PhosCage Claims Record-Setting Uranium Extraction Rate From Seawater

Uranium dissolved in seawater has been treated as a resource everyone knew about and nobody could actually use. That may be changing.

A team at the Qingdao Institute of Bioenergy and Bioprocess Technology, part of the Chinese Academy of Sciences, built a material called PhosCage: a phosphate-functionalized porous organic cage engineered specifically to grab uranium atoms out of real seawater. In lab testing on actual seawater samples, it captured 50.4 milligrams of uranium per gram of material, and it reached that saturation point in about five minutes.

That number only makes sense next to the competition. The US Department of Energy has spent years developing amidoxime-based adsorbents through Oak Ridge National Laboratory, field-tested in real ocean conditions by Pacific Northwest National Laboratory. After 42 to 60 days actually floating in seawater, around 2015 and 2016, the best of those materials pulled in roughly 6 milligrams per gram, the figure the US had set as its own viability target. PhosCage cleared that target by about eight times, and did it in minutes instead of months.

There's a real tradeoff behind the headline number. Loose powder is hard to deploy in the ocean, so the team pressed PhosCage into millimeter-sized beads that are easier to handle. The beads captured less uranium, 22.55 milligrams per gram, but kept working through at least seven reuse cycles, which matters more than peak capacity if the material has to sit in the water long term instead of being used once and discarded.

None of this is a finished mining operation. It's a lab result. But it's a lab result that closes most of the gap between "uranium is technically dissolved in every ocean on Earth" and "we could actually go get it," which is the gap that has kept seawater uranium a footnote instead of a fuel source for half a century.