Nice. Here's MP Minerals' plant for doing that, in Alliance, TX.[1] It's a modest sized plant in an industrial park. It's fed by a huge mine in California, which has an onsite beneficiation plant. Beneficiation is the first step of separation - sorting the good stuff out from the unwanted dirt, with rock crushers, screens, and flotation. This being "rare" earth mining, the amount of good stuff is tiny relative to the unwanted dirt. This new technology works on the separated good stuff.

Although these separation plants aren't big compared to mines, US mines had been sending rare earth ores to China for processing. That's gradually moving back to the US as more separating plants are built.

[1] https://vimeo.com/1062796280/dc953ac6d5?

> Chong Liu and her colleagues knew that one of the differences between rare earth ions was the size of the water shell surrounding each one when they are dissolved in solution. Lighter rare earths like lanthanum have larger first water shell, while heavier rare earths like dysprosium have a smaller first shell. Taking advantage of that size difference, Chong Liu’s group engineered manganese oxide so that the gaps between its stacked layers were only a few water molecules wide. Then, they squeezed raw mixtures of rare earth elements inside.

Cool! Does this only work with a mixture of mostly rare earths, or can ores be "squeezed...inside"? Also, is the end product metal or intercalated manganese oxide?

• gilleain

  today at 7:55 PM

  Interestingly (well to me) this is also how some ion channels in cells work - the solvation shell (water cage) allows protein pores to distinguish between sodium and potassium.

  Not sure this is the best paper, just a random pick :

  https://www.sciencedirect.com/science/article/abs/pii/S09692...

  Huh. More complex than I understood:

  "...there are two groups of hypotheses explaining the selectivity on the basis of molecular dynamics (MD) simulations. The first group mainly considers flexibility/mobility of the carboxyl groups in the EEEE ring that provides a preferable space-charge environment for partly hydrated Na+ ions to pass and an unfavorable environment for K+.19,20,21 The second group proposes the “steric” selectivity mechanism, suggesting that the SF of Navs is not wide enough to let a fully hydrated K+ pass through, while fully hydrated Na+ traverses through the pore without a significant barrier"

  Different paper about the 'selectivity filter' https://www.frontiersin.org/journals/physiology/articles/10....

  "The backbone carbonyl oxygens plus the hydroxyl group of the threonine form four ion binding sites, called S1 to S4 from the extracellular side (see Figure 1A), and they perfectly mimic the hydration shell of potassium ions"

  What I like about the selectivity filter is that it uses the backbone carbonyls.