Electrolyte-Driven Oxidant Generation on Ti/IrO2–SnO2–Sb2O5 Electrodes for the Efficient Removal of Alachlor and Isoproturon from Water

In this study, anodic oxidation (AO) was evaluated using Ti/IrO2–SnO2–Sb2O5 electrodes in chloride, sulfate, and mixed electrolytes, along with electro-Fenton (EF) and photoelectro-Fenton (PEF) at pH 3.0, for the degradation of alachlor and isoproturon, each 50 mg L−1. Active chlorine species were monitored using UV–Vis, while the removal of both herbicides was quantified using High Performance Liquid Chromatography (HPLC), along with the reduction in Total Organic Carbon (TOC), mineralization current efficiency (MCE), and specific energy per TOC removed (ECTOC). The results show that electrolyte composition influences AO more than current density. In a chloride medium, isoproturon was eliminated within minutes, whereas alachlor required mixed electrolytes of Cl−/SO42−, allowing simultaneous combination of HClO/ClO−, ●OH, and S2O82−/SO4●−, or coupling with EF. An optimal current density of ~30 mA cm−2 limited voltage rise and radical scavenging. EF introduced measurable mineralization (15% TOC), whereas PEF achieved rapid alachlor reduction and TOC reductions of up to 76% at low Fe2+. Overall, sequential AO followed by PEF maximized mineralization per unit of energy, and the mixed electrolytes provided a controllable pathway to scale up oxidant speciation generation.