Abstract
The effect of hydrogen peroxide (H
2O
2) on photocatalytic oxidation of phenol and monochlorophenols (CP) in aqueous suspensions of commercial TiO
2 rutile was investigated. Various concentrations of H
2O
2 were used without and with the presence of TiO
2 under different atmospheres, e.g., N
2 or O
2. Sources of hydroxyl radicals for photocatalytic processes are suggested through the surface hydroxyl group reacting with hole, dissolved oxygen trapping an electron, and photolytic H
2O
2. The combination of TiO
2 and H
2O
2 under UV illumination can greatly enhance the degradation rates of the phenol and chlorophenols. The photocatalytic oxidation with the H
2O
2/UV/TiO
2 system was found to be much more effective than either UV/TiO
2 or UV/H
2O
2 alone. The efficiency of the photocatalytic degradation of phenol was improved from 30 to 97% due to the presence of H
2O
2. As the H
2O
2 concentration increases, more hydroxyl radicals are produced, and the phenol oxidation rate increases. At high H
2O
2 concentration (≥10
−2
M), O
2 or N
2 atmospheres are not important factors for phenol oxidation in the H
2O
2/UV/TiO
2 system.