Kinetics and products of ozonation of CI Reactive Red 195 in a semi-batch reactor

Textile wastewater shows great threats to the environment if not well pretreated before discharge. A promising technique, ozonation, was applied to remove the color in dye solutions containing C.I. Reactive Red 195 (RR195) in a semi-batch reactor. The decolorization of RR195 by the ozone process followed pseudo-first-order kinetics. Several factors which influenced the efficiency of decolorization were studied and the reaction rate constant (k) obtained with different operational parameters was compared. Our results showed that RR195 was more easily degraded in acidic than in alkaline conditions. The dyeing auxiliaries (sodium carbonate and sodium chloride) that acted as radical scavengers could enhance the decolorization process, and the ozonation time for total color removal lengthened if the initial dye concentration was higher. The analysis of the ozonation products was performed by liquid chromatography tandem mass spectrometer and a possible degradation pathway was predicted according to the ozonation products and structure of RR195. Our results indicated that ozonation was effective in the color removal of dyes, but further treatment might be necessary since the ozonation products are high toxic. (C) 2014 Dong-Xing Yuan. Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. All rights reserved.