Extraction of uranium

For extraction of uranium from sulfate leach Hquors, alkyl phosphoric acids, alkyl phosphates, and secondary and tertiary alkyl amines are used in an inert diluent such as kerosene. The formation of a third phase is suppressed by addition of modifiers such as long-chain alcohols or neutral phosphate esters. Such compounds also increase the solubihty of the amine salt in the diluent and improve phase separation. 

Ryon, Daley, and Lowrie [Chem. Eng. Ftog., 55(10), 70, (1959), U.S. AFC ORNL-2951, I960]. Continuous extraction of uranium from sulfate-ore-leach liquors and kerosine -t- trihiityl phosphate and di(2-ethylhexyl)-phosphoric acid baffled vessels, turbine agitated. There is strong evidence of the influence of a slow chemical reaction. 

Ryon and Lowrie (U.S. AEC ORNL-3.381, 1960). Batch and continuous extraction of uranium from aqueous sulfate solutions into kerosine -t- amines, stripping of extract with aqueous sodium carbonate baffled vessels, turbine agitated. A detailed process study. 

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

White, D.A., Fathurrachman, Extraction of uranium (VI) and uranium (IV) from hydrochloric acid using tri-n-octylamine in a benzene diluent, Hydrometallurgy, v.36, pp. 161-168, 1994. 

As the parent of actinium in this series it was named protoactinium, shortened in 1949 to protactinium. Because of its low natural abundance its chemistry was obscure until 1960 when A. G. Maddock and co-workers at the UK Atomic Energy Authority worked up about 130g from 60 tons of sludge which had accumulated during the extraction of uranium from UO2 ores. It is from this sample, distributed to numerous laboratories throughout the world, that the bulk of our knowledge of the element s chemistry was gleaned. 

The extraction of metals by liquid amines has been widely investigated and depends on the formation of anionic complexes of the metals in aqueous solution. Such applications are illustrated by the use of Amberlite LA.l for extraction of zirconium and hafnium from hydrochloric acid solutions, and the use of liquid amines for extraction of uranium from sulphuric acid solutions.42,43... 

Solvent Extraction. A modified, one-cycle PUREX process is used at Rocky Flats to recover plutonium from miscellaneous Pu-U residues (11). The process utilizes the extraction of uranium (VI) into tributyl phosphate (TBP), leaving plutonium (III) in the raffinate. The plutonium is then sent to ion exchange for... 

Solvent extraction, also called liquid-liquid extraction, can be used to separate a substance from a solution by extraction into another solvent. It can be used ether to recover a valuable substance from the original solution, or to purify the original solvent by removing an unwanted component. Examples of solvent extraction are the extraction of uranium and plutonium salts from solution in nitric acid, in the nuclear industry and the purification of water. 

This technology lends itself to continuous, rather than batch, processing and has been proven robust since first applied for the extraction of uranium in the early 1940s.10 The types of extractant used can be classified according to the types of reactions involved in phase transfer.111... 

Pai, S. A. Lohithakshan, K. V. Mithapara, P. D. Aggarwal, S. K. Solvent extraction of uranium(VI) plutonium(VI) and americium(III) with HTTA/HPMBP using mono-and bi-functional neutral donors Synergismand thermodynamics. J. Radioanal. Nucl. Chem. 2000, 245, 623-628. 

Chloroform extraction of uranium quinoline complex Uranium adsorbed as azide on basic ion exchange column, uranium desorbed with 1 M hydrochloric acid Uranium adsorbed on bismuthol(II) modified anion exchange resin, desorbed with 0.1 M cysteine Uranium, by square wave adsorptive stripping voltammetry... 

AMEX [Amine extraction] A process for the solvent extraction of uranium from sulfuric acid solutions using an amine extractant ... 

Dapex [Di-alkylphosphoric acid extraction] A process for the solvent extraction of uranium from sulfuric acid solutions using di-(2-ethylhexyl) phosphoric acid (HDEHP). The HDEHP is dissolved in kerosene containing 4 percent of tributyl phosphate. The uranium is stripped from the organic phase by aqueous sodium carbonate and precipitated as uranyl peroxide (yellow cake). The process was no longer in use in 1988. See also Amex. 

Uses Denaturant for ethyl alcohol solvent for paints, varnishes, cellulose acetate, nitrocellulose lacquers, resins, fats, oils, and waxes preparation of methyl amyl alcohol in hydraulic fluids and antifreeze extraction of uranium from fission products organic synthesis. 

Amine extraction is used also in another important industrial process, the extraction of uranium from sulphuric acid leached ores, which uses trilauryl amine (TLA). In that case, the extraction reaction is... 

The object of equilibration is to provide a solvent that will effectively extract the required species, either because of the form of the active constituent of the solvent or by maintaining the necessary extraction pH. As an example of the former condition, consider the extraction of uranium using a tertiary aliphatic amine as extractant. Extraction of metal species by such amines is considered to occur by liquid ion exchange (see Chapters 3 and 4). For a tertiary amine to act in this manner, it must be first converted to an amine salt ... 

Having formed the amine salt, the solvent can be used for the extraction of uranium. This is shown as an ion exchange process in Eq. (7.3) ... 

High-grade pitchblende ores are leached with nitric acid to recover uranium. Extraction of uranium from nitrate solutions is usually performed with TBP. TBP-based solvents are used in several areas of the nuclear industry, especially for reprocessing of spent nuclear fuels and for refining the uranium product of the Amex and Dapex processes. Extraction of uranium by TBP solvents is described in sections 12.3.4 and 12.5. 

As noted earlier (see section 12.3.1), the Amex process, which uses long-chain amines, is preferred over the Dapex process, which uses HDEHP, for solvent extraction of uranium from H2SO4 leach solutions. Because the surfactant properties of amine sulfates are conducive to formation of objectionable emulsions, the Amex process is very sensitive to the presence of solids in the H2SO4 leachate. For acceptable phase coalescence in the Amex process, feeds should contain no more than 20 ppm solids. The Dapex process can tolerate feeds containing as much as 100 ppm solids. 

Concentration/purification by solvent extraction usually involves four steps (a) extraction of uranium from the leach liquor in a solvent, (b) scrubbing to remove impurities from the solvent, (c) stripping to remove uranium from the solvent, and (d) regeneration of the solvent. The solvent phase in solvent extraction will contain the extractant that complexes uranium to make it soluble in the organic phase, a diluent, an inexpensive material to dilute the extractant, and a modifier to improve the solubility of the extractant in the diluent. Typical extractants are amines with isode-canol acting as a modifier to improve the amine solubility in a diluent such as kerosene. The typical chemistry of the extraction would involve the reactions... 

Solvent extraction is a well-established method of separation in the field of extractive metallurgy. First applied to the extraction of uranium for nuclear purposes in the early 1940s, the technique currently now finds widespread use in the recovery of uranium, copper, zinc, cobalt, nickel,... 

The extraction of uranium(VI) by D2EHPA has been shown115 to proceed according to the stoichiometry... 

In contrast to the chemistry of extraction of uranium(VI) by organophosphorus acids, that of uranium(IV) has not been widely studied. It is known,135 however, that the extraction of U4+ by mono(2-ethylhexyl)phosphoric acid (2-ethylhexyl dihydrogen phosphate), for example, exceeds that of U022+ by a factor of 105. This clearly provides the basis for the strong extraction of uranium(IV) from phosphoric acid solutions by extractants containing monoalkyl phosphates. The existence of a synergistic effect in the extraction of uranium(IV) by mixtures of mono(2-ethylhexyl)phosphoric acid and neutral organophosphorus compounds was also reported recently.136... 

Amine salts represent the only commercially important class of extractants of the anion-exchange type. Their most widespread use is in the extraction of uranium from sulfate leach liquors, but they have found application in the recovery of cobalt, zinc and copper from chloride solutions, as well as in the extraction of metals that readily form oxyanions, such as vanadium, molybdenum and tungsten. 

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