Nanocomposite Pyrite–Greigite Reactivity toward Se(IV)/Se(VI)

• Published in: Environmental science & technology Vol. 46; no. 9; pp. 4869 - 4876
• Main Authors: Charlet, Laurent, Kang, Mingliang, Bardelli, Fabrizio, Kirsch, Regina, Géhin, Antoine, Grenèche, Jean-Marc, Chen, Fanrong
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.05.2012
• Subjects: Applied sciences; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Hydrogen-Ion Concentration; Iron - chemistry; Nanocomposites - chemistry; Phase transitions; Pollution; Pollution, environment geology; Radioactive wastes; Reaction kinetics; Selenium Compounds - chemistry; Spectrum analysis; Sulfides - chemistry; Thermodynamics; Wastes; X-Ray Absorption Spectroscopy; Performance evaluation; XANES spectrometry; Underground storage; Immobilization; Hazardous waste; Radioisotope; Iron sulfide; EXAFS spectrometry; Pyrite; Selenium 79; Barrier material; Radioactive waste storage; Nanocomposite; Chemical reactivity; Nanostructured materials
• DOI: 10.1021/es204181q
• ISSN: 0013-936X

A nanopyrite/greigite composite was synthesized by reacting FeCl3 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 (Fe2+Fe3+ 2S4) and 72% pyrite (FeS2). 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 Fe2+. XANES-EXAFS spectroscopic techniques revealed, for the first time, the formation of ferroselite (FeSe2) as the predominant reaction product, along with elemental Se. In the present experimental conditions, at pH 6 and in equilibrium with Se0, the solution is oversaturated with respect to ferrosilite. Furthermore, thermodynamic computations show that reaction kinetics likely played a significant role in our experimental system.