Kinetics and mechanism of formation and destruction of N-nitrosodimethylamine in water – A review

Abstract

This paper presents an overview on the current knowledge of the mechanism of formation of N-nitrosodimethylamine (NDMA) in water. The kinetics of the reactions of NDMA precursors (amines and dimethylsulfamide) with disinfectants (ClO2, O3, OH, and Fe(VI)) is presented. The second-order rate constants were determined as 10−2–108, 10−1–109, 10−1–>106, and 108–1010M−1s−1 for reactions with ClO2, O3, OH, and Fe(VI), respectively, at pH 7.0. The rate constants for reactions with most of the secondary and tertiary amines were of the order of 102–1010M−1s−1, which suggest that the moieties of dimethylamine (DMA) and tertiary amine in nitrogen-containing precursors may largely be the sources of the NDMA formation potentials (NDMA-FPs) in treated water. The proposed mechanisms of the reactions involve one-electron transfers in the initial step in the case of ClO2, O3, and OH as oxidants while Fe(VI) prefers a two-electron transfer (oxygen atom transfer) step. NDMA destruction methods include biodegradation, reduction, and oxidation (photolytic, photocatalytic, chemical, and electrochemical). Current concepts of the proposed mechanisms of NDMA transformations are briefly described.