Decolorization of a Reactive Dye by UV-Enhanced Ozonation

I n 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.‎