Removal of COD and color from Direct Blue 71 azo dye wastewater by Fenton’s oxidation: Kinetic study

In this paper, degradation of Direct Blue 71 (DB71) by Fenton's oxidation process was investigated. The effect of initial pH, dosages of Fe2+ and H2O2, dye concentration and temperature on the color and Chemical Oxygen Demand (COD) removal was studied in a batch reactor. The optimal conditions for the decolorization and COD removal of DB71 were determined as pH = 3.0, Fe2+ = 3 mg L−1 and H2O2 = 125 mg L−1. Under the optimal conditions 94% color and 50.7% COD removal efficiency of the dye in 100 mg L−1 aqueous solution were achieved after 20 min of reaction. Results indicated that the removal efficiency was strongly dependent on initial pH, initial concentration of Fenton's reagents, initial DB71 concentration and reaction temperature. Additionally increasing the reaction temperature from 20 to 60 °C showed a positive effect on the decolorization efficiency of DB71. The experimental data were analyzed using the first and second-order and Behnajady–Modirshahla–Ghanbery (BMG) kinetic models. BMG model provides the best correlation of the data. The present study can provide guidance to relational industry operators and planners to effectively treat the DB71 contaminated wastewater by Fenton's oxidation process.