Constructing a heterogenous catalyst β-FeOOH@ZnO for effective sulfadimethoxine elimination with peroxymonosulfate activation: Non-radical dominance

The residues of sulfonamide antibiotics in the environment would pose a threat to aquatic ecosystem and human health. In this study, β-FeOOH@ZnO was synthesized by using a hydrothermal method to activate peroxymonosulfate (PMS) for the degradation of the typical sulfonamide antibiotic sulfadimethoxine (SDM), in which 98.89 % of SDM was removed in 60 min with activating 0.5 mM PMS. Moreover, the influence of catalyst dosage, PMS dosage, solution pH and anions on the degradation efficiency of SDM was investigated in the system. The results indicated that the material exhibited good applicability and β-FeOOH@ZnO performed well in a wide pH range (5–11). ${}^1{O}_2$ was the major reactive oxygen species (ROS) rather than $\dot{}\mathrm{OH}$, $S{O}_4^{\dot{}-}$ and $O_2^{\dot{}-}$ through free radical quenching experiments and electron paramagnetic resonance experiments (EPR). Furthermore, the mechanism was found that ZnO could enhance the electron transfer pathway of β-FeOOH, which accelerated the degradation of SDM. Possible intermediate products and degradation pathways were proposed through LC-MS analysis. In summary, this study offered a new strategy for the efficient degradation of sulfonamide antibiotics in water treatment.