Performance and mechanism of sulfadiazine degradation in UV/Fe2+/H₂O₂ system enhanced by chelating agents

Chelating agents significantly enhanced SDZ degradation in UV/Fe 2+ /H₂O₂ system. • The CA-enhanced systems operate efficiently across pH 3–8. • OH was the dominant reactive species, O₂· − and 1 O₂ played minor roles in SDZ removal. • Degradation pathways produced intermediates with lower toxicity than SDZ. • The system showed broad-spectrum reactivity and stability in natural freshwater. Antibiotics, widely detected in aquatic environments, pose significant threats to ecosystems and human health due to their recalcitrance in conventional wastewater treatment processes. This study systematically investigated the enhancement effects and mechanisms of three chelating agents (CAs) including NTA, EDTA and EDDS on sulfadiazine (SDZ) degradation in the UV/Fe 2+ /H₂O₂ system. Results showed that CAs significantly improved SDZ removal efficiency by complexing iron ions, promoting Fe 2+ /Fe 3+ cycling thereby enhancing photo-induced Fenton reactions. The NTA/UV/Fe 2+ /H₂O₂ system exhibited the highest performance, achieving 90.5% SDZ removal within 20 min, followed by EDTA (90.1%) and EDDS (88.7%) and without CAs (<35%). The CAs/UV/Fe 2+ /H₂O₂ system maintained high efficiency over a broad pH range (3–8), overcoming the pH limitation of traditional UV-Fenton processes. Electron paramagnetic resonance (EPR) and quenching experiments confirmed ·OH was the dominant reactive oxygen species and O₂· − and 1 O₂ also played minor roles. Degradation pathways of SDZ included ·OH oxidation, S N bond cleavage, and ring-opening reactions, producing intermediates with lower toxicity than SDZ. Meanwhile, the CAs/UV/Fe 2+ /H₂O₂ system could effectively remove various antibiotics (e.g., sulfamethoxazole, tetracycline) and maintain stability in the presence of inorganic anions and humic acid. Moreover, the CAs/UV/Fe 2+ /H₂O₂ system performed well in natural fresh water matrices, highlighting its practical application potential for antibiotic-contaminated water treatment. Download: Download high-res image (100KB) Download: Download full-size image