Factors influencing the photodegradation of N-nitrosodimethylamine in drinking water

Abstract

In order to provide basic data for practical application,photodegradation experiment of N-nitrosodimethylamine (NDMA) in aqueous solution was carried out with a low-pressure Hg lamp. Effects of the initial concentration of NDMA, solution pH, dissolved oxygen, and the presence of humic acid on NDMA photodegradation were investigated. NDMA at various initial concentrations selected in this study was almost completely photodegraded by UV irradiation within 20 min, except that at 1.07 mmol/L, NDMA could be photodegraded almost completely in the acidic and neutral solutions, while the removal efficiency decreased remarkably in the alkaline solution. Dissolved oxygen enhanced the NDMA photodegradation, and the presence of humic acid inhibited the degradation of NDMA. Depending on the initial concentration of NDMA, NDMA photodegradation by UV obeyed the pseudo-first-order kinetics. Dimethylamine, nitrite, and nitrate were detected as the photodegradation products of NDMA. ¹O₂ was found to be the reactive oxygen species present in the NDMA photodegradation process by UV, based on the inhibiting experiments using tert-butanol and sodium azide.

Keywords

N-nitrosodimethylamine (NDMA) / ultraviolet irradiation / degradation kinetic / dimethylamine / photodegradation product

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Acknowledgements

This work was supported the National High Technology Research and Development Program of China (Grant No. 2007AA06Z339), the National Natural Science Foundation of China (Grant No. 50578052), and the National Basic Research Program of China (2008CB418200).

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