Reduction of Chemical Oxygen Demand from Refinery Wastewater by Three-Dimensional Electrode-Electro-Fenton Process

In this work, a three-dimensional electrode-electro-Fenton system (3DE-EF), where Fe particles and air were introduced simultaneously into a traditional two-dimensional reactor, was employed to treat refinery wastewater. The effect of operating conditions—initial pH, electrolytic voltage, amount of Fe particles, electrolyte type and electrolyte amount—on chemical oxygen demand (COD) reduction were explored and optimized by response surface methodology (RSM). The possible reaction mechanisms of these processes were also discussed by comparing the results of COD reduction. The results showed that the COD of refinery wastewater nearly reached the grade I wastewater discharge standard (100 mg L−1) when the initial pH was 2.98, cell voltage was 13 V, electrolysis time was 60 min, and NaCl and Fe particles were added at 2.70 g/300 mL NaCl and 3.12 g/300 mL, respectively. The results indicated that the 3DE-EF system is a highly efficient COD reduction technology, successfully combining the features of a three-dimensional electrode and an electro-Fenton system.