Sunlight Photodegradation of 2,4,5-Trichlorophenoxy-acetic Acid and 2,4,5-Trichlorophenol on TiO2. Identification of Intermediates and Degradation Pathway

The photocatalytic degradation of 2,4,5-trichlorophenoxyacetic acid and 2,4,5-trichlorophenol has been investigated in oxygenated aqueous suspensions of TiO2. Complete mineralization to CO2 and HC1 occurs with half-lives of 30–90 minutes. The effect of loading and thermal pre-treatment of the semi-conductor catalyst, as well as the influence of added chloride ions have been examined. In the degradation of the 2,4,5-trichlorophenoxyacetic acid, several intermediates were detected by gas-chromatographic/mass-spectrometric techniques. A scheme for the photodegradation is formulated.