title: Nanocomposite pyrite-greigite reactivity toward Se(IV)/Se(VI).
abstract: A nanopyrite/greigite composite was synthesized by reacting FeCl(3) and NaHS in a ratio of 1:2 (Wei et al. 1996). Following this procedure, the obtained solid phases consisted of 30-50 nm sized particles containing 28% of greigite (Fe(2+)Fe(3+)(2)S(4)) and 72% pyrite (FeS(2)). Batch reactor experiments were performed with selenite or selenate by equilibrating suspensions containing the nanosized pyrite-greigite solid phase at different pH-values and with or without the addition of extra Fe(2+). XANES-EXAFS spectroscopic techniques revealed, for the first time, the formation of ferroselite (FeSe(2)) as the predominant reaction product, along with elemental Se. In the present experimental conditions, at pH 6 and in equilibrium with Se(0), the solution is oversaturated with respect to ferrosilite. Furthermore, thermodynamic computations show that reaction kinetics likely played a significant role in our experimental system.
authors.affiliation: Environmental Geochemistry Group, ISTerre, University of Grenoble I, 38041 Grenoble, France. charlet38@gmail.com
authors.forename: Laurent
authors.initials: L
authors.lastname: Charlet
authors.forename: Mingliang
authors.initials: M
authors.lastname: Kang
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Bardelli
authors.forename: Regina
authors.initials: R
authors.lastname: Kirsch
authors.forename: Antoine
authors.initials: A
authors.lastname: Géhin
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Grenèche
authors.forename: Fanrong
authors.initials: F
authors.lastname: Chen
mesh_terms: D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D053761:Nanocomposites / Q000737:chemistry; D018036:Selenium Compounds / Q000737:chemistry*; D013440:Sulfides / Q000737:chemistry*; D013816:Thermodynamics; D056928:X-Ray Absorption Spectroscopy
chemical_list: D018036:Selenium Compounds; D013440:Sulfides; C111959:greigite; C011342:pyrite; D007501:Iron