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Sample records for metastable iron sulfide

  1. Uniform yolk-shell iron sulfide-carbon nanospheres for superior sodium-iron sulfide batteries

    NASA Astrophysics Data System (ADS)

    Wang, Yun-Xiao; Yang, Jianping; Chou, Shu-Lei; Liu, Hua Kun; Zhang, Wei-Xian; Zhao, Dongyuan; Dou, Shi Xue

    2015-10-01

    Sodium-metal sulfide battery holds great promise for sustainable and cost-effective applications. Nevertheless, achieving high capacity and cycling stability remains a great challenge. Here, uniform yolk-shell iron sulfide-carbon nanospheres have been synthesized as cathode materials for the emerging sodium sulfide battery to achieve remarkable capacity of ~545 mA h g-1 over 100 cycles at 0.2 C (100 mA g-1), delivering ultrahigh energy density of ~438 Wh kg-1. The proven conversion reaction between sodium and iron sulfide results in high capacity but severe volume changes. Nanostructural design, including of nanosized iron sulfide yolks (~170 nm) with porous carbon shells (~30 nm) and extra void space (~20 nm) in between, has been used to achieve excellent cycling performance without sacrificing capacity. This sustainable sodium-iron sulfide battery is a promising candidate for stationary energy storage. Furthermore, this spatially confined sulfuration strategy offers a general method for other yolk-shell metal sulfide-carbon composites.

  2. Uniform yolk-shell iron sulfide-carbon nanospheres for superior sodium-iron sulfide batteries.

    PubMed

    Wang, Yun-Xiao; Yang, Jianping; Chou, Shu-Lei; Liu, Hua Kun; Zhang, Wei-Xian; Zhao, Dongyuan; Dou, Shi Xue

    2015-01-01

    Sodium-metal sulfide battery holds great promise for sustainable and cost-effective applications. Nevertheless, achieving high capacity and cycling stability remains a great challenge. Here, uniform yolk-shell iron sulfide-carbon nanospheres have been synthesized as cathode materials for the emerging sodium sulfide battery to achieve remarkable capacity of ∼ 545 mA h g(-1) over 100 cycles at 0.2 C (100 mA g(-1)), delivering ultrahigh energy density of ∼ 438 Wh kg(-1). The proven conversion reaction between sodium and iron sulfide results in high capacity but severe volume changes. Nanostructural design, including of nanosized iron sulfide yolks (∼ 170 nm) with porous carbon shells (∼ 30 nm) and extra void space (∼ 20 nm) in between, has been used to achieve excellent cycling performance without sacrificing capacity. This sustainable sodium-iron sulfide battery is a promising candidate for stationary energy storage. Furthermore, this spatially confined sulfuration strategy offers a general method for other yolk-shell metal sulfide-carbon composites. PMID:26507613

  3. Iron-sulfide redox flow batteries

    DOEpatents

    Xia, Guan-Guang; Yang, Zhenguo; Li, Liyu; Kim, Soowhan; Liu, Jun; Graff, Gordon L

    2013-12-17

    Iron-sulfide redox flow battery (RFB) systems can be advantageous for energy storage, particularly when the electrolytes have pH values greater than 6. Such systems can exhibit excellent energy conversion efficiency and stability and can utilize low-cost materials that are relatively safer and more environmentally friendly. One example of an iron-sulfide RFB is characterized by a positive electrolyte that comprises Fe(III) and/or Fe(II) in a positive electrolyte supporting solution, a negative electrolyte that comprises S.sup.2- and/or S in a negative electrolyte supporting solution, and a membrane, or a separator, that separates the positive electrolyte and electrode from the negative electrolyte and electrode.

  4. Iron-sulfide redox flow batteries

    DOEpatents

    Xia, Guanguang; Yang, Zhenguo; Li, Liyu; Kim, Soowhan; Liu, Jun; Graff, Gordon L

    2016-06-14

    Iron-sulfide redox flow battery (RFB) systems can be advantageous for energy storage, particularly when the electrolytes have pH values greater than 6. Such systems can exhibit excellent energy conversion efficiency and stability and can utilize low-cost materials that are relatively safer and more environmentally friendly. One example of an iron-sulfide RFB is characterized by a positive electrolyte that comprises Fe(III) and/or Fe(II) in a positive electrolyte supporting solution, a negative electrolyte that comprises S.sup.2- and/or S in a negative electrolyte supporting solution, and a membrane, or a separator, that separates the positive electrolyte and electrode from the negative electrolyte and electrode.

  5. Physical and microstructural aspects of iron sulfide degradation in concrete

    SciTech Connect

    Schmidt, Thomas; Gallucci, Emanuel; Scrivener, Karen

    2011-03-15

    The microstructural aspects of iron sulfide degradation in dam concrete were investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) in both dam concrete samples and laboratory concrete. The results show that iron sulfide inclusions with a diameter of a few micrometers in the aggregates are reactive and appear to generate expansion first in the aggregates and consequently in the cement paste. The expansion from the iron sulfides is a consequence of the increase in volume of the reaction products formed. The types of iron sulfide present in the aggregate, mainly pyrrhotite (FeS) and pyrite (FeS{sub 2}), show similar reaction behavior in the aggregates. The released sulfate can lead to a secondary ettringite formation in the concrete matrix, but the degradation associated with this appears to be minor. The reaction of the iron sulfides was found to be very slow even when laboratory samples were exposed to elevated temperatures.

  6. Enhanced reductive dechlorination of trichloroethylene by sulfidated nanoscale zerovalent iron.

    PubMed

    Rajajayavel, Sai Rajasekar C; Ghoshal, Subhasis

    2015-07-01

    Direct injection of reactive nanoscale zerovalent iron particles (NZVI) is considered to be a promising approach for remediation of aquifers contaminated by chlorinated organic pollutants. In this study we show that the extent of sulfidation of NZVI enhances the rate of dechlorination of trichloroethylene (TCE) compared to that by unamended NZVI, and the enhancement depends on the Fe/S molar ratio. Experiments where TCE was reacted with NZVI sulfidated to different extents (Fe/S molar ratios 0.62-66) showed that the surface-area normalized first-order TCE degradation rate constant increased up to 40 folds compared to non-sulfidated NZVI. Fe/S ratios in the range of 12-25 provided the highest TCE dechlorination rates, and rates decreased at both higher and lower Fe/S. In contrast, sulfidated NZVI exposed to water in the absence of TCE showed significantly lower hydrogen evolution rate (2.75 μmol L(-1) h(-1)) compared to that by an unamended NZVI (6.92 μmol L(-1) h(-1)), indicating that sulfidation of NZVI suppressed corrosion reactions with water. Sulfide (HS(-)) ions reacted rapidly with NZVI and X-ray photoelectron spectroscopy analyses showed formation of a surface layer of FeS and FeS2. We propose that more electrons are preferentially conducted from sulfidated NZVI than from unamended NZVI to TCE, likely because of greater binding of TCE on the reactive sites of the iron sulfide outer layer. Resuspending sulfidated NZVI in sulfide-free or sulfide containing solutions altered the TCE degradation rate constants because of changes in the FeS layer thickness. Sulfidated NZVI maintained its high reactivity in the presence of multiple mono and divalent ions and with polyelectrolyte coatings. Thus, sulfide ions in groundwater can significantly alter NZVI reactivity. PMID:25935369

  7. Comparison of Carbon XANES Spectra from an Iron Sulfide from Comet Wild 2 with an Iron Sulfide Interplanetary Dust Particle

    NASA Technical Reports Server (NTRS)

    Wirick, S.; Flynn, G. J.; Keller, L. P.; Sanford, S. A.; Zolensky, M. E.; Messenger, Nakamura K.; Jacobsen, C.

    2008-01-01

    Among one of the first particles removed from the aerogel collector from the Stardust sample return mission was an approx. 5 micron sized iron sulfide. The majority of the spectra from 5 different sections of this particle suggests the presence of aliphatic compounds. Due to the heat of capture in the aerogel we initially assumed these aliphatic compounds were not cometary but after comparing these results to a heated iron sulfide interplanetary dust particle (IDP) we believe our initial interpretation of these spectra was not correct. It has been suggested that ice coating on iron sulfides leads to aqueous alteration in IDP clusters which can then lead to the formation of complex organic compounds from unprocessed organics in the IDPs similar to unprocessed organics found in comets [1]. Iron sulfides have been demonstrated to not only transform halogenated aliphatic hydrocarbons but also enhance the bonding of rubber to steel [2,3]. Bromfield and Coville (1997) demonstrated using Xray photoelectron spectroscopy that "the surface enhancement of segregated sulfur to the surface of sulfided precipitated iron catalysts facilitates the formation of a low-dimensional structure of extraordinary properties" [4]. It may be that the iron sulfide acts in some way to protect aliphatic compounds from alteration due to heat.

  8. Lithium-aluminum/iron sulfide batteries

    NASA Astrophysics Data System (ADS)

    Henriksen, G. L.; Vissers, D. R.

    Lithium-alloy/metal sulfide batteries have been under development at Argonne National Laboratory since 1972. ANL's technology employs a two-phase Li alloy negative electrode, low-melting point LiCl-rich LiCl-LiBr-KBr molten salt electrolyte, and either an FeS or an upper-plateau (UP) FeS 2 positive electrode. These components are assembled in an 'electrolyte-starved' bipolar cell configuration. Use of the multi-phase Li alloy ((α+β)-Li-Al and Li 5Al 5Fe 2) negative electrode provides in situ overcharge tolerance that renders the bipolar design viable. Employing LiCl-rich LiCl-LiBr-KBr electrolyte is 'electrolyte-starved" cells achieves low-burdened cells that possess low area-specific impedance, comparable with that of flooded cells using LiCl-LiBr-KBr eutectic electrolyte. The combination of dense UP FeS 2 electrodes and low-melting electrolyte produces a stable and reversible couple, achieving over 1000 cycles in flooded cells, with high power capabilities. In addition, a new class of stable chalcogenide ceramic/sealant materials was developed. These materials produce high-strength bonds between a variety of metals and ceramics, which make fabrication of lithium/iron sulfide bipolar stacks practical. Bipolar Li-Al/FeS and Li-Al/FeS 2 cells and four-cell stacks using these seals have been built and tested for electric vehicle (EV) applications. When cell performance characteristics are used to model full-scale EV ad hybrid vehicle (HV) batteries, they are projected to meet or exceed the performance requirements for a large variety of EV and HV applications. In 1992, the US Advanced Battery Consortium awarded contracts to ANL and SAFT America to continue the development of the bipolar Li-Al/FeS 2 battery to meet their long-term criteria. Both ANL and sAFT are working together to refine this technology for EV applications and scale it up to larger stacks and fully integrated battery modules.

  9. IRON SULFIDES IN THE ENVIRONMENT: FORMATION, FATE, AND SIGNIFICANCE TO CONTAMINANT BEHAVIOR

    EPA Science Inventory

    This seminar will cover aspects of the geochemistry of iron sulfides, their formation in sedimentary and aquifer environments, and their roles in sequestering and releasing contaminants. A special emphasis will be placed on the interactions between iron sulfides and arsenic.

  10. Penning ionization electron spectroscopy of hydrogen sulfide by metastable helium and neon atoms.

    PubMed

    Falcinelli, Stefano; Candori, Pietro; Bettoni, Marta; Pirani, Fernando; Vecchiocattivi, Franco

    2014-08-21

    The dynamics of the Penning ionization of hydrogen sulfide molecules by collision with helium and metastable neon atoms, occurring in the thermal energy range, has been studied by analyzing the energy spectra of the emitted electrons obtained in our laboratory in a crossed beam experiment. These spectra are compared with the photoelectron spectra measured by using He(I) and Ne(I) photons under the same experimental conditions. In this way we obtained the negative energy shifts for the formation of H2S(+) ions in the first three accessible electronic states by He*(2(3,1)S1,0) and Ne*((3)P2,0) Penning ionization collisions: the 2b1 (X̃(2)B1) fundamental one, the first 5a1 (Ã(2)A1), and the second 2b2 (B̃(2)B2) excited states, respectively. The recorded energy shifts indicate that in the case of He* and Ne*-H2S the autoionization dynamics depends on the features of the collision complex and is mainly driven by an effective global attraction that comes from a balance among several non covalent intermolecular interaction components. This suggests that the Penning ionization should take place, in a specific range of intermolecular distances, as we have already observed in the case of Penning ionization of water molecules [Brunetti, B. G.; Candori, P.; Falcinelli, S.; Pirani, F.; Vecchiocattivi, F. J. Chem. Phys. 2013, 139, 164305-1-164305-8]. PMID:24796487

  11. Impact of Iron Sulfide Transformation on Trichloroethylene Degradation

    EPA Science Inventory

    Trichloroethylene (TCE) is one of the most common and persistent groundwater contaminants encountered at hazardous waste sites around the world. A growing body of evidence indicates that iron sulfides play an important role in degrading TCE in natural environments and in enginee...

  12. Discrimination among iron sulfide species formed in microbial cultures.

    PubMed

    Popa, R; Kinkle, B K

    2000-10-01

    A quantitative method for the study of iron sulfides precipitated in liquid cultures of bacteria is described. This method can be used to quantify and discriminate among amorphous iron sulfide (FeS(amorph)), iron monosulfide minerals such as mackinawite or greigite (FeS(min)), and iron disulfide minerals such as pyrite or marcasite (FeS(2min)) formed in liquid cultures. Degradation of iron sulfides is performed using a modified Cr(2+) reduction method with reflux distillation. The basic steps of the method are: first, separation of FeS(amorph); second, elimination of interfering species of S such as colloidal sulfur (S(c) degrees ), thiosulphate (S(2)O(3)(2-)) and polysulfides (S(x)(2-)); third, separation of FeS(min); and fourth, separation of FeS(2min). The final product is H(2)S which is determined after trapping. The efficiency of recovery is 96-99% for FeS(amorph), 76-88% for FeS(min), and >97% for FeS(2min). This method has a high reproducibility if the experimental conditions are rigorously applied and only glass conduits are used. A well ventilated fume hood must be used because of the toxicity and volatility of several reagents and products. The advantage relative to previously described methods are better resolution for iron sulfide species and use of the same bottles for both incubation of cultures and acid degradation. The method can also be used for Fe/S stoichiometry with sub-sampling and Fe analysis. PMID:11018273

  13. Reactivity screening of microscale zerovalent irons and iron sulfides towards different CAHs under standardized experimental conditions.

    PubMed

    Velimirovic, Milica; Larsson, Per-Olof; Simons, Queenie; Bastiaens, Leen

    2013-05-15

    A standardized batch test procedure was developed and used to evaluate the reactivity of twelve newly designed microscale zerovalent iron (mZVI) particles and two biogenic iron sulfides towards a mixture of chlorinated aliphatic hydrocarbons (CAHs) and their breakdown products. For comparison, commercially available mZVIs, nanoscale zerovalent irons (nZVIs), iron sulfides (FeS) and granular zerovalent iron were also tested. Reactivity of the particles was based on observed (kobs) and mass normalized (kM) pseudo-first-order degradation rate constants, as well as specific surface area normalized reaction rate constants (kSA). Sorption characteristics of the particles were based on mass balance data. Among the new mZVIs, significant differences in reactivity were observed and the most reactive particles were identified. Based on kM data, nZVI degraded the examined contaminants one to two orders of magnitude faster than the mZVIs. kM values for biogenic iron sulfides were similar to the least reactive mZVIs. On the other hand, comparison of kSA data revealed that the reactivity of some newly designed mZVIs was similar to highly reactive nZVIs, and even up to one order of magnitude higher. kSA values for biogenic iron sulfides were one to two orders of magnitude lower than those reported for reactive mZVIs. PMID:23510992

  14. Physical properties of superconducting single crystal iron sulfide

    NASA Astrophysics Data System (ADS)

    Rodriguez, Efrain E.; Borg, Christopher K. H.; Zhou, Xiuquan; Paglione, Johnpierre; University of Maryland Collaboration

    Recently, the simple binary tetragonal iron sulfide, FeS, was found to be a superconductor with a Tc = 5 K. We have prepared single crystals of tetragonal iron sulfide through hydrothermal de-intercalation of KxFe2-yS2. The KxFe2-yS2 single crystal precursors were grown by slow cooling of stoichiometric melts of K, Fe and S. The silver, plate-like FeS single crystals were highly crystalline with a superconducting transition temperature (Tc) of 4 K. The high quality of the FeS crystals revealed highly anisotropic nature of the magnetic and electronic properties intrinsic to FeS. The physical properties and thermal stability of single crystal FeS will be discussed in detail.

  15. Efficient iron sulfide counter electrode for quantum dots-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Chen, Haining; Zhu, Liqun; Liu, Huicong; Li, Weiping

    2014-01-01

    Iron sulfide is explored as the counter electrode (CE) in quantum dots-sensitized solar cells (QDSCs), which is prepared by simply immersing carbon steel in Na2S solution. The photoelectrochemical performance and the electrocatalytic property of iron sulfide are much higher than those of Pt and are very close to those of Cu2S. Since the preparation method of iron sulfide CE is simple, carbon steel substrate is stable in polysulfide electrolyte, the storage of Fe element in earth is very abundant and iron ions are environmentally friendly, iron sulfide shows much prospect as the efficient, stable, lost-cost and environmentally friendly CE of QDSCs.

  16. A new nanoscale metastable iron phase in carbon steels.

    PubMed

    Liu, Tianwei; Zhang, Danxia; Liu, Qing; Zheng, Yanjun; Su, Yanjing; Zhao, Xinqing; Yin, Jiang; Song, Minghui; Ping, Dehai

    2015-01-01

    Metastable ω phase is common in body-centred cubic (bcc) metals and alloys, including high-alloying steels. Recent theoretical calculations also suggest that the ω structure may act as an intermediate phase for face-centred cubic (fcc)-to-bcc transformation. Thus far, the role of the ω phase played in fcc-bcc martensitic transformation in carbon steels has not been reported. In previous investigations on martensitic carbon steels, extra electron diffraction spots were frequently observed by transmission electron microscopy (TEM), and these spots were historically ascribed to the diffraction arising from either internal twins or carbides. In this paper, an intensive TEM investigation revealed that the extra spots are in fact attributed to the metastable ω phase in particle-like morphology with an overall size of several or dozens of nanometres. The strict orientation relationships between the ω phase and the ferrite matrix are in good agreement with those of the hexagonal (P6/mmm) ω phase in other bcc metals and alloys. The identification of the ω phase as well as the extra diffraction spots might provide a clue to help understand the physical mechanism of martensitic transformation in steels. PMID:26503890

  17. A new nanoscale metastable iron phase in carbon steels

    PubMed Central

    Liu, Tianwei; Zhang, Danxia; Liu, Qing; Zheng, Yanjun; Su, Yanjing; Zhao, Xinqing; Yin, Jiang; Song, Minghui; Ping, Dehai

    2015-01-01

    Metastable ω phase is common in body-centred cubic (bcc) metals and alloys, including high-alloying steels. Recent theoretical calculations also suggest that the ω structure may act as an intermediate phase for face-centred cubic (fcc)-to-bcc transformation. Thus far, the role of the ω phase played in fcc-bcc martensitic transformation in carbon steels has not been reported. In previous investigations on martensitic carbon steels, extra electron diffraction spots were frequently observed by transmission electron microscopy (TEM), and these spots were historically ascribed to the diffraction arising from either internal twins or carbides. In this paper, an intensive TEM investigation revealed that the extra spots are in fact attributed to the metastable ω phase in particle-like morphology with an overall size of several or dozens of nanometres. The strict orientation relationships between the ω phase and the ferrite matrix are in good agreement with those of the hexagonal (P6/mmm) ω phase in other bcc metals and alloys. The identification of the ω phase as well as the extra diffraction spots might provide a clue to help understand the physical mechanism of martensitic transformation in steels. PMID:26503890

  18. Uniform yolk-shell iron sulfide–carbon nanospheres for superior sodium–iron sulfide batteries

    PubMed Central

    Wang, Yun-Xiao; Yang, Jianping; Chou, Shu-Lei; Liu, Hua Kun; Zhang, Wei-xian; Zhao, Dongyuan; Dou, Shi Xue

    2015-01-01

    Sodium–metal sulfide battery holds great promise for sustainable and cost-effective applications. Nevertheless, achieving high capacity and cycling stability remains a great challenge. Here, uniform yolk-shell iron sulfide–carbon nanospheres have been synthesized as cathode materials for the emerging sodium sulfide battery to achieve remarkable capacity of ∼545 mA h g−1 over 100 cycles at 0.2 C (100 mA g−1), delivering ultrahigh energy density of ∼438 Wh kg−1. The proven conversion reaction between sodium and iron sulfide results in high capacity but severe volume changes. Nanostructural design, including of nanosized iron sulfide yolks (∼170 nm) with porous carbon shells (∼30 nm) and extra void space (∼20 nm) in between, has been used to achieve excellent cycling performance without sacrificing capacity. This sustainable sodium–iron sulfide battery is a promising candidate for stationary energy storage. Furthermore, this spatially confined sulfuration strategy offers a general method for other yolk-shell metal sulfide–carbon composites. PMID:26507613

  19. Bacteria-mediated precursor-dependent biosynthesis of superparamagnetic iron oxide and iron sulfide nanoparticles.

    PubMed

    Bharde, Atul A; Parikh, Rasesh Y; Baidakova, Maria; Jouen, Samuel; Hannoyer, Baetrice; Enoki, Toshiaki; Prasad, B L V; Shouche, Yogesh S; Ogale, Satish; Sastry, Murali

    2008-06-01

    The bacterium Actinobacter sp. has been shown to be capable of extracellularly synthesizing iron based magnetic nanoparticles, namely maghemite (gamma-Fe2O3) and greigite (Fe3S4) under ambient conditions depending on the nature of precursors used. More precisely, the bacterium synthesized maghemite when reacted with ferric chloride and iron sulfide when exposed to the aqueous solution of ferric chloride-ferrous sulfate. Challenging the bacterium with different metal ions resulted in induction of different proteins, which bring about the specific biochemical transformations in each case leading to the observed products. Maghemite and iron sulfide nanoparticles show superparamagnetic characteristics as expected. Compared to the earlier reports of magnetite and greigite synthesis by magnetotactic bacteria and iron reducing bacteria, which take place strictly under anaerobic conditions, the present procedure offers significant advancement since the reaction occurs under aerobic condition. Moreover, reaction end products can be tuned by the choice of precursors used. PMID:18454562

  20. Spectral induced polarization and electrodic potential monitoring of microbially mediated iron sulfide transformations

    SciTech Connect

    Hubbard, Susan; Personna, Y.R.; Ntarlagiannis, D.; Slater, L.; Yee, N.; O'Brien, M.; Hubbard, S.

    2008-02-15

    Stimulated sulfate-reduction is a bioremediation technique utilized for the sequestration of heavy metals in the subsurface.We performed laboratory column experiments to investigate the geoelectrical response of iron sulfide transformations by Desulfo vibriovulgaris. Two geoelectrical methods, (1) spectral induced polarization (SIP), and (2) electrodic potential measurements, were investigated. Aqueous geochemistry (sulfate, lactate, sulfide, and acetate), observations of precipitates (identified from electron microscopy as iron sulfide), and electrodic potentials on bisulfide ion (HS) sensitive silver-silver chloride (Ag-AgCl) electrodes (630 mV) were diagnostic of induced transitions between an aerobic iron sulfide forming conditions and aerobic conditions promoting iron sulfide dissolution. The SIP data showed 10m rad anomalies during iron sulfide mineralization accompanying microbial activity under an anaerobic transition. These anomalies disappeared during iron sulfide dissolution under the subsequent aerobic transition. SIP model parameters based on a Cole-Cole relaxation model of the polarization at the mineral-fluid interface were converted to (1) estimated biomineral surface area to pore volume (Sp), and (2) an equivalent polarizable sphere diameter (d) controlling the relaxation time. The temporal variation in these model parameters is consistent with filling and emptying of pores by iron sulfide biofilms, as the system transitions between anaerobic (pore filling) and aerobic (pore emptying) conditions. The results suggest that combined SIP and electrodic potential measurements might be used to monitor spatiotemporal variability in microbial iron sulfide transformations in the field.

  1. Spectral induced polarization and electrodic potential monitoring of microbially mediated iron sulfide transformations

    NASA Astrophysics Data System (ADS)

    Personna, Yves Robert; Ntarlagiannis, Dimitrios; Slater, Lee; Yee, Nathan; O'Brien, Michael; Hubbard, Susan

    2008-06-01

    Stimulated sulfate-reduction is a bioremediation technique utilized for the sequestration of heavy metals in the subsurface. We performed laboratory column experiments to investigate the geoelectrical response of iron sulfide transformations by Desulfovibrio vulgaris. Two geoelectrical methods, (1) spectral induced polarization (SIP), and (2) electrodic potential measurements, were investigated. Aqueous geochemistry (sulfate, lactate, sulfide, and acetate), observations of precipitates (identified from electron microscopy as iron sulfide), and electrodic potentials on bisulfide ion (HS-) sensitive silver-silver chloride (Ag-AgCl) electrodes (˜-630 mV) were diagnostic of induced transitions between anaerobic iron sulfide forming conditions and aerobic conditions promoting iron sulfide dissolution. The SIP data showed ˜10 mrad anomalies during iron sulfide mineralization accompanying microbial activity under an anaerobic transition. These anomalies disappeared during iron sulfide dissolution under the subsequent aerobic transition. SIP model parameters based on a Cole-Cole relaxation model of the polarization at the mineral-fluid interface were converted to (1) estimated biomineral surface area to pore volume (Sp), and (2) an equivalent polarizable sphere diameter (d) controlling the relaxation time. The temporal variation in these model parameters is consistent with filling and emptying of pores by iron sulfide biofilms, as the system transitions between anaerobic (pore filling) and aerobic (pore emptying) conditions. The results suggest that combined SIP and electrodic potential measurements might be used to monitor spatiotemporal variability in microbial iron sulfide transformations in the field.

  2. Iron (III) sulfide particles produced by a polyol method

    NASA Astrophysics Data System (ADS)

    Shimizu, Ryo; Kubono, Ippei; Kobayashi, Yoshio; Yamada, Yasuhiro

    2015-04-01

    Iron(III) sulfide Fe2S3 particles were produced using a polyol method. Although pyrrhotite Fe1-xS appeared together with Fe2S3, the relative yield of Fe2S3 changed when the concentration of reagents in the oleylamine changed. Mössbauer spectra of the particles showed superparamagnetic doublets due to Fe2S3 at 293 K, along with a hyperfine magnetic splitting of H = 24.7 T at 6 K. XRD patterns of the Fe2S3 suggested a structure similar to that of greigite Fe3S4.

  3. Formation, stability, and reactivity studies of neutral iron sulfide clusters

    NASA Astrophysics Data System (ADS)

    Yin, Shi; Wang, Zhechen; Bernstein, Elliot

    2014-03-01

    Different methods are used to generate neutral iron sulfide clusters to study their formation, stability, and reactivity, employing a time of flight mass spectrometer (TOFMS) with VUV (118 nm) radiation single photon ionization (SPI). Neutral FemSn (m = 1-4, n = 1-6), and hydrogen containing FemSnHx (x >0, n > m) clusters are generated by the reaction of seeded H2S in a helium carrier gas with laser ablated iron metal within a supersonic nozzle. The observed strong signal of association products Fe2S2(SH)0,1 M (M = CO, C2H4, C3H6) suggest that the Fe2S2(SH)0,1 clusters have the high activity for interactions with these small molecules. In order to avoid the effect for reactivity from hydrogen containing clusters, pure FemSnclusters are generated through laser ablation of a mixed iron/sulfur target in the presence of a pure helium carrier gas. (FeS)m (m = 1-4) is observed to be the most stable series. Reaction of CO and H2 on neutral (FeS)1,2clusters is farther investigated both experimentally and theoretically. A size dependent reactivity of iron sulfide clusters toward CO is characterized. The reaction FeS + CO --> Fe + OCS is found for the FeS cluster. Products Fe2S 213COH2 and Fe2S 213COH4 are identified for reactions of 13CO and H2 on Fe2S2 clusters: this suggests that the Fe2S2 cluster has a high catalytic activity for hydrogenation reactions of CO to form formaldehyde and methanol. DFT calculations are performed to explore the potential energy surfaces for the two reactions: Fe2S2 + CO + 2H2 --> Fe2S2 + CH3OH; and Fe2S2 + CO + H2 --> Fe2S2 + CH2O.

  4. Microbial Synthesis of Iron Sulfide (FeS) and Iron Carbonate (FeCO3) Nanoparticles.

    PubMed

    Kim, Yumi; Lee, Yuri; Roh, Yul

    2015-08-01

    This study examined mineral transformations during anoxic bioreduction of iron hydroxide and iron oxyhydroxysulfate found in acid mine drainage (AMD) into iron sulfide (FeS) and siderite (FeCO3) nanoparticles. Glucose (10 mM) was inoculated into AMD to stimulate indigenous bacterial growth for bioreduction of Fe(III)-containing minerals. Changes in microbial, geochemical, and mineralogical characteristics were monitored via 16S rRNA, XRD, SEM-EDX, TEM-EDX, ICP-AES, and IC analyses. The AMD was found to be rich in elements, including Fe, Al, Mn, Na, and S (SO4), and had a pH of 5.2. The mineral contents mainly consisted of Fe(III)-containing minerals, such as schwertmannite [Fe8O8 (OH)8-2x(SO4)x · nH2O] and akaganeite [β-FeO(OH)]. During anoxic bioreduction of AMD, the Fe(III)-containing minerals were transformed by indigenous iron-reducing bacteria (e.g., Geobactersp.) into Fe(II)-containing minerals, such as iron sulfide (FeS) and iron carbonate, siderite (FeCO3), within 3-4 days. The microbially-formed iron sulfide (FeS) and siderite (FeCO3) were of 40-60 nm and 10 nm-3 µm in size, respectively. These results not only show that indigenous iron-reducing bacteria in AMD can aid or accelerate formation of Fe(II)-containing minerals when under anoxic environments, but can also offer a simple method for microbial synthesis of nano-sized Fe(II)-containing minerals that can be used as catalysts for environmental remediation by recycling AMD. PMID:26369153

  5. Arsenic Bioremediation by Biogenic Iron Oxides and Sulfides

    PubMed Central

    Couture, Raoul-Marie; Van Cappellen, Philippe; Corkhill, Claire L.; Charnock, John M.; Polya, David A.; Vaughan, David; Vanbroekhoven, Karolien; Lloyd, Jonathan R.

    2013-01-01

    Microcosms containing sediment from an aquifer in Cambodia with naturally elevated levels of arsenic in the associated groundwater were used to evaluate the effectiveness of microbially mediated production of iron minerals for in situ As remediation. The microcosms were first incubated without amendments for 28 days, and the release of As and other geogenic chemicals from the sediments into the aqueous phase was monitored. Nitrate or a mixture of sulfate and lactate was then added to stimulate biological Fe(II) oxidation or sulfate reduction, respectively. Without treatment, soluble As concentrations reached 3.9 ± 0.9 μM at the end of the 143-day experiment. However, in the nitrate- and sulfate-plus-lactate-amended microcosms, soluble As levels decreased to 0.01 and 0.41 ± 0.13 μM, respectively, by the end of the experiment. Analyses using a range of biogeochemical and mineralogical tools indicated that sorption onto freshly formed hydrous ferric oxide (HFO) and iron sulfide mineral phases are the likely mechanisms for As removal in the respective treatments. Incorporation of the experimental results into a one-dimensional transport-reaction model suggests that, under conditions representative of the Cambodian aquifer, the in situ precipitation of HFO would be effective in bringing groundwater into compliance with the World Health Organization (WHO) provisional guideline value for As (10 ppb or 0.13 μM), although soluble Mn release accompanying microbial Fe(II) oxidation presents a potential health concern. In contrast, production of biogenic iron sulfide minerals would not remediate the groundwater As concentration below the recommended WHO limit. PMID:23666325

  6. Geomicrobiological Regeneration of Iron Sulfides in Engineered barrier Systems

    NASA Astrophysics Data System (ADS)

    Vannela, R.; Adriaens, P.; Hayes, K. F.

    2005-12-01

    The reactive capacity of iron sulfide-based permeable reactive barriers (PRB) to complex and co-precipitate heavy metal ions from groundwater will depend on the potential for regeneration of reactive FeS during the expected lifetime of the PRB. FeS reactivity may decrease in a PRB in time as the result of the following processes: (i) oxidation of FeS and the formation of ferric iron (Fe(III)) oxide solids in the presence of oxygenated groundwater at the entrance of the PRB, (ii) oxidation of FeS in the presence of redox active metals like As(V) with the formation of ferric solids, (iii) co-precipitation of heavy metals within the PRB with the reactive FeS leading to the formation of insoluble metal sulfides co-precipitates with the concomitant release of ferrous iron and formation of ferrous (Fe(II) oxide, hydroxide, or carbonate solids, (iv) clogging of the PRB structure due to formation of precipitate products from processes (i) - (iii).. We have demonstrated the formation of triolite in the presence of an oxidized form of hydrous ferric oxide (HFO), various sulfate concentrations, and biomass densities for the sulfate reducing bacterium (SRB) Desulfovibrio vulgaris. This result has allowed us to demonstrate the feasibility of regeneration of FeS from the ferric oxide and hydroxide solids that may be produced under scenarios (i) and (ii) above as well as to establish the electron donor and acceptor requirements for this SRB. Using Desulfobacterium autotrophicum, both HFO and soluble complexed forms of ferric iron gave rise to the formation of mackinawite. The latter have been shown to react with As (V) and Cd (II) to form ferric solids. Both organisms will be used to generate FeS solids in the presence of crystalline forms of ferric solids expected to form from scenarios (i) and (ii) (e.g., goethite and the mixed Fe(II)/(Fe(III) magnetite, and green rusts) and ferrous iron solids from scenarios (iii) and (iv) (Fe(II) oxides and siderite). Similar to the study

  7. Iron isotope fractionation in sulfides: constraints on mechanisms of sulfide formations in hydrothermal and magmatic systems.

    NASA Astrophysics Data System (ADS)

    Polyakov, Veniamin; Soultanov, Dilshod

    2010-05-01

    Data on non-traditional stable isotope fractionations (e.g., Fe, Cu) provide further insight into mechanisms of sulfide mineralization. Correct interpretation of these data is impossible without knowledge on equilibrium isotopic fractionation factors of sulfides. We present data on iron isotope fractionation factors (β-factors) of chalcopyrite (CuFeS2) and mackinawite (FeS). Iron β-factors for chalcopyrite were derived from synchrotron experimental data on inelastic nuclear resonant x-ray scattering (INRXS) [1] using the method described elsewhere [2,3]. The β-factors for mackinawite were found from the Moessbauer second-order Doppler shift data [4] by the method presented in [5]. The temperature dependence of the iron β-factors are fitted by following third-order polynomials: 103lnβcpy = 0.82560x - 0.01298x2 + 0.0005246x3 103lnβmcw = 0.2542x - 0.0001847x2 + 2.072×103x3 where x=106/T2 Using these data along with β-factors for pyrite and troilite [3,6], we compared iron isotope fractionation between pyrite and chalcopyrite in hydrothermal and magmatic conditions. Rouxel et al. [7] studied iron isotope of seafloor of hydrothermal vents in detail. They found that pyrite is enriched in light iron isotope relative to chalcopyrite in the case of black smoker Bio 9. This result evidences absence of iron isotope equilibrium between pyrite and chalcopyrite, because in equilibrium pyrite is enriched in heavy iron isotope (βpy > βcpy). Quantitatively, iron isotope fractionation between chalcolpyrite and pyrite is very close to equilibrium iron isotope fractionation between chalcolpyrite and FeS phase (mackinawite or troilite). This agrees the mechanism of pyrite formation through intermidient FeS phase if to assume isotopic equilibrium between the FeS phase and dissolved iron and no isotopic effect in the final stage of conversion FeS to FeS2 (pyrite). Another iron isotope fractionation was observed between pyrite and chalcopyrite in the case of the Cu-Au porphyry

  8. Impact of iron sulfide transformation on trichloroethylene degradation

    SciTech Connect

    He, Y. Thomas; Wilson, John T.; Wilkin, Richard T.

    2010-05-04

    Trichloroethylene (TCE) is one of the most common and persistent groundwater contaminants encountered at hazardous waste sites around the world. A growing body of evidence indicates that iron sulfides play an important role in degrading TCE in natural environments and in engineered systems designed for groundwater cleanup. In this study, we investigate transformation processes of iron sulfides and consequent impacts on TCE degradation using batch experimental techniques, transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS). Our results show that mackinawite is highly reactive toward TCE and no detectable mineralogical changes were detected during the course of reaction. However, freeze-dried FeS transformed to a mixture of mackinawite and greigite during the freeze drying process, with further mineralogical changes during reaction with TCE to lepidocrocite, goethite and pyrite. Newly formed lepidocrocite is a transient phase, with conversion to goethite over time. TCE transformation kinetics show that freeze-dried FeS is 20-50 times less reactive in degrading TCE than non-freeze-dried FeS, and the TCE degradation rate increases with pH (from 5.4 to 8.3), possibly due to an increase of surface deprotonation or electron transfer at higher pH. Results suggest that freeze drying could cause FeS particle aggregation, decreased surface area and availability of reactive sites; it also could change FeS mineralogy and accelerate mineral transformation. These aspects could contribute to the lower reactivity of freeze-dried FeS toward TCE degradation. Modeling results show that FeS transformation in natural environments depends on specific biogeochemical conditions, and natural FeS transformation may affect mineral reactivity in a similar way as compared to the freeze drying process. Rapid transformation of FeS to FeS{sub 2} could significantly slow down TCE degradation in both natural and engineered systems.

  9. Impact of iron sulfide transformation on trichloroethylene degradation

    NASA Astrophysics Data System (ADS)

    He, Y. Thomas; Wilson, John T.; Wilkin, Richard T.

    2010-04-01

    Trichloroethylene (TCE) is one of the most common and persistent groundwater contaminants encountered at hazardous waste sites around the world. A growing body of evidence indicates that iron sulfides play an important role in degrading TCE in natural environments and in engineered systems designed for groundwater cleanup. In this study, we investigate transformation processes of iron sulfides and consequent impacts on TCE degradation using batch experimental techniques, transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS). Our results show that mackinawite is highly reactive toward TCE and no detectable mineralogical changes were detected during the course of reaction. However, freeze-dried FeS transformed to a mixture of mackinawite and greigite during the freeze drying process, with further mineralogical changes during reaction with TCE to lepidocrocite, goethite and pyrite. Newly formed lepidocrocite is a transient phase, with conversion to goethite over time. TCE transformation kinetics show that freeze-dried FeS is 20-50 times less reactive in degrading TCE than non-freeze-dried FeS, and the TCE degradation rate increases with pH (from 5.4 to 8.3), possibly due to an increase of surface deprotonation or electron transfer at higher pH. Results suggest that freeze drying could cause FeS particle aggregation, decreased surface area and availability of reactive sites; it also could change FeS mineralogy and accelerate mineral transformation. These aspects could contribute to the lower reactivity of freeze-dried FeS toward TCE degradation. Modeling results show that FeS transformation in natural environments depends on specific biogeochemical conditions, and natural FeS transformation may affect mineral reactivity in a similar way as compared to the freeze drying process. Rapid transformation of FeS to FeS 2 could significantly slow down TCE degradation in both natural and engineered systems.

  10. [Investigation of nitrobenzene removal by iron sulfide (FeS)].

    PubMed

    Wang, Xia-Lin; Li, Rui-Hua

    2012-12-01

    The nitrobenzene removal performance by iron sulfide was investigated in batch experiments. The effects of different factors were studied. The results showed that the removal efficiency of nitrobenzene was 90% as initial nitrobenzene concentration was 0.96 mmol x L(-1), dosage of FeS was 1.2 g and the reaction time was 180 minutes. Initial nitrobenzene concentration, dosage of FeS, temperature and reused times of FeS had a significant influence on the removal efficiency of nitrobenzene. As the initial nitrobenzene concentration was in range of 0.74 to 1.74 mmol x L(-1), the removal efficiency of nitrobenzene decreased by 4.7% with every 0.1 mmol x L(-1) increasing of initial nitrobenzene concentration. As the dosage of FeS was in the range of 0.3 to 1.5 g, the removal efficiency of nitrobenzene increased by 20% with every 0.3 g increasing of FeS. As the dosage of FeS was 1.8 g, the removal efficiency of nitrobenzene was 100%. In the temperature range of 10 to 25 degrees C, the removal efficiency of nitrobenzene increased by 1.6% with 1 degrees C increasing. As the temperature was 30 degrees C, the removal efficiency of nitrobenzene was 100%. The removal efficiency of nitrobenzene decreased as the reused times of FeS increased. Rotational speed hardly had any influence on the removal efficiency of nitrobenzene. As the rotational speed was in the range of 10 to 80 r x min(-1), the removal efficiency of nitrobenzene was around 75%. The nitrobenzene removal performance by iron sulfide was satisfied in the treatment of simulated chemical industrial wastewater, and after 60 min, the removal efficiency of nitrobenzene was 100%. PMID:23379163

  11. Surficial weathering of iron sulfide mine tailings under semi-arid climate.

    PubMed

    Hayes, Sarah M; Root, Robert A; Perdrial, Nicolas; Maier, Raina; Chorover, Jon

    2014-09-15

    Mine wastes introduce anthropogenic weathering profiles to the critical zone that often remain unvegetated for decades after mining cessation. As such, they are vulnerable to wind and water dispersion of particulate matter to adjacent ecosystems and residential communities. In sulfide-rich ore tailings, propagation to depth of the oxidative weathering front controls the depth-variation in speciation of major and trace elements. Despite the prevalence of surficial mine waste deposits in arid regions of the globe, few prior studies have been conducted to resolve the near-surface profile of sulfide ore tailings weathered under semi-arid climate. We investigated relations between gossan oxidative reaction-front propagation and the molecular speciation of iron and sulfur in tailings subjected to weathering under semi-arid climate at an EPA Superfund Site in semi-arid central Arizona (USA). Here we report a multi-method data set combining wet chemical and synchrotron-based X-ray diffraction (XRD) and X-ray absorption near-edge spectroscopy (XANES) methods to resolve the tight coupling of iron (Fe) and sulfur (S) geochemical changes in the top 2 m of tailings. Despite nearly invariant Fe and S concentration with depth (130-140 and 100-120 g kg(-1), respectively), a sharp redox gradient and distinct morphological change was observed within the top 0.5 m, associated with a progressive oxidative alteration of ferrous sulfides to (oxyhydr)oxides and (hydroxy)sulfates. Transformation is nearly complete in surficial samples. Trends in molecular-scale alteration were co-located with a decrease in pH from 7.3 to 2.3, and shifts in Fe and S lability as measured via chemical extraction. Initial weathering products, ferrihydrite and gypsum, transform to schwertmannite, then jarosite-group minerals with an accompanying decrease in pH. Interestingly, thermodynamically stable phases such as goethite and hematite were not detected in any samples, but ferrihydrite was observed even in

  12. Surficial weathering of iron sulfide mine tailings under semi-arid climate

    PubMed Central

    Hayes, Sarah M.; Root, Robert A.; Perdrial, Nicolas; Maier, Raina; Chorover, Jon

    2014-01-01

    Mine wastes introduce anthropogenic weathering profiles to the critical zone that often remain unvegetated for decades after mining cessation. As such, they are vulnerable to wind and water dispersion of particulate matter to adjacent ecosystems and residential communities. In sulfide-rich ore tailings, propagation to depth of the oxidative weathering front controls the depth-variation in speciation of major and trace elements. Despite the prevalence of surficial mine waste deposits in arid regions of the globe, few prior studies have been conducted to resolve the near-surface profile of sulfide ore tailings weathered under semi-arid climate. We investigated relations between gossan oxidative reaction-front propagation and the molecular speciation of iron and sulfur in tailings subjected to weathering under semi-arid climate at an EPA Superfund Site in semi-arid central Arizona (USA). Here we report a multi-method data set combining wet chemical and synchrotron-based X-ray diffraction (XRD) and X-ray absorption near-edge spectroscopy (XANES) methods to resolve the tight coupling of iron (Fe) and sulfur (S) geochemical changes in the top 2 m of tailings. Despite nearly invariant Fe and S concentration with depth (130–140 and 100–120 g kg−1, respectively), a sharp redox gradient and distinct morphological change was observed within the top 0.5 m, associated with a progressive oxidative alteration of ferrous sulfides to (oxyhydr)oxides and (hydroxy)sulfates. Transformation is nearly complete in surficial samples. Trends in molecular-scale alteration were co-located with a decrease in pH from 7.3 to 2.3, and shifts in Fe and S lability as measured via chemical extraction. Initial weathering products, ferrihydrite and gypsum, transform to schwertmannite, then jarosite-group minerals with an accompanying decrease in pH. Interestingly, thermodynamically stable phases such as goethite and hematite were not detected in any samples, but ferrihydrite was observed even

  13. Surficial weathering of iron sulfide mine tailings under semi-arid climate

    NASA Astrophysics Data System (ADS)

    Hayes, Sarah M.; Root, Robert A.; Perdrial, Nicolas; Maier, Raina M.; Chorover, Jon

    2014-09-01

    Mine wastes introduce anthropogenic weathering profiles to the critical zone that often remain unvegetated for decades after mining cessation. As such, they are vulnerable to wind and water dispersion of particulate matter to adjacent ecosystems and residential communities. In sulfide-rich ore tailings, propagation to depth of the oxidative weathering front controls the depth-variation in speciation of major and trace elements. Despite the prevalence of surficial mine waste deposits in arid regions of the globe, few prior studies have been conducted to resolve the near-surface profile of sulfide ore tailings weathered under semi-arid climate. We investigated relations between gossan oxidative reaction-front propagation and the molecular speciation of iron and sulfur in tailings subjected to weathering in a semi-arid climate at an EPA Superfund Site in central Arizona (USA). Here we report a multi-method data set combining wet chemical and synchrotron-based X-ray diffraction (XRD) and X-ray absorption near-edge spectroscopy (XANES) methods to resolve the tight coupling of iron (Fe) and sulfur (S) geochemical changes in the top 2 m of tailings. Despite nearly invariant Fe and S concentration with depth (130-140 and 100-120 g kg-1, respectively), a sharp redox gradient and distinct morphological change was observed within the top 0.5 m, associated with a progressive oxidative alteration of ferrous sulfides to (oxyhydr)oxides and (hydroxy)sulfates. Transformation is nearly complete in surficial samples. Trends in molecular-scale alteration were co-located with a decrease in pH from 7.3 to 2.3, and shifts in Fe and S lability as measured via chemical extraction. Initial weathering products, ferrihydrite and gypsum, transform to schwertmannite, then jarosite-group minerals with an accompanying decrease in pH. Interestingly, thermodynamically stable phases such as goethite and hematite were not detected in any samples, but ferrihydrite was observed even in samples with

  14. Reductive immobilization of uranium(VI) by amorphous iron sulfide.

    PubMed

    Hua, Bin; Deng, Baolin

    2008-12-01

    Batch experiments were used to evaluate the reductive immobilization of hexavalent uranium (U(VI)) by synthesized, amorphous iron sulfide (FeS) in the anoxic environment. The tests were initiated by spiking 168.0 microM U(VI) to 0.18 g/L FeS suspensions under a CO2-free condition with pH varied from 5.99 to 10.17. The immobilization rate of U(VI) was determined by monitoring the changes of aqueous U(VI) concentration, and the reduction rate of U(VI) associated with FeS was determined by the difference between the total spiked U(VI) and the extractable amount of U(VI) by 25 mM NaHCO3 solution. The results showed that a rapid removal of U(VI) from the aqueous phase occurred within 1 h under all pH conditions accompanied by a simultaneous release of Fe(ll), whereas the reduction of U(VI) associated with FeS took hours to over a week for completion. The reduction rate was greatly increased with decreasing pH within the examined pH range. Product analysis by X-ray photoelectron spectroscopy showed the formation of U3O8/4O9/UO2, polysulfide, and ferric iron. PMID:19192785

  15. Anoxic Iron Cycling Bacteria from an Iron Sulfide- and Nitrate-Rich Freshwater Environment

    PubMed Central

    Haaijer, Suzanne C. M.; Crienen, Gijs; Jetten, Mike S. M.; Op den Camp, Huub J. M.

    2012-01-01

    In this study, both culture-dependent and culture-independent methods were used to determine whether the iron sulfide mineral- and nitrate-rich freshwater nature reserve Het Zwart Water accommodates anoxic microbial iron cycling. Molecular analyses (16S rRNA gene clone library and fluorescence in situ hybridization, FISH) showed that sulfur-oxidizing denitrifiers dominated the microbial population. In addition, bacteria resembling the iron-oxidizing, nitrate-reducing Acidovorax strain BrG1 accounted for a major part of the microbial community in the groundwater of this ecosystem. Despite the apparent abundance of strain BrG1-like bacteria, iron-oxidizing nitrate reducers could not be isolated, likely due to the strictly autotrophic cultivation conditions adopted in our study. In contrast an iron-reducing Geobacter sp. was isolated from this environment while FISH and 16S rRNA gene clone library analyses did not reveal any Geobacter sp.-related sequences in the groundwater. Our findings indicate that iron-oxidizing nitrate reducers may be of importance to the redox cycling of iron in the groundwater of our study site and illustrate the necessity of employing both culture-dependent and independent methods in studies on microbial processes. PMID:22347219

  16. What do we really know about the role of microorganisms in iron sulfide mineral formation?

    NASA Astrophysics Data System (ADS)

    Picard, Aude; Gartman, Amy; Girguis, Peter

    2016-06-01

    Iron sulfide mineralization in low-temperature systems is a result of biotic and abiotic processes, though the delineation between these two modes of formation is not always straightforward. Here we review the role of microorganisms in the precipitation of extracellular iron sulfide minerals. We summarize the evidence that links sulfur-metabolizing microorganisms and sulfide minerals in nature and we present a critical overview of laboratory-based studies of the nucleation and growth of iron sulfide minerals in microbial cultures. We discuss whether biologically derived minerals are distinguishable from abiotic minerals, possessing attributes that are uniquely diagnostic of biomineralization. These inquiries have revealed the need for additional thorough, mechanistic and high-resolution studies to understand microbially mediated formation of a variety of sulfide minerals across a range of natural environments.

  17. Morphological development of oxide-sulfide scales on iron and iron-manganese alloys

    SciTech Connect

    McAdam, G.; Young, D.J.

    1987-10-01

    Pure iron and alloys containing 2, 15, 25, and 50 wt.% manganese have been reacted at 1073 K in controlled gas atmospheres of SO/sub 2/-CO/sub 2/-CO-N/sub 2/. Equilibrium gas compositions were such that (1) FeS was stable but not FeO, or (2) both FeS and FeO were stable, or (3) FeO was stable but not FeS; in all cases, both MnS and MnO were stable. Under all reaction conditions, pure iron corroded to produce both sulfide and oxide. The resultant scale morphologies were consistent with local solid-gas equilibrium for the case in which both oxide and sulfide were stable but in the other cases indicated that equilibrium was not achieved and that direct reaction with SO/sub 2/(g) was responsible for corrosion. Additions of manganese did not greatly alter the scale morphologies. Under reaction conditions that were oxidizing and sulfidizing, very high levels of manganese were required to reduce the corrosion rate. On the other hand, relatively low levels had a beneficial effect both when FeO but not FeS was thermodynamically stable and similarly when FeS but not FeO was stable.

  18. VAPOR PHASE MERCURY SORPTION BY ORGANIC SULFIDE MODIFIED BIMETALLIC IRON-COPPER NANOPARTICLE AGGREGATES

    EPA Science Inventory

    Novel organic sulfide modified bimetallic iron-copper nanoparticle aggregate sorbent materials have been synthesized for removing elemental mercury from vapor streams at elevated temperatures (120-140 °C). Silane based (disulfide silane and tetrasulfide silane) and alkyl sulfide ...

  19. Iron sulfide as a water-deposited scale in sour gas wells

    SciTech Connect

    Claassen, E.J.

    1988-01-01

    Iron is soluble in reservoir waters which have high salinity and high hydrogen sulfide content. As the well produces, iron sulfide is precipitated due to the drop in pressure with the resultant increase in pH. The crystallines attach to the lower portion of the tubing, where either bimetallic or crevice corrosion occur beneath the crystallines. Gas condensate wells deposit a high molecular weight material, such as asphaltene, on the iron sulfide crystallites as they deposit. Under these conditions the scale cannot be removed by hydrochloric acid, surfactants, or chelating agents. Corrosion of the metal continues if the combination layer of iron sulfide and asphaltene is cracked, porous, or spalls, but stops if the layer is dense and non-friable. The layer of scale can be removed only by mechanical means, or by removing the binder chemically.

  20. Iron Isotope Fractionation in Iron Meteorites: New Insights into Metal-Sulfide Segregation and Core Crystallization

    NASA Astrophysics Data System (ADS)

    Williams, H. M.; Halliday, A. N.; Teutsch, N.; Levasseur, S.

    2004-12-01

    Recent studies have demonstrated that substantial iron isotope fractionation occurs between pallasite metal, troilite and olivine [1,2] and that smaller variations exist in the iron isotope compositions (δ 57/54Fe) of bulk meteorites [3-5]. Interpreting such isotopic variations in terms of planetary formation processes is hampered by a lack of knowledge regarding the behavior of iron isotopes during accretion and core-mantle differentiation. Many iron meteorites are considered to be remnants of asteroidal cores and may be used to place preliminary constraints on the behavior of iron isotopes during planetary core formation and crystallization. We present iron isotope data obtained using standard MC-ICPMS methods [6] for metal and sulfide fractions extracted from iron meteorites. The metal fractions have δ 57/54Fe values ranging from 0.02‰ to 0.27‰ . Replicate large samples (10-15g) of the metal fractions of several meteorites have δ 57/54Fe values within 0.02‰ of each other. There do not appear to be any strong relationships between the δ 57/54Fe values of the metal phases and the trace element compositions of the meteorites studied. However, considerable variation exists in the δ 57/54Fe values of the troilites. These range from -0.40‰ to 0.29‰ . In most cases, the troilites have δ 57/54Fe values that are lighter than those of the corresponding metal fractions by ˜ 0.5‰ . Given the slow cooling rates inferred for iron meteorites it is likely that these phases are in isotopic equilibrium. If the isotopic fractionation between metal and troilite is representative of the fractionation between sulfide and melt during core crystallization, then the large differences recently proposed for the initial S contents of the cores of the different iron meteorite parent bodies [7] could be reflected in the δ 57/54Fe values of bulk iron meteorites. This hypothesis will be evaluated in the light of further data. 1 F. Poitrasson et al., Lunar and Planetary

  1. Dissolved Oxygen and Sulfide Define the Boundaries of Thermophilic Microbial Iron Mats

    NASA Astrophysics Data System (ADS)

    St Clair, B.; Shock, E.

    2014-12-01

    Microbial iron cycling can be found in hot springs throughout Yellowstone National Park, where the process is often visibly apparent as red iron oxyhydroxide staining. We measured rates of microbial and abiotic iron oxidation and reduction in systems ranging from pH 2 to 6 and 40° to 90°C. Measurements of numerous solutes, including oxygen, sulfide, and iron, were also made on outflow channels of springs containing apparent iron metabolism. In all cases, > 16 μM dissolved oxygen was required for visible iron oxidation products to occur. Oxygen concentrations below this level do not necessarily preclude microbial iron oxidation coupled to oxygen, only the accumulation of oxidation products. Kinetics experiments conducted at these iron mats suggest that the rate of microbial iron oxidation falls below the rate of microbial reduction when dissolved oxygen falls below this concentration. In outflow channels, this is often visibly apparent as a sharp boundary between the presence and lack of red iron oxidation products. Locations with changing temperature, pH, flow rate and other factors experience changing oxygen concentrations, which causes the boundary to shift from year to year. The boundaries of iron mats are also influenced in several locations by the concentration of total dissolved sulfide. Experiments with enrichment cultures and field observations show that sulfide is not toxic to iron oxidizers, but rather inhibits the accumulation of dissolved oxygen. Microbial and abiotic sulfide oxidation, leading to visible sulfur precipitation, together with degassing of hydrogen sulfide, contribute to keeping oxygen levels low. Typically, only where sulfide concentrations fall below 20 μM are iron mats able to form. Enrichment cultures of iron oxidizers, however, grow easily at levels exceeding 100 μM sulfide. Only a handful of field locations appear to have simultaneous sulfur and iron precipitation zones. Formation of iron oxidation mats occurs at highly

  2. Synthesis and characterization of hybrid materials containing iron oxide for removal of sulfides from water.

    PubMed

    Jacukowicz-Sobala, Irena; Wilk, Łukasz J; Drabent, Krzysztof; Kociołek-Balawejder, Elżbieta

    2015-12-15

    Hybrid materials containing iron oxides based on macroporous and gel-type sulfonic and carboxylic cation exchangers as supporting materials were obtained. Multiple factors, including the kind of functional groups, ion exchange capacity, and polymer matrix type (chemical constitution and porous structure), affected the amount of iron oxides introduced into their matrix (7.8-35.2% Fe). Products containing the highest iron content were obtained using carboxylic cation exchangers, with their inorganic deposit being mostly a mixture of iron(III) oxides, including maghemite. Obtained hybrid polymers were used for removal of sulfides from anoxic aqueous solutions (50-200mgS(2-)/dm(3)). The research showed that the form (Na(+) or H(+)) of ionic groups of hybrid materials had a crucial impact on the sulfide removal process. Due to high iron oxide content (35% Fe), advantageous chemical constitution and porous structure, the highest removal efficiency (60mgS(2-)/g) was exhibited by a hybrid polymer obtained using a macroporous carboxylic cation exchanger as the host material. The process of sulfide removal was very complex and proceeded with heterogeneous oxidation, iron(III) oxide reductive dissolution and formation of sulfide oxidation and precipitation products such as iron(II) sulfides, thiosulfates and polysulfides. PMID:26319332

  3. Feasibility of sulfide control in sewers by reuse of iron rich drinking water treatment sludge.

    PubMed

    Sun, Jing; Pikaar, Ilje; Sharma, Keshab Raj; Keller, Jürg; Yuan, Zhiguo

    2015-03-15

    Dosage of iron salt is the most commonly used method for sulfide control in sewer networks but incurs high chemical costs. In this study, we experimentally investigate the feasibility of using iron rich drinking water treatment sludge for sulfide control in sewers. A lab-scale rising main sewer biofilm reactor was used. The sulfide concentration in the effluent decreased from 15.5 to 19.8 mgS/L (without dosing) to below 0.7-2.3 mgS/L at a sludge dosing rate achieving an iron to total dissolved inorganic sulfur molar ratio (Fe:S) of 1:1, with further removal of sulfide possible by prolonging the reaction time. In fact, batch tests revealed an Fe consumption to sulfide removal ratio of 0.5 ± 0.02 (mole:mole), suggesting the possible occurrence of other reactions involving the removal of sulfide. Modelling revealed that the reaction between iron in sludge and sulfide has reaction orders of 0.65 ± 0.01 and 0.77 ± 0.02 with respect to the Fe and sulfide concentrations, respectively. The addition of sludge slightly increased the total chemical oxidation demand (tCOD) concentration (by approximately 12%) as expected, but decreased the soluble chemical oxidation demand (sCOD) concentration and methane formation by 7% and 20%, respectively. Some phosphate removal (13%) was also observed at the sludge dosing rate of 1:1 (Fe:S), which is beneficial to nutrient removal from the wastewater. Overall, this study suggests that dosing iron-rich drinking water sludge to sewers could be an effective strategy for sulfide removal in sewer systems, which would also reduce the sludge disposal costs for drinking water treatment works. However, its potential side-effects on sewer sedimentation and on the wastewater treatment plant effluent remain to be investigated. PMID:25616115

  4. Enhancing the Performance of the Rechargeable Iron Electrode in Alkaline Batteries with Bismuth Oxide and Iron Sulfide Additives

    SciTech Connect

    Manohar, AK; Yang, CG; Malkhandi, S; Prakash, GKS; Narayanan, SR

    2013-09-07

    Iron-based alkaline rechargeable batteries have the potential of meeting the needs of large-scale electrical energy storage because of their low-cost, robustness and eco-friendliness. However, the widespread commercial deployment of iron-based batteries has been limited by the low charging efficiency and the poor discharge rate capability of the iron electrode. In this study, we have demonstrated iron electrodes containing bismuth oxide and iron sulfide with a charging efficiency of 92% and capable of being discharged at the 3C rate. Such a high value of charging efficiency combined with the ability to discharge at high rates is being reported for the first time. The bismuth oxide additive led to the in situ formation of elemental bismuth and a consequent increase in the overpotential for the hydrogen evolution reaction leading to an increase in the charging efficiency. We observed that the sulfide ions added to the electrolyte and iron sulfide added to the electrode mitigated-electrode passivation and allowed for continuous discharge at high rates. At the 3C discharge rate, a utilization of 0.2 Ah/g was achieved. The performance level of the rechargeable iron electrode demonstrated here is attractive for designing economically-viable large-scale energy storage systems based on alkaline nickel-iron and iron-air batteries. (C) 2013 The Electrochemical Society. All rights reserved.

  5. VAPOR PHASE MERCURY SORPTION BY ORGANIC-SULFIDE COATED BIMETALLIC IRON-COPPER NANOPARTICLE AGGREGATES

    EPA Science Inventory

    Tetra sulfide silane coated iron-copper nano-particle aggregates are found to be potentially very high capacity sorbents for vapor phase mercury capture. High equilibrium capacities were obtained for the silane coated iron copper nano-aggregate sorbent at 70 oC and 120 oC. Even a...

  6. After more than a century, iron sponge still soaks up hydrogen sulfide problems

    SciTech Connect

    Anerousis, J.P. )

    1994-09-01

    The oldest and simplest method for removing H[sub 2]S and other sulfur compounds, such as mercaptans, from gaseous streams is the iron sponge process. The basic technique consists of passing a sour gas stream (one containing H[sub 2]S or mercaptans, or both) across a bed of hydrated iron oxide. The chemical reaction produces iron sulfide and a small amount of by-product water. Although not a common practice, the spent material may be regenerated by exposing it to oxygen, which converts the mixed iron sulfides to their original iron oxide form. The iron sponge technique originated in Europe more than 100 years ago, and the earliest operators used a naturally occurring form of hydrated iron oxide known as bog iron or bog ore. As refinements were made in the process, it was found that more efficient sulfur removal could be attained by uniformly distributing the iron oxide hydrate across a substrate, and that active iron oxide could be prepared synthetically. Continual improvements in the synthetic iron sponge's composition focused on such issues as the crystalline forms of the hydrated iron oxide, size distribution of the active iron oxide particulates, overall chemical composition, size and nature of the typical wood substrate, moisture content, and degree of buffering. Modern iron sponge products are prepared with careful attention to each of these issues. The synthetic materials are characterized by high quality and uniform composition, and their overall characteristics optimize performance in typical gas-sweetening applications.

  7. Iron sulfide oxidation and the chemistry of acid generation

    NASA Astrophysics Data System (ADS)

    Sullivan, Patrick J.; Yelton, Jennifer L.; Reddy, K. J.

    1988-06-01

    Acid mine drainage, produced from the oxidation of iron sulfides, often contains elevated levels of dissolved aluminum (AI), iron (Fe), and sulfate (SO4) and low pH. Understanding the interactions of these elements associated with acid mine drainage is necessary for proper solid waste management planning. Two eastern oil shales were leached using humidity cell methods. This study used a New Albany Shale (4.6 percent pyrite) and a Chattanooga Shale (1.5 percent pyrite). The leachates from the humidity cells were filtered, and the filtrates were analyzed for total concentrations of cations and anions. After correcting for significant solution species and complexes, ion activities were calculated from total concentrations. The results show that the activities of Fe3+, Fe2+, Al3+, and SO4 2- increased due to the oxidation of pyrite. Furthermore, the oxidation of pyrite resulted in a decreased pH and an increased pe+pH (redox-potential). The Fe3+ and Fe2+ activities appeared to be controlled by amorphous Fe(OH)3 solid phase above a pH of 6.0 and below pe+pH 11.0. The Fe3+, Fe2+, and SO4 2- activities reached saturation with respect to FeOHSO4 solid phase between pH 3.0 and 6.0 and below pe+pH 11.0 Below a pH of 3.0 and above a pe+pH of 11.0, Fe2+, Fe3+, and SO4 2- activities are supported by FeSO4·7H2O solid phase. Above a pH of 6.0, the Al3+ activity showed an equilibrium with amorphous Al(OH)3 solid phase. Below pH 6.0, Al3+ and SO4 2- activities are regulated by the AlOHSO4 solid phase, irrespective of pe+pH. The results of this study suggest that under oxidizing conditions with low to high leaching potential, activities of Al and Fe can be predicted on the basis of secondary mineral formation over a wide range of pH and redox. As a result, the long-term chemistry associated with disposal environments can be largely predicted (including trace elements).

  8. Kinetic studies on the sulfidation of iron by sulfur bearing low-Btu gases

    SciTech Connect

    Joyce, E.L. Jr.; Li, K.; Philbrook, W.O.

    1988-01-01

    The use of a low-Btu gas as a reducing agent for iron oxide was shown to be favorable at temperatures of 800/sup 0/C or greater. Little benefit was seen in terms of increased reduction rates at higher pressures (up to 5 atmospheres) or in varying either the H/sub 2/ concentration or CO/CO/sub 2/ ratio, within the range of a low-Btu gas. Sulfidation was found to occur in reaction with iron and not iron oxide. It was found that to avoid contamination of the reduced iron, very low levels of H/sub 2/S are necessary in the gas phase (approx. =0.05%). Kinetic data for the sulfidation of reduced iron oxide discs by a sulfur bearing low-Btu gas were taken to clarify the mechanism for the sulfidation reaction. Sulfidation was found to increase with H/sub 2/S concentration, system pressure and temperature, and to depend weakly on H/sub 2/ concentration and CO/CO/sub 2/ ratio. A model based on combined Multicomponent and Knudsen diffusion through the FeS product layer was developed and used to describe sulfidation. 40 refs., 16 figs.

  9. Speciation and Distribution of Trace Metals Associated with Iron Sulfides in the Marcellus Shale

    NASA Astrophysics Data System (ADS)

    Singer, D. M.; Cahill, M.

    2014-12-01

    Black shales underlying the areas from Eastern Ohio, through Pennsylvania, and into Central New York State have become of economic interest lately due to the recent economic viability of shale gas extraction. Sulfide minerals such as pyrite and marcasite occurring in these shales are often the primary phases that trace metals are associated with. Trace metals can be incorporated into these sulfides via various pathways during initial shale deposition and secondary diagenesis including substitution for Fe (Co and Ni), substitution for S (As and Se), and excluded to form other sulfide phases (Cu and Zn). The manner in which these trace metals are incorporated directly influences how they are released into the environment during sulfide oxidation following shale weathering or hydraulic fracturing. The aim of this research is to examine the distribution of trace metals in iron sulfides from black shales using Synchrotron-based X-ray microprobe techniques including micro-X-ray fluorescence and micro-X-ray diffraction of shale thin sections. Marcellus Shale samples were collected from: (1) outcrops from the Oatka member in Leroy, NY and Jersey Shore, PA and the Union Springs member in Lewiston, PA, and (2) drilling core sample from Beaver Meadow, NY and Hancock Co, TN (Chattanooga shale). Analyses have shown that the sulfide grains are a combination of pyrite and marcasite. As and Se are spatially correlated with each other and within the pyrite grains. Ni is spatially correlated with larger euhedral pyrite, as well as smaller non-iron sulfide grains. Cu and Zn are not spatially correlated with the pyrite and form separate Cu- and Zn- sulfides. During iron sulfide oxidative dissolution, these differences in distribution of trace metals will affect the order and rate in which they are released into the environment.

  10. Trace element siting in iron sulfides from coal determined by secondary ion mass spectrometry

    SciTech Connect

    Wiese, R.G. Jr. ); Muir, I.J.; Fyfe, W.S. )

    1990-01-01

    Intact samples of coal have been analyzed by SIMS (secondary ion mass spectrometry) ion imaging and ion probe techniques for determination of the distribution of trace elements in pyrite and marcasite and in the associated clay minerals. Ion mapping of site-specific concentrations of trace elements is important as one considers the environmental consequences of not only the combustion of coal, but also the disposal of coal-washing plant refuse and the placement of mine spoils during reclamation. Iron sulfides and clays are both involved in the oxidation-hydration reactions that result in the formation of acid waters and the release of trace elements into the ecosystem. Iron sulfides from selected Ohio coals contain site-specific concentrations of Mn, Co, Ni, Cu, As, and Pb. Clay minerals found within and marginal to the sulfides contain V, Cr, and also As and Co. The distribution of trace elements in the sulfides and associated clays clearly is related to microenvironments that existed during the formation of successive parts of the sulfide grains. The sulfide-clay relationships determine the extent to which the sulfides break down in oxidation-hydration reactions.

  11. Potential for biogeochemical cycling of sulfur, iron and carbon within massive sulfide deposits below the seafloor.

    PubMed

    Kato, Shingo; Ikehata, Kei; Shibuya, Takazo; Urabe, Tetsuro; Ohkuma, Moriya; Yamagishi, Akihiko

    2015-05-01

    Seafloor massive sulfides are a potential energy source for the support of chemosynthetic ecosystems in dark, deep-sea environments; however, little is known about microbial communities in these ecosystems, especially below the seafloor. In the present study, we performed culture-independent molecular analyses of sub-seafloor sulfide samples collected in the Southern Mariana Trough by drilling. The depth for the samples ranged from 0.52 m to 2.67 m below the seafloor. A combination of 16S rRNA and functional gene analyses suggested the presence of chemoautotrophs, sulfur-oxidizers, sulfate-reducers, iron-oxidizers and iron-reducers. In addition, mineralogical and thermodynamic analyses are consistent with chemosynthetic microbial communities sustained by sulfide minerals below the seafloor. Although distinct bacterial community compositions were found among the sub-seafloor sulfide samples and hydrothermally inactive sulfide chimneys on the seafloor collected from various areas, we also found common bacterial members at species level including the sulfur-oxidizers and sulfate-reducers, suggesting that the common members are widely distributed within massive sulfide deposits on and below the seafloor and play a key role in the ecosystem function. PMID:25330135

  12. Use of iron salts to control dissolved sulfide in trunk sewers

    SciTech Connect

    Padival, N.A.; Kimbell, W.A.; Redner, J.A.

    1995-11-01

    Sewer headspace H{sub 2}S reduction by precipitating dissolved sulfide in wastewater was investigated using iron salt (FeCl{sub 3} and FeCl{sub 2}). Full-scale experiments were conducted in a 40-km (25 mi) sewer with an average flow of 8.7 m{sup 3}/s (200 mgd). Results were sensitive to total Fe dosages and Fe(III)/Fe(II) blend ratios injected. A concentration of 16 mg/L total Fe and a blend ratio of 1.9:1 [Fe(III):Fe(II)] reduced dissolved sulfide levels by 97%. Total sulfide and headspace H{sub 2}S were reduced by 63% and 79%, respectively. Liquid and gas-phase sulfide reductions were largely due to the effective precipitation of sulfide with Fe(III) and Fe(II) and the limited volatilization of H{sub 2}S, respectively. Oxidation of sulfide in the presence of Fe(II) and minute amounts of O{sub 2} may have occurred. A combination of Fe(III) and Fe(II) proved more effective than either salt alone. By using excess Fe(III), dissolved sulfide can be reduced to undetectable levels. No specific relation between the concentration of Fe or Fe(III)/Fe(II) blend ratio and sewer crown pH was inferred. Iron salts may retard crown corrosion rates by precipitating free sulfide and reducing its release to the sewer headspace as H{sub 2}S. A mechanism to inhibit certain responsible bacteria was not established in the 40-km (25 mi) sewer.

  13. Reductive dechlorination of chlorinated solvents by zero-valent iron, iron oxide and iron sulfide minerals

    SciTech Connect

    Sivavec, T.M.; Horney, D.P.

    1996-10-01

    The degradation of chlorinated solvents by reduction at the surface of zero-valent metals and bimetallic systems has emerged as an important approach to the in-situ remediation of ground water. Reduction by iron metal was studied in batch and column systems to develop a mechanistic understanding of the reaction chemistry and to determine the factors that affect dechlorination rate and long term performance in field applications.

  14. Rotational Remanent Magnetization (RRM) to Identify Pyrrhotite in Natural Iron-Sulfide-Bearing Samples

    NASA Astrophysics Data System (ADS)

    Slotznick, S. P.; Kirschvink, J. L.; Fischer, W. W.; Webb, S. M.

    2014-12-01

    Pyrrhotite has been known for several decades to have anomalous demagnetization behavior when using tumbling AF techniques. This was quantified by Thomson (1990) to show that pyrrhotite can acquire rotational remanent magnetization (RRM) similar to the more intensely-studied iron sulfide, greigite. Use of RRM as an identification tool in natural samples has not become standard practice, perhaps due to the decrease in use of tumbling AF techniques. However, using the 2G SQuID magnetometer with in-line AF/ARM coils and RAPID automated protocols (Kirschvink et al. 2008), one can easily produce and measure RRM. This method of measuring RRM has been used to identify greigite (Suzuki et al. 2006), but not pyrrhotite. We present room temperature RRM measurements for samples spinning from -20 to +20 rev/sec, perpendicular to peak AF fields of 90mT (at 950 Hz) in iron-sulfide-bearing shales, argillites, and carbonates throughout Earth History (Miocene, Cretaceous, Mesoproterozoic, Late Archean). Presence of pyrrhotite was confirmed using AF demagnetization of NRM (GRM), IRM acquisition/AF demagnetization (Cisowski plots), Kappabridge thermal susceptibility, ultra-high resolution scanning SQuID microscopy (UHRSSM), and/or X-ray absorption near edge spectroscopy (XANES)/multiple energy X-ray fluorescence (XRF) imaging. Although the total absence of pyrrhotite cannot be proven, the same techniques were applied to rocks that do not gain RRM easily to identify their iron sulfides and ferromagnetic minerals, and no magnetic iron sulfides were found. The RRM signal for pyrrhotite is distinct from that of greigite, suggesting it could be used as a tool for distinguishing these magnetic iron sulfides from each other. Further work on room temperature RRM could define a unique non-destructive rock magnetic test for pyrrhotite.

  15. Transformations of mercury, iron, and sulfur during the reductive dissolution of iron oxyhydroxide by sulfide

    NASA Astrophysics Data System (ADS)

    Slowey, Aaron J.; Brown, Gordon E.

    2007-02-01

    Methylmercury can accumulate in fish to concentrations unhealthy for humans and other predatory mammals. Most sources of mercury (Hg) emit inorganic species to the environment. Therefore, ecological harm occurs when inorganic Hg is converted to methylmercury. Sulfate- and iron-reducing bacteria (SRB and FeRB) methylate Hg, but the effects of processes involving oxidized and reduced forms of sulfur and iron on the reactivity of Hg, including the propensity of inorganic Hg to be methylated, are poorly understood. Under abiotic conditions, using a laboratory flow reactor, bisulfide (HS -) was added at 40 to 250 μM h -1 to 5 g L -1 goethite (α-FeOOH) suspensions to which Hg(II) was adsorbed (30-100 nmol m -2) at pH 7.5. Dissolved Hg initially decreased from 10 3 or 10 4 nM (depending on initial conditions) to 10 -1 nM, during which the concentration of Hg(II) adsorbed to goethite decreased by 80% and metacinnabar (β-HgS (s)) formed, based on identification using Hg L III-edge extended X-ray absorption fine structure (EXAFS) spectroscopic analysis. The apparent coordination of oxygens surrounding Hg(II), measured with EXAFS spectroscopy, increased during one flow experiment, suggesting desorption of monodentate-bound Hg(II) while bidentate-bound Hg(II) persisted on the goethite surface. Further sulfidation increased dissolved Hg concentrations by one to two orders of magnitude (0.5 to 10 nM or 30 nM), suggesting that byproducts of bisulfide oxidation and Fe(III) reduction, primarily polysulfide and potentially Fe(II), enhanced the dissolution of β-HgS (s) and/or desorption of Hg(II). Rapid accumulation of Fe(II) in the solid phase (up to 40 μmol g -1) coincided with faster elevation of dissolved Hg concentrations. Fe(II) served as a proxy for elemental sulfur [S(0)], as S(0) was the dominant bisulfide oxidation product coupled to Fe(III) reduction, based on sulfur K-edge X-ray absorption near edge structure (XANES) spectroscopy. In one experiment, dissolved Hg

  16. Iron-Nickel Sulfide Compositional Ranges in CM Chondrites: No Simple Plan

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael; Le, Loan

    2003-01-01

    Iron-nickel sulfides are found in most or all solar system environments, and are probably the only minerals found in all extraterrestrial materials on hand. Despite this ubiquity, they have only just begun the attention they deserve. The most common Fe-Ni sulfides in chondrites are troilite (FeS), pyrrhotite (Fe(1-x)S) and pentlandite (Fe,Ni)9S8. Troilite is believed to have resulted from sulfidation of metal (Fe-Ni) grains in an H2S-containing environment. Pyrrhotite is produced when friable troilite grains, which are exfoliated from the metal nucleus, are submitted to continued sulfidation. Some asteroids are known to have experienced aqueous alteration, forming products including new generations of sulfides (pyrrhotite and pentlandite). Pentlandite in particular is known to form during such alteration. However, experimental work by Lauretta has indicated that pentlandite may also have been formed during the initial sulfidation process, due to the faster diffusion rate of nickel into the forming sulfide, as compared to iron. Finally, there is considerable evidence for a family of phases intermediate between pyrrhotite and pentlandite, following the trend of the high temperature monosulfide solid solution, something not encountered in terrestrial rocks. Each sulfide has its own particular stability conditions, which have been determined for most phases. The long-term objective of our research is to characterize sulfides in chondritic materials in order to better establish the conditions under which they formed, and the subsequent processes they experienced. Ultimately, it will be possible to infer whether the sulfides in the chondrites were formed in the solar nebula or on asteroids, and if formed on the asteroids, deduce how much alteration has occurred there. Here we explore the relationships between the finest grain size portions of carbonaceous chondrites, these being matrix and chondrule rims; fine-grained materials are the most sensitive to their environment

  17. Experimental segregation of iron-nickel metal, iron-sulfide, and olivine in a thermal gradient: Preliminary results

    NASA Technical Reports Server (NTRS)

    Jurewicz, Stephen R.; Jones, J. H.

    1993-01-01

    Speculation about the possible mechanisms for core formation in small asteroids raises more questions than answers. Petrologic evidence from iron meteorites, pallasites, and astronomical observations of M asteroids suggests that many small bodies were capable of core formation. Recent work by Taylor reviews the geochemical evidence and examines the possible physical/mechanical constraints on segregation processes. Taylor's evaluation suggests that extensive silicate partial melting (preferably 50 vol. percent or greater) is required before metal can segregate from the surrounding silicate and form a metal core. The arguments for large degrees of silicate partial melting are two-fold: (1) elemental trends in iron meteorites require that the metal was at is liquidus; and (2) experimental observations of metal/sulfide inclusions in partially molten silicate meteorites show that the metal/sulfide tends to form spherules in the liquid silicate due to surface tension effects. Taylor points out that for these metal spherules to sink through a silicate mush, high degrees of silicate partial melting are required to lower the silicate yield strength. Although some qualitative experimental data exists, little is actually known about the behavior of metals and liquid sulfides dispersed in silicate systems. In addition, we have been impressed with the ability of cumulative olivine to expel trapped liquid when placed in a thermal gradient. Consequently, we undertook to accomplish the following: (1) experimentally evaluate the potential for metal/sulfide/silicate segregation in a thermal gradient; and (2) obtain quantitative data of the wetting parameters of metal-sulfide melts among silicate grains.

  18. Effect of growth conditions on microbial activity and iron-sulfide production by Desulfovibrio vulgaris.

    PubMed

    Zhou, Chen; Vannela, Raveender; Hayes, Kim F; Rittmann, Bruce E

    2014-05-15

    Sulfate-reducing bacteria (SRB) can produce iron sulfide (FeS) solids with mineralogical characteristics that may be beneficial for a variety of biogeochemical applications, such as long-term immobilization of uranium. In this study, the growth and metabolism of Desulfovibrio vulgaris, one of the best-studied SRB species, were comprehensively monitored in batch studies, and the biogenic FeS solids were characterized by X-ray diffraction. Controlling the pH by varying the initial pH, the iron-to-sulfate ratio, or the electron donor - affected the growth of D. vulgaris and strongly influenced the formation and growth of FeS solids. In particular, lower pH (from initial conditions or a decrease caused by less sulfate reduction, FeS precipitation, or using pyruvate as the electron donor) produced larger-sized mackinawite (Fe1+xS). Greater accumulation of free sulfide, from more sulfate reduction by D. vulgaris, also led to larger-sized mackinawite and particularly stimulated mackinawite transformation to greigite (Fe3S4) when the free sulfide concentration was 29.3mM. Furthermore, sufficient free Fe(2+) led to the additional formation of vivianite [Fe3(PO4)2·8(H2O)]. Thus, microbially relevant conditions (initial pH, choice of electron donor, and excess or deficiency of sulfide) are tools to generate biogenic FeS solids of different characteristics. PMID:24675611

  19. Geochemical affinities of cobalt and germanium toward metal, silicate, and sulfide phases at high temperature. [in iron meteorites

    NASA Technical Reports Server (NTRS)

    Wai, C. M.

    1974-01-01

    Hydrothermal studies indicate that Co and Ge are strongly siderophile when metallic iron is in equilibrium with olivine at 900 C and 500 bars. If the metal is replaced by troilite (FeS), Ge is strongly lithophile whereas Co tends to concentrate in the sulfide phase. If iron meteorites were formed in a core derived from the sulfide phase, they would be depleted in Ge but retain Co.

  20. Hydrogen sulfide removal from sediment and water in box culverts/storm drains by iron-based granules.

    PubMed

    Sun, J L; Shang, C; Kikkert, G A

    2013-01-01

    A renewable granular iron-based technology for hydrogen sulfide removal from sediment and water in box culverts and storm drains is discussed. Iron granules, including granular ferric hydroxide (GFH), granular ferric oxide (GFO) and rusted waste iron crusts (RWIC) embedded in the sediment phase removed aqueous hydrogen sulfide formed from sedimentary biological sulfate reduction. The exhausted iron granules were exposed to dissolved oxygen and this regeneration process recovered the sulfide removal capacities of the granules. The recovery is likely attributable to the oxidation of the ferrous iron precipitates film and the formation of new reactive ferric iron surface sites on the iron granules and sand particles. GFH and RWIC showed larger sulfide removal capacities in the sediment phase than GFO, likely due to the less ordered crystal structures on their surfaces. This study demonstrates that the iron granules are able to remove hydrogen sulfide from sediment and water in box culverts and storm drains and they have the potential to be regenerated and reused by contacting with dissolved oxygen. PMID:24355850

  1. Geology of the Brick Flat massive sulfide body, Iron Mountain cluster, West Shasta district, California ( USA).

    USGS Publications Warehouse

    Albers, J.P.

    1985-01-01

    The Brick Flat massive sulfide body is one of a group of 8 individual bodies that constitute the Iron Mountain cluster in the S part of the West Shasta district. Before they were separated by postmineral faulting, 5 of the 8 sulfide bodies formed a single large deposit about 1375 m long with a mass of some 23 million metric tons. The pyritic Brick Flat sulfide body is one of the 5 faulted segements of this deposit. The Brick Flat massive sulfide lies within medium phenocryst rhyolite that is characteristic of the ore-bearing middle unit of the Balaklala Rhyolite. It is interpreted to be downfaulted a vertical distance of 75 to 85 m from the Old Mine sulfide-gossan orebody along the N-dipping Camden South fault. It is bounded in turn on its N side by another parallel fault, the Camden North, which drops the orebody down another 75 m to the level of the Richmond orebody. -from Author

  2. Transformation of iron sulfide to greigite by nitrite produced by oil field bacteria.

    PubMed

    Lin, Shiping; Krause, Federico; Voordouw, Gerrit

    2009-05-01

    Nitrate, injected into oil fields, can oxidize sulfide formed by sulfate-reducing bacteria (SRB) through the action of nitrate-reducing sulfide-oxidizing bacteria (NR-SOB). When reservoir rock contains siderite (FeCO(3)), the sulfide formed is immobilized as iron sulfide minerals, e.g. mackinawite (FeS). The aim of our study was to determine the extent to which oil field NR-SOB can oxidize or transform FeS. Because no NR-SOB capable of growth with FeS were isolated, the well-characterized oil field isolate Sulfurimonas sp. strain CVO was used. When strain CVO was presented with a mixture of chemically formed FeS and dissolved sulfide (HS(-)), it only oxidized the HS(-). The FeS remained acid soluble and non-magnetic indicating that it was not transformed. In contrast, when the FeS was formed by adding FeCl(2) to a culture of SRB which gradually produced sulfide, precipitating FeS, and to which strain CVO and nitrate were subsequently added, transformation of the FeS to a magnetic, less acid-soluble form was observed. X-ray diffraction and energy-dispersive spectrometry indicated the transformed mineral to be greigite (Fe(3)S(4)). Addition of nitrite to cultures of SRB, containing microbially formed FeS, was similarly effective. Nitrite reacts chemically with HS(-) to form polysulfide and sulfur (S(0)), which then transforms SRB-formed FeS to greigite, possibly via a sulfur addition pathway (3FeS + S(0) --> Fe(3)S(4)). Further chemical transformation to pyrite (FeS(2)) is expected at higher temperatures (>60 degrees C). Hence, nitrate injection into oil fields may lead to NR-SOB-mediated and chemical mineral transformations, increasing the sulfide-binding capacity of reservoir rock. Because of mineral volume decreases, these transformations may also increase reservoir injectivity. PMID:19290520

  3. Oxidation, carburization and/or sulfidation resistant iron aluminide alloy

    DOEpatents

    Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier S.; Hajaligol, Mohammad R.; Lilly, Jr., A. Clifton

    2003-08-19

    The invention relates generally to aluminum containing iron-base alloys useful as electrical resistance heating elements. The aluminum containing iron-base alloys have improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The alloy has an entirely ferritic microstructure which is free of austenite and includes, in weight %, over 4% Al, .ltoreq.1% Cr and either .gtoreq.0.05% Zr or Zro.sub.2 stringers extending perpendicular to an exposed surface of the heating element or .gtoreq.0.1% oxide dispersoid particles. The alloy can contain 14-32% Al, .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Zr, .ltoreq.1% C, .ltoreq.0.1% B. .ltoreq.30% oxide dispersoid and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, .ltoreq.1% oxygen, .ltoreq.3% Cu, balance Fe.

  4. New Measurements of the Densities of Copper, Nickel, and Iron Sulfide Liquids

    NASA Astrophysics Data System (ADS)

    Mioduszewski, L.; Kress, V. C.

    2005-12-01

    Density measurements of sulfide liquids in the Fe-Ni-Cu-S-O system were performed from 1150°C-1250°C under controlled oxygen and sulfur fugacities. Measurements were made using the modified single bob (MSB) Archimedean method using zirconia ceramic bobs and crucibles. A 0.005mm resolution micrometer was attached to an elevator, which raised the crucible and melt relative to the free-hanging, stationary bob. A 0.001 g resolution analytical balance connected to a laptop computer continuously recorded the buoyancy as a function of crucible elevation. Densities were calculated by converting elevation to immersed volume and regressing the slope of buoyancy versus volume immersed. log(fO2) in the experiments ranged from -7.8 to -12.6 and log(fS2) ranged from -0.9 to -3.3. 38 successful sulfide liquid density measurements were performed, with values ranging from 3.8 g/cc to 6.6 g/cc. Regression of the resulting data suggests that a simple linear volume mixing model is adequate to represent the compositional dependence of density in copper- and nickel-sulfide liquids. A moderate positive excess mixing volume appears to be justified in iron-sulfide liquids. This result, along with high derived partial molar volumes for oxygen and sulfur components, are qualitatively consistent with the suggestion that increasing pressure will partition oxygen and sulfur out of the sulfide liquid during planetary accretion. The MSB density measurement also provides information on the relative magnitude of gas-zirconia and sulfide-zirconia surface energies. Assuming most of the observed variation results from sulfide chemistry it appears that oxidizing conditions significantly decrease sulfide-zirconia surface energies (increase wetting). If we can extrapolate this result to silicate minerals, this would suggest that oxidizing conditions will decrease wetting angle and thus increase the potential for sulfide segregation during planetary formation. We hope to test this hypothesis soon. Our

  5. Removal of copper from carbon-saturated iron with an aluminum sulfide ferrous sulfide flux.

    SciTech Connect

    Cohen, A.; Blander, M.; Energy Technology

    1998-04-01

    Scrap iron and steel have long been considered as resources in the steelmaking industry, and their value is largely determined by the impurity content. Copper is a particularly troublesome impurity because of its role in causing hot shortness and should be kept below ==0.1 wt pct. A method for reducing copper content in steel to <0.1 wt pct could lead to increased use of lower-quality scrap.

  6. Disturbed iron metabolism among workers exposed to organic sulfides in a pulp plant.

    PubMed

    Klingberg, J; Beviz, A; Ohlson, C G; Tenhunen, R

    1988-02-01

    The aim of this study was to investigate a possible relationship between exposure to sulfides and disturbances of the synthesis of heme and the erythrocytes. Eighteen workers exposed to sulfides at a pulp and paper plant were examined and compared with individually matched referents from a thermomechanical pulp plant without such exposure. The exposure levels of methylmercaptan, dimethylsulfide, and dimethyldisulfide were low. However, five subjects were exposed to high levels of short duration, and their data were analyzed separately. The activity of the enzymes delta-aminolevulinic acid synthase and heme synthase in reticulocytes, characteristics of the erythrocytes, and the iron status were analyzed. A minor decrease, not statistically significant, was observed for the enzymes among the five highly exposed subjects. However, the concentrations of iron and transferrin were elevated and the concentration of ferritin was low in comparison to the corresponding levels of the referents. This combination will not occur spontaneously. A previous study indicated that sulfides may inhibit heme synthesis, and the present study suggests that they may also disturb iron metabolism. PMID:3353691

  7. High-temperature oxidation/sulfidation resistance of iron-aluminide coatings

    SciTech Connect

    Tortorelli, P.F.; Wright, I.G.; Goodwin, G.M.; Howell, M.

    1996-04-01

    Iron aluminides containing > 20-25 at. % Al have oxidation and sulfidation resistance at temperatures well above those at which these alloys have adequate mechanical strength. Accordingly, these alloys may find application as coatings or claddings on more conventional higher-strength materials which are generally less corrosion-resistant at high temperatures. To this end, iron-aluminide coatings were prepared by gas tungsten arc and gas metal arc weld-overlay techniques. Specimens were cut from weld deposits and exposed to a highly aggressive oxidizing-sulfidizing (H2S-H2-H2O-Ar) environment at 800 C. All the weld overlayers showed good corrosion behavior under isothermal conditions, including a gas metal arc-produced deposit with only 21 at. % Al. Rapid degradation in corrosion resistance was observed under thermal cycling conditions when the initally grown scales spalled and the rate of reaction was then not controlled by formation of slowly growing Al oxide. Higher starting Al concentrations (> {approximately} 25 at. %) are needed to assure overall oxidation-sulfidation resistance of the weld overlays, but hydrogen cracking susceptibility must be minimized in order to physically separate the corrosive species from the reactive substrate material.

  8. Sulfide oxidation by hydrogen peroxide catalyzed by iron complexes: two metal centers are better than one.

    PubMed

    Mekmouche, Yasmina; Hummel, Helga; Ho, Raymond Y N; Que, Lawrence; Schünemann, Volker; Thomas, Fabrice; Trautwein, Alfred X; Lebrun, Colette; Gorgy, Karine; Leprêtre, Jean-Claude; Collomb, Marie-Noëlle; Deronzier, Alain; Fontecave, Marc; Ménage, Stéphane

    2002-03-01

    Peroxoiron species have been proposed to be involved in catalytic cycles of iron-dependent oxygenases and in some cases as the active intermediates during oxygen-transfer reactions. The catalytic properties of a mononuclear iron complex, [Fe(II)(pb)(2)(CH(3)CN)(2)] (pb=(-)4,5-pinene-2,2'-bipyridine), have been compared to those of its related dinuclear analogue. Each system generates specific peroxo adducts, which are responsible for the oxidation of sulfides to sulfoxides. The dinuclear catalyst was found to be more reactive and (enantio)selective than its mononuclear counterpart, suggesting that a second metal site affords specific advantages for stereoselective catalysis. These results might help for the design of future enantioselective iron catalysts. PMID:11891908

  9. Synthesis and characterisation of magnetic iron sulfide nanocrystals

    SciTech Connect

    Beal, John H.L.; Etchegoin, Pablo G.; Tilley, Richard D.

    2012-05-15

    Fe{sub 1-x}S and Fe{sub 3}S{sub 4} nanocrystals with a variety of morphologies and average sizes were synthesised by the reaction of iron(II) acetylacetonate (Fe(acac){sub 2}) and elemental sulfur in oleylamine. Reaction at 200 Degree-Sign C for 240 min produced extremely thin Fe{sub 3}S{sub 4} sheets, which displayed low coercivities (14 kA m{sup -1}) suggestive of pseudosingle-domain or multidomain particles. Reaction temperatures {>=}300 Degree-Sign C for 30 min produced 70 nm Fe{sub 1-x}S nanocrystals with hexagonal plate and hexagonal prism morphologies, which displayed high magnetic coercivities (110 kA m{sup -1}) characteristic of single magnetic domain particles. Rapid injection of sulfur solution at 280 Degree-Sign C followed by immediate cooling produced a mixture of Fe{sub 1-x}S nanocrystals and spherical, polydisperse {approx}5 nm Fe{sub 3}S{sub 4} nanocrystals, which displayed superparamagnetism above an average blocking temperature of 55 K. - Graphical abstract: Reaction of Fe(acac){sub 2} and sulfur in oleylamine produces Fe{sub 3}S{sub 4} nanocrystals at 200 Degree-Sign C and Fe{sub 1-x}S nanocrystals at 310 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Synthesis of Fe{sub 1-x}S and Fe{sub 3}S{sub 4} nanocrystals from Fe(acac){sub 2} and sulfur. Black-Right-Pointing-Pointer Fe{sub 3}S{sub 4} sheets formed after 4 h at 200 Degree-Sign C. Black-Right-Pointing-Pointer Fe{sub 1-x}S nanocrystals formed above 200 Degree-Sign C. Black-Right-Pointing-Pointer Five nanometre Fe{sub 3}S{sub 4} formed by rapid injection. Black-Right-Pointing-Pointer Five nanometre Fe{sub 3}S{sub 4} nanocrystals superparamagnetic above blocking temperature of 55 K.

  10. Surface chemistry and structural properties of mackinawite prepared by reaction of sulfide ions with metallic iron

    NASA Astrophysics Data System (ADS)

    Mullet, Martine; Boursiquot, Sophie; Abdelmoula, Mustapha; Génin, Jean-Marie; Ehrhardt, Jean-Jacques

    2002-03-01

    Tetragonal FeS 1- x mackinawite, has been synthesized by reacting metallic iron with a sodium sulfide solution and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), transmission Mössbauer spectroscopy (TMS) and X-ray photoelectron spectroscopy (XPS). Based on XRD and TEM analyses, synthetic mackinawite exhibits crystallization and is identical to the natural mineral. Unit cell parameters derived from XRD data are a = b = 0.3670 nm and c = 0.5049 nm. The bulk Fe:S ratio derived from the quantitative dispersive energy analysis is practically 1. XPS analyses, however, showed that mackinawite surface is composed of both Fe(II) and Fe(III) species bound to monosulfide. Accordingly, monosulfide is the dominant S species observed at the surface with lesser amount of polysulfides and elemental sulfur. TMS analysis revealed the presence of both Fe(II) and Fe(III) in the mackinawite structure, thus supporting the XPS analysis. We propose that the iron monosulfide phase synthesized by reacting metallic iron and dissolved sulfide is composed of Fe(II) and S(-II) atoms with the presence of a weathered thin layer covering the bulk material that consists of both Fe(II) and Fe(III) bound to S(-II) atoms and in a less extent of polysulfide and elemental sulfur.

  11. Relationship between the properties of iron sulfides and their catalytic activity

    SciTech Connect

    Stohl, F. V.; Granoff, B.

    1981-01-01

    Iron sulfides, such as pyrite, are known catalysts in coal liquefaction and produce significant increases in both conversion and distillate (850 F/sup -/) yield. The main objective of this work is to increase the catalytic activity of iron sulfides by systematically changing the following properties: composition, source, particle size, surface area, morphology and defect level. Several iron sulfides have been synthesized including pyrite (FeS/sub 2/) with 46.6 wt % Fe, pyrrhotite (Fe/sub 1-x/S) with about 60 wt % Fe and mackinawite (Fe/sub 9/S/sub 8/) with 66.2 wt % Fe. The source variations have included commercial material and minerals. The pyrite particle sizes ranged from -350 to -5..mu..m, the pyrite surface areas varied from 2 to >10 m/sup 2//g, the mackinawite surface areas ranged from 40 to 80 m/sup 2//g, and pyrite morphologies included massive material and a concentrate of framboids from Iowa coal. Moessbauer studies of the pyrrhotites in coal liquefaction residues have shown that there is a direct correlation between conversion and the number of vacancies in the pyrrhotite. Pyrites with enhanced defect levels were prepared by explosively shock loading Robena pyrite at 15 GPa. All these materials have been tested in either tubing reactor or autoclave runs with West Virginia Blacksville No. 2 coal and SRC-II heavy distillate (550/sup 0/F/sup +/). The runs were carried out at 425/sup 0/C, 500 psi H/sub 2/ (cold charge) for 30 minutes with a 7.5 wt % catalyst loading. All these materials have shown catalytic effects as compared to uncatalyzed thermal runs.

  12. Prevention of iron-sulfide deposition in petroleum processing. Final CRADA report.

    SciTech Connect

    Doctor, R. D.; Panchal, C. B.; Energy Systems

    2010-03-25

    The purpose of this CRADA extension which effectively ended in 2003 was to quantify the effect of iron-sulfide formation on the fouling propensity of crude oil. The specific objectives are focused on fouling of the Crude Distillation Unit (CDU-1) at the Shell Refinery in Mobile, Alabama. The technical approach consists of analyzing the plant data, chemical analysis of crude oil to detect key precursors, performing refinery tests using the Argonne Field Fouling Unit, and verifying the effectiveness of a physical device of tube insert and enhanced tubes to change threshold conditions and thereby reducing fouling.

  13. Heterocyclic dithiocarbamato-iron(III) complexes: single-source precursors for aerosol-assisted chemical vapour deposition (AACVD) of iron sulfide thin films.

    PubMed

    Mlowe, Sixberth; Lewis, David J; Malik, Mohammad Azad; Raftery, James; Mubofu, Egid B; O'Brien, Paul; Revaprasadu, Neerish

    2016-02-14

    Tris-(piperidinedithiocarbamato)iron(III) (1) and tris-(tetrahydroquinolinedithiocarbamato)iron(iii) (2) complexes have been synthesized and their single-crystal X-ray structures were determined. Thermogravimetric analysis (TGA) of the complexes showed decomposition to iron sulfide. Both complexes were then used as single-source precursors for the deposition of iron sulfide thin films by aerosol-assisted chemical vapour deposition (AACVD). Energy-dispersive X-ray (EDX) spectroscopy confirmed the formation of iron sulfide films. The addition of tert-butyl thiol almost doubled the sulfur content in the deposited films. Scanning electron microscopy (SEM) images of the iron sulfide films from both complexes showed flakes/leaves/sheets, spherical granules and nanofibres. The sizes and shapes of these crystallites depended on the nature of the precursor, temperature, solvent and the amount of tert-butyl thiol used. The observed optical properties are dependent upon the variation of reaction parameters such as temperature and solvent. Powder X-ray diffraction (p-XRD) studies revealed that pyrrhotite, hexagonal (Fe0.975S), marcasite and smythite (Fe3S4) phases were differently deposited. PMID:26732865

  14. Iron-sulfide-bearing chimneys as potential catalytic energy traps at life's emergence.

    PubMed

    Mielke, Randall E; Robinson, Kirtland J; White, Lauren M; McGlynn, Shawn E; McEachern, Kavan; Bhartia, Rohit; Kanik, Isik; Russell, Michael J

    2011-12-01

    The concept that life emerged where alkaline hydrogen-bearing submarine hot springs exhaled into the most ancient acidulous ocean was used as a working hypothesis to investigate the nature of precipitate membranes. Alkaline solutions at 25-70°C and pH between 8 and 12, bearing HS(-)±silicate, were injected slowly into visi-jars containing ferrous chloride to partially simulate the early ocean on this or any other wet and icy, geologically active rocky world. Dependent on pH and sulfide content, fine tubular chimneys and geodal bubbles were generated with semipermeable walls 4-100 μm thick that comprised radial platelets of nanometric mackinawite [FeS]±ferrous hydroxide [∼Fe(OH)(2)], accompanied by silica and, at the higher temperature, greigite [Fe(3)S(4)]. Within the chimney walls, these platelets define a myriad of micropores. The interior walls of the chimneys host iron sulfide framboids, while, in cases where the alkaline solution has a pH>11 or relatively low sulfide content, their exteriors exhibit radial flanges with a spacing of ∼4 μm that comprise microdendrites of ferrous hydroxide. We speculate that this pattern results from outward and inward radial flow through the chimney walls. The outer Fe(OH)(2) flanges perhaps precipitate where the highly alkaline flow meets the ambient ferrous iron-bearing fluid, while the intervening troughs signal where the acidulous iron-bearing solutions could gain access to the sulfidic and alkaline interior of the chimneys, thereby leading to the precipitation of the framboids. Addition of soluble pentameric peptides enhances membrane durability and accentuates the crenulations on the chimney exteriors. These dynamic patterns may have implications for acid-base catalysis and the natural proton motive force acting through the matrix of the porous inorganic membrane. Thus, within such membranes, steep redox and pH gradients would bear across the nanometric platelets and separate the two counter-flowing solutions

  15. Discovery and Characterization of Iron Sulfide and Polyphosphate Bodies Coexisting in Archaeoglobus fulgidus Cells.

    PubMed

    Toso, Daniel B; Javed, Muhammad Mohsin; Czornyj, Elizabeth; Gunsalus, Robert P; Zhou, Z Hong

    2016-01-01

    Inorganic storage granules have long been recognized in bacterial and eukaryotic cells but were only recently identified in archaeal cells. Here, we report the cellular organization and chemical compositions of storage granules in the Euryarchaeon, Archaeoglobus fulgidus strain VC16, a hyperthermophilic, anaerobic, and sulfate-reducing microorganism. Dense granules were apparent in A. fulgidus cells imaged by cryo electron microscopy (cryoEM) but not so by negative stain electron microscopy. Cryo electron tomography (cryoET) revealed that each cell contains one to several dense granules located near the cell membrane. Energy dispersive X-ray (EDX) spectroscopy and scanning transmission electron microscopy (STEM) show that, surprisingly, each cell contains not just one but often two types of granules with different elemental compositions. One type, named iron sulfide body (ISB), is composed mainly of the elements iron and sulfur plus copper; and the other one, called polyphosphate body (PPB), is composed of phosphorus and oxygen plus magnesium, calcium, and aluminum. PPBs are likely used for energy storage and/or metal sequestration/detoxification. ISBs could result from the reduction of sulfate to sulfide via anaerobic energy harvesting pathways and may be associated with energy and/or metal storage or detoxification. The exceptional ability of these archaeal cells to sequester different elements may have novel bioengineering applications. PMID:27194953

  16. Magnetic sulfide-modified nanoscale zerovalent iron (S-nZVI) for dissolved metal ion removal.

    PubMed

    Su, Yiming; Adeleye, Adeyemi S; Keller, Arturo A; Huang, Yuxiong; Dai, Chaomeng; Zhou, Xuefei; Zhang, Yalei

    2015-05-01

    Sulfide-modified nanoscale zerovalent iron (S-nZVI) is attracting a lot of attention due to its ease of production and high reactivity with organic pollutants. However, its structure is still poorly understood and its potential application in heavy metal remediation has not been explored. Herein, the structure of S-nZVI and its cadmium (Cd) removal performance under different aqueous conditions were carefully investigated. Transmission electron microscopy (TEM) with an energy-dispersive X-ray spectroscopy (EDS) analysis suggested that sulfur was incorporated into the zerovalent iron core. Scanning electron microscopy (SEM) with EDS analysis demonstrated that sulfur was also homogeneously distributed within the nanoparticles. When the concentration of Na2S2O4 was increased during synthesis, a flake-like structure (FeSx) increased significantly. S-nZVI had an optimal Cd removal capacity of 85 mg/g, which was >100% higher than for pristine nZVI. Even at pH 5, over 95% removal efficiency was observed, indicating sulfide compounds played a crucial role in metal ion removal and particle chemical stability. Oxygen impaired the structure of S-nZVI but enhanced Cd removal capacity to about 120 mg/g. Particle aging had no negative effect on removal capacity of S-nZVI, and Cd-containing mixtures remained stable in a two months experiment. S-nZVI can efficiently sequester dissolved metal ions from different contaminated water matrices. PMID:25706223

  17. Discovery and Characterization of Iron Sulfide and Polyphosphate Bodies Coexisting in Archaeoglobus fulgidus Cells

    PubMed Central

    Toso, Daniel B.; Javed, Muhammad Mohsin; Czornyj, Elizabeth; Zhou, Z. Hong

    2016-01-01

    Inorganic storage granules have long been recognized in bacterial and eukaryotic cells but were only recently identified in archaeal cells. Here, we report the cellular organization and chemical compositions of storage granules in the Euryarchaeon, Archaeoglobus fulgidus strain VC16, a hyperthermophilic, anaerobic, and sulfate-reducing microorganism. Dense granules were apparent in A. fulgidus cells imaged by cryo electron microscopy (cryoEM) but not so by negative stain electron microscopy. Cryo electron tomography (cryoET) revealed that each cell contains one to several dense granules located near the cell membrane. Energy dispersive X-ray (EDX) spectroscopy and scanning transmission electron microscopy (STEM) show that, surprisingly, each cell contains not just one but often two types of granules with different elemental compositions. One type, named iron sulfide body (ISB), is composed mainly of the elements iron and sulfur plus copper; and the other one, called polyphosphate body (PPB), is composed of phosphorus and oxygen plus magnesium, calcium, and aluminum. PPBs are likely used for energy storage and/or metal sequestration/detoxification. ISBs could result from the reduction of sulfate to sulfide via anaerobic energy harvesting pathways and may be associated with energy and/or metal storage or detoxification. The exceptional ability of these archaeal cells to sequester different elements may have novel bioengineering applications. PMID:27194953

  18. Discovery and Characterization of Iron Sulfide and Polyphosphate Bodies Coexisting in Archaeoglobus fulgidus Cells

    DOE PAGESBeta

    Toso, Daniel B.; Javed, Muhammad Mohsin; Czornyj, Elizabeth; Gunsalus, Robert P.; Zhou, Z. Hong

    2016-01-01

    Inorganic storage granules have long been recognized in bacterial and eukaryotic cells but were only recently identified in archaeal cells. Here, we report the cellular organization and chemical compositions of storage granules in the Euryarchaeon , Archaeoglobus fulgidus strain VC16, a hyperthermophilic, anaerobic, and sulfate-reducing microorganism. Dense granules were apparent in A. fulgidus cells imaged by cryo electron microscopy (cryoEM) but not so by negative stain electron microscopy. Cryo electron tomography (cryoET) revealed that each cell contains one to several dense granules located near the cell membrane. Energy dispersive X-ray (EDX) spectroscopy and scanning transmission electron microscopy (STEM) showmore » that, surprisingly, each cell contains not just one but often two types of granules with different elemental compositions. One type, named iron sulfide body (ISB), is composed mainly of the elements iron and sulfur plus copper; and the other one, called polyphosphate body (PPB), is composed of phosphorus and oxygen plus magnesium, calcium, and aluminum. PPBs are likely used for energy storage and/or metal sequestration/detoxification. ISBs could result from the reduction of sulfate to sulfide via anaerobic energy harvesting pathways and may be associated with energy and/or metal storage or detoxification. The exceptional ability of these archaeal cells to sequester different elements may have novel bioengineering applications.« less

  19. Ion activity products of iron sulfides in groundwaters: Implications from the Choshui fan-delta, Western Taiwan

    NASA Astrophysics Data System (ADS)

    Chen, Wen-Fu; Liu, Tsung-Kwei

    2005-07-01

    Precipitation of iron sulfides is an important process in groundwater geochemistry because it reduces iron mobility in anaerobic aquifers. Iron sulfides occur in various allotropic forms such as amorphous FeS and pyrite, and their solubility products differ up to 13 orders of magnitude. However, few data for ion activity products (IAP) of iron sulfides defined by the equation: H + + FeS (S) = Fe 2+ + HS - in groundwater have been reported in the literature. We computed IAP values of iron sulfides for 46 groundwater samples from the Choshui fan-delta of Taiwan and 65 samples from other areas of the world. The mean of -log(IAP) values obtained for the 46 samples is 3.07 ± 0.34 (1σ), which is consistent with the solubility constant 3.00 ± 0.12 ( Davison et al., 1999) of amorphous FeS, implying that the anaerobic aquifers in the Choshui fan-delta are still undergoing active sulfate-reduction processes and keeping the groundwater saturated with amorphous FeS. We suggest that the -logKsp value 3.91 of amorphous FeS adopted in the databases for WATEQF and PHREEQC computer programs ought to be revised to 3.00. Otherwise, the saturation indices (SI) calculated by the two computer programs will be an order of magnitude too high.

  20. Abrasive resistance of metastable V-Cr-Mn-Ni spheroidal carbide cast irons using the factorial design method

    NASA Astrophysics Data System (ADS)

    Efremenko, V. G.; Shimizu, K.; Cheiliakh, A. P.; Pastukhova, T. V.; Chabak, Yu. G.; Kusumoto, K.

    2016-06-01

    Full factorial design was used to evaluate the two-body abrasive resistance of 3wt%C-4wt%Mn-1.5wt%Ni spheroidal carbide cast irons with varying vanadium (5.0wt%-10.0wt%) and chromium (up to 9.0wt%) contents. The alloys were quenched at 920°C. The regression equation of wear rate as a function of V and Cr contents was proposed. This regression equation shows that the wear rate decreases with increasing V content because of the growth of spheroidal VC carbide amount. Cr influences the overall response in a complex manner both by reducing the wear rate owing to eutectic carbides (M7C3) and by increasing the wear rate though stabilizing austenite to deformation-induced martensite transformation. This transformation is recognized as an important factor in increasing the abrasive response of the alloys. By analyzing the regression equation, the optimal content ranges are found to be 7.5wt%-10.0wt% for V and 2.5wt%-4.5wt% for Cr, which corresponds to the alloys containing 9vol%-15vol% spheroidal VC carbides, 8vol%-16vol% M7C3, and a metastable austenite/martensite matrix. The wear resistance is 1.9-2.3 times that of the traditional 12wt% V-13wt% Mn spheroidal carbide cast iron.

  1. Arsenic chemistry with sulfide, pyrite, zero-valent iron, and magnetite

    NASA Astrophysics Data System (ADS)

    Sun, Fenglong

    The aim of this thesis is to study the immobilization reactions of arsenic in water. Since compounds containing iron or sulfide are common in most natural and engineered systems, the research focused on the redox reactions and adsorption of arsenic with sulfide, pyrite, zero-valent iron (ZVI), and magnetite which were studied through wet chemistry methods and spectroscopic techniques. The kinetic and thermodynamic information of the reactions of As(V) with S(-II), As(V)/As(III) with pyrite and surface-oxidized pyrite, As(V) with ZVI and acid-treated ZVI, As(III) with magnetite was used to identify mechanisms. The necessity to maintain strictly anoxic conditions was emphasized for the study of arsenic redox chemistry with sulfides and ZVI. The major findings of this research can be stated as follows. First, dissolved sulfide reduced As(V) to lower valences to form a yellow precipitate at acidic pH. The reaction involved the formation of thioarsenic intermediate species. Dissolved O2, granular activated carbon (GAC) and dissolved Fe(II) inhibited the removal of As(V) by sulfide. Elemental sulfur catalyzed the reduction of As(V) by sulfide, which implied the possible benefit of using sulfur-loaded GAC for arsenic removal. Possible reaction mechanisms were discussed. Second, As(III) adsorbed on pristine pyrite over a broader pH range than on surface-oxidized pyrite, while As(V) adsorbed over a narrower pH range with pristine pyrite. As(V) was completely reduced to As(III) on pristine pyrite at acidic pH but not at higher pH. The reduction was first-order with respect to As(V). As(V) was not reduced on surface-oxidized pyrite at pH = 4--11. The different behaviors of As(V) and As(III) on pristine and surface oxidized pyrite determines the toxicity and mobility of arsenic under oxic/anoxic environments. Third, commercial ZVI reduced As(V) to As(III) at low pH (<9) but not at higher pH. Acid-treated ZVI reduced As(V) to As(0), indicated by wet chemical analyses and by

  2. Involvement of sulfide:quinone oxidoreductase in sulfur oxidation of an acidophilic iron-oxidizing bacterium, Acidithiobacillus ferrooxidans NASF-1.

    PubMed

    Wakai, Satoshi; Kikumoto, Mei; Kanao, Tadayoshi; Kamimura, Kazuo

    2004-12-01

    The effects of cyanide, azide, and 2-n-Heptyl-4-hydroxy-quinoline-N-oxide (HQNO) on the oxidation of ferrous ion or elemental sulfur with Acidithiobacillus ferrooxidans NASF-1 cells grown in iron- or sulfur-medium were examined. The iron oxidation of both iron- and sulfur-grown cells was strongly inhibited by cyanide and azide, but not by HQNO. Sulfur oxidation was relatively resistant to cyanide and azide, and inhibited by HQNO. Higher sulfide oxidation, ubiquinol dehydrogenase activity, and sulfide:quinone oxidoreductase (SQR) activity were observed in sulfur-grown cells more than in iron-grown cells. Sulfide oxidation in the presence of ubiquinone with the membrane fraction was inhibited by HQNO, but not by cyanide, azide, antimycin A, and myxothiazol. The transcription of three genes, encoding an aa(3)-type cytochrome c oxidase (coxB), a bd-type ubiquinol oxidase (cydA), and an sqr, were measured by real-time reverse transcription polymerase chain reaction. The transcriptional levels of coxB and cydA genes were similar in sulfur- and iron-grown cells, but that of sqr was 3-fold higher in sulfur-grown cells than in iron-grown cells. A model is proposed for the oxidation of reduced inorganic sulfur compounds in A. ferrooxidans NASF-1 cells. PMID:15618623

  3. Influence of iron sulfides on abiotic oxidation of UO2 by nitrite and dissolved oxygen in natural sediments.

    PubMed

    Carpenter, Julian; Bi, Yuqiang; Hayes, Kim F

    2015-01-20

    Iron sulfide precipitates formed under sulfate reducing conditions may buffer U(IV) insoluble solid phases from reoxidation after oxidants re-enter the reducing zone. In this study, sediment column experiments were performed to quantify the effect of biogenic mackinawite on U(IV) stability in the presence of nitrite or dissolved oxygen (DO). Two columns, packed with sediment from an abandoned U contaminated mill tailings site near Rifle, CO, were biostimulated for 62 days with an electron donor (3 mM acetate) in the presence (BRS+) and absence (BRS−) of 7 mM sulfate. The bioreduced sediment was supplemented with synthetic uraninite (UO2(s)), sterilized by gamma-irradiation, and then subjected to a sequential oxidation by nitrite and DO. Biogenic iron sulfides produced in the BRS+ column, mostly as mackinawite, inhibited U(IV) reoxidation and mobilization by both nitrite and oxygen. Most of the influent nitrite (0.53 mM) exited the columns without oxidizing UO2, while a small amount of nitrite was consumed by iron sulfides precipitates. An additional 10-day supply of 0.25 mM DO influent resulted in the release of about 10% and 49% of total U in BRS+ and BRS– columns, respectively. Influent DO was effectively consumed by biogenic iron sulfides in the BRS+ column, while DO and a large U spike were detected after only a brief period in the effluent in the BRS– column. PMID:25525972

  4. Rates of microbial sulfate reduction control the sizes of biogenic iron sulfide aggregates

    NASA Astrophysics Data System (ADS)

    Jin, Q.

    2005-12-01

    Sulfide minerals occur widely in freshwater and marine sediments as byproducts of microbial sulfate reduction and as end products of heavy metal bioremediation. They form when metals in the environments combine with sulfide produced from the metabolism of sulfate reducing bacteria. We used chemostat bioreactors to study sizes and crystal structures of iron sulfide (FeS) minerals produced by Desulfovibrio vulgaris, D. desulfuricans strain G20, and subspecies desulfuricans. FeS nanoparticles and their aggregates are characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and dynamic light scattering (DLS). FeS nanoparticles produced by sulfate reducing bacteria are extremely small, usually less than around 10 nm in diameter. Nanoparticles do not occur as individual nanoparticles, but as aggregates. The sizes of FeS aggregates are affected by sulfate reduction rates, Fe(II) concentration, pH, ionic strength, organic matter concentration, bacterial species, etc. Aggregate size ranges from about 500 nm at very large sulfate reduction rates to about 1,500 nm at very small rates. Variations in Fe(II) concentration also lead to a difference up to 500 nm in FeS aggregate size. Different bacterial species produce nanoparticle aggregates of different sizes under similar growth conditions. For example, D. vulgaris produces FeS aggregates with sizes 500 nm smaller than those by strain G20. The inverse relationship between FeS aggregate sizes and sulfate reduction rates is important in evaluating metal bioremediation strategies. Previous approaches have focused on stimulating microbial activities in natural environments. However, our experimental results suggest that increasing metabolic rates may decrease the aggregate size, increasing the mobility of colloidal aggregates. Therefore, the balance between microbial activities and sizes of biogenic aggregates may be an important consideration in the design and

  5. Application of iron sulfide particles for groundwater and soil remediation: A review.

    PubMed

    Gong, Yanyan; Tang, Jingchun; Zhao, Dongye

    2016-02-01

    Rapid industrialization and urbanization have resulted in elevated concentrations of hazardous inorganic and organic contaminants in groundwater and soil, which has become a paramount concern to the environment and the public health. In recent years, iron sulfide (FeS), a major constituent of acid-volatile sulfides, has elicited extensive interests in environmental remediation due to its ubiquitous presence and high treatment efficiency in anoxic environment. This paper provides a comprehensive review on recent advances in: (1) synthesis of FeS particles (including nanoscale FeS); and (2) reactivity of FeS towards a variety of common environmental contaminants in groundwater and soil over extended periods of time, namely, heavy metals (Hg(II), Cu(II), Pb(II), and Cr(VI)), oxyanions (arsenite, arsenate, selenite, and selenate), radionuclides (e.g., uranium (U) and neptunium (Np)), chlorinated organic compounds (e.g., trichloroethane, trichloroethylene, and p-chloroaniline), nitroaromatic compounds, and polychlorinated biphenyls. Different physiochemical and biological methods for preparing FeS with desired particle size, structure, and surface properties are discussed. Reaction principles and removal effectiveness/constraints are discussed in details. Special attention is placed to the application of nanoscale FeS particles because of their unique properties, such as small particle size, large specific surface area, high surface reactivity, and soil deliverability in the subsurface. Moreover, current knowledge gaps and further research needs are identified. PMID:26707732

  6. Self-heating of dried industrial tannery wastewater sludge induced by pyrophoric iron sulfides formation.

    PubMed

    Bertani, R; Biasin, A; Canu, P; Della Zassa, M; Refosco, D; Simionato, F; Zerlottin, M

    2016-03-15

    Similarly to many powders of solids, dried sludge originated from tannery wastewater may result in a self-heating process, under given circumstances. In most cases, it causes a moderate heating (reaching 70-90°C), but larger, off-design residence times in the drier, in a suboxic atmosphere, extremely reactive solids can be produced. Tannery waste contains several chemicals that mostly end up in the wastewater treatment sludge. Unexpected and uncontrolled self heating could lead to a combustion and even to environmental problems. Elaborating on previous studies, with the addition of several analytical determinations, before and after the self-heating, we attempted to formulate a mechanism for the onset of heating. We demonstrated that the system Fe/S/O has been involved in the process. We proved that the formation of small quantities of pyrophoric iron sulfides is the key. They are converted to sulfated by reaction with water and oxygen with exothermic processes. The pyrite/pyrrhotite production depends on the sludge drying process. The oxidation of sulfides to oxides and sulfates through exothermic steps, reasonably catalyzed by metals in the sludge, occurs preferentially in a moist environment. The mechanism has been proved by reproducing in the laboratory prolonged heating under anoxic/suboxic atmosphere. PMID:26651067

  7. Mössbauer study of electrochemically deposited amorphous iron-sulfide-oxide thin films

    NASA Astrophysics Data System (ADS)

    Ichimura, Masaya; Kajima, Takahiro; Kawai, Shoichi; Mibu, Ko

    2016-03-01

    Iron-sulfide-oxide thin films, which are promising candidates for solar cell materials, were deposited by electrochemical deposition. As-deposited and annealed films were characterized by Mössbauer spectroscopy, X-ray diffraction (XRD), and Raman scattering at room temperature. The as-deposited film is amorphous, and the oxygen content is about 1/4 of the sulfur content (S/Fe ≈ 1.5, O/Fe ≈ 0.4). The Mössbauer spectrum for the as-deposited film is a doublet with a broad line profile having hyperfine parameters similar to those of FeS2 pyrite or marcasite. This indicates that Fe atoms are in the Fe2+ low-spin state, as in FeS2.

  8. Highly siderophile elements were stripped from Earth's mantle by iron sulfide segregation.

    PubMed

    Rubie, David C; Laurenz, Vera; Jacobson, Seth A; Morbidelli, Alessandro; Palme, Herbert; Vogel, Antje K; Frost, Daniel J

    2016-09-01

    Highly siderophile elements (HSEs) are strongly depleted in the bulk silicate Earth (BSE) but are present in near-chondritic relative abundances. The conventional explanation is that the HSEs were stripped from the mantle by the segregation of metal during core formation but were added back in near-chondritic proportions by late accretion, after core formation had ceased. Here we show that metal-silicate equilibration and segregation during Earth's core formation actually increased HSE mantle concentrations because HSE partition coefficients are relatively low at the high pressures of core formation within Earth. The pervasive exsolution and segregation of iron sulfide liquid from silicate liquid (the "Hadean matte") stripped magma oceans of HSEs during cooling and crystallization, before late accretion, and resulted in slightly suprachondritic palladium/iridium and ruthenium/iridium ratios. PMID:27609889

  9. Immobilization of heavy metals in electroplating sludge by biochar and iron sulfide.

    PubMed

    Lyu, Honghong; Gong, Yanyan; Tang, Jingcshun; Huang, Yao; Wang, Qilin

    2016-07-01

    Electroplating sludge (ES) containing large quantities of heavy metals is regarded as a hazardous waste in China. This paper introduced a simple method of treating ES using environmentally friendly fixatives biochar (BC) and iron sulfide (FeS), respectively. After 3 days of treatment with FeS at a FeS-to-ES mass ratio of 1:5, the toxicity characteristic leaching procedure (TCLP)-based leachability of total Cr (TCr), Cu(II), Ni(II), Pb(II), and Zn(II) was decreased by 59.6, 100, 63.8, 73.5, and 90.5 %, respectively. After 5 days of treatment with BC at a BC-to-ES mass ratio of 1:2, the TCLP-based leachability was declined by 35.1, 30.6, 22.3, 23.1, and 22.4 %, respectively. Pseudo first-order kinetic model adequately simulated the sorption kinetic data. Structure and morphology analysis showed that adsorption, electrostatic attraction, surface complexation, and chemical precipitation were dominant mechanisms for heavy metals immobilization by BC, and that chemical precipitation (formation of metal sulfide and hydroxide precipitates), iron exchange (formation of CuFeS2), and surface complexation were mainly responsible for heavy metals removal by FeS. Economic costs of BC and FeS were 500 and 768 CNY/t, lower than that of Na2S (940 CNY/t). The results suggest that BC and FeS are effective, economic, and environmentally friendly fixatives for immobilization of heavy metals in ES before landfill disposal. PMID:27068904

  10. Aqueous Iron-Sulfide Clusters in Variably Saturated Soil Systems: Implications for Iron Cycling and Fluid Flow

    NASA Astrophysics Data System (ADS)

    McGuire, J. T.; Hansen, D. J.; Mohanty, B. P.

    2008-12-01

    Iron and sulfur cycling is an important control on contaminant fate and transport, the availability of micronutrients and the physics of water flow. This study explores the effects of soil structure (i.e. layers, lenses, macropores, or fractures) on linked biogeochemical and hydrological processes involving Fe and S cycling in the vadose zone using packed soil columns. Three laboratory soil columns were constructed: a homogenized medium-grained sand, homogenized organic-rich loam, and a sand-over-loam layered column. Both upward and downward infiltration of water was evaluated during experiments to simulate rising water table and rainfall events respectively. Water samples extracted by lysimeter were analyzed for reduced species (including total sulfide, Fe(II), and FeSaq) voltammetrically using a mercury drop electrode. In addition to other reduced species, aqueous FeS clusters (FeSaq) were observed in two of the columns, with the greatest concentrations of FeSaq occurring in close proximity to the soil interface in the layered column. To our knowledge, this is the first documentation of aqueous FeS clusters in partially saturated sediments. The aqueous nature of FeSaq allows it to be transported instead of precipitating and suggests that current conceptual models of iron-sulfur cycling may need to be adapted to account for an aqueous phase. The presence of iron-rich soil aggregates near the soil interface may indicate that FeS clusters played a critical role in the formation of soil aggregates that subsequently caused up to an order of magnitude decrease in hydraulic conductivity.

  11. Sulfidization of Organic Freshwater Flocs from a Minerotrophic Peatland: Speciation Changes of Iron, Sulfur, and Arsenic.

    PubMed

    ThomasArrigo, Laurel K; Mikutta, Christian; Lohmayer, Regina; Planer-Friedrich, Britta; Kretzschmar, Ruben

    2016-04-01

    Iron-rich organic flocs are frequently observed in surface waters of wetlands and show a high affinity for trace metal(loid)s. Under low-flow stream conditions, flocs may settle, become buried, and eventually be subjected to reducing conditions facilitating trace metal(loid) release. In this study, we reacted freshwater flocs (704-1280 mg As/kg) from a minerotrophic peatland (Gola di Lago, Switzerland) with sulfide (5.2 mM, S(-II)spike/Fe = 0.75-1.62 mol/mol) at neutral pH and studied the speciation changes of Fe, S, and As at 25 ± 1 °C over 1 week through a combination of synchrotron X-ray techniques and wet-chemical analyses. Sulfidization of floc ferrihydrite and nanocrystalline lepidocrocite caused the rapid formation of mackinawite (52-81% of Fesolid at day 7) as well as solid-phase associated S(0) and polysulfides. Ferrihydrite was preferentially reduced over lepidocrocite, although neoformation of lepidocrocite from ferrihydrite could not be excluded. Sulfide-reacted flocs contained primarily arsenate (47-72%) which preferentially adsorbed to Fe(III)-(oxyhydr)oxides, despite abundant mackinawite precipitation. At higher S(-II)spike/Fe molar ratios (≥1.0), the formation of an orpiment-like phase accounted for up to 35% of solid-phase As. Despite Fe and As sulfide precipitation and the presence of residual Fe(III)-(oxyhydr)oxides, mobilization of As was recorded in all samples (Asaq = 0.45-7.0 μM at 7 days). Aqueous As speciation analyses documented the formation of thioarsenates contributing up to 33% of Asaq. Our findings show that freshwater flocs from the Gola di Lago peatland may become a source of As under sulfate-reducing conditions and emphasize the pivotal role Fe-rich organic freshwater flocs play in trace metal(loid) cycling in S-rich wetlands characterized by oscillating redox conditions. PMID:26967672

  12. Effect of iron sulfides on space weathering: Lessons from the Itokawa particles and laboratory simulations

    NASA Astrophysics Data System (ADS)

    Okazaki, M.; Sasaki, S.; Tsuchiyama, A.; Miyake, A.; Matsumoto, T.; Hirata, T.; Hiroi, T.

    2014-07-01

    Space weathering is the process invoked to explain the spectral mismatch between S-type asteroids and ordinary chondrites: darkening, spectral reddening, and attenuation of absorption bands in the reflectance spectra. These changes of optical properties of the surface of airless silicate bodies are explained by nanophase metallic iron (nanoFe) particles, which are formed on regolith particles by high-velocity dust impacts as well as irradiation of the solar-wind ions (Hapke 2001). Those nanoFe particles were discovered in lunar soils, Kapoeta meteorite, and regolith grains from the surface of S-type asteroid Itokawa. Experimental studies using a nano-second-pulse laser confirmed that nanoFe should control the spectral darkening and reddening. The observed reddening of S-type asteroid families is correlated with dynamical asteroid ages after family-forming disruption (Jedicke, et al. 2004). Still, experiments showed that the weathering degree should depend on the composition such as the olivine/pyroxene ratio (Hiroi and Sasaki 2001). In ordinary chondrites, iron sulfides, typically, troilite FeS is the main sulfur-bearing mineral. TEM observation of a dust grain of Itokawa showed the presence of not only iron, but also nanophase FeS particles, which are embedded within a vapor-deposited thin surface layer (thinner than 10-15 nm; Noguchi et al. 2011). One of the Itokawa grains is composed mainly of FeS (about 40 microns) with smaller olivine and pyroxene particles (Yada et al., 2014). On the other hand, the surface sulfur depletion of S-type asteroid Eros was explained by the same mechanism (high-velocity dust and solar-wind particle impacts) of space weathering (Loeffler et al. 2008). To examine the effect of FeS on the surface optical properties of silicate bodies, we conducted pulse-laser irradiation experiments on mixtures of olivine (and pyroxene) and FeS particles with typical sizes of 45--75 micron, for varying FeS fractions (0--0.2 by weight). We find that

  13. Evaluation of the diagenetic role of iron as a sulfide buffer at Cape Lookout Bight, North Carolina (USA)

    NASA Astrophysics Data System (ADS)

    He, B.; Meyers, S. R.; Alperin, M.

    2009-12-01

    Iron availability has critical impacts on primary productivity (micronutrient for cyanobacteria) and organic matter decomposition, as well as sedimentary diagenesis. This study is investigating the hypothesis that changes in iron concentration within marine sediments can control organic matter burial, via early diagenetic processes that impact pore water sulfide concentration (iron sulfidization), and phosphorus return flux to the water column (iron scavenging phosphorus and changing redox condition within sediments). The initial phase of this study is specifically focused on the diagenetic role of iron as a sulfide buffer in pore water, and its impact on bioturbation/bioirrigation. In this presentation, we outline a new approach to investigate the biogeochemistry of iron during early diagenesis, using controlled laboratory macrocosm experiments. Organic-rich coastal marine sediments were collected from Cape Lookout Bight (Outer Banks, North Carolina), a shallow coastal marine environment (depth < 8m) with an oxygenated water column, but organic-rich sediments dominated by sulfate reduction and methanogenesis. The uppermost portion of each sediment core was amended with synthetic sediment composed of kaolinite, variable amounts of hematite, and a geochemical tracer used to monitor bioturbation (samarium). The impact of iron concentration on oxygen penetration depth and bioturbation/bioirrigation is assessed using (1) detailed contour mapping of oxygen microelectrode measurements, and (2) X-ray fluorescence scanning of sub cores, which allows quantification for bioturbation induced samarium redistribution. The results from the experiments and employed statistical approaches (linear regressions and ANOVA) suggest that the oxygen penetration depth is determined by the number of the organisms in the sediments and the amount of iron addition. Future macrocosm study will develop quantitative diagenetic models that can provide insights for investigations of ancient

  14. Sulfidation of Nano Zerovalent Iron (nZVI) for Improved Selectivity During In-Situ Chemical Reduction (ISCR).

    PubMed

    Fan, Dimin; O'Brien Johnson, Graham; Tratnyek, Paul G; Johnson, Richard L

    2016-09-01

    The high reactivity of nano zerovalent iron (nZVI) leads to inefficient treatment due to competition with various natural reductant demand (NRD) processes, especially the reduction of water to hydrogen. Here we show that this limitation can be alleviated by sulfidation (i.e., modification by reducing sulfur compounds). nZVI synthesized on carboxylmethylcelluose (CMC-nZVI) was sulfidated with either sulfide or dithionite. The reactivity of the resulting materials was examined with three complementary assays: (i) direct measurement of hydrogen production, (ii) reduction of a colorimetric redox probe (indigo disulfonate, I2S), and (iii) dechlorination of trichloroethylene (TCE). The results indicate that sulfidation at S/Fe molar ratios of ≥0.3, effectively eliminates reaction with water, but retains significant reactivity with TCE. However, sulfidation with sulfide leaves most of the nZVI as Fe(0), whereas dithionite converts a majority of the nZVI to FeS (thus consuming much of the reducing capacity originally provided by the Fe(0)). Simplified numerical models show that the reduction kinetics of I2S and TCE are mainly dependent on the initial reducing equivalents and that the TCE reduction rate is affected by the aging of FeS. Overall, the results suggest that pretreatment of nZVI with reducing sulfur compounds could result in substantial improvement in nZVI selectivity. PMID:27454131

  15. Sulfur isotope patterns of iron sulfide and barite nodules in the Upper Cretaceous Chalk of England and their regional significance in the origin of coloured chalks

    NASA Astrophysics Data System (ADS)

    Jeans, Christopher V.; Turchyn, Alexandra V.; Hu, Xu-Fang

    2016-06-01

    The relationship between the development of iron sulfide and barite nodules in the Cenomanian Chalk of England and the presence of a red hematitic pigment has been investigated using sulfur isotopes. In southern England where red and pink chalks are absent, iron sulfide nodules are widespread. Two typical large iron sulfide nodules exhibit δ34S ranging from -48.6‰ at their core to -32.6‰ at their outer margins. In eastern England, where red and pink chalks occur in three main bands, there is an antipathetic relationship between the coloured chalks and the occurrence of iron sulfide or barite nodules. Here iron sulfide, or its oxidised remnants, are restricted to two situations: (1) in association with hard grounds that developed originally in chalks that contained the hematite pigment or its postulated precursor FeOH3, or (2) in regional sulfidization zones that cut across the stratigraphy. In the Cenomanian Chalk exposed in the cliffs at Speeton, Yorkshire, pyrite and marcasite (both iron sulfide) nodules range in δ34S from -34.7‰ to +40.0‰. In the lower part of the section δ34S vary from -34.8‰ to +7.8‰, a single barite nodule has δ34S between +26.9‰ and +29.9‰. In the middle part of the section δ34S ranges from +23.8‰ to +40.0‰. In the sulfidization zones that cut across the Cenomanian Chalk of Lincolnshire the iron sulfide nodules are typically heavily weathered but these may contain patches of unoxidised pyrite. In these zones, δ34S ranges from -32.9‰ to +7.9‰. The cross-cutting zones of sulfidization in eastern England are linked to three basement faults - the Flamborough Head Fault Zone, the Caistor Fault and the postulated Wash Line of Jeans (1980) - that have affected the deposition of the Chalk. It is argued that these faults have been both the conduits by which allochthonous fluids - rich in hydrogen sulfide/sulfate, hydrocarbons and possibly charged with sulfate-reducing bacteria - have penetrated the Cenomanian Chalk as

  16. Deposition of iron sulfide thin films by AACVD from single source precursors

    NASA Astrophysics Data System (ADS)

    Akhtar, Masood; Abdelhady, Ahmed Lutfi; Azad Malik, M.; O'Brien, Paul

    2012-05-01

    The unsymmetrical [Fe(S2CNEtiPr)3] (1), [Fe(S2CNEtMe)3] (2) and symmetrical [Fe(S2CN(Hex)2)3] (3), [Fe(S2CN(Et)2)3] (4) tris(dialkyldithiocarbamato)iron(III) complexes were used as single source precursors for the deposition of iron sulfide thin films by the aerosol assisted chemical vapor Deposition (AACVD) method. The unsymmetrical complexes deposited the mixed phases (pyrite and marcasite) at all deposition temperatures except the complex (2) which deposited pyrite and pyrrhotite at 400 °C. The symmetrical complex (3) with longer alkyl groups produced a mixture of pyrite and pyrrhotite phases at 350 and 450 °C but pyrite and mackinawite at 400 °C whereas the complex (4) with shorter alkyl groups deposited a mixture of pyrite and marcasite at 350 °C but a pure pyrrhotite phase at 400 and 450 °C.

  17. Permeability of iron sulfide (FeS)-based materials for groundwater remediation.

    PubMed

    Henderson, Andrew D; Demond, Avery H

    2013-03-01

    Iron sulfide (FeS) has been extensively assessed as a reactive medium to remove both metals and halogenated organics from groundwater. However, to address its suitability as a material for permeable reactive barriers (PRBs), its propensity for solids and gas production, which result in reduced permeability, must be evaluated. The reduction in permeability for sands coated with FeS (as mackinawite), under the anoxic conditions often encountered at contaminated groundwater sites, was examined through column experiments and geochemical modeling under conditions of high calcium and nitrate, which have been previously shown to cause significant permeability reduction in zero-valent iron (ZVI) systems. The column experiments showed negligible production of both solids and gases. The geochemical modeling predicted a maximum reduction in permeability of 1% due to solids and about 30% due to gas formation under conditions for which a complete loss of permeability was predicted for ZVI systems. This difference in permeability reduction is driven by the differences in thermodynamic stability of ZVI and FeS in aqueous solutions. The results suggest that geochemical conditions that result in high permeability losses for ZVI systems will likely not be problematic for FeS-based reactive materials. PMID:23246668

  18. Iron sulfides and sulfur species produced at hematite surfaces in the presence of sulfate-reducing bacteria 1

    NASA Astrophysics Data System (ADS)

    Neal, Andrew L.; Techkarnjanaruk, Somkiet; Dohnalkova, Alice; McCready, David; Peyton, Brent M.; Geesey, Gill G.

    2001-01-01

    In the presence of sulfate-reducing bacteria ( Desulfovibrio desulfuricans) hematite (α-Fe 2O 3) dissolution is affected potentially by a combination of enzymatic (hydrogenase) reduction and hydrogen sulfide oxidation. As a consequence, ferrous ions are free to react with excess H 2S to form insoluble ferrous sulfides. X-ray photoelectron spectra indicate binding energies similar to ferrous sulfides having pyrrhotite-like structures (Fe2 p3/2 708.4 eV; S2 p3/2 161.5 eV). Other sulfur species identified at the surface include sulfate, sulfite and polysulfides. Thin film X-ray diffraction identifies a limited number of peaks, the principal one of which may be assigned to the hexagonal pyrrhotite (102) peak (d = 2.09 Å; 2θ = 43.22°), at the hematite surface within 3 months exposure to sulfate-reducing bacteria (SRB). High-resolution transmission electron microscopy identifies the presence of a hexagonal structure associated with observed crystallites. Although none of the analytical techniques employed provide unequivocal evidence as to the nature of the ferrous sulfide formed in the presence of SRB at hematite surfaces, we conclude from the available evidence that a pyrrhotite stiochiometry and structure is the best description of the sulfides we observe. Such ferrous sulfide production is inconsistent with previous reports in which mackinawite and greigite were products of biological sulfate reduction (Rickard 1969a; Herbert et al., 1998; Benning et al., 1999). The apparent differences in stoichiometry may be related to sulfide activity at the mineral surface, controlled in part by H 2S autooxidation in the presence of iron oxides. Due to the relative stability of pyrrhotite at low temperatures, ferrous sulfide dissolution is likely to be reduced compared to the more commonly observed products of SRB activity. Additionally, biogenic pyrrhotite formation will also have implications for geomagnetic field behavior of sediments.

  19. Polymersomes containing iron sulfide (FeS) as primordial cell model : for the investigation of energy providing redox reactions.

    PubMed

    Alpermann, Theodor; Rüdel, Kristin; Rüger, Ronny; Steiniger, Frank; Nietzsche, Sandor; Filiz, Volkan; Förster, Stephan; Fahr, Alfred; Weigand, Wolfgang

    2011-04-01

    According to Wächtershäuser's "Iron-Sulfur-World" one major requirement for the development of life on the prebiotic Earth is compartmentalization. Vesicles spontaneously formed from amphiphilic components containing a specific set of molecules including sulfide minerals may have lead to the first autotrophic prebiotic units. The iron sulfide minerals may have been formed by geological conversions in the environment of deep-sea volcanos (black smokers), which can be observed even today. Wächtershäuser postulated the evolution of chemical pathways as fundamentals of the origin of life on earth. In contrast to the classical Miller-Urey experiment, depending on external energy sources, the "Iron-Sulfur-World" is based on the catalytic and energy reproducing redox system FeS+H2S-->FeS2+H2. The energy release out of this redox reaction (∆RG°=-38 kJ/mol, pH 0) could be the cause for the subsequent synthesis of complex organic molecules and the precondition for the development of more complex units similar to cells known today. Here we show the possibility for precipitating iron sulfide inside vesicles composed of amphiphilic block-copolymers as a model system for a first prebiotic unit. Our findings could be an indication for a chemoautotrophic FeS based origin of life. PMID:20697814

  20. Polymersomes Containing Iron Sulfide (FeS) as Primordial Cell Model. For the investigation of energy providing redox reactions

    NASA Astrophysics Data System (ADS)

    Alpermann, Theodor; Rüdel, Kristin; Rüger, Ronny; Steiniger, Frank; Nietzsche, Sandor; Filiz, Volkan; Förster, Stephan; Fahr, Alfred; Weigand, Wolfgang

    2011-04-01

    According to Wächtershäuser's "Iron-Sulfur-World" one major requirement for the development of life on the prebiotic Earth is compartmentalization. Vesicles spontaneously formed from amphiphilic components containing a specific set of molecules including sulfide minerals may have lead to the first autotrophic prebiotic units. The iron sulfide minerals may have been formed by geological conversions in the environment of deep-sea volcanos (black smokers), which can be observed even today. Wächtershäuser postulated the evolution of chemical pathways as fundamentals of the origin of life on earth. In contrast to the classical Miller-Urey experiment, depending on external energy sources, the "Iron-Sulfur-World" is based on the catalytic and energy reproducing redox system FeS + {H_2}S to FeS{}_2 + {H_2} . The energy release out of this redox reaction (∆RG° = -38 kJ/mol, pH 0) could be the cause for the subsequent synthesis of complex organic molecules and the precondition for the development of more complex units similar to cells known today. Here we show the possibility for precipitating iron sulfide inside vesicles composed of amphiphilic block-copolymers as a model system for a first prebiotic unit. Our findings could be an indication for a chemoautotrophic FeS based origin of life.

  1. Possible Evidence for Iron Sulfates, Iron Sulfides, and Elemental Sulfur at Gusev Crater, Mars, from Mer, Crism, and Analog Data

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; Ming, D. W.; Yen, A.; Arvidson, R. E.; Gruener, J.; Humm, D.; Klingelhoefer, G.; Murchie, S.; Schroeder, C.; Seelos, F., IV; Squyres, S.; Wiseman, S.; Wolff, M.

    2007-01-01

    The Mossbauer (MB) spectrometers on the Mars Exploration Rovers (MER) Spirit (Gusev crater) and Opportunity (Meridiani Planum) have detected 14 Fe-bearing phases, and mineralogical assignments have been made for all except 3. Identified Fe2+-bearing phases are olivine, pyroxene, ilmenite, and troilite. Magnetite and chromite are present as mixed Fe(2+) and Fe(3+) phases. Identified Fe(3+) phase are jarosite, hematite, goethite, and nanophase ferric oxide (npOx). Fe(sup 0) (iron metal) is present as kamacite. Nanophase ferric oxide (npOx) is a generic name for octahedrally coordinated Fe(3+) alteration products that cannot be otherwise mineralogically assigned on the basis of MER data. On the Earth, npOx would include ferrihydrite, iddingsite, schwertmannite, akaganeite, and superparamagnetic hematite and goethite. The Mars Reconnaissance Orbiter CRISM instrument, a visible, near-IR hyperspectral imager (approximately 0.35 to 4 micron) enables mineralogical examination of Mars with a tool that is sensitive to H2O and to M-OH (M = Al, Si, Fe, Mg, etc.) at spatial resolution of about 20 m/pixel. We examined a CRISM image of the MER region of Gusev crater (Columbia Hills and plains to the west), looking for spectral evidence of the aqueous process apparent from the MER analyses. We also searched for spectral constraints for the mineralogical composition of our unidentified Fe-bearing phases and the forms of npOx present on Mars. We also consider evidence from analogue samples that the precursor for the goethite detected by MB in Clovis Class rocks is an iron sulfide. We suggest that there is some indirect evidence that elemental sulfur might be present to different extents in Clovis Class rocks, the Fe3Sulfate-rich soils, and perhaps even typical (Laguna Class) surface soils.

  2. Studies on the regeneration of sulfided iron oxide sorbent with steam-air mixtures. Final technical report

    SciTech Connect

    Tamhankar, S.S.

    1982-10-01

    The work reported here was performed as a continuation of studies conducted previously at West Virginia University (WVU), Department of Chemical Engineering on a hot-fuel-gas desulfurization process using a regenerable iron oxide-silica sorbent. The overall process consists of two stages: the absorption or the H/sub 2/S removal stage and the sorbent regeneration stage. In the absorption stage the iron oxide reacts with H/sub 2/S to form iron sulfide. For regeneration of the sulfided sorbent, various schemes have been proposed. Studies at WVU have been aimed at identifying the important reactions involved in absorption and regeneration stages, elucidating their mechanisms and investigating detailed kinetics. In the first two phases of the study, reactions in H/sub 2/S absorption and in sorbent regeneration by air/SO/sub 2/ were investigated. This report addresses regeneration of the sulfided sorbent using steam-air mixtures. Experiments were conducted in a thermo-gravimetric analyzer (TGA) apparatus. The weight changes were recorded as a function of time during the reactions of iron sulfide (in the presulfided sorbent) with nitrogen-stream and air-steam mixtures. In addition, several solid samples at different conversion levels were anlayzed by LECO sulfur anlaysis technique and by Mossbauer spectroscopy. Based on these results, a reaction mechanism has been postulated. Additional work is necessary to investigate the gas-phase reactions which may be taking place simultaneously in a fixed - or a fluidized-bed reactor, and to formulate the overall reaction scheme. 14 figures, 3 tables.

  3. Assessing the Role of Iron Sulfides in the Long Term Sequestration of U by Sulfate Reducing Bacteria

    SciTech Connect

    Rittman, Bruce; Zhou, Chen; Vannela, Raveender

    2013-12-31

    This four-year project’s overarching aim was to identify the role of biogenic and synthetic iron-sulfide minerals in the long-term sequestration of reduced U(IV) formed under sulfate-reducing conditions when subjected to re-oxidizing conditions. As stated in this final report, significant progress was achieved through the collaborative research effort conducted at Arizona State University (ASU) and the University of Michigan (UM).

  4. Failure analysis of Mark IA lithium/iron sulfide battery. [Two 20-kWh modules

    SciTech Connect

    Kolba, V M; Battles, J E; Geller, J D; Gentry, K

    1980-10-01

    The Mark IA lithium/iron sulfide electric-vehicle battery, which consisted of two 20-kWh modules containing 60 cells each, was fabricated by Eagle-Picher Industries, Inc. and delivered to ANL for testing in May 1979. During startup heating prior to electrical testing, a short circuit developed in one of the modules, which resulted in a progressive failure of the cells. The other module, which was alongside and connected in series, was unaffected by the failure. The initial indication of difficulty was a small drop in the voltage of several cells, followed by short circuits in the balance of the cells and localized temperatures above 1000/sup 0/C. A team consisting of ANL and Eagle-Picher personnel conducted a detailed failure analysis as the failed module was disassembled. The other module was also examined for purposes of comparison. The general conclusion was that the short circuit was initiated by electrolyte leakage and resulting corrosion in the nearby region which formed metallic bridges between cells and the cell tray, or arcing between cells and the cell tray through the butt joints in the electrical insulation. The above two mechanisms were also believed to be responsible for the failure propagation. 66 figures, 11 tables.

  5. Iron-Sulfide-Associated Products Formed during Reductive Dechlorination of Carbon Tetrachloride.

    PubMed

    Lan, Ying; Butler, Elizabeth C

    2016-06-01

    This paper investigated the mackinawite (FeS)-associated products formed during reaction between FeS and carbon tetrachloride (CT) at pH 7 and 8. At pH 8, reaction of FeS with CT led to formation of abundant spherical particles with diameters between 50 and 400 nm on the FeS surface and in solution; far fewer such particles were observed at pH 7. Analysis of the FeS surface by energy dispersive X-ray spectroscopy after reaction with CT at pH 8 showed decreased sulfur and elevated oxygen compared to unreacted FeS. The spherical particles that formed upon FeS reaction with CT were mostly amorphous with localized areas of poorly crystalline two-line ferrihydrite. X-ray photoelectron spectroscopy indicated that the predominant Fe surface species after reaction with CT at pH 8 was Fe(III)-O, consistent with ferrihydrite and other amorphous iron (hydr)oxides as major products. Powder X-ray diffraction analysis suggested formation of greigite upon reaction of FeS with CT at pH 7. Both ferrihydrite and Fe(2+), which is a product of greigite dissolution, can react with dissolved HS(-) to form FeS, suggesting that, after oxidation by chlorinated aliphatics, FeS can be regenerated by addition or microbial generation of sulfide. PMID:27138348

  6. Kinetics and mechanisms of iron sulfide reductions in hydrogen and in carbon monoxide

    USGS Publications Warehouse

    Wiltowski, T.; Hinckley, C.C.; Smith, Gerard V.; Nishizawa, T.; Saporoschenko, Mykola; Shiley, R.H.; Webster, J.R.

    1987-01-01

    The reduction of iron sulfides by hydrogen and by carbon monoxide has been studied using plug flow and thermogravimetric methods. The reactions were studied in the 523-723??K temperature range and were found to be first-order processes. Plug flow studies were used to correlate reaction rates between pyrite and the gases as a function of the surface area of the pyrite. The rate of H2S formation increases with the surface area of the pyrite sample. The results of thermogravimetric experiments indicate that the reactions consist of several steps. Rate constants for the pyrite reduction by H2 and by CO were obtained. The activation energies increased with degree of reduction. Values of Ea were 113.2 (step I) and 122.5 kJ/mole (step II) for pyrite reduction with CO and 99.4 (step I), 122.4 (step II), 125.2 (step III), and 142.6 kJ/mole (step IV) for pyrite reduction with hydrogen. ?? 1987.

  7. Comparison of Iron Sulfide and Zero-Valent Iron as Reactive Materials for the Removal of Arsenic From Groundwater

    NASA Astrophysics Data System (ADS)

    Henderson, A. D.; Demond, A. H.

    2007-12-01

    Zero-valent iron (ZVI) installed in permeable reactive barriers (PRBs) has been shown to be an effective remediation agent for several contaminants, including arsenic (As), a redox-active oxyanion present in reduced form as arsenite, AsO3(3-), and in oxidized form as arsenate, AsO4(3-). Work performed has shown greater removal of arsenic by iron sulfide (FeS), as mackinawite, than by ZVI under anaerobic conditions, recommending the use of FeS in PRB systems. For both ZVI and FeS PRB systems, the interaction of the reactive porous media with groundwater species, and calcium and carbonate in particular, is key to maintaining the permeability and reactivity of the PRB, both of which are necessary for continued treatment. If geochemical conditions are favorable, CaCO3(s) may precipitate, thus reducing permeability and passivating the reactive surface, preventing further remediation. In a statistical review of field PRB performance (Henderson and Demond, Env. Eng. Sci., 2007), it was found that alkalinity, as an indicator of the potential for precipitation of carbonate solids, was correlated to increased risk of PRB failure. A combination of experimental and geochemical modeling approaches is being used to investigate the quantity of calcium carbonate formation in anaerobic FeS and ZVI systems. Column tests with FeS to date have resulted in behavior unlike that observed with ZVI. In the ZVI columns, a pH increase has allowed the precipitation of CaCO3(s), which led to a reduction in permeability. In the FeS columns, the effluent pH and aqueous calcium concentrations were essentially the same as the influent, suggesting that the buffer capacity of carbonate prevented a pH increase, thus precluding the precipitation of CaCO3(s). Geochemical modeling suggests that the interaction of carbonate and FeS may self-regulate in PRB systems: at high carbonate concentrations, when the precipitation of CaCO3(s) could reduce permeability, the buffer capacity provided by the carbonate

  8. Coupled micro-scale magnetic and spectroscopic techniques to understand the petrogenesis of iron sulfides in sedimentary rocks

    NASA Astrophysics Data System (ADS)

    Slotznick, S. P.; Webb, S. M.; Johnson, J. E.; Kirschvink, J. L.; Fischer, W. W.

    2013-12-01

    Paleomagnetism in sedimentary rocks containing iron sulfide mineral phases is challenging due to questions about the timing of formation, the potential for multiple-stages of iron sulfide growth, and their metastabilty in nature and in the laboratory. Bulk rock magnetic techniques have been developed and applied to identify and characterize ferromagnetic iron sulfides in a wide array of rock types from the geologic record (including some containing stable ChRM), but petrographic textural observations are required to inform the timing of their mineralization in any given sample. The solid-solution of pyrite/pyrrhotite/troilite and intimate intergrowth patterns of iron sulfides is difficult to untangle with standard light and electron microscopy. Here we report the development and application of a complementary set of techniques designed to inform and untangle the history and processes involved in the mineralization of sulfur-bearing minerals in sedimentary rocks. X-ray absorption spectroscopy of the S K-edge provides insight into the chemistry (such as valence state, electronic structure, type of neighbors) of sulfur-bearing solids. We used a new synchrotron-based X-ray microprobe developed at SSRL to measure, distinguish, and then image sulfur phases via multiple energy maps at micron scales. From these maps we can quantitatively differentiate a wide range of sulfur-bearing phases in polished thin sections, such as pyrrhotite, pyrite, and greigite, and ordinate them into a petrogenic scheme. At a similar scale, using SQUID microscopy allows us to identify and map the presence and field strength of ferromagnetic minerals within a sample. Combined with bulk rock magnetic techniques, these two micro-scale methods pair well to confirm textural observations, beyond those already noted using optical and scanning electron microscopy. Here we will present work from a study of middle Proterozoic age sedimentary rocks from the Belt Supergroup, MT. By collecting a wide array

  9. Kinetic and morphological development of oxide-sulfide scales on iron at 1,073 K

    SciTech Connect

    McAdam, G.; Young, D.J. )

    1992-04-01

    The corrosion behavior of pure iron has been investigated at 1,073 K in controlled gas atmospheres of SO{sub 2}-CO{sub 2}-CO-N{sub 2}. The equilibrium gas compositions were such that: (1) FeS was stable with respect to FeO, (2) FeO was stable with respect to FeS, and (3) only one of the solids was stable with respect to the gas sulfur and oxygen activities. The resultant scale morphologies are discussed along with the observed parabolic corrosion kinetics. It was shown that duplex (oxide plus sulfide) scales could be produced under all three reaction conditions. Careful adjustment of gas compositions permitted comparisons to be made among sets of experiments having (1) the same p{sub s{sub 2}} value but different p{sub so{sub 2}} and p{sub o{sub 2}}values, (2) the same p{sub o{sub 2}} value but different p{sub so{sub 2}} and p{sub s{sub 2}} values, and (3) the same p{sub so{sub 2}}value but different p{sub s{sub 2}} and p{sub o{sub 2}}values. In this way it was confirmed that the reactant species was SO{sub 2} over a wide range of gas compositions, and under conditions in which solid-state diffusion was rate-controlling. The exception was found at very high p{sub s{sub 2}} values, where elemental sulfur was the reactant. Catalysis of the reactant gas demonstrated that the results could be affected by the slow approach to equilibrium of the gas phase.

  10. Assessing the Role of Iron Sulfides in the Long Term Sequestration of Uranium by Sulfate-Reducing Bacteria

    SciTech Connect

    Hayes, Kim F.; Bi, Yuqiang; Carpenter, Julian; Hyng, Sung Pil; Rittmann, Bruce E.; Zhou, Chen; Vannela, Raveender; Davis, James A.

    2014-01-01

    This overarching aim of this project was to identify the role of biogenic and synthetic iron-sulfide minerals in the long-term sequestration of reduced U(IV) formed under sulfate-reducing conditions when subjected to re-oxidizing conditions. The work reported herein was achieved through the collaborative research effort conducted at Arizona State University (ASU) and the University of Michigan (UM). Research at ASU, focused on the biogenesis aspects, examined the biogeochemical bases for iron-sulfide production by Desulfovibrio vulgaris, a Gram-negative bacterium that is one of the most-studied strains of sulfate-reducing bacteria. A series of experimental studies were performed to investigate comprehensively important metabolic and environmental factors that affect the rates of sulfate reduction and iron-sulfide precipitation, the mineralogical characteristics of the iron sulfides, and how uranium is reduced or co-reduced by D. vulagaris. FeS production studies revealed that controlling the pH affected the growth of D. vulgaris and strongly influenced the formation and growth of FeS solids. In particular, lower pH produced larger-sized mackinawite (Fe1+xS). Greater accumulation of free sulfide, from more sulfate reduction by D. vulgaris, also led to larger-sized mackinawite and stimulated mackinawite transformation to greigite (Fe3S4) when the free sulfide concentration was 29.3 mM. On the other hand, using solid Fe(III) (hydr)oxides as the iron source led to less productivity of FeS due to their slow and incomplete dissolution and scavenging of sulfide. Furthermore, sufficient free Fe2+, particularly during Fe(III) (hydr)oxide reductions, led to the additional formation of vivianite [Fe3(PO4)2•8(H2O)]. The U(VI) reduction studies revealed that D. vulgaris reduced U(VI) fastest when accumulating sulfide from concomitant sulfate reduction, since direct enzymatic and sulfide-based reductions of U(VI) occurred in parallel. The UO2 produced in presence of ferrous

  11. Stabilization of Sulfur and Arsenic Species in Sulfidic, Iron-rich Geothermal Waters Using Solid Phase Extraction

    NASA Astrophysics Data System (ADS)

    Ullrich, M. K.; Gayout, A.; Misiari, V.; Planer-Friedrich, B.

    2015-12-01

    Iron-rich geothermal waters pose a special challenge regarding sample stabilization for sulfur and arsenic speciation analysis. Standard stabilization techniques fail to preserve speciation due to precipitating iron oxyhydroxides and thus adsorption of arsenic when flash-freezing a sample or precipitation of orpiment (As2S3)-like phases when adding HNO3. Solid phase extraction has the potential to extract anionic sulfur and arsenic species from solution and consequently separate them from cationic iron. This method was tested by applying synthetic solutions of sulfur and arsenic species onto Bio-Rad AG2-X8 resin and eluting the target species using 0.5 M Na-Salicylate. Complete retention of the initially applied amount on the resin was found for sulfate, thiosulfate, arsenate, monothioarsenate and trithioarsenate with 100.0 %, 99.7 %, 95.1 %, 98.9 %, and 99.8 %, respectively. Arsenite passed the resin without binding (3.0 % retention). All species bound to the resin could be eluted quantitatively and species-conserving with a recovery of 98.4 %, 102.8 %, 95.3 %, 90.5 % and 85.3 % for sulfate, thiosulfate, arsenate, monothioarsenate and trithioarsenate, respectively. Addition of 5 ppm FeCl2 did not reduce method efficiency with 98.7 % retention and 105.1 % recovery for monothioarsenate, while all of the applied iron passed the resin without binding as hypothesized. However, in solutions containing a mixture of arsenite, arsenate, monothioarsenate and trithioarsenate we found arsenite retention up to 59.1 % both in the presence and absence of iron. This effect cannot be fully explained yet and might be attributed to free sulfide in these mixed solutions facilitating arsenite binding via sulfide sorbed onto the resin. The interaction between different species needs to be further investigated. Samples from geothermal features in Yellowstone and mineral springs in the Czech Republic have been collected and results of immediate elution and stability during storage will

  12. Study on application of biological iron sulfide composites in treating vanadium-extraction wastewater containing chromium (VI) and chromium reclamation.

    PubMed

    Xie, Yi-Fei; Li, Xu-Dong; Li, Fu-De

    2013-04-01

    In this study, the Cr(VI)-resistant properties and regeneration characteristics of biological iron sulfide composites were investigated, which consist of sulfate reducing bacteria (SRB) and its in situ synthesized nanosized iron sulfides. Then the application of the composites in treating vanadium-extraction wastewater containing high concentration Cr(VI) and reclaiming Cr were performed. It was found that SRB in composites still survived after being used to treat vanadium-extraction wastewater, which could reduce reaction products Fe3+ and sulphur into Fe2+ and S2 by using them as the electron accepters and thus regenerating biological iron sulfide composites. The SRB also could be resistant to 600 mgl(-1) Cr(VI) and reduce it gradually. Based on the Cr(VI)-resistant properties and regeneration characteristics of the composites, a reduction-regeneration recirculation process for treating vanadium-extraction wastewater and reclamation of Cr was developed. The results indicated that the contaminants in effluent reached the Chinese discharge standard of pollutants for vanadium industry (GB 26452-2011), i.e. the concentration of total Cr(TCr) was less than 0.912 mgl(-1), Cr(VI) was less than 0.017 mgl(-1) and V was less than 0.260 mgl(-1). After 10 cycles of treatment, the Cr2O3 content in sludge reached 41.03%, and the ratio of Cr2O3/FeO was 7.35. The sludge reached the chemical and metallurgical (hydrometallurgy) grade of chromite ore and could be reclaimed. PMID:24620597

  13. Application of MC-ICPMS to the precise determination of tellurium isotope compositions in chondrites, iron meteorites and sulfides

    NASA Astrophysics Data System (ADS)

    Fehr, Manuela A.; Rehkämper, Mark; Halliday, Alex N.

    2004-03-01

    New mass spectrometric techniques have been developed for the precise and accurate determination of Te isotope compositions. The methods are suitable for the analysis of stony and iron meteorites as well as sulfide mineral separates, such that they can be applied to search for Te isotope anomalies in various solar system materials. Tellurium is first separated from its matrix with a two-stage liquid chromatographic procedure. For iron meteorites, solvent-extraction is used to isolate Te from Fe prior to the column separation. The isotope composition of Te is then determined by multiple-collector inductively coupled plasma-mass spectrometry (MC-ICPMS). Tellurium has a very high first ionization potential and thus MC-ICPMS is much more suitable for the isotopic analyses than positive ion thermal ionization mass spectrometry (TIMS). Only about 100 ng Te are required for a single high precision measurement. Analyses of two terrestrial sulfides, the carbonaceous chondrite Allende and the iron meteorite Canyon Diablo reveal that these have Te isotope compositions that are identical to the terrestrial standard within uncertainty. The Te isotope data acquired for standard solutions as well as meteorites and sulfides display reproducibilities (2[sigma]) of approximately +/-4500 ppm for 120Te/128Te, +/-140 ppm for 122Te/128Te, +/-100 ppm for 124Te/128Te, +/-30 ppm for 126Te/128Te, and +/-60 ppm for 130Te/128Te. Compared to published results for meteorite samples obtained by TIMS, this represents an improvement in precision of about one to two orders of magnitude for 122-130Te/128Te and by a factor of 4 for 120Te/128Te. A number of experiments furthermore demonstrate that the isotope data acquired by MC-ICPMS are accurate, even for complex geological samples.

  14. Iron Sulfide as a Sustainable Reactive Material for Permeable Reactive Barriers

    NASA Astrophysics Data System (ADS)

    Henderson, A. D.; Demond, A. H.

    2012-12-01

    Permeable reactive barriers (PRBs) are gaining acceptance for groundwater remediation, as they operate in situ and do not require continuous energy input. The majority of PRBs use zero-valent iron (ZVI). However, some ZVI PRBs have hydraulically failed [1,2], due to the fact that ZVI may reduce not only contaminants but also water and non-contaminant solutes. These reactions may form precipitates or gas phases that reduce permeability. Therefore, there is a need to assess the hydraulic suitability of possible alternatives, such as iron sulfide (FeS). The capability of FeS to remove both metals and halogenated organics from aqueous systems has been demonstrated previously [3,4], and FeS formed in situ within a ZVI PRB has been linked to contaminant removal [5]. These results suggest possible applications in groundwater remediation as a permeable reactive barrier (PRB) material. However, the propensity of FeS for permeability loss, due to solids and gas production, must be evaluated in order to address its suitability for PRBs. The reduction in permeability for FeS-coated sands under the anoxic conditions often encountered at contaminated groundwater sites was examined through column experiments and geochemical modeling under conditions of high calcium and nitrate, which have been previously shown to cause significant permeability reduction in zero-valent iron (ZVI) systems [6]. The column experiments showed negligible production of both solids and gases. The geochemical model was used to estimate solid and gas volumes generated under conditions of varying FeS concentration. Then, the Kozeny-Carman equation and a power-law relationship was used to predict permeability reduction, with a maximum reduction in permeability of 1% due to solids and about 30% due to gas formation under conditions for which a complete loss of permeability was predicted for ZVI systems. This difference in permeability reduction is driven by the differences in thermodynamic stability of ZVI

  15. Rock magnetic characterization of ferrimagnetic iron sulfides in gas hydrate-bearing marine sediments at Site C0008, Nankai Trough, Pacific Ocean, off-coast Japan

    NASA Astrophysics Data System (ADS)

    Kars, Myriam; Kodama, Kazuto

    2015-07-01

    A high-resolution rock magnetic study was carried out in Integrated Ocean Drilling Program (IODP) Expedition 316 Hole C0008A located in the Megasplay Fault Zone of the Nankai Trough, SW offshore Japan, in order to document changes in magnetic properties throughout gas hydrate-bearing horizons. A total of 169 Pleistocene discrete samples were collected from ~110 to 153 m core depth below sea floor (CSF), and their magnetic minerals concentration, grain size, composition, and rock magnetic parameters were estimated. Results showed the presence of iron oxides ((titano)-magnetite), iron sulfides (greigite and pyrrhotite), and their mixture, among which single-domain greigite is the most major magnetic mineral present in the samples. Two horizons containing ferrimagnetic iron sulfides (114.5-127.5 and 129.5-150 m CSF) covering almost the entire studied interval were identified, both associated with slight local pore water anomalies, suggesting occurrence of gas hydrates and anoxic conditions. These results are different from the neighboring Hole C0008C (215 m away from Hole C0008A) where four pore water anomalies and six iron sulfide-rich intervals were identified for the same time slice. Comparison of the lithology, physical properties, and geochemical data of the two boreholes at Site C0008 suggests that a combination of processes (e.g., availability of reactive iron, microbial activity) is responsible for such laterally varying distribution of the ferrimagnetic iron sulfides.

  16. Iron and sulfide oxidation within the basaltic ocean crust: implications for chemolithoautotrophic microbial biomass production

    NASA Astrophysics Data System (ADS)

    Bach, Wolfgang; Edwards, Katrina J.

    2003-10-01

    Microbial processes within the ocean crust are of potential importance in controlling rates of chemical reactions and thereby affecting chemical exchange between the oceans and lithosphere. We here assess the oxidation state of altered ocean crust and estimate the magnitude of microbial biomass production that might be supported by oxidative and nonoxidative alteration. Compilations of Fe 2O 3, FeO, and S concentrations from DSDP/ODP drill core samples representing upper basaltic ocean crust suggest that Fe 3+/ΣFe increases from 0.15 ± 0.05 to 0.45 ± 0.15 within the first 10-20 Myr of crustal evolution. Within the same time frame 70 ± 25% of primary sulfides in basalt are oxidized. With an annual production of 4.0 ± 1.8 × 10 15 g of upper (500 ± 200 m) crust and average initial concentrations of 8.0 ± 1.3 wt% Fe and 0.125 ± 0.020 wt% S, we estimate annual oxidation rates of 1.7 ± 1.2 × 10 12 mol Fe and 1.1 ± 0.7 × 10 11 mol S. We estimate that 50% of Fe oxidation may be attributed to hydrolysis, producing 4.5 ± 3.0 × 10 11 mol H 2/yr. Thermodynamic and bioenergetic calculations were used to estimate the potential chemolithoautotrophic microbial biomass production within ridge flanks. Combined, aerobic and anaerobic Fe and S oxidation may support production of up to 48 ± 21 × 10 10 g cellular carbon (C). Hydrogen-consuming reactions may support production of a similar or larger microbial biomass if iron reduction, nitrate reduction, or hydrogen oxidation by O 2(aq) are the prevailing metabolic reactions. If autotrophic sulfate reduction or methanogenesis prevail, the potential biomass production is 9 ± 7 × 10 10 g C/yr and 3 ± 2 × 10 10 g C/yr, respectively. Combined primary biomass production of up to ˜1 × 10 12 g C/yr may be similar to that fueled by anaerobic oxidation of organic matter in deep-seated heterotrophic systems. These estimates suggest that water-rock reactions may support significant microbial life within ridge flank

  17. Phase control in the synthesis of magnetic iron sulfide nanocrystals from a cubane-type Fe-S cluster.

    PubMed

    Vanitha, P V; O'Brien, Paul

    2008-12-24

    Phase control has been achieved in the synthesis of magnetic iron sulfide nanocrystals by the use of a single source precursor, a cubane type Fe-S cluster, bis(tetra-n-butylammonium) tetrakis[benezenethiolato-mu3-sulfido-iron]. This cluster cleanly decomposes in alkylamines to yield nanocrystals whose composition, structure, and dimensions are dependent on the temperature employed. At low temperatures, pyrrhotite type Fe7S8 nanocrystals with an average diameter of 5.6 nm are obtained. Higher temperatures yield griegite-Fe3S4 nanocrystals whose dimensions are tunable in the range 2.5-4.5 nm. All the obtained nanocrystals are superparamagnetic at room temperature. PMID:19035629

  18. Microscopic characteristic of biological iron sulfide composites during the generation process and the association with treatment effect on heavy metal wastewater.

    PubMed

    Yang, Yang; Xie, Yifei; Li, Xudong; Zhou, Jingchao; Liu, Jingwei

    2014-01-01

    Heavy metal pollution is a serious environmental concern worldwide, resulting in both environmental and human harm. Recently, studies have shown that environmental biotechnologies based on sulfate reduction offer a potential for removal of toxic heavy metals. Biological iron sulfide composites are iron sulfide compounds generated in situ by sulfate-reducing bacteria. In this study, microscopic morphological changes during the composites' generation process were studied, and the effect of biological iron sulfide composites in different generation phases on treatment of heavy metal wastewater was investigated to establish the correlation between macro-effect and micro-properties. The results revealed that the generation process of biological iron sulfide composites occurs in three phases: the formation phase, stationary phase, and agglomeration phase. The stationary phase can be divided into a pre-stationary phase and post-stationary phase. It was found that the best treatment time for Cr(6+) is in the pre-stationary phase, while the best treatment time for Cu(2+)and Cd(2+) is in the post-stationary phase. The results of this study further prove the benefits of treatment of heavy metal wastewater using biological sulfide composites and provide theoretical guidance in practical applications. PMID:25325556

  19. Suboxic deep seawater in the late Paleoproterozoic: Evidence from hematitic chert and iron formation related to seafloor-hydrothermal sulfide deposits, central Arizona, USA

    NASA Astrophysics Data System (ADS)

    Slack, J. F.; Grenne, T.; Bekker, A.; Rouxel, O. J.; Lindberg, P. A.

    2007-03-01

    A current model for the evolution of Proterozoic deep seawater composition involves a change from anoxic sulfide-free to sulfidic conditions 1.8 Ga. In an earlier model the deep ocean became oxic at that time. Both models are based on the secular distribution of banded iron formation (BIF) in shallow marine sequences. We here present a new model based on rare earth elements, especially redox-sensitive Ce, in hydrothermal silica-iron oxide sediments from deeper-water, open-marine settings related to volcanogenic massive sulfide (VMS) deposits. In contrast to Archean, Paleozoic, and modern hydrothermal iron oxide sediments, 1.74 to 1.71 Ga hematitic chert (jasper) and iron formation in central Arizona, USA, show moderate positive to small negative Ce anomalies, suggesting that the redox state of the deep ocean then was at a transitional, suboxic state with low concentrations of dissolved O 2 but no H 2S. The presence of jasper and/or iron formation related to VMS deposits in other volcanosedimentary sequences ca. 1.79-1.69 Ga, 1.40 Ga, and 1.24 Ga also reflects oxygenated and not sulfidic deep ocean waters during these time periods. Suboxic conditions in the deep ocean are consistent with the lack of shallow-marine BIF ˜ 1.8 to 0.8 Ga, and likely limited nutrient concentrations in seawater and, consequently, may have constrained biological evolution.

  20. Stereodynamics in the Collisional Autoionization of Water, Ammonia, and Hydrogen Sulfide with Metastable Rare Gas Atoms: Competition Between Intermolecular Halogen and Hydrogen Bonds.

    PubMed

    Falcinelli, Stefano; Bartocci, Alessio; Cavalli, Simonetta; Pirani, Fernando; Vecchiocattivi, Franco

    2016-01-11

    Recent experiments on the title subject, performed with a high-resolution crossed-beam apparatus, have provided the total ionization cross sections as a function of the collision energy between noble gas atoms, electronically excited in their metastable states (Ng*), and H2 O, H2 S, and NH3 reagents, as well as the emitted electron energy spectra. This paper presents a rationalization of all the experimental findings in a unifying picture to cast light on the basic chemical properties of Ng* under conditions of great relevance both from a fundamental and from an applied point of view. The importance of this investigation is that it isolates the selective role of the intermolecular halogen and hydrogen bonds, to assess their anisotropic effects on the stereodynamics of the promoted ionization reactions, and to model energy transfer and reactivity in systems of applied interest, such as planetary atmospheres, plasmas, lasers, and flames. PMID:26633846

  1. Reference design of 100 MW-h lithium/iron sulfide battery system for utility load leveling

    SciTech Connect

    Zivi, S.M.; Kacinskas, H.; Pollack, I.; Chilenskas, A.A.; Barney, D.L.; Grieve, W.; McFarland, B.L.; Sudar, S.; Goldstein, E.; Adler, E.

    1980-03-01

    The first year in a two-year cooperative effort between Argonne National Laboratory and Rockwell International to develop a conceptual design of a lithium alloy/iron sulfide battery for utility load leveling is presented. A conceptual design was developed for a 100 MW-h battery system based upon a parallel-series arrangement of 2.5 kW-h capacity cells. The sales price of such a battery system was estimated to be very high, $80.25/kW-h, exclusive of the cost of the individual cells, the dc-to-ac converters, site preparation, or land acquisition costs. Consequently, the second year's efforts were directed towards developing modified designs with significantly lower potential costs.

  2. Micrometeorite dynamic pyrometamorphism: Observation of a thermal gradient in iron-nickel sulfide

    NASA Technical Reports Server (NTRS)

    Rietmeijer, Frans J. M.

    1993-01-01

    Dynamic pyrometamorphism describes the mineralogical changes in a micrometeorite that occur in response to flash-heating during atmospheric entry. Mineral reactions during this event will be endothermic and act as local sinks for thermal energy which delays a uniform temperature distribution in decelerating micrometeorites. The most common pyrometamorphic reaction is formation of magnetite nanocrystal decorations on Mg,Fe-silicate grains and magnetite or (partial) maghemite rims. Constituent silicates also respond to this thermal event and show formation of olivine-maghemite symplectites and growth of garnet and partial laihunitisation. In continued effort to constrain dynamic pyrometamorphism of unmelted interplanetary dust particles (IDP's), I determined the mineralogical composition, and Fe,Ni-sulfide chemistry, in the sulfide-rich particles L2005C39, L2005E40, and L2006A28 using a JEOL 2000FX analytical electron microscope equipped with a TN5500 energy dispersive spectrometer for in situ microanalysis. Sulfide compositions in these three IDP's are distinctly different from those in silicate-rich particle L2005T13 which might suggest a delicate balance of the fO2/fS2 ratios during dynamic pyrometamorphism.

  3. Temporal trends in vent fluid iron and sulfide chemistry following the 2005/2006 eruption at East Pacific Rise, 9°50'N

    NASA Astrophysics Data System (ADS)

    Yücel, Mustafa; Luther, George W.

    2013-04-01

    The chemistry of vent fluids that emanate to the seafloor undergoes dramatic changes after volcanic eruptions. Data on these changes are still limited, but the best studied example is the East Pacific Rise (EPR) at 9°50'N, where the temporal evolution of the vent fluid chemistry after the 1991/1992 eruption was documented. The area underwent another eruption sequence during late 2005/early 2006, and here we show that a similar evolution is recurring in the iron and sulfide contents of the high-temperature fluids sampled in June 2006, January 2007, and June 2008. The vents have had increasing dissolved iron and decreasing acid-volatile sulfide (free sulfide plus FeS) concentrations with 1 order of magnitude variation. In addition, chromium reducible sulfide (mainly pyrite) also had fivefold decreasing concentrations over the 3 years. Our results confirm a pattern that was noted only once before for 9°50'N EPR and emphasize the dramatic yearly variability in the concentrations of iron-sulfur species emanating from vents.

  4. Oxidative Remobilization of Technetium Sequestered by Sulfide-Transformed Nano Zerovalent Iron

    SciTech Connect

    Fan, Dimin; Anitori, Roberto; Tebo, Bradley M.; Tratnyek, P. G.; Lezama Pacheco, Juan S.; Kukkadapu, Ravi K.; Kovarik, Libor; Engelhard, Mark H.; Bowden, Mark E.

    2014-06-02

    The dissolution of Tc(IV) sulfide and concurrent transformation of sulfidated ZVI during 2 oxidation were examined. Kinetic data obtained with 10 mL batch reactors showed that Tc(VII) 3 reduced by sulfidated nZVI has significantly slower reoxidation rates than Tc(VII) reduced by 4 nZVI only. In a 50 mL batch reactor, initial inhibition of Tc(IV) dissolution was apparent and 5 lasted until 120 hours at S/Fe = 0.112, presumably due to the redox buffer capacity of FeS. This 6 is evidenced by the parallel trends in oxidation-reduction potentials (ORP) and Tc dissolution 7 kinetics. Mӧssbauer spectra and micro X-ray diffraction of S/Fe = 0.112 suggested the 8 persistence of FeS after 24-h oxidation although X-ray photoelectron spectroscopy indicated 9 substantial surface oxidation. After 120-h oxidation, all characterizations showed complete 10 oxidation of FeS, which further indicates that FeS inhibits Tc oxidation. X-ray absorption 11 spectroscopy for S/Fe = 0.011 showed significantly increasing percentage of TcS2 in the solid 12 phase after 24-h oxidation, indicating TcS2 is more resistant to oxidation than TcO2. At S/Fe = 13 0.112, the XAS results revealed significant transformation of Tc speciation from TcS2 to TcO2 14 after 120-h oxidation at S/Fe = 0.112. Given that no apparent Tc dissolution occurred during this 15 period, the speciation transformation might play a secondary role in hindering Tc oxidation, 16 especially as redox buffer capacity approached depletion.

  5. Cronstedtite and iron sulfide mineralogy of CM-type carbonaceous chondrites from cryogenic Moessbauer spectra

    NASA Technical Reports Server (NTRS)

    Fisher, Duncan S.; Burns, Roger G.

    1993-01-01

    Determinations of oxidation states and the crystal chemistry of iron-bearing minerals in CM meteorites by Moessbauer spectroscopy are complicated by thermally-induced electron hopping in cronstedtite and by ill-defined contributions from the hydrous iron sulphide phase believed to be tochilinite. Moessbauer spectral measurements at 30 K of several cronstedtite and tochilinite specimens have enabled modal proportions of these minerals, as well as Fe(3+)/Fe(2+) ratios, to be determined quantitatively for a suite of CM-type carbonaceous chondrites that included Murchison, Murray, Cold Bokkeveld, ALH 83100, and LEW 90500.

  6. Iron isotope fractionation during sulfide-rich felsic partial melting in early planetesimals

    NASA Astrophysics Data System (ADS)

    Wang, Kun; Day, James M. D.; Korotev, Randy L.; Zeigler, Ryan A.; Moynier, Frédéric

    2014-04-01

    New Fe isotope data of feldspar-rich meteorites Graves Nunataks 06128 and 06129 (GRA 06128/9) reveal that they are the only known examples of crustal materials with isotopically light Fe isotope compositions (δFe56=-0.08±0.06‰; δ56Fe is defined as the per mille deviation of a sample's 56Fe/54Fe ratio from the IRMM-014 standard) in the Solar System. In contrast, associated brachinites, as well as brachinite-like achondrites, have Fe isotope compositions (δFe56=+0.01±0.02‰) that are isotopically similar to carbonaceous chondrites and the bulk terrestrial mantle. In order to understand the cause of Fe isotope variations in the GRA 06128/9 and brachinite parent body, we also report the Fe isotope compositions of metal, silicate and sulfide fractions from three ordinary chondrites (Semarkona, Kernouve, Saint-Séverin). Metals from ordinary chondrites are enriched in the heavier isotopes of Fe (average δFe56=0.15‰), sulfide fractions are enriched in the lighter isotopes of Fe (average δFe56=-0.14‰), and the δ56Fe values of the silicates are coincident with that of the bulk rock (average δFe56=0.03‰). The enrichment of light isotopes of Fe isotopes in GRA 06128/9 is consistent with preferential melting of sulfides in precursor chondritic source materials leading to the formation of Fe-S-rich felsic melts. Conceptual models show that melt generation to form a GRA 06128/9 parental melt occurred prior to the onset of higher-temperature basaltic melting (<1200 °C) in a volatile-rich precursor and led to the generation of buoyant felsic melt with a strong Fe-S signature. These models not only reveal the origin of enrichment in light isotopes of Fe for GRA 06128/9, but are also consistent with petrological and geochemical observations, experimental studies for the origin of Fe-S-rich felsic melts, and for the cessation of early melting on some asteroidal parent bodies because of the effective removal of the major radioactive heat-source, 26Al. The mode of

  7. Removal of EDB and 1,2-DCA by Abiotic Reaction with Iron (II) Sulfide

    EPA Science Inventory

    To properly evaluate the risk associated with exposure to EDB and 1,2-DCA in ground water from old spills of leaded gasoline, it is necessary to understand the mechanisms that may attenuate concentrations of these compounds in ground water. TCE reacts rapidly with iron (II) sulf...

  8. Iron sulfide attenuates the methanogenic toxicity of elemental copper and zinc oxide nanoparticles and their soluble metal ion analogs.

    PubMed

    Gonzalez-Estrella, Jorge; Gallagher, Sara; Sierra-Alvarez, Reyes; Field, Jim A

    2016-04-01

    Elemental copper (Cu(0)) and zinc oxide (ZnO) nanoparticle (NP) toxicity to methanogens has been attributed to the release of soluble metal ions. Iron sulfide (FeS) partially controls the soluble concentration of heavy metals and their toxicity in aquatic environments. Heavy metals displace the Fe from FeS forming poorly soluble metal sulfides in the FeS matrix. Therefore, FeS may be expected to attenuate the NP toxicity. This work assessed FeS as an attenuator of the methanogenic toxicity of Cu(0) and ZnO NPs and their soluble salt analogs. The toxicity attenuation capacity of fine (25-75μm) and coarse (500 to 1200μm) preparations of FeS (FeS-f and FeS-c respectively) was tested in the presence of highly inhibitory concentrations of CuCl2, ZnCl2 Cu(0) and ZnO NPs. FeS-f attenuated methanogenic toxicity better than FeS-c. The results revealed that 2.5× less FeS-f than FeS-c was required to recover the methanogenic activity to 50% (activity normalized to uninhibited controls). The results also indicated that a molar FeS-f/Cu(0) NP, FeS-f/ZnO NP, FeS-f/ZnCl2, and FeS-f/CuCl2 ratio of 2.14, 2.14, 4.28, and 8.56 respectively, was necessary to recover the methanogenic activity to >75%. Displacement experiments demonstrated that CuCl2 and ZnCl2 partially displaced Fe from FeS. As a whole, the results indicate that not all the sulfide in FeS was readily available to react with the soluble Cu and Zn ions which may explain the need for a large stoichiometric excess of FeS to highly attenuate Cu and Zn toxicity. Overall, this study provides evidence that FeS attenuates the toxicity caused by Cu(0) and ZnO NPs and their soluble ion analogs to methanogens. PMID:26803736

  9. Covalent entrapment of cobalt-iron sulfides in N-doped mesoporous carbon: extraordinary bifunctional electrocatalysts for oxygen reduction and evolution reactions.

    PubMed

    Shen, Mengxia; Ruan, Changping; Chen, Yan; Jiang, Chunhuan; Ai, Kelong; Lu, Lehui

    2015-01-21

    To alleviate the kinetic barriers associated with ORR (oxygen reduction reaction) and OER (oxygen evolution reaction) in electrochemical systems, efficient nonprecious electrocatalysts are urgently required. Here we report a facile soft-template mediated approach for fabrication of nanostructured cobalt-iron double sulfides that are covalently entrapped in nitrogen-doped mesoporous graphitic carbon (Co0.5Fe0.5S@N-MC). Notably, with a positive half-wave potential (0.808 V) and a high diffusion-limiting current density, the composite material delivers unprecedentedly striking ORR electrocatalytic activity among recently reported nonprecious late transition metal chalcogenide materials in alkaline medium. Various characterization techniques, including X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction, are conducted to elucidate the correlation between structural features and catalytic activities of the composite. Moderate substitution and well-dispersion of iron in bimetallic sulfide composites are believed to have positive effect on the adsorption and activation of oxygen-containing species, thus leading to conspicuous ORR and OER catalytic enhancement compared to their monometallic counterparts. Besides, the covalent bridge between active sulfide particles and mesoporous carbon shells provides facile pathways for electron and mass transport. Beneficially, the intimate coupling interaction renders prolonged electrocatalytic performances to the composite. Our results may possibly lend a new impetus to the rational design of bi- or multimetallic sulfides encapsulated in porous carbon with improved performance for electrocatalysis and energy storage applications. PMID:25531776

  10. Coordinated Analysis of Two Graphite Grains from the CO3.0 LAP 031117 Meteorite: First Identification of a CO Nova Graphite and a Presolar Iron Sulfide Subgrain

    NASA Astrophysics Data System (ADS)

    Haenecour, Pierre; Floss, Christine; José, Jordi; Amari, Sachiko; Lodders, Katharina; Jadhav, Manavi; Wang, Alian; Gyngard, Frank

    2016-07-01

    Presolar grains constitute the remnants of stars that existed before the formation of the solar system. In addition to providing direct information on the materials from which the solar system formed, these grains provide ground-truth information for models of stellar evolution and nucleosynthesis. Here we report the in situ identification of two unique presolar graphite grains from the primitive meteorite LaPaz Icefield 031117. Based on these two graphite grains, we estimate a bulk presolar graphite abundance of {5}-3+7 ppm in this meteorite. One of the grains (LAP-141) is characterized by an enrichment in 12C and depletions in 33,34S, and contains a small iron sulfide subgrain, representing the first unambiguous identification of presolar iron sulfide. The other grain (LAP-149) is extremely 13C-rich and 15N-poor, with one of the lowest 12C/13C ratios observed among presolar grains. Comparison of its isotopic compositions with new stellar nucleosynthesis and dust condensation models indicates an origin in the ejecta of a low-mass CO nova. Grain LAP-149 is the first putative nova grain that quantitatively best matches nova model predictions, providing the first strong evidence for graphite condensation in nova ejecta. Our discovery confirms that CO nova graphite and presolar iron sulfide contributed to the original building blocks of the solar system.

  11. Nickel-cobalt-iron-copper sulfides and arsenides in solution-collapse breccia pipes, northwestern Arizona

    SciTech Connect

    Wenrich, K.J. ); Hlava, P.F. )

    1993-04-01

    An extensive suite of Ni-Co-Fe-Cu sulfides and arsenides lies within the matrix of solution-collapse breccias buried deep within the plateaus of the Grand Canyon region. Ceilings over large caverns in the Redwall collapsed, brecciating the overlying sandstone and forming cylindrical breccia pipes up to 300 ft in diameter that extend vertically as much as 3,000 ft. These highly permeable breccias served as a host for the precipitation of a suite of over 100 minerals, including uraninite, sphalerite, galena and various copper phases, in addition to the Ni-Co-bearing-phase discussed here. Intricately zoned crystals of small (<1 mm), euhedral Ni-Co-Fe-As-S minerals were the first to form during the second major episode of mineralization in these pipes. Several of these phases replace minerals, such as barite and anhydrite, from the first episode. Extensive microprobe work has been done on samples from two breccia pipe mines, the Hack 2 and Orphan, which are about 50 miles apart. Mineral compositions are similar except that no copper is found in the Ni-Co-Fe phases from the Hack 2 mine, while pyrites containing 1 wt % Cu are common from the Orphan, which was mined for copper. In some of these pyrites', Cu is dominant and the mineral is actually villamaninite. Pyrites from both mines characteristically contain 0.5 to 3 wt % As. Metal contents in zones pyrite-bravoite-vaesite (M[sub 1]S[sub 2]) crystals at the Hack 2 mine range from Fe[sub 1] to Fe[sub .12], Ni[sub 0] to Ni[sub .86], and Co[sub 0] to Co[sub .10]. The metal content for polydymite-siegenite-violarite averages about (Ni[sub 2.33]Co[sub .39]Fe[sub .23])(S[sub 3.9]As[sub .1]). Orphan mine pyrite-bravoite-vaesite-villamaninite ranges in composition from pure FeS[sub 2] to (Ni[sub .6]Fe[sub .21]Co[sub .17])S[sub 2], and (Cu[sub .46]Ni[sub .27]Fe[sub .21]Co[sub .13])S[sub 2]. Of all the sulfides or arsenides found in these breccia pipes, only nickeline consistently occurs as the pure end member.

  12. Reaction Mechanisms of Metals with Hydrogen Sulfide and Thiols in Model Wine. Part 2: Iron- and Copper-Catalyzed Oxidation.

    PubMed

    Kreitman, Gal Y; Danilewicz, John C; Jeffery, David W; Elias, Ryan J

    2016-05-25

    Sulfidic off-odors arising during wine production are frequently removed by Cu(II) fining. In part 1 of this study ( 10.1021/acs.jafc.6b00641 ), the reaction of H2S and thiols with Cu(II) was examined; however, the interaction of iron and copper is also known to play an important synergistic role in mediating non-enzymatic wine oxidation. The interaction of these two metals in the oxidation of H2S and thiols (cysteine, 3-sulfanylhexan-1-ol, and 6-sulfanylhexan-1-ol) was therefore examined under wine-like conditions. H2S and thiols (300 μM) were reacted with Fe(III) (100 or 200 μM) alone and in combination with Cu(II) (25 or 50 μM), and concentrations of H2S and thiols, oxygen, and acetaldehyde were monitored over time. H2S and thiols were shown to be slowly oxidized in the presence of Fe(III) alone and were not bound to Fe(III) under model wine conditions. However, Cu(II) added to model wine containing Fe(III) was quickly reduced by H2S and thiols to form Cu(I) complexes, which then rapidly reduced Fe(III) to Fe(II). Oxidation of Fe(II) in the presence of oxygen regenerated Fe(III) and completed the iron redox cycle. In addition, sulfur-derived oxidation products were observed, and the formation of organic polysulfanes was demonstrated. PMID:27133088

  13. Ferric Iron and Cobalt (III) compounds to safely decrease hydrogen sulfide in the body?

    PubMed

    Van de Louw, Andry; Haouzi, Philippe

    2013-08-10

    To sort out the putative roles of endogenous hydrogen sulfide (H2S) in clinical conditions wherein systemic inflammation or hypoxia is present, it becomes crucial to develop approaches capable of affecting H2S concentration that can be safely applied in humans. We have investigated a paradigm, which could achieve such a goal, using vitamin B12 (vit.B12), at the dose recommended in cyanide poisoning, and very low levels of methemoglobin (MetHb). Hydroxocobalamin in the plasma, supernatant of kidney, and heart tissue homogenates of rats that had received vit.B12 (140 mg.kg(-1) intravenous) was found in the μM range. Exogenous H2S (100 μM) added to the plasma or supernatants of these rats decreased at a significantly higher rate than in control rats. In the latter however a spontaneous oxidation of exogenous H2S occurred. In vitro, hydroxocobalamin solution (100 μM) decreased, within <2 min, an equimolar concentration of H2S by 80%. Three to five percent MetHb prevented H2S induced hyperventilation in vivo and decreased exogenous H2S in vitro by 25-40 μM within 30 s. Our observations lead to the hypothesis that innocuous levels of MetHb and vit.B12 could be a used as an effective and safe way to test the role of endogenous H2S in vivo. PMID:22233239

  14. Lithium/iron sulfide batteries for electric-vehicle propulsion and other applications. Progress report, October 1979-March 1980

    SciTech Connect

    Barney, D. L.; Steunenberg, R. K.; Chilenskas, A. A.; Gay, E. C.; Battles, J. E.; Miller, W. E.; Vissers, D. R.; Shimotake, H.

    1980-08-01

    The research and development activities of the program at Argonne National Laboratory (ANL) on lithium/iron sulfide batteries during the period October 1979-March 1980 is described. Although the major emphasis is currently on batteries for electric-vehicle propulsion, stationary energy-storage applications are also under investigation. The individual battery cells, which operate at 400 to 500/sup 0/C, are of a vertically oriented, prismatic design with two or more positive electrodes of FeS or FeS/sub 2/, facing negative electrodes of lithium-aluminum or lithium-silicon alloy, and molten LiCl-KCl electrolyte. The ANL program consists of cell chemistry studies, materials engineering, and component and auxiliary systems development. Important elements of this program are studies of the effects of design modifications on cell performance and post-test examinations of cells. During the reporting period, cell and battery development work has been aimed primarily at the first phase of the Mark II electric-vehicle battery program, which consists of an effort to develop high-reliability cells having boron nitride felt separators. Later in the Mark II program, the cells will be tested in 10-cell modules. Work on stationary energy-storage batteries during this period has consisted mainly of conceptual design studies. 23 figures, 9 tables.

  15. Reaction sequence of iron sulfide minerals in bacteria and their use as biomarkers.

    PubMed

    Pósfai, M; Buseck, P R; Bazylinski, D A; Frankel, R B

    1998-05-01

    Some bacteria form intracellular nanometer-scale crystals of greigite (Fe3S4) that cause the bacteria to be oriented in magnetic fields. Transmission electron microscope observations showed that ferrimagnetic greigite in these bacteria forms from nonmagnetic mackinawite (tetragonal FeS) and possibly from cubic FeS. These precursors apparently transform into greigite by rearrangement of iron atoms over a period of days to weeks. Neither pyrrhotite nor pyrite was found. These results have implications for the interpretation of the presence of pyrrhotite and greigite in the martian meteorite ALH84001. PMID:9572727

  16. Production of hydrogen sulfide from tetrathionate by the iron-oxidizing bacterium Thiobacillus ferrooxidans NASF-1.

    PubMed

    Ng, K Y; Kamimura, K; Sugio, T

    2000-01-01

    When incubated under anaerobic conditions, five strains of Thiobacillus ferrooxidans tested produced hydrogen sulfide (H2S) from elemental sulfur at pH 1.5. However, among the strains, T. ferrooxidans NASF-1 and AP19-3 were able to use both elemental sulfur and tetrathionate as electron acceptors for H2S production at pH 1.5. The mechanism of H2S production from tetrathionate was studied with intact cells of strain NASF-1. Strain NASF-1 was unable to use dithionate, trithionate, or pentathionate as an electron acceptor. After 12 h of incubation under anaerobic conditions at 30 degrees C, 1.3 micromol of tetrathionate in the reaction mixture was decomposed, and 0.78 micromol of H2S and 0.6 micromol of trithionate were produced. Thiosulfate and sulfite were not detected in the reaction mixture. From these results, we propose that H2S is produced at pH 1.5 from tetrathionate by T. ferrooxidans NASF-1, via the following two-step reaction, in which AH2 represents an unknown electron donor in NASF-1 cells. Namely, tetrathionate is decomposed by tetrathionate-decomposing enzyme to give trithionate and elemental sulfur (S4O6(2-)-->S3O6(2-) + S(o), Eq. 1), and the elemental sulfur thus produced is reduced by sulfur reductase using electrons from AH2 to give H2S (S(o) + AH2-->H2S + A, Eq. 2). The optimum pH and temperature for H2S production from tetrathionate under argon gas were 1.5 and 30 degrees C, respectively. Under argon gas, the H2S production from tetrathionate stopped after 1 d of incubation, producing a total of 2.5 micromol of H2S/5 mg protein. In contrast, under H2 conditions, H2S production continued for 6 d, producing a total of 10.0 micromol of H2S/5 mg protein. These results suggest that electrons from H2 were used to reduce elemental sulfur produced as an intermediate to give H2S. Potassium cyanide at 0.5 mM slightly inhibited H2S production from tetrathionate, but increased that from elemental sulfur 3-fold. 2,4-Dinitrophenol at 0.05 mM, carbonylcyanide

  17. Reductive Sequestration Of Pertechnetate (99TcO4–) By Nano Zerovalent Iron (nZVI) Transformed By Abiotic Sulfide

    SciTech Connect

    Fan, Dimin; Anitori, Roberto; Tebo, Bradley M.; Tratnyek, Paul G.; Lezama Pacheco, Juan S.; Kukkadapu, Ravi K.; Engelhard, Mark H.; Bowden, Mark E.; Kovarik, Libor; Arey, Bruce W.

    2013-04-24

    Under anoxic conditions, soluble 99TcO4– can be reduced to less soluble TcO2•nH2O, but the oxide is highly susceptible to reoxidation. Here we investigate an alternative strategy for remediation of Tc-contaminated groundwater whereby sequestration as Tc sulfide is favored by sulfidic conditions stimulated by nano zero-valent iron (nZVI). nZVI was pre-exposed to increasing concentrations of sulfide in simulated Hanford groundwater for 24 hrs to mimic the stages of aquifer sulfate reduction and onset of biotic sulfidogenesis. Solid-phase characterizations of the sulfidated nZVI confirmed the formation of nanocrystalline FeS phases, but higher S/Fe ratios (>0.112) did not result in the formation of significantly more FeS. The kinetics of Tc sequestration by these materials showed faster Tc removal rates with increasing S/Fe between S/Fe = 0–0.056, but decreasing Tc removal rates with S/Fe > 0.224. The more favorable Tc removal kinetics at low S/Fe could be due to a higher affinity of TcO4– for FeS (over iron oxides), and electron microscopy confirmed that the majority of the Tc was associated with FeS phases. The inhibition of Tc removal at high S/Fe appears to have been caused by excess HS–. X-ray absorption spectroscopy revealed that as S/Fe increased, Tc speciation shifted from TcO2•nH2O to TcS2. The most substantial change of Tc speciation occurred at low S/Fe, coinciding with the rapid increase of Tc removal rate. This agreement further confirms the importance of FeS in Tc sequestration.

  18. Environmental control on the occurrence of high-coercivity magnetic minerals and formation of iron sulfides in a 640 ka sediment sequence from Lake Ohrid (Balkans)

    NASA Astrophysics Data System (ADS)

    Just, Janna; Nowaczyk, Norbert R.; Sagnotti, Leonardo; Francke, Alexander; Vogel, Hendrik; Lacey, Jack H.; Wagner, Bernd

    2016-04-01

    The bulk magnetic mineral record from Lake Ohrid, spanning the past 637 kyr, reflects large-scale shifts in hydrological conditions, and, superimposed, a strong signal of environmental conditions on glacial-interglacial and millennial timescales. A shift in the formation of early diagenetic ferrimagnetic iron sulfides to siderites is observed around 320 ka. This change is probably associated with variable availability of sulfide in the pore water. We propose that sulfate concentrations were significantly higher before ˜ 320 ka, due to either a higher sulfate flux or lower dilution of lake sulfate due to a smaller water volume. Diagenetic iron minerals appear more abundant during glacials, which are generally characterized by higher Fe / Ca ratios in the sediments. While in the lower part of the core the ferrimagnetic sulfide signal overprints the primary detrital magnetic signal, the upper part of the core is dominated by variable proportions of high- to low-coercivity iron oxides. Glacial sediments are characterized by high concentration of high-coercivity magnetic minerals (hematite, goethite), which relate to enhanced erosion of soils that had formed during preceding interglacials. Superimposed on the glacial-interglacial behavior are millennial-scale oscillations in the magnetic mineral composition that parallel variations in summer insolation. Like the processes on glacial-interglacial timescales, low summer insolation and a retreat in vegetation resulted in enhanced erosion of soil material. Our study highlights that rock-magnetic studies, in concert with geochemical and sedimentological investigations, provide a multi-level contribution to environmental reconstructions, since the magnetic properties can mirror both environmental conditions on land and intra-lake processes.

  19. Synthesis and magnetic properties of the chromium-doped iron sulfide Fe1-xCrxS single crystalline nanoplates with a NiAs crystal structure.

    PubMed

    Starchikov, S S; Lyubutin, I S; Lin, Chun-Rong; Tseng, Yaw-Teng; Funtov, K O; Ogarkova, Yu L; Dmitrieva, T V; Ivanova, A G

    2015-06-28

    Single crystalline iron sulfide nanoparticles doped with chromium Fe1-xCrxS (0 ≤x≤ 0.15) have been successfully prepared by a thermal decomposition method. The particles are self-organized into the single crystalline plates with the accurate hexagonal shape and dimensions up to 1 μ in plane and about 30-40 nm in thickness. The samples have the NiAs-type crystal structure (P63/mmc) at all Cr concentrations up to x = 0.15. Fe(57)-Mössbauer spectroscopy data reveal four nonequivalent iron sites in these nanocrystals related to the different number of cation vacancies in neighboring of the iron atoms. A 2C-type superstructure or a mixture of 2C and 3C superstructures of vacancy ordering can appear in these samples. It was established that in the Fe1-xCrxS series chromium prefers to replace iron in the cation layers containing vacancies at 0.00 < x < 0.10 and Cr atoms occupy both iron and vacant sites at x > 0.10. The specific magnetic properties, which can be tuned by chromium doping, enable potential applications of these nanoparticles in technical devices using the material with thermally activated magnetic memory, for example, switches or storages. PMID:26018943

  20. Mineralogy of iron sulfides in CM1 and CI1 lithologies of the Kaidun breccia: Records of extreme to intense hydrothermal alteration

    NASA Astrophysics Data System (ADS)

    Harries, Dennis; Zolensky, Michael E.

    2016-06-01

    The polymict Kaidun microbreccia contains lithologies of C-type chondrites with euhedral iron sulfide crystals of hydrothermal origin. Our FIB-TEM study reveals that acicular sulfides in a CM1 lithology are composed of Fe-rich pyrrhotite with nonintegral vacancy superstructures (NC-pyrrhotite), troilite, and pentlandite, all showing distinct exsolution textures. Based on phase relations in the Fe-Ni-S system, we constrain the temperature of formation of the originally homogeneous monosulfide solid solution to the range of 100-300 °C. In some crystals the exsolution of pentlandite and the microtextural equilibration was incomplete, probably due to rapid cooling. We use thermodynamic modeling to constrain the physicochemical conditions of the extreme hydrothermal alteration in this lithology. Unless the CM1 lithology was sourced from a large depth in the parent body (internal pressure >85 bar) or the temperatures were in the lower range of the interval determined, the water was likely present as vapor. Previously described light δ34S compositions of sulfides in Kaidun's CM1 lithology are likely due to the loss of 34S-enriched H2S during boiling. Platy sulfide crystals in an adjacent, intensely altered CI1 lithology are composed of Fe-poor, monoclinic 4C-pyrrhotite and NC-pyrrhotite and probably formed at lower temperatures and higher fS2 relative to the CM1 lithology. However, a better understanding of the stability of Fe-poor pyrrhotites at temperatures below 300 °C is required to better constrain these conditions.

  1. Mineralogy of iron sulfides in CM1 and CI1 lithologies of the Kaidun breccia: Records of extreme to intense hydrothermal alteration

    NASA Astrophysics Data System (ADS)

    Harries, Dennis; Zolensky, Michael E.

    2016-05-01

    The polymict Kaidun microbreccia contains lithologies of C-type chondrites with euhedral iron sulfide crystals of hydrothermal origin. Our FIB-TEM study reveals that acicular sulfides in a CM1 lithology are composed of Fe-rich pyrrhotite with nonintegral vacancy superstructures (NC-pyrrhotite), troilite, and pentlandite, all showing distinct exsolution textures. Based on phase relations in the Fe-Ni-S system, we constrain the temperature of formation of the originally homogeneous monosulfide solid solution to the range of 100-300 °C. In some crystals the exsolution of pentlandite and the microtextural equilibration was incomplete, probably due to rapid cooling. We use thermodynamic modeling to constrain the physicochemical conditions of the extreme hydrothermal alteration in this lithology. Unless the CM1 lithology was sourced from a large depth in the parent body (internal pressure >85 bar) or the temperatures were in the lower range of the interval determined, the water was likely present as vapor. Previously described light δ34S compositions of sulfides in Kaidun's CM1 lithology are likely due to the loss of 34S-enriched H2S during boiling. Platy sulfide crystals in an adjacent, intensely altered CI1 lithology are composed of Fe-poor, monoclinic 4C-pyrrhotite and NC-pyrrhotite and probably formed at lower temperatures and higher fS2 relative to the CM1 lithology. However, a better understanding of the stability of Fe-poor pyrrhotites at temperatures below 300 °C is required to better constrain these conditions.

  2. Direct Synthesis of Novel and Reactive Sulfide-modified Nano Iron through Nanoparticle Seeding for Improved Cadmium-Contaminated Water Treatment

    PubMed Central

    Su, Yiming; Adeleye, Adeyemi S.; Huang, Yuxiong; Zhou, Xuefei; Keller, Arturo A.; Zhang, Yalei

    2016-01-01

    Magnetic sulfide-modified nanoscale zerovalent iron (S-nZVI) is of great technical and scientific interest because of its promising application in groundwater remediation, although its synthesis is still a challenge. We develop a new nanoparticle seeding method to obtain a novel and reactive nanohybrid, which contains an Fe(0) core covered by a highly sulfidized layer under high extent of sulfidation. Syntheses monitoring experiments show that seeding accelerates the reduction rate from Fe2+ to Fe0 by 19%. X-ray adsorption near edge structure (XANES) spectroscopy and extended X-ray absorption fine structure analyses demonstrate the hexahedral Fe-Fe bond (2.45 and 2.83 Å) formation through breaking down of the 1.99 Å Fe-O bond both in crystalline and amorphous iron oxide. The XANES analysis also shows 24.2% (wt%) of FeS with bond length of 2.4 Å in final nanohybrid. Both X-ray diffraction and Mössbauer analyses further confirm that increased nanoparticle seeding results in formation of more Fe0 crystals. Nano-SiO2 seeding brings down the size of single Fe0 grain from 32.4 nm to 18.7 nm, enhances final Fe0 content from 5.9% to 55.6%, and increases magnetization from 4.7 to 65.5 emu/g. The synthesized nanohybrid has high cadmium removal capacity and holds promising prospects for treatment of metal-contaminated water. PMID:27095387

  3. Direct Synthesis of Novel and Reactive Sulfide-modified Nano Iron through Nanoparticle Seeding for Improved Cadmium-Contaminated Water Treatment.

    PubMed

    Su, Yiming; Adeleye, Adeyemi S; Huang, Yuxiong; Zhou, Xuefei; Keller, Arturo A; Zhang, Yalei

    2016-01-01

    Magnetic sulfide-modified nanoscale zerovalent iron (S-nZVI) is of great technical and scientific interest because of its promising application in groundwater remediation, although its synthesis is still a challenge. We develop a new nanoparticle seeding method to obtain a novel and reactive nanohybrid, which contains an Fe(0) core covered by a highly sulfidized layer under high extent of sulfidation. Syntheses monitoring experiments show that seeding accelerates the reduction rate from Fe(2+) to Fe(0) by 19%. X-ray adsorption near edge structure (XANES) spectroscopy and extended X-ray absorption fine structure analyses demonstrate the hexahedral Fe-Fe bond (2.45 and 2.83 Å) formation through breaking down of the 1.99 Å Fe-O bond both in crystalline and amorphous iron oxide. The XANES analysis also shows 24.2% (wt%) of FeS with bond length of 2.4 Å in final nanohybrid. Both X-ray diffraction and Mössbauer analyses further confirm that increased nanoparticle seeding results in formation of more Fe(0) crystals. Nano-SiO2 seeding brings down the size of single Fe(0) grain from 32.4 nm to 18.7 nm, enhances final Fe(0) content from 5.9% to 55.6%, and increases magnetization from 4.7 to 65.5 emu/g. The synthesized nanohybrid has high cadmium removal capacity and holds promising prospects for treatment of metal-contaminated water. PMID:27095387

  4. Direct Synthesis of Novel and Reactive Sulfide-modified Nano Iron through Nanoparticle Seeding for Improved Cadmium-Contaminated Water Treatment

    NASA Astrophysics Data System (ADS)

    Su, Yiming; Adeleye, Adeyemi S.; Huang, Yuxiong; Zhou, Xuefei; Keller, Arturo A.; Zhang, Yalei

    2016-04-01

    Magnetic sulfide-modified nanoscale zerovalent iron (S-nZVI) is of great technical and scientific interest because of its promising application in groundwater remediation, although its synthesis is still a challenge. We develop a new nanoparticle seeding method to obtain a novel and reactive nanohybrid, which contains an Fe(0) core covered by a highly sulfidized layer under high extent of sulfidation. Syntheses monitoring experiments show that seeding accelerates the reduction rate from Fe2+ to Fe0 by 19%. X-ray adsorption near edge structure (XANES) spectroscopy and extended X-ray absorption fine structure analyses demonstrate the hexahedral Fe-Fe bond (2.45 and 2.83 Å) formation through breaking down of the 1.99 Å Fe-O bond both in crystalline and amorphous iron oxide. The XANES analysis also shows 24.2% (wt%) of FeS with bond length of 2.4 Å in final nanohybrid. Both X-ray diffraction and Mössbauer analyses further confirm that increased nanoparticle seeding results in formation of more Fe0 crystals. Nano-SiO2 seeding brings down the size of single Fe0 grain from 32.4 nm to 18.7 nm, enhances final Fe0 content from 5.9% to 55.6%, and increases magnetization from 4.7 to 65.5 emu/g. The synthesized nanohybrid has high cadmium removal capacity and holds promising prospects for treatment of metal-contaminated water.

  5. Stabilities of thiomolybdate complexes of iron; implications for retention of essential trace elements (Fe, Cu, Mo) in sulfidic waters.

    PubMed

    Helz, George R; Erickson, Britt E; Vorlicek, Trent P

    2014-06-01

    In aquatic ecosystems, availabilities of Fe, Mo and Cu potentially limit rates of critical biological processes, including nitrogen fixation, nitrate assimilation and N2O decomposition. During long periods in Earth's history when large parts of the ocean were sulfidic, what prevented these elements' quantitative loss from marine habitats as insoluble sulfide phases? They must have been retained by formation of soluble complexes. Identities of the key ligands are poorly known but probably include thioanions. Here, the first determinations of stability constants for Fe(2+)-[MoS4](2-) complexes in aqueous solution are reported based on measurements of pyrrhotite (hexagonal FeS) solubility under mildly alkaline conditions. Two linear complexes, [FeO(OH)MoS4](3-) and [(Fe2S2)(MoS4)2](4-), best explain the observed solubility variations. Complexes that would be consistent with cuboid cluster structures were less successful, implying that such clusters probably are minor or absent in aqueous solution under the conditions studied. The new data, together with prior data on stabilities of Cu(+)-[MoS4](2-) complexes, are used to explore computationally how competition of Fe(2+) and Cu(+) for [MoS4](2-), as well as competition of [MoS4](2-) and HS(-) for both metals would be resolved in solutions representative of sulfidic natural waters. Thiomolybdate complexes will be most important at sulfide concentrations near the [MoO4](2-)-[MoS4](2-) equivalence point. At lower sulfide concentrations, thiomolybdates are insufficiently stable to be competitive ligands in natural waters and at higher sulfide concentrations HS(-) ligands out-compete thiomolybdates. PMID:24226648

  6. Chemical insights into the synthesis and properties of polycrystalline and single crystal iron scandium sulfide (FeSc2S4)

    NASA Astrophysics Data System (ADS)

    Morey, Jennifer R.; Plumb, Kemp W.; Koohpayeh, Seyed M.; Broholm, Collin L.; McQueen, Tyrel M.

    Iron scandium sulfide, FeSc2S4, has recently attracted significant theoretical and experimental interest as a candidate spin-orbital liquid. An AB2X4 spinel, FeSc2S4 (space group Fd-3m, No. 227) features a high degree of frustration associated with the Fe2+, which occupies the A-site diamond sublattice and is tetrahedrally coordinated by sulfur. The Fe2+ ion is in a high spin (S =2) state, resulting in orbital degeneracy due to a single hole on the e orbitals. We report the strides we have made to produce material in powder and single crystal form, and the relationship between the chemistry and the structural, magnetic, and thermodynamic properties of FeSc2S4. This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Material Sciences and Engineering, under Grant No. DEFG02-08ER46544.

  7. Purification and characterization of sulfide:quinone oxidoreductase from an acidophilic iron-oxidizing bacterium, Acidithiobacillus ferrooxidans.

    PubMed

    Wakai, Satoshi; Tsujita, Mizuho; Kikumoto, Mei; Manchur, Mohammed A; Kanao, Tadayoshi; Kamimura, Kazuo

    2007-11-01

    Sulfide:quinone oxidoreductase (SQR) was purified from membrane of acidophilic chemolithotrophic bacterium Acidithiobacillus ferrooxidans NASF-1 cells grown on sulfur medium. It was composed of a single polypeptide with an apparent molecular mass of 47 kDa. The apparent K(m) values for sulfide and ubiquinone were 42 and 14 muM respectively. The apparent optimum pH for the SQR activity was about 7.0. A gene encoding a putative SQR of A. ferrooxidans NASF-1 was cloned and sequenced. The gene was expressed in Escherichia coli as a thioredoxin-fusion protein in inclusion bodies in an inactive form. A polyclonal antibody prepared against the recombinant protein reacted immunologically with the purified SQR. Western blotting analysis using the antibody revealed an increased level of SQR synthesis in sulfur-grown A. ferrooxidans NASF-1 cells, implying the involvement of SQR in elemental sulfur oxidation in sulfur-grown A. ferrooxidans NASF-1 cells. PMID:17986789

  8. Representative measurement of two-dimensional reactive phosphate distributions and co-distributed iron(II) and sulfide in seagrass sediment porewaters.

    PubMed

    Pagès, Anaïs; Teasdale, Peter R; Robertson, David; Bennett, William W; Schäfer, Jörg; Welsh, David T

    2011-11-01

    The high degree of heterogeneity within sediments can make interpreting one-dimensional measurements difficult. The recent development and use of in situ techniques that measure two-dimensional distributions of porewater solutes have facilitated investigation of the role of spatial heterogeneity in sediment biogeochemistry. A colourimetric diffusive equilibration in thin films method has been developed that allows two-dimensional, high-resolution measurement of reactive phosphate in sediment porewaters. A method detection limit of 0.22 μM, an effective upper limit of ~1000 μM and relative standard deviations typically below 5% were achieved. This method was evaluated by deployment in seagrass (Zostera capricorni) colonised sediments, as part of combined probes with similar colourimetric methods for sulfide and iron(II). The two-dimensional, high resolution distributions obtained provide a highly representative measurement of the co-distributions of porewater solutes, allowing heterogeneous features and biogeochemical processes to be observed and interpreted. Microniches of high phosphate concentration >100 μM were observed throughout the distributions and were interpreted to be due to localised zones of rapid organic matter mineralisation, possibly using electron acceptors other than iron(III) oxyhydroxides (e.g. aerobic respiration) as often they did not correspond with microniches of higher Fe(II) concentration. PMID:21855104

  9. Selenium Sulfide

    MedlinePlus

    Selenium sulfide, an anti-infective agent, relieves itching and flaking of the scalp and removes the dry, ... Selenium sulfide comes in a lotion and is usually applied as a shampoo. As a shampoo, selenium ...

  10. Iron

    MedlinePlus

    Iron is a mineral that our bodies need for many functions. For example, iron is part of hemoglobin, a protein which carries ... It helps our muscles store and use oxygen. Iron is also part of many other proteins and ...

  11. Sulfide detoxification in plant mitochondria.

    PubMed

    Birke, Hannah; Hildebrandt, Tatjana M; Wirtz, Markus; Hell, Rüdiger

    2015-01-01

    In contrast to animals, which release the signal molecule sulfide in small amounts from cysteine and its derivates, phototrophic eukaryotes generate sulfide as an essential intermediate of the sulfur assimilation pathway. Additionally, iron-sulfur cluster turnover and cyanide detoxification might contribute to the release of sulfide in mitochondria. However, sulfide is a potent inhibitor of cytochrome c oxidase in mitochondria. Thus, efficient sulfide detoxification mechanisms are required in mitochondria to ensure adequate energy production and consequently survival of the plant cell. Two enzymes have been recently described to catalyze sulfide detoxification in mitochondria of Arabidopsis thaliana, O-acetylserine(thiol)lyase C (OAS-TL C), and the sulfur dioxygenase (SDO) ethylmalonic encephalopathy protein 1 (ETHE1). Biochemical characterization of sulfide producing and consuming enzymes in mitochondria of plants is fundamental to understand the regulatory network that enables mitochondrial sulfide homeostasis under nonstressed and stressed conditions. In this chapter, we provide established protocols to determine the activity of the sulfide releasing enzyme β-cyanoalanine synthase as well as sulfide-consuming enzymes OAS-TL and SDO. Additionally, we describe a reliable and efficient method to purify OAS-TL proteins from plant material. PMID:25747485

  12. Iron-control additives improve acidizing

    SciTech Connect

    Walker, M.; Dill, W. ); Besler, M. )

    1989-07-24

    Iron sulfide and sulfur precipitation in sour wells can be controlled with iron-sequestering agents and sulfide modifiers. Oil production has been routinely increased in sour wells where precipitation of iron sulfide and elemental sulfur has been brought under control. Production increases have been especially noteworthy on wells that had a history of rapid production decline after acid stimulation. Twenty-fold production increases have been recorded. Key to the production increase has been to increase permeability with: Iron chelating agents that control precipitation of iron sulfide. A sulfide modifier that reduces precipitation of solids in the presence of excessive amounts of hydrogen sulfide and prevents precipitation of elemental sulfur.

  13. The metastable brain.

    PubMed

    Tognoli, Emmanuelle; Kelso, J A Scott

    2014-01-01

    Neural ensembles oscillate across a broad range of frequencies and are transiently coupled or "bound" together when people attend to a stimulus, perceive, think, and act. This is a dynamic, self-assembling process, with parts of the brain engaging and disengaging in time. But how is it done? The theory of Coordination Dynamics proposes a mechanism called metastability, a subtle blend of integration and segregation. Tendencies for brain regions to express their individual autonomy and specialized functions (segregation, modularity) coexist with tendencies to couple and coordinate globally for multiple functions (integration). Although metastability has garnered increasing attention, it has yet to be demonstrated and treated within a fully spatiotemporal perspective. Here, we illustrate metastability in continuous neural and behavioral recordings, and we discuss theory and experiments at multiple scales, suggesting that metastable dynamics underlie the real-time coordination necessary for the brain's dynamic cognitive, behavioral, and social functions. PMID:24411730

  14. The Metastable Brain

    PubMed Central

    Tognoli, Emmanuelle; Kelso, J. A. Scott

    2014-01-01

    Neural ensembles oscillate across a broad range of frequencies and are transiently coupled or “bound” together when people attend to a stimulus, perceive, think and act. This is a dynamic, self-assembling process, with parts of the brain engaging and disengaging in time. But how is it done? The theory of Coordination Dynamics proposes a mechanism called metastability, a subtle blend of integration and segregation. Tendencies for brain regions to express their individual autonomy and specialized functions (segregation, modularity) coexist with tendencies to couple and coordinate globally for multiple functions (integration). Although metastability has garnered increasing attention, it has yet to be demonstrated and treated within a fully spatiotemporal perspective. Here, we illustrate metastability in continuous neural and behavioral recordings, and we discuss theory and experiments at multiple scales suggesting that metastable dynamics underlie the real-time coordination necessary for the brain's dynamic cognitive, behavioral and social functions. PMID:24411730

  15. Oxidation of Aryl Diphenylmethyl Sulfides Promoted by a Nonheme Iron(IV)-Oxo Complex: Evidence for an Electron Transfer-Oxygen Transfer Mechanism.

    PubMed

    Barbieri, Alessia; De Carlo Chimienti, Rosemilia; Del Giacco, Tiziana; Di Stefano, Stefano; Lanzalunga, Osvaldo; Lapi, Andrea; Mazzonna, Marco; Olivo, Giorgio; Salamone, Michela

    2016-03-18

    The oxidation of a series of aryl diphenylmethyl sulfides (4-X-C6H4SCH(C6H5)2, where X = OCH3 (1), X = CH3 (2), X = H (3), and X = CF3 (4)) promoted by the nonheme iron(IV)-oxo complex [(N4Py)Fe(IV)═O](2+) occurs by an electron transfer-oxygen transfer (ET-OT) mechanism as supported by the observation of products (diphenylmethanol, benzophenone, and diaryl disulfides) deriving from α-C-S and α-C-H fragmentation of radical cations 1(+•)-4(+•), formed besides the S-oxidation products (aryl diphenylmethyl sulfoxides). The fragmentation/S-oxidation product ratios regularly increase through a decrease in the electron-donating power of the aryl substituents, that is, by increasing the fragmentation rate constants of the radical cations as indicated by a laser flash photolysis (LFP) study of the photochemical oxidation of 1-4 carried out in the presence of N-methoxyphenanthridinium hexafluorophosphate (MeOP(+)PF6(-)). PMID:26886491

  16. Iron isotope composition of particles produced by UV-femtosecond laser ablation of natural oxides, sulfides, and carbonates.

    PubMed

    d'Abzac, Francois-Xavier; Beard, Brian L; Czaja, Andrew D; Konishi, Hiromi; Schauer, James J; Johnson, Clark M

    2013-12-17

    The need for femtosecond laser ablation (fs-LA) systems coupled to MC-ICP-MS to accurately perform in situ stable isotope analyses remains an open question, because of the lack of knowledge concerning ablation-related isotopic fractionation in this regime. We report the first iron isotope analysis of size-resolved, laser-induced particles of natural magnetite, siderite, pyrrhotite, and pyrite, collected through cascade impaction, followed by analysis by solution nebulization MC-ICP-MS, as well as imaging using electron microscopy. Iron mass distributions are independent of mineralogy, and particle morphology includes both spheres and agglomerates for all ablated phases. X-ray spectroscopy shows elemental fractionation in siderite (C-rich agglomerates) and pyrrhotite/pyrite (S-rich spheres). We find an increase in (56)Fe/(54)Fe ratios of +2‰, +1.2‰, and +0.8‰ with increasing particle size for magnetite, siderite, and pyrrhotite, respectively. Fe isotope differences in size-sorted aerosols from pyrite ablation are not analytically resolvable. Experimental data are discussed using models of particles generation by Hergenröder and elemental/isotopic fractionation by Richter. We interpret the isotopic fractionation to be related to the iron condensation time scale, dependent on its saturation in the gas phase, as a function of mineral composition. Despite the isotopic variations across aerosol size fractions, total aerosol composition, as calculated from mass balance, confirms that fs-LA produces a stoichiometric sampling in terms of isotopic composition. Specifically, both elemental and isotopic fractionation are produced by particle generation processes and not by femtosecond laser-matter interactions. These results provide critical insights into the analytical requirements for laser-ablation-based stable isotope measurements of high-precision and accuracy in geological samples, including the importance of quantitative aerosol transport to the ICP. PMID

  17. Re-Os in FeNi, Sulfide, and Phosphide: The Possible Determination of Internal Isochrons for Iron Meteorites

    NASA Astrophysics Data System (ADS)

    Papanastassiou, D. A.; Shen, J. J.; Wasserburg, G. J.

    1995-09-01

    For age determinations of specific events in the evolution of iron meteorites it is essential to obtain a reasonable range of physical-chemical fractionation of Re/Os. The possible stages of iron meteorite evolution which can, in principle, result in Re-Os fractionation include: a) condensation of PGE and of FeNi in the solar nebula; b) subsequent oxidation of part of the Fe by reaction with S; c) segregation and partial removal of massive FeS during melting on parent planetesimals; d) melting followed by fractional crystallization of the metal phase and crystallization of the remaining FeS; e) element redistribution during subsolidus phase transformations to produce schreibersite sheaves and finally precipitation or exsolution of minor micro-phases, e.g., rhabdite, at a later stage. Using negative ion, thermal ionization, we have determined the Re and Os concentrations and Os isotopic compositions in metal samples of iron meteorites. We have also analyzed metal-FeS pairs from two IA iron meteorites and a metal-phosphide pair from one IIIA iron. The analytical results for the paired analyses are shown in Table 1. The Re, Os partition coefficients between these coexisting phases are shown in Table 2. The whole-rock, metal samples for group IA, IIA, IIIA, IVA and IVB irons are consistent with a single, well-defined best fit line which yields a slope of 0.07863+/-0.00031 (corresponding to an age of 4.62+/-0.02 AE;lambda=1.64x10^(-11) a^(-1)) and an initial ^(187)Os/^(188)Os = 0.09560+/-0.00018 (all uncertainties are 2 sigma). There is also a suggestion from the data for the IIA and IVA groups of a difference in ages of 60+/-45 m.y. We find that, in the presence of the metal phase, neither Re nor Os enter into the sulphide. Therefore, the production or segregation of sulphide [e.g., under steps (b) and (c), above] act only as diluents for the Re and Os concentrations and can have no influence on the Re-Os isotope systematics and age determinations. Given the refractory

  18. Composition of Aqueous Solutions in Equilibrium with Sulfides and Oxides of Iron at 350{degrees}C.

    PubMed

    Raymahashay, B C; Holland, H D

    1968-11-22

    Solutions of potassium chloride (pH-buffered and 1-molal) equilibrated at 350 degrees C with pyrrhotite, pyrite, and magnetite contained approximately 1 millimole of reduced sulfur and less than 0.1 millimole of oxidized sulfur per kilogram. Similar solutions equilibrated with pyrite, magnetite, and hematite contained approximately 1 millimole of reduced sulfur, but 3 to 6 millimoles of oxidized sulfur per kilogram. Both types of solutions contained less than 0.1 millimole of iron per kilogram at pH >/= 6 and approximately 100 millimoles per kilogram at pH 2. PMID:17769075

  19. Polarization of metastable 129Xe

    NASA Astrophysics Data System (ADS)

    Xia, Tian; Morgan, Steven; Jau, Yuan-Yu; Happer, William

    2008-05-01

    We have measured atomic polarization of metastable 129Xe in a pyrex cell by optical pumping, while metastability exchange optical pumping of 3He is routinely done. The atomic polarization of metastable Xe is on the order of 10%. Metastable xenon is created by electrodeless rf discharge. The hyperfine transition of metastable 129Xe is observed by microwave excitation. Atomic polarization can be demonstrated by comparison of the intensities of the transitions between different Zeeman sublevels, while pumping a specific optical transition of metastable Xe with circularly polarized light. This work offers insight into attempts to polarize 129Xe nuclei by metastability exchange optical pumping.

  20. The iron isotope composition of enstatite meteorites: Implications for their origin and the metal/sulfide Fe isotopic fractionation factor

    NASA Astrophysics Data System (ADS)

    Wang, Kun; Savage, Paul S.; Moynier, Frédéric

    2014-10-01

    Despite their unusual chemical composition, it is often proposed that the enstatite chondrites represent a significant component of Earth’s building materials, based on their terrestrial similarity for numerous isotope systems. In order to investigate a possible genetic relationship between the Fe isotope composition of enstatite chondrites and the Earth, we have analyzed 22 samples from different subgroups of the enstatite meteorites, including EH and EL chondrites, aubrites (main group and Shallowater) and the Happy Canyon impact melt. We have also analyzed the Fe isotopic compositions of separated (magnetic and non-magnetic) phases from both enstatite chondrites and achondrites. On average, EH3-5 chondrites (δ56Fe = 0.003 ± 0.042‰; 2 standard deviation; n = 9; including previous literature data) as well as EL3 chondrites (δ56Fe = 0.030 ± 0.038‰; 2 SD; n = 2) have identical and homogeneous Fe isotopic compositions, indistinguishable from those of the carbonaceous chondrites and average terrestrial peridotite. In contrast, EL6 chondrites display a larger range of isotopic compositions (-0.180‰ < δ56Fe < 0.181‰; n = 11), a result of mixing between isotopically distinct mineral phases (metal, sulfide and silicate). The large Fe isotopic heterogeneity of EL6 is best explained by chemical/mineralogical fragmentation and brecciation during the complex impact history of the EL parent body. Enstatite achondrites (aubrites) also exhibit a relatively large range of Fe isotope compositions: all main group aubrites are enriched in the light Fe isotopes (δ56Fe = -0.170 ± 0.189‰; 2 SD; n = 6), while Shallowater is, isotopically, relatively heavy (δ56Fe = 0.045 ± 0.101‰; 2 SD; n = 4; number of chips). We take this variation to suggest that the main group aubrite parent body formed a discreet heavy Fe isotope-enriched core, whilst the Shallowater meteorite is most likely from a different parent body where core and silicate material remixed. This could be

  1. Synthesis of alkenyl sulfides through the iron-catalyzed cross-coupling reaction of vinyl halides with thiols.

    PubMed

    Lin, Yun-Yung; Wang, Yu-Jen; Lin, Che-Hung; Cheng, Jun-Hao; Lee, Chin-Fa

    2012-07-20

    We report here the iron-catalyzed cross-coupling reaction of alkyl vinyl halides with thiols. While many works are devoted to the coupling of thiols with alkyl vinyl iodides, interestingly, the known S-vinylation of vinyl bromides and chlorides is limited to 1-(2-bromovinyl)benzene and 1-(2-chlorovinyl)benzene. Investigation on the coupling reaction of challenging alkyl vinyl bromides and chlorides with thiols is rare. Since the coupling of 1-(2-bromovinyl)benzene and 1-(2-chlorovinyl)benzene with thiols can be performed in the absence of any catalyst, here we focus on the coupling of thiols with alkyl vinyl halides. This system is generally reactive for alkyl vinyl iodides and bromides to provide the products in good yields. 1-(Chloromethylidene)-4-tert-butyl-cyclohexane was also coupled with thiols, giving the targets in moderate yields. PMID:22708836

  2. Micro-scale Complexity in Iron-Sulfide Phases in Precambrian Sedimentary Rocks Determined by Synchrotron Microprobe Spectroscopy

    NASA Astrophysics Data System (ADS)

    Webb, S.; Johnson, J. E.; Slotznick, S. P.; Roach, C.; Fischer, W. W.

    2014-12-01

    The record of sedimentary pyrite forms the foundation for most isotope records working to define the coupled evolution and behavior of the ancient iron and sulfur cycles. In order to assess the strengths and limitations of records derived from pyrite-rich rocks (e.g. iron speciation, sulfur isotope ratios), we need to understand more about the processes that form and alter sedimentary pyrite. From samples of the Archean/early Proterozoic Transvaal and middle Proterozoic Belt Supergroups, petrography reveals that what might operationally be called sedimentary pyrite has complex textures that hint at a rich process history of sulfur mineralization. A common limitation of virtually all proxy measurements employed to date is that they operate on 'bulk' samples, typically gram-sized or larger pieces. As such, they lose the ability to relate geochemistry to petrography at the scale of mineral grains. Many of the sedimentary pyrites in the Transvaal Supergroup exhibit complex redox and electronic structures of S and Fe, with crystals of pyrite, pyrrhotite, and sulfate-bearing minerals throughout. Parallel application of multiple techniques on the same samples across micron bases spatial scales, provide an opportunity to diagnose issues resulting from post-depositional alteration of sedimentary rocks. We have integrated light and electron microscopy for petrography, electron microprobe and synchrotron XRF for elemental composition, synchrotron X-ray spectroscopy for redox and chemical state, and secondary ion mass spectrometry (SIMS) for isotopic composition. The coupling of these tools allows in essence "images" of the proxy data at the micrometer scale, giving a wide array of textural and mineralogical information designed to inform and untangle the complicated histories of these early Precambrian rocks.

  3. Hydrogen Sulfide Oxidation by Myoglobin.

    PubMed

    Bostelaar, Trever; Vitvitsky, Victor; Kumutima, Jacques; Lewis, Brianne E; Yadav, Pramod K; Brunold, Thomas C; Filipovic, Milos; Lehnert, Nicolai; Stemmler, Timothy L; Banerjee, Ruma

    2016-07-13

    Enzymes in the sulfur network generate the signaling molecule, hydrogen sulfide (H2S), from the amino acids cysteine and homocysteine. Since it is toxic at elevated concentrations, cells are equipped to clear H2S. A canonical sulfide oxidation pathway operates in mitochondria, converting H2S to thiosulfate and sulfate. We have recently discovered the ability of ferric hemoglobin to oxidize sulfide to thiosulfate and iron-bound hydropolysulfides. In this study, we report that myoglobin exhibits a similar capacity for sulfide oxidation. We have trapped and characterized iron-bound sulfur intermediates using cryo-mass spectrometry and X-ray absorption spectroscopy. Further support for the postulated intermediates in the chemically challenging conversion of H2S to thiosulfate and iron-bound catenated sulfur products is provided by EPR and resonance Raman spectroscopy in addition to density functional theory computational results. We speculate that the unusual sensitivity of skeletal muscle cytochrome c oxidase to sulfide poisoning in ethylmalonic encephalopathy, resulting from the deficiency in a mitochondrial sulfide oxidation enzyme, might be due to the concentration of H2S by myoglobin in this tissue. PMID:27310035

  4. IRON

    EPA Science Inventory

    The document surveys the effects of organic and inorganic iron that are relevant to humans and their environment. The biology and chemistry of iron are complex and only partially understood. Iron participates in oxidation reduction processes that not only affect its geochemical m...

  5. Selenium Sulfide

    MedlinePlus

    Selenium sulfide comes in a lotion and is usually applied as a shampoo. As a shampoo, selenium sulfide usually is used twice a week for the first ... it is irritating. Rinse off all of the lotion.Do not use this medication on children younger ...

  6. Synthesis of magnetic rhenium sulfide composite nanoparticles

    NASA Astrophysics Data System (ADS)

    Tang, Naimei; Tu, Weixia

    2009-10-01

    Rhenium sulfide nanoparticles are associated with magnetic iron oxide through coprecipitation of iron salts with tetramethylammonium hydroxide. Sizes of the formed magnetic rhenium sulfide composite particles are in the range 5.5-12.5 nm. X-ray diffraction and energy-dispersive analysis of X-rays spectra demonstrate the coexistence of Fe 3O 4 and ReS 2 in the composite particle, which confirm the formation of the magnetic rhenium sulfide composite nanoparticles. The association of rhenium sulfide with iron oxide not only keeps electronic state and composition of the rhenium sulfide nanoparticles, but also introduces magnetism with the level of 24.1 emu g -1 at 14 kOe. Surface modification with monocarboxyl-terminated poly(ethylene glycol) (MPEG-COOH) has the role of deaggregating the composite nanoparticles to be with average hydrodynamic size of 27.3 nm and improving the dispersion and the stability of the composite nanoparticles in water.

  7. Reactive iron sulfide (FeS)-supported ultrafiltration for removal of mercury (Hg(II)) from water.

    PubMed

    Han, Dong Suk; Orillano, Maria; Khodary, Ahmed; Duan, Yuhang; Batchelor, Bill; Abdel-Wahab, Ahmed

    2014-04-15

    This study investigated removal of Hg(II) from water using FeS(s) with batch and continuous contact filtration systems. For the batch system, kinetic experiments showed that removal of Hg(II) by FeS(s) was rapid at lower concentration (500 μM), but at higher concentration (1000 and 1250 μM), more time was required to achieve greater than 99% removal. The concentration of iron released to the solution remained relatively low, typically below 3 μM. This would theoretically present less than 1% of the Hg(II) removed. Thus, a simple exchange of Hg(II) for Fe(II) in the solid (FeS(s)) does not explain the results, but if the Fe(II) released could react to form another solids, low concentrations of Fe do not preclude a mechanism in which Hg(II) reacts to form HgS and release Fe(II). A continuous contact dead-end ultrafiltration (DE/UF) system was developed to treat water containing Hg(II) by applying a FeS(s) suspension with stirred or non-stirred modes. A major reason for applying stirring to the system was to investigate the role of "shear" flow in rejection of Hg(II)-contacted FeS(s) by a UF membrane and the stability of Hg on the FeS(s). The Hg(II)-contacted FeS(s) was completely rejected by the DE/UF system and mercury was strongly retained on the FeS(s) particles. Almost no release of Hg(II) (≈0 mM) from the FeS(s) solids was observed when they were contacted with 0.1M-thiosulfate, regardless of whether the system was operated in stirred or non-stirred mode. However, rapid oxidation of FeS(s) was observed in the stirred system but not in the non-stirred system. Determining the mechanism of oxidation requires further study, but it is important because oxidation reduces the ability of the solids to remove additional Hg(II). PMID:24530550

  8. Sulfur and sulfides in chondrules

    NASA Astrophysics Data System (ADS)

    Marrocchi, Yves; Libourel, Guy

    2013-10-01

    The nature and distribution of sulfides within type I PO, POP and PP chondrules of the carbonaceous chondrite Vigarano (CV3) have been studied by secondary electron microscopy and electron microprobe. They occur predominantly as spheroidal blebs composed entirely of low-Ni iron sulfide (troilite, FeS) or troilite + magnetite but in less abundance in association with metallic Fe-Ni beads in opaque assemblages. Troilites are mainly located within the low-Ca pyroxene outer zone and their amounts increase with the abundance of low-Ca pyroxene within chondrules, suggesting co-crystallization of troilite and low-Ca pyroxene during high-temperature events. We show that sulfur concentration and sulfide occurrence in chondrules obey high temperature sulfur solubility and saturation laws. Depending on the fS2 and fO2 of the surrounding gas and on the melt composition, mainly the FeO content, sulfur dissolved in chondrule melts may eventually reach a concentration limit, the sulfur content at sulfide saturation (SCSS), at which an immiscible iron sulfide liquid separates from the silicate melt. The occurrence of both a silicate melt and an immiscible iron sulfide liquid is further supported by the non-wetting behavior of sulfides on silicate phases in chondrules due to the high interfacial tension between their precursor iron-sulfide liquid droplets and the surrounding silicate melt during the high temperature chondrule-forming event. The evolution of chondrule melts from PO to PP towards more silicic compositions, very likely due to high PSiO(g) of the surrounding nebular gas, induces saturation of FeS at much lower S content in PP than in PO chondrules, leading to the co-crystallization of iron sulfides and low-Ca pyroxenes. Conditions of co-saturation of low-Ca pyroxene and FeS are only achieved in non canonical environments characterized by high partial pressures of sulfur and SiO and redox conditions more oxidizing than IW-3. Fe and S mass balance calculations also

  9. Nanostructured metal sulfides for energy storage.

    PubMed

    Rui, Xianhong; Tan, Huiteng; Yan, Qingyu

    2014-09-01

    Advanced electrodes with a high energy density at high power are urgently needed for high-performance energy storage devices, including lithium-ion batteries (LIBs) and supercapacitors (SCs), to fulfil the requirements of future electrochemical power sources for applications such as in hybrid electric/plug-in-hybrid (HEV/PHEV) vehicles. Metal sulfides with unique physical and chemical properties, as well as high specific capacity/capacitance, which are typically multiple times higher than that of the carbon/graphite-based materials, are currently studied as promising electrode materials. However, the implementation of these sulfide electrodes in practical applications is hindered by their inferior rate performance and cycling stability. Nanostructures offering the advantages of high surface-to-volume ratios, favourable transport properties, and high freedom for the volume change upon ion insertion/extraction and other reactions, present an opportunity to build next-generation LIBs and SCs. Thus, the development of novel concepts in material research to achieve new nanostructures paves the way for improved electrochemical performance. Herein, we summarize recent advances in nanostructured metal sulfides, such as iron sulfides, copper sulfides, cobalt sulfides, nickel sulfides, manganese sulfides, molybdenum sulfides, tin sulfides, with zero-, one-, two-, and three-dimensional morphologies for LIB and SC applications. In addition, the recently emerged concept of incorporating conductive matrices, especially graphene, with metal sulfide nanomaterials will also be highlighted. Finally, some remarks are made on the challenges and perspectives for the future development of metal sulfide-based LIB and SC devices. PMID:25073046

  10. Process for removing technetium from iron and other metals

    DOEpatents

    Leitnaker, J.M.; Trowbridge, L.D.

    1999-03-23

    A process for removing technetium from iron and other metals comprises the steps of converting the molten, alloyed technetium to a sulfide dissolved in manganese sulfide, and removing the sulfide from the molten metal as a slag. 4 figs.

  11. Process for removing technetium from iron and other metals

    DOEpatents

    Leitnaker, James M.; Trowbridge, Lee D.

    1999-01-01

    A process for removing technetium from iron and other metals comprises the steps of converting the molten, alloyed technetium to a sulfide dissolved in manganese sulfide, and removing the sulfide from the molten metal as a slag.

  12. Sulfide clean-up of solutions from heavy metal ions

    SciTech Connect

    Kislinskaya, G.E.; Kozachek, N.N.; Krasnova, G.M.; Shenk, N.I.

    1982-09-20

    The object of the present research was to determine the conditions for thorough clean-up of solutions from cadmium or mercury contamination by use of iron sulfide. Results indicated that the shape of the dependence of the degree of extraction of copper with iron sulfide on the pH value is analogous to the curve for cadmium; that is, copper, like cadmium, is precipitated by chemical reaction. In distinction from cadmium and copper, mercury is extracted by iron sulfide both in acid and also in neutral solutions, that is, it is possible to attain a direct ion exchange by reaction. At high pH values, only small amounts of iron go into solution, therefore FeS can be used very rationally for the extraction of both small (about 1 mg/liter), and also of large (about 1 mg/liter) amounts of mercury from solutions, which are nearly neutral. By adding sodium sulfide and a flocculant, one can accelerate the process of mercury precipitation, and also reduce the solution of iron sulfide. In the present case, iron sulfide plays the role of a substrate for the crystallization of mercury sulfide, since in dilute solutions the latter forms poorly filterable colloidal solutions. Thus when one uses fused iron sulfide with addition of sodium sulfide, a high degree of mercury extraction is attained, and the spent sorbent is filtered well.

  13. Metastable nematic hedgehogs

    NASA Astrophysics Data System (ADS)

    Rosso, Riccardo; Virga, Epifanio G.

    1996-07-01

    For nematic liquid crystals, we study the local stability of a radial hedgehog against biaxial perturbations. Our analysis employs the Landau - de Gennes functional to describe the free energy stored in a ball, whose radius is a parameter of the model. We find that a radial hedgehog may be either unstable or metastable, depending on the values of the elastic constants. For unstable hedgehogs, we give an explicit expression for the radius of the ball within which the instability manifests itself: it can be interpreted as the size of the biaxial core of the defect; it is of the same order of magnitude as the radius of the disclination ring predicted by Penzenstadler and Trebin's model. The metastable hedgehogs predicted by our model are the major novelty of the paper. They tell us that we may also expect truly uniaxial point defects, whose core contains no biaxial structure.

  14. Iron

    MedlinePlus

    ... organ failure, coma, convulsions, and death. Child-proof packaging and warning labels on iron supplements have greatly ... levodopa that the body absorbs, making it less effective. Levodopa, found in Sinemet® and Stalevo®, is used ...

  15. Metallic sulfide additives for positive electrode material within a secondary electrochemical cell

    DOEpatents

    Walsh, William J.; McPheeters, Charles C.; Yao, Neng-ping; Koura, Kobuyuki

    1976-01-01

    An improved active material for use within the positive electrode of a secondary electrochemical cell includes a mixture of iron disulfide and a sulfide of a polyvalent metal. Various metal sulfides, particularly sulfides of cobalt, nickel, copper, cerium and manganese, are added in minor weight proportion in respect to iron disulfide for improving the electrode performance and reducing current collector requirements.

  16. Iron Transformation Pathways and Redox Micro-Environments in Seafloor Sulfide-Mineral Deposits: Spatially Resolved Fe XAS and δ57/54Fe Observations

    PubMed Central

    Toner, Brandy M.; Rouxel, Olivier J.; Santelli, Cara M.; Bach, Wolfgang; Edwards, Katrina J.

    2016-01-01

    Hydrothermal sulfide chimneys located along the global system of oceanic spreading centers are habitats for microbial life during active venting. Hydrothermally extinct, or inactive, sulfide deposits also host microbial communities at globally distributed sites. The main goal of this study is to describe Fe transformation pathways, through precipitation and oxidation-reduction (redox) reactions, and examine transformation products for signatures of biological activity using Fe mineralogy and stable isotope approaches. The study includes active and inactive sulfides from the East Pacific Rise 9°50′N vent field. First, the mineralogy of Fe(III)-bearing precipitates is investigated using microprobe X-ray absorption spectroscopy (μXAS) and X-ray diffraction (μXRD). Second, laser-ablation (LA) and micro-drilling (MD) are used to obtain spatially-resolved Fe stable isotope analysis by multicollector-inductively coupled plasma-mass spectrometry (MC-ICP-MS). Eight Fe-bearing minerals representing three mineralogical classes are present in the samples: oxyhydroxides, secondary phyllosilicates, and sulfides. For Fe oxyhydroxides within chimney walls and layers of Si-rich material, enrichments in both heavy and light Fe isotopes relative to pyrite are observed, yielding a range of δ57Fe values up to 6‰. Overall, several pathways for Fe transformation are observed. Pathway 1 is characterized by precipitation of primary sulfide minerals from Fe(II)aq-rich fluids in zones of mixing between vent fluids and seawater. Pathway 2 is also consistent with zones of mixing but involves precipitation of sulfide minerals from Fe(II)aq generated by Fe(III) reduction. Pathway 3 is direct oxidation of Fe(II) aq from hydrothermal fluids to form Fe(III) precipitates. Finally, Pathway 4 involves oxidative alteration of pre-existing sulfide minerals to form Fe(III). The Fe mineralogy and isotope data do not support or refute a unique biological role in sulfide alteration. The findings

  17. Iron Transformation Pathways and Redox Micro-Environments in Seafloor Sulfide-Mineral Deposits: Spatially Resolved Fe XAS and δ(57/54)Fe Observations.

    PubMed

    Toner, Brandy M; Rouxel, Olivier J; Santelli, Cara M; Bach, Wolfgang; Edwards, Katrina J

    2016-01-01

    Hydrothermal sulfide chimneys located along the global system of oceanic spreading centers are habitats for microbial life during active venting. Hydrothermally extinct, or inactive, sulfide deposits also host microbial communities at globally distributed sites. The main goal of this study is to describe Fe transformation pathways, through precipitation and oxidation-reduction (redox) reactions, and examine transformation products for signatures of biological activity using Fe mineralogy and stable isotope approaches. The study includes active and inactive sulfides from the East Pacific Rise 9°50'N vent field. First, the mineralogy of Fe(III)-bearing precipitates is investigated using microprobe X-ray absorption spectroscopy (μXAS) and X-ray diffraction (μXRD). Second, laser-ablation (LA) and micro-drilling (MD) are used to obtain spatially-resolved Fe stable isotope analysis by multicollector-inductively coupled plasma-mass spectrometry (MC-ICP-MS). Eight Fe-bearing minerals representing three mineralogical classes are present in the samples: oxyhydroxides, secondary phyllosilicates, and sulfides. For Fe oxyhydroxides within chimney walls and layers of Si-rich material, enrichments in both heavy and light Fe isotopes relative to pyrite are observed, yielding a range of δ(57)Fe values up to 6‰. Overall, several pathways for Fe transformation are observed. Pathway 1 is characterized by precipitation of primary sulfide minerals from Fe(II)aq-rich fluids in zones of mixing between vent fluids and seawater. Pathway 2 is also consistent with zones of mixing but involves precipitation of sulfide minerals from Fe(II)aq generated by Fe(III) reduction. Pathway 3 is direct oxidation of Fe(II) aq from hydrothermal fluids to form Fe(III) precipitates. Finally, Pathway 4 involves oxidative alteration of pre-existing sulfide minerals to form Fe(III). The Fe mineralogy and isotope data do not support or refute a unique biological role in sulfide alteration. The findings

  18. Iron transformation pathways and redox micro-environments in seafloor sulfide-mineral deposits: Spatially resolved Fe XAS and δ57/54Fe observations

    DOE PAGESBeta

    Toner, Brandy M.; Rouxel, Olivier J.; Santelli, Cara M.; Bach, Wolfgang; Edwards, Katrina J.

    2016-05-10

    Hydrothermal sulfide chimneys located along the global system of oceanic spreading centers are habitats for microbial life during active venting. Hydrothermally extinct, or inactive, sulfide deposits also host microbial communities at globally distributed sites. The main goal of this study is to describe Fe transformation pathways, through precipitation and oxidation-reduction (redox) reactions, and examine transformation products for signatures of biological activity using Fe mineralogy and stable isotope approaches. The study includes active and inactive sulfides from the East Pacific Rise 9°50'N vent field. First, the mineralogy of Fe(III)-bearing precipitates is investigated using microprobe X-ray absorption spectroscopy (μXAS) and X-ray diffractionmore » (μXRD). Second, laser-ablation (LA) and micro-drilling (MD) are used to obtain spatially-resolved Fe stable isotope analysis by multicollector-inductively coupled plasma-mass spectrometry (MC-ICP-MS). Eight Fe-bearing minerals representing three mineralogical classes are present in the samples: oxyhydroxides, secondary phyllosilicates, and sulfides. For Fe oxyhydroxides within chimney walls and layers of Si-rich material, enrichments in both heavy and light Fe isotopes relative to pyrite are observed, yielding a range of δ57Fe values up to 6‰. Overall, several pathways for Fe transformation are observed. Pathway 1 is characterized by precipitation of primary sulfide minerals from Fe(II)aq-rich fluids in zones of mixing between vent fluids and seawater. Pathway 2 is also consistent with zones of mixing but involves precipitation of sulfide minerals from Fe(II)aq generated by Fe(III) reduction. Pathway 3 is direct oxidation of Fe(II) aq from hydrothermal fluids to form Fe(III) precipitates. Finally, Pathway 4 involves oxidative alteration of pre-existing sulfide minerals to form Fe(III). The Fe mineralogy and isotope data do not support or refute a unique biological role in sulfide alteration. The

  19. Catalytic performance and deactivation of precipitated iron catalyst for selective oxidation of hydrogen sulfide to elemental sulfur in the waste gas streams from coal gasification

    SciTech Connect

    Mashapa, T.N.; Rademan, J.D.; van Vuuren, M.J.J.

    2007-09-15

    The selective oxidation of hydrogen sulfide to elemental sulfur, using a commercial, precipitated silica promoted ferric oxide based catalyst, was investigated in laboratory and pilot-plant reactors. Low levels of hydrogen sulfide (1-3 vol%) can be readily removed, but a continuous slow decrease in catalyst activity was apparent. X-ray photoelectron spectroscopy showed that the loss of activity was due to the formation of ferrous sulfate, which is known to be less active than the ferric oxide. In addition, studies using a model feed showed that the propene and HCN impurities in the plant feed stocks also act as potent catalyst poisons.

  20. Selenium sulfide

    Integrated Risk Information System (IRIS)

    Selenium sulfide ; CASRN 7446 - 34 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic

  1. Hydrogen sulfide

    Integrated Risk Information System (IRIS)

    Hydrogen sulfide ; 7783 - 06 - 4 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effec

  2. Carbonyl sulfide

    Integrated Risk Information System (IRIS)

    Carbonyl sulfide ; CASRN 463 - 58 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic

  3. Digital Synchronizer without Metastability

    NASA Technical Reports Server (NTRS)

    Simle, Robert M.; Cavazos, Jose A.

    2009-01-01

    A proposed design for a digital synchronizing circuit would eliminate metastability that plagues flip-flop circuits in digital input/output interfaces. This metastability is associated with sampling, by use of flip-flops, of an external signal that is asynchronous with a clock signal that drives the flip-flops: it is a temporary flip-flop failure that can occur when a rising or falling edge of an asynchronous signal occurs during the setup and/or hold time of a flip-flop. The proposed design calls for (1) use of a clock frequency greater than the frequency of the asynchronous signal, (2) use of flip-flop asynchronous preset or clear signals for the asynchronous input, (3) use of a clock asynchronous recovery delay with pulse width discriminator, and (4) tying the data inputs to constant logic levels to obtain (5) two half-rate synchronous partial signals - one for the falling and one for the rising edge. Inasmuch as the flip-flop data inputs would be permanently tied to constant logic levels, setup and hold times would not be violated. The half-rate partial signals would be recombined to construct a signal that would replicate the original asynchronous signal at its original rate but would be synchronous with the clock signal.

  4. Iron monosulfide accumulation and pyrite formation in eutrophic estuarine sediments

    NASA Astrophysics Data System (ADS)

    Kraal, Peter; Burton, Edward D.; Bush, Richard T.

    2013-12-01

    This study investigates iron (Fe) and sulfur (S) cycling in sediments from the eutrophic Peel-Harvey Estuary in Western Australia, which is subject to localized accumulation of strongly reducing, organic- and sulfide-rich sediments. Sedimentary iron was mostly present in highly reactive form (on average 73% of total Fe) and showed extensive sulfidization even in surface sediments, despite being overlain by a well-mixed oxygenated water column. This indicates that, under eutrophic marine conditions, Fe sulfidization may be driven by reductive processes in the sediment without requiring oxygen depletion in the overlying waters. Strong enrichments in iron monosulfide (FeS > 300 μmol g-1) were observed in fine-grained sediment intervals up to 45 cm depth. This metastable Fe sulfide is commonly restricted to thin subsurface sediment intervals, below which pyrite (FeS2) dominates. Our findings suggest inhibition of the dissolution-precipitation processes that replace FeS with FeS2 in sediments. Rates of pyrite formation based on the FeS2 profiles were much lower than those predicted by applying commonly used kinetic equations for pyrite formation. Dissolved H2S was present at millimolar levels throughout the investigated sediment profiles. This may indicate that (i) pyrite formation via reaction between dissolved Fe (including Fe clusters) and H2S was limited by low availability of dissolved Fe or (ii) reaction kinetics of pyrite formation via the H2S pathway may be relatively slow in natural reducing sediments. We propose that rapid burial of the FeS under anoxic conditions in these organic-rich reducing sediments minimizes the potential for pyrite formation, possibly by preventing dissolution of FeS or by limiting the availability of oxidized sulfur species that are required for pyrite formation via the polysulfide pathway.

  5. Desensitization of metastable intermolecular composites

    DOEpatents

    Busse, James R.; Dye, Robert C.; Foley, Timothy J.; Higa, Kelvin T.; Jorgensen, Betty S.; Sanders, Victor E.; Son, Steven F.

    2011-04-26

    A method to substantially desensitize a metastable intermolecular composite material to electrostatic discharge and friction comprising mixing the composite material with an organic diluent and removing enough organic diluent from the mixture to form a mixture with a substantially putty-like consistency, as well as a concomitant method of recovering the metastable intermolecular composite material.

  6. Complexity, Metastability and Nonextensivity

    NASA Astrophysics Data System (ADS)

    Beck, C.; Benedek, G.; Rapisarda, A.; Tsallis, C.

    Work and heat fluctuations in systems with deterministic and stochastic forces / E. G. D. Cohen and R. Van Zon -- Is the entropy S[symbol] extensive or nonextensive? / C. Tsallis -- Superstatistics: recent developments and applications / C. Beck -- Two stories outside Boltzmann-Gibbs statistics: Mori's Q-phase transitions and glassy dynamics at the onset of chaos / A. Robledo, F. Baldovin and E. Mayoral -- Time-averages and the heat theorem / A. Carati -- Fundamental formulae and numerical evidences for the central limit theorem in Tsallis statistics / H. Suyari -- Generalizing the Planck distribution / A. M. C. Soma and C. Tsallis -- The physical roots of complexity: renewal or modulation? / P. Grigolini -- Nonequivalent ensembles and metastability / H. Touchette and R. S. Ellis -- Statistical physics for cosmic structures / L. Pietronero and F. Sylos Labini -- Metastability and anomalous behavior in the HMF model: connections to nonextensive thermodynamics and glassy dynamics / A. Pluchino, A. Rapisarda and V. Latora -- Vlasov analysis of relaxation and meta-equilibrium / C. Anteneodo and R. O. Vallejos -- Weak chaos in large conservative systems - infinite-range coupled standard maps / L. G. Moyano, A. P. Majtey and C. Tsallis -- Deterministc aging / E. Barkai -- Edge of chaos of the classical kicked top map: sensitivity to initial conditions / S. M. Duarte Queirós and C. Tsallis -- What entropy at the edge of chaos? / M. Lissia, M. Coraddu and R. Tonelli -- Fractal growth of carbon schwarzites / G. Benedek ... [et al.] -- Clustering and interface propagation in interacting particle dynamics / A. Provata and V. K. Noussiou -- Resonant activation and noise enhanced stability in Josephson junctions / A. L. Pankratov and B. Spagnolo -- Symmetry breaking induced directed motions / C.-H. Chang and T. Y. Tsong -- General theory of Galilean-invariant entropic lattic Boltzmann models / B. M. Boghosian -- Unifying approach to the jamming transition in granular media and

  7. Hydrothermal ore-forming processes in the light of studies in rock- buffered systems: I. Iron-copper-zinc-lead sulfide solubility relations

    USGS Publications Warehouse

    Hemley, J.J.; Cygan, G.L.; Fein, J.B.; Robinson, G.R.; d'Angelo, W. M.

    1992-01-01

    Experimental studies, using cold-seal and extraction vessel techniques, were conducted on Fe, Pb, Zn, and Cu sulfide solubilities in chloride soultions at temperatures from 300?? to 700??C and pressures from 0.5 to 2 kbars. The solutions were buffered in pH by quartz monzonite and the pure potassium feldspar-muscovite-quartz assemblage and in fS2-fO2 largely by the assemblage pyrite-pyrrhotite-magnetite. Solubilities increase with increasing temperature and total chloride, and decrease with increasing pressure. The effect of increasing chloride concentration on solubility reflects primarily a shift to lower pH via the silicate buffer reactions. Similarity in behaviour with respect to the temperature and pressure of Fe, Zn, and Pb sulfide solubilities points to similarity in chloride speciation, and the neutral species appear to be dominant in the high-temperature region. -from Authors

  8. Interaction between aqueous uranium (VI) and sulfide minerals: Spectroscopic evidence for sorption and reduction

    SciTech Connect

    Wersin, P.; Hochella, M.F. Jr.; Persson, P.; Redden, G.; Leckie, J.O. ); Harris, D.W. )

    1994-07-01

    The interaction of aqueous U(VI) with galena and pyrite surfaces under anoxic conditions has been studied by solution analysis and by spectroscopic methods. The solution data indicate that uranyl uptake is strongly dependent on pH; maximum uptake (>98%) occurs above a pH range of between 4.8 and 5.5, depending on experimental conditions. Increasing the sorbate/sorbent ratio results in a relative decrease in uptake of uranyl and in slower sorption kinetics. Auger electron spectroscopy analysis indicates an inhomogeneous distribution of sorbed uranium at the surface. In the case of galena, formation of small precipitates ([approximately] 40 nm wide needles) of a uranium oxide compound are found. Pyrite shows a patchy distribution of uranium, mainly associated with oxidized surface species of sulfur and iron. X-ray photoelectron spectroscopy yields insight into possible redox processes indicating, for both sulfides, the concomitant formation of polysulfides and a uranium oxide compound with a mixed oxidation state at a U(VI)/U(IV) ratio of [approximately] 2. Furthermore, in the case of pyrite, at pH above 6 increased oxidation of sulfur and iron and higher relative amounts of unreduced surface-uranyl are observed. Fourier Transformed Infrared analysis of surface-bound uranyl shows a significant shift of the asymmetric stretching frequency to lower wavenumbers which is consistent with the formation of a U[sub 3]O[sub 8]-type compound and thus, independently, confirms the partial reduction of uranyl at the sulfide surface. The combination of AES, XPS, and FTIR provides a powerful approach for identifying mechanisms that govern the interaction of redox sensitive compounds in aqueous systems. The overall results indicate that sulfide minerals are efficient scavengers of soluble uranyl. Comparing the results with recent field observations, the authors suggest that thermodynamically metastable U[sub 3]O[sub 8] controls uranium concentrations in many anoxic groundwaters.

  9. Modulated voltage metastable ionization detector

    NASA Technical Reports Server (NTRS)

    Carle, G. C.; Kojiro, D. R.; Humphrey, D. E. (Inventor)

    1985-01-01

    The output current from a metastable ionization detector (MID) is applied to a modulation voltage circuit. An adjustment is made to balance out the background current, and an output current, above background, is applied to an input of a strip chart recorder. For low level concentrations, i.e., low detected output current, the ionization potential will be at a maximum and the metastable ionization detector will operate at its most sensitive level. When the detected current from the metastable ionization detector increases above a predetermined threshold level, a voltage control circuit is activated which turns on a high voltage transistor which acts to reduce the ionization potential. The ionization potential applied to the metastable ionization detector is then varied so as to maintain the detected signal level constant. The variation in ionization potential is now related to the concentration of the constituent and a representative amplitude is applied to another input of said strip chart recorder.

  10. Polar domains and charge-density waves in the acentric cerium(III) iron(II) sulfide Ce{sub 22}Fe{sub 21}S{sub 54}

    SciTech Connect

    Mills, Allison M.; Ruck, Michael

    2008-11-15

    The cerium(III) iron(II) sulfide Ce{sub 22}Fe{sub 21}S{sub 54} was synthesized through reaction of the binary sulfides C-Ce{sub 2}S{sub 3} and FeS in a LiCl/KCl flux at 1170 K, and its structure was determined by single-crystal X-ray diffraction. Ce{sub 22}Fe{sub 21}S{sub 54} crystallizes in the polar monoclinic space group Cm with a=16.3912(7) A, b=3.9554(1) A, c=62.028(3) A, {beta}=94.831(4){sup o}, and Z=2. The structure is a superstructure of the La{sub 2}Fe{sub 2}S{sub 5} structure type. Akin to the parent structure, trans-edge-sharing [FeS{sub 6}]-octahedra form linear chains, which are isotactically capped on one side by [FeS{sub 4}]-tetrahedra. The polarity of the resulting {sub {infinity}}{sup 1}[Fe{sub 2}S{sub 5}]-chains is transferred to the entire structure, as the unit cell contains two layered domains of opposite polarity with the unbalanced size ratio of 4:6. The domain walls are intrinsically centrosymmetric (layer group c 1 2/m 1). One wall consists of trigonal [FeS{sub 5}]-bipyramids, which are linked by corners and edges into a {sub {infinity}}{sup 2}[Fe{sub 2}S{sub 5}]-layer. In the other wall, the [FeS{sub 4}]-tetrahedra of two opposing {sub {infinity}}{sup 1}[Fe{sub 2}S{sub 5}]-chains share their vertices. The sulfur anions eliminated thereby are counterbalanced by vacancies in the iron sites, which follow a sinusoidal occupation modulation corresponding to a frozen charge-density wave with the wave vector k=4{pi}c*. The coordination polyhedra of all the cerium cations are bicapped trigonal prisms. - Graphical Abstract: Chains of [FeS{sub 6}]-octahedra that are isotactically capped on one side by [FeS{sub 4}]-tetrahedra dominate the acentric structure. The unit cell contains two layered domains of opposite polarity with unbalanced size ratio. Vacancies in the iron sites follow a sinusoidal occupation modulation corresponding to a frozen charge-density wave.

  11. Point Defect Concentrations in Metastable Fe-C Alloys

    NASA Astrophysics Data System (ADS)

    Först, Clemens J.; Slycke, Jan; van Vliet, Krystyn J.; Yip, Sidney

    2006-05-01

    Point defect species and concentrations in metastable Fe-C alloys are determined using density functional theory and a constrained free-energy functional. Carbon interstitials dominate unless iron vacancies are in significant excess, whereas excess carbon causes greatly enhanced vacancy concentration. Our predictions are amenable to experimental verification; they provide a baseline for rationalizing complex microstructures known in hardened and tempered steels, and by extension other technological materials created by or subjected to extreme environments.

  12. Persistency-field Eh-pH diagrams for sulfides and their application to supergene oxidation and enrichment of sulfide ore bodies

    USGS Publications Warehouse

    Sato, M.

    1992-01-01

    At temperatures prevailing near the Earth's surface, metastable co-existence of chemical substances is common because chemical reactions that would directly lead to the attainment of thermody-namically most stable equilibria are often blocked by high activation energy barriers. The persistency of a metastable assemblage is then governed by alternative reaction paths that provide lower activation energy barriers. Comparison of observed mineral assemblages in the supergene oxidized and enriched sulfide ores with corresponding stability Eh-pH diagrams reveals that the supergene assemblages are mostly metastable due primarily to the persistency of sulfide minerals beyond stability boundaries. A new set of diagrams called persistency-field Eh-pH diagrams has been constructed for binary metal sulfides on the basis of electrochemical and other experimental data. Each diagram delineates the persistency field, which is a combined field of thermodynamic stability and reaction path-controlled metastability, for a specific sulfide mineral. When applied to the supergene assemblages, these new diagrams show much better correspondence to the field observations. Although there may still be room for further refinement, the new diagrams appear to provide a strong visual aid to the understanding of the behavior of sulfide minerals in the supergene conditions. ?? 1992.

  13. Strata-bound, silver-bearing iron, lead, and zinc sulfide deposits in Silurian and Ordovician rocks of allochthonous terranes, Nevada and northern Mexico

    USGS Publications Warehouse

    Ketner, Keith Brindley

    1983-01-01

    Allochthonous terranes in northern Nevada contain strata-bound sulfide deposits at two horizons in Silurian and Ordovician siliceous sedimentary rocks. The most intensively mineralized horizon and most extensive deposit is at the base of the Silurian. Another less extensive deposit is in the lower Middle Ordovician. Spectrographic analyses of gossan from the basal Silurian horizon indicate anomalously high values of lead and zinc; and in about 40 percent of the samples, silver values are anomalously high. Suhsurface samples contain the primary minerals pyrite, galena, and sphalerite. The basal Silurian deposits are in thick-bedded chert that is overlain by micaceous siltstone. They are underlain by a thick-bedded black chert unit of Late Ordovician age. The basal Silurian gossan has been identified also in southwestern Nevada and in northern Mexico in stratigraphic sequences very similar to that of northern Nevada.

  14. Sulfide chemiluminescence detection

    DOEpatents

    Spurlin, Stanford R.; Yeung, Edward S.

    1985-01-01

    A method of chemiluminescently determining a sulfide which is either hydrogen sulfide or methyl mercaptan by reacting the sulfide with chlorine dioxide at low pressure and under conditions which allow a longer reaction time in emission of a single photon for every two sulfide containing species, and thereafter, chemiluminescently detecting and determining the sulfide. The invention also relates not only to the detection method, but the novel chemical reaction and a specifically designed chemiluminescence detection cell for the reaction.

  15. Sulfide chemiluminescence detection

    DOEpatents

    Spurlin, S.R.; Yeung, E.S.

    1985-11-26

    A method is described for chemiluminescently determining a sulfide which is either hydrogen sulfide or methyl mercaptan by reacting the sulfide with chlorine dioxide at low pressure and under conditions which allow a longer reaction time in emission of a single photon for every two sulfide containing species, and thereafter, chemiluminescently detecting and determining the sulfide. The invention also relates not only to the detection method, but the novel chemical reaction and a specifically designed chemiluminescence detection cell for the reaction. 4 figs.

  16. Platinum metals magmatic sulfide ores.

    PubMed

    Naldrett, A J; Duke, J M

    1980-06-27

    Platinum-group elements (PGE) are mined predominantly from deposits that have formed by the segregation of molten iron-nickel-copper sulfides from silicate magmas. The absolute concentrations of PGE in sulfides from different deposits vary over a range of five orders of magnitude, whereas those of other chalcophile elements vary by factors of only 2 to 100. However, the relative proportions of the different PGE in a given deposit are systematically related to the nature of the parent magma. The absolute and relative concentrations of PGE in magmatic sulfides are explained in terms of the degree of partial melting of mantle peridotite required to produce the parent magma and the processes of batch equilibration and fractional segregation of sulfides. The Republic of South Africa and the U.S.S.R. together possess more than 97 percent of the world PGE reserves, but significant undeveloped resources occur in North America. The Stillwater complex in Montana is perhaps the most important example. PMID:17796685

  17. Pulsed discharge production Ar* metastables

    NASA Astrophysics Data System (ADS)

    Han, Jiande; Heaven, Michael C.; Emmons, Daniel; Perram, Glen P.; Weeks, David E.; Bailey, William F.

    2016-03-01

    The production of relatively high densities of Ar* metastables (>1012 cm-3) in Ar/He mixtures, at total pressures close to 1 atm, is essential for the efficient operation of an optically pumped Ar* laser. We have used emission spectroscopy and diode laser absorption spectroscopy measurements to observe the production and decay of Ar* in a parallel plate pulsed discharge. With discharge pulses of 1 μs duration we find that metastable production is dominated by processes occurring within the first 100 ns of the gas break-down. Application of multiple, closely spaced discharge pulses yields insights concerning conditions that favor metastable production. This information has been combined with time-resolved measurements of voltage and current. The experimental results and preliminary modeling of the discharge kinetics are presented.

  18. Metastable metallic hydrogen glass

    SciTech Connect

    Nellis, W J

    2001-02-06

    pushing the molecules together sufficiently that an electron on one molecule can delocalize and move to an adjacent molecule, if the pressure is released the system will simply revert back to a diatomic insulator. Additives will probably be necessary to produce bonding which will inhibit the reverse transformation when pressure is released. One technique for rapidly quenching metallic fluid hydrogen is to use a thin micron-thick layer of condensed hydrogen contained between metal or diamond layers, which have a high thermal conductivity to quench shock temperature before pressure is released. An appropriate planar shock wave can probably be driven by a laser or small two-stage gun to achieve the necessary pressures, temperatures, and quench rates. In this way many experiments might be performed to find the appropriate combination of materials and shock-pressure history to achieve a shock-pressure-quenched metastable metallic hydrogen glass.

  19. Metastable vacua and complex deformations

    SciTech Connect

    Tatar, Radu; Wetenhall, Ben

    2007-12-15

    We use the non-normalizable complex deformations to describe the stringy realizations of the metastable vacua in N=1, SU(N{sub c}) SUSY theories with N{sub f}>N{sub c} massive fundamental flavors. The consideration of the non-normalizable deformations requires a modified toric duality. The new approach considers the tachyon condensation between pairs of wrapped D5 branes and anti-D5 branes and the resulting mixing between some cycles in the geometry. We enlarge the class of metastable vacua to the case of branes-antibranes wrapped on cycles of deformed A{sub n} singularities.

  20. Potassium-bearing Iron-Nickel Sulfides in Nature and High-Pressure Experiments: Geochemical Consequences of Potassium in the Earth's Core

    NASA Technical Reports Server (NTRS)

    Keshav, S.; Corgne, A.; McDonough, W. F.; Fei, Y.

    2005-01-01

    Introduction: Potassium (K) as a large ion lithophile element has dominantly been concentrated in the Earth s crust and the mantle through differentiation, and in the form of K-40 contributes to the planet s heat budget. However, whether or not K also enters core-forming phases, has been debated for over three decades. Arguments favoring entry of K in the core are based on: (1) K-sulfide (with Fe, Ni, Cu, Na, and Cl; djerfisherite) found in highly reduced enstatite chondrites (or aubrites, enstatite achondrites); (2) demonstration that K, owing to an s-d electronic switch at high-pressure, exhibits transition- element like character, (3) solubility of measurable K in Fe-Ni-S liquids at high pressure, temperature conditions, and (4) models of cooling of the core that seem to require, besides convection, some form of radioactivity, and thus lending support to the experimental work. In this contribution, we assess the effect of sequestering K in the core, as it is perhaps an element that is a key to reconciling geochemistry, paleomagnetism, accretion, and thermal evolution models for the planet.

  1. Marine diagenesis of hydrothermal sulfide

    SciTech Connect

    Moammar, M.O.

    1985-01-01

    An attempt is made to discuss the artificial and natural oxidation and hydrolysis of hydrothermal sulfide upon interaction with normal seawater. Synthetic and natural ferrosphalerite particles used in kinetic oxidation and hydrolysis studies in seawater develop dense, crystalline coatings consisting of ordered and ferrimagnetic delta-(Fe, Zn)OOH. Due to the formation of this reactive diffusion barrier, the release of Zn into solution decreases rapidly, and sulfide oxidation is reduced to a low rate determined by the diffusion of oxygen through the oxyhydroxide film. This also acts as an efficient solvent for ions such as Zn/sup 2 +/, Ca/sup 2 +/, and possibly Cd/sup 2 +/, which contribute to the stabilization of the delta-FeOOH structure. The oxidation of sulfide occurs in many seafloor spreading areas, such as 21/sup 0/N on the East Pacific Ridge. In these areas the old surface of the sulfide chimneys are found to be covered by an orange stain, and sediment near the base of nonactive vents is also found to consist of what has been referred to as amorphous iron oxide and hydroxide. This thesis also discusses the exceedingly low solubility of zinc in seawater, from delta-(Fe, Zn)OOH and the analogous phase (zinc-ferrihydroxide) and the zinc exchange minerals, 10-A manganate and montmorillonite. The concentrations of all four are of the same magnitude (16, 36.4, and 12 nM, respectively) as the zinc concentration in deep ocean water (approx. 10 nM), which suggests that manganates and montmorillonite with iron oxyhydroxides control zinc concentration in the deep ocean.

  2. Special simulator to study metastability

    NASA Astrophysics Data System (ADS)

    Haydt, Mary Sue V.; Mourad, Samiha

    2000-08-01

    Metastability has been long documented as a problem in digital systems with asynchronous inputs. This problem has been analyzed in CMOS latches using a 2nd order small signal model. However, uses of a third order model taking into account that the effect of the feedback transistor. While second order models are helpful in understanding how to model the circuit in the region, they do not provide sufficient information to accurately predict the essential parameter (tau) the maximum time at which the circuit may leave the metastable state. The only way to analyze such a circuit is to simulate it, using a simulator that combines small signal and large signal analysis. Future work on metastability will include modeling the feedback transistor as a resistor, and determining whether such a model is a reasonable simplification. The simulator can be modified easily to model small transistor geometries devices and to study the effect of large signal noise, such as ground and power supply bounce, on metastability. The model may also be applied to an interconnect model to improve delay and cross-talk simulations.

  3. Production of glycolic acid by chemolithotrophic iron- and sulfur-oxidizing bacteria and its role in delineating and sustaining acidophilic sulfide mineral-oxidizing consortia.

    PubMed

    Nancucheo, Ivan; Johnson, D Barrie

    2010-01-01

    Glycolic acid was detected as an exudate in actively growing cultures of three chemolithotrophic acidophiles that are important in biomining operations, Leptospirillum ferriphilum, Acidithiobacillus (At.) ferrooxidans, and At. caldus. Although similar concentrations of glycolic acid were found in all cases, the concentrations corresponded to ca. 24% of the total dissolved organic carbon (DOC) in cultures of L. ferriphilum but only ca. 5% of the total DOC in cultures of the two Acidithiobacillus spp. Rapid acidification (to pH 1.0) of the culture medium of At. caldus resulted in a large increase in the level of DOC, although the concentration of glycolic acid did not change in proportion. The archaeon Ferroplasma acidiphilum grew in the cell-free spent medium of At. caldus; glycolic acid was not metabolized, although other unidentified compounds in the DOC pool were metabolized. Glycolic acid exhibited levels of toxicity with 21 strains of acidophiles screened similar to those of acetic acid. The most sensitive species were chemolithotrophs (L. ferriphilum and At. ferrivorans), while the most tolerant species were chemoorganotrophs (Acidocella, Acidobacterium, and Ferroplasma species), and the ability to metabolize glycolic acid appeared to be restricted (among acidophiles) to Firmicutes (chiefly Sulfobacillus spp.). Results of this study help explain why Sulfobacillus spp. rather than other acidophiles are the main organic carbon-degrading bacteria in continuously fed stirred tanks used to bioprocess sulfide mineral concentrates and also why temporary cessation of pH control in these systems, resulting in rapid acidification, often results in a plume of the archaeon Ferroplasma. PMID:19933342

  4. Metal sulfide initiators for metal oxide sorbent regeneration

    DOEpatents

    Turk, Brian S.; Gupta, Raghubir P.

    1999-01-01

    A process of regenerating a sulfided sorbent is provided. According to the process of the invention, a substantial portion of the energy necessary to initiate the regeneration reaction is provided by the combustion of a particulate metal sulfide additive. In using the particulate metal sulfide additive, the oxygen-containing gas used to regenerate the sulfided sorbent can be fed to the regeneration zone without heating or at a lower temperature than used in conventional processes wherein the regeneration reaction is initiated only by heating the oxygen-containing. The particulate metal sulfide additive is preferably an inexpensive mineral ore such as iron pyrite which does not adversely affect the regeneration or corresponding desulfurization reactions. The invention further includes a sorbent composition comprising the particulate metal sulfide additive in admixture with an active metal oxide sorbent capable of removing one or more sulfur compounds from a sulfur-containing gas stream.

  5. Metal sulfide initiators for metal oxide sorbent regeneration

    DOEpatents

    Turk, Brian S.; Gupta, Raghubir P.

    2001-01-01

    A process of regenerating a sulfided sorbent is provided. According to the process of the invention, a substantial portion of the energy necessary to initiate the regeneration reaction is provided by the combustion of a particulate metal sulfide additive. In using the particulate metal sulfide additive, the oxygen-containing gas used to regenerate the sulfided sorbent can be fed to the regeneration zone without heating or at a lower temperature than used in conventional processes wherein the regeneration reaction is initiated only by heating the oxygen-containing gas. The particulate metal sulfide additive is preferably an inexpensive mineral ore such as iron pyrite which does not adversely affect the regeneration or corresponding desulfurization reactions. The invention further includes a sorbent composition comprising the particulate metal sulfide additive in admixture with an active metal oxide sorbent capable of removing one or more sulfur compounds from a sulfur-containing gas stream.

  6. Metal sulfide initiators for metal oxide sorbent regeneration

    DOEpatents

    Turk, B.S.; Gupta, R.P.

    1999-06-22

    A process of regenerating a sulfided sorbent is provided. According to the process of the invention, a substantial portion of the energy necessary to initiate the regeneration reaction is provided by the combustion of a particulate metal sulfide additive. In using the particulate metal sulfide additive, the oxygen-containing gas used to regenerate the sulfided sorbent can be fed to the regeneration zone without heating or at a lower temperature than used in conventional processes wherein the regeneration reaction is initiated only by heating the oxygen-containing gas. The particulate metal sulfide additive is preferably an inexpensive mineral ore such as iron pyrite which does not adversely affect the regeneration or corresponding desulfurization reactions. The invention further includes a sorbent composition comprising the particulate metal sulfide additive in admixture with an active metal oxide sorbent capable of removing one or more sulfur compounds from a sulfur-containing gas stream. 1 fig.

  7. Cadmium sulfide membranes

    DOEpatents

    Spanhel, Lubomir; Anderson, Marc A.

    1992-07-07

    A method is described for the creation of novel q-effect cadmium sulfide membranes. The membranes are made by first creating a dilute cadmium sulfide colloid in aqueous suspension and then removing the water and excess salts therefrom. The cadmium sulfide membrane thus produced is luminescent at room temperature and may have application in laser fabrication.

  8. Cadmium sulfide membranes

    DOEpatents

    Spanhel, Lubomir; Anderson, Marc A.

    1991-10-22

    A method is described for the creation of novel q-effect cadmium sulfide membranes. The membranes are made by first creating a dilute cadmium sulfide colloid in aqueous suspension and then removing the water and excess salts therefrom. The cadmium sulfide membrane thus produced is luminescent at room temperature and may have application in laser fabrication.

  9. Metastable Phases in Ice Clouds

    NASA Astrophysics Data System (ADS)

    Weiss, Fabian; Baloh, Philipp; Kubel, Frank; Hoelzel, Markus; Parker, Stewart; Grothe, Hinrich

    2014-05-01

    Polar Stratospheric Clouds and Cirrus Clouds contain both, pure water ice and phases of nitric acid hydrates. Preferentially for the latter, the thermodynamically stable phases have intensively been investigated in the past (e.g. nitric acid trihydrate, beta-NAT). As shown by Peter et al. [1] the water activity inside clouds is higher than expected, which might be explained by the presence of metastable stable phases (e.g. cubic ice). However, also metastable nitric acid hydrates might be important due to the inherent non-equilibrium freezing conditions in the upper atmosphere. The delta ice theory of Gao et al. [2] presents a model approach to solve this problem by involving both metastable ice and NAT as well. So it is of high interest to investigate the metastable phase of NAT (i.e. alpha-NAT), the structure of which was unknown up to the presence. In our laboratory a production procedure for metastable alpha-NAT has been developed, which gives access to neutron diffraction and X-ray diffraction measurements, where sample quantities of several Gramm are required. The diffraction techniques were used to solve the unknown crystalline structure of metastable alpha-NAT, which in turn allows the calculation of the vibrational spectra, which have also been recorded by us in the past. Rerefences [1] Peter, T., C. Marcolli, P. Spichtinger, T. Corti, M. B. Baker, and T. Koop. When dry air is too humid. Science, 314:1399-1402, 2006. [2] Gao, R., P. Popp, D. Fahey, T. Marcy, R. L. Herman, E. Weinstock, D. Baumgardener, T. Garrett, K. Rosenlof, T. Thompson, T. P. Bui, B. Ridley, S. C. Wofsy, O. B. Toon, M. Tolbert, B. Kärcher, Th. Peter, P. K. Hudson, A. Weinheimer, and A. Heymsfield. Evidence That Nitric Acid Increases Relative Humidity in Low-Temperature Cirrus Clouds, Science, 303:516-520, 2004. [3] Tizek, H., E. Knözinger, and H. Grothe. Formation and phase distribution of nitric acid hydrates in the mole fraction range xHNO3<0.25: A combined XRD and IR study, PCCP, 6

  10. Evolution of sulfide mineralization on Mars

    SciTech Connect

    Burns, R.G.; Fisher, D.S. )

    1990-08-30

    The presence of komatiitic igneous rocks on Marks, based on geochemical evidence from SNC meteorites and Viking X ray fluorescence analyses of the regolith, suggests that massive and disseminated iron sulfide mineralization occurs near the Martian surface. Analogies are drawn between possible ultramafic Fe-Ni sulfides on Mars and terrestrial pyrrhotite-pentlandite ore deposits associated with Archean komatiites formed during early crustal development on Earth. Partial melting of the mantle as a result of high radiogenic heat production then, extrusion of turbulent high-temperature ultramafic lavas, segregation of immiscible FeS melts during cooling, gravitational settling and fractional crystallization of sulfide minerals in magma chambers or lava flows produced massive and disseminated sulfide mineralization associated with terrestrial komatiites. Comparable processes probably occurred on Mars where, on account of the inferred higher Fe/(Fe + Mg) ratio of the X ray mantle (estimated to contain {approximately}4.5 wt % S), iron-rich basaltic magmas were produced by partial melting at depths and temperatures exceeding 165 km and 1,400{degree}C, respectively. Adiabatic diapiric emplacement of these iron-rich, very low viscosity basaltic melts transported significant concentrations of dissolved sulfur as S{sup 2{minus}} and HS{sup {minus}} from the mantle. Ensuing sulfide mineralization may have been either thinly disseminated within ultramafic lavas erupting over large areas of Mars or concentrated locally at the base of structural depressions. Cumulate ore deposits several meters thick may occur at the base of intrusions or in near-surface magma chambers. The evidence for insignificant plate tectonic activity on Mars and minimal interactions of Martian mantle with crust, hydrosphere and atmosphere has restricted the evolution of sulfide ore deposits there.

  11. NATURAL ATTENUATION OF INORGANICS DURING METAL SULFIDE FORMATION

    EPA Science Inventory

    Three different types of experiments will be carried out to investigate metal uptake during iron sulfide formation. These experimental designs were developed to examine the effects of the reactive iron source, and the extent to which nucleation and growth processes influence met...

  12. Decay of metastable topological defects

    SciTech Connect

    Preskill, J. ); Vilenkin, A. Lyman Laboratory of Physics, Harvard University, Cambridge, Massachusetts 02138 )

    1993-03-15

    We systematically analyze the decay of metastable topological defects that arise from the spontaneous breakdown of gauge or global symmetries. Quantum-mechanical tunneling rates are estimated for a variety of decay processes. The decay rate for a global string, vortex, domain wall, or kink is typically suppressed compared to the decay rate for its gauged counterpart. We also discuss the decay of global texture, and of semilocal and electroweak strings.

  13. Investigation of xenon metastable atoms

    NASA Astrophysics Data System (ADS)

    Xia, Tian; Jau, Yuan-Yu; Happer, William

    2007-06-01

    The electron configuration of a xenon atom in its metastable state consists of tightly bound core electrons with a single missing electron in the 5P shell, and a loosely bound ``valence electron'' in the 6S shell. For our current work, we have been using pyrex cells with internal tungsten electrodes, filled with isotopically enriched Xe129 gas. Ti-sapphire laser is used to pump the metastable atom from 6S2 to 6P2 and 6P3 at 823nm and 882nm respectively. The absorption spectrum is able to resolve the hyperfine structure of Xe129 in 6S2, 6P2 and 6P3 state. The hyperfine coefficients for 6S2, 6P2 agree with previously reported measurements. And the hyperfine coefficient for 6P3 state has not been reported before. If the pumping wavelength is locked at any one of the hyperfine transitions of Xenon129 atom, zero-field magnetic resonances of metastable Xenon atoms could be observed by pumping with circularly polarized laser beam. Since relaxation between magnetic sublevels is very fast due to the big depolarization collisional cross section, the linewidth of the magnetic resonant signal is broad.

  14. Iron-Nitride-Based Magnets: Synthesis and Phase Stabilization of Body Center Tetragonal (BCT) Metastable Fe-N Anisotropic Nanocomposite Magnet- A Path to Fabricate Rare Earth Free Magnet

    SciTech Connect

    2012-01-01

    REACT Project: The University of Minnesota will develop an early stage prototype of an iron-nitride permanent magnet material for EVs and renewable power generators. This new material, comprised entirely of low-cost and abundant resources, has the potential to demonstrate the highest energy potential of any magnet to date. This project will provide the basis for an entirely new class of rare-earth-free magnets capable of generating power without costly and scarce rare earth materials. The ultimate goal of this project is to demonstrate a prototype with magnetic properties exceeding state-of-the-art commercial magnets.

  15. Vibrational, X-ray absorption, and Mössbauer spectra of sulfate minerals from the weathered massive sulfide deposit at Iron Mountain, California

    USGS Publications Warehouse

    Majzlan, Juraj; Alpers, Charles N.; Bender Koch, Christian; McCleskey, R. Blaine; Myneni, Satish B.C.; Neil, John M.

    2014-01-01

    The Iron Mountain Mine Superfund site in California is a prime example of an acid mine drainage (AMD) system with well developed assemblages of sulfate minerals typical for such settings. Here we present and discuss the vibrational (infrared), X-ray absorption, and Mössbauer spectra of a number of these phases, augmented by spectra of a few synthetic sulfates related to the AMD phases. The minerals and related phases studied in this work are (in order of increasing Fe2O3/FeO): szomolnokite, rozenite, siderotil, halotrichite, römerite, voltaite, copiapite, monoclinic Fe2(SO4)3, Fe2(SO4)3·5H2O, kornelite, coquimbite, Fe(SO4)(OH), jarosite and rhomboclase. Fourier transform infrared spectra in the region 750–4000 cm−1 are presented for all studied phases. Position of the FTIR bands is discussed in terms of the vibrations of sulfate ions, hydroxyl groups, and water molecules. Sulfur K-edge X-ray absorption near-edge structure (XANES) spectra were collected for selected samples. The feature of greatest interest is a series of weak pre-edge peaks whose position is determined by the number of bridging oxygen atoms between Fe3+ octahedra and sulfate tetrahedra. Mössbauer spectra of selected samples were obtained at room temperature and 80 K for ferric minerals jarosite and rhomboclase and mixed ferric–ferrous minerals römerite, voltaite, and copiapite. Values of Fe2+/[Fe2+ + Fe3+] determined by Mössbauer spectroscopy agree well with those determined by wet chemical analysis. The data presented here can be used as standards in spectroscopic work where spectra of well-characterized compounds are required to identify complex mixtures of minerals and related phases.

  16. Vibrational, X-ray absorption, and Mössbauer spectra of sulfate minerals from the weathered massive sulfide deposit at Iron Mountain, California

    USGS Publications Warehouse

    Majzlan, Juraj; Alpers, Charles N.; Bender Koch, Christian; McCleskey, R. Blaine; Myneni, Satish B.C.; Neil, John M.

    2011-01-01

    The Iron Mountain Mine Superfund site in California is a prime example of an acid mine drainage (AMD) system with well developed assemblages of sulfate minerals typical for such settings. Here we present and discuss the vibrational (infrared), X-ray absorption, and M??ssbauer spectra of a number of these phases, augmented by spectra of a few synthetic sulfates related to the AMD phases. The minerals and related phases studied in this work are (in order of increasing Fe2O3/FeO): szomolnokite, rozenite, siderotil, halotrichite, r??merite, voltaite, copiapite, monoclinic Fe2(SO4)3, Fe2(SO4)3??5H2O, kornelite, coquimbite, Fe(SO4)(OH), jarosite and rhomboclase. Fourier transform infrared spectra in the region 750-4000cm-1 are presented for all studied phases. Position of the FTIR bands is discussed in terms of the vibrations of sulfate ions, hydroxyl groups, and water molecules. Sulfur K-edge X-ray absorption near-edge structure (XANES) spectra were collected for selected samples. The feature of greatest interest is a series of weak pre-edge peaks whose position is determined by the number of bridging oxygen atoms between Fe3+ octahedra and sulfate tetrahedra. M??ssbauer spectra of selected samples were obtained at room temperature and 80K for ferric minerals jarosite and rhomboclase and mixed ferric-ferrous minerals r??merite, voltaite, and copiapite. Values of Fe2+/[Fe2++Fe3+] determined by M??ssbauer spectroscopy agree well with those determined by wet chemical analysis. The data presented here can be used as standards in spectroscopic work where spectra of well-characterized compounds are required to identify complex mixtures of minerals and related phases. ?? 2011 Elsevier B.V.

  17. Mitochondrial adaptations to utilize hydrogen sulfide for energy and signaling.

    PubMed

    Olson, Kenneth R

    2012-10-01

    Sulfur is a versatile molecule with oxidation states ranging from -2 to +6. From the beginning, sulfur has been inexorably entwined with the evolution of organisms. Reduced sulfur, prevalent in the prebiotic Earth and supplied from interstellar sources, was an integral component of early life as it could provide energy through oxidization, even in a weakly oxidizing environment, and it spontaneously reacted with iron to form iron-sulfur clusters that became the earliest biological catalysts and structural components of cells. The ability to cycle sulfur between reduced and oxidized states may have been key in the great endosymbiotic event that incorporated a sulfide-oxidizing α-protobacteria into a host sulfide-reducing Archea, resulting in the eukaryotic cell. As eukaryotes slowly adapted from a sulfidic and anoxic (euxinic) world to one that was highly oxidizing, numerous mechanisms developed to deal with increasing oxidants; namely, oxygen, and decreasing sulfide. Because there is rarely any reduced sulfur in the present-day environment, sulfur was historically ignored by biologists, except for an occasional report of sulfide toxicity. Twenty-five years ago, it became evident that the organisms in sulfide-rich environments could synthesize ATP from sulfide, 10 years later came the realization that animals might use sulfide as a signaling molecule, and only within the last 4 years did it become apparent that even mammals could derive energy from sulfide generated in the gastrointestinal tract. It has also become evident that, even in the present-day oxic environment, cells can exploit the redox chemistry of sulfide, most notably as a physiological transducer of oxygen availability. This review will examine how the legacy of sulfide metabolism has shaped natural selection and how some of these ancient biochemical pathways are still employed by modern-day eukaryotes. PMID:22430869

  18. Metal-atom fluorescence from the quenching of metastable rare gases by metal carbonyls

    SciTech Connect

    Hollingsworth, W.E.

    1982-11-01

    A flowing afterglow apparatus was used to study the metal fluorescence resulting from the quenching of metastable rare-gas states by metal carbonyls. The data from the quenching or argon, neon, and helium by iron and nickel carbonyl agreed well with a restricted degree of freedom model indicating a concerted bond-breaking dissociation.

  19. Laser Cooling of Metastable Helium

    NASA Astrophysics Data System (ADS)

    Chuang, Ti.

    An experiment on the laser cooling of a metastable helium beam has been carried out. This experiment is appropriate to be described theoretically under a semiclassical framework. The experiment is the first phase of a large experimental project, whose ultimate goal is to investigate the behavior of laser -cooled metastable helium atoms in the quantum mechanical domain. This first phase is to provide the foundation for the second phase, which will be described in a full quantum mechanical framework. To reach this goal, an atomic beam source and a detection and data acquisition system were designed and constructed to be used in both phases. A laser system that is necessary for the first phase was also designed and constructed. This experiment was designed so that the studies of the atomic behavior, both in the semiclassical and quantum mechanical regions, can be investigated almost simultaneously. This experiment mainly consists of a one-dimensional transverse Doppler cooling of a metastable helium beam. The theory of Doppler cooling, based upon previous work of others, is discussed in this thesis as well. A final velocity width (HWHM) of ~0.62 m/s has been achieved, which is about 2.5 times larger than the Doppler velocity predicted by the theory. The two most likely reasons for not obtaining the Doppler velocity have been carefully examined. Sub-Doppler cooling of the helium beam was also tried, but was unsuccessful. It is our belief that the very same reasons prevent us from achieving sub -Doppler cooling as well.

  20. Extinction of metastable stochastic populations.

    PubMed

    Assaf, Michael; Meerson, Baruch

    2010-02-01

    We investigate the phenomenon of extinction of a long-lived self-regulating stochastic population, caused by intrinsic (demographic) noise. Extinction typically occurs via one of two scenarios depending on whether the absorbing state n=0 is a repelling (scenario A) or attracting (scenario B) point of the deterministic rate equation. In scenario A the metastable stochastic population resides in the vicinity of an attracting fixed point next to the repelling point n=0 . In scenario B there is an intermediate repelling point n=n1 between the attracting point n=0 and another attracting point n=n2 in the vicinity of which the metastable population resides. The crux of the theory is a dissipative variant of WKB (Wentzel-Kramers-Brillouin) approximation which assumes that the typical population size in the metastable state is large. Starting from the master equation, we calculate the quasistationary probability distribution of the population sizes and the (exponentially long) mean time to extinction for each of the two scenarios. When necessary, the WKB approximation is complemented (i) by a recursive solution of the quasistationary master equation at small n and (ii) by the van Kampen system-size expansion, valid near the fixed points of the deterministic rate equation. The theory yields both entropic barriers to extinction and pre-exponential factors, and holds for a general set of multistep processes when detailed balance is broken. The results simplify considerably for single-step processes and near the characteristic bifurcations of scenarios A and B. PMID:20365539

  1. Geometrically induced metastability and holography

    SciTech Connect

    Aganagic, Mina; Aganagic, Mina; Beem, Christopher; Seo, Jihye; Vafa, Cumrun

    2006-10-23

    We construct metastable configurations of branes and anti-branes wrapping 2-spheres inside local Calabi-Yau manifolds and study their large N duals. These duals are Calabi-Yau manifolds in which the wrapped 2-spheres have been replaced by 3-spheres with flux through them, and supersymmetry is spontaneously broken. The geometry of the non-supersymmetric vacuum is exactly calculable to all orders of the't Hooft parameter, and to the leading order in 1/N. The computation utilizes the same matrix model techniques that were used in the supersymmetric context. This provides a novel mechanism for breaking supersymmetry in the context of flux compactifications.

  2. Probing Metastability at the LHC

    SciTech Connect

    Clavelli, L.

    2010-02-10

    Current attempts to understand supersymmetry (susy) breaking are focused on the idea that we are not in the ground state of the universe but, instead, in a metastable state that will ultimately decay to an exactly susy ground state. It is interesting to ask how experiments at the Large Hadron Collider (LHC) will shed light on the properties of this future supersymmetric universe. In particular we ask how we can determine whether this final state has the possibility of supporting atoms and molecules in a susy background.

  3. EFFECT OF BACTERIAL SULFATE REDUCTION ON IRON-CORROSION SCALES

    EPA Science Inventory

    Iron-sulfur geochemistry is important in many natural and engineered environments including drinking water systems. In the anaerobic environment beneath scales of corroding iron drinking water distribution system pipes, sulfate reducing bacteria (SRB) produce sulfide from natura...

  4. Desensitization and recovery of metastable intermolecular composites

    DOEpatents

    Busse, James R.; Dye, Robert C.; Foley, Timothy J.; Higa, Kelvin T.; Jorgensen, Betty S.; Sanders, Victor E.; Son, Steven F.

    2010-09-07

    A method to substantially desensitize a metastable intermolecular composite material to electrostatic discharge and friction comprising mixing the composite material with an organic diluent and removing enough organic diluent from the mixture to form a mixture with a substantially putty-like consistency, as well as a concomitant method of recovering the metastable intermolecular composite material.

  5. Iron catalyzed coal liquefaction process

    DOEpatents

    Garg, Diwakar; Givens, Edwin N.

    1983-01-01

    A process is described for the solvent refining of coal into a gas product, a liquid product and a normally solid dissolved product. Particulate coal and a unique co-catalyst system are suspended in a coal solvent and processed in a coal liquefaction reactor, preferably an ebullated bed reactor. The co-catalyst system comprises a combination of a stoichiometric excess of iron oxide and pyrite which reduce predominantly to active iron sulfide catalysts in the reaction zone. This catalyst system results in increased catalytic activity with attendant improved coal conversion and enhanced oil product distribution as well as reduced sulfide effluent. Iron oxide is used in a stoichiometric excess of that required to react with sulfur indigenous to the feed coal and that produced during reduction of the pyrite catalyst to iron sulfide.

  6. Sulfide Mineralogy and Geochemistry

    NASA Astrophysics Data System (ADS)

    Dilles, John

    2007-02-01

    Reviews in Mineralogy and Geochemistry Series, Volume 61 David J. Vaughan, Editor Geochemical Society and Mineralogical Society of America; ISBN 0-939950-73-1 xiii + 714 pp.; 2006; $40. Sulfide minerals as a class represent important minor rock-forming minerals, but they are generally known as the chief sources of many economic metallic ores. In the past two decades, sulfide research has been extended to include important roles in environmental geology of sulfide weathering and resultant acid mine drainage, as well as in geomicrobiology in which bacteria make use of sulfides for metabolic energy sources. In the latter respect, sulfides played an important role in early evolution of life on Earth and in geochemical cycling of elements in the Earth's crust and hydrosphere.

  7. Iron clad wetlands: Soil iron-sulfur buffering determines coastal wetland response to salt water incursion

    NASA Astrophysics Data System (ADS)

    Schoepfer, Valerie A.; Bernhardt, Emily S.; Burgin, Amy J.

    2014-12-01

    Coastal freshwater wetland chemistry is rapidly changing due to increased frequency of salt water incursion, a consequence of global change. Seasonal salt water incursion introduces sulfate, which microbially reduces to sulfide. Sulfide binds with reduced iron, producing iron sulfide (FeS), recognizable in wetland soils by its characteristic black color. The objective of this study is to document iron and sulfate reduction rates, as well as product formation (acid volatile sulfide (AVS) and chromium reducible sulfide (CRS)) in a coastal freshwater wetland undergoing seasonal salt water incursion. Understanding iron and sulfur cycling, as well as their reduction products, allows us to calculate the degree of sulfidization (DOS), from which we can estimate how long soil iron will buffer against chemical effects of sea level rise. We show that soil chloride, a direct indicator of the degree of incursion, best predicted iron and sulfate reduction rates. Correlations between soil chloride and iron or sulfur reduction rates were strongest in the surface layer (0-3 cm), indicative of surface water incursion, rather than groundwater intrusion at our site. The interaction between soil moisture and extractable chloride was significantly related to increased AVS, whereas increased soil chloride was a stronger predictor of CRS. The current DOS in this coastal plains wetland is very low, resulting from high soil iron content and relatively small degree of salt water incursion. However, with time and continuous salt water exposure, iron will bind with incoming sulfur, creating FeS complexes, and DOS will increase.

  8. Iron and sulfur in the pre-biologic ocean

    NASA Technical Reports Server (NTRS)

    Walker, J. C.; Brimblecombe, P.

    1985-01-01

    Tentative geochemical cycles for the pre-biologic Earth are developed by comparing the relative fluxes of oxygen, dissolved iron, and sulfide to the atmosphere and ocean. The flux of iron is found to exceed both the oxygen and the sulfide fluxes. Because of the insolubility of iron oxides and sulfides the implication is that dissolved iron was fairly abundant and that oxygen and sulfide were rare in the atmosphere and ocean. Sulfate, produced by the oxidation of volcanogenic sulfur gases, was the most abundant sulfur species in the ocean, but its concentration was low by modern standards because of the absence of the river-borne flux of dissolved sulfate produced by oxidative weathering of the continents. These findings are consistent with the geologic record of the isotopic composition of sedimentary sulfates and sulfides. Except in restricted environments, the sulfur metabolism of the earliest organisms probably involved oxidized sulfur species not sulfide.

  9. Metastable Tight Knots in DNA

    NASA Astrophysics Data System (ADS)

    Dai, Liang; Renner, C. Benjamin; Doyle, Patrick

    2015-03-01

    Knotted structures can spontaneously occur in polymers such as DNA and proteins, and the formation of knots affects biological functions, mechanical strength and rheological properties. In this work, we calculate the equilibrium size distribution of trefoil knots in linear DNA using off-lattice simulations. We observe metastable knots on DNA, as predicted by Grosberg and Rabin. Furthermore, we extend their theory to incorporate the finite width of chains and show an agreement between our simulations and the modified theory for real chains. Our results suggest localized knots spontaneously occur in long DNA and the contour length in the knot ranges from 600 to 1800 nm. This research was supported by the National Research Foundation Singapore through the Singapore MIT Alliance for Research and Technology's research program in BioSystems and Micromechanics, the National Science Foundation (Grant No. 1335938).

  10. Atom lithography with metastable helium

    SciTech Connect

    Allred, Claire S.; Reeves, Jason; Corder, Christopher; Metcalf, Harold

    2010-02-15

    A bright metastable helium (He*) beam is collimated sequentially with the bichromatic force and three optical molasses velocity compression stages. Each He* atom in the beam has 20 eV of internal energy that can destroy a molecular resist assembled on a gold coated silicon wafer. Patterns in the resist are imprinted onto the gold layer with a standard selective etch. Patterning of the wafer with the He{sup *} was demonstrated with two methods. First, a mesh was used to protect parts of the wafer making an array of grid lines. Second, a standing wave of {lambda}=1083 nm light was used to channel and focus the He* atoms into lines separated by {lambda}/2. The patterns were measured with an atomic force microscope establishing an edge resolution of 80 nm. Our results are reliable and repeatable.

  11. Combined adsorption and oxidation mechanisms of hydrogen sulfide on granulated coal ash.

    PubMed

    Asaoka, Satoshi; Hayakawa, Shinjiro; Kim, Kyung-Hoi; Takeda, Kazuhiko; Katayama, Misaki; Yamamoto, Tamiji

    2012-07-01

    Hydrogen sulfide is highly toxic to benthic organisms and may cause blue tide with depletion of dissolved oxygen in water column due to its oxidation. The purpose of this study is to reveal the combined adsorption and oxidation mechanisms of hydrogen sulfide on granulated coal ash that is a byproduct from coal electric power stations to apply the material as an adsorbent for hydrogen sulfide in natural fields. Sulfur species were identified in both liquid and solid phases to discuss removal mechanisms of the hydrogen sulfide with the granulated coal ash. Batch experiments revealed that hydrogen sulfide decreased significantly by addition of the granulated coal ash and simultaneously the sulfate ion concentration increased. X-ray absorption fine structure analyses showed hydrogen sulfide was adsorbed onto the granulated coal ash and successively oxidized by manganese oxide (III) contained in the material. The oxidation reaction of hydrogen sulfide was coupling with reduction of manganese oxide. On the other hand, iron containing in the granulated coal ash was not involved in hydrogen sulfide oxidation, because the major species of iron in the granulated coal ash was ferrous iron that is not easily reduced by hydrogen sulfide. PMID:22487226

  12. Volcanogenic massive sulfide occurrence model: Chapter C in Mineral deposit models for resource assessment

    USGS Publications Warehouse

    Shanks, W.C. Pat, III; Koski, Randolph A.; Mosier, Dan L.; Schulz, Klaus J.; Morgan, Lisa A.; Slack, John F.; Ridley, W. Ian; Dusel-Bacon, Cynthia; Seal, Robert R., II; Piatak, Nadine M.

    2012-01-01

    An unusual feature of VMS deposits is the common association of stratiform "exhalative" deposits precipitated from hydrothermal fluids emanating into bottom waters. These deposits may extend well beyond the margins of massive sulfide and are typically composed of silica, iron, and manganese oxides, carbonates, sulfates, sulfides, and tourmaline.

  13. Intracellular iron minerals in a dissimilatory iron-reducing bacterium.

    PubMed

    Glasauer, Susan; Langley, Sean; Beveridge, Terry J

    2002-01-01

    Among prokaryotes, there are few examples of controlled mineral formation; the formation of crystalline iron oxides and sulfides [magnetite (Fe3O4) or greigite (Fe3S4)] by magnetotactic bacteria is an exception. Shewanella putrefaciens CN32, a Gram-negative, facultative anaerobic bacterium that is capable of dissimilatory iron reduction, produced microscopic intracellular grains of iron oxide minerals during growth on two-line ferrihydrite in a hydrogen-argon atmosphere. The minerals, formed at iron concentrations found in the soil and sedimentary environments where these bacteria are active, could represent an unexplored pathway for the cycling of iron by bacteria. PMID:11778045

  14. Vegetation successfully prevents oxidization of sulfide minerals in mine tailings.

    PubMed

    Li, Yang; Sun, Qingye; Zhan, Jing; Yang, Yang; Wang, Dan

    2016-07-15

    The oxidization of metal sulfide in tailings causes acid mine drainage. However, it remains unclear whether vegetation prevents the oxidization of metal sulfides. The oxidization characteristics and microbial indices of the tailings in the presence of various plant species were investigated to explore the effects of vegetation on the oxidization of sulfide minerals in tailings. The pH, reducing sulfur, free iron oxides (Fed), chemical oxygen consumption (COC) and biological oxygen consumption (BOC) were measured. Key iron- and sulfur-oxidizing bacteria (Acidithiobacillus spp., Leptospirillum spp. and Thiobacillus spp.) were quantified using real-time PCR. The results indicate that vegetation growing on tailings can effectively prevent the oxidization of sulfide minerals in tailings. A higher pH and reducing-sulfur content and lower Fed were observed in the 0-30 cm depth interval in the presence of vegetation compared to bare tailings (BT). The COC gradually decreased with depth in all of the soil profiles; specifically, the COC rapidly decreased in the 10-20 cm interval in the presence of vegetation but gradually decreased in the BT profiles. Imperata cylindrica (IC) and Chrysopogon zizanoides (CZ) profiles contained the highest BOC in the 10-20 cm interval. The abundance of key iron- and sulfur-oxidizing bacteria in the vegetated tailings were significantly lower than in the BT; in particular, IC was associated with the lowest iron- and sulfur-oxidizing bacterial abundance. In conclusion, vegetation successfully prevented the oxidization of sulfide minerals in the tailings, and Imperata cylindrica is the most effective in reducing the number of iron- and sulfur-oxidizing bacteria and helped to prevent the oxidization of sulfide minerals in the long term. PMID:27093236

  15. Metastable supersymmetry breaking vacua from conformal dynamics

    SciTech Connect

    Omura, Yuji

    2008-11-23

    We study the scenario that conformal dynamics leads to metastable supersymmetry breaking vacua. At a high energy scale, the superpotential is not R-symmetric, and has a supersymmetric minimum. However, conformal dynamics suppresses several operators along renormalization group flow toward the infrared fixed point. Then we can find an approximately R-symmetric superpotential, which has a metastable supersymmetry breaking vacuum, and the supersymmetric vacuum moves far away from the metastable supersymmetry breaking vacuum. We show a 4D simple model. Furthermore, we can construct 5D models with the same behavior, because of the AdS/CFT dual.

  16. Detection of sputtered metastable atoms by autoionization

    SciTech Connect

    Wucher, A.; Berthold, W.; Oechsner, H.; Franzreb, K.

    1994-03-01

    We report on a scheme for the detection of sputter-generated metastable atoms that is based on the resonant excitation of an autoionizing state by single-photon absorption from a tunable laser. Using this technique, sputtered silver atoms ejected in the metastable 4{ital d}{sup 9}5{ital s}{sup 2}{ital D}{sub 5/2} state with an excitation energy of 3.75 eV have been detected. This represents the highest excitation energy of sputtered metastable atoms observed so far.

  17. Metastable configurations of small-world networks.

    PubMed

    Heylen, R; Skantzos, N S; Blanco, J Busquets; Bollé, D

    2006-01-01

    We calculate the number of metastable configurations of Ising small-world networks that are constructed upon superimposing sparse Poisson random graphs onto a one-dimensional chain. Our solution is based on replicated transfer-matrix techniques. We examine the denegeracy of the ground state and find a jump in the entropy of metastable configurations exactly at the crossover between the small-world and the Poisson random graph structures. We also examine the difference in entropy between metastable and all possible configurations, for both ferromagnetic and bond-disordered long-range couplings. PMID:16486247

  18. Metastable configurations of small-world networks

    NASA Astrophysics Data System (ADS)

    Heylen, R.; Skantzos, N. S.; Blanco, J. Busquets; Bollé, D.

    2006-01-01

    We calculate the number of metastable configurations of Ising small-world networks that are constructed upon superimposing sparse Poisson random graphs onto a one-dimensional chain. Our solution is based on replicated transfer-matrix techniques. We examine the denegeracy of the ground state and find a jump in the entropy of metastable configurations exactly at the crossover between the small-world and the Poisson random graph structures. We also examine the difference in entropy between metastable and all possible configurations, for both ferromagnetic and bond-disordered long-range couplings.

  19. Platinum metals in magmatic sulfide ores

    USGS Publications Warehouse

    Naldrett, A.J.; Duke, J.M.

    1980-01-01

    Platinum-group elements (PGE) are mined predominantly from deposits that have formed by the segregation of molten iron-nickel-copper sulfides from silicate magmas. The absolute concentrations of PGE in sulfides from different deposits vary over a range of five orders of magnitude, whereas those of other chalcophile elements vary by factors of only 2 to 100. However, the relative proportions of the different PGE in a given deposit are systematically related to the nature of the parent magma. The absolute and relative concentrations of PGE in magmatic sulfides are explained in terms of the degree of partial melting of mantle peridotite required to produce the parent magma and the processes of batch equilibration and fractional segregation of sulfides. The Republic of South Africa and the U.S.S.R. together possess more than 97 percent of the world PGE reserves, but significant undeveloped resources occur in North America. The Stillwater complex in Montana is perhaps the most important example. Copyright ?? 1980 AAAS.

  20. Monitoring sulfide and sulfate-reducing bacteria

    SciTech Connect

    Tanner, R.S.

    1995-12-31

    Simple yet precise and accurate methods for monitoring sulfate-reducing bacteria (SRB) and sulfide remain useful for the study of bacterial souring and corrosion. Test kits are available to measure sulfide in field samples. A more precise methylene blue sulfide assay for both field and laboratory studies is described here. Improved media, compared to that in API RP-38, for enumeration of SRB have been formulated. One of these, API-RST, contained cysteine (1.1 mM) as a reducing agent, which may be a confounding source of sulfide. While cysteine was required for rapid enumeration of SRB from environmental samples, the concentration of cysteine in medium could be reduced to 0.4 mM. It was also determined that elevated levels of yeast extract (>1 g/liter) could interfere with enumeration of SRB from environmental samples. The API-RST medium was modified to a RST-11 medium. Other changes in medium composition, in addition to reduction of cysteine, included reduction of the concentration of phosphate from 3.4 mM to 2.2 mM, reduction of the concentration of ferrous iron from 0.8 mM to 0.5 mM and preparation of a stock mineral solution to ease medium preparation. SRB from environmental samples could be enumerated in a week in this medium.

  1. Metastability of a Supercompressed Fluid Monolayer

    PubMed Central

    Smith, Ethan C.; Crane, Jonathan M.; Laderas, Ted G.; Hall, Stephen B.

    2003-01-01

    Previous studies showed that monomolecular films of extracted calf surfactant collapse at the equilibrium spreading pressure during quasi-static compressions but become metastable at much higher surface pressures when compressed faster than a threshold rate. To determine the mechanism by which the films become metastable, we studied single-component films of 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC). Initial experiments confirmed similar metastability of POPC if compressed above a threshold rate. Measurements at different surface pressures then showed that rates of collapse, although initially increasing above the equilibrium spreading pressure, reached a sharply defined maximum and then slowed considerably. When heated, rapidly compressed films recovered their ability to collapse with no discontinuous change in area, arguing that the metastability does not reflect transition of the POPC film to a new phase. These observations indicate that in several respects, the supercompression of POPC monolayers resembles the supercooling of three-dimensional liquids toward a glass transition. PMID:14581205

  2. Metastability of Northern Hemisphere Teleconnection modes

    NASA Astrophysics Data System (ADS)

    Risbey, James; O'Kane, Terence; Monselesan, Didier; Franzke, Christian; Horenko, Ilia

    2014-05-01

    This work applies the FEM-BV-VARX method to study of the large scale modes of variability in the Northern Hemisphere as manifest in 500hPa geopotential height fields. The FEM-BV-VARX method identifies metastable states of the system. The results for regional domains confirm that the teleconnection modes referred to as the NAO in the Atlantic domain, PNA in the Pacific domain, and Scandanavian blocking in the Eurasian domain, all exhibit metastability. For the full Northern Hemisphere domain the metastable state combines the AO and a midlatitude circumglobal wavetrain pattern. These results are shown in a set of reanalysis products from NCEP; the 20th century reanalysis, NNR1, and the CFSR coupled reanalysis. The reanalysis products are all able to simulate the structure and temporal switching of regime states. Decadal and multidecadal regimes are clearly apparent in the model affiliation sequence of metastable states and correspond to known transition points for the teleconnection modes.

  3. Microbiological Leaching of Metallic Sulfides

    PubMed Central

    Razzell, W. E.; Trussell, P. C.

    1963-01-01

    The percentage of chalcopyrite leached in percolators by Thiobacillus ferrooxidans was dependent on the surface area of the ore but not on the amount. Typical examples of ore leaching, which demonstrate the role of the bacteria, are presented. In stationary fermentations, changes in KH2PO4 concentration above or below 0.1% decreased copper leaching as did reduction in the MgSO4·7H2O and increase in the (NH4)2SO4 concentration. Bacterial leaching of chalcopyrite was more effective than nonbiological leaching with ferric sulfate; ferric sulfate appeared to retard biological leaching, but this effect was likely caused by formation of an insoluble copper-iron complex. Ferrous sulfate and sodium chloride singly accentuated both bacterial and nonbiological leaching of chalcocite but jointly depressed bacterial action. Sodium chloride appeared to block bacterial iron oxidation without interfering with sulfide oxidation. Bacterial leaching of millerite, bornite, and chalcocite was greatest at pH 2.5. The economics of leaching a number of British Columbia ore bodies was discussed. PMID:16349627

  4. Non-paragenesis of Authigenic Sulfide Minerals: Mackinawite and Greigite are Not Precursors of Sedimentary Pyrite

    NASA Astrophysics Data System (ADS)

    Morse, J. W.; Rickard, D.

    2004-12-01

    Sedimentary sulfide minerals have traditionally been "operationally" divided into pyrite and acid volatile sulfide (AVS) minerals. AVS minerals have generally, with very scant direct evidence, been held to be comprised of mackinawite (tetragonal FeS) and greigite (cubic Fe3S4). They are also often referred to in the literature generically as FeS or iron monosulfides. Based largely on experimental studies at elevated temperatures over almost a third of a century and their metastability relative to pyrite, it has become almost dogma among sedimentary geochemists that mackinawite and or griegite are necessary precursors for pyrite formation in sediments. Being precursors to pyrite necessarily implies that they must be formed before pyrite and the normal paragenesis is supposed to be mackinawite to greigite to pyrite. The implication is that in their absence no authigenic sedimentary pyrite can be produced. This is not supported by many observations of pyrite formation in sediments where, during early diagenesis, abundant pyrite is commonly produced in the absence of any detectable AVS. Reactions for pyrite formation such as FeS(s) + S0(s) = FeS2(s) or FeS(s) + H2S = FeS2(s) + H2S, for example, represent the net mass balances and do not describe the process. More recently, two reaction mechanisms for pyrite formation, the "polysulfide" and "H2S" pathways, have gained wide acceptance. The reaction mechanisms involve dissolved species.If present at all, mackinawite and greigite contribute to pyrite formation via their dissolution which provides reactive components to solution. However, these dissolved components do not necessarily require mackinawite or greigite as their source. For the polysulfide pathway for pyrite formation the net reaction is better expressed as Fe2+ + S2-n = FeS2(s) + S2-n-2 and for the H2S pathway the reaction is FeS(aq) + H2S = FeS2(s) + H2S. FeS(aq) represents aqueous FeS clusters that are true solution components formed by the reaction between

  5. Use of hydrochloric acid for determinining solid-phase arsenic partitioning in sulfidic sediments.

    PubMed

    Wilkin, Richard T; Ford, Robert G

    2002-11-15

    We examined the use of room-temperature hydrochloric acid (1-6 M) and salt solutions of magnesium chloride, sodium carbonate, and sodium sulfide for the removal of arsenic from synthetic iron monosulfides and contaminated sediments containing acid-volatile sulfides (AVS). Results indicate that acid-soluble arsenic reacts with H2S released from AVS phases and precipitates at low pH as disordered orpiment or alacranite. Arsenic sulfide precipitation is consistent with geochemical modeling in that conditions during acid extraction are predicted to be oversaturated with respect to orpiment, realgar, or both. Binding of arsenic with sulfide at low pH is sufficiently strong that 6 M HCl will not keep spiked arsenic in the dissolved fraction. Over a wide range of AVS concentrations and molar [As]/[AVS] ratios, acid extraction of arsenic from sulfide-bearing sediments will give biased results that overestimate the stability or underestimate the bioavailability of sediment-bound arsenic. Alkaline solutions of sodium sulfide and sodium carbonate are efficient in removing arsenic from arsenic sulfides and mixed iron-arsenic sulfides because of the high solubility of arsenic at alkaline pH, the formation of stable arsenic complexes with sulfide or carbonate, or both. PMID:12487318

  6. Sulfidization and magnetization above hydrocarbon reservoirs

    SciTech Connect

    Reynolds, R.L.; Goldhaber, M.B.; Tuttle, M.L. )

    1991-03-01

    Geochemical and rock magnetic studies of strata over Cement oil field (Anadarko basin, Oklahoma), Simpson oil field (North Slope basin, Alaska), and the Edwards deep gas trend, south Texas coastal plain, document changes in original magnetizations caused by postdepositional iron sulfide minerals that are, or may be, related to hydrocarbon seepage. At Cement, ferrimagnetic pyrrhotite (Fe{sub 7}S{sub 8}) formed with pyrite and marcasite in Permian red beds. The Fe-S minerals contain isotopically heavy, abiogenic sulfur derived from thermal degradation of petroleum and (or) isotopically light sulfur derived from sulfate-reducing bacteria fed by leaking hydrocarbons. At Simpson, ferrimagnetic greigite (Fe{sub 3}S{sub 4}) dominates magnetizations in Upper Cretaceous nonmarine beds that contain biodegraded oil. Sulfur isotopic data are consistent with, but do not prove, a genetic link between the greigite ({delta}{sup 34}S {gt} +20 per mil) and seepage. In middle Tertiary sandstones of southeast Texas, pyrite and marcasite formed when abiogenic H{sub 2}S migrated upward from deep reservoirs, or when H{sub 2}S was produced at shallow depths by bacteria that utilized organic material dissolved in migrating water from depth. The sulfide minerals replaced detrital magnetite to result in a systematic decrease in magnetic susceptibility toward faults that connect deep petroleum reservoirs to shallow sandstone. The authors results show that abiologic and biologic mechanisms can generate magnetic sulfide minerals in some sulfidic zones of hydrocarbon seepage. The magnetizations in such zones are diminished most commonly by replacement of detrital magnetic minerals with nonmagnetic sulfide minerals or are unchanged if such detrital minerals were originally absent.

  7. Authigenesis of vivianite as influenced by methane-induced sulfidization in cold-seep sediments off southwestern Taiwan

    NASA Astrophysics Data System (ADS)

    Hsu, Ta-Wei; Jiang, Wei-Teh; Wang, Yunshuen

    2014-08-01

    Authigenesis of iron-rich phosphate nodules occurs in iron-rich cold-seep sediments (MD052911 core) at Yung-An Ridge offshore southwestern Taiwan. Raman, FTIR, and quantitative X-ray energy-dispersive spectroscopic analyses indicate that the phosphate mineral is vivianite (or barićite) and shows Fe/Mg molar ratios spanning from ca. 0.6 to 4.0 and a general down core trend of increasing Fe/Mg ratios. The formation of vivianite is limited to a depth interval of 13-17 mbsf (meters below seafloor) and is most prominent at ∼16 mbsf in association with high dissolved iron concentrations and depleted dissolved sulfide below a peak sulfidization zone (enriched in mackinawite and greigite). Alternate growths of vivianite and iron monosulfides and compositional zoning with Mg enriched towards the peripheries of individual nodules occur in the transition from the zone of vivianite mineralization to the sulfidization zone. The crystallization of vivianite below the sulfidization front could have been favored by scavenging of downward diffusive dissolved sulfide from pore waters in the sulfidization zone. Alternate growths and overlapping of the zones of iron monosulfides and vivianite can be attributed to fluctuations of the sulfidization front and methane flux. The discovery of vivianite in the Yung-An Ridge sediments implies that authigenic vivianite can be an important sink for phosphorus burial in cold-seep sediments that have high reactive-iron contents and high sedimentation rates.

  8. Transformation of Reactive Iron Minerals in a Permeable Reactive Barrier (Biowall) Used to Treat TCE in Groundwater

    EPA Science Inventory

    Abstract: Iron and sulfur reducing conditions are generally created in permeable reactive barrier (PRB) systems constructed for groundwater treatment, which usually leads to formation of iron sulfide phases. Iron sulfides have been shown to play an important role in degrading ch...

  9. Optical Forces on Metastable Helium

    NASA Astrophysics Data System (ADS)

    Corder, Christopher Scott

    Optical forces using lasers allow precise control over the motion of atoms. The bichromatic optical force (BF) is unique in its large magnitude and velocity range, arising from the absorption and stimulated emission processes. These properties were used to transversely collimate a beam of metastable helium (He*) using the 23S - 23P transition. The collimation created a very bright beam of He*, allowing experiments of neutral atom lithography. The He* beam was used to pattern material surfaces using a resist-based lithography technique, where the pattern was determined by either mechanical or optical masks. The optical masks produced features with a separation of half the wavelength of the light used. Patterning was successfully demonstrated with both IR and UV optical masks. The etched pattern resolution was ˜ 100 nm and limited by the material surface. Further experiments were performed studying the ability of the bichromatic force to cool. The finite velocity range of the BF allows estimation of a characteristic cooling time which is independent of the excited state lifetime, only depending on the atomic mass and optical transition energy. Past experiments, including the helium collimation used for neutral atom lithography, have demonstrated that the BF can collimate and longitudinally slow atomic beams, but required long interaction times that included many spontaneous emission (SE) events. The effect of SE can be mitigated, and is predicted to not be necessary for BF cooling. Since the BF cooling time is not related to the excited state lifetime, a transition can be chosen such that the cooling time is shorter than the SE cycle time, allowing direct laser cooling on atoms and molecules that do not have cycling transitions. Experiments using the helium 2 3S-3P transition were chosen because the BF cooling time (285 ns) is on the order of the average SE cycle time (260 ns). Numerical simulations of the experimental system were run predicting compression of the

  10. Sulfidation of silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Levard, C.; Michel, F. M.; Brown, G. E.

    2010-12-01

    Rapid development of nanotechnologies that exploit the properties of silver nanoparticles (Ag-NPs) raises questions concerning the impact of Ag on the environment. Ag-NPs are currently among the most widely used in the nanotechnology industry and the amount released into the environment is expected to increase along with production (1). When present in geochemical systems, Ag-NPs may undergo a variety of changes due to varying redox, pH, and chemical conditions. Expected changes range from surface modification (e.g., oxidation, sulfidation, chloridation etc.) to complete dissolution and re-precipitation. In this context, the focus of our work is on understanding the behavior of synthetic Ag-NPs with different particle sizes under varying conditions relevant to the environment. Sulfidation of Ag-NPs is of particular interest since it among the processes most likely to occur in aqueous systems, in particular under reducing conditions. Three sizes of Ag-NPs coated with polyvinyl pyrrolidone were produced using the polyol process (2) (7 ±1; 20 ±4, and 40 ±9 nm). Batch solutions containing the different Ag-NPs were subsequently reacted with Na2S solutions of different concentrations. The sulfidation process was followed step-wise for 24 hours and the corrosion products formed were characterized by electron microscopy (TEM/SEM), diffraction (XRD), and photo-electron spectroscopy (XPS). Surface charge (pHPZC) of the products formed during this process was also measured, as were changes in solubility and reactivity. Based on experimental observations we infer that the sulfidation process is the result of dissolution-precipitation and find that: (i) acanthite (Ag2S) is formed as a corrosion product; (ii) Ag-NPs aggregation increased with sulfidation rate; (iii) pHPZC increases with the rate of sulfidation; and (iv) the solubility of the corrosion products formed from sulfidation appears lower than that of non-sulfidated Ag-NPs. We observe size-dependent differences in