Phosphorus‐Modified Siderite/nZVI Composite for Peroxymonosulfate Activation and Sulfamethoxazole Degradation in Groundwater

ABSTRACT

Sulfamethoxazole (SMX) contamination in groundwater has attracted increasing concern because of its potential ecological risks. In this study, a phosphorus‐modified siderite/nanoscale zero‐valent iron composite (P@FFC) was developed for peroxymonosulfate (PMS) activation and SMX degradation in real groundwater. Under the standard conditions of an initial SMX concentration of 5 mg L ⁻¹ , a PMS concentration of 4 mM, a P@FFC dosage of 0.6 g L ⁻¹ , an initial pH of 5.0, and a temperature of 25°C, 98.34% SMX removal was achieved within 4 min. The apparent rate constant increased from 0.0122 min ⁻¹ for FFC/PMS to 0.887 min ⁻¹ for P@FFC/PMS. A TOC removal of 60.49% was achieved within 35 min, indicating substantial mineralization. Characterization and DFT calculations suggested that phosphorus modification regulated the catalyst interface by increasing surface roughness, introducing P–O‐containing surface species, and promoting PMS adsorption. ROS analyses revealed coupled radical and nonradical pathways. SO ₄ ^•− was the major radical species, while ^• OH and ¹ O ₂ were also involved and O ₂ ^•− played a limited role. Rapid SMX degradation was also retained in unadjusted groundwater. Although catalytic activity declined during repeated use, Fe and P leaching remained limited. NaBH ₄ treatment partially restored the activity of used P@FFC. These results provide insight into phosphorus‐mediated interfacial regulation during PMS activation and support the potential of P@FFC for groundwater remediation.