Laminated polyacrylonitrile nanofiber membrane codoped with boehmite nanoparticles for efficient electrostatic capture of particulate matters

Advancement in nanomaterials for environmental pollutants remediation: a systematic review on bibliometrics analysis, material types, synthesis pathways, and related mechanisms

Environmental pollution is a major issue that requires effective solutions. Nanomaterials (NMs) have emerged as promising candidates for pollution remediation due to their unique properties. This review paper provides a systematic analysis of the potential of NMs for environmental pollution remediation compared to conventional techniques. It elaborates on several aspects, including conventional and advanced techniques for removing pollutants, classification of NMs (organic, inorganic, and composite base). The efficiency of NMs in remediation of pollutants depends on their dispersion and retention, with each type of NM having different advantages and disadvantages. Various synthesis pathways for NMs, including traditional synthesis (chemical and physical) and biological synthesis pathways, mechanisms of reaction for pollutants removal using NMs, such as adsorption, filtration, disinfection, photocatalysis, and oxidation, also are evaluated. Additionally, this review presents suggestions for future investigation strategies to improve the efficacy of NMs in environmental remediation. The research so far provides strong evidence that NMs could effectively remove contaminants and may be valuable assets for various industrial purposes. However, further research and development are necessary to fully realize this potential, such as exploring new synthesis pathways and improving the dispersion and retention of NMs in the environment. Furthermore, there is a need to compare the efficacy of different types of NMs for remediating specific pollutants. Overall, this review highlights the immense potential of NMs for mitigating environmental pollutants and calls for more research in this direction.

Nude and Modified Electrospun Nanofibers, Application to Air Purification

Air transports several pollutants, including particulate matter (PM), which can produce cardiovascular and respiratory diseases. Thus, it is a challenge to control pollutant emissions before releasing them to the environment. Until now, filtration has been the most efficient processes for removing PM. Therefore, the electrospinning procedure has been applied to obtain membranes with a high filtration efficiency and low pressure drop. This review addressed the synthesis of polymers that are used for fabricating high-performance membranes by electrospinning to remove air pollutants. Then, the most influential parameters to produce electrospun membranes are indicated. The main results show that electrospun membranes are an excellent alternative to having air filters due to the versatility of the process, the capacity for controlling the fiber diameter, porosity, high filtration efficiency and low-pressure drop.

Preparation and Characterization of Electrospun PAN-CuCl2 Composite Nanofiber Membranes with a Special Net Structure for High-Performance Air Filters

The growing issue of particulate matter (PM) air pollution has given rise to extensive research into the development of high-performance air filters recently. As the core of air filters, various types of electrospun nanofiber membranes have been fabricated and developed. With the novel poly(acrylonitrile) (PAN)-CuCl₂ composite nanofiber membranes as the filter membranes, we demonstrate the high PM removal efficiency exceeding 99% and can last a long service time. The nanoscale morphological characteristics of nanofiber membranes were investigated by scanning electron microscopy, transmission electron microscopy, and mercury intrusion porosimeter. It is found that they appear to have a special net structure at specific CuCl₂ concentrations, which substantially improves PM removal efficiency. We anticipate the PAN-CuCl₂ composite nanofiber membranes will be expected to effectively solve some pressing problems in air filtration.

Electrospun PAN-HNTs composite nanofiber membranes for efficient electrostatic capture of particulate matters

The fine particulate matter (PM) pollution has become a serious concern to public health. As the core part of PM air filters, high-performance electrostatic nanofiber membranes are urgently needed. However, the existing air filters remain challenging to further decrease the pressure drop to improve the wearer comfort. On the other hand, the rapidly disappearing static electricity of the existing electrostatic nanofiber inevitably gives rise to a relatively short service life. Here, we demonstrate a novel and enhanced electrostatic nanofiber membrane by introducing the halloysite nanotubes (HNTs) to the traditional electrospun PAN nanofiber membrane. The optimal PAN-HNTs nanofiber membrane shows a high removal efficiency of 99.54%, a low pressure drop of 39 Pa, and a high quality factor of 0.89 Pa^-1. This greatly improved filtration performance can be attributed to the increased surface area and diameter of nanofiber after introducing the HNTs as additives with suitable doping concentrations. More importantly, compared with the pure PAN nanofiber membrane, the electrostatic capacity of the PAN-HNTs nanofiber membrane is significantly enhanced, which is confirmed by the leaf electroscope. After introducing the HNTs as additives, the surface of the PAN-HNTs nanofiber membrane becomes hydrophilic, which benefits for preventing foulants from attaching to the surface. We anticipate that the PAN-HNTs nanofibers as high-performance membrane air filters will bring great benefits to public health.

High-performance Electret and Antibacterial Polypropylene Meltblown Nonwoven Materials Doped with Boehmite and ZnO Nanoparticles for Air Filtration

The current pandemic caused by COVID-19 has intensively triggered the development of high-performance air filters. Polypropylene (PP) is widely used as the raw material of meltblown nonwoven materials and is the core layer in air filters, such as masks. In this study, an electret PP meltblown nonwoven with antibacterial activity was developed, and nano boehmite (AlOOH) and nano-ZnO were employed as electret and antibacterial agents, respectively. AlOOH (0.5–2.0 wt%) and ZnO (1.0 wt%) were doped into the PP matrix using a twin-screw extruder, and the resulting masterbatches were applied as raw materials to produce nonwoven materials via a meltblown process. The as-prepared nonwoven samples were characterized by means of SEM, IR and DSC/TG. After corona charging, the filtration efficiency was determined by a filtration tester, charge decay was measured by an infrared electrostatic tester, and the antibacterial properties were evaluated (evaluation method: AATCC 100–2012). A dosage of AlOOH greater than 1.0 wt% endowed the nonwoven material with high filtration efficiency, and 1.0 wt% ZnO brought about antibacterial activity. Corona charging was an effective means to charge the nonwoven electret, and the charges were quicker to decay in air than in a sealed bag. The as-prepared meltblown nonwoven filter is a remarkably promising filter for air filtration.

Toward nanotechnology-enabled face masks against SARS-CoV-2 and pandemic respiratory diseases

Wearing a face mask has become a necessity following the outbreak of the coronavirus (COVID-19) disease, where its effectiveness in containing the pandemic has been confirmed. Nevertheless, the pandemic has revealed major deficiencies in the ability to manufacture and ramp up worldwide production of efficient surgical-grade face masks. As a result, many researchers have focused their efforts on the development of low cost, smart and effective face covers. In this article, following a short introduction concerning face mask requirements, the different nanotechnology-enabled techniques for achieving better protection against the SARS-CoV-2 virus are reviewed, including the development of nanoporous and nanofibrous membranes in addition to triboelectric nanogenerators based masks, which can filter the virus using various mechanisms such as straining, electrostatic attraction and electrocution. The development of nanomaterials-based mask coatings to achieve virus repellent and sterilizing capabilities, including antiviral, hydrophobic and photothermal features are also discussed. Finally, the usability of nanotechnology-enabled face masks is discussed and compared with that of current commercial-grade N95 masks. To conclude, we highlight the challenges associated with the quick transfer of nanomaterials-enabled face masks and provide an overall outlook of the importance of nanotechnology in counteracting the COVID-19 and future pandemics.

Evaluations of Electrostatic Filtration Efficiency and Antibacterial Efficacy of Antibacterial Electret Polypropylene Filters: Effects of Using Low Molecular Antibacterial Agent as Additive

In recent years, air filtration has been gaining much attention, and now people are much more concerned about antibacterial filters due to the spreading of COVID-19. The electret polypropylene (PP) nonwoven fabrics possess excellent filtration efficiency but a limited antibacterial effect against S. aureus and E. coli, and therefore triclosan is used in this study. Serving as an antibacterial agent, triclosan with a low molecular weight is an effective additive for the test results, indicating that the presence of triclosan strengthens the antibacterial effects of the filters. In addition, triclosan also strengthens the PP’s crystallinity, which in turn betters the filtration efficiency of the filters concurrently. Demonstrating powerful filtration and antibacterial performances, the antibacterial electret PP filters are highly qualified for filter applications.

Removal of Particulate Matters by Using Zeolitic Imidazolate Framework-8s (ZIF-8s) Coated onto Cotton: Effect of the Pore Size of ZIF-8s on Removal

Removal of particulate matter (PM) like PM2.5 and PM10 from air was carried out with cotton coated with metal-organic frameworks (MOFs) having various pore sizes to understand the effect of the pore size of MOFs (here, ZIF-8s) on the performances in PM elimination. Both removal efficiency and quality factor, based on the unit surface area of ZIF-8s, in the filtration of PMs with ZIF-8/cotton did not rely considerably on the pore size of ZIF-8s. More importantly, small pores (even less than 0.5 nm) of conventional MOFs like ZIF-8 are more than enough in the elimination of large PMs like PM10 with a size of microns probably because small active sites (such as polar functional groups) on PMs can interact with porous materials having polarity. Additionally, electrostatic interactions between PMs and porous materials could be confirmed as a plausible mechanism for PM removal with ZIF-8/cotton.