Americium solubility constant

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... 

For zero ionic strength, Guillaumont et al. (2003) determined a solubility constant of 15.6 0.6 for Am(OH)3(s) at zero ionic strength in their review of the thermochemistry of americium, and this value was later accepted by Neck et al. (2009). This value is also accepted in the present review but is coupled with the data of Stadler and Kim (1988) and Runde and Kim (1994) to determine the ionic strength dependence of the solubility constant in NaCl media using... 

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 ... 

Tin and americium were so extensively sorbed under all conditions that isotherm data could not be obtained. These elements are not significantly mobile in the Mabton Interbed aquifer. Values of Freundlich constants for technetium, radium, uranium, neptunium, and plutonium are given in Table IV. The Freundlich equation did not fit the selenium sorption data very well probably because of slow sorption kinetics or precipitation. Precipitation was also observed for technetium at 23°C for concentrations above 10 7M. This is about the same solubility observed for technetium in the sandstone isotherm measurements. Linear isotherms were observed only in the case of radium sorption. In general, sorption on the Mabton Interbed was greater than on the Rattlesnake Ridge sandstone. This is probably due to the greater clay content of the Mabton standard. 

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 ... 

Studies of the speciation of actinides in environmental waters are made difficult by the very low concentrations involved and the possibility that minor, undetected contaminants may dominate the binding of a particular metal ion. The environmental behaviour of the actinides has been reviewed. Americium and thorium exhibit simpler behaviour than other actinides since their oxidation states under such conditions are limited to Am and Th. Both are readily adsorbed by granitic rocks and tend to exhibit low solubilities, The thermodynamic solubility product of amorphous Am(OH)3 has been measured as log = 17.5 0.3 and no evidence for amphoteric behaviour or the formation of Am(OH)4 was found below pH 13. Stability constants for the binding of Am to humic acid have been found to vary with the degree of ionization, a, and were given by log = 10.58a -1-3.84 and log 2 = 5.32a -b 10.42. These were larger than the corresponding values for Eu. Humic acids also bind Th as described in Section 65.2.1. 

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. 

There have been a number of studies that have obtained the hydrolysis constants of americium(III) from solubility measurements. In addition, there have also been a few studies that have obtained constants using other techniques. The data are listed in Table 9.22. 

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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