First acidification step of the tris(carbonato)dioxouranate(VI) ion, UO/sub 2/(CO/sub 3/)/sub 3//sup 4 -/

Journal Article · Sun Feb 01 00:00:00 EST 1981 · Inorg. Chem.; (United States)

DOI:https://doi.org/10.1021/ic50216a029· OSTI ID:6572381

Ciavatta, L ^[1]; Ferri, D; Grenthe, I; Salvatore, F

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1. Royal Inst. of Technology, Stockholm, Sweden

Potentiometric measurements with a glass electrode combined with solubility determinations of CO/sub 2/(g) have indicated that, at 25/sup 0/C in 3 M NaClO/sub 4/ medium with (U(VI)) < 0.05 M and log (HCO/sub 3//sup -/) greater than or equal to -1.2, the prevailing form of uranium (VI) is the species UO/sub 2/(CO/sub 3/0/sub 3//sup 4 -/ (= UO/sub 2/(OH)/sub 6/(CO/sub 2/)/sub 2//sup 4 -/). On acidification of UO/sub 2/(CO/sub 3/)/sub 3//sup 4 -/, and before solid uranyl carbonates start to precipitate, a polynuclear complex (UO/sub 2/0/sub 3/(CO/sub 3/)/sub 6//sup 6 -/ (= UO/sub 2/)/sub 3/(OH)/sub 12/(CO/sub 2/)/sub 6//sup 6 -/) was found to form according to 3UO/sub 2/(CO/sub 3/)/sub 3//sup 4 -/ + 3CO/sub 2/(g) + 3H/sub 2/O reversible (UO/sub 2/)/sub 3/(CO/sub 3/)/sub 6//sup 6 -/ + 6HCO/sub 3//sup -/ with the equilibrium constant, log *..beta../sub 3,12,6/ = -6.43 +- 0.08. No evidence for the species UO/sub 2/(CO/sub 3/)/sub 2//sup 2 -/ or mixed species (UO/sub 2/)/sub p/(OH)/sub q/(CO/sub 3/)/sub r/ was obtained in the experimental range investigated: 10/sup -3/ less than or equal to (U(VI)) less than or equal to P/sub CO/sub 2// less than or equal to 1 atm, and -3.0 less than or equal to log (HCO/sub 3//sup -/) less than or equal to -0.7. The /sup 13/C NMR spectra of the two complexes indicate the presence of three equivalent groups in the mononuclear complex and two different carbonate sites with the ratio 1:2 between the integrated intensities in the trinuclear complex. The NMR data are compatible with a structure containing both bridging and terminal carbonate groups.

• OSTI ID: 6572381
• Journal Information: Inorg. Chem.; (United States), Vol. 20:2
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
URANYL COMPLEXES
CHEMICAL REACTION YIELD
CARBON 13
CARBONATES
CHEMICAL STATE
HYDRATION
MOLECULAR STRUCTURE
NUCLEAR MAGNETIC RESONANCE
URANYL COMPOUNDS
ACTINIDE COMPLEXES
ACTINIDE COMPOUNDS
CARBON COMPOUNDS
CARBON ISOTOPES
COMPLEXES
EVEN-ODD NUCLEI
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
NUCLEI
OXYGEN COMPOUNDS
RESONANCE
SOLVATION
STABLE ISOTOPES
URANIUM COMPLEXES
URANIUM COMPOUNDS
YIELDS
400702* - Radiochemistry &amp; Nuclear Chemistry- Properties of Radioactive Materials