Selenate
{{Short description|Ion}}
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| ImageFileL1 = Selenate.png
| ImageFileR1 = Selenate-3D-vdW.svg
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| IUPACName = selenate
| SystematicName =
| OtherNames =selenate ion
| Section1 = {{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|??}}
| CASNo = 14124-68-6
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 6X37R1DB70
| PubChem = 26473
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID =
| SMILES = [O-][Se+2]([O-])([O-])[O-]
| InChI =
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| Section2 = {{Chembox Properties
| Formula = {{chem|SeO|4|2-}}
| ConjugateAcid = Hydrogen selenate
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Selenates are analogous to sulfates and have similar chemistry. They are highly soluble in aqueous solutions at ambient temperatures.{{Cite journal |last1=Jegadeesan |first1=G. |last2=Mondal |first2=K. |last3=Lalvani |first3=S. B. |date=May 11, 2010 |title=Selenate removal from sulfate containing aqueous solutions |url=https://pubmed.ncbi.nlm.nih.gov/16342540/ |journal=Environmental Technology |volume=26 |issue=10 |pages=1181–1187 |doi=10.1080/09593332608618475 |issn=0959-3330 |pmid=16342540|s2cid=10304488 }}
Unlike sulfate, selenate is a somewhat good oxidizer; it can be reduced to selenite or selenium.{{Cite journal |last1=Sarathchandra |first1=S. U. |last2=Watkinson |first2=J. H. |date=1981-02-06 |title=Oxidation of elemental selenium to selenite by Bacillus megaterium |url=https://pubmed.ncbi.nlm.nih.gov/6779378/ |journal=Science |volume=211 |issue=4482 |pages=600–601 |doi=10.1126/science.6779378 |issn=0036-8075 |pmid=6779378|bibcode=1981Sci...211..600S }}
In strongly acidic conditions, the hydrogen selenate ion, {{chem|HSe|O|4|−}}, is formed.{{Cite journal |last1=Kong |first1=Linghao |last2=Hu |first2=Xingyun |last3=Peng |first3=Xianjia |last4=Wang |first4=Xianliang |date=2020-11-03 |title=Specific H2S Release from Thiosulfate Promoted by UV Irradiation for Removal of Arsenic and Heavy Metals from Strongly Acidic Wastewater |url=https://pubmed.ncbi.nlm.nih.gov/33058725/ |journal=Environmental Science & Technology |volume=54 |issue=21 |pages=14076–14084 |doi=10.1021/acs.est.0c05166 |issn=1520-5851 |pmid=33058725|bibcode=2020EnST...5414076K |s2cid=222821717 }} It corresponds to the selenic acid, H2SeO4, which is a strong acid and can in its concentrated form dissolve gold.{{Citation |last1=Plant |first1=JA. |title=11.2 - Arsenic and Selenium |date=2014-01-01 |url=https://www.sciencedirect.com/science/article/pii/B9780080959757009025 |work=Treatise on Geochemistry (Second Edition) |pages=13–57 |editor-last=Holland |editor-first=Heinrich D. |place=Oxford |publisher=Elsevier |language=en |isbn=978-0-08-098300-4 |access-date=2023-01-03 |last2=Bone |first2=J. |last3=Voulvoulis |first3=N. |last4=Kinniburgh |first4=DG. |last5=Smedley |first5=PL. |last6=Fordyce |first6=FM. |last7=Klinck |first7=B. |editor2-last=Turekian |editor2-first=Karl K.}}
The element selenium exhibits several valence states. Selenate is the least reduced, followed by selenite, and elemental selenium; selenide is even more reduced than elemental selenium.{{Cite journal |last1=Mangiapane |first1=Erika |last2=Pessione |first2=Alessandro |last3=Pessione |first3=Enrica |date=2014 |title=Selenium and selenoproteins: an overview on different biological systems |url=https://pubmed.ncbi.nlm.nih.gov/24910086/ |journal=Current Protein & Peptide Science |volume=15 |issue=6 |pages=598–607 |doi=10.2174/1389203715666140608151134 |issn=1875-5550 |pmid=24910086|hdl=2318/147957 |hdl-access=free }} The valence state is an important factor to the toxicity of selenium. Selenate is the form required by organisms that need selenium as a micronutrient. These organisms have the ability to acquire, metabolize and excrete selenium.{{Cite journal |last1=Tan |first1=Lea Chua |last2=Nancharaiah |first2=Yarlagadda V. |last3=van Hullebusch |first3=Eric D. |last4=Lens |first4=Piet N. L. |date=2016 |title=Selenium: environmental significance, pollution, and biological treatment technologies |url=https://pubmed.ncbi.nlm.nih.gov/27235190/ |journal=Biotechnology Advances |volume=34 |issue=5 |pages=886–907 |doi=10.1016/j.biotechadv.2016.05.005 |issn=1873-1899 |pmid=27235190}} The level at which selenium becomes toxic varies from species to species and is related to other environmental factors like pH and alkalinity that influence the concentration of selenite over selenate.{{Cite journal |last1=Xie |first1=Lingtian |last2=Wu |first2=Xing |last3=Chen |first3=Hongxing |last4=Dong |first4=Wu |last5=Cazan |first5=Alfy Morales |last6=Klerks |first6=Paul L. |year=2016 |title=A low level of dietary selenium has both beneficial and toxic effects and is protective against Cd-toxicity in the least killifish Heterandria formosa |url=https://pubmed.ncbi.nlm.nih.gov/27448316/ |journal=Chemosphere |volume=161 |pages=358–364 |doi=10.1016/j.chemosphere.2016.07.035 |issn=1879-1298 |pmid=27448316|bibcode=2016Chmsp.161..358X }}
Selenate and other forms of selenium are highest in areas where ancient seas have evaporated. These areas are enriched in selenium and over millennia, biologic adaptation has occurred.{{Cite journal |last1=Domokos-Szabolcsy |first1=Éva |last2=Fári |first2=Miklós |last3=Márton |first3=László |last4=Czakó |first4=Mihály |last5=Veres |first5=Szilvia |last6=Elhawat |first6=Nevien |last7=Antal |first7=Gabriella |last8=El-Ramady |first8=Hassan |last9=Zsíros |first9=Ottó |last10=Garab |first10=Győző |last11=Alshaal |first11=Tarek |date=2018-09-08 |title=Selenate tolerance and selenium hyperaccumulation in the monocot giant reed (Arundo donax), a biomass crop plant with phytoremediation potential |url=https://pubmed.ncbi.nlm.nih.gov/30196460/ |journal=Environmental Science and Pollution Research International |volume=25 |issue=31 |pages=31368–31380 |doi=10.1007/s11356-018-3127-3 |issn=1614-7499 |pmid=30196460|bibcode=2018ESPR...2531368D |s2cid=52177009 }}