Photocatalyst TiO2 supported on glass fiber for indoor air purification: effect of NO on the photodegradation of CO and NO2

A synthetic photocatalyst TiO2 prepared using the sol–gel method showed a higher activity than commercial photocatalyst TiO2 (P25), for the photodegradation of NO and benzene, toluene, ethylbenzene, o-xylene (BTEX) at typical indoor air parts-per-billion (ppb) levels. The Brunauer–Emmett–Teller (BET) surface area was found to be the vital parameter for the increased activity of the photocatalyst. The photocatalyst was immobilized on a glass fiber filter and evaluated under different humidity levels and residence time. The conversion of the synthetic photocatalyst and P25 were adversely affected by the increase of humidity, and decreased with decreasing residence time. The synthetic photocatalyst, however, was less affected by the levels of humidity. To evaluate the feasibility of photocatalytic technology for indoor air purification, other common indoor air pollutants such as CO and NO2 at ppb levels were co-injected with NO. Results showed that the conversion of CO was not promoted by the photodegradation of NO. No competitive effect was observed between CO and NO. The presence of NO promoted the conversion of NO2 while the conversion of NO is decreased due the competition of adsorption site on catalyst between NO and NO2.