An EXAFS spectroscopic study of Am(III) complexation with lactate

Fröhlich, Daniel R.; Skerencak-Frech, Andrej; Kaplan, Ugras; Koke, Carsten; Roßberg, André; Panak, Petra J.

doi:10.1107/s1600577515017853

Cited by 8 publications

(12 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Lactate can either coordinate 'end-on' through the carboxylic group only or 'side-on' through both, the carboxylic and the hydroxyl group. It was shown earlier that lactate binds 'side-on' to Am(III) [39] as well as to Eu(III) [40]. A similar coordination can be expected for Np(V) lactate complexation.…”

Section: Effect Of Temperaturesupporting

confidence: 70%

Determination of complex formation constants of neptunium(V) with propionate and lactate in 0.5–2.6 m NaCl solutions at 22–60°C using a solvent extraction technique

et al. 2019

View full text Add to dashboard Cite

Natural clay rocks like Opalinus (OPA) and Callovo-Oxfordian (COx) clay rock are considered as potential host rocks for deep geological disposal of nuclear waste. However, small organic molecules such as propionate and lactate exist in clay rock pore water and might enhance Np mobility through a complexation process. Therefore, reliable complex formation data are required in the frame of the Safety Case for a nuclear waste repository. A solvent extraction technique was applied for the determination of ${\rm{NpO}}_2^ + $ complexation with propionate and lactate. Extraction was conducted from isoamyl alcohol solution containing 10−3 M TTA and 5 · 10−4 M 1,10-phenanthroline. Experiments were performed in 0.5–2.6 m NaCl solutions at temperatures ranging from 22 to 60 °C. Formation of 1:1 Np(V) complexes for propionate and lactate was found under the studied conditions. The SIT approach was applied to calculate equilibrium constants β°(T) at zero ionic strength from the experimental data. Log β°(T) is found linearly correlated to 1/T for propionate and lactate, evidencing that heat capacity change is near 0. Molal reaction enthalpy and entropy ( ${\Delta _{\rm{r}}}H_{\rm{m}}^ \circ $ and ${\Delta _{\rm{r}}}S_{\rm{m}}^ \circ $ ) could therefore be derived from the integrated van’t Hoff equation. Data for log β° (298.15 K) are in agreement with literature values for propionate and lactate. Np(V) speciation was calculated for concentrations of acetate, propionate and lactate measured in clay pore waters of COx. In addition, the two site protolysis non-electrostatic surface complexation and cation exchange (2SPNE SC/CE) model was applied to quantitatively describe the influence of Np(V) complexation on its uptake on Na-illite, a relevant clay mineral of OPA and COx.

show abstract

Section: Effect Of Temperaturesupporting

confidence: 70%

Determination of complex formation constants of neptunium(V) with propionate and lactate in 0.5–2.6 m NaCl solutions at 22–60°C using a solvent extraction technique

et al. 2019

View full text Add to dashboard Cite

show abstract

“…The EXAFS spectra and their respective Fourier transforms (FT) show very similar shapes (Figure S11), and the spectral information on the different species occurring can only be revealed by a comprehensive numerical analysis such as iterative transformation factor analysis (ITFA) (see Supporting Information section 7.2). This technique has been well-established for the decomposition of series of EXAFS spectra into linearly independent spectra and for the determination of the fractions of the single spectral components. ,,− These components might represent spectra of single-molecule complexes but also show backscattering signals stemming from structural fragments and/or single atoms. ITFA allows a decomposition of these spectral mixtures into their single components, even if these components will not occur purely or if the pH-dependent spectral changes will be small compared to the overall signal intensity.…”

Section: Resultsmentioning

confidence: 99%

“…ITFA allows a decomposition of these spectral mixtures into their single components, even if these components will not occur purely or if the pH-dependent spectral changes will be small compared to the overall signal intensity. This was successfully shown for the extraction of structural information on aqueous Am(III)–complexes of lactate, acetate, and formate . A detailed description of the entire procedure applied for the Am(III)–MAL complex system and the results obtained are presented in the Supporting Information.…”

Section: Resultsmentioning

confidence: 99%

“…From a qualitative inspection of the eigenvectors (Figure S9), a prevalent monodentate coordination of the carboxylate groups in the Am–MAL species was suggested (see Supporting Information section 7.3). Similar distances were derived earlier from the Am(III) formic acid or the Am(III) lactate system where the carboxylate groups are monodentately coordinated. , A contribution of the hydroxyl group to the complex remains unclear from the ITFA at this stage.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Thermodynamic and Structural Studies on the Ln(III)/An(III) Malate Complexation

et al. 2018

Self Cite

View full text Add to dashboard Cite

The complexation of the trivalent lanthanides Nd(III) and Eu(III) and of the actinide Am(III) with malate was studied using a multi-method approach. The combination of structural and thermodynamic studies was required for the interpretation of the stoichiometry and thermodynamic data (log β0, Δr H 0 m, Δr S 0 m, Δr G 0 m) of the lanthanide/actinide malate complexes leading to a profound molecular understanding of the system. The structure-sensitive methods vibrational spectroscopy and extended X-ray absorption fine structure spectroscopy complemented with quantum-mechanical ab initio molecular dynamics calculations revealed a tridentate ring structure of the respective metal complexes. The metal is coordinated by two carboxylate groups and a hydroxyl group. UV–vis, laser fluorescence, and calorimetric studies consistently yielded two complex species having a 1:1 and a 1:2 (metal/malate) stoichiometry. Parallel factor analysis and iterative transformation factor analysis were applied to decompose experimental spectra into their single components and to determine stability constants. The 1:1 and 1:2 Nd(III) malate complexation constants determined by isothermal titration calorimetry were extrapolated to zero ionic strength using the specific ion interaction theory, yielding log β1 0 and log β2 0 of about 6 and 9, respectively. The respective complexation enthalpies Δr H 0 m,1 and Δr H 0 m,2 showed average values of 5 kJ·mol–1 which are typical for small organic molecules. The comparison of Nd(III) and Am(III) malate complexes showed that the malate binding motif, the speciation, and the thermodynamics can be transferred from lanthanides(III) to actinides(III) supporting the 4f/5f element homology.

show abstract

“…The studies range from small organic ligands present in natural clay formations (e.g. formate [2,3], acetate [4 8], etc.) to simple dicarboxylates (e.g.…”

Section: Introductionmentioning

confidence: 99%

The complexation of Eu(III) and Cm(III) with polyacrylate as a model compound for complex polycarboxylates studied by laser fluorescence spectroscopy

Fröhlich

Panak

2019

Journal of Luminescence

Self Cite

View full text Add to dashboard Cite

The complexation of the trivalent heavy metals Eu(III) and Cm(III) with polyacrylate as a model ligand is investigated by time-resolved laser fluorescence spectroscopy (TRLFS) and subsequent thermodynamic modelling (charge neutralization model). The aqueous speciation of both metals is investigated as a function of temperature (20-60°C) and ligand concentration (0-0.4 g/kg) in 0.1 mol/kg NaCl solution ([H + ] total ≈ 10 −4 mol/kg). Only one complex species is observed at all experimental conditions. With increasing temperature the aqueous Eu(III) and Cm(III) speciation is slightly shifted towards the complexes species. This effect is attributed to the stronger deprotonation of the polymer, which is also reflected by an increase of its loading capacity. The complex stability constants, however, show no visible temperature dependency. Log β'(T) ranges between 5.8 and 5.9 for both Eu(III) and Cm(III) over the whole range of experimental conditions.

show abstract

An EXAFS spectroscopic study of Am(III) complexation with lactate

Cited by 8 publications

References 18 publications

Determination of complex formation constants of neptunium(V) with propionate and lactate in 0.5–2.6 m NaCl solutions at 22–60°C using a solvent extraction technique

Determination of complex formation constants of neptunium(V) with propionate and lactate in 0.5–2.6 m NaCl solutions at 22–60°C using a solvent extraction technique

Thermodynamic and Structural Studies on the Ln(III)/An(III) Malate Complexation

The complexation of Eu(III) and Cm(III) with polyacrylate as a model compound for complex polycarboxylates studied by laser fluorescence spectroscopy

Contact Info

Product

Resources

About