Decolorization of a Reactive Dye by UV-Enhanced Ozonation

In the present study the treatment efficiency of O3 and UV+O3 processes were compared for the oxidation of simulated dyebath effluent containing a mixture of a reactive dye (C.I. Reactive Blue 19) and various dye auxiliary chemicals. The color, COD and TOC removal rates were assessed for different processes. The effect of initial dye concentration and presence of sodium hydroxide and sodium carbonate on decolorization kinetics were studied. The decolorization kinetics decreased by increase of initial dye concentration and addition of sodium hydroxide. The addition of sodium carbonate resulted in a lower COD removal. The experimental results showed that ozonation combined with UV irradiation (9-watt low-pressure mercury lamp) was slightly more efficient than ozonation alone in COD removal with no change in color removal efficiencies. At an initial pH of 6.2, bulk temperature of 25°C, ozone dosage of 55 g/m3 and initial dye concentration of 800 mg/L, the TOC removal efficiency of RB19 reached 19% and 27% after 90 min for O3 and UV+O3 processes, respectively.