Investigations into the Reusability of Amidoxime-Based Polymeric Adsorbents for Seawater Uranium Extraction
- Marine Sciences Laboratory, Pacific Northwest National Laboratory, Sequim, Washington 98382, United States
- Department of Chemistry, University of Idaho, Moscow, Idaho 83844, United States
- Nuclear and Radiation Engineering Program, The University of Texas at Austin, Austin, Texas 78712, United States
- Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831, United States
The ability to re-use amidoxime-based polymeric adsorbents is a critical component in reducing the overall cost of the technology to extract uranium from seawater. This report describes an evaluation of adsorbent reusability in multiple re-use (adsorption/stripping) cycles in real seawater exposures with potassium bicarbonate (KHCO3) elution using several amidoxime-based polymeric adsorbents. The KHCO3 elution technique achieved ~100% recovery of uranium adsorption capacity in the first re-use. Subsequent re-uses showed significant drops in adsorption capacity. After the 4th re-use with the ORNL AI8 adsorbent, the 56-day adsorption capacity dropped to 28% of its original capacity. FTIR spectra revealed that there was a conversion of the amidoxime ligands to carboxylate groups during extended seawater exposure, becoming more significant with longer the exposure time. Ca and Mg adsorption capacities also increased with each re-use cycle supporting the hypothesis that long term exposure resulted in converting amidoxime to carboxylate, enhancing the adsorption of Ca and Mg. Shorter seawater exposure (adsorption/stripping) cycles (28 vs. 42 days) had higher adsorption capacities after re-use, but the shorter exposure cycle time did not produce an overall better performance in terms of cumulative exposure time. Recovery of uranium capacity in re-uses may also vary across different adsorbent formulations. Through multiple re-use the adsorbent AI8 can harvest 10 g uranium/kg adsorbent in ~140 days, using a 28-day adsorption/stripping cycle, a performance much better than would be achieved with a single use of the adsorbent through very long-term exposure (saturation capacity = 7.4 g U/kg adsorbent). A time dependent seawater exposure model to evaluate the cost associated with reusing amidoxime-based adsorbents in real seawater exposures was developed. The cost to extract uranium from seawater ranged from $610-830/kg U was predicted. Model simulation suggests that a short seawater exposure cycle (< 15 days) is the optimal deployment period for lower uranium production cost in seawater uranium mining.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE Office of Nuclear Energy (NE)
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1406714
- Report Number(s):
- PNNL-SA-127685; AF5855000
- Journal Information:
- Industrial and Engineering Chemistry Research, Vol. 56, Issue 40; ISSN 0888-5885
- Publisher:
- American Chemical Society (ACS)
- Country of Publication:
- United States
- Language:
- English
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Investigations into the Reusability of Amidoxime-Based Polymeric Adsorbents for Seawater Uranium Extraction
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