A biochar-based material offers a promising route for uranium recovery from seawater
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Synergistic adsorptive reduction for enhanced U(VI) recovery from seawater via Fe3S4-decorated biochar nanosphere hybrids
view moreCredit: Shijing Zhang, Shuang-Shuang Liu, Daiming Liu, Geyi Xu, Mengting Huang, Yuhui Zeng & Si Luo
\Researchers have developed a new biochar-based composite that can capture uranium from water while also converting part of it into a less toxic chemical form, offering a potential strategy for recovering uranium from seawater and supporting future nuclear energy resources.
Uranium is a key fuel for nuclear power, but land-based uranium reserves are unevenly distributed and limited. Seawater contains an enormous amount of dissolved uranium, estimated to be roughly 1,000 times greater than the reserves found in terrestrial ores. However, extracting uranium from seawater remains difficult because uranium occurs at very low concentrations and must be selectively separated from many competing ions.
In a new study published in Biochar, researchers report the design of a novel material called BN-PDA@Fe3S4. The material combines biochar nanospheres, a polydopamine coating, and iron sulfide Fe3S4. Together, these components create a hybrid adsorbent that can bind uranium efficiently and promote its chemical reduction.
“Seawater uranium extraction is a long-standing challenge because the material must be efficient, selective, stable, and practical for recovery,” said corresponding author Si Luo. “Our study shows that a biochar nanosphere platform decorated with Fe3S4 can not only adsorb U(VI), but also help convert part of it into less toxic U(IV), which is important for both resource recovery and environmental safety.”
The team synthesized the composite through a two-step method. First, biochar nanospheres were functionalized with polydopamine, a mussel-inspired material rich in active groups that can interact with metal ions. Then, Fe3S4 was grown on the surface to introduce iron and sulfur sites with strong affinity for uranium.
Laboratory tests showed that the composite achieved a maximum U(VI) adsorption capacity of 203.4 mg g⁻¹ at pH 5 and 298 K. The adsorption process followed the Langmuir isotherm model and pseudo-second-order kinetic model, indicating a monolayer chemisorption process. Thermodynamic analysis further showed that the adsorption was spontaneous and endothermic.
The material also performed well in more complex conditions. Tests with coexisting ions suggested that BN-PDA@Fe3S4 maintained strong uranium removal ability in the presence of several common ions, although carbonate and sulfate reduced performance by forming stable uranium complexes in solution. In natural seawater experiments, the composite reached a uranium extraction capacity of 4.5 mg g⁻¹ after 15 days.
A key finding of the study is the dual adsorption and reduction mechanism. Spectroscopic analyses showed that uranium was successfully immobilized on the composite surface. X-ray photoelectron spectroscopy revealed that part of the captured U(VI) was converted to U(IV). The researchers attributed this reduction to Fe(II) and S(-II) species in Fe3S4, while amino groups from the polydopamine layer also contributed to uranium binding. Density functional theory calculations supported the strong interaction between uranium species and the Fe3S4 surface.
The composite also showed magnetic separability, which could simplify recovery after use, and antibacterial activity against S. aureus and E. coli, suggesting potential resistance to biofouling in marine environments.
Although further optimization is needed to improve long-term cycling stability, the study presents a promising biochar-based platform for uranium recovery from seawater. By combining adsorption, reduction, magnetic recovery, and biofouling resistance, BN-PDA@Fe3S4 may provide a useful direction for future materials designed for sustainable nuclear fuel recovery and radionuclide pollution control.
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Journal Reference: Zhang, S., Liu, SS., Liu, D. et al. Synergistic adsorptive reduction for enhanced U(VI) recovery from seawater via Fe3S4-decorated biochar nanosphere hybrids. Biochar 8, 99 (2026).
https://doi.org/10.1007/s42773-026-00605-z
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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.
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Journal
Biochar
Method of Research
Experimental study
Article Title
Synergistic adsorptive reduction for enhanced U(VI) recovery from seawater via Fe3S4-decorated biochar nanosphere hybrids
Article Publication Date
8-May-2026
Iron minerals help decide whether dissolved organic matter becomes microbial food or long-term carbon
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Iron oxide fractionation alters the biodegradability of dissolved organic matter: molecular dynamics and microbial interactions
view moreCredit: Yuzhen Liang, Tongxin Liu, Zishan Cen & Zhenqing Shi
Dissolved organic matter, a complex mixture of carbon-containing molecules found in soils, rivers, lakes, wetlands, and sediments, plays a central role in how carbon moves through the environment. It can feed microbes, bind pollutants, influence nutrient availability, and affect how much carbon is stored or released as carbon dioxide. Yet scientists are still working to understand why some dissolved organic matter is quickly consumed by microbes, while other portions persist much longer.
A new study published in Carbon Research offers fresh insight into this question by showing how iron oxide minerals can reshape dissolved organic matter before microbes begin to break it down. The research focuses on goethite, a common iron oxide mineral found in soils and aquatic environments, and reveals that mineral adsorption does not simply remove organic matter from water. Instead, it selectively sorts organic molecules, changing what remains available for microbial degradation.
“Our study shows that minerals and microbes should not be treated as separate controls on dissolved organic matter,” said the study’s corresponding authors. “Iron oxides can first filter the molecular composition of organic matter, and this filtering process then influences which microbes become active and how fast carbon is transformed.”
The researchers extracted dissolved organic matter from forest soil and exposed it to goethite under two pH conditions, 4.5 and 6.5. They then incubated the original and mineral-fractionated samples with native soil microbes for 63 days. To track what happened, the team combined ultraviolet-visible spectroscopy, fluorescence spectroscopy, ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry, and 16S rRNA gene sequencing.
The results showed that goethite preferentially adsorbed aromatic, high-molecular-weight compounds, including lignin-like, tannin-like, and condensed aromatic molecules. These compounds are often more resistant to microbial degradation. In contrast, more biodegradable components, such as proteins, aliphatics, and some low-molecular-weight molecules, were enriched in the remaining solution. This effect was stronger at lower pH.
That mineral-driven sorting had major consequences for biodegradation. Dissolved organic matter fractionated at pH 6.5 showed the greatest overall degradation, with dissolved organic carbon loss reaching about 63.1 percent by Day 63. The pH 4.5 fractionated sample, however, degraded more rapidly at first, reaching about 52.4 percent loss by Day 49, before declining later as the easily degradable pool was depleted. The authors suggest that this later decline reflected microbial cell death and release of intracellular materials back into the solution.
The study also revealed a clear sequence in microbial feeding behavior. Microbial communities first consumed protein-like and lipid-like compounds, then shifted toward quinone-like molecules, and later made greater use of humic-like substances such as lignins. Different bacterial groups were linked to different types of organic matter. Gammaproteobacteria and Actinobacteria were mainly associated with degradation of labile protein-like and lipid-like fractions, while Alphaproteobacteria, Acidimicrobiia, Planctomycetes, and related groups became more important as humic-like compounds accumulated.
These findings are important because iron oxides are widespread in natural and engineered environments. By changing which organic molecules stay dissolved and which are removed, minerals may influence whether carbon is rapidly respired by microbes, transported through water, or stabilized for longer periods.
The study provides a more detailed molecular picture of how mineral surfaces and microbial communities work together to regulate carbon cycling. It may help improve predictions of carbon fate in iron-rich soils, wetlands, sediments, and water treatment systems, especially under changing pH conditions.
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Journal reference: Liang, Y., Liu, T., Cen, Z. et al. Iron oxide fractionation alters the biodegradability of dissolved organic matter: molecular dynamics and microbial interactions. Carbon Res. 5, 28 (2026).
https://doi.org/10.1007/s44246-026-00272-6
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About Carbon Research
The journal Carbon Research is an international multidisciplinary platform for communicating advances in fundamental and applied research on natural and engineered carbonaceous materials that are associated with ecological and environmental functions, energy generation, and global change. It is a fully Open Access (OA) journal and the Article Publishing Charges (APC) are waived until Dec 31, 2025. It is dedicated to serving as an innovative, efficient and professional platform for researchers in the field of carbon functions around the world to deliver findings from this rapidly expanding field of science. The journal is currently indexed by Scopus and Ei Compendex, and as of June 2025, the dynamic CiteScore value is 15.4.
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Journal
Carbon Research
Method of Research
Experimental study
Article Title
Iron oxide fractionation alters the biodegradability of dissolved organic matter: molecular dynamics and microbial interactions
Article Publication Date
1-May-2026
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