Detoxification of aqueous chlorophenol solutions by ionizing radiation

The radiolytic degradation of aerated aqueous 5×10−5 M (6–10 ppm) 2-, 3- and 4-chlorophenol, 2,4-di- and 2,4,6-trichlorophenol has been investigated by determination of the dose needed for complete substrate degradation as well as by analysing the dehalogenation process, the toxicity and the dissolved organic carbon (DOC) in dependence of dose. A radiation dose of 500 Gy leads to a 100% decomposition (corresponding to substrate concentrations ≤1×10−6 M) for all compounds except 2-chlorophenol, for which 600 Gy are required. No influence of dose rate on the degradation rate could be observed in the range from 21 to 183 Gy min−1. Dechlorination is completed at 1 kGy, its rate increases markedly with increasing number of chlorine atoms. At a dose of 1 kGy the decrease of DOC is approximately 20%. A bacterial bioluminescence test was used for evaluating the toxicity of the final radiolytic products. Total detoxification could be achieved by carrying out the irradiation procedure under air saturation and by doses of 500 Gy, which equals that for complete degradation.