ACTIVATION OF HYDROGEN-PEROXIDE BY IRON(III) CHELATES FOR ABIOTIC DEGRADATION OF HERBICIDES AND INSECTICIDES IN WATER

Degradation of selected pesticides was carried out in water at pH 6 using hydrogen peroxide and soluble Fe(III) chelates of picolinic acid, gallic acid, or rhodizonic acid as catalysts and with or without near-UV irradiation. The catalysts were selected on the basis of an earlier screening. Without UV light, transformation of baygon, carbaryl, picloram, 2,4-D, 2,4,5-T, and atrazine was complete within a few minutes to about 2 h. Trifluralin reacted slowly. Ring- and carboxy-labeled [C-14]-2,4-D and ring-labeled [C-14]-2,4,5-T were 70-80% mineralized to (CO2)-C-14 in 2-4 h. Ring-labeled [C-14]atrazine yielded no (CO2)-C-14. UV light accelerated degradation by the above chelates, as well as by thermally inactive oxalate and citrate chelates. UV acceleration is most likely due to charge-transfer photoreduction of the chelate to give Fe(II), which then reacts with H2O2 to generate hydroxyl radical in the Fenton reaction. These reactions are potentially useful for detoxifying pesticide wastes.