UNDERSTANDING VARIATION IN PARTITION COEFFICIENT, Kd ...

In addition to hydrolytic complexes, thorium can also form various aqueous complexes with
inorganic anions such as dissolved fluoride, phosphate, chloride, and nitrate. Studies (e.g.,
LaFamme and Murray, 1987) completed since the review by Langmuir and Herman (1980)
indicate the presence of dissolved thorium carbonate complexes and their importance to the
solution chemistry of thorium. Due to the lack of available data, no thorium carbonate species
were listed by Langmuir and Herman (1980). Östhols et al. (1994) have recently published
- and Th(CO3) 5
thermodynamic constants for the thorium carbonate complexes Th(OH) 3CO 3
Percent Distribution
100
80
60
40
20
0
Th 4+
ThOH +
2+
Th(OH) 2
+
Th(OH) 3
3 4 5 6 7 8 9 10
5.57
pH
o
Th(OH) 4 (aq)
6- that
are based on their solubility studies of microcrystalline ThO 2 at different partial pressures of CO 2
in aqueous media.
Figure 5.4. Calculated distribution of thorium hydrolytic species as a function of pH.
[The species distribution is based on a concentration of 1 µg/l total
dissolved thorium in pure water (i.e., absence of complexing ligands other
than OH - ) and thermodynamic data from Langmuir and Herman (1980).]