Treatment of petroleum refinery wastewater by photo-anodic oxidation process with Gr /Bi-Ni-Sb-SnO2 rotating photo-anode: Performance and kinetic study

Abstract

This work explores the use of photoelectrocatalysis (PEC) as one of the most advanced oxidation processes (AOPs) for petroleum refinery wastewater (PRW) treatment. A photoelectrochemical reactor equipped with a Gr/Bi − Ni − Sb − SnO2 photoanode and UVC irradiation was designed to enhance the degradation of pollutants. The effects of key operational parameters, including current density, pH, and anode rotation speed, on the treatment efficiency were systematically evaluated. The results confirmed that increasing the current density provided better chemical oxygen demand (COD) removal, while increasing pH above 5 results in a decrease in COD removal. In addition, increasing the anode rotation speed improved mass transfer and pollutant decomposition up to 200 rpm; after that, no significant improvement was observed, with a slight decrease in COD removal. According to the results, the best performance was achieved at a pH of 5, a current density of 6 mA/cm2, and a rotation speed of 200 rpm, achieving a COD removal efficiency of 86.2% in 90 min with an energy consumption of 110.34 kWh/kg−1 COD. Kinetic studies confirmed that the degradation of COD over time exhibited pseudo-first-order kinetics, with an R2 of at least 0.999. Considering all factors, the results demonstrate that PEC technology, using Gr/Bi−Ni−Sb−SnO2 Photoanode, offers a low-energy, sustainable, and facilitating method for the degradation of complex petroleum-derived pollutants. This study highlights the potential of PEC as a practical alternative to conventional industrial wastewater treatment methods.