
Yarn-like material collects largest amount of uranium from seawater to date - rbanffy
https://www.pnnl.gov/news/release.aspx?id=4514
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philipkglass
People have been working on uranium extraction from seawater, and making
gradual progress, for a long time. Unfortunately, this article doesn't
quantify anything about how this improves over older efforts.

Some key parameters for uranium-from-seawater absorbent materials:

\- How much uranium a given mass of absorbent can hold at saturation.

\- How fast it reaches saturation.

\- Selectivity for uranium -- there are _many_ metals in seawater, and
competing absorption can doom a material that does perfectly well with uranium
diluted in distilled water. IIRC, calcium, iron, and vanadium are common
competing elements.

\- The number of absorption/desorption cycles the material can endure before
its performance degrades too badly.

The linked article discloses none of these important facts.

I _did_ find this recent, relevant patent application from this group:

[https://patents.google.com/patent/US20170355621A1/en?oq=2017...](https://patents.google.com/patent/US20170355621A1/en?oq=20170355621)

The patent claims several advantages over previous absorbents:

\- Less expensive absorbent-group grafting onto the polymer (plain chemical
synthesis instead of radiation-induced grafting).

\- Faster saturation.

\- Superior selectivity for uranium over vanadium.

Surprisingly, the patent does not claim a particularly high U:absorbent mass
ratio -- just "greater than 3.0 mg U per g of adsorbent." Higher numbers were
demonstrated in the 1990s. But I suppose that a really impressive number would
also be "greater than" that relatively low one.

The patent fortunately also mentions other publications that contain further
reports of the researchers' work:

Kuo et al, "Characterization and Testing of Amidoxime-Based Adsorbent
Materials to Extract Uranium from Natural Seawater." _Ind Eng Chem Res_ 2016,
55, 4285-4293

(no public PDF)

Gill et al., "The Uranium from Seawater Program at the Pacific Northwest
National Laboratory: Overview of Marine Testing, Adsorbent Characterization,
Adsorbent Durability, Adsorbent Toxicity, and Deployment Studies." _Ind Eng
Chem Res_ 2016, 55, 4264-4277

[http://cafethorium.whoi.edu/website/publications/Gill%20et%2...](http://cafethorium.whoi.edu/website/publications/Gill%20et%20al%20U%20from%20seawater%20E&EC%202016.pdf)

Pan et al, "Towards Understanding KOH Conditioning of Amidoxime-based Polymer
Adsorbents for Sequestering Uranium from Seawater." _RSC Advances 2015_ , 5,
100715-100721

[https://www.osti.gov/pages/servlets/purl/1286877](https://www.osti.gov/pages/servlets/purl/1286877)

\-----------

After reading the papers cited in the patent, I'm still unsure what underlies
the claim "Yarn-like material collects largest amount of uranium to date."
Maybe they just mean "the largest amount collected to date with this
particular material under development." That's not as exciting as I'd hoped
from the headline.

It looks like the U absorption capacity of this material isn't very high. Its
good U absorption kinetics permit a good uranium:vanadium absorption ratio if
exposure times are limited. Fully stripping absorbed vanadium is difficult, as
it has been for other materials. I couldn't find any disclosure of the
capacity fade over successive absoprtion-desorption cycles.

The most significant improvement disclosed, IMO, is that they make this
material without radiation grafting -- just chemical synthesis. The final
material performance is not remarkably improved over prior efforts. Still,
eliminating radiation grafting could make affordable large-scale production
considerably easier.

~~~
FreeFull
The question I have is, why would it be preferable to extract Uranium from
seawater (where it has a very low concentration) rather than finding a deposit
of Uranium somewhere and mining it?

~~~
philipkglass
The oceans represent, in principle, an extremely large but extremely dilute
uranium resource. So far nobody has managed to make seawater extraction of
uranium even close to competitive with terrestrial mining. But if it _could_
get within spitting distance of terrestrial mining, there would be multiple
advantages:

\- Eliminating geostrategic concerns about import dependency: any nation with
a coastline could extract its own uranium.

\- Extreme abundance: uranium dissolved in the oceans dwarfs that known to
exist in identified terrestrial ore bodies.

\- Lower environmental and worker health risks: no production of waste
tailings, no digging into ore bodies. There's very limited worker exposure to
uranium decay chain daughters (radium, radon) with the oceanic approach.
Terrestrial ore bodies contain uranium plus its decay products while the
absorbent won't concentrate the decay products.

Japan has been a leader in researching this approach. It was originally driven
by concern over energy import dependency: Japan is very reliant on imports for
both fossil and nuclear fuels. But Japan does have easy access to seawater.

~~~
vladTheInhaler
Do we really want to democratize access to uranium? For nonproliferation it
seems really convenient that uranium access is so limited.

~~~
08-15
To recreate "little boy", you would need about 10 tons of natural uranium.
Absent any better ores, you could mine that from coal ash, which typically has
a uranium concentration of 10-100ppm. You really think that's limiting? It's
not... for a weapons program, that kind of ridiculously expensive process
would be worth it.

For comparison, to fuel one reactor of 1GW(e) for a year, you need about 200
tons of uranium. Even that could be taken from coal ash, but part of the
appeal of nuclear power is that you don't want to produce coal ash anymore...

------
carapace
It's hard to represent _how much more_ power uranium holds than, say, fossil
fuels. However: [https://www.xkcd.com/1162/](https://www.xkcd.com/1162/)

