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

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