{{Short description|none}} {{Use dmy dates|date=February 2023}} {{chembox | ImageFileL1 = Arsenate ion.svg | ImageClassL1 = skin-invert-image | ImageFileR1 = Arsenate-anion-3D-spacefill.png | ImageClassR1 = bg-transparent | IUPACName = Arsenate | OtherNames = | Section1 = {{Chembox Identifiers | CASNo_Ref = {{cascite|correct|CAS}} | CASNo = 15584-04-0 | UNII_Ref = {{fdacite|correct|FDA}} | UNII = G1DBI405OK | PubChem = 27401 | SMILES = [O-][As+]([O-])([O-])[O-] | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID = 25498 | InChI = 1/AsH3O4/c2-1(3,4)5/h(H3,2,3,4,5)/p-3 | InChIKey = DJHGAFSJWGLOIV-DFZHHIFOAQ | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI = 1S/AsH3O4/c2-1(3,4)5/h(H3,2,3,4,5)/p-3 | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = DJHGAFSJWGLOIV-UHFFFAOYSA-K }} | Section2 = {{Chembox Properties | Formula = {{chem2|AsO4(3−)}} | As=1|O=4 | Appearance = | Solubility = | ConjugateAcid = [[Arsenic acid]] }} | Section7 = {{Chembox Hazards | MainHazards = Extremely toxic, carcinogenic }} }} The '''arsenate''' is an [[ion]] with the [[chemical formula]] {{chem2|AsO4(3-)}}.<ref>{{Cite web |last=PubChem |title=Arsenate ion |url=https://pubchem.ncbi.nlm.nih.gov/compound/27401 |access-date=2023-04-02 |website=pubchem.ncbi.nlm.nih.gov |language=en}}</ref> Bonding in arsenate consists of a central [[arsenic]] atom, with [[oxidation state]] +5, [[Double bond|double bonded]] to one oxygen atom and [[Single bond|single bonded]] to a further three [[oxygen]] atoms.<ref name=":0">{{Cite web |title=Arsenate mineral {{!}} Britannica |url=https://www.britannica.com/science/arsenate-mineral |access-date=2023-04-02 |website=www.britannica.com |language=en}}</ref> The four oxygen atoms orient around the arsenic atom in a [[Tetrahedral molecular geometry|tetrahedral geometry]].<ref name=":0" /> [[Resonance (chemistry)|Resonance]] disperses the ion's −3 charge across all four oxygen atoms.
Arsenate readily reacts with metals to form arsenate metal [[Arsenic compounds|compounds]].<ref name=":0" /><ref>{{Citation |last=Waalkes |first=Michael P. |title=Arsenic and metals |date=2019 |url=https://www.ncbi.nlm.nih.gov/books/NBK570318/ |work=Tumour Site Concordance and Mechanisms of Carcinogenesis |editor-last=Baan |editor-first=Robert A. |access-date=2023-04-02 |series=IARC Scientific Publications |place=Lyon (FR) |publisher=International Agency for Research on Cancer |isbn=978-92-832-2217-0 |pmid=33979075 |editor2-last=Stewart |editor2-first=Bernard W. |editor3-last=Straif |editor3-first=Kurt}}</ref> Arsenate is a moderate [[Oxidant|oxidizer]] and an [[electron acceptor]], with an [[electrode potential]] of +0.56 [[Volt|V]] for its [[Reduction potential|reduction]] to [[arsenite]].<ref>{{Cite web |date=2013-12-02 |title=P1: Standard Reduction Potentials by Element |url=https://chem.libretexts.org/Ancillary_Materials/Reference/Reference_Tables/Electrochemistry_Tables/P1%3A_Standard_Reduction_Potentials_by_Element |access-date=2023-03-29 |website=Chemistry LibreTexts |language=en}}</ref> Due to arsenic having the same [[Valence (chemistry)|valency]] and similar [[Atomic radii of the elements (data page)|atomic radius]] to [[phosphorus]], arsenate shares similar [[Tetrahedral molecular geometry|geometry]] and [[Reactivity (chemistry)|reactivity]] with [[phosphate]].<ref name=":1">{{Cite book |last=Pollutants |first=National Research Council (US) Committee on Medical and Biological Effects of Environmental |url=https://www.ncbi.nlm.nih.gov/books/NBK231019/ |title=Chemistry of Arsenic |date=1977 |publisher=National Academies Press (US) |language=en}}</ref> Arsenate can replace phosphate in [[Biochemistry|biochemical reactions]] and is [[Toxicity|toxic]] to most [[Organism|organisms]].<ref name=":1" /><ref>{{Cite journal |last1=Elias |first1=Mikael |last2=Wellner |first2=Alon |last3=Goldin-Azulay |first3=Korina |last4=Chabriere |first4=Eric |last5=Vorholt |first5=Julia A. |last6=Erb |first6=Tobias J. |last7=Tawfik |first7=Dan S. |date=2012 |title=The molecular basis of phosphate discrimination in arsenate-rich environments |url=https://www.nature.com/articles/nature11517 |journal=Nature |language=en |volume=491 |issue=7422 |pages=134–137 |doi=10.1038/nature11517 |pmid=23034649 |bibcode=2012Natur.491..134E |s2cid=99851438 |issn=1476-4687|url-access=subscription }}</ref> ==Natural occurrence== [[File:Adamite-209883.jpg|left|thumb|180x180px|[[Adamite]], a naturally occurring arsenate mineral.]] Arsenates occur naturally, in [[Hydrate|hydrated]] and [[anhydrous]] form, in a variety of [[Mineral|minerals]]. Examples of arsenate-containing minerals include [[adamite]], [[alarsite]], [[annabergite]], [[erythrite]] and [[legrandite]].<ref>{{Cite web |title=The mineralogy of Arsenic |url=https://www.mindat.org/element/Arsenic |website=Mindat.org}}</ref> When two arsenate ions balance the [[Nuclear charge|charge]] in a formula, it is called diarsenate for example zinc diarsenate, {{chem2|Zn3(AsO4)2}}.
== Uses == Arsenate-based [[Pesticide|pesticides]] such as [[lead hydrogen arsenate]] were commonly used until their replacement by newer pesticides such as [[DDT]] and subsequent ban by multiple regulatory bodies due to health concerns.<ref>{{Cite web |title=The Evolution of Chemical Pesticides |url=https://www.fishersci.ca/ca/en/publications/lab-reporter/2016/issue-4/the-evolution-chemical-pesticides.html |access-date=2023-04-02 |website=www.fishersci.ca}}</ref><ref>{{Cite web |title=The Global Problem of Lead Arsenate Pesticide |url=https://lead.org.au/lanv10n3/lanv10n3-7.html |access-date=2023-04-02 |website=lead.org.au}}</ref>
[[Transition metal]] arsenate compounds are often brightly coloured and have been used to make [[Pigment|pigments]]. [[Copper(II) arsenate|Copper arsenate]] was a minor compound used in the [[Egyptian blue]] pigment used by the [[ancient Egyptians]] and [[Ancient Rome|Romans]].<ref>{{Cite journal |last1=Dariz |first1=Petra |last2=Schmid |first2=Thomas |date=2021-05-28 |title=Trace compounds in Early Medieval Egyptian blue carry information on provenance, manufacture, application, and ageing |journal=Scientific Reports |language=en |volume=11 |issue=1 |pages=11296 |doi=10.1038/s41598-021-90759-6 |pmid=34050218 |pmc=8163881 |bibcode=2021NatSR..1111296D |issn=2045-2322}}</ref> [[Cobalt(II) phosphate|Cobalt violet]] pigment was made from cobalt arsenate before its toxicity led to its replacement by [[Cobalt(II) phosphate|cobalt phosphate]].<ref>{{Cite journal |last1=Corbeil |first1=Marie-Claude |last2=Charland |first2=Jean-Pierre |last3=Moffatt |first3=Elizabeth A. |date=2002 |title=The Characterization of Cobalt Violet Pigments |url=https://www.jstor.org/stable/1506784 |journal=Studies in Conservation |volume=47 |issue=4 |pages=237–249 |doi=10.2307/1506784 |jstor=1506784 |issn=0039-3630|url-access=subscription }}</ref><ref>{{Cite web |title=Cobalt violet |url=https://colourlex.com/project/cobalt-violet/ |access-date=2023-04-10 |website=ColourLex |language=en-US}}</ref><ref>{{Cite web |title=Cobaltous arsenate - CAMEO |url=https://cameo.mfa.org/wiki/Cobaltous_arsenate |access-date=2023-04-10 |website=cameo.mfa.org |language=en}}</ref>
[[Chromated copper arsenate]] (CCA) has been a widely used [[Wood preservation|wood preservative]] since the 1930s.<ref name=":02">{{Citation |last=Barton |first=C. |title=CCA-Treated Wood |date=2014-01-01 |url=https://www.sciencedirect.com/science/article/pii/B9780123864543002724 |encyclopedia=Encyclopedia of Toxicology (Third Edition) |pages=751–752 |editor-last=Wexler |editor-first=Philip |access-date=2023-04-10 |place=Oxford |publisher=Academic Press |language=en |isbn=978-0-12-386455-0}}</ref> Safety concerns have led to the phasing out of CCA-treated wood for [[Residential area|residential]] projects in many countries.<ref name=":02" /> CCA remains a common and economical treatment choice for non-residential uses such as [[agriculture]]. <ref name=":02" /><ref>{{Cite journal |last1=Likar |first1=M |last2=Schauer |first2=P |last3=Japelj |first3=M |last4=Globokar |first4=M |last5=Oklobdzija |first5=M |last6=Povse |first6=A |last7=Sunjić |first7=V |date=1970-01-01 |title=Synthesis and antimicrobial activity of some thenoyl amides |url=https://doi.org/10.1021/jm00295a053 |journal=Journal of Medicinal Chemistry |volume=13 |issue=1 |pages=159–161 |doi=10.1021/jm00295a053 |issn=1520-4804 |pmid=5412102|url-access=subscription }}</ref>
== Speciation == [[File:Pourbaix_diagram_of_arsenic.jpg|thumb|302x302px|[[Pourbaix diagram]] showing the distribution of arsenate and [[arsenite]] species in water. [[Oxygenation (environmental)|Oxygenated]] waters have a high [[Redox potential|pe]] value and arsenate species dominate. In deoxygenated water, with low pe, arsenite species dominate.<ref name=":3">{{Cite journal |last1=Marinho |first1=Belisa A. |last2=Cristóvão |first2=Raquel O. |last3=Boaventura |first3=Rui A. R. |last4=Vilar |first4=Vítor J. P. |date=2019-01-01 |title=As(III) and Cr(VI) oxyanion removal from water by advanced oxidation/reduction processes—a review |url=https://doi.org/10.1007/s11356-018-3595-5 |journal=Environmental Science and Pollution Research |language=en |volume=26 |issue=3 |pages=2203–2227 |doi=10.1007/s11356-018-3595-5 |pmid=30474808 |bibcode=2019ESPR...26.2203M |s2cid=53783178 |issn=1614-7499|url-access=subscription }}</ref><ref name=":4">{{Citation |last1=Jekel |first1=M. |title=Chapter 11 - Arsenic removal during drinking water treatment |date=2006-01-01 |url=https://www.sciencedirect.com/science/article/pii/S1573428506800803 |work=Interface Science and Technology |volume=10 |pages=193–206 |editor-last=Newcombe |editor-first=Gayle |access-date=2023-04-15 |series=Interface Science in Drinking Water Treatment |publisher=Elsevier |language=en |last2=Amy |first2=G. L. |doi=10.1016/S1573-4285(06)80080-3 |isbn=978-0-12-088380-6 |editor2-last=Dixon |editor2-first=David|url-access=subscription }}</ref>]] Depending on the [[pH]], arsenate can be found as trihydrogen arsenate (that is [[arsenic acid]] {{chem2|H3AsO4}}), dihydrogen arsenate ({{chem2|H2AsO4-}}), hydrogen arsenate ({{chem2|HAsO4(2-)}}), or arsenate ({{chem2|AsO4(3-)}}).<ref name=":12">{{Cite book |last=Pollutants |first=National Research Council (US) Committee on Medical and Biological Effects of Environmental |url=https://www.ncbi.nlm.nih.gov/books/NBK231019/ |title=Chemistry of Arsenic |date=1977 |publisher=National Academies Press (US) |language=en}}</ref> Trihydrogen arsenate is also known as [[arsenic acid]]. At a given [[pH]], the distribution of these arsenate [[Ion speciation|species]] can be determined from their respective [[Acid dissociation constant|acid dissociation constants]].<ref name=":4" /> :{{chem2|H3AsO4 + H2O ⇌ H2AsO4− + [H3O]+}}{{pad|3em}}(p''K''<sub>a1</sub> = 2.19) :{{chem2|H2AsO4− + H2O ⇌ HAsO4(2−) + [H3O]+}}{{pad|3em}}(p''K''<sub>a2</sub> = 6.94) :{{chem2|HAsO4(2−) + H2O ⇌ AsO4(3−) + [H3O]+}}{{0|H}}{{pad|3em}}(p''K''<sub>a3</sub> = 11.5)
These values are similar to those of [[phosphoric acid]]. Hydrogen arsenate and dihydrogen arsenate predominate in aqueous solution near neutral pH.<ref name=":4" />
The [[reduction potential]] (pe) of a solution also affects arsenate speciation. In natural waters, the [[Dissolved Oxygen|dissolved oxygen content]] is the main factor influencing reduction potential. Arsenates occur in oxygenated waters, which have a high pe, while arsenites are the main arsenic species in [[anoxic waters]] with a low pe.<ref name=":3" />
A [[Pourbaix diagram]] shows the combined influence of pH and pe on arsenate speciation.
== Contamination == Arsenates, along with arsenites, are a significant source of [[Contamination of drinking water|contamination]] in some natural [[Water source|water sources]] and can lead to [[arsenic poisoning]] with repeated exposure.<ref>{{Cite journal |last1=Sánchez-Rodas |first1=Daniel |last2=Luis Gómez-Ariza |first2=José |last3=Giráldez |first3=Inmaculada |last4=Velasco |first4=Alfredo |last5=Morales |first5=Emilio |date=2005-06-01 |title=Arsenic speciation in river and estuarine waters from southwest Spain |journal=The Science of the Total Environment |volume=345 |issue=1–3 |pages=207–217 |doi=10.1016/j.scitotenv.2004.10.029 |issn=0048-9697 |pmid=15919540|bibcode=2005ScTEn.345..207S }}</ref><ref name=":03">{{Cite web |title=Arsenic |url=https://www.who.int/news-room/fact-sheets/detail/arsenic |access-date=2023-04-15 |website=www.who.int |language=en}}</ref> Countries with high levels of arsenic minerals in [[sediment]] and rock, such as [[Bangladesh]], are especially at risk of arsenate contamination.<ref>{{Cite web |last=UCL |date=2022-05-10 |title=Reducing population exposure to groundwater arsenic in Bangladesh |url=https://www.ucl.ac.uk/earth-sciences/news/2022/may/reducing-population-exposure-groundwater-arsenic-bangladesh |access-date=2023-04-15 |website=UCL Earth Sciences |language=en}}</ref><ref name=":03" />
== Arsenate poisoning == Arsenate is harmful to [[Human|humans]] and [[Animal|animals]] as it interferes with the normal functioning of [[glycolysis]] and the [[Citric acid cycle|Krebs cycle]]. Arsenate replaces inorganic [[phosphate]] in the step of [[glycolysis]] that produces [[1,3-bisphosphoglycerate]] from [[glyceraldehyde 3-phosphate]]. This yields [[1-arseno-3-phosphoglycerate]] instead, which is unstable and quickly [[Hydrolysis|hydrolyzes]], forming the next intermediate in the pathway, [[3-phosphoglycerate]]. Therefore, glycolysis proceeds, but the [[Adenosine triphosphate|ATP]] molecule that would be generated from [[1,3-bisphosphoglycerate]] is lost – arsenate is an [[uncoupler]] of glycolysis, explaining its toxicity.<ref>{{Cite web |date= 21 June 2022|title=How does arsenic kill? |url=https://www.livescience.com/how-does-arsenic-kill |access-date=2023-03-31 |website=livescience.com |language=en}}</ref><ref name=":2">{{Cite journal |last=Hughes |first=Michael F. |date=2002-07-07 |title=Arsenic toxicity and potential mechanisms of action |journal=Toxicology Letters |volume=133 |issue=1 |pages=1–16 |doi=10.1016/s0378-4274(02)00084-x |issn=0378-4274 |pmid=12076506}}</ref>
As with other arsenic compounds, arsenate binds to [[lipoic acid]], inhibiting the conversion of [[pyruvate]] into [[acetyl-CoA]], blocking the [[Krebs cycle]] and therefore resulting in further loss of ATP.<ref name=":2" />
==See also== *[[:Category:Arsenates]]
==References== {{Reflist}} {{Wiktionary|arsenate|arsenation}}
[[Category:Arsenates| ]] [[Category:Arsenic(V) compounds]] [[Category:Pnictogen oxyanions]]