Iranian Journal of

Backgrounds and Objectives: Carcinogenic and mutagenic potential of some azo dyes as a category of common dyes in different types of industries has been reported. The degradation of one commercially available dyestuff [C.I. Reactive Red 198 (RR 198)] by means of ultraviolet radiation (UV), ultrasonic irradiation (US), UV/H2O2 and US/H2O2 processes was investigated.
Materials and Methods: Photolysis process was accomplished in a laboratory-scale batch photoreactor equipped with an 55W immersed-type low-pressure mercury vapour lamp (UVC) and sonication in a sonoreactor with low frequency (42 kHz) plate type transducer at 170W of acoustic power with emphasis on the effect of various parameters on decolouration and degradation efficiency.
Results: Initial results showed that, color removal efficiencies by US and US/H2O2 processes were negligible. Almost complete disappearance of RR 198 (20 mg/L) in UV/H2O2 process was possible to achieve after 10 min of irradiation. It is found that lower pH and lower concentration of dye favor the dye degradation. Hence any increase in initial dye concentration results in decreased decolouration rates. Also, the experimental results indicated that the kinetics of sono-oxidation and photo-oxidation processes fit well by pseudo-first order kinetics and first order reaction kinetics, respectively.
Conclusion: It is concluded that UV/H2O2 reaction was more effective than other reactions in bleaching and the reaction rate was sensitive to the operational parameters and increased with increasing H2O2 concentration up to 15 mM.