Modified biochar boosts pollutant removal by unlocking hidden free radicals
image: Collaborative modification strategy to improve the formation of biochar-derived persistent free radicals for aniline removal via peroxymonosulfate activation
Credit: Zilong Zhao, Shuting Zhu, Shuyu Qi, Ting Zhou, Yang Yang, Feng Wang, Qi Han, Wenyi Dong, Hongjie Wang & Feiyun Sun
A new study reveals how engineered biochar can dramatically improve the removal of toxic pollutants from water by harnessing the power of persistent free radicals. The research offers a promising pathway for developing low cost, high efficiency materials for environmental cleanup.
Biochar, a carbon rich material made from biomass such as agricultural waste, has long been studied for its ability to remove contaminants. However, its performance is often limited by a lack of active sites and inefficient catalytic behavior. In this new work, researchers developed a collaborative modification strategy that enhances the formation of persistent free radicals on biochar surfaces, significantly improving its reactivity.
“Our goal was to better understand how to control the formation of persistent free radicals and use them to drive pollutant degradation,” said the study’s lead author. “By tailoring the biochar structure, we were able to achieve much higher efficiency than traditional materials.”
The team used corncob biomass and introduced nitrogen containing compounds together with sodium carbonate during pyrolysis. By carefully adjusting temperature and composition, they created a modified biochar with a high concentration of persistent free radicals. These radicals are stable, long lived species that can transfer electrons and activate oxidants, making them highly effective for breaking down pollutants.
The optimized material, produced at 500 degrees Celsius, showed outstanding performance. When combined with peroxymonosulfate, a common oxidant, the system removed up to 92 percent of aniline, a toxic industrial chemical, within just 30 minutes. This level of efficiency represents a significant improvement compared to unmodified biochar.
Importantly, the study demonstrates that pollutant removal occurs through two complementary pathways. First, persistent free radicals can directly oxidize contaminants. Second, they activate the oxidant to generate reactive oxygen species such as superoxide radicals, which further degrade pollutants. Among these, superoxide was identified as the dominant species responsible for degradation.
The researchers also uncovered key factors that control radical formation. Structural features such as aromatic carbon bonds, defect density, and specific nitrogen configurations were found to play critical roles. In particular, pyridinic nitrogen sites were strongly linked to higher radical concentrations and improved catalytic performance.
Beyond efficiency, the material showed good stability under different water conditions, including the presence of common ions. Although performance gradually decreased after repeated use due to loss of active sites, the system maintained substantial activity after multiple cycles, highlighting its practical potential.
This work provides new insights into how biochar can be engineered at the molecular level to enhance its environmental performance. By linking structure, chemistry, and reactivity, the study offers a roadmap for designing next generation carbon based catalysts.
The findings are especially relevant for water treatment applications, where removing persistent organic pollutants remains a major challenge. With further development, such materials could contribute to scalable and sustainable solutions for wastewater remediation.
“Our study shows that biochar is more than just a passive adsorbent,” the author added. “It can be transformed into a highly active catalyst by controlling its chemistry. This opens up exciting opportunities for environmental technologies.”
The research highlights the growing potential of biochar based materials as versatile tools for pollution control, combining low cost feedstocks with advanced functional design.
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Journal Reference: Zhao, Z., Zhu, S., Qi, S. et al. Collaborative modification strategy to improve the formation of biochar-derived persistent free radicals for aniline removal via peroxymonosulfate activation. Biochar 7, 24 (2025).
https://doi.org/10.1007/s42773-024-00416-0
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About Biochar
Biochar (e-ISSN: 2524-7867) 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.