Optimizing the combined electrocoagulation (EC) and electrochemical oxidation (EO) for treating the petroleum wastewater from crude oil storage tank bottoms

This study investigated the treatment of petroleum-contaminated water from the crude oil storage tank by employing sequential coupling electrocoagulation and electrochemical oxidation using Fe and Ti/Sb–SnO₂ electrodes as the sacrificial and oxidation anodes, respectively. Although the Ti/Sb–SnO₂ electrode is commonly used, its short lifetime disadvantages have limited its performance in industrial applications. A long-standing (highly stable) Ti/Sb–SnO₂ electrode with high electrooxidation capability was fabricated by applying an electrodeposited-annealed Sb–SnO₂ interlayer between the Ti substrate and the Top Sb–SnO₂ coating. The physical characterization results, including field emission scanning electron microscopy, X-ray diffraction, and energy-dispersive spectroscopy, revealed the presence of SnO₂ and Sb in the anode composition. The surface appeared flat with a uniform spherical shape, averaging about 13–22 nm in size. The 2 V oxygen evolution overpotential and the accelerated lifetimes of 11 h demonstrated that using the electrodeposited interlayer improved the electrocatalytic performance and stability of the electrode for electrooxidation applications. The highest COD removal of the mentioned wastewater was optimized using the RSM methodology for EC and EO, respectively. The integrated EC–EO process achieved a maximum COD reduction efficiency of 96.5% at a current density of 20 mA/cm², with electrodes placed 2.5 cm apart in a neutral pH environment for 120 min.