Enhancement effect of TiO₂immobilized on activated carbon filter for the photodegradation of pollutants at typical indoor air level

The competition effect between water vapor and pollutants at ppb level for adsorption sites has been previously reported. It was found that at high humidity levels, the pollutant photodegradation rate reduced drastically. To improve the photodegradation of pollutants at ppb level and at high humidity levels, TiO2is immobilized on an activated carbon (AC) filter. 200 ppb of nitrogen oxide (NO) and 20 ppb of benzene, toluene, ethylbenzene and o-xylene (BTEX) were chosen as target pollutants. Sensitivity analyses were conducted for NO and BTEX under different residence times and levels of humidity. Results showed that the combination of TiO2and AC significantly increased NO and BTEX removals at short residence time and high humidity levels. TiO2immobilized on AC filter was less affected by the increasing humidity levels. NO2, as an intermediate generated from the photodegradation of NO, was also successively suppressed from exiting the system. Deactivation from the photodegradation of NO was suppressed by immobilizing TiO2on an activated carbon filter. The use of activated carbon acted as a local pollutant concentrator by adsorbing pollutants from the air stream and thereby diffused to the TiO2for photodegradation.