Antibiotics are becoming ubiquitous emerging contaminants in the aquatic environments due to their large amount of production and extensive application, which have received increasing public concern. In this paper, the degradation and mineralization of sulfamethoxazole (SMX) by ionizing radiation in the presence of Fe3O4 as Fenton-like catalyst were evaluated, the influencing factors, such as the initial SMX concentration, initial pH, water matrix, and radical scavenger, etc. were examined. The results demonstrated that SMX could be efficiently degraded. The addition of Fe3O4 could improve the degradation efficiency of SMX and increased the dose constant at various SMX initial concentrations. More than 98% of SMX was degraded in Fe3O4/gamma radiation system at a wide range of pH (about 3.0-11.0). The mineralization of SMX in the presence of Fe3O4 was increased by 200%. Adding free radical scavenger (tert-butyl alcohol) inhibited the degradation of SMX. The addition of Fe3O4 enhanced the dose constant of ·OH, indicating that Fe3O4 promoted the formation of hydroxyl radicals (·OH) and then improved SMX degradation and mineralization. The degradation efficiency of SMX in secondary effluent of WWTP decreased from 100 to 84% in secondary effluent compared with that in deionized water. The intermediate products during the degradation of SMX by ionizing radiation were identified by high-performance liquid chromatography, and a possible pathway of SMX degradation in such a system was tentatively proposed. Graphical abstract Schema illustration of SMX degradation by irradiation in the presence of Fe3O4.
Keywords: Advanced oxidation processes; Antibiotics; Fenton reaction; Magnetite; Radiation; Sulfamethoxazole.