Understanding the Adsorption Properties of Terbium for Future Medical Use

Scientists investigate the adsorption, thermodynamics, and kinetic properties of terbium on two popular resins for lanthanide separations: DGA and LN.

The Science

Terbium-161 (Tb-161) is a radioactive isotope that shows great promise for use in theranostic nuclear medicine. This is a type of medicine where doctors use isotopes to both image and diagnose cancer, then to treat the disease. As it decays, Tb-161 emits beta particles and a type of electrons that can be used for cancer therapy. It also emits low-energy photons that are suitable for cancer imaging. To obtain Tb-161 in a form amenable for medical use, the isotope must be separated from gadolinium. Researchers generally use two specific resins to purify radiolanthanides. These are the radioactive isotopes of elements in the lanthanide, or rare earth, series. This study investigated the interactions between terbium and these resins to gain more insight into how these resins separate Tb-161 from gadolinium.

The Impact

This study looked for the first time at how terbium binds to two types of special materials. These materials, often called resins, are very small particles that have chemical extractants inside them. This study examined DGA (N,N,N’,N’-tetra-n-octyldiglycolamide) and LN (Bis(2-ethylhexyl) phosphate) resins. The research measured how much terbium the materials can absorb, how fast this happens, and what conditions affect the process. The results show that terbium gets absorbed in two main ways: it moves into the material quickly at first, then more slowly as it spreads deeper. After that, terbium binds tightly to specific parts of chemical extractants inside the resin. The researchers also found that this binding becomes weaker as the temperature goes up. Learning how these materials absorb terbium can help us understand how other similar lanthanides behave. This knowledge can help scientists use these materials to better separate and purify other radiolanthanides and develop new ways to make the separation process more efficient.

Summary

To effectively separate similar metals in the lanthanide series, scientists need to take advantage of the small chemical differences between them. One method researchers use is column chromatography with special materials like DGA and LN resins. Most scientists change the acidity or add chemicals to improve the separation of these metals. Instead of focusing on these traditional methods, this study sought to gain a deeper understanding of the overall uptake process and identify ways to improve the separation of adjacent metals.

In this study, researchers explored how terbium binds to these resins as a function of temperature. The results showed that as the temperature goes up, these resins become less able to hold terbium. The researchers’ future studies will look at the uptake of gadolinium on these resins (terbium’s adjacent neighbor) to investigate if similar trends exist between both metals and if temperature impacts the ability to separate them. The research also studied how much terbium the resins could absorb at different concentrations and times using mathematical models to describe the process. More complex models worked better at explaining how terbium was absorbed, even though they were harder to interpret in terms of the physical process. Overall, this study provides important insights that can help design better methods for separating and purifying other radiolanthanides.

Contact

Funding

This research is supported by the Department of Energy Isotope Program, managed by the Department of Energy Office of Science for Isotope R&D and Production. This work was also supported by the Undergraduate Research Opportunities Program at the University of Utah.

Publications

Holiski, C.K., et al., Adsorption of terbium (III) on DGA and LN resins: Thermodynamics, isotherms, and kinetics, Journal of Chromatography A 1732, 465211 (2024). [DOI: 10.1016/j.chroma.2024.465211]

Highlight Categories

Program: IP

Performer: University