Actinides ions in aqueous solution

Table 6. Stability of Actinide Ions in Aqueous Solution...

Jones, A.D. Choppin, G.R. Complexes of actinide ions in aqueous solution, Actinides Rev. 1 (1969)311-336. 

Photochemical manipulation of actinide valence states has been studied as a means towards a salt-free method for actinide separation during fuel processing. This section summarises the points of relevance to photocatalytic valence manipulation and places them in the context of the dark redox reactions of actinide ions in aqueous solution. 

Table 20-6 The Principal Actinide Ions in Aqueous Solution"... 

R. Stumpe, J. I. Kim, W. Schrepp, H. Walther, Speciation of Actinide Ions in Aqueous Solution by Laser-induced Pulsed Spectrophotoacoustic Spectroscopy, Appl. Phys. B 34, 203 (1984)... 

David F. (1986) Thermodynamic properties of lanthanide and actinide ions in aqueous solution. J. Less-Common Metals 121, 27-42. 

Figure 3. Intraconfiguration absorption spectra of the heavier tripositive actinide ions in aqueous solution. The vertical lines are the calculated positions of the free-ion energy levels. A broad background absorption has been subtracted from the data. No measurements have been obtained for fermium.

The formal reduction potentials of actinide ions in aqueous solution are given in Table 28-6, from which it is clear that the electropositive character of the metals increases with increasing Z and that the stability of the higher oxidation states decreases. A comparison of various actinide ions is given in Table 28-7. It must be noted also that, for comparatively short-lived isotopes decaying by a-emission or spontaneous fission, heating and chemical effects due to the high level of radioactivity occur in both solids and aqueous solu-... 

TABLE 16.2. Prepanaion methods and stability of actinide ions in aqueous solutions... 

Observed optical absorption spectra of trivalent lanthanide and actinide ions in aqueous solution at ambient temperature (nominally 295 K) are shown in figs. 1-21. The data are from the files of W.T. Carnall. The lanthanide-ion absorption data from Ce through Yb " are essentially those reported by Carnall (1979) and the actinide data somewhat extend the spectra given by Carnall (1986) for U through Es. The spectra were recorded in dilute mineral acid solution (generally HCIO ) and solvent... 

On the basis of the limited data available, Moskvin [300] has presented some generalizations of the thermodynamics of the formation of actinide ions in aqueous solutions. His analysis includes discussion of the heat capacities of triply charged actinide ions and the changes in their heat capacities on hydration and when transferred from a crystal lattice to solution. Moskvin concludes that further accumulation of thermochemical data for actinide ions, including those of americium, is one of the most urgent contemporary problems in actinide chemistry. 

Table 14j6 Stability of actinide ions in aqueous solution. 

The actinide ions in aqueous solution resemble the tripositive lanthanide ions in their precipitation reactions, allowing for differences in the redox properties of early members of the actinide series. The chloride, bromide, nitrate, bromate, and perchlorate anions form water-soluble salts, which can be isolated as hydrated solids by evaporation. The acetates, iodates, and iodides are somewhat less soluble in water. The sulfates are sparingly soluble in hot solutions, somewhat more soluble in the cold. Insoluble precipitates are formed with hydroxide, fluoride, carbonate, oxalate, and phosphate anions. Precipitates formed from aqueous solution are usually hydrated, and the preparation of anhydrous salts from the hydrates without formation of hydrolyzed species can only be accomplished with difficulty. The actinide(iv) ions resemble Ce(iv) in forming fluorides and oxalates insoluble even in acid solution. The nitrates, sulfates, perchlorates, and sulfides are all water-soluble. The iv state actinide ions form insoluble iodates and arsenates even in rather strong acid solution. The... 

Real F, Trnmm M, Schimmelpfennig B, Masella M, Vallet V. Further insights in the ability of classical non-additive potentials to model actinide ions in aqueous solution. J Comput Chem. 

For a metal cation in aqueous solution, hydrolysis occurs when the first-shell water molecule is sufficiently polarized to promote a proton transfer to a second-shell water molecule. The deprotonated species often forms a mixture of new aqua species and precipitates, depending on the pH and other thermodynamic conditions. Therefore, knowledge of the hydrolysis of actinide ions in aqueous solution enhances our ability to accurately predict the chemistry and thermodynamics of nuclear waste remediation. Hydrolysis occurs easily for highly charged actinide ions in solution, since the highly charged ion weakens the O-H bond in the first-shell water molecule, leading to the release of H (aq). 

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