Ultraviolet radiation from the pulsed corona discharge in water

Abstract

Quantitative analysis of ultraviolet radiation from the pulsed corona discharge in water with needle-plate electrode geometry (∼1-3 J pulse −1 ) was performed using the potassium ferrioxalate actinometry. Photon flux J 190-280 and radiant energy Q 190-280 of the UV light emitted from the discharge at spectral region 190-280 nm was determined in dependence on the applied voltage (17-29 kV, positive polarity) and the solution conductivity (100-500 µS cm −1 ). The intensity of the UV radiation strongly increased with increasing water conductivity and applied voltage. Depending on the applied voltage the determined photon flux varied by more than two orders of magnitude within the range of solution conductivities 100-500 µS cm −1 . It was found that photon flux from the discharge may be directly related to the discharge pulse mean power P p as J 190-280 = 44.33 P 2.11 p (quanta pulse −1 ). A significant role of UV radiation in the production of hydrogen peroxide and bacterial inactivation by the corona discharge in water has been identified. As the solution conductivity increased the yield of H 2 O 2 produced by the discharge decreased due to increasing photolysis of H 2 O 2 accounting for up to 14% of the total decomposition rate of H 2 O 2 . As regards bactericidal effects, it was estimated that the UV radiation contributes about 30% to the overall inactivation of Escherichia coli.

Chemistry of the Positive and Negative Electrical Discharges Formed in Liquid Water and Above a Gas–Liquid Surface

“…If the UV intensity is an indirect measure of the temperature inside plasma then we must assume that the temperature inside the negative polarity plasma streamers is much lower than that of the positive polarity since negative streamers emit significantly smaller amounts of UV light [6,7]. As a consequence, the chemistry inside plasma channels is also different for the negative and positive electrode polarity, which is seen from the emission spectroscopy measurements.…”

“…This study uses the measurement of hydrogen peroxide that is produced by the positive and negative polarity electrical discharge as an indirect way to get an insight into the processes that take place at the plasma gas-liquid interface. Currently, there are only a few published studies that report hydrogen peroxide production in the positive electrical and negative discharge in water and above the water's surface [5][6][7]. Lukes [6], for example, measured hydrogen peroxide formation at conductivities up to 500 lS/cm and concluded that the UV induced decomposition of hydrogen peroxide is the process that dominates over all other effects, such as electrolyte concentration at such high conductivities.…”

“…Lukes [6], for example, measured hydrogen peroxide formation at conductivities up to 500 lS/cm and concluded that the UV induced decomposition of hydrogen peroxide is the process that dominates over all other effects, such as electrolyte concentration at such high conductivities. In another study, Lukes [7] compared the hydrogen peroxide production for negative and positive high-voltage electrode polarity as a function of solution conductivity. He reported that the H 2 O 2 production in negative polarity was less than half that of the positive polarity, but no explanation for the observed result was given.…”

“…Again, no explanation was given to explain this behavior. Although studies done in [7] and [8] report hydrogen peroxide formation in negative polarity discharge, no attempt to explain these results was done. The work presented in this study provides an insight into processes taking place in the high temperature plasma zone, as well as on the plasma gasliquid interface.…”

Destructive effect of atmospheric pressure pulsed corona discharge plasma in air on biofilms of opportunistic bacteria

“…Mechanisms of bactericidal effect can be greatly different versus the properties of a treated medium and the supply parameters of an electric discharge setup. Main agents causing inactivation of microorganisms at the electric discharge in gas or water are an electric current [12,13], chemical reactive species including bactericides appearing as a result of the electric current passing through a medium containing oxygen and/or nitrogen [14] and ultraviolet radiation accompanying excitation and ionization acts [15].…”