Complex formation of Cm(III) with formate studied by time-resolved laser fluorescence spectroscopy

Fröhlich, Daniel R.; Skerencak-Frech, Andrej; Panak, Petra J.

doi:10.1016/j.apgeochem.2015.06.015

Cited by 5 publications

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“…In aqueous solution, formate is in chemical equilibrium with its protonated form (formic acid). The Henderson–Hasselbalch equation is used to calculate the free formate concentration [Form – ] eq at a given temperature and ionic strength according to literature procedure. , Therefore, the protonation constant as a function of the temperature and ionic strength is calculated from p K 0 a with the specific ion interaction theory and the integrated Van’t Hoff equation. Details on this procedure are given in the literature .…”

Section: Resultsmentioning

confidence: 99%

“…This significant difference of the thermodynamic stability between acetate and formate was also observed for trivalent actinides. 46,52 The stability constant of Cm(Ac) 2+ was determined to log β 0 1 (25 °C) = 3.12 ± 0.32 whereas log β 0 1 (25 °C) of Cm(Form) 2+ is 2.11 ± 0.01. Furthermore, the stability constants of the NpO 2 (L) complexes of formate and propionate also differ by approximately 0.6 logarithmic units.…”

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confidence: 99%

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Thermodynamics and Structure of Neptunium(V) Complexes with Formate. Spectroscopic and Theoretical Study

et al. 2020

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The temperature and ionic strength dependences of the complex formation of NpO 2 + with formate in aqueous solution are studied by absorption spectroscopy (I m = 0.5−4.0 mol kg −1 , T = 20−85 °C, [Form − ] total = 0−0.65 mol kg −1 ), extended X-ray absorption fine structure spectroscopy (EXAFS) and quantum chemical methods. The complex stoichiometry and the thermodynamic functions of the complexation reactions are determined by peak deconvolution of the absorption spectra and slope analyses. Besides the solvated NpO 2 + ion, two NpO 2 + formate species (NpO 2 (Form) n 1-n ; n = 1, 2) are identified. Application of the law of mass action yields the temperature dependent conditional stability constants log β′ n (T) at a given ionic strength. These data are extrapolated to IUPAC reference state conditions (I m = 0) using the specific ion interaction theory (SIT). The results show, that log β 0 1 (20 °C) = 0.67 ± 0.04 decreases by approximately 0.1 logarithmic units with increasing temperature, log β 0 2 (20 °C) = 0.11 ± 0.11 increases by about 0.2 logarithmic units. The temperature dependence of the log β 0 n (T) values is modeled with the integrated Van't Hoff equation yielding the standard reaction enthalpy Δ r H 0 and entropy Δ r S 0 of the complexation reactions. The results show that the formation of NpO 2 (Form) is exothermic (Δ r H 0 1 = −2.8 ± 0.9 kJ mol −1 ) whereas the formation of NpO 2 (Form) 2 − is endothermic (Δ r H 0 2 = 6.7 ± 4.1 kJ mol −1 ). Furthermore, the binary ion−ion interaction coefficients ε T (i,k) of the formed complexes are determined in NaClO 4 and NaCl media as a function of the temperature. The coordination mode of formate toward the metal ion is investigated by EXAFS spectroscopy and quantum chemical calculations. A coordination of the ligand via only one O atom of formate to the metal ion is identified.

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Section: Resultsmentioning

confidence: 99%

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Thermodynamics and Structure of Neptunium(V) Complexes with Formate. Spectroscopic and Theoretical Study

et al. 2020

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“…With increasing pH the impact of [Am(Form) 2 ] + increases continuously and it becomes the dominating species in samples 5–7 with a maximum fraction of 62% in sample 7. A complex species with three coordinating formate ligands has been observed spectroscopically for the complexation of Cm(III) with formate . With respect to nuclear waste disposal such neutral species might be important due to their high mobility and low sorption affinity.…”

Section: Resultsmentioning

confidence: 99%

“…Thermodynamic speciation calculations were performed with the software package Visual MINTEQ 3.1 using the SIT (specific ion interaction theory) approach. As only conditional , but no thermodynamic stability constants for the complexation of Am(III) with formate are available in the literature, stability constants for the formation of the respective Cm(III) complexes have been used to estimate the impact of formate on the aqueous speciation of Am(III). All other stability constants originate from the NIST databases 46.6 and 46.7 or ref .…”

Section: Methodsmentioning

confidence: 99%

Combined EXAFS Spectroscopic and Quantum Chemical Study on the Complex Formation of Am(III) with Formate

et al. 2017

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The complexation of Am(III) with formate in aqueous solution is studied as a function of the pH value using a combination of extended X-ray absorption fine structure (EXAFS) spectroscopy, iterative transformation factor analysis (ITFA), and quantum chemical calculations. The Am L-edge EXAFS spectra are analyzed to determine the molecular structure (coordination numbers; Am-O and Am-C distances) of the formed Am(III)-formate species and to track the shift of the Am(III) speciation with increasing pH. The experimental data are compared to predictions from density functional calculations. The results indicate that formate binds to Am(III) in a monodentate fashion, in agreement with crystal structures of lanthanide formates. Furthermore, the investigations are complemented by thermodynamic speciation calculations to verify further the results obtained.

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“…The analysis of XAFS spectra is crucial to get the information of the microstructures and the species of radionuclides on solid particles. The time resolved laser fluorescence spectroscopy (TRLFS) can provide the information of the number of water molecules in the first coordination sphere from the analysis of the fluorescence lifetime, which is crucial to identify the formation of outer-sphere or innersphere surface complexes [15][16][17][18][19]. From the loss of water molecular number in the sorption process, the interaction mechanism and the binding state of radionuclides at solid/ water interfaces can be evaluated.…”

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confidence: 99%

Application of graphene oxides and graphene oxide-based nanomaterials in radionuclide removal from aqueous solutions

et al. 2016

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Complex formation of Cm(III) with formate studied by time-resolved laser fluorescence spectroscopy

Cited by 5 publications

References 7 publications

Thermodynamics and Structure of Neptunium(V) Complexes with Formate. Spectroscopic and Theoretical Study

Thermodynamics and Structure of Neptunium(V) Complexes with Formate. Spectroscopic and Theoretical Study

Combined EXAFS Spectroscopic and Quantum Chemical Study on the Complex Formation of Am(III) with Formate

Application of graphene oxides and graphene oxide-based nanomaterials in radionuclide removal from aqueous solutions

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