Synthesis of a Quaternary Ammonium-Halamine and Preparation on the Modified Nanofibrous Filter with Superior Sterilization, Air Filtration, and Biodegradability

The outbreak of the 2019 coronavirus pandemic has raised worldwide attention about self-protection from airborne diseases. Air filtration and wearing mask have been proven to be effective measures in reducing the pathogenic aerosol's transmission. Those lead to an increasing demand of high-efficient filters. However, the nonbiodegradable polymeric materials used in filters can accumulate in landfills or ecosystems, potentially causing pollution after improper disposals. Sustainable and biodegradable alternatives to current filter materials are urgently needed. Yet, very few commercial filters meet these needs. In this paper, a novel quaternary ammonium-halamine compound containing Schiff base and a sandwich-structured preparation strategy were developed. The obtained multifunctional filter consists of a PLA fleece as a support layer, an antimicrobial coating for bactericidal function, and a nanofibrous membrane for the particle removal. The filter demonstrates strong bactericidal properties, killing 97% of Escherichia coli and Staphylococcus aureus at a biocide concentration of only 1 mg/mL. It can rapidly kill bacteria within 5 min contact without leaching antimicrobial substances. Furthermore, it boasts a filtration performance with a success rate over 99.99% and a pressure drop of 45 Pa, which surpasses that of commercial N95 filters for PM0.3. Even under humid conditions, it maintains excellent filtration performance. Our reusability testing result of the developed filters shows that a simple halogenation treatment can renew the halamines and restore the filter's antimicrobial activity. The filters can degrade in natural soil. The successful development of this sustainable and biodegradable filter material offers a new alternative for high-performance air quality control that protect public health.