Flash-Heated iron–carbon catalyst rapidly breaks down persistent antibiotics in water and soil

The catalysts generate abundant hydroxyl radicals (•OH) without requiring added chemical oxidants, enabling the breakdown of the antibiotic sulfamethoxazole (SMX) with up to 94.6% removal efficiency. The materials remain effective across a wide pH range and even in complex soil environments, offering a scalable and environmentally friendly solution for treating emerging contaminants.

Antibiotics and other persistent organic pollutants increasingly contaminate aquatic and terrestrial environments, demanding more sustainable and high-efficiency treatment technologies. Hydroxyl-radical-based advanced oxidation processes (AOPs) are among the most powerful remediation methods, yet traditional systems rely heavily on external oxidants such as H₂O₂, which impose cost, handling, and selectivity constraints. Iron-based catalysts that activate O₂ directly offer a greener alternative, but their performance depends on maintaining abundant Fe⁰/Fe²⁺ species and rapid electron transfer—conditions that are difficult to achieve using conventional pyrolysis or chemical synthesis. These limitations often lead to poor graphitization, low catalyst stability, and restricted pollutant removal efficiency. Due to these persistent bottlenecks, there is a need to develop catalysts that can efficiently activate oxygen and support multiple oxidation pathways for real-world pollution control.

A study (DOI: 10.48130/scm-0025-0006) published in Sustainable Carbon Materials on 27 October 2025 by Xiangdong Zhu’s team, Fudan University, provides the mechanistic understanding and structural design principles needed to advance next-generation AOPs.

The researchers first synthesized Fe/C composite catalysts by subjecting a precursor of FeCl₃, biochar, and carbon black to flash Joule heating (FJH), where transient, high currents rapidly raised the temperature to ~4,000 K. They systematically characterized the resulting materials using electron microscopy, HAADF imaging, element mapping, XRD, XPS, and Raman spectroscopy to track structural and redox evolution, and then evaluated catalytic performance by monitoring SMX degradation in oxygenated and anoxic systems, with and without radical quenchers, over a range of voltages, pH values, and catalyst dosages. Further tests in soil matrices, along with electron paramagnetic resonance (EPR) spectroscopy and radical-quenching experiments (using methanol, SOD, and catalase), were employed to identify reactive oxygen species (ROS) and clarify oxygen activation pathways, while dissolved Fe²⁺/Fe³⁺ dynamics were monitored to link iron speciation with •OH production and SMX removal. These methods revealed uniformly dispersed, ~34 nm Fe nanoparticles embedded in a partially graphitized carbon matrix, rich in Fe⁰ and Fe²⁺ and coated by few-layer graphene, which enhanced electrical conductivity and structural stability. The optimized Fe/C-250V catalyst achieved 94.6% SMX removal in 4 h in the O₂ system, with •OH as the dominant oxidant and superoxide (O₂•⁻) providing auxiliary oxidation pathways; both •OH production and removal efficiency decreased sharply under anoxic conditions or in the presence of quenchers. Higher synthesis voltages and catalyst dosages yielded greater •OH concentrations and up to 99.9% SMX removal, while the material maintained high activity across a broad pH range and remained effective, though partially inhibited, in soil. EPR and quenching experiments confirmed a stepwise O₂ → O₂•⁻ → H₂O₂ → •OH pathway, with O₂•⁻ and H₂O₂ acting as crucial intermediates, and a strong correlation between dissolved Fe species, cumulative •OH, and SMX degradation, demonstrating that •OH-driven oxidation is the primary mechanism in this Fe/C-based advanced oxidation system.

The new flash-heated Fe/C composite offers a green, low-chemical-input strategy for removing pharmaceuticals, antibiotics, and other toxic organic pollutants from wastewater and contaminated soils. Because the catalyst activates oxygen directly, it reduces reliance on chemical oxidants. The material’s high stability, strong radical production, and ability to function in variable pH and heterogeneous soil environments highlight its practical value for scalable environmental remediation.

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References

DOI

10.48130/scm-0025-0006

Original Source URL

https://doi.org/10.48130/scm-0025-0006

Funding information

This work was supported by the National Natural Science Foundation of China (Grant No. 22276040).

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Sustainable Carbon Materials is a multidisciplinary platform for communicating advances in fundamental and applied research on carbon-based materials. It is dedicated to serving as an innovative, efficient and professional platform for researchers in the field of carbon materials around the world to deliver findings from this rapidly expanding field of science. It is a peer-reviewed, open-access journal that publishes review, original research, invited review, rapid report, perspective, commentary and correspondence papers.