Ar-Rehman

Chinese team extracts uranium from seawater at fastest rate

The world’s oceans are estimated to hold 4.5 billion tonnes of uranium, but getting at it is extremely difficult. Researchers have developed a material that they say opens up a ‘novel approach’ to recover the nuclear fuel from the world’s oceans. Chinese researchers have found a way to extract uranium from seawater at several times the target rate set by the US Department of Energy, putting China at the forefront of a global quest to tap into a vast source of nuclear fuel. The team from the Chinese Academy of Sciences in Qingdao did this using a material they developed called PhosCage, a sponge-like molecular structure filled with phosphate groups that act as chemical traps. Seawater contains huge amounts of uranium and Chinese Researchers just found a better trap. ORNL researchers have also developed chemically coated fiber braids that can trap and extract uranium directly from seawater. A team of Chinese researchers has developed a sponge-like material that they say can recover uranium from seawater at more than eight times the extraction rate targeted by the US. The material, called PhosCage, uses phosphate groups as chemical traps to selectively capture uranium from seawater. The research could offer another route to accessing the enormous quantity of uranium dissolved in the world’s oceans, although substantial engineering and economic hurdles remain before the technology could become commercially viable.

Details of this breakthrough were detailed by the South China Morning Post. Scientists at the Qingdao Institute of Bioenergy and Bioprocess Technology created PhosCage, a porous, sponge-like structure. The material uses phosphate groups (chemical compounds containing phosphorus) to catch uranium ions as water flows through it. Researchers shaped the material into millimeter-sized beads so it is easier to put into and take out of the water. Seawater contains other elements like vanadium that normally interfere with collection, but PhosCage shows a strong preference for capturing uranium first. The team reported recovering up to 50.4 milligrams of uranium/gram of adsorbent from natural seawater samples. This compares with the 6 mg/gram benchmark achieved by the best US adsorbents after extended seawater exposure around 2016, making the reported laboratory result more than eight times higher. In a statement, the researchers said they had recovered up to 50.4mg of uranium for every gram of the adsorbent from natural seawater samples. They then turned PhosCage into millimetre-sized beads that are easier to deploy and retrieve in the open ocean. The beads captured 22.55mg/gram and continued to work through seven cycles of reuse. “This work opens up a novel approach to extracting uranium from seawater and lays the groundwork for adsorbents that can capture more uranium and eventually be used on a large scale,” the team from the CAS’ Qingdao Institute of Bioenergy and Bioprocess Technology said. The technology could be particularly important for China, which has sizeable uranium reserves but uses far more than it produces as it expands the use of nuclear power.

The approach addresses a particularly difficult materials problem. Seawater contains only around 3.3 mg of uranium/tonne of water, meaning enormous quantities of seawater have to be processed to recover meaningful amounts. Uranium must also be separated from a mixture containing many other dissolved elements. Vanadium, in particular, can interact with the same chemical sites used to capture uranium, making selective extraction difficult. In tests containing multiple metals, the researchers found that their bead-based material showed a preference for uranium, including over vanadium. In 2024, domestic mines produced just 1,600 tonnes of uranium, a fraction of the roughly 13,000 tonnes required by its nuclear reactors, according to the World Nuclear Association. That has left China heavily reliant on imports. The world has about 7.9 million tonnes of known uranium resources on land. But the oceans hold an estimated 4.5 billion tonnes, much of it accumulated over time as uranium was washed from rocks by rain and carried by rivers into the sea. The Mediterranean alone contains an estimated 12 million tonnes of uranium, enough to meet the world’s current nuclear fuel needs for about 180 years. But getting at it is extremely difficult. A tonne of seawater contains only about 3.3mg of uranium, so the element must be sifted from vast quantities of water.

Seawater is a soup of dissolved elements, some far more abundant than the prize itself. Vanadium is especially troublesome because it can stick to the same chemical traps, making the two difficult to separate. For years, scientists at US Department of Energy national labs in Tennessee and Washington have tried to crack the problem. Oak Ridge National Laboratory developed special fibres which grab uranium, while Pacific Northwest National Laboratory tested them in flowing natural seawater from Washington’s Sequim Bay. The attraction of seawater uranium is the sheer size of the potential resource. For countries expanding nuclear power, that could represent a potentially enormous additional source of nuclear fuel. China is particularly dependent on uranium imports. The US has spent decades investigating whether seawater could help close this gap. Researchers at Oak Ridge National Laboratory and Pacific Northwest National Laboratory developed and tested uranium-absorbing fibers in natural seawater, including experiments at Washington’s Sequim Bay.

The US program ultimately found that the economics remained unfavorable compared with conventional land-based mining. PhosCage has so far only been demonstrated under controlled laboratory conditions. The Qingdao researchers collected seawater off the coast of Qingdao and processed 25 liters through a laboratory flow system rather than deploying the material directly in the ocean. Large-scale ocean deployment would introduce challenges involving currents, waves, fouling by marine organisms, material durability, recovery of the adsorbent and processing costs. The researchers also did not provide a cost estimate for the uranium recovered in their experiments. They say their next steps include scaling up the material and reducing the overall cost of extracting uranium from seawater. China uses far more nuclear fuel than it produces in local mines, making it heavily dependent on foreign imports.Vast Ocean Supply: While land reserves are limited. The test was done using 25 liters of coastal water in a lab flow system, not out in the open ocean. Scientists still need to test how the material handles real ocean waves, currents and marine life, as well as figure out how to produce it cheaply on a large scale.

By 2016, the best US adsorbents were collecting around 6mg/gram after extended exposure to seawater. But the method remained far more expensive than land mining, and the DOE largely pulled back after its programme wrapped up in 2018. The Qingdao team’s work overcame some of the major extraction hurdles, according to two earlier papers. For instance, in tests with several metals present, the bead-like material showed a clear preference for uranium, including over vanadium, one of the hardest elements to separate from it. However, the experiments have limitations. The researchers collected seawater off the coast of Qingdao and ran 25 litres (6.6 gallons) of it through a laboratory flow system, instead of leaving the adsorbents in the open ocean, where waves, currents and marine life would make the job much harder. Meanwhile, neither study put a price on the uranium it recovered. The researchers said further work would focus on scaling up the materials and bringing down the overall cost of extracting uranium from seawater.