Photochemical oxidation of phenol and chlorophenol by UV/H2O2/TiO2 process: A kinetic study

摘要

In the present work, the photochemical oxidation of phenol and chlorophenol aqueous solutions in a batch recycle photochemical reactor using ultraviolet irradiation, hydrogen peroxide and TiO2 (as photocatalyst) was studied. The study showed that the combined treatment process was the most effective process under acidic conditions and showed a higher rate of degradation of phenol and chlorophenol at a very short radiation time. The reaction was found to follow the first order kinetics and was influenced by the pH, the input concentration of H2O2 and the dosing amount of the TiO2 photocatalyst. The results indicate maximum 74.6% and 79.8% degradation of phenol and chlorophenol respectively within 90 minutes of radiation time. The experimental results showed that the optimum conditions were obtained at a pH value of 4, with H2O2 concentration ranging from 200–550 ml/L, and TiO2 dosing ranging from 1–2 g/L for UV/H2O2/TiO2 combined system. The reactions were accompanied by the reduction of COD and generation of Cl⁻ ion, which reached its maximum value at a short reaction time. Finally a rough comparison of energy consumption shows that UV/H2O2/TiO2 process reduced the energy consumption by 40–50% compared with the UV/H2O2 and UV/TiO2 processes.