Decolorization of wastewater containing direct dye by ozonation in a batch bubble column reactor

Abstract

Decolorization of wastewater containing direct dye (Isma Fast Red 8B) by ozonation was studied in an attempt to abate pollution caused by textile dyeing houses and dye-producing plants. The decolorization process of the direct dye was carried out by bubbling ozone at the bottom of a bubble column reactor containing the dye solution. The effect of dye concentration, ozone dose, ozone air flow rate and solution pH on the rate of decolorization was studied. The reaction rate was followed by measuring the dye concentration at different times of the decolorization process. The rate of dye oxidation was found to increase with increasing ozone concentration in the gas phase (air-ozone) and decreases with increasing the dye concentration. The rate of dye oxidation increases with increasing gas flow rate, reaches a maximum and then decreases with a further increase in the gas flow rate. The rate of dye oxidation was found to increase with increasing solution pH. The decoloration breakdown products were tested for toxicity and were found to be nontoxic.