Comparison of Different Advanced Oxidation Processes for Degrading 4-Chlorophenol

The removal efficiency of 4-chlorophenol with different advanced oxidation processes have been studied. Oxidation experiments were carried out using two 4-chlorophenol concentrations: 100 mg L and 250 mg L and UV generated from a KrCl excilamp with (molar ratio H2O2: 4-chlorophenol = 25:1) and without H2O2, and, with Fenton process (molar ratio H2O2:4chlorophenol of 25:1 and Fe concentration of 5 mg L). The results show that there is no significant difference in the 4chlorophenol conversion when using one of the three assayed methods. However, significant concentrations of the photoproductos still remained in the media when the chosen treatment involves UV without hydrogen peroxide. Fenton process removed all the intermediate photoproducts except for the hydroquinone and the 1,2,4-trihydroxybenzene. In the case of UV and hydrogen peroxide all the intermediate photoproducts are removed. Microbial bioassays were carried out utilising the naturally luminescent bacterium Vibrio fischeri and a genetically modified Pseudomonas putida isolated from a waste treatment plant receiving phenolic waste. The results using V. fischeri show that with samples after degradation, only the UV treatment showed toxicity (IC50 =38) whereas with H2O2 and Fenton reactions the samples exhibited no toxicity after treatment in the range of concentrations studied. Using the Pseudomonas putida biosensor no toxicity could be detected for all the samples following treatment due to the higher tolerance of the organism to phenol concentrations encountered. Keywords—4-chlorophenol, Fenton, photodegradation, UV, excilamp.