HCOOaq degradation in droplets by OHaq in an atmospheric pressure glow discharge

Mackenzie Meyer, Gaurav Nayak, Peter J. Bruggeman, Mark J. Kushner

Research output: Contribution to journalArticlepeer-review


Plasmas in contact with liquids can degrade organic molecules in a solution, as reactive oxygen and nitrogen species produced in the plasma solvate into the liquid. Immersing small droplets (tens of microns in diameter) in the plasma can more rapidly activate the liquid compared to treating a large volume of liquid with a smaller surface-to-volume ratio. The interactions between a radio frequency glow discharge sustained in He/H2O and a water droplet containing formate (HCOOaq) immersed in and flowing through the plasma were modeled using a zero-dimensional global plasma chemistry model to investigate these activation processes. HCOO aq interacts with OHaq, which is produced from the solvation of OH from the gas phase. The resulting HCOO aq concentrations were benchmarked with previously reported experimental measurements. The diameter of the droplet, initial HCOO aq concentration, and gas flow rate affect only the HCOO aq concentration and OHaq density, leaving the OH density in the gas phase unaffected. Power deposition and gas mixture (e.g. percentage of H2O) change both the gas and liquid phase chemistry. A general trend was observed: during the first portion of droplet exposure to the plasma, OHaq primarily consumes HCOO aq. However, O2aq, a byproduct of HCOO aq consumption, consumes OHaq once O2aq reaches a critically large density. Using HCOO aq as a surrogate for OHaq-sensitive contaminants, combinations of residence time, droplet diameter, water vapor density, and power will determine the optimum remediation strategy.

Original languageEnglish (US)
Article number285202
JournalJournal of Physics D: Applied Physics
Issue number28
StatePublished - Jul 13 2023

Bibliographical note

Funding Information:
This work was supported by the National Science Foundation (PHY-1902878, PHY 1903151, and CBET-2032604). This material was also based upon work supported by the US Department of Energy, Office of Science, Office of Fusion Energy Sciences under Award No. DE-SC0020232 and the Army Research Office accomplished under Grant No. W911NF-20-1-0105.

Publisher Copyright:
© 2023 The Author(s). Published by IOP Publishing Ltd.


  • atmospheric pressure plasma
  • droplet activation
  • formate degradation
  • modeling


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