PHOTOCATALYTIC DEGRADATION OF 2,4-DICHLOROPHENOXYACETIC ACID AND 4-CHLORO-2-METHYLPHENOXYACETIC ACID IN WATER BY USING TiO_2

摘要

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 TiO_2 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 TiO_2 in solution containing hydrogen peroxide has been also studied. H_2O_2 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.