The oceans hold an enormous amount of very diluted uranium that could potentially serve as a sustainable fuel source for nuclear power. But how can uranium be extracted quickly and efficiently from seawater?
Balancing high selectivity for uranium ions with rapid transport of those ions has long been a major challenge in obtaining uranium from the sea. Now, however, a groundbreaking study suggests a solution.
A research team led by Prof. WEN Liping from the Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences has developed a biomimetic adsorbent that can attract and hold uranium ions. The inspiration for this adsorbent is the natural porous structure of the spiky, globular fruit of the Chinese sweet gum tree, Liquidambar formosana. The team's findings were recently published in Matter.
Traditional framework-based adsorbents-those with regular, structured, and often crystalline architecture-can precisely position functional groups on their pore surfaces to create nanoscale "traps" that capture specific metal ions, such as uranium. However, nano-traps engineered to precisely fit uranium ions may instead cause self-blockage due to steric hindrance, thus limiting ion transport and reducing the overall efficiency of uranium capture.
To address this, Prof. WEN's team studied the hierarchical structure of Liquidambar formosana fruit, which features radial macropores and a lignin fiber network. This design allows substances to move from the pore surface to the core in just 0.3 seconds. Inspired by this efficient natural mechanism, the researchers developed a spherical adsorbent material incorporating similar hierarchical channels, effectively mitigating blockage and enhancing ion transport.
Experimental and theoretical studies demonstrated that the biomimetic hierarchical structure significantly enhanced ion diffusion into the interior of adsorbents, increasing uranium adsorption capacity by up to 213%.
The researchers further discovered that controlling the soft-template size used during synthesis allows fine-tuning of pore density and pore-wall thickness, directly influencing adsorption performance-a finding confirmed by numerical simulations.
Tests conducted in real seawater showed that this hierarchical adsorbent demonstrated exceptional selectivity for uranium, effectively outperforming common competitive ions such as vanadium and iron, and achieving a 150% improvement in adsorption capacity compared to adsorbents without hierarchical microstructures.
The results highlight the power of nature-inspired engineering in addressing critical resource-recovery challenges.
This work was supported by the National Key R&D Program of China, the National Natural Science Foundation of China, and the China Postdoctoral Science Foundation.
Schematic illustration of the bio-inspired design strategy for hierarchical porous adsorbents. (Image by WEN's Group)
