Investigations into the Reusability of Amidoxime-Based Polymeric Adsorbents for Seawater Uranium Extraction

Journal Article · Wed Sep 13 00:00:00 EDT 2017 · Industrial and Engineering Chemistry Research

DOI:https://doi.org/10.1021/acs.iecr.7b02893· OSTI ID:1471881

Kuo, Li-Jung  ^[1]; Pan, Horng-Bin ^[2]; Wai, Chien M. ^[2]; Byers, Margaret F. ^[3]; Schneider, Erich ^[3]; Strivens, Jonathan E.  ^[1]; Janke, Christopher J. ^[4]; Das, Sadananda ^[4]; Mayes, Richard T.  ^[4]; Wood, Jordana R. ^[1]; Schlafer, Nicholas ^[1]; Gill, Gary A. ^[1]

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1. Pacific Northwest National Lab. (PNNL), Sequim, WA (United States). Marine Sciences Lab.
2. Univ. of Idaho, Moscow, ID (United States). Dept. of Chemistry
3. Univ. of Texas, Austin, TX (United States). Nuclear and Radiation Engineering Program
4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

The ability to reuse amidoxime-based polymeric adsorbents is a critical component in reducing the overall cost of the technology to extract uranium from seawater. This paper describes an evaluation of adsorbent reusability in multiple reuse (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 reuse. Subsequent reuses showed significant drops in adsorption capacity. After the fourth reuse 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 exposure times. Ca and Mg adsorption capacities also increased with each reuse 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 reuse, but the shorter exposure cycle time did not produce an overall better performance in terms of cumulative exposure time. Recovery of uranium capacity in reuses may also vary across different adsorbent formulations. Through multiple reuses, the AI8 adsorbent 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 a very long-term exposure (saturation capacity of 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 predicted cost to extract uranium from seawater ranged from $610/kg U to 830/kg U. Finally, 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: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE), Fuel Cycle Technologies (NE-5)
• Grant/Contract Number: AC05-00OR22725; AC05-76RL01830
• OSTI ID: 1471881
• 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

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY