Degradation of polychlorinated biphenyls induced by ionizing radiation in aqueous micellar solutions

This investigation examines the gamma-radiation-induced degradation of polychlorinated biphenyls (PCBs) in aqueous surfactant solutions. Dichloro-, tetrachloro-, and decachlorobiphenyl congeners were solubilized in water using a commercially available non-ionic surfacta nt, Triton X-100, and subsequently irradiated by a Co-60 gamma-source. Rates and extent of dechlorination were determined at different surfactant concentrations, and intermediate species and byproducts were quantified. Pulse radiolysis was used to measure rates of reaction between PCBs and the solvated electron as well as rates of electron scavenging by the surfactant. Experiments were also conducted in organic solvents, and these results have been compared to those observed in the aqueous surfactant solutions. Each PCB congener was fully dechlorinated by ionizing radiation in the micellar systems. Initial chloride yields were directly proportional to the level of chlorination of the PCB congeners. Scavenging of the aqueous electron by the surfactant was significant, and PCB degradation efficiency improved markedly at lower surfactant concentrations. PCB transformation occurred primarily through reductive dechlorination, forming lower chlorinated PCBs and biphenyl. Rates of PCB degradation were substantially higher in aqueous surfactant solutions than in diethyl ether and petroleum ether. This suggests that solubilizing PCBs in water using a surfactant prior to irradiation may provide a considerable improvement in contaminant degradation efficiency in comparison to using an organic solvent or irradiating PCBs directly in oil.