Towards understanding KOH conditioning of amidoxime-based polymer adsorbents for sequestering uranium from seawater

Journal Article · Thu Jan 01 00:00:00 EST 2015 · RSC Advances

DOI:https://doi.org/10.1039/c5ra14095a· OSTI ID:1243260

Pan, Horng-Bin; Kuo, Li-Jung; Wood, Jordana; Strivens, Jonathan; Gill, Gary A.; Janke, Christopher J.; Wai, Chien M.

Conditioning of polymer fiber adsorbents grafted with amidoxime and carboxylic acid groups is necessary to make the materials hydrophilic for sequestering uranium from seawater. Spectroscopic techniques were employed to study the effectiveness of the traditional KOH conditioning method (2.5% KOH at 80 oC) on recently developed high-surface-area amidoxime-based polymer fiber adsorbents developed at Oak Ridge National Laboratory. FTIR spectra reveal that the KOH conditioning process removes the proton from the carboxylic acids and also converts the amidoxime groups to carboxylate groups in the adsorbent. With prolonged KOH treatment (>1 hr) at 80 oC, physical damage to the adsorbent material occurs which can lead to a significant reduction in the adsorbent’s uranium adsorption capability in real seawater during extended exposure times (>21 days). The physical damage to the adsorbent can be minimized by lowering KOH conditioning temperature. For the high-surface-area amidoxime-based adsorbents, 20 min of conditioning in 2.5% KOH at 80 oC or 1 hr of conditioning in 2.5% KOH at 60 oC appears sufficient to achieve de-protonation of the carboxylic acid with minimal harmful effects to the adsorbent material. The use of NaOH instead of KOH can also reduce the cost of the base treatment process required for conditioning the amidoxime-based sorbents with minimal loss of adsorption capacity (≤ 7%).

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1243260
• Report Number(s): PNNL-SA-110707; AF5855000
• Journal Information: RSC Advances, Vol. 5, Issue 122; ISSN 2046-2069
• Publisher: Royal Society of Chemistry
• Country of Publication: United States
• Language: English