Chinese Research Team Develops Novel Adsorbent Material for Uranium Extraction from Seawater

On September 2, it was learned from the Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences (hereinafter referred to as "QIBEBT") that the research team has recently made a series of advances in the field of uranium extraction materials from seawater. The team introduced discrete molecular topological design into porous organic cage systems for the first time, synthesizing the phosphate-functionalized material PhosCage, and further compounded it with aramid nanofibers to prepare composite aerogel microspheres AC-POC possessing high selectivity, high capacity, and anti-biofouling capability. The relevant results were published in the international academic journals Journal of Hazardous Materials and Separation and Purification Technology.

The deep ocean harbors a vast "uranium reservoir," yet how to economically and efficiently "prospect for uranium" from it remains a worldwide challenge. Uranium in seawater primarily exists in the form of uranyl ions, with extremely low concentrations and accompanied by large quantities of other metal ions and microorganisms. Traditional adsorbent materials often "grab the wrong targets" or become hindered by microbial attachment. Therefore, developing adsorbent materials with high selectivity, high capacity, and anti-fouling resistance is key to making uranium extraction from seawater practically viable.

The QIBEBT team proposed a discrete molecular topological design strategy, constructing oriented phosphate adsorption clusters within the interlayer nanospace of porous organic cages, and prepared the first phosphate-functionalized porous organic cage material — PhosCage. Under laboratory conditions, PhosCage achieves adsorption equilibrium in just 5 minutes; in real seawater samples from multiple sea areas, its maximum uranium extraction capacity reaches 50.4 mg/g, which is 8.4 times the relevant benchmark set by the U.S. Department of Energy.

To enable the practical application of this material in marine engineering, challenges such as the difficulty of deploying powder materials and microbial attachment must also be addressed. To this end, the team compounded PhosCage with aramid nanofibers, and through the synergy of physical entanglement and chemical cross-linking locking, scaled up the preparation of dual-network composite aerogel microspheres AC-POC. The microspheres feature interconnected pore channels internally, and the interwoven phosphate groups and carboxyl groups within construct a powerful synergistic electron-donating coordination environment, effectively lowering the coordination energy barrier for uranyl ions — that is, the energy threshold that must be crossed before a chemical reaction occurs. This makes the capture reaction more readily achievable, thereby enhancing the capture efficiency of uranyl ions.

Research shows that in multi-ion competitive systems, AC-POC exhibits high selectivity; after 15 days of continuous operation in natural seawater, its dynamic uranium extraction capacity reaches 22.55 mg/g, achieving 3.8 times the relevant benchmark of the U.S. Department of Energy. Meanwhile, the negative surface charge of the microspheres inhibits microbial attachment and biofilm formation, contributing to improved service stability of the material in real marine environments.

This research fills the gap in the application of porous organic cage materials in the field of uranium extraction from seawater, and also lays a theoretical and engineering foundation for the design of sustainable seawater uranium adsorbent materials with high anti-fouling resistance, high selectivity, and high capacity.