As China expands its nuclear energy infrastructure and increases its power capacity, the demand for uranium also rises. In 2024, the country imported 13,000 tonnes of natural uranium, while SCMP reports that domestic production is only around 1,700 tonnes. International Atomic Energy Agency estimates that China’s uranium demand will cross 40,000 tonnes by 2040.
Demands have long reached the point where China’s uranium mines fail to keep up and to close this gap, Chinese scientists have directed their attention to the sea. The world’s oceans are estimated to carry 1,000 times more uranium ore reserves than on the ground, which is about 4.5 billion tonnes of uranium.
The process, however, is not as easy as it sounds. In seawater, the concentration of heavy metals is extremely low, at just 3.3 milligrams per tonne. Moreover, the presence of the transition metal vanadium in the sea presents a challenge as it has chemical properties similar to uranium, and the two must first be separated through a complicated extraction process.
Greater demand for marine uranium extraction has led to groundbreaking research. Lanzhou University’s Frontiers Science Centre for Rare Isotopes has developed a technology that enhances uranium-vanadium separation efficiency by 40 folds. This breakthrough can selectively capture uranium ions over vanadium ions.
The study, led by Professor Pan Duoqiang at the Frontiers Science Centre, was published in the international journal Nature Communications earlier this month. Adapting to large-scale use could secure China a sustainable and independent way of ensuring a dependable uranium supply.
Metal-organic frameworks (MOFs) are a unique class of compounds that blend inorganic and organic elements. They form a coordination polymer, distinguished from conventional adsorbents by their highly tunable structures, diverse functions, and vast surface areas. These qualities make MOFs highly effective for selectively separating uranium.
Using existing MOFs, however, presents certain challenges. “Designing MOFs with overly precise structure-activity relationships often results in a decrease in the specific surface area of the materials and a reduction in the density of active sites,” explained Professor Pan in an interview with Science and Technology Daily.
To address this issue, researchers integrated hydrocarbon diphenylethylene (DAE) molecules into the MOF materials. This innovative approach allows the MOFs to adjust their pore size when exposed to ultraviolet light.
The modified DAE-MOF material was then tested in both simulated and real seawater containing metals similar to uranium to evaluate its uranium adsorption capabilities.
The tests revealed that the DAE-MOF material has a uranium adsorption capacity of 588 mg per gram and a uranium-vanadium separation factor of 215, significantly outperforming all previous materials tested in both simulated and natural seawater conditions.
Surpassing Japan and then the world
From the 1980s to the 1990s, Japan led the development of seawater uranium extraction, achieving the extraction of 1 kg (2.2 pounds) of yellowcake, or uranium concentrate, through extensive marine trials, the highest yield reported to date.
In November 2019, the state-owned China National Nuclear Corporation, which manages all sector aspects, formed the Seawater Uranium Extraction Technology Innovation Alliance with 14 domestic research institutes.
The alliance has established ambitious objectives for the next 30 years, up to 2050. From 2021 to 2025, the first phase aims to replicate Japan’s kilogram-level achievement. The alliance’s long-term plan includes constructing a tonne-scale demonstration plant by 2035 and achieving continuous industrial production by 2050.
