Water Treatment with the Cold Plasma of a Diffuse Nanosecond Discharge in Air at Atmospheric Pressure
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WATER TREATMENT WITH THE COLD PLASMA OF A DIFFUSE NANOSECOND DISCHARGE IN AIR AT ATMOSPHERIC PRESSURE V. S. Ripenko, D. V. Beloplotov, M. V. Erofeev, and D. A. Sorokin
UDC 537.523.9
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. Keywords: methylene blue, wastewater, cold plasma, nanosecond discharge, streamer.
INTRODUCTION Recently the amount of various pollutants (organic compounds, plastics, and dyes) in different water reservoirs increases. This is a serious problem both for public health service and ecology. For example, only the textile industry emits 1 mln kg of polluting dyes per year [1]. Therefore, decolonization of dyes from wastewaters of textile industry is very important for ecology. This will permits reuse of water for textile treatment. However, many dyes are highly resistant to degradation, and modern organic dyes have stable molecular structures, and the conventional methods of wastewater treatment are inefficient. As a result, new technologies of dye removal are developed [2–5]. Treatment with cold diffuse nanosecond plasma generated by runaway electrons can become an effective method of wastewater treatment from organic dyes. In [4, 5] it was shown that after treatment of the metal surface by this discharge, the concentration of carbon-containing compounds in the layer above the surface decreases, they are also activated. In addition, the adhesion of the surface increases, it is smoothed, and its roughness changes. The diffuse nanosecond discharge is formed in a highly inhomogeneous electric field. This electric field distribution is established in the discharge gap with the tip-plane electrode geometry. Due to the amplification of the electric field in the vicinity of the tip electrode, conditions arise for the occurrence of a considerable number of f
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