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Scorodite Precipitation in the Presence of Antimony

DOI: 10.1016/j.chemgeo.2015.04.013 DOI Help

Authors: David Kossoff (Birkbeck College) , Mark Welch (Natural History Museum) , Karen Hudson-edwards (Birkbeck College)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemical Geology , VOL 406 , PAGES 1-9

State: Published (Approved)
Published: June 2015
Diamond Proposal Number(s): 8462

Open Access Open Access

Abstract: The effects of Sb on the precipitation of synthetic scorodite, and the resultant phases formed, were investigated. Nine synthetic precipitates with varying concentrations of Sb, together with As-only and Sb-only end members, were prepared using a scorodite synthesis method, and these were characterized using XRD, SEM, chemical digestion and μXRF mapping. XRD analysis shows that the end members are scorodite (FeAsO4.2H2O) and tripuhyite (FeSbO4), and that the intermediate members are not Sb-substituted scorodite, but instead are physical mixtures of scorodite and tripuhyite, with tripuhyite becoming more prominent with increasing amounts of Sb in the synthesis. Electron microprobe analysis on natural scorodites confirms that they contain negligible concentrations of Sb. With increasing Sb in the synthesis, the morphology of the scorodite changes from rosettes of intergrown crystals to anhedral masses of smaller crystallites. Chemical digestion of the series also became increasingly difficult with increasing Sb content. We conclude that Sb is not taken up in scorodite (perhaps due to its larger ionic radius and different co-ordination with O compared to As), that increasing amounts of Sb in the system affect scorodite morphology, and that tripuhyite is a highly stable and perhaps underestimated Sb-sink.

Journal Keywords: Antimony; Arsenic; Scorodite; Tripuhyite; Mine Waste

Subject Areas: Environment, Earth Science, Chemistry


Instruments: I18-Microfocus Spectroscopy

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