Photocatalytic degradation of 2,4-dichlorophenoxyacetic acid and 4-chloro-2-methylphenoxyacetic acid in water by using TiO2.

The photocatalytic degradation of many chlorinated organic compounds by semiconductor particles, has been widely recognised as a promising method of water and wastewater treatment process. In the present work the photocatalytic transformation of 2,4-D and MCPA in aqueous solution with 2 g l(-1) suspended TiO2 is demonstrated. The formation of several intermediates has been observed. The photodegradation rate increases with increasing pH. The photocatalytic transformation of 2,4-D and MCPA over TiO2 in solution containing hydrogen peroxide has been also studied. H2O, accelerated significantly the reaction rate of 2, 4-D and MCPA. The partial inhibition by ethanol is attributed to the scavenging of OH radicals involved in the first step of the reaction. Finally, from these results, a mechanism is proposed. This photocatalytic method has good potential for application on a large scale.