Abstract—The effectiveness of Fenton’s reagent (H 2 O 2 /Fe 2+ ) for chemical oxidation of the organic content of wastewater generated from a textile industry has been studied. The oxidative agent generates reactive hydroxyl radical species which degrades the reactive dye under study: Remazol brilliant orange 3RID (RBO3RID). The experimental results indicate that the oxidation process leads to a reduction in the chemical oxygen demand (COD) concentration up to 97%. Response surface methodology was used to optimize three different process variables: COD to Hydrogen peroxide ratio, Hydrogen peroxide-to-Fe (II) ratio and time. Analysis of variance (ANOVA) showed a high coefficient of determination value (R 2 =0.997). Effect of experimental parameters on the COD removal efficiency of RBO3RID was established by the response surface and contour plots. Results showed that COD removal increases with increasing oxidation time and initial Fe 2+ concentration. Index Terms—Fenton’s oxidation, reactive dye, response surface methodology, optimization. I. INTRODUCTION Among the several types of dyes used worldwide, reactive azo dyes are frequently used for dyeing cotton and other cellulose fibers. The covalent bonds that attach reactive dyes to natural fibers make them among the most permanent of dyes [1]. More than 10% of dyestuff used during the coloring processes does not bind to the fibers and therefore these excess dyes are released into the environment producing serious environmental pollution. The presence of these dyes in wastewater and subsequently in water resources, even at very low concentrations, is easy to observe visually as the result of textile industry activities. They may increase effluent toxicity and lead to environmental damage [2], [3]. Several treatment options are available for the degradation of dyes before their discharge like coagulation, flocculation, activated sludge process, advanced oxidation processes etc. Among all the processes stated above, advanced oxidation processes (AOPs) stand out to be better treatment method than the rest [4], [5]. The main advantage of AOPs over other biological, physico-chemical and classical chemical processes are their pronounced destructive nature leading to complete mineralization of the Manuscript received November 9, 2014; revised January 20, 2015. Suvanka Dutta, Ananya Ghosh, Sankar Chandra Moi, and Rajnarayan Saha are with the Department of Chemistry, National Institute of Technology, Durgapur-713209, West Bengal, India (e-mail: rajusaharupa@yahoo.com). pollutants present in wastewater. AOPs generate less sludge and involve short-lived chemical species with high oxidation power [6]. In these processes, hydroxyl radicals ( . OH) generated from different sources like H 2 O 2 and ozone in presence of catalysts (Fe 2+ , Ce 4+ , Ti 4+ etc.) and H 2 O 2 /O 3 in presence of UV light. Photocatalysts (TiO 2 , ZnO and different metal doped photocatalysts) in presence of UV light is also used in AOP’s. An old yet effective method among the AOPs is the use of Fenton’s reagent for the degradation process. This method which involves generation of reactive oxygenated species from H 2 O 2 in presence of ferrous catalyst is a fast and commercial way to deal with harmful organic contaminants in a green manner. In this process, H 2 O 2 is decomposed catalytically by Fe 2+ in the pH range of 3-3.5, giving rise to hydroxyl radicals [7]. Oxidation by H 2 O 2 alone is not effective for high concentrations of certain refractory contaminants, such as highly chlorinated aromatic compounds and inorganic compounds (e.g. cyanides), because of low rates of reaction at reasonable H 2 O 2 concentrations. Transition metal salts (e.g. iron salts), ozone and UV-light can activate H 2 O 2 to form hydroxyl radicals which are strong oxidants [8]. Iron (II) is oxidized by hydrogen peroxide to iron (III), forming a hydroxyl radical and a hydroxide ion in the process. Iron (III) is then reduced back to iron (II) by another molecule of hydrogen peroxide, forming a hydroperoxyl radical and a proton. The net effect is a disproportionation of hydrogen peroxide to create two different oxygen-radical species, with water (H + + OH – ) as a byproduct. The chemical equation which is followed during the reaction is as follows: Fe 2+ + H 2 O 2 → Fe 3+ + • OH + OH – (a) Fe 3+ + H 2 O 2 → Fe 2+ + • OOH + H + (b) The generated free radicals attack C-H bond of organic molecules and initiates several chain reaction. RH + OH . → R . + H 2 O (c) RH + 2OOH . → ROO . + RO . + H 2 O (d) ROO . + RH → ROOH + R (e) . RO . + RH → ROH + R (f) 2ROO . → ROOR+ O 2 (g) These reactions generate organic radicals and other free Application of Response Surface Methodology for Optimization of Reactive Azo Dye Degradation Process by Fenton’s Oxidation Suvanka Dutta, Ananya Ghosh, Sankar Chandra Moi, and Rajnarayan Saha International Journal of Environmental Science and Development, Vol. 6, No. 11, November 2015 818 DOI: 10.7763/IJESD.2015.V6.705