Decolorization of reactive black 5 using a dielectric barrier discharge in the presence of inorganic salts

Abstract

Inorganic salts improve the coloration of textiles, which increase pollution load on dyehouse effluent in general. Decolorization of reactive textile dye C.I. Reactive Black 5 was studied using Advanced Oxidation Processes (AOPs) in a non-thermal plasma reactor, based on coaxial water falling film Dielectric Barrier Discharge (DBD). Initial dye concentration in the solution was 40.0 mg L-1. The effects of addition of inorganic salt different high concentrations (NaCl, Na2SO4 and Na2CO3) on the degree of decolorization were studied. Recirculation of dye solution through the DBD reactor with applied energy density 45-315 kJ L-1 was used. The influence of residence time was investigated after 5 minutes and 24 hours of plasma treatment. Decolorization of the dyes was monitored by spectrophotometric measurement. Changes of pH values and the conductivity of dye solution after each recirculation were tested. The most effective decolorization of over 90% was obtained with the addition of NaCl (50 g L-1), applied energy density of 135 kJ L-1 and after residence time of 24 hours of plasma treatment. Decolorization of solutions containing inorganic salts Na2SO4 and Na2CO3 were lower than for the solution without salt.