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Selenium Speciation in Framboidal and Euhedral Pyrites in Shales

DOI: 10.1021/es405686q DOI Help

Authors: Adriana Matamoros-veloza (University of Leeds, U.K.) , Caroline Peacock (University of Leeds, U.K.) , Liane G Benning (University of Leeds, U.K.)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Environmental Science & Technology , VOL 48 (16) , PAGES 3603-3616

State: Published (Approved)
Published: July 2014
Diamond Proposal Number(s): 6477

Abstract: The release of Se from shales is poorly understood because its occurrence, distribution, and speciation in the various components of shale are unknown. To address this gap we combined bulk characterization, sequential extractions, and spatially resolved μ-focus spectroscopic analyses and investigated the occurrence and distribution of Se and other associated elements (Fe, As, Cr, Ni, and Zn) and determined the Se speciation at the μ-scale in typical, low bulk Se containing shales. Our results revealed Se primarily correlated with the pyrite fraction with exact Se speciation highly dependent on pyrite morphology. In euhedral pyrites, we found Se(-II) substitutes for S in the mineral structure. However, we also demonstrate that Se is associated with framboidal pyrite grains as a discrete, independent FeSex phase. The presence of this FeSex species has major implications for Se release, because FeSex species oxidize much faster than Se substituted in the euhedral pyrite lattice. Thus, such an FeSex species will enhance and control the dynamics of Se weathering and release into the aqueous environment.

Subject Areas: Environment, Materials

Instruments: I18-Microfocus Spectroscopy

Added On: 28/07/2014 08:34

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