Photocatalytic degradation of 3,4-xylyl N-methylcarbamate (MPMC) and othercarbamate pesticides in aqueous TiO2 suspensions

Five carbamate pesticides were degraded photocatalytically on TiO2. The com parison of their disappearance rates showed that the degradation rate is go verned predominantly by their adsorbability to TiO2, and followed Hammett's law in a different manner from ordinary electrophilic reaction, As a degra dation pathway of 3,4-xylyl N-methylcarbamate (MPMC) successive hydroxylati on of aromatic ring was suggested, and polyhydroxylation is considered to l ead to the opening of the aromatic ring to form oxygenated aliphatic interm ediates. It was indicated in this process that the formation of acetic acid , one of the major aliphatic intermediates, mainly originates from methyl s ubstituents on the aromatic ring. (C) 1999 Elsevier Science B.V. All rights reserved.