Chemical degradation of polychlorinated biphenyls by the UV-Fe 2+/Fe 3+-H 2O 2 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: Fe 2+/Fe 3+ concentration (16 mM), H 2O 2 concentration (12%), temperature (70° C), pH (2.0), reaction time under stirring (> 2 hr), re-addition of iron solution (1 hr intervals) and H 2O 2 (30min intervals) and UV irradiation (254 nm, intensity 0.4mWcm -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-Fe 2+/Fe 3+-H 2O 2 system could be employed as a new technique for combating persistent organic pollutants such as PCBs. © 2011 The Pharmaceutical Society of Japan.