Hydrogen peroxide-assisted photocatalytic oxidation of phenolic compounds

The effect of hydrogen peroxide (H2O2) on photocatalytic oxidation of phenol and monochlorophenols (CP) in aqueous suspensions of commercial TiO2 rutile was investigated. Various concentrations of H2O2 were used without and with the presence of TiO2 under different atmospheres, e.g., N2 or O2. Sources of hydroxyl radicals for photocatalytic processes are suggested through the surface hydroxyl group reacting with hole, dissolved oxygen trapping an electron, and photolytic H2O2. The combination of TiO2 and H2O2 under UV illumination can greatly enhance the degradation rates of the phenol and chlorophenols. The photocatalytic oxidation with the H2O2/UV/TiO2 system was found to be much more effective than either UV/TiO2 or UV/H2O2 alone. The efficiency of the photocatalytic degradation of phenol was improved from 30 to 97% due to the presence of H2O2. As the H2O2 concentration increases, more hydroxyl radicals are produced, and the phenol oxidation rate increases. At high H2O2 concentration (≥10−2 M), O2 or N2 atmospheres are not important factors for phenol oxidation in the H2O2/UV/TiO2 system.