Influence of Pulsed Discharge Timing on Decolorization of Indigo-carmine Solution with Periodic Electrospray

Abstract

This paper presents an experimental study on electrospray with pulsed streamer discharges from a syringe needle for de-colorization of a blue dye. To spread fine mists of an indigo-carmine solution from the syringe electrode with a constant frequency, a sinusoidal voltage is superimposed onto a positive dc applied voltage. The voltage ripple produce by the ac component has as an important role to repeat the electro-spray intermittently at a phase θ₀=150° of the sinusoidal wave. In addition, high voltage nanosecond pulses are repeatedly superimposed at another phase θ_p to propagate positive streamer discharges from the syringe. Results show that the de-colorization rate of the blue dye increases with decreasing the phase lag φ=θ_p-θ₀. If the phase lag is sufficiently reduced, the electro-spray is immediately followed by the pulsed streamer discharge, so that the streamer discharge channels can be propagated into the gap filled with the mist. We confirm that the streamer discharges from the tip of the water taylor cone can propagate with a high probability when φ=10°. These facts indicate that the timing control of the pulse superposition is very important for the water treatment with the electrospray.