Tributyl phosphate nitrates

N5. Nichols, G. S. Decomposition of Tributyl Phosphate-Nitrate Complexes, Report DP-526, Nov. 1960. 

Nichols, G.S. 1960. Decomposition of the Tributyl Phosphate Nitrate Complexes. AEC DP-526, 31. Aiken, SC Savannah River Laboratory. 

In TBP extraction, the yeUowcake is dissolved ia nitric acid and extracted with tributyl phosphate ia a kerosene or hexane diluent. The uranyl ion forms the mixed complex U02(N02)2(TBP)2 which is extracted iato the diluent. The purified uranium is then back-extracted iato nitric acid or water, and concentrated. The uranyl nitrate solution is evaporated to uranyl nitrate hexahydrate [13520-83-7], U02(N02)2 6H20. The uranyl nitrate hexahydrate is dehydrated and denitrated duting a pyrolysis step to form uranium trioxide [1344-58-7], UO, as shown ia equation 10. The pyrolysis is most often carried out ia either a batch reactor (Fig. 2) or a fluidized-bed denitrator (Fig. 3). The UO is reduced with hydrogen to uranium dioxide [1344-57-6], UO2 (eq. 11), and converted to uranium tetrafluoride [10049-14-6], UF, with HF at elevated temperatures (eq. 12). The UF can be either reduced to uranium metal or fluotinated to uranium hexafluoride [7783-81-5], UF, for isotope enrichment. The chemistry and operating conditions of the TBP refining process, and conversion to UO, UO2, and ultimately UF have been discussed ia detail (40). 

In practice, uranium ore concentrates are first purified by solvent extraction with tributyl phosphate in kerosene to give uranyl nitrate hexahydrate. The purified uranyl nitrate is then decomposed thermally to UO (eq. 10), which is reduced with H2 to UO2 (eq. 11), which in turn is converted to UF by high temperature hydrofluorination (eq. 12). The UF is then converted to uranium metal with Mg (eq. 19). 

Ce(IV) extracts more readily iato organic solvents than do the trivalent Ln(III) ions providing a route to 99% and higher purity cerium compounds. Any Ce(III) content of mixed lanthanide aqueous systems can be oxidi2ed to Ce(IV) and the resultiag solutioa, eg, of nitrates, contacted with an organic extractant such as tributyl phosphate dissolved in kerosene. The Ce(IV) preferentially transfers into the organic phase. In a separate step the cerium can be recovered by reduction to Ce(III) followed by extraction back into the aqueous phase. Cerium is then precipitated and calcined to produce the oxide. 

Di-n-amyl n-amylphosphonate [6418-56-0] M 292.4, b 150-151°/2mm, n 1.4378. Purified by three crystns of its uranyl nitrate complex from hexane (see tributyl phosphate). Extracts Zr " from NaCl solns. 

Di-n-butyl n-butylphosphonate [78-46-6] M 250.3, b 150-151°/10mm, 160-162°/20mm, n 1.4302. Purified by three recrystallisations of its compound with uranyl nitrate, from hexane. For method, see tributyl phosphate. 

Triisoamyl phosphate [919-62-0] M 308.4, b 143"/3mm. Purified by repeated crystallisation, from hexane, of its addition compound with uranyl nitrate, (see tributyl phosphate.) [Siddall J Am Chem Soc 81 4176 7959]. 

Spectrophotometric methods may often be applied directly to the solvent extract utilising the absorption of the extracted species in the ultraviolet or visible region. A typical example is the extraction and determination of nickel as dimethylglyoximate in chloroform by measuring the absorption of the complex at 366 nm. Direct measurement of absorbance may also be made with appropriate ion association complexes, e.g. the ferroin anionic detergent system, but improved results can sometimes be obtained by developing a chelate complex after extraction. An example is the extraction of uranyl nitrate from nitric acid into tributyl phosphate and the subsequent addition of dibenzoylmethane to the solvent to form a soluble coloured chelate. 

A diverse range of neutral organic molecules has been used to stabilize or to enhance the solubilities of neutral metal-containing entities in an organic phase. Some examples of commercial significance are listed in Table 6. When used alone they efficiently transport metal salts across a circuit. An example is the use of tributyl phosphate (TBP) in recovery of uranyl nitrate,... 

Campbell has studied the separation of technetium by extraction with tributyl phosphate from a mixture of fission products cooled for 200 days. Nearly complete separation of pertechnetate is achieved by extraction from 2 N sulfuric acid using a 45 % solution of tributyl phosphate in kerosene. Ruthenium interferes with the separation and is difficult to remove without loss of technetium other radioisotopes can be removed by a cation-exchange process. However, this separation procedure has not been widely applied because of the adverse influence of nitrate. 

Lanthanum also may be separated from aqueous solutions of rare-earth nitrates by liquid-hquid extraction using a suitable water-immiscible organic hquid such as tributyl phosphate or another complexing agent dissolved in it. 

Warp [54] was the first to report a preferential extraction of Ce4 into tributyl phosphate (TBP) from a nitrate solution of other rare earths. In a system equilibrated between the aqueous phase containing nitrate ion and TBP, the extraction process may be represented by eq. (3). 

Z. Kolarik. The formation of a third phase in the extraction of Pu(IV), U(VI) and Th(IV) nitrates with tributyl phosphate in alkane diluents. In Proceeding of the International Solvent Extraction Conference (ISEC-77), 1977. 

Hahn, H.T., Vander Wall, E.M. 1964. Complex formation in the dilute uranyl nitrate-nitric acid-dibutyl phosphoric acid-tributyl phosphate-amsco system. J. Inorg. Nucl. Chem. 26 191-192. 

CJ. Hartzell et al., Molecular modeling of the tributyl phosphate complex of europium nitrate in the clay hectorite. J. Phys. Chem. A 102, 6722-6729 (1998)... 

Hartzell CJ, Cygan RT, Nagy KJ (1998) Molecular Modeling of the Tributyl Phosphate Complex of Europium Nitrate in the ( lay Hectorite, J Phys Chem A 102(34) 6722-6729... 

Advantage may be taken of these conditions by use of solvent extraction techniques. It is known (25-30) that Am extraction with TBP ( tributyl phosphate) or DBBP (dibutyl butyl phos-phonate) is enhanced by high nitrate salt concentrations in the aqueous phase, particularly at HN03 concentrations below 1.0 N. 

Solvent Extraction. The yellow cake is dissolved in nitric acid and extracted from this aqueous phase by 5 percent tributyl phosphate (TBP) in a hydrocarbon diluent. The diluent reduces the density and viscosity of the TBP, enhancing the aqueous/solvent phase separation. The extraction is very specific for uranium, with separation factors of 103 to 105. The product thus obtained is an aqueous uranyl nitrate solution (Fig. 21.14). 

Extractability into Organic Solvents. As noted previously, the MO + ions can be extracted from nitrate solutions into organic solvents. The M4+ ions can be extracted into tributyl phosphate in kerosene from 6 M nitric acid solutions the M3+ ions can be similarly extracted from 10 to 16 M nitric acid and neighboring actinides can be separated by a choice of conditions. 

Uranium is deposited widely in the Earth s crust, hence it has few ores, notably the oxides uraninite and pitchblende. The ores are leached with H2SO4 in the presence of an oxidizing agent such as NaClOs or Mn02, to oxidize all the uranium to the (+6) state as a sulfate or chloride complex. On neutralization with ammonia a precipitate of yellow cake , a yellow solid with the approximate composition (NH4)2U207 is formed. This is converted into UO3 on ignition at 300 °C. This can be purified further by conversion into uranyl nitrate, followed by solvent extraction using tributyl phosphate in kerosene as the extractant. 

Simard et al. [Can. J. Chem. Eng., 39, 229 (1961)]. Continuous extraction of uranium from aqueous nitrate solutions into kerosine + tributyl phosphate and from sulfate solutions containing tricaprylamine unbaffled vessel, propeller agitated. Process details for high recovery and low reagent costs. 

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