Design Strategies to Enhance Amidoxime Chelators for Uranium Recovery

Abstract

To move nuclear as a primary energy source, uranium resources must be secured beyond what terrestrial reserves can provide. Given the vast quantity of uranium naturally found in the ocean, adsorbent materials have been investigated to recover this vital fuel source. Amidoxime (AO) has been found to be the state-of-theart functional group for this purpose, however, improvements must still be made to overcome the issues with selectively capturing uranium at such a low concentration found in the ocean. Herein, we report PAF-1 as a platform to study the effects of two amidoxime ligands. The synthesized adsorbents, PAF-1-CH 2 NHAO and PAF-1-NH(CH 2 ) 2 AO, with varying chain lengths and grafting degrees, were investigated for their uranium uptakes and kinetic efficiency. PAF-1-NH(CH 2 ) 2 AO was found to outperform PAF-1-CH 2 NHAO, with a maximum uptake capacity of 385 mg/g and able to reduce a uranium-spiked solution to ppb level within 10 min. Further studies with PAF-1-NH(CH 2 ) 2 AO demonstrated effective elution for multiple adsorption cycles and showed promising results for uranium recovery in the diverse composition of a spiked seawater solution. The work presented here moves forward design principles for amidoxime-functionalized ligands and provides scope for strategies to enhance the capture of uranium as a sustainable nuclear fuel source.

Regenerable and stable sp2 carbon-conjugated covalent organic frameworks for selective detection and extraction of uranium

“…After treating the TFPT-BTAN-AO with UO 2 2+ , distinctive U 4 f-binding energy peaks emerged, revealing that UO 2 2+ was successfully loaded onto the TFPT-BTAN-AO ( Supplementary Fig. 15) 43,44 .…”

Low Band Gap Benzoxazole‐Linked Covalent Organic Frameworks for Photo‐Enhanced Targeted Uranium Recovery

“…Many porous framework adsorbents such as covalent organic frameworks (COFs), [ 7 ] metal‐organic frameworks (MOFs), [ 8 ] and porous aromatic frameworks (PAFs) [ 9 ] have been developed for the recovery of uranium from seawater. Due to its relatively high affinity to uranium, amidoxime‐based porous framework materials are promising in practical uranium recovery from seawater.…”

De novo synthesis of bifunctional conjugated microporous polymers for synergistic coordination mediated uranium entrapment

“…In this regard, substantial efforts have been devoted to the synthesis of CMPs from monomers containing different functionalities [30,31], or the post-modification of intrinsic CMPs by introducing different ligands [18,32]. Among the known functional groups, amidoxime, usually converted from nitriles, stands out because of its high affinity and specificity toward uranium under neutral and slightly alkaline conditions [33][34][35]. Such affinity can be ascribed to the rearrangement of protons in oxime group and the deprotonation in imide group, which results in a conjugated system with delocalized electron density to trap uranyl ions by in-plane coordination [36,37].…”