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Lee, Changha
Advanced Redox Technology (ART) Lab
Research Interests
  • Water Treatment, Advanced Oxidation/Reduction, Water Chemistry, Environmental Catalyst

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UV photolytic mechanism of N-nitrosodimethylamine in water: Roles of dissolved oxygen and solution pH

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Title
UV photolytic mechanism of N-nitrosodimethylamine in water: Roles of dissolved oxygen and solution pH
Author
Lee, ChanghaChoi, WYoon, J
Keywords
NITRIC-OXIDE; NITROSAMINES; SUPEROXIDE; NDMA; PEROXYNITRITE; DIMETHYLAMINE; DEGRADATION; CHEMISTRY; PRODUCT
Issue Date
2005-12
Publisher
AMER CHEMICAL SOC
Citation
ENVIRONMENTAL SCIENCE & TECHNOLOGY, v.39, no.24, pp.9702 - 9709
Abstract
The photolytic mechanism of N-nitrosodimethylamine (NDMA) in aqueous solution was investigated under ultraviolet (UV) irradiation at 253.7 nm, by determining the quantum yield of NDMA photolysis and analyzing the photolysis products in the pH range of 2-11 under O2 or N2 saturation. Several important photolytic behaviors of NDMA photolysis regarding the roles of dissolved oxygen and solution pH were newly observed, and novel photolytic mechanisms were proposed based on these observations. First, the presence of dissolved oxygen clearly increased the quantum yield of the NDMA photolysis, and promoted the photolytic pathway leading to the formation of methylamine and nitrate. The direct oxidation of photoexcited NDMA by dissolved oxygen (photooxidation) was suggested as a novel photolytic pathway to explain the observed effect of dissolved oxygen. This photooxidation mechanism was supported by the detection of superoxide radicals during the photolysis of NDMA under O2 saturation. Second, the dependence of the quantum yield of NDMA photolysis and the yields of the known photolysis products (methylamine, dimethylamine, nitrite, and nitrate) on the solution pH were different under O2 and N2 saturation. N-Methylformamide was observed as the novel photolysis product of NDMA in the neutral pH region under N 2 saturation. These pH-dependent photolytic behaviors of NDMA were successfully explained by the interaction of the photoexcited NDMA with a proton, and the pH-dependent secondary reactions between the primary photolysis products.
URI
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DOI
10.1021/es051235j
ISSN
0013-936X
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