Influence Of Modified TiO₂ On Intermediates Distributions And Health Risk Of Photocatalytic Oxidation Of VOCs In Indoor Air

Much more investigations and widespread attention are paid to the photocatalytic degradation of VOCs in indoor air by nanomaterials in recent years. From the viewpoint of the intermediates distribution and risk assessment during the photocatalytic oxidation (PCO) reaction, TiO2 (Degussa P25), N-doped TiO2, C-doped TiO2 and Cu-doped TiO2 were chosen as the photocatalysts, and VUV irradiation to study the intermediates distribution and health risk of gaseous toluene and benzaldehyde of indoor air concentration level. During the photocatalytic degradation of toluene by N-TiO2, there are some transition states generated which can be composed in different pathways to get some selective intermediates as acetaldehyde and acetone. And there is no significant relationship with band strucuture with the intermediates distribution. The main intermediates of benzaldehyde by Cu-TiO2 and C-TiO2 are formaldehyde, methanol, propylene, acetaldehyde, ethanol,1,3-butadiene, acraldehyde, acetone, formic acid, and propionic acid. Compared with C-doped TiO2, the concentration of the more toxic intermediates than benzaldehyde, such as acetaldehyde,1,3-butadiene, and acraldehyde by Cu-TiO2 are lower. And the health risk is lower.Because that the Cu-TiO2 had O2- that had higher photocatalytic conversion rate than C-TiO2. Compared with UV lamp, the wavelenghth of 185nm contained in VUV light resource can react with O2 and on the surface of the photocatalyst to generat O(3P), O3,·O3-, O(1D),·O and·OH which can promote the photocatalytic degradation minerization of the toluene. Under the VUV irradiation, the more toxic intermediates such as formaldehyde and acetaldehyde are oxidize to formic acid and acetic acid whose toxicity is lower and the health risk influence value decreases from 2.46 (UV irradiation) to 0.96.