XAFS spectroscopic study of uranyl coordination in solids and aqueous solution

Abstract

Other| June 01, 1997 XAFS spectroscopic study of uranyl coordination in solids and aqueous solution Hillary A. Thompson; Hillary A. Thompson Stanford University, Department of Geological and Environmental Sciences, Stanford, CA, United States Search for other works by this author on: GSW Google Scholar Gordon E. Brown; Gordon E. Brown Search for other works by this author on: GSW Google Scholar George A. Parks George A. Parks Search for other works by this author on: GSW Google Scholar American Mineralogist (1997) 82 (5-6): 483–496. https://doi.org/10.2138/am-1997-5-607 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Hillary A. Thompson, Gordon E. Brown, George A. Parks; XAFS spectroscopic study of uranyl coordination in solids and aqueous solution. American Mineralogist 1997;; 82 (5-6): 483–496. doi: https://doi.org/10.2138/am-1997-5-607 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract To evaluate the ability of X-ray absorption fine structure (XAFS) spectroscopy to elucidate the coordination environment of U6+ at the solid-water interface, we conducted an in-depth analysis of experimental XAFS data from U6+ solid and solution model compounds. Using the ab initio XAFS code FEFF6, we calculated phase-shift and amplitude functions for fitting experimental data. The code FEFF6 does a good job of reproducing experimental data and is particularly valuable for providing phase-shift and amplitude functions for neighboring atoms whose spectral contributions are difficult to isolate from experimental data because of overlap of Fourier transform features. In solid-phase model compounds at ambient temperature, we were able to fit spectral contributions from axial O (1.8 Å), equatorial O (2.2–2.5 Å), N (2.9 Å), C (2.9 Å), Si (3.2 Å), P (3.6 Å), distant O (4.3 Å), and U (4.0, 4.3, 4.9, and 5.2 Å) atoms. Contributions from N, C, Si, P, distant O, and distant U (4.9 and 5.2 Å) are weak and therefore might go undetected in a sample of unknown composition. Lowering the temperature to 10 K extends detection of U neighbors to 7.0 Å. The ability to detect these atoms suggests that XAFS might be capable of discerning inner-sphere U sorption at solid aluminosilicate-water interfaces. XAFS should definitely detect multinuclear U complexes and precipitates. Multiple-scattering paths are minor contributors to uranyl XAFS beyond k = 3 Å –1. Allowing shell-dependent disorder parameters (σ2) to vary, we observed narrow ranges of σ2 values for similar shells of neighboring atoms. Knowledge of these ranges is necessary to constrain the fit of XAFS spectra for unknowns. Finally, we found that structures reported in the literature for uranyl diacetate and rutherfordine are not completely correct. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not currently have access to this article.