The unusual extraction behavior of americium(III) and dioxouranium(VI) from picric acid medium using neutral oxodonors - II. A thermodynamic study

The role of temperature on the distribution of Am3+ and UO22+ was investiga ted in the extraction systems involving TBP and DOSO as the neutral oxodono rs and picrate as the organophilic counter anion. The inner-sphere water mo lecules and their substitution by the oxodonor molecules appeared to influe nce the extraction constants of these metal ions. The conditional extractio n constants for Am3+ were found to be larger (about 3 order of magnitude) t han those for UO22+. From the thermodynamics data it appeared that both TBP as well as DOSO bind Am3+ ion through outer-sphere coordination. In presen ce of 1M NaCl, though the interaction with TBP remains unaltered DOSO tend to form an inner-sphere complex. On the other hand, UO22+ forms inner-spher e complexes with DOSO and outer-sphere complex with TBP in the absence of s alt. In the presence of 1M NaCl, both TBP and DOSO form inner-sphere comple xes. The effect of ionic strength on metal ion extraction was also investig ated.