Thorium nitrate solubility

Thorium Nitrate Solubility in Nitric Acid-Aluminium Nitrate at 25 and 50°C [56]. 

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... 

Yaffe, L. Solubility of Uranyl Nitrate Hexahydrate and Thorium Nitrate... 

Thorium nitrate is very soluble in water, to the extent of 65.6 g Th(NO3)4/100 g solution at 20°C. It can be crystallized from solution as the nominal tetrahydrate. Thorium nitrate solutions are used for purifying thorium by solvent extraction. Sec. 9. ... 

Hydrated thorium fluoride is precipitated when a soluble fluoride is added to a solution of thorium nitrate. Precipitation can be prevented by addition of aluminum nitrate to complex the fluoride ion, an expedient used in the Thorex process (Chap. 10, Sec. 5). 

Thorium orthophosphate Th3(P04)4 is precipitated by phosphate ion from neutral or slightly acid solutions of thorium nitrate or sulfate. It is soluble in concentrated phosphoric or sulfuric acid, such as is present when monazite is dissolved in sulfuric add. 

The thorium nitrate solution from the dissolver will be about 9 Af in nitric acid. To obtain satisfactory decontamination of thorium from fission-product protactinium, ruthenium, and zirconium-niobium, it was found necessary to remove all of the nitric acid from the solution and make the solution around 0.15 Af acid-deficient in nitrate ion by converting a fraction of the A1(N03)3 to a water-soluble basic nitrate. This also converts the readily hydrolyzed nitrates of these fission products to basic nitrates that are less extractable than the species present in the acid dissolver solution. 

Higashi measured the solubility of thorium hydroxide at room temperature from the direction of oversaturation. Thorium nitrate solutions (3 x 10 M, pH 2.5) were titrated with 0.1 M NaOH to pH values in the range 4-8. After precipitation of Th(OH)4(s), the Th concentration and pH were measured after 30 minutes, 12 hours, 1, 2, 3, 7, 15, 30 and 100 days. No ionic medium was used in the experiments and the pH was measured using a glass electrode, but with no information about calibration procedures. Thorium concentrations were measured by a colorimetric method after filtration through filter... 

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. 

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... 

The thorium nitrate-water system has been reported [22] as having considerable solubility up to about 225°C, at which point hydrolytic precipitation occurs. Further investigation [23] revealed a maximal stability for the 80w/o material (to around 255°C). Increasing the acidity of the solutions (increasing the N03 /Th ratio) suppresses hydrolysis and increases the stability of the solutions as indicated by Figure 3-16, which shows the precipitation temperatures for various solutions [24]. The intensity of vapor phase coloration at elevated temperatures (rapidly reversible) increased as the nitrate/thorium ratio was raised above 4.0. 

Thorium oxide, has the highest melting point of the usual ceramic materials (3390°C). It is used to form ceramics, Th02, as the so-called meta-Th02, freshly prepared by low temperature decomposition of thorium oxalate it is fairly soluble in acids and tends (especially in the presence of nitrate ions) to form colloidal solutions which can be dried to form stable gels that can be sintered to give high-density ceramic bodies. 

Crystallisation was one of the earliest methods used for separation of radioactive microcomponents from a mass of inert material. Uranium X, a thorium isotope, is readily concentrated in good yield in the mother liquors of crystallisation of uranyl nitrate (11), (33), (108). A similar method has been used to separate sulphur-35 [produced by the (n, p) reaction on chlorine-35] from pile irradiated sodium ot potassium chloride (54), (133). Advantage is taken of the low solubility of the target materials in concentrated ice-cold hydrochloric acid, when the sulphur-35 as sulphate remains in the mother-liquors. Subsequent purification of the sulphur-35 from small amounts of phosphorus-32 produced by the (n, a) reaction on the chlorine is, of course, required. Other examples are the precipitation of barium chloride containing barium-1 from concentrated hydrochloric acid solution, leaving the daughter product, carrier-free caesium-131, in solution (21) and a similar separation of calcium-45 from added barium carrier has been used (60). 

The physical and chemical properties of elemental thorium and a few representative water soluble and insoluble thorium compounds are presented in Table 3-2. Water soluble thorium compounds include the chloride, fluoride, nitrate, and sulfate salts (Weast 1983). These compounds dissolve fairly readily in water. Soluble thorium compounds, as a class, have greater bioavailability than the insoluble thorium compounds. Water insoluble thorium compounds include the dioxide, carbonate, hydroxide, oxalate, and phosphate salts. Thorium carbonate is soluble in concentrated sodium carbonate (Weast 1983). Thorium metal and several of its compounds are commercially available. No general specifications for commercially prepared thorium metal or compounds have been established. Manufacturers prepare thorium products according to contractual specifications (Hedrick 1985). 

After removing cerium (and thorium), the nitric acid solution of rare earths is treated with ammonium nitrate. Lanthanum forms the least soluble double salt with ammonium nitrate, which may be removed from tbe solution by repeated crystallization. Neodymium is recovered from this solution as the double magnesium nitrate by continued fractionation. 

The monazite sand is heated with sulfuric acid at about 120 to 170°C. An exothermic reaction ensues raising the temperature to above 200°C. Samarium and other rare earths are converted to their water-soluble sulfates. The residue is extracted with water and the solution is treated with sodium pyrophosphate to precipitate thorium. After removing thorium, the solution is treated with sodium sulfate to precipitate rare earths as their double sulfates, that is, rare earth sulfates-sodium sulfate. The double sulfates are heated with sodium hydroxide to convert them into rare earth hydroxides. The hydroxides are treated with hydrochloric or nitric acid to solubihze all rare earths except cerium. The insoluble cerium(IV) hydroxide is filtered. Lanthanum and other rare earths are then separated by fractional crystallization after converting them to double salts with ammonium or magnesium nitrate. The samarium—europium fraction is converted to acetates and reduced with sodium amalgam to low valence states. The reduced metals are extracted with dilute acid. As mentioned above, this fractional crystallization process is very tedious, time-consuming, and currently rare earths are separated by relatively easier methods based on ion exchange and solvent extraction. 

The possibility of dissolving the mixed hydroxide in HNOs and obtaining direct extraction of thorium (and uranium) from the nitrate solution has been studied [155,156], but does not seem to be too promising, possibly due to the partial oxidation of tripositive cerium to the tetrapositive state. Kraitzer [157] was able to separate thorium from the mixed hydroxide cake by extracting the cake with sodium carbonate buffer at pH 9.5—10. Thorium was found to form a soluble carbonate complex and a recovery of better than 99% of thorium was claimed after only four extractions. 

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