Optimization of H2O2/COD and Fe3+/H2O2 Ratios in Combined Electrocoagulation-Fenton System for Petrochemical Wastewater Treatment

Abstract

Petrochemical wastewater is characterized by a high organic load and complex composition, which can limit the effectiveness of conventional biological treatment and necessitate advanced treatment technologies. This study evaluated an integrated electrocoagulation–Fenton process for petrochemical wastewater treatment, focusing on optimizing the H2O2/COD and Fe3+/H2O2 ratios and assessing their effects on COD degradation kinetics. Electrocoagulation was initially conducted under previously optimized conditions of 5 V, initial pH 7, and 60 min, followed by Fenton oxidation at pH 3. The H2O2/COD ratio was varied at 5, 10, 15, and 20 g/g, while the Fe3+/H2O2 ratio was adjusted to 0, 0.013, 0.02, and 0.04 g/g. The optimum H2O2/COD ratio of 15 g/g achieved a COD removal efficiency of 48.14%. Further optimization identified an Fe3+/H2O2 ratio of 0.02 g/g as the optimal condition, yielding the highest COD removal efficiency of 88.75%. The achieved removal efficiency is comparable to the upper end of the range reported for integrated electrocoagulation–Fenton treatment of refractory industrial wastewater. Kinetic analysis showed that both first-order and second-order models adequately described COD degradation; however, the second-order model provided a slightly better fit, with R² values of 0.98–0.99. This result suggests that the oxidation process was governed primarily by interactions between oxidizing species and organic pollutants rather than simple first-order degradation. Overall, optimizing oxidant and catalyst dosages substantially improved the integrated electrocoagulation–Fenton process, demonstrating its potential as an effective treatment strategy for petrochemical wastewater and providing practical operating conditions for advanced wastewater treatment applications.