Comparing the Degradation Pathways of Hydrochlorothiazide and Sulfamethoxazole Using Ozone, Anodic Oxidation, and Electro-Fenton Processes

This study compared the performance of ozonation (O3), anodic oxidation (AO), and electro-Fenton (EF) as advanced oxidation processes (AOPs) in the degradation and mineralization of two prevalent pharmaceutical pollutants: sulfamethoxazole (SMX) and hydrochlorothiazide (HCTZ). The effects of varying currents (150–500 mA) on AO and different Fe2+ concentrations (0–42 mg L–1) on EF were examined. Both EF and O3 achieved full removal of SMX and HCTZ, whereas AO resulted in 90% removal. EF demonstrated the highest mineralization efficiency, with 88% total organic carbon (TOC) removal, followed by AO at 74% and O3 at 24%. Investigations into the degradation pathways of SMX and HCTZ under each AOP revealed identical degradation mechanisms for EF and AO, with hydroxyl (•OH) radicals playing a crucial role. When tested on real municipal effluent, EF showed superior mineralization efficiency and was least affected by the water matrix. This study underscores the effectiveness of EF in the degradation and mineralization of pharmaceutical pollutants, presenting it as a viable option for large-scale wastewater treatment. This work provides the first side-by-side benchmark of O3, AO, and the combined AO + EF process for a SMX/HCTZ mixture while jointly evaluating kinetics, TOC mineralization, transformation products, and real-effluent matrix effects.