1. Origin of the unusually strong and selective binding of vanadium by polyamidoximes in seawater.
- Author
-
Ivanov, Alexander S, Leggett, Christina J, Parker, Bernard F, Zhang, Zhicheng, Arnold, John, Dai, Sheng, Abney, Carter W, Bryantsev, Vyacheslav S, and Rao, Linfeng
- Abstract
Amidoxime-functionalized polymeric adsorbents are the current state-of-the-art materials for collecting uranium (U) from seawater. However, marine tests show that vanadium (V) is preferentially extracted over U and many other cations. Herein, we report a complementary and comprehensive investigation integrating ab initio simulations with thermochemical titrations and XAFS spectroscopy to understand the unusually strong and selective binding of V by polyamidoximes. While the open-chain amidoxime functionalities do not bind V, the cyclic imide-dioxime group of the adsorbent forms a peculiar non-oxido V5+ complex, exhibiting the highest stability constant value ever observed for the V5+ species. XAFS analysis of adsorbents following deployment in environmental seawater confirms V binding solely by the imide-dioximes. Our fundamental findings offer not only guidance for future optimization of selectivity in amidoxime-based sorbent materials, but may also afford insight to understanding the extensive accumulation of V in some marine organisms.
- Published
- 2017