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Atmospheric Oxidation of Piperazine Initiated by ·cl: Unexpected High Nitrosamine Yield

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  • Fangfang Ma, Dalian University of Technology
  • ,
  • Zhezheng Ding, Dalian University of Technology
  • ,
  • Jonas Elm
  • Hong Bin Xie, Dalian University of Technology
  • ,
  • Qi Yu, Dalian University of Technology
  • ,
  • Cong Liu, Key Laboratory of Industrial Ecology and Environmental Engineering, Dalian University of Technology
  • ,
  • Chao Li, Northeast Normal University
  • ,
  • Zhiqiang Fu, Dalian University of Technology
  • ,
  • Lili Zhang, Dalian University of Technology
  • ,
  • Jingwen Chen, Dalian University of Technology

Chlorine radicals (·Cl) initiated amine oxidation plays an important role for the formation of carcinogenic nitrosamine in the atmosphere. Piperazine (PZ) is considered as a potential atmospheric pollutant since it is an alternative solvent to monoethanolamine (MEA), a benchmark solvent in a leading CO2 capture technology. Here, we employed quantum chemical methods and kinetics modeling to investigate ·Cl-initiated atmospheric oxidation of PZ, particularly concerning the potential of PZ to form nitrosamine compared to MEA. Results showed that the ·Cl-initiated PZ reaction exclusively leads to N-center radicals (PZ-N) that mainly react with NO to produce nitrosamine in their further reaction with O2/NO. Together with the PZ + ·OH reaction, the PZ-N yield from PZ oxidation is still lower than that of the corresponding MEA reactions. However, the nitrosamine yield of PZ is higher than the reported value for MEA when [NO] is <5 ppb, a concentration commonly encountered in a polluted urban atmosphere. The unexpected high nitrosamine yield from PZ compared to MEA results from a more favorable reaction of N-center radicals with NO compared to O2. These findings show that the yield of N-center radicals cannot directly be used as a metric for the yield of the corresponding carcinogenic nitrosamine.

Original languageEnglish
JournalEnvironmental Science and Technology
Pages (from-to)9801-9809
Number of pages9
Publication statusPublished - 4 Sep 2018

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