Key Takeaways & Executive Findings
- •• • B-BC@Fe3S4 and N-BC@Fe3S4 achieved ENR removal efficiencies of 90.72% and 91.89%, respectively, representing 10.4% and 11.8% relative improvements over unmodified BC@Fe3S4 (82.21%), indicating that heteroatom doping significantly enhances catalytic activity for PDS activation. • • N-BC@Fe3S4 exhibited superior resistance to Fe3+ leaching compared to B-BC@Fe3S4, reducing secondary pollution risk and enhancing catalyst stability for repeated use in wastewater treatment. • • Mechanistic analysis identified both radical (SO4•−, •OH, O2•−) and non-radical (1O2) pathways contributing to ENR degradation, with B/N functional groups facilitating non-radical oxidation, broadening the applicability to complex water matrices. • • N-BC@Fe3S4 demonstrated stronger environmental adaptability, maintaining high degradation efficiency across varying pH, anion, and humic acid conditions, outperforming B-BC@Fe3S4 in resistance to interference, which is critical for real-world wastewater applications.
Abstract
Rice husk biochar (BC) was modified with boron (B) and nitrogen (N) doping and loaded with Fe3S4 to fabricate B-BC@Fe3S4 and N-BC@Fe3S4 catalysts for peroxydisulfate (PDS) activation and enrofloxacin (ENR) degradation. Characterization via SEM, BET, XRD, Raman, and XPS confirmed successful heteroatom incorporation and uniform Fe3S4 dispersion, enhancing specific surface area and defect sites. Degradation experiments showed that B-BC@Fe3S4 and N-BC@Fe3S4 achieved ENR removal efficiencies of 90.72% and 91.89%, respectively, significantly outperforming unmodified BC@Fe3S4 (82.21%). Mechanistic studies revealed that PDS activation proceeded via Fe3S4-mediated electron transfer generating radical species (SO4•−, •OH, O2•−) and via B/N functional groups promoting non-radical singlet oxygen (1O2) formation. Notably, N-BC@Fe3S4 exhibited superior resistance to Fe3+ leaching and greater environmental adaptability under varying pH, anion, and humic acid conditions. These findings demonstrate that B/N-doped biochar-supported Fe3S4 are effective catalysts for PDS activation, offering promising potential for antibiotic removal from real wastewater matrices.
1. Introduction
Antibiotic contamination in aquatic environments poses a significant threat to ecosystems and human health, primarily due to the incomplete metabolism of antibiotics in humans and animals, with 50-90% excreted as active compounds. Conventional treatment methods such as adsorption, ozonation, and photocatalysis often suffer from limitations including secondary pollution, high energy consumption, or incomplete mineralization. Advanced oxidation processes (AOPs) based on sulfate radicals (SO4•−) have emerged as a promising alternative due to their high redox potential (2.5-3.1 eV), longer half-life (30-40 µs), and wide pH applicability. However, the practical deployment of SO4•−-based AOPs is constrained by the high cost of activators and the tendency of iron-based catalysts to agglomerate, reducing active site exposure and catalytic efficiency.
This study addresses these bottlenecks by developing biochar-supported Fe3S4 catalysts with boron or nitrogen doping. Rice husk biochar provides a porous scaffold that disperses Fe3S4 nanoparticles, mitigating agglomeration, while heteroatom doping introduces defects and functional groups that enhance electron transfer and PDS activation. The resulting B-BC@Fe3S4 and N-BC@Fe3S4 catalysts achieve significantly higher ENR degradation efficiencies (90.72% and 91.89%) compared to undoped BC@Fe3S4 (82.21%), with N-BC@Fe3S4 also demonstrating superior resistance to Fe3+ leaching and environmental adaptability. These findings offer a cost-effective and efficient catalytic system for antibiotic removal from real wastewater, addressing key limitations of existing technologies.
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LIU Lei, ZHENG Tianyu, WANG Yimeng, ZHENG Hao, GAO Yifan, XIE Yulin, CHANG Qing, XING Xuan (2026). Comparative Effectiveness and Mechanism of Antibiotic Degradation by B/N-Doped Biochar-Supported Fe3S4 Activating Peroxydisulfate. Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2025042502
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Frequently Asked Questions
What is the specific contribution of B/N doping to the enhanced catalytic activity of Fe3S4-loaded biochar in PDS activation?
B/N doping increases the specific surface area and defect sites of the biochar, as confirmed by BET and Raman analyses. These defects serve as active centers for PDS adsorption and activation. Additionally, B/N functional groups facilitate the generation of non-radical reactive species (1O2), while Fe3S4 promotes radical formation via electron transfer. This dual pathway enhances overall degradation efficiency, with B-BC@Fe3S4 and N-BC@Fe3S4 achieving 90.72% and 91.89% ENR removal, respectively, compared to 82.21% for undoped BC@Fe3S4.
How does N-BC@Fe3S4 exhibit superior resistance to Fe3+ leaching compared to B-BC@Fe3S4, and what are the implications for long-term stability?
N-BC@Fe3S4 showed lower Fe3+ leaching during the reaction, as indicated by iron dissolution measurements. This is likely due to stronger coordination between nitrogen functional groups and iron ions, stabilizing the Fe3S4 structure. Reduced Fe3+ leaching minimizes secondary pollution and catalyst deactivation, enhancing reusability and operational lifespan in continuous wastewater treatment systems.
What are the dominant reactive species responsible for ENR degradation, and how do they differ between B-BC@Fe3S4 and N-BC@Fe3S4?
EPR and quenching experiments identified SO4•−, •OH, O2•−, and 1O2 as the main reactive species. Both catalysts generate radicals via Fe3S4-mediated electron transfer and non-radical 1O2 via B/N functional groups. However, N-BC@Fe3S4 exhibited a higher contribution from non-radical pathways, which are less affected by background anions and natural organic matter, explaining its superior environmental adaptability.
How do solution pH, anions, and humic acid affect the degradation efficiency of ENR by these catalysts?
The degradation efficiency of ENR was influenced by solution pH, anions, and humic acid. N-BC@Fe3S4 demonstrated stronger resistance to these interferences, maintaining high removal rates across a wider pH range and in the presence of common anions (e.g., Cl−, NO3−, HCO3−) and humic acid. This robustness is attributed to the enhanced non-radical pathway, which is less susceptible to scavenging by background constituents.
What is the practical feasibility of scaling up B/N-doped biochar-supported Fe3S4 for real wastewater treatment?
The catalysts are synthesized from low-cost rice husk biochar and inexpensive precursors (FeSO4·7H2O, boric acid, urea), making them economically viable. Their high degradation efficiencies (90.72% and 91.89%) and stability, particularly N-BC@Fe3S4 with low iron leaching, suggest potential for scalable application. However, further studies on continuous-flow reactors, long-term stability, and treatment of real wastewater matrices are needed to assess full-scale feasibility.
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