Uranium from phosphates

The concentration of uranium contained in phosphate rocks (50 200 ppm) is higher than that in seawater (see section 12.3.5). Even though economic recovery of uranium from phosphate rock is difficult, several phosphoric acid plants include operation of uranium recovery facilities. 

Hurst, F.J., Uranium from phosphate ores. Oak Ridge Nat. Lab. Report CONF-830788-2. 

Uranium from Phosphate Ores and Wet Phosphoric Acid... 

F. Habashi, Recovery of uranium from phosphate rock, in (9). 

There are two other aspects that should be mentioned here that may directly affect the choice of the milling process. First, the uranium ore often contains other metals that have commercial value, like vanadium or niobium, for example, and their recovery may influence the process selected for uranium recuperation. Second, uranium itself may be a by-product of other processes like gold extraction, niobium, and tantalum production or phosphoric acid manufacture. Thus, recovery of low levels of uranium from phosphates, columbite, or gold-bearing minerals may not be economical in itself, but extracting uranium as a by-product from the waste streams of these operations could be commercially sensible. 

PhosEnergy A process for recovering uranium from phosphate production. Iron is first removed as iron ammonium phosphate. Developed by Uranium Equities (a subsidiary of Urtek, United States) and ANSTO. 

N-Laurvl-lauramldlne. This reagent also has been tested for the separation of uranium from phosphate solutions. At pH 2.45, 05 of the uranium was precipitated. 

Although the process requires the addition of a phosphate donor, such as glycerol-2-phosphate, it may be a valuable tool for cleaning water contaminated with radionuchdes. An alternative mode of uranium precipitation is driven by sulfate-reducing bacteria such as Desulfovibrio desulfuricans which reduce U(VI) to insoluble U(IV). When combined with bicarbonate extraction of contaminated soil, this may provide an effective treatment for removing uranium from contaminated soil (85). 

The O or S atoms in P=0 and P=S groups may act as electron donors although these groups form relatively weak complexes with electron acceptor compounds such as nonpolarizable, more electropositive (ie, hard) acids, including protons (14). Use is made of this property in the recovery of uranium from wet-process phosphoric acid by extractants such as trioctylphosphine oxide [78-50-2] and di(2-ethylhexyl) hydrogen phosphate [298-07-7]. 

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. 

The bulk of world vanadium production is derived as a by-product or coproduct ia processiag iron, titanium, and uranium ores, and, to a lesser extent, from phosphate, bauxite, and chromium ores and the ash, fume, or coke from burning or refining petroleum. Total world production of V20 was ca 131 X 10 lbs in 1996. 

Another example of a cost-effective liquid-liquid extraction process is the one used for recoveiw of uranium from ore leach liquors (Fig. 15-3). In this case the solvents, alkyl phosphates in kerosine, are recovered by liquid-liquid extraclion using a strip solution, and the... 

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. 

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. 

The effect of irradiation on the extractability of sulfoxides towards plutonium, uranium and some fission products were studied by Subramanian and coworkers . They studied mainly the effect of irradiation on dihexyl sulfoxide (DHSO) and found that irradiation did not change the distribution coefficient for Ru, Eu and Ce but increases the distribution coefficient for Zr and Pu. When comparing DHSO and tributyl phosphate (TBP), the usual solvent for the recovery and purification of plutonium and uranium from spent nuclear fuels, the effect of irradiation to deteriorate the extraction capability is much larger in TBP. Lan and coworkers studied diphenyl sulfoxides as protectors for the gamma radiolysis of TBP. It was found that diphenyl sulfoxide can accept energy from two different kinds of excited TBP and thus inhibits the decomposition of the latter. 

In most other countries regulations or recommendations for a decrease of the radon daughter concentrations in homes have not been established. In USA and Canada limits have been given only for special cases, for example building on waste from uranium and phosphate industries (Atomic Energy Control Board, 1977 EPA, 1979 EPA, 1980). In Finland, there are general recommendations for homes (Finnish Radon Commission, 1982). 

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. 

Tobacco plants accumulate radon from the soil. Uranium from the phosphate fertilizer used on the plants is also another source of radiation. Small amounts of lead-210 are spread on the tobacco leaves. Thus, smokers are exposed to levels of radiation that is about 1,000 times higher than the radiation exposure of workers in nuclear power plants. 

The vendor claims that the following metals have been successfully treated to parts per biUion (ppb) and detection limit levels aluminum, arsenic, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, molybdenum, nickel, selenium, silver, tin, uranium, vanadium, and zinc. The system is also able to remove ammonia, nitrates, phosphates, potassium, fluorides, and sodium. Studies have also been performed using Aqua-Fix to remove radionuchdes such as uranium from waste streams. 

Shimada, T., Ogumo, S., Sawada, K., Enokida, Y., Yamamoto, I. 2006. Selective extraction of uranium from a mixture of metal or metal oxides by a tri-n-butyl- phosphate complex with HN03 and H20 in supercritical C02. Anal. Sci. 22 (11) 1387-1391. 

As was mentioned before, Arey et al. [19] conducted batch equilibration experiments to evaluate the ability of hydroxyapatite to remove uranium from contaminated sediments at the Savannah River Site of DOE and showed that removal of U was due to secondary phosphate minerals that had solubility even lower than autunite (Ca(U02)2(P04)2- IOH2O). The authors suggest formation of Al/Fe secondary phosphate. A similar conclusion was reached by Fuller et al. [20], who showed that uranyl ions can be removed by using hydroxyapatite. 

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