Uranium IV sulfate

The work of Sakuma, Okamoto, and Kakihana is an example of the use of band displacement chromatography for the cation exchange separation of uranium isotopes, employing uranium(IV) sulfate and displacement with 0.40mollMgS044-0.02 mol 1 H2SO4. At the rear end of the band, magnesium ions displace the uranium(IV) ions that form much stronger sulfate complexes as in reaction [Ilia] ... 

Sulfates. Uranium (iV) sulfate Is practically Insoluble In 47 per cent perchloric acid. Precipitation Is made In a sulfuric acid medium. Uranium Is reduced on a mercury cathode and concentrated perchloric acid Is then added. 

Comparison of these results for plutonium with those for other tetravalent metals reveals some interesting facts. Thor-ium(IV), uranium(IV) and neptunium(IV) sulfates have been investigated under hydrothermal hydrolytic conditions. For uranium, the stable phases which have been reported include U(0H)2S0i (2), U60i, (OH)i, (SO.,) 6 (2). U (SOi,) 2 4H20 (23) and IKSO (24). 

Organophosphorus acid extractants have also been used commercially to recover thorium from barren solutions obtained from uranium ion-exchange plants. For instance, Rio Tinto Dow Ltd of Canada installed a plant at Elliot Lake in 1959 to extract thorium(IV) from solutions containing only 0.15 g of thorium per litre.137 The loaded organic phase is stripped with 5 M sulfuric acid, from which the product subsequently crystallizes as an acid thorium(IV) sulfate. 

Bacterial leaching with thiobacillus thiooxidans is also an acid leaching process. Sulfidic sulfur, e.g. in pyrites, is oxidized to sulfate and iron(II) is oxidized to iron(lll), which itself oxidizes uranium(IV) to uranium(VI). This process has not yet been operated industrially. 

Uranium(IV) oxalate has been prepared by the reaction of uranium(IV) chloride,sulfate, and hydroxide with a saturated solution of oxalic acid, or by the reduction of a water-soluble uranyl compound with copper, zinc, or sodium dithionite (Na2S204), followed by treatment with oxalic acid. It is prepared conveniently by the reduction of the readily available uranyl acetate 2-hydrate with sodium dithionite. 

C2H18Ce2NaOi9S3, Cerium sulfate 2-urea 5-water, 44B, 962 C2H22B11OU, Uranium(IV) borohydride - dimethyl ether, 44B, 963... 

C,2H36C0N12O10S, Hexakis(N-methylurea)cobalt(II) sulfate, 46B, 1148 Cl2H60B8O2U2, Uranium(IV) borohydride - n-propyl ether, 44B, 971 Cl3HioFMn30i1, 1,1,1,2,2,2,3,3,3-Nonacarbonyl di-M3"ethoxy-l,2-m fluoro-trimanganese, 45B, 1215... 

In most concentrations of uranyl sulfate at temperatures greater than 200°C (and probably even at somewhat lower temperatures), iron (III), chromium(III), and uranium(IV) are present in solution only briefly before hydrolyzing in the following manner ... 

Phosphate precipitation of uranium (IV) is more selective. It is made from dilute hydrochloric or perchloric acid solutions. Separation is made from manganese, iron, vanadium and most other elements. Zirconium, thorium, and, to a smaller extent, titanium and tin precipitate.-Aluminum Interferes by the formation of soluble complexea with uraniiuii and phosphate lons. With sulfate and aluminum present, uranium is precipitated in a narrow pH-range around one. At higher pH, the soluble alumlnum-uranlum-phosphate complex is formed at lower pH, the soluble uranium-sulfate... 

Uranium (IV), In general, should behave similarly as neptunium (IV) and plutonium (IV). These are carried by lanthanum fluoride, ceric and zirconium lodates, ceric and thorium oxalates, barium sulfate, zlrconliun phosphate, and bismuth fifrsonate.- Uranium (Vl) does not carry with these agents providing the concentration of either carrier or uranlxun Is not too large. 

The factors that influence uranium extraction have been studied most extensively for amine-sulfate systemsThe effect of amine structure on the extraction of uranium and other metal ions is illustrated in Table XXX.Uranium (IV) is efficiently extracted by primary amines. The efficiency decreases with secondary and tertiary amines. With uranium (Vl) there does not seem to be much correlation between and amine class. With primary, secondary, and tertiary laurylamlnes, conditions given in... 

Eactraotlon and Measurement at Microgram Urahlum Level. A solution of uranium-233 (10 to 10 gram) together with about 20 y of natural iiranlum (as sulfate) was submitted to reductive extraction with cupferron for about 50 to 66 minutes. The uranium (IV/III) cupferrate was then re-extracted In cell D from the ether solution Into three suooesslve 15-ml. portions of 7H... 

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 incorporation of anions, as for example, S04 , CO2-, etc., makes leaching possible through the formation of stable uranyl (VI) oxyanions. In sulfate leaching, an observation of the potential-pH diagram for the uranium system reveals that uranium species in solution may be in the form of cations U02+, neutral species U02(S04)2 or anions U02(S04)4-. The oxidation of uraninite, U02, in acid solutions, transforming U(IV) to U(VI), yields soluble uranyl sulfate through the reaction as shown below ... 

Biological activity can be used in two ways for the bioremediation of metal-contaminated soils to immobilize the contaminants in situ or to remove them permanently from the soil matrix, depending on the properties of the reduced elements. Chromium and uranium are typical candidates for in situ immobilization processes. The bioreduction of Cr(VI) and Ur(VI) transforms highly soluble ions such as CrO and UO + to insoluble solid compounds, such as Cr(OH)3 and U02. The selenate anions SeO are also reduced to insoluble elemental selenium Se°. Bioprecipitation of heavy metals, such as Pb, Cd, and Zn, in the form of sulfides, is another in situ immobilization option that exploits the metabolic activity of sulfate-reducing bacteria without altering the valence state of metals. The removal of contaminants from the soil matrix is the most appropriate remediation strategy when bioreduction results in species that are more soluble compared to the initial oxidized element. This is the case for As(V) and Pu(IV), which are transformed to the more soluble As(III) and Pu(III) forms. This treatment option presupposes an installation for the efficient recovery and treatment of the aqueous phase containing the solubilized contaminants. 

The (IV) and (VI) are the important oxidation states and therefore tlie more important phases of the chemistry of uranium may be related to the two oxides UO> and UO3. uranium dioxide and uranium trioxide. A series of salts such as the chloride and sulfate, UC14 and U(S04)2 9H20 is... 

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