Analysis of the iron coatings formed during marcasite and arsenopyrite oxidation at neutral-alkaline conditions
Asta Andrés, María Pilar (Consejo Superior de Investigaciones Científicas (Espanya). Institut de Ciències de la Terra Jaume Almera)
Pérez-López, Rafael (Universidad de Huelva. Departamento de Ciencias de la Tierra)
Román-Ross, G. (Amphos 21)
Illera, V. (University of California. School of Natural Sciences)
Cama Robert, Jordi (Institut de Diagnòstic Ambiental i Estudis de l'Aigua)
Cotte, M. (European Synchrotron Facility)
Tucoulou, R. (European Synchrotron Facility)

Date:	2013
Abstract:	In order to study the nature of the precipitates formed on arsenopyrite and marcasite after reacting with neutral to alkaline solutions, a combination of techniques including Scanning Electron Microscope-Energy Dispersive Spectroscopy (SEM-EDS), X-ray Photoelectron Spectroscopy (XPS) and synchrotron-based techniques such as micro-X-Ray diffraction (µXRD) and Micro-X-ray Absorption Near Edge Structure (µXANES) have been used. The results showed that the oxidation of marcasite and arsenopyrite under neutral to alkaline conditions leads to the formation of an Fe rich coating which seems to prevent the oxidation of these sulphides. SEM observations confirmed the presence newly-formed phases after the sulphides reaction under the studied conditions. XPS analysis showed that iron, sulphur and arsenic in the case of the arsenopyrite are in oxidized states in the sulphide surfaces. The microscale analysis of the S and Fe speciation performed by µXANES suggested that due to the sulphide oxidation an increase in the oxidation state of those elements took place together with an increase of the sulphate content in the surface layer (grain boundary). Micro-X-ray diffraction results indicated that goethite (a-FeOOH) is the only crystalline newly-formed phase when the reaction occurs at pH 12 whereas at lower pH the products formed on the sulphide surfaces seem to be poorly crystalline and they do not contribute to the diffraction effects in the XRD diagrams.
Rights:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, sempre i quan aquestes es distribueixin sota la mateixa llicència que regula l'obra original i es reconegui l'autoria.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Subject:	Sulphide oxidation ; Iron phases ; Arsenopyrite ; Marcasite ; Neutral-basic pH
Published in:	Geologica acta, Vol. 11, Núm. 4 (December 2013) , p. 465-481, ISSN 1696-5728

Adreça alternativa: https://raco.cat/index.php/GeologicaActa/article/view/271214
Adreça alternativa: https://revistes.ub.edu/index.php/GEOACTA/article/view/105.000002062
DOI: 10.1344/105.000002062

17 p, 2.2 MB

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