There is no doubt about it. Uranium prices are steadily soaring, and there aren’t any signs that they’ll be declining anytime soon. With this in mind, experts are seeking new methods to extract this highly valuable metal. One approach that is showing considerable promise is based on the extraction of low concentrations of uranium from seawater. Although uranium has been extracted from seawater before, Dr. Shengqian Ma, the Robert A. Welch chair of the University of North Texas’s Department of Chemistry, had a concept unlike any other, an innovative – arguably transformative – idea.
In 2020 he began to conduct research, wondering if conductive polymer molecules could be introduced at the molecular level of a covalent organic framework (COF). To determine if his idea was feasible, he worked alongside a variety of other professors and researchers, who are either based at the University of North Texas or other institutions. For instance, he steadily spoke to Dr. Qi Sun, professor, College of Chemical and Biological Engineering, Zhejiang University, who proposed the original concept.
After several months of research, they developed an advanced, electrodeposition-based uranium extraction technology. Differing fundamentally from conventional passive adsorption, the technology is an amidoxime-functionalised, fully π-conjugated sp2c-COF-AO.
This is a type of porous crystalline polymer material, specifically the COF that Dr. Ma first brainstormed in 2020. Since its 1D pores are infiltrated with the conductive polymer PEDOT, it has been able to yield PEDOT@sp2c-COF-AO, too. Simply put, the sp2c-COF-AO contains microscopic, tunnel-like pores, which are infused with a conductive polymer (PEDOT). From there, a hybrid material (the PEDOT@sp2c-COF-AO) has been created, which can conduct electricity more efficiently, via its porous network.
“We created molecule-level electrical junctions that directly wire amidoxime chelators into the electron-conducting network, something unattainable with conventional COFs or physical polymer blends,” Dr. Ma said. “This unprecedented design enables the material to function as a true high-surface-area electrode for uranium electrodeposition.”
As a result, the team’s uranium extraction technology can achieve rapid electron and ion transfer, as well as impressive uranium uptake from seawater. In doing so, it has established a possible alternative route to commercial uranium recovery.
Crucially, since the uranium extraction technology only requires users to coat a very thin layer of PEDOT@sp2c-COF-AO on an electrode, the electrode can be regenerated and reused for numerous cycles without ever losing power. Furthermore, the amount of material that’s used is not only minimal but its overall preparation is consistently straightforward, too.
Therefore, its cost of production will likely be competitive, when compared to conventional mining. Additionally, in comparison to the traditional, slow passive sorption that’s used in uranium ore processing, it provides a higher mass-normalised uranium uptake, rapidly and directly from seawater. Thus, the need for energy-intensive mining and chemical processing diminishes, leading to a decline in the environmental disruption and pollution that’s often associated with traditional mining.
“Seawater contains an immense reservoir of uranium, estimated at around 4.5 billion tons globally, which far exceeds terrestrial uranium deposits,” Dr. Ma said. “Moreover, our method is inherently sustainable, as seawater continuously replenishes uranium, allowing for a long-term, eco-friendly supply without depleting terrestrial resources.”
Of equal importance, the team’s uranium extraction technology also offers faster kinetics than uranium ore processing, as well as a continuous electrochemical operation.
“These advantages greatly increase uranium yield per unit of material and time, reducing both material and operational costs in a scalable system,” Dr. Ma added.
In addition to having an electrode that can be steadily regenerated and reused, the technology uses considerably less energy than other uranium extraction methods, such as those that utilise fibers coated with amidoxime groups. The primary reason? It operates through electrodeposition, rather than passive adsorption.
During conventional adsorption methods used in terrestrial extraction processes, uranium capture will be constrained by slow diffusion, as well as sorption sites’ inevitable saturation. In turn, deployment times rise, while frequent regeneration cycles will indirectly increase the total amount of energy that’s required. In contrast, electrodeposition will actively drive uranyl ions toward the electrode surface under an applied potential. Thus, uranium will be deposited continuously – without ever being limited by site saturation.
“The amidoxime sites in PEDOT@sp2c-COF-AO are fully electrochemically wired, ensuring efficient electron transfer and rapid uranium conversion,” Dr. Ma said. “This combination delivers much higher yields in shorter operating windows, reducing both processing duration and ancillary energy use. Thereby, electrodeposition requires significantly less energy than conventional adsorption methods.”
Stable performance, continuous enrichment
Interestingly, the uranium extraction technology doesn’t have copper electrodes, which are generally used in traditional electroplating. Instead, it has a working electrode that’s coated with PEDOT@sp2c-COF-AO. Consequently, it provides selective binding sites that can rapidly capture and enrich uranyl ions while simultaneously enabling efficient electrodeposition.
Since the technology has one graphite electrode, in addition to the working electrode – rather than copper electrodes – a variety of benefits have been noticed so far. First, copper dissolution has been avoided altogether. Second, uranium won’t ever be embedded into the electrode. And third, since uranium embedment is circumvented, the technology will operate smoothly and steadily, leading to a more straightforward, simplified recovery of uranium, when compared to other extraction methods.
The technology extracts very quickly, too. According to Dr. Ma, it can complete most uranium extraction from seawater in 24 to 48 hours.
“However, because natural seawater contains uranium at extremely low concentrations (~3.3 ppb), real-seawater tests require much longer deployment times,” Dr. Ma said. “So far, our material typically removes more than half of
the uranium under realistic seawater conditions. All reported experiments are repeatable and not one-off results.”
Its fast extraction process is due to its innovative electrode design. Since its working electrode combines highly selective adsorption sites with a conductive framework, the technology can promptly recognise and capture uranyl ions. At the same time, it also enables electrons to be transferred rapidly.
“This synergy between molecular-level recognition and efficient electrochemical deposition ensures that once uranyl ions reach the electrode surface, they are immediately fixed, preventing loss and enabling continuous enrichment,” said Dr. Yanpei Song, a former PhD. student of Dr. Ma’s.
Currently a postdoctoral research associate at Oak Ridge National Laboratory, Dr. Song built upon Dr Ma’s conceptual design while creating specific experiments and carrying them out in the lab to prove the concept –particularly by conducting seawater uranium adsorption experiments.
A leap forward
As a result of the technology’s innovations, Dr. Song believes it is “a leap forward in uranium extraction.” While reflecting on its results so far, he doesn’t know of any other technology that can capture uranium from seawater faster and more efficiently.
“Conductive polymer inside COF pores creates direct electron pathways to the chelators, avoiding any loss of performance, while the combination of selective binding and active electrodeposition ensures we never hit a saturation limit,” he said.
Moreover, the technology has a distinctive, spontaneous redox loop. Through this loop, the technology can convert temporary uranium forms into a stable deposit, leading to even higher efficiency long term.
“Altogether, this makes our approach highly effective, scalable and a clear step toward the future of sustainable uranium recovery,” Dr. Ma added.
So far, no nuclear companies have expressed interest in the technology. Nonetheless, Dr. Song thinks nuclear companies will implement it within the next five to 10 years, especially as industrial integration continues to progress. Along with the technology’s extraction speed, he said another key positive will be noticed: low costs, in comparison to other extraction methods.
Although the covalent organic frameworks (COF) materials that are used in the technology have some synthesis expenses, the total costs for each electrode (two in all) are minimal, again when compared to other extraction methods. Additionally, according to Dr. Song, each electrode can maintain its activity long term.
“In practice, material and operational costs are minimised, making the technology economically competitive, despite the initial preparation expense,” he said.
As evidenced, Dr. Ma and his team have implemented all of the necessary steps so far – by creating a fast extraction process that will save nuclear companies time, energy and money down the road. Before these benefits are realised though, another step must occur, as the technology has to be scaled up, too.
To do so, Dr. Ma and his team plan on producing large form-factor electrodes, such as coated metal foils or meshes with PEDOT@sp2c-COF-AO films. They will also implement continuous-flow or large immersed modules with Pt/graphitic/current-collector architectures, which will be fully optimised to diminish electrolysis losses. Finally, they will apply pulse biasing and duty cycles, which have been proven to be beneficial during their lab experiments.
“In addition, careful engineering of counter-electrodes and cell geometry is needed to manage evolved gases and galvanic recycle pathways, while regeneration cycles using HNO3 or NaHCO3 should be integrated into the module design,” Dr. Ma said. “Although our research demonstrates lab-scale regeneration and long-term exposure tests of up to 56 days, industrial engineering designs need to be developed as the next step.”
Practical, high-performance functionality
Due to the team’s innovations, it was able to couple highly conductive and highly selective COF materials with electrochemical deposition, resulting in uranium extraction from seawater. Prior to this advancement, conductive polymer molecules had never been introduced at the molecular level into the pores of a COF before. In doing so, adsorption sites’ conductivity has been enhanced, while electro-assisted uranium adsorption’s efficiency has been improved considerably, too. Furthermore, according to Dr. Ma, his team’s approach has highlighted a close synergy: between molecular-level design and functional implementation.
“By embedding conductive polymers within the COF pores, we established continuous electron pathways to the adsorption sites, enabling rapid and efficient uranium capture,” Dr. Ma said.
Through the combination of selective chelation and active electrodeposition, the team also ensured that uptake will never be limited by passive sorption saturation. Not to mention, the team’s technology will be able to remain highly robust at all times, even when it’s encountering real seawater conditions.
“Our work has demonstrated a highly integrated strategy where precise molecular design directly translates into practical, high-performance functionality,” Dr. Song said.
Looking ahead
Before the team’s uranium extraction technology is fully implemented, more facile and scalable synthesis routes must be advanced though, with regard to the COF materials. The technology’s electrodes will also need to be engineered into more “robust, device-level architectures” that can efficiently extract uranium, even “under the complex physicochemical conditions of real seawater,” according to Dr. Song.
Moreover, the conductive COF adsorbent must be fabricated as durable electrode devices, designed for deployment in real ocean environments. Material synthesis will also need to be scaled up, while prototypes will have to be built and tested and multi-site field trials will need to be performed too, in order to evaluate uptake, kinetics and long-term stability.
“Efficient regeneration, lifecycle analysis and pilot deployments with industry partners will follow, along with necessary regulatory and safety approvals,” Dr. Ma said. “Once these steps are completed, nuclear companies will be able to acquire and deploy the technology through commercial modules or licensing agreements, enabling sustainable uranium recovery from seawater.”
Currently, his team is focused on offering an integrated, field-ready seawater uranium extraction solution within three to five years. Once the solution is fully implemented, Dr. Ma believes it will offer nuclear companies a practical uranium extraction solution. Companies will not only be able to recover uranium from seawater quickly, but in a highly efficient manner too – all “on a large scale.”
“It will open up exciting possibilities for sustainable nuclear fuel supply,” he said. “In addition, the underlying principles of combining selective adsorption with electrochemical deposition could provide valuable guidance for developing efficient electro-deposition methods for other critical metals, extending the potential applications of this approach.”
