Study of photocatalytic inactivation of airborne microorganisms on various functionalized filter media: comparative analysis

Airborne microorganisms can cause various adverse effects, including infectious, allergic, and immunotoxic diseases. Bioaerosols are also one of the main causes of morbidity and mortality, as well as a heavy burden on health costs. The present study models and compares the inactivation performance of three commercial air filters, industrial and domestic use (vacuum cleaner) with and without catalyst (TiO2) deposition for a model microorganism under UVA radiation. The filters were studied regarding catalysis load, adherence, optical properties, morphology, and cost. The microorganism used was E. coli, it was distributed emulating Flügge droplets on coated and uncoated filters and then exposed to UVA radiation at different humidity conditions. Different methods of bacterial spreading and counting on filters were tested. A simple kinetic model was proposed and validated to compare the inactivation performances of photocatalysis and photolysis; the modeling results enabled the prediction of inactivation efficiency and analysis of several parameters. To compare the photocatalytic activity of the functionalized filters we calculated D90, the dose to reduce one bacterial log, and a pseudo-constant of the inactivation rate per unit mass of catalyst deposited. Our experimental findings of TiO2-coated fiberglass filters presented in this study suggest that scaling up and its subsequent development in ventilation systems would be successful.