Sensitized photolysis of polychlorobiphenyls in alkaline 2-propanol: dechlorination of Aroclor 1254 in soil samples by solar radiation

Hawari, Jalal and Demeter, Attila and Samson, Rejean (1992) Sensitized photolysis of polychlorobiphenyls in alkaline 2-propanol: dechlorination of Aroclor 1254 in soil samples by solar radiation. Environmental Science and Technology, 26 (10). pp. 2022-2027. ISSN 0013-936X (print), 1520-5851 (online)

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Abstract

Photodechlorination of Aroclor 1254 (1000 mg/L) in an alkaline 2-propanol solution at \lambda = 254 nm proceeded with a high quantum yield (\phi = 35.0) as determined by C1- release. The Aroclor was completely dechlorinated in 30 min and gave predominantly biphenyl (BP). After 20 h of solar irradiation, only partial dechlorination (25%) was observed, and no BP was formed. In the presence of phenothiazine (PT) sensitizer (5 mM) the Aroclor was completely dechlorinated to BP in 1 h at 350 nm (\phi = 2.33) and in 4 h by exposure to sunlight. Under the same conditions, Aroclor 1254 extracts of contaminated soil (730 mg/L) were dechlorinated in 2 h at 350 nm (\phi = 0.28) and in 20 h on exposure to sunlight. The photoreaction was completely quenched by oxygen and nitrobenzene (0.1 M). Moreover the Aroclor was thermally (ca. 80 "C) dechlorinated to BP using di-tert-butyl peroxide. A free-radical chain reaction was suggested in which the aryl radical anion, Ar(*-)-Cl, was a key intermediate in the dechlorination process.

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