Scientists at the Qinghai Institute of Salt Lakes in China have developed microscopic material that can hunt for uranium ions in oceans or wastewater. Unlike previous attempts to develop such a method, this material actively seeks out uranium ions like a predator and is powered by light, making it a more active and eco-friendly way to trap them. 

Uranium is a well-known radioactive substance used as fuel in nuclear fission reactors. As China embarks on a mission to move away from fossil fuels and toward a mix of renewable and nuclear fission energy, it needs a steady supply of uranium to power its reactors.

Last year, the largest uranium mining project in the country began operations. However, the Asian giant remains dependent on imports to power its reactors.  

Estimates suggest that seawater contains about 4.5 billion tonnes of uranium. However, its concentration is too low to make extraction easy and economically feasible.

China is currently exploiting its salt lakes to source potassium and lithium. A research team led by Yongquan Zhou at the Institute of Salt Lakes found a way to extract uranium from these lakes using micromotors. 

Hunting uranium

The approach used by the Chinese researchers involves a metal-organic framework (MOF) micromotor. These microscopic particles are about 30 times smaller than a human hair, measuring just 2 micrometers wide. 

The material is like a sponge, but the researchers modified its internal structure to keep it stable inside water for long periods. The molecule is activated with hydrogen peroxide, and the micromotors move the particle at 7 micrometers per second. Sunlight can be used as a boost, since it can double the propelling speed of the particle. 

In laboratory settings, the researchers use the material to extract 406 milligrams of uranium per gram. Once the material encounters a uranium ion, it locks it into a stable mineral form and stores it safely. 

A system that runs itself

Previous attempts at extracting uranium ions have relied on a passive system in which adsorbents remain stationary and wait for uranium ions to pass through them for trapping. This new system, though, actively seeks uranium ions as it moves through the water. 

Interestingly, the researchers also observed collective behaviors in these micromotors, including hunting, escape, and swarming with colloidal particles as fuel concentrations changed. This resembled the predator-prey systems seen in biology. 

However, the researchers added a note of caution, noting that the technology was still in its early stages and could not be deployed at large scales immediately. In specific systems, such as the salt lakes China is currently using for potassium and lithium, salinity is too high for the systems to run efficiently. 

Zhou believes that there is much more in the salt lakes that can be extracted apart from potassium and lithium. Other than uranium, strategic elements such as rubidium and cesium are also found in these lakes, and China is leaving them as waste. 

The micromotors can also be adapted to recover these strategic materials, according to a South China Morning Post report.