Aqueous thorium nitrates

In the corresponding U(IV)-nitrate system one observes a change in the UV/Vis absorption spectrum of the ion on addition of nitrate, an observation that is difficult to reconcile with the ion-interaction model. As the chemistiy of Th(IV) and U(IV) is very similar we have additional support for the complex formation model  

Despite the few experimental data for the Th(IV)-nitrate system, this review has selected the equilibrium constants  

It has to be emphasised that these equilibrium constants must not be combined with 8(ThAN03) = (0.31 +0.12) kg-mol used in the Sections VII.3 and VIII. 1.2 on aqueous thorium hydroxide and fluoride complexes this value refers to a strict ion interaction approach where the effect of nitrate complexation is included in the interaction coefficient. The equilibrium constants for the formation of nitrate complexes must be combined with s(ThA NOj) = e(ThA CIO ,) = (0.70 + 0.10) kg-mol,  

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Figure 10.25 Distribution coefficient of nitric acid between 30 v/o TBP in hydrocarbon diluent and aqueous thorium nitrate at 30 C, from SEPHIS code.

Apelblat, A., Azoulay, D., Sahar, A., Properties of aqueous thorium nitrate solutions. 1. Densities, viscosities, conductivities, pH, solubility, and activities at freezing point, J Chem. Soc. Faraday Trans. I, 69, (1973), 1618-1623. Cited on pages 98, 317, 558. 

Purification or refining of thorium. Thorium produced previously is too impure to be used as nuclear fuel. In fact, impurities such as rare earths and uranium, owing to their elevated thermal neutron cross sections, are objectionable. Hence, the objective of the thorium refining process is to remove these impurities until concentrations below gg/kg (i.e., ppb wt.) are reached. Solvent extraction of an aqueous thorium nitrate solution with n-tributyl phosphate (TBP) in kerosene is a common procedure to perform the refining of thorium. At the end of the purification process, the thorium is recovered in the form of an aqueous solution of thorium nitrate or crystals of hydrated thorium nitrate. 

Although there has been considerable interest in the soluble hydrolysed species in aqueous thorium nitrate solutions (see, for example, [1 to 6]) few solid hydroxide nitrate compounds have been isolated (Table 18, p. 70) and of these only one has been fully characterized. Thus... 

Oxo Ion Salts. Salts of 0x0 ions, eg, nitrate, sulfate, perchlorate, hydroxide, iodate, phosphate, and oxalate, are readily obtained from aqueous solution. Thorium nitrate is readily formed by dissolution of thorium hydroxide in nitric acid from which, depending on the pH of solution, crystalline Th(N02)4 5H20 [33088-17 ] or Th(N02)4 4H20 [33088-16-3] can be obtained (23). Thorium nitrate is very soluble in water and in a host of oxygen-containing organic solvents, including alcohols, ethers, esters, and ketones. Hydrated thorium sulfate, Th(S0 2 H20, where n = 9, 8, 6, or 4, is... 

Thorium Dihydrogen Orihoarsenate, Th(H2As04)4.4H20, is obtained in a manner similar to the above, using 50 per cent, aqueous arsenic acid and thorium nitrate solution containing the equivalent of 5 per cent, thoria. It separates as colourless crystals. The salt is converted to the nronohydrogen salt by the action of water. 

Suresh et al. investigated the extraction of uranium and thorium by TsBP and TiBP (isomers of TBP with branched carbon chain) as an alternative choice for TBP (47). Higher homologues of TBP, for example, THP and TEHP, were reported to have higher extraction ability with reduced tendency toward third-phase formation (50, 51). The esters with bulkier substituents in place of the butyl group were proposed to be of practical value for the process applications in uranium and thorium separation (54). The LOC of thorium in equilibrium with aqueous nitric acid-thorium nitrate was reported to decrease in the order THP > TAP > TBP. Pathak et al. showed that TEHP can be a better choice for U/Th separation compared to TBP and TsBP (55). 

Principle of Separation. Uranium forms a nitrate complex that is extractable into ethyl acetate (as well as other organic extractants). Thorium does not readily form an extractable nitrate complex. When ethyl acetate is contacted with an aqueous solution, the uranium-nitrate complex is partitioned favorably into the ethyl acetate whereas thorium nitrate is not. The distribution of the metal ion between the two phases is expressed as D = Corganic/Caqueous where C is the concentration in moles or dps per unit volume in the respective phases. The thorium remains in the aqueous phase and is precipitated as the hydroxide for counting. 

It maj- also be separated from solutions of uranium salts bj the addition of a little cerium salt and precipitation with aqueous hydrofluoric acid, or with oxalic acid or bj adding a small quantity of thorium nitrate and precipitating with t-nitrobenzoic acid. It may also be absorbed bj- charcoal,iDasic ferric acetate, and by various oxides, sulphides, sulphates, and gelatinous silica. In the case of charcoal the uranium X is completely removed from a solution of a... 

Liquid-liquid extraction (LLE) systems using neutral phosphorus-based organic compounds have been the subject of extensive study since Warf (1) first reported the use of tributyl phosphate, TBP, as a useful extractant for cerium(IV), uranyl and thorium nitrates. After more than twenty years, liquid-liquid extraction systems (such as the Purex and Thorex processes) employing TBP dissolved in a suitable diluent versus an aqueous HNO3 phase remain the most widely accepted systems for reactor fuel reprocessing. 

The more important properties of the tetrahalides, from reference [11], are listed in Table 6.10. Many of these properties, especially for ThCU, ThBr4, and TI1I4, are known only semiquantitatively. Anhydrous Thp4 is made by passing an excess of HF vapor over ThOj or ThOFj at temperatures between 550 and 600 C. The anhydrous double fluoride KThFs is precipitated from aqueous solutions of thorium nitrate by addition of an excess of KF. It has been used for electrolytic production of thorium metal. Table 6.10 Thorium Tetrahalides ... 

Purified thorium is usually produced in the form of an aqueous solution of thorium nitrate or crystals of hydrated thorium nitrate. The principal forms in which thorium is used in nuclear systems are the oxide Th02, the carbide ThC2, the fluoride Thp4, the chloride ThCl4, or the metal. Conversion to oxide, fluoride, chloride, and metal are discussed in this section production of thorium carbide was discussed in Sec. 5.3. 

As in the Purex process, the Thorex process uses a solution of TBP in hydrocarbon diluent to extract the desired elements, uranium and thorium, from an aqueous solution of nitrates. Thorium nitrate however, has a much lower distribution coefficient between an aqueous solution and TBP than uranium or plutonium. To drive thorium into the TBP, the Thorex process as first developed at the Knolls Atomic Power Laboratory [HI] and the Oak Ridge National Laboratory [G14] added aluminum nitrate to the thorium nitrate in dissolved fuel. This had the disadvantage of increasing the bulk of the high-level wastes, which then contained almost as many moles of metallic elements as the original fuel. To reduce the metal content of the waste, the Oak Ridge National Laboratory in the late 1950s [Rl, R2] developed the acid Thorex process, in which nitric acid is substituted for most of the aluminum nitrate in the first extraction section. The nitric acid is later evaporated from the wastes, as in the Purex process. 

Adequate data on distribution coefficients of uranyl nitrate between 30 v/o TBP and aqueous solutions of thorium nitrate and nitric acid are not available. Examination of concentrations of coexistent phases in Thorex process mixer-settler runs reported in references [Rll], [01], and [02] indicate that the distribution coefficient of uranium Dy when present at uranium concentrations below 0.02 M in Thorex systems at thorium concentrations above 0.1 Mis given approximately by... 

THORIUM NITRATE (13823-29-5) Noncombustible but will intensify an existing fire. Reacts with water, forming a weak nitric acid solution. A strong oxidizer reacts violently with reducing agents, combustible materials, organic substances, finely divided metals. Aqueous solution reacts with alkalis. Attacks metals in the presence of moisture. 

Bilinski and Ingri [1967BIL/ING2] investigated the precipitation of thorium from aqueous solutions of thorium nitrate (1.25 luM) and ammonium oxalate (2.5-80 mM) at pH 1 to 10 and a temperature of 20°C. Ionic strength was kept constant at 7 = 1.0 M (NaC104). The H concentration in the perchlorate solutions was decreased coulometri-... 

Bilinski, H., Ingri, N., Precipitation and hydrolysis of thorium(lV) in aqueous solution. V. Studies of the system thorium nitrate-ammonium oxalate, Croat. Chem. Acta, 39, (1967), 235-243. Cited on pages 156,502,503. 

Neutral salts, such as sodium chloride, potassium chloride, magnesium chloride, calcium chloride, and thorium nitrate, have only a small influence on the viscosity of aqueous solutions of the gum a slight increase can be detected. It is noteworthy that sodium hydroxide changes the viscosity to a high degree, as shown in Figure 4. 

Thorium acetylacetonate was first described by Urbain, who synthesized it by the action of an alcoholic solution of acetylacetone on freshly precipitated hydrous thorium oxide and by a metathetical reaction between sodium acetylacetonate and a thorium salt such as thorium nitrate. The crude product was purified by sublimation and by crystallization from chloroform. BUtz, - who subsequently determined the atomic weight of thorium by means of the acetylacetonate, added a solution of acetylacetone in aqueous ammonia to a solution of thorium nitrate and crystallized the precipitate from alcohol. 

Vapour pressures of thorium nitrate aqueous solutions have been reported by Robinson, Levinson [1]. 

Information on vibrational spectra of thorium nitrate recorded in aqueous media is available in [2, 4, 7, 10 to 14] and details of NMR investigations of similar solutions will be found, for example, in [15 to 17]. An NMR study of Th(N03)4 4H20 in acetone-acetonitrile mixture has also been reported [18]. 

Stationary phase 0.1% Thorium nitrate impregnated silica layer. Mobile phase 1.0 M Aqueous sodium formate solution (pH 7.65). Detection 0.1% Dithizone in CCL for Zn " and Cd hydrogen sulfide gas for TD and Hg ". Conditions Ascending technique, run 10 cm. layer thickness 0.25 mm, plate activation at 100° for I h, loading volume 0.01 ml of 1% test solution, pH value of spiked industrial wastewater and seawater were 1.5 and 8.3 respectively. Remarks Th -impregnated silica layers were found useful for the detection and separation of zinc, cadmium, mercury, and thallium from industrial wastewater and seawater in the presence of common pesticides. 

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