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•High-performance electrospun air filters for personal protection were introduced.•The mechanisms of high filtration performance electrospun air filter were summarized.•The ...realizations of high filtration performance electrospun air filter were listed.•Limitations and perspectives of high-performance air filter were presented.
With the increasingly serious air pollution and the rampant coronavirus disease 2019 (COVID–19), preparing high–performance air filter to achieve the effective personal protection has become a research hotspot. Electrospun nanofibrous membrane has become the first choice of air filter because of its small diameter, high specific surface area and porosity. However, improving the filtration performance of the filter only cannot meet the personal needs: it should be given more functions based on high filtration performance to maximize the personal benefits, called, multifunctional, which can also be easily realized by electrospinning technology, and hasattractedmuchattention. In this review, the filtration mechanism of high–performance electrospun air filter is innovatively summarized from the perspective of membrane. On this basis, the specific preparation process, advantages and disadvantages are analyzed in detail. Furthermore, other functions required for achieving maximum personal protection benefits are introduced specifically, and the existing high–performance electrospun air filter with multiple functions are summarized. Finally, the challenges, limitations, and development trends of manufacturing high–performance air filter with multiple functions for personal protection are presented.
This work demonstrates a new type of multilayer membranes that exhibit excellent filtration efficiencies for PM2.5, low air resistance and good directional moisture transport properties.
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•Gradient multilayer fibrous membranes are prepared from polymers and ZIF-8.•The membranes have multiscale pore structure and rough fiber surface with high BET.•The features enable efficient capture of fine and ultrafine particles at low ΔP.•The membranes show large hydrophilicity gradient, facilitating fast moisture wicking.
Particulate matter (PM)-induced air pollution has become a serious threat to public health in many regions. There is, therefore, a need for development of advanced respirator materials that can efficiently capture PM and also exhibit both low breathing resistance and good moisture wicking properties to ensure physiological comfort of the wearers. Herein, we report a new type of multilayer membranes that exhibit excellent filtration efficiencies for PM of various sizes, low air resistance and good directional moisture transport properties. We incorporated a type of metal-organic framework, ZIF-8, into polyacrylonitrile (PAN) to prepare microfibers with high surface roughness, and alternatingly stacked layers of rough microfibers with layers of PAN nanofibers via electrospinning, resulting in multi-level structured membranes. Moreover, subsequent acid and base treatments could not only tailor the hydrophilicity of fiber surfaces, but also induce multiscale surface roughness, facilitating both moisture wicking and PM adsorption. This allowed us to construct a unique multilayer membrane composed of a super-hydrophilic outer layer made of PAN fibers with multiscale surface roughness, a hydrophilic composite intermediate layer consisting of porous PAN-ZIF-8 microfibers and PAN nanofibers, and a hydrophobic polystyrene fibrous inner layer, which could offer excellent directional moisture transport performance and a high water vapor transmission rate of 10.56 kg m−2 d−1 due to strong capillary force and push-pull effect. More importantly, benefiting from the large specific surface area, rough fiber surface, and hierarchical pore structure, the membrane exhibits high removal efficiencies of 99.973% for 0.3-μm particles and ≧99.99% for particles of other sizes, including the more harmful ultrafine particles, at a low pressure drop of 80.1 Pa. Moreover, the multilayer composite filter still maintains a high removal efficiency of 99.951% after continuous air purification for 48 h in a high PM2.5 concentration (>300 μg m−3) environment. These make such membranes promising high-performance filtration media for respirator applications.
The purification process of wastewater containing heavy metal ions (HMIs) using nano-fibrous metal-organic frameworks, MOF-808, embedded polyacrylonitrile membrane has been studied. The process ...parameters that were evaluated included feed concentration, transmembrane pressure (TMP), and membrane thickness. The effect of coexisting cations in the solution upon the removal efficiencies of Zn2+, Cd2+, Pb2+ and Hg2+ ions was also investigated. Results from the filtration experiments indicate a substantial variation in the feed volume that the membrane can treat before the permeate lead concentration reaches the allowable limit of 10 ppb, depending on the process parameter. An increase in the membrane thickness showed a significant improvement (26%) with 440 L of the treated feed volume after doubling the membrane layer. An increase in TMP could reduce the treated feed volume by 38% while a decrease in feed concentration led to a 21% increase in the treated feed volume. In the presence of other common background cations in the solution, the removal efficiency of HMIs by adsorption onto MOF-808 dropped by 18 to 37%. This result was dependent upon the HMIs, in the presence of up to three other cations but was minimal in the presence of a single cation indicative of good selectivity.
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•Metal-organic frameworks particles were enmeshed into polyacrylonitrile nanofiber membranes.•The membranes were used for the removal of Pb2+ ions from aqueous solution by adsorption.•The effects of transmembrane pressure, feed conc., and membrane thickness were investigated.•The presence of background ions on adsorption Zn2+, Cd2+, Pb2+ and Hg2+ ions was studied.•The filtration system could produce >500 L of pure water per m2 of membrane.
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•Preparation of a novel adsorbent with antibacterial properties.•Ce-MOF loading can greatly improve the adsorption capacity of fibers for 2,4-D.•The haloperoxidase activity of Ce-MOF ...can give the fiber excellent antibacterial activity.•Ce-MOF@ABP is easier to recycle than powdered Ce-MOF.•Ce-MOF@ABP can be used as a filtration membrane to purify organic wastewater.
2,4-dichlorophenoxyacetic acid (2,4-D) is one of the most widely used herbicides with strong environmental toxicity, and it is necessary to be removed from water. However, some traditional adsorbents may be contaminated by bacteria during the removal process, which will affect the adsorption performance. Therefore, a novel adsorbent (Ce-MOF@ABP) with antibacterial properties was developed for the removal of 2,4-D. The adsorbent is prepared by in-situ growth of Ce-based MOF with UiO-66 structure on the surface of electrospun nanofibers by solvothermal method. The results of static adsorption experiments show that the composite fibrous membrane has a good removal effect on 2,4-D. The adsorption process is more consistent with the pseudo-second-order model and Langmuir model. The theoretical maximum adsorption capacity is 200.80 mg/g. The dynamic filtration experiment also shows a removal rate of 90.3% within 6 min (the membrane thickness is 0.12 mm). And most importantly, the haloperoxidase activity of Ce-MOF could endows fibrous membrane with excellent antibacterial properties, and the bacteriostatic rate of Escherichia coli is 92.91%. This study provides an innovative idea for the development of adsorbents/membranes with organic contaminant removal and antibacterial capabilities.
Here, a robust antifouling NH2-MIL-88B coated quartz fibrous membrane (NM88B@QFM) was developed for efficient oil-water emulsion separation via a one-step solvothermal method. The effects of NM88B ...precursor concentration on the morphology and surface wettability of the membranes were investigated. The prepared NM88B@QFM showed good photo-Fenton self-cleaning ability and superhydrophilicity/underwater superoleophobicity with water contact angle and underwater oil contact angle of 0° and 161.3°, respectively. The NM88B@QFM exhibited high separation efficiencies and high permeation fluxes (up to 99.4% and above 350 L m−2 h−1, respectively for a series of surfactant-stabilized oil-in-water emulsions under solely gravity-driven separation. Moreover, the NM88B@QFM showed good antifouling self-cleaning ability because Fenton-like catalytic NM88B can degrade the foulant on the membrane surface, enabling it to maintain its performance over many separation cycles. In view of the advantages of NM88B@QFM such as high separation efficiency, excellent self-cleaning and gravity self-driven performance, this type of membrane appears to be a promising candidate for low energy input, long-lasting oil-water separation.
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•A antifouling NH2-MIL-88B coated quartz fibrous membrane was developed via a one-step solvothermal method.•The membrane exhibited high separation efficiencies and fluxes for oil-in-water emulsions under solely gravity-driven separation.•The FRR of the membrane is as high as 98.46%.•This study is expected to make an important contribution to existing literature on self-cleaning membranes.
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•The light weight YZFM has excellent flexibility and strength (6.49 MPa) at 1200 °C.•The YZFM has excellent high temperature resistance and low thermal conductivity.•The YZFM have ...better acoustic absorption performance than commercial materials.
At high temperatures, lightweight ceramic and aerogel materials have serious problems such as volume shrinkage, increased density, loss of flexibility, and decreased thermal insulation performances. The research on high-performance, lightweight, and flexible materials, which can meet the requirements of high-temperature applications, is a challenging topic in the industry. In this work, we developed a defective fluorite phase Y2Zr2O7 flexible fibrous membrane (YZFM) material which has excellent thermal stability, no phase change until 1200 °C, and excellent flexibility until 1200 °C. The dense single fiber structure results in the tensile strength of the YZFM as high as 8.27 MPa. The low density (44 mg/cm3), high porosity (99.2%), and excellent heat radiation reflectivity (750–2500 nm: Avg. 96.34%) endow the YZFM with outstanding thermal insulation performance (the thermal conductivity: 38 mW m−1 K−1). The 30 mm thick YZFM can reduce the high temperature of 1260 °C to 185 °C. The anisotropic layered structure makes YZFM have better acoustic absorption performance than commercial materials. These robust performances make our YZFM suitable for fields with strict requirements on material usage conditions, such as aerospace and cutting-edge industries.
•The fibrous membrane with hierarchical structure was fabricated by sequential electrospinning.•The trilayered fibrous membrane had high filtration efficiency and low pressure drop.•The fibrous ...membrane exhibited antibacterial activity and biodegradability.•The trilayered fibrous membrane possessed directional water transport performance.
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.
The treatment of hypersaline wastewaters with membrane distillation (MD) is significant but challenging, owing to the critical limitations of severe membrane wetting and fouling. Herein, a monolithic ...and self-roughened Janus fibrous membrane (FM) with asymmetrical superwettability was developed via sequential electrospinning and electrospraying in combination with thermal treatment. We detailedly discussed the formation mechanism of the roughness on the fiber surface via electrospinning/electrospraying technique and explored the asymmetrical wettability and the monolithic performance of Janus FM for the synergistic resistance of membrane wetting and fouling. Benefiting from the high in-air water contact of 157° of the omniphobic surface, the high underwater oil contact angle of 156° of the superhydrophilic skin layer, as well as the monolithic performance of the resultant membrane, the newly developed Janus FM achieves a high water flux of over 27 L m−2 h−1 and high desalination efficiency of ~100% when desalination of the simulated hypersaline wastewater composed of 3.5 wt% of NaCl, 0.1 g of SDBS and 1.0 g of lubricating oil. The presented strategy on Janus FM fabrication is believed to open a new direction to prepare monolithic, self-roughened, and asymmetrically superwettable Janus FM and applied in a wide field of other selective separation applications.
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•Asymmetrical superwettable and interconnected pore Janus membrane was fabricated.•The Janus membrane roughness was self-constructed without nanoparticle decoration.•The Janus membrane shows high breathability and monolithic performances.•The Janus membrane shows robust antiwetting and antifouling properties.
With increasing water pollution and human health problems caused by oily wastewater, the fabrication of oil–water separation materials has become an urgent task. However, most of the reported ...materials have a single function and poor performance. In this paper, a multifunctional zinc oxide/polyaniline/polyacrylonitrile (ZnO/PANI/PAN) nanofibrous membrane with needle-like ZnO nanorods was prepared by in situ synthesis of PANI and a hydrothermal reaction on a highly stable self-standing PAN blow-spinning fibrous membrane. Due to the electronic synergistic effect of ZnO and PANI, the fibrous membrane exhibits excellent antibacterial activity and visible-light degradation ability of organic dyes. Moreover, the micro-/nanosized pores of the ZnO/PANI/PAN fibrous membranes also guarantee its excellent emulsion separation performance, including an ultrahigh surfactant-free emulsion permeate flux (∼8597.40 L/(m2 h)), ultrahigh surfactant-stabilized emulsion permeate flux (∼2253.50 L/(m2 h)), and excellent separation efficiency (above 99%). Furthermore, the composite membrane maintains stable underwater superoleophobicity and hydrophilicity under adverse conditions, shows good biological safety, and is harmless to the water environment. These excellent properties endow the ZnO/PANI/PAN nanofibrous membranes with great potential in treating oily wastewater.
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•The 2D BC nano-mesh is self-assembled by the electrospray strategy.•The multi-scale micro-/submicron-/nano-fibrous membrane is designed.•The prepared filter exhibits efficient, ...wet-stable, and durable PM0.3 removal.•The multi-scale fibrous filter is biodegradable.
Airborne pollution, derived from tiny particulate matter (PM) and the pandemic virus, strongly stimulates the demand for personal protective materials but also causes serious environmental issues due to the mass discarding of disposable nondegradable face masks. Despite a few reports of bio-based filters, however, it remains a challenge to develop biodegradable respirators with efficient, wet-stable PM0.3 filtration and low pressure drop. Herein, the degradable multi-scale fibrous filter composed of polylactic acid (PLA) micro-/submicron-fibers and bacterial cellulose (BC) nanofibers was rationally designed to balance the filtration efficiency and resistance. The 2D BC nano-mesh with the small pores was self-assembled by the electro-spraying technique and the PLA submicron-fibrous networks with medium pores were prepared by the electrospinning technology. The multilayer micro-/submicron-/nano-fiber construction endowed the membrane with a low pore size of 1.27 μm and also extended the particle flow path, which contributed to the efficient and durable PM0.3 interception. As a result, the prepared filter showed over 99.89% PM0.3 filtration efficiency but a low pressure drop of 104 Pa. More significantly, it still presented over 99.68% PM0.3 removal after long-term filtration under 90% RH. This work may provide meaningful guidance for the development of biodegradable high-protective air filters.
