degradation (air filtration efficiency of 95.99% and 87.90% and pressure drop of 55 and 65 Pa, respectively) after 24 h of heating at 120 °C and 1 h immersion in isopropanol.