Complexation of uranium(VI) with protocatechuic acid?application of iterative transformation factor analysis to EXAFS spectroscopy

Abstract

The speciation of 1 mM uranium(VI) in carbonate-free aqueous solutions of 50 mM protocatechuic acid (PCA, 3,4-dihydroxybenzoic acid) was studied in the pH range of 4.0 to 6.8 using EXAFS spectroscopy. The uranium L(III)-edge EXAFS spectra were analyzed using a newly developed computer algorithm for iterative transformation factor analysis (FA). Two structural different uranium(VI) complexes were observed. The speciation in the pH range of 4.0 to 4.8 is dominated by a 1:2 or 1:3 uranium(VI)/PCA complex with bidentate coordination of the carboxyl group to the uranium(VI) moiety. Already at pH 4.6 significant amounts of a second species are formed. This uranium(VI) species contains two PCA ligands that are bound to the uranium via their neighboring phenolic hydroxyl groups under formation of five-member rings.

Sub-micron Polymer–Zeolitic Imidazolate Framework Layered Hybrids via Controlled Chemical Transformation of Naked ZnO Nanocrystal Films

“…PCA and least-squares fits were performed on the data set using routines previously described. 54,55,56 These analyses and all other data processing were completed using software provided at the beamline. …”

Quantitative antimony speciation in shooting-range soils by EXAFS spectroscopy

“…In situ analysis of species by EXAFS spectroscopy has proven to be a powerful tool for metal speciation in soils (Manceau et al, 1996), especially if supplemented by synchrotron microbeam techniques such as l-XRF, l-XAS and l-XRD (Manceau et al, 2000;Roberts et al, 2002), by advanced statistical analysis tools (Wasserman et al, 1999;Rossberg et al, 2003;Scheinost et al, 2005), or by chemical extractions . XAS has only rarely been applied to Sb speciation, with a prime focus on the determination of Sb complexation with chloride and sulfide in aqueous solutions (Oelkers et al, 1998;Mosselmans et al, 2000;Sherman et al, 2000).…”

Electron transfer at the mineral/water interface: Selenium reduction by ferrous iron sorbed on clay

“…Factor Analysis (ITFA) to the normalized XANES spectra and to the k 3 -weighted chi spectra (Rossberg et al, 2003). This method combines principal component analysis (PCA) and iterative target test (ITT) to derive real spectra of endmember species and their relative contribution to each sample spectrum, i.e.…”

“…In order to determine the number of spectral contributions, their identity and relative contribution, we analyzed the spectral data set with Iterative Transformation Factor Analysis (ITFA) (Rossberg et al, 2003). In contrast to using edge positions as proxies of oxidation state, this method has the advantage of making use of the combined information of oxidation state and coordination geometry contained in the XANES spectra.…”