Decolorization of indigo carmine solution by argon dielectric barrier discharge produced on liquid surface

The decolorization of the indigo carmine solution was performed by argon dielectric barrier discharge (DBD) excited on a target solution and the effect of the gap distance on the water treatment characteristics were investigated for the gap distance between 1.0 and 2.5 mm. The argon DBD was excited by the 3-kHz sinusoidal voltage with the fixed discharge power between 1.72 and 1.76 W for any gap distance. Voltage and current waveforms and Lissajous figures were acquired to investigate the electrical characteristics of the DBD. Compared with fixing the discharge energy, the higher decolorization rate was obtained with the shorter gap distance. Therefore, shortening gap distance could lead to increased decolorization efficiency of the indigo carmine solution. The mechanism of the higher efficiency with the shorter gap distance was discussed on the basis of the electrical characteristics and possible plasma chemical reactions in the argon DBD on the solution surface.