ABSTRACT
The photodegradation of carbetamide, chloridazon, and metoxuron in water in the presence of ozone, hydrogen peroxide, and oxygenated aqueous suspensions of titanium dioxide has been investigated. Photolysis kinetics were determined using solutions irradiated with a laboratory light source >290 nm and Heraeus suntest apparatus. The time required for 90% destruction was correlated to the concentration of the pesticides. The effect of the H2O2 concentration on the rate of carbetamide oxidation was determined. Several photoproducts were isolated and identified by spectroscopic methods. The results suggest that the degradation pathways of these compounds in the presence UV H2O2 and UV TiO2 are hydroxylations of the aromatic ring. UV ozonation rapidly photooxidized all pesticides. The openings of the aromatic ring were observed, which produces lower molecular weight carboxylic acids; and further photooxidation, which eventually converts the acids to CO2, H2O, HCl, and NH3.
