Discarded shrimp shells can be useful to harvest uranium. (Photo: Stock File)
Shrimp shells could help harvest uranium from seawater
Thursday, August 23, 2012, 06:20 (GMT + 9)
Discarded shrimp shells from the seafood industry could help harvest uranium from seawater in a potentially economically feasible way, according to a report at the 244th meeting of the American Chemical Society.
Uranium is a finite resource for nuclear power currently mined from ore deposits worldwide. Extraction from seawater remains about five times more expensive than uranium mined from the ground.
A range of improved approaches -- key to a future nuclear power industry -- were outlined at a symposium at the meeting.
The current goal is not to make seawater extraction as economical as terrestrial mining, but instead to establish uranium from the ocean as a sort of "economic backstop" that will ensure there will be enough uranium to sustain nuclear power through this century and beyond.
"This uncertainty around whether there's enough terrestrial uranium is impacting the decision-making in the industry because it's hard to make long-term research and development or deployment decisions in the face of big uncertainties about the resource," said Erich Schneider, PhD, a speaker at the symposium. "So if we can tap into uranium from seawater, we can remove that uncertainty."
The tremendously low concentration of uranium in seawater, about three parts per billion, makes extracting it inherently costly, however.
Researchers in Japan came up with a design of a mat of plastic fibres impregnated with molecules that both lock onto the fibres and absorb uranium. That work bred a 2003 field test that netted a kg of uranium and research has since focused on improving both the braided fibres of the mat and the "ligand" that captures the uranium.
Several groups at the conference said they had been exploring variations on this molecular theme.
Robin Rogers of the University of Alabama, who organised the symposium, described an improvement developed in his own group that involves using seafood shells.
After both Hurricane Katrina and the BP oil spill in the Mexican Gulf region, "we began working with the Gulf Coast Agricultural and Seafood Co-operative... and with the shrimpers and crabbers there, and found they were paying hundreds of thousands of dollars to get rid of their waste [shells]," Rogers stated, BBC reports.
"We discovered an 'ionic liquid' - a molten salt - could extract a very important polymer called chitin directly from shrimp shells," he continued.
Chitin -- the principal protein in crustaceans' shells -- is tough and can be "electrospun" into fibres that can be made into mats, making it an ideal sustainable and biodegradable option for uranium harvesting.
While Rogers and his team have not reached a point where they can 'downselect' to a single technology, they have been able to double the capacity of what the Japanese have done, he said.
"But the economic analysis being done at the University of Texas has told us that we're not good enough yet, even in today's economy, so we have to improve," Rogers added.
By Natalia Real