Actinyl(VI) Speciation in Concentrated Sodium Chloride Solutions

摘要

Thermodynamic parameters and sorption coefficients provide the fundamentaldatabase for the mathematical abstraction of environmental transport of actinides. We have been investigating the chemistry of the hexavalent actinides, U and Pu, in the solid state in concentrated salt (NaCl) solutions representative of conditions within geologic salt formations, sites for nuclear waste disposal. Chloride complexation is proven to play an important role for actinyl(VI) volubility and speciation. We investigated U(VI) and Pu(VI) equilibria with the predominant inorganic ligands hydroxide and carbonate in the presence of chloride. We used a number of spectroscopic techniques (UV-vis-NIR, Raman, FTIR, NMR, XAS) and Xray diffraction to characterize solution species and solid phases as a function of pH, carbonate concentration, and ionic strength.