Integrated-micro-solution plasma in porous dielectric electrodes and its application to water treatment

Organic contamination in water should be removed from the view point of environmental protection. Many plasma techniques have been applied for this issue. Atmospheric pressure plasma in water or on water surface is one of the candidates which can handle this issue. In our previous work, we have successfully obtained glow discharges in water (solution plasma). However, our solution plasma is ignited between two stylus electrodes, and actual treatment area is very small. In this work, we have obtained integrated microplasmas between a dielectric plate and a porous dielectric electrode which contain the water to be treated. The discharge area is 4 cm x 3 cm at this moment, but this can be scaled up. The applied voltage is 5 kV with pulsed waveform (frequency 15 kHz, pulse width 2 us). We have performed optical emission spectroscopy on this discharge, and confirmed that emission of OH radicals is available. We have applied this technique for decomposing organic materials in water. Methyleneblue has been used as the organic material in this work, and its decoloration rate has been investigated through the transmittance measurements on the solution. The methylene blue concentration has been reduced down to 50{\%} of the initial value for 26 minutes, which is comparable or faster than the rate reported by the other researchers.