Ligand-Based Separation Processes in Nuclear Fuel Cycles

Ligand-based separation processes play a central role in the management and recycling of nuclear fuel. They rely on organic or hybrid molecules that selectively coordinate to f-block cations, allowing the partitioning of actinides from lanthanides and other fission products. The nearly identical ionic radii and coordination chemistry of trivalent actinides and lanthanides pose significant challenges for traditional solvent extraction methods. Recent advances have addressed these issues through exploitation of differences in oxidation state, geometry or size: for example, polydentate ligands that stabilise high-valent actinyl ions enable redox switching, while tailored nanochannels and membrane materials effect size-based ion sieving. These approaches reduce energy consumption, minimise use of hazardous organic solvents and enhance process robustness under highly acidic conditions. By improving selectivity and efficiency of minor actinide partitioning, ligand-based strategies contribute to reducing the radiotoxicity and heat load of high-level waste, closing the fuel cycle and enhancing the sustainability of nuclear energy worldwide. Continuous innovation in ligand design, process intensification and hybrid separation platforms promises to reshape fuel cycle engineering in the decades to come.

Research from Nature Portfolio

Two recent studies have demonstrated novel separation strategies using designed coordination environments at the nanoscale. One approach employs a nanoscale polyoxometalate cluster bearing a tailored vacancy site that selectively binds hexavalent actinides over trivalent lanthanides in nitric acid. The resulting actinyl–polyoxometalate complexes remain stable in aqueous media and can be separated via ultrafiltration membranes, enabling rapid, organic-free partitioning with minimal energy input. A complementary strategy uses a task-specific graphene oxide membrane to exploit ion sieving: in strong oxidising conditions, linear actinyl ions are rejected by a nanochannel network, while smaller spherical lanthanide ions permeate, yielding separation factors up to four hundred under highly acidic conditions. Together, these studies highlight the power of combining ligand chemistry with membrane architectures to achieve robust, scalable separations for advanced fuel cycle applications.

Ligand-Based Separation Processes in Nuclear Fuel Cycles publication trend

The graph below shows the total number of articles in ligand-based separation processes in nuclear fuel cycles across all publications each year (not limited to Nature Index journals).

Technical terms

Ligand: A molecule that binds to a central metal atom via coordination bonds, influencing solubility and selectivity in separation processes.

Actinide: A series of heavy radioactive elements from thorium to lawrencium, including uranium and americium, present in nuclear fuel and waste.

Lanthanide: A group of fifteen elements from lanthanum to lutetium with similar chemical behaviour, often co-occurring with actinides in nuclear fuel cycles.

Actinyl ion: A linear dioxo cation of high-valent actinides (such as UO22+), used to distinguish actinides from lanthanides in separation systems.

Separation factor: A quantitative measure of the efficacy of a separation, defined as the ratio of distribution coefficients of two species.

References

1. Ultrafiltration separation of Am(VI)-polyoxometalate from lanthanides. Nature (2023).
2. Ion sieving in graphene oxide membrane enables efficient actinides/lanthanides separation. Nature Communications (2023).
3. A Simple yet Efficient Hydrophilic Phenanthroline-Based Ligand for Selective Am(III) Separation under High Acidity. ACS Central Science (2023).
4. Effective separation of Am( iii ) and Eu( iii ) from HNO 3 solutions using CyMe 4 -BTPhen-functionalized silica-coated magnetic nanoparticles. Chemical Communications (2014).