The oxidation of phenylurea herbicides (chlortoluron, isoproturon and diuron) by chlorine dioxide (ClO2) and the formation of disinfection by-products (DBPs) during followed chlorination and chloramination were investigated in this paper. Results showed that the reactivity between phenylurea herbicides and ClO2 were highly depended on the different substituted groups on the aromatic ring. The degradation rates were found as diuron >> chlortoluron > isoproturon under circumneutral condition. Chlortoluron and isoproturon disappearance significantly enhanced under the acid conditions. Degradation of phenylureas was subjected to steps including radical intermediates formation, hydroxylation reactions and cleavage of the N-C bond of the ureic side-chain. The degradation pathways of phenylureas were then proposed. Oxidation of phenylureas by ClO2 alone did not produce chlorinated DBPs. ClO2 oxidation reduced chloroform (CF), dichloroacetic acid (DCAA), dichloroacetonitrile(DCAN) and dichloropropanone(DCP) formation during subsequent chlor(am)ination, but enhancement of DCAA was observed during chloramination. Formation of trichloroacetic acid (TCAA) was induced by ClO2 oxidation in subsequent chlor(am)ination.

Degradation of phenylurea herbicides by chlorine dioxide and formation of disinfection byproducts during subsequent chlor(am)ination

248th National Meeting (2014)

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