Hybrid UV/TiO₂/H₂O₂-Driven Degradation of Sulfamethoxazole and Trimethoprim: Kinetics, Synergistic Effects, and Degradation Pathways
摘要
The occurrence of antibiotic residues in aquatic environments has become a major environmental concern because of their persistence, ecological toxicity, and contribution to antimicrobial resistance. This study systematically evaluated the simultaneous degradation of sulfamethoxazole (SMX) and trimethoprim (TMP) using individual and hybrid advanced oxidation processes, including UV photolysis, UV/TiO₂, UV/H₂O₂, and UV/TiO₂/H₂O₂. Among the investigated system, UV/TiO₂/H₂O₂ showed the highest performance, achieving removal efficiencies above 99% for both SMX and TMP within 90 min under the optimum conditions of 0.02 g L⁻1 TiO₂ and 2 mM H₂O₂. The apparent first-order rate constants were 0.0827 min⁻1 for SMX and 0.0514 min⁻1 for TMP, both substantially higher than those obtained for the individual system. Synergistic factors of 1.67 for SMX and 2.17 for TMP confirmed a pronounced synergistic effect, mainly attributable to enhanced hydroxyl radical generation and suppressed electron–hole recombination. LC–MS analysis indicated that hydroxylation, bond cleavage, and progressive oxidation were the main transformation pathways for both antibiotics. Toxicity prediction using ECOSAR V2.2 suggested that most transformation products were less acutely and chronically toxic to fish, daphnia, and green algae than the parent compounds, although several intermediates still posed residual ecological risks. In addition, degradation kinetics were slower in lake water and hospital wastewater than in deionized water, highlighting the influence of radical-scavenging species and suspended solids under realistic conditions. Overall, the results demonstrate that the UV/TiO₂/H₂O₂ system is an efficient and mechanistically robust approach for treating antibiotic-contaminated wastewater.