A team from the Chinese Academy of Sciences in Qingdao has developed a material that fundamentally reframes the challenge: PhosCage, a sponge-like molecular structure loaded with phosphate groups, has successfully recovered up to 50.4 milligrams of uranium per gram of adsorbent from real seawater samples. The baseline reference was the US Department of Energy’s benchmark of 6 mg per gram — a target the Chinese result exceeds by more than eightfold.
The phosphate groups that make up PhosCage act as selective chemical traps, capturing dissolved uranium ions while screening out the vast majority of other elements. This selectivity is the most technically significant aspect of the material. Uranium in seawater is present at extremely low concentrations — around 3 micrograms per liter — mixed in with an enormous variety of competing ionic species. Extracting it efficiently demands highly specific materials. PhosCage appears to meet this requirement better than any solution previously tested under real-world conditions.
The broader context of this research is unmistakably strategic. China mined approximately 1,600 tonnes of uranium domestically in 2024, while its nuclear program consumed around 13,000 tonnes in the same year. The gap is covered by imports, leaving Beijing exposed to fluctuations in the international market. With a nuclear fleet set to surpass the combined installed capacity of the United States and Europe by 2030 — according to International Energy Agency projections — dependence on foreign uranium represents a structural constraint. Seawater extraction research is a direct response to that pressure.
The world’s oceans hold an estimated 4.5 billion tonnes of dissolved uranium, more than a thousand times the known terrestrial reserves. Accessing even a fraction of this resource would secure nuclear fuel supplies for centuries, without relying on deposits concentrated in a handful of countries. This is not a near-term prospect: the researchers themselves acknowledge that significant engineering and economic hurdles remain before any industrial application becomes feasible. Yet every meaningful increase in extraction yield reduces the projected cost and brings the threshold of economic viability closer.
India is evaluating sites for modular reactors in the Andaman Islands. Lithuania is set to hold public consultations on SMRs within the next eighteen months. NANO Nuclear Energy has signed a memorandum of understanding with Enveniam covering the US nuclear fuel cycle. China’s PhosCage research fits squarely into this picture of global acceleration: different countries, different strategies, but all grappling with the same fundamental question — where to source the fuel for tomorrow’s reactors. For the first time, the ocean is beginning to look like a credible answer.
