Ionizing Radiation Induced Degradation of a Tetrachlorobiphenyl in Transformer Oil

Published

November 1, 1999

Author(s)

M Chaychian, Joseph Silverman, M I. Al-Sheikhly, Dianne L. Poster, Pedatsur Neta

Abstract

Complete degradation of 2,2',6,6'-tetrachlorobiphenyl (PCB 54) in transformer oil is achieved by ionizing radiation without degradation of the oil. Gamma irradiation of transformer oil containing PCB 54 (0.27 mg/g) with a dose of 200 kGy results in complete (>99%) destruction of the PCB. Analysis of samples irradiated with various doses demonstrated the gradual degradation of PCB 54 and the successive formation and degradation of trichloro-, dichloro-, and monochlorobiphenyl. The final products are mainly biphenyl and inorganic chloride. The mechanism of reductive degradation of chlorinated biphenyls in transformer oil is studied by pulse radiolysis. The oil contains varying concentrations of many aromatic hydrocarbons; the most abundant compounds are biphenyl, fluorene, and phenanthrene. Solvated electrons formed by irradiation of the oil react either with the PCB, to lead to dechlorination, or with the aromatic hydrocarbons present in the oil, to form of radical anions. These species are shown to transfer an electron to chlorinated biphenyls relatively rapidly, leading to dechlorination. The rate constants for several such reactions, determined in 2-propanol solutions, are in the range of 10⁷ mol^-1 s^-1 . These relatively rapid reactions explain why PCB can be dechlorinated in oil despite the presence of aromatic hydrocarbons in the oil and despite the formation of biphenyl as a radiolysis product which reacts rapidly with solvated electrons.

Citation

Environmental Science & Technology

Volume

33

Issue

Pub Type

Journals

Keywords

dechlorination, PCB, radiolysis, transformer oil

Citation

Chaychian, M. , Silverman, J. , Al-Sheikhly, M. , Poster, D. and Neta, P. (1999), Ionizing Radiation Induced Degradation of a Tetrachlorobiphenyl in Transformer Oil, Environmental Science & Technology (Accessed April 25, 2024)