Die chelatbildung und extraktion des dreiwertigen actiniums, americiums, curiums und californiums mit acetylaceton und einigen seiner derivate

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 NaClO4or 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 the241Am 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±0.7)×10-3[log K1= -2.16±0.04] at I = 0.2 M was calculated.