Hydrolysis of Np(IV) and Pu(IV) and their complexation by aqueous Si(OH)4
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A. B. Yusov
Summary
The hydrolysis and interaction of Np(IV) and Pu(IV) with orthosilicic acid, Si(OH)4, were studied in 0.1–1.0 M ionic strength aqueous solutions. Spectrophotometry was used to study these reactions at about 10–4 M Np(IV) and Pu(IV) concentrations. The first hydrolysis constants, Khydr, agree with the majority of earlier spectrophotometric and potentiometric data. The absorption spectra of NpOH3+ and PuOH3+ were obtained by spectral deconvolution. Reasons to explain the overestimation of Khydr obtained by other methods [by extraction of trace amounts of Np(IV) and Pu(IV) and by solubility] are discussed. Formation of the complexes NpOSi(OH)33+ and PuOSi(OH)33+ is demonstrated in the presence of 0.005–0.016 M Si(OH)4 in the p[H+] range 1.0–2.2 and 0.3–1.4, respectively. Measured values of equilibrium constants of the reaction
M4+ + Si(OH)4 ↔ MOSi(OH)33+ + H+
at ionic strength I=1.0 are lg K1 = 0.41±0.02 and 1.04±0.04, respectively, for Np(IV) and Pu(IV). The stability constants of the NpOSi(OH)33+ and PuOSi(OH)33+ complexes, recalculated to zero ionic strength, are lg β10 = 11.2 and 11.8, respectively. The correlation between Khydr and K1, as observed for all earlier studied metal ions, also occurs for both Np(IV) and Pu(IV).
© 2004 Oldenbourg Wissenschaftsverlag GmbH
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Artikel in diesem Heft
- Evidence for the formation of sodium hassate(VIII)
- Study of nitrate complex formation with trivalent Pm, Eu, Am and Cm using a solvent extraction technique
- Hydrolysis of Np(IV) and Pu(IV) and their complexation by aqueous Si(OH)4
- Reduction kinetics of Np(VI) by n-butyraldehyde in tributyl phosphate diluted with n-dodecane
- Speciation study on complex formation of uranium(VI) with phosphate and fluoride at high temperatures and pressures by time-resolved laser-induced fluorescence spectroscopy
- Stability constants of uranium(IV)-α-isosaccharinic acid and gluconic acid complexes
- Uranium(VI) complexes with sugar phosphates in aqueous solution
- Uranium kernel formation via internal gelation
- Investigation of evaporation characteristics of polonium and its lighter homologues selenium and tellurium from liquid Pb-Bi-eutecticum
- Synergistic extraction of Ce(III), Eu(III) and Tm(III) with a mixture of picrolonic acid and tributylphosphine oxide in chloroform
- Synthesis of malonic acid-functionalized Amberlite XAD-4 and its use in solid phase extraction/preconcentrative separation of thorium(IV)
- INAA methodology using low power reactor for the characterization of IAEA-433; Coastal marine sediment as a potential reference material
- Determination of natural radioactivity in building materials used in the Karachi area by γ-ray spectrometry and INAA
- Improved targetry and production of iodine-124 for PET studies
