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Sulfonamides, including sulfadoxine (SDX), are widely used antibiotics, particularly for malaria treatment. However, their extensive use has led to environmental pollution, microbial resistance, and public health risks. Advanced Oxidation Processes (AOPs) offer promising methods to degrade such pollutants in water, though they may generate more toxic by-products. This study evaluates three AOPs with different hydroxyl radical generation principles: the Fenton reagent (H2O2/Fe2+), hydrogen peroxide photolysis (UV-C/H2O2), and heterogeneous photocatalysis (UV-A/TiO2). Heterogeneous photocatalysis showed superior performance, achieving 100% degradation and 77% mineralization under optimized conditions. Further analysis explored the effects of UV dose, catalyst concentration, and pH on process efficiency. The influence of water matrices, including Ultrapure Water (UW), Tap Water (TW), and Surface Water (SW) from the Aliakmonas River, was also examined. High-Resolution Mass Spectrometry identified 11 SDX transformation products formed during photocatalysis, with their formation mechanisms reported for the first time. An ecotoxicity assessment using ECOSAR software revealed insights into the potential environmental impact of these by-products. [ABSTRACT FROM AUTHOR]

BACKGROUND: The present study investigates the in situ electrogeneration of H2O2 by the 2e− oxygen reduction reaction in an electrochemical flow cell using three commercially available cathodic electrode materials with different interfacial properties; that is, activated carbon felt (ACF), non‐activated carbon felt (NACF) and gas diffusion electrode (GDE). RESULTS: Experiments were first performed to optimize the operating parameters and to determine the yield of H2O2 electrosynthesis. The estimated maximum yield of ~40% was achieved with the NACF electrode after 30 min of operation. Furthermore, the performance of the electrodes was investigated in two scenarios, namely (i) under conditions with O2‐saturated electrolyte and (ii) under continuous air supply, to study the differences in O2 distribution within the electrode material as a function of its interfacial properties. The maximum H2O2 concentration for the first scenario was 3.86 mg L−1 after 60 min of operation, which was obtained with the NACF electrode. In contrast, in the second scenario, H2O2 electrogeneration was significantly increased for all three electrodes, with the GDE exhibiting the best performance, at 43.3 mg L−1 after 60 min of operation. CONCLUSIONS: The properties of the electrode material play a decisive role in H2O2 electrogeneration. The hydrophilicity of the electrode is very important when O2 is dissolved in the electrolyte. Hydrophobicity is preferable when gaseous O2 is applied to the electrode as a three‐phase interface is formed, which favors the transfer/penetration of O2. The pore size of the electrode is of crucial importance, as mesoporous materials facilitate the distribution of gaseous O2 in the electrode body. © 2024 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]