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Wolfgang Wadsak, E. Hrnecek, K. Irlweck

Formation of americium(III) complexes with aqueous silicic acid

The interaction of americium(III) with aqueous silicic acid was studied by competitive solvent extraction with 0.1 M thenoyltrifluoroacetone (HTTA) as extractant. The aqueous phase contained only 0.2 M NaClO₄ or additionally 0.03 M silicic acid at p[H] 3.0-3.8 adjusted with perchloric acid. ²⁴¹Am was used in tracer amounts and its distribution ratio was measured γ -spectrometrically. Silicic acid solutions were prepared by hydrolysis of tetramethylorthosilicate (TMOS). Kinetic investigations with the molybdate reaction showed polymeric silica fractions between 10-17% within the p[H] range investigated. Extraction times of about 1.5 hours were taken to assure distribution equilibrium for the ²⁴¹Am extraction. The occurrence of a 1:1 complex of americium with silicic acid according to the reaction Am³⁺ + Si(OH)₄ ↔ AmOSi(OH)₃²⁺ + H⁺ could be demonstrated and a formation constant of K₁ = (6.9&plusm;0.7)×10^-3 [log K₁ = -2.16&plusm;0.04] at I = 0.2 M was calculated.

Radiochimica Acta, Oldenbourg Wissenschaftsverlag

Print ISSN: 0033-8230
Volume: 88, 02/2000
Pages: 061

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