Abstract
An application of underwater discharge is one possible way how make the destruction of organic dyes. This contribution presents results of Direct Blue 106 destruction in discharge generated in bubbles. The initial conductivity value of 30 μS.cm−1 was obtained using electrolyte; the starting dye concentration was 20 mg.l−1. The DC voltage from 1.5 kV to 3.0 kV was applied to generate the discharge at the mean current of 10-30 mA. The system was bubbled through the high voltage capillary electrode by He, Ar and N2 at the constant gas follow of 200 sccm. The dye destruction rate was directly proportional to the applied discharge current, so the highest efficiency was reached at the current of 30 mA. The destruction rate was strongly dependent on the filling gas. While using He and Ar only 4% destruction was obtained during the 20 minutes treatment at 10 mA of discharge current but the decomposition of 52 % was reached if nitrogen was introduced into the high voltage electrode. The destruction efficiency of about 40 % (He, Ar) and over 60 % in nitrogen was reached at discharge current of 30 mA. This enormous difference was probably connected not only to the production of hydrogen peroxide that seems to be usually the main oxidative specie in under water discharges but also atomic and excited nitrogen particles, both atomic and molecular, can have very positive effect in the dye destruction. The detailed study of the kinetic mechanisms leading to the Direct Blue 106 dye destruction will be a subject of the further studies.
Highlights
Direct Blue 106 dye belongs under the group of Organic Synthetic Dyes
In advanced oxidation processes (AOP), generally reactive, strongly oxidizing ·OH radicals play the main role in destruction of the dye molecules
Maximal destruction of about 64 % was achieved in N2 plasma at the highest applied current. We suppose that this effect is connected to the formation of HNO3 in case of N2 due to oxidation of N2 that leads to the decrease of solution pH down to 2
Summary
Direct Blue 106 dye belongs under the group of Organic Synthetic Dyes. By definition, dyes are colored, ionizing and aromatic organic compounds which show an affinity towards the substrate to which it is being applied. In AOP, generally reactive, strongly oxidizing ·OH radicals play the main role in destruction of the dye molecules. Besides well described pulsed corona like systems in point to plane [3] and coaxial configurations [4] and so called electrode less configurations (diaphragm [5] and capillary [6]), the discharge created in the bubbles introduced into the systems can be applied.
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