Mechanism and kinetics of H-acid degradation in TiO2/O3/UV process

The mechanism and kinetics of synergetic effect in TiO 2 /O 3 /UV process on H-acid degradation were investigated. The experimental results showed that H-acid removal rate of TiO 2 /O 3 /UV process was the highest among TiO 2 /UV, O 3 /UV and TiO 2 /O 3 /UV processes. The investigation of reactions with suitable active species scavengers confirmed that H-acid was mainly oxidised by ozone and holes on TiO 2 in the TiO 2 /O 3 /UV process. The recombination between holes and electrons in TiO 2 reduced in the presence of ozone, as indicated by fluorescence emission spectra. Moreover, the intermediates generated during H-acid oxidation in various processes were analysed by LC/MSD trap. It is proposed that H-acid was oxidised to polyhydroxy aromatics, benzene carboxylic acids and quinoids in the first step. Then, saturated aliphatics carboxylic acids were formed and mineralised to inorganic compounds through the Photo-Kolbe reaction. Finally, a kinetic study on TiO 2 /UV, O 3 /UV and TiO 2 /O 3 /UV processes was conducted and it was confirmed that both ozonation and photocatalytic activity were improved in TiO 2 /O 3 /UV process because of the synergetic effect.