The world’s oceans contain a near-limitless source of untapped uranium for nuclear power production—some 4.5 billion tons, or nearly 1,000 times as much as land resources, according to Christina Leggett of Lawrence Berkeley National Laboratory. Leggett was a speaker at a two-day Division of Industrial & Engineering Chemistry symposium on extracting uranium from seawater at the American Chemical Society national meeting in Denver last month.
In Denver, the symposium speakers largely focused on new developments in preparing adsorbent materials for economically viable and environmentally friendly uranium harvesting. These materials are simply dropped into the ocean where they soak up uranium. The sorbents are periodically plucked from the water, stripped of uranium, and plunged back in.
Uranium extraction is complicated, Leggett explained, because under the slightly alkaline conditions of seawater uranium exists as the very stable and inert Ca2[UO2(CO3)3] complex. Leggett and her coworkers are investigating poly(acrylamidoxime) sorbents in which the amidoxime groups, –C(NH2)NOH, are selective for UO22+ ions. The technique could also be expanded to fish out other valuable metals from the sea.
But the sorbent technology is still too inefficient and too expensive to compete with mining on land. The researchers are looking at alternative polymers and functional groups as well as coming up with new braided textile designs that could improve sorbent capacity and durability.
The effort is not just about finding any solution, said Robin D. Rogers of McGill University, in Montreal, who co organized the symposium. “This is an effort to develop a green extraction process to get around existing processes that can be quite dirty, and to do it economically.”