SCIENCE OF THE TOTAL ENVIRONMENT
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2022
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IF 10.753
Menglan Gao,Zhibin Jiang,Xiaobin Liao,Huan Qi,Lei Zhao,Chao Chen,Danielle Westerman
Aliphatic amines, common constituents that contribute to dissolved organic nitrogen (DON), can quickly react with ozone due to the lone electron pair on the nitrogen atom and this may produce carcinogen N -Nitrosodimethylamine (NDMA). 3-(Dimethylamino)-1-propylamine (DMAPA) was chosen as a representative to elucidate the NDMA formation characteristics, kinetic rates, reaction pathways, and influencing factors during ozonation in this study. The results demonstrated that NDMA generated directly from DMAPA during ozonation. Moreover, the NDMA yields increased with ozone dosages. The NDMA molar yield increased and then decreased when the pH raised from 5 to 9, achieving the maximum value at pH 8. Hydroxyl radical (∙OH) played a promotional role in NDMA formation, and its scavenger dramatically cut down its yields. Low levels of Br − facilitated NDMA formation, while the value significantly reduced when Br − was up to 1 mM. The NDMA amount was slightly raised by NO 2 − , but it was inhibited by NH 4 + and NO 3 − . Moreover, it was also depressed by co-existing components in actual lake water. Based on the result of the Gaussian calculation, the LC-MS/MS and GC–MS analysis, four possible transformation pathways were proposed. The radical recombination was verified to be the primary pathway for ozone promoting NDMA formation from DMAPA.
研究领域:
环境科学
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化学
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DOI
PubMed
高影响因子
JOURNAL OF HAZARDOUS MATERIALS
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2022
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IF 14.224
Menglan Gao,Xiaobin Liao,Jing Yu,Xinna Lin,Huan Qi,Linlu Shen,Shupo Liu,Zhimin Yang
Bromide ions (Br - ) affected non-brominated nitroso-dimethylamine (NDMA) formation during ozonation , but the mechanism is still unclear. 1,1,1′,1′-tetramethyl-4,4′-(methylene-di- p -phenylene) di-semicarbazide (TMDS) was chosen to further probe this problem. The results indicated that low levels of Br - (≤20 μM) enhanced NDMA from 3.27 to 7.56 μg/L, while its amount slightly dropped to 6.22 μg/L raising Br - to 100 μM. It was experimentally verified that intermediates 1,1-dimethylsemicarbazide (DMSC) and 1,1-dimethylhydrazine (UDMH) played important roles on promoting NDMA generation, whose contribution rates were 40.2% and 32.2%, respectively. The brominated substances with higher NDMA molar yields were detected. ∙OH reduced NDMA formation without Br - , while it played promotion role with Br - ; the corresponding contribution rates were − 26.9% and 29.2%, respectively. No matter with or without Br - , both ∙O 2 - and l O 2 brought a boost to NDMA formation, their contribution ratios were 34.9% and 58.1% without Br - , while raised significantly to 64.6% and 81.5% when Br - existed. Br - not only facilitated NDMA formation, but also benefited the degradation of TMDS. Based on the calculation results and intermediates detected, the influence mechanisms of Br - were proposed. The results would provide theoretical basis and technical guarantee for treating NDMA precursors and bromide co-existing water in the future.
研究领域:
环境科学
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水处理工程
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DOI
PubMed
高影响因子
SCIENCE OF THE TOTAL ENVIRONMENT
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2021
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IF 7.963
Xiaobin Liao,Linlu Shen,Zhibin Jiang,Menglan Gao,Yu Qiu,Huan Qi,Chao Chen
Metformin, a high-consumed pharmaceutical for diabetes, has been reported to generate carcinogenic nitroso-dimethylamine (NDMA) during treatment of its containing wastewater. However, whether it would produce NDMA during ozonation or not is unclear, let alone discriminate roles of ozone (O 3 ) and hydroxyl radicals ( OH). In this paper, effects of ozonation on NDMA formation from metformin were investigated, roles of O 3 and OH were also distinguished by adding tert-butyl alcohol (tBA) as OH scavenger. Moreover, various influencing factors and reaction mechanisms were demonstrated. The results indicated that NDMA could be directly formed from metformin during ozonation, the addition of OH scavenger significantly enhanced its formation (0–46.2 ng/L vs 0–139.1 ng/L). The formation of NDMA by O 3 and OH was more affected by bromide and HCO 3 − than those with only O 3 ; while the impacts of pH and sulphate on the latter were more notable. No matter without/with tBA in the solution, the formed NDMA during ozonation of metformin increased with raising pH (from 5 to 9) and achieved the maximum 69.6 ng/L and 235.9 ng/L at pH 9, respectively; small amount of bromide (0.1 μM) promoted NDMA production, high levels of bromide (10 μM) inhibited its formation; the existence of HCO 3 − enhanced the amounts of NDMA from 44.5 to 73.5 ng/L (raised by 65.2%) by O 3 and OH and from 102.9 to 130 ng/L with only O 3 (raised by 26.3%); with the addition of sulphate, NDMA concentration raised by 43.8% by O 3 and OH, while the value was high up to 134.6% with only O 3 . Based on the result of UPLC-Q-TOF and density functional theory , the oxidation intermediates were identified and possible transformation pathways of metformin during ozonation were proposed. The findings in this paper would provide reference when treating metformin-containing water in future.
研究领域:
环境科学
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药学
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DOI
高影响因子
Environmental Science-Water Research & Technology
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2022
·Vol. 8
·期 6
·1252-1260
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IF 5.819
Wei Zhang,Nan Li,Caiwen Wang,Guangchao Li,Julong Sun,Shumin Zhu
Diuron, a persistent organic herbicide, was effectively degraded by the solar/chlorine process in this study. The solar/chlorine process could not only produce HO˙ (hydroxyl radicals) and reactive chlorine species (RCS), but also O3. They are the major contributors to diuron degradation at different solution pH values (6–8). Natural organic matter (NOM), NO2− and a high dosage of Cl−, NO3−, and HCO3− could inhibit the efficiency of diuron degradation. Moreover, a possible degradation pathway of diuron was proposed, which gives detailed reactions in the solar/chlorine process. The co-existence of NO2− in diuron degradation has risks of producing N-nitrosodimethylamine (NDMA). Finally, the ecotoxicity of diuron and its oxidation byproducts was reduced overall according to the calculated results from the Ecological Structure Activity Relationships (ECOSAR) program. But the toxicity of the products is still very high. For that, the solar/chlorine process should be of concern when it is used for diuron degradation.
研究领域:
环境科学
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化学
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DOI
高影响因子
危险品化学品经营许可证（带存储）