According to the Nuclear Energy Agency, it's estimated that there are at least four billion tons of uranium in the oceans, which corresponds to about 500 times the amount of uranium known to exist in land-based ores. But mining and extracting that uranium from the sea has been notoriously hard to execute, until now.
Linsen Yang at the Chinese Academy of Sciences in Beijing and colleagues created a polymer membrane that mimics the way that blood vessels operate and added a material that was impregnated with a compound called amidoxime which binds to uranium ions. In this fashion, they managed to create new material that can absorb 20 times more uranium from seawater than its predecessors.
To detect whether uranium was truly captured, the team used X-ray photoelectron spectroscopy. They further discovered that the uranium-laced material could also be cleaned with hydrochloric acid, removing 98 percent of the uranium. They also found that their solution allowed their material to be used for long periods of time over and over again, significantly reducing the cost of uranium mining.
The scientists said that they were inspired by the geometry of blood vessels. "Here, inspired by the ubiquitous fractal structure in biology that is favorable for mass and fluid transfer, we describe a hierarchical porous membrane based on polymers of intrinsic microporosity that can capture uranium in seawater," wrote the researchers in their study.
"This biomimetic membrane allows for rapid diffusion of uranium species, leading to a 20-fold higher uranium adsorption capacity in a uranium-spiked water solution (32 ppm) than the membrane with only intrinsic microporosity."
For those worrying that the uranium would not be replenished in the oceans at a reasonable rate, it should be noted that the reservoir of the substance is so vast in seawater that it does not really matter whether the uranium is replenished or not. To get a feel about the state of uranium extraction from seawater in 2018, check out this article.