A bio-inspired material targets the ocean's uranium reserves for sustainable nuclear energy

Scientists have introduced a new bio-inspired material for an ecological and cost-effective approach to recovering uranium from the seawater.

A research team from the Oak Ridge and Lawrence Berkeley National Laboratories of the Department of Energy, the University of California at Berkeley and the University of South Florida has developed a material that binds selectively dissolved uranium with the aid of a low cost polymer adsorbent. The results, published in Nature Communications, could help eliminate bottlenecks in the cost and efficiency of extracting the ocean's uranium resources for sustainable energy production.

"Our approach represents a significant leap forward," said Ilja Popovs, co-author of the ORNL's Chemical Sciences Division. "Our material is custom designed for the selection of uranium over other metals found in seawater and can easily be recycled for reuse, making it much more convenient and effective than previously developed adsorbents. "

Popovs is inspired by the chemistry of iron-starved microorganisms. Microbes such as bacteria and fungi hide natural compounds known as "siderophores" to siphon essential nutrients like iron from their hosts. "We have essentially created an artificial siderophore to improve the way materials select and bind uranium," he said.

The team used computer and experimental methods to develop a new functional group called "H₂BHT "- 2,6-bis[hydroxy(methyl)amino]-4-morpholino-1,3,5-triazine – which preferentially selects uranyl ions, or water-soluble uranium, compared to competing metal ions from other elements of the body. seawater, such as vanadium.

The fundamental discovery is based on the promising performance of proof of principle H₂BHT polymer adsorbent. Uranyl ions are easily "adsorbed" or bound to the fiber surface of the material due to the unique chemistry of H₂BHT. The prototype differs from other synthetic materials in increasing uranium storage space, producing a highly selective and recyclable material that recovers uranium more efficiently than the previous methods.

With a practical recovery method, seawater extraction is a sustainable alternative to uranium mining land, which could support the production of nuclear energy for millennia .

Uranium deposits are abundant and can be replenished in seawater through the natural erosion of rocks and soils containing ore. Despite diluted concentrations, about 3 milligrams of uranium per ton of seawater, the world's oceans contain huge stocks of the element, an estimated total value of four billion tons, or 1,000 times more than all sources combined.

The development of effective uranium adsorbents to exploit this potential resource is, however, a quest difficult to achieve since the 1960s.

"The goal is to develop low-cost effective adsorbent materials that can be processed under mild conditions to recover uranium, and reused for multiple extraction cycles," said Alexander Ivanov, of ORNL, which carried out computer studies on H₂BHT.

Backed by the DOE Nuclear Energy Office's Fuel Cycle Research and Development Program, the team is focused on determining the underlying factors that influence selectivity and increase recoverable uranium volume with new materials.

Previous studies on amidoxime compounds have revealed a fundamentally stronger appeal for vanadium than for uranium that might be difficult to overcome. The development of H₂BHT offers an alternative approach, using non-amidoximic materials, to better target uranium in multi-metal environments.

Selectivity has long been a stumbling block on the way to more efficient adsorbent materials. Early progress, based on trial and error, has revealed that amidoxime – based functional groups bind uranium effectively in water but recover even better vanadium, although vanadium has a comparatively lower concentration in seawater.

"As a result, amidoxime-based materials, which are currently at the forefront of commercially available adsorbents, fill up vanadium faster than uranium, which is difficult and expensive to eliminate." said Popovs.

Highly concentrated acid solutions used to remove vanadium represent an increased expense over mild or basic treatment solutions and are full of caustic waste streams. In addition, the acid treatment can damage the material fibers, which limits their reuse and makes the commercial adoption too expensive.

"To function as a large-scale concept, ideally, the unwanted elements would not adsorb or could easily be removed during processing and the material reused for several cycles to maximize the amount of uranium collected," Popovs said. .

Unlike materials loaded with vanadium, the H₂The BHT polymer can be treated with mild basic solutions and recycled for prolonged reuse. Eco-friendly features also bring significant cost benefits to potential real-world applications.

The next step, say the researchers, is to refine the approach to increase efficiency and create opportunities on a commercial scale. The article's review is published in "A Siderophore-inspired Chelator Diverts Uranium from an Aqueous Medium".