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Title: Comparisons of structural Fe reduction in smectites by bacteria and dithionite: an infrared spectroscopic study

Authors:
; ;
Publication Date:
Research Org.:
Subsurface Biogeochemical Research (SBR)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
OSTI Identifier:
1154607
Resource Type:
Journal Article
Resource Relation:
Journal Name: Clays and Clay Minerals; Journal Volume: 54; Journal Issue: 2
Country of Publication:
United States
Language:
English

Citation Formats

Kangwon,Lee, Joel E.,Kostka, and Joseph W.,Stucki. Comparisons of structural Fe reduction in smectites by bacteria and dithionite: an infrared spectroscopic study. United States: N. p., 2006. Web. doi:10.1346/CCMN.2006.0540205.
Kangwon,Lee, Joel E.,Kostka, & Joseph W.,Stucki. Comparisons of structural Fe reduction in smectites by bacteria and dithionite: an infrared spectroscopic study. United States. doi:10.1346/CCMN.2006.0540205.
Kangwon,Lee, Joel E.,Kostka, and Joseph W.,Stucki. Sat . "Comparisons of structural Fe reduction in smectites by bacteria and dithionite: an infrared spectroscopic study". United States. doi:10.1346/CCMN.2006.0540205.
@article{osti_1154607,
title = {Comparisons of structural Fe reduction in smectites by bacteria and dithionite: an infrared spectroscopic study},
author = {Kangwon,Lee and Joel E.,Kostka and Joseph W.,Stucki},
abstractNote = {},
doi = {10.1346/CCMN.2006.0540205},
journal = {Clays and Clay Minerals},
number = 2,
volume = 54,
place = {United States},
year = {Sat Apr 01 00:00:00 EST 2006},
month = {Sat Apr 01 00:00:00 EST 2006}
}
  • The reduction of structural Fe in smectite may be mediated either abiotically by reaction with chemical reducing agents or biotically by reaction with various bacterial species. The effects of abiotic reduction on clay surface chemistry are much better known than the effects of biotic reduction, and differences between them are still in need of investigation. The purpose of the present study was to compare the effects of dithionite (abiotic) and bacteria (biotic) reduction of structural Fe in nontronite on the clay structure as observed by variable-temperature Mössbauer spectroscopy. Biotic reduction was accomplished by incubating Na-saturated Garfield nontronite (sample API 33a)more » with« less
  • Although clay mineral reduction is thought to occur primarily as a result of the activity of indigenous microorganisms in soil, most research has focused on chemical mechanisms of Fe reduction within clay minerals. Here the authors show that bacteria isolated from soils and sediments catalyze the rapid reduction of structural Fe(III) in the smectite clay minerals. The extent of Fe(III) reduction is large, from 46% to {gt}90%. Furthermore, the effects of structural Fe(III) reduction by bacteria on the surface chemistry of smectites are dramatic. Swelling pressure, as measured by water content, was shown to decrease by 40% to 44% inmore » smectites reduced by bacteria as compared to unaltered or reoxidized smectites. particle surface area decreased by 26% to 46% in response to bacterial reduction, and the surface charge density as measured by the ratio of cation exchange capacity to specific surface area increased over the same scale. Measurements of swelling pressure in smectite saturated with the organic cation trimethylphenylammonium (TMPA) indicated that the hydrophilic character of the clay mineral surface was enhanced upon reduction. The valence state of Fe in the octahedral layer of smectite, as revealed through reflectance spectra, correlated to the amount of Fe(III) reduced in bacterial cultures, providing information on the mechanism of intervalence electron transfer in bacterially reduced clay minerals. The extent of reduction and surface chemical effects catalyzed by bacteria in this study are similar in magnitude to those observed previously for potent inorganic reductants. Given that clay minerals dominate the solid phase of porous media and that Fe(III)-reducing bacteria are abundant in solid and aquatic sediments, these data suggest that bacterial clay mineral reduction may play an important role in soil biogeochemistry, affecting processes such as nutrient cycles and the fate of organic contaminants.« less
  • Reaction kinetics and infrared spectroscopic studies of the selective catalytic reduction of nitric oxide by ammonia were conducted at reactant concentrations near 500 ppm and temperatures from 473 to 623 K, over Fe-Y zeolites having Si/Al ratios of 2.4, 3.2, and 4.4. The presence of iron cations within the zeolite was necessary to sustain steady-state catalytic activity, which was enhanced by about two orders of magnitude in the presence of oxygen. The reaction was near first order in NO and near zero orders of magnitude in the presence of oxygen. The reaction was near first order in NO and nearmore » zero order in ammonia. Ammonia oxidation was found to become a significant competing reaction between 493 and 543 K over zeolites with Si/Al ratios equal to 2.4 and 3.2 species observed under reaction conditions by in situ IR spectroscopy were NH[sub 3] and NH[sub 4][sup +]. In the absence of oxygen, the rate-limiting step appears to be the reoxidation of iron. 48 refs., 10 figs., 4 tabs.« less
  • Along with crystallographic data of Ln[Fe(CN){sub 6}].4H{sub 2}O (Ln=lanthanide), the infrared spectra are reassigned to examine bond length trends across the series of Ln. The changes in mean Ln-O, Ln-N, C{identical_to}N and Fe-C distances are discussed and the bond natures of Ln-N and Ln-O are studied by bond length linear or quadratic fitting and comparisons with relevant ionic radii. The two different C{identical_to}N bond distances have been simulated by the covalo-electrostatic model. - Graphical abstract: Crystallographic and FTIR data for Ln[Fe(CN){sub 6}].4H{sub 2}O enable the changes in Ln-O, Ln-N, C{identical_to}N and Fe-C distances to be determined and modeled across themore » lanthanide series.« less