OZONATION OF AQUEOUS DYES AND DYEHOUSE EFFLUENT IN A BUBBLE-COLUMN REACTOR

ABSTRACT

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. Substituent groups attached to the dye structure affected decolorization efficiency in the ozonation process.

Keywords:

• Decolorization
• Aqueous dyes
• Effect of pH
• Applied ozone dose
• Substituent groups
• Acid dyes
• Reactive dyes
• COD

ACKNOWLEDGMENTS

The authors wish to acknowledge the financial help received from Air Products Ltd., Environmental Technology Group, Basingstoke, UK and sponsorship of Commonwealth Scholarship Commission of the UK for Md. Mahbubul Hassan.