119th General Meeting of the KCS

Type Poster Presentation
Area 환경에너지
Room No. 포스터발표장
Time 4월 20일 (목요일) 11:00~12:30
Code ENVR.P-504
Subject N-nitrosodimethylamine (NDMA) formation during chlorination and ozonation of N,N-dimethylhydrazine compounds: Reaction kinetics, mechanisms and implications for NDMA formation control
Authors 이웅배, 이윤호1,*
GIST 지구·환경공학부, Korea
1GIST 지구환경공학부, Korea
Abstract Compounds with N,N-dimethylhydrazine moieties ((CH3)2N-N) form N-nitrisodimethylamine (NDMA), which is a suspected human carcinogen, during ozonation, but the relevent reaction chemistry is hitherto poorly understood. This study investigated the reaction kinetics and mechanisms of NDMA formation during chlorination and ozonation of daminozide (DMZ) as structural model N,N-dimethylhydrazine compounds for a more generalized prediction of NDMA formation in various water qualities and ozonation treatment conditions. Pre-chlorination as mitigation strategies against NDMA was also tested. The reaction of ozone with DMZ was fast (kO3 5 105 M-1s-1 at pH 7). Molar NDMA yields (i.e., Δ[NDMA]/Δ[precursor] 100) were 100% for DMZ in the presence of tert-butanol as hydroxyl radical (·OH) scavenger. The molar NDMA yield decreased significantly in the absence of tert-butanol, indicating ·OH formation and its subsequent reaction with the parent precursors forming negligible NDMA. The reaction of with DMZ was relatively slow (k·OH 3.4 × 109 M-1 s-1 at pH 7). The reaction mechanism in the reaction of DMZ with ozone was proposed, forming NDMA as a final product. The reaction of DMZ with chlorine was moderately fast (kHOCl 60 M-1s-1 at pH 7) and gives no NDMA as product. Chlorinated byproducts of DMZ did not form NDMA in ozonation, Overall, significant NDMA formation was found to be unavoidable during ozonation of water containing N,N-dimethylhydrazine compounds due to their rapid reaction with ozone forming NDMA with high yield, while pre-chlorination can be an effective measure to minimize the NDMA formation during ozonation of water containing N,N-dimethylhydrazine compounds.
E-mail wbl0402@gist.ac.kr