X-ray Absorption and X-ray Photoelectron Spectroscopic Study of Arsenic Mobilization during Mackinawite (FeS) Oxidation

In this study we investigated the speciation of the solid-phase As formed by reacting 2 × 10−4 M As(III) with 1.0 g/L mackinawite and the potential for these sorbed species to be mobilized (released into the aqueous phase) upon exposure to atmospheric oxygen at pH 4.9, 7.1, and 9.1. Before oxygen ex...

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Bibliographic Details
Published in:Environmental science & technology 2010-02, Vol.44 (3), p.955-961
Main Authors: Jeong, Hoon Y, Han, Young-Soo, Hayes, Kim F
Format: Article
Language:English
Subjects:
Absorptiometry, Photon
Applied sciences
Arsenic
Arsenic - chemistry
Biological and physicochemical phenomena
Electrons
Environmental Processes
Exact sciences and technology
Ferrous Compounds - chemistry
Hydrogen-Ion Concentration
Iron
Iron - chemistry
Natural water pollution
Oxidation
Oxidation-Reduction
Pollution
Sorption
Spectrum analysis
Sulfur - chemistry
Surface Properties
Water - chemistry
Water Pollutants, Chemical - chemistry
Water treatment and pollution
X-Ray Absorption Spectroscopy
X-rays
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Summary:In this study we investigated the speciation of the solid-phase As formed by reacting 2 × 10−4 M As(III) with 1.0 g/L mackinawite and the potential for these sorbed species to be mobilized (released into the aqueous phase) upon exposure to atmospheric oxygen at pH 4.9, 7.1, and 9.1. Before oxygen exposure, X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) analyses indicated that As(III) was removed from the aqueous phase by forming As(0), AsS, and surface precipitates as thioarsenites at pH 4.9 and As(0) and thioarsenite surface precipitates at pH 7.1 and 9.1. When oxygen was introduced, XAS analysis indicated that As(0) and the surface precipitates were quickly transformed, whereas AsS was persistent. During intermediate oxygen exposure times, dissolved As increased at pH 4.9 and 7.1 due to the rapid oxidation of As(0) and the slow precipitation of iron (oxyhydr)oxides, the oxidation products of mackinawite. This indicates that oxidative mobilization is a potential pathway for arsenic contamination of water at acidic to neutral pH. The mobilized As was eventually resorbed by forming edge-sharing and double-corner-sharing surface complexes with iron (oxyhydr)oxides.
ISSN:0013-936X
1520-5851
DOI:10.1021/es902577y