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

Li Jung Kuo, Horng Bin Pan, Chien M. Wai, Margaret F. Byers, Erich Schneider, Jonathan E. Strivens, Christopher J. Janke, Sadananda Das, Richard T. Mayes, Jordana R. Wood, Nicholas Schlafer, Gary A. Gill

Research output: Contribution to journalArticlepeer-review

43 Scopus citations

Abstract

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 report 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. 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.

Original languageEnglish
Pages (from-to)11603-11611
Number of pages9
JournalIndustrial and Engineering Chemistry Research
Volume56
Issue number40
DOIs
StatePublished - Oct 11 2017

Funding

This work was funded by the U.S. Department of Energy, Office of Nuclear Energy, Fuel Cycle Research and Development Program, Fuel Resources Program (Contract DE-AC05-76RL01830). The University of Idaho team was supported by a DOE-NEUP grant (Contract 00042246). We thank Brett A. Romano for help with construction, maintenance, and operation of the marine testing facility.

FundersFunder number
DOE-NEUP00042246
University of
U.S. Department of Energy
Office of Nuclear Energy
Research and DevelopmentDE-AC05-76RL01830

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