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Kinetics of homogeneous and surface-catalyzed mercury(II) reduction by iron(II)

Environmental Science and Technology

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, , ,
DOI: 10.1021/es401459p

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Abstract

Production of elemental mercury, Hg(0), via Hg(II) reduction is an important pathway that should be considered when studying Hg fate in environment. We conducted a kinetic study of abiotic homogeneous and surface-catalyzed Hg(0) production by Fe(II) under dark anoxic conditions. Hg(0) production rate, from initial 50 pM Hg(II) concentration, increased with increasing pH (5.5–8.1) and aqueous Fe(II) concentration (0.1–1 mM). The homogeneous rate was best described by the expression, rhom = khom [FeOH+] [Hg(OH)2]; khom = 7.19 × 10+3 L (mol min)−1. Compared to the homogeneous case, goethite (α-FeOOH) and hematite (α-Fe2O3) increased and γ-alumina (γ-Al2O3) decreased the Hg(0) production rate. Heterogeneous Hg(0) production rates were well described by a model incorporating equilibrium Fe(II) adsorption, rate-limited Hg(II) reduction by dissolved and adsorbed Fe(II), and rate-limited Hg(II) adsorption. Equilibrium Fe(II) adsorption was described using a surface complexation model calibrated with previously published experimental data. The Hg(0) production rate was well described by the expression rhet = khet [>SOFe(II)] [Hg(OH)2], where >SOFe(II) is the total adsorbed Fe(II) concentration; khet values were 5.36 × 10+3, 4.69 × 10+3, and 1.08 × 10+2 L (mol min)−1 for hematite, goethite, and γ-alumina, respectively. Hg(0) production coupled to reduction by Fe(II) may be an important process to consider in ecosystem Hg studies.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Kinetics of homogeneous and surface-catalyzed mercury(II) reduction by iron(II)
Series title:
Environmental Science and Technology
DOI:
10.1021/es401459p
Volume
47
Issue:
13
Year Published:
2013
Language:
English
Publisher:
ACS Publications
Contributing office(s):
National Research Program - Western Branch
Description:
10 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Environmental Science and Technology
First page:
7204
Last page:
7213