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.
Original language | English |
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Article number | 1560 |
Journal | Nature Communications |
Volume | 8 |
Issue number | 1 |
DOIs | |
State | Published - Dec 1 2017 |
Funding
The computational work (A.S.I. and V.S.B.) used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. XAFS work (C.W.A.) used the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357 and (Z.Z. and L.R.) the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. The thermodynamic experimental work (potentiometric and calorimetric titrations, C.J. L. and L.R.), collection and analysis of the EXAFS data for seawater-contacted adsorbents (C.W.A.) and all computational studies (A.S.I. and V.S.B.) were supported by the Fuel Cycle Research and Development Campaign (FCRD)/Fuel Resources Program, Office of Nuclear Energy, U.S. Department of Energy (USDOE). Experimental work by B.F.P. and J.A. was supported by the Nuclear Energy University Program (NEUP) at the University of California, Berkeley (UCB). Collection and analysis of the EXAFS data for small-molecule standards (Z.Z. and L.R.) was supported by USDOE, Office of Science, Office of Basic Energy Sciences, the Heavy Element Chemistry Program at Lawrence Berkeley National Laboratory. The work at Oak Ridge National Laboratory was sponsored by the U.S. Department of Energy, Office of Nuclear Energy, under Contract DE-AC05-00OR22725 with Oak Ridge National Laboratory, managed by UT-Battelle, LLC. The work at Lawrence Berkeley National Laboratory was supported by the U.S. Department of Energy, Office of Nuclear Energy and Office of Science under Contract No. DE-AC02-05CH11231 with Lawrence Berkeley National Laboratory, managed by University of California.