Insights into the efficient mineralization of antibiotic trimethoprim in aqueous media by Fe2+ catalytically enhanced vacuum-UV irradiation: Kinetics, mechanisms, and toxicity evaluation

The widespread existence of antibiotics in the environment has attracted growing concerns regarding the potential adverse effects on aquatic organisms, ecosystems, and human health even at low concentrations. Extensive efforts have been devoted to developing new methods for effective elimination of antibiotics from wastewater. Herein, a novel process of Fe 2+ catalytically enhanced vacuum ultraviolet (VUV) irradiation was proposed as a promising approach for the removal of antibiotic trimethoprim (TMP) in water. Compared with UVC photolysis, VUV photolysis, and UVC/Fe 2+ , VUV/Fe 2+ could increase the pseudo-first-order reaction rate constant of TMP removal by 6.6–38.4 times and the mineralization rate by 36.5%–59.9%. The excellent performance might originate from the synergistic effect of VUV and Fe 2+ , i.e., VUV irradiation could effectively split water and largely accelerate the Fe 3+ /Fe 2+ cycle to generate more reactive oxygen species (ROS). EPR results indicated that • OH and O 2 •- were identified as the main ROS in the UVC/Fe 2+ and VUV/Fe 2+ processes, while • OH, O 2 •- , and 1 O 2 were involved in the VUV process. The operating parameters, such as Fe 2+ dosage and initial TMP contents, were evaluated and optimized. Up to 8 aromatic intermediates derived from hydroxylation, demethylation, carbonylation, and methylene group cleavage were identified by UPLC-QTOF-MS/MS technique, the possible pathways of TMP degradation were proposed. Finally, the acute and chronic toxicity of intermediates formed during TMP degradation in the VUV/Fe 2+ process were also evaluated.