Toxicity Reduction of Reactive Black 5 and Disperse Orange 25 by Advanced Oxidation Processes

The toxicity reduction of two commercially available dyestuffs, Reactive Black 5 and Disperse Orange 25, by means of ultraviolet radiation and ultrasonic irradiation using H2O2 was investigated with emphasis on the effect of various parameters on decolorization and degradation efficiency. The toxicity was also evaluated in acute toxicity studies using Daphnia magna. Results showed that both dyes were toxic to D. magna. The toxicity tests with D. magna showed lesser toxicity than parent form of both dyes after UV and US processes. However, UV process was more effective than US process in reducing dye toxicity. The toxicity level of dyes solution after US plus H2O2 and UV plus H2O2 processes were even higher than the toxicity level found for the dye solution without any color removal treatment, indicating that even with a removal of 100% of the dye RB5 from the aqueous solution, an expressive mortality of the D. magna occurred. One possible reason for this increase in toxicity could be due to the presence of H2O2 in the effluents. J. Color Sci. Tech. 3(2009), 17-23.© Institute for Color Science and Technology.