Seawater contains huge amounts of dissolved metals and other substances which could potentially be useful, but which have remained too expensive to extract in large amounts. Now, scientists with the Oak Ridge National Laboratory (ORNL) in Tennessee say they have developed a new material which could lead the way to the efficient extraction of dissolved uranium from seawater, providing a huge source of uranium to power nuclear reactors.
“We have shown that our adsorbents can extract five to seven times more uranium at uptake rates seven times faster than the world’s best adsorbents,” said Chris Janke, of the ORNL’s Materials Science and Technology Division.
The material, called HiCap, is produced by combining adsorbent materials produced by the ORNL with high surface area polyethylene fibers. The fibers are able to quickly and selectively pull dissolved metals from the water. The new adsorbent materials are more economical than any previously developed technology to extract substances from seawater, according to the ORNL.
Janke explains, “Our HiCap adsorbents are made by subjecting high-surface area polyethylene fibers to ionizing radiation, then reacting these pre-irradiated fibers with chemical compounds that have a high affinity for selected metals.”
The new fibers outperformed the leading state of the art adsorbent, exceeding the next-best material’s adsorbency by a factor of seven. “These results clearly demonstrate that higher surface area fibers translate to higher capacity,” Janke said.
Scientists estimate the world’s oceans contain 4.5 billion tons of uranium, enough to fuel the world’s nuclear reactors for several centuries. In nuclear power plants, the controlled decay of radioactive uranium is used to heat water to generate the steam to turn electricity-producing turbines. The dissolved uranium in seawater exists at a concentration of only 3.2 parts per billion, however, making it difficult to effectively remove in usable amounts at an economically efficient cost.
The results of the tests on the material were presented today at the fall meeting of the American Chemical Society in Philadelphia. Funding for the project was provided by DOE’s Office of Nuclear Energy.