Investigating the Efficiency of Advanced Photochemical Oxidation (APO) Technology in Degradation of Direct Azo Dye by UV/H2O2 Process

Document Type : Research Paper


1 Associate Professor, Department of Environmental Health Engineering, Isfahan University of Medical Sciences

2 M.Sc. Graduate, Department of Environmental Health Engineering ,Isfahan University of Medical Sciences


Every year more than 700,000 tons of dyestuff is produced, 50% of which is azo. Azo dyes contain one or more azo bonds (-N=N-) and are among the most important synthetic dyes because they are produced in high amounts and also have many applications in different industries especially in textile industries. This study was done to investigate dye removal of dyed effluents in textile industries as well as COD removal through advanced photochemical oxidation by the application of UV/ H2O2. A low-pressure 55-watt (UVC) mercury ultraviolet lamp as radiation source and H2O2 30 %( Merck) as oxidant were used. Dyestuff of C.I. Direct Red 80 of azo group was selected as model due to its high use and application. Some important parameters such as the effect of UV, duration of UV radiation, H2O2 concentration, dyestuff concentration and pH were studied in five separate stages based on the standard methods. The results showed that after 20 minutes, UV individually could remove 33.3 and 18.4 percent of color and COD, respectively; while, H2O2 could remove only 5.7% of color and 3.5%  of COD after 24 hr. In UV/ H2O2 system, color removal reaches 100% in optimum conditions after 5 min radiation; however, after 20 min of radiation, COD removal was 77.3 %. Optimum conditions for color removal (30 mg/L) and the COD resulting from the color in H2O2 process included 150 mg/L of pure H2O2, neutral pH and low concentrations of color. Therefore, UV/H2O2 system proved to be an effective method for removing color and the COD produced by color. However, removal efficiency of UV radiation and H2O2 individually was not appropriate because they can not individually generate enough OH˚ radicals, which are the main decomposing agents.


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