Nitrite ion mitigates the formation of N-nitrosodimethylamine (NDMA) during chloramination of ranitidine.

Citation data:

The Science of the total environment, ISSN: 1879-1026, Vol: 633, Page: 352-359

Publication Year:
2018
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Repository URL:
http://scholarworks.unist.ac.kr/handle/201301/24136
PMID:
29597157
DOI:
10.1016/j.scitotenv.2018.03.181
Author(s):
Seid, Mingizem Gashaw; Cho, Kangwoo; Lee, Changha; Park, Hyun-Mee; Hong, Seok Won
Publisher(s):
Elsevier BV; ELSEVIER SCIENCE BV
Tags:
Environmental Science; N-nitrosodimethylamine; Ranitidine; Nitrite ion; Chloramination; Kinetics; Reaction pathway
article description
Ranitidine (RNT) has been an important tertiary amine precursor of N-nitrosodimethylamine (NDMA) in chlorine-based water treatment, due to reaction with monochloramine (NHCl) with exceptionally high molar yields up to 90%. This study examined the effects of nitrite ions (NO) on the kinetics of NDMA formation during the chloramination of RNT under variable concentrations of dissolved oxygen (DO, 0.7-7.5mg/L), RNT (5-30μM), NHCl (5-20mM), NO or NO (0-2mM) and pH (5.6-8.6). In the absence of the NO, the ultimate molar yield of NDMA after 6h of reaction was primarily influenced by [DO] and pH, while marginally affected by initial [RNT] and [NHCl]. A kinetic model, prepared in accordance with the reaction sequence of NDMA formation, suggested that the rate determining step was accelerated with increasing [NHCl], [DO], and pH. A Kinetic study together with ultra-performance liquid chromatography-quadrupole-time of flight mass spectrometer (UPLC-Q-TOF MS) and gas chromatography (GC)/TOF MS analyses in parallel demonstrated that the nitrite ion inhibited the nucleophilic substitution of the terminal amine on NHCl, and reduced the pseudo-steady state concentration of N-peroxyl radicals, significantly decreasing the ultimate yields of NDMA.