Am³⁺-F^- Interaction in Mixed System of Dimethyl Sulfoxide and Water

Abstract

Americium / Mixed solvent / Stability constant / Monofluoride complex / Solvation number SummaryThe stability constant (/?,) of AmF 2+ in the mixed solvent system of dimethyl sulfoxide and water with 0.1 moldm -3 ionic strength was determined using a solvent extraction technique to compare with Nd(III) bearing similar chemical properties to Am(III). The value of In ß, was nearly constant when the mole fraction of DMSO in the bulk solution (X s ) was less than 0.04 and it increased with an increase in X a in the range of 0.04 < X s < 0.25. The variation of In β, with X x is obviously different from the result of Nd(III). The difference between the variations of In β, of Am(III) and Nd(III) with X, could be associated with (1) the cation solvation effect (containing the variation effect of the solvation number in the primary solvation sphere of tripositive cation) and (2) the variation effect of interionic distance between tripositive cation and fluoride ion. The variation of In β, of Am(IIl) in 0.04 < X, < 0.25 of the DMS0-H 2 0 system is considerably influenced by both effects due to the variation of solvation number in the primary solvation sphere and the variation of interionic distance, but that of Nd(III) in X, < 0.28 hardly contains those effects.

Coordination of perchlorate ion in the secondary solvation sphere of Am3+ in the tracer concentrations in mixed system of dimethyl sulfoxide/water with 1.00M (H,Na)(Cl,ClO4)

“…SUGANUMA et al examined the variation of the stability constant of AmF 2+ ([~I(F, DMSO)) at a tracer concentration against the mole fraction (Xs) of dimethyl sulfoxide (DMSO) of the mixed DMSO+H20 solutions. 4 The Donor Number (DN) of DMSO is larger than those of CH3OH and H20.5 They also showed that the variation of In [~I(F,DMSO) against X s was governed by the variation of the interionic distance between Am 3+ and F-in addition to the effects of (1A) and (2A) described previously.…”

A critical review on the stability constants of the fluoride complexes of actinides in aqueous solution and their correlation with fundamental properties of the ions

“…The electrons in the 5f-orbital may have a repulsive effect on the F-ion that is not effective up to Pu 3+ (5t 5) and becomes effective only from Am3+(5f 6) onwards. SUGANUMA et al 124,125 have recently reported studies on Am3+-F -interaction in mixed solvent media. The effects due to the variations of solvation number and inter-ionic distance considerably influenced the values of log[31 in these media.…”