Synergistic decolorization and detoxication of reactive dye Navy Blue 250 (NB250) and dye wastewater by the UV/Chlorine process

Abstract

The research aims for the simultaneous use of chlorine and UV irradiation (UV/Chlorine) to decolorize and detoxify Navy Blue 250 (NB250) and raw dye wastewater. The UV/Chlorine was the most effective in removing NB250 and color intensity (American Dye Manufacturers Institute, ADMI unit). The UV/Chlorine removed NB250 approximately 1.47–1.50 times faster than chlorination alone. The degradation constants in UV/Chlorine were 0.3317 mM-1min-1 and 0.3384 mM-1min-1 for NB250 and its ADMI color intensity, respectively. The optimum pH for decolorization was between 6 and 7. The UV/Chlorine with a chlorine dose of 1.0–2.0 mM was recommended for decolorization to meet the industrial discharge standard (300 ADMI). Reactive chlorine species (RCS) were more significant oxidants for NB250 removal than HO•. The presence of NB250 inhibited the germination of morning glory (Ipomoea aquatica) seeds, and exposure to raw dye wastewater (color = 6,658 ± 227 ADMI) completely inhibited seed germination. However, the samples treated by the UV/Chlorine were less toxic to seed germination and root growth. Therefore, the UV/Chlorine has a high potential in the decolorization and detoxification of dye wastewater. This is the first study to use the UV/Chlorine to treat industrial dye wastewater.