Reaction behaviors of decomposition of monocrotophos in aqueous solution by UV and UV/O-3 processes

The decomposition of monocrotophos (cis-3-dimethoxyphosphinyloxy-N-methyl-c in aqueous solution by UV and UV/O-3 processes was studied. The experiment s were carried out under various solution pH values to investigate the deco mposition efficiencies of the reactant and organic intermediates in order t o determine the completeness of decomposition. The photolytic decomposition rate of monocrotophos was increased with increasing solution pH because th e solution pH affects the distribution and light absorbance of monocrotopho s species, The combination of O-3 with UV light apparently promoted the dec omposition and mineralization of monocrotophos in aqueous solution, For the UV/O-3 process, the breakage of the [C=C] bond of monocrotophos by ozone m olecules was found to occur first, followed by mineralization by hydroxyl r adicals to generate CO32-, PO43-, and NO3- anions in sequence. The quasi-gl obal kinetics based on a simplified consecutive-parallel reaction scheme wa s developed to describe the temporal behavior of monocrotophos decompositio n in aqueous solution by the UV/O-3 process, (C) 2000 Elsevier Science B.V. All rights reserved.