Enhanced decomposition of caffeine by water plasma combined with mist generator: Effect of operational parameter and decomposition pathway

Soon Ho Kim, Manabu Tanaka, Myeong Hoon Lee, Takayuki Watanabe

Research output: Contribution to journalArticlepeer-review

Abstract

Water plasma coupled with mist generator was introduced to perform the decomposition of caffeine (CAF) wastewater. The mist-shaped water molecule was directly used for plasma-forming gas with no additional gas. The influence of arc current on the decomposition of CAF was elucidated in detail. With the increase of input power from 0.8 to 1.1 kW according to arc current, the removal efficiency of total organic carbon (TOC) and CAF increased, reaching 91.1 and 99.8% at 9.5 A, respectively. H2, CO, CO2, and N2 were major effluent gaseous species, of which the H2 generation was more than 40% for all conditions. The concentration of nitrate in the effluent liquids was the highest at 9.5 A due to a higher oxidation environment. The H, O, and OH as reactive species formed via the dissociation of water molecules were demonstrated, and the plasma temperatures were at over 5000 K. The detailed decomposition pathway was deduced based on eleven intermediate products identified in this process. Electron impact and hydroxyl radical were found to take leading roles in the decomposition of CAF.

Original languageEnglish
Article number136056
JournalChemosphere
Volume307
DOIs
Publication statusPublished - Nov 2022

All Science Journal Classification (ASJC) codes

  • Environmental Engineering
  • Environmental Chemistry
  • Chemistry(all)
  • Pollution
  • Public Health, Environmental and Occupational Health
  • Health, Toxicology and Mutagenesis

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