Optical study of active species produced by a pulsed streamer corona discharge in water

Various active species (· OH, · H, · O, 1O2, · HO2, O2−, etc.) can be formed by a pulsed streamer corona discharge in water and these active species may play an important role in the killing of bacteria and degrading of organic compounds. Therefore, it is necessary to identify the active species produced by the pulsed discharge and to investigate the effects of the discharge parameters on species production. In the present investigation, analysis of optical emission spectra was used for the detection of O, H and OH radicals, and the effects of the physicochemical parameters and discharge conditions on radical formation were studied. The influence of gas bubbling was also studied and compared with the case without bubbling. It was found that radical formation due to the streamer corona discharge was very dependent on the discharge conditions (applied voltage polarity and peak value, discharge electrode tip curvature radius) and on the physicochemical parameters (pH, conductivity of the water and additives). The radical density increased greatly when gas was bubbled in the discharge region. However, some O radicals were detected using both voltage polarities even when oxygen or inert gas was not bubbled in the discharge region.