Application of non-thermal plasma reactor for degradation and detoxification of high concentrations of dye Reactive Black 5 in water

Abstract

Degradation and detoxification efficiency of high concentrations of commercially available reactive textile dye Reactive Black 5 solution (40, 80, 200, 500, 1000 mg L^-1), were studied. Advanced oxidation processes in water falling film based on dielectric barrier discharge in a non-thermal plasma reactor were used. For the first time, this reactor was used for the treatment of high concentrations of organic pollutants such as reactive textile dye Reactive Black 5 in water. Solution of the dye was plasma treated in a thin aqueous solution film that was constantly regenerated. The reactor works as a con­tinuous flow reactor and the electrical discharge itself takes place at the gas–
–liquid interphase. The dye solution was recirculated through the reactor with an applied energy density of 0–374 kJ L^-1. Decolorization efficiency (%) was monitored by UV–Vis spectrophotometry. Samples were taken after every recirculation (~ 22 kJ L^-1) and decolorization percentage was measured after 5 min and 24 h post plasma treatment. The efficiency of degradation (i.e., mineralization) and possible degradation products were also monitored by determination of the chemical oxygen demand (COD) and by ion chroma­tography (IC).Initial toxicity and toxicity of the solutions after the treatment were studied using Artemia salina test organisms. Efficiency of decolorization decreased with the increase of the dye concentration. Complete decolorization, high mineralization and non-toxicity of the solution (<10%) were acomplished after plasma treatment using energy density of 242 kJ L^-1, while the initial concentrations of Reactive Black 5 were 40 and 80 mg L^-1.