Removal of Azo Dyes From Aqueous Solution Using Fenton and Modified Fenton Processes

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Background: Fenton (Fe2+ and H2O2) and modified Fenton (Fe3+ and H2O2) are two popular methods used in advanced oxidation processes (AOP) and degradation of persistent organic pollutants (POPs), such as dye compounds. In these processes, Fe2+ and Fe3+ as catalysts and H2O2 as the oxidizing agent are added to the reactor. Objectives: The aim of the current study is to assess the abovementioned methods for removal of Reactive Red 198 and Blue Reactive 19 from aqueous solutions. Materials and Methods: This research was carried out using lab-scale. After preparation of RB-19 and RR-198 stock solutions (1000 ppm), optimum pH and temperature were determined within the range of (3-11) and (15C - 40C) respectively, and specific amounts of Fe2+ and Fe3+ (0.8, 1, 3, 7, 14 and 32 mM) were prepared by adding FeSo4. 7H2O and FeCl3, and H2O2 30% W/W (2, 5, 11, 23, 47 and 94 mM) were added to the solutions to establish the H2O2/Fe2+, Fe3+ molar ratios. Standard jar tests were conducted using jar test apparatus. After sedimentation time, samples were filtered through a 0.45 m fiber membrane, and then final dye concentrations were measured using a UV/VIS spectrophotometer. Results: The highest dye removal efficiency in both Fenton and modified Fenton methods were obtained at the optimum pH = 3, optimum reaction time of 10 minutes, optimum temperature at 25C and H2O2/Fe2+ and H2O2/Fe3+ concentrations of 11.3 and 5.1 mM, respectively. In the Fenton reaction the maximum efficiency was obtained at 94.70% and 99.31% for reactive red 198 and reactive blue 19, respectively. Moreover, by the modified Fenton method the maximum removal efficiency for reactive red 198 and reactive blue 19 was 94.8% and 99.43%. Conclusions: Fenton and modified Fenton processes could be used as very effective methods for removal of reactive red 198 and blue reactive 19 from aqueous solutions.