Nakagawa, H.; Takagi, S.; Maekawa, J. (2015) Proceedings of APCChE 2015, pp. 3132287
Abstract: Fenton oxidation, which utilizes hydroxyl radical generated by Fenton reaction, is well known as an efficient process for degrading organic pollutants in wastewaters. A large amount of ferrous irons is, however, dosed in many cases, generating much iron hydroxide sludge. To overcome this disadvantage, electrochemical reduction of ferric ions is carried out in situ, which is so-called electro-Fenton process. In this study, 1,4-dioxane, which is a hot issue in the world, is degraded by the electro-Fenton oxidation and kinetic analysis is carried out. A sheet (2.5 cm x 2.5 cm) made of pulverized activated carbon with PTFE binder is used as a cathodic electrode. Two compartments cell with 250 mL in reaction volume is used for degradation experiments. 1,4-dioxane of 40 mg/L can be degraded to less than 1 mg/L in 120 min. Degradation experiments under various conditions indicate that degradation rate of 1,4-dioxane has a closely relationship with reduction rate of ferric ions on cathode and the reduction rate of ferric ions is not affected by the presence of degradation products. It was also found that reactivity of 1,4-dioxane with hydroxyl radicals is much higher than that of degradation products. Reaction model including active radicals is constructed and concentration of each component is calculated assuming steady-state approximation for active radicals. Changes of 1,4-dioxane and hydrogen peroxide concentrations can be well fitted with experimental data under various conditions. Simulation results indicate that the concentrations of hydroxyl radicals and ferrous ions increase with the progress of degradation.