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HERO ID
5343877
Reference Type
Journal Article
Title
NDMA formation from 4,4'-hexamethylenebis (HDMS) during ozonation: influencing factors and mechanisms
Author(s)
Shen, L; Liao, X; Qi, H; Zhao, L; Li, F; Yuan, B
Year
2019
Is Peer Reviewed?
Yes
Journal
Environmental Science and Pollution Research
ISSN:
0944-1344
EISSN:
1614-7499
Publisher
SPRINGER HEIDELBERG
Location
HEIDELBERG
Volume
26
Issue
2
Page Numbers
1584-1594
Language
English
PMID
30443725
DOI
10.1007/s11356-018-3684-5
Web of Science Id
WOS:000455814700052
Abstract
N-nitrosodimethylamine (NDMA), a toxic disinfection byproduct commonly associated with chloramination, has recently been found to form from an anti-yellowing agent (4,4'-hexamethylenebis (1,1-dimethylsemicarbazide) (HDMS)) during ozonation but the mechanisms are unclear. In this paper, the potential roles of molecular ozone (O3) and hydroxyl radical (∙OH) on NDMA formation from HDMS were investigated under various oxidation conditions (ozone dosages, pH) and different components in water (bromide ion (Br-), bicarbonate ion (HCO3-), sulfate ion (SO42-), and humic acid (HA), as well as natural organic matter (NOM) from a lake). Moreover, HDMS transformation pathways by ozonation were determined. The results indicated that the formation of NDMA was enhanced through the combined effect of O3 and ∙OH compared to that by O3 alone (addition of tert-butyl alcohol (tBA) as ∙OH scavenger). ∙OH itself cannot generate NDMA directly; however, it can transform HDMS to intermediates with higher NDMA yield than parent compound. The NDMA generation was affected (small dosages promoted but high dosages inhibited) by HA or Br- no matter with or without tBA. The presence of SO42- and HCO3- ions lowered NDMA formation through ∙OH scavenging effect. Increasing pH not only increased degradation rate constant by enhancing ∙OH generation but also affected HDMS dissociation ratio, reaching the maximum NDMA formation at pH 7-8. Natural constituents in selected water matrix inhibited NDMA formation. Impacts of these influencing factors on NDMA formation by only O3 however were significantly less pronounced over that by the joint roles of O3 and ∙OH. Based on the result of Q-TOF, LC/MS/MS, and GC/MS, the possible transformation pathways of HDMS by ozonation were proposed. The NDMA enhancement mechanism by the combined effect of O3 and ∙OH can be attributed to greater amounts of intermediates with higher NDMA yield (such as unsymmetrical dimethylhydrazine (UDMH)) produced. These findings provide new understanding of NDMA formation upon ozonation of typical amine-based compounds.
Tags
IRIS
•
tert-Butanol
Excluded/ Not on Topic
Methodology/Solvent
LitSearch: Jan 2017 - July 2019
PubMed
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