Spectroscopic characterization of trivalent f-element (Eu, Am) solid carbonates

Solubility studies show that trivalent f-element carbonate compounds are the predominant solids that primarily limit the soluble metal ion concentration under environmental conditions. We systematically investigated the spectroscopic characteristics of a series of solid f-element (Eu and Am-243) carbonates. Varying pH, ionic strength, and carbonate concentration results in the formation of M(OH)(3), MOHCO3, M-2(CO3)(3). nH(2)O, and NaM(CO3)(2). nH(2)O, where M=Eu(III) or Am(III). Solids were characterized by FTIR, fluorescence, and EXAFS spectroscopies that determined and confirmed the coordination environment, and by their individual X-ray diffraction powder patterns. The number of coordinated crystal waters was determined to be 2-3 for Eu-2(CO3)(3). nH(2)O and 5 for NaEu(CO3)(2). nH(2)O using thermogravimetric/differential thermal analysis and fluorescence lifetime. We report studies of the fluorescence of Am(III) and the effect of carbonate coordination on the D-5(1) --> F-7(1) transition. (C) 2000 Elsevier Science S.A. All rights reserved.