Fe_1-xS@BC prepared from natural pyrite and biomass as peroxydisulfate activator for sulfadiazine degradation

The efficient degradation of SAs is a significant challenge for the treatment of wastewater. To address this, the Fe_1-xS@BC was prepared by calcining a mixture of pyrite and biomass, and used to activate peroxydisulfate (PDS) to degrade sulfadiazine (SDZ). The effect of carbon sources (wheat straw, rice husk, and corn cob) on catalytic activity of Fe_1-xS@BC were investigated by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), total Fe dissolution and free radical quantification. The results indicate that Fe_1-xS@WBC with carbon defects and oxygenated functional groups facilitate the dissolution of Fe and the generation of ·OH and ·SO₄^-. Additionally, the electron-rich the thiophene S facilitate the regeneration of Fe(II). In the Fe_1-xS@WBC/PDS system, 90.3% of SDZ degradation could be achieved under optimal conditions: Fe_1-xS@WBC = 0.5 g∙L^-1, SDZ = 10 mg∙L^-1, PDS = 2.0 mM, initial solution pH = 7.0. In addition, Fe_1-xS@WBC/PDS system exhibits strong resistance to interference from Cl^-, and NO₃^-, while elevated concentrations of HCO₃^-, HPO₄^2-, and HA hinder SDZ degradation. The Fe_1-xS@WBC/PDS system shows excellent selectivity and recoverability. Quenching experiments and electron spin resonance (ESR) reveal the involvement of ·OH, ·SO₄^-, and ¹O₂ in the degradation of SDZ within Fe_1-xS@WBC/PDS system. Furthermore, four possible degradation pathways for SDZ were proposed based on density functional theory (DFT) and liquid chromatography-mass spectrometry (LC-MS) analysis, while assessing the toxicity of degradation intermediates. This study not only introduces a novel catalytic system for the efficient degradation of antibiotic-contaminated wastewater, but also provides a theoretical foundation for the development and application of iron sulfide-biomass composite catalysts.