Stanford researchers improve extraction of uranium from seawater

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Scientists around the world are working to improve renewable energy as we continue to confront the challenges of climate change. It might take time for solar or wind to reach the point they can sustain the needs of humanity, but in the meantime we have nuclear power. Despite the risks, nuclear comes with a low carbon footprint, and much of that is from mining. A new process for obtaining uranium from seawater could make the process cleaner, cheaper, and more accessible to countries around the world.

Most of the world’s uranium is mined by Kazakhstan, Canada, and Australia, but smaller mining operations are active in a number of other countries. This is currently the easiest way to get uranium, but the cost and efficiency of nuclear power could be improved if the fuel was more readily available. Thus, the desire to perfect uranium extraction from seawater. Uranium atoms are found in seawater at roughly 3.3 parts per billion or 3.3 micrograms per liter. Researchers from Stanford have developed a process for extracting these atoms that could make it a viable source of nuclear fuel.

Uranium dissolved in water combines with oxygen to form uranyl ions with a positive charge. The approach developed at Stanford is based on a standard technique involving plastic strands composed of a material called amidoxime. The strands are dipped into seawater, where uranyl ions bind to it. When the strands are saturated, they are removed and chemically treated to remove the uranyl. These molecules then need to be refined to harvest the uranium for enrichment and use in a reactor.

Uranyl-ion-structure

Uranyl ion structure.

Stanford scientists focused their efforts on the composition of the amidoxime fibers to make them better at leaching uranyl from water. The effectiveness of amidoxime fibers are based on three variables: capacity, rate, and reuse. The Stanford team improved all three with the use of a hybrid fiber that incorporates carbon into the amidoxime structure. By sending electric pulses down the fiber, scientists were able to bind more uranyl ions — at least nine times more than standard amidoxime fibers. This process also happens faster, and the fibers last longer before needing to be replaced — about three times longer in this case.

The US currently generates about 20% of its electricity from nuclear. Stanford’s Yi Cui, a co-author of the new study, notes that improvements in uranium extraction must go hand-in-hand with advances in reactor design and safety. Better policies for dealing with the eventual waste products are necessary as well.

Now read: How does nuclear energy work?



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