Air pollution is a growing global concern with severe impacts on human health, leading to a surge in demand for ventilators, respirators, face masks, and air filtration systems during the COVID-19 pandemic. Nanofiber membranes, known for their high specific surface area and porous microstructure, are efficient in capturing fine particles like bacteria, fungi, and viruses. The history of air filtration media development dates back to the 1930s, with significant advancements in nanofiber filters post-World War II. The filtration mechanisms primarily depend on factors like fiber diameter, airflow velocity, and particle size, including inertial impaction, diffusion, interception, electrostatic attraction, gravitational effect, and thermophoresis.
Polymeric nanofiber-based filters offer higher efficiency compared to traditional filters, with the ability to remove various bacteria, viruses, and organic contaminants effectively. Strategies for antimicrobial filters include using polymers with inherent antimicrobial properties, introducing antimicrobial nanoparticles, or coating filters with bio-antibacterial molecules. Examples of antimicrobial agents commonly used include silver, gold, copper nanoparticles, and metal oxides like TiO2 and ZnO. By stacking multiple layers of nanofibers, filtration efficiency can be enhanced without increasing pressure drop, while electrostatically charged filters improve nano-aerosol capture.
Antibacterial air filters utilize various polymers like poly(lactic acid) (PLA), chitosan, silver nanoparticles, and keratin to achieve high bacterial filtration efficiency. These filters exhibit inhibition against common bacteria like Escherichia coli and Staphylococcus aureus. Multifunctional air filtration membranes, such as soy protein isolate (SPI)/polyvinyl alcohol (PVA) nanofibers, demonstrate high filtration efficiency and antibacterial properties. Electrospun nanofibers combined with herbal extracts or metal nanoparticles show promising results in air filtration applications.
In the realm of antiviral air filters, studies focus on fabricating nanofiber membranes with virus-inactivating properties using materials like polyvinylidene fluoride (PVDF), zein, and silver nanoparticles. These membranes exhibit high virus removal efficiency against model viruses like coliphage. Electrospun air filters with polyelectrolyte coatings or photosensitizers show enhanced efficiency in removing and inactivating coronavirus aerosols. Nanocomposite filters containing activated charcoal, titanium nanotubes, and other additives show high antibacterial and antiviral efficacy, making them suitable for applications in virus removal.
The future of nanofiber-based air filtration lies in developing reusable filters from biodegradable polymers, renewable resources, and biowaste to minimize environmental impact. Intelligent filters with active ingredients that selectively capture pollutants and extend filter lifespan are poised for growth. By enhancing the antibacterial and antiviral properties of nanofibers through surface modifications and the addition of antimicrobial agents, researchers aim to create advanced filtration systems with improved efficiency and selectivity in capturing harmful particles, addressing challenges posed by environmental pollution and the spread of infectious diseases.
Tags: fungi, biodegradable polymers, filtration
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