Selective capture of radionuclides (U, Pu, Th, Am and Co) using functional nanoporous sorbents

Enhanced Separation Performance of Radioactive Cesium and Cobalt in Graphene Oxide Membrane via Cationic Control

The great applications of nuclear power for the most promising clean energy sources have been challenged by a large amount of radioactive wastewater generated, specifically the Cs⁺/Co²⁺ separation for nuclear waste storage, retreatment or recycling of radioactive wastewater, because of their wide difference in half-life and high heat release. In this work, graphene oxide membranes (GOMs) with interlayer spacing controlled by cations were used to separate mixed Cs⁺/Co²⁺ ions. The separation factors of Cs⁺/Co²⁺ for K⁺-controlled graphene oxide membranes (K-GOMs) was 2∼3 times higher than that of GOMs without treatment. In addition, the separation factors of Cs⁺/Co²⁺ for K-GOMs can be further enhanced with the increase of membranes thickness and change the initial ratios of the two ions. Typically, the separation factors of K-GOMs with a thickness of ∼300 nm reached up to 73.7 ± 3.9. Moreover, the K-GOM showed outstanding stability of the separation performance under long-term operation within 7 days. First-principles calculation revealed that the enhanced ionic selectivity of controlled GOM is induced by the difference of adsorption energies between the hydrated cations and aromatic rings, resulting in a significant increase in the mobility differences between Cs⁺ and Co²⁺ through a fixed narrow interlayer spacing. This study demonstrated excellent separation performances of GO-based membranes based on their size-exclusion effect rather than electrostatic repulsion effect, and we believe this work can enable potential efficient treatment technologies for radioactive wastewater needed urgently.

Stable sp2 carbon-conjugated covalent organic framework for detection and efficient adsorption of uranium from radioactive wastewater

Uranium is an important element in the nuclear industry while the discharge of radioactive wastewater can cause serious damages to the environment. In this work, an ultra-stable sp² carbon-conjugated covalent organic framework (COF-PDAN-AO) is synthesized with amidoxime-substituted monomers for detection and efficient adsorption of uranium from radioactive wastewater. Abundant amidoxime groups laced on the open 1D channels of COF-PDAN-AO exhibit exceptional accessibility and the regular pores facilitate the mass transfer. Based on these features, COF-PDAN-AO achieves ultra-low detection limit of 6.5 nM, high uranium adsorption capacity (410 mg/g) and selective interaction with uranium. In addition, various spectroscopies verify COF-PDAN-AO possesses excellent radioresistance in acidic solution. Regeneration studies have shown that COF-PDAN-AO maintained good structural stability after seven cycles. These results indicate that our sp² carbon conjugated COF can be potentially used for practical detection and adsorption of uranium from radioactive wastewater. This strategy can be extended to detection and extraction of other contaminants by designing the target ligand.