A heterogeneous domain-limited core–shell Fe3O4@C UV–Fenton system for mixed antibiotics degradation: insights into the synergistic effect and mechanisms

The discharge of antibiotics into the environment has emerged as a pressing global issue. In particular, the removal of refractory mixed antibiotics requires advanced technologies with high adsorption efficiency and powerful degradation ability. In this study, we synthesized a heterogeneous core–shell Fe3O4@C catalyst as an efficient microreactor for adsorbing and degrading mixed antibiotics of sulfadimidine (SM2) and enrofloxacin (ENR) in aqueous solution under UV–Fenton conditions. The effects of different experimental conditions on the removal of antibiotics were investigated through L9(43) orthogonal experiments, and the synergistic effect and degradation mechanisms were systematically revealed. The results showed that the Fe3O4@C Fenton system demonstrated significantly enhanced catalytic activity, with hydroxyl radical (OH˙) concentrations of approximately 6.2 and 6.7 times higher than those observed in the Fe3O4 and Fe3O4 + AC Fenton systems, respectively. Moreover, the degradation pathway and mechanism analysis revealed that the adsorption and degradation behavior of the two mixed antibiotics in the Fe3O4@C Fenton system could be better described using pseudo-secondary kinetic models. The substantial improvement clearly indicates that the Fe3O4@C composite serves as a highly efficient microreactor for H2O2 decomposition in the Fenton process, thus providing a new avenue for the degradation of mixed antibiotics in water.