Ozonation of aqueous dyes and dyehouse effluent in a bubble-column reactor

Decolorization of a number of aqueous water-soluble acid and reactive dyes was investigated to cover a range of structural types. The effect of various parameters including pH, initial concentration of dyes, applied ozone dose and the influence of the substituent groups of the dye were investigated. Ozonation was found effective for decolorization of all types of dyes studied. The total ozone consumption for decolorization varied from dye to dye depending upon their chemical structure. Ozonation reduced COD of the dye solution to a small extent, which was affected by the number of azo groups in the dye. The pH had a mixed effect on decolorization efficiency as some dyes showed high decolorization efficiency with increasing pH and decolorization of some dyes was independent of pH.