Thorium species

Perry DL, Tsao L. n.d. Thorium species on basalt surfaces. Lawrence Berkeley Laboratory, Berkeley, CA. 

Amine reagents also extract thorium from carbonate solutions and the use of a primary amine, RNH3C1, where R = C10 to Cl3 alkyl, as a 20% solution in kerosene allowed the concentrations of impurities in the extracted thorium to be reduced by factors of 33.8 for UVI, 111.4 for MoVI, 18.9 for Zrlv and 6167 for Mg11.177 The extracted thorium species was shown to be of the composition (RNH3)4Th(C03)4(H20)x. Di(tridecyl)amine has been used to extract thorium from barren uranium process liquors in the Blind River plant in Canada147 and flowsheets for the recovery of lanthanides, U03 and high-purity Th(S04)2 from the Elliot Lake area in Ontario using Primene/isodecanol have been described.178... 

Thorium oxide would not be expected to react with molten alkali metal nitrates. Brambilla claims, however, that a soluble thorium species is produced in the molten phase when nitric acid vapor is combined with fluoride ion in molten nitrates (10). 

Although Th02 will not be oxidized by the melt, it may be possible to produce a soluble thorium species. This has not been investigated in experiments to date. 

The present review does not include any compounds or complexes of elements in Groups 3 to 13 of the Periodic Table (which are mostly alloys), nor species containing organic hgands or species in non-aqueous solvents. Organic species were subject of the ninth volume in the NEA-TDB series [2005HUM/AND], although this does not include any data for thorium species. 

Chapters III contains a table of selected thermodynamic data for individual compounds and complexes of thorium (Table III-l), a table of selected reaction data (Table III-2) for reactions concerning thorium species and a table containing the heat capacities of individual species of thorium (Table III-3) that have been used in the evaluations. The selection of all these data is discussed in Chapters V to XII. For the gaseous species, in particular, only the more important of the heat capacity equations have been given explicitly in the relevant sections of these chapters. 

This chapter presents the chemical thermodynamic data set for thorium species that has been selected in this review. Table 111-1 contains the recommended thermodynamic data of the thorium compounds and species, Table 111-2 the recommended thermodynamic data of chemical equilibrium reactions by which the thorium compounds and complexes are formed, and Table 111-3 the temperature coefficients of the heat capacity data of Table 111-1 where available. 

The species and reactions in the tables appear in standard order of arrangement. Table III-2 contains information only on those reactions for which primary data selections are made in Chapter V of this review. These selected reaction data are used, together with data for key thorium species and auxiliary data selected in this review, to derive the corresponding formation data in Table III-l. The imcertainties associated with values for key thorium species and the auxiliary data are in some cases substantial, leading to comparatively large uncertainties in the formation quantities derived in this maimer. 

In the case of the non-hydrolysed thorium species we have the choice of using either the ion interaction model (with s(Th", NO3) = (0.31+0.12) kg-mol ) or calculating the free Th" concentration using the complex formation model and the corresponding equilibrium constants logm (VII.15) selected for Th(IV) nitrate complexes. However, there is no quantitative information on the ternary Th(lV)-hydroxide-nitrate complexes formed by Reactions (VII. 16). Therefore it is more convenient to use the ion interaction model for both the Th" ion and the hydroxide complexes, i.e., to use ion interaction coefficients e(Th", NOj) and... 

Figure VIII-4 Observed [1993FEL/RAI] and predicted solubilities of thorium double salts in NaF and NH4F solutions at 25°C using the thermodynamic data reported in Table VIII-8 and Table VIII-9. The solid line depicts predicted total thorium concentration and the other lines depict predicted concentrations of different thorium species as marked (a) ThF4-NaF-H20(cr) and (b) ThF4-NH4F(cr).

Figure IX-2 Observed and predicted aqueous concentrations at 25°C for solvent extraction studies in Na2S04 solutions [1963ALL/MCD], The solid line depicts the predicted total aqueous thorium concentration and the other lines depict the predicted concentrations of the individual thorium species in the aqueous phase as indicated, based on thermodynamic data (Table IX-5) and ion interaction parameters (Table IX-2) selected in this review.

As can be seen, the nitrate complexes are, in the main, the dominant thorium species in solution. As there are no experimental values for the enthalpy of formation of these complexes (neither for thorium nor for uratuum), we will not attempt to use further the experimental results of [1956FER/KAT] which are given here for information only. 

Danon points out that the data can also be described with a model where no cationic complexes are formed. The key conclusion of this study is that the uncharged complex Th(N03)4(aq) is predominant when the activity of the nitrate is about 0.5 M and that anionic complexes are formed at higher nitrate activities. In the analysis of the experimental data, Danon has not considered the variation of the activity coefficients of the thorium species participating in the reactions and there is no justification for this approximation. Because of this, the present review has not accepted the equilibrium constants proposed by Danon. It should be noted that the experimental mean-activity... 

Finally pH, ionic thorium species and colloids were found to approach a steady state which is comparable to the solid-liquid equilibrium of amorphous Th(IV) hydroxide determined in [2002NEC/MUL] with the coulometric titration-LIBD method. 

The experimental data consists of measured thorium concentrations at different given H2SO4 concentrations in equilibrium with Th(S04)2 9H20(cr). The total measured aqueous thorium concentration is the sum of all the major aqueous thorium species (D.4) and the total experimental sulphate concentration is the sum of all the aqueous sulphate species (D.5). 

Table E-1 gives the molecular parameters of all the gaseous thorium species for which data are selected. Part A gives the selected parameters of the ground states of diatomic molecules, where r is the interatomic distance, and the remaining symbols are described above higher electronic levels were included only for ThO(g) and ThS(g). The parameters for the excited states of ThO(g) are given in detail in Table VII-1 the energy levels assumed for ThS(g) are included below.

Table E-1 Molecular parameters of gaseous thorium species Part A diatomic species.

Thorium species, (48), known to activate C-H bonds, oxidatively adds two carbon sites of group IV metallocene, (49), according to reaction (14). The product, (50), shows some agostic character. 

However not all the available methyl groups evolve methane this is especially so on a dehydroxylated alumina. The diamagnetic thorium species were studied by CP-MAS NMR to provide further evidence about the surface organometallic centres [100]. Only the major species could be observed due to sensitivity limitations, but the results clearly demonstrated that on the dehydroxylated alumina there is a transfer of a methyl group from thorium to aluminium. The chemical... 

Table 10.10 Thermodynamic data for thorium species at 25 °C determined in the present review together with data available In the literature. 

Data have been reported on the stability of polymeric thorium species in a relatively large number of studies. From the data reported in the studies, Rand et al (2007) selected six species, two dimers, two tetramers and two hexamers Th2(OH)2 +, Th2(OH)3 +, Th4(OH)g +, Th4(OH)i2, Th6(OH)i4i°+... 

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