Abstract
•Degradation of Acid Orange 7 (AO7) by Galvano-Fenton process (GFP) is examined.•Free radicals’ generation by GFP is modeled, simulated and compared with those of classic Fenton and electro-Fenton.•Significant contribution of SO4•−in the initiation reaction is demonstrated numerically.•Steady state inHO• and SO4•− concentrations is expected at high corrosion current.
In the present study, the kinetics of degradation of acid orange 7 (AO7) by the Galvano-Fenton process is assessed experimentally and simulated numerically in order to figure out the mechanism of generation and consumption of free radicals with this novel advanced oxidation process. 10 mg/L of the azo dye are degraded during 20 min by combining a copper-iron Galvanic cell to Fenton mechanism at pH 3. The electrochemical and electrolytic reactions are approached following two scenarios, whose the more complex includes the cathodic and anodic reactions, the Fenton scheme and the formation of ferric and ferrous irons complexes and salt as well as the reactivity of sulfate ions. The numerical results demonstrated a high correlation coefficient of 93.5% with experimental results using this latter scenario, while the identified pathways of generation and consumption of HO• and SO4•−, considering their contribution to the initiation reactions of the chain mechanism of AO7 degradation, demonstrated a significant participation of SO4•−. The sensitivity of the process to the corrosion current was examined numerically over the range 0.3 to 1 mA, the results exhibited the achievement of a steady state for the molar concentrations of HO• and SO4•−. This observation was explained by the continuous release of Fe2+ catalyst in the Galvano-Fenton process, in contrast with the classic Fenton scheme. The comparison of both Galvano-Fenton and classic Fenton processes in one hand, and Galvano-Fenton and electro-Fenton processes in the other hand, was further investigated and discussed numerically.