Estimation of Hydroxyl Radicals Produced by Pulsed Discharge Inside Bubble in Water Using Indigo Carmine as Chemical Probe

Amount of hydroxyl radicals produced by pulsed discharge inside bubble in water is estimated with the decomposition of indigo carmine as a chemical probe. Argon gas (99.99 vol.% purity) is injected into the water through a vertically positioned glass tube, in which high-voltage wire electrode is placed to generate plasmas at low applied voltage. Amount of the indigo carmine decomposition increases with increasing indigo carmine concentration and held a constant value at 1.5×10 ^-6 mol when indigo carmine concentration is higher than 2.5 mM. The amount of hydroxyl radicals is estimated as 1.3 × 10 ^-6 mol by measuring the hydrogen peroxide production in the potassium solution, which corresponds to the amount of hydroxyl radicals obtained from indigo carmine decomposition. The energy yield of dissolved hydroxyl radical, which contributes to react with the solutes in the solutions, is estimated to be 4 ~ 5 × 10 ^-9 mol/J.