Electrical discharges in bubbled water

Summary form only given. Electrical discharges in gas bubbles in water are investigated by applying microsecond long rectangular pulses of 6-20 kV to needle-to-plane electrodes submerged in water. Ar or O₂ bubbles; 1-5 mm in diameter, are introduced through the Pt needle that serves as the negative electrode. A bubble remains on the needle through numerous discharge processes. The voltage across the electrodes and the current to the ground are measured. Electrical measurements suggest that a corona-type atmospheric-pressure discharge is ignited in the gas bubble (composed of Ar or O₂ gas and water vapor) without the electrical breakdown of the entire water filled electrode gap. The discharge characteristics are investigated as a function of the applied voltage, the distance between the electrodes, the bubbled gas (Ar or O₂), the size of the gas bubble, and the pH and conductivity of the water. Optical and electrical measurements are used to explore the properties of the discharge. The size of the bubble as compared to the electrode distance affects the electrical characteristics of the discharge. The liquid water-metal interface and the liquid water-gas interface both play an important role in the initiation and the development of the electrical discharge in the gas bubbles. Evidence from environmental application studies supports the strong dependence of the discharge properties, active species production, and cleaning efficiency on all the parameters mentioned above including the applied voltage, the electrode distance, bubble size, and the initial characteristics of the solution