Can you imagine that a large amount of uranium can be fished out of seawater with a magic cloth and supplied to the world's growing small modular nuclear reactors, thus providing mankind with almost unlimited carbon-free energy? This uranium magic cloth has been developed by a team at Northeast Normal University in China and has elucidated the electrochemical mechanism, 1 gram of this material can fish out 12.6 milligrams of uranium from seawater in 24 days, providing great potential for large-scale applications.
Compared with the 18% of nuclear power generation in the United States, China's nuclear power accounted for only 4.7% in 2022, but in recent years, China has invested heavily in nuclear energy, and various types of reactors have been developed simultaneously, and great progress has been made in modularization and miniaturization.
However, China's uranium resources are extremely scarce, and they are mainly of medium and low grade, with only 1,885 tons of uranium produced in 2021, more than 80% of which need to be imported, and 12,200 tons in 2022. With the completion of more nuclear power units and the maturity of safer small modular nuclear reactors (SMRs), the global demand for uranium may soon increase significantly, and many companies in China, the United States, Canada and other countries have developed SMRs and put them into trial operation one after another, with the goal of seizing the global market as soon as possible.
At present, the main source of uranium in the market is Kazakhstan, which accounts for about 45%, Namibia 12%, followed by Canada, Australia, Uzbekistan, Russia and Nigeria, and China is only in eighth place.
According to the statistics of the World Nuclear Association in August 2023, the proven uranium resources on the earth are 6.08 million tons, of which Australia ranks first with 28%, Kazakhstan with 13%, Canada with 10%, and China with only 4% ranks ninth.
It is precisely because of the extreme shortage of uranium resources that China urgently needs to find more uranium, so where will this uranium come from? You can easily think that the ocean! Compared with the 6.08 million tons of uranium found on land, the entire earth's oceans contain 4.5 billion tons of uranium, which can be described as inexhaustible. However, these 4.5 billion tons of uranium are dispersed into the world's seawater at a concentration of only 3 parts per billion, and it may be more difficult to extract it than to reach the sky, because you have to filter 300,000 tons of seawater to get 1 kilogram of uranium!
However, the temptation of uranium is extremely huge, and countries have invested in the research and development of uranium extraction from seawater, and the United Kingdom first started the oyster program in the 1950s, trying to extract uranium from seawater through inorganic adsorbents, liquid-liquid extraction, etc. The United States, Germany, Japan, Italy and other countries have also invested in research and development, but the first breakthrough was made by China's East China Normal University, which extracted 30 grams of uranium from seawater in 1970, becoming the first country in the world to fish uranium from seawater.
After Japanese scientists invented a new adsorbent, including titanium hydroxide and activated carbon, 1 gram of adsorbent can extract 1 mg of uranium, in 1986 Japan built an annual output of 10 kilograms of uranium seawater extraction plant, ambitious to reach 1000 tons in 2000, but soon found that there were too many impurities, the economic benefits were too poor, two years later had to stop running.
At the same time, American scientists also found a kind of amidoxime adsorbent, which reached a uranium adsorption capacity of 0.45mg/g in seawater tests, and still performed well after 10 cycles. In 2012, Oak Ridge National Laboratory developed an adsorbent material called HiCap, which reached an adsorption capacity of 3.94mg/g.
In 2021, the Shanghai Advanced Research Institute of the Chinese Academy of Sciences built a kilogram-level sea trial platform in the South China Sea based on nanomembrane technology, reaching an adsorption capacity of 3.63mg/g.
This breakthrough was made by the Northeast Normal University team, note that it is not the world's first seawater uranium fishing East China Normal University mentioned above, East China Normal is located in Shanghai, and Northeast Normal is located in Changchun, Jilin Province. Using an electrochemical approach, the team at Northeast Normal University specifically constructed a self-standing, binder-free, metal-free, porous aromatic skeleton electrode on soft carbon fiber, which resembles a small pocket containing a modified amidoxime group that adsorbs uranyl ions.
When this cloth is put into seawater and the graphite anode is energized, the uranyl ions will be selectively captured under the action of an alternating electric field, and then sodium uranate oxide {Na2O(UO3· H2O)x} precipitate. In simple terms, this process involves an electrochemical reaction in which uranyl ions are adsorbed, then reduced and oxidized by electron transfer, and finally a bright yellow precipitate that can be collected.
According to experiments conducted by scientists in natural seas, the method reached 12.6mg/g uranium adsorption after 24 days of operation and was still not saturated, and also showed satisfactory selectivity for common competing ions. What does this mean? There are also a large number of other metal ions in the seawater, that is, the so-called impurities, which are also easily adsorbed, and the ambition of Japanese scientists has been worn out by them.
According to the researchers, this is the fastest and most abundant adsorption method among the many seawater uranium fishing methods in the world so far, and it clarifies the mechanism of material conversion in the catalytic process of PAF electrode adsorption, providing great potential for the large-scale application of seawater uranium fishing.
The World Nuclear Association believes that uranium extraction from seawater needs to be kept below the international uranium price in order to be of mining value. In 2016, the United States did a technical cost analysis that the recyclable adsorption material needs to reach 11mg/g uranium adsorption capacity to meet this requirement.
The study was published Dec. 13 in ACS Central Science, a journal of the American Chemical Society.