Locking away toxic metals into tiny holes

Toxic and radioactive metals left over from the nuclear fuel cycle are of primary concern to the health of humans and the environment. Why? Because as the uranium from the reactor core ‘burns’, it decays to other elements, and leaving a pile of toxic material. Most of these remaining elements are still radioactive, and of particular concern are cesium (Cs) and strontium (Sr), which have the highest level of radioactivity in the waste. Check out this show by John Oliver over at HBO PR, in a hilariously disturbing portrayal of America’s nuclear waste problem, he accurately points out many issues that never seem to go away.

Image of gaidonnayite, a hydrated sodium zirconium silicate mineral, taken by the RRUFF project. A very rare mineral found only in a few places on Earth, but very easy to make in the lab.
A internal mold view showing the pores/tunnels in gaidonnayite, with some of the tunnels shown in cross-section. The inside of the tunnels/cages are shown as purple, the outside is shown in tan colors. There are large cages where atoms, like cesium and sodium, can be held; however there are bottlenecked tunnels between these cages (conduit between cages), which make it hard for atoms to move around unless hydrogen is there to prop open tunnels and relieve the bottleneck. Made with OLEX2, (Celestian 2019).
Illustration of cesium (dark green) trapped in a cage of gaidonnayite. The tunnels leading to these cages are small, and are usually inaccessible to large metals, like cesium, unless hydrogen is present. Red is oxygen, blue is silicon, light green is zirconium, dark green is cesium (Celestian 2019).
Putting hydrogen into gaidonnayite was an important step for enhancing cesium uptake and selectivity. This is an example of the gaidonnayite performance for cesium exchange at three different conditions as measured by Raman spectroscopy. Raw mineral (green), heated mineral (blue), hydrogen-bearing mineral (orange) (Celestian 2019).

Reference to original paper

  • Aaron J. Celestian, Jason Lively, Wenqian Xu. In Situ Cs and H Exchange into Gaidonnayite and Proposed Mechanisms of Ion Diffusion. Inorganic Chemistry 58, 1919–1928 American Chemical Society (ACS), 2019. Link

Keeping science accessible. Researching how minerals can be used to solve problems like climate change, pollution, and disease. @ NHMLA, USC, NASA-JPL

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