Oceans hold billions of tonnes of uranium at tiny concentrations, but extracting it remains uneconomical.
A report at the 244th meeting of the American Chemical Society described a new technique using uranium-absorbing mats made from discarded shrimp shells.
Uranium is currently mined from ore deposits around the world, but there are fears that demand may outstrip the supply of ore as nuclear power becomes more widespread.
At issue is the tremendously low concentration of uranium in seawater: about three parts per billion, so that just 3.3mg exist in a full tonne of water. As a result, extracting it is an inherently costly process. Much work carried out in Japan in recent decades has sought to address that.
Researchers in Japan came up with a design of a mat of plastic fibres impregnated with molecules that both lock onto the fibres and preferentially absorb uranium. That work culminated in a 2003 field test that netted a kilogram of the metal.