Marine biomass turns into a powerful green catalyst for antibiotic wastewater cleanup

By converting κ-carrageenan—a naturally sulfur-rich polysaccharide extracted from red algae—into a nitrogen- and sulfur-codoped porous carbon, the researchers achieved rapid and highly selective degradation of norfloxacin, a widely used fluoroquinolone antibiotic. The catalyst eliminates over 97% of the pollutant within 90 minutes while avoiding toxic metal additives, offering a greener and more practical solution for antibiotic wastewater treatment.

Antibiotics are essential in medicine and animal husbandry, yet their widespread and often uncontrolled release into water bodies has raised serious environmental and public-health concerns. Norfloxacin is a representative example, as it is persistent, poorly biodegradable, and toxic, promoting antibiotic resistance and long-term ecological risks. Conventional wastewater treatments are largely ineffective against such refractory pollutants. Peroxymonosulfate (PMS)–based advanced oxidation processes can degrade stable organic molecules, but many rely on metal catalysts or energy-intensive methods that increase costs, risk secondary pollution, and limit durability. Carbon-based catalysts provide a promising alternative; however, materials such as graphene and carbon nanotubes are costly and difficult to scale. Biomass-derived carbon is renewable and economical, but typically requires further modification to achieve sufficient catalytic activity.

A study (DOI:10.48130/bchax-0025-0012) published in Biochar X on 10 December 2025 by Dongjiang Yang’s & Bin Hui’s team, Qingdao University, demonstrates a green and scalable strategy to transform sulfur-rich marine biomass into a high-performance, metal-free carbon catalyst that enables efficient, selective, and robust non-radical degradation of persistent antibiotic pollutants in water.

Using κ-carrageenan as a renewable dual source of carbon and sulfur, melamine as a nitrogen precursor, and K₂CO₃ as a pore-forming activator, the researchers developed and evaluated biomass-derived carbon catalysts to address the low activity and sustainability issues of conventional PMS activators. Three materials—SC-700 (direct carbonization), SPC-700 (K₂CO₃ activation), and NSPC-700 (K₂CO₃ activation with N,S codoping)—were systematically characterized by SEM/EDS, Raman spectroscopy, N₂ adsorption–desorption, and XPS, followed by catalytic tests for norfloxacin (NOR) degradation. Structural analyses revealed that K₂CO₃ activation converted smooth, nonporous SC-700 into SPC-700 with abundant interconnected micro- and mesopores, while NSPC-700 preserved this hierarchical porous architecture after nitrogen doping, increasing the surface area from 23.58 to 1,219.31 m² g⁻¹ and pore volume from 0.022 to 0.87 cm³ g⁻¹. Raman and XPS results showed pronounced defect enrichment and the formation of stable graphitic N and thiophenic S species, which increased up to a pyrolysis temperature of 700 °C and acted as synergistic active sites for PMS activation. In degradation experiments, PMS alone removed only 15.59% of NOR, whereas SPC-700 and NSPC-700 achieved 80.69% and 97.16% removal, respectively, confirming the strong N–S synergy. NSPC-700 prepared at 700 °C with a κ-carrageenan/melamine ratio of 2:1 exhibited the highest reaction rate constant (Kobs = 0.0403 min⁻¹) and nearly 50% total organic carbon mineralization within 90 min. Despite partial inhibition under extreme pH conditions or in the presence of coexisting anions, the system maintained over 66% NOR removal in complex water matrices. Continuous-flow and cycling tests demonstrated practical robustness, sustaining ~89% removal over 5 h and retaining more than 90% efficiency after five reuse cycles. Mechanistic investigations using quenching, EPR, and electrochemical analyses showed that degradation was dominated by non-radical pathways, with singlet oxygen and electron transfer contributing over 84%, explaining the catalyst’s high selectivity, stability, and resistance to interference.

In conclusion, this study presents a sustainable, metal-free N,S-codoped porous carbon catalyst derived from sulfur-rich marine biomass for efficient antibiotic degradation. NSPC-700 combines high activity, durability, and resistance to water-matrix interference, achieving robust norfloxacin removal through dominant non-radical pathways. Its strong performance under continuous-flow and reuse conditions highlights its promise for practical antibiotic wastewater treatment applications.

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References

DOI

10.48130/bchax-0025-0012

Original Source URL

https://doi.org/10.48130/bchax-0025-0012

Funding information

The authors are grateful to financial support by Excellent Youth Foundation of Shandong Province (Grant No. ZR2022YQ22), National Natural Science Foundation of China (Grant Nos 32571960 and 32101451), and the Youth Innovation Team Project of Shandong Province (Grant No. 2022KJ303).

About Biochar X

Biochar X is an open access, online-only journal aims to transcend traditional disciplinary boundaries by providing a multidisciplinary platform for the exchange of cutting-edge research in both fundamental and applied aspects of biochar. The journal is dedicated to supporting the global biochar research community by offering an innovative, efficient, and professional outlet for sharing new findings and perspectives. Its core focus lies in the discovery of novel insights and the development of emerging applications in the rapidly growing field of biochar science.