DECOLORIZATION OF DISPERSE RED 354 AZO DYE IN WATER BY SEVERAL OXIDATION PROCESSES-A COMPARATIVE STUDY

The degradation of the Disperse Red 354 azo dye in water was investigated in laboratory-scale experiments, using four advanced oxidation processes (AOPs): ozonation, Fenton, UV/H2O2, and photo-Fenton. The photodegradation experiments were carried out in a stirred batch photoreactor equipped with an immersed low-pressure mercury lamp as UV source. Besides the conventional parameters, on acute toxicity test with a LUMIStox 300 instrument was conducted and the results were expressed as the percentage inhibition of the luminescence of the bacteria Vibrio fisheri. The results obtained showed that the decolorization rate was quite different for each oxidation process. After 30 min reaction time the relative order established was: UV/H2O2/Fe(II) > Dark/H2O2/Fe(II) > UV/H2O2=O3 > UV/H2O2/Lyocol. During the same reaction period the relative order for COD removal rate was slightly different: UV/H2O2/Fe(II) > Dark/H2O2/Fe(II) > UV/H2O2 > UV/H2O2/Lyocol > O3. A color removal of 85% and COD of more than 90% were already achieved after 10 min of reaction time for the photo-Fenton process. Therefore, the photo- Fenton process seems to be more appropriate as the pre-treatment method for decolorization and detoxification of effluents from textile dyeing and finishing processes. Sulphate, nitrate, chloride, formate and oxalate were identified as main oxidation products.