View source for Chemistry:Uranium(IV) sulfate

{{chembox
| Verifiedfields = changed
| verifiedrevid = 403120211
|   Name = Uranium(IV) sulfate
|   ImageFile = <!--Uranium sulfate.jpg-->
<!-- | ImageSize = 200px -->
|   ImageName = Uranium sulfate
|   OtherNames =
| Section1 = {{Chembox Identifiers
|   ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 11383849
| PubChem2 = 51035180
| InChI = 1/H2O4S.U/c1-5(2,3)4;/h(H2,1,2,3,4);/q;+2/p-2
| InChIKey = SMWCBVIJCHHBAU-NUQVWONBAD
| SMILES = [U+2].[O-]S([O-])(=O)=O
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/H2O4S.U/c1-5(2,3)4;/h(H2,1,2,3,4);/q;+2/p-2
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = SMWCBVIJCHHBAU-UHFFFAOYSA-L
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 13470-23-0
| CASNo_Comment = (tetrahydrate)
| CASNo2_Ref = {{cascite|correct|CAS}}
| CASNo2 = 14355-39-6
| CASNo2_Comment = (anhydrous)
  }}
| Section2 = {{Chembox Properties
|   Formula = U(SO<sub>4</sub>)<sub>2</sub>
|   MolarMass =430.15 g/mol
|   Density = 
|   Solvent = 
|   SolubleOther = 
|   MeltingPt =
|   BoilingPt = }}
}}
'''Uranium(IV) sulfate''' (U(SO<sub>4</sub>)<sub>2</sub>) is a water-soluble [[Chemistry:Salt|salt]] of [[Chemistry:Uranium|uranium]]. It is a very [[Medicine:Toxicity|toxic]] [[Chemistry:Chemical compound|compound]]. Uranium sulfate minerals commonly are widespread around uranium bearing mine sites, where they usually form during the evaporation of acid sulfate-rich mine tailings which have been leached by oxygen-bearing waters. Uranium sulfate is a transitional [[Chemistry:Chemical compound|compound]] in the production of [[Chemistry:Uranium hexafluoride|uranium hexafluoride]]. It was also used to fuel [[Engineering:Aqueous homogeneous reactor|aqueous homogeneous reactors]].

==Preparation==
[[Chemistry:Uranyl sulfate|Uranyl sulfate]] in solution is readily [[Chemistry:Photochemistry|photochemically]] reduced to uranium(IV) sulfate. The photoreduction is carried out in the sun and requires the addition of [[Chemistry:Ethanol|ethanol]] as a reducing agent. Uranium(IV) crystallizes or is precipitated by ethanol in excess. It can be obtained with different degrees of hydration. U(SO<sub>4</sub>)<sub>2</sub> can also be prepared through [[Chemistry:Electrochemistry|electrochemical reduction]] of U(VI) and the addition of sulfates. Reduction of U(VI) to U(IV) occurs naturally through a variety of means, including through the actions of microorganisms. Formation of U(SO<sub>4</sub>)<sub>2</sub> is an entropically and thermodynamically favorable reaction.

==Mining and presence in the environment==
[[Earth:In situ leach|In-situ leaching]] (ISL), a widespread technique used to mine uranium, is implicated in the artificial increase of uranium sulfate compounds. ISL was the most widely used method to mine uranium in the United States during the 1990s. The method involves pumping an extraction liquid (either [[Chemistry:Sulfuric acid|sulfuric acid]] or an alkaline carbonate solution) into an ore deposit, where it complexes with the uranium, removing the liquid and purifying the uranium. This synthetic addition of sulfuric acid unnaturally raises the abundance of uranium sulfate complexes at the site. The lower [[Chemistry:PH|pH]] caused by the introduction of acid increases the solubility of U(IV), which is typically relatively insoluble and precipitates out of solution at neutral pH. Oxidation states for uranium range from U<sup>3+</sup> to U<sup>6+</sup>, U(III) and U(V) are rarely found, while U(VI) and U(IV) predominate. U(VI) forms stable aqueous complexes and is thus fairly mobile. Preventing the spread of toxic uranium compounds from mining sites often involves reduction of U(VI) to the far less soluble U(IV). The presence of sulfuric acid and sulfates prevents this sequestration, however, by both lowering the pH and through the formation of uranium salts. U(SO<sub>4</sub>)<sub>2</sub> is soluble in water, and thus far more mobile. Uranium sulfate complexes also form quite readily.

==Environmental and health effects==
U(IV) is much less soluble, and thus less environmentally mobile, than U(VI), which also forms sulfate compounds such as UO<sub>2</sub>(SO<sub>4</sub>). [[Biology:Bacteria|Bacteria]] which are able to reduce uranium have been proposed as a means of eliminating U(VI) from contaminated areas, such as [[Engineering:Tailings|mine tailings]] and [[Engineering:Nuclear weapon|nuclear weapon]]s manufacture sites. Contamination of [[Earth:Groundwater|groundwater]] by uranium is considered a serious health risk, and can be damaging to the environment as well. Several species of [[Earth:Sulfate-reducing microorganisms|sulfate reducing bacteria]] also have the ability to reduce uranium. The ability to clear the environment of both sulfate (which solubilizes reduced uranium) and mobile U(VI) makes [[Earth:Bioremediation|bioremediation]] of ISL mining sites a possibility.

==Related compounds==
U(SO<sub>4</sub>)<sub>2</sub> is a semi-soluble compound and exists in a variety of [[Chemistry:Hydrate|hydration states]], with up to nine coordinating waters.
U(IV) can have up to five coordinating sulfates, although nothing above U(SO<sub>4</sub>)<sub>2</sub> has been significantly described.  Kinetics data for U(SO<sub>4</sub>)<sup>2+</sup> and U(SO<sub>4</sub>)<sub>2</sub> reveal that the bidentate complex is strongly favored thermodynamically, with a reported K<sup>0</sup> of 10.51, as compared to K<sup>0</sup>=6.58 for the monodentate complex. U(IV) is much more stable as a sulfate compound, particularly as U(SO<sub>4</sub>)<sub>2</sub>. Běhounekite is a recently (2011) described U(IV) mineral with the chemical composition U(SO<sub>4</sub>)<sub>2</sub> (H<sub>2</sub>O)<sub>4</sub>. The uranium center has eight oxygen ligands, four provided by the sulfate groups and four from the water ligands. U(SO<sub>4</sub>)<sub>2</sub> (H<sub>2</sub>O)<sub>4</sub> forms short, green crystals. Běhounekite is the first naturally occurring U(IV) sulfate to be described.

==References==
{{reflist}}
* {{Cite journal | last1 = Perez | first1 = F. M. | last2 = Gil | first2 = J. M. | last3 = Gil | first3 = F. J. M. | title = Preparation, infrared and visible spectra of Sulfate Complexes of Uranium(IV) | doi = 10.1002/zaac.19804620127 | journal = Zeitschrift für anorganische und allgemeine Chemie| volume = 462 | pages = 231–240 | year = 1980 | url = https://www.researchgate.net/publication/230420833}}
* Merkel, B.; Hasche-Berger, A. (2008). Uranium, Mining and Hydrogeology. Springer. {{ISBN|978-3-540-87745-5}}
* Hennig, C.; Schmeide, K.; Brendler, V.; Moll, H.; Tsushima, S.; Scheinost, A.C. (2007). “EXAFS Investigation of U(VI), U(IV), and Th(IV) Sulfato Complexes in Aqueous Solution”. Inorganic Chemistry 46 (15): 5882–5892.
* Cardenas, E.; Watson, D.; Gu, B.; Ginder-Vogel, M.; Kitanidis, P.K.; Jardin, P.M.; Wu, W.; Leigh, M.B.; Carley, J.; Carroll, S.; Gentry, T.; Luoe, J.; Zhou, J.; Criddle, C.S.; Marsh, T.L.; Tiedje, J.M. (2010). “Significant Association between Sulfate-Reducing Bacteria and Uranium-Reducing Microbial Communities as Revealed by a Combined Massively Parallel Sequencing-Indicator Species Approach”. Applied and Environmental Microbiology 76 (20): 6778-6786.
* Converse, B.J.; Wua, T.; Findlay, R.H.; Roden, E.E. (2013). “U(VI) Reduction in Sulfate-Reducing Subsurface Sediments Amended with Ethanol or Acetate”.  Applied and Environmental Microbiology 79 (13): 4173-4177.
* Day, R. A.; Wilhite, R. N.; Hamilton, F.R. (1955). “Stability of Complexes of Uranium(IV) with Chloride, Sulfate and Thiocyanate”. Journal of the American Chemical Society 77 (12):3180-3182.
* Hennig, C.; Kraus, W.; Emmerling, F.; Ikeda, A.;. Scheinost, A.C. (2008). “Coordination of a Uranium(IV) Sulfate Monomer in an Aqueous Solution and in the Solid State”. Inorganic Chemistry 47 (5): 1634-1638.
* Plášil, J.; Fejfarová, K.; Novák, M.; Dušek, M.; Škoda, R.; Hloušek, J.; Čejka, J.; Majzlan, J.; Sejkora, J.; Machovič, V.; Talla, D. (2011). “Běhounekite, U(SO4)2(H2O)4, from Jáchymov (St Joachimsthal), Czech Republic: the first natural U4+ sulphate”. Mineralogical Magazine 75 (6): 2739-2753.
* Mudd, G.M. (2001). “Critical Review of Acid in situ leach uranium mining: 1. USA and Australia”. Environmental Geology 41 (3-4): 390-403.
* Závodská, L.; Kosorínová, E.; Scerbáková, L.; Lesny, J. (2008). “Environmental Chemistry of Uranium”. HV {{ISSN|1418-7108}}.

{{Uranium compounds}}
{{Sulfates}}

{{DEFAULTSORT:Uranium Sulfate}}
[[Category:Uranium(IV) compounds]]
[[Category:Sulfates]]

{{Sourceattribution|Uranium(IV) sulfate}}