C J Hawkyard

Ferral-catalyzed ozonation of aqueous dyes in a bubble-column reactor

Abstract The decolorization of aqueous solutions of textile dyes by Ferral-catalyzed ozonation using a bubble-column reactor was investigated. The optimum catalyst concentration and pH for decolorization was determined. Experimental results show that Ferral-catalyzed ozonation can be an effective method for decolorization of various aqueous dyes. Ferral showed their catalytic activity at highly acidic conditions with considerable reduction of chemical oxygen demand (COD).

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.

Effect of Dyebath Additives on Decolorization Efficiency in the Ozonation of Dyehouse Effluent

Abstract It is necessary to study the effect of dyebath additives on decolorization efficiency in order to optimize ozone-based decolorization processes as the consumption of ozone can be reduced through selecting ozone favorable additives. The effect of 5 dyebath additives viz. electrolytes (sodium chloride and sodium sulfate), chelating agent (ethylene diamine tetra acetic acid or EDTA), reducing agent (sodium dithionite), optical brightener (Uvitex BHT), and dispersing agent (Zetex DNVL) was investigated. All of the additives showed synergistic effect as addition of sodium chloride, sodium dithionite and Zetex DN-VL markedly improved decolorization efficiency, but EDTA and optical brightener showed negative effect. Sodium sulfate did not show any positive or negative effect on decolorization efficiency.