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A. B. Yusov, V. P. Shilov, A. M. Fedosseev

Properties of U(VI)/U(IV) and Fe(III)/Fe(II) pairs and equilibrium U(VI)+2Fe(II)↔U(IV)+2Fe(III) in solutions of unsaturated heteropolytungstates K₁₀P₂W₁₇O₆₁ and K₈SiW₁₁O₃₉

Keywords: Uranium, Iron, Heteropolyanion, Redox

The unsaturated phosphotungstate K₁₀P₂W₁₇O₆₁ and silicotungstate K₈SiW₁₁O₃₉ are strong and selective complexants of An(IV) in aqueous solution. In presence of these complexants, the redox properties of actinides are changed drastically due to stabilization of the tetravalent actinides.

Redox potentials of Fe(III)/Fe(II) and U(VI)/U(IV) pairs were measured in K₁₀P₂W₁₇O₆₁ and K₈SiW₁₁O₃₉, solutions with various HClO₄ concentration and absolute complexes stability constants of Fe(III) ions with phosphotungstate and silicotungstate ions were determined: logβ_abs^Fe(III)=17.4±0.8 and 20.1±0.8 respectively. The equilibrium constant of reaction between U(VI) and Fe(II) in 1 M HClO₄ was determined. The equilibrium constant, K_eq, depends on excess of heteropolyanion, and is close to 10⁴ in 1 M HClO₄ at [P₂W₁₇O₆₁]_free∼5×10^-4 M.

Radiochimica Acta, Oldenbourg Wissenschaftsverlag

Print ISSN: 0033-8230
Volume: 95, 04/2007
Pages: 209 - 216

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