Carbonate Complexation of Np(VI) in Near-Neutral Solutions.

Pratopo, Mochammad Ilham; Moriyama, Hirotake; Higashi, Kunio

doi:10.3327/jnst.30.1024

Cited by 6 publications

(19 citation statements)

References 10 publications

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“…The spectra observed at this pH region is the same as the previous result [12], and similar characteristic absorption bands have also been reported by others [9][10][11]14]. In the case of the spectra at high pH, on the other hand, there is no detailed analysis in the literature up to the present.…”

Section: Spectrophotometric Observationssupporting

confidence: 87%

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Hydrolysis and Carbonate Complexation of Np(VI) in High pH Solutions

1995

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A spectroscopic study of Np(VI) was performed in carbonate solutions of high pH. Up to pH 12.5, the characteristic absorption bands were observed at 625, 670, and 703 nm. By considering the presence of Np0 2 (0H) 2(s) as the solid phase, the result was analyzed by the reaction of Np0 2 (0H) 2(s , + CO?" = Np0 2 (0H) 2 C0r.At pH>12.5, the new characteristic absorption bands centered at 530, 600, and 640 nm were observed in place of 625, 670, and 703 nm. The absorbancies increased with the increase of pH. From the observations, it was predicted that the Np0 2 (0H) 2 C0r was transformed to Np0 2 (0H) 3 " at high pH.Np0 2 (0H) 2 C0f" + OH" = Np0 2 (OH) 3 " + CO?"· By measuring the solubility and taking the literature value of the Np0 2 (0H) 2(5) solubility product, the stability constant of Np0 2 (0H) 2 C0r was derived to be log ß 2 , = 20.11 ±0.23. The stability constant of Np0 2 (0H) 3 " was obtained as log/?·, = 19.61 ±0.11.

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Section: Spectrophotometric Observationssupporting

confidence: 87%

“…On the other hand, the formation of Np0 2 (C0 3 )r, Np0 2 (C0 3 )r and (Np0 2 ) 2 (0H) 3 C0 3~ has been considered in the Potentiometrie titration study of Maya [11]. In our recent report [12], a spectrophotometric observation has been combined with a solubility measurement for the speciation of Np(VI) in carbonate solutions up to pH 10.5.…”

Section: Introductionmentioning

confidence: 97%

Hydrolysis and Carbonate Complexation of Np(VI) in High pH Solutions

1995

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“…a oH-y (10) (11) Brought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 7/30/15 10:37 PM Thus the stability constants β° can be evaluated by combining the solubility product of the solid compound Na 2 U 2 O v · χ H z O with the apparent equilibrium constant K' 0 for reaction (3),…”

Section: Calculation Of the Equilibrium Constantsmentioning

confidence: 99%

“…For U(VI), the existence of [(U0 2 ) 2 (C0 3 )(0H) 3 ]" [6][7][8] and [U0 2 (C0 3 )(0H)]" [9] have been suggested. In the solubility study of Np(VI), on the other hand, the formation of [Np0 2 (C0 3 )(0H) 2 ] 2 -and [Np0 2 (C0 3 ) 2 (0H) 2 ] 4~ have been proposed to explain the increase in the solubility with increasing carbonate ion concentration and the decrease with increasing pH of solutions from 12 to 13 [10][11][12], These types of complexes have not been proposed in the analysis of the solubility of U(VI) because no investigations were reported for hydroxide-carbonate systems in such highly basic solutions.…”

Section: Introductionmentioning

confidence: 99%

Solubility of U(YI) in Highly Basic Solutions

et al. 1998

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The solubility of U(VI) was measured in highly basic solutions (pOHc = -logfOH"] ranges from 3 down to 0) at the ionic strength I = 0.5-2.0 Μ (Μ: mol dm -3 ) over a wide range of carbonate ion concentrations C = IX 10~3-0.5 Μ by both oversaturation and undersaturation methods. In oversaturation experiments, the solubility of U(VI) decreased with increasing equilibration time from 1 week to 1 year, suggesting an increase in the crystallinity of the solid phase with aging. The solid phase was identified as Na 2 U 2 0 7 · χ H 2 0 (x = 3-5) by X-ray diffraction. Undersaturation experiments conducted for 1 month with this solid phase indicated a rapid attainment of equilibrium. These data were well interpreted by considering the formation of [U0 2 (0H) 3 ]", [U0 2 (0H) 4 ] 2 " and [U0 2 (C0 3 ) 3 ] 4 ", and the apparent equilibrium constants for [UO 2 (0H) 3 ]~ and [U0 2 (0H) 4 ] 2 " were determined with fairly small deviations. Using the evaluated solubility product of Na 2 U 2 0 7 · χ H 2 0 (χ = 3-5), the stability constants for the above species were evaluated. The upper limit values of the stability constants of the carbonatohydroxodioxouranium(VI) complexes were also evaluated.

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“…1.0 Μ (= mol · dm" 3 ) ionic strength under different C0 2 partial pressures, similarly to the study of U(VI) [9]. Furthermore, Moriyama et al [10][11][12] performed spectrophotometry observations and solubility measurements of Np(VI) in the pH range of 9.6 to 13.6 in 0.1 Μ NaC10 4 under atmospheric condition. The formation of NpO 2 (0H) 2 C0i~, Np0 2 (0H) 2 (C0 3 )r and Np0 2 (C0 3 ) 3 was suggested in equilibrium with Np0 2 (0H) 2 (s).…”

Section: Introductionmentioning

confidence: 98%

Carbonate Complexation of Neptunyl(VI) Ion

Kato¹,

Kimura²,

Yoshida³

et al. 1998

Radiochimica Acta

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The neptunyl(VI) ion in aqueous carbonate system has been investigated by solubility measurements in 0.1 Μ NaC10 4 at 25 ± 0.1 °C in equilibrium with 80% C0 2 /0 2 atmosphere. Neptunium was oxidized and stabilized in hexavalent state in the presence of ozone during the experiment. The solubility limiting solid phase was characterized as Np0 2 C0 3 (s) by X-ray crystallography, UV-Vis-NIR photoacoustic spectroscopy and FT-IR photoacoustic spectroscopy. For this solid phase the solubility product lgiT^iNpOaCO,) = -14.04 ± 0.07 was obtained. The stability constants of Np(VI) carbonate complexes, i.e., lgyS, 01 (NpO 2 CO?) = 9.02 ± 0.10 and lg/? 10 ,(NpO 2 (CO 3 )r) = 20.41 ± 0.09, were determined together with upper limits of the dicarbonate complex, lg/? 102 (NpO 2 (CO 3 )!~) < 14.2, and the monohydrolyzed species, lg/?,, 0 (NpO 2 OH + ) < 9.0. These results were compared with those of uranyl(VI) and plutonyl(VI) ions in the literature.

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Carbonate Complexation of Np(VI) in Near-Neutral Solutions.

Cited by 6 publications

References 10 publications

Hydrolysis and Carbonate Complexation of Np(VI) in High pH Solutions

Hydrolysis and Carbonate Complexation of Np(VI) in High pH Solutions

Solubility of U(YI) in Highly Basic Solutions

Carbonate Complexation of Neptunyl(VI) Ion

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