No abstract

We have investigated water purifications by a discharge propagating in a bubble in water containing two organic compounds, phenol and sodium formate. In order to evaluate decomposition rate of phenol and sodium formate, the mixed solution of them were employed. Oxygen gas was injected into the water through a vertically positioned glass tube, in which the high-voltage wire electrode was placed to generate plasmas at low applied voltage. The phenol in the mixed solution was easier to decompose than the phenol in the single ingredient solution. The pH value of the solution after the discharge treatment increased with increasing initial concentration of the sodium formate, which enhanced the decomposition of phenol in mixed solution. The amount of decomposed sodium formate decreased with increasing initial concentration of the phenol.

Water purification by discharge inside bubble in water containing organic dye has been investigated. The discharge reactor consists of a glass tube and a tungsten wire inserted into the glass tube, which is immersed in the water. Room air is injected into the glass tube to generate bubbles in the water. The high voltage pulses are generated by a magnetic pulse compression circuit and a pulsed power generator with inductive-energy storage using semiconductor opening switch. The pulse width is adjusted in the range from 61 to 570 ns. The high voltage is applied to the tungsten wire to generate streamer discharges, which propagate into the bubble from the tip of wire. Indigo carmine is employed as a specimen to evaluate decolorization efficiency. Potassium nitrate is used to adjust the solution conductivity. Decolorization rate increases with increasing conductivity of the solution and the applied voltage. The solution of 1,830 S/cm in conductivity is successfully decolorized. Energy efficiency for decolorization increases with decreasing ohmic loss by decreasing the applied voltage and the pulse width.