The complexation of neptunium(V) with fluoride at elevated temperatures: Speciation and thermodynamics

Maiwald, Martin; Fellhauer, David; Skerencak-Frech, Andrej; Panak, Petra J.

doi:10.1016/j.apgeochem.2019.03.004

Cited by 9 publications

(14 citation statements)

References 22 publications

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“…At 20 °C and I m (NaClO 4 ) = 1.0 mol kg –1 , the absorption band of the NpO 2 + aquo ion is located at 980.1 ± 0.1 nm with a molar attenuation coefficient of ε 20°C = 396 ± 4 L mol –1 cm –1 and a full width at half maximum (fwhm) of 7.4 nm. This is in excellent agreement with literature data and corresponds to the E 4g to E 2g transition. − With increasing ligand concentration, a bathochromic shift of the absorption band is observed for both ligand systems. In the case of malonate, the bathochromic shift accompanies the formation of two additional absorption bands at 988.0 ± 0.1 and 994.1 ± 0.2 nm.…”

Section: Resultssupporting

confidence: 90%

“…In all systems, no significant temperature dependence of Δε n ° (Θ) is observed and averaged, temperature-independent Δε n ° values are calculated (given as solid lines). This is in good agreement with the negligible temperature dependence of Δε n ° (Θ) values for Np(V) and An(III) complexes with various organic and inorganic ligands described in the literature . ,,,,,, The binary ion–ion interaction coefficients ε j , k of the NpO 2 (L) n 1–2 n complexes (L 2– = Mal 2– , Succ 2– ) with Na + are calculated according to the SIT using eq and the interaction coefficients ε(NpO 2 + , ClO 4 – ) = 0.25 ± 0.05 and ε(NpO 2 + , Cl – ) = 0.09 ± 0.05 given in the NEA-TDB. The values of ε(Na + , Mal 2– ) = −0.05 ± 0.03 and ε(Na + , Succ 2– ) = 0.09 ± 0.02 are calculated from literature data using the SIT procedure. ,, …”

Section: Resultssupporting

confidence: 81%

“…This is not the case for NpO 2 (Mal) n 1–2 n and NpO 2 (Succ) n 1–2 n ( n = 1, 2) as slight deviations are observed for the values determined in NaCl or NaClO 4 media. In previous studies, it was shown that these discrepancies originate from a defective ε(NpO 2 + , ClO 4 – ) = 0.25 ± 0.05 reported in the NEA-TDB. ,,, Nevertheless, the log β n ° (Θ) of the respective complex species obtained in NaCl or NaClO 4 are in excellent agreement. Thus, the ionic strength dependence of log β n ° (Θ) is accurately described with the Δε n ° determined in this work.…”

Section: Resultsmentioning

confidence: 90%

“…This is in good agreement with the negligible temperature dependence of Δε n °(Θ) values for Np(V) and An(III) complexes with various organic and inorganic ligands described in the literature . 23,32,53,54,56,71,72 The binary ion− ion interaction coefficients ε j,k of the NpO 2 (L) n 1−2n complexes (L 2− = Mal 2− , Succ 2− ) with Na + are calculated according to the SIT using eq 6 and the interaction coefficients ε(NpO and ε(Na + , Succ 2− ) = 0.09 ± 0.02 are calculated from literature data using the SIT procedure. 63,64,73 products educts…”

Section: Methodsmentioning

confidence: 99%

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Complexation of Np(V) with the Dicarboxylates, Malonate, and Succinate: Complex Stoichiometry, Thermodynamic Data, and Structural Information

et al. 2021

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The complexation of Np(V) with malonate and succinate is studied by different spectroscopic techniques, namely, attenuated total reflection Fourier transform infrared (ATR FT-IR) and extended X-ray absorption fine-structure (EXAFS) spectroscopy, as well as by quantum chemistry to determine the speciation, thermodynamic data, and structural information of the formed complexes. For complex stoichiometries and the thermodynamic functions (log β n °(Θ), ΔrH n °, ΔrS n °), near infrared absorption spectroscopy (vis/NIR) is applied. The complexation reactions are investigated as a function of the total concentration of malonate ([Mal2–]total) and succinate ([Succ2–]total), ionic strength [I m = 0.5–4.0 mol kg–1 Na+(Cl–/ClO4 –)], and temperature (Θ = 20–85 °C). Besides the solvated NpO2 + ion, the formation of two Np(V) species with the stoichiometry NpO2(L) n 1–2n (n = 1, 2, L = Mal2–, Succ2–) is observed. With increasing temperature, the molar fractions of both complex species increase and the temperature-dependent conditional stability constants log β n ′(Θ) at given ionic strengths are determined by the law of mass action. The log β n ′(Θ) are extrapolated to IUPAC reference-state conditions (I m = 0) according to the specific ion interaction theory (SIT), revealing thermodynamic log β n °(Θ) values. For all formed complexes, [NpO2(Mal)−: log β1 °(25 °C) = 3.36 ± 0.11, NpO2(Mal)2 3–: log β2 °(25 °C) = 3.95 ± 0.19, NpO2(Succ)−: log β1 °(25 °C) = 2.05 ± 0.45, NpO2(Succ)2 3–: log β2 °(25 °C) = 0.75 ± 1.22], an increase of the stability constants with increasing temperature was observed. This confirmed an endothermic complexation reaction. The temperature dependence of the log β n °(T) values is described by the integrated Van’t Hoff equation, and the standard reaction enthalpies and entropies for the complexation reactions are determined. Furthermore, the sum of the specific binary ion–ion interaction coefficients Δεn °(Θ) for the complexation reactions are obtained as a function of the t from the respective SIT modeling as a function of the temperature. In addition to the thermodynamic data, the structures of the complexes and the coordination modes of malonate and succinate are investigated using EXAFS spectroscopy, ATR-FT-IR spectroscopy, and quantum chemical calculations. The results show that in the case of malonate, six-membered chelate complexes are formed, whereas for succinate, seven-membered rings form. The latter ones are energetically unfavorable due to the limited space in the equatorial plane of the Np(V) ion (as NpO2 + cation).

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Section: Resultssupporting

confidence: 90%

Section: Resultssupporting

confidence: 81%

Section: Resultsmentioning

confidence: 90%

Section: Methodsmentioning

confidence: 99%

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Complexation of Np(V) with the Dicarboxylates, Malonate, and Succinate: Complex Stoichiometry, Thermodynamic Data, and Structural Information

et al. 2021

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“…结果表明, 该配位过程为吸热反应, 随着温度的升高 log β(NpO 2 F)值增大, 在 298 K, I＝1.0 mol/L NaClO 4 条件下其配位常数 log β 0 (NpO 2 F)为 1.42±0.10. Maiwald 等 [45] 利用可见/近红外吸收光谱(Vis/NIR)研究了 2 NpO ＋与氟化物在水溶液中的配位反应, 光谱监测得出反应生成两种复杂物种(NpO 2 F n 1n , n＝1, 2), 其在 25 ℃时的配位常数及热力学信息见表 6, 该反应为吸热反应, 配位主要由熵驱动. 此外, Tian 等 [46] 采用分光光度法和微量热法研究了不同温度下 Np(V)与氟化物在 Cl -与 Np(V)/Pu(V) 之间的配位相对较弱.…”

Section: Npunclassified

Advances in Environmental Coordination Chemistry of Np and Pu with Inorganic Anions in Aqueous Solution

Dong¹,

Cao²,

Xu³

et al. 2021

Acta Chimica Sinica

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Neptunium (Np) and plutonium (Pu) are two important actinides in nuclear industry. They can be generated through neutron capture of uranium (U) in reactors or decay from other transuranic elements. Representative isotopes of Np and Pu such as 237 Np and 239 Pu have long half-lives and possess high radiotoxicity, therefore may impose great hazard to biological system if they are released into the environment. The rich redox chemistry of Np and Pu further adds complexity of their chemical behavior in the environment. The coordination chemistry of Np and Pu in aqueous solution is of great significance to help understand and control their speciation distribution and migration behaviors in aqua environment. This article reviews the advances in coordination chemistry of Np and Pu with several common inorganic anions (OH -,PO -) in aqueous solution, especially the speciation and coordination thermodynamics between Np/Pu in different oxidation states and these anions. In general, Np and Pu ions in the same oxidation state exhibit similar coordination behavior (species, structure, stability constants, etc.) when coordinating with the same anion. The coordination strength for Np/Pu ions in different oxidation states with the same anion ligand is roughly in the order of IV＞III, VI＞V. For the coordination of Np/Pu ions with different anions, the strength sequences are OH -＞F -＞ 2 4 H PO -＞ 3 NO -＞Cl for monovalent anions andHPO -＞ 2 4 SOfor divalent anions. Factors such as instability of Np/Pu ions in some oxidation states, weak complexation, and low solubility of the complexes in the aqueous solution cause difficulties in obtaining precise and reliable coordination parameters for these ions experimentally. Moreover, the coordination parameters determined by different methods may vary with each other. To obtain more reliable parameters for the coordination of Np/Pu ions with these anions in the future, the use of more advanced characterization methods and the assistance of theoretical computation may provide strong support.

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Optically “silent” neptunium(V)-nitrate complex in ionic liquid

Dong

Wang

Yan

et al. 2022

Chinese Chemical Letters

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The complexation of neptunium(V) with fluoride at elevated temperatures: Speciation and thermodynamics

Cited by 9 publications

References 22 publications

Complexation of Np(V) with the Dicarboxylates, Malonate, and Succinate: Complex Stoichiometry, Thermodynamic Data, and Structural Information

Complexation of Np(V) with the Dicarboxylates, Malonate, and Succinate: Complex Stoichiometry, Thermodynamic Data, and Structural Information

Advances in Environmental Coordination Chemistry of Np and Pu with Inorganic Anions in Aqueous Solution

Optically “silent” neptunium(V)-nitrate complex in ionic liquid

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