Inactivation and Mineralization of Aerosol Deposited Model Pathogenic Microorganisms over TiO2 and Pt/TiO2

Air disinfection from bacteria and viruses by means of photocatalytic oxidation is investigated with microorganisms loaded over photocatalysts' films from aerosols. Deposition method and equipment have been developed to load Mycobacterium smegmatis, Bacillus thuringiensis, vaccinia virus, and influenza A (H3N2) virus on slides with undoped TiO2 and platinized sulfated TiO2 (Pt/TiO2). Inactivation dynamics was measured under UVA irradiation and in the dark. About 90% inactivation is reached in 30 min irradiation on TiO2 and from 90 to 99.8% on Pt/TiO2. The first-order inactivation rate coefficient ranged from 0.18 to 0.03 min(-1), over Pt/TiO2 being higher than on TiO2 for all microorganisms except Bacillus thuringiensis. The photocatalytic mineralization of Bacillus thuringiensis was performed on TiO2 and Pt/TiO2 with different photocatalyst and microorganism loadings. Completeness of mineralization depended on the TiO2 to bacteria mass ratio. The rate of the photocatalytic carbon dioxide production grows with both the cell mass increase and the photocatalyst mass increase. Pt/TiO2 showed increased rate of mineralization as well as of the inactivation likely due to a better charge carrier separation in the doped semiconductor photocatalyst The results demonstrate that photocatalytic filters with deposited TiO2 or Pt/TiO2 are able to inactivate aerosol microorganisms and completely decompose them into inorganic products and Pt/TiO2 provides higher disinfection and mineralization rates.