Study reveals how nitrogen atmosphere enhances performance of iron-biochar catalysts in wastewater treatment

A recent study published in Biochar demonstrates that the atmosphere used during ball milling plays a critical role in determining the effectiveness of iron-biochar composites for degrading organic pollutants in water. The research, conducted by a team from Hebei University of Technology and Nankai University, shows that composites prepared under a nitrogen atmosphere exhibit superior catalytic performance compared to those milled in air or vacuum.

Ball milling is a widely used technique for modifying materials to enhance their environmental applications. However, most studies have focused on optimizing mechanical parameters, while the influence of the milling atmosphere has remained underexplored. This study systematically investigates how different atmospheres—air, nitrogen, and vacuum—affect the properties and reactivity of siderite-biochar composites (BM-SD/BCs).

The team found that the composite milled under nitrogen (N/BM-SD/BC) achieved a phenol removal rate of 90.3% within 120 minutes when used to activate persulfate (PS), a common oxidant. This was significantly higher than composites milled in air (73.8%) or vacuum (81.3%). The nitrogen atmosphere helped preserve reduced iron species (Fe(II)), which are crucial for activating PS to generate sulfate and hydroxyl radicals that break down pollutants.

Characterization revealed that the nitrogen-milled composite had a smaller particle size, larger specific surface area (187.6 m² g⁻¹), and more uniform distribution of iron and functional groups. These properties enhanced electron transfer and provided more active sites for reaction.

The system also showed strong performance across a wide pH range, including conditions typical of real wastewater, highlighting its potential for practical use. Radical quenching experiments confirmed that hydroxyl radicals (·OH) and superoxide radicals (O₂·⁻) were the primary reactive species, contributing 50.7% and 25.3% to phenol degradation, respectively.

“This work underscores the importance of controlling the ball milling atmosphere to tailor material properties for environmental catalysis,” said Dr. Honghong Lyu, corresponding author of the study. “Using nitrogen during milling helps maintain high Fe(II) content and functional group integrity, leading to more efficient pollutant degradation.”

The study provides new insights into the design of high-performance catalysts for advanced oxidation processes and supports the application of ball-milled composites in real-world water treatment scenarios.

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Reference: Zhang, H., Cheng, Z., Hu, K. et al. Atmosphere regulation: unraveling effective strategies for creating high-performance iron ore/biochar composite nanomaterials in ball milling processes. Biochar 7, 82 (2025). https://doi.org/10.1007/s42773-025-00474-y

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Media Contact:
Wushuang Li
liwushuang@vip.126.com

About Biochar

Biochar is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field. 

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