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Liu T, Liao X, Lin X, Yu J, Qi H, Jiang Z, Zou J, Li Q. Influencing pathways and toxicity changes of pre-ozonation on carcinogenic NDEA formation from greenhouse gas adsorbent DEAPA in subsequent disinfection processes. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 873:162355. [PMID: 36822419 DOI: 10.1016/j.scitotenv.2023.162355] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 02/13/2023] [Accepted: 02/16/2023] [Indexed: 06/18/2023]
Abstract
This study was to evaluate the feasibility of controlling carcinogenic nitrosodiethylamine (NDEA) formation from greenhouse gas adsorbent 3-diethylaminopropylamine (DEAPA) by pre-O3 in subsequent chlorination/chloramination processes. The result indicated that the NDEA yields (0.4 %) during chlorination was 1.3 times of that during chloramination (0.3 %); pre-oxidation with 4 mg/L O3 significantly cut down its formation; the reduction rates were up to 67.5 and 48.5 %, respectively. OH scavenger greatly augmented the final NDEA amount from 1.86 to 5.05 μg/L during ozonation, while its roles on subsequent processes differed with disinfection methods as well as O3(g) dosages. Most of co-existed substances inhibited NDEA generation, except NO2-, CO32- and SO42-, which slightly promoted during ozonation. Basing on Gaussian calculation, GC/MS and UPLC-Q-TOF-MS analysis, the influencing mechanisms of pre-O3 on NDEA formation in subsequent disinfection processes were proposed. In addition, the calculated toxicity analysis as well as the whole toxicity was applied to evaluate the possibility of pre-O3 on risk control.
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Affiliation(s)
- Tianze Liu
- Institute of Municipal and Environmental Engineering, College of Civil Engineering, Huaqiao University, Fujian 361021, China
| | - Xiaobin Liao
- Institute of Municipal and Environmental Engineering, College of Civil Engineering, Huaqiao University, Fujian 361021, China.
| | - Xinna Lin
- Institute of Municipal and Environmental Engineering, College of Civil Engineering, Huaqiao University, Fujian 361021, China
| | - Jing Yu
- Institute of Municipal and Environmental Engineering, College of Civil Engineering, Huaqiao University, Fujian 361021, China
| | - Huan Qi
- College of Textiles and Appearl, Quanzhou Normal University, Fujian 362002, China
| | - Zhibin Jiang
- Institute of Municipal and Environmental Engineering, College of Civil Engineering, Huaqiao University, Fujian 361021, China
| | - Jing Zou
- Institute of Municipal and Environmental Engineering, College of Civil Engineering, Huaqiao University, Fujian 361021, China
| | - Qingsong Li
- Water Resources and Environmental Institute, Xiamen University of Technology, Xiamen, Fujian 361005, China
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Sulay R, Mathew J, Krishnan A, Thomas DVI. Comprehensive computational study on reaction mechanism of N-Nitroso dimethyl amine formation from substituted hydrazine derivatives during ozonation. Heliyon 2023; 9:e14511. [PMID: 36967895 PMCID: PMC10033754 DOI: 10.1016/j.heliyon.2023.e14511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 03/09/2023] [Accepted: 03/09/2023] [Indexed: 03/18/2023] Open
Abstract
N- Nitrosodimethyl amine, the simplest member of the N-Nitrosamine family, is a carcinogenic and mutagenic agent that has gained considerable research interest owing to its toxic nature. Ozonation of industrially important hydrazines, such as unsymmetrical dimethylhydrazine (UDMH) or monomethylhydrazine (MMH), has been associated with NDMA formation and accumulation in the environment. UDMH/MMH - ozonation also leads to several other transformation products such as acetaldehyde dimethyl hydrazine (ADMH), tetramethyl tetra azene (TMT), diazomethane, methyl diazene, etc, which can be either precursors or competitors for NDMA formation. However, the relevant chemistry detailing the formation of these transformation products from UDMH/MMH -ozone reaction and their subsequent conversion to NDMA is not well understood. In this work, we explored the formation mechanism of ADMH and TMT from UDMH-ozonation and their further oxidation to NDMA using the second-order Moller Plesset perturbation theory employing the 6-311G(d) basis set. We have also investigated how MMH selectively forms methyl diazene and diazomethane under normal conditions and NDMA in the presence of excess ozone. Our calculations indicate that the reactions proceed via an initial H abstraction from the hydrazine -NH2 group, followed by the oxidation of the generated N-radical species. The formation of ADMH from the UDMH-ozone reaction involves an acetaldehyde intermediate, which then reacts with a second UDMH molecule to generate ADMH. The preferable attack of ozone molecule on N=C bond of ADMH generates DMAN intermediate, which subsequently undergoes oxidation to form NDMA. Unlike other transformation products, TMT formation occurs via the dimerization of DMAN. 1Though there exists an N=N bond in the TMT, which are preferable attacking sites for ozone, experimental studies show the lower yields of NDMA formation, which corroborates with the high activation barrier required for the process (42 kcal/mol). Overall, our calculated results agree well with the experimental observations and rate constants. Computational calculations bring new insights into the electronic nature and kinetics of the elementary reactions of this pathway, enabled by computed energies of structures that are not possible to access experimentally.
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Affiliation(s)
- Rehin Sulay
- Department of Chemistry, CMS College (Autonomous), Kottayam, 686001, Kerala, India
| | - Jintumol Mathew
- Department of Chemistry, CMS College (Autonomous), Kottayam, 686001, Kerala, India
| | - Anandhu Krishnan
- Department of Chemistry, CMS College (Autonomous), Kottayam, 686001, Kerala, India
| | - Dr. Vibin Ipe Thomas
- Department of Chemistry, CMS College (Autonomous), Kottayam, 686001, Kerala, India
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Song Y, Feng S, Qin W, Li J, Guan C, Zhou Y, Gao Y, Zhang Z, Jiang J. Formation mechanism and control strategies of N-nitrosodimethylamine (NDMA) formation during ozonation. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 823:153679. [PMID: 35131246 DOI: 10.1016/j.scitotenv.2022.153679] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 01/06/2022] [Accepted: 01/31/2022] [Indexed: 06/14/2023]
Abstract
This review summarizes major findings over the last decade related to N-nitrosodimethylamine (NDMA) formed upon ozonation, which was regarded as highly toxic and carcinogenic disinfection by-products. The reaction kinetics, chemical yields and mechanisms were assessed for the ozonation of potential precursors including dimethylamine (DMA), N,N-dimethylsulfamide, hydrazines, N-containing water and wastewater polymers, dyes containing a dimethylamino function, N-functionalized carbon nanotubes, guanidine, and phenylurea. The effects of bromide on the NDMA formation during ozonation of different types of precursors were also discussed. The mechanism for NDMA formation during ozonation of DMA was re-summarized and new perspectives were proposed to assess on this mechanism. Effect of hydroxyl radicals (•OH) on NDMA formation during ozonation was also discussed due to the noticeable oxidation of NDMA by •OH. Surrogate parameters including nitrate formation and UV254 after ozonation may be useful parameters to estimate NDMA formation for practical application. The strategies for NDMA formation control were proposed through improving the ozonation process such as ozone/hydrogen peroxide, ozone/peroxymonosulfate and catalytic ozonation process based on membrane pores aeration (MEMBRO3X).
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Affiliation(s)
- Yang Song
- School of Civil and Transportation Engineering, Guangdong University of Technology, Guangzhou 510006, Guangdong, China
| | - Sha Feng
- School of Civil and Transportation Engineering, Guangdong University of Technology, Guangzhou 510006, Guangdong, China
| | - Wen Qin
- School of Civil and Transportation Engineering, Guangdong University of Technology, Guangzhou 510006, Guangdong, China
| | - Juan Li
- Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China; Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China
| | - Chaoting Guan
- Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China; Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China
| | - Yang Zhou
- Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China; Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China
| | - Yuan Gao
- Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China; Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China
| | - Zhong Zhang
- Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China; Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China
| | - Jin Jiang
- Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China; Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China.
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Gao M, Jiang Z, Liao X, Bai X, Qi H, Zou J, Cao W. Validation of the promotion mechanism between bromide and UDMH to form NDMA during ozonation. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 792:148316. [PMID: 34147807 DOI: 10.1016/j.scitotenv.2021.148316] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 06/02/2021] [Accepted: 06/04/2021] [Indexed: 06/12/2023]
Abstract
Unsymmetrical dimethylhydrazine (UDMH) is found to generate substantial carcinogenic nitroso-dimethylamine (NDMA) during ozonation, moreover, its formation is promoted by ubiquitous bromide ions (Br-) in water matrixes, but the mechanism is still unclear. In this study, effects of Br- on NDMA formation during ozonation of UDMH were studied, meanwhile, its promotion pathways were also determined. The results demonstrated that Br- promoted NDMA formation from UDMH during ozonation, the formation rate constant with Br- is over 7 times of that without Br-. NDMA amount raised from 142.5 to 327.5 μg/L when Br- dosages increased from 0 to 100 μM. No matter with or without Br-, the augment of O3 dosages facilitated NDMA formation; the maximum value was achieved at pH 8. NDMA decreased dramatically from 173.8 to 123.5 μg/L with HCO3- raising from 0 to 160 μM, while increasing remarkably to 222.5 μg/L with SO42- dosing. In addition, NOM inhibited NDMA formation from UDMH during ozonation. The mass spectrum of LC-MS/MS verified that the generation of Br-UDMH was main cause for promoting NDMA formation. Moreover, hypobromous acid (HBrO) was confirmed to be responsible for Br-UDMH formation. In addition, the position that oxidants and Br- attacked was demonstrated based on Gaussian calculation. The results of this study could provide theoretical basis for the application of ozonation in bromine-containing water matrixes.
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Affiliation(s)
- Menglan Gao
- Institute of Municipal and Environmental Engineering, College of Civil Engineering, Huaqiao University, Fujian 361021, China
| | - Zhibin Jiang
- Institute of Municipal and Environmental Engineering, College of Civil Engineering, Huaqiao University, Fujian 361021, China
| | - Xiaobin Liao
- Institute of Municipal and Environmental Engineering, College of Civil Engineering, Huaqiao University, Fujian 361021, China.
| | - Xingji Bai
- Institute of Municipal and Environmental Engineering, College of Civil Engineering, Huaqiao University, Fujian 361021, China
| | - Huan Qi
- College of Textiles and Appearl, Quanzhou Normal University, Fujian 362002, China.
| | - Jing Zou
- Institute of Municipal and Environmental Engineering, College of Civil Engineering, Huaqiao University, Fujian 361021, China
| | - Wei Cao
- Institute of Municipal and Environmental Engineering, College of Civil Engineering, Huaqiao University, Fujian 361021, China
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5
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Huang Y, Jia Y, Hou R, Huang Z, Shen K, Jin G, Hou L. Photocatalytic degradation of unsymmetrical dimethylhydrazine on TiO 2/SBA-15 under 185/254 nm vacuum-ultraviolet. RSC Adv 2021; 11:24172-24182. [PMID: 35479060 PMCID: PMC9036703 DOI: 10.1039/d1ra03599a] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2021] [Accepted: 07/01/2021] [Indexed: 11/21/2022] Open
Abstract
In this work, TiO2/SBA-15 was synthesized via an in situ hydrothermal method and was used for vacuum-ultraviolet (VUV) photocatalytic degradation of unsymmetrical dimethylhydrazine (UDMH) for the first time. Compared with photocatalysis under UV irradiation, VUV photocatalysis exhibited higher photodegradation efficiency due to the synergetic effect of direct photolysis, indirect photooxidation and photocatalytic oxidation. The synthesized TiO2/SBA-15 catalysts exhibited ordered mesoporous structure and anatase phase TiO2. Titanium content, initial pH and substrate concentration impacted degradation efficiency of UDMH in the VUV photocatalysis process. Among the prepared catalysts, TiO2/SBA-15 with the molar ratio of Ti/Si = 1 : 3 (TS-2) showed the best photocatalytic activity under VUV light, with the rate constant of 0.02511 min−1, which is 1.91 times that with VUV/P25. The superior photocatalytic activity of TS-2 is mainly related to the good balance between the specific surface area and TiO2 contents. The photodegradation efficiency decreases with the increase in the initial UDMH concentration and the maximum degradation rate was obtained at pH 9.0. In the VUV/TS-2 process, ˙OH played a more important role in the degradation of UDMH than ˙O2− and the degradation pathways contained bond breaking, amidation, isomerisation and oxidation reactions. The TS-2 also showed good reusability with the rate constant maintained at above 90% after five cycles and exhibited satisfactory degradation efficiency in tap water. Mesoporous TiO2/SBA-15 under VUV irradiation: enhanced photocatalytic oxidation for UDMH degradation.![]()
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Affiliation(s)
| | - Ying Jia
- Xi'an High Technology Institute Xi'an 710025 China
| | - Ruomeng Hou
- Xi'an High Technology Institute Xi'an 710025 China
| | | | - Keke Shen
- Xi'an High Technology Institute Xi'an 710025 China
| | - Guofeng Jin
- Xi'an High Technology Institute Xi'an 710025 China
| | - Li'an Hou
- Xi'an High Technology Institute Xi'an 710025 China
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Shen Q, Liu YD, Zhong R. Degradation mechanisms of simple aliphatic amines under ozonation: a DFT study. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2021; 23:480-490. [PMID: 33595042 DOI: 10.1039/d0em00476f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Aliphatic amines as common constituents of dissolved organic nitrogen (DON) exhibit high reactivity during ozonation; however, our understanding of their degradation mechanisms is very limited. In this study, methylamine (MA) and ethylamine (EA), as well as their secondary and tertiary amines (DMA, DEA, TMA and TEA) were chosen as aliphatic amine models and their degradation mechanisms during ozonation were investigated by using the DFT method. The oxygen-transfer reaction occurs initially and rapidly in the ozonation of all the above amines with a ΔG≠ value of 8-10 kcal mol-1 in great agreement with the experimental rate constant of 104 to 107 M-1 s-1. Moreover, N-oxide as the main degradation product for tertiary amines directly forms after oxygen-transfer, while nitroalkanes as main products for secondary and primary amines are yielded after a series of reactions mediated by hydroxylamine and nitrosoalkane with a ΔG≠ value of 10-13 kcal mol-1. Regarding the minor N-dealkylated products for all amines, alkylamino alcohol is an important intermediate possibly generated via a radical reaction pathway with a ΔG≠ value of 21-34 kcal mol-1. Additionally, comparison of the reactivity of aliphatic amines, hydroxylamines and alkylamino alcohols with ozone was made and elucidated in this study. The results are expected to expand our understanding of the degradation mechanisms for nitrogenous compounds during ozonation.
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Affiliation(s)
- Qunfang Shen
- Beijing Key Laboratory of Environmental and Viral Oncology, College of Life Science & Bioengineering, Beijing University of Technology, Beijing 100124, China.
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Seid MG, Chung J, Choe J, Cho K, Hong SW. Role of ranitidine in N-nitrosodimethylamine formation during chloramination of competing micropollutants. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 756:144156. [PMID: 33302063 DOI: 10.1016/j.scitotenv.2020.144156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 11/24/2020] [Accepted: 11/26/2020] [Indexed: 06/12/2023]
Abstract
Ranitidine (RNT) is a widely known precursor of N-nitrosodimethylamine (NDMA) as evinced by the self-catalytic formation of NDMA during chloramination. In the present study, the NDMA formation potentials (NDMA-FP) of 26 micropollutants were assessed, particularly when mixed with RNT. 11 compounds were identified as individual precursors, including trimebutine and cimetidine, which exhibited substantial NDMA-FP, with up to 10% molar yield. In addition, nitrosamines, other than NDMA, namely N-nitrosodiethylamine and N-nitrosomethylamine, were observed from diethylamine-containing precursors, such as metoclopramide. In a 1:1 mixture of RNT and a competitor, the change in NDMA-FP was mostly comparable (within 20% deviation), while antagonistic interactions were observed for competitors, such as diethylhydroxylamine. The scattered overall NDMA-FP should be considered as a product of competition among the precursors for core substrates and intermediates for NDMA formation. The co-existence of either trimebutine or metoclopramide with RNT led to an exceptionally synergetic NDMA generation. Degradation kinetics and chlorination/nitrosation experiments combined with mass spectroscopy analyses indicated that RNT would accelerate both the initial chlorination and nitrosation of trimebutine and metoclopramide, leading to N-nitroso complexes, which have well-understood NDMA formation pathways, i.e., amination with subsequent aminyl radical generation. This work demonstrates a wide array of precursors with NDMA-FP, suggesting that nitrosamine formation is potentially underestimated in field environments.
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Affiliation(s)
- Mingizem Gashaw Seid
- Division of Energy and Environment Technology, KIST-School, University of Science and Technology, Seoul 02792, Republic of Korea; Water Cycle Research Center, Korea Institute of Science and Technology, Seoul 136-791, Republic of Korea
| | - Jaeshik Chung
- Water Cycle Research Center, Korea Institute of Science and Technology, Seoul 136-791, Republic of Korea
| | - Jaewan Choe
- Department of Civil Engineering, Gwangju University, Gwangju 61743, Republic of Korea
| | - Kangwoo Cho
- Division of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea; Institute for Convergence Research and Education in Advanced Technology (I-CREATE), Yonsei University, Incheon 406-840, Republic of Korea.
| | - Seok Won Hong
- Division of Energy and Environment Technology, KIST-School, University of Science and Technology, Seoul 02792, Republic of Korea; Water Cycle Research Center, Korea Institute of Science and Technology, Seoul 136-791, Republic of Korea.
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Wang W, Yang P, Guo Y, Ji H, Liang F. Phenylurea herbicide degradation and N-nitrosodimethylamine formation under various oxidation conditions: Relationships and transformation pathways. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 269:116122. [PMID: 33248834 DOI: 10.1016/j.envpol.2020.116122] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Revised: 11/11/2020] [Accepted: 11/16/2020] [Indexed: 06/12/2023]
Abstract
Four phenylurea herbicides (PUHs) were assessed for degradation and transformation into N-nitrosodimethylamine (NDMA) under three oxidation conditions (chlorine (Cl2), chlorine dioxide (ClO2), and ozone (O3)) from an aqueous solution. Removal ratios correlated with the numbers of halogen elements contained in PUHs (isoproturon (0) > chlorotoluron (1 Cl) > diuron (2 Cl) > fluometuron (3 F)), and the degradation efficiencies of oxidants from fastest to slowest were: O3, ClO2, and Cl2. NDMA can be generated directly from the ozonation of PUHs. Further, compared with chloramination alone, ozonation prominently promoted NDMA formation potential (NDMA-FP) during post-chloramination, and NDMA-FPs increased approximately 23-68 times than those during ozonation only at 2.5 mg/L O3 over 10 min; molar yields of NDMA from highest to lowest were 11.1% (isoproturon), 1.17% (chlorotoluron), 1.0% (diuron), and 0.73% (fluometuron). The PUH degradation kinetics data during ozonation agreed with the pseudo-first-order model. The rate constant kobs were 0.31 × 10-3-19.8 × 10-3 s-1. The kobs and removal ratios of PUHs during ozonation partially scaled with the mass, LogKow, and Henry's constants of PUHs. Comparisons of measured NDMA-FPs with calculated NDMA-FPs from residual PUH after oxidation showed that the intermediates produced during ozonation facilitated NDMA-FPs; this contribution was also observed for chlorotoluron and isoproturon during ClO2 oxidation. Examination of reaction mechanisms revealed that tertiary amine ozonation, N-dealkylation, hydroxylation, the cleavage of N-C bonds, ammonification, and nitrification occurred during the ozonation of PUHs, and the dimethylamine (DMA) functional groups could be decomposed directly and transformed into NDMA via the formation of the intermediate unsymmetrical dimethylhydrazine. NDMA is also formed from the reaction between DMA and phenylamino-compounds. Clarifying primary degradation products of PUHs and transformation pathways of NDMA during oxidation processes is useful to optimize treatment processes for water supplies.
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Affiliation(s)
- Wanfeng Wang
- Key Laboratory for Yellow River and Huai River Water Environmental and Pollution Control, Ministry of Education, Henan Key Laboratory for Environmental Pollution Control, School of Environment, Henan Normal University, Xinxiang, 453007, China.
| | - Panqing Yang
- Key Laboratory for Yellow River and Huai River Water Environmental and Pollution Control, Ministry of Education, Henan Key Laboratory for Environmental Pollution Control, School of Environment, Henan Normal University, Xinxiang, 453007, China
| | - Yanling Guo
- College of Resource and Environment, Henan Institute of Science and Technology, Xinxiang, 453003, China
| | - Haoran Ji
- Key Laboratory for Yellow River and Huai River Water Environmental and Pollution Control, Ministry of Education, Henan Key Laboratory for Environmental Pollution Control, School of Environment, Henan Normal University, Xinxiang, 453007, China
| | - Fang Liang
- Key Laboratory for Yellow River and Huai River Water Environmental and Pollution Control, Ministry of Education, Henan Key Laboratory for Environmental Pollution Control, School of Environment, Henan Normal University, Xinxiang, 453007, China
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Huang D, Liu X, Wang X, Zuo C, Xie Z, Gao X. The competitive formation mechanism of N-nitrosodimethylamine and formaldehyde dimethylhydrazone from 1,1-dimethylhydrazine during ozonation in air: A combined theoretical and experimental study. Chem Phys 2019. [DOI: 10.1016/j.chemphys.2019.01.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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10
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Han C, Zhao H, Dong M, Liu YD, Zhong R. The formation mechanism of chloropicrin from methylamine during chlorination: a DFT study. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2019; 21:761-770. [PMID: 30916670 DOI: 10.1039/c8em00581h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Chloropicrin (TCNM) as one of the most frequently detected nitrogenous disinfection byproducts (N-DBPs) has attracted extensive attention due to its high toxicity. Although much research work on TCNM has been done, its formation mechanism during chlorination has not been known clearly yet. In this study, TCNM formation mechanisms from methylamine (MA) during chlorination, including N-chlorination of MA by hypochlorous acid to generate dichloromethylamine (DCMA) first and then oxidation of DCMA to form nitromethane (NM) and chloronitromethane (CNM), and finally TCNM formation from C-chlorination of NM and CNM, were investigated by using the DFT method. The calculated results show that in N-chlorination of MA, 2-3 water molecules involved in the reaction facilitate Cl+ and proton transfer with the activation free energies (ΔG≠) for the first and second chlorination in the range of 4-7 and 14-17 kcal mol-1, respectively, which are in good agreement with the experimental results. Formation of NM and CNM proceeds through a series of elimination, addition, and oxidation reactions with ΔG≠ of the rate-limiting steps being around 34-37 kcal mol-1, and the subsequent C-chlorination of methyl in NM and CNM by hypochlorous acid is a rapid process with ΔG≠ below 7 kcal mol-1. This infers that the TCNM formation mechanism from DCMA is more likely to undergo first N-oxidation and then C-chlorination. These results can explain the experimental findings that the molar yield of TCNM from MA during chlorination is low (<0.1%) whereas that from NM is rather high (∼45%). This work will be helpful to elucidate formation mechanisms of all the halonitromethanes during chlorination.
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Affiliation(s)
- Chunxiu Han
- Beijing Key Laboratory of Environmental and Viral Oncology, College of Life Science & Bioengineering, Beijing University of Technology, Beijing 100124, China.
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11
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Dong M, Liu YD, Zhong R. NDMA formation mechanisms from typical hydrazines and hydrazones during ozonation: A computational study. JOURNAL OF HAZARDOUS MATERIALS 2019; 366:370-377. [PMID: 30544038 DOI: 10.1016/j.jhazmat.2018.12.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Revised: 12/01/2018] [Accepted: 12/03/2018] [Indexed: 06/09/2023]
Abstract
N-nitrosodimethylamine (NDMA) as the most frequently detected disinfection by-product has aroused widespread concern due to its unusually high carcinogenicity, however, there is still limited understanding of its formation mechanisms. In this study, the formation mechanisms of NDMA from some typical hydrazines and hydrazones with high NDMA conversion yields (60%∼90%) during ozonation, i.e., unsymmetrical dimethylhydrazine (UDMH), 1-formyl-2,2-dimethylhydrazine (FDMH), formaldehyde dimethylhydrazone (FDH) and acetone dimethylhydrazone (ADMH), were investigated by using DFT method with the M05 functional. A new NDMA formation mechanism from hydrazines during ozonation was proposed, in which the initial step is hydrogen abstraction rather than previously reported oxygen addition. For hydrazones, the C atom of the -N = C moiety in hydrazones is preferred to be attacked by ozone to generate N,N-dimethylaminonitrene (DMAN), which is an important intermediate in NDMA formation during ozonation. Moreover, the reactivity order of the following H atoms in hydrogen/hydride ion abstraction (HA) by ozone is -NH2 > -N(CH3)2 > -CO-NH ∼ =C(CH3)2 > =CH-. Additionally, formation pathways of some experimentally detected compounds, i.e., HOOOH, HOOH and HCOH, in the ozonation of hydrazine were elucidated in this study. The results are expected to expand our understanding of NDMA formation mechanisms and ozone reaction characteristics.
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Affiliation(s)
- Meng Dong
- Beijing Key Laboratory of Environmental and Viral Oncology, College of Life Science & Bioengineering, Beijing University of Technology, Beijing, 100124, China
| | - Yong Dong Liu
- Beijing Key Laboratory of Environmental and Viral Oncology, College of Life Science & Bioengineering, Beijing University of Technology, Beijing, 100124, China.
| | - Rugang Zhong
- Beijing Key Laboratory of Environmental and Viral Oncology, College of Life Science & Bioengineering, Beijing University of Technology, Beijing, 100124, China
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12
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Products and Mechanistic Investigations on the Reactions of Hydrazines with Ozone in Gas-Phase. Symmetry (Basel) 2018. [DOI: 10.3390/sym10090394] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The toxic transformation products of hydrazines are of great concern. These products’ properties combined with their formation mechanisms are needed to assess their potential environmental and human impacts. In this study, the gas-phase reaction of hydrazine (N2H4), monomethyldrazine (MMH) and unsymmetrical dimethyhydrazine (UDMH) with O3 have been studied at varying reactant ratios, both in the presence and absence of a radical trap. Gas chromatography-mass spectroscopy (GC-MS) has been implied to follow reactant consumption and product formation. Apart from the reported products detected by Fourier transform infrared spectroscopy (FT-IR), the newly found compounds (hydrazones, formamides, dimethylamine, 1,1,4,4-tetramethyl-1,2-tetrazene,dimethylamino-acetonitrile, N2, H2O, et al.) are identified by GC-MS. The relative yields of the organic products vary considerably at different O3/MMH or UDMH ratios. UDMH and MMH are confirmed as high potential precursors of N-nitrosodimethylamine (NDMA). The presence of hydroxyl radicals (HO·) hinders NDMA formation in MMH-O3 system. Meanwhile, it increases NDMA formation in UDMH-O3 system. The suggested reaction mechanisms which account for the observed products are discussed.
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Deng Y, Bonilla M, Ren H, Zhang Y. Health risk assessment of reclaimed wastewater: A case study of a conventional water reclamation plant in Nanjing, China. ENVIRONMENT INTERNATIONAL 2018; 112:235-242. [PMID: 29291449 DOI: 10.1016/j.envint.2017.12.034] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 12/22/2017] [Accepted: 12/22/2017] [Indexed: 06/07/2023]
Abstract
Contaminated reclaimed wastewater has the potential to induce adverse effects on the health of wastewater workers and residents. However, few studies have focused on these health risks. In this study, we assessed the health risk of samples collected from different treatment processing units used in a typical water reclamation plant in Nanjing, China. Chemical analysis revealed that 40 semi-volatile organic compounds (SVOCs) and 6 N-nitrosamines (NAs) persisted after wastewater treatment. A health risk assessment revealed that the SVOCs in effluents pose negligible non-carcinogenic risk to wastewater workers and local residents as both the hazard quotient (HQ) and hazard index (HI) were all below 1.00. However, polycyclic aromatic hydrocarbons (PAHs), phthalate esters (PAEs) and NAs may present a carcinogenic risk, since their risk index via dermal exposure exceeded the safety limit (1.00×106), indicating that conventional treatment processes cannot effectively reduce the health risk in reclaimed wastewater. These results strongly suggest the need for the introduction of advanced treatment technologies capable of effectively removing SVOCs and NAs in water reclamation plants.
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Affiliation(s)
- Yongfeng Deng
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu 210023, China
| | - Melvin Bonilla
- Program in Molecular and Integrative Physiological Sciences, Department of Environmental Health, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA
| | - Hongqiang Ren
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu 210023, China
| | - Yan Zhang
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu 210023, China.
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