Chemical Degradation of Polychlorinated Biphenyls by the UV-Fe²⁺/Fe³⁺-H₂O₂ System and its Application for Polychlorinated Biphenyl-polluted Electric Insulating Oil

Abstract

The application of an optimized Fenton reaction and UV irradiation to the degradation of highly chlorinated biphenyls (PCBs) was performed. Recommended conditions were: Fe²⁺/Fe³⁺ concentration (16mM), H₂O₂ concentration (12%), temperature (70°C), pH (2.0), reaction time under stirring (≥2hr), re-addition of iron solution (1 hr intervals) and H₂O₂ (30 min intervals) and UV irradiation (254 nm, intensity 0.4mW cm^-2). When the system was applied to mixtures of PCBs at 5 ppm [PCBs congeners Kanechlor (KC)-400/600], low chlorine substituted biphenyls (Cl: 2-5) were completely decomposed after 2 hr, and even >90% of high chlorine substituted biphenyls (Cl: 6-8) could be degraded. When the present system was first applied to PCBs present in polluted electric insulating oil (25 ppm), >80% of PCBs were successfully degraded after 8 hr. These results suggest that the present UV-Fe²⁺/Fe³⁺-H₂O₂ system could be employed as a new technique for combating persistent organic pollutants such as PCBs.