Modeling of radionuclides in natural fluids: synthesis and characterization of the Na4(UO2)2(OH)4(C2O4)2 complex

The coordination chemistry of dioxouranium(VI) with organic ligands may represent an useful model to describe the migration of radionuclides in natural fluids. A new dioxouranium(VI) ternary complex of formula Na4(UO2)2(OH)4(C2O4)2 was precipitated at pH≅8. It was characterized by elemental analysis, ICP and IR spectroscopy, thermogravimetry (TG) and coupled TG–IR evolved gas analysis. Potentiometric measurements in the solution suggest that the equilibrium shifts from the prevalence of the (UO2)2(OH)2(C2O4)46− complex to the [(UO2)2(OH)4(C2O4)2]4− complex before the formation of a solid phase.