Abstract
The ocean contains uranium with an approximate concentration of 3.34 ppb,
which can serve as an incredible supply source to sustain nuclear energy in the United
States. Unfortunately, technology currently available to recover uranium from seawater is
not efficient enough and mining uranium on land is still more economical. We have
developed polymer-based adsorbents with high uranium adsorption capacities by grafting
amidoxime onto high surface-area polyethylene (PE) fibers. Various process conditions
were screened in combination with developing a rapid testing protocol (<24 h) to optimize
the process. These adsorbents are synthesized through radiation induced grafting of
acrylonitrile (AN) and methacrylic acid (MAA) onto PE fibers followed by the conversion
of nitriles to amidoximes and basic conditioning. Additionally, the uranium adsorption
capacity, measured in gU/kgads, was greatly increased by reducing the PE fiber’s diameter
or changing the fiber’s morphology. An increase in the surface-area of the PE polymer
fiber allowed for more grafting sites that are positioned in more accessible locations;
therefore, increasing access to grafted molecules that would normally be located in the
interior of a fiber with a larger diameter. Polymer fibers with hollow morphologies were
able to adsorb beyond one order of magnitude more uranium from simulated seawater than
current commercially available adsorbents. Several high surface-area fibers were tested in natural seawater and were able to extract 5 – 7 times more uranium than any adsorbent
reported to date.
