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Repositorio de la Universidad de Oviedo. > Producción Bibliográfica de UniOvi: RECOPILA > Artículos >

Please use this identifier to cite or link to this item: http://hdl.handle.net/10651/5785

Title: Interaction of gypsum with AS(V)-beraing aqueous solutions: surface precipitation of guerinite, sainfeldite, and CA2NAH(ASO4)2"6H2O, asynthetic arsenate
Author(s): Rodríguez Blanco, Juan Diego
Jiménez Bautista, Amalia
Prieto Rubio, Manuel
Torre Fernández, Laura
García-Granda, Santiago
Keywords: Crystal Growth, Calcium Arsenate, Analysis Chemical, Sainfeldite, Phase Equilibrium, Guerinite, Gypsum
Issue date: 2008
Publisher version: http://dx.doi.org/10.2138/am.2008.2750
Citation: American Mineralogist, 93(5-6), p. 928 -939 (2008); doi:10.2138/am.2008.2750
Format extent: p. 928 -939
Abstract: The interaction of arsenate-bearing aqueous solutions with gypsum at a starting pH of 9 and 25 °C results in surface precipitation of guerinite, Ca5(HAsO4)2(AsO4)2·9H2O, sainfeldite, Ca5(HAsO4)2(AsO4)2·4H2O, and occasionally Ca2Na(HAsO4)(AsO4)·6H2O, a new arsenate. These three solid phases are characterized by the simultaneous presence of HAsO42− and AsO43− groups in their structure, which is explainable since crystallization occurs within a pH range in which both HAsO42− and AsO43− are available in the aqueous solution. The interaction leads to a decrease in the As(V) concentration in the aqueous phase to reach values controlled by the solubility of these solid phases. The study combines several macroscopic experiments, in which changes in the solution chemistry are monitored as a function of time, with the characterization of solid phases by SEM-EDS and XRD. The crystal morphologies of the precipitating phases are interpreted on the basis of their respective structures. The thermodynamic solubility products of both guerinite and the new arsenate have been determined, being 10−31.17±0.05 and 10−13.83±0.03, respectively. The reaction paths followed by the system and the equilibrium endpoints have been modeled using the geochemical code PHREEQC.
URI: http://hdl.handle.net/10651/5785
ISSN: 0003-004X
Local identifier: 20080066
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