The Influence of Aqueous Se(IV) on the Stability of Different CaCO3 Polymorphs Precipitated under Ambient Conditions

Selenium is an essential bio-element, but because of its bioaccumulation potential, it can become toxic and is an important pollutant. The ubiquitous mineral calcite (CaCO3) has the ability to immobilize anions as SeO32− by differe...

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Autores principales:	Angeles Fernandez-Gonzalez, Alba Lozano-Letellier, Begoña Fernandez
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	calcium carbonate polymorphism selenite calcium carbonate precipitation vaterite Mineralogy QE351-399.2
Acceso en línea:	https://doaj.org/article/8b93eeda16af44ce8c94d0a159e90408
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spelling	oai:doaj.org-article:8b93eeda16af44ce8c94d0a159e904082021-11-25T18:26:30ZThe Influence of Aqueous Se(IV) on the Stability of Different CaCO<sub>3</sub> Polymorphs Precipitated under Ambient Conditions10.3390/min111112382075-163Xhttps://doaj.org/article/8b93eeda16af44ce8c94d0a159e904082021-11-01T00:00:00Zhttps://www.mdpi.com/2075-163X/11/11/1238https://doaj.org/toc/2075-163XSelenium is an essential bio-element, but because of its bioaccumulation potential, it can become toxic and is an important pollutant. The ubiquitous mineral calcite (CaCO<sub>3</sub>) has the ability to immobilize anions as SeO<sub>3</sub><sup>2−</sup> by different sorption or coprecipitation processes. Experimental studies have found that SeO<sub>3</sub><sup>2−</sup> can incorporate in the crystal structure of calcite by substituting CO<sub>3</sub><sup>2−</sup>. The presence of foreign ions in aqueous solution strongly affects CaCO<sub>3</sub> precipitation, helping stabilize less stable polymorphs such as vaterite and aragonite or hydrated phases. In this work, we studied the aging process of calcium carbonates precipitated from aqueous solutions highly supersaturated with respect to CaCO<sub>3</sub> and slightly supersaturated with respect to CaSeO<sub>3</sub>·H<sub>2</sub>O under ambient conditions, for times up to 30 days in which solids were kept in the remaining aqueous solution. Under these conditions, CaCO<sub>3</sub> precipitated mainly as low crystallinity vaterite aggregates that hosted up to 16% atomic ratio Se:C. Vaterite purified and increased its crystallinity with aging time, but the vaterite–calcite transformation was strongly inhibited. The incorporation of Se(IV) in vaterite did not significantly affect the cell parameters or the external morphology of the aggregates. The precipitation of selenite as CaSeO<sub>3</sub>·H<sub>2</sub>O was conditioned by the availability of free Ca<sup>2+</sup> and SeO<sub>3</sub><sup>2−</sup> that was not previously incorporated into precipitated carbonates.Angeles Fernandez-GonzalezAlba Lozano-LetellierBegoña FernandezMDPI AGarticlecalcium carbonate polymorphismselenitecalcium carbonate precipitationvateriteMineralogyQE351-399.2ENMinerals, Vol 11, Iss 1238, p 1238 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	calcium carbonate polymorphism selenite calcium carbonate precipitation vaterite Mineralogy QE351-399.2
spellingShingle	calcium carbonate polymorphism selenite calcium carbonate precipitation vaterite Mineralogy QE351-399.2 Angeles Fernandez-Gonzalez Alba Lozano-Letellier Begoña Fernandez The Influence of Aqueous Se(IV) on the Stability of Different CaCO<sub>3</sub> Polymorphs Precipitated under Ambient Conditions
description	Selenium is an essential bio-element, but because of its bioaccumulation potential, it can become toxic and is an important pollutant. The ubiquitous mineral calcite (CaCO<sub>3</sub>) has the ability to immobilize anions as SeO<sub>3</sub><sup>2−</sup> by different sorption or coprecipitation processes. Experimental studies have found that SeO<sub>3</sub><sup>2−</sup> can incorporate in the crystal structure of calcite by substituting CO<sub>3</sub><sup>2−</sup>. The presence of foreign ions in aqueous solution strongly affects CaCO<sub>3</sub> precipitation, helping stabilize less stable polymorphs such as vaterite and aragonite or hydrated phases. In this work, we studied the aging process of calcium carbonates precipitated from aqueous solutions highly supersaturated with respect to CaCO<sub>3</sub> and slightly supersaturated with respect to CaSeO<sub>3</sub>·H<sub>2</sub>O under ambient conditions, for times up to 30 days in which solids were kept in the remaining aqueous solution. Under these conditions, CaCO<sub>3</sub> precipitated mainly as low crystallinity vaterite aggregates that hosted up to 16% atomic ratio Se:C. Vaterite purified and increased its crystallinity with aging time, but the vaterite–calcite transformation was strongly inhibited. The incorporation of Se(IV) in vaterite did not significantly affect the cell parameters or the external morphology of the aggregates. The precipitation of selenite as CaSeO<sub>3</sub>·H<sub>2</sub>O was conditioned by the availability of free Ca<sup>2+</sup> and SeO<sub>3</sub><sup>2−</sup> that was not previously incorporated into precipitated carbonates.
format	article
author	Angeles Fernandez-Gonzalez Alba Lozano-Letellier Begoña Fernandez
author_facet	Angeles Fernandez-Gonzalez Alba Lozano-Letellier Begoña Fernandez
author_sort	Angeles Fernandez-Gonzalez
title	The Influence of Aqueous Se(IV) on the Stability of Different CaCO<sub>3</sub> Polymorphs Precipitated under Ambient Conditions
title_short	The Influence of Aqueous Se(IV) on the Stability of Different CaCO<sub>3</sub> Polymorphs Precipitated under Ambient Conditions
title_full	The Influence of Aqueous Se(IV) on the Stability of Different CaCO<sub>3</sub> Polymorphs Precipitated under Ambient Conditions
title_fullStr	The Influence of Aqueous Se(IV) on the Stability of Different CaCO<sub>3</sub> Polymorphs Precipitated under Ambient Conditions
title_full_unstemmed	The Influence of Aqueous Se(IV) on the Stability of Different CaCO<sub>3</sub> Polymorphs Precipitated under Ambient Conditions
title_sort	influence of aqueous se(iv) on the stability of different caco<sub>3</sub> polymorphs precipitated under ambient conditions
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/8b93eeda16af44ce8c94d0a159e90408
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The Influence of Aqueous Se(IV) on the Stability of Different CaCO<sub>3</sub> Polymorphs Precipitated under Ambient Conditions

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