SENSITIZED PHOTOLYSIS OF POLYCHLOROBIPHENYLS IN ALKALINE 2-PROPANOL - DECHLORINATION OF AROCLOR 1254 IN SOIL SAMPLES BY SOLAR-RADIATION

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 Cl- 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-degrees-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.