Nuclear power can be obtained from seawater, say scientists


07 June 2010

Nuclear weapons and power stations could be developed in the future using seawater, according to research published by the Royal Society of Chemistry.

Scientists in the United States have devised a new way to extract uranyl ions from water. Due to the rapid depletion of fossil fuels, the search for alternative power sources has become extremely important. One alternative is nuclear fission, making uranium - the fuel used in nuclear reactors - an important target for isolation.

In a report released in the United States on 2 August, 1999, then President Clinton's Committee of Advisors on Science and Technology (PCAST) recommended that the US consider participating in international research on extracting uranium from seawater. Now a team at the Scripps Research Institute in La Jolla, San Diego, have created a new way of efficiently isolating uranium from the sea.

Their research is published in the latest edition of the RSC's Chemical Science journal.

Although uranium is currently extracted from solid ores such as uraninite, it also exists in large quantities as uranyl ions (UO22+) in seawater. However, it is difficult to extract the ions from seawater because their linear shape prevents conventional chelating ligands (molecules used to bind ions) from grabbing hold of it.

Although uranium can be found everywhere - in almost every rock as well as seawater - its concentration in seawater is far less than in solids. For example, in high grade uranium ore there is 20,000 parts per million (ppm) whereas in seawater the rate is 0.003ppm. Yet the volume of the world's oceans is so huge that seawater extraction is an attractive proposition for scientists, providing an almost limitless resource to worldwide demand.

Orion Berryman, a member of the research team, said: "There is about 4.5 billion tons of dissolved uranium in the ocean. This is nearly 1000 times more than the terrestrial uranium sources in the western world. Our work addresses the challenges of uranium extraction from a unique perspective - isolating the uranium atom from its native environment through encapsulation."

"It's certainly confronting a significant problem and it's an interesting piece of work," says Jack Harrowfield, an expert in coordination chemistry at Louis Pasteur University in Strasbourg, France. "But it needs to be shown that it is selective," he adds.

Rebek and his colleagues now plan to address this problem by developing ligands that will exhibit a higher affinity for uranium, which will also allow its extraction at much lower concentrations than currently possible.

References

Encapsulation of the uranyl dication
Stephan Beer, Orion B. Berryman, Dariush Ajami and Julius Rebek Jr., Chem. Sci., 2010, 1, 43
DOI: 10.1039/c0sc00116c

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