Assessing the electrochemical oxidation of benzoic acid in synthetic oilfield produced water over Ti/IrO2-RuO2 electrodes

Oilfield-produced water (OPW) contains a complex mixture of recalcitrant organic contaminants, known as water-soluble oil (WSO) compounds, which pose significant environmental and operational challenges. Benzoic acid (BA), a highly soluble and toxic compound with low biodegradability, serves as a suitable model molecule for developing water-soluble oil (WSO) removal technologies. In this study, the radical-generating capability of a Ti/IrO 2 –RuO 2 active electrode and its electro-oxidation (EO) efficiency for BA removal were evaluated under synthetic OPW conditions. The electrode demonstrated the generation of hydroxyl (•OH) and chlorine (•Cl) radicals, enabling BA degradation through both indirect oxidation by electrogenerated species and direct electron transfer at the electrode surface. High salinity promoted the formation of multiple chlorine species, as confirmed by UV–Vis spectroscopy, with their generation being influenced by both current density and temperature. Using a 2.0 L electrochemical reactor, equipped with an electrode module with an anodic area of 390 cm 2 , kinetic modeling based on isothermal experiments was performed to describe BA removal under non-isothermal conditions at 30 mA∙cm −2 . At higher current densities (50 mA∙cm −2 ), BA degradation approached complete removal (~100%). However, the process exhibited low current efficiencies due to competitive oxygen, hydrogen, and chlorine evolution reactions. These results demonstrate the potential of Ti/IrO 2 –RuO 2 electrodes for the treatment of WSO molecules in OPW, while underscoring the need to mitigate current efficiency losses and control chlorine by-product formation for large-scale applications.