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Journal of Radioanalytical and Nuclear Chemistry

, Volume 143, Issue 2, pp 403–414 | Cite as

Temperature and ionic strength influence on U(VI/V) and U(IV/III) redox potentials in aqueous acidic and carbonate solutions

  • H. Capdevila
  • P. Vitorge
Solution Chemistry

Abstract

Redox potentials: E(UO 2 2+ /UO 2 + )=60±4 mV/NHE, E(U4+/U3+)=−630±4mV/NHE measured at 25°C in acidic medium (HClO4 1M) using cyclic voltametry are in accordance with the published data. From 5°C to 55°C the variations of the potentials of these systems (measured against Ag/AgCl electrode) are linear. The entropies are then constant: [ΔS(UO 2 2+ /UO 2 + )−ΔS(Ag/AgCl)]/F=0±0.3 mV/°C, [ΔS(U4+/U3+)−ΔS(Ag/AgCl)]/F=1.5±0.3 mV/°C. From 5°C to 55°C, in carbonate medium (Na2CO3=0.2M), the Specific Ionic Interaction Theory can model the experimental results up to I=2M (Na+, ClO 4 , CO 3 2− ): E(UO2(CO3) 3 4− /UO2(CO3) 3 5− )=−778±5 mv/NHE (I=0, T=25°C, Δ∈(25°C)=∈(UO2(CO3) 3 4− , Na+)−∈(UO2(CO3) 3 5− , Na+)=0.92 kg/mole, ΔS(UO2(CO3) 3 4− /UO2(CO3) 3 5− =−1.8±0.5 mV/°C (I=0), Δ∈=∈(Cl, Na+)=(1.14−0.007T) kg/mole. The U(VI/V) potential shift, between carbonate and acidic media, is used to calculate (at I=0,25°C):
$$\log \frac{{\beta _3 U(V)}}{{\beta _3 U(VI)}} = - 14.7 \pm 0.5$$
and then
$$\log \beta _3 U(V) = 6.6 \pm 0.3.$$

Keywords

Entropy Physical Chemistry Inorganic Chemistry Ionic Strength Redox Potential 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Akadémiai Kiadó 1990

Authors and Affiliations

  • H. Capdevila
    • 1
  • P. Vitorge
    • 1
  1. 1.Laboratoire de Chimie CEA IRDI/DERDCA/DRDD/SESD/SCPCSFontenay aux Roses, CedexFrance

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