Decolorization of Reactive Black 5 using a dielectric barrier discharge in the presence of inorganic salts

Inorganic salts improve the coloration of textiles, which increases the pollution load of dye-house effluent in general. Decolorization of the reactive textile dye C.I. Reactive Black 5 was studied using Advanced Oxidation Processes (AOPs) in a non-thermal plasma reactor, based on the coaxial water falling film Dielectric Barrier Discharge (DBD). The initial dye concentration in the solution was 40.0 mg L-1. The effects of the addition of different high concentrations of inorganic salt (NaCl, Na2SO4 and Na2CO3) on the degree of decolorization were studied. The dye solution was recirculated through the DBD reactor with an applied energy density of 45.0-315 kJ L-1. The influence of residence time was investigated after 5 min and 24 h of plasma treatment. Decolorization of the dye was monitored spectrophotometrically. The pH value and the conductivity of the dye solution were measured after each recirculation. The most effective decolorization of over 90 % was obtained with the addition of NaCl (50 g L-1) with an applied energy density of 135 kJ L-1 and after a residence time of 24 h of plasma treatment. Decolorization of the solutions containing inorganic salts Na2SO4 and Na2CO3 were lower than for the solution without salt.