Hydrolysis Reactions of Am (II I) and Am(V)

Abstract

Hydrolysis reactions of Am (III) have been investigated in noncomplexing solution as well as saline solutions under CO,-free conditions. The solubility experiment in combination with radiometric pH-titration is carried out for the pH range from 6 to 13, at different ionic strengths. In non-complexing solution, the solubility product is found to be increasing along with an increase of the specific α-activity in a given experimental solution. In concentrated NaO solutions (I è 3M, pH > 7) with high specific inactivities ( > 1 Ci/L), the α-radiolysis starts generating substantial amounts of oxidized chlorine species, e. g. CIO", which results in the oxidation of Am (III) to Am(V). The hydrolysis reaction of Am(V) in 3 Af NaCl is also investigated by radiometric pH-titration. Solubility products (Ksp) of Am(OH) 3 (s) and AmO,(OH)(s) and hydrolysis constants of Am (III) and Am(V) are calculated from the solubility data. The speciation of different hydrolysis products, undertaken by laser-induced photoacoustic spectroscopy (LPAS), has verified probable species assessed theoretically on the basis of solubility experiments.

Solubility of Nd3+ and UO22+ in WIPP brine as oxidation-state invariant analogs for plutonium

“…The contribution of carbonate complexation to the solubility of Nd(III) has already been investigated by others in low ionic strength solutions [8][9][10][11][12][13][14][15]. The goal of our study was to extend these results to higher ionic strength brines to determine the realistic effect of hydrolysis and carbonate complexation on Nd(III) solubility as a function of pH in simulated ERDA-6 and GWB brines.…”

Actinide (III) solubility in WIPP Brine: data summary and recommendations

“…Actinide (III) Solubility in WIPP Brine: Data Summary and Recommendations Page 12 Stadler and Kim (1988) investigated the pH dependence of Am(OH) 3 (s) solubility in 0.1 M NaClO 4 and more concentrated sodium chloride and perchlorate solutions at 25 ±0.5 o C. The effect of α-induced radiolysis on solubility was also studied using different total concentrations of americium-241. The solid phase was not characterized in this work.…”

Actinides in Solution: Complexation and Kinetics

“…Of the common oxidation states, the trivalent actinides have been the most intensively studied species. Solubility experiments (Rai et al, 1983), solvent extraction (Caceci and Choppin, 1983a), spectroscopy (Stadler and Kim, 1988), and other techniques (Shalinets and Stepanov, 1972) have been used. The low solubility of An(OH) 3 in neutral/basic solutions prevents use of conventional absorption spectroscopy.…”

“…The low solubility of An(OH) 3 in neutral/basic solutions prevents use of conventional absorption spectroscopy. However, time-resolved laser fluorescence spectroscopy allows measurements at the very low concentrations present in neutral/ alkaline solutions (Stadler and Kim, 1988). This laser spectroscopy technique was used to study the hydrolysis of Cm(III) at concentrations as low as 3 Â 10 The laser fluorescence method has been used by Fanghänel and Kim (1994) to measure the values of log b 11 and log b 12 for Cm(III) over a range of ionic strengths from 0.011 to 6.15 M in NaCl solution at pH 8.6.…”

“…Because of the strong sorption characteristics of the hydroxide species, Am(III) is frequently removed from solution onto colloids, sediments, and humic substances. Stadler and Kim (1988) and the OECD-NEA (Silva et al, 1995, Guillaumont et al, 2003 have reviewed americium hydrolysis, while the hydrolysis of trivalent actinides has been reviewed by Fuger et al (1992) and Rizkalla and Choppin (1994).…”