A new method allows scientists to pull uranium from seawater
Imagine an artificial kelp forest of yarn that can extract uranium from seawater. Sound like science fiction? Not if Chien Wai has anything to say about it.
Wai is president of LCW Supercritical Technologies, a company based in Moscow, which develops green technologies for environmental and materials research. Together with researchers at the Pacific Northwest National Laboratory in Sequim, Washington, they have created a technology that is capable of filtering uranium and other heavy metals from the open ocean.
Where is this uranium coming from? It’s all perfectly natural. Over billions of years, it’s been eroded from rocks on the Earth’s surface, leached from the ocean floor, and ejected from volcanic activity. It’s a process that’s been happening for so long, the ocean is almost perfectly mixed. If you were to get glass of seawater from anywhere on Earth, you would find approximately the same amount of uranium compounds in it.
Pulling materials like uranium from the seawater is of great interest to the Department of Energy, said Gary Gill, a researcher at national laboratory who is working with Wai to develop and test this method. Traditional sources of uranium, mined from the ground, are limited and have a high environmental cost. The ocean represents a vast untapped source free of these concerns.
How much uranium are we talking about? An Olympic swimming pool of full of seawater would contain approximately eight grams of uranium, the mass of a U.S. dollar coin. That may not sound like a lot, says Gill, but you have to appreciate just how big the ocean is. There’s more than 500 times more uranium floating in the sea than there are in all the world’s land-based ore sites combined, approximately four billion tons.
The Department of Energy’s Office of Nuclear Energy has been working on this issue for years, Gill said, with some success. Wai’s contribution, however, has opened up the research by greatly reducing the cost of the materials involved.
Wai’s method of extraction involves altering commercially available acrylic yarn. With his additions, molecules in the yarn become attractive places for the uranium compounds to attach, a process known as adsorption.
“I’m old, and I’m a chemist,” Wai said. “I have some tricks.”
Once prepared, the fibers were tested at the national lab by pumping seawater through small fiber bundles in a system designed to replicate conditions in the open ocean. Each of the three experimental runs lasted for a month. “You have to process a huge amount of water,” Gill said.
After the experiments, Wai took the fibers back to his company’s lab, located on the University of Idaho campus, where he was a professor for 35 years. There, he and his team performed the chemistry needed to extract the uranium as a compound known as yellowcake. This material could then be enriched for use as nuclear fuel. The team was able to extract five grams of yellowcake from the fibers, about the mass of a nickel.
The fibers are reusable once the uranium is extracted, though Wai pointed out that it is not clear what kind of lifetime they have.
Based on this success, Wai’s company has applied for further funding to test the technology in the field. This test, to be led by the national lab’s researchers, would be in the Gulf of Mexico. The adsorption process is more efficient in warm water and the expect an increase in the amount of yellowcake that can be extracted by three to five times.
UNDER THE SEA
What would this technology look like if developed into commercial use? Gill says there are several options, all currently under exploration.
The simplest deployment would be essentially a vast artificial kelp forest on the ocean floor. Long bundles, perhaps 60 yards long, would pull heavy metals out of the sea as ocean currents passed through them. This forest could be deployed behind ships in similar fashion to fishing nets, the bundles connected together with large cables. Once they do their work, the could be reeled in and sent off for processing.
Another option, Gill said, could be something akin to an oil platform. With a source of power on board, such as wind or wave turbines, the bundles could be actively moved on a conveyor belt like system where they could be deployed and processed continuously.
Of course, any kind of large scale deployment in the oceans requires a lot of study on the possible environmental effects. At this point, the fibers have been tested and found to be themselves non-toxic, Gill said. Preliminary evidence shows that the chemicals used to collect the uranium, both before and after being loaded, also exhibited no toxic effects.
One issue that Gill is worried about is the danger of marine animals becoming entangled, something that has not yet been explored. For any kind of commercial development, he said, “that’s an issue that we will have to deal with down the road.”
Wai is excited about some of the other applications of this technology as well. He has found that a whole range of elements could be extracted, not just uranium. One of the most promising is vanadium, an important metal used in battery and steel production.
There is the potential to use this a tool to address environmental disaster as well. Wai envisions the technology being used to clean up mining sites and tailing ponds or even to removed metals such as lead from drinking water.
“I imagine this can be used for environmental heavy metal cleanup,” he said.