| Summary: |
The degradation of 4-chlorophenol (4-CP) by UV di-rect photolysis was compared with that by TiO2 photo-catalysis and carried out in a microwave-assisted elec-trodeless discharge UV system. The photocatalytic degra-dation rate of 4-CP increased with the dosage of TiO2, but an overdose would retard the reaction due to light attenua-tion. The effects of different pH values, irradiation inten-sity, aeration and dosages of H2O2 on both the direct photolysis and TiO2 photocatalysis were assessed. Both 4-CP degradation methodologies follow pseudo-first-order decay kinetics. The direct photolysis of 4-CP was domi-nant, even when TiO2 was present in the solution. Using TiO2 as catalyst, the process goes through the same mecha-nism as directly without TiO2, generating the same major intermediates detected by GC/MS analysis, namely hydro-quinone, benzoquinone and 4-chlorocatechol. Therefore, a general reaction pathway for the degradation of 4-CP was proposed. |