Americium hydroxide solubility

Solubility of Americium Hydroxide. Solutions containing greater than 10-6 M americium were examined by spectrophotometry to verify whether or not polymers were present. The molar extinction coefficient measured for the 503 nm absorption band was found to remain constant at e = 390 5 for all investigated solutions at pH = 3 6. Spectra recorded up to 850 nm in this pH range show the typical absorption bands of the Am3+ ion, which are similar to those observed in a dilute HCIO4 solution, without broadening or displacement. The concentration of americium ions in equilibrium solutions, [Am]s, is, therefore, considered a composite of only monomer species ... 

Synthesis of crystalline americium hydroxide, Am(OH)j, and determination of its enthalpy of formation. Estimation of the solubility-product constants of actinide(lll) hydroxides. Radiochim. Acta, 66/67, 89-93. 

Rai et al. (1983), Edelstein et al. (1983) and Nitsche and Edelstein (1985) studied the solubility of amorphous americium hydroxide. GuUlaumont etal. (2003) reviewed these data and determined a solubility constant at zero ionic strength of... 

Morss and Wilhams (1994) also estimated the solubility constant data for Bk(OH)g(s) and Cf(OH)g(s) from thermodynamic data determined for americium hydroxide and the relative change across the solubility of the lanthanide hydroxide phases. The solubilities (log determined for the two phases were 13.5 2.0 and 13.0 2.0, respectively. These values are retained in the present study ... 

In summary, the solubility and sorption reactions of cobalt, strontium, neptunium, plutonium, and americium were found to be dependent on HLW compositions. Evidence revealed the formation in HLW of organic complexes of cobalt, strontium, and americium, and of hydroxide complexes of neptunium(V) and plutonium(V). Sorption reactions were dependent on radioelement complex formation and suspected waste/sediment reactions. These data can aid in assessing effects of future HLW processing operations as well as in judging the feasibility of continued storage of HLW in existing tanks. 

In a separate experiment, the hydroxide precipitate of americium was produced directly in each experimental solution 10 mL solution of 0.1 M HCIO4 containing 1.3 x 10-3 M americium was mixed with 10 mL of 0.1 M NaC104 and made alkaline to produce the hydroxide precipitate by adjusting the pH with addition of NaOH. Solutions thus prepared were left under argon gas to attain the solubility equilibrium. 

Americium oxides. Keller [K2, K3] reports three stoichiometric binary oxides of americium AmO, Amj O3, Am02. The dioxide Am02 is the most stable of the americium oxides. It crystallizes with the cubic fluorite structure of aU the actinide dioxides. It can be formed as a dark brown powder, stable up to 1000°C, by heating trivalent americium nitrate, hydroxide, or oxalate in oxygen to 700 to 800 C. Americium dioxide is readily soluble in mineral acids. Hydrogen reduction of the dioxide yields Am2 O3. 

There have been no solubility data reported for americium(VI) oxide/hydroxide phases or stability data for hydrolysis species. 

Pazukhin, E.M. and Kochergin, S.M. (1989) Stability constants of hydrolysis species of americium(III) and solubility product of its hydroxide. Radiokhimiya, 31, 72-78. 

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