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Hydration of arsenic oxyacid species
Swedish University of Agricultural Sciences.
Swedish University of Agricultural Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
2013 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 42, no 5, 1364-1377 p.Article in journal (Refereed) Published
Abstract [en]

The bond distances in hydrated arsenic oxyacid species in aqueous solution have been studied by EXAFSspectroscopy and large angle X-ray scattering, LAXS. These results have been compared to structures inthe solid state, as found in an extensive survey of available crystal structures. Protonated oxygen atomscan be distinguished with a longer As–O distance for both arsenic(V) and arsenic(III) species in the crystallinestate. However, the average As–O distance for the HnAsO4(3−n)− species (0 ≤ n ≤ 3) remains the same.These average values are slightly shorter, ca. 0.02 Å, than in aqueous solution due to the hydration asdetermined by EXAFS and LAXS. The K absorption edges for arsenic(V) and arsenic(III) species are separatedby 4.0 eV, and the shape of the absorption edges differs as well. Small but significant differences inthe absorption edge features are seen between the neutral acids and the charged oxyacid species. Themost important arsenic species from an environmental point of view is arsenous acid, As(OH)3. Inaddition to arsenous acid, we have used orthotelluric acid, Te(OH)6, for comparison with arsenous acidand for detailed studies of the hydration of covalently bound hydroxo groups. Arsenous acid cannot bestudied with the same accuracy as orthotelluric acid, due to a relatively low solubility of As2O3(s) inneutral to acidic aqueous solution. The results from the DDIR studies support the assignment of As(OH)3 as a weak structure maker analogous to Te(OH)6, both being neutral weak oxyacids.

Place, publisher, year, edition, pages
2013. Vol. 42, no 5, 1364-1377 p.
National Category
Physical Chemistry
URN: urn:nbn:se:uu:diva-185015DOI: 10.1039/c2dt31906cISI: 000313616600010PubMedID: 23135316OAI: oai:DiVA.org:uu-185015DiVA: diva2:570264
Available from: 2012-11-18 Created: 2012-11-18 Last updated: 2015-03-23Bibliographically approved

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