Uranyl nitrate extractants

Moyer, B.A., Baes Jr. C.F., Case, F.I., Driver, J.L. 2001. Liquid-liquid equilibrium analysis in perspective II. Complete model of water, nitric acid, and uranyl nitrate extraction by di-2-ethylhexyl sulfoxide in dodecane. Solvent Extr. Ion Exch. 19 (5) 757-790. 

Rabbe, C., Madic, C., Godard, A. 1998. Molecular modeling study of uranyl nitrate extraction with monoamides I. Quantum chemistry approach. Solvent Extr. Ion Exch. 16 (1) 91-103. 

From other experiments in which the effects of mass transfer have been analyzed, it appears that the following systems are mass transfer limited uranyl nitrate extraction by TBP, copper extraction by sodium-loaded DEHPA.19 and extraction of zinc and copperfll) chlorides by TIOA.20 Zinc extraction by dithizone in carbon tetrachloride is mass transfer limited at high zinc concentrations but kineticaily controlled at low zinc levels.21 Ferric ion extractions are repoted to be slow because of its sluggish llgand-excbenge kinetics.22 Extraction of ferric chloride by TIOA, for example, is controlled by a slow heterogeneous reaction.21... 

Table XXV lists the partition coefficients of a number of elements other than uranium between pentaether and various aqueous media.2 Uranium la extracted by pentaether from aqueous solutions containing ammonium nitrate and/or nitric acid In the presence of sulfate, phosphate, or silicate Ions.2 Phosphate Ion, In large quantity, and soluble silicate Ions are extracted by the solvent.2 Fluoride Ion, In significant quantity. Interferes with uranyl nitrate extraction.

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). 

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. 

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. 

We solved the first problem by bombarding large amounts of uranyl nitrate with neutrons at the cyclotrons at the University of California and Washington University plutonium concentrates were derived from these sources through the efforts of teams of chemists who used ether extractions to separate the bulk of the uranium and an oxidation-reduction cycle with rare earth fluoride carrier to concentrate the product. I managed to convince chemists trained in the techniques of ultramicrochemistry to join us to solve the second problem—Burris B. Cunningham and Louis B. Werner of the University of California and Michael Cefola from New York University. 

The last paragraph in this extract refers to work on the separation of uranium by ether extraction as a step toward obtaining a plutonium concentrate from a large sample of neutron-irradiated uranyl nitrate. 

See Uranyl nitrate Diethyl ether Wood pulp extracts... 

Inorganic extractions seem to have come into practical use without any great notice. Although Peligot in 1842 reported that uranyl nitrate could be recrystalhzed from ether, he never mentioned extraction of this salt from aqueous solutions. In textbooks after 1870, however, it is stated briefly that ether can even withdraw sublimate (HgCy from aqueous solution. It was also reported, for example, that cobalt thiocyanate is weakly extracted by ether, better by amyl alcohol, and even better by a mixture of both. 

Case I Extraction of Uranyl Nitrate by Adduct Formation... 

The extraction of uranyl nitrate from 1 M aqueous solution into 30% tributylphosphate in oil is accompanied by an initial interfacial turbulence (41), with more transfer than calculated, even though re-solvation of each uranyl ion at the interface must be a relatively complex process. If the turbulence is suppressed with sorbitan mono-oleate, transfer proceeds at a rate in excellent agreement with theory. 

In liquid-liquid extraction using wetted-wall columns, analysis is possible only by dimensionless groups (75) for the core fluid, flowing up inside the tube, k varies as approximately D and for the fluid falling down the inner walls, varies as Systems studied include phenol-kerosene-water, acetic acid-methylisobutylketone-water, and uranyl nitrate between water and organic solvents (7S, 80-82) interfacial resistances of the order 100 sec.cm." are observed in the last system. These resistances are interpreted as being caused by a rather slow third-order interfacial exchange of of solvent molecules (S) coordinated about each UOa" ion ... 

Uranium dioxide occurs in mineral uraninite. Purified oxide may be obtained from uraninite after purification. The commercial material, however, also is recovered from other uranium sources. Uranium dioxide is obtained as an intermediate during production of uranium metal (See Uranium). Uranyl nitrate, U02(N03)2, obtained from digesting the mineral uraninite or pitchblende with concentrated nitric acid and separated by solvent extraction, is reduced with hydrogen at high temperatures to yield the dioxide. 

Uranyl nitrate is obtained as an intermediate in recovering uranium from its minerals. The compound can be prepared by reacting triuranium octaoxide, UsOs, with nitric acid. It is separated and purified by extraction with ether. 

Detailed data on reaction (3) are not available and would be difficult to obtain. Certain qualitative relations can be seen, however. The effective retention of the full complement of water molecules by uranyl nitrate in extraction has been noted (4), indicating that, in systems in which the activity of water is reasonably high, ordinary oxygenated organic bases do not compete efficiently. In cobaltous nitrate solutions of low water content, addition of small amounts of water produces very marked effects, detectable spectrophotometrically (7). Similarly, for solutions of tctCoCl2 in acetone,... 

Color Plate 25 Extraction of Uranyl Nitrate from Water into Ether (Section 23-1)... 

Figure 10 The extraction of uranyl nitrate U02(N03)2, from 1 M nitric acid by a number of different phosphorus extractants...

Uranyl ions form complexes in solutions with most anions. Uranyl sulfate and carbonate complexes are especially strong and are used in extracting uranium from its ores. Of great practical importance are the complexes of the uranyl ions with nitrate that are soluble in organic liquids such as alcohols, ethers, ketones, and esters. One of the most important of these reactions is that involving the extraction of uranyl nitrate into TBP (the Purex process) ... 

Among the neutral extractants, alcohols, ethers, and ketones have been used extensively. The most fatuous example of these is the extraction of uranyl nitrate into diethyl ether, the process used in the Manhattan Project to purify the uranium... 

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