PHOTOCATALYTIC DEGRADATION OF MONURON IN AQUEOUS TIO2 DISPERSIONS

The light-induced degradation of Monuron [3-(4-chlorophenyl)-1,1-dimethylurea] under simulated solar irradiation has been investigated in aqueous solutions containing TiO2 suspensions as photocatalysts. The herbicide (present at ppm level) was mineralized to CO2 and Cl-, whereas oxidation of nitrogen to NO3- occurs more slowly, via the intermediate formation of NH3. The primary degradation of the pollutant follows a pseudo-first-order kinetics. Several reaction intermediates were identified using HPLC and GC-MS techniques. The formation and fate of some of these compounds under irradiation were also investigated. Together with the expected formation of several hydroxyaromatic derivatives, the unexpected hydrophobic compound 4-chlorophenyl isocyanate was recognized as a major reaction intermediate. From the analytical data, a reaction scheme was proposed.