PHOTODEGRADATION OF 2-CHLOROPHENOL AND 3-CHLOROPHENOL IN TIO2 AQUEOUS SUSPENSIONS

The photocatalytic degradations of 2-chlorophenol (2CP) and 3-chlorophenol (3CP) in TiO2 aqueous suspensions at λ > 340 nm have been studied. They are faster than direct photolysis at λ > 290 nm despite the additional number of photons available in this wavelength region and produce lower maximal concentrations of intermediates. Complete mineralization is achieved eventually; however, it requires a much longer time than dechlorination and dearomatization. Effects of radiant flux, wavelength, initial concentration, and pH are examined. Para hydroxylation is the main pathway, so that 2CP and 3CP both give rise to chlorohydroquinone (CHQ), whereas formation of catechol (CT) is a very minor pathway in the degradation of 2CP. Further hydroxylation of CHQ and CT forms hydroxyhydroquinone, which rapidly decomposes to carboxylic acids and carbonyl compounds not identified yet. © 1990, American Chemical Society. All rights reserved.