A group of Department of Energy (DOE)-funded researchers has developed a new, inexpensive approach to harvest uranium from seawater.
Extracting the nuclear fuel from the ocean isn't a brand new idea. There is approximately 1,000 times more uranium (in the form of uranyl ions) in the ocean than buried underground, estimated at 4.5 billion metric tons. But pulling uranium out of seawater is tricky, for the concentration of uranium in the sea is very low, only a few nanograms in one liter of water.
In 2009, Japanese scientists announced their plan to build a 400-square mile underwater "uranium farm" along its eastern seaboard, which will be filled with uranium-attracting polyethylene fabrics.
However, the 2011 earthquake and the subsequent Fukushima nuclear crisis resulted in a huge decline of nuclear energy in Japan as well as other parts of the world. Slumming demand and costly operation led to the dwindling supply of uranium ores. With the up-and-coming of seawater uranium extraction technology, scientists can now explore an inexpensive, environmentally friendly way to harvest uranium, in order to eventually replace conventional mining operations.
The earliest attempts in the 1960s, led by Oak Ridge National Laboratory researchers, proved the concept of under-ocean uranium farm feasible: sponge-like plastic fibers coated in a chemical called amidoxime was able to attract and retain uranyl as well as other metal ions from a seawater-like aqueous medium.
In the early 2010s, a Stanford team improved the method by using conductive fibers and electronic pulses, which led to the better capacity and longer shelf life of absorbent materials.
The current DOE team, consisting of material researchers from the Oak Ridge and Lawrence Berkeley National Laboratories, UC Berkeley, and the University of South Florida, based their design on a type of microorganisms that can selectively siphon iron as a nutrient.
They covered their absorbent fibers with a novel functional group known as “H2BHT”, which is capable of "capturing" uranyl ions meanwhile ignoring other competing metal ions in seawater. In the proof-of-principle tests, the H2BHT polymer adsorbent beat out other synthetic materials for soaking up more uranium faster, with better metal selectivity.
Tapping into the uranium in oceans will certainly prolong the life span of nuclear fission technology, but it does not make nuclear energy a renewable source like solar or wind power. Nevertheless, harvest nuclear fuel from seawater would provide the world a critical bridge toward a future powered by fully-sustainable energy.
The development of H2BHT polymer fiber is a promising eco-friendly alternative for harvesting uranium, and the researchers hope it can be brought into real-world applications in the near future. Their next step is to refine the prototype and look for room for improving efficiency and ability for commercialization.
This research was published in the journal Nature Communications.
The Ocean Holds Enough Uranium To Power The Planet For 10,000 Years (Seeker)
Source: Innovation Toronto