Equilibrium of Nitrous Acid-Catalyzed Oxidation of Neptunium in Nitric Acid-TBP Extraction System

Osamu Tochiyama; Yoshinobu Nakamura; Yasushi Katayama; Yasushi Inoue

doi:10.3327/jnst.32.50

Equilibrium of Nitrous Acid-Catalyzed Oxidation of Neptunium in Nitric Acid-TBP Extraction System

Osamu Tochiyama, Yoshinobu Nakamura, Yasushi Katayama, Yasushi Inoue

Research output: Contribution to journal › Article › peer-review

3 Citations (Scopus)

Abstract

The redox equilibrium of neptunium with nitric and nitrous acids, NpO₂⁺+(3/2)H⁺+(1/2)NO₃^-=NpO₂²⁺+(1/2)HNO₂+(1/2)H₂O was studied in 3 to 6M nitric acid solutions by 30 vol% TBP-dodecane extraction. The equilibrium distribution ratio of neptunium was shown to be expressed by D=D₆R/(1+R), where R is [Np(VI)]/[Np(V)] and D₆ the distribution ratio of pure Np(VI). To examine the dependence of the apparent concentration constant for the reaction, K_app=[NP(VI)][HNO₂]^1/2/[Np(V)][HNO₃]_t² on nitric acid concentration, the redox potentials of HNO₃/HNO₂ solutions were measured which revealed that the activity correction on H⁺, NO₃^-, HNO₂ and H₂O was effective enough to give an ideal Nernst relationship for the potential of HNO₃/HNO₂. With using the activity coefficient quotient, Y=y_S²/(y_ua_w)^1/2 (y_S: stoichiometric activity coefficient of nitric acid, y_u: activity coefficient of HNO₂, aw: rational activity of water), the apparent concentration constant Kapp was shown to be expressed by K_app=K_mixY, where K_mix=[Np(VI)]{HNO₂}^1/2{H₂O}^1/2/[NP(V)]{H⁺}^3/2{NO₃^-}^1/2 and log K_mix=-2.77 and log Y=-0.13, 0.02 and 0.28 for [HNO₃]_t=3, 4 and 6M, respectively.

Original language	English
Pages (from-to)	50-59
Number of pages	10
Journal	Journal of Nuclear Science and Technology
Volume	32
Issue number	1
DOIs	https://doi.org/10.3327/jnst.32.50
Publication status	Published - 1995 Jan 1
Externally published	Yes

Keywords

Purex process
TBP
activity coefficient
neptunium
nitric acid
nitrous acid
pH value
redox potential
redox reaction
solvent extraction

ASJC Scopus subject areas

Nuclear and High Energy Physics
Nuclear Energy and Engineering

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@article{3d4f257b86644d07be32cc10b94b9ccd,

title = "Equilibrium of Nitrous Acid-Catalyzed Oxidation of Neptunium in Nitric Acid-TBP Extraction System",

abstract = "The redox equilibrium of neptunium with nitric and nitrous acids, NpO2++(3/2)H++(1/2)NO3-=NpO22++(1/2)HNO2+(1/2)H2O was studied in 3 to 6M nitric acid solutions by 30 vol% TBP-dodecane extraction. The equilibrium distribution ratio of neptunium was shown to be expressed by D=D6R/(1+R), where R is [Np(VI)]/[Np(V)] and D6 the distribution ratio of pure Np(VI). To examine the dependence of the apparent concentration constant for the reaction, Kapp=[NP(VI)][HNO2]1/2/[Np(V)][HNO3]t2 on nitric acid concentration, the redox potentials of HNO3/HNO2 solutions were measured which revealed that the activity correction on H+, NO3-, HNO2 and H2O was effective enough to give an ideal Nernst relationship for the potential of HNO3/HNO2. With using the activity coefficient quotient, Y=yS2/(yuaw)1/2 (yS: stoichiometric activity coefficient of nitric acid, yu: activity coefficient of HNO2, aw: rational activity of water), the apparent concentration constant Kapp was shown to be expressed by Kapp=KmixY, where Kmix=[Np(VI)]{HNO2}1/2{H2O}1/2/[NP(V)]{H+}3/2{NO3-}1/2 and log Kmix=-2.77 and log Y=-0.13, 0.02 and 0.28 for [HNO3]t=3, 4 and 6M, respectively.",

keywords = "Purex process, TBP, activity coefficient, neptunium, nitric acid, nitrous acid, pH value, redox potential, redox reaction, solvent extraction",

author = "Osamu Tochiyama and Yoshinobu Nakamura and Yasushi Katayama and Yasushi Inoue",

year = "1995",

month = jan,

day = "1",

doi = "10.3327/jnst.32.50",

language = "English",

volume = "32",

pages = "50--59",

journal = "Journal of Nuclear Science and Technology",

issn = "0022-3131",

publisher = "Atomic Energy Society of Japan",

number = "1",

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TY - JOUR

T1 - Equilibrium of Nitrous Acid-Catalyzed Oxidation of Neptunium in Nitric Acid-TBP Extraction System

AU - Tochiyama, Osamu

AU - Nakamura, Yoshinobu

AU - Katayama, Yasushi

AU - Inoue, Yasushi

PY - 1995/1/1

Y1 - 1995/1/1

N2 - The redox equilibrium of neptunium with nitric and nitrous acids, NpO2++(3/2)H++(1/2)NO3-=NpO22++(1/2)HNO2+(1/2)H2O was studied in 3 to 6M nitric acid solutions by 30 vol% TBP-dodecane extraction. The equilibrium distribution ratio of neptunium was shown to be expressed by D=D6R/(1+R), where R is [Np(VI)]/[Np(V)] and D6 the distribution ratio of pure Np(VI). To examine the dependence of the apparent concentration constant for the reaction, Kapp=[NP(VI)][HNO2]1/2/[Np(V)][HNO3]t2 on nitric acid concentration, the redox potentials of HNO3/HNO2 solutions were measured which revealed that the activity correction on H+, NO3-, HNO2 and H2O was effective enough to give an ideal Nernst relationship for the potential of HNO3/HNO2. With using the activity coefficient quotient, Y=yS2/(yuaw)1/2 (yS: stoichiometric activity coefficient of nitric acid, yu: activity coefficient of HNO2, aw: rational activity of water), the apparent concentration constant Kapp was shown to be expressed by Kapp=KmixY, where Kmix=[Np(VI)]{HNO2}1/2{H2O}1/2/[NP(V)]{H+}3/2{NO3-}1/2 and log Kmix=-2.77 and log Y=-0.13, 0.02 and 0.28 for [HNO3]t=3, 4 and 6M, respectively.

AB - The redox equilibrium of neptunium with nitric and nitrous acids, NpO2++(3/2)H++(1/2)NO3-=NpO22++(1/2)HNO2+(1/2)H2O was studied in 3 to 6M nitric acid solutions by 30 vol% TBP-dodecane extraction. The equilibrium distribution ratio of neptunium was shown to be expressed by D=D6R/(1+R), where R is [Np(VI)]/[Np(V)] and D6 the distribution ratio of pure Np(VI). To examine the dependence of the apparent concentration constant for the reaction, Kapp=[NP(VI)][HNO2]1/2/[Np(V)][HNO3]t2 on nitric acid concentration, the redox potentials of HNO3/HNO2 solutions were measured which revealed that the activity correction on H+, NO3-, HNO2 and H2O was effective enough to give an ideal Nernst relationship for the potential of HNO3/HNO2. With using the activity coefficient quotient, Y=yS2/(yuaw)1/2 (yS: stoichiometric activity coefficient of nitric acid, yu: activity coefficient of HNO2, aw: rational activity of water), the apparent concentration constant Kapp was shown to be expressed by Kapp=KmixY, where Kmix=[Np(VI)]{HNO2}1/2{H2O}1/2/[NP(V)]{H+}3/2{NO3-}1/2 and log Kmix=-2.77 and log Y=-0.13, 0.02 and 0.28 for [HNO3]t=3, 4 and 6M, respectively.

KW - Purex process

KW - TBP

KW - activity coefficient

KW - neptunium

KW - nitric acid

KW - nitrous acid

KW - pH value

KW - redox potential

KW - redox reaction

KW - solvent extraction

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U2 - 10.3327/jnst.32.50

DO - 10.3327/jnst.32.50

M3 - Article

AN - SCOPUS:85007983789

VL - 32

SP - 50

EP - 59

JO - Journal of Nuclear Science and Technology

JF - Journal of Nuclear Science and Technology

SN - 0022-3131

IS - 1

ER -

Equilibrium of Nitrous Acid-Catalyzed Oxidation of Neptunium in Nitric Acid-TBP Extraction System

Abstract

Keywords

ASJC Scopus subject areas

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