Perfluorooctane sulfonate, or PFOS, is one of the most persistent members of the PFAS family of "forever chemicals." Widely detected in groundwater, surface water, and drinking water sources, PFOS is difficult to remove because of its extremely strong carbon-fluorine bonds and high chemical stability. Now, researchers have developed a new biochar-based material that not only captures PFOS from water, but also helps destroy it through light-driven reactions.
In a new study published in Biochar, a research team led by Prof. Yanyan Gong from Jinan University and Prof. Dongye Zhao from San Diego State University reports a novel β-Ga₂O₃-functionalized biochar, called Ga₂O₃@biochar, designed for a practical "concentrate and destroy" approach. The material first adsorbs PFOS from water, concentrating the pollutant onto its surface, and then uses ultraviolet light to trigger photocatalytic degradation of the captured PFOS.
"PFOS is especially challenging because many technologies can separate it from water, but they do not truly destroy it," said Prof. Gong. "Our goal was to design a material that could combine strong adsorption with efficient photodegradation, reducing the need for chemical regeneration and minimizing secondary waste."
The team prepared the material by integrating β-Ga₂O₃, a stable semiconductor photocatalyst, into a porous biochar matrix derived from wheat straw. Among the materials tested, the composite containing 1% gallium showed the best overall performance. The incorporation of β-Ga₂O₃ altered the pore structure and electronic properties of biochar, increasing mesoporosity, improving light absorption, narrowing the bandgap, and promoting charge separation.
These changes translated into strong PFOS removal and degradation. The optimized material achieved more than 99% PFOS adsorption within 30 minutes under tested conditions. After the PFOS was pre-concentrated on the material, 80.8% of the adsorbed PFOS was photodegraded within 8 hours of UV irradiation, with 70.5% defluorination, indicating substantial cleavage of carbon-fluorine bonds.
The researchers also used density functional theory calculations to understand why the composite worked so effectively. The calculations showed that electrons could transfer efficiently from biochar to β-Ga₂O₃, helping separate photogenerated charge carriers and enhancing photocatalytic reactions. Experiments further identified photogenerated electrons, superoxide radicals, and singlet oxygen as the major reactive species driving PFOS breakdown.
"The biochar does more than serve as a support," said Prof. Zhao. "It helps concentrate PFOS near the photocatalytic sites and participates in electronic interactions that improve degradation efficiency. This synergy is central to the material's performance."
Mechanistic analysis suggested that PFOS degradation followed a stepwise chain-shortening pathway, beginning with desulfonation and followed by decarboxylation and progressive defluorination. Importantly, the photodegradation process also regenerated the adsorbent, allowing the material to be reused through multiple adsorption and photodegradation cycles.
The material also showed promising performance in real groundwater, although the authors note that natural water chemistry can influence treatment efficiency. Future studies will focus on testing the technology under more complex environmental conditions, assessing degradation byproducts, evaluating economic and environmental impacts, and expanding the approach to other PFAS compounds.
"This study provides a promising pathway toward sustainable PFAS treatment," Prof. Gong said. "By combining adsorption, photocatalytic destruction, and photoregeneration in one material, Ga₂O₃@biochar may help move PFAS remediation from simple separation toward actual contaminant destruction."
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Journal Reference: Gong, Y., Lin, D., Liu, Y. et al. Promoted sequestration and photo-induced destruction of perfluorooctane sulfonate using photoregenerable β-Ga2O3-functionalized biochar: superior defluorination and mechanistic insights. Biochar 8, 120 (2026).
https://doi.org/10.1007/s42773-026-00642-8
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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.
