Highly efficient photocatalytic inactivation of flowing bioaerosol by using visible light-assisted titanium-based composite: Application and mechanism

Some pathogenic microorganisms can survive and spread as bioaerosols which is a serious threat to human health. Hence, a visible light-assisted photocatalytic inactivation system for bioaerosol inactivation was constructed based on the novel P/Ag/Ag₂O/Ag₃PO₄/TiO₂ (PAgT) composite photocatalyst. The highest inactivation efficiency for 10⁸ CFU/m³ Escherichia coli bioaerosol could reach 99.3 % within just 14.1 s under visible light irradiation. The effect of various operational conditions on photocatalytic inactivation efficiency were investigated, including light intensity, bioaerosol concentration and residence time. Furthermore, during the bioaerosol inactivation process, the changes of cell morphology and intracellular reactive oxygen species were clarified. The oxidizing substances h⁺, O₂⁻ and OH produced on the surface of the photocatalyst under the irradiation of visible light were the direct cause of cell oxidizing damage. It disrupted cell membrane permeability and cause an increase in intracellular reactive oxygen species, ultimately leading to cell death. The system possessed an irreversible and efficient photocatalytic bioaerosol sterilization ability toward different airborne pathogenic bacteria, including Gram-positive and Gram-negative bacteria. In addition, the PAgT photocatalytic system demonstrated good cyclability and stability for bioaerosol inactivation, providing a promising strategy to reduce the airborne pathogenic microbial contamination, especially for indoor or occupied space.