Nuclear reactors could soon be fueled with uranium harvested from the ocean, thanks to a new material.
Developed at the Department of Energy's Oak Ridge National Laboratory, HiCap combines high-capacity reusable adsorbents and high-surface-area polyethylene fibers.
It vastly outperforms today's best adsorbents, which perform surface retention of solid or gas molecules, atoms or ions, says the team, and also effectively removes toxic metals from water.
"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," says inventor Chris Janke.
The discovery could mean that it is for the first time economically viable to extract some of the ocean's estimated 4.5 billion tons of uranium. Although it's spread pretty thinly, just 3.2 parts per billion, the sheer volume means there would be enough to fuel the world's nuclear reactors for centuries.
Scientists around the world, especially in Japan, have been attempting to extract uranium from the oceans at a reasonable cost since the 1960s - until now, without success.
But the ORNL team believes it's finally done it, by making the adsorbents from small-diameter, round or non-round fibers with high surface areas. By tailoring the diameter and shape of the fibers, they can significantly increase surface area and adsorption capacity.
ORNL has also come up with a new way of manufacturing the adsorbent fibers that means they can recover metals more quickly and with increased adsorption capacity.
"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," says Janke.
When HiCap adsorbents are placed in water, the uranium's quickly trapped. When they're taken out, the metals are extracted using a simple acid elution method, and the adsorbent treated and reused.