title: Reduction of Hg(II) to Hg(0) by magnetite.
abstract: Mercury (Hg) is a highly toxic element, and its contamination of groundwater presents a significant threat to terrestrial ecosystems. Understanding the geochemical processes that mediate mercury transformations in the subsurface is necessary to predict its fate and transport. In this study, we investigated the redox transformation of mercuric Hg (Hg[II]) in the presence of the Fe(II)/Fe(III) mixed valence iron oxide mineral magnetite. Kinetic and spectroscopic experiments were performed to elucidate reaction rates and mechanisms. The experimental data demonstrated that reaction of Hg(II) with magnetite resulted in the loss of Hg(II) and the formation of volatile elemental Hg (Hg[0]). Kinetic experiments showed that Hg(II) reduction occurred within minutes, with reaction rates increasing with increasing magnetite surface area (0.5 to 2 m2/L) and solution pH (4.8 to 6.7), and decreasing with increasing chloride concentration (10(-6) to 10(-2) mol/L). Mössbauer spectroscopic analysis of reacted magnetite samples revealed a decrease in Fe(II) content, corresponding to the oxidation of Fe(II) to Fe(III) in the magnetite structure. X-ray photoelectron spectroscopy detected the presence of Hg(II) on magnetite surfaces, implying that adsorption is involved in the electron transfer process. These results suggest that Hg(II) reaction with solid-phase Fe(II) is a kinetically favorable pathway for Hg(II) reduction in magnetite-hearing environmental systems.
authors.affiliation: Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, New Jersey, USA.
authors.forename: Heather A
authors.initials: HA
authors.lastname: Wiatrowski
authors.forename: Soumya
authors.initials: S
authors.lastname: Das
authors.forename: Ravi
authors.initials: R
authors.lastname: Kukkadapu
authors.forename: Eugene S
authors.initials: ES
authors.lastname: Ilton
authors.forename: Tamar
authors.initials: T
authors.lastname: Barkay
authors.forename: Nathan
authors.initials: N
authors.lastname: Yee
mesh_terms: D002712:Chlorides / Q000737:chemistry; D005290:Ferric Compounds / Q000737:chemistry; D052203:Ferrosoferric Oxide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008628:Mercury / Q000737:chemistry*; D010084:Oxidation-Reduction; D015204:Spectroscopy, Mossbauer; D014965:X-Rays
chemical_list: D002712:Chlorides; D005290:Ferric Compounds; C000499:ferric oxide; D008628:Mercury; D052203:Ferrosoferric Oxide