HEPA filter is normally recommended for removal of Mycobacterium tuberculosis from the airstream. Due to its high cost, a cheaper air-filter substitution is proposed in this study. Both low- and high-grade glass fiber air filters were coated with 5% TiO2 using either polyethylene glycol (PEG), Silane (Si-69), or DURAMAX (D-3005) as a binder. The coated filter was placed in a test duct and irradiated with UVA at an intensity of 4.85 ± 0.41 mW/cm2 to investigate photocatalysis for M. tuberculosis. The effects of dark and light conditions as well as initial exposure to UVA on bacterial removal were studied. Silver-doped and iron-doped TiO2 at different concentrations were also tested using face velocities of 0.1 and 1 m/s and humidity levels of 50 ± 10% and 70 ± 10% RH.
The most appropriate binder for coating TiO2 onto filters was 3% D3005. Using 0.1% metal-doping, 100% removal efficiencies were found. Dark/light conditions affected the hydrophobic/hydrophilic properties of TiO2-coated filters and the removal efficiencies. The removal rate could be increased by extending the warm up period of the lamps. When the face velocity was increased, the removal efficiency dropped in both filters. Similarly, high humidity adversely affected the removal efficiency, particularly with the coated high grade air filter.