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Title: Influence of soil minerals on chromium(VI) reduction by sulfide under anoxic conditions

Authors:
; ; ;
Publication Date:
Research Org.:
Subsurface Biogeochemical Research (SBR)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
OSTI Identifier:
1154597
Resource Type:
Journal Article
Resource Relation:
Journal Name: Geochemical Transactions; Journal Volume: 8; Journal Issue: 1
Country of Publication:
United States
Language:
English

Citation Formats

Yeqing,Lan, Baolin,Deng, Chulsung,Kim, and Edward C,Thornton. Influence of soil minerals on chromium(VI) reduction by sulfide under anoxic conditions. United States: N. p., 2007. Web. doi:10.1186/1467-4866-8-4.
Yeqing,Lan, Baolin,Deng, Chulsung,Kim, & Edward C,Thornton. Influence of soil minerals on chromium(VI) reduction by sulfide under anoxic conditions. United States. doi:10.1186/1467-4866-8-4.
Yeqing,Lan, Baolin,Deng, Chulsung,Kim, and Edward C,Thornton. Mon . "Influence of soil minerals on chromium(VI) reduction by sulfide under anoxic conditions". United States. doi:10.1186/1467-4866-8-4.
@article{osti_1154597,
title = {Influence of soil minerals on chromium(VI) reduction by sulfide under anoxic conditions},
author = {Yeqing,Lan and Baolin,Deng and Chulsung,Kim and Edward C,Thornton},
abstractNote = {},
doi = {10.1186/1467-4866-8-4},
journal = {Geochemical Transactions},
number = 1,
volume = 8,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • No abstract prepared.
  • Chromate (CrVI) reduction by sulfide was conducted in anaerobic batch experimental systems. The molar ratio of the reduced CrVI to the oxidized S-II was 1:1.5 during the reaction, suggesting that the product of sulfide oxidation was elemental sulfur. Under the anaerobic condition, the reaction was pseudo first order initially with respect to CrVI, but the rate was dramatically accelerated at the later stage of the reaction. The rate acceleration was due to catalysis by elemental sulfur nanoparticles; dissolved species such as monomeric elemental sulfur and polysulfides appeared to be ineffective catalysts. Elemental sulfur nanoparticles were capable of adsorbing sulfide andmore » such adsorbed sulfide exhibited much higher reactivity toward CrVI reduction than the aqueous-phase sulfide, resulting in the observed rate acceleration.« less
  • Chromium isotopes are potentially useful indicators of Cr(VI) reduction reactions in groundwater flow systems; however, the influence of transport on Cr isotope fractionation has not been fully examined. Laboratory batch and column experiments were conducted to evaluate isotopic fractionation of Cr during Cr(VI) reduction under both static and controlled flow conditions. Organic carbon was used to reduce Cr(VI) in simulated groundwater containing 20 mg L{sup -1} Cr(VI) in both batch and column experiments. Isotope measurements were performed on dissolved Cr on samples from the batch experiments, and on effluent and profile samples from the column experiment. Analysis of the residualmore » solid-phase materials by scanning electron microscopy (SEM) and by X-ray absorption near edge structure (XANES) spectroscopy confirmed association of Cr(III) with organic carbon in the column solids. Decreases in dissolved Cr(VI) concentrations were coupled with increases in {delta}{sup 53}Cr, indicating that Cr isotope enrichment occurred during reduction of Cr(VI). The {delta}{sup 53}Cr data from the column experiment was fit by linear regression yielding a fractionation factor ({alpha}) of 0.9979, whereas the batch experiments exhibited Rayleigh-type isotope fractionation ({alpha} = 0.9965). The linear characteristic of the column {delta}{sup 53}Cr data may reflect the contribution of transport on Cr isotope fractionation.« less
  • The behavior of technetium in the geosphere is of particular importance in nuclear fuel waste management studies because this man-made element has a long half-life and, under ambient conditions in the laboratory, is not readily sorbed on geologic materials. Autoradiographic analyses of rock and mineral thin sections contacted with /sup 95/TcO/sub 4//sup -/-containing solutions, under oxic and anoxic conditions, have confirmed that virtually no sorption takes place in the presence of oxygen. However, under anoxic conditions (< 0.2 ..mu..g/g oxygen in the atmosphere), sorption of technetium was observed on iron-oxide inclusions in ferrous-iron-containing minerals (biotite, and olivine, pyroxene, hornblende) andmore » on iron-oxide coatings on microfractures in granite, but not on the ferrous-iron minerals within the granite themselves. Subsequent static sorption tests with crushed magnetite showed that sorption is a function of the composition of the solution and of the radionuclide concentration, and again occurred only in the absence of oxygen. This behavior is in contrast with that observed with metallic iron, which sorbs technetium strongly, even in the presence of air. These results show that technetium can be contained by magnetite in the geosphere, provided reducing conditions can be maintained. This can be aided, for example, by the incorporation of iron or iron oxides in the buffer and backfill materials in the waste disposal vault. 11 references, 8 figures, 6 tables.« less