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-SnO ₂ electrodes as the sacrificial and oxidation anodes respectively. Although the Ti/Sb-SnO ₂ electrode is commonly used, its short lifetime disadvantages have limited its performance in industrial applications. A long-standing (highly stable) Ti/Sb-SnO ₂ electrode with high electro-oxidation capability was fabricated by applying an electrodeposited-annealed Sb-SnO ₂ interlayer between the Ti substrate and the Top Sb-SnO ₂ coating. Physical characterization results, including Field Emission Scanning Electron Microscopy (FESEM), X-ray diffraction (XRD), and Energy Dispersive Spectroscopy (EDS), revealed the presence of SnO ₂ 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 hours demonstrated that using the electro-deposited interlayer improved the electrocatalytic performance and stability of the electrode for electro-oxidation 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/cm ² , with electrodes placed 2.5 cm apart in a neutral pH environment for 120 minutes.