Tributylphosphate Extraction Behavior of Bismuthate-Oxidized Americium

• Published in: Inorganic chemistry Vol. 47; no. 15; pp. 6984 - 6989
• Main Authors: Mincher, Bruce J, Martin, Leigh R, Schmitt, Nicholas C
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 04.08.2008
• Subjects: Absorbance; Acidic oxides; ACTINIDES; AMERICIUM; Contact; DODECANE; FLUORIDES; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; NITRIC ACID; OXIDATION; OXIDIZERS; Phosphates; PRECIPITATION; PRODUCTION; SODIUM; SOLVENT EXTRACTION; TBP; VALENCE; WAVEGUIDES
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic800667h

Higher oxidation states of americium have long been known; however, options for their preparation in acidic solution are limited. The conventional choice, silver-catalyzed peroxydisulfate, is not useful at nitric acid concentrations above about 0.3 M. We investigated the use of sodium bismuthate as an oxidant for Am3+ in acidic solution. Room-temperature oxidation produced AmO2 2+ quantitatively, whereas oxidation at 80 °C produced AmO2 + quantitatively. The efficacy of the method for the production of oxidized americium was verified by fluoride precipitation and by spectroscopic absorbance measurements. We performed absorbance measurements using a conventional 1 cm cell for high americium concentrations and a 100 cm liquid waveguide capillary cell for low americium concentrations. Extinction coefficients for the absorbance of Am3+ at 503 nm, AmO2 + at 514 nm, and AmO2 2+ at 666 nm in 0.1 M nitric acid are reported. We also performed solvent extraction experiments with the hexavalent americium using the common actinide extraction ligand tributyl phosphate (TBP) for comparison to the other hexavalent actinides. Contact with 30% tributyl phosphate in dodecane reduced americium; it was nevertheless extracted using short contact times. The TBP extraction of AmO2 2+ over a range of nitric acid concentrations is shown for the first time and was found to be analogous to that of uranyl, neptunyl, and plutonyl ions.