23-12-2023 (BEIJING) Chinese scientists from Northeast Normal University in Changchun, Jilin province have made a significant breakthrough in extracting uranium, a heavy metal used to fuel nuclear reactors, from seawater using electricity. The team has developed an electrode that captures uranium through electrochemical reactions, a process that is at least three times faster than existing methods. Moreover, the electrode proves effective in shielding against impurities in the seawater, making it suitable for large-scale applications.
The groundbreaking study, led by Associate Professor Zhao Rui and Professor Zhu Guangshan, was published in the peer-reviewed journal ACS Central Science on December 13. This development is of particular importance to China, as the country is currently constructing more nuclear power plants than any other nation. However, China’s domestic uranium ore is low grade, necessitating imports to fuel its reactors.
The ability to extract uranium from seawater could revolutionize China’s energy structure, as well as have global implications. Policymakers and the nuclear industry closely monitor progress on this technology. While uranium has been a vital element for nuclear power since 1942, when physicist Enrico Fermi built the first nuclear reactor in Chicago, traditional extraction methods from terrestrial rock formations have limitations due to the finite nature of these deposits. As a result, scientists have been searching for alternative sources of uranium, with the oceans being a key focus.
According to the Nuclear Energy Agency, the oceans hold an estimated 4.5 billion tonnes of uranium, nearly a thousand times more than land-based reserves. However, extracting uranium from seawater poses immense challenges due to its extremely low concentration of 3.3 parts per billion and the presence of interfering ions in the complex marine environment. The task is comparable to finding a gram of salt in 300,000 liters of fresh water, if not more challenging.
To address this challenge, the research team created an electrode by coating a carbon fiber woven fabric with two monomers that react with other molecules to form structures known as porous aromatic frameworks (PAFs). These PAFs have catalytic sites that transform uranium ions into uranium compounds and adsorption sites to collect the compounds. The porous nature of the carbon fiber fabric further aids in trapping uranium ions. The study reveals that this electrochemical method significantly enhances the capacity and rate of extraction compared to the more traditional physicochemical adsorption method.
Zhu, one of the lead researchers, stated, “Uranium extraction with PAF electrodes (PAF-E) shows higher uptake and faster kinetics compared to physicochemical adsorption.” In tests conducted using water from the Bohai Sea, the team successfully extracted 12.6 milligrams of uranium per gram of material over 24 days, with saturation still not reached. This result surpasses most other reported uranium extraction methods. Furthermore, the tests indicated that the electrode remained stable through multiple extraction cycles, despite the presence of competing metal ions in the seawater. Zhu attributes this good selectivity to the alternating voltage applied to the electrodes, which repels unbound ions.
The development of these electrodes offers a more efficient and effective way to extract uranium from seawater, while also improving understanding of the mechanisms behind electrochemical uranium extraction. The study received funding from the National Key R&D Programme of China and the National Natural Science Foundation of China.
