Photo-Assisted Mineralization Of The Agrochemical Pesticides Oxamyl And Methomyl And The Herbicides Diphenamid And Asulam

Pesticides of the oximecarbamate type, such as Oxamyl and Methomyl, and the aromatic-bearing herbicides, Diphenamid and Asulam, undergo photo-assisted mineralization nearly quantitatively (ca. 90-100% within similar to 4 h) in aerated UV-illuminated aqueous TiO2 dispersions. The complex structure of the agrochemicals that bear carbon, nitrogen, and sulfur functions are easily mineralized to CO2, NH4+ and NO3- ions, and SO42- ions, respectively. Evolution of carbon dioxide has been monitored by gas chromatography and by loss of total organic carbon (TOC). The site and mode of adsorption of these agrochemicals onto the TiO2 particle surface has been inferred from point charge calculations, whereas the position of attack by reactive oxygen species such as OH radicals has been estimated by frontier electron density calculations.