| Photooxidation experiments of p-chlorophenol in an annular reactor were conducted by the application of three different photochemical processes (UV/H2O2, UV/Fenton and UV/ferrioxalate/H2O2). The effect of reaction conditions such as the dosage of H2O2, initial p-chlorophenol, the dosage of catalyzer addition, initial pH, reaction temperature, carrier gas were studied in terms of phenol concentration and chemical oxygen demand (CODcr). The role of oxygen in the reaction was evaluated in the photochemical systems with a small dosage of H2O2 addition. From the experiments results, we can conclude that dioxygen continued the reaction as the mainly oxidant after H2O2 consumed entirely. Evidently, reducing the dosage of H2O2 addition can save the running cost to a certain degree and make the techniques more possible to apply in industry.For UV/H2O2 system, under the condition of adding H2O2 (l/2Qth), 20 ℃, initial pH=6.5 and adding of air, 85% phenol was degraded and 30% CODcr was removed after 60min. For UV/Fenton system, the removal of COD and phenol can be achieved over 75% and 90% respectively after 60min, under the condition of adding H2O2(0.25Qth), Fe2+:H2O2=l :20, 20℃, initial pH=3.0 and adding of air.The distinct difference of UV-VIS spectra between UV/Fenton and UV/H2O2 showed that the complex mechanism was more reasonable than the classic free radical theory in Fenton process. It can also been proved by the quantum yields calculated and the degradation of p-chlorophenol in batch reaction.Kinetic models were established for UV/H2O2 and UV/Fenton systems respectively which were well supported by the experiment results. Moreover, the model parameters showed that decomposition of Fe(IV)-complex is the main reaction way in UV/Fenton process and hydroxyl radicals just play a minor role.
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