Water treatment using discharge on the surface of a bubble in water

A new method for water treatment utilizing radicals produced by a discharge on the surface of a bubble in water is proposed and this method is applied to the de-color of indigo solution whose original color is blue. The discharge of this method begins at the crossing points of mesh electrode, acrylic resin spacer, and bubbling gas (i.e., called a triple junction where there is a weak point for the electrical breakdown in the electrical power devices). This weak point for the electrical breakdown is used very actively for the surface discharge. The discharge process on the surface of the bubble in water is also observed using a wire-to-plane electrode system to fix the observation region of discharge (type-A reactor). The streamer length estimated by photographs increased linearly with the applied voltage. The energy consumption of discharge for type-B reactor with a mesh-to-plane electrode in oxygen is about 0.09 J when the applied voltage is 20 W. Production efficiency of the H2O2 concentration of about 27 mg . L-1 in oxygen (46 mg - L-1 in helium) has been obtained when the repetition rate of discharge operated by a pulsed-power generator, the peak value of applied voltage, and the discharge period are 100 pps (pulsed power generator), 25 kV and 60 min, respectively.