IISc Researchers Design Selective Membranes to Recover Uranium From Seawater

Researchers at the Indian Institute of Science have identified a promising membrane architecture capable of selectively blocking uranium-containing ions while allowing water and many of the common ions found in seawater to pass through, offering a possible new route for recovering uranium from the oceans and removing uranium contamination from water.

The work focuses on covalent organic framework, or COF, membranes, whose nanoscale pores can be precisely controlled. Using molecular-dynamics simulations, the IISc team showed that particular arrangements of these membranes can completely reject uranyl ions, the form in which uranium commonly occurs in water, without depending on the strong chemical binding mechanisms traditionally used in uranium-capture materials.

The research was carried out by Binu Varghese and Yogendra Kumar from IISc’s Centre for Condensed Matter Theory in the Department of Physics, along with Shubhashis Sengupta of Accenture Labs and Professor Prabal K Maiti of IISc. The study was published in the journal Small on August 17, 2026, and subsequently highlighted by IISc on September 10.

Why Recovering Uranium From Seawater Is Difficult

Uranium is present naturally in seawater, principally in the form of dissolved uranyl ions. The total amount available across the world’s oceans is enormous, making seawater an attractive potential long-term source of nuclear fuel.

The difficulty is that uranium occurs at extremely low concentrations and is surrounded by vastly larger quantities of sodium, potassium, magnesium, calcium and other dissolved ions. Any practical extraction technology therefore has to distinguish uranium from a chemically complex mixture while allowing large volumes of water to pass through efficiently.

Researchers around the world have developed polymers, nanomaterials and porous adsorbents capable of capturing uranium. Many of these systems use chemical functional groups that preferentially bind to uranyl ions.

The IISc work approaches the problem differently. Instead of relying primarily on chemical attraction, the researchers investigated whether the physical arrangement and nanoscale geometry of the membrane itself could create a barrier that uranium ions cannot easily cross.

Covalent Organic Frameworks Provide Precisely Controlled Pores

Covalent organic frameworks are crystalline materials constructed from organic molecular building blocks joined together into repeating networks. One of their most useful properties is that their pore dimensions and internal structures can be engineered at the molecular scale.

The IISc researchers studied several types of layered COF membranes and examined what happens when the individual layers are slightly displaced, or “slipped,” relative to one another.

This seemingly small structural change alters the pathway through which water and dissolved ions must travel.

Two of the structures investigated, known as TpPa-1 and TpPa-F4, showed particularly strong behaviour. In the molecular simulations, their slipped configurations produced complete rejection of uranyl ions, while water and many common monovalent seawater ions were still able to move through the membrane.

Other COF structures examined in the study, including TpBpy and Tp-Azo, provided only partial uranyl rejection, demonstrating that the precise geometry of the layered material strongly influences separation performance.

A Nanoscale Barrier Stops the Uranium Ion

The researchers investigated why the slipped membranes behaved so differently.

Their calculations show that when COF layers are arranged in the appropriate configuration, the resulting bilayer pore environment creates an energy barrier of about 3.6 kilocalories per mole for uranyl ions.

That barrier is large enough to inhibit the uranium-containing ion from travelling through the membrane while still allowing water and smaller or more favourably hydrated ions to cross.

The TpPa-1 structure highlighted by IISc has a pore dimension of approximately 5.7 angstroms, illustrating the extremely small scale at which the separation mechanism operates.

The effect is not simply a matter of the bare size of the uranium ion. Ions travelling through water are surrounded by shells of water molecules, and their interaction with the membrane depends on this hydration structure, the geometry of the pore, molecular friction and the energetic cost required to move through the confined space.

By analysing all of these factors, the researchers were able to establish a relationship between the stacking architecture of the COF and the movement of different ions through it.

Structure Rather Than Chemical Binding

This is one of the more interesting feIIT Bhilaiatures of the IISc approach.

Many conventional uranium-capture materials contain chemical groups specifically designed to bind strongly to uranyl ions. Although such systems can be effective, adding and controlling those functional groups can make material design and manufacturing more complicated.

The IISc study shows that selectivity can instead emerge from structural confinement.

By shifting the COF layers relative to one another, researchers can alter the transport pathway without necessarily having to introduce large numbers of uranium-binding chemical groups.

This gives materials scientists another variable to work with. Rather than designing only the chemistry of a membrane, they can potentially tune the arrangement of its layers and pores to decide which ions can pass through and which remain behind.

Not Every Competing Ion Passes Freely

The results also reveal an important limitation that should not be overlooked.

Although the slipped TpPa-1 and TpPa-F4 membranes allowed water and many common monovalent ions to pass while completely rejecting uranyl ions, the study found that they also suppressed the movement of other divalent ions such as calcium and magnesium.

This means the membrane is not yet a system that separates uranium perfectly from every other substance present in seawater.

Instead, it demonstrates a strong structural preference against uranyl and other multivalent ions. Further membrane design and experimental optimisation would be necessary to improve discrimination between uranium and competing divalent species.

That challenge is particularly important in seawater because magnesium and calcium are present at concentrations enormously higher than uranium.

Separation Effect Survives in Thicker Membranes

Another encouraging result emerged when the researchers examined membranes containing more than two COF layers.

The selective barrier remained effective in multilayer TpPa-1 structures, suggesting that the mechanism does not disappear immediately as membrane thickness increases.

This is relevant because a useful membrane must ultimately contain enough material to provide structural stability and practical separation performance. A mechanism that worked only in an idealised single molecular layer would be much harder to translate into a usable device.

The multilayer simulations therefore provide an early indication that the principle could remain applicable in more realistic membrane architectures.

Potential Source of Nuclear Fuel

If such membranes can eventually be manufactured and validated experimentally, uranium recovery from seawater could have long-term strategic importance.

Land-based uranium deposits are finite and geographically concentrated, while the oceans contain a vastly larger distributed uranium resource. Technologies capable of economically recovering even a fraction of that material could supplement conventional mining and provide another source of fuel for nuclear power.

The concept is especially attractive for countries operating or expanding civilian nuclear-energy programmes because seawater represents a geographically widespread resource rather than a conventional mineral deposit controlled by a limited number of producers.

The IISc study does not establish that seawater uranium recovery is already commercially viable. It instead identifies a new molecular mechanism that could contribute to future separation systems.

Any practical technology would still need to demonstrate that the membranes can be manufactured at scale, survive prolonged exposure to seawater, resist fouling and retain selectivity while processing very large volumes of water.

Possible Use in Uranium-Contaminated Groundwater

The same separation principle could also address a more immediate environmental problem.

Uranium occurs naturally in geological formations and can enter groundwater. Where concentrations become elevated, drinking-water contamination can create environmental and public-health concerns.

A membrane capable of selectively retaining uranyl ions while allowing water and common dissolved salts to pass could potentially form part of a water-treatment system for affected regions.

IISc specifically identifies uranium resource recovery and mitigation of uranium contamination in aquatic environments as two potential applications of the research.

This dual use makes the technology relevant both to the nuclear-energy sector and to environmental remediation.

Molecular Simulations Point the Way, but Experimental Validation Comes Next

The present work is fundamentally a computational investigation.

The researchers used molecular-dynamics simulations to model how uranyl ions, water molecules and competing ions interact with different COF architectures. The results establish a detailed theoretical mechanism and identify promising membrane structures, but the study does not report a full experimental membrane operating on natural seawater.

That distinction is important because real seawater presents additional complications, including dissolved organic material, microorganisms, suspended particles and changing salt concentrations. Membranes also have to withstand pressure, mechanical stress and prolonged chemical exposure.

The logical next stage would be to fabricate the most promising slipped COF structures and determine whether their simulated selectivity survives under laboratory and eventually real-water conditions.

Designing Membranes Atom by Atom

The wider significance of the IISc work lies in the way the researchers approached the separation problem.

Instead of searching only for a molecule that chemically attracts uranium, they examined how atomic-scale architecture can control the movement of ions through a membrane.

The simulations show that changing how COF layers are stacked alters hydration, friction and the free-energy landscape encountered by different ions. With the correct architecture, that change is sufficient to stop uranyl ions while permitting water and many common ions to continue through the membrane.

This provides a design principle that could potentially extend beyond uranium. Similar approaches might eventually be used to create membranes tailored for recovering or removing other strategically important or environmentally harmful ions from water.

For uranium, the immediate result is a promising theoretical framework rather than a finished extraction technology. The IISc team has shown that slipped covalent organic framework membranes can, in molecular simulations, completely reject uranyl ions through nanoscale structural confinement, providing a new direction for future uranium recovery and water-remediation research.

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