Water Treatment with the Cold Plasma of a Diffuse Nanosecond Discharge in Air at Atmospheric Pressure

The treatment of wastewater with the atmospheric cold plasma is a promising method to purify it by means of neutralizing various toxic components. The degradation of an aqueous methylene blue solution used as a model dye was studied. The surface treatment of the solution was carried out with cold plasma of a diffuse nanosecond discharge in air at atmospheric pressure. It has been found that the efficiency of removing pollutants increased when the treatment time increases from 5 to 20 min. Optical UV-IR spectroscopy was used to determine the transmittance of aqueous solutions before and after treatment. Experimental results showed that the transmittance of the aqueous methylene blue solution after 20 min treatment with the diffuse discharge plasma increased by several times. The discharge formation under these conditions has also been studied by analyzing the waveforms of the current and voltage. It has been established that regardless of the presence of a cuvette on the flat grounded electrode, a large-diameter streamer is formed in the discharge gap. If there is a cuvette filled with the solution on the grounded electrode, a breakdown is initiated over the dielectric surface after the streamer reaches the dielectric. In this case, the plasma channel is closed on the grounded flat electrode.