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Environ Sci Technol

Title:		Influence of chloride and Fe(II) content on the reduction of Hg(II) by magnetite
Author(s):		Pasakarnis TS; Boyanov MI; Kemner KM; Mishra B; O'Loughlin EJ; Parkin G; Scherer MM;
Address:		"Department of Civil and Environmental Engineering, The University of Iowa, Iowa City, Iowa 52242, United States"
Journal Title:		Environ Sci Technol
Year:		2013
Volume:		20130426
Issue:		13
Page Number:		6987 - 6994
DOI:		10.1021/es304761u
ISSN/ISBN:		1520-5851 (Electronic) 0013-936X (Linking)
Abstract:		"Abiotic reduction of inorganic mercury by natural organic matter and native soils is well-known, and recently there is evidence that reduced iron (Fe) species, such as magnetite, green rust, and Fe sulfides, can also reduce Hg(II). Here, we evaluated the reduction of Hg(II) by magnetites with varying Fe(II) content in both the absence and presence of chloride. Specifically, we evaluated whether magnetite stoichiometry (x = Fe(II)/Fe(III)) influences the rate of Hg(II) reduction and formation of products. In the absence of chloride, reduction of Hg(II) to Hg(0) is observed over a range of magnetite stoichiometries (0.29 < x < 0.50) in purged headspace reactors and unpurged low headspace reactors, as evidenced by Hg recovery in a volatile product trap solution and Hg L(III)-edge X-ray absorption near edge spectroscopy (XANES). In the presence of chloride, however, XANES spectra indicate the formation of a metastable Hg(I) calomel species (Hg2Cl2) from the reduction of Hg(II). Interestingly, Hg(I) species are only observed for the more oxidized magnetite particles that contain lower Fe(II) content (x < 0.42). For the more reduced magnetite particles (x >/= 0.42), Hg(II) is reduced to Hg(0) even in the presence of high chloride concentrations. As previously observed for nitroaromatic compounds and uranium, magnetite stoichiometry appears to influence the rate of Hg(II) reduction (both in the presence and absence of chloride) confirming that it is important to consider magnetite stoichiometry when assessing the fate of contaminants in Fe-rich subsurface environments"
Keywords:		"Chlorides/*chemistry Ferrosoferric Oxide/*chemistry Iron/*chemistry Mercury/*chemistry Oxidation-Reduction Water Pollutants, Chemical/*chemistry X-Ray Absorption Spectroscopy;"
Notes:		"MedlinePasakarnis, Timothy S Boyanov, Maxim I Kemner, Kenneth M Mishra, Bhoopesh O'Loughlin, Edward J Parkin, Gene Scherer, Michelle M eng Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. 2013/04/30 Environ Sci Technol. 2013 Jul 2; 47(13):6987-94. doi: 10.1021/es304761u. Epub 2013 Apr 26"