Review on Polymeric, Inorganic, and Composite Materials for Air Filters: From Processing to Properties

Abstract

Particulate and gaseous air pollutants pose a threat to human health and contribute to climate change. By today, air filters, stationary and portable, are markedly improved and can often provide innocuous air pollution levels. After introducing the classification and standards on air filters, the influence of the processing route and its parameters on the resulting air filter properties and consequently its performance are discussed. Numerous tools are presented to adjust structural properties such as fiber or pore diameter, specific surface area, surface charge, hydrophilicity, or photocatalytic activity to achieve the desired performance in terms of high filtration efficiencies, sufficient mechanical stability, regeneration eligibility, antimicrobial and optical properties. In particular, inorganic and composite materials as well as nonfibrous structures are covered, which are currently holding an outsider position in an air filter community dominated by polymeric materials and fibrous structures.

Fabrication of air filters with advanced filtration performance for removal of viral aerosols and control the spread of COVID-19

“…An environmental study has shown that prolonged exposure to these particles increases mortality due to COVID-19. In fact, particles with high surface-to-volume ratios can absorb the virus-containing SARS-CoV-2 and spread viral infection [ [15] , [16] , [17] ].…”

“…2 ). For gaseous pollutants, it is based on physisorption (based on weak Vander Waals force), and chemisorption (strong connection among pollutant and the filter material) [ 12 , [14] , [15] , [16] ].

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“…Today, high-performance and efficient air filters are made using polymer nano-fibers as well as nanomaterials that have anti-viral and antimicrobial features such as metals, metal oxides, biopolymers, and carbon-based nanomaterials like graphene and carbon nanotubes [ 15 , 16 , 21 , 23 , 24 ]. In this review, we summarized the utilization of diverse materials in the preparation of efficient air filters to apply in the preparation of medical masks and ventilation systems.…”

Approaches to Preceramic Polymer Fiber Fabrication and On-Demand Applications

“…Inorganic fibers are formed by pyrolysis of an organic template fiber, which is then soaked in preceramic precursor materials, or precursor materials are deposited on its surface. A direct process involves the direct spinning of inorganic precursors (solutions of salt, suns, or molten precursors) into "green fibers", sometimes using organic polymer additives [15][16][17][18][19][20].…”

Trapping virus-loaded aerosols using granular protein nanofibrils and iron oxyhydroxides nanoparticles

“…Producing HEPA filters requires relatively advanced fabrication technologies, 39 with a large proportion made of either glass fibers or plastics, the former of which requires an energy-intensive fabrication process, and the latter of which relies heavily on the petrochemical industries. 39,40 In addition, over time, a filter cake builds up on the fibers of the filter, resulting in increased resistance to airflow and the imminent need to replace the whole filter, with very limited options of cleaning and/or reuse. 40 Indeed, using HEPA filters on a global scale to combat the transmission of airborne viruses in indoor spaces incur prohibitive environmental and financial costs.…”