Investigation of RONS Production and Complex Molecules Degradation Induced by an APPJ Generated by Two Different Sources

The interaction of a helium/0.2% oxygen plasma jet with a liquid target is investigated for two sources having different geometries. One of these sources is symmetric representing the conventional source in the cold plasma jet community with electrodes of the same size. The other source is asymmetric, as it has a larger diameter in the upper part. The importance of the plasma source geometry on the quantity of reactive oxygen and nitrogen species (RONSs) in the liquid phase and on methylene blue degradation is investigated. Intensified CCD camera measurements show the spatio-temporal distribution of several excited species in the gas phase responsible for the RONS formation in the gas phase. Nitrites concentration reaches its peak after 10 min, before converting into nitrates at acidic pH. The concentrations of hydrogen peroxide and nitrate both increase with treatment time. The plasma created with the asymmetric source provides a higher RONS concentration into the liquid phase in all the conditions used in this paper. Methylene blue, considered as a complex water contaminant, is degraded faster when the asymmetric source was used.