Study of the plasma–liquid interaction for an argon nonthermal microwave plasma jet from the analysis of benzene degradation

Abstract

The interaction of an argon microwave plasma jet with a benzene layer on water has been analyzed under different conditions (power, gas flow, plasma-sample distance, and treatment time) in this study. Main products formed upon treatment are phenol, catechol, and nitrobenzene, which shows that this jet is a source of radicals •OH and •NO2, inducing benzene oxidation and nitration. Excited argon species in the plasma have been proven to play an outstanding role in degradation processes, which mostly occur at the gas phase. Results are compared with those from the direct interaction of the plasma jet with water. For this purpose, aqueous solutions of 3-coumarin carboxylic acid are treated and the hydroxylation of this compound is studied. The effect of the benzene layer preventing water evaporation is demonstrated.