Spectrophotmetric determination of mixtures of neptumium (IV) and Neptunium (V) in nitric acid solutions

Dukes, E.K.; Shuler, W. E.

doi:10.2172/4093004

Cited by 2 publications

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“…At times it can be convenient to remove the supernate by centrifugation and restart the H 3 BO 3 /HCl additions on the remaining solid. After complete dissolution of the green solid, fractions were combined, and the Np oxidation state was confirmed to be +4 by UV–vis–NIR spectroscopy. , …”

Section: Methodsmentioning

confidence: 99%

Advancing Understanding of the +4 Metal Extractant Thenoyltrifluoroacetonate (TTA^–); Synthesis and Structure of M^IVTTA₄(M^IV= Zr, Hf, Ce, Th, U, Np, Pu) and M^III(TTA)₄^–(M^III= Ce, Nd, Sm, Yb)

et al. 2018

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Thenoyltrifluoroacetone (HTTA)-based extractions represent popular methods for separating microscopic amounts of transuranic actinides (i.e., Np and Pu) from macroscopic actinide matrixes (e.g. bulk uranium). It is well-established that this procedure enables +4 actinides to be selectively removed from +3, + 5, and +6 f-elements. However, even highly skilled and well-trained researchers find this process complicated and (at times) unpredictable. It is difficult to improve the HTTA extraction-or find alternatives-because little is understood about why this separation works. Even the identities of the extracted species are unknown. In addressing this knowledge gap, we report here advances in fundamental understanding of the HTTA-based extraction. This effort included comparatively evaluating HTTA complexation with +4 and +3 metals (M = Zr, Hf, Ce, Th, U, Np, and Pu vs M = Ce, Nd, Sm, and Yb). We observed +4 metals formed neutral complexes of the general formula M(TTA). Meanwhile, +3 metals formed anionic M(TTA) species. Characterization of these M(TTA) ( x = 0, 1) compounds by UV-vis-NIR, IR, H andF NMR, single-crystal X-ray diffraction, and X-ray absorption spectroscopy (both near-edge and extended fine structure) was critical for determining that Np(TTA) and Pu(TTA) were the primary species extracted by HTTA. Furthermore, this information lays the foundation to begin developing and understanding of why the HTTA extraction works so well. The data suggest that the solubility differences between M(TTA) and M(TTA) are likely a major contributor to the selectivity of HTTA extractions for +4 cations over +3 metals. Moreover, these results will enable future studies focused on explaining HTTA extractions preference for +4 cations, which increases from Np to Pu, Hf, and Zr.

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Section: Methodsmentioning

confidence: 99%

Advancing Understanding of the +4 Metal Extractant Thenoyltrifluoroacetonate (TTA^–); Synthesis and Structure of M^IVTTA₄(M^IV= Zr, Hf, Ce, Th, U, Np, Pu) and M^III(TTA)₄^–(M^III= Ce, Nd, Sm, Yb)

et al. 2018

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Section: Qualification Of the Np Stock Solutionmentioning

confidence: 99%

“…The Np aqueous system follows the Beer−Lambert law, and hence, the measured absorbance at a given wavelength (A λ ) is related to the concentration of Np ions (c(Np(V)) and c(Np(VI)) in the present case) and their respective molar extinction coefficients (ε λ ). 56 Therefore, by choosing two absorption bands, a system of two equations is obtained from which the individual fractions of Np(V) and Np(VI) can be derived In this work, the two distinct absorption bands in the nearinfrared region with local maxima at 1097 and 1223 nm, which are associated predominantly with Np(V) and Np(VI), respectively, will be used. Note that the strong absorption band associated with the free NpO 2 + ion, occurring at 980 nm, 41 was not selected for this purpose to avoid a bias when approaching detector saturation.…”

Section: Qualification Of the Np Stock Solutionmentioning

confidence: 99%

Speciation and Ammonia-Induced Precipitation of Neptunium and Uranium Ions

et al. 2023

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The pH evolution and corresponding changes in the UV−Vis−NIR absorption spectra of oxygenated neptunium (NpO 2 + and NpO 2 2+) and uranyl ions (UO 2 2+ ) in nitric acid are investigated during titration with an aqueous NH 3 solution. The speciation and precipitation regimes between acidic (pH 1.5) and alkaline (pH 10) conditions at room temperature are discussed to assess the suitability of Np(V) or Np(VI) in sol−gel conversion processes for fuel target fabrication. Under the applied experimental conditions, Np(V) hydrolyzes and precipitates into the insoluble hydroxide NpO 2 OH only above pH values 7.5 and an increase up to pH 10.0 is required to precipitate quantitatively. Np(VI) displays changes in the coordination environment of NpO 2 2+ ions in the pH interval 1.6− 4.0, similar to what is observed for U(VI). Precipitation into NpO 3 •H 2 O or other hydroxide compounds takes place between pH 4.0 and 5.9, which overlaps largely with precipitation of ammonium diuranate species from the U(VI) solution. The use of concentrated NH 3 aqueous solution, as commonly used in the external gelation process, will allow to quantitatively precipitate both Np(V) and Np(VI) species. Internal gelation process conditions, on the other hand, seem incompatible with the high pH required to precipitate Np(V) completely. For fabricating mixed-oxide (U,Np) targets using sol−gel conversion, a feed broth containing Np(VI) and U(VI) will be required to achieve homogeneous gelation.

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Spectrophotmetric determination of mixtures of neptumium (IV) and Neptunium (V) in nitric acid solutions

Cited by 2 publications

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Advancing Understanding of the +4 Metal Extractant Thenoyltrifluoroacetonate (TTA^–); Synthesis and Structure of M^IVTTA₄(M^IV= Zr, Hf, Ce, Th, U, Np, Pu) and M^III(TTA)₄^–(M^III= Ce, Nd, Sm, Yb)

Advancing Understanding of the +4 Metal Extractant Thenoyltrifluoroacetonate (TTA^–); Synthesis and Structure of M^IVTTA₄(M^IV= Zr, Hf, Ce, Th, U, Np, Pu) and M^III(TTA)₄^–(M^III= Ce, Nd, Sm, Yb)

Speciation and Ammonia-Induced Precipitation of Neptunium and Uranium Ions

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Spectrophotmetric determination of mixtures of neptumium (IV) and Neptunium (V) in nitric acid solutions

Cited by 2 publications

References 0 publications

Advancing Understanding of the +4 Metal Extractant Thenoyltrifluoroacetonate (TTA–); Synthesis and Structure of MIVTTA4(MIV= Zr, Hf, Ce, Th, U, Np, Pu) and MIII(TTA)4–(MIII= Ce, Nd, Sm, Yb)

Advancing Understanding of the +4 Metal Extractant Thenoyltrifluoroacetonate (TTA–); Synthesis and Structure of MIVTTA4(MIV= Zr, Hf, Ce, Th, U, Np, Pu) and MIII(TTA)4–(MIII= Ce, Nd, Sm, Yb)

Speciation and Ammonia-Induced Precipitation of Neptunium and Uranium Ions

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Advancing Understanding of the +4 Metal Extractant Thenoyltrifluoroacetonate (TTA^–); Synthesis and Structure of M^IVTTA₄(M^IV= Zr, Hf, Ce, Th, U, Np, Pu) and M^III(TTA)₄^–(M^III= Ce, Nd, Sm, Yb)

Advancing Understanding of the +4 Metal Extractant Thenoyltrifluoroacetonate (TTA^–); Synthesis and Structure of M^IVTTA₄(M^IV= Zr, Hf, Ce, Th, U, Np, Pu) and M^III(TTA)₄^–(M^III= Ce, Nd, Sm, Yb)