title: Abiotic reductive immobilization of U(VI) by biogenic mackinawite.
abstract: During subsurface bioremediation of uranium-contaminated sites, indigenous metal and sulfate-reducing bacteria may utilize a variety of electron acceptors, including ferric iron and sulfate that could lead to the formation of various biogenic minerals in situ. Sulfides, as well as structural and adsorbed Fe(II) associated with biogenic Fe(II)-sulfide phases, can potentially catalyze abiotic U(VI) reduction via direct electron transfer processes. In the present work, the propensity of biogenic mackinawite (Fe 1+x S, x = 0 to 0.11) to reduce U(VI) abiotically was investigated. The biogenic mackinawite produced by Shewanella putrefaciens strain CN32 was characterized by employing a suite of analytical techniques including TEM, SEM, XAS, and Mössbauer analyses. Nanoscale and bulk analyses (microscopic and spectroscopic techniques, respectively) of biogenic mackinawite after exposure to U(VI) indicate the formation of nanoparticulate UO2. This study suggests the relevance of sulfide-bearing biogenic minerals in mediating abiotic U(VI) reduction, an alternative pathway in addition to direct enzymatic U(VI) reduction.
authors: Department of Geosciences, Virginia Tech , Blacksburg, Virginia, United States.
authors: Harish
authors: H
authors: Veeramani
authors: Andreas C
authors: AC
authors: Scheinost
authors: Niven
authors: N
authors: Monsegue
authors: Nikolla P
authors: NP
authors: Qafoku
authors: Ravi
authors: R
authors: Kukkadapu
authors: Matt
authors: M
authors: Newville
authors: Antonio
authors: A
authors: Lanzirotti
authors: Amy
authors: A
authors: Pruden
authors: Mitsuhiro
authors: M
authors: Murayama
authors: Michael F
authors: MF
authors: Hochella
mesh_terms: D000327:Adsorption; D001673:Biodegradation, Environmental; D004579:Electron Transport; D005296:Ferrous Compounds / Q000032:analysis* / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D010084:Oxidation-Reduction; D020614:Shewanella putrefaciens / Q000737:chemistry* / Q000378:metabolism; D015204:Spectroscopy, Mossbauer; D013440:Sulfides / Q000378:metabolism; D014501:Uranium / Q000737:chemistry* / Q000378:metabolism; D056928:X-Ray Absorption Spectroscopy
chemical_list: D005296:Ferrous Compounds; D013440:Sulfides; D014501:Uranium; C022597:ferrous sulfide