Physiology, Fe(II oxidation, and Fe mineral formation by a marine planktonic cyanobacterium grown under ferruginous conditions

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Elizabeth D. Swanner

2015-10-01

Full Text Available Evidence for Fe(II oxidation and deposition of Fe(III-bearing minerals from anoxic or redox-stratified Precambrian oceans has received support from decades of sedimentological and geochemical investigation of Banded Iron Formations (BIF. While the exact mechanisms of Fe(II oxidation remains equivocal, reaction with O2 in the marine water column, produced by cyanobacteria or early oxygenic phototrophs, was likely. In order to understand the role of cyanobacteria in the deposition of Fe(III minerals to BIF, we must first know how planktonic marine cyanobacteria respond to ferruginous (anoxic and Fe(II-rich waters in terms of growth, Fe uptake and homeostasis, and Fe mineral formation. We therefore grew the common marine cyanobacterium Synechococcus PCC 7002 in closed bottles that began anoxic, and contained Fe(II concentrations that span the range of possible concentrations in Precambrian seawater. These results, along with cell suspension experiments, indicate that Fe(II is likely oxidized by this strain via chemical oxidation with oxygen produced during photosynthesis, and not via any direct enzymatic or photosynthetic pathway. Imaging of the cell-mineral aggregates with scanning electron microscopy (SEM and confocal laser scanning microscopy (CLSM are consistent with extracellular precipitation of Fe(III (oxyhydroxide minerals, but that >10% of Fe(III sorbs to cell surfaces rather than precipitating. Proteomic experiments support the role of reactive oxygen species (ROS in Fe(II toxicity to Synechococcus PCC 7002. The proteome expressed under low Fe conditions included multiple siderophore biosynthesis and siderophore and Fe transporter proteins, but most siderophores are not expressed during growth with Fe(II. These results provide a mechanistic and quantitative framework for evaluating the geochemical consequences of perhaps life’s greatest metabolic innovation, i.e. the evolution and activity of oxygenic photosynthesis, in ferruginous

Abiotic and microbial interactions during anaerobic transformations of Fe(II and NOx-

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Flynn ePicardal

2012-03-01

Full Text Available Microbial Fe(II oxidation using NO3- as the terminal electron acceptor (nitrate-dependent Fe(II oxidation; NDFO has been studied for over 15 years. Although there are reports of autotrophic isolates and stable enrichments, many of the bacteria capable of NDFO are known organotrophic NO3- -reducers that require the presence of an organic, primary substrate, e.g., acetate, for significant amounts of Fe(II oxidation. Although the thermodynamics of Fe(II oxidation are favorable when coupled to either NO3- or NO2- reduction, the kinetics of abiotic Fe(II oxidation by NO3- are relatively slow except under special conditions. NDFO is typically studied in batch cultures containing millimolar concentrations of Fe(II, NO3-, and the primary substrate. In such systems, NO2- is often observed to accumulate in culture media during Fe(II oxidation. Compared to NO3-, abiotic reactions of biogenic NO2- and Fe(II are relatively rapid. The kinetics and reaction pathways of Fe(II oxidation by NO2- are strongly affected by medium composition and pH, reactant concentration, and the presence of Fe(II-sorptive surfaces, e.g., Fe(III oxyhydroxides and cellular surfaces. In batch cultures, the combination of abiotic and microbial Fe(II oxidation can alter product distribution and, more importantly, results in the formation of intracellular precipitates and extracellular Fe(III oxyhydroxide encrustations that apparently limit further cell growth and Fe(II oxidation. Unless steps are taken to minimize or account for potential abiotic reactions, results of microbial NDFO studies can be obfuscated by artifacts of the chosen experimental conditions, the use of inappropriate analytical methods, and the resulting uncertainties about the relative importance of abiotic and microbial reactions.In this manuscript, abiotic reactions of NO3- and NO2- with aqueous Fe2+, chelated Fe(II, and solid-phase Fe(II are reviewed along with factors that can influence overall NDFO reac

Synthesis and Characterization of Multimetallic Fe(II) and Mn(II ...

African Journals Online (AJOL)

Iron(II) and Manganese(II) complexes of the resulting ligand were obtained from its reactions with Fe(II) and Mn(II) salts in absolute methanol for the metal to ligand ratio 2:3. These complexes were characterized by Solubility, Conductivity, IR and UV-VIS spectrometry, elemental analysis and mass spectrometry. Keywords: ...

Speciative Determination of Dissolved Inorganic Fe(II), Fe(III) and Total Fe in Natural Waters by Coupling CPE with FAAS

International Nuclear Information System (INIS)

Gurkan, R.; Altunay, N.

2013-01-01

A new cloud point extraction (CPE) method for the preconcentration of trace iron speciation in natural waters prior to determination by flame atomic absorption spectrometry (FAAS) was developed in the present study. In this method, Fe(II) sensitively and selectively reacts with Calcon carboxylic acid (CCA) in presence of cetylpyridinium chloride (CPC) yielding a hydrophobic complex at pH 10.5, which is then entrapped in surfactant-rich phase. Total Fe was accurately and reliably determined after the reduction of Fe(III) to Fe(II) with sulfite. The amount of Fe(III) in samples was determined from the difference between total Fe and Fe(II). CPC was used not only as an auxiliary ligand in CPE, but also as sensitivity enhancement agent in FAAS. The nonionic surfactant, polyethylene glycol tert-octylphenyl ether (Triton X-114) was used as an extracting agent. The analytical variables affecting CPE efficiency were investigated in detail. The preconcentration/enhancement factors of 50 and 82 respectively, were obtained for the preconcentration of Fe(II) with 50 mL solution. Under the optimized conditions, the detection limit of Fe(II) in linear range of 0.2-60 μg L/sup -1/ was 0.06 μg L/sup -1/. The relative standard deviation was 2.7 percentage (20 μg L/sup -1/, N: 5), recoveries for Fe(II) were in range of 99.0-102.0 percentage for all water samples including certified reference materials (CRMs). In order to verify its accuracy, two CRMs were analyzed and the results obtained were statistically in good agreement with the certified values. (author)

Reactive Fe(II) layers in deep-sea sediments

Science.gov (United States)

König, Iris; Haeckel, Matthias; Drodt, Matthias; Suess, Erwin; Trautwein, Alfred X.

1999-05-01

The percentage of the structural Fe(II) in clay minerals that is readily oxidized to Fe(III) upon contact with atmospheric oxygen was determined across the downcore tan-green color change in Peru Basin sediments. This latent fraction of reactive Fe(II) was only found in the green strata, where it proved to be large enough to constitute a deep reaction layer with respect to the pore water O 2 and NO 3-. Large variations were detected in the proportion of the reactive Fe(II) concentration to the organic matter content along core profiles. Hence, the commonly observed tan-green color change in marine sediments marks the top of a reactive Fe(II) layer, which may represent the major barrier to the movement of oxidation fronts in pelagic subsurface sediments. This is also demonstrated by numerical model simulations. The findings imply that geochemical barriers to pore water oxidation fronts form diagenetically in the sea floor wherever the stage of iron reduction is reached, provided that the sediments contain a significant amount of structural iron in clay minerals.

Fe-Ti/Fe (II)-loading on ceramic filter materials for residual chlorine removal from drinking water.

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Man, Kexin; Zhu, Qi; Guo, Zheng; Xing, Zipeng

2018-06-01

Ceramic filter material was prepared with silicon dioxide (SiO 2 ), which was recovered from red mud and then modified with Fe (II) and Fe-Ti bimetal oxide. Ceramic filter material can be used to reduce the content of residual chlorine from drinking water. The results showed that after a two-step leaching process with 3 M hydrochloric acid (HCl) and 90% sulfuric acid (H 2 SO 4 ), the recovery of SiO 2 exceeded 80%. Fe (II)/Fe-Ti bimetal oxide, with a high adsorption capacity of residual chlorine, was prepared using a 3:1 M ratio of Fe/Ti and a concentration of 0.4 mol/L Fe 2+ . According to the zeta-potential, scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis, Fe (II) and Fe-Ti bimetal oxide altered the zeta potential and structural properties of the ceramic filter material. There was a synergistic interaction between Fe and Ti in which FeOTi bonds on the material surface and hydroxyl groups provided the active sites for adsorption. Through a redox reaction, Fe (II) transfers hypochlorite to chloride, and FeOTiCl bonds were formed after adsorption. Copyright © 2018 Elsevier Ltd. All rights reserved.

Hydroxyl Radical Formation from HULIS and Fe(II) Interactions: Fulvic Acid-Fe(II) Complexes in Simulated and Human Lung Fluids

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Gonzalez, D.

2017-12-01

Inhalation of fine particulate matter (PM2.5) has long been associated with adverse health outcomes. However, the causative agents and underlying mechanisms for these health effects have yet to be identified. One hypothesis is that PM2.5 deposited in the alveoli produce an excess of highly reactive radicals, leading to oxidative stress. The OH radical may be the most physiologically damaging, capable of oxidizing of lipids, proteins and DNA. Due to the variability and uncertainty in PM2.5 composition, the components that contribute to OH formation are not well understood. Soluble Fe is a component of PM2.5that produces OH under physiological conditions. Humic-like substances are water soluble organics found in biomass burning and tobacco smoke. Humic-like substances are capable of binding to Fe and enhancing OH formation, but this chemistry is not well understood. In this work, we use soil derived fulvic acid as a surrogate for Humic-like substances and investigate its effect on OH formation from Fe(II) under conditions relevant to the lungs. We use a fluorescent OH trapping probe, chemical kinetics and thermodynamic modeling to investigate OH formation from fulvic acid and Fe(II) dissolved in simulated and human lung fluids. In simulated lung fluid, we find that fulvic acid binds to Fe(II) and enhances the rate of key reactions that form OH. When fulvic acid is added to human lung fluids containing Fe(II), an enhancement of OH formation is observed. In human lung fluid, fulvic acid and metal binding proteins compete for Fe binding. These metal binding proteins are typically not found in simulated lung fluids. Results show that fulvic acid strongly binds Fe(II) and catalyzes key reactions that form OH in both simulated and human lung fluids. These results may help explain the role of Humic-like substances and Fe in oxidative stress and adverse health outcomes. Furthermore, we suggest that future studies employ simulated lung fluids containing metal binding proteins

Efficiency of Chitosan for the Removal of Pb (II, Fe (II and Cu (II Ions from Aqueous Solutions

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Soheil Sobhanardakani

2014-09-01

Full Text Available Background: Heavy metals have been recognized as harmful environmental pollutant known to produce highly toxic effects on different organs and systems of both humans and animals. The aim of this paper is to evaluate the adsorption potential of chitosan for the removal of Pb(II, Fe(II and Cu(II ions from aqueous solutions. Methods: This study was conducted in laboratory scale. In this paper chitosan has been used as an adsorbent for the removal of Pb(II, Fe(II and Cu(II from aqueous solution. In batch tests, the effects of parameters like pH solution (1.0-8.0, initial metal concentrations (100-1000 mgL-1, contact time (5.0-150 min and adsorbent dose (1.0-7.0 g on the adsorption process were studied. Results: The results showed that the adsorption of Pb(II, Fe(II and Cu(II ions on chitosan strongly depends on pH. The experimental isothermal data were analyzed using the Langmuir and Freundlich equations and it was found that the removal process followed the Langmuir isotherm and maximum adsorption capacity for the adsorption of Pb(II, Fe(II and Cu(II ions by the chitosan were 55.5mg g−1, 71.4 mg g−1 and 59 mg g−1, respectively, under equilibrium conditions at 25±1 ºC. The adsorption process was found to be well described by the pseudo-second-order rate model. Conclusion: The obtained results showed that chitosan is a readily, available, economic adsorbent and was found suitable for removing Pb(II, Fe(II and Cu(II ions from aqueous solution.

Sorption and catalytic oxidation of Fe(II) at the surface of calcite

NARCIS (Netherlands)

Mettler, S.; Wolthers, M.; Charlet, L.; Von Gunten, U.

The effect of sorption and coprecipitation of Fe(II) with calcite on the kinetics of Fe(II) oxidation was investigated. The interaction of Fe(II) with calcite was studied experimentally in the absence and presence of oxygen. The sorption of Fe(II) on calcite occurred in two distinguishable steps:

Ab initio calculations of the Fe(II) and Fe(III) isotopic effects in citrates, nicotianamine, and phytosiderophore, and new Fe isotopic measurements in higher plants

Science.gov (United States)

Moynier, Frédéric; Fujii, Toshiyuki; Wang, Kun; Foriel, Julien

2013-05-01

Iron is one of the most abundant transition metal in higher plants and variations in its isotopic compositions can be used to trace its utilization. In order to better understand the effect of plant-induced isotopic fractionation on the global Fe cycling, we have estimated by quantum chemical calculations the magnitude of the isotopic fractionation between different Fe species relevant to the transport and storage of Fe in higher plants: Fe(II)-citrate, Fe(III)-citrate, Fe(II)-nicotianamine, and Fe(III)-phytosiderophore. The ab initio calculations show firstly, that Fe(II)-nicotianamine is ˜3‰ (56Fe/54Fe) isotopically lighter than Fe(III)-phytosiderophore; secondly, even in the absence of redox changes of Fe, change in the speciation alone can create up to ˜1.5‰ isotopic fractionation. For example, Fe(III)-phytosiderophore is up to 1.5‰ heavier than Fe(III)-citrate2 and Fe(II)-nicotianamine is up to 1‰ heavier than Fe(II)-citrate. In addition, in order to better understand the Fe isotopic fractionation between different plant components, we have analyzed the iron isotopic composition of different organs (roots, seeds, germinated seeds, leaves and stems) from six species of higher plants: the dicot lentil (Lens culinaris), and the graminaceous monocots Virginia wild rye (Elymus virginicus), Johnsongrass (Sorghum halepense), Kentucky bluegrass (Poa pratensis), river oat (Uniola latifolia), and Indian goosegrass (Eleusine indica). The calculations may explain that the roots of strategy-II plants (Fe(III)-phytosiderophore) are isotopically heavier (by about 1‰ for the δ56Fe) than the upper parts of the plants (Fe transported as Fe(III)-citrate in the xylem or Fe(II)-nicotianamine in the phloem). In addition, we suggest that the isotopic variations observed between younger and older leaves could be explained by mixing of Fe received from the xylem and the phloem.

The reduction of 4-chloronitrobenzene by Fe(II)-Fe(III) oxide systems - correlations with reduction potential and inhibition by silicate

Energy Technology Data Exchange (ETDEWEB)

Jones, Adele M., E-mail: adele.jones1@unsw.edu.au; Kinsela, Andrew S.; Collins, Richard N.; Waite, T. David, E-mail: d.waite@unsw.edu.au

2016-12-15

Recent studies have demonstrated that the rate at which Fe(II)-Fe(III) oxyhydroxide systems catalyze the reduction of reducible contaminants, such as 4-chloronitrobenzene, is well correlated to their thermodynamic reduction potential. Here we confirm this effect in the presence of Fe(III) oxyhydroxide phases not previously assessed, namely ferrihydrite and nano-goethite, as well as Fe(III) oxyhydroxide phases previously examined. In addition, silicate is found to decrease the extent of Fe(II) sorption to the Fe(III) oxyhydroxide surface, increasing the reduction potential of the Fe(II)-Fe(III) oxyhydroxide suspension and, accordingly, decreasing the rate of 4-chloronitrobenzene reduction. A linear relationship between the reduction potential of the Fe(II)-Fe(III) oxyhydroxide suspensions and the reduction rate of 4-chloronitrobenzene (normalized to surface area and concentration of sorbed Fe(II)) was obtained in the presence and absence of silicate. However, when ferrihydrite was doped with Si (through co-precipitation) the reduction of 4-chloronitrobenzene was much slower than predicted from its reduction potential. The results obtained have significant implications to the likely effectiveness of naturally occurring contaminant degradation processes involving Fe(II) and Fe(III) oxyhydroxides in groundwater environments containing high concentrations of silicate, or other species which compete with Fe(II) for sorption sites.

Atom exchange between aqueous Fe(II) and structural Fe in clay minerals.

Science.gov (United States)

Neumann, Anke; Wu, Lingling; Li, Weiqiang; Beard, Brian L; Johnson, Clark M; Rosso, Kevin M; Frierdich, Andrew J; Scherer, Michelle M

2015-03-03

Due to their stability toward reductive dissolution, Fe-bearing clay minerals are viewed as a renewable source of Fe redox activity in diverse environments. Recent findings of interfacial electron transfer between aqueous Fe(II) and structural Fe in clay minerals and electron conduction in octahedral sheets of nontronite, however, raise the question whether Fe interaction with clay minerals is more dynamic than previously thought. Here, we use an enriched isotope tracer approach to simultaneously trace Fe atom movement from the aqueous phase to the solid ((57)Fe) and from the solid into the aqueous phase ((56)Fe). Over 6 months, we observed a significant decrease in aqueous (57)Fe isotope fraction, with a fast initial decrease which slowed after 3 days and stabilized after about 50 days. For the aqueous (56)Fe isotope fraction, we observed a similar but opposite trend, indicating that Fe atom movement had occurred in both directions: from the aqueous phase into the solid and from the solid into aqueous phase. We calculated that 5-20% of structural Fe in clay minerals NAu-1, NAu-2, and SWa-1 exchanged with aqueous Fe(II), which significantly exceeds the Fe atom layer exposed directly to solution. Calculations based on electron-hopping rates in nontronite suggest that the bulk conduction mechanism previously demonstrated for hematite1 and suggested as an explanation for the significant Fe atom exchange observed in goethite2 may be a plausible mechanism for Fe atom exchange in Fe-bearing clay minerals. Our finding of 5-20% Fe atom exchange in clay minerals indicates that we need to rethink how Fe mobility affects the macroscopic properties of Fe-bearing phyllosilicates and its role in Fe biogeochemical cycling, as well as its use in a variety of engineered applications, such as landfill liners and nuclear repositories.

Structure and dynamics of hydrated Fe(II) and Fe(III) ions. Quantum mechanical and molecular mechanical simulations

International Nuclear Information System (INIS)

Remsungnen, T.

2002-11-01

Classical molecular dynamics (MD) and combined em ab initio quantum mechanical/molecular mechanical molecular dynamics (QM/MM-MD) simulations have been performed to investigate structural, dynamical and energetical properties of Fe(II), and Fe(III) transition metal ions in aqueous solution. In the QM/MM-MD simulations the ion and its first hydration sphere were treated at the Hartree-Fock ab initio quantum mechanical level, while ab initio generated pair plus three-body potentials were employed for the remaining system. For the classical MD simulation the pair plus three-body potential were employed for all ion-water interactions. The coordination number of the first hydration shell is 100 % of 6 in both cases. The number of waters in the second hydration shell obtained from classical simulations are 13.4 and 15.1 for Fe(II) and Fe(III), respectively, while QM/MM-MD gives the values of 12.4 and 13.4 for Fe(II) and Fe(III). The energies of hydration obtained from MD and QM/MM-MD for Fe(II) are 520 and 500 kcal/mol, and for Fe(III) 1160 and 1100 kcal/mol respectively. The mean residence times of water in the second shell obtained from QM/MM-MD are 24 and 48 ps for Fe(II) and Fe(III), respectively. In contrast to the data obtained from classical MD simulation, the QM/MM-MD values are all in good agreement with the experimental data available. These investigations and results clearly indicate that many-body effects are essential for the proper description of all properties of the aqueous solution of both Fe(II) and Fe(III) ions. (author)

On the ortho-positronium quenching reactions promoted by Fe(II), Fe(III), Co(III), Ni(II), Zn(II) and Cd(II) cyanocomplexes

Science.gov (United States)

Fantola Lazzarini, Anna L.; Lazzarini, Ennio

The o-Ps quenching reactions promoted in aqueous solutions by the following six cyanocomplexes: [Fe(CN) 6] 4-; [Co(CN) 6] 3-; [Zn(CN) 4] 2-; [Cd(CN) 6] 2-; [Fe(CN) 6] 3-; [Ni(CN) 4] 2- were investigated. The first four reactions probably consist in o-Ps addition across the CN bond, their rate constants at room temperature, Tr, being ⩽(0.04±0.02) × 10 9 M -1 s -1, i.e. almost at the limit of experimental errors. The rate constant of the fifth reaction, in o-Ps oxydation, at Tr is (20.3±0.4) × 10 9 M -1 s -1. The [Ni(CN) 4] 2-k value at Tr, is (0.27±0.01) × 10 9 M -1 s -1, i.e. 100 times less than the rate constants of o-Ps oxydation, but 10 times larger than those of the o-Ps addition across the CN bond. The [Ni(CN) 4] 2- reaction probably results in formation of the following positronido complex: [Ni(CN) 4Ps] 2-. However, it is worth noting that the existence of such a complex is only indirectly deduced. In fact it arises from comparison of the [Ni(CN) 4] 2- rate constant with those of the Fe(II), Zn(II), Cd(II), and Co(III) cyanocomplexes, which, like the Ni(II) cyanocomplex, do not promote o-Ps oxydation or spin exchange reactions.

Probing Fe (III)/Fe (II) redox potential in a clayey material

International Nuclear Information System (INIS)

Tournassat, Christophe; Chainet, Fabien; Betelu, Stephanie; Hadi, Jebril; Gaucher, Eric C.; Ignatiadis, Ioannis; Greneche, Jean-Marc; Charlet, Laurent

2010-01-01

Document available in extended abstract form only. Redox is one of the main factors affecting the migration of redox-sensitive radionuclides. As a consequence reducing conditions are considered of strategic importance for the confinement properties of a clayey formation towards nuclear waste. A representative redox potential of clay formation such as Callovian- Oxfordian (COx) can be derived from thermodynamic calculations considering equilibrium between observed redox phases such as pyrite and siderite. However, there is little information on the reactivity of the different reservoirs of redox constituents in this type of complex material. The present study aims at investigating the reactivity of the Fe(III)/Fe(II) redox couple in the structure of clay minerals using different investigation methods: electrochemistry and O 2 reduction kinetic experiments. Clay modified electrodes were specifically designed to probe Fe(III)/Fe(II) redox potential in the structure of clay minerals. The clay fraction of a Callovian-Oxfordian argillite sample originating from the same level than ANDRA underground research laboratory was used after pre-treatment to remove organic matter and accessory minerals such as pyrite that could influence redox potential measurements. These electrodes were used to verify the validity of the model of Favre et al. (2006) that links the redox potential (E clay ) to the the Fe(II)/Fe tot ratio in the structure (m rel ), the pH and the sodium concentration in solution: equation 1. The good agreement between direct potential measurements and model prediction provides a strong evidence of the relevance of this model in our experimental conditions although the clay composition and its too low Fe content do not a priori fulfil the conditions set by Drits and Manceau (2000) for the calculation of K 0 parameter. Following the verification of the model, we tried to apply it to the specific case of a Callovian-Oxfordian sample that had been very well preserved

Fe(II)-induced transformation from ferrihydrite to lepidocrocite and goethite

International Nuclear Information System (INIS)

Liu Hui; Li Ping; Zhu Meiying; Wei Yu; Sun Yuhan

2007-01-01

The transformation of Fe(II)-adsorbed ferrihydrite was studied. Data tracking the formation of products as a function of pH, temperature and time is presented. The results indicate that trace of Fe(II) adsorbed on ferrihydrite can accelerate its transformation obviously. The products are lepidocrocite and/or goethite and/or hematite, which is different from those without Fe(II). That is, Fe(II) not only accelerates the transformation of ferrihydrite but also leads to the formation of lepidocrocite by a new path. The behavior of Fe(II) is shown in two aspects-catalytic dissolution-reprecipitation and catalytic solid-state transformation. The results indicate that a high temperature and a high pH(in the range from 5 to 9) are favorable to solid-state transformation and the formation of hematite, while a low temperature and a low pH are favorable to dissolution-reprecipitation mechanism and the formation of lepidocrocite. Special attentions were given to the formation mechanism of lepidocrocite and goethite. - Graphical abstract: Fe(II)-adsorbed ferrihydrite can rapidly transform into lepidocrocite or/and goethite or/and hematite. Which product dominates depends on the transformation conditions of ferrihydrite such as temperature, pH, reaction time, etc. In the current system, there exist two transformation mechanisms. One is dissolution/reprecipitation and the other is solid-state transformation. The transformation mechanisms from Fe(II)-adsorbed ferrihydrite to lepidocrocite and goethite were investigated

Spin Crossover in Fe(II)-M(II) Cyanoheterobimetallic Frameworks (M = Ni, Pd, Pt) with 2-Substituted Pyrazines.

Science.gov (United States)

Kucheriv, Olesia I; Shylin, Sergii I; Ksenofontov, Vadim; Dechert, Sebastian; Haukka, Matti; Fritsky, Igor O; Gural'skiy, Il'ya A

2016-05-16

Discovery of spin-crossover (SCO) behavior in the family of Fe(II)-based Hofmann clathrates has led to a "new rush" in the field of bistable molecular materials. To date this class of SCO complexes is represented by several dozens of individual compounds, and areas of their potential application steadily increase. Starting from Fe(2+), square planar tetracyanometalates M(II)(CN)4(2-) (M(II) = Ni, Pd, Pt) and 2-substituted pyrazines Xpz (X = Cl, Me, I) as coligands we obtained a series of nine new Hofmann clathrate-like coordination frameworks. X-ray diffraction reveals that in these complexes Fe(II) ion has a pseudo-octahedral coordination environment supported by four μ4-tetracyanometallates forming its equatorial coordination environment. Depending on the nature of X and M, axial positions are occupied by two 2X-pyrazines (X = Cl and M(II) = Ni (1), Pd (2), Pt (3); X = Me and M(II) = Ni (4), Pd (5)) or one 2X-pyrazine and one water molecule (X = I and M(II) = Ni (7), Pd (8), Pt (9)), or, alternatively, two distinct Fe(II) positions with either two pyrazines or two water molecules (X = Me and M(II) = Pt (6)) are observed. Temperature behavior of magnetic susceptibility indicates that all compounds bearing FeN6 units (1-6) display cooperative spin transition, while Fe(II) ions in N5O or N4O2 surrounding are high spin (HS). Structural changes in the nearest Fe(II) environment upon low-spin (LS) to HS transition, which include ca. 10% Fe-N distance increase, lead to the cell expansion. Mössbauer spectroscopy is used to characterize the spin state of all HS, LS, and intermediate phases of 1-9 (see abstract figure). Effects of a pyrazine substituent and M(II) nature on the hyperfine parameters in both spin states are established.

Sophisticated Players and Sophisticated Agents

NARCIS (Netherlands)

Rustichini, A.

1998-01-01

A sophisticated player is an individual who takes the action of the opponents, in a strategic situation, as determined by decision of rational opponents, and acts accordingly. A sophisticated agent is rational in the choice of his action, but ignores the fact that he is part of a strategic

Chelation of Cu(II, Zn(II, and Fe(II by Tannin Constituents of Selected Edible Nuts

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Magdalena Karamać

2009-12-01

Full Text Available The tannin fractions isolated from hazelnuts, walnuts and almonds were characterised by colorimetric assays and by an SE-HPLC technique. The complexation of Cu(II and Zn(II was determined by the reaction with tetramethylmurexide, whereas for Fe(II, ferrozine was employed. The walnut tannins exhibited a significantly weaker reaction with the vanillin/HCl reagent than hazelnut and almond tannins, but the protein precipitation capacity of the walnut fraction was high. The SE-HPLC chromatogram of the tannin fraction from hazelnuts revealed the presence of oligomers with higher molecular weights compared to that of almonds. Copper ions were most effectively chelated by the constituents of the tannin fractions of hazelnuts, walnuts and almonds. At a 0.2 mg/assay addition level, the walnut tannins complexed almost 100% Cu(II. The Fe(II complexation capacities of the tannin fractions of walnuts and hazelnuts were weaker in comparison to that of the almond tannin fraction, which at a 2.5 mg/assay addition level, bound Fe(II by ~90%. The capacity to chelate Zn(II was quite varied for the different nut tannin fractions: almond tannins bound as much as 84% Zn(II, whereas the value for walnut tannins was only 8.7%; and for hazelnut tannins, no Zn(II chelation took place at the levels tested.

Thermodynamic controls on the kinetics of microbial low-pH Fe(II) oxidation.

Science.gov (United States)

Larson, Lance N; Sánchez-España, Javier; Kaley, Bradley; Sheng, Yizhi; Bibby, Kyle; Burgos, William D

2014-08-19

Acid mine drainage (AMD) is a major worldwide environmental threat to surface and groundwater quality. Microbial low-pH Fe(II) oxidation could be exploited for cost-effective AMD treatment; however, its use is limited because of uncertainties associated with its rate and ability to remove Fe from solution. We developed a thermodynamic-based framework to evaluate the kinetics of low-pH Fe(II) oxidation. We measured the kinetics of low-pH Fe(II) oxidation at five sites in the Appalachian Coal Basin in the US and three sites in the Iberian Pyrite Belt in Spain and found that the fastest rates of Fe(II) oxidation occurred at the sites with the lowest pH values. Thermodynamic calculations showed that the Gibbs free energy of Fe(II) oxidation (ΔG(oxidation)) was also most negative at the sites with the lowest pH values. We then conducted two series of microbial Fe(II) oxidation experiments in laboratory-scale chemostatic bioreactors operated through a series of pH values (2.1-4.2) and found the same relationships between Fe(II) oxidation kinetics, ΔG(oxidation), and pH. Conditions that favored the fastest rates of Fe(II) oxidation coincided with higher Fe(III) solubility. The solubility of Fe(III) minerals, thus plays an important role on Fe(II) oxidation kinetics. Methods to incorporate microbial low-pH Fe(II) oxidation into active and passive AMD treatment systems are discussed in the context of these findings. This study presents a simplified model that describes the relationship between free energy and microbial kinetics and should be broadly applicable to many biogeochemical systems.

Fe(II)/Cu(II) interaction on goethite stimulated by an iron-reducing bacteria Aeromonas Hydrophila HS01 under anaerobic conditions.

Science.gov (United States)

Tao, Liang; Zhu, Zhen-Ke; Li, Fang-Bai; Wang, Shan-Li

2017-11-01

Copper is a trace element essential for living creatures, but copper content in soil should be controlled, as it is toxic. The physical-chemical-biological features of Cu in soil have a significant correlation with the Fe(II)/Cu(II) interaction in soil. Of significant interest to the current study is the effect of Fe(II)/Cu(II) interaction conducted on goethite under anaerobic conditions stimulated by HS01 (a dissimilatory iron reduction (DIR) microbial). The following four treatments were designed: HS01 with α-FeOOH and Cu(II) (T1), HS01 with α-FeOOH (T2), HS01 with Cu(II) (T3), and α-FeOOH with Cu(II) (T4). HS01 presents a negligible impact on copper species transformation (T3), whereas the presence of α-FeOOH significantly enhanced copper aging contributing to the DIR effect (T1). Moreover, the violent reaction between adsorbed Fe(II) and Cu(II) leads to the decreased concentration of the active Fe(II) species (T1), further inhibiting reactions between Fe(II) and iron (hydr)oxides and decelerating the phase transformation of iron (hydr)oxides (T1). From this study, the effects of the Fe(II)/Cu(II) interaction on goethite under anaerobic conditions by HS01 are presented in three aspects: (1) the accelerating effect of copper aging, (2) the reductive transformation of copper, and (3) the inhibition effect of the phase transformation of iron (hydr)oxides. Copyright © 2017 Elsevier Ltd. All rights reserved.

Single peak parameters technique for simultaneous measurements: Spectrophotometric sequential injection determination of Fe(II) and Fe(III).

Science.gov (United States)

Kozak, J; Paluch, J; Węgrzecka, A; Kozak, M; Wieczorek, M; Kochana, J; Kościelniak, P

2016-02-01

Spectrophotometric sequential injection system (SI) is proposed to automate the method of simultaneous determination of Fe(II) and Fe(III) on the basis of parameters of a single peak. In the developed SI system, sample and mixture of reagents (1,10-phenanthroline and sulfosalicylic acid) are introduced into a vessel, where in an acid environment (pH≅3) appropriate compounds of Fe(II) and Fe(III) with 1,10-phenanthroline and sulfosalicylic acid are formed, respectively. Then, in turn, air, sample, EDTA and sample again, are introduced into a holding coil. After the flow reversal, a segment of air is removed from the system by an additional valve and as EDTA replaces sulfosalicylic acid forming a more stable colorless compound with Fe(III), a complex signal is registered. Measurements are performed at wavelength 530 nm. The absorbance measured at minimum of the negative peak and the area or the absorbance measured at maximum of the signal can be used as measures corresponding to Fe(II) and Fe(III) concentrations, respectively. The time of the peak registration is about 2 min. Two-component calibration has been applied to analysis. Fe(II) and Fe(III) can be determined within the concentration ranges of 0.04-4.00 and 0.1-5.00 mg L(-1), with precision less than 2.8% and 1.7% (RSD), respectively and accuracy better than 7% (RE). The detection limit is 0.04 and 0.09 mg L(-1) for Fe(II) and Fe(III), respectively. The method was applied to analysis of artesian water samples. Copyright © 2015 Elsevier B.V. All rights reserved.

SEPARATION OF Fe (III, Cr(III, Cu(II, Ni(II, Co(II, AND Pb(II METAL IONS USING POLY(EUGENYL OXYACETIC ACID AS AN ION CARRIER BY A LIQUID MEMBRANE TRANSPORT METHOD

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La Harimu

2010-06-01

Full Text Available Fe (III, Cr(III, Cu(II, Ni(II, Co(II, and Pb(II  metal ions had been separated using poly(eugenyl oxyacetic acid as an ion carrier by bulk liquid membrane transport method. The effect of pH, polyeugenyl oxyacetic acid ion carrier concentration, nitric acid concentration in the stripping solution, transport time, and metal concentration were optimized. The result showed that the optimum condition for transport of metal ions was at pH 4 for ion Fe(III and at pH 5 for Cr(III, Cu(II, Ni(II, Co(II, and Pb(II ions. The carrier volumes were optimum with concentration of 1 x 10-3 M at 7.5 mL for Cr(III, Cu (II,  Ni(II, Co(II ions and at 8.5 mL for Fe(III and Pb(II ions. The concentration of HNO3 in stripping phase was optimum at 2 M for Fe(III and Cu(II ions, 1 M for Cr(III, Ni(II and Co(II ions, and 0.5 M for Pb(II ion. The optimum transport times were 36 h for Fe(III and Co(II ions, and 48 h for Cr(III, Cu (II, Ni(II, and Pb(II ions. The concentration of metal ions accurately transported were 2.5 x 10-4 M for Fe(III and Cr(III ions, and 1 M for Cu (II, Ni(II, Co(II, and Pb(II ions. Compared to other metal ions the transport of Fe(III was the highest with selectivity order of Fe(III > Cr(III > Pb(II > Cu(II > Ni(II > Co(II. At optimum condition, Fe(III ion was transported through the membrane at 46.46%.   Keywords: poly(eugenyl oxyacetic acid, transport, liquid membrane, Fe (III, Cr(III, Cu(II, Ni(II, Co(II, and Pb(II ions

Redox characterization of the Fe(II)-catalyzed transformation of ferrihydrite to goethite

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Jones, Adele M.; Collins, Richard N.; Waite, T. David

2017-12-01

The reduction potential of Fe(II)-Fe(III) (oxyhydr)oxide systems provides an important control on the biogeochemical cycling of redox-sensitive elements such as carbon and nitrogen as well as trace metals and organic contaminants in natural systems. As such, an in-depth understanding of the factors controlling the reduction potential of such systems is critical to predicting the likely transformation, transport and fate of these species in natural and perturbed environments. In this study the mineralogy and reduction potential of ferrihydrite suspensions at pH 6.50 and pH 7.00 were determined over the course of their Fe(II)-catalyzed transformation to lepidocrocite and goethite using X-ray absorption spectroscopy and mediated electrochemical approaches. The measured reduction potentials were compared to those of analogous Fe(II)-Fe(III) (oxyhydr)oxide suspensions reacted for 5 min containing pure ferrihydrite (Fh), lepidocrocite (L) and goethite (Gt). The reduction potentials of the pure Fe(II)-Fe(III) (oxyhydr)oxide suspensions were, respectively, +47.5, -13.5 and -122.3 mV vs. SHE at pH 6.5, and -22.9, -84.1 and -189.7 mV vs. SHE at pH 7. These values are in good agreement with reduction potentials calculated using the Nernst equation and reported thermodynamic solubility products indicating that these suspensions had reached equilibrium within 5 min. The reduction potential of the pH 6.50 Fe(II)-ferrihydrite suspension decreased from +47.4 mV to -126.4 mV over a week, and from -20.1 mV to -188.4 mV (all vs. SHE) after 24 h at pH 7. The changes in reduction potential over time matched well to those calculated from the relative proportion of each pure Fe(III) (oxyhydr)oxide present suggesting that Fe3+ activity was influenced by the mix of iron oxides present rather than the most insoluble solid species. Finally, evidence is provided that adsorbed Fe(II) has the capacity to reduce a significantly larger fraction of a reducible species than the aqueous Fe(II

A study of the Fe(III)/Fe(II)-triethanolamine complex redox couple for redox flow battery application

International Nuclear Information System (INIS)

Wen, Y.H.; Zhang, H.M.; Qian, P.; Zhou, H.T.; Zhao, P.; Yi, B.L.; Yang, Y.S.

2006-01-01

The electrochemical behavior of the Fe(III)/Fe(II)-triethanolamine(TEA) complex redox couple in alkaline medium and influence of the concentration of TEA were investigated. A change of the concentration of TEA mainly produces the following two results. (1) With an increase of the concentration of TEA, the solubility of the Fe(III)-TEA can be increased to 0.6 M, and the solubility of the Fe(II)-TEA is up to 0.4 M. (2) In high concentration of TEA with the ratio of TEA to NaOH ranging from 1 to 6, side reaction peaks on the cathodic main reaction of the Fe(III)-TEA complex at low scan rate can be minimized. The electrode process of Fe(III)-TEA/Fe(II)-TEA is electrochemically reversible with higher reaction rate constant than the uncomplexed species. Constant current charge-discharge shows that applying anodic active materials of relatively high concentrations facilitates the improvement of cell performance. The open-circuit voltage of the Fe-TEA/Br 2 cell with the Fe(III)-TEA of 0.4 M, after full charging, is nearly 2.0 V and is about 32% higher than that of the all-vanadium batteries, together with the energy efficiency of approximately 70%. The preliminary exploration shows that the Fe(III)-TEA/Fe(II)-TEA couple is electrochemically promising as negative redox couple for redox flow battery (RFB) application

Rate law of Fe(II) oxidation under low O2 conditions

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Kanzaki, Yoshiki; Murakami, Takashi

2013-12-01

Despite intensive studies on Fe(II) oxidation kinetics, the oxidation rate law has not been established under low O2 conditions. The importance of Fe(II) oxidation under low O2 conditions has been recently recognized; for instance, the Fe(II)/Fe(III) compositions of paleosols, ancient soils formed by weathering, can produce a quantitative pattern of the atmospheric oxygen increase during the Paleoproterozoic. The effects of partial pressure of atmospheric oxygen (PO2) on the Fe(II) oxidation rate were investigated to establish the Fe(II) oxidation rate - PO2 relationships under low O2 conditions. All oxidation experiments were carried out in a glove box by introducing Ar gas at ∼10-5-∼10-4 atm of PO2, pH 7.57-8.09 and 22 °C. Luminol chemiluminescence was adopted to measure low Fe(II) concentrations (down to ∼2 nM). Combining previous data under higher PO2 conditions (10-3-0.2 atm) with the present data, the rate law for Fe(II) oxidation over a wide range of PO2 (10-5-0.2 atm) was found to be written as: d[Fe(II)]/dt=-k[Fe(II)][[]2 where the exponent of [O2], x, and the rate constant, k, change from x = 0.98 (±0.04) and log k = 15.46 (±0.06) at ∼6 × 10-3-0.2 atm of PO2 to x = 0.58 (±0.02) and log k = 13.41 (±0.03) at 10-5-∼6 × 10-3 atm of PO2. The most plausible mechanism that explains the change in x under low O2 conditions is that, instead of O2, oxygen-derived oxidants, H2O2 and to some extent, O2rad -, dominate the oxidation reactions at PO2. The rate law found in the present study requires us to reconsider distributions of Fe redox species at low PO2 in natural environments, especially in paleoweathering profiles, and may provide a deeper understanding of the evolution of atmospheric oxygen in the Precambrian.

New method for simultaneous determination of Fe(II) and Fe(III) in water using flow injection technique

International Nuclear Information System (INIS)

Kozak, J.; Gutowski, J.; Kozak, M.; Wieczorek, M.; Koscielniak, P.

2010-01-01

The method exploits the possibilities of flow injection gradient titration in a system of reversed flow with spectrophotometric detection. In the developed approach a small amount of titrant (EDTA) is injected into a stream of sample containing a mixture of indicators (sulfosalicylic acid and 1,10-phenanthroline). In acid environment sulfosalicylic acid forms a complex with Fe(III), whereas 1,10-phenanthroline forms a complex with Fe(II). Measurements are performed at wavelength λ = 530 nm when radiation is absorbed by both complexes. After injection EDTA replaces sulfosalicylic acid and forms with Fe(III) more stable colourless complex. As a result, a characteristic 'cut off' peak is registered with a width corresponding to the Fe(III) concentration and with a height corresponding to the Fe(II) concentration. Calibration was performed by titration of four two-component standard solutions of the Fe(II)/Fe(III) concentrations established in accordance with 2 2 factorial plan. The method was tested with the use of synthetic samples and then it was applied to the analysis of water samples taken from artesian wells. Under optimized experimental conditions Fe(II) and Fe(III) were determined with precision less than 0.8 and 2.5% (RSD) and accuracy less than 3.2 and 5.1% (relative error) within the concentration ranges of 0.1-3.0 and 0.9-3.5 mg L -1 of both analytes, respectively.

Characterisation and application of the Fe(II)/Fe(III) redox reaction in an ionic liquid analogue

International Nuclear Information System (INIS)

Lloyd, David; Vainikka, Tuomas; Ronkainen, Markus; Kontturi, Kyösti

2013-01-01

Highlights: • The Fe(II)/Fe(III) reaction is shown to be facile using a wall-jet electrode and RDE. • Deposition/stripping of iron has equally slow kinetics as in aqueous systems. • An IL based all-iron RFB is reported for the first time, energy efficiency is 37%. • An Zn–Fe complex is shown to form. In an RFB this gives an energy efficiency of 78%. • Problems resulting from the use of redox probes and urea-based DES are demonstrated. -- Abstract: In this paper we report the properties of the Fe(II)/Fe(III) reaction in a deep eutectic solvent based on choline chloride and ethylene glycol. This reaction is shown to be facile using a wall-jet electrode and rotating disc electrode. The deposition and stripping of iron exhibits equally slow kinetics as in aqueous systems. Using these two reactions an all-iron redox flow battery based on ionic liquids is reported for the first time. An energy efficiency of 37% is attained at a current density of 0.5 mA cm −2 . A Zn(II)–Fe(II) complex is shown to form when zinc is oxidized by Fe(III). When this complex is applied in a redox flow battery energy efficiencies of 78% are achieved at a current density of 0.5 mA cm −2

Protection of Nitrate-Reducing Fe(II)-Oxidizing Bacteria from UV Radiation by Biogenic Fe(III) Minerals

Science.gov (United States)

Gauger, Tina; Konhauser, Kurt; Kappler, Andreas

2016-04-01

Due to the lack of an ozone layer in the Archean, ultraviolet radiation (UVR) reached early Earth's surface almost unattenuated; as a consequence, a terrestrial biosphere in the form of biological soil crusts would have been highly susceptible to lethal doses of irradiation. However, a self-produced external screen in the form of nanoparticular Fe(III) minerals could have effectively protected those early microorganisms. In this study, we use viability studies by quantifying colony-forming units (CFUs), as well as Fe(II) oxidation and nitrate reduction rates, to show that encrustation in biogenic and abiogenic Fe(III) minerals can protect a common soil bacteria such as the nitrate-reducing Fe(II)-oxidizing microorganisms Acidovorax sp. strain BoFeN1 and strain 2AN from harmful UVC radiation. Analysis of DNA damage by quantifying cyclobutane pyrimidine dimers (CPD) confirmed the protecting effect by Fe(III) minerals. This study suggests that Fe(II)-oxidizing microorganisms, as would have grown in association with mafic and ultramafic soils/outcrops, would have been able to produce their own UV screen, enabling them to live in terrestrial habitats on early Earth.

Adsorption of Pb(II), Cu(II), Cd(II), Zn(II), Ni(II), Fe(II), and As(V) on bacterially produced metal sulfides.

Science.gov (United States)

Jong, Tony; Parry, David L

2004-07-01

The adsorption of Pb(II), Cu(II), Cd(II), Zn(II), Ni(II), Fe(II) and As(V) onto bacterially produced metal sulfide (BPMS) material was investigated using a batch equilibrium method. It was found that the sulfide material had adsorptive properties comparable with those of other adsorbents with respect to the specific uptake of a range of metals and, the levels to which dissolved metal concentrations in solution can be reduced. The percentage of adsorption increased with increasing pH and adsorbent dose, but decreased with increasing initial dissolved metal concentration. The pH of the solution was the most important parameter controlling adsorption of Cd(II), Cu(II), Fe(II), Ni(II), Pb(II), Zn(II), and As(V) by BPMS. The adsorption data were successfully modeled using the Langmuir adsorption isotherm. Desorption experiments showed that the reversibility of adsorption was low, suggesting high-affinity adsorption governed by chemisorption. The mechanism of adsorption for the divalent metals was thought to be the formation of strong, inner-sphere complexes involving surface hydroxyl groups. However, the mechanism for the adsorption of As(V) by BPMS appears to be distinct from that of surface hydroxyl exchange. These results have important implications to the management of metal sulfide sludge produced by bacterial sulfate reduction.

Characterization of β-FeSi II films as a novel solar cell semiconductor

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Fukuzawa, Yasuhiro; Ootsuka, Teruhisa; Otogawa, Naotaka; Abe, Hironori; Nakayama, Yasuhiko; Makita, Yunosuke

2006-04-01

β-FeSi II is an attractive semiconductor owing to its extremely high optical absorption coefficient (α>10 5 cm -1), and is expected to be an ideal semiconductor as a thin film solar cell. For solar cell use, to prepare high quality β-FeSi II films holding a desired Fe/Si ratio, we chose two methods; one is a molecular beam epitaxy (MBE) method in which Fe and Si were evaporated by using normal Knudsen cells, and occasionally by e-gun for Si. Another one is the facing-target sputtering (FTS) method in which deposition of β-FeSi II films is made on Si substrate that is placed out of gas plasma cloud. In both methods to obtain β-FeSi II films with a tuned Fe/Si ratio, Fe/Si super lattice was fabricated by varying Fe and Si deposition thickness. Results showed significant in- and out-diffusion of host Fe and Si atoms at the interface of Si substrates into β-FeSi II layers. It was experimentally demonstrated that this diffusion can be suppressed by the formation of template layer between the epitaxial β-FeSi II layer and the substrate. The template layer was prepared by reactive deposition epitaxy (RDE) method. By fixing the Fe/Si ratio as precisely as possible at 1/2, systematic doping experiments of acceptor (Ga and B) and donor (As) impurities into β-FeSi II were carried out. Systematical changes of electron and hole carrier concentration in these samples along variation of incorporated impurities were observed through Hall effect measurements. Residual carrier concentrations can be ascribed to not only the remaining undesired impurities contained in source materials but also to a variety of point defects mainly produced by the uncontrolled stoichiometry. A preliminary structure of n-β-FeSi II/p-Si used as a solar cell indicated a conversion efficiency of 3.7%.

Electrochemical Studies of Interactions Between Fe(II/Fe(III and Amino Acids Using Ferrocene-Modified Carbon Paste Electrode

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Vatrál Jaroslav

2014-12-01

Full Text Available The electrochemical behavior of an Fe(II/Fe(III redox couple in the presence of various selected amino acids has been studied using ferrocene-modified carbon paste electrode at pH = 7.4. Because of Fe(II/Fe(III solubility issues at physiological pH, ferrocene was used as a source of iron. Anodic oxidation of iron (pH = 7.2 occurred at 0.356 V and cathodic oxidation at 0.231 V, both vs Ag|AgCl. Treatment of the voltammetric data showed that it was a purely diffusion-controlled reaction with the involvement of one electron. After addition of amino acids, potential shifts and current changes can be observed on the voltammograms. Cyclic voltammetry experiments revealed the capability of amino acids to change the electrochemical behavior of the Fe(II/Fe(III redox couple.

Stochastic Simulation of Isotopic Exchange Mechanisms for Fe(II)-Catalyzed Recrystallization of Goethite

Energy Technology Data Exchange (ETDEWEB)

Zarzycki, Piotr [Energy; Institute; Rosso, Kevin M. [Pacific Northwest

2017-06-15

Understanding Fe(II)-catalyzed transformations of Fe(III)- (oxyhydr)oxides is critical for correctly interpreting stable isotopic distributions and for predicting the fate of metal ions in the environment. Recent Fe isotopic tracer experiments have shown that goethite undergoes rapid recrystallization without phase change when exposed to aqueous Fe(II). The proposed explanation is oxidation of sorbed Fe(II) and reductive Fe(II) release coupled 1:1 by electron conduction through crystallites. Given the availability of two tracer exchange data sets that explore pH and particle size effects (e.g., Handler et al. Environ. Sci. Technol. 2014, 48, 11302-11311; Joshi and Gorski Environ. Sci. Technol. 2016, 50, 7315-7324), we developed a stochastic simulation that exactly mimics these experiments, while imposing the 1:1 constraint. We find that all data can be represented by this model, and unifying mechanistic information emerges. At pH 7.5 a rapid initial exchange is followed by slower exchange, consistent with mixed surface- and diffusion-limited kinetics arising from prominent particle aggregation. At pH 5.0 where aggregation and net Fe(II) sorption are minimal, that exchange is quantitatively proportional to available particle surface area and the density of sorbed Fe(II) is more readily evident. Our analysis reveals a fundamental atom exchange rate of ~10-5 Fe nm-2 s-1, commensurate with some of the reported reductive dissolution rates of goethite, suggesting Fe(II) release is the rate-limiting step in the conduction mechanism during recrystallization.

The influence of Fe(II) competition on the sorption and migration of Ni(II) in MX-80 bentonite

International Nuclear Information System (INIS)

Pfingsten, Wilfried; Bradbury, Mike; Baeyens, Bart

2011-01-01

Highlights: → We model the diffusion of Ni(II) through bentonite using different sorption models. → We examine sorption competition of Fe(II) and Ni(II) at different concentrations. → Ni(II) breakthrough is 15 times earlier with Fe(II) sorption competition. → Ni(II) sorption is non-linear and depends on the Fe(II) concentration levels. → Sorption competition is important and has to be modelled by reactive transport codes. - Abstract: The results from batch sorption experiments on montmorillonite systems have demonstrated that bivalent transition metals compete with one another for sorption sites. For safety analysis studies of high level radioactive waste repositories with compacted bentonite near fields, the importance of competitive sorption on the migration of radionuclides needs to be evaluated. Under reducing conditions, the bentonite porewater chosen has a Fe(II) concentration of ∼5.3 x 10 -5 M through saturation with siderite. The purpose of this paper is to assess the influence of such high Fe(II) concentrations on the transport of Ni(II) through compacted bentonite, Ni(II) was chosen as an example of a bivalent transition metal. The one-dimensional calculations were carried out at different Ni(II) equilibrium concentrations at the boundary (Ni(II) EQBM ) with the reactive transport code MCOTAC incorporating the two site protolysis non electrostatic surface complexation/cation exchange sorption model, MCOTAC-sorb. At a Ni(II) EQBM level of 10 -7 M without Fe(II) competition, the reactive transport calculations using a constant K d approach and the MCOTAC-sorb calculation yielded the same breakthrough curves. At higher Ni(II) EQBM (10 -5 M), the model calculations with MCOTAC-sorb indicated a breakthrough which was shifted to later times by a factor of ∼5 compared with the use of the constant K d approach. When sorption competition was included in the calculations, the magnitude of the influence depended on the sorption characteristics of the

Phototrophic Fe(II-oxidation in the chemocline of a ferruginous meromictic lake

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Xavier Alexis eWalter

2014-12-01

Full Text Available Precambrian Banded Iron Formation (BIF deposition was conventionally attributed to the precipitation of iron-oxides resulting from the abiotic reaction of ferrous iron (Fe(II with photosynthetically-produced oxygen. Earliest traces of oxygen date from 2.7 Ga, thus raising questions as to what may have caused BIF precipitation before oxygenic photosynthesis evolved. The discovery of anoxygenic phototrophic bacteria thriving through the oxidation of Fe(II has provided support for a biological origin for some BIFs, but despite reports suggesting that anoxygenic phototrophs may oxidize Fe(II in the environment, a model ecosystem of an ancient ocean where they are demonstrably active was lacking. Here we show that anoxygenic phototrophic bacteria contribute to Fe(II oxidation in the water column of the ferruginous sulfate-poor, meromictic lake La Cruz (Spain. We observed in-situ photoferrotrophic activity through stimulation of phototrophic carbon uptake in the presence of Fe(II, and determined light-dependent Fe(II-oxidation by the natural chemocline microbiota. Moreover, a photoferrotrophic bacterium most closely related to Chlorobium ferrooxidans was enriched from the ferruginous water column. Our study for the first time demonstrates a direct link between anoxygenic photoferrotrophy and the anoxic precipitation of Fe(III-oxides in a ferruginous water column, providing a plausible mechanism for the bacterial origin of BIF’s before the advent of free oxygen.

One-step green synthesis of bimetallic Fe/Pd nanoparticles used to degrade Orange II

Energy Technology Data Exchange (ETDEWEB)

Luo, Fang; Yang, Die; Chen, Zuliang, E-mail: zuliang.chen@newcastle.edu.au; Megharaj, Mallavarapu; Naidu, Ravendra

2016-02-13

Highlights: • Green synthesis of bimetallic Fe/Pd NPs was firstly reported using the one-step method. • 98.0% of Orange II was removed by Fe/Pd NPs, but only 16.0% by Fe NPs. • Fe/Pd NPs with a diameter ranging from 10 to 100 nm were observed. • Removing Orange II using Fe/Pd NPs involved both adsorption and catalytic degradation. - Abstract: To reduce cost and enhance reactivity, bimetallic Fe/Pd nanoparticles (NPs) were firstly synthesized using grape leaf aqueous extract to remove Orange II. Green synthesized bimetallic Fe/Pd NPs (98.0%) demonstrated a far higher ability to remove Orange II in 12 h compared to Fe NPs (16.0%). Meanwhile, all precursors, e.g., grape leaf extract, Fe{sup 2+} and Pd{sup 2+}, had no obvious effect on removing Orange II since less than 2.0% was removed. Kinetics study revealed that the removal rate fitted well to the pseudo-first-order reduction and pseudo-second-order adsorption model, meaning that removing Orange II via Fe/Pd NPs involved both adsorption and catalytic reduction. The remarkable stability of Fe/Pd NPs showed the potential application for removing azo dyes. Furthermore, Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) confirmed the changes in Fe/Pd NPs before and after reaction with Orange II. High Performance Liquid Chromatography–Mass Spectrum (HPLC–MS) identified the degraded products in the removal of Orange II, and finally a removal mechanism was proposed. This one-step strategy using grape leaf aqueous extract to synthesize Fe/Pd NPs is simple, cost-effective and environmentally benign, making possible the large-scale production of Fe/Pd NPs for field remediation.

Mechanisms of electron transfer from structrual Fe(II) in reduced nontronite to oxygen for production of hydroxyl radicals

Science.gov (United States)

Yuan, Songhu; Liu, Xixiang; Liao, Wenjuan; Zhang, Peng; Wang, Xiaoming; Tong, Man

2018-02-01

Production of hydroxyl radicals (radOH) has been recently revealed upon oxygenation of sediments in redox-dynamic subsurface environments. In particular, Fe(II)-bearing clay minerals are the major sediment components contributing to radOH production upon oxygenation, and the produced radOH can oxidize contaminants and inactivate bacteria. Whereas, the mechanisms of radOH production from oxygenation of Fe(II)-bearing clay minerals remain elusive. The objectives of this study were to identify the structural variation of Fe(II) entities during the oxidation of Fe(II)-bearing clay minerals by O2, and to unravel the mechanisms of electron transfer within the mineral structure and from mineral to O2 for radOH production. Nontronite (NAu-2, 23% Fe) which was chemically reduced to 54.5% Fe(II) in total Fe was used as a model Fe(II)-bearing clay mineral. Production of radOH and oxidation of Fe(II) were measured during the oxidation of reduced NAu-2 by O2. A wide spectrum of spectroscopic techniques, including Fourier transform infrared spectroscopy (FTIR), Fe K-edge X-ray absorption spectroscopy (XAS), Mössbauer spectra, and X-ray photoelectron spectroscopy (XPS), were employed to explore the structural variation of Fe(II) entities in NAu-2 and the electron transfer within NAu-2 and from NAu-2 to O2. For 180 min oxidation of 1 g/L reduced NAu-2, a biphasic radOH production was observed, being quick within the initial 15 min and slow afterwards. Production of radOH correlates well with oxidation of Fe(II) in the reduced NAu-2. Within the initial 15 min, trioctahedral Fe(II)-Fe(II)-Fe(II) entities and edge Fe(II) in the reduced NAu-2 were preferentially and quickly oxidized, and electrons from the interior Fe(II)-Fe(II)-Fe(II) entities were most likely ejected from the basal siloxane plane to O2. Meanwhile, trioctahedral Fe(II)-Fe(II)-Fe(II) entities were mainly transformed to dioctahedral Fe(II)-Fe(II) entities. When the time of oxygenation was longer than 15 min

Electron Transfer Pathways Facilitating U(VI) Reduction by Fe(II) on Al- vs Fe-Oxides

Energy Technology Data Exchange (ETDEWEB)

Taylor, S. D. [Pacific Northwest National Laboratory, Physical Sciences Division, P.O. Box; Becker, U. [The University of Michigan, Department of Earth; Rosso, K. M. [Pacific Northwest National Laboratory, Physical Sciences Division, P.O. Box

2017-09-06

This study continues mechanistic development of heterogeneous electron transfer (ET) pathways at mineral surfaces in aquatic environments that enable the reduction U(VI) by surface-associated Fe(II). Using computational molecular simulation within the framework of Marcus Theory, our findings highlight the importance of the configurations and interaction of the electron donor and acceptor species with the substrate, with respect to influencing its electronic structure and thereby the ability of semiconducting minerals to facilitate ET. U(VI) reduction by surface-associated Fe(II) (adsorbed or structurally incorporated into the lattice) on an insulating, corundum (001) surface (α-Al2O3) occurs when proximal inner-sphere (IS) surface complexes are formed, such that ET occurs through a combination of direct exchange (i.e., Fe d- and U f-orbitals overlap through space) and superexchange via intervening surface oxygen atoms. U(VI) reduction by coadsorbed Fe(II) on the isostructural semiconducting hematite (α-Fe2O3) basal surface requires either their direct electronic interaction (e.g., IS complexation) or mediation of this interaction indirectly through the surface via an intrasurface pathway. Conceptually possible longer-range ET by charge-hopping through surface Fe atoms was investigated to determine whether this indirect pathway is competitive with direct ET. The calculations show that energy barriers are large for this conduction-based pathway; interfacial ET into the hematite surface is endothermic (+80.1 kJ/mol) and comprises the rate-limiting step (10–6 s–1). The presence of the IS adsorbates appears to weaken the electronic coupling between underlying Fe ions within the surface, resulting in slower intra-surface ET (10–5 s–1) than expected in the bulk basal plane. Our findings lay out first insights into donor-acceptor communication via a charge-hopping pathway through the surface for heterogeneous reduction of U(VI) by Fe(II) and help provide a basis

Fine-structure excitation of Fe II and Fe III due to collisions with electrons

Science.gov (United States)

Wan, Yier; Qi, Yueying; Favreau, Connor; Loch, Stuart; Stancil, P.; Ballance, Connor; McLaughlin, Brendan

2018-06-01

Atomic data of iron peak elements are of great importance in astronomical observations. Among all the ionization stages of iron, Fe II and Fe III are of particular importance because of the high cosmic abundance, relatively low ionization potential and complex open d-shell atomic structure. Fe II and Fe III emission are observed from nearly all classes of astronomical objects over a wide spectral range from the infrared to the ultraviolet. To meaningfully interpret these spectra, astronomers have to employ highly complex modeling codes with reliable collision data to simulate the astrophysical observations. The major aim of this work is to provide reliable atomic data for diagnostics. We present new collision strengths and effective collisions for electron impact excitation of Fe II and Fe III for the forbidden transitions among the fine-structure levels of the ground terms. A very fine energy mesh is used for the collision strengths and the effective collision strengths are calculated over a wide range of electron temperatures of astrophysical importance (10-2000 K). The configuration interaction state wave functions are generated with a scaled Thomas-Fermi-Dirac-Amaldi (TFDA) potential, while the R-matrix plus intermediate coupling frame transformation (ICFT), Breit-Pauli R-matrix and Dirac R-matrix packages are used to obtain collision strengths. Influences of the different methods and configuration expansions on the collisional data are discussed. Comparison is made with earlier theoretical work and differences are found to occur at the low temperatures considered here.This work was funded by NASA grant NNX15AE47G.

Synthesis, Characterization, and Biological Activity of Mn(II, Fe(II, Co(II, Ni(II, Cu(II, Zn(II, and Cd(II Complexes of N-Thiophenoyl-N′-Phenylthiocarbohydrazide

Directory of Open Access Journals (Sweden)

M. Yadav

2013-01-01

Full Text Available Mn(II, Fe(II, Co(II, Ni(II, Cu(II, Zn(II, and Cd(II complex of N-thiophenoyl -N′-phenylthiocarbohydrazide (H2 TPTH have been synthesized and characterized by elemental analysis, magnetic susceptibility measurements, infrared, NMR, electronic, and ESR spectral studies. The complexes were found to have compositions [Mn(H TPTH2], [Co(TPTH (H2O2], [Ni(TPTH (H2O2], [Cu(TPTH], [Zn(H TPTH], [Cd(H TPTH2], and [Fe(H TPTH2(EtOH]. The magnetic and electronic spectral studies suggest square planar geometry for [Cu(TPTH], tetrahedral geometry for [Zn(TPTH] and [Cd(H TPTH2], and octahedral geometry for rest of the complexes. The infrared spectral studies of the 1 : 1 deprotonated complexes suggest bonding through enolic oxygen, thiolato sulfur, and both the hydrazinic nitrogens. Thus, H2TPTH acts as a binegative tetradentate ligand. H2 TPTH and its metal complexes have been screened against several bacteria and fungi.

Competing retention pathways of uranium upon reaction with Fe(II)

Science.gov (United States)

Massey, Michael S.; Lezama-Pacheco, Juan S.; Jones, Morris E.; Ilton, Eugene S.; Cerrato, José M.; Bargar, John R.; Fendorf, Scott

2014-10-01

Biogeochemical retention processes, including adsorption, reductive precipitation, and incorporation into host minerals, are important in contaminant transport, remediation, and geologic deposition of uranium. Recent work has shown that U can become incorporated into iron (hydr)oxide minerals, with a key pathway arising from Fe(II)-induced transformation of ferrihydrite, (Fe(OH)3·nH2O) to goethite (α-FeO(OH)); this is a possible U retention mechanism in soils and sediments. Several key questions, however, remain unanswered regarding U incorporation into iron (hydr)oxides and this pathway's contribution to U retention, including: (i) the competitiveness of U incorporation versus reduction to U(IV) and subsequent precipitation of UO2; (ii) the oxidation state of incorporated U; (iii) the effects of uranyl aqueous speciation on U incorporation; and, (iv) the mechanism of U incorporation. Here we use a series of batch reactions conducted at pH ∼7, [U(VI)] from 1 to 170 μM, [Fe(II)] from 0 to 3 mM, and [Ca] at 0 or 4 mM coupled with spectroscopic examination of reaction products of Fe(II)-induced ferrihydrite transformation to address these outstanding questions. Uranium retention pathways were identified and quantified using extended X-ray absorption fine structure (EXAFS) spectroscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. Analysis of EXAFS spectra showed that 14-89% of total U was incorporated into goethite, upon reaction with Fe(II) and ferrihydrite. Uranium incorporation was a particularly dominant retention pathway at U concentrations ⩽50 μM when either uranyl-carbonato or calcium-uranyl-carbonato complexes were dominant, accounting for 64-89% of total U. With increasing U(VI) and Fe(II) concentrations, U(VI) reduction to U(IV) became more prevalent, but U incorporation remained a functioning retention pathway. These findings highlight the potential importance of U(V) incorporation within iron

Sorption and reduction of selenite on chlorite surfaces in the presence of Fe(II) ions.

Science.gov (United States)

Baik, Min Hoon; Lee, Seung Yeop; Jeong, Jongtae

2013-12-01

The sorption and reduction of selenite on chlorite surfaces in the presence of Fe(II) ions were investigated as a function of pH, Se(IV) concentration, and Fe(II) concentration under an anoxic condition. The sorption of Se(IV) onto chlorite surfaces followed the Langmuir isotherm regardless of the presence of Fe(II) ions in the solution. The Se(IV) sorption was observed to be very low at all pH values when the solution was Fe(II)-free or the concentration of Fe(II) ions was as low as 0.5 mg/L. However, the Se(IV) sorption was enhanced at a pH > 6.5 when the Fe(II) concentration was higher than 5 mg/L because of the increased sorption of Fe(II) onto the chlorite surfaces. XANES (X-ray absorption near edge structure) spectra of the Se K-edge showed that most of the sorbed Se(IV) was reduced to Se(0) by Fe(II) sorbed onto the chlorite surfaces, especially at pH > 9. The combined results of field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) also showed that elemental selenium and goethite were formed and precipitated on the chlorite surfaces during the sorption of selenite. Consequently it can be concluded that Se(IV) can be reduced to Se(0) in the presence of Fe(II) ions by the surface catalytic oxidation of Fe(II) into Fe(III) and the formation of goethite at neutral and particularly alkaline conditions. Thus the mobility of selenite in groundwater is expected to be reduced by the presence of a relatively higher concentration of Fe(II) in subsurface environments. Copyright © 2013 Elsevier Ltd. All rights reserved.

Fe(II) oxidation kinetics and Fe hydroxyphosphate precipitation upon aeration of anaerobic (ground)water

NARCIS (Netherlands)

van der Grift, B.; Griffioen, J.; Behrends, T.; Wassen, M.J.; Schot, P.P.; Osté, Leonard

2015-01-01

Exfiltration of anaerobic Fe-rich groundwater into surface water plays an important role in controlling the transport of phosphate (P) from agricultural areas to the sea. Previous laboratory and field studies showed that Fe(II) oxidation upon aeration leads to effective immobilization of dissolved P

Effect of Dunaliella tertiolecta organic exudates on the Fe(II) oxidation kinetics in seawater.

Science.gov (United States)

González, A G; Santana-Casiano, J M; González-Dávila, M; Pérez-Almeida, N; Suárez de Tangil, M

2014-07-15

The role played by the natural organic ligands excreted by the green algae Dunaliella tertiolecta on the Fe(II) oxidation rate constants was studied at different stages of growth. The concentration of dissolved organic carbon increased from 2.1 to 7.1 mg L(-1) over time of culture. The oxidation kinetics of Fe(II) was studied at nanomolar levels and under different physicochemical conditions of pH (7.2-8.2), temperature (5-35 °C), salinity (10-37), and dissolved organic carbon produced by cells (2.1-7.1 mg L(-1)). The experimental rate always decreased in the presence of organic exudates with respect to that in the control seawater. The Fe(II) oxidation rate constant was also studied in the context of Marcus theory, where ΔG° was 39.31-51.48 kJ mol(-1). A kinetic modeling approach was applied for computing the equilibrium and rate constants for Fe(II) and exudates present in solution, the Fe(II) speciation, and the contribution of each Fe(II) species to the overall oxidation rate constant. The best fit model took into account two acidity equilibrium constants for the Fe(II) complexing ligands with pKa,1=9.45 and pKa,2=4.9. The Fe(II) complexing constants were KFe(II)-LH=3×10(10) and KFe(II)-L=10(7), and the corresponding computed oxidation rates were 68±2 and 36±8 M(-1) min(-1), respectively.

Treatment of groundwater containing Mn(II), Fe(II), As(III) and Sb(III) by bioaugmented quartz-sand filters.

Science.gov (United States)

Bai, Yaohui; Chang, Yangyang; Liang, Jinsong; Chen, Chen; Qu, Jiuhui

2016-12-01

High concentrations of iron (Fe(II)) and manganese (Mn(II)) often occur simultaneously in groundwater. Previously, we demonstrated that Fe(II) and Mn(II) could be oxidized to biogenic Fe-Mn oxides (BFMO) via aeration and microbial oxidation, and the formed BFMO could further oxidize and adsorb other pollutants (e.g., arsenic (As(III)) and antimony (Sb(III))). To apply this finding to groundwater remediation, we established four quartz-sand columns for treating groundwater containing Fe(II), Mn(II), As(III), and Sb(III). A Mn-oxidizing bacterium (Pseudomonas sp. QJX-1) was inoculated into two parallel bioaugmented columns. Long-term treatment (120 d) showed that bioaugmentation accelerated the formation of Fe-Mn oxides, resulting in an increase in As and Sb removal. The bioaugmented columns also exhibited higher overall treatment effect and anti-shock load capacity than that of the non-bioaugmented columns. To clarify the causal relationship between the microbial community and treatment effect, we compared the biomass of active bacteria (reverse-transcribed real-time PCR), bacterial community composition (Miseq 16S rRNA sequencing) and community function (metagenomic sequencing) between the bioaugmented and non-bioaugmented columns. Results indicated that the QJX1 strain grew steadily and attached onto the filter material surface in the bioaugmented columns. In general, the inoculated strain did not significantly alter the composition of the indigenous bacterial community, but did improve the relative abundances of xenobiotic metabolism genes and Mn oxidation gene. Thus, bioaugmentation intensified microbial degradation/utilization for the direct removal of pollutants and increased the formation of Fe-Mn oxides for the indirect removal of pollutants. Our study provides an alternative method for the treatment of groundwater containing high Fe(II), Mn(II) and As/Sb. Copyright © 2016 Elsevier Ltd. All rights reserved.

Sphaerotilus natans encrusted with nanoball-shaped Fe(III) oxide minerals formed by nitrate-reducing mixotrophic Fe(II) oxidation.

Science.gov (United States)

Park, Sunhwa; Kim, Dong-Hun; Lee, Ji-Hoon; Hur, Hor-Gil

2014-10-01

Ferrous iron has been known to function as an electron source for iron-oxidizing microorganisms in both anoxic and oxic environments. A diversity of bacteria has been known to oxidize both soluble and solid-phase Fe(II) forms coupled to the reduction of nitrate. Here, we show for the first time Fe(II) oxidation by Sphaerotilus natans strain DSM 6575(T) under mixotrophic condition. Sphaerotilus natans has been known to form a sheath structure enclosing long chains of rod-shaped cells, resulting in a thick biofilm formation under oxic conditions. Here, we also demonstrate that strain DSM 6575(T) grows mixotrophically with pyruvate, Fe(II) as electron donors and nitrate as an electron acceptor and single cells of strain DSM 6575(T) are dominant under anoxic conditions. Furthermore, strain DSM 6575(T) forms nanoball-shaped amorphous Fe(III) oxide minerals encrusting on the cell surfaces through the mixotrophic iron oxidation reaction under anoxic conditions. We propose that cell encrustation results from the indirect Fe(II) oxidation by biogenic nitrite during nitrate reduction and that causes the bacterial morphological change to individual rod-shaped single cells from filamentous sheath structures. This study extends the group of existing microorganisms capable of mixotrophic Fe(II) oxidation by a new strain, S. natans strain DSM 6575(T) , and could contribute to biogeochemical cycles of Fe and N in the environment. © 2014 The Authors. FEMS Microbiology Ecology published by John Wiley & Sons Ltd on behalf of Federation of European Microbiological Societies.

THE SPECTRUM OF Fe II

Energy Technology Data Exchange (ETDEWEB)

Nave, Gillian [National Institute of Standards and Technology, Gaithersburg, MD 20899-8422 (United States); Johansson, Sveneric, E-mail: gillian.nave@nist.gov [Lund Observatory, University of Lund, Box 43, SE-22100 Lund (Sweden)

2013-01-15

The spectrum of singly ionized iron (Fe II) has been recorded using high-resolution Fourier transform (FT) and grating spectroscopy over the wavelength range 900 A to 5.5 {mu}m. The spectra were observed in high-current continuous and pulsed hollow cathode discharges using FT spectrometers at the Kitt Peak National Observatory, Tucson, AZ and Imperial College, London and with the 10.7 m Normal Incidence Spectrograph at the National Institute of Standards and Technology. Roughly 12,900 lines were classified using 1027 energy levels of Fe II that were optimized to measured wavenumbers. The wavenumber uncertainties of lines in the FT spectra range from 10{sup -4} cm{sup -1} for strong lines around 4 {mu}m to 0.05 cm{sup -1} for weaker lines around 1500 A. The wavelength uncertainty of lines in the grating spectra is 0.005 A. The ionization energy of (130,655.4 {+-} 0.4) cm{sup -1} was estimated from the 3d{sup 6}({sup 5}D)5g and 3d{sup 6}({sup 5}D)6h levels.

Biosorption of Fe (II) and Cd (II) ions from aqueous solution using a ...

African Journals Online (AJOL)

ADOWIE PERE

Biosorption of Fe (II) and Cd (II) ions from aqueous solution using a low cost ... human activities in the environment poses a lot of risk ... ion exchange or reverse osmosis, electrochemical treatment ..... is the adsorption coefficient, n indicates the.

THE Fe II EMISSION IN ACTIVE GALACTIC NUCLEI: EXCITATION MECHANISMS AND LOCATION OF THE EMITTING REGION

International Nuclear Information System (INIS)

Marinello, M.; Rodríguez-Ardila, A.; Garcia-Rissmann, A.; Sigut, T. A. A.; Pradhan, A. K.

2016-01-01

We present a study of Fe ii emission in the near-infrared region (NIR) for 25 active galactic nuclei (AGNs) to obtain information about the excitation mechanisms that power it and the location where it is formed. We employ an NIR Fe ii template derived in the literature and find that it successfully reproduces the observed Fe ii spectrum. The Fe ii bump at 9200 Å detected in all objects studied confirms that Lyα fluorescence is always present in AGNs. The correlation found between the flux of the 9200 Å bump, the 1 μm lines, and the optical Fe ii implies that Lyα fluorescence plays an important role in Fe ii production. We determined that at least 18% of the optical Fe ii is due to this process, while collisional excitation dominates the production of the observed Fe ii. The line profiles of Fe ii λ10502, O i λ11287, Ca ii λ8664, and Paβ were compared to gather information about the most likely location where they are emitted. We found that Fe ii, O i and Ca ii have similar widths and are, on average, 30% narrower than Paβ. Assuming that the clouds emitting the lines are virialized, we show that the Fe ii is emitted in a region twice as far from the central source than Paβ. The distance, though, strongly varies: from 8.5 light-days for NGC 4051 to 198.2 light-days for Mrk 509. Our results reinforce the importance of the Fe ii in the NIR to constrain critical parameters that drive its physics and the underlying AGN kinematics, as well as more accurate models aimed at reproducing this complex emission

THE Fe II EMISSION IN ACTIVE GALACTIC NUCLEI: EXCITATION MECHANISMS AND LOCATION OF THE EMITTING REGION

Energy Technology Data Exchange (ETDEWEB)

Marinello, M. [Universidade Federal de Itajubá, Rua Doutor Pereira Cabral 1303, 37500-903, Itajubá, MG (Brazil); Rodríguez-Ardila, A.; Garcia-Rissmann, A. [Laboratório Nacional de Astrofísica, Rua Estados Unidos 154, Itajubá, MG, 37504-364 (Brazil); Sigut, T. A. A. [The University of Western Ontario, London, ON N6A 3K7 (Canada); Pradhan, A. K., E-mail: murilo.marinello@gmail.com [McPherson Laboratory, The Ohio State University, 140 W. 18th Ave., Columbus, OH 43210-1173 (United States)

2016-04-01

We present a study of Fe ii emission in the near-infrared region (NIR) for 25 active galactic nuclei (AGNs) to obtain information about the excitation mechanisms that power it and the location where it is formed. We employ an NIR Fe ii template derived in the literature and find that it successfully reproduces the observed Fe ii spectrum. The Fe ii bump at 9200 Å detected in all objects studied confirms that Lyα fluorescence is always present in AGNs. The correlation found between the flux of the 9200 Å bump, the 1 μm lines, and the optical Fe ii implies that Lyα fluorescence plays an important role in Fe ii production. We determined that at least 18% of the optical Fe ii is due to this process, while collisional excitation dominates the production of the observed Fe ii. The line profiles of Fe ii λ10502, O i λ11287, Ca ii λ8664, and Paβ were compared to gather information about the most likely location where they are emitted. We found that Fe ii, O i and Ca ii have similar widths and are, on average, 30% narrower than Paβ. Assuming that the clouds emitting the lines are virialized, we show that the Fe ii is emitted in a region twice as far from the central source than Paβ. The distance, though, strongly varies: from 8.5 light-days for NGC 4051 to 198.2 light-days for Mrk 509. Our results reinforce the importance of the Fe ii in the NIR to constrain critical parameters that drive its physics and the underlying AGN kinematics, as well as more accurate models aimed at reproducing this complex emission.

Average [O II] nebular emission associated with Mg II absorbers: dependence on Fe II absorption

Science.gov (United States)

Joshi, Ravi; Srianand, Raghunathan; Petitjean, Patrick; Noterdaeme, Pasquier

2018-05-01

We investigate the effect of Fe II equivalent width (W2600) and fibre size on the average luminosity of [O II] λλ3727, 3729 nebular emission associated with Mg II absorbers (at 0.55 ≤ z ≤ 1.3) in the composite spectra of quasars obtained with 3 and 2 arcsec fibres in the Sloan Digital Sky Survey. We confirm the presence of strong correlations between [O II] luminosity (L_{[O II]}) and equivalent width (W2796) and redshift of Mg II absorbers. However, we show L_{[O II]} and average luminosity surface density suffer from fibre size effects. More importantly, for a given fibre size, the average L_{[O II]} strongly depends on the equivalent width of Fe II absorption lines and found to be higher for Mg II absorbers with R ≡W2600/W2796 ≥ 0.5. In fact, we show the observed strong correlations of L_{[O II]} with W2796 and z of Mg II absorbers are mainly driven by such systems. Direct [O II] detections also confirm the link between L_{[O II]} and R. Therefore, one has to pay attention to the fibre losses and dependence of redshift evolution of Mg II absorbers on W2600 before using them as a luminosity unbiased probe of global star formation rate density. We show that the [O II] nebular emission detected in the stacked spectrum is not dominated by few direct detections (i.e. detections ≥3σ significant level). On an average, the systems with R ≥ 0.5 and W2796 ≥ 2 Å are more reddened, showing colour excess E(B - V) ˜ 0.02, with respect to the systems with R < 0.5 and most likely trace the high H I column density systems.

Kinetics of transformation of 1,1,1-trichloroethane by Fe(II) in cement slurries

International Nuclear Information System (INIS)

Jung, Bahngmi; Batchelor, Bill

2009-01-01

This study examines the applicability of the iron-based degradative solidification/stabilization (DS/S-Fe(II)) process to 1,1,1-trichloroethane (1,1,1-TCA), which is one of common chlorinated aliphatic hydrocarbons (CAHs) of concern at contaminated sites. DS/S-Fe(II) combines contaminant degradation by Fe(II) and immobilization by the hydration reactions of Portland cement. The transformation of 1,1,1-TCA by Fe(II) in 10% Portland cement slurries was studied using a batch slurry reactor system. The effects of Fe(II) dose, pH, and initial concentration of 1,1,1-TCA on the kinetics of 1,1,1-TCA degradation were evaluated. Degradation of 1,1,1-TCA in cement slurries including Fe(II) was very rapid and could be described by a pseudo-first-order rate law. The half-lives for 1,1,1-TCA were measured between 0.4 and 5 h when Fe(II) dose ranged from 4.9 to 39.2 mM. The pseudo-first-order rate constant increased with pH to a maximum near pH 12.5. A saturation rate equation was able to predict degradation kinetics over a wide range of target organic concentrations and at higher Fe(II) doses. The major transformation product of 1,1,1-TCA in mixtures of Fe(II) and cement was 1,1-dichloroethane (1,1-DCA), which indicates that degradation occurred by a hydrogenolysis pathway. A small amount of ethane was observed. The conversion of 1,1,1-TCA to ethane was better described by a parallel reaction model than by a consecutive reaction model

Correlation of reactivity with structural factors in a series of Fe(II) substituted cobalt ferrites

International Nuclear Information System (INIS)

Sileo, Elsa E.; Garcia Rodenas, Luis; Paiva-Santos, Carlos O.; Stephens, Peter W.; Morando, Pedro J.; Blesa, Miguel A.

2006-01-01

A series of powdered cobalt ferrites, Co x Fe 3- x O 4 with 0.66≤x II , were synthesized by a mild procedure, and their Fe and Co site occupancies and structural characteristics were explored using X-ray anomalous scattering and the Rietveld refinement method. The dissolution kinetics, measured in 0.1 M oxalic acid aqueous solution at 70 deg. C, indicate in all cases the operation of a contracting volume rate law. The specific rates increased with the Fe II content following approximately a second-order polynomial expression. This result suggests that the transfer of Fe III controls the dissolution rate, and that the leaching of a first layer of ions Co II and Fe II leaves exposed a surface enriched in slower dissolving octahedral Fe III ions. Within this model, inner vicinal lattice Fe II accelerates the rate of Fe III transfer via internal electron hopping. A chain mechanism, involving successive electron transfers, fits the data very well. - Graphical abstract: The electron exchange between octahedral Fe II and Fe III ions has important consequences on the specific dissolution rates. Display Omitted

FeII/MgII Emission Line Ratio in High Redshift Quasars

DEFF Research Database (Denmark)

Dietrich, M.; Hamann, F.; Appenzeller, I.

2003-01-01

the evolution of the FeII/MgII ratio over a wider range in cosmic time, we measured this ratio for composite quasar spectra which cover a redshift range of 0 4 quasars must have started already at an epoch corresponding to z_f = 6 to 9, when the age of the universe was ~0.5 Gyr (H_o = 72 km/s/Mpc, Omega_M = 0...

Evaluation of Fe(II) oxidation at an acid mine drainage site using laboratory-scale reactors

Science.gov (United States)

Brown, Juliana; Burgos, William

2010-05-01

Acid mine drainage (AMD) is a severe environmental threat to the Appalachian region of the Eastern United States. The Susquehanna and Potomac River basins of Pennsylvania drain to the Chesapeake Bay, which is heavily polluted by acidity and metals from AMD. This study attempted to unravel the complex relationships between AMD geochemistry, microbial communities, hydrodynamic conditions, and the mineral precipitates for low-pH Fe mounds formed downstream of deep mine discharges, such as Lower Red Eyes in Somerset County, PA, USA. This site is contaminated with high concentrations of Fe (550 mg/L), Mn (115 mg/L), and other trace metals. At the site 95% of dissolved Fe(II) and 56% of total dissolved Fe is removed without treatment, across the mound, but there is no change in the concentration of trace metals. Fe(III) oxides were collected across the Red Eyes Fe mound and precipitates were analyzed by X-ray diffraction, electron microscopy and elemental analysis. Schwertmannite was the dominant mineral phase with traces of goethite. The precipitates also contained minor amounts of Al2O3, MgO,and P2O5. Laboratory flow-through reactors were constructed to quantify Fe(II) oxidation and Fe removal over time at terrace and pool depositional facies. Conditions such as residence time, number of reactors in sequence and water column height were varied to determine optimal conditions for Fe removal. Reactors with sediments collected from an upstream terrace oxidized more than 50% of dissolved Fe(II) at a ten hour residence time, while upstream pool sediments only oxidized 40% of dissolved Fe(II). Downstream terrace and pool sediments were only capable of oxidizing 25% and 20% of Fe(II), respectively. Fe(II) oxidation rates measured in the reactors were determined to be between 3.99 x 10-8and 1.94 x 10-7mol L-1s-1. The sediments were not as efficient for total dissolved Fe removal and only 25% was removed under optimal conditions. The removal efficiency for all sediments

Kinetic and spectroscopic investigation of CoII, NiII, and N-oxalylglycine inhibition of the FeII/α-ketoglutarate dioxygenase, TauD

International Nuclear Information System (INIS)

Kalliri, Efthalia; Grzyska, Piotr K.; Hausinger, Robert P.

2005-01-01

Co II , Ni II , and N-oxalylglycine (NOG) are well-known inhibitors of Fe II /α-ketoglutarate (αKG)-dependent hydroxylases, but few studies describe their kinetics and no spectroscopic investigations have been reported. Using taurine/αKG dioxygenase (TauD) as a paradigm for this enzyme family, time-dependent inhibition assays showed that Co II and Ni II follow slow-binding inhibition kinetics. Whereas Ni II -substituted TauD was non-chromophoric, spectroscopic studies of the Co II -substituted enzyme revealed a six-coordinate site (protein alone or with αKG) that became five-coordinate upon taurine addition. The Co II spectrum was not perturbed by a series of anions or oxidants, suggesting the Co II is inaccessible and could be used to stabilize the protein. NOG competed weakly (K i ∼ 290 μM) with αKG for binding to TauD, with the increased electron density of NOG yielding electronic transitions for NOG-Fe II -TauD and taurine-NOG-Fe II -TauD at 380 nm (ε 38 90-105 M -1 cm -1 ). The spectra of the NOG-bound TauD species did not change significantly upon oxygen exposure, arguing against the formation of an oxygen-bound state mimicking an early intermediate in catalysis

Solid Phase Extraction of Trace Al(III), Fe(II), Co(II), Cu(II), Cd(II) and Pb(II) Ions in Beverages on Functionalized Polymer Microspheres Prior to Flame Atomic Absorption Spectrometric Determinations.

Science.gov (United States)

Berber, Hale; Alpdogan, Güzin

2017-01-01

In this study, poly(glycidyl methacrylate-methyl methacrylate-divinylbenzene) was synthesized in the form of microspheres, and then functionalized by 2-aminobenzothiazole ligand. The sorption properties of these functionalized microspheres were investigated for separation, preconcentration and determination of Al(III), Fe(II), Co(II), Cu(II), Cd(II) and Pb(II) ions using flame atomic absorption spectrometry. The optimum pH values for quantitative sorption were 2 - 4, 5 - 8, 6 - 8, 4 - 6, 2 - 6 and 2 - 3 for Al(III), Fe(II), Co(II), Cu(II), Cd(II) and Pb(II), respectively, and also the highest sorption capacity of the functionalized microspheres was found to be for Cu(II) with the value of 1.87 mmol g -1 . The detection limits (3σ; N = 6) obtained for the studied metals in the optimal conditions were observed in the range of 0.26 - 2.20 μg L -1 . The proposed method was successfully applied to different beverage samples for the determination of Al(III), Fe(II), Co(II), Cu(II), Cd(II) and Pb(II) ions, with the relative standard deviation of <3.7%.

LARGE-AREA [Fe II] LINE MAPPING OF THE SUPERNOVA REMNANT IC 443 WITH THE IRSF/SIRIUS

Energy Technology Data Exchange (ETDEWEB)

Kokusho, Takuma; Nagayama, Takahiro; Kaneda, Hidehiro; Ishihara, Daisuke [Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602 (Japan); Lee, Ho-Gyu; Onaka, Takashi, E-mail: kokusho@u.phys.nagoya-u.ac.jp [Department of Astronomy, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2013-05-01

We present the results of near-infrared (near-IR) [Fe II] line mapping of the supernova remnant IC 443 with IRSF/SIRIUS, using the two narrow-band filters tuned for the [Fe II] 1.257 {mu}m and [Fe II] 1.644 {mu}m lines. Covering a large area of 30' Multiplication-Sign 35', our observations reveal that [Fe II] filamentary structures exist all over the remnant, not only in an ionic shock shell, but also in a molecular shock shell and a central region inside the shells. With the two [Fe II] lines, we performed corrections for dust extinction to derive the intrinsic line intensities. We also obtained the intensities of thermal emission from the warm dust associated with IC 443, using the far- and mid-IR images taken with AKARI and Spitzer, respectively. As a result, we find that the [Fe II] line emission relative to the dust emission notably enhances in the inner central region. We discuss causes of the enhanced [Fe II] line emission, estimating the Fe{sup +} and dust masses.

Cr(III,Mn(II,Fe(III,Co(II,Ni(II,Cu(II and Zn(II Complexes with Diisobutyldithiocarbamato Ligand

Directory of Open Access Journals (Sweden)

Mohammad Tarique

2011-01-01

Full Text Available The synthesis of sulphur and nitrogen containing dithiocarbamato ligand derived from diisobutylamine as well as its coordination compounds with 3d series transition metals is presented. These synthesized compounds were characterized on the basis of elemental analysis, conductometric measurements and IR spectral studies. The analytical data showed the stoichiometry 1:2 and 1:3 for the compounds of the types ML2 {M=Mn(II, Co(II, Ni(II, Cu(II and Zn(II} and M'L3{M'=Cr(III and Fe(III} respectively. The conductometric measurements proved the non-electrolytic behaviour of all the compounds. The bidentate nature of dithiocarbamato moiety was confirmed on the basis of IR spectral data.

Infrared Fe II lines in Eta Carinae and a possible interpretation of infrared excesses

International Nuclear Information System (INIS)

Thackeray, A.D.

1978-01-01

The identification of very strong emission lines in the near infrared spectrum of Eta Carinae with newly recognised high-level transitions of Fe II raises the possibility that the infrared excesses of hot emission-line stars may be due to dielectronic recombination of Fe II. Johansson's Fe II lines also need to be considered in the interpretation of the infrared spectra of supernovae. (author)

Fe uptake from meso and D,L-racemic Fe(o,o-EDDHA) isomers by strategy I and II plants.

Science.gov (United States)

Cerdán, Mar; Alcañiz, Sara; Juárez, Margarita; Jordá, Juana D; Bermúdez, Dolores

2006-02-22

One of the most efficient fertilizers to correct Fe deficiency in calcareous soils and waters with high bicarbonate content is based on ferric ethylenediamine-N,N'-bis(o-hydroxyphenylacetic) acid [Fe(o,o-EDDHA)]. Fe(o,o-EDDHA) forms two groups of geometric isomers known as meso and D,L-racemic. To determine the Fe uptake from meso and D,L-racemic Fe(o,o-EDDHA), four iron-efficient plants, two plants representative of strategy I (tomato and pepper) and two plants representative of strategy II (wheat and oats), were grown in hydroponic culture. Results indicated that strategy II plants took up iron from both Fe(o,o-EDDHA) isomers equally. However, strategy I plants took mainly the iron associated with the meso form (the lowest stability isomer).

Uptake and Release of Cerium During Fe-Oxide Formation and Transformation in Fe(II) Solutions

DEFF Research Database (Denmark)

Nedel, Sorin; Dideriksen, Knud; Christiansen, Bo C.

2010-01-01

Fe-oxides are ubiquitous in soils and sediments and form during Fe(0) corrosion. Depending on redox conditions and solution composition, Fe-oxides such as ferrihydrite, goethite, magnetite, and green rust (GR) may form. These phases typically have high surface area and large affinity for adsorption......(III) release. X-ray photoelectron spectroscopy revealed Ce(III) adsorbed on magnetite. When Fe-oxides were synthesized by air oxidation of Fe(II) solutions at pH 7, GR(Na,SO4) played a catalytic role in the oxidation of Ce(III) to Ce(IV) by O-2, removing more than 90% of the dissolved Ce. Transmission electron...

Kinetics of Fe(II)-catalyzed transformation of 6-line ferrihydrite under anaerobic flow conditions

Energy Technology Data Exchange (ETDEWEB)

Yang, L.; Steefel, C.I.; Marcus, M.A.; Bargar, J.R.

2010-04-01

The readsorption of ferrous ions produced by the abiotic and microbially-mediated reductive dissolution of iron oxy-hydroxides drives a series of transformations of the host minerals. To further understand the mechanisms by which these transformations occur and their kinetics within a microporous flow environment, flow-through experiments were conducted in which capillary tubes packed with ferrihydrite-coated glass spheres were injected with inorganic Fe(II) solutions under circumneutral pH conditions at 25 C. Synchrotron X-ray diffraction was used to identify the secondary phase(s) formed and to provide data for quantitative kinetic analysis. At concentrations at and above 1.8 mM Fe(II) in the injection solution, magnetite was the only secondary phase formed (no intermediates were detected), with complete transformation following a nonlinear rate law requiring 28 hours and 150 hours of reaction at 18 and 1.8 mM Fe(II), respectively. However, when the injection solution consisted of 0.36 mM Fe(II), goethite was the predominant reaction product and formed much more slowly according to a linear rate law, while only minor magnetite was formed. When the rates are normalized based on the time to react half of the ferrihydrite on a reduced time plot, it is apparent that the 1.8 mM and 18 mM input Fe(II) experiments can be described by the same reaction mechanism, while the 0.36 input Fe(II) experiment is distinct. The analysis of the transformation kinetics suggest that the transformations involved an electron transfer reaction between the aqueous as well as sorbed Fe(II) and ferrihydrite acting as a semiconductor, rather than a simple dissolution and recrystallization mechanism. A transformation mechanism involving sorbed inner sphere Fe(II) alone is not supported, since the essentially equal coverage of sorption sites in the 18 mM and 1.8 mM Fe(II) injections cannot explain the difference in the transformation rates observed.

Enhancement effects of reducing agents on the degradation of tetrachloroethene in the Fe(II)/Fe(III) catalyzed percarbonate system

International Nuclear Information System (INIS)

Miao, Zhouwei; Gu, Xiaogang; Lu, Shuguang; Brusseau, Mark L.; Yan, Ni; Qiu, Zhaofu; Sui, Qian

2015-01-01

Highlights: • PCE degradation by reducing-agent modified Fe-catalyzed percarbonate was studied. • The addition of reducing agents significantly increased PCE degradation. • Hydroxylamine hydrochloride showed the best effect on enhancing PCE degradation. • The primary PCE degradation mechanism was oxidation by hydroxyl radical. • O_2·"− participated in the degradation of PCE in reducing-agent modified system. - Abstract: In this study, the effects of reducing agents on the degradation of tetrachloroethene (PCE) were investigated in the Fe(II)/Fe(III) catalyzed sodium percarbonate (SPC) system. The addition of reducing agents, including hydroxylamine hydrochloride, sodium sulfite, ascorbic acid and sodium ascorbate, accelerated the Fe(III)/Fe(II) redox cycle, leading to a relatively steady Fe(II) concentration and higher production of free radicals. This, in turn, resulted in enhanced PCE oxidation by SPC, with almost complete PCE removal obtained for appropriate Fe and SPC concentrations. The chemical probe tests, using nitrobenzene and carbon tetrachloride, demonstrated that HO· was the predominant radical in the system and that O_2·"− played a minor role, which was further confirmed by the results of electron spin resonance measurements. PCE degradation decreased significantly with the addition of isopropanol, a HO· scavenger, supporting the hypothesis that HO· was primarily responsible for PCE degradation. It is noteworthy that Cl"− release was slightly delayed in the first 20 min, indicating that intermediate products were produced. However, these intermediates were further degraded, resulting in the complete conversion of PCE to CO_2. In conclusion, the use of reducing agents to enhance Fe(II)/Fe(III) catalyzed SPC oxidation appears to be a promising approach for the rapid degradation of organic contaminants in groundwater.

Enhancement effects of reducing agents on the degradation of tetrachloroethene in the Fe(II)/Fe(III) catalyzed percarbonate system

Energy Technology Data Exchange (ETDEWEB)

Miao, Zhouwei [State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, East China University of Science and Technology, Shanghai 200237 (China); Soil, Water and Environmental Science Department, School of Earth and Environmental Sciences, The University of Arizona, 429 Shantz Building, Tucson, AZ 85721 (United States); Gu, Xiaogang [State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, East China University of Science and Technology, Shanghai 200237 (China); Lu, Shuguang, E-mail: lvshuguang@ecust.edu.cn [State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, East China University of Science and Technology, Shanghai 200237 (China); Brusseau, Mark L. [Soil, Water and Environmental Science Department, School of Earth and Environmental Sciences, The University of Arizona, 429 Shantz Building, Tucson, AZ 85721 (United States); Yan, Ni [Hydrology and Water Resources Department, School of Earth and Environmental Sciences, University of Arizona, 429 Shantz Building, Tucson, AZ 85721 (United States); Qiu, Zhaofu; Sui, Qian [State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, East China University of Science and Technology, Shanghai 200237 (China)

2015-12-30

Highlights: • PCE degradation by reducing-agent modified Fe-catalyzed percarbonate was studied. • The addition of reducing agents significantly increased PCE degradation. • Hydroxylamine hydrochloride showed the best effect on enhancing PCE degradation. • The primary PCE degradation mechanism was oxidation by hydroxyl radical. • O{sub 2}·{sup −} participated in the degradation of PCE in reducing-agent modified system. - Abstract: In this study, the effects of reducing agents on the degradation of tetrachloroethene (PCE) were investigated in the Fe(II)/Fe(III) catalyzed sodium percarbonate (SPC) system. The addition of reducing agents, including hydroxylamine hydrochloride, sodium sulfite, ascorbic acid and sodium ascorbate, accelerated the Fe(III)/Fe(II) redox cycle, leading to a relatively steady Fe(II) concentration and higher production of free radicals. This, in turn, resulted in enhanced PCE oxidation by SPC, with almost complete PCE removal obtained for appropriate Fe and SPC concentrations. The chemical probe tests, using nitrobenzene and carbon tetrachloride, demonstrated that HO· was the predominant radical in the system and that O{sub 2}·{sup −} played a minor role, which was further confirmed by the results of electron spin resonance measurements. PCE degradation decreased significantly with the addition of isopropanol, a HO· scavenger, supporting the hypothesis that HO· was primarily responsible for PCE degradation. It is noteworthy that Cl{sup −} release was slightly delayed in the first 20 min, indicating that intermediate products were produced. However, these intermediates were further degraded, resulting in the complete conversion of PCE to CO{sub 2}. In conclusion, the use of reducing agents to enhance Fe(II)/Fe(III) catalyzed SPC oxidation appears to be a promising approach for the rapid degradation of organic contaminants in groundwater.

Effect of pH and Fe/U ratio on the U(VI) removal rate by the synergistic effect of Fe(II) and O2

Science.gov (United States)

Fu, Yukui; Luo, Yingfeng; Fang, Qi; Xie, Yanpei; Wang, Zhihong; Zhu, Xiangyu

2018-02-01

As for the decommissioned uranium deposits of acid in-situ leaching, both of the concentrations of U(VI) and Fe(II) are relatively high in groundwater. In the presence of O2, the oxidation of Fe(II) into Fe(III) that forms Fe-hydroxides could effectively remove U(VI) in the forms of sorption or co-precipitation. In this process, pH condition and Fe content will have a significant effect on the U(VI) removal rate by the synergistic effect of Fe(II) and O2. In the present work, a series of batch experiments were carried out to investigate the effect of pH values and Fe/U mass ratio on the U(VI) removal rate by the synergistic effect of Fe(II) and O2. Experiment results show that the removal rate of U(VI) is mainly controlled by pH and secondly by Fe/U mass ratio. In the neutral conditions with pH at 7 and 8, the removal rate of U(VI) reaches up to 90% for all solutions with different initial Fe(II) concentrations. The optimal pH for the removal rate of U(VI) is above 7. In the acidic conditions with pH below 6, the effect of Fe/U mass ratio on the removal rate of U(VI) becomes more obvious and the optimal Fe/U mass ratio for U(VI) removal is 1:2.

Moessbauer spectra of some complex compounds of Fe(II) with pyridine

International Nuclear Information System (INIS)

Teodorescu, M.; Filoti, G.

1975-01-01

The Moessbauer spectra of [Fe(II)py 6 ]Br 2 at 298 and 80 K and the reflectance spectra of the same compound at room temperature are presented. Isomer shift and quadrupole splitting were determined for [Fe(II)py 6 ]Br 2 at 298 and 80 K, their values being correlated with those obtained from electronic spectra measured in the solid state. (Z.S.)

Sorption of Pb(II and Cu(II by low-cost magnetic eggshells-Fe3O4 powder

Directory of Open Access Journals (Sweden)

Ren Jianwei

2012-01-01

Full Text Available This study explored the feasibility of using magnetic eggshell-Fe3O4 powder as adsorbent for the removal of Pb(II and Cu(II ions from aqueous solution. The metal ionsadsorption media interaction was characterized using XRD and FTIR. The effects of contact time, initial concentrations, temperature, solution pH and reusability of the adsorption media were investigated. The metal ions adsorption was fast and the amount of metal ions adsorbed increased with an increase in temperature, suggesting an endothermic adsorption. The kinetic data showed that the adsorption process followed the pseudo-second-order kinetic model. The optimal adsorption pH value was around 5.5 at which condition the equilibrium capacity was 263.2 mg/g for Pb(II and 250.0 for Cu(II. The adsorption equilibrium data fitted very well to the Langmuir and Freundlich adsorption isotherm models. The thermodynamics of Pb(II and Cu(II adsorption onto the magnetic eggshell-Fe3O4 powder indicated that the adsorption was spontaneous. The reusability study has proven that magnetic eggshell-Fe3O4 powder can be employed as a low-cost and easy to separate adsorbent.

Near-Infrared [Fe II] and H2 Study of the Galactic Supernova Remnants

Science.gov (United States)

Lee, Yong-Hyun; Koo, Bon-Chul; Lee, Jae-Joon; Jaffe, Daniel T.; Burton, Michael G.; Ryder, Stuart D.

2018-01-01

We have searched for near-infrared (NIR) [Fe II] (1.644 μm) and H2 1-0 S(1) (2.122 μm) emission features associated with Galactic supernova remnants (SNRs) using the narrow-band imaging surveys UWIFE / UWISH2 (UKIRT Widefield Infrared Survey for [Fe II] / H2). Both surveys cover about 180 square degrees of the first Galactic quadrant (7° reversal” phenomenon, i.e., the H2 emission features are detected outside the [Fe II] emission boundary. We carried out high resolution (R~40,000) NIR H- and K-band spectroscopy of the five SNRs showing the [Fe II]-H2 reversal (G11.2-0.3, KES 73, W44, 3C 396, W49B) using IGRINS (Immersion GRating INfrared Spectrograph). Various ro-vibrational H2 lines have been detected, which are used to derive the kinematic distances to the SNRs and to investigate the origin of the H2 emission. The detected H2 lines show broad line width (> 10 km s-1) and line flux ratios of thermal excitation. We discuss the origin of the extended H2 emission features beyond the the [Fe II] emission boundary.

Green rusts synthesis by coprecipitation of Fe II-Fe III ions and mass-balance diagram

Science.gov (United States)

Ruby, Christian; Aïssa, Rabha; Géhin, Antoine; Cortot, Jérôme; Abdelmoula, Mustapha; Génin, Jean-Marie

2006-06-01

A basic solution is progressively added to various mixed Fe II-Fe III solutions. The nature and the relative quantities of the compounds that form can be visualised in a mass-balance diagram. The formation of hydroxysulphate green rust {GR( SO42-)} is preceded by the precipitation of a sulphated ferric basic salt that transforms in a badly ordered ferric oxyhydroxide. Then octahedrally coordinated Fe II species and SO42- anions are adsorbed on the FeOOH surface and GR( SO42-) is formed at the solid/solution interface. By using the same method of preparation, other types of green rust were synthesised, e.g. hydroxycarbonate green rust {GR( CO32-)}. Like other layered double hydroxides, green rusts obey the general chemical formula [ṡ[ṡmHO]x+ with x⩽1/3. Al-substituted hydroxysulphate green rust consists of small hexagonal crystals with a lateral size ˜50 nm, which is significantly smaller than the size of the GR( SO42-) crystals (˜500 nm). To cite this article: C. Ruby et al., C. R. Geoscience 338 (2006).

Potentiometric and electrokinetic signatures of iron(II) interactions with (α,γ)-Fe2O3.

Science.gov (United States)

Toczydłowska, Diana; Kędra-Królik, Karolina; Nejbert, Krzysztof; Preočanin, Tajana; Rosso, Kevin M; Zarzycki, Piotr

2015-10-21

The electrochemical signatures of Fe(II) interactions with iron(III) oxides are poorly understood, despite their importance in controlling the amount of mobilized iron. Here, we report the potentiometric titration of α,γ-Fe2O3 oxides exposed to Fe(II) ions. We monitored in situ surface and ζ potentials, the ratio of mobilized ferric to ferrous, and the periodically analyzed nanoparticle crystal structure using X-ray diffraction. Electrokinetic potential reveals weak but still noticeable specific sorption of Fe(II) to the oxide surface under acidic conditions, and pronounced adsorption under alkaline conditions that results in a surface potential reversal. By monitoring the aqueous iron(II/III) fraction, we found that the addition of Fe(II) ions produces platinum electrode response consistent with the iron solubility-activity curve. Although, XRD analysis showed no evidence of γ-Fe2O3 transformations along the titration pathway despite iron cycling between aqueous and solid reservoirs, the magnetite formation cannot be ruled out.

Potential Role of Nitrite for Abiotic Fe(II) Oxidation and Cell Encrustation during Nitrate Reduction by Denitrifying Bacteria

Science.gov (United States)

Klueglein, Nicole; Zeitvogel, Fabian; Stierhof, York-Dieter; Floetenmeyer, Matthias; Konhauser, Kurt O.; Obst, Martin

2014-01-01

Microorganisms have been observed to oxidize Fe(II) at neutral pH under anoxic and microoxic conditions. While most of the mixotrophic nitrate-reducing Fe(II)-oxidizing bacteria become encrusted with Fe(III)-rich minerals, photoautotrophic and microaerophilic Fe(II) oxidizers avoid cell encrustation. The Fe(II) oxidation mechanisms and the reasons for encrustation remain largely unresolved. Here we used cultivation-based methods and electron microscopy to compare two previously described nitrate-reducing Fe(II) oxidizers ( Acidovorax sp. strain BoFeN1 and Pseudogulbenkiania sp. strain 2002) and two heterotrophic nitrate reducers (Paracoccus denitrificans ATCC 19367 and P. denitrificans Pd 1222). All four strains oxidized ∼8 mM Fe(II) within 5 days in the presence of 5 mM acetate and accumulated nitrite (maximum concentrations of 0.8 to 1.0 mM) in the culture media. Iron(III) minerals, mainly goethite, formed and precipitated extracellularly in close proximity to the cell surface. Interestingly, mineral formation was also observed within the periplasm and cytoplasm; intracellular mineralization is expected to be physiologically disadvantageous, yet acetate consumption continued to be observed even at an advanced stage of Fe(II) oxidation. Extracellular polymeric substances (EPS) were detected by lectin staining with fluorescence microscopy, particularly in the presence of Fe(II), suggesting that EPS production is a response to Fe(II) toxicity or a strategy to decrease encrustation. Based on the data presented here, we propose a nitrite-driven, indirect mechanism of cell encrustation whereby nitrite forms during heterotrophic denitrification and abiotically oxidizes Fe(II). This work adds to the known assemblage of Fe(II)-oxidizing bacteria in nature and complicates our ability to delineate microbial Fe(II) oxidation in ancient microbes preserved as fossils in the geological record. PMID:24271182

Iron Isotope Fractionation during Fe(II) Oxidation Mediated by the Oxygen-Producing Marine Cyanobacterium Synechococcus PCC 7002

Energy Technology Data Exchange (ETDEWEB)

Swanner, E. D.; Bayer, T.; Wu, W.; Hao, L.; Obst, M.; Sundman, A.; Byrne, J. M.; Michel, F. M.; Kleinhanns, I. C.; Kappler, A.; Schoenberg, R.

2017-04-11

In this study, we couple iron isotope analysis to microscopic and mineralogical investigation of iron speciation during circumneutral Fe(II) oxidation and Fe(III) precipitation with photosynthetically produced oxygen. In the presence of the cyanobacterium Synechococcus PCC 7002, aqueous Fe(II) (Fe(II)_aq) is oxidized and precipitated as amorphous Fe(III) oxyhydroxide minerals (iron precipitates, Fe_ppt), with distinct isotopic fractionation (ε⁵⁶Fe) values determined from fitting the δ⁵⁶Fe(II)_aq (1.79‰ and 2.15‰) and the δ⁵⁶Fe_ppt (2.44‰ and 2.98‰) data trends from two replicate experiments. Additional Fe(II) and Fe(III) phases were detected using microscopy and chemical extractions and likely represent Fe(II) and Fe(III) sorbed to minerals and cells. The iron desorbed with sodium acetate (FeNaAc) yielded heavier δ⁵⁶Fe compositions than Fe(II)_aq. Modeling of the fractionation during Fe(III) sorption to cells and Fe(II) sorption to Feppt, combined with equilibration of sorbed iron and with Fe(II)_aq using published fractionation factors, is consistent with our resulting δ⁵⁶FeNaAc. The δ⁵⁶Fe_ppt data trend is inconsistent with complete equilibrium exchange with Fe(II)aq. Because of this and our detection of microbially excreted organics (e.g., exopolysaccharides) coating Feppt in our microscopic analysis, we suggest that electron and atom exchange is partially suppressed in this system by biologically produced organics. These results indicate that cyanobacteria influence the fate and composition of iron in sunlit environments via their role in Fe(II) oxidation through O₂ production, the capacity of their cell surfaces to sorb iron, and the interaction of secreted organics with Fe(III) minerals.

Effects of waterborne Fe(II) on juvenile turbot Scophthalmus maximus: analysis of respiratory rate, hematology and gill histology

Science.gov (United States)

Wu, Zhihao; You, Feng; Liu, Hongjun; Liu, Mengxia; Li, Jun; Zhang, Peijun

2012-03-01

The concentration of Fe(II) is high in some groundwater supplies used in turbot culture, and the toxicity of waterborne Fe(II) is unknown. We investigated the stress responses of juvenile turbot, Scophthalmus maximus, exposed to Fe(II) of different concentrations (0.01, 0.05, 0.1, 0.5, 1, and 2 mg/L) for 1, 7, 14, and 28 d, under the same ambient conditions of other parameters. Changes in respiratory rate, hematological parameters, and gill structure were determined. The results show that waterborne Fe(II) did not cause severe hematological perturbation to turbot. A low-medium Fe(II) concentration (lower than 0.1 mg/L) could boost the respiratory rate, and caused no or very limited damage to fish. A high Fe(II) concentration (0.1 mg/L or higher), however, caused gill damage, such as vacuoles in branchial lamellae, epithelial necrosis, and hypertrophy of epithelial cells, and even death after extended exposure time. Therefore, excess waterborne Fe(II) and long-term exposure to Fe(II) could be responsible for poor growth and high mortality of turbot in culture. The concentration of waterborne Fe(II) in turbot culture should be kept below 0.1 mg/L.

Uranium Immobilization through Fe(II) bio-oxidation: A Column study

Energy Technology Data Exchange (ETDEWEB)

Coates, John D.

2009-09-14

Current research on the bioremediation of heavy metals and radionuclides is focused on the ability of reducing organisms to use these metals as alternative electron acceptors in the absence of oxygen and thus precipitate them out of solution. However, many aspects of this proposed scheme need to be resolved, not the least of which is the time frame of the treatment process. Once treatment is complete and the electron donor addition is halted, the system will ultimately revert back to an oxic state and potentially result in the abiotic reoxidation and remobilization of the immobilized metals. In addition, the possibility exists that the presence of more electropositive electron acceptors such as nitrate or oxygen will also stimulate the biological oxidation and remobilization of these contaminants. The selective nitrate-dependent biooxidation of added Fe(II) may offer an effective means of “capping off” and completing the attenuation of these contaminants in a reducing environment making the contaminants less accessible to abiotic and biotic reactions and allowing the system to naturally revert to an oxic state. Our previous DOE-NABIR funded studies demonstrated that radionuclides such as uranium and cobalt are rapidly removed from solution during the biogenic formation of Fe(III)-oxides. In the case of uranium, X-ray spectroscopy analysis indicated that the uranium was in the hexavalent form (normally soluble) and was bound to the precipitated Fe(III)-oxides thus demonstrating the bioremediative potential of this process. We also demonstrated that nitrate-dependent Fe(II)- oxidizing bacteria are prevalent in the sediment and groundwater samples collected from sites 1 and 2 and the background site of the NABIR FRC in Oakridge, TN. However, all of these studies were performed in batch experiments in the laboratory with pure cultures and although a significant amount was learned about the microbiology of nitrate-dependent bio-oxidation of Fe(II), the effects of

Sorption and diffusion of FE(II) in bentonite

International Nuclear Information System (INIS)

Muurinen, A.; Tournassat, C.; Hadi, J.; Greneche, J.-M.

2014-02-01

The iron in the engineering barrier system of a nuclear waste repository interacts via the corrosion process with the swelling clay intended as the buffer material. This interaction may affect the sealing properties of the clay. In the case of iron-bentonite interaction, redox reactions, dissolution/precipitation, the diffusion and sorption are coupled together. In a combined study different processes are difficult to distinguish from each other, and more specific studies are needed for the separate processes. In particular, there is a need for well-controlled diffusion and sorption experiments where iron is kept as Fe(II). In this project, sorption and diffusion of Fe(II) in bentonite have been studied. The experiments were carried out under low-oxygen conditions in an anaerobic glove-box. The radioactive isotope ( 55 Fe) was used as a tracer in the experiments. The sorption experiments were carried out with two batches of purified MX-80 bentonite. One was purified at Bureau de Recherches Geologiques et Minieres, French Geological Survey (BRGM) and the other one at VTT Technical Research Centre of Finland (VTT). Experiments were also carried out with synthetic smectite, which did not include iron, which was prepared at LMPC (ENSC, F 68093 Mulhouse, France). The sorption experiments were carried out in 0.3 M and 0.05 M NaCl solutions as a function of pH, and in 0.3 M NaCl solution buffered at pH 5 as a function of added Fe(II) concentration. The separation of bentonite and solution at the end of the sorption experiment was carried out in the early phase by centrifuging only. In the later phase, ultrafiltering was added in order to improve the separation. The diffusion experiments were carried out in compacted samples prepared from MX-80 purified at VTT and saturated with 0.3 M NaCl at pH 8 and 5. A non-steady-state diffusion experiment method, where the tracer was introduced as an impulse source between two bentonite plugs was used in the measurements

Sorption and diffusion of FE(II) in bentonite

Energy Technology Data Exchange (ETDEWEB)

Muurinen, A. [VTT Technical Research Centre of Finland, Espoo (Finland); Tournassat, C.; Hadi, J. [BRGM, Orleans (France); Greneche, J.-M. [LPCE, Le Mans (France)

2014-02-15

The iron in the engineering barrier system of a nuclear waste repository interacts via the corrosion process with the swelling clay intended as the buffer material. This interaction may affect the sealing properties of the clay. In the case of iron-bentonite interaction, redox reactions, dissolution/precipitation, the diffusion and sorption are coupled together. In a combined study different processes are difficult to distinguish from each other, and more specific studies are needed for the separate processes. In particular, there is a need for well-controlled diffusion and sorption experiments where iron is kept as Fe(II). In this project, sorption and diffusion of Fe(II) in bentonite have been studied. The experiments were carried out under low-oxygen conditions in an anaerobic glove-box. The radioactive isotope ({sup 55}Fe) was used as a tracer in the experiments. The sorption experiments were carried out with two batches of purified MX-80 bentonite. One was purified at Bureau de Recherches Geologiques et Minieres, French Geological Survey (BRGM) and the other one at VTT Technical Research Centre of Finland (VTT). Experiments were also carried out with synthetic smectite, which did not include iron, which was prepared at LMPC (ENSC, F 68093 Mulhouse, France). The sorption experiments were carried out in 0.3 M and 0.05 M NaCl solutions as a function of pH, and in 0.3 M NaCl solution buffered at pH 5 as a function of added Fe(II) concentration. The separation of bentonite and solution at the end of the sorption experiment was carried out in the early phase by centrifuging only. In the later phase, ultrafiltering was added in order to improve the separation. The diffusion experiments were carried out in compacted samples prepared from MX-80 purified at VTT and saturated with 0.3 M NaCl at pH 8 and 5. A non-steady-state diffusion experiment method, where the tracer was introduced as an impulse source between two bentonite plugs was used in the measurements

Oxygen dependency of neutrophilic Fe(II) oxidation by Leptothrix differs from abiotic reaction

NARCIS (Netherlands)

Vollrath, S.; Behrends, T.; Van Cappellen, P.

2012-01-01

Neutrophilic Fe(II) oxidizing microorganisms are found in many natural environments. It has been hypothesized that, at low oxygen concentrations, microbial iron oxidation is favored over abiotic oxidation. Here, we compare the kinetics of abiotic Fe(II) oxidation to oxidation in the presence of

Effect of Organic Fe-Ligands, Released by Emiliania huxleyi, on Fe(II Oxidation Rate in Seawater Under Simulated Ocean Acidification Conditions: A Modeling Approach

Directory of Open Access Journals (Sweden)

Guillermo Samperio-Ramos

2018-06-01

Full Text Available The potential effect of ocean acidification on the exudation of organic matter by phytoplankton and, consequently, on the iron redox chemistry is largely unknown. In this study, the coccolithophorid Emiliania huxleyi was exposed to different pCO2 conditions (225–900 μatm, in order to determine the role of natural organic ligands on the Fe(II oxidation rate. Oxidation kinetics of Fe(II were studied as a function of pH (7.75–8.25 and dissolved organic carbon levels produced (0–141.11 μmol C L−1 during the different growth stages. The Fe(II oxidation rate always decreased in the presence of exudates as compared to that in the exudates-free seawater. The organic ligands present in the coccolithophorid exudates were responsible for this decrease. The oxidation of Fe(II in artificial seawater was also investigated at nanomolar levels over a range of pH (7.75–8.25 at 25°C in the presence of different glucuronic acid concentrations. Dissolved uronic acids (DUA slightly increased the experimental rate compared to control artificial seawater (ASW which can be ascribed to the stabilization of the oxidized form by chelation. This behavior was a function of the Fe(II:DUA ratio and was a pH dependent process. A kinetic model in ASW, with a single organic ligand, was applied for computing the equilibrium constant (log KFeCHO+ = 3.68 ± 0.81 M−1 and the oxidation rate (log kFeCHO+ = 3.28 ± 0.41 M−1 min−1 for the Fe(II-DUA complex (FeCHO+, providing an excellent description of data obtained over a wide range of DUA concentrations and pH conditions. Considering the Marcus theory the Fe(III complexing constant with DUA was limited to between 1013 and 1016. For the seawater enriched with exudates of E. huxleyi a second kinetic modeling approach was carried out for fitting the Fe(II speciation, and the contribution of each Fe(II species to the overall oxidation rate as a function of the pH/pCO2 conditions. The influence of organic ligands in the

Crystal structure of the coordination polymer [FeIII2{PtII(CN4}3

Directory of Open Access Journals (Sweden)

Maksym Seredyuk

2015-01-01

Full Text Available The title complex, poly[dodeca-μ-cyanido-diiron(IIItriplatinum(II], [FeIII2{PtII(CN4}3], has a three-dimensional polymeric structure. It is built-up from square-planar [PtII(CN4]2− anions (point group symmetry 2/m bridging cationic [FeIIIPtII(CN4]+∞ layers extending in the bc plane. The FeII atoms of the layers are located on inversion centres and exhibit an octahedral coordination sphere defined by six N atoms of cyanide ligands, while the PtII atoms are located on twofold rotation axes and are surrounded by four C atoms of the cyanide ligands in a square-planar coordination. The geometrical preferences of the two cations for octahedral and square-planar coordination, respectively, lead to a corrugated organisation of the layers. The distance between neighbouring [FeIIIPtII(CN4]+∞ layers corresponds to the length a/2 = 8.0070 (3 Å, and the separation between two neighbouring PtII atoms of the bridging [PtII(CN4]2− groups corresponds to the length of the c axis [7.5720 (2 Å]. The structure is porous with accessible voids of 390 Å3 per unit cell.

Speciation of Fe(II) and Fe(III) in Contaminated Aquifer Sediments Using Chemical Extraction Techniques

DEFF Research Database (Denmark)

Heron, Gorm; Crouzet, Catherine.; Bourg, Alain C. M.

1994-01-01

The iron mineralogy of aquifer sediments was described by chemical extraction techniques. Single-step extractions including 1 M CaC12, NaAc, oxalate, dithionite, Ti(II1)- EDTA, 0.5 M HC1,5 M HC1, hot 6 M HC1, and a sequential extraction by HI and CrIIHC1 were tested on standard iron minerals...... species are distinguished as AVS (acid volatile sulfide, hot 6 M HC1 extraction) and pyrite (sequential HI and CrIIHC1 extraction). By including a cold 5 M HC1 extraction, the total distribution of the major reactive Fe(I1) and Fe(II1) fractions in aquifer sediments can be assessed....

Synthesis and characterisation of the Fe(II-III) hydroxy-formate green rust

International Nuclear Information System (INIS)

Refait, P.; Abdelmoula, M.; Genin, J.-M. R.; Jeannin, M.

2006-01-01

A new methodology was envisioned in order to prepare green rust compounds build on organic anions that could intervene in microbiologically influenced corrosion processes of iron and steel. The formate ion was chosen as an example. The formation of rust was simulated by the oxidation of aqueous suspensions of Fe(OH) 2 precipitated from Fe(II) lactate and sodium hydroxide, in the presence of sodium formate to promote the formation of the corresponding green rust. The evolution of the precipitate with time was followed by transmission Moessbauer spectroscopy at 15 K. It was observed that the initial hydroxide was transformed into a new GR compound. Its spectrum is composed of three quadrupole doublets, D 1 (δ = 1.28 mm s -1 , Δ = 2.75 mm s -1 ) and D 2 (δ = 1.28 mm s -1 , Δ 2.48 mm s -1 ) that correspond to Fe(II) and D 3 (δ = 0.49 mm s -1 , Δ = 0.37 mm s -1 ) that corresponds to Fe(III). The relative area of D 3 , close to the proportion of Fe(III) in the GR, was found at 28.5 ± 1.5% (∼2/7). Raman spectroscopy confirmed that the intermediate compound was a Fe(II-III) hydroxy-formate, GR(HCOO - ).

Biologically active new Fe(II, Co(II, Ni(II, Cu(II, Zn(II and Cd(II complexes of N-(2-thienylmethylenemethanamine

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C. SPÎNU

2008-04-01

Full Text Available Iron(II, cobalt(II, nickel (II, copper (II, zinc(II and cadmium(II complexes of the type ML2Cl2, where M is a metal and L is the Schiff base N-(2-thienylmethylenemethanamine (TNAM formed by the condensation of 2-thiophenecarboxaldehyde and methylamine, were prepared and characterized by elemental analysis as well as magnetic and spectroscopic measurements. The elemental analyses suggest the stoichiometry to be 1:2 (metal:ligand. Magnetic susceptibility data coupled with electronic, ESR and Mössbauer spectra suggest a distorted octahedral structure for the Fe(II, Co(II and Ni(II complexes, a square-planar geometry for the Cu(II compound and a tetrahedral geometry for the Zn(II and Cd(II complexes. The infrared and NMR spectra of the complexes agree with co-ordination to the central metal atom through nitrogen and sulphur atoms. Conductance measurements suggest the non-electrolytic nature of the complexes, except for the Cu(II, Zn(II and Cd(II complexes, which are 1:2 electrolytes. The Schiff base and its metal chelates were screened for their biological activity against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa and the metal chelates were found to possess better antibacterial activity than that of the uncomplexed Schiff base.

Constraining the role of anoxygenic phototrophic Fe(II)-oxidizing bacteria in deposition of BIFs

Science.gov (United States)

Kappler, A.; Posth, N. R.; Hegler, F.; Wartha, E.; Huelin, S.

2007-12-01

Banded Iron Formations (BIFs) are Precambrian sedimentary deposits of alternating iron oxide and silica mineral layers. Their presence in the rock record ca.3.8-2.2 Ga makes them particularly intriguing formations for the debate over when oxygen became dominant on Earth. The mechanism(s) of BIF deposition is still unclear; suggestions including both abiotic and biotic processes. We are interested in constraining one of these proposed mechanisms; the direct biological oxidation of Fe(II) via anoxygenic Fe(II)-oxidizing autophototrophs. In order to find the limitations of photoferrotrophic BIF deposition, we take a holistic approach, investigating the oxidation of Fe(II) by modern Fe(II)-oxidizing phototrophs, the precipitation of Fe(III) (hydr)oxides, and the fate of the cell-mineral aggregates in the water column and at the basin floor. Specifically, physiology experiments with Fe(II)-oxidizing phototrophs under various conditions of light intensity, pH, Fe(II) concentration and temperature allow us to determine the environmental limits of such organisms. We carry out precipitation experiments to characterize the sedimentation rates, aggregate size and composition in order to resolve the effect of reactions in the water column. Finally, we simulate the diagenetic fate of these aggregates on the basin floor by placing them in gold capsules under T and P conditions relevant for the Transvaal Supergroup BIFs of South Africa. Recently, we have developed a tank simulating the Archean ocean in which the strains grow in continuous culture and collect the aggregates formed under various geochemical conditions. We aim to model the extent of and limitations to photoferrotrophs in BIF deposition. This information will help constrain whether biotic processes were dominant in the Archean ocean and will offer insight to the evolution of the early biogeosphere.

Fe biomineralization mirrors individual metabolic activity in a nitrate-dependent Fe(II-oxidizer

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Jennyfer eMIOT

2015-09-01

Full Text Available Microbial biomineralization sometimes leads to periplasmic encrustation, which is predicted to enhance microorganism preservation in the fossil record. Mineral precipitation within the periplasm is however thought to induce death, as a result of permeability loss preventing nutrient and waste transit across the cell wall. This hypothesis had however never been investigated down to the single cell level. Here, we cultured the nitrate reducing Fe(II oxidizing bacteria Acidovorax sp. strain BoFeN1 that have been previously shown to promote the precipitation of a diversity of Fe minerals (lepidocrocite, goethite, Fe phosphate encrusting the periplasm. We investigated the connection of Fe biomineralization with carbon assimilation at the single cell level, using a combination of electron microscopy and Nano-Secondary Ion Mass Spectrometry (NanoSIMS. Our analyses revealed strong individual heterogeneities of Fe biomineralization. Noteworthy, a small proportion of cells remaining free of any precipitate persisted even at advanced stages of biomineralization. Using pulse chase experiments with 13C-acetate, we provide evidences of individual phenotypic heterogeneities of carbon assimilation, correlated with the level of Fe biomineralization. Whereas non- and moderately encrusted cells were able to assimilate acetate, higher levels of periplasm encrustation prevented any carbon incorporation. Carbon assimilation only depended on the level of Fe encrustation and not on the nature of Fe minerals precipitated in the cell wall. Carbon assimilation decreased exponentially with increasing cell-associated Fe content. Persistence of a small proportion of non-mineralized and metabolically active cells might constitute a strategy of survival in highly ferruginous environments. Eventually, our results suggest that periplasmic Fe biomineralization may provide a signature of individual metabolic status, which could be looked for in the fossil record and in modern

Immobilization of radionuclides and heavy metals through anaerobic bio-oxidation of Fe(II)

International Nuclear Information System (INIS)

Lack, J.G.; Chaudhuri, S.K.; Kelly, S.D.; Kemner, K.M.; O'Connor, S.M.; Coates, J.D.

2002-01-01

Adsorption of heavy metals and radionuclides (HMR) onto iron and manganese oxides has long been recognized as an important reaction for the immobilization of these compounds. However, in environments containing elevated concentrations of these HMR the adsorptive capacity of the iron and manganese oxides may well be exceeded, and the HMR can migrate as soluble compounds in aqueous systems. Here we demonstrate the potential of a bioremediative strategy for HMR stabilization in reducing environments based on the recently described anaerobic nitrate-dependent Fe(II) oxidation by Dechlorosoma species. Bio-oxidation of 10 mM Fe(II) and precipitation of Fe(III) oxides by these organisms resulted in rapid adsorption and removal of 55 μM uranium and 81 μM cobalt from solution. The adsorptive capacity of the biogenic Fe(III) oxides was lower than that of abiotically produced Fe(III) oxides (100 μM for both metals), which may have been a result of steric hindrance by the microbial cells on the iron oxide surfaces. The binding capacity of the biogenic oxides for different heavy metals was indirectly correlated to the atomic radius of the bound element. X-ray absorption spectroscopy indicated that the uranium was bound to the biogenically produced Fe(III) oxides as U(VI) and that the U(VI) formed bidentate and tridentate inner-sphere complexes with the Fe(III) oxide surfaces. Dechlorosoma suillum oxidation was specific for Fe(II), and the organism did not enzymatically oxidize U(IV) or Co(II). Small amounts (less than 2.5 μM) of Cr(III) were reoxidized by D. suillum; however, this appeared to be inversely dependent on the initial concentration of the Cr(III). The results of this study demonstrate the potential of this novel approach for stabilization and immobilization of HMR in the environment.

Sol-gel based optical sensor for determination of Fe (II): a novel probe for iron speciation.

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Samadi-Maybodi, Abdolraouf; Rezaei, Vida; Rastegarzadeh, Saadat

2015-02-05

A highly selective optical sensor for Fe (II) ions was developed based on entrapment of a sensitive reagent, 2,4,6-tri(2-pyridyl)-s-triazine (TPTZ), in a silica sol-gel thin film coated on a glass substrate. The thin films fabricated based on tetraethoxysilane (TEOS) as precursor, sol-gel pH∼3, water:alkoxyde ratio of 4:1 and TPTZ concentration of 0.112 mol L(-1). The influence of sol-gel parameters on sensing behavior of the fabricated sensor was also investigated. The fabricated sensor can be used for determination of Fe (II) ion with an outstanding high selectivity over a dynamic range of 5-115 ng mL(-1) and a detection limit of 1.68 ng mL(-1). It also showed reproducible results with relative standard deviation of 3.5% and 1.27% for 10 and 90 ng mL(-1) of Fe (II), respectively, along with a fast response time of ∼120 s. Total iron also was determined after reduction of Fe (III) to Fe (II) using ascorbic acid as reducing agent. Then, the concentration of Fe (III) was calculated by subtracting the concentration of Fe (II) from the total iron concentration. Interference studies showed a good selectivity for Fe (II) with trapping TPTZ into sol-gel matrix and appropriately adjusting the structure of doped sol-gel. The sensor was compared with other sensors and was applied to determine iron in different water samples with good results. Copyright © 2014 Elsevier B.V. All rights reserved.

Identification of new fluorescence processes in the UV spectra of cool stars from new energy levels of Fe II and Cr II

Science.gov (United States)

Johansson, Sveneric; Carpenter, Kenneth G.

1988-01-01

Two fluorescence processes operating in atmospheres of cool stars, symbiotic stars, and the Sun are presented. Two emission lines, at 1347.03 and 1360.17 A, are identified as fluorescence lines of Cr II and Fe II. The lines are due to transitions from highly excited levels, which are populated radiatively by the hydrogen Lyman alpha line due to accidental wavelength coincidences. Three energy levels, one in Cr II and two in Fe II, are reported.

Study of thermal spin crossover in [Fe(II)(isoxazole)(6)](BF4)(2) with Mossbauer spectroscopy

NARCIS (Netherlands)

Bhattacharjee, A.; van Koningsbruggen, P. J.; Hibbs, W.; Miller, Joel S.; Guetlich, P.

2007-01-01

Fe-57 Mossbauer spectroscopy of the mononuclear [Fe( II)( isoxazole)(6)]( BF4)(2) compound has been studied to reveal the thermal spin crossover of Fe( II) between low- spin ( S = 0) and high- spin ( S = 2) states. A temperature-dependent spin transition curve has been constructed with the least-

Formation of iron (hydr)oxides during the abiotic oxidation of Fe(II) in the presence of arsenate.

Science.gov (United States)

Song, Jia; Jia, Shao-Yi; Yu, Bo; Wu, Song-Hai; Han, Xu

2015-08-30

Abiotic oxidation of Fe(II) is a common pathway in the formation of Fe (hydr)oxides under natural conditions, however, little is known regarding the presence of arsenate on this process. In hence, the effect of arsenate on the precipitation of Fe (hydr)oxides during the oxidation of Fe(II) is investigated. Formation of arsenic-containing Fe (hydr)oxides is constrained by pH and molar ratios of As:Fe during the oxidation Fe(II). At pH 6.0, arsenate inhibits the formation of lepidocrocite and goethite, while favors the formation of ferric arsenate with the increasing As:Fe ratio. At pH 7.0, arsenate promotes the formation of hollow-structured Fe (hydr)oxides containing arsenate, as the As:Fe ratio reaches 0.07. Arsenate effectively inhibits the formation of magnetite at pH 8.0 even at As:Fe ratio of 0.01, while favors the formation of lepidocrocite and green rust, which can be latterly degenerated and replaced by ferric arsenate with the increasing As:Fe ratio. This study indicates that arsenate and low pH value favor the slow growth of dense-structured Fe (hydr)oxides like spherical ferric arsenate. With the rapid oxidation rate of Fe(II) at high pH, ferric (hydr)oxides prefer to precipitate in the formation of loose-structured Fe (hydr)oxides like lepidocrocite and green rust. Copyright © 2015 Elsevier B.V. All rights reserved.

Low-temperature, non-stoichiometric oxygen isotope exchange coupled to Fe(II)-goethite interactions

Energy Technology Data Exchange (ETDEWEB)

Frierdich, Andrew J. [Univ. of Wisconsin, Madison, WI (United States); Univ. of Iowa, Iowa City, IA (United States); Beard, Brian L. [Univ. of Wisconsin, Madison, WI (United States); Rosso, Kevin M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Scherer, Michelle M. [Univ. of Iowa, Iowa City, IA (United States); Spicuzza, Michael J. [Univ. of Wisconsin, Madison, WI (United States); Valley, John W. [Univ. of Wisconsin, Madison, WI (United States); Johnson, Clark M. [Univ. of Wisconsin, Madison, WI (United States)

2015-07-01

The oxygen isotope composition of natural iron oxide minerals has been widely used as a paleoclimate proxy. Interpretation of their stable isotope compositions, however, requires accurate knowledge of isotopic fractionation factors and an understanding of their isotopic exchange kinetics, the latter of which informs us how diagenetic processes may alter their isotopic compositions. Prior work has demonstrated that crystalline iron oxides do not significantly exchange oxygen isotopes with pure water at low temperature, which has restricted studies of isotopic fractionation factors to precipitation experiments or theoretical calculations. Using a double three-isotope method (¹⁸O-¹⁷O-¹⁶O and ⁵⁷Fe-⁵⁶Fe-⁵⁴Fe) we compare O and Fe isotope exchange kinetics, and demonstrate, for the first time, that O isotope exchange between structural O in crystalline goethite and water occurs in the presence of aqueous Fe(II) (Fe(II)_aq) at ambient temperature (i.e., 22–50 °C). The three-isotope method was used to extrapolate partial exchange results to infer the equilibrium, mass-dependent isotope fractionations between goethite and water. In addition, this was combined with a reversal approach to equilibrium by reacting goethite in two unique waters that vary in composition by about 16‰ in ¹⁸O/¹⁶O ratios. Our results show that interactions between Fe(II)_aq and goethite catalyzes O isotope exchange between the mineral and bulk fluid; no exchange (within error) is observed when goethite is suspended in ¹⁷O-enriched water in the absence of Fe(II)_aq. In contrast, Fe(II)-catalyzed O isotope exchange is accompanied by significant changes in ¹⁸O/¹⁶O ratios. Despite significant O exchange, however, we observed disproportionate amounts of Fe versus O exchange, where Fe isotope exchange in goethite was roughly three times that of O. This disparity provides novel insight into the reactivity of oxide minerals in aqueous

Mtr Extracellular Electron Transfer Pathways in Fe(III)-reducing or Fe(II)-oxidizing Bacteria: A Genomic Perspective

Energy Technology Data Exchange (ETDEWEB)

Shi, Liang; Rosso, Kevin M.; Zachara, John M.; Fredrickson, Jim K.

2012-12-01

Originally discovered in the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1 (MR-1), the Mtr (i.e., metal-reducing) pathway exists in all characterized strains of metal-reducing Shewanella. The protein components identified to date for the Mtr pathway of MR-1 include four multi-heme c-type cytochromes (c-Cyts), CymA, MtrA, MtrC and OmcA, and a porin-like, outer membrane protein MtrB. They are strategically positioned along the width of the MR-1 cell envelope to mediate electron transfer from the quinone/quinol pool in the inner-membrane to the Fe(III)-containing minerals external to the bacterial cells. A survey of microbial genomes revealed homologues of the Mtr pathway in other dissimilatory Fe(III)-reducing bacteria, including Aeromonas hydrophila, Ferrimonas balearica and Rhodoferax ferrireducens, and in the Fe(II)-oxidizing bacteria Dechloromonas aromatica RCB, Gallionella capsiferriformans ES-2 and Sideroxydans lithotrophicus ES-1. The widespread distribution of Mtr pathways in Fe(III)-reducing or Fe(II)-oxidizing bacteria emphasizes the importance of this type of extracellular electron transfer pathway in microbial redox transformation of Fe. Their distribution in these two different functional groups of bacteria also emphasizes the bi-directional nature of electron transfer reactions carried out by the Mtr pathways. The characteristics of the Mtr pathways may be shared by other pathways used by microorganisms for exchanging electrons with their extracellular environments.

Reactive Transport Modeling of Microbe-mediated Fe (II) Oxidation for Enhanced Oil Recovery

Science.gov (United States)

Surasani, V.; Li, L.

2011-12-01

Microbially Enhanced Oil Recovery (MEOR) aims to improve the recovery of entrapped heavy oil in depleted reservoirs using microbe-based technology. Reservoir ecosystems often contain diverse microbial communities those can interact with subsurface fluids and minerals through a network of nutrients and energy fluxes. Microbe-mediated reactions products include gases, biosurfactants, biopolymers those can alter the properties of oil and interfacial interactions between oil, brine, and rocks. In addition, the produced biomass and mineral precipitates can change the reservoir permeability profile and increase sweeping efficiency. Under subsurface conditions, the injection of nitrate and Fe (II) as the electron acceptor and donor allows bacteria to grow. The reaction products include minerals such as Fe(OH)3 and nitrogen containing gases. These reaction products can have large impact on oil and reservoir properties and can enhance the recovery of trapped oil. This work aims to understand the Fe(II) oxidation by nitrate under conditions relevant to MEOR. Reactive transport modeling is used to simulate the fluid flow, transport, and reactions involved in this process. Here we developed a complex reactive network for microbial mediated nitrate-dependent Fe (II) oxidation that involves both thermodynamic controlled aqueous reactions and kinetic controlled Fe (II) mineral reaction. Reactive transport modeling is used to understand and quantify the coupling between flow, transport, and reaction processes. Our results identify key parameter controls those are important for the alteration of permeability profile under field conditions.

The Physiological Functions and Structural Determinants of Catalytic Bias in the [FeFe]-Hydrogenases CpI and CpII of Clostridium pasteurianum Strain W5

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Jesse B. Therien

2017-07-01

Full Text Available The first generation of biochemical studies of complex, iron-sulfur-cluster-containing [FeFe]-hydrogenases and Mo-nitrogenase were carried out on enzymes purified from Clostridium pasteurianum (strain W5. Previous studies suggested that two distinct [FeFe]-hydrogenases are expressed differentially under nitrogen-fixing and non-nitrogen-fixing conditions. As a result, the first characterized [FeFe]-hydrogenase (CpI is presumed to have a primary role in central metabolism, recycling reduced electron carriers that accumulate during fermentation via proton reduction. A role for capturing reducing equivalents released as hydrogen during nitrogen fixation has been proposed for the second hydrogenase, CpII. Biochemical characterization of CpI and CpII indicated CpI has extremely high hydrogen production activity in comparison to CpII, while CpII has elevated hydrogen oxidation activity in comparison to CpI when assayed under the same conditions. This suggests that these enzymes have evolved a catalytic bias to support their respective physiological functions. Using the published genome of C. pasteurianum (strain W5 hydrogenase sequences were identified, including the already known [NiFe]-hydrogenase, CpI, and CpII sequences, and a third hydrogenase, CpIII was identified in the genome as well. Quantitative real-time PCR experiments were performed in order to analyze transcript abundance of the hydrogenases under diazotrophic and non-diazotrophic growth conditions. There is a markedly reduced level of CpI gene expression together with concomitant increases in CpII gene expression under nitrogen-fixing conditions. Structure-based analyses of the CpI and CpII sequences reveal variations in their catalytic sites that may contribute to their alternative physiological roles. This work demonstrates that the physiological roles of CpI and CpII are to evolve and to consume hydrogen, respectively, in concurrence with their catalytic activities in vitro, with CpII

The Physiological Functions and Structural Determinants of Catalytic Bias in the [FeFe]-Hydrogenases CpI and CpII of Clostridium pasteurianum Strain W5

Science.gov (United States)

Therien, Jesse B.; Artz, Jacob H.; Poudel, Saroj; Hamilton, Trinity L.; Liu, Zhenfeng; Noone, Seth M.; Adams, Michael W. W.; King, Paul W.; Bryant, Donald A.; Boyd, Eric S.; Peters, John W.

2017-01-01

The first generation of biochemical studies of complex, iron-sulfur-cluster-containing [FeFe]-hydrogenases and Mo-nitrogenase were carried out on enzymes purified from Clostridium pasteurianum (strain W5). Previous studies suggested that two distinct [FeFe]-hydrogenases are expressed differentially under nitrogen-fixing and non-nitrogen-fixing conditions. As a result, the first characterized [FeFe]-hydrogenase (CpI) is presumed to have a primary role in central metabolism, recycling reduced electron carriers that accumulate during fermentation via proton reduction. A role for capturing reducing equivalents released as hydrogen during nitrogen fixation has been proposed for the second hydrogenase, CpII. Biochemical characterization of CpI and CpII indicated CpI has extremely high hydrogen production activity in comparison to CpII, while CpII has elevated hydrogen oxidation activity in comparison to CpI when assayed under the same conditions. This suggests that these enzymes have evolved a catalytic bias to support their respective physiological functions. Using the published genome of C. pasteurianum (strain W5) hydrogenase sequences were identified, including the already known [NiFe]-hydrogenase, CpI, and CpII sequences, and a third hydrogenase, CpIII was identified in the genome as well. Quantitative real-time PCR experiments were performed in order to analyze transcript abundance of the hydrogenases under diazotrophic and non-diazotrophic growth conditions. There is a markedly reduced level of CpI gene expression together with concomitant increases in CpII gene expression under nitrogen-fixing conditions. Structure-based analyses of the CpI and CpII sequences reveal variations in their catalytic sites that may contribute to their alternative physiological roles. This work demonstrates that the physiological roles of CpI and CpII are to evolve and to consume hydrogen, respectively, in concurrence with their catalytic activities in vitro, with CpII capturing excess

Fe(II-III) Hydroxysalt Green Rusts; from Corrosion to Mineralogy and Abiotic to Biotic Reactions by Moessbauer Spectroscopy

International Nuclear Information System (INIS)

Genin, J.-M. R.

2004-01-01

Fe(II)-Fe(III) hydroxysalts commonly called green rusts are layered double hydroxides of formula [Fe II (1-x) Fe III x (OH) 2 ] x+ .[(x/n)A n- .(m/n)H 2 O] x- constituted of brucite-like layers containing Fe cations in the centres of OH - octahedrons and interlayers, which anions and water molecules belong to. They play a key role in corrosion and environmental sciences as well as mineralogy since they are, on the one hand, intermediate products between Fe(II) and Fe(III) states and, on the other hand, can be the major iron-bearing mineral in hydromorphic gley soils. Their crystal structure, Moessbauer spectra, methods of synthesis, abiotic as well as biotic, and some applications are presented here.

The topotactic reduction of Sr3Fe2O5Cl2-square planar Fe(II) in an extended oxyhalide.

Science.gov (United States)

Dixon, Edward; Hayward, Michael A

2010-10-18

The topotactic reduction of the oxychloride Sr(3)Fe(2)O(5)Cl(2) with LiH results in the formation of Sr(3)Fe(2)O(4)Cl(2). Neutron powder diffraction data show that Sr(3)Fe(2)O(4)Cl(2) adopts a body-centered tetragonal crystal structure (I4/mmm, a = 4.008(1) Å, c = 22.653(1) Å at 388 K) with anion vacancies located within the SrO layer of the phase. This leads to a structure consisting of infinite sheets of corner-sharing Fe(II)O(4) square planes. Variable-temperature neutron diffraction data show that Sr(3)Fe(2)O(4)Cl(2) adopts G-type antiferromagnetic order below T(N) ∼ 378(10) K with an ordered moment of 2.81(9) μ(B) per iron center at 5 K consistent with the presence of high-spin Fe(II). The observed structural and chemical selectivity of the reduction reaction is discussed. The contrast between the structure of Sr(3)Fe(2)O(4)Cl(2) and the isoelectronic all-oxide analogue (Sr(3)Fe(2)O(5)) suggests that by careful selection of substrate phases, the topotactic reduction of complex transition metal oxychlorides can lead to the preparation of novel anion-deficient phases with unique transition metal-oxygen sublattices which cannot be prepared via the reduction of all-oxide substrates.

Emissions of Fe(II) and its kinetic of oxidation at Tagoro submarine volcano, El Hierro (Canary Islands)

Science.gov (United States)

González-Dávila, M.; Santana-González, C.; Santana-Casiano, J. M.

2017-12-01

The eruptive process that took place in October 2011 in the submarine volcano Tagoro off the Island of El Hierro (Canary Island) and the subsequent degasification stage, five months later, have increased the concentration of TdFe(II) (Total dissolved iron(II)) in the waters nearest to the volcanic edifice. In order to detect any variation in concentrations of TdFe(II) due to hydrothermal emissions, three cruises were carried out two years after the eruptive process in October 2013, March 2014, May 2015, March 2016 and November 2016. The results from these cruises confirmed important positive anomalies in TdFe(II), which coincided with negatives anomalies in pHF,is (pH in free scale, at in situ conditions) located in the proximity of the main cone. Maximum values in TdFe(II) both at the surface, associated to chlorophyll a maximum, and at the sea bottom, were also observed, showing the important influence of organic complexation and particle re-suspension processes. Temporal variability studies were carried out over periods ranging from hours to days in the stations located over the main and two secondary cones in the volcanic edifice with positive anomalies in TdFe(II) concentrations and negative anomalies in pHF,is values. Observations showed an important variability in both pHF,is and TdFe(II) concentrations, which indicated the volcanic area was affected by a degasification process that remained in the volcano after the eruptive phase had ceased. Fe(II) oxidation kinetic studies were also undertaken in order to analyze the effects of the seawater properties in the proximities of the volcano on the oxidation rate constants and t1/2 (half-life time) of ferrous iron. The increased TdFe(II) concentrations and the low associated pHF,is values acted as an important fertilization event in the seawater around the Tagoro volcano at the Island of El Hierro providing optimal conditions for the regeneration of the area.

Reduction and long-term immobilization of technetium by Fe(II) associated with clay mineral nontronite

International Nuclear Information System (INIS)

Jaisi, Deb P.; Dong, Hailiang; Plymale, Andrew E.; Fredrickson, Jim K.; Zachara, John M.; Heald, S.; Liu, Chongxuan

2009-01-01

99Tc is formed mostly during nuclear reactions and is released into the environment during weapons testing and inadvertent waste disposal. The long half-life, high environmental mobility (as Tc(VII)O4-) and its possible uptake into the food chain cause 99Tc to be a significant environmental contaminant. In this study, we evaluated the role of Fe(II) in biologically reduced clay mineral, nontronite (NAu-2), in reducing Tc(VII)O4- to poorly soluble Tc(IV) species as a function of pH and Fe(II) concentration. The rate of Tc(VII) reduction by Fe(II) in NAu-2 was higher at neutral pH (pH 7.0) than at acidic and basic pHs when Fe(II) concentration was low (< 1 mmol/g). The effect of pH, however, was insignificant at higher Fe(II) concentrations. The reduction of Tc(VII) by Fe(II) associated with NAu-2 was also studied in the presence of common subsurface oxidants including iron and manganese oxides, nitrate, and oxygen, to evaluate the effect of the oxidants on the enhancement and inhibition of Tc(VII) reduction, and reoxidation of Tc(IV). Addition of iron oxides (goethite and hematite) to the Tc(VII)-NAu-2 system, where Tc(VII) reduction was ongoing, enhanced reduction of Tc(VII), apparently as a result of re-distribution of reactive Fe(II) from NAu-2 to more reactive goethite/hematite surfaces. Addition of manganese oxides stopped further Tc(VII) reduction, and in case of K+-birnessite, it reoxidized previously reduced Tc(IV). Nitrate neither enhanced reduction of Tc(VII) nor promoted reoxidation of Tc(IV). Approximately 11% of Tc(IV) was oxidized by oxygen. The rate and extent of Tc(IV) reoxidation was found to strongly depend on the nature of the oxidants and concentration of Fe(II). When the same oxidants were added to aged Tc reduction products (mainly NAu-2 and TcO2nH2O), the extent of Tc(IV) reoxidation decreased significantly relative to fresh Tc(IV) products. Increasing NAu-2 concentration also resulted in the decreased extent of Tc(IV) reoxidation. The results

Laser direct-write and crystallization of FeSi II micro-dot array for NIR light-emitting device application

Science.gov (United States)

Narazaki, Aiko; Kurosaki, Ryozo; Sato, Tadatake; Kawaguchi, Yoshizo; Niino, Hiroyuki

2007-02-01

We printed FeSi II micro-dot array on various kinds of substrates utilizing laser-induced forward transfer (LIFT). An amorphous FeSi II was deposited by sputtering on a transparent plate as a source film. A single KrF excimer laser pulse through a mask-projection system was imaged with a small micrometer-sized grid pattern onto a film/plate interface, resulting in the deposition of FeSi II micro-dot array on a facing substrate with a high number density of 10 4 mm -2. FeSi II in the β crystalline phase is a promising eco-friendly semiconductor because of NIR electroluminescence used for optical networking as well as abundant components reserve on the earth and non-toxicity. However, the β-FeSi II film fabrication generally required high-temperature multi-processes which hamper its integration and performance reproducibility. Using the LIFT of micro-dot array, we succeeded in room-temperature preparation of β-FeSi II. Micro-Raman spectroscopy confirmed the β crystalline phase in the micro-dots deposited on an unheated silica glass substrate. Thus, the LIFT is useful for integrating functional micro-dot array accompanied by the crystallization at lower temperatures.

Effectively simultaneous naked-eye detection of Cu(II), Pb(II), Al(III) and Fe(III) using cyanidin extracted from red cabbage as chelating agent

Science.gov (United States)

Khaodee, Warangkhana; Aeungmaitrepirom, Wanlapa; Tuntulani, Thawatchai

Simultaneous determination of Cu(II), Pb(II), Al(III) and Fe(III) using cyanidin as a chelating agent was investigated in terms of both quantitative and qualitative detections. Cyanidin was extracted and purified from red cabbage which is a local plant in Thailand. The selectivity of this method was examined by regulating the pH of cyanidin solution operated together with masking agents. It was found that Cu(II), Pb(II), Al(III) and Fe(III) simultaneously responded with the color change at pH 7, pH 6, pH 5 and pH 4, respectively. KF, DMG and the mixture of KF and DMG were used as masking agents for the determination of Fe(III), Al(III) and Pb(II), respectively. Results from naked-eye detection were evaluated by comparing with those of inductively coupled plasma (ICP), and there was no significant difference noticed. Cyanidin using as a multianalyte reagent could be employed for simultaneous determination of Cu(II), Pb(II), Al(III) and Fe(III) at the lowest concentration at 50, 80, 50 and 200 μM, respectively, by slightly varying pHs. Moreover, the proposed method could be potentially applied for real water samples with simplicity, rapidity, low cost and environmental safety.

Anoxic and Oxic Oxidation of Rocks Containing Fe(II)Mg-Silicates and Fe(II)-Monosulfides as Source of Fe(III)-Minerals and Hydrogen. Geobiotropy.

Science.gov (United States)

Bassez, Marie-Paule

2017-12-01

In this article, anoxic and oxic hydrolyses of rocks containing Fe (II) Mg-silicates and Fe (II)-monosulfides are analyzed at 25 °C and 250-350 °C. A table of the products is drawn. It is shown that magnetite and hydrogen can be produced during low-temperature (25 °C) anoxic hydrolysis/oxidation of ferrous silicates and during high-temperature (250 °C) anoxic hydrolysis/oxidation of ferrous monosulfides. The high-T (350 °C) anoxic hydrolysis of ferrous silicates leads mainly to ferric oxides/hydroxides such as the hydroxide ferric trihydroxide, the oxide hydroxide goethite/lepidocrocite and the oxide hematite, and to Fe(III)-phyllosilicates. Magnetite is not a primary product. While the low-T (25 °C) anoxic hydrolysis of ferrous monosulfides leads to pyrite. Thermodynamic functions are calculated for elementary reactions of hydrolysis and carbonation of olivine and pyroxene and E-pH diagrams are analyzed. It is shown that the hydrolysis of the iron endmember is endothermic and can proceed within the exothermic hydrolysis of the magnesium endmember and also within the exothermic reactions of carbonations. The distinction between three products of the iron hydrolysis, magnetite, goethite and hematite is determined with E-pH diagrams. The hydrolysis/oxidation of the sulfides mackinawite/troilite/pyrrhotite is highly endothermic but can proceed within the heat produced by the exothermic hydrolyses and carbonations of ferromagnesian silicates and also by other sources such as magma, hydrothermal sources, impacts. These theoretical results are confirmed by the products observed in several related laboratory experiments. The case of radiolyzed water is studied. It is shown that magnetite and ferric oxides/hydroxides such as ferric trihydroxide, goethite/lepidocrocite and hematite are formed in oxic hydrolysis of ferromagnesian silicates at 25 °C and 350 °C. Oxic oxidation of ferrous monosulfides at 25 °C leads mainly to pyrite and ferric oxides/hydroxides such as

Variability of Fe II Emission Features in the Seyfert 1 Galaxy NGC 5548

DEFF Research Database (Denmark)

Vestergaard, Marianne; Peterson, B. M.

2005-01-01

We study the low-contrast Fe II emission blends in the ultraviolet (1250--2200A) and optical (4000--6000A) spectra of the Seyfert 1 galaxy NGC 5548 and show that these features vary in flux and that these variations are correlated with those of the optical continuum. The amplitude of variability ...... are correlated indicates that line fluorescence in a photoionized plasma, rather than collisional excitation, is responsible for the Fe II emission. The iron emission templates are available upon request....

Importance of reduced sulfur for the equilibrium chemistry and kinetics of Fe(II), Co(II) and Ni(II) supplemented to semi-continuous stirred tank biogas reactors fed with stillage

Energy Technology Data Exchange (ETDEWEB)

Shakeri Yekta, Sepehr, E-mail: sepehr.shakeri.yekta@liu.se [Department of Thematic Studies – Water and Environmental Studies, Linköping University, SE-581 83 Linköping (Sweden); Lindmark, Amanda [Department of Thematic Studies – Water and Environmental Studies, Linköping University, SE-581 83 Linköping (Sweden); Skyllberg, Ulf [Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå (Sweden); Danielsson, Åsa; Svensson, Bo H. [Department of Thematic Studies – Water and Environmental Studies, Linköping University, SE-581 83 Linköping (Sweden)

2014-03-01

Highlights: • Thermodynamics and kinetics of Fe, Co and Ni added to biogas reactors were studied. • Formation of Fe-sulfide and Fe-thiol aqueous complexes controlled the Fe solubility. • Cobalt solubility was controlled by processes independent of Co-sulfide interaction. • Iron added to the biogas reactors effected the Ni speciation and solubility. - Abstract: The objective of the present study was to assess major chemical reactions and chemical forms contributing to solubility and speciation of Fe(II), Co(II), and Ni(II) during anaerobic digestion of sulfur (S)-rich stillage in semi-continuous stirred tank biogas reactors (SCSTR). These metals are essential supplements for efficient and stable performance of stillage-fed SCSTR. In particular, the influence of reduced inorganic and organic S species on kinetics and thermodynamics of the metals and their partitioning between aqueous and solid phases were investigated. Solid phase S speciation was determined by use of S K-edge X-ray absorption near-edge spectroscopy. Results demonstrated that the solubility and speciation of supplemented Fe were controlled by precipitation of FeS(s) and formation of the aqueous complexes of Fe-sulfide and Fe-thiol. The relatively high solubility of Co (∼20% of total Co content) was attributed to the formation of compounds other than Co-sulfide and Co-thiol, presumably of microbial origin. Nickel had lower solubility than Co and its speciation was regulated by interactions with FeS(s) (e.g. co-precipitation, adsorption, and ion substitution) in addition to precipitation/dissolution of discrete NiS(s) phase and formation of aqueous Ni-sulfide complexes.

Importance of reduced sulfur for the equilibrium chemistry and kinetics of Fe(II), Co(II) and Ni(II) supplemented to semi-continuous stirred tank biogas reactors fed with stillage

International Nuclear Information System (INIS)

Shakeri Yekta, Sepehr; Lindmark, Amanda; Skyllberg, Ulf; Danielsson, Åsa; Svensson, Bo H.

2014-01-01

Highlights: • Thermodynamics and kinetics of Fe, Co and Ni added to biogas reactors were studied. • Formation of Fe-sulfide and Fe-thiol aqueous complexes controlled the Fe solubility. • Cobalt solubility was controlled by processes independent of Co-sulfide interaction. • Iron added to the biogas reactors effected the Ni speciation and solubility. - Abstract: The objective of the present study was to assess major chemical reactions and chemical forms contributing to solubility and speciation of Fe(II), Co(II), and Ni(II) during anaerobic digestion of sulfur (S)-rich stillage in semi-continuous stirred tank biogas reactors (SCSTR). These metals are essential supplements for efficient and stable performance of stillage-fed SCSTR. In particular, the influence of reduced inorganic and organic S species on kinetics and thermodynamics of the metals and their partitioning between aqueous and solid phases were investigated. Solid phase S speciation was determined by use of S K-edge X-ray absorption near-edge spectroscopy. Results demonstrated that the solubility and speciation of supplemented Fe were controlled by precipitation of FeS(s) and formation of the aqueous complexes of Fe-sulfide and Fe-thiol. The relatively high solubility of Co (∼20% of total Co content) was attributed to the formation of compounds other than Co-sulfide and Co-thiol, presumably of microbial origin. Nickel had lower solubility than Co and its speciation was regulated by interactions with FeS(s) (e.g. co-precipitation, adsorption, and ion substitution) in addition to precipitation/dissolution of discrete NiS(s) phase and formation of aqueous Ni-sulfide complexes

Analysis of dechlorination kinetics of chlorinated aliphatic hydrocarbons by Fe(II) in cement slurries

Energy Technology Data Exchange (ETDEWEB)

Jung, Bahngmi [Department of Earth and Environmental Sciences, Wright State University, Dayton, OH 45435-0001 (United States)], E-mail: jung.bahngmi@gmail.com; Batchelor, Bill [Department of Civil Engineering, Texas A and M University, College Station, TX 77843-3136 (United States)

2008-03-21

Degradative solidification/stabilization with ferrous iron (DS/S-Fe(II)) has been found to be effective in degrading a number of chlorinated aliphatic hydrocarbons including 1,1,1-trichloroethane (1,1,1-TCA), 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA), tetrachloroethylene (PCE), trichloroethylene (TCE), 1,1-dichloroethylene (1,1-DCE), vinyl chloride (VC), carbon tetrachloride (CT) and chloroform (CF). Previous studies have characterized degradation kinetics in DS/S-Fe(II) systems as affected by Fe(II) dose, pH and initial target organic concentration. The goal of this study is to investigate the importance of various chemical properties on degradation kinetics of DS/S-Fe(II). This was accomplished by first measuring rate constants for degradation of 1,1,1-TCA, 1,1,2,2-TeCA and 1,2-dichloroethane (1,2-DCA) in individual batch experiments. Rate constants developed in these experiments and those obtained from the literature were related to thermodynamic parameters including one-electron reduction potential, two-electron reduction potential, bond dissociation energy and lowest unoccupied molecular orbital energies. Degradation kinetics by Fe(II) in cement slurries were generally represented by a pseudo-first-order rate law. The results showed that the rate constants for chlorinated methanes (e.g. CT, CF) and chlorinated ethanes (e.g. 1,1,1-TCA) were higher than those for chlorinated ethylenes (e.g. PCE, TCE, 1,1-DCE and VC) under similar experimental conditions. The log of the pseudo-first-order rate constant (k) was found to correlate better with lowest unoccupied molecular orbital energies (E{sub LUMO}) (R{sup 2} = 0.874) than with other thermodynamic parameter descriptors.

Transformation impacts of dissolved and solid phase Fe(II) on trichloroethylene (TCE) reduction in an iron-reducing bacteria (IRB) mixed column system: a mathematical model.

Science.gov (United States)

Bae, Yeunook; Kim, Dooil; Cho, Hyun-Hee; Singhal, Naresh; Park, Jae-Woo

2012-12-01

In this research, we conducted trichloroethylene (TCE) reduction in a column filled with iron and iron-reducing bacteria (IRB) and developed a mathematical model to investigate the critical reactions between active species in iron/IRB/contaminant systems. The formation of ferrous iron (Fe(II)) in this system with IRB and zero-valent iron (ZVI, Fe(0)) coated with a ferric iron (Fe(III)) crust significantly affected TCE reduction and IRB respiration in various ways. This study presents a new framework for transformation property and reducing ability of both dissolved (Fe(II)(dissolved)) and solid form ferrous iron (Fe(II)(solid)). Results showed that TCE reduction was strongly depressed by Fe(II)(solid) rather than by other inhibitors (e.g., Fe(III) and lactate), suggesting that Fe(II)(solid) might reduce IRB activation due to attachment to IRB cells. Newly exposed Fe(0) from the released Fe(II)(dissolved) was a strong contributor to TCE reduction compared to Fe(II)(solid). In addition, our research confirmed that less Fe(II)(solid) production strongly supported long-term TCE reduction because it may create an easier TCE approach to Fe(0) or increase IRB growth. Our findings will aid the understanding of the contributions of iron media (e.g., Fe(II)(solid), Fe(II)(dissolved), Fe(III), and Fe(0)) to IRB for decontamination in natural groundwater systems. Copyright © 2012 Elsevier Ltd. All rights reserved.

Nickel incorporation in Fe(II, III hydroxysulfate Green Rust: effect on crystal lattice spacing and oxidation products Incorporação de níquel em Fe (II-III Grenn Rust hidroxisulfato: efeito sobre a estrutura cristalina e produtos de oxidação

Directory of Open Access Journals (Sweden)

Lucia Helena Garófalo Chaves

2009-10-01

Full Text Available Ni(II-Fe(II-Fe(III layered double hydroxides (LDH or Ni-containing sulfate green rust (GR2 samples were prepared from Ni(II, Fe(II and Fe(III sulfate salts and analyzed with X ray diffraction. Nickel is readily incorporated in the GR2 structure and forms a solid solution between GR2 and a Ni(II-Fe(III LDH. There is a correlation between the unit cell a-value and the fraction of Ni(II incorporated into the Ni(II-GR2 structure. Since there is strong evidence that the divalent/trivalent cation ratio in GR2 is fixed at 2, it is possible in principle to determine the extent of divalent cation substitution for Fe(II in GR2 from the unit cell a-value. Oxidation forms a mixture of minerals but the LDH structure is retained if at least 20 % of the divalent cations in the initial solution are Ni(II. It appears that Ni(II is incorporated in a stable LDH structure. This may be important for two reasons, first for understanding the formation of LDHs, which are anion exchangers, in the natural environment. Secondly, this is important for understanding the fate of transition metals in the environment, particularly in the presence of reduced Fe compounds.Amostras de hidróxidos de dupla camada (HDC, ou "sulfate green rust" (GR2, contendo Ni foram preparadas utilizando-se sulfatos de Ni(II, Fe(II e Fe(III e analisadas por difração de raios X. O Ni está incorporado na estrutura do GR2 e forma um sólido entre GR2 e um HDC contendo Ni(II-Fe(III. Há correlação entre os valores de "a" da célula unitária e os da fração de Ni(II incorporado na estrutura do Ni(II-GR2. Desde que haja forte evidência de que a razão entre os cátions divalente/trivalente no GR2 seja igual a 2, é possível, a princípio, determinar a extensão da substituição do cátion divalente por Fe(II no GR2 a partir dos valores de "a" da célula unitária do cristal. Sob o efeito da oxidação, é formada uma mistura de minerais, porém a estrutura do HDC não é alterada se pelo menos

Insights into Nitrate-Reducing Fe(II) Oxidation Mechanisms through Analysis of Cell-Mineral Associations, Cell Encrustation, and Mineralogy in the Chemolithoautotrophic Enrichment Culture KS.

Science.gov (United States)

Nordhoff, M; Tominski, C; Halama, M; Byrne, J M; Obst, M; Kleindienst, S; Behrens, S; Kappler, A

2017-07-01

Most described nitrate-reducing Fe(II)-oxidizing bacteria (NRFeOB) are mixotrophic and depend on organic cosubstrates for growth. Encrustation of cells in Fe(III) minerals has been observed for mixotrophic NRFeOB but not for autotrophic phototrophic and microaerophilic Fe(II) oxidizers. So far, little is known about cell-mineral associations in the few existing autotrophic NRFeOB. Here, we investigate whether the designated autotrophic Fe(II)-oxidizing strain (closely related to Gallionella and Sideroxydans ) or the heterotrophic nitrate reducers that are present in the autotrophic nitrate-reducing Fe(II)-oxidizing enrichment culture KS form mineral crusts during Fe(II) oxidation under autotrophic and mixotrophic conditions. In the mixed culture, we found no significant encrustation of any of the cells both during autotrophic oxidation of 8 to 10 mM Fe(II) coupled to nitrate reduction and during cultivation under mixotrophic conditions with 8 to 10 mM Fe(II), 5 mM acetate, and 4 mM nitrate, where higher numbers of heterotrophic nitrate reducers were present. Two pure cultures of heterotrophic nitrate reducers ( Nocardioides and Rhodanobacter ) isolated from culture KS were analyzed under mixotrophic growth conditions. We found green rust formation, no cell encrustation, and only a few mineral particles on some cell surfaces with 5 mM Fe(II) and some encrustation with 10 mM Fe(II). Our findings suggest that enzymatic, autotrophic Fe(II) oxidation coupled to nitrate reduction forms poorly crystalline Fe(III) oxyhydroxides and proceeds without cellular encrustation while indirect Fe(II) oxidation via heterotrophic nitrate-reduction-derived nitrite can lead to green rust as an intermediate mineral and significant cell encrustation. The extent of encrustation caused by indirect Fe(II) oxidation by reactive nitrogen species depends on Fe(II) concentrations and is probably negligible under environmental conditions in most habitats. IMPORTANCE Most described nitrate

Insights into Nitrate-Reducing Fe(II) Oxidation Mechanisms through Analysis of Cell-Mineral Associations, Cell Encrustation, and Mineralogy in the Chemolithoautotrophic Enrichment Culture KS

Science.gov (United States)

Nordhoff, M.; Tominski, C.; Halama, M.; Byrne, J. M.; Obst, M.; Behrens, S.

2017-01-01

ABSTRACT Most described nitrate-reducing Fe(II)-oxidizing bacteria (NRFeOB) are mixotrophic and depend on organic cosubstrates for growth. Encrustation of cells in Fe(III) minerals has been observed for mixotrophic NRFeOB but not for autotrophic phototrophic and microaerophilic Fe(II) oxidizers. So far, little is known about cell-mineral associations in the few existing autotrophic NRFeOB. Here, we investigate whether the designated autotrophic Fe(II)-oxidizing strain (closely related to Gallionella and Sideroxydans) or the heterotrophic nitrate reducers that are present in the autotrophic nitrate-reducing Fe(II)-oxidizing enrichment culture KS form mineral crusts during Fe(II) oxidation under autotrophic and mixotrophic conditions. In the mixed culture, we found no significant encrustation of any of the cells both during autotrophic oxidation of 8 to 10 mM Fe(II) coupled to nitrate reduction and during cultivation under mixotrophic conditions with 8 to 10 mM Fe(II), 5 mM acetate, and 4 mM nitrate, where higher numbers of heterotrophic nitrate reducers were present. Two pure cultures of heterotrophic nitrate reducers (Nocardioides and Rhodanobacter) isolated from culture KS were analyzed under mixotrophic growth conditions. We found green rust formation, no cell encrustation, and only a few mineral particles on some cell surfaces with 5 mM Fe(II) and some encrustation with 10 mM Fe(II). Our findings suggest that enzymatic, autotrophic Fe(II) oxidation coupled to nitrate reduction forms poorly crystalline Fe(III) oxyhydroxides and proceeds without cellular encrustation while indirect Fe(II) oxidation via heterotrophic nitrate-reduction-derived nitrite can lead to green rust as an intermediate mineral and significant cell encrustation. The extent of encrustation caused by indirect Fe(II) oxidation by reactive nitrogen species depends on Fe(II) concentrations and is probably negligible under environmental conditions in most habitats. IMPORTANCE Most described nitrate

Quantitative analysis of O-2 and Fe2+ profiles in gradient tubes for cultivation of microaerophilic Iron(II)-oxidizing bacteria

DEFF Research Database (Denmark)

Lueder, U.; Druschel, G.; Emerson, D.

2018-01-01

The classical approach for the cultivation of neutrophilic microaerophilic Fe(II)-oxidizing bacteria is agar-based gradient tubes where these bacteria find optimal growth conditions in opposing gradients of oxygen (O-2) and dissolved Fe(II) (Fe2+). The goals of this study were to quantify...... imply that transfer of cultures to fresh tubes within 48-72 h is crucial to provide optimal growth conditions for microaerophilic Fe(II)-oxidizers, particularly for the isolation of new strains....

Potential function of added minerals as nucleation sites and effect of humic substances on mineral formation by the nitrate-reducing Fe(II)-oxidizer Acidovorax sp. BoFeN1.

Science.gov (United States)

Dippon, Urs; Pantke, Claudia; Porsch, Katharina; Larese-Casanova, Phil; Kappler, Andreas

2012-06-19

The mobility of toxic metals and the transformation of organic pollutants in the environment are influenced and in many cases even controlled by iron minerals. Therefore knowing the factors influencing iron mineral formation and transformation by Fe(II)-oxidizing and Fe(III)-reducing bacteria is crucial for understanding the fate of contaminants and for the development of remediation technologies. In this study we followed mineral formation by the nitrate-reducing Fe(II)-oxidizing strain Acidovorax sp. BoFeN1 in the presence of the crystalline Fe(III) (oxyhydr)oxides goethite, magnetite and hematite added as potential nucleation sites. Mössbauer spectroscopy analysis of minerals precipitated by BoFeN1 in (57)Fe(II)-spiked microbial growth medium showed that goethite was formed in the absence of mineral additions as well as in the presence of goethite or hematite. The presence of magnetite minerals during Fe(II) oxidation induced the formation of magnetite in addition to goethite, while the addition of humic substances along with magnetite also led to goethite but no magnetite. This study showed that mineral formation not only depends on the aqueous geochemical conditions but can also be affected by the presence of mineral nucleation sites that initiate precipitation of the same underlying mineral phases.

Microbial Fe(II) oxidation at circumneutral pH: Reaction kinetics, mineral products, and distribution of neutrophilic iron oxidizers in wetland soils

NARCIS (Netherlands)

Vollrath, S.

2012-01-01

Multiple studies have shown that neutrophilic Fe(II) oxidizers can conserve energy from Fe(II) oxidation, however, it is still unclear how they can compete against the fast abiotic reaction at neutral pH, or to which extent these bacteria increase the overall Fe(II) oxidation rate. Similar to

Ubiquitous presence of Fe(II) in aquatic colloids and its association with organic carbon

CSIR Research Space (South Africa)

von der Heyden, BP

2014-08-01

Full Text Available and freshwater environments. We show that Fe(II)-rich phases are prevalent throughout different aquatic regimes yet exhibit a high degree of chemical heterogeneity. Furthermore, we show that Fe-rich particles show strong associations with organic carbon...

Pension fund sophistication and investment policy

NARCIS (Netherlands)

de Dreu, J.|info:eu-repo/dai/nl/364537906; Bikker, J.A.|info:eu-repo/dai/nl/06912261X

This paper assesses the sophistication of pension funds’ investment policies using data on 748 Dutch pension funds during the 1999–2006 period. We develop three indicators of sophistication: gross rounding of investment choices, investments in alternative sophisticated asset classes and ‘home bias’.

Advanced oxidation removal of hypophosphite by O3/H2O2 combined with sequential Fe(II) catalytic process.

Science.gov (United States)

Zhao, Zilong; Dong, Wenyi; Wang, Hongjie; Chen, Guanhan; Wang, Wei; Liu, Zekun; Gao, Yaguang; Zhou, Beili

2017-08-01

Elimination of hypophosphite (HP) was studied as an example of nickel plating effluents treatment by O 3 /H 2 O 2 and sequential Fe(II) catalytic oxidation process. Performance assessment performed with artificial HP solution by varying initial pH and employing various oxidation processes clearly showed that the O 3 /H 2 O 2 ─Fe(II) two-step oxidation process possessed the highest removal efficiency when operating under the same conditions. The effects of O 3 dosing, H 2 O 2 concentration, Fe(II) addition and Fe(II) feeding time on the removal efficiency of HP were further evaluated in terms of apparent kinetic rate constant. Under improved conditions (initial HP concentration of 50 mg L -1 , 75 mg L -1 O 3 , 1 mL L -1 H 2 O 2 , 150 mg L -1 Fe(II) and pH 7.0), standard discharge (<0.5 mg L -1 in China) could be achieved, and the Fe(II) feeding time was found to be the limiting factor for the evolution of apparent kinetic rate constant in the second stage. Characterization studies showed that neutralization process after oxidation treatment favored the improvement of phosphorus removal due to the formation of more metal hydroxides. Moreover, as a comparison with lab-scale Fenton approach, the O 3 /H 2 O 2 ─Fe(II) oxidation process had more competitive advantages with respect to applicable pH range, removal efficiency, sludge production as well as economic costs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Molecular magnetism of a linear Fe(III)-Mn(II)-Fe(III) complex. Influence of long-range exchange interaction

International Nuclear Information System (INIS)

Lengen, M.; Chaudhuri, P.

1994-01-01

The magnetic properties of [L-Fe(III)-dmg 3 Mn(II)-Fe(III)-L] (ClO 4 ) 2 have been characterized by magnetic susceptibility, EPR, and Moessbauer studies. L represents 1,4,7-trimethyl-,1,4,7-triazacyclononane and dmg represents dimethylglyoxime. X-ray diffraction measurements yield that the arrangement of the three metal centers is strictly linear with atomic distances d Fe-Mn 0.35 nm and d Fe-Fe = 0.7 nm. Magnetic susceptibility measurements (3-295 K) were analyzed in the framework of the spin-Hamiltonian formalism considering Heisenberg exchange and Zeeman interaction: H = J Fe-Mn (S Fe1 + S Fe2 )S Mn + J Fe-Fe S Fe1 S Fe2 + gμ B S total B. The spins S Fe1 = S Fe2 = S Mn = 5/2 of the complex are antiferromagnetically coupled, yielding a total spin of S total = 5/2 with exchange coupling constants F Fe-Mn = 13.4 cm -1 and J Fe-Fe = 4.5 cm -1 . Magnetically split Moessbauer spectra were recorded at 1.5 K under various applied fields (20 mT, 170 mT, 4 T). The spin-Hamiltonian analysis of these spectra yields isotropic magnetic hyperfine coupling with A total /(g N μ N ) = -18.5 T. The corresponding local component A Fe is related to A total via spin-projection: A total = (6/7)A Fe . The resulting A Fe /(g N μ N ) -21.6 T is in agreement with standard values of ferric high-spin complexes. Spin-Hamiltonian parameters as obtained from Moessbauer studies and exchange coupling constants as derived from susceptibility measurements are corroborated by temperature-dependent EPR studies. (orig.)

Prevalencia de infeccion por HTLV-I/II en donantes de sangre de la provincia de Santa Fe, Argentina Prevalence of HTLV-I/II infection among blood donors in Santa Fe Province, Argentina

Directory of Open Access Journals (Sweden)

Roque O. Brun

2004-04-01

Full Text Available Subsecuentemente a que en 1997 el Programa Nacional de SIDA implementó un Programa deVigilancia Epidemiológica a escala nacional, se comenzaron a detectar anticuerpos anti-HTLV-I/II en donantes de sangre de la Provincia de Santa Fe. En base a ese hallazgo inicial, se consideró pertinente estimar la seroprevalencia de HTLV-I/II en donantes santafecinos en el curso de los 4 años siguientes. Así, desde 1997 hasta 2002, se estudiaron 9425 muestras provenientes de 17 de los 19 departamentos de la Provincia. Del total de muestras, 38 resultaron reactivas por técnicas de tamizaje, y de ellas 18 fueron confirmadas por western blot (WB. De esas muestras, 10 fueron HTLV-I/II seropositivas con una prevalencia final de 0.1% (10/9425, en tanto que 7 resultaron indeterminadas y 1 negativa. De las seropositivas, 2 (0.02 % eran HTLV, 3 (0.03 % HTLV-I, y 5 (0.05 % HTLV-II. Cabe destacar que por primera vez se constató la presencia de infección por HTLV-I/II en donantes de sangre de Santa Fe, y con una prevalencia mayor a las referidas para donantes de sangre de áreas no endémicas de Argentina. Estos datos fundamentan la necesidad de un screening sistemático para la infección por HTLV-I/II mediante normas regulatorias en bancos de sangre de esta provincia.Subsequent to the National Epidemiologic Surveillance Program developed in 1997 by the National AIDS Program, anti-HTLV-I/II antibodies among blood donors in Santa Fe Province started to be detected. On the basis of this initial finding, it was regarded of interest to evaluate the true HTLV-I/II seroprevalence in this population during a four-year survey. Thus, from 1997 up to 2002, 9425 samples were studied from 17 out of the 19 provincial departments. Out of the total sampling, 38 proved reactive by agglutination techniques, 18 of which were confirmed by western blot (WB. Out of the latter, 10 were HTLV-I/II seropositive with a final prevalence of 0.1% (10/9425, whereas 7 were indeterminate and 1

One-step synthesis of water-dispersible cysteine functionalized magnetic Fe3O4 nanoparticles for mercury(II) removal from aqueous solutions

International Nuclear Information System (INIS)

Shen, Xiaofang; Wang, Qin; Chen, WenLing; Pang, Yuehong

2014-01-01

Graphical abstract: Using Fe 2+ as precursors, air as oxidant and cysteine as protectant, this novel cysteine functionalized Fe 3 O 4 magnetic nanoparticles (Cys-Fe 3 O 4 MNPs) was facilely one-pot synthesized at room temperature by oxidation–precipitation method with the assistance of sonication. Then the Cys-Fe 3 O 4 MNPs were demonstrated as an inexpensive and quite efficient magnetic nano-adsorbent for as high as 95% Hg(II) removal efficiency. These results indicated that Cys-Fe 3 O 4 MNPs is a potentially attractive material for the removal of Hg(II) from water. - Highlights: • A simplified one-step synthesis method of superparamagnetic Cys-Fe 3 O 4 MNPs was developed. • It was synthesized at room temperature by oxidation-precipitation method with the assistance of sonication. • It was demonstrated as an inexpensive and quite efficient magnetic nano-adsorbent for Hg(II) removal. - Abstract: Cysteine functionalized Fe 3 O 4 magnetic nanoparticles (Cys-Fe 3 O 4 MNPs) were prepared facilely for Hg(II) removal from aqueous solutions. Using Fe 2+ as precursors, air as oxidant and Cys as protectant, this novel material was one-pot synthesis at room temperature by oxidation–precipitation method with the assistance of sonication. The MNPs were characterized by TEM, VSM, FTIR, X-ray powder diffraction analysis (XRD) and TGA methods. Under the optimum experimental conditions, the removal efficiency was as high as 95% and the maximum sorption capacity is found to be 380 mg/mol for Hg(II). Study on adsorption kinetics shows that adsorption of Hg(II) onto Cys-Fe 3 O 4 MNPs follows pseudo-first-order kinetic model and the adsorption rate constant was 0.22 min −1 . Additionally, the Hg(II)-loaded Cys-Fe 3 O 4 MNPs could be easily regenerated up to 95% using 1.0 M acetic acid. These results indicated that Cys-Fe 3 O 4 MNPs is a potentially attractive material for the removal of Hg(II) from water

The reactivity of Fe(II) associated with goethite formed during short redox cycles toward Cr(VI) reduction under oxic conditions

Energy Technology Data Exchange (ETDEWEB)

Tomaszewski, Elizabeth J.; Lee, Seungyeol; Rudolph, Jared; Xu, Huifang; Ginder-Vogel, Matthew (UW)

2017-08-01

Chromium (Cr) is a toxic metal that causes a myriad of health problems and enters the environment as a result of anthropogenic activities and/or natural processes. The toxicity and solubility of chromium is linked to its oxidation state; Cr(III) is poorly soluble and relatively nontoxic, while Cr(VI) is soluble and a known carcinogen. Solid Fe(II) in iron-bearing minerals, such as pyrite, magnetite, and green rusts, reduce the oxidation state of chromium, reducing its toxicity and mobility. However, these minerals are not the only potential sources of solid-associated Fe(II) available for Cr(VI) reduction. For example, ferric (Fe(III)) (hydr)oxides, such as goethite or hematite, can have Fe(II) in the solid without phase transformation; however, the reactivity of Fe(II) within Fe(III) (hydr)oxides with contaminants, has not been previously investigated. Here, we cyclically react goethite with dissolved Fe(II) followed by dissolved O2, leading to the formation of reactive Fe(II) associated with goethite. In separate reactors, the reactivity of this Fe(II) is probed under oxic conditions, by exposure to chromate (CrO42 -) after either one, two, three or four redox cycles. Cr is not present during redox cycling; rather, it is introduced to a subset of the solid after each oxidation half-cycle. Analysis of X-ray absorption near edge structure (XANES) spectra reveals that the extent of Cr(VI) reduction to Cr(III) depends not only on solid Fe(II) content but also surface area and mean size of ordered crystalline domains, determined by BET surface area analysis and X-ray diffraction (XRD), respectively. Shell-by-shell fitting of the extended X-ray absorption fine structure (EXAFS) spectra demonstrates chromium forms both single and double corner sharing complexes on the surface of goethite, in addition to sorbed Cr(III) species. Finally, transmission electron microscope (TEM) imaging and X-ray energy-dispersive spectroscopy (EDS) illustrate that Cr preferentially

In Praise of the Sophists.

Science.gov (United States)

Gibson, Walker

1993-01-01

Discusses the thinking of the Greek Sophist philosophers, particularly Gorgias and Protagoras, and their importance and relevance for contemporary English instructors. Considers the problem of language as signs of reality in the context of Sophist philosophy. (HB)

Importance of reduced sulfur for the equilibrium chemistry and kinetics of Fe(II), Co(II) and Ni(II) supplemented to semi-continuous stirred tank biogas reactors fed with stillage.

Science.gov (United States)

Shakeri Yekta, Sepehr; Lindmark, Amanda; Skyllberg, Ulf; Danielsson, Asa; Svensson, Bo H

2014-03-30

The objective of the present study was to assess major chemical reactions and chemical forms contributing to solubility and speciation of Fe(II), Co(II), and Ni(II) during anaerobic digestion of sulfur (S)-rich stillage in semi-continuous stirred tank biogas reactors (SCSTR). These metals are essential supplements for efficient and stable performance of stillage-fed SCSTR. In particular, the influence of reduced inorganic and organic S species on kinetics and thermodynamics of the metals and their partitioning between aqueous and solid phases were investigated. Solid phase S speciation was determined by use of S K-edge X-ray absorption near-edge spectroscopy. Results demonstrated that the solubility and speciation of supplemented Fe were controlled by precipitation of FeS(s) and formation of the aqueous complexes of Fe-sulfide and Fe-thiol. The relatively high solubility of Co (∼ 20% of total Co content) was attributed to the formation of compounds other than Co-sulfide and Co-thiol, presumably of microbial origin. Nickel had lower solubility than Co and its speciation was regulated by interactions with FeS(s) (e.g. co-precipitation, adsorption, and ion substitution) in addition to precipitation/dissolution of discrete NiS(s) phase and formation of aqueous Ni-sulfide complexes. Copyright © 2014 Elsevier B.V. All rights reserved.

TEMPERATURE DEPENDENCE OF 57Fe-MÖSSBAUER SPECTRA FOR A 〖〖Fe〗_Fc^II-Fe〗_tpy^II-〖Fe〗_Fc^II TRINUCLEAR SYSTEM

Directory of Open Access Journals (Sweden)

Dumitru Sirbu

2015-06-01

Full Text Available 57Fe Mӧssbauer spectra were recorded for 1'-terpyridine ferrocenecarboxylic acid and [bis(1'-terpyridine ferrocenecarboxylic acid Fe(II]2+ in the temperature range 7 – 293 K. The temperature dependence of the Quadrupole Splitting, Isomer Shift and Debye-Waller factor are discussed. The Debye temperature for the iron nuclei in the investigated compounds was determined.

Application of Fe(II)/peroxymonosulfate for improving ultrafiltration membrane performance in surface water treatment: Comparison with coagulation and ozonation.

Science.gov (United States)

Cheng, Xiaoxiang; Liang, Heng; Ding, An; Zhu, Xuewu; Tang, Xiaobin; Gan, Zhendong; Xing, Jiajian; Wu, Daoji; Li, Guibai

2017-11-01

Coagulation and ozonation have been widely used as pretreatments for ultrafiltration (UF) membrane in drinking water treatment. While beneficial, coagulation or ozonation alone is unable to both efficiently control membrane fouling and product water quality in many cases. Thus, in this study an emerging alternative of ferrous iron/peroxymonosulfate (Fe(II)/PMS), which can act as both an oxidant and a coagulant was employed prior to UF for treatment of natural surface water, and compared with conventional coagulation and ozonation. The results showed that the Fe(II)/PMS-UF system exhibited the best performance for dissolved organic carbon removal, likely due to the dual functions of coagulation and oxidation in the single process. The fluorescent and UV-absorbing organic components were more susceptible to ozonation than Fe(II)/PMS treatment. Fe(II)/PMS and ozonation pretreatments significantly increased the removal efficiency of atrazine, p-chloronitrobenzene and sulfamethazine by 12-76% and 50-94%, respectively, whereas coagulation exerted a minor influence. The Fe(II)/PMS pretreatment also showed the best performance for the reduction of both reversible and irreversible membrane fouling, and the performance was hardly affected by membrane pore size and surface hydrophobicity. In addition, the characterization of hydraulic irreversible organic foulants confirmed its effectiveness. These results demonstrate the potential advantages of applying Fe(II)/PMS as a pretreatment for UF to simultaneously control membrane fouling and improve the permeate quality. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of the tether on the Mg(II), Ca(II), Cu(II) and Fe(III) stability constants and pM values of chelating agents related to EDDHA.

Science.gov (United States)

Sierra, Miguel A; Gómez-Gallego, Mar; Alcázar, Roberto; Lucena, Juan J; Yunta, Felipe; García-Marco, Sonia

2004-11-07

The effect of the length and the structure of the tether on the chelating ability of EDDHA-like chelates have not been established. In this work, PDDHA (propylenediamine-N,N'-bis(o-hydroxyphenyl)acetic acid), BDDHA (butylenediamine-N,N'-bis(o-hydroxyphenyl)acetic acid) and XDDHA (p-xylylenediamine-N,N'-bis(o-hydroxyphenyl)acetic acid) have been obtained and their chemical behaviour has been studied and compared with that of EDDHA following our methodology. The purity of the chelating agents, and their protonation, Ca(II), Mg(II), Fe(III) and Cu(II) stability constants and pM values have been determined. The stability constants and pM values indicate that EDDHA forms the most stable chelates followed by PDDHA. However, the differences among the pFe values are small when a nutrient solution is used, and in these conditions the XDDHA/Fe(III) chelate is the most stable. The results obtained in this work indicate that all the chelating agents studied can be used as iron chlorosis correctors and they can be applied to soil/plant systems.

Feasibility of closed Fe(II)/Fe(III) system for product-reflux in Nitrox process

International Nuclear Information System (INIS)

Adachi, M.; Ishida, T.

1981-01-01

A concept of closed reflux system for stable isotope fractionation by chemical exchange method has been introduced. In a closed system a chemical agent used to convert one chemical species of an isotopic exchange reaction into the other at the product end is regenerated on site by means of an electrochemical or thermal process. It offers a convenience of eliminating the needs for transporting chemicals to and from the site and an advantage of allowing leniency in the degree of completeness of the reflux reaction. Feasibility of use of Fe(II) salt solutions in a closed reflux system for the Nitrox process for 15 N fractionation has been studied. Two of such systems, FeSO 4 in H 2 SO 4 and Fe(ClO 4 ) 2 in HClO 4 , are adopted for packed column operation. For both systems, the rate of reduction of nitric acid increases with increasing acid concentration, the solubility of the salts decreases with the increasing acid concentration, and the reflux reaction can be made to go to completion. Evaluation of such a closed reflux system will have to include that of performance of regenerative process

Interaction between U(VI) and Fe(II) in aqueous solution under anaerobic conditions. Closed system experiments

International Nuclear Information System (INIS)

Myllykylae, E.; Ollila, K.

2011-01-01

The aim of these experiments is to investigate the potential reduction of U(VI) carbonate and hydroxide complexes by aqueous Fe(II). This reduction phenomenon could be important under the disposal conditions of spent fuel. If groundwater enters the copper/iron canister, alpha radiolysis of the water may locally induce oxidizing conditions on the surface of UO 2 fuel, leading to the dissolution of UO 2 as more soluble U(VI) species. A potential reducing agent in the intruding water is Fe(II)(aq) from anaerobic corrosion of the copper/iron canister. The reduction of U(VI) to U(IV) would substantially decrease the solubility of U as well as co-precipitate other actinides and radionuclides. The interaction experiments were conducted in 0.01 M NaCl and 0.002 M NaHCO 3 solutions using an initial uranium concentration of either 8.4 x 10 -8 or 4.2 x 10 -7 mol/L with an initial Fe(II) concentration of 1.8 x 10 -6 in the NaCl solutions and 1.3 x 10 -6 mol/L in the NaHCO 3 solutions. Only after an equilibration period for U(VI) complexation was Fe(II) added to the solutions. The reaction times varied from 1 week to 5 months. For extra protection against O 2 , even inside a glove-box (N 2 atmosphere), the plastic reaction vessels were closed in metallic containers. The concentrations of U, Fe TOT and Fe(II) were analysed as a function of time for unfiltered, micro- and ultrafiltered samples. In addition, the precipitate on the ultrafilters was analysed with ESEM-EDS. The evolution of pH and Eh values was measured. The oxidation state of U in solution was preliminarily analysed for chosen periods. The results of the tests in 0.01 M NaCl showed an initial rapid decrease in U concentration after the addition of Fe(II) to the solution. The U found on test vessel walls at the end of the reaction periods, as well as the ESEM-EDS analyses of the filtered precipitates from the test solutions, showed that precipitation of U had occurred. The oxidation state analyses showed the presence

Studies of the yields of 57Fe(II)-species produced after the EC-decay and of 60Co(II)-species produced in the (n, γ) reaction in cobalt(III) coordination compounds

International Nuclear Information System (INIS)

Sano, Hirotoshi; Harada, Masayuki; Endo, Kazutoyo

1978-01-01

The yields of 57 Fe(II)-species produced after EC-decay were compared with those of 60 Co(II)-species produced in the 59 Co(n, γ) 60 Co reaction for twelve cobalt(III) coordination compounds. The results indicate that the radiochemical yield of 60 Co(II)-species correlates with the yield of 57 Fe(II)-species except in the case of [Co(NH 3 ) 6 ] 2 (CrO 4 ) 3 . The anomalously low yield of 57 Fe(II)-species in [Co(NH 3 ) 6 ] 2 (CrO 4 ) 3 is ascribed to the reaction of chromate anions with ammine ligands initiated by the nuclear transformation in a solid. (author)

Moessbauer spectroscopic study of Fe{sup II}-doped sulphonated poly(ether-urethane)-styrene-acrylate copolymer

Energy Technology Data Exchange (ETDEWEB)

Kamnev, A. A. [Russian Academy of Sciences, Institute of Biochemistry and Physiology of Plants and Microorganisms (Russian Federation); Grigoryeva, O. P.; Fainleib, A. M. [National Academy of Sciences of Ukraine, Institute of Macromolecular Chemistry (Ukraine); Kuzmann, E., E-mail: kuzmann@ludens.elte.hu [Eoetvoes Lorand University, Institute of Chemistry (Hungary)

2013-04-15

Thermoplastic linear ionomer based on sulphonated poly(ether-urethane)-styrene-acrylate copolymer, doped with natural Fe{sup 2 + }, was studied by Moessbauer spectroscopy at T = 78 and 290 K to monitor the chemical state of Fe species. The Fe{sup 2 + } added to aqueous suspension of the system was only partly oxidised in the course of polymer film preparation and drying in air. The oxidised part comprised a magnetic phase ({approx}19 % of total Fe both at T = 78 and 298 K) and a quadrupole doublet ({approx}40 %), while Fe{sup II} (over 40 %) stabilised in two types of microenvironments.

Interaction of Fe(II) with Polyacrylic Acid as a Simplification of Humic Acid: Comparison of Ion Exchange and Solvent Extraction Methods

International Nuclear Information System (INIS)

Budi Setiawan

2007-01-01

To estimate the safety assessment around the disposal facility, the interaction behavior of radionuclides/metal ions into organic material (such as humic acids) exist in natural water becomes an important study. To avoid the effect of heterogeneous composition of humic acid, polyacrylic acids (abbrev. APA) was used as are representative of homogeneous polymeric weak acid. The experiments have been carried out by solvent extraction and ion exchange methods to find out the suitable method for the study of complex formation of Fe(II) with humic acid(AH) and APA. The solvent extraction experiment has been done by using diphenylthiocarbazone (dithizone) in CCl 4 and C Fe(II) were 10 -8 M to 10 -5 M, pH around 5 and I=0.1M NaCI. In ionic exchange experiment, C Fe(II) were 10 -8 to 10 -4 M, pH from 4.8 to 5.5 in I=0.1M NaCl. The apparent complex formation constant is defined as β α = [ML]/([M][R]), where [M] and [ML] are concentration of free and bound of Fe(II) and [R] is the concentration of dissociated carboxylic group in macromolecules of PAA. The results shown that, for solvent extraction experiments, variable concentration of Fe(II) had no appreciable influence on the distribution ratio of Fe(II)-polyacrylate at the tracer concentration with the log D to be 1.32 ± 0.03 (pcH 5.25). At macro concentration, the distribution ratio of Fe(II) becomes smaller due to oxidation and obtained log D value to be 1.04 ± 0.07 (pcH 5.34). An interest kind was observed at higher PAA concentration, the distribution ratio curve becomes higher presumably due to the problem on redox sensitive characteristic of Fe(II) and/or coagulation of Fe(II)-polyacrylate at the interface of aqueous-organic phases. In case of ionic exchange method, the plot of I/Kd versus [R] gives a straight line result indicating this method is appropriate and more superior compare than solvent extraction method to determine the complex formation constant. (author)

Spatial and temporal distribution of Fe(II) and H2O2 during EisenEx, an open ocean mescoscale iron enrichment

NARCIS (Netherlands)

Croot, Peter L.; Laan, Patrick; Nishioka, Jun; Strass, Volker; Cisewski, Boris; Boye, Marie; Timmermans, Klaas R.; Bellerby, Richard G.; Goldson, Laura; Nightingale, Phil; Baar, Hein J.W. de

2005-01-01

Measurements of Fe(II) and H2O2 were carried out in the Atlantic sector of the Southern Ocean during EisenEx, an iron enrichment experiment. Iron was added on three separate occasions, approximately every 8 days, as a ferrous sulfate (FeSO4) solution. Vertical profiles of Fe(II) showed maxima

Nitrite to nitric oxide interconversion by heme FeII complex assisted by [CuI(tmpa)]+

KAUST Repository

Turias, Francesc; Solà , Miquel; Falivene, Laura; Cavallo, Luigi; Poater, Albert

2015-01-01

The present computational study complements the recent experimental efforts by Karlin and coworkers to describe the interconversion of nitrite to nitric oxide by means of an iron porphyrin complex together with a Cu chemical system, i.e., the iron(II) complex (F8TPP)FeII [F8TPP = tetrakis(2,6-difluorophenyl)porphyrinate(2−)] and a preformed copper(II)–nitrito complex [(tmpa)CuII(NO2)][B(C6F5)4] [tmpa = tris(2-pyridylmethyl)amine], being the latter an oxidized species of [(tmpa)CuI(MeCN)]+. By DFT calculations, we unravel how the reduction of nitrite to nitric oxide takes place through a μ-oxo heme-FeIII–O–CuII complex, following a mimetic path as in the cytochrome c oxidase. Mayer bond order (MBO) and energy decomposition analyses are used to analyze the bonding strength of such nitro derivatives to either copper or iron. © 2015 Springer Science+Business Media New York

Nitrite to nitric oxide interconversion by heme FeII complex assisted by [CuI(tmpa)]+

KAUST Repository

Turias, Francesc

2015-09-09

The present computational study complements the recent experimental efforts by Karlin and coworkers to describe the interconversion of nitrite to nitric oxide by means of an iron porphyrin complex together with a Cu chemical system, i.e., the iron(II) complex (F8TPP)FeII [F8TPP = tetrakis(2,6-difluorophenyl)porphyrinate(2−)] and a preformed copper(II)–nitrito complex [(tmpa)CuII(NO2)][B(C6F5)4] [tmpa = tris(2-pyridylmethyl)amine], being the latter an oxidized species of [(tmpa)CuI(MeCN)]+. By DFT calculations, we unravel how the reduction of nitrite to nitric oxide takes place through a μ-oxo heme-FeIII–O–CuII complex, following a mimetic path as in the cytochrome c oxidase. Mayer bond order (MBO) and energy decomposition analyses are used to analyze the bonding strength of such nitro derivatives to either copper or iron. © 2015 Springer Science+Business Media New York

Moderate KMnO4-Fe(II) pre-oxidation for alleviating ultrafiltration membrane fouling by algae during drinking water treatment.

Science.gov (United States)

Ma, Baiwen; Qi, Jing; Wang, Xing; Ma, Min; Miao, Shiyu; Li, Wenjiang; Liu, Ruiping; Liu, Huijuan; Qu, Jiuhui

2018-05-21

Although ultrafiltration (UF) membranes are highly beneficial for removing algae, the removal process causes serious UF membrane fouling. To avoid the unfavorable effects of algal cells that have been damaged by oxidants, our previous study reported a novel, moderate pre-oxidation method (KMnO 4 -Fe(II) process) that aimed to achieve a balance between the release of intracellular organic matter and enhanced algae removal. This study further investigated the performance of a UF membrane with KMnO 4 -Fe(II) pretreatment in the presence of algae-laden reservoir water after a long running time. We found that algae could be completely removed, membrane fouling was significantly alleviated, and the overall performance was much better than that of Fe(III) coagulation alone. The transmembrane pressure (TMP) during Fe(III) coagulation increased to 42.8 kPa, however, that of the KMnO 4 -Fe(II) process only increased to 25.1 kPa for after running for 90 d. The slower transmembrane pressure was attributed to the larger floc size, higher surface activity, and inactivation of algae. Although there was little effect on microorganism development, lower microorganism abundance (20.7%) was observed during the KMnO 4 -Fe(II) process than during coagulation alone (44.9%) due to the release of extracellular polymeric substances. We also found that the floc cake layer was easily removed by washing, and many of the original membrane pores were clearly observed. Further analysis demonstrated that the effluent quality was excellent, especially its turbidity, chromaticity, and Mn and Fe concentrations. Based on the outstanding UF membrane performance, it may be concluded that the KMnO 4 -Fe(II) process exhibits considerable potential for application in the treatment of algae-laden water. Copyright © 2018. Published by Elsevier Ltd.

Cacotheline as an oxidimetric reagent. Determination of Sn(II), Cu(I), Ti(III), Fe(II), V(II) and V(III)

International Nuclear Information System (INIS)

Nemani Murty, K.; Yedluri Rao, P.; Geddada Chalam, K.

1982-01-01

Sn(II), Ti(III), Cu(I),Fe(II), V(III) and V(II) can be titrated potentiometrically with cacotheline in 1-4 M hydrochloric acid, 0.5-2 M hydrochloric acid, 0.5-1.5 M sulphuric acid in presence of 4 ml of 10% EDTA solution in a total volume of 50 ml, 9-10 M phosphoric acid, 4-8 M acetic acid and 3-8 M acetic acid respectively. Cacotheline can be used for the assay of tin plate and solder. The cacotheline undergoes a 2-electron reduction reaction. A cacotheline solution (0.005 M) in 0.02 M hydrochloric acid is fairly stable for several months. The conditional redox potentials of cacotheline have been determined in sulphuric, phosphoric and acetic acid medium. (Author)

Impact of Microcystis aeruginosa Exudate on the Formation and Reactivity of Iron Oxide Particles Following Fe(II) and Fe(III) Addition.

Science.gov (United States)

Garg, Shikha; Wang, Kai; Waite, T David

2017-05-16

Impact of the organic exudate secreted by a toxic strain of Microcystis aeruginosa on the formation, aggregation, and reactivity of iron oxides that are formed on addition of Fe(II) and Fe(III) salts to a solution of the exudate is investigated in this study. The exudate has a stabilizing effect on the particles formed with decreased aggregation rate and increased critical coagulant concentration required for diffusion-limited aggregation to occur. These results suggest that the presence of algal exudates from Microcystis aeruginosa may significantly influence particle aggregation both in natural water bodies where Fe(II) oxidation results in oxide formation and in water treatment where Fe(III) salts are commonly added to aid particle growth and contaminant capture. The exudate also affects the reactivity of iron oxide particles formed with exudate coated particles undergoing faster dissolution than bare iron oxide particles. This has implications to iron availability, especially where algae procure iron via dissolution of iron oxide particles as a result of either reaction with reducing moieties, light-mediated ligand to metal charge transfer and/or reaction with siderophores. The increased reactivity of exudate coated particles is attributed, for the most part, to the smaller size of these particles, higher surface area and increased accessibility of surface sites.

Influence of iron-bearing phyllosilicates on the dechlorination kinetics of 1,1,1-trichloroethane in Fe(II)/cement slurries.

Science.gov (United States)

Jung, Bahngmi; Batchelor, Bill

2007-07-01

This study examines the effect of iron-bearing phyllosilicates on dechlorination rates of chlorinated aliphatic hydrocarbons (CAHs) in iron-based degradative solidification/stabilization (DS/S-Fe(II)). Laboratory batch experiments were conducted to evaluate dechlorination rates of 1,1,1-trichloroethane (1,1,1-TCA) in a mixture solution of Fe(II), cement and three different iron-bearing phyllosilicates (biotite, vermiculite, and montmorillonite). A first-order rate model was generally used to describe the dechlorination kinetics and the rate constants were dependent on soil mineral type (biotite, vermiculite, and montmorillonite), Fe(II) dose, and the mass ratio of cement to soil mineral. The pseudo-first-order rate constant for montmorillonite was lower than that for biotite and vermiculite by factors of 11-27 when the mass ratio of cement to phyllosilicates was fixed at one. The presence of biotite and vermiculite increase and the presence of montmorillonite decrease the degradation rate that would be observed in their absence. The effect of cement/mineral ratio on rate constants with three different soil minerals indicates that biotite was more reactive than the other two phyllosilicates. This may be due to high accessible natural Fe(II) content in biotite. Montmorillonite appears to inhibit dechlorination by either inactivating Fe(II) by ion exchange or by physically blocking active sites on cement hydration products.

Magneto-structural correlations in a family of Fe(II)Re(IV)(CN)2 single-chain magnets: density functional theory and ab initio calculations.

Science.gov (United States)

Zhang, Yi-Quan; Luo, Cheng-Lin; Wu, Xin-Bao; Wang, Bing-Wu; Gao, Song

2014-04-07

Until now, the expressions of the anisotropic energy barriers Δξ and ΔA, using the uniaxial magnetic anisotropy D, the intrachain coupling strength J, and the high-spin ground state S for single-chain magnets (SCMs) in the intermediate region between the Ising and the Heisenberg limits, were unknown. To explore this relationship, we used density functional theory and ab initio methods to obtain expressions of Δξ and ΔA in terms of D, J, and S of six R4Fe(II)-Re(IV)Cl4(CN)2 (R = diethylformamide (1), dibutylformamide (2), dimethylformamide (3), dimethylbutyramide (4), dimethylpropionamide (5), and diethylacetamide (6)) SCMs in the intermediate region. The ΔA value for compounds 1-3 was very similar to the magnetic anisotropic energy of a single Fe(II), while the value of Δξ was predicted using the exchange interaction of Fe(II) with the neighboring Re(IV), which could be expressed as 2JSReSFe. Similar to compounds 1-3, the anisotropy energy barrier ΔA of compounds 4 and 5 was also equal to (Di - Ei)SFe(2), but the correlation energy Δξ was closely equal to 2JSReSFe(cos 98.4 - cos 180) due to the reversal of the spins on the opposite Fe(II). For compound 6, one unit cell of Re(IV)Fe(II) was regarded as a domain wall since it had two different Re(IV)-Fe(II) couplings. Thus, the Δξ of compound 6 was expressed as 4J″SRe1Fe1SRe2Fe2, where J″ was the coupling constant of the neighboring unit cells of Re1Fe1 and Re2Fe2, and ΔA was equal to the anisotropic energy barrier of one domain wall given by DRe1Fe1(S(2)Re1Fe1 - 1/4).

Spectroscopic, Elemental and Thermal Analysis, and Positron Annihilation Studies on Ca(II), Sr(II), Ba(II), Pb(II), and Fe(III) Penicillin G Potassium Complexes

Science.gov (United States)

Refat, M. S.; Sharshara, T.

2015-11-01

The [Pb(Pin)2] · 3H2O, [M(Pin)(H2O)2(Cl)] · nH2O (M = SrII, CaII or BaII; n = 0-1), and [Fe(Pin)2(Cl)(H2O)] · H2O penicillin G potassium (Pin) complexes were synthesized and characterized using elemental analyses, molar conductivity, thermal analysis and electronic spectroscopy techniques. The positron annihilation lifetime (PAL) and Doppler broadening (DB) techniques have been employed to probe the defects and structural changes of Pin ligand and its complexes. The PAL and DB line-shape parameters were discussed in terms of the structure, molecular weight, ligand-metal molar ratio, and other properties of the Pin complexes.

Crystal structure of (NH4)2[Fe(II) 5(HPO3)6], a new open-framework phosphite.

Science.gov (United States)

Berrocal, Teresa; Mesa, Jose Luis; Larrea, Edurne; Arrieta, Juan Manuel

2014-11-01

Di-ammonium hexa-phosphito-penta-ferrate(II), (NH4)2[Fe5(HPO3)6], was synthesized under mild hydro-thermal conditions and autogeneous pressure, yielding twinned crystals. The crystal structure exhibits an [Fe(II) 5(HPO3)6](2-) open framework with NH4 (+) groups as counter-cations. The anionic skeleton is based on (001) sheets of [FeO6] octa-hedra (one with point-group symmetry 3.. and one with .2.) linked along [001] through [HPO3](2-) oxoanions. Each sheet is constructed from 12-membered rings of edge-sharing [FeO6] octa-hedra, giving rise to channels with a radius of ca 3.1 Å in which the disordered NH4 (+) cations are located. The IR spectrum shows vibrational bands typical for phosphite and ammonium groups.

Degradation of a xanthene dye by Fe(II)-mediated activation of Oxone process.

Science.gov (United States)

Wang, Y R; Chu, W

2011-02-28

A powerful oxidation process using sulfate radicals activated by transition metal mediated Oxone process has been evaluated in depth by monitoring the degradation of a xanthene dye Rhodamine B (RhB) in aqueous solution. Ferrous ion was chosen as the transition metal due to its potential catalytic effect and wide availability in dyeing industrial effluent. The effects of parameters including reactant dosing sequence, Fe(II)/Oxone molar ratio and concentration, solution pH, and inorganic salts on the process performance have been investigated. Total RhB removal was obtained within 90 min under an optimal Fe(II)/Oxone molar ratio of 1:1. The RhB degradation was found to be a two-stage kinetics, consisting of a rapid initial decay and followed by a retarded stage. Additionally, experimental results indicated that the presence of certain anions had either a positive or negative effect on the process. The inhibitory effect in the presence of SO(4)(2-) was elucidated by a proposed formula using Nernst equation. Furthermore, dye mineralization in terms of TOC removal indicates that stepwise addition of Fe(II) and Oxone can significantly improve the process performance by about 20%, and the retention time required can be greatly reduced comparing with the conventional one-off dosing method. Copyright © 2010 Elsevier B.V. All rights reserved.

Interfacial charge separation and photovoltaic efficiency in Fe(ii)-carbene sensitized solar cells.

Science.gov (United States)

Pastore, Mariachiara; Duchanois, Thibaut; Liu, Li; Monari, Antonio; Assfeld, Xavier; Haacke, Stefan; Gros, Philippe C

2016-10-12

The first combined theoretical and photovoltaic characterization of both homoleptic and heteroleptic Fe(ii)-carbene sensitized photoanodes in working dye sensitized solar cells (DSSCs) has been performed. Three new heteroleptic Fe(ii)-NHC dye sensitizers have been synthesized, characterized and tested. Despite an improved interfacial charge separation in comparison to the homoleptic compounds, the heteroleptic complexes did not show boosted photovoltaic performances. The ab initio quantitative analysis of the interfacial electron and hole transfers and the measured photovoltaic data clearly evidenced fast recombination reactions for heteroleptics, even associated with un unfavorable directional electron flow, and hence slower injection rates, in the case of homoleptics. Notably, quantum mechanics calculations revealed that deprotonation of the not anchored carboxylic function in the homoleptic complex can effectively accelerate the electron injection rate and completely suppress the electron recombination to the oxidized dye. This result suggests that introduction of strong electron-donating substituents on the not-anchored carbene ligand in heteroleptic complexes, in such a way of mimicking the electronic effects of the carboxylate functionality, should yield markedly improved interfacial charge generation properties. The present results, providing for the first time a detailed understanding of the interfacial electron transfers and photovoltaic characterization in Fe(ii)-carbene sensitized solar cells, open the way to a rational molecular engineering of efficient iron-based dyes for photoelectrochemical applications.

Effect of Organic Substances on the Efficiency of Fe(Ii to Fe(Iii Oxidation and Removal of Iron Compounds from Groundwater in the Sedimentation Process

Directory of Open Access Journals (Sweden)

Krupińska Izabela

2017-09-01

Full Text Available One of the problems with iron removal from groundwater is organic matter. The article presents the experiments involved groundwater samples with a high concentration of total iron - amounting to 7.20 mgFe/dm3 and an increased amount of organic substances (TOC from 5.50 to 7.50 mgC/dm3. The water samples examined differed in terms of the value of the ratio of the TOC concentration and the concentration of total iron (D. It was concluded that with increase in the coexistence ratio of organic substances and total iron in water (D = [TOC]/[Fetot], efficiency of Fe(II to Fe(III oxidization with dissolved oxygen decreased, while the oxidation time was increasing. This rule was not demonstrated for potassium manganate (VII when used as an oxidizing agent. The application of potassium manganate (VII for oxidation of Fe(II ions produced the better results in terms of total iron concentration reduction in the sedimentation process than the oxidation with dissolved oxygen.

Effect of Organic Substances on the Efficiency of Fe(Ii) to Fe(Iii) Oxidation and Removal of Iron Compounds from Groundwater in the Sedimentation Process

Science.gov (United States)

Krupińska, Izabela

2017-09-01

One of the problems with iron removal from groundwater is organic matter. The article presents the experiments involved groundwater samples with a high concentration of total iron - amounting to 7.20 mgFe/dm3 and an increased amount of organic substances (TOC from 5.50 to 7.50 mgC/dm3). The water samples examined differed in terms of the value of the ratio of the TOC concentration and the concentration of total iron (D). It was concluded that with increase in the coexistence ratio of organic substances and total iron in water (D = [TOC]/[Fetot]), efficiency of Fe(II) to Fe(III) oxidization with dissolved oxygen decreased, while the oxidation time was increasing. This rule was not demonstrated for potassium manganate (VII) when used as an oxidizing agent. The application of potassium manganate (VII) for oxidation of Fe(II) ions produced the better results in terms of total iron concentration reduction in the sedimentation process than the oxidation with dissolved oxygen.

Voltammetric determination of Zn(II in Zn-Fe alloy electroplating baths using square-wave voltammetry

Directory of Open Access Journals (Sweden)

Favaron Regiane

2001-01-01

Full Text Available A routine analytical method for zinc (II determination in Zn-Fe alloy galvanic baths was developed employing square-wave voltammetry with the static mercury drop electrode (SMDE as working electrode. Real alloy bath samples were analyzed by the standard addition method and recovery tests were undertaken. The supporting electrolytes used in the analyses were 1.0 mol L-1 NH3 / 0.2 mol L-1 NH4Cl or 0.1 mol L-1 citric acid (pH=3, presenting peak potentials for zinc (II, respectively, at -1.30 V and -0.99 V vs. Ag|AgCl (saturated KCl. The proposed voltammetric method showed a linear response range at 25 °C between 1.0 x 10-5 and 2.2 x 10-4 mol L-1 for zinc (II, in both electrolytes studied. The interference levels for some metals, such as Cu (II, Pb (II, Cr (III and Mn (II, which could prejudice Zn-Fe alloy deposition, were evaluated. These ions did not present significant degrees of interference in the zinc (II determination. The zinc (II recovery tests for the proposed method exhibited a good agreement with the reference method, showing relative errors lower than 3.0%.

Interaction of red pepper (Capsicum annum, Tepin) polyphenols with Fe(II)-induced lipid peroxidation in brain and liver

Energy Technology Data Exchange (ETDEWEB)

Oboh, G [Biochemistry Department, Federal University of Technology, Akure, Ondo State (Nigeria); [Departamento de Quimica, Universidade Federal de Santa Maria (UFSM), Campus Universitario - Camobi, Santa Maria RS (Brazil); [Abdus Salam International Centre for Theoretical Physics, Trieste (Italy)]. E-mail: goboh2001@yahoo.com; Rocha, J B.T. [Campus Universitario - Camobi, Santa Maria RS (Brazil)

2006-03-15

Polyphenols exhibit a wide range of biological effects because of their antioxidant properties. Several types of polyphenols (phenolic acids, hydrolyzable tannins, and flavonoids) show anticarcinogenic and antimutagenic effects. Comparative studies were carried on the protective ability of free and bound polyphenol extracts of red Capsicum annuum Tepin (CAT) on brain and liver - In vitro. Free polyphenols of red Capsicum annuum Tepin (CAT) were extracted with 80% acetone, while the bound polyphenols were extracted with ethyl acetate from acid and alkaline hydrolysis of the pepper residue from free polyphenols extract. The phenol content, Fe (II) chelating ability, OH radical scavenging ability and protective ability of the extract against Fe (II)-induced lipid peroxidation in brain and liver was subsequently determined. The results of the study revealed that the free polyphenols (218.2mg/100g) content of the pepper were significantly higher than the bound polyphenols (42.5mg/100g). Furthermore, the free polyphenol extract had a significantly higher (<0.05) Fe (II) chelating ability, OH radical scavenging ability than the bound polyphenols. In addition, both extracts significantly inhibited (P<0.05) basal and 25{mu}M Fe (II)- induced lipid peroxidation in Rat's brain and liver in a dose dependent. However, the free polyphenols caused a significantly higher inhibition in the MDA (Malondialdehyde) production in the brain and liver homogenates than the bound phenols. Furthermore, the polyphenols protected the liver more than the brain. In conclusion, free polyphenols from Capsicum annuum protects both the liver and brain from Fe{sup 2+} induced lipid peroxidation, and this is probably due to the higher Fe (II) chelating ability and OH radical scavenging ability of the free polyphenols from the pepper. (author)

Spectrophotometric analysis of vitamin E using Cu(I)-Bathocuproine or/and Fe(II)-2,4,6-tris-(2'-pyridyl)-s-triazine complexes

International Nuclear Information System (INIS)

Devi, I.; Memon, S. A.; Khuhawar, M.Y.

2004-01-01

Vitamin E (tocopherols and tocotrienols) antioxidants are determined by reducing Cu(II) to Cu(I) or Fe(III) to Fe(II) in presence of vitamin E and subsequent complexation of Cu(I) with bathocuproine and/or Fe(II) with 2,4,6-tris-(2'-pyridyl)-s-triazine (TPTZ). Both the reactions are monitored separately, Cu(I)-bathocuproine at 479 nm where as, Fe(II)-(TPTZ) at 595 nm spectrophotometrically. Linear calibration curves are achieved for both complexes between I to 5mu g ml-1 for vitamin E. The methods were applied for the determination of vitamin E in pharmaceutical preparations and edible oils. Vitamin E, from edible oils, was solvent extracted into n-hexane prior to saponification. Furthermore, a single lined flow was also examined. A larger excess of Cu(II) or Fe =(II) with different concentrations of vitamin E in buffer pH 4 was run on the line and constant amounts of reagent bathocuproine or TPTZ in each case was injected through the injector. The peak height shows a linear relationship for vitamin E between 0.5 to 2.5 mu g ml-1 for both complexes. (author)

Effect of Organic Matter on Cr(VI Removal from Groundwaters by Fe(II Reductive Precipitation for Groundwater Treatment

Directory of Open Access Journals (Sweden)

Anna Gröhlich

2017-06-01

Full Text Available Due to its toxicity, Cr(VI is undesirable in groundwater. Its chemical reduction to Cr(III species, followed by precipitation is the most widely practiced treatment technique for the removal of Cr(VI from polluted waters. The resulting Cr(III species present low solubility, is much less toxic, and can be subsequently removed either by precipitation, or by adsorption onto iron oxy-hydroxides and co-precipitation. The effects of several parameters, such as the pH value of water to be treated, the applied Fe(II dose, and the presence of appropriate mineral surfaces, are well investigated and understood. However, the impact of the presence of humic acids (HAs in this process has only been considered by rather few studies. The main aim of this study was to determine the effect of humic substances on Fe(II reductive precipitation of Cr(VI within a pH range relevant for drinking water treatment. Jar test experiments were performed, using artificial groundwater of defined composition and initial Cr(VI concentration 100 μg/L, ferrous sulphate dosages 0.25–2 mg Fe(II/L, and pH values 6.5–8. It was found that Cr(VI and total chromium (Cr(total can be reliably removed in the absence of HAs in the tested pH range with the addition of Fe(II dosage of 1 mg Fe(II/L. Further on, the results indicated that the reduction of Cr(VI is only slightly affected by the presence of HAs. However, increased residual total Cr concentrations were found at lower Fe(II dosages and/or higher pH values. Additionally, the removal of the Cr(III species formed during Cr(VI reduction was strongly inhibited by the presence of HAs under the examined experimental conditions, since residual concentrations higher than 60 μg/L were determined. The results of this study will have implications to the ongoing discussion of a new, stricter, European Union regulation limit, regarding the presence of total chromium in drinking water.

Chiral analysis of alpha-diimine Ru(II) and Fe(II) complexes by capillary electrophoresis using sulfated cyclodextrins as stereoselectors

Czech Academy of Sciences Publication Activity Database

Sázelová, Petra; Koval, Dušan; Severa, Lukáš; Teplý, Filip; Kašička, Václav

2017-01-01

Roč. 38, č. 15 (2017), s. 1913-1921 ISSN 0173-0835 R&D Projects: GA ČR(CZ) GA15-01948S; GA ČR GA13-32974S; GA ČR GA13-19213S Institutional support: RVO:61388963 Keywords : binding constant * capillary electrophoresis * chiral separation * polypyridyl Fe(II) complex * polypyridyl Ru(II) complex Subject RIV: CB - Analytical Chemistry, Separation OBOR OECD: Analytical chemistry Impact factor: 2.744, year: 2016

Thermal, spectral, magnetic and biological studies of thiosemicarbazones complexes with metal ions: Cu(II), Co(II), Ni(II), Fe(III), Zn(II), Mn(II) and UO2(VI)

International Nuclear Information System (INIS)

Mashaly, M.M.; Seleem, H.S.; El-Behairy, M.A.; Habib, H.A.

2004-01-01

Thiosemicarbazones ligands, isatin-3-thiosemicarbazone(HIT) and N-acetylisatin-3-thiosemicarbazone (HAIT), which have tridentate ONN coordinating sites were prepared. The complexes of both ligands with Cu(II), Co(II), Ni(II), Fe(III), Zn(II), Mn(II) and UO 2 (VI) ions were isolated. The ligands and their metal complexes were characterized by elemental analysis, IR, UV-Vis and mass spectra, also by conductance, magnetic moment and TG-DSC measurements. All the transition metal complexes have octahedral configurations, except Cu-complexes which have planar geometry and the UO 2 (VI) complexes which have coordination number 8 and may acquire the distorted dodecahedral geometry. Thermal studies explored the possibility of obtaining new complexes. Inversion from octahedral to square-planar configuration occurred upon heating the parent Ni-HIAT complex to form the corresponding pyrolytic product. The antifungal activity against the tested organisms showed that some metal complexes enhanced the activity with respect to the parent ligands. (author)

Size, density and composition of cell-mineral aggregates formed during anoxygenic phototrophic Fe(II) oxidation: Impact on modern and ancient environments

DEFF Research Database (Denmark)

Posth, Nicole R.; Huelin, Sonia; Konhauser, Kurt O.

2010-01-01

Cell-Fe(III) mineral aggregates produced by anoxygenic Fe(II)-oxidizing photoautotrophic microorganisms (photoferrotrophs) may be influential in the modern Fe cycle and were likely an integral part of ancient biogeochemical cycles on early Earth. While studies have focused on the environmental...... conditions under which modern photoferrotrophs grow and the kinetics, physiology and mechanism of Fe(II) oxidation, no systematic analyses of the physico-chemical characteristics of those aggregates, such as shape, size, density and chemical composition, have as yet been conducted. Herein, experimental...... results show most aggregates are bulbous or ragged in shape, with an average particle size of 10-40??m, and densities that typically range between 2.0 and 2.4g/cm 3; the cell fraction of the aggregates increased and their density decreased with initial Fe(II) concentration. The mineralogy of the ferric...

Fe(II)-substituted cobalt ferrite nanoparticles against multidrug resistant microorganisms

Science.gov (United States)

Žalnėravičius, Rokas; Paškevičius, Algimantas; Mažeika, Kęstutis; Jagminas, Arūnas

2018-03-01

The present study is focused on the determination the influence of cobalt content in the magnetic cobalt ferrite nanoparticles (Nps) on their antibacterial efficiency against gram-negative Escherichia coli and gram-positive Staphylococcus aureus bacteria and several Candida species, in particular C. parapsilosis and C. albicans. For the synthesis of Fe(II) substituted cobalt ferrite Nps by co-precipitation way, the L-lysine was used as the capping biocompatible agent and the particle size was successfully controlled to be in the range of 5-6.4 nm. The antimicrobial efficiencies of the CoxFe1-xFe2O4@Lys Nps, where x varies from 0.2 to 1.0, were evaluated through the quantitative analysis by comparing with that of Fe3O4@Lys Nps and L-lysine. In this way, it was evidenced that increase in the Co2+ content in the similar sized cobalt ferrite Nps resulted in an increase in their antimicrobial potency into 93.1-86.3 % for eukaryotic and into 96.4-42.7 % for prokaryotic strains. For characterization the composition, structure, and morphology of the tested herein Nps inductively coupled plasma optical emission spectrometry, X-ray diffraction, high-resolution transmission electron microscopy, Mössbauer, and FTIR spectroscopy techniques were conferred.

Reactivity of Nanoscale Zero-Valent Iron in Unbuffered Systems: Effect of pH and Fe(II) Dissolution.

Science.gov (United States)

Bae, Sungjun; Hanna, Khalil

2015-09-01

While most published studies used buffers to maintain the pH, there is limited knowledge regarding the reactivity of nanoscale zerovalent iron (NZVI) in poorly buffered pH systems to date. In this work, the effect of pH and Fe(II) dissolution on the reactivity of NZVI was investigated during the reduction of 4-nitrophenol (4-NP) in unbuffered pH systems. The reduction rate increased exponentially with respect to the NZVI concentration, and the ratio of dissolved Fe(II)/initial NZVI was related proportionally to the initial pH values, suggesting that lower pH (6-7) with low NZVI loading may slow the 4-NP reduction through acceleration of the dissolution of NZVI particles. Additional experiments using buffered pH systems confirmed that high pH values (8-9) can preserve the NZVI particles against dissolution, thereby enhancing the reduction kinetics of 4-NP. Furthermore, reduction tests using ferrous ion in suspensions of magnetite and maghemite showed that surface-bound Fe(II) on oxide coatings can play an important role in enhancing 4-NP reduction by NZVI at pH 8. These unexpected results highlight the importance of pH and Fe(II) dissolution when NZVI technology is applied to poorly buffered systems, particularly at a low amount of NZVI (i.e., <0.075 g/L).

Fe (III), Co(II), Ni(II), Cu(II) and Zn(II) complexes of schiff bases based-on glycine and phenylalanine: Synthesis, magnetic/thermal properties and antimicrobial activity

Science.gov (United States)

Sevgi, Fatih; Bagkesici, Ugur; Kursunlu, Ahmed Nuri; Guler, Ersin

2018-02-01

Zinc (II), copper (II), nickel (II), cobalt (II) and iron (III) complexes of Schiff bases (LG, LP) derived from 2-hydroxynaphthaldehyde with glycine and phenylalanine were reported and characterized by 1H NMR, 13C NMR, elemental analyses, melting point, FT-IR, magnetic susceptibility and thermal analyses (TGA). TGA data show that iron and cobalt include to the coordinated water and metal:ligand ratio is 1:2 while the complex stoichiometry for Ni (II), Cu (II) and Zn (II) complexes is 1:1. As expected, Ni (II) and Zn (II) complexes are diamagnetic; Cu (II), Co (II) and Fe (III) complexes are paramagnetic character due to a strong ligand of LG and LP. The LG, LP and their metal complexes were screened for their antimicrobial activities against five Gram-positive (Staphylococcus aureus, Methicillin resistant Staphylococcus aureus (MRSA), Bacillus cereus, Streptococcus mutans and Enterococcus faecalis) and three Gram-negative (Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa) and one fungi (Candida albicans) by using broth microdilution techniques. The activity data show that ligands and their metal complexes exhibited moderate to good activity against Gram-positive bacteria and fungi.

Indolenine meso-substituted dibenzotetraaza[14]annulene and its coordination chemistry toward the transition metal ions Mn(III), Fe(III), Co(II), Ni(II), Cu(II), and Pd(II).

Science.gov (United States)

Khaledi, Hamid; Olmstead, Marilyn M; Ali, Hapipah Mohd; Thomas, Noel F

2013-02-18

A new dibenzotetraaza[14]annulene bearing two 3,3-dimethylindolenine fragments at the meso positions (LH(2)), has been synthesized through a nontemplate method. X-ray crystallography shows that the whole molecule is planar. The basicity of the indolenine ring permits the macrocycle to be protonated external to the core and form LH(4)(2+)·2Cl(-). Yet another structural modification having strong C-H···π interactions was found in the chloroform solvate of LH(2). The latter two modifications are accompanied by a degree of nonplanar distortion. The antiaromatic core of the macrocycle can accommodate a number of metal ions, Mn(III), Fe(III), Co(II), Ni(II) and Cu(II), to form complexes of [Mn(L)Br], [Mn(L)Cl], [Fe(LH(2))Cl(2)](+)·Cl(-), [Co(L)], [Ni(L)], and [Cu(L)]. In addition, the reaction of LH(2) with the larger Pd(II) ion leads to the formation of [Pd(2)(LH(2))(2)(OAc)(4)] wherein the macrocycle acts as a semiflexible ditopic ligand to coordinate pairs of metal ions via its indolenine N atoms into dinuclear metallocycles. The compounds LH(2), [Co(L)], and [Ni(L)] are isostructural and feature close π-stacking as well as linear chain arrangements in the case of the metal complexes. Variable temperature magnetic susceptibility measurements showed thermally induced paramagnetism in [Ni(L)].

Biochemistry and Ecology of Novel Cytochromes Catalyzing Fe(II) Oxidation by an Acidophilic Microbial Community

Science.gov (United States)

Singer, S. W.; Jeans, C. J.; Thelen, M. P.; Verberkmoes, N. C.; Hettich, R. C.; Chan, C. S.; Banfield, J. F.

2007-12-01

An acidophilic microbial community found in the Richmond Mine at Iron Mountain, CA forms abundant biofilms in extremely acidic (pHindicated that several variants of Cyt579 were present in Leptospirillum strains. Intact protein MS analysis identified the dominant variants in each biofilm and documented multiple N-terminal cleavage sites for Cyt579. By combining biochemical, geochemical and microbiological data, we established that the sequence variation and N-terminal processing of Cyt579 are selected by ecological conditions. In addition to the soluble Cyt579, the second cytochrome appears as a much larger protein complex of ~210 kDa predominant in the biofilm membrane fraction, and has an alpha-band absorption at 572 nm. The 60 kDa cytochrome subunit, Cyt572, resides in the outer membrane of LeptoII, and readily oxidizes Fe(II) at low pH (0.95 - 3.0). Several genes encoding Cyt572 were localized within a recombination hotspot between two strains of LeptoII, causing a large range of variation in the sequences. Genomic sequencing and MS proteomic studies established that the variants were also selected by ecological conditions. A general mechanistic model for Fe(II) oxidation has been developed from these studies. Initial Fe(II) oxidation by Cyt572 occurs at the outer membrane. Cyt572 then transfers electrons to Cyt579, perhaps representing an initial step in energy flow to the biofilm community. Amino acid variations and post-translational modifications of these unique cytochromes may represent fine-tuning of function in response to local environmental conditions.

FeII induced mineralogical transformations of ferric oxyhydroxides into magnetite of variable stoichiometry and morphology

International Nuclear Information System (INIS)

Usman, M.; Abdelmoula, M.; Hanna, K.

2012-01-01

The Mössbauer spectroscopy was used to monitor the mineralogical transformations of ferrihydrite (F), lepidocrocite (L) and goethite (G) into magnetite as a function of aging time. Ferric oxyhydroxides were reacted with soluble Fe II and OH – in stoichiometric amounts to form magnetite at an initial pH of ∼9.7. Observed transformation extent into magnetite followed the order: F>L>G with almost 30% of untransformed G after 1 month. The departure from stoichiometry, δ, of magnetite (Fe 3−δ O 4 ) generated from F (δ∼0.04) and L (δ∼0.05) was relatively low as compared to that in magnetite from G (δ∼0.08). The analysis by transmission electron microscopy and BET revealed that generated magnetite was also different in terms of morphology, particle size and surface area depending on the nature of initial ferric oxyhydroxide. This method of preparation is a possible way to form nano-sized magnetite. - Graphical abstract: Mössbauer spectrum of the early stage of magnetite formation formed from the interaction of adsorbed Fe II species with goethite. Highlights: ► Ferric oxides were reacted with hydroxylated Fe II to form magnetite. ► Magnetite formation was quantified as a function of aging time. ► Complete transformation of ferrihydrite and lepidocrocite was achieved. ► Almost 70% of initial goethite was transformed. ► Resulting magnetites have differences in stoichiometry and morphological properties.

Fe(III) and Fe(II) ions different effects on Enterococcus hirae cell growth and membrane-associated ATPase activity

Energy Technology Data Exchange (ETDEWEB)

Vardanyan, Zaruhi [Department of Biophysics of the Biology Faculty, Yerevan State University, 1 A. Manoukian Str., 0025 Yerevan (Armenia); Trchounian, Armen, E-mail: trchounian@ysu.am [Department of Biophysics of the Biology Faculty, Yerevan State University, 1 A. Manoukian Str., 0025 Yerevan (Armenia)

2012-01-06

Highlights: Black-Right-Pointing-Pointer Fe{sup 3+} stimulates but Fe{sup 2+} suppresses Enterococcus hirae wild-type and atpD mutant growth. Black-Right-Pointing-Pointer Fe ions change oxidation-reduction potential drop during cell growth. Black-Right-Pointing-Pointer Fe{sup 3+} and Fe{sup 2+} have opposite effects on a membrane-associated ATPase activity. Black-Right-Pointing-Pointer These effects are either in the presence of F{sub 0}F{sub 1} inhibitor or non-functional F{sub 0}F{sub 1}. Black-Right-Pointing-Pointer Fe ions decrease protons and coupled potassium ions fluxes across the membrane. -- Abstract: Enterococcus hirae is able to grow under anaerobic conditions during glucose fermentation (pH 8.0) which is accompanied by acidification of the medium and drop in its oxidation-reduction potential (E{sub h}) from positive values to negative ones (down to {approx}-200 mV). In this study, iron (III) ions (Fe{sup 3+}) have been shown to affect bacterial growth in a concentration-dependent manner (within the range of 0.05-2 mM) by decreasing lag phase duration and increasing specific growth rate. While iron(II) ions (Fe{sup 2+}) had opposite effects which were reflected by suppressing bacterial growth. These ions also affected the changes in E{sub h} values during bacterial growth. It was revealed that ATPase activity with and without N,N Prime -dicyclohexylcarbodiimide (DCCD), an inhibitor of the F{sub 0}F{sub 1}-ATPase, increased in the presence of even low Fe{sup 3+} concentration (0.05 mM) but decreased in the presence of Fe{sup 2+}. It was established that Fe{sup 3+} and Fe{sup 2+} both significantly inhibited the proton-potassium exchange of bacteria, but stronger effects were in the case of Fe{sup 2+} with DCCD. Such results were observed with both wild-type ATCC9790 and atpD mutant (with defective F{sub 0}F{sub 1}) MS116 strains but they were different with Fe{sup 3+} and Fe{sup 2+}. It is suggested that the effects of Fe{sup 3+} might be due to

[Fe II] 1.64 μm FEATURES OF JETS AND OUTFLOWS FROM YOUNG STELLAR OBJECTS IN THE CARINA NEBULA

Energy Technology Data Exchange (ETDEWEB)

Shinn, Jong-Ho; Lee, Jae-Joon; Chun, Moo-Young; Lyo, A.-Ran; Moon, Dae-Sik; Kyeong, Jaemann; Park, Byeong-Gon [Korea Astronomy and Space Science Institute, 776 Daeduk-daero, Yuseong-gu, Daejeon 305-348 (Korea, Republic of); Pyo, Tae-Soo [Subaru Telescope, National Astronomical Observatory of Japan, 650 North A' ohōkū Place, Hilo, HI 96720 (United States); Lee, Ho-Gyu [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Kim, Hyun-Jeong; Koo, Bon-Chul; Lee, Yong-Hyun [Department of Physics and Astronomy, Seoul National University, 599 Gwanangno, Gwanak-gu, Seoul 151-747 (Korea, Republic of); Sung, Hwankyung; Hur, Hyeonoh, E-mail: jhshinn@kasi.re.kr [Department of Astronomy and Space Science, Sejong University, 98 Kunja-dong, Kwangjin-gu, Seoul 143-747 (Korea, Republic of)

2013-11-01

We present [Fe II] 1.64 μm imaging observations for jets and outflows from young stellar objects (YSOs) over the northern part (∼24' × 45') of the Carina Nebula, a massive star-forming region. The observations were performed with IRIS2 of the Anglo-Australian Telescope and the seeing was ∼1.''5 ± 0.''5. Eleven jet and outflow features are detected at eight different regions and are termed ionized Fe objects (IFOs). One Herbig-Haro candidate that was missed in Hubble Space Telescope Hα observations is newly identified as HHc-16, referring to our [Fe II] images. IFOs have knotty or longish shapes, and the detection rate of IFOs against previously identified YSOs is 1.4%, which should be treated as a lower limit. Four IFOs show anti-correlated peak intensities in [Fe II] and Hα, where the ratio I([Fe II])/I(Hα) is higher for longish IFOs than for knotty IFOs. We estimate the outflow mass loss rate from the [Fe II] flux using two different methods. The jet-driving objects are identified for three IFOs (IFO-2, -4, and -7) for which we study the relations between the outflow mass loss rate and the YSO physical parameters from the radiative transfer model fitting. The ratios of the outflow mass loss rate over the disk accretion rate for IFO-4 and -7 are consistent with the previously reported values (10{sup –2}-10{sup +1}), while the ratio is higher for IFO-2. This excess may result from underestimating the disk accretion rate. The jet-driving objects are likely to be low- or intermediate-mass stars. Other YSO physical parameters, such as luminosity and age, show reasonable relations or trends.

Highly sensitive amperometric sensor for micromolar detection of trichloroacetic acid based on multiwalled carbon nanotubes and Fe(II)–phtalocyanine modified glassy carbon electrode

International Nuclear Information System (INIS)

Kurd, Masoumeh; Salimi, Abdollah; Hallaj, Rahman

2013-01-01

A highly sensitive electrochemical sensor for the detection of trichloroacetic acid (TCA) is developed by subsequent immobilization of phthalocyanine (Pc) and Fe(II) onto multiwalled carbon nanotubes (MWCNTs) modified glassy carbon (GC) electrode. The GC/MWCNTs/Pc/Fe(II) electrode showed a pair of well-defined and nearly reversible redox couple correspondent to (Fe(III)Pc/Fe(II)Pc) with surface-confined characteristics. The surface coverage (Γ) and heterogeneous electron transfer rate constant (k s ) of immobilized Fe(II)–Pc were calculated as 1.26 × 10 −10 mol cm −2 and 28.13 s −1 , respectively. Excellent electrocatalytic activity of the proposed GC/MWCNTs/Pc/Fe(II) system toward TCA reduction has been indicated and the three consequent irreversible peaks for electroreduction of CCl 3 COOH to CH 3 COOH have been clearly seen. The observed chronoamperometric currents are linearly increased with the concentration of TCA at concentration range up to 20 mM. Detection limit and sensitivity of the modified electrode were 2.0 μM and 0.10 μA μM −1 cm −2 , respectively. The applicability of the sensor for TCA detection in real samples was tested. The obtained results suggest that the proposed system can serve as a promising electrochemical platform for TCA detection. Highlights: ► Phthalocyanine (PC) and Fe(II) immobilized onto MWCNTs modified GC electrode. ► A pair of well-defined redox couple correspondent to (Fe(III)Pc/Fe(II)Pc) observed. ► Modified electrode shows excellent catalytic activity to electroreduction of CCl 3 COOH. ► Amperometry and cyclic voltammetry techniques were used for detection of CCl 3 COOH. ► Detection limit and sensitivity were 2.0 μM and 0.10 μA μM −1 cm −2 , respectively

Heterogeneous Photodecolorization of Methyl Green Catalyzed by Fe(II-o-Phenanthroline/Zeolite Y Nanocluster

Directory of Open Access Journals (Sweden)

Alireza Nezamzadeh-Ejhieh

2011-01-01

Full Text Available The potential of Fe(II-orthophenatrolin, as doped with synthetic zeolite Y nanocluster (Na-Y via complexation process, after wet impregnation of parent zeolite with FeSO4 aqueous solution, was studied as a photocatalyst in decolorization of Methyl Green (MG under UV irradiation. The characterization of the synthesized zeolite nanocluster and the prepared catalyst was studied using X-ray powder diffraction (XRD, infrared spectroscopy (FT-IR, thermal analysis, and SEM methods. The dye photodecolorization process was studied considering the influence of experimental parameters and it was observed that photoreactivity of the photocatalyst was varied with catalyst amount, initial dye concentration, pH of dye solution, temperature, and the presence of KBrO3. The optimal experimental parameters were obtained as follows: catalyst amount: 1 gL−1, dye concentration: 40 ppm, pH: 9, and active component value: 100 mg Fe(II-orthophenatrolin per g catalyst. The reusability of the intended catalyst was also investigated. The degradation process obeyed first-order kinetics.

Nanosized yolk–shell Fe{sub 3}O{sub 4}@Zr(OH){sub x} spheres for efficient removal of Pb(II) from aqueous solution

Energy Technology Data Exchange (ETDEWEB)

Pan, Shunlong [Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Li, Jiansheng, E-mail: lijsh@mail.njust.edu.cn [Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Wan, Gaojie; Liu, Chao [Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Fan, Wenhong, E-mail: fanwh@buaa.edu.cn [Department of Environmental Science and Engineering, School of Chemistry and Environment, Beihang University, Beijing 100191 (China); Wang, Lianjun, E-mail: wanglj@mail.njust.edu.cn [Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China)

2016-05-15

Highlights: • Well dispersed and easy separated nanoadsorbents with stable chemical property are highly desired. • Fe{sub 3}O{sub 4}@Zr(OH){sub x} yolk–shell nanospheres (YSNs) nanoadsorbents were prepared. • Enhanced Pb(II) adsorption capacity of 310.8 mg/g was achieved on Fe{sub 3}O{sub 4}@Zr(OH){sub x} YSNs based on Zr weight. • The cavities in Fe{sub 3}O{sub 4}@Zr(OH){sub x} YSNs is responsible for the improved performance. - Abstract: In this work, Fe{sub 3}O{sub 4}@Zr(OH){sub x} yolk–shell nanospheres (YSNs) were synthesized via a two-step process and further examined as adsorbents for the removal of Pb(II). To understand the hollow structure on the adsorption properties of Pb(II), another adsorbent without hollow cavities, i.e., Fe{sub 3}O{sub 4}@SiO{sub 2}@Zr(OH){sub x} core–shell nanospheres (CSNs), was also prepared for comparison. The adsorption results showed that Fe{sub 3}O{sub 4}@Zr(OH){sub x} YSNs exhibited 41.6% higher Pb(II) adsorption capacity as compared to that of Fe{sub 3}O{sub 4}@SiO{sub 2}@Zr(OH){sub x} CSNs. The isotherm was well fitted to Langmuir adsorption model with q{sub max} value of 310.8 mg/g after normalized by the weight of Zr in Fe{sub 3}O{sub 4}@Zr(OH){sub x} YSNs. Scanning transmission electron microscopy (STEM) mapping results revealed that the existence of cavities between Fe{sub 3}O{sub 4} cores and Zr(OH){sub x} shells is responsible for the improved adsorption performance. XPS analysis indicated the surface hydroxyl groups played a key role in the Pb(II) adsorption. The removal efficiency of Pb(II) was maintained above 90% in five consecutive adsorption–desorption cycles.

Optimized Gen-II FeCrAl cladding production in large quantity for campaign testing

Energy Technology Data Exchange (ETDEWEB)

Yamamoto, Yukinori [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Sun, Zhiqian [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Pint, Bruce A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Terrani, Kurt A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2016-06-03

There are two major objectives in this report; (1) to optimize microstructure control of ATF FeCrAl alloys during tube drawing processes, and (2) to provide an update on the progress of ATF FeCrAl tube production via commercial manufacturers. Experimental efforts have been made to optimize the process parameters balancing the tube fabricability, especially for tube drawing processes, and microstructure control of the final tube products. Lab-scale sheet materials of Gen II FeCrAl alloys (Mo-containing and Nb-containing FeCrAl alloys) were used in the study, combined with a stepwise warm-rolling process and intermediate annealing, aiming to simulate the tube drawing process in a commercial tube manufacturer. The intermediate annealing at 650ºC for 1h was suggested for the tube-drawing process of Mo-containing FeCrAl alloys because it successfully softened the material by recovering the work hardening introduced through the rolling step, without inducing grain coarsening due to recrystallization. The final tube product is expected to have stabilized deformed microstructure providing the improved tensile properties with sufficient ductility. Optimization efforts on Nb-containing FeCrAl alloys focused on the effect of alloying additions and annealing conditions on the stability of deformed microstructure. Relationships between the second-phase precipitates (Fe₂Nb-Laves phase) and microstructure stability are discussed. FeCrAl tube production through commercial tube manufacturers is currently in progress. Three different manufacturers, Century Tubes, Inc. (CTI), Rhenium Alloys, Inc. (RAI), and Superior Tube Company, Inc. (STC), are providing capabilities for cold-drawing, warm-drawing, and HPTR cold-pilgering, respectively. The first two companies are currently working on large quantity tube production (expected 250 ft length) of Gen I model FeCrAl alloy (B136Y3, at CTI) and Gen II (C35M4, at RAI), with the process parameters obtained from the experimental

Analysis of a 4f-5g supermultiplet of Fe II around 1 μm

International Nuclear Information System (INIS)

Rosberg, M.; Johansson, S.

1992-01-01

The Fourier-transform spectrum from an iron-neon hollow-cathode lamp has been studied in the region 9000-11000A. The 3d 6 ( 5 D)5g subconfiguration of Fe II has been established by means of about 220 newly identified 4f-5g transitions. The 5g configuration is well represented by JK coupling, which is demonstrated by the application of the quadrupolic approximation. A consistent pattern in the FWHM for various types of Fe II transitions has been observed. Calculated oscillator strengths are given for all observed lines and their relative accuracy is estimated from observed intensities. The new data offer unprecedented tools for diagnostics of stellar atmospheres. (orig.)

Estudio de reacciones de oxidación catalizadas por complejos biomiméticos de Fe (II), Fe (III) y Mn (III)

OpenAIRE

Clemente Tejeda, David

2015-01-01

[ES]Se ha desarrollado una metodología económicamente asequible y medioambientalmente sostenible para la oxidación catalítica de sustratos orgánicos con interés preparativo, utilizando para ello sistemas biomiméticos de Fe(II), Fe(III) y Mn(III). En primer lugar se ha llevado a cabo la síntesis de los complejos metálicos catalizadores, optimizando los procedimientos descritos en la bibliografía precedente. Asimismo se ha llevado a cabo un análisis exhaustivo de todas las variables implicadas ...

Monitoring, field experiments, and geochemical modeling of Fe(II) oxidation kinetics in a stream dominated by net-alkaline coal-mine drainage, Pennsylvania, USA

Science.gov (United States)

Cravotta,, Charles A.

2015-01-01

Watershed-scale monitoring, field aeration experiments, and geochemical equilibrium and kinetic modeling were conducted to evaluate interdependent changes in pH, dissolved CO2, O2, and Fe(II) concentrations that typically take place downstream of net-alkaline, circumneutral coal-mine drainage (CMD) outfalls and during aerobic treatment of such CMD. The kinetic modeling approach, using PHREEQC, accurately simulates observed variations in pH, Fe(II) oxidation, alkalinity consumption, and associated dissolved gas concentrations during transport downstream of the CMD outfalls (natural attenuation) and during 6-h batch aeration tests on the CMD using bubble diffusers (enhanced attenuation). The batch aeration experiments demonstrated that aeration promoted CO2 outgassing, thereby increasing pH and the rate of Fe(II) oxidation. The rate of Fe(II) oxidation was accurately estimated by the abiotic homogeneous oxidation rate law −d[Fe(II)]/dt = k1·[O2]·[H+]−2·[Fe(II)] that indicates an increase in pH by 1 unit at pH 5–8 and at constant dissolved O2 (DO) concentration results in a 100-fold increase in the rate of Fe(II) oxidation. Adjusting for sample temperature, a narrow range of values for the apparent homogeneous Fe(II) oxidation rate constant (k1′) of 0.5–1.7 times the reference value of k1 = 3 × 10−12 mol/L/min (for pH 5–8 and 20 °C), reported by Stumm and Morgan (1996), was indicated by the calibrated models for the 5-km stream reach below the CMD outfalls and the aerated CMD. The rates of CO2 outgassing and O2ingassing in the model were estimated with first-order asymptotic functions, whereby the driving force is the gradient of the dissolved gas concentration relative to equilibrium with the ambient atmosphere. Although the progressive increase in DO concentration to saturation could be accurately modeled as a kinetic function for the conditions evaluated, the simulation of DO as an instantaneous equilibrium process did not affect the

The value of multivariate model sophistication

DEFF Research Database (Denmark)

Rombouts, Jeroen; Stentoft, Lars; Violante, Francesco

2014-01-01

We assess the predictive accuracies of a large number of multivariate volatility models in terms of pricing options on the Dow Jones Industrial Average. We measure the value of model sophistication in terms of dollar losses by considering a set of 444 multivariate models that differ in their spec....... In addition to investigating the value of model sophistication in terms of dollar losses directly, we also use the model confidence set approach to statistically infer the set of models that delivers the best pricing performances.......We assess the predictive accuracies of a large number of multivariate volatility models in terms of pricing options on the Dow Jones Industrial Average. We measure the value of model sophistication in terms of dollar losses by considering a set of 444 multivariate models that differ...

Fe(II) and Co (II) complexes of (4-(4-bromophenyl)-[2,2'-bipyridine]-6-carboxylic acid) synthesis, characterization and electrochromic studies

International Nuclear Information System (INIS)

Saba, A.; Maqsood, Z.T.; Wasim, A.A.; Basha, F.Z.

2017-01-01

In this study novel complexes of substituted bipyridine (4-(4-bromophenyl)-[2,2'-bipyridine]-6-carboxylic acid) with Fe/sup +2/ and Co/sup +2/ were synthesized and characterized by different physical, analytical and spectral techniques which includes /sup 1/ H-NMR, MALDI-MS, FTIR, UV-VIS Spectrophotometry, CHN analysis and conductometry. Mole ratio method revealed that both complexes satisfied ML2 stoichiometry. Other characterization studies showed that substituted bipyridine acted as a tridentate ligand, with two pyridine N and one carboxylic O atom as binding sites per ligand molecule. The complexes were found octahedral, neutral and possessed fairly high molar absorptivities in visible region. Electrochromic studies revealed that Fe (II) complex had relatively good electrochromic properties with a reversible color change from blue to pale yellow. Co (II) complex, however, did not show significant electrochromic properties in the visible region. (author)

Study of the interference of uranium, vanadium, aluminium and molebdenum in the determination of FeII, FeIII in Syrian phosphoric acid by spectrophotometry

International Nuclear Information System (INIS)

Zaizafoun, Ghadir; Elian, Nazha

1991-04-01

The spectrophotometric determination of the ratio of iron I I to iron I II in crude phosphoric acid is of great importance because of its influence on the redox potential in the different stages which lead to the extraction of uranium from crude phosphoric acid. The suitability of a number of reagents for this determination was examined and only 1,10-phenanthroline, 5-sulfosalicylic acid and 2,2'-bipyridine were selected for further experimentation. 1-10-phenanthroline can give a deep red complex with Fe I I, in phosphoric acid medium at PH 4-6, absorbs at λ = 510 nm. The total iron was determined by reducing Fe I II to Fe I I using hydroxylamine hydrochloride. The second reagent was found capable of forming a yellow complex absorbs light at λ = 430 nm in amonia medium at PH 8.5 - 11 with Fe I II. The adopted procedure was to determine total iron first by oxidation with nitric acid. Then iron I I was determined in a second test at PH 1.5 and at λ = 500 nm. The third reagent i.e. 2-2' bipyridine is capable of forming a red complex with iron I I absorbs at λ = 522 nm. The interference of U, V, Al, and Mo was investigated. These elements were selected because of their presence in considerable amounts in Syrian commercial phosphoric acid. The work was designed so that the effect of the presence of each element as well as the presence of all possible combinations of these elements can be estimated. The investigation revealed that the interference is very high in the case of 2-2' bipyridine in addition to the instability of the complex. In the case of 1,10-phenanthroline the interference was also found high. Thus these two reagents were disregarded. The 5-sulfosalicylic reagent was found satisfactory when determining iron I II, However when Fe I I is considered the error resulting from interference ranges between 17.5 - 50%. This error was found very dependent on the PH of the medium and further work is in progress in order to lower the value of interferences

Immobilization of 99-Technetium (VII) by Fe(II)-Goethite and Limited Reoxidation

International Nuclear Information System (INIS)

Um, Wooyong; Chang, Hyun-Shik; Icenhower, Jonathan P.; Lukens, Wayne W.; Serne, R. Jeffrey; Qafoku, Nikolla; Westsik, Joseph H.; Buck, Edgar C.; Smith, Steven C.

2011-01-01

Synthesized goethite was successfully used with addition of Fe(II) to sequester Tc present in both deionized water and simulated off-gas scrubber waste solutions. Pertechnetate concentration in solution decreased immediately when the pH was raised above 7 by addition of sodium hydroxide. Removal of Tc(VII) from solution occurred most likely as a result of heterogeneous surface-catalyzed reduction to Tc(IV) and subsequent co-precipitation onto the goethite. The final Tc-bearing solid was identified as goethite-dominated Fe(III)-(oxy)hydroxide based on XRD analysis, confirming the widespread observation of its characteristic acicular habit by TEM/SEM images. Analysis of the solid precipitate by XAFS showed that the dominant oxidation state of Tc was Tc(IV) and was in octahedral coordination with Tc-O, Fe-O, and Tc-Fe bond distances that are consistent with direct substitution of Tc for Fe in the goethite structure. In some experiments the final Tc-goethite product was subsequently armored with additional layers of freshly precipitated goethite. Successful incorporation of Tc(IV) within the goethite mineral lattice and subsequent goethite armoring can limit re-oxidation of Tc(IV) and its subsequent release from Tc-goethite waste forms, even when the final product is placed in oxidizing environments that typify shallow waste burial facilities.

Highly sensitive amperometric sensor for micromolar detection of trichloroacetic acid based on multiwalled carbon nanotubes and Fe(II)–phtalocyanine modified glassy carbon electrode

Energy Technology Data Exchange (ETDEWEB)

Kurd, Masoumeh [Department of Chemistry, University of Kurdistan, P. O. Box 416, Sanandaj (Iran, Islamic Republic of); Salimi, Abdollah, E-mail: absalimi@uok.ac.ir [Department of Chemistry, University of Kurdistan, P. O. Box 416, Sanandaj (Iran, Islamic Republic of); Research Center for Nanotechnology, University of Kurdistan, P. O. Box 416, Sanandaj (Iran, Islamic Republic of); Hallaj, Rahman [Department of Chemistry, University of Kurdistan, P. O. Box 416, Sanandaj (Iran, Islamic Republic of)

2013-04-01

A highly sensitive electrochemical sensor for the detection of trichloroacetic acid (TCA) is developed by subsequent immobilization of phthalocyanine (Pc) and Fe(II) onto multiwalled carbon nanotubes (MWCNTs) modified glassy carbon (GC) electrode. The GC/MWCNTs/Pc/Fe(II) electrode showed a pair of well-defined and nearly reversible redox couple correspondent to (Fe(III)Pc/Fe(II)Pc) with surface-confined characteristics. The surface coverage (Γ) and heterogeneous electron transfer rate constant (k{sub s}) of immobilized Fe(II)–Pc were calculated as 1.26 × 10{sup −10} mol cm{sup −2} and 28.13 s{sup −1}, respectively. Excellent electrocatalytic activity of the proposed GC/MWCNTs/Pc/Fe(II) system toward TCA reduction has been indicated and the three consequent irreversible peaks for electroreduction of CCl{sub 3}COOH to CH{sub 3}COOH have been clearly seen. The observed chronoamperometric currents are linearly increased with the concentration of TCA at concentration range up to 20 mM. Detection limit and sensitivity of the modified electrode were 2.0 μM and 0.10 μA μM{sup −1} cm{sup −2}, respectively. The applicability of the sensor for TCA detection in real samples was tested. The obtained results suggest that the proposed system can serve as a promising electrochemical platform for TCA detection. Highlights: ► Phthalocyanine (PC) and Fe(II) immobilized onto MWCNTs modified GC electrode. ► A pair of well-defined redox couple correspondent to (Fe(III)Pc/Fe(II)Pc) observed. ► Modified electrode shows excellent catalytic activity to electroreduction of CCl{sub 3}COOH. ► Amperometry and cyclic voltammetry techniques were used for detection of CCl{sub 3}COOH. ► Detection limit and sensitivity were 2.0 μM and 0.10 μA μM{sup −1} cm{sup −2}, respectively.

Remediation of Soil and Ground Water Contaminated with PAH using Heat and Fe(II)-EDTA Catalyzed Persulfate Oxidation

International Nuclear Information System (INIS)

Nadim, Farhad; Huang, Kun-Chang; Dahmani, Amine M.

2006-01-01

The feasibility of degrading 16 USEPA priority polycyclic aromatic (PAH) hydrocarbons (PAHs) with heat and Fe(II)-EDTA catalyzed persulfate oxidation was investigated in the laboratory. The experiments were conducted to determine the effects of temperature (i.e. 20 deg. C, 30 deg. C and 40 deg. C) and iron-chelate levels (i.e., 250 mg/L-, 375 mg/L- and 500 mg/L-Fe(II)) on the degradation of dissolved PAHs in aqueous systems, using a series of amber glass jars as the reactors that were placed on a shaker inside an incubator for temperature control. Each experiment was run in duplicate and had two controls (i.e., no persulfate in systems). Samples were collected after a reaction period of 144 hrs and measured for PAHs, pH and sodium persulfate levels. The extent of degradation of PAHs was determined by comparing the data for samples with the controls.The experimental results showed that persulfate oxidation under each of the tested conditions effectively degraded the 16 target PAHs. All of the targeted PAHs were degraded to below the instrument detection limits (∼4 μ/L) from a range of initial concentration (i.e., 5 μ/L for benzo(a)pyrene to 57 μ/L for Phenanthrene) within 144 hrs with 5 g/L of sodium persulfate at 20 deg. C, 30 deg. C and 40 deg. C. The data indicated that the persulfate oxidation was effective in degrading the PAHs and that external heat and iron catalysts might not be needed for the degradation of PAHs.The Fe(II)-EDTA catalyzed persulfate also effectively degraded PAHs in the study. In addition, the data on the variation of persulfate concentrations during the experiments indicated that Fe(II)-EDTA accelerated the consumption of persulfate ions.The obtained degradation data cannot be used to evaluate the influence of temperature and Fe(II) levels on the PAH degradation because the PAHs under each of the tested conditions were degraded to below the instrument detection limit within the first sampling point. However, these experiments have

Effects of citrate on hexavalent chromium reduction by structural Fe(II) in nontronite

Energy Technology Data Exchange (ETDEWEB)

Liu, Xiaolei; Dong, Hailiang; Yang, Xuewei; Kovarik, Libor; Chen, Yu; Zeng, Qiang

2018-02-01

Iron-bearing clay minerals and organic matter are two important components in natural environments that influence hexavalent chromium (Cr(VI)) reduction. Previous studies have shown that organic ligands could influence Cr(VI) reduction by aqueous Fe2+ and pyrite. However, the effects of organic ligands on Cr(VI) reduction by structural Fe(II) in clays are not well understood. In this study, the effects of citrate on Cr(VI) reduction by nontronite (NAu-2) were investigated under near neutral pH condition (pH=6). Our results showed that the presence of citrate decreased the rate but increased the amount of Cr(VI) reduction by structural Fe(II) in NAu-2. The decreased reaction rate was likely due to competitive sorption of citrate and polyanionic dichromate (Cr2O7- ), because sorption of dichromate appeared to be the first step for subsequent Cr(VI) reduction. The increased amount of Cr(VI) reduction in the presence of citrate was likely because citrate provided additional reducing power through ligand-metal electron transfer in the presence of soluble Fe 3+ derived from dissolution of reduced NAu-2. Soluble Cr(III)-citrate complex was the possible form of reduced chromium when citrate was present. In contrast, nanometer-sized Cr2O3 particles were the product of Cr(VI) reduction by reduced NAu-2 without citrate. Our study highlights the importance of organic ligands on Cr(VI) reduction and immobilization when iron-bearing clay minerals are applied to treat Cr(VI) contaminant in organic matter rich environments.

Immobilization and Limited Reoxidation of Technetium-99 by Fe(II)-Goethite

International Nuclear Information System (INIS)

Um, Wooyong; Chang, Hyun-shik; Icenhower, Jonathan P.; Qafoku, Nikolla; Smith, Steven C.; Serne, R. Jeffrey; Buck, Edgar C.; Kukkadapu, Ravi K.; Bowden, Mark E.; Westsik, Joseph H.; Lukens, Wayne W.

2010-01-01

This report summarizes the methodology used to test the sequestration of technetium-99 present in both deionized water and simulated Hanford Tank Waste Treatment and Immobilization Plant waste solutions. Synthesized goethite, α-FeOOH, was successfully used with the addition of aqueous Fe(II) to sequester technetium (Tc) present in both deionized water and waste solutions simulated to represent tank waste solutions derived from low-activity-waste glass melter off-gas scrubbers used at the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Perrhenate, Re(VII), was also tested as a nonradiological surrogate of pertechnetate (Tc(VII)). In a slurry of goethite and dissolved Fe(II), Tc(VII) concentrations in solution decreased immediately when the slurry pH was raised above 7.0 by adding sodium hydroxide (NaOH). The total amount of Tc present in the final solid as determined by acid digestion showed a high degree of Tc sequestration, 90% to 100%, in the final Tc-goethite solids. In contrast, a relatively small percentage (0% to 43%) of Re removal was found even though the Re-goethite solid was prepared by the same method as the Tc-goethite. The difference in sequestration is caused by the different Re solubility and redox potential vs pH. Removal of Tc(VII) from solution occurred most likely as a result of heterogeneous surface-catalyzed reduction to Tc(IV) and subsequent co-precipitation with newly formed magnetite or goethite during the Fe(II) treatment and pH adjustment. One of the final Tc-goethite products, Sample 2-5, was subsequently armored through a mineral transformation process that involved adding additional Fe(III) and NaOH to isolate the reduced Tc(IV) from future oxidizing agents. Although the dominant major mineral in Tc-goethite samples prepared without armoring was magnetite, the final Tc-bearing solid in Tc-goethite samples prepared with the additional armoring process was identified as goethite-dominated Fe(III)-(oxy)hydroxide based on x

Accumulation of Fe oxyhydroxides in the Peruvian oxygen deficient zone implies non-oxygen dependent Fe oxidation

Science.gov (United States)

Heller, Maija I.; Lam, Phoebe J.; Moffett, James W.; Till, Claire P.; Lee, Jong-Mi; Toner, Brandy M.; Marcus, Matthew A.

2017-08-01

Oxygen minimum zones (OMZs) have been proposed to be an important source of dissolved iron (Fe) into the interior ocean. However, previous studies in OMZs have shown a sharp decrease in total dissolved Fe (dFe) and/or dissolved Fe(II) (dFe(II)) concentrations at the shelf-break, despite constant temperature, salinity and continued lack of oxygen across the shelf-break. The loss of both total dFe and dFe(II) suggests a conversion of the dFe to particulate form, but studies that have coupled the reduction-oxidation (redox) speciation of both dissolved and particulate phases have not previously been done. Here we have measured the redox speciation and concentrations of both dissolved and particulate forms of Fe in samples collected during the U.S. GEOTRACES Eastern tropical Pacific Zonal Transect (EPZT) cruise in 2013 (GP16). This complete data set allows us to assess possible mechanisms for loss of dFe. We observed an offshore loss of dFe(II) within the oxygen deficient zone (ODZ), where dissolved oxygen is undetectable, accompanied by an increase in total particulate Fe (pFe). Total pFe concentrations were highest in the upper ODZ. X-ray absorption spectroscopy revealed that the pFe maximum was primarily in the Fe(III) form as Fe(III) oxyhydroxides. The remarkable similarity in the distributions of total particulate iron and nitrite suggests a role for nitrite in the oxidation of dFe(II) to pFe(III). We present a conceptual model for the rapid redox cycling of Fe that occurs in ODZs, despite the absence of oxygen.

Na7 [Fe2S6 ] , Na2 [FeS2 ] and Na2 [FeSe2 ] : New 'reduced' sodium chalcogenido ferrates

Science.gov (United States)

Stüble, Pirmin; Peschke, Simon; Johrendt, Dirk; Röhr, Caroline

2018-02-01

Three new 'reduced' FeII containing sodium chalcogenido ferrates were obtained applying a reductive synthetic route. The mixed-valent sulfido ferrate Na7 [Fe2S6 ] , which forms bar-shaped crystals with metallic greenish luster, was synthesized in pure phase from natural pyrite and elemental sodium at a maximum temperature of 800 °C. Its centrosymmetric triclinic structure (SG P 1 bar , a = 764.15(2), b = 1153.70(2), c = 1272.58(3) pm, α = 62.3325 (7) , β = 72.8345 (8) , γ = 84.6394 (8) ° , Z = 3, R1 = 0.0185) exhibits two crystallographically different [Fe2S6 ] 7 - dimers of edge-sharing [FeS4 ] tetrahedra, with somewhat larger Fe-S distances than in the fully oxidized FeIII dimers of e.g. Na6 [Fe2III S6 ] . In contrast to the localized AFM ordered pure di-ferrates(III), the Curie-Weiss behavior of the magnetic susceptibility proves the rarely observed valence-delocalized S = 9/2 state of the mixed-valent FeIII /FeII dimer. The nearly spin-only value of the magnetic moment combined with the chemical bonding not generally differing from that in pure ferrates(II) and (III), provides a striking argument, that the reduction of the local Fe spin moments observed in all condensed sulfido ferrate moieties is connected with the AFM spin ordering. The two isotypic ferrates(II) Na2 [FeS2 ] and Na2 [FeSe2 ] with chain-like structural units (SG Ibam, a = 643.54(8)/ 660.81(1), b = 1140.2(2)/1190.30(2) c = 562.90(6)/585.59(1) pm, Z = 4, R1 = 0.0372/0.0466) crystallize in the K2 [ZnO2 ] -type structure. Although representing merely further members of the common series of chalcogenido metallates(II) Na2 [MIIQ2 ] , these two new phases, together with Na6 [FeS4 ] and Li2 [FeS2 ] , are the only examples of pure FeII alkali chalcogenido ferrates. The new compounds allow for a general comparison of di- and chain ferrates(II) and (III) and mixed-valent analogs concerning the electronic and magnetic properties (including Heisenberg super-exchange and double-exchange interactions

Charge transport in micas: The kinetics of FeII/III electron transfer in the octahedral sheet

International Nuclear Information System (INIS)

Rosso, Kevin M.; Ilton, Eugene S.

2003-01-01

The two principal FeII/III electron exchange reactions underlying charge transport in the octahedral sheet of ideal end-member annite were modeled using a combination of ab initio calculations and Marcus electron transfer theory. A small polaron model was applied which yielded electron hopping activation energies that agree well with the limited available experimental data. A small ab initio cluster model successfully reproduced several important structural, energetic, and magnetic characteristics of the M1 and M2 Fe sites in the annite octahedral sheet. The cluster enabled calculation of the internal reorganization energy and electronic coupling matrix elements for the M2-M2 and M1-M2 electron transfer reactions. The M2-M2 electron transfer is symmetric with a predicted forward/reverse electron hopping rate of 106 s-1. The M1-M2 electron transfers are asymmetric due to the higher ionization potential by 0.46 eV of FeII in the M1 site. The electronic coupling matrix elements for these reactions are predicted to be small and of similar magnitude, suggesting the possibility that the coupling is essentially direction independent amongst hopping directions in the octahedral sheet. M1 Fe sites are predicted to be efficient electron traps and charge transport should occur by nearest-neighbor electron hops along the M2 Fe sublattice

The reaction of hydrogen peroxide with Fe(II) ions at elevated temperatures

DEFF Research Database (Denmark)

Christensen, H.; Sehested, K.; Løgager, T.

1993-01-01

The rate constant for the reaction between Fe(II) ions and H2O2 has been determined at pH 0.4-2 as a function of temperature in the range 5-300-degrees-C. H2O2 was produced by irradiating the aqueous solution with a pulse of electrons. The rate constants at 20 and 300-degrees-C were determined...

Investigating the effect of ascorbate on the Fe(II)-catalyzed transformation of the poorly crystalline iron mineral ferrihydrite.

Science.gov (United States)

Xiao, Wei; Jones, Adele M; Collins, Richard N; Waite, T David

2018-05-09

The inorganic core of the iron storage protein, ferritin, is recognized as being analogous to the poorly crystalline iron mineral, ferrihydrite (Fh). Fh is also abundant in soils where it is central to the redox cycling of particular soil contaminants and trace elements. In geochemical circles, it is recognized that Fh can undergo Fe(II)-catalyzed transformation to form more crystalline iron minerals, vastly altering the reactivity of the iron oxide and, in some cases, the redox poise of the system. Of relevance to both geochemical and biological systems, we investigate here if the naturally occurring reducing agent, ascorbate, can effect such an Fe(II)-catalyzed transformation of Fh at 25 °C and circumneutral pH. The transformation of ferrihydrite to possible secondary Fe(III) mineralization products was quantified using Fourier transform infrared (FTIR) spectroscopy, with supporting data obtained using X-ray absorbance spectroscopy (XAS) and X-ray diffraction (XRD). Whilst the amount of Fe(II) formed in the presence of ascorbate has resulted in Fh transformation in previous studies, no transformation of Fh to more crystalline Fe(III) (oxyhydr)oxides was observed in this study. Further experiments indicated this was due to the ability of ascorbate to inhibit the formation of goethite, lepidocrocite and magnetite. The manner in which ascorbate associated with Fh was investigated using FTIR and total organic carbon (TOC) analysis. The majority of ascorbate was found to adsorb to the Fh surface under anoxic conditions but, under oxic conditions, ascorbate was initially adsorbed then became incorporated within the Fe(III) (oxyhydr)oxide structure (i.e., co-precipitated) over time. Copyright © 2018 Elsevier B.V. All rights reserved.

Formation and stability of Fe-rich precipitates in dilute Zr(Fe) single-crystal alloys

International Nuclear Information System (INIS)

Zou, H.; Hood, G.M.; Roy, J.A.; Schultz, R.J.

1993-02-01

The formation and stability of Fe-rich precipitates in two α-Zr(Fe) single-crystal alloys with nominal compositions (I, 50 ppma Fe, and II, 650 ppma Fe) have been investigated (the maximum solid solubility of Fe in α-Zr is 180 ppma - 800 C). Optical microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been used to examine the characteristics of Fe-rich precipitates. SEM and TEM micrographs show that in as-grown alloy II, Zr 2 Fe precipitates are located at 'stringers'. Precipitates were not observed in as-grown alloy I. During annealing, below the solvus, Fe diffuses to the surfaces to form Zr 3 Fe precipitates in both alloys. The precipitates on the surfaces of alloy I tend to be star-like (0001) or pyramidal (1010), and their distribution is heterogeneous. Dissolution of Zr 3 Fe surface precipitates of alloy I (annealing above the solvus) leaves precipitate-like features on the surfaces. Zr 2 Fe precipitates in as-grown alloy II can be dissolved only by β-phase annealing. (Author) 8 figs., 18 refs

Fe hydroxyphosphate precipitation and Fe(II) oxidation kinetics upon aeration of Fe(II) and phosphate-containing synthetic and natural solutions

NARCIS (Netherlands)

Grift, B. van der; Behrends, T.; Osté, L.A.; Schot, P.P.; Wassen, M.J.; Griffioen, J.

2016-01-01

Exfiltration of anoxic Fe-rich groundwater into surface water and the concomitant oxidative precipitation of Fe are important processes controlling the transport of phosphate (PO4) from agricultural areas to aquatic systems. Here, we explored the relationship between solution composition, reaction

Fe hydroxyphosphate precipitation and Fe(II) oxidation kinetics upon aeration of Fe(II) and phosphate-containing synthetic and natural solutions

NARCIS (Netherlands)

van der Grift, B.; Behrends, T.; Osté, L.A.; Schot, P.P.; Wassen, M.J.; Griffioen, J.

2016-01-01

Abstract Exfiltration of anoxic Fe-rich groundwater into surface water and the concomitant oxidative precipitation of Fe are important processes controlling the transport of phosphate (PO4) from agricultural areas to aquatic systems. Here, we explored the relationship between solution composition,

Sophistication and Performance of Italian Agri‐food Exports

Directory of Open Access Journals (Sweden)

Anna Carbone

2012-06-01

Full Text Available Nonprice competition is increasingly important in world food markets. Recently, the expression ‘export sophistication’ has been introduced in the economic literature to refer to a wide set of attributes that increase product value. An index has been proposed to measure sophistication in an indirect way through the per capita GDP of exporting countries (Lall et al., 2006; Haussmann et al., 2007.The paper applies the sophistication measure to the Italian food export sector, moving from an analysis of trends and performance of Italian food exports. An original way to disentangle different components in the temporal variation of the sophistication index is also proposed.Results show that the sophistication index offers original insights on recent trends in world food exports and with respect to Italian core food exports.

Removal of Organic Dyes from Industrial Wastewaters Using UV/H2O2, UV/H2O2/Fe (II, UV/H2O2/Fe (III Processes

Directory of Open Access Journals (Sweden)

Nezamaddin Daneshvar

2007-03-01

Full Text Available UV/H2O2, UV/H2O2/Fe (II and UV/H2O2/Fe (III processes are very effective in removing pollutants from wastewater and can be used for treatment of dyestuff units wastewaters. In this study, Rhodamine B was used as a typical organic dye. Rhodamine B has found wide applications in wax, leather, and paper industries. The results from this study showed that this dye was degradable in the presence of hydrogen peroxide under UV-C irradiation (30W mercury light and Photo-Fenton process. The dye was resistant to UV irradiation. In the absence of UV irradiation, the decolorization efficiency was very negligible in the presence of hydrogen. The effects of different system variables such as initial dye concentration, duration of UV irradiation, and initial hydrogen peroxide concentration were investigated in the UV/H2O2 process. Investigation of the kinetics of the UV/H2O2 process showed that the semi-log plot of the dye concentration versus time was linear, suggesting a first order reaction. It was found that Rhodamine B decolorization efficiencies in the UV/H2O2/Fe (II and UV/H2O2/Fe (III processes were higher than that in the UV/H2O2 process. Furthermore, a solution containing 20 ppm of Rhodamine B was decolorized in the presence 18 mM of H2O2 under UV irradiation for 15 minutes. It was also found that addition of 0.1 mM Fe(II or Fe(III to the solution containing  20  ppm of the dye and 5 mM H2O2 under UV light  illumination decreased removal time to 10 min.

A subsurface Fe-silicate weathering microbiome

Science.gov (United States)

Napieralski, S. A.; Buss, H. L.; Roden, E. E.

2017-12-01

Traditional models of microbially mediated weathering of primary Fe-bearing minerals often invoke organic ligands (e.g. siderophores) used for nutrient acquisition. However, it is well known that the oxidation of Fe(II) governs the overall rate of Fe-silicate mineral dissolution. Recent work has demonstrated the ability of lithtrophic iron oxidizing bacteria (FeOB) to grow via the oxidation of structural Fe(II) in biotite as a source of metabolic energy with evidence suggesting a direct enzymatic attack on the mineral surface. This process necessitates the involvement of dedicated outer membrane proteins that interact with insoluble mineral phases in a process known as extracellular electron transfer (EET). To investigate the potential role FeOB in a terrestrial subsurface weathering system, samples were obtained from the bedrock-saprolite interface (785 cm depth) within the Rio Icacos Watershed of the Luquillo Mountains in Puerto Rico. Prior geochemical evidence suggests the flux of Fe(II) from the weathering bedrock supports a robust lithotrophic microbial community at depth. Current work confirms the activity of microorganism in situ, with a marked increase in ATP near the bedrock-saprolite interface. Regolith recovered from the interface was used as inoculum to establish enrichment cultures with powderized Fe(II)-bearing minerals serving as the sole energy source. Monitoring of the Fe(II)/Fe(total) ratio and ATP generation suggests growth of microorganisms coupled to the oxidation of mineral bound Fe(II). Analysis of 16S rRNA gene and shotgun metagenomic libraries from in situ and enrichment culture samples lends further support to FeOB involvement in the weathering process. Multiple metagenomic bins related to known FeOB, including Betaproteobacteria genera, contain homologs to model EET systems, including Cyc2 and MtoAB. Our approach combining geochemistry and metagenomics with ongoing microbiological and genomic characterization of novel isolates obtained

Polypyrrole-polyaniline/Fe{sub 3}O{sub 4} magnetic nanocomposite for the removal of Pb(II) from aqueous solution

Energy Technology Data Exchange (ETDEWEB)

Afshar, Amirhossein; Sadjadi, Seyed Abolfazl Seyed; Mollahosseini, Afsaneh; Eskandarian, Mohammad Reza [Iran University of Science and Technology, Tehran (Iran, Islamic Republic of)

2016-02-15

Lead ion which is engaged in aqueous solution has been successfully removed. A novel technique was utilized for the separation and absorption of Pb(II) ions from aqueous solution. Magnetic Fe{sub 3}O{sub 4} coated with newly investigated polypyrrole-polyaniline nanocomposite was used for the removal of extremely noxious Pb(II). Characteristic of the prepared magnetic nanocomposite was done using X-ray diffraction pattern, Field emission scanning electron microscopy (FE-SEM), Fourier transform-infrared spectroscopy (FT-IR) and energy dispersive x-ray spectroscopy (EDX). Up to 100% adsorption was found with 20mg/L Pb(II) aqueous solution in the range of pH=8-10. Adsorption results illustrated that Pb(II) removal efficiency by the nanocomposite increased with an enhance in pH. Adsorption kinetics was best expressed by the pseudo-second-order rate form. Isotherm data fitted well to the Freundlich isotherm model. Upon using HCl and HNO{sub 3}, 75% PPy-PAn/Fe{sub 3}O{sub 4} nanocomposite, desorption experiment showed that regenerated adsorbent can be reused successfully for two successive adsorption-desorption cycles without appreciable loss of its original capacity.

Characterizing the production and retention of dissolved iron as Fe(II) across a natural gradient in chlorophyll concentrations in the Southern Drake Passage - Final Technical Report

Energy Technology Data Exchange (ETDEWEB)

Katherine Barbeau

2007-04-10

Recent mesoscale iron fertilization studies in the Southern Ocean (e.g. SOIREE, EisenEx, SOFeX) have demonstrated the importance of iron as a limiting factor for phytoplankton growth in these high nutrient, low-chlorophyll (HNLC) waters. Results of these experiments have demonstrated that factors which influence the biological availability of the iron supplied to phytoplankton are crucial in bloom development, longevity, and generation of carbon export flux. These findings have important implications for the future development of iron fertilization protocols to enhance carbon sequestration in high-latitude oceans. In particular, processes which lead to the mobilization and retention of iron in dissolved form in the upper ocean are important in promoting continued biological availability of iron. Such processes can include photochemical redox cycling, which leads to the formation of soluble reduced iron, Fe(II), within iron-enriched waters. Creation of effective fertilization schemes will thus require more information about Fe(II) photoproduction in Southern Ocean waters as a means to retain new iron within the euphotic zone. To contribute to our knowledge base in this area, this project was funded by DOE with a goal of characterizing the production and retention of dissolved Fe as Fe(II) in an area of the southern Drake Passage near the Shackleton Transverse Ridge, a region with a strong recurrent chlorophyll gradient which is believed to be a site of natural iron enrichment in the Southern Ocean. This area was the focus of a multidisciplinary NSF/OPP-funded investigation in February 2004 (OPP02-30443, lead PI Greg Mitchell, SIO/UCSD) to determine the influence of mesoscale circulation and iron transport with regard to the observed patterns in sea surface chlorophyll in the region near the Shackleton Transverse Ridge. A number of parameters were assessed across this gradient in order to reveal interactions between plankton community structure and iron distributions

Crystallization and preliminary crystallographic studies of FoxE from Rhodobacter ferrooxidans SW2, an FeII oxidoreductase involved in photoferrotrophy

International Nuclear Information System (INIS)

Pereira, L.; Saraiva, I. H.; Coelho, R.; Newman, D. K.; Louro, R. O.; Frazão, C.

2012-01-01

Crystals of the R. ferrooxidans SW2 iron oxidoreductase FoxE were obtained and the phase problem was solved by Fe SAD at 2.44 Å resolution. FoxE is a protein encoded by the foxEYZ operon of Rhodobacter ferrooxidans SW2 that is involved in Fe II -based anoxygenic photosynthesis (‘photoferrotrophy’). It is thought to reside in the periplasm, where it stimulates light-dependent Fe II oxidation. It contains 259 residues, including two haem c-binding motifs. As no three-dimensional model is available and there is no structure with a similar sequence, crystals of FoxE were produced. They diffracted to 2.44 Å resolution using synchrotron radiation at the Fe edge. The phase problem was solved by SAD using SHELXC/D/E and the experimental maps confirmed the presence of two haems per molecule

Creation of a 3Mn/1Fe cluster in the oxygen-evolving complex of photosystem II and investigation of its functional activity.

Science.gov (United States)

Semin, B К; Davletshina, L N; Seibert, M; Rubin, A B

2018-01-01

Extraction of Mn cations from the oxygen-evolving complex (OEC) of Ca-depleted PSII membranes (PSII[-Ca,4Mn]) by reductants like hydroquinone (H 2 Q) occurs with lower efficiency at acidic pH (2Mn/reaction center [RC] are extracted at pH5.7) than at neutral pH (3Mn/RC are extracted at pH6.5) [Semin et al. Photosynth. Res. 125 (2015) 95]. Fe(II) also extracts Mn cations from PSII(-Ca,4Mn), but only 2Mn/RC at pH6.5, forming a heteronuclear 2Mn/2Fe cluster [Semin and Seibert, J. Bioenerg. Biomembr. 48 (2016) 227]. Here we investigated the efficiency of Mn extraction by Fe(II) at acidic pH and found that Fe(II) cations can extract only 1Mn/RC from PSII(-Ca,4Mn) membranes at pH 5.7, forming a 3Mn/1Fe cluster. Also we found that the presence of Fe cations in a heteronuclear cluster (2Mn/2Fe) increases the resistance of the remaining Mn cations to H 2 Q action, since H 2 Q can extract Mn cations from homonuclear Mn clusters of PSII(-Ca,4Mn) and PSII(-Ca,2Mn) membranes but not from the heteronuclear cluster in PSII(-Ca,2Mn,2Fe) membranes. H 2 Q also cannot extract Mn from PSII membranes obtained by incubation of PSII(-Ca,4Mn) membranes with Fe(II) cations at pH5.7, which suggests the formation of a heteronuclear 3Mn/1Fe cluster in the OEC. Functional activity of PSII with a 3Mn/1Fe cluster was investigated. PSII preparations with a 3Mn/1Fe cluster in the OEC are able to photoreduce the exogenous electron acceptor 2,6-dichlorophenolindophenol, possibly due to incomplete oxidation of water molecules as is the case with PSII(-Ca,2Mn,2Fe) samples. However, in the contrast to PSII(-Ca,2Mn,2Fe) samples PSII(-Ca,3Mn,1Fe) membranes can evolve O 2 at a low rate in the presence of exogenous Ca 2+ (at about 27% of the rate of O 2 evolution in native PSII membranes). The explanation for this phenomenon (either water splitting and production of molecular O 2 by the 3Mn/1Fe cluster or apparent O 2 evolution due to minor contamination of PSII(3Mn,1Fe) samples with PSII(-Ca,4Mn) membranes

Iron and Arsenic Speciation During As(III) Oxidation by Manganese Oxides in the Presence of Fe(II): Molecular-Level Characterization Using XAFS, Mössbauer, and TEM Analysis

Energy Technology Data Exchange (ETDEWEB)

Wu, Yun [Environmental Soil Chemistry Research Group, Delaware Environmental Institute, University of Delaware, Newark, Delaware 19716, United States; Kukkadapu, Ravi K. [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99354, United States; Livi, Kenneth J. T. [The High-Resolution Analytical Electron Microbeam Facility, Department of Earth and Planetary Sciences, The Johns Hopkins University, Baltimore, Maryland 21218, United States; Xu, Wenqian [Department of Chemistry, Brookhaven National Lab, Upton, New York 11796, United States; Li, Wei [Environmental Soil Chemistry Research Group, Delaware Environmental Institute, University of Delaware, Newark, Delaware 19716, United States; Key Laboratory of Surficial Geochemistry, Ministry of Education, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210046, People’s Republic of China; Sparks, Donald L. [Environmental Soil Chemistry Research Group, Delaware Environmental Institute, University of Delaware, Newark, Delaware 19716, United States

2018-01-17

The redox state and speciation of metalloid arsenic (As) determine its toxicity and mobility. Knowledge of biogeochemical processes influencing the As redox state is therefore important to understand and predict its environmental behavior. Many previous studies examined As(III) oxidation by various Mn-oxides, but little is known the environmental influences (e.g. co-existing ions) on such process. In this study, we investigated the mechanisms of As(III) oxidation by a poorly crystalline hexagonal birnessite (δ-MnO2) in the presence of Fe(II) using X-ray absorption spectroscopy (XAS), Mössbauer spectroscopy and transmission electron microscopy (TEM) coupled with energy-dispersive X-ray spectroscopy (EDS). As K-edge X-ray absorption near edge spectroscopy (XANES) analysis revealed that, at low Fe(II) concentration (100 μM), As(V) was the predominant As species on the solid phase, while at higher Fe(II) concentration (200-1000 μM), both As(III) and As(V) were sorbed on the solid phase. As K-edge extended X-ray absorption fine structure spectroscopy (EXAFS) analysis showed an increasing As-Mn/Fe distance over time, indicating As prefers to bind with the newly formed Fe(III)-(hydr)oxides. As adsorbed on Fe(III)-(hydr)oxides as a bidentate binuclear corner-sharing complex. Both Mössbauer and TEM-EDS investigations demonstrated that the oxidized Fe(III) products formed during Fe(II) oxidation by δ-MnO2 were predominantly ferrihydrite, goethite, and ferric arsenate like compounds. However, Fe EXAFS analysis also suggested the formation of a small amount of lepidocrocite. The Mn K-edge XANES data indicated that As(III) and Fe(II) oxidation occurs as a two electron transfer with δ-MnO2 and the observed Mn(III) is due to conproportionation of surface sorbed Mn(II) with Mn(IV) in δ-MnO2 structure. This study reveals that the mechanisms of As(III) oxidation by δ-MnO2 in the presence of Fe(II) are very complex, involving many simultaneous reactions, and the formation of

Adsorption and separation of CO{sub 2} on Fe(II)-MOF-74: Effect of the open metal coordination site

Energy Technology Data Exchange (ETDEWEB)

Lou, Wolong; Yang, Jiangfeng; Li, Libo; Li, Jinping, E-mail: Jpli211@hotmail.com

2014-05-01

We describe the successful synthesis of Fe{sub 2}(dobdc) (dobdc{sup 4−}=2, 5-dioxido-1, 4-benzenedicarboxylate), which has an open metal coordination site Fe(II), and investigate the adsorption properties of three important molecules CO{sub 2}, CH{sub 4} and N{sub 2} on Fe{sub 2}(dobdc) and an oxidized analog, Fe{sub 2}(O{sub 2})(dobdc). We found that CO{sub 2} adsorption isotherm of Fe{sub 2}(dobdc) at 10 bar was very different from Fe{sub 2}(O{sub 2})(dobdc), with the capacities of 144.5 cm{sup 3} g{sup −1} and 98.1 cm{sup 3} g{sup −1}, respectively. The adsorption capacities for CH{sub 4} were 75.8 cm{sup 3} g{sup −1} and 36.8 cm{sup 3} g{sup −1}, respectively, at 10 bar in these materials. Using ideal adsorbed solution theory (IAST), we obtain the adsorption selectivity for CO{sub 2} using equimolar mixtures of CO{sub 2}/CH{sub 4} and CO{sub 2}/N{sub 2} with Fe{sub 2}(dobdc) and Fe{sub 2}(O{sub 2})(dobdc) as a function of pressure. Fe{sub 2}(dobdc) has a higher, more stable separation factor. - Graphical abstract: The selectivity of CO{sub 2}/CH{sub 4} mixture (50%/50%) on Fe{sub 2}(dobdc) and Fe{sub 2}(O{sub 2})(dobdc). - Highlights: • We explored the contrastive adsorption of CO{sub 2}, CH{sub 4}, and N{sub 2} in Fe{sub 2}(dobdc) and Fe{sub 2}(O{sub 2})(dobdc) for the first time. • Through IAST, we obtain the adsorption selectivity for CO{sub 2} from the equimolar mixture of CO{sub 2}/CH{sub 4} and CO{sub 2}/N{sub 2} for Fe{sub 2}(dobdc) and Fe{sub 2}(O{sub 2})(dobdc). • We determined that the open coordination site of Fe(II) is the main reason for different adsorption performances.

Magnetic nanoparticle (Fe3O4) impregnated onto tea waste for the removal of nickel(II) from aqueous solution

International Nuclear Information System (INIS)

Panneerselvam, P.; Morad, Norhashimah; Tan, Kah Aik

2011-01-01

The removal of Ni(II) from aqueous solution by magnetic nanoparticles prepared and impregnated onto tea waste (Fe 3 O 4 -TW) from agriculture biomass was investigated. Magnetic nanoparticles (Fe 3 O 4 ) were prepared by chemical precipitation of a Fe 2+ and Fe 3+ salts from aqueous solution by ammonia solution. These magnetic nanoparticles of the adsorbent Fe 3 O 4 were characterized by surface area (BET), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Fourier Transform-Infrared Spectroscopy (FT-IR). The effects of various parameters, such as contact time, pH, concentration, adsorbent dosage and temperature were studied. The kinetics followed is first order in nature, and the value of rate constant was found to be 1.90 x 10 -2 min -1 at 100 mg L -1 and 303 K. Removal efficiency decreases from 99 to 87% by increasing the concentration of Ni(II) in solution from 50 to 100 mg L -1 . It was found that the adsorption of Ni(II) increases by increasing temperature from 303 to 323 K and the process is endothermic in nature. The adsorption isotherm data were fitted to Langmuir and Freundlich equation, and the Langmuir adsorption capacity, Q o , was found to be (38.3) mg g -1 . The results also revealed that nanoparticle impregnated onto tea waste from agriculture biomass, can be an attractive option for metal removal from industrial effluent.

Cations-clays interactions: the Fe(II) case; application to the problematic of the French deep nuclear repository field concept

International Nuclear Information System (INIS)

Tournassat, Ch.

2003-07-01

Solute Fe(II) - montmorillonite interactions are studied in anoxic conditions and at room temperature for reaction times from hour to week. Fe 2+ is shown to be sorbed on cation exchange site with the same affinity than Ca 2+ . In chloride anionic medium, Fe(II) form ionic pairs - FeCl + - which is sorbed with almost the same affinity than CaCl + and MgCl + are. The exchange thermodynamics constants derived from this study are used to simulate the change in the exchanger composition as clay river particles enter seawater. In high concentration chloride medium, as seawater, monovalent ions (Na + and CaCl + , MgCl + ionic pairs) are shown to be the major species of the exchanger. Fe 2+ is sorbed specifically on the montmorillonite edge surfaces with a very high affinity. Simple complexation model are able to model the sorption data and show that the Fe 2+ affinity for clay edge surfaces is ∼ 1000 times higher than the Zn 2+ one. Moessbauer experiments combined to sorption, titration and dissolution experiments show that the Fe 2+ sorption is due to several different reactions: - effective competitive sorption with replacement of previously sorbed or structural cations (Zn 2+ , Mg 2+ ); - cooperative sorption together with H 4 SiO 4 , in agreement with a possible surface precipitation of a Fe - Si phase; - a sorption mechanism followed by an oxidation reaction, with a release of two H + in solution per Fe(II) sorbed, and a product (Fe(Ill)) fitting better octahedral surface 'sites'. All these phenomena can not be taken into account in a classical surface complexation model. Hence, an innovative model is developed to model clay - solute interactions, based on a morphological and structural approach. Montmorillonite edge surface area was determined using two independent methods, AFM measurement and low-pressure gas adsorption, that give the same value for this area, i.e. 8.5 m 2 g -1 . The clay - solute interface was found to be constituted by a mix of, at least, 27

Use of Fe(III) oxalate for oxidativewastewater treatment; Einsatz von Fe(III)-Oxalat zur chemisch-oxidativen Abwasserbehandlung

Energy Technology Data Exchange (ETDEWEB)

Kim, S.M.; Vogelpohl, A. [Clausthal Univ., Clausthal-Zellerfeld (Germany). Inst. fuer Thermische Verfahrenstechnik

1998-08-01

Iron(III)-oxalate was used as an iron catalyst for the Photo Fenton reaction. Iron(III) oxalations ([Fe(C{sub 2}O{sub 4}){sub 3}]{sup 3-}) are reduced to Fe(II) by irradiation using near UV-light ({lambda} = 300 - 400 nm) or visible light ({lambda} > 400 nm). At the same time, CO{sub 2}{sup -} or C{sub 2}O{sub 4}{sup -}-radicals originate, which cause the secondary reduction of Fe(III) to Fe(II). By means of the photolytically regenerated Fe(II) ions, hydroxyl radicals are increasingly formed, so that the degradation of organic substances is accelerated. The work aimed to assess the catalytic effect of Fe(III) oxalate for photochemical oxidation processes and to establish the parameters influencing further treatment of leachate from a municipal waste sanitary landfill by means of technical-scale experiments. (orig.) [Deutsch] In der vorliegenden Arbeit wurde Eisen(III)-Oxalat als Eisenkatalysator fuer die Photo-Fenton-Reaktion eingesetzt. Eisen(III)-Oxalationen ([Fe(C{sub 2}O{sub 4}){sub 3}]{sup 3-}) werden durch Strahlung mit nahem UV-Licht ({lambda}=300 bis 400 nm) oder mit sichtbarem Licht ({lambda}>400 nm) zu Fe(II) reduziert. Gleichzeitig entstehen CO{sub 2}{sup .-} oder C{sub 2}O{sub 4}{sup .-}-Radikale, die eine sekundaere Reduktion von Fe(III) zu Fe(II) bewirken. Mit Hilfe der photolytiisch regenerierten Fe(II)-Ionen werden vermehrt Hydroxylradikale gebildet und damit die Abbaugeschwindigkeit der organischen Substanzen beschleunigt. Ziel der hier vorgestellten Arbeit war es, die katalytische Wirkung von Fe(III)-Oxalat fuer photochemische Oxidationsverfahren abzuschaetzen und die Einflussparameter zur weitergehenden Behandlung eines Deponiesickerwassers aus Hausmuelldeponie anhand von Technikumsversuchen zu ermitteln. (orig.)

Fe++/Fe+++ concentration relationship and mechanical properties of phosphate glasses useful for wastes immobilization

International Nuclear Information System (INIS)

Garcia, D.A.; Prado, Miguel O.

2007-01-01

Under different melting conditions, glasses with different Fe(II)/Fe(III) concentration relationship were prepared within each type of glass 43Fe 2 O 3 -57P 2 O 5 and 33,33Fe 2 O 3 - 66,67P 2 O 5 . Using Moessbauer spectroscopy Fe(II)/Fe(III) concentration values were determined. Vickers and Knoop indentations were used for determining their hardness, toughness, Young modulus and brittleness. The same measurements were carried on some silicate and aluminosilicate glasses. Also Weibull statistics was done to determine the characteristics (Weibull modulus and and fracture probability) of glass fracture. We found that silicate glasses (SG) are harder than phosphate glasses (PG). Toughness values for PG, are in the same range than for SG, although for the same density exhibit larger values or smaller brittleness than silicate glasses. For one of the glasses it was found that the mechanical load P 0 needed for a fracture probability of 63% increases with the Fe(II) content. (author)

Interaction of red pepper (Capsicum annum, Tepin) polyphenols with Fe(II)-induced lipid peroxidation in brain and liver

International Nuclear Information System (INIS)

Oboh, G.; Rocha, J.B.T.

2006-03-01

Polyphenols exhibit a wide range of biological effects because of their antioxidant properties. Several types of polyphenols (phenolic acids, hydrolyzable tannins, and flavonoids) show anticarcinogenic and antimutagenic effects. Comparative studies were carried on the protective ability of free and bound polyphenol extracts of red Capsicum annuum Tepin (CAT) on brain and liver - In vitro. Free polyphenols of red Capsicum annuum Tepin (CAT) were extracted with 80% acetone, while the bound polyphenols were extracted with ethyl acetate from acid and alkaline hydrolysis of the pepper residue from free polyphenols extract. The phenol content, Fe (II) chelating ability, OH radical scavenging ability and protective ability of the extract against Fe (II)-induced lipid peroxidation in brain and liver was subsequently determined. The results of the study revealed that the free polyphenols (218.2mg/100g) content of the pepper were significantly higher than the bound polyphenols (42.5mg/100g). Furthermore, the free polyphenol extract had a significantly higher ( 2+ induced lipid peroxidation, and this is probably due to the higher Fe (II) chelating ability and OH radical scavenging ability of the free polyphenols from the pepper. (author)

Fe(II) oxidation during acid mine drainage neutralization in a pilot-scale sequencing batch reactor

CSIR Research Space (South Africa)

Zvimba, JN

2013-10-01

Full Text Available crystallization for metal content using ICP-OES (Varian: Vista Pro CCD Simultaneous ICP- OES). The pH, acidity and alkalinity of the AMD were determined using a Mettler Toledo Auto-titrator following filtration. Fe(II) was determined by standard permanganate...

Redox topotactic reactions in Fe{sup II - III} (oxy)hydroxycarbonate new minerals related to fougerite in gleysols: 'trebeurdenite and moessbauerite'

Energy Technology Data Exchange (ETDEWEB)

Genin, Jean-Marie R., E-mail: jean-marie.genin@esstin.uhp-nancy.fr [Institut Jean Barriol FR2843 CNRS-Universite de Lorraine, ESSTIN (France); Guerin, O. [Ecole Pratique des Hautes Etudes, Laboratoire de Geomorphologie (France); Herbillon, A. J. [Universite Catholique de Louvain, Unite des Sciences du Sol (Belgium); Kuzmann, E. [Eoetvoes Lorand Univ., Chemistry Department (Hungary); Mills, S. J. [Geosciences Museum Victoria (Australia); Morin, G.; Ona-Nguema, G. [Univ. P. and M. Curie, Institut Mineralogie and Phys. Milieux Condenses (France); Ruby, C. [Institut Jean Barriol FR2843 CNRS-Universite de Lorraine, ESSTIN (France); Upadhyay, C. [IT-Banaras Hindu Univ., School of Materials Science and Technology (India)

2012-03-15

Fougerite mineral responsible for the bluish-green shade of gleysols in aquifers was identified as Fe{sup II - III} oxyhydroxycarbonate, [Fe{sub 6}({sub 1-x)}{sup II} Fe{sub 6x}{sup III} O{sub 12}H{sub 2(7 - 3x)}]{sup 2 + } {center_dot} [CO{sub 3}{sup 2-} {center_dot} 3H{sub 2}O]{sup 2 - } where the average ferric molar fraction x = [Fe{sup III}/Fe{sub total}] was restricted to the [1/3-2/3] range, up till now. In this paper, Moessbauer spectra of gleys extracted from the schorre of maritime marshes have values of x in the [2/3-1] range. Magnetic properties of homologous chemical compounds studied by Moessbauer spectroscopy are explained with long range order of Fe{sup III} ions within Fe cation layers for x = 1/3, 2/3 and 1. Observed values are mixtures of topotactic domains that are in fact minerals with names proposed to IMA: fougerite for x = 1/3, trebeurdenite for x = 2/3 and moessbauerite for x = 1.

Immobilization of 99-Technetium (VII) by Fe(II)-Goethite and Limited Reoxidation

Energy Technology Data Exchange (ETDEWEB)

W Um; H Chang; J Icenhower; W Lukens; R Serne; N Qafoku; J Westsik Jr.; E Buck; S Smith

2011-12-31

During the nuclear waste vitrification process volatilized {sup 99}Tc will be trapped by melter off-gas scrubbers and then washed out into caustic solutions, and plans are currently being contemplated for the disposal of such secondary waste. Solutions containing pertechnetate [{sup 99}Tc(VII)O{sub 4}{sup -}] were mixed with precipitating goethite and dissolved Fe(II) to determine if an iron (oxy)hydroxide-based waste form can reduce Tc(VII) and isolate Tc(IV) from oxygen. The results of these experiments demonstrate that Fe(II) with goethite efficiently catalyzes the reduction of technetium in deionized water and complex solutions that mimic the chemical composition of caustic waste scrubber media. Identification of the phases, goethite + magnetite, was performed using XRD, SEM and TEM methods. Analyses of the Tc-bearing solid products by XAFS indicate that all of the Tc(VII) was reduced to Tc(IV) and that the latter is incorporated into goethite or magnetite as octahedral Tc(IV). Batch dissolution experiments, conducted under ambient oxidizing conditions for more than 180 days, demonstrated a very limited release of Tc to solution (2-7 {micro}g Tc/g solid). Incorporation of Tc(IV) into the goethite lattice thus provides significant advantages for limiting reoxidation and curtailing release of Tc disposed in nuclear waste repositories.

Removal of phosphonates from industrial wastewater with UV/FeII, Fenton and UV/Fenton treatment.

Science.gov (United States)

Rott, Eduard; Minke, Ralf; Bali, Ulusoy; Steinmetz, Heidrun

2017-10-01

Phosphonates are an important group of phosphorus-containing compounds due to their increasing industrial use and possible eutrophication potential. This study involves investigations into the methods UV/Fe II , Fenton and UV/Fenton for their removal from a pure water matrix and industrial wastewaters. It could be shown that the degradability of phosphonates by UV/Fe II (6 kWh/m 3 ) in pure water crucially depended on the pH and was higher the less phosphonate groups a phosphonate contains. The UV/Fe II method is recommended in particular for the treatment of concentrates with nitrogen-free phosphonates, only little turbidity and a low content of organic compounds. Using Fenton reagent, the degradation of polyphosphonates was relatively weak in a pure water matrix (Fenton method (6 kWh/m 3 ), those phosphonates with the smallest numbers of phosphonate groups were easier degraded as well at pH 3.5 in a pure water matrix (o-PO 4 3- formation rates of up to 80%). Despite an incomplete transformation of organically bound phosphorus to o-PO 4 3- with Fenton reagent in an organically highly polluted wastewater (max. 15%), an almost total removal of the total P occurred. The most efficient total P elimination rates were achieved in accordance with the following Fenton implementation: reaction → sludge separation (acidic) → neutralization of the supernatant → sludge separation (neutral). Accordingly, a neutralization directly after the reaction phase led to a lower total P removal extent. Copyright © 2017 Elsevier Ltd. All rights reserved.

The First Sophists and the Uses of History.

Science.gov (United States)

Jarratt, Susan C.

1987-01-01

Reviews the history of intellectual views on the Greek sophists in three phases: (1) their disparagement by Plato and Aristotle as the morally disgraceful "other"; (2) nineteenth century British positivists' reappraisal of these relativists as ethically and scientifically superior; and (3) twentieth century versions of the sophists as…

Batch adsorptive removal of Fe(III), Cu(II) and Zn(II) ions in aqueous and aqueous organic–HCl media by Dowex HYRW2-Na Polisher resin as adsorbents

OpenAIRE

Aboul-Magd, Abdul-Aleem Soliman; Al-Husain, Salwa Al-Rashed; Al-Zahrani, Salma Ahmed

2016-01-01

Of the metal ions in tap, Nile, waste and sea water samples and some ores were carried out. Removal of heavy metal ions such as Fe(III), Cd(II), Zn(II), Cu(II), Mn(II), Mg(II), and Pb(II) from water and wastewater is obligatory in order to avoid water pollution. Batch shaking adsorption experiments to evaluate the performance of nitric and hydrochloric acid solutions in the removal of metal ions by cation exchange resin at the same conditions for both, such as the effect of initial metal ion ...

Facile colorimetric assay of alkaline phosphatase activity using Fe(II)-phenanthroline reporter.

Science.gov (United States)

Hu, Qiong; Zhou, Baojing; Dang, Pengyun; Li, Lianzhi; Kong, Jinming; Zhang, Xueji

2017-01-15

We report a versatile approach for the colorimetric assay of alkaline phosphatase (ALP) activity based on the distinctive metal-to-ligand charge-transfer (MLCT) absorption properties of Fe(II)-phenanthroline reporter. In the presence of ALP, the applied substrate ascorbic acid 2-phosphate is enzymatically hydrolyzed to produce ascorbic acid, which then reduces Fe 3+ to Fe 2+ . The complexation of Fe 2+ with the bathophenanthroline disulfonate (BPS) ligand generates a blood-red Fe(BPS) 3 4- reporter, which is characterized by an intense MLCT absorption band at 535 nm in the visible range. Under optimal conditions, the spectral output exhibits a good quantitative relationship with ALP activity over the range of 0-220 mU mL -1 with a detection limit of 0.94 mU mL -1 . Moreover, the activity of ALP can also be conveniently judged through naked-eye observations. Results indicate that it is highly selective and can be applied to the screening of ALP inhibitors. In addition, it has been successfully employed to detect the endogenous ALP level of undiluted human serum samples, with a detection limit of 1.05 mU mL -1 being achieved. This approach avoids any elaborately designed substrates and holds considerable simplicity and flexibility for reporter design. This study broadens the horizon of the applications of phenanthroline-based transition metal complexes. Furthermore, an efficient and practical method like this has the potential to be widely used in clinical applications and in the point-of-care testing. Copyright © 2016 Elsevier B.V. All rights reserved.

Cumulative Dominance and Probabilistic Sophistication

NARCIS (Netherlands)

Wakker, P.P.; Sarin, R.H.

2000-01-01

Machina & Schmeidler (Econometrica, 60, 1992) gave preference conditions for probabilistic sophistication, i.e. decision making where uncertainty can be expressed in terms of (subjective) probabilities without commitment to expected utility maximization. This note shows that simpler and more general

Boletus edulis loaded with γ-Fe2O3 nanoparticles as a magnetic sorbent for preconcentration of Co(II) and Sn(II) prior to their determination by ICP-OES.

Science.gov (United States)

Ozdemir, Sadin; Serkan Yalcin, M; Kilinc, Ersin; Soylak, Mustafa

2017-12-20

The authors show that the fungus Boletus edulis loaded with γ-Fe 2 O 3 nanoparticles is a viable sorbent for magnetic solid phase extraction of trace levels of Co(II) and Sn(II). The surface structure of immobilized magnetized B. edulis was characterized by FT-IR, SEM and EDX. Experimental parameters were optimized. Following elution with 1 M HCl, the ions were quantified by ICP-OES. The limits of detection are 21 pg·mL -1 for Co(II), and 19 pg·mL -1 for Sn(II). The preconcentration factors are 100 for both ions. The sorption capacities of the sorbent are 35.8 mg·g -1 for Co(II) and 29.6 mg·g -1 for Sn(II). The method was applied to the analysis of certificated reference materials and gave ≥95% recoveries with low RSDs. It was also successfully applied to the quantification of Co(II) and Sn(II) in spiked environmental and food samples. Graphical abstract The fungus Boletus edulis loaded with γ-Fe 2 O 3 nanoparticles is a viable biosorbent for magnetic solid phase extraction (MSPE) of trace levels of Co(II) and Sn(II). The surface structure of immobilized magnetized B. edulis was characterized by FT-IR, SEM and EDX. Experimental parameters were optimized.

Copper(II) cyanido-bridged bimetallic nitroprusside-based complexes: Syntheses, X-ray structures, magnetic properties, 57Fe Moessbauer spectroscopy and thermal studies

International Nuclear Information System (INIS)

Travnicek, Zdenek; Herchel, Radovan; Mikulik, Jiri; Zboril, Radek

2010-01-01

Three heterobimetallic cyanido-bridged copper(II) nitroprusside-based complexes of the compositions [Cu(tet)Fe(CN) 5 NO].H 2 O (1), where tet=N,N'-bis(3-aminopropyl)ethylenediamine, [Cu(hto)Fe(CN) 5 NO].2H 2 O (2), where hto=1,3,6,9,11,14-hexaazatricyclo[12.2.1.1 6,9 ]octadecane and [Cu(nme) 2 Fe(CN) 5 NO].H 2 O (3), where nme=N-methylethylenediamine, were synthesized and characterized by elemental analyses, 57 Fe Moessbauer and FTIR spectroscopies, thermal analysis, magnetic measurements and single-crystal X-ray analysis. The products of thermal degradation processes of 2 and 3 were studied by XRD, 57 Fe Moessbauer spectroscopy, SEM and EDS, and they were identified as mixtures of CuFe 2 O 4 and CuO. - Three heterobimetallic cyano-bridged copper(II) nitroprusside-based complexes of the general compositions of [Cu(L)Fe(CN) 5 NO].xH 2 O, where L=N,N'-bis(3-aminopropyl)ethylenediamine (complex 1), 1,3,6,9,11,14-hexaazatricyclo[12.2.1.1 6,9 ]-octadecane (complex 2) and N-methylethylenediamine (complex 3), were synthesized, and fully structurally and magnetically characterized. SEM, EDS, XRD and 57 Fe Moessbauer experiments were used for characterization of thermal decomposition products of complexes 2 and 3.

Abiotic Deposition of Fe Complexes onto Leptothrix Sheaths

Science.gov (United States)

Kunoh, Tatsuki; Hashimoto, Hideki; McFarlane, Ian R.; Hayashi, Naoaki; Suzuki, Tomoko; Taketa, Eisuke; Tamura, Katsunori; Takano, Mikio; El-Naggar, Mohamed Y.; Kunoh, Hitoshi; Takada, Jun

2016-01-01

Bacteria classified in species of the genus Leptothrix produce extracellular, microtubular, Fe-encrusted sheaths. The encrustation has been previously linked to bacterial Fe oxidases, which oxidize Fe(II) to Fe(III) and/or active groups of bacterial exopolymers within sheaths to attract and bind aqueous-phase inorganics. When L. cholodnii SP-6 cells were cultured in media amended with high Fe(II) concentrations, Fe(III) precipitates visibly formed immediately after addition of Fe(II) to the medium, suggesting prompt abiotic oxidation of Fe(II) to Fe(III). Intriguingly, these precipitates were deposited onto the sheath surface of bacterial cells as the population was actively growing. When Fe(III) was added to the medium, similar precipitates formed in the medium first and were abiotically deposited onto the sheath surfaces. The precipitates in the Fe(II) medium were composed of assemblies of globular, amorphous particles (ca. 50 nm diameter), while those in the Fe(III) medium were composed of large, aggregated particles (≥3 µm diameter) with a similar amorphous structure. These precipitates also adhered to cell-free sheaths. We thus concluded that direct abiotic deposition of Fe complexes onto the sheath surface occurs independently of cellular activity in liquid media containing Fe salts, although it remains unclear how this deposition is associated with the previously proposed mechanisms (oxidation enzyme- and/or active group of organic components-involved) of Fe encrustation of the Leptothrix sheaths. PMID:27271677

Abiotic Deposition of Fe Complexes onto Leptothrix Sheaths

Directory of Open Access Journals (Sweden)

Tatsuki Kunoh

2016-06-01

Full Text Available Bacteria classified in species of the genus Leptothrix produce extracellular, microtubular, Fe-encrusted sheaths. The encrustation has been previously linked to bacterial Fe oxidases, which oxidize Fe(II to Fe(III and/or active groups of bacterial exopolymers within sheaths to attract and bind aqueous-phase inorganics. When L. cholodnii SP-6 cells were cultured in media amended with high Fe(II concentrations, Fe(III precipitates visibly formed immediately after addition of Fe(II to the medium, suggesting prompt abiotic oxidation of Fe(II to Fe(III. Intriguingly, these precipitates were deposited onto the sheath surface of bacterial cells as the population was actively growing. When Fe(III was added to the medium, similar precipitates formed in the medium first and were abiotically deposited onto the sheath surfaces. The precipitates in the Fe(II medium were composed of assemblies of globular, amorphous particles (ca. 50 nm diameter, while those in the Fe(III medium were composed of large, aggregated particles (≥3 µm diameter with a similar amorphous structure. These precipitates also adhered to cell-free sheaths. We thus concluded that direct abiotic deposition of Fe complexes onto the sheath surface occurs independently of cellular activity in liquid media containing Fe salts, although it remains unclear how this deposition is associated with the previously proposed mechanisms (oxidation enzyme- and/or active group of organic components-involved of Fe encrustation of the Leptothrix sheaths.

Emissão de hidrogênio molecular e [FeII] em núcleos Seyfert

Science.gov (United States)

Rodríguez-Ardila, A.; Pastoriza, M. G.; Viegas, S.

2003-08-01

Um dos problemas fundamentais em núcleos ativos de galáxias (AGN) é determinar os mecanismos de excitação dominantes do gás emissor de linhas estreitas, seja este excitado por mecanismos não-estelares (fotoionização por uma fonte central ou choques produzidos por um jato rádio no gás circumnuclear) ou estelares (fotoionização por estrelas OB ou choques originados por um remanescente de supernova em expansão). Essa ambiguedade se faz mais evidente ao intepretar o espectro de espécies tais como H2 e [FeII]. Na primeira, fluorescência UV, processos térmicos (choques e/ou aquecimento por fótons) ou illuminação por raios-x, podem ser responsáveis pelo espectro observado enquanto que na segunda, os dois últimos mechanismos seriam relevantes. Neste trabalho, utilizando espectroscópia JHK de média resolução para uma amostra de AGN encontramos que o H2 observado é gerado principalmente por processos térmicos associados à presença de episódios de formação estelar circumnuclear. No entanto, em galáxias tais como NGC4151 as observações mostram que o hidrogênio molecular origina-se, principalmente, da interação entre o jato radio e o gás da NLR. Esses resultados baseiam-se nos valores das razões de linhas H2 2.24/2.12 mm e H2 2.03/2.22 mm. H2 2.24/2.12 separa claramente processos não-térmicos dos térmicos enquanto H2 2.03/2.22 serve como indicador de temperatura da componente térmica, e portanto, discrimina entre choques e associações OB. Já para o [FeII], as observações são compatíveis com excitação produzida diretamente pela fonte central ou choques associados com o jato rádio. A comparação da largura dos perfis de linhas observados permite concluir que não há correlação entre a emissão de H2 e [FeII]. Em praticamente todos os casos analisados, os perfis das linhas de H2 são não-resolvidos, enquanto que os perfis de [FeII] indicam, em alguns casos, velocidades de até 600 km/s.

Fe(II)-regulated moderate pre-oxidation of Microcystis aeruginosa and formation of size-controlled algae flocs for efficient flotation of algae cell and organic matter.

Science.gov (United States)

Qi, Jing; Lan, Huachun; Liu, Ruiping; Liu, Huijuan; Qu, Jiuhui

2018-06-15

The coagulation/flocculation/flotation (C/F/F) process is becoming a popular method for algae-laden water treatment. However, the efficiency of flotation is highly dependent on the ability of the preceding coagulation/flocculation process to form flocculated algae flocs. This study aims to improve the Microcystis aeruginosa flotation efficiency from algae cell and organic matter aspects by applying Fe(II)-regulated pretreatment enhanced Al coagulation process. The ability of the C/F/F process to remove cyanobacterial cells can be enhanced from 8% to 99% at a Fe(II) dose of 30 μM. The Al dose needed can be reduced by more than half while achieving successful flotation. The introduced Fe(II) after KMnO 4 can not only realize moderate pre-oxidation of cyanobacterial cells, but also form in-situ Fe(III). The DOC value can also be decreased significantly due to the formation of in-situ Fe(III), which is more efficient in dissolved organic matter (DOM) removal compared with pre-formed Fe(III). In addition, the gradually hydrolyzed in-situ Fe(III) can facilitate the hydrolysis of Al as a dual-coagulant and promote the clustering and cross-linking of Al hydrolyzates, which can enhance the formation of size-controlled algae flocs. Finally, the size-controlled algae flocs can be effectively floated by the bubbles released in the flotation process due to the efficient collision and attachment between flocs and bubbles. Therefore, the efficient flotation of algae cell and organic matter can be realized by the Fe(II) regulated moderate pre-oxidation of M. aeruginosa and formation of size-controlled algae flocs. Copyright © 2018 Elsevier Ltd. All rights reserved.

Preparation and estimation of thermodynamic properties of Fe(II)-, Co(II)-, Ni(II)- and Zr(IV)-containing layered double hydroxides

Energy Technology Data Exchange (ETDEWEB)

Rozov, Konstantin; Curtius, Hilde; Bosbach, Dirk [Forschungszentrum Juelich GmbH (Germany). Inst. for Nuclear Waste Management and Reactor Safety (IEK-6)

2015-07-01

The investigation of layered double hydroxides (LDHs) was performed because they and similar 'green rust' phases were identified as specific secondary phases forming during the evolution of the disposed research reactor fuel elements under nuclear repository relevant conditions. LDHs or 'hydrotalcite-like' solids are of interest in environmental geochemistry because they can substitute various cations and especially due to the anion-exchange properties and, therefore, can be considered as buffer materials for retention of mobile and hazardous radionuclides (like, {sup 14}C, {sup 129}I, {sup 36}Cl, {sup 79}Se etc.). In our study Fe{sup 2+}-, Co{sup 2+}-, Ni{sup 2+}- and Zr{sup 4+}-containing LDHs have been synthesized by co-precipitation method and characterized (PXRD, FT-IR, SEM-EDX, TGA-DSC) in order to investigate the effect of substitution of 2- and 4-valent cations on the stability of LDHs. PXRD measurements demonstrated that: (1) pure Mg-Al-Fe(II) LDHs are existing in the range of the mole fraction of iron x{sub Fe} = Fe/(Mg+Fe) between 0 and 0.13. Unit-cell parameters (a{sub o}=b{sub o}) as a function of x{sub Fe} follow Vegard's law corroborating the existence of a solid solution when x{sub Fe} = 0 - 0.13. Products of syntheses with x{sub Fe} ≥ 0.13 contain detectable amounts (≥1-2 wt%) of additional phases (like, magnetite, maghemite, lepidocrocite); (2) pure Ni{sup 2+}- and Co{sup 2+}-containing LDHs (mole fractions of Ni and Co were equal to 0.1) have been synthesized successfully; (3) Mg-Al-Zr(IV) precipitates with mole fraction of zirconium x{sub Zr} = Zr/(Zr+Al) = 0.0 - 0.5 show PXRD patterns attributed to pure LDHs and the variation of lattice parameters a{sub o}=b{sub o} as a function of x{sub Zr} is in agreement with Vegard's law demonstrating the presence of solid solution. In contrast, PXRD analyses of precipitates with x{sub Zr} ≥ 0.5 have shown the presence of additional X-ray reflexes typical for brucite. The

Does Investors' Sophistication Affect Persistence and Pricing of Discretionary Accruals?

OpenAIRE

Lanfeng Kao

2007-01-01

This paper examines whether the sophistication of market investors influences management's strategy on discretionary accounting choice, and thus changes the persistence of discretionary accruals. The results show that the persistence of discretionary accruals for firms face with naive investors is lower than that for firms face with sophisticated investors. The results also demonstrate that sophisticated investors indeed incorporate the implications of current earnings components into future ...

Fe3O4@SiO2@CS-TETA functionalized graphene oxide for the adsorption of methylene blue (MB) and Cu(II)

Science.gov (United States)

Wang, Fan; Zhang, Lijuan; Wang, Yeying; Liu, Xijian; Rohani, Sohrab; Lu, Jie

2017-10-01

The graphene oxide (GO) functionalized by Fe3O4@SiO2@CS-TETA nanoparticles, Fe3O4@SiO2@CS-TETA-GO, was firstly fabricated in a mild way as a novel adsorbent for the removal of Cu(II) ions and methylene blue (MB) from aqueous solutions. The magnetic composites showed a good dispersity in water and can be conveniently collected for reuse through magnetic separation due to its excellent magnetism. When the Fe3O4@SiO2@CS- TETA-GO was used as an absorbent for the absorption of MB and Cu(II), the adsorption kinetics and isotherms data well fitted the pseudo-second-order model and the Langmuir model, respectively. Under the optimized pH and initial concentration, the maximum adsorption capacity was about 529.1 mg g-1 for MB in 20 min and 324.7 mg g-1 for Cu(II) in 16 min, respectively, exhibiting a better adsorption performance than other GO-based adsorbents reported recently. More importantly, the synthesized adsorbent could be effectively regenerated and repeatedly utilized without significant capacity loss after six times cycles. All the results demonstrated that Fe3O4@SiO2@CS-TETA-GO could be used as an excellent adsorbent for the adsorption of Cu(II) and MB in many fields.

Physical conditions in CaFe interstellar clouds

OpenAIRE

Gnacinski, P.; Krogulec, M.

2007-01-01

Interstellar clouds that exhibit strong Ca I and Fe I lines were called CaFe clouds. The ionisation equilibrium equations were used to model the column densities of Ca II, Ca I, K I, Na I, Fe I and Ti II in CaFe clouds. The chemical composition of CaFe clouds is that of the Solar System and no depletion of elements onto dust grains is seen. The CaFe clouds have high electron densities n=1 cm^-3 that leads to high column densities of neutral Ca and Fe.

The conceptualization and measurement of cognitive health sophistication.

Science.gov (United States)

Bodie, Graham D; Collins, William B; Jensen, Jakob D; Davis, Lashara A; Guntzviller, Lisa M; King, Andy J

2013-01-01

This article develops a conceptualization and measure of cognitive health sophistication--the complexity of an individual's conceptual knowledge about health. Study 1 provides initial validity evidence for the measure--the Healthy-Unhealthy Other Instrument--by showing its association with other cognitive health constructs indicative of higher health sophistication. Study 2 presents data from a sample of low-income adults to provide evidence that the measure does not depend heavily on health-related vocabulary or ethnicity. Results from both studies suggest that the Healthy-Unhealthy Other Instrument can be used to capture variability in the sophistication or complexity of an individual's health-related schematic structures on the basis of responses to two simple open-ended questions. Methodological advantages of the Healthy-Unhealthy Other Instrument and suggestions for future research are highlighted in the discussion.

Insights into the crystal-packing effects on the spin crossover of [Fe(II)(1-bpp)](2+)-based materials.

Science.gov (United States)

Vela, Sergi; Novoa, Juan J; Ribas-Arino, Jordi

2014-12-28

Iron(II) complexes of the [Fe(II)(1-bpp2)](2+) type (1-bpp = 2,6-di(pyrazol-1-yl)pyridine) have been intensively investigated in the context of crystal engineering of switchable materials because their spin-crossover (SCO) properties dramatically depend on the counterions. Here, by means of DFT + U calculations at the molecular and solid state levels we provide a rationale for the different SCO behaviour of the BF4(-) and ClO4(-) salts of the parent complex; the former features Fe(II) complexes with a regular coordination geometry and undergoes a spin transition, whereas the Fe(II) complexes of the latter adopt a distorted structure and remain in the high-spin state at all temperatures. The different SCO behaviour of both salts can be explained on the basis of a combination of thermodynamic and kinetic effects. The shape of the SCO units at high temperature is thermodynamically controlled by the intermolecular interactions between the SCO units and counterions within the crystal. The spin trapping at low temperatures in the ClO4(-) salt, in turn, is traced back to a kinetic effect because our calculations have revealed the existence of a more stable polymorph having SCO units in their low-spin state that feature a regular structure. From the computational point of view, it is the first time that the U parameter is fine-tuned on the basis of CASPT2 calculations, thereby enabling an accurate description of the energetics of the spin transition at both molecular and solid-state levels.

Obfuscation, Learning, and the Evolution of Investor Sophistication

OpenAIRE

Bruce Ian Carlin; Gustavo Manso

2011-01-01

Investor sophistication has lagged behind the growing complexity of retail financial markets. To explore this, we develop a dynamic model to study the interaction between obfuscation and investor sophistication in mutual fund markets. Taking into account different learning mechanisms within the investor population, we characterize the optimal timing of obfuscation for financial institutions who offer retail products. We show that educational initiatives that are directed to facilitate learnin...

Mössbauer spectroscopy of reduced forms of a Fe-tetraphenylporphyrine complex

Directory of Open Access Journals (Sweden)

Kaczmarzyk Tomasz

2015-03-01

Full Text Available Molecular and electronic structure changes during successive reduction of a Fe-tetraphenylporphyrin chloride [Fe(III(TPP:Cl] complex are reported on the basis of Mössbauer spectroscopy and DFT calculations. It is established that the attachment of additional electrons to a neutral Fe(III(TPP:Cl molecule leads to significant shortening of Fe-N distances at the first stage of the reduction Fe(III(TPP:Cl → Fe(II(TPP and lengthening of these bonds at the second stage Fe(II(TPP → Fe(I(TPP. Changes of other bond lengths of the porphyrin ring also appear but in less degree. Interaction of Fe(II and Fe(I(TPP with tetrahydrofuran (THF solvent is considered. Electron configuration of Fe(II(TPP corresponds to intermediate-spin (S = 1 state and in the case of Fe(I(TPP low-spin state (S = ½ is observed. Electron density distribution in Fe(II- and Fe(I(TPP complexes, in association with Mössbauer data, is analyzed. Good correlation between experimental and theoretical results was obtained.

Research by Moessbauer and infrared spectroscopy of films of polyacrylonitrile doped with FeCl2 and FeCl3

International Nuclear Information System (INIS)

Santos, Vadilson M. dos; Silva Filho, Eloi A. da; Nunes Filho, Evaristo

2009-01-01

The heating effect on films of polyacrylonitrile and doping of the ions Fe(II) and Fe (III) may reveal important aspects of the use of this polymer in the search for new materials. This paper was done the doping of the films of PAN with ions Fe(II) and Fe (III), with thermo heating is range of 60 a 90 deg C e de 90 a 170 deg C through the alkaline and acid hydrolysis of the CN groups used spectroscopy of FTIR and Moessbauer techniques to evaluate the structural changes results of doping process this polymer. The results showed that the FTIR spectral have a strong interaction of the ions Fe(II) and Fe (III) with PAN and confirmed by Moessbauer data. (author)

Probabilistic Sophistication, Second Order Stochastic Dominance, and Uncertainty Aversion

OpenAIRE

Simone Cerreia-Vioglio; Fabio Maccheroni; Massimo Marinacci; Luigi Montrucchio

2010-01-01

We study the interplay of probabilistic sophistication, second order stochastic dominance, and uncertainty aversion, three fundamental notions in choice under uncertainty. In particular, our main result, Theorem 2, characterizes uncertainty averse preferences that satisfy second order stochastic dominance, as well as uncertainty averse preferences that are probabilistically sophisticated.

The lowest 5g-6h supermultiplet of Fe II

International Nuclear Information System (INIS)

Biemont, E.; Palmeri, P.

1997-01-01

The 3d 6 ( 5 D)6h subconfiguration of Fe II is established by means of 74 newly identified 5g-6h transitions. These lines are observed in a Fourier-transform spectrum of iron emitted from a hollow-cathode discharge in the region 5350-5410 cm -1 . The application of the ''quadrupolic'' approximation shows that the JK coupling is well represented in the 3d 6 6h configuration. The identification of the lines in the spectra was facilitated by the comparison of the observed intensities with oscillator strengths calculated in the framework of the relativistic Hartree-Fock (HFR) approximation and also by consideration of the full width at half maximum (FWHM) of the profiles. (orig.)

IR, UV-Vis, magnetic and thermal characterization of chelates of some catecholamines and 4-aminoantipyrine with Fe(III) and Cu(II)

Science.gov (United States)

Mohamed, Gehad G.; Zayed, M. A.; El-Dien, F. A. Nour; El-Nahas, Reham G.

2004-07-01

The dopamine derivatives participate in the regulation of wide variety of physiological functions in the human body and in medication life. Increase and/or decrease in the concentration of dopamine in human body reflect an indication for diseases such as Schizophrenia and/or Parkinson diseases. α-Methyldopa (α-MD) in tablets is used in medication of hypertension. The Fe(III) and Cu(II) chelates with coupled products of adrenaline hydrogen tartarate (AHT), levodopa (LD), α-MD and carbidopa (CD) with 4-aminoantipyrine (4-AAP) are prepared and characterized. Different physico-chemical methods like IR, magnetic and UV-Vis spectra are used to investigate the structure of these chelates. Fe(III) form 1:2 (M:catecholamines) chelates while Cu(II) form 1:1 chelates. Catecholamines behave as a bidentate mono- or dibasic ligands in binding to the metal ions. IR spectra show that the catecholamines are coordinated to the metal ions in a bidentate manner with O,O donor sites of the phenolic - OH. Magnetic moment measurements reveal the presence of Fe(III) chelates in octahedral geometry while the Cu(II) chelates are square planar. The thermal decomposition of Fe(III) and Cu(II) complexes is studied using thermogravimetric (TGA) and differential thermal analysis (DTA) techniques. The water molecules are removed in the first step followed immediately by decomposition of the ligand molecules. The activation thermodynamic parameters, such as, energy of activation, enthalpy, entropy and free energy change of the complexes are evaluated and the relative thermal stability of the complexes are discussed.

Automatically Assessing Lexical Sophistication: Indices, Tools, Findings, and Application

Science.gov (United States)

Kyle, Kristopher; Crossley, Scott A.

2015-01-01

This study explores the construct of lexical sophistication and its applications for measuring second language lexical and speaking proficiency. In doing so, the study introduces the Tool for the Automatic Analysis of LExical Sophistication (TAALES), which calculates text scores for 135 classic and newly developed lexical indices related to word…

Luminescently tagged 2,2'-bipyridine complex of FeII: synthesis and photophysical studies of 4-[N-(2-anthryl)carbamoyl]-4'-methyl-2,2'-bipyridine.

Science.gov (United States)

Zigler, David F; Elvington, Mark C; Heinecke, Julie; Brewer, Karen J

2006-08-21

The anthracene lumiphore was linked to the chelating ligand 2,2'-bipyridine, forming 4-[N-(2-anthryl)carbamoyl]-4'-methyl-2,2'-bipyridine (bpyAnth). Coupling through an amide linkage provides some electronic isolation of the anthracene lumiphore. Electrochemistry suggested little change of the anthracene oxidation whether free (1.35 V) linked to 2,2'-bipyridine as bpyAnth (1.30 V) or appended to Fe(II) (1.29 V). The bpyAnth ligand retained the structured luminescence characteristic of anthracene at 375, 400, 419, and 441 nm. This anthracene emission persists even when bpyAnth is complexed to an Fe(II) center. The complex [Fe(bpyAnth)3]2+ is emissive, in marked contrast to typical polyazine iron(II) complexes. This bpyAnth ligand serves as a luminescently tagged analogue of 2,2'-bipyridine, useful for coordination to a variety of metals.

Elimination par électrodialyse des ions Fe(II) d'une solution d'acide ...

African Journals Online (AJOL)

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concentration de l'acide (H2SO4) et la température sur l'efficacité d'élimination de Fe(II) a été étudiée. Les .... C. Negro et al. [20] ont étudié la possibilité de récupérer l'acide sulfurique à partir de solution d'acide sulfurique contenant du sulfate de cuivre. L. Cifuentes et al. ..... removal from rinsing water after metal etching,.

Redox topotactic reactions in Fe II - III (oxy)hydroxycarbonate new minerals related to fougèrite in gleysols: "trébeurdenite and mössbauerite"

Science.gov (United States)

Génin, Jean-Marie R.; Guérin, O.; Herbillon, A. J.; Kuzmann, E.; Mills, S. J.; Morin, G.; Ona-Nguema, G.; Ruby, C.; Upadhyay, C.

2012-03-01

Fougèrite mineral responsible for the bluish-green shade of gleysols in aquifers was identified as FeII - III oxyhydroxycarbonate, [Fe^II_{6(1-x) }Fe^III_{6x}O12H2(7 - 3 x)]2 + · [CO3^{2-} · 3H2O]2 - where the average ferric molar fraction x = [FeIII/Fetotal] was restricted to the [1/3-2/3] range, up till now. In this paper, Mössbauer spectra of gleys extracted from the schorre of maritime marshes have values of x in the [2/3-1] range. Magnetic properties of homologous chemical compounds studied by Mössbauer spectroscopy are explained with long range order of FeIII ions within Fe cation layers for x = 1/3, 2/3 and 1. Observed values are mixtures of topotactic domains that are in fact minerals with names proposed to IMA: fougèrite for x = 1/3, trébeurdenite for x = 2/3 and mössbauerite for x = 1.

Radiotracer study of the adsorption of Fe(III), Cr(III) and Cd(II) on natural and chemically modified Slovak zeolite

International Nuclear Information System (INIS)

Foeldesova, M.; Dillinger, P.; Lukac, P.

1998-01-01

In order to minimize the contamination of environment with metals in ionic form the more types of natural and chemically modified zeolites were examined to their uptake of Fe(III), Cr(III) and Cd(II) from water solutions by batch radio-exchange equilibration method. In this study was used zeolitic tuff from deposit Nizny Hrabovec (content of clinoptilolite 50-70%) with the grain size from 1.2 to 2.2 mm. The granules of zeolite were modified with the following NaOH solutions: ).5, 1, 2 and 4 mol.l -1 at 80 grad C for 4 hours. The sorption of Fe, Cr and Cd ions on all types of zeolites was studied by radio-exchange method and the sorption of Fe and Cr also flame atomic absorption method. From sorption curves the sorption coefficients were calculated. The results obtained in this work show that zeolites modified with NaOH solution are suitable for adsorption of Fe(III), Cr(III) and Cd(II) from underwater, waste water, feed water and coolant water from nuclear plants. The adsorbed zeolites can be solidified by conventional way

Redox reactions of [FeFe]-hydrogenase models containing an internal amine and a pendant phosphine.

Science.gov (United States)

Zheng, Dehua; Wang, Mei; Chen, Lin; Wang, Ning; Sun, Licheng

2014-02-03

A diiron dithiolate complex with a pendant phosphine coordinated to one of the iron centers, [(μ-SCH2)2N(CH2C6H4-o-PPh2){Fe2(CO)5}] (1), was prepared and structurally characterized. The pendant phosphine is dissociated together with a CO ligand in the presence of excess PMe3, to afford [(μ-SCH2)2N(CH2C6H4-o-PPh2){Fe(CO)2(PMe3)}2] (2). Redox reactions of 2 and related complexes were studied in detail by in situ IR spectroscopy. A series of new Fe(II)Fe(I) ([3](+) and [6](+)), Fe(II)Fe(II) ([4](2+)), and Fe(I)Fe(I) (5) complexes relevant to Hox, Hox(CO), and Hred states of the [FeFe]-hydrogenase active site were detected. Among these complexes, the molecular structures of the diferrous complex [4](2+) with the internal amine and the pendant phosphine co-coordinated to the same iron center and the triphosphine diiron complex 5 were determined by X-ray crystallography. To make a comparison, the redox reactions of an analogous complex, [(μ-SCH2)2N(CH2C6H5){Fe(CO)2(PMe3)}2] (7), were also investigated by in situ IR spectroscopy in the absence or presence of extrinsic PPh3, which has no influence on the oxidation reaction of 7. The pendant phosphine in the second coordination sphere makes the redox reaction of 2 different from that of its analogue 7.

The solubility of {sup 242}PuO{sub 2} in the presence of aqueous Fe(II). The impact of precipitate preparation

Energy Technology Data Exchange (ETDEWEB)

Felmy, Andrew R.; Moore, Dean A.; Buck, Edgar; Kukkadapu, Ravi; Sweet, Lucas; Abrecht, David; Ilton, Eugene S. [Pacific Northwest National Laboratory, Richland, WA (United States); Conrados, Steven D. [Los Alamos National Laboratory, Los Alamos, NM (United States)

2014-07-01

The solubility of different forms of precipitated {sup 242}PuO{sub 2}(am) were examined in solutions containing aqueous Fe(II) over a range of pH values. The first series of {sup 242}PuO{sub 2}(am) suspensions were prepared from a {sup 242}Pu(IV) stock that had been treated with thenoyltrifluoroacetone (TTA) to remove the {sup 241}Am originating from the decay of {sup 241}Pu. These {sup 242}PuO{sub 2}(am) suspensions showed much higher solubilities at the same pH value and Fe(II) concentration than previous studies using {sup 239}PuO{sub 2}(am). X-ray absorption fine structure (XAFS) spectroscopy of the precipitates showed a substantially reduced Pu-Pu backscatter over that previously observed in {sup 239}PuO{sub 2}(am) precipitates, indicating that the {sup 242}PuO{sub 2}(am) precipitates purified using TTA lacked the long range order previously found in{sup 239}PuO{sub 2}(am) precipitates. The Pu(IV) stock solution was subsequently re-purified using an ion exchange resin and an additional series of {sup 242}PuO{sub 2}(am) precipitates prepared. These suspensions showed higher redox potentials and total aqueous Pu concentrations than the TTA purified stock solution. The higher redox potential and aqueous Pu concentrations were in general agreement with previous studies on {sup 242}PuO{sub 2}(am) precipitates, presumably due to the removal of possible organic compounds originally present in the TTA purified stock. {sup 242}PuO{sub 2}(am) suspensions prepared with both stock solutions showed almost identical solubilities in Fe(II) containing solutions even though the initial aqueous Pu concentrations before the addition of Fe(II) were orders of magnitude different. By examining the solubility of {sup 242}PuO{sub 2}(am) prepared from both stocks in this way we have essentially approached equilibrium from both the undersaturated and oversaturated conditions. The final aqueous Pu concentrations are predictable using a chemical equilibrium model which includes the

Mechanochemical synthesis and intercalation of Ca(II)Fe(III)-layered double hydroxides

Energy Technology Data Exchange (ETDEWEB)

Ferencz, Zs.; Szabados, M.; Varga, G.; Csendes, Z. [Department of Organic Chemistry, University of Szeged, Dóm tér 8, Szeged H-6720 (Hungary); Materials and Solution Structure Research Group, Institute of Chemistry, University of Szeged, Aradi Vértanúk tere 1, Szeged H-6720 (Hungary); Kukovecz, Á. [Department of Applied and Environmental Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720 (Hungary); MTA-SZTE “Lendület” Porous Nanocomposites Research Group, Rerrich Béla tér 1, Szeged H-6720 (Hungary); Kónya, Z. [Department of Applied and Environmental Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720 (Hungary); MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, Rerrich Béla tér 1, Szeged H-6720 (Hungary); Carlson, S. [MAX IV Laboratory, Ole Römers väg 1, Lund SE-223 63 (Sweden); Sipos, P. [Materials and Solution Structure Research Group, Institute of Chemistry, University of Szeged, Aradi Vértanúk tere 1, Szeged H-6720 (Hungary); Department of Inorganic and Analytical Chemistry, University of Szeged, Dóm tér 7, Szeged H-6720 (Hungary); and others

2016-01-15

A mechanochemical method (grinding the components without added water – dry grinding, followed by further grinding in the presence of minute amount of water or NaOH solution – wet grinding) was used in this work for the preparation and intercalation of CaFe-layered double hydroxides (LDHs). Both the pristine LDHs and the amino acid anion (cystinate and tyrosinate) intercalated varieties were prepared by the two-step grinding procedure in a mixer mill. By systematically changing the conditions of the preparation method, a set of parameters could be determined, which led to the formation of close to phase-pure LDH. The optimisation procedure was also applied for the intercalation processes of the amino acid anions. The resulting materials were structurally characterised by a range of methods (X-ray diffractometry, scanning electron microscopy, energy dispersive analysis, thermogravimetry, X-ray absorption and infra-red spectroscopies). It was proven that this simple mechanochemical procedure was able to produce complex organic–inorganic nanocomposites: LDHs intercalated with amino acid anions. - Graphical abstract: Amino acid anion-Ca(II)Fe(III)-LDHs were successfully prepared by a two-step milling procedure. - Highlights: • Synthesis of pristine and amino acid intercalated CaFe-LDHs by two-step milling. • Identifying the optimum synthesis and intercalation parameters. • Characterisation of the samples with a range of instrumental methods.

Effect of Iron Fe (II and Fe (III in a Binary System Evaluated Bioluminescent Method

Directory of Open Access Journals (Sweden)

Elena Sorokina

2013-01-01

Full Text Available The effect of iron ions Fe2+ and Fe3+ on the bioluminescent recombinant strain of Escherichia coli in a single-component and binary system. Found that for the bacteria E. coli Fe3+ ions are more toxic than Fe2+. Under the combined effect of iron toxicity increases, the percentage of luminescence quenching increases, but the value is much less than the sum of the indicator for the Fe2+ and Fe3+. The biological effect of insertion of iron is not proportional to their content in the mixture.

The role of sophisticated accounting system in strategy management

OpenAIRE

Naranjo Gil, David

2004-01-01

Organizations are designing more sophisticated accounting information systems to meet the strategic goals and enhance their performance. This study examines the effect of accounting information system design on the performance of organizations pursuing different strategic priorities. The alignment between sophisticated accounting information systems and organizational strategy is analyzed. The enabling effect of the accounting information system on performance is also examined. Relationships ...

Financial Literacy and Financial Sophistication in the Older Population

Science.gov (United States)

Lusardi, Annamaria; Mitchell, Olivia S.; Curto, Vilsa

2017-01-01

Using a special-purpose module implemented in the Health and Retirement Study, we evaluate financial sophistication in the American population over the age of 50. We combine several financial literacy questions into an overall index to highlight which questions best capture financial sophistication and examine the sensitivity of financial literacy responses to framing effects. Results show that many older respondents are not financially sophisticated: they fail to grasp essential aspects of risk diversification, asset valuation, portfolio choice, and investment fees. Subgroups with notable deficits include women, the least educated, non-Whites, and those over age 75. In view of the fact that retirees increasingly must take on responsibility for their own retirement security, such meager levels of knowledge have potentially serious and negative implications. PMID:28553191

Financial Literacy and Financial Sophistication in the Older Population.

Science.gov (United States)

Lusardi, Annamaria; Mitchell, Olivia S; Curto, Vilsa

2014-10-01

Using a special-purpose module implemented in the Health and Retirement Study, we evaluate financial sophistication in the American population over the age of 50. We combine several financial literacy questions into an overall index to highlight which questions best capture financial sophistication and examine the sensitivity of financial literacy responses to framing effects. Results show that many older respondents are not financially sophisticated: they fail to grasp essential aspects of risk diversification, asset valuation, portfolio choice, and investment fees. Subgroups with notable deficits include women, the least educated, non-Whites, and those over age 75. In view of the fact that retirees increasingly must take on responsibility for their own retirement security, such meager levels of knowledge have potentially serious and negative implications.

Synthesis and characterization of novel Cu(II) complex coated Fe3O4@SiO2 nanoparticles for catalytic performance

Science.gov (United States)

Nasrollahzadeh, Mahmoud; Sajjadi, Mohaddeseh; Khonakdar, Hossein Ali

2018-06-01

In this study, a convenient method for the synthesis of arylaminotetrazoles has been developed using a copper (II)-aminotetrazole complex immobilized on silica-coated Fe3O4 (Fe3O4@SiO2) nanoparticles (Fe3O4@SiO2-aminotet-Cu(II)) as a novel and efficient magnetically catalyst. The constructed superparamagnetic core-shell nanoparticles were successfully prepared, as proven using different spectroscopic techniques such as fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscope (TEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetry and differential thermogravimetry (TG-DTG) and vibrating sample magnetometer (VSM) analysis. The applicability of Fe3O4@SiO2-aminotet-Cu(II) magnetic catalyst allows the efficient synthesis of a variety of arylaminotetrazoles from the reaction between various arylcyanamides with sodium azide in high yields. The effect of catalyst loading was investigated. In addition, the reaction mechanism for the synthesis of arylaminotetrazoles was reasonably proposed. Results show that the 1-aryl-5-amino-1H-tetrazole (B isomer) and 5-arylamino-1H-tetrazole (A isomer) can be obtained from the arylcyanamides carrying electron-donating and electron-withdrawing substituents, respectively. This procedure offers a simple methodology, relatively short reaction times, easy work-up, high yields of the products and a cleaner reaction with elimination of hydrazoic acid (HN3). Moreover, catalyst can be conveniently recovered through the use of external magnet and reused for at least 6 times without any significant loss of its activity.

RESEARCH CONCERNING THE Fe CIRCUIT IN THE ENVIRONMENT

Directory of Open Access Journals (Sweden)

MARIOARA NICOLETA FILIMON

2007-01-01

Full Text Available The iron is an organogenous chemical element which, although in small quantities, is absolutely needed for live. The iron can be present in nature under 2 forms: bivalent or trivalent. Microorganism has an important role concerning the iron circuit in the biosphere. The iron cycle has 4 microbial processes: mineralizing the organic iron, forming the organic compounds with iron, the bivalent iron oxidity and the reduction of the trivalent iron. The Fe III and Fe II reduction, under the action of iron reductive bacteria, has a biological significance and a special a practical importance. Several proceedings used in mining, pottery and in the discovery of toxicity of certain compounds, at the level of anaerobic environment, are based on this process of reduction. The Fe III and Fe II reductive process can also have dangerous negative effects, due to the huge quantity of the accumulated Fe II. This huge quantity of Fe II is a big problem for the level of underground water, because Fe II compromises the water quality and the damaged metal plumbing. Under the action of microbial population, the trivalent iron is reduced to bivalent one, which is soluble. The bivalent iron is mostly evidenced with α,α-dipiridil reactive.

Spin crossover behaviour in Hofmann-like coordination polymer Fe(py)2[Pd(CN)4] with 57Fe Mössbauer spectra

Science.gov (United States)

Kitazawa, Takafumi; Kishida, Takanori; Kawasaki, Takeshi; Takahashi, Masashi

2017-11-01

We have prepared the 2D spin crossover complexes Fe(L)2Pd(CN)4 (L = py : 1a; py-D5 : 1b and py-15N : 1c). 1a has been characterised by 57Fe Mossbauer spectroscopic measurements, single crystal X-ray determination and SQUID measurements. The Mössbauer spectra for 1a indicate that the iron(II) spin states are in high spin states at 298 K and are in low spin states at 77 K. The crystal structures of 1a at 298 K and 90 K also show the high spin state and the low spin state respectively, associated with the Fe(II)-N distances. The spin transition temperature range of 1a is higher than that of Fe(py)2Ni(CN)4 since Pd(II) ions are larger and heavier than Ni(II) ions. SQUID data indicate isotope effects among 1a, 1b and 1c are observed in very small shifts of the transition temperatures probably due to larger and heavier Pd(II) ions. The delicate shifts would be associated with subtle balances between different vibrations around Fe(II) atoms and electronic factors.

Applicability of anaerobic nitrate-dependent Fe(II) oxidation to microbial enhanced oil recovery (MEOR).

Science.gov (United States)

Zhu, Hongbo; Carlson, Han K; Coates, John D

2013-08-06

Microbial processes that produce solid-phase minerals could be judiciously applied to modify rock porosity with subsequent alteration and improvement of floodwater sweep in petroleum reservoirs. However, there has been little investigation of the application of this to enhanced oil recovery (EOR). Here, we investigate a unique approach of altering reservoir petrology through the biogenesis of authigenic rock minerals. This process is mediated by anaerobic chemolithotrophic nitrate-dependent Fe(II)-oxidizing microorganisms that precipitate iron minerals from the metabolism of soluble ferrous iron (Fe(2+)) coupled to the reduction of nitrate. This mineral biogenesis can result in pore restriction and reduced pore throat diameter. Advantageously and unlike biomass plugs, these biominerals are not susceptible to pressure or thermal degradation. Furthermore, they do not require continual substrate addition for maintenance. Our studies demonstrate that the biogenesis of insoluble iron minerals in packed-bed columns results in effective hydrology alteration and homogenization of heterogeneous flowpaths upon stimulated microbial Fe(2+) biooxidation. We also demonstrate almost 100% improvement in oil recovery from hydrocarbon-saturated packed-bed columns as a result of this metabolism. These studies represent a novel departure from traditional microbial EOR approaches and indicate the potential for nitrate-dependent Fe(2+) biooxidation to improve volumetric sweep efficiency and enhance both the quality and quantity of oil recovered.

Reactions of H2O3 in the pulse-irradiated Fe(II)-O2 system

DEFF Research Database (Denmark)

Sehested, Knud; Bjergbakke, Erling; Lang Rasmussen, O.

1969-01-01

G(Fe(III)] is measured in pulse-irradiated O2-saturated solutions of 20 to 160 μMFe(II), at the p H's 0.46, 1.51, and 2.74 H2SO4 and HClO4 and with dose rates between 1 and 8 krad/1 μsec pulse. Based on homogeneous kinetics, the results are interpreted by a system of 18 reactions. The formation...

Cyanobacterium removal and control of algal organic matter (AOM) release by UV/H2O2 pre-oxidation enhanced Fe(II) coagulation.

Science.gov (United States)

Jia, Peili; Zhou, Yanping; Zhang, Xufeng; Zhang, Yi; Dai, Ruihua

2017-12-11

Harmful algal blooms in source water are a worldwide issue for drinking water production and safety. UV/H 2 O 2 , a pre-oxidation process, was firstly applied to enhance Fe(II) coagulation for the removal of Microcystis aeruginosa [M. aeruginosa, 2.0 (±0.5) × 10 6  cell/mL] in bench scale. It significantly improved both algae cells removal and algal organic matter (AOM) control, compared with UV irradiation alone (254 nm UVC, 5.4 mJ/cm 2 ). About 94.7% of algae cells were removed after 5 min UV/H 2 O 2 pre-treatment with H 2 O 2 dose 375 μmol/L, FeSO 4 coagulation (dose 125 μmol/L). It was also certified that low residue Fe level and AOM control was simultaneously achieved due to low dose of Fe(II) to settle down the cells as well as the AOM. The result of L 9 (3) 4 orthogonal experiment demonstrated that H 2 O 2 and FeSO 4 dose was significantly influenced the algae removal. UV/H 2 O 2 induced an increase of intracellular reactive oxidant species (ROS) and a decrease in zeta potential, which might contribute to the algae removal. The total microcystins (MCs) concentration was 1.5 μg/L after UV/H 2 O 2 pre-oxidation, however, it could be removed simultaneously with the algae cells and AOM. This study suggested a novel application of UV/H 2 O 2 -Fe(II) process to promote algae removal and simultaneously control AOM release in source waters, which is a green and promising technology without secondary pollution. Copyright © 2017 Elsevier Ltd. All rights reserved.

1D and 2D assembly structures by imidazole···chloride hydrogen bonds of iron(II) complexes [Fe(II)(HL(n-Pr))3]Cl·Y (HL(n-Pr) = 2-methylimidazol-4-yl-methylideneamino-n-propyl; Y = AsF6, BF4) and their spin states.

Science.gov (United States)

Fujinami, Takeshi; Nishi, Koshiro; Matsumoto, Naohide; Iijima, Seiichiro; Halcrow, Malcolm A; Sunatsuki, Yukinari; Kojima, Masaaki

2011-12-07

Two Fe(II) complexes fac-[Fe(II)(HL(n-Pr))(3)]Cl·Y (Y = AsF(6) (1) and BF(4) (2)) were synthesized, where HL(n-Pr) is 2-methylimidazole-4-yl-methylideneamino-n-propyl. Each complex-cation has the same octahedral N(6) geometry coordinated by three bidentate ligands and assumes facial-isomerism, fac-[Fe(II)(HL(n-Pr))(3)](2+) with Δ- and Λ-enantiomorphs. Three imidazole groups per Δ- or Λ-fac-[Fe(II)(HL(n-Pr))(3)](2+) are hydrogen-bonded to three Cl(-) ions or, from the viewpoint of the Cl(-) ion, one Cl(-) ion is hydrogen-bonded to three neighbouring fac-[Fe(II)(HL(n-Pr))(3)](2+) cations. The 3 : 3 NH···Cl(-) hydrogen bonds between Δ- or Λ-fac-[Fe(II)(HL(n-Pr))(3)](2+) and Cl(-) generate two kinds of assembly structures. The directions of the 3 : 3 NH···Cl(-) hydrogen bonds and hence the resulting assembly structures are determined by the size of the anion Y, though Y is not involved into the network structure and just accommodated in the cavity. Compound 1 has a 1D ladder structure giving a larger cavity, in which the Δ- and Λ-fac-[Fe(II)(HL(n-Pr))(3)](2+) enantiomorphs are bridged by two NH···Cl(-) hydrogen bonds. Compound 2 has a 2D network structure with a net unit of a cyclic trimer of {fac-[Fe(II)(HL(n-Pr))(3)](2+)···Cl(-)}(3) giving a smaller cavity, in which Δ- or Λ-fac-[Fe(II)(HL(n-Pr))(3)](2+) species with the same chirality are linked by NH···Cl(-) hydrogen bonds to give a homochiral 2D network structure. Magnetic susceptibility and Mössbauer spectral measurements demonstrated that compound 1 showed an abrupt one-step spin crossover with 4.0 K thermal hysteresis of T(c↓) = 125.5 K and T(c↑) = 129.5 K and compound 2 showed no spin transition and stayed in the high-spin state over the 5-300 K temperature range.

Determination of Fe²⁺ and Fe³⁺ species by FIA-CRC-ICP-MS in Antarctic ice samples

DEFF Research Database (Denmark)

Spolaor, A; Vallelonga, Paul Travis; Gabrieli, J

2012-01-01

contexts depends strongly on its oxidation state. Solubility in water and the capacity to form complexes are just two important characteristics that are species dependent. Distinguishing between the two iron species, Fe(II) and Fe(III), is necessary to evaluate bioavailability, as Fe(II) is more soluble...... detection limit is 0.01 ng g-1. A chelating resin, Ni-NTA Superflow, was used to separate the Fe species: At pH 2 the resin is capable of retaining Fe3+ with no retention of Fe2+. After the initial separation, we oxidized the Fe2+ using H2O2, and determined the Fe2+ concentration as the difference between...

The role of iron(II) dilution in the magnetic and photomagnetic properties of the series [Fe(x)Zn(1-x)(bpp)₂](NCSe)₂.

Science.gov (United States)

Baldé, Chérif; Desplanches, Cédric; Le Gac, Fréderic; Guionneau, Philippe; Létard, Jean-François

2014-06-07

The effects of metal dilution on the spin-crossover behavior of iron(II) in the mixed crystal series [Fe(x)Zn(1-x)(bpp)2](NCSe)2 (bpp = 2,6-bis(pyrazol-3-yl)pyridine) have been studied using magnetic susceptibility, photomagnetism and diffuse reflectivity measurements. For each mixed-crystal system, the thermal spin transition temperature, T(1/2), and the relaxation temperature of the photo-induced high-spin state, T(LIESST), have been systematically determined. It appears that T(1/2) decreases with the metal dilution while T(LIESST) remains unchanged. Dilution also tends to decrease the hysteresis width and smooth the transition curves. These effects were discussed first qualitatively and then quantitatively on the basis of a kinetic study governing the photo-induced back conversion taking into account the relative sizes of Zn(II) and Fe(II) ions. Interestingly, single crystals were obtained for [Fe(0.6)Zn(0.4)(bpp)2](NCSe)2 allowing the X-ray diffraction crystal-structure determination.

The Impact of Financial Sophistication on Adjustable Rate Mortgage Ownership

Science.gov (United States)

Smith, Hyrum; Finke, Michael S.; Huston, Sandra J.

2011-01-01

The influence of a financial sophistication scale on adjustable-rate mortgage (ARM) borrowing is explored. Descriptive statistics and regression analysis using recent data from the Survey of Consumer Finances reveal that ARM borrowing is driven by both the least and most financially sophisticated households but for different reasons. Less…

Synthesis of amino functionalized magnetic graphenes composite material and its application to remove Cr(VI), Pb(II), Hg(II), Cd(II) and Ni(II) from contaminated water

International Nuclear Information System (INIS)

Guo, Xiaoyao; Du, Bin; Wei, Qin; Yang, Jian; Hu, Lihua; Yan, Liangguo; Xu, Weiying

2014-01-01

Highlights: • Graphenes magnetic composite nanoparticles (Fe 3 O 4 -GS) were used to adsorb metal ions. • The adsorption of metal ions onto Fe 3 O 4 -GS could be well interpreted by the Freundlich equation. • The adsorption of metal ions onto Fe 3 O 4 -GS fit pseudo-second order kinetic model. • Thermodynamic studies illustrated that the adsorption process was endothermic and spontaneous in nature. - Abstract: In the present study, a kind of graphenes magnetic material (Fe 3 O 4 -GS) was prepared by compositing graphene sheet with ferroferric oxide, and shown to be effictive for removing Cr(VI), Pb(II), Hg(II), Cd(II) and Ni(II) ions from aqueous solution. The synthesized sorbent was characterized by SEM, TEM, FTIR, XRD, XPS and BET, respectively. The pH ZPC value of the sorbent was estimated to be 3.5 by alkaline-titration methods. Fe 3 O 4 -GS can be simply recovered from water with magnetic separation at low magnetic field within one minute. The sorption capacities of the metals were 17.29, 27.95, 23.03, 27.83 and 22.07 mg g −1 for Cr(VI), Pb(II), Hg(II), Cd(II) and Ni(II), respectively. Kinetic data showed good correlation with pseudo-second-order equation and the Freundlich model was found to fit for the isotherm data of all the heavy metal ions. It was found that the metals sorption was accomplished mainly via chelation or ion exchange. The results of thermodynamic studies illustrate that the adsorption process was endothermic and spontaneous in nature

Effects of tillage on the Fe oxides activation in soil

Science.gov (United States)

Chi, Guangyu; Chen, Xin; Shi, Yi; Wang, Jun; Zheng, Taihui

2009-07-01

Since mid-1950s, the wetland ecosystems in Sanjiang Plain of Northeast China have been experiencing greater changes in land use, which had negative effects on the soil environments. This study assessed the effects of soil tillage on the activation of soil Fe in the region. The test ecosystems included natural wetland, paddy field and upland field converted from wetland. Soil samples at the depths of 0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm, 40-60 cm, 60-90 cm and 90-120 cm were collected from each of the ecosystems for the analysis of vertical distribution of soil pH, organic carbon, chelate Fe oxides and Fe(II). The results showed that the conversion of wetland into paddy field and upland field induced a decrease of organic carbon content in 0-10 cm soil layer by 61.8% (P carbon showed that chelate Fe oxides and Fe(II) was correlated positively with soil organic carbon and chelate ratio had a more positive relationship with organic carbon than chelate Fe oxides and Fe(II). The results of chelate Fe oxides, Fe(II) and chelate ratio of Fe suggested that reclamation could prevent the Fe activation and organic matter is credited for having an important influence on the process of Fe activation.

Ligand field and intermolecular interactions tuning the magnetic properties of spin-crossover Fe(II) polymer with 4,4′-bipyridine

Energy Technology Data Exchange (ETDEWEB)

Luo, Yang-Hui; Liu, Qing-Ling; Yang, Li-Jing; Ling, Yang; Wang, Wei; Sun, Bai-Wang, E-mail: chmsunbw@seu.edu.cn

2015-02-15

A new spin crossover coordination polymer (SCO-CPs) of Fe(II)-4,4′-bipyridine (4,4′-bipy) family: (Fe(4,4′-bipy){sub 2}(H{sub 2}O){sub 2})·(4,4′-bipy)· 8(H{sub 2}O)·2(ClO{sub 4}) (3), which displays half spin transitions between 100 and 300 K, has been synthesized and structurally characterized. Compound 3 featured with two-dimensional (2-D) grids connected by hydrogen bonds and π…π packing between one-dimensional (1-D) chains, the 2-D grids expand to three-dimensional (3-D) architecture supported by a “S-shaped holder” involving lattice 4-4′-bipy, water molecules and perchlorate anion. We compared 3 with the other two analogous complexes: ((Fe(4,4′-bipy) (H{sub 2}O){sub 2} (NCS){sub 2})·4,4′-bipy, 1 and (Fe(4,4′-bipy){sub 2}(NCS){sub 2})·mSolv, 2) through Hirshfeld surfaces analysis, which revealed that the low ligand field strength (NCS{sup −}) and lone-pair…H contacts contribute to the stabilization of HS (high-spin) state of the Fe(II) ion, while the high ligand field strength (4,4′-bipy) and strong intermolecular contacts (hydrogen bonds and π…π packing interactions) make for the LS (low-spin) state. - Highlights: ●A new member of Fe(||)-4,4′-bipy family has been prepared. ●It displays half spin transitions tuned by ligand field and intermolecular interactions. ●We have made a detailed comparison of this new member with two other analogous complexes.

Stable Fe isotope fractionation during anaerobic microbial dissimilatory iron reduction at low pH

Science.gov (United States)

Chanda, P.; Amenabar, M. J.; Boyd, E. S.; Beard, B. L.; Johnson, C.

2017-12-01

In low-temperature anaerobic environments microbial dissimilatory iron reduction (DIR) plays an important role in Fe cycling. At neutral pH, sorption of aqueous Fe(II) (Fe(II)aq, produced by DIR) catalyzes isotopic exchange between Fe(II) and solid Fe(III), producing 56Fe/54Fe fractionations on the order of 3‰ during DIR[1,2,3]. At low pH, however, the absence of sorbed Fe(II) produces only limited abiologic isotopic exchange[4]. Here we investigated the scope of isotopic exchange between Fe(II)aq and ferric (hydr)oxides (ferrihydrite and goethite) and the associated stable Fe isotope fractionation during DIR by Acidianus strain DS80 at pH 3.0 and 80°C[5]. Over 19 days, 13% reduction of both minerals via microbial DIR was observed. The δ56Fe values of the fluid varied from -2.31 to -1.63‰ (ferrihydrite) and -0.45 to 0.02‰ (goethite). Partial leaching of bulk solid from each reactor with dilute HCl showed no sorption of Fe(II), and the surface layers of the solids were composed of Fe(III) with high δ56Fe values (ferrihydrite: 0.20 to 0.48‰ and goethite: 1.20 to 1.30‰). These results contrast with the lack of Fe isotope exchange in abiologic low-pH systems and indicate a key role for biology in catalyzing Fe isotope exchange between Fe(II)aq and Fe(III) solids, despite the absence of sorbed Fe(II). The estimated fractionation factor (ΔFeFe(III) -Fe(II)aq 2.6‰) from leaching of ferrihydrite is similar to the abiologic equilibrium fractionation factor ( 3.0‰)[3]. The fractionation factor (ΔFeFe(III) -Fe(II)aq 2.0‰) for goethite is higher than the abiologic fractionation factor ( 1.05‰)[2], but is consistent with the previously proposed "distorted surface layer" of goethite produced during the exchange with Fe(II)aq at neutral pH[1]. This study indicates that significant variations in Fe isotope compositions may be produced in low-pH environments where biological cycling of Fe occurs, in contrast to the expected lack of isotopic fractionation in

Kinetics of dissolution of {alpha}-Fe{sub 2}O{sub 3} and {gamma}-Fe{sub 2}O{sub 3} in EDTA and NTA-based formulations

Energy Technology Data Exchange (ETDEWEB)

Ranganathan, S. [Dept. of Chemical Engineering, Univ. of New Brunswick, Fredericton, N.B. (Canada); Srinivasan, M.P. [Water and Steam Chemistry Lab. of Bhabha Atomic Research Centre (BARC) (India); Narasimhan, S.V. [Bhabha Atomic Research Centre (India); Raghavan, P.S. [Madras Christian Coll., Chennai (India); Gopalan, R. [Dept. of Chemistry, Madras Christian Coll., Chennai (India)

2004-06-01

The dissolution studies were carried out on haematite ({alpha}-Fe{sub 2}O{sub 3}) and maghemite ({gamma}-Fe{sub 2}O{sub 3}) in two different formulations of ethylenediaminetetraacetic acid (EDTA) and nitrilotriaceticacid (NTA). The rate constants were calculated using the ''inverse cubic rate law.'' The leaching of the metal ions from the oxide is controlled partly by the Fe(II)-L{sub n} (L is a complexing ligand and n is the number of ligands attached to Fe{sup 2+}), a dissolution product arising from the oxides having Fe{sup 2+} in the lattice. The addition of Fe(II)-L{sub n} along with the formulation greatly increased the initial rate of dissolution. The effect of the addition of Fe(II)-L as a reductant on the dissolution of {alpha}-Fe{sub 2}O{sub 3} was not the same as in the case of {gamma}-Fe{sub 2}O{sub 3}. The rate constants (k{sub obs}) for the dissolution of {alpha}-Fe{sub 2}O{sub 3} and {gamma}-Fe{sub 2}O{sub 3} in the presence of ascorbic acid were less in the EDTA formulation than in the NTA formulation. The studies using Fe(II)-NTA and Fe(II)-EDTA with varying compositions of citric acid and ascorbic acid revealed that a minimum quantity of the chelant is sufficient to initiate the dissolution process, which can be further controlled by the reductants and weaker chelants such as citric acid. (orig.)

Magnetic properties of Fe-doped organic-inorganic nanohybrids

Science.gov (United States)

Silva, N. J. O.; Amaral, V. S.; Carlos, L. D.; de Zea Bermudez, V.

2003-05-01

We present a magnetic study of Fe-doped diureasils (siloxane-based networks to which poly(ethylene oxide)-based chains are grafted by urea cross linkages doped with Fe(II) or Fe(III) ions. Structural studies show that the Fe(II) ions interact mainly with the organic chain, whereas the incorporation of Fe(III) leads to the formation of iron-based nanoclusters, with radius increasing from 20 to 40 Å. Fe(II)-doped samples behave as simple paramagnets, with μeff=5.32μB. Fe(III)-doped hybrids present antiferromagnetic interactions, with TN increasing with Fe(III) concentration up to 13.6 K for 6% doping. Thermal irreversibility was observed below ˜40 K and is stronger for higher concentrations. The coercive fields (HC) are of the order of 1000 Oe at 5 K. Hysteresis cycles are shifted to negative fields, revealing the presence of exchange anisotropy interactions with exchange fields (HE) of the order of 100 Oe. Both fields decrease rapidly with increasing temperature. We analyze this behavior in terms of the contribution of surface spin disorder to exchange anisotropy.

Light-Induced Type-II Band Inversion and Quantum Anomalous Hall State in Monolayer FeSe

Science.gov (United States)

Wang, Z. F.; Liu, Zhao; Yang, Jinlong; Liu, Feng

2018-04-01

Coupling a quantum anomalous Hall (QAH) state with a superconducting state offers an attractive approach to detect the signature alluding to a topological superconducting state [Q. L. He et al., Science 357, 294 (2017), 10.1126/science.aag2792], but its explanation could be clouded by disorder effects in magnetic doped QAH materials. On the other hand, an antiferromagnetic (AFM) quantum spin Hall (QSH) state is identified in the well-known high-temperature 2D superconductor of monolayer FeSe [Z. F. Wang et al., Nat. Mater. 15, 968 (2016), 10.1038/nmat4686]. Here, we report a light-induced type-II band inversion (BI) and a QSH-to-QAH phase transition in the monolayer FeSe. Depending on the handedness of light, a spin-tunable QAH state with a high Chern number of ±2 is realized. In contrast to the conventional type-I BI resulting from intrinsic spin-orbital coupling (SOC), which inverts the band an odd number of times and respects time reversal symmetry, the type-II BI results from a light-induced handedness-dependent effective SOC, which inverts the band an even number of times and does not respect time reversal symmetry. The interplay between these two SOC terms makes the spin-up and -down bands of an AFM QSH state respond oppositely to a circularly polarized light, leading to the type-II BI and an exotic topological phase transition. Our finding affords an exciting opportunity to detect Majorana fermions in one single material without magnetic doping.

Synthesis and characterization of chromium(III), manganese(II), iron(III), cobalt(II), nickel(II), copper(II), cadmium(II) and dioxouranium(VI) complexes of 4(2-pyridyl)-1-(2,4-dihydroxybenzaldehyde)-3-thiosemicarbazone

International Nuclear Information System (INIS)

Abu El-Reash, G.M.; Ibrahim, M.M.; Kenawy; El-Ayaan, Usama; Khattab, M.A.

1994-01-01

A few complexes of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and dioxouranium(VI) with 4(2-pyridyl)-1-(2,4-dihydroxybenzaldehyde)-3-thiosemicarbazone have been synthesised and characterized on the basis of elemental analysis, IR, electronic NMR, and magnetic moment data. An octahedral structure is proposed for the Cr(III), Fe(III), Co(II) and Ni(H 3 PBT) 2 Cl 2 .2H 2 O complexes; a tetrahedral structure for the Mn(II) and Ni 2 (PBT)OAc.H 2 0 complexes and a square planar structure for the Cu(II) complexes. The antimicrobial and antifungal activities of H 3 PBT and of its metal(II) complexes are investigated. The results reveal that H 3 PBT exhibits greater antimicrobial activities than its complexes. (author). 34 refs., 4 figs., 2 tabs

Synthesis, characterization and performance in arsenic removal of iron-doped activated carbons prepared by impregnation with Fe(III) and Fe(II)

International Nuclear Information System (INIS)

Muniz, G.; Fierro, V.; Celzard, A.; Furdin, G.; Gonzalez-Sanchez, G.; Ballinas, M.L.

2009-01-01

Arsenic removal from natural well water from the state of Chihuahua (Mexico) is investigated by adsorption using a commercial activated carbon (AC). The latter is used as such, or after oxidation by several chemicals in aqueous solution: nitric acid, hydrogen peroxide, and ammonium persulphate. Raw and oxidised activated carbons are fully characterised (elementary analysis, surface chemistry, pore texture parameters, pH ZC , and TEM observation). Adsorption of As is measured in the aforementioned water, containing ca. 300 ppb of arsenic: removal of As is poor with the raw AC, and only the most oxidised carbons exhibit higher performances. By contrast, iron-doped ACs are much more efficient for that purpose, though their As uptake strongly depends on their preparation conditions: a number of samples were synthesised by impregnation of raw and oxidised ACs with HCl aqueous solutions of either FeCl 3 or FeCl 2 at various concentrations and various pH. It is shown that iron(II) chloride is better for obtaining high iron contents in the resultant ACs (up to 8.34 wt.%), leading to high As uptake, close to 0.036 mg As/g C. In these conditions, 100% of the As initially present in the natural well water is removed, as soon as the Fe content of the adsorbent is higher than 2 wt.%.

Electron impact excitation of the iron peak element Fe II

International Nuclear Information System (INIS)

Ramsbottom, C.A.; Scott, M.P.; Bell, K.L.; McLaughlin, B.M.; Burke, P.G.; Keenan, F.P.; Sunderland, A.G.; Burke, V.M.; Noble, C.J.

2002-01-01

Effective collision strengths for electron-impact excitation of Fe II are presented for all sextet-to-quartet transitions among the 38 LS states formed from the basis configurations 3d 6 4s, 3d 7 and 3d 6 4p. A total of 112 individual transitions are considered at electron temperatures in the range 30-100,000 K, encompassing values of importance for applications in astrophysics as well as laboratory plasmas. A limited comparison is made with earlier theoretical work and large differences are found to occur at the temperatures considered. In particular, it is found that the inclusion or omission of some (N+1)-bound configurations in the Hamiltonian matrices describing the collision process can have a huge effect on the resulting effective collision strengths, by up to a factor of four in some cases. (author)

Decoupling photochemical Fe(II) oxidation from shallow-water BIF deposition

DEFF Research Database (Denmark)

Konhauser, Kurt; Amskold, Larry; Lalonde, Stefan

2007-01-01

to the rise of atmospheric oxygen and the development of a protective ozone layer, the Earth's surface was subjected to high levels of ultraviolet radiation. Bulk ocean waters that were anoxic at this time could have supported high concentrations of dissolved Fe(II). Under such conditions, dissolved ferrous...... for biology [Fran??ois, L.M., 1986, Extensive deposition of banded iron formations was possible without photosynthesis. Nature 320, 352-354]. Here, we evaluate the potential importance of photochemical oxidation using a combination of experiments and thermodynamic models. The experiments simulate......-type systems, then we are driven to conclude that oxide-facies BIF are the product of a rapid, non-photochemical oxidative process, the most likely candidates being direct or indirect biological oxidation, and that a significant fraction of BIF could have initially been deposited as ferrous minerals. ?? 2007...

Mechanisms of Fe biofortification and mitigation of Cd accumulation in rice (Oryza sativa L.) grown hydroponically with Fe chelate fertilization.

Science.gov (United States)

Chen, Zhe; Tang, Ye-Tao; Zhou, Can; Xie, Shu-Ting; Xiao, Shi; Baker, Alan J M; Qiu, Rong-Liang

2017-05-01

Cadmium contaminated rice from China has become a global food safety issue. Some research has suggested that chelate addition to substrates can affect metal speciation and plant metal content. We investigated the mitigation of Cd accumulation in hydroponically-grown rice supplied with EDTANa 2 Fe(II) or EDDHAFe(III). A japonica rice variety (Nipponbare) was grown in modified Kimura B solution containing three concentrations (0, 10, 100 μΜ) of the iron chelates EDTANa 2 Fe(II) or EDDHAFe(III) and 1 μΜ Cd. Metal speciation in solution was simulated by Geochem-EZ; growth and photosynthetic efficiency of rice were evaluated, and accumulation of Cd and Fe in plant parts was determined. Net Cd fluxes in the meristematic zone, growth zone, and maturation zone of roots were monitored by a non-invasive micro-test technology. Expression of Fe- and Cd-related genes in Fe-sufficient or Fe-deficient roots and leaves were studied by QRT-PCR. Compared to Fe deficiency, a sufficient or excess supply of Fe chelates significantly enhanced rice growth by elevating photosynthetic efficiency. Both Fe chelates increased the Fe content and decreased the Cd content of rice organs, except for the Cd content of roots treated with excess EDDHAFe(III). Compared to EDDHAFe(III), EDTANa 2 Fe(II) exhibited better mitigation of Cd accumulation in rice by generating the EDTANa 2 Cd complex in solution, decreasing net Cd influx and increasing net Cd efflux in root micro-zones. Application of EDTANa 2 Fe(II) and EDDHAFe(III) also reduced Cd accumulation in rice by inhibiting expression of genes involved in transport of Fe and Cd in the xylem and phloem. The 'win-win' situation of Fe biofortification and Cd mitigation in rice was achieved by application of Fe chelates. Root-to-stem xylem transport of Cd and redistribution of Cd in leaves by phloem transport can be regulated in rice through the use of Fe chelates that influence Fe availability and Fe-related gene expression. Fe fertilization

Sophisticated Epistemologies of Physics versus High-Stakes Tests: How Do Elite High School Students Respond to Competing Influences about How to Learn Physics?

Science.gov (United States)

Yerdelen-Damar, Sevda; Elby, Andrew

2016-01-01

This study investigates how elite Turkish high school physics students claim to approach learning physics when they are simultaneously (i) engaged in a curriculum that led to significant gains in their epistemological sophistication and (ii) subject to a high-stakes college entrance exam. Students reported taking surface (rote) approaches to…

Cognitive Load and Strategic Sophistication

OpenAIRE

Allred, Sarah; Duffy, Sean; Smith, John

2013-01-01

We study the relationship between the cognitive load manipulation and strategic sophistication. The cognitive load manipulation is designed to reduce the subject's cognitive resources that are available for deliberation on a choice. In our experiment, subjects are placed under a large cognitive load (given a difficult number to remember) or a low cognitive load (given a number which is not difficult to remember). Subsequently, the subjects play a one-shot game then they are asked to recall...

Iodometric determination of peroxydiphosphate in the presence of copper(II) or iron(II) as catalyst.

Science.gov (United States)

Kapoor, S; Sharma, P D; Gupta, Y K

1975-09-01

Peroxydiphosphate can be determined iodometrically in the presence of a large excess of potassium iodide with copper(II) or iron(II) as catalyst through the operation of the Cu(II)/Cu(I) or Fe(II)/Fe(III) cycle. The method is applicable in HClO(4), H(2)SO(4), HCl and CH(3)COOH acid media in the range 0.1-1.0M studied. Nickel, manganese(II), cobalt(II), silver, chloride and phosphate are without effect.

Moral foundations and political attitudes: The moderating role of political sophistication.

Science.gov (United States)

Milesi, Patrizia

2016-08-01

Political attitudes can be associated with moral concerns. This research investigated whether people's level of political sophistication moderates this association. Based on the Moral Foundations Theory, this article examined whether political sophistication moderates the extent to which reliance on moral foundations, as categories of moral concerns, predicts judgements about policy positions. With this aim, two studies examined four policy positions shown by previous research to be best predicted by the endorsement of Sanctity, that is, the category of moral concerns focused on the preservation of physical and spiritual purity. The results showed that reliance on Sanctity predicted political sophisticates' judgements, as opposed to those of unsophisticates, on policy positions dealing with equal rights for same-sex and unmarried couples and with euthanasia. Political sophistication also interacted with Fairness endorsement, which includes moral concerns for equal treatment of everybody and reciprocity, in predicting judgements about equal rights for unmarried couples, and interacted with reliance on Authority, which includes moral concerns for obedience and respect for traditional authorities, in predicting opposition to stem cell research. Those findings suggest that, at least for these particular issues, endorsement of moral foundations can be associated with political attitudes more strongly among sophisticates than unsophisticates. © 2015 International Union of Psychological Science.

Detection of broad ultraviolet Fe II lines in the spectrum of NGC 1068

International Nuclear Information System (INIS)

Snijders, M.A.J.; Netzer, Hagai; Boksenberg, A.

1986-01-01

Ultraviolet observations of the nucleus of NGC 1068, obtained by the IUE over a period of 5 yr, are combined to give a high signal-to-noise spectrum of this source. The ultraviolet stellar continuum, obtained by comparison with ground-based data, is subtracted to show the nuclear non-stellar component. The resulting spectrum shows clearly the presence of strong broad FeII emission bands similar to those observed in many broad-line objects. Broad profiles are also seen in other strong emission lines. These observations confirm the recent discovery of an optical Seyfert type 1 spectrum in NGC 1068. (author)

2D parallel interpenetration of [M2(bpp)4X4] [M, Fe(II)/Co(II); bpp, 4,4'-trimethylenedipyridine; X, SCN-, SeCN- and N3-] complexes: Pseudohalide-dependent conformation of bpp

International Nuclear Information System (INIS)

Manna, Subal Chandra; Jana, Atish Dipankar; Rosair, Georgina M.; Drew, Michael G.B.; Mostafa, Golam; Ray Chaudhuri, Nirmalendu

2008-01-01

Three coordination complexes of Co(II)/Fe(II) with 4,4'-trimethylenedipyridine (bpp) and pseudohalides (SCN - , SeCN - and N 3 - ) have been synthesized. The complexes have been characterized by X-ray single crystal structure determination. They are isomorphous having 2D layers in which two independent wavy nets display parallel interwoven structures. Pseudohalide binds metal centers through N terminal and occupies the trans axial positions of the octahedral metal coordination environment. Pseudohalide remains pendant on both sides of the polymeric layer and help the stacking through hydrogen bonding. The conformation of bpp in the interpenetrated nets is observed to be dependent on the choice of pseudohalide. - Graphical abstract: Complexes of [M 2 (bpp) 4 X 4 ] [M, Fe(II)/Co(II); bpp, 4,4'-trimethylenedipyridine; X, SCN - , SeCN - and N3 - ] have been synthesized. The structural analysis reveals undulated 2D network with (4,4) net topology adopting two different conformations of bpp alternately. Two such networks undergo parallel interpenetration. Pseudohalides are observed to help in stacking the interpenetrated nets through hydrogen bonding

Photoassisted Fenton degradation of phthalocyanine dyes from wastewater of printing industry using Fe(II)/γ-Al2O3 catalyst in up-flow fluidized-bed.

Science.gov (United States)

Cheng, Hsuhui; Chou, Shihjie; Chen, Shiaoshing; Yu, Chiajen

2014-06-01

Fe(II)/γ-Al2O3 powders synthesized using the dipping method were produced from a mixed aqueous solution containing aluminium oxide (γ-Al2O3) and iron(II)-precursor (FeSO4), and used for photo-Fenton degradation of phthalocyanine dyes (PCS) under ultraviolet (UV) irradiation in an up-flow fluidized bed. The catalysts were characterized by XRD, ESCA, BET, EDS and SEM. The results showed that Fe(2+) ion was compounded on the γ-Al2O3 carrier. The effects of different reaction parameters such as catalyst activity, dosage and solution pH on the decolorization of PCS were assessed. Results indicated that maximum decolorization (more than 95%) of PCS occurred with 20 wt% Fe(II)/γ-Al2O3 catalyst (dosage of 60 g/L) using a combination of UV irradiation and heterogeneous Fenton system. The degradation efficiency of PCS increases as pH decreases, exhibiting a maximum efficiency at pH 3.5. The recycled catalyst was capable of repeating three runs without a significant decrease in treatment efficiency, and this demonstrated the stability and reusability of catalyst. Copyright © 2014 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Synthesis of Zn–Fe layered double hydroxides via an oxidation process and structural analysis of products

Energy Technology Data Exchange (ETDEWEB)

Morimoto, Kazuya, E-mail: kazuya.morimoto@aist.go.jp [Institute for Geo-Resources and Environment, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8567 (Japan); Tamura, Kenji [Environmental Remediation Materials Unit, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Anraku, Sohtaro [Graduate School of Engineering, Hokkaido University, Kita 13 Nishi 8, Kita-ku, Sapporo 060-8628 (Japan); Sato, Tsutomu [Faculty of Engineering, Hokkaido University, Kita 13 Nishi 8, Kita-ku, Sapporo 060-8628 (Japan); Suzuki, Masaya [Institute for Geo-Resources and Environment, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8567 (Japan); Yamada, Hirohisa [Environmental Remediation Materials Unit, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

2015-08-15

The synthesis of Zn–Fe(III) layered double hydroxides was attempted, employing different pathways using either Fe(II) or Fe(III) species together with Zn as the initial reagents. The product derived from the synthesis employing Fe(II) was found to transition to a Zn–Fe(III) layered double hydroxides phase following oxidation process. In contrast, the product obtained with Fe(III) did not contain a layered double hydroxides phase, but rather consisted of simonkolleite and hydrous ferric oxide. It was determined that the valency of the Fe reagent used in the initial synthesis affected the generation of the layered double hydroxides phase. Fe(II) species have ionic radii and electronegativities similar to those of Zn, and therefore are more likely to form trioctahedral hydroxide layers with Zn species. - Graphical abstract: The synthesis of Zn–Fe(III) layered double hydroxides was attempted, employing different pathways using either Fe(II) or Fe(III) species together with Zn as the initial reagents. - Highlights: • Iron valency affected the generation of Zn–Fe layered double hydroxides. • Zn–Fe layered double hydroxides were successfully synthesized using Fe(II). • Fe(II) species were likely to form trioctahedral hydroxide layers with Zn species.

Aristotle and Social-Epistemic Rhetoric: The Systematizing of the Sophistic Legacy.

Science.gov (United States)

Allen, James E.

While Aristotle's philosophical views are more foundational than those of many of the Older Sophists, Aristotle's rhetorical theories inherit and incorporate many of the central tenets ascribed to Sophistic rhetoric, albeit in a more systematic fashion, as represented in the "Rhetoric." However, Aristotle was more than just a rhetorical…

Design, synthesis and photoelectrochemical properties of hexagonal metallomacrocycles based on triphenylamine: [M6(4,4'-bis(2,2':6',2''-terpyridinyl)triphenylamine)6(X)12]; [M = Fe(II), PF6- and Zn(II), BF4-].

Science.gov (United States)

Hwang, Seok-Ho; Moorefield, Charles N; Wang, Pingshan; Fronczek, Frank R; Courtney, Brandy H; Newkome, George R

2006-08-07

Synthesis of a novel bis(terpyridine) ligand, 4,4'-bis(2,2':6',2''-terpyridinyl)triphenylamine, utilizing triphenylamine, as a specific angle controller, has led to the self-assembly of a unique hexagonal metallomacrocycle family, [Fe6(2)6(PF6)12] and [Zn6(2)6(BF4)12], utilizing terpyridine-metal(II)-terpyridine connectivity. The crystal structure of the novel ligand shows that the angle between the two terpyridinyl moieties is 119.69 degrees , which enabled the formation of the hexagonal-shaped macrocycles. The crystal packing architectures of this starting ligand revealed channels induced by solvent encapsulation. Following complexation of this ligand with transition metals [Fe(II) or Zn(II)] in a one-pot reaction, the resultant structures were characterized by (1)H and (13)C NMR, UV/Vis and mass spectroscopies. The expected metal-to-ligand charge transfer (MLCT; lambda(max) = 582 nm) and emission (lambda(em) = 575 nm) characteristics were exhibited by both [Fe6(2)6(PF6)12] and[Zn6(2)6(BF4)12]. The photoelectrochemical characteristics of these hexagonal metallomacrocycles demonstrate that they can be used as sensitizers in dye-sensitized solar cells.

Fe2(AsO4)F: A new three-dimensional condensed fluoro-arsenate iron(II) compound with antiferromagnetic interactions

International Nuclear Information System (INIS)

Berrocal, Teresa; Mesa, Jose L.; Pizarro, Jose L.; Urtiaga, Miren K.; Arriortua, Maria I.; Rojo, Teofilo

2006-01-01

Fe 2 (AsO 4 )F has been synthesized under mild hydrothermal conditions in the form of single crystals. The compound crystallizes in C2/c monoclinic space group with the unit cell parameters a=13.214(1), b=6.623(1), c=10.045(1)A and β=116.90(2) deg. with Z=8. The crystal structure consists of a three-dimensional framework constructed by two kinds of chains, A and B, with 50% of population. In the chains, the environments for the iron(II) cations show penta- and hexa-coordination. The chains establish an angle of approximately 120 deg. between them. The disordered fluoride anions in these chains given rise to [Fe(1)O 4 F(1) 0.5 (F(2) 0.5 ) 2 ] and [Fe(2)O 4 (F(1) 0.5 ) 2 F(2) 0.5 ] edge-shared polyhedra in which the fluoride anions have occupancy factors of 50% over two distinct crystallographic sites. The IR spectrum shows the characteristic bands of the (AsO 4 ) 3- groups. From the diffuse reflectance spectrum a D q parameter of 650cm -1 has been calculated for the Fe(II) d 6 high spin cation. The Mossbauer spectrum in the paramagnetic state shows a doublet that has been fitted, according to the existence of two crystallographically independent iron environments, with two Lorentzian doublets. Magnetic measurements performed between room temperature and 5K exhibit a maximum at 22.6K, characteristic of antiferromagnetic interactions with a estimated 'J'-exchange parameter of -1.2K

Characterization of recombinant nitrile-specifier proteins (NSPs) of Arabidopsis thaliana: dependency on Fe(II) ions and the effect of glucosinolate substrate and reaction conditions.

Science.gov (United States)

Kong, Xiang Yi; Kissen, Ralph; Bones, Atle M

2012-12-01

Glucosinolates are plant secondary metabolites that are part of a plant defence system against pathogens and pests, the myrosinase-glucosinolate system, in which glucosinolates get activated by enzymic degradation through thioglucoside glucohydrolases called myrosinases. Epithiospecifier protein (ESP) and nitrile-specifier proteins (NSPs) divert myrosinase-catalyzed hydrolysis of a given glucosinolate from the formation of isothiocyanate to that of epithionitrile and/or nitrile. As the biological activity of glucosinolate hydrolysis products varies considerably, a detailed characterization of these specifier proteins is of utmost importance to understand their biological role. Therefore, the Arabidopsis thaliana AtNSP1, AtNSP2 and AtNSP5 and a supposed ancestor protein AtNSP-like1 were expressed in Escherichia coli and the activity of the purified recombinant proteins was tested in vitro on three highly different glucosinolates and compared to that of purified AtESP. As previously reported, only AtESP showed epithiospecifier activity on 2-propenylglucosinolate. We further confirmed that purified AtNSP1, AtNSP2 and AtNSP5, but not the ancestor AtNSP-like1 protein, show nitrile-specifier activity on 2-propenylglucosinolate and benzylglucosinolate. We now show for the first time that in vitro AtNSP1, AtNSP2 and AtNSP5 are able to generate nitrile from indol-3-ylmethylglucosinolate. We also tested the effect of different Fe(II) ion concentrations on the nitrile-specifier activity of purified AtNSP1, AtNSP2 and AtNSP5 on 2-propenylglucosinolate and benzylglucosinolate. AtNSP-related nitrile production was highly dependent on the presence of Fe(II) ions in the reaction assay. In the absence of added Fe(II) ions nitriles were only detected when benzylglucosinolate was incubated with AtNSP1. While AtNSP1 also exhibited overall higher nitrile-specifier activity than AtNSP2 and AtNSP5 at a given Fe(II) ion concentration, the pattern of nitrile formation in relation to Fe(II

Screen-Printed Electrode Modified by Bismuth /Fe3O4 Nanoparticle/Ionic Liquid Composite Using Internal Standard Normalization for Accurate Determination of Cd(II in Soil

Directory of Open Access Journals (Sweden)

Hui Wang

2017-12-01

Full Text Available The quality and safety of agricultural products are threatened by heavy metal ions in soil, which can be absorbed by the crops, and then accumulated in the human body through the food chain. In this paper, we report a low-cost and easy-to-use screen-printed electrode (SPE for cadmium ion (Cd(II detection based on differential pulse voltammetry (DPV, which decorated with ionic liquid (IL, magnetite nanoparticle (Fe3O4, and deposited a bismuth film (Bi. The characteristics of Bi/Fe3O4/ILSPE were investigated using scanning electron microscopy, cyclic voltammetry, impedance spectroscopy, and linear sweep voltammetry. We found that the sensitivity of SPE was improved dramatically after functionalized with Bi/Fe3O4/IL. Under optimized conditions, the concentrations of Cd(II are linear with current responses in a range from 0.5 to 40 µg/L with the lowest detection limit of 0.05 µg/L (S/N = 3. Additionally, the internal standard normalization (ISN was used to process the response signals of Bi/Fe3O4/ILSPE and established a new linear equation. For detecting three different Cd(II concentrations, the root-mean-square error using ISN (0.25 is lower than linear method (0.36. Finally, the proposed electrode was applied to trace Cd(II in soil samples with the recovery in the range from 91.77 to 107.83%.

Hydrothermal synthesis of graphene oxide/multiwalled carbon nanotube/Fe3O4 ternary nanocomposite for removal of Cu (II) and methylene blue

Science.gov (United States)

Long, Zhihang; Zhan, Yingqing; Li, Fei; Wan, Xinyi; He, Yi; Hou, Chunyan; Hu, Hai

2017-09-01

In this work, highly activated graphene oxide/multiwalled carbon nanotube/Fe3O4 ternary nanocomposite adsorbent was prepared from a simple hydrothermal route by using ferrous sulfate as precursor. For this purpose, the graphene oxide/multiwalled carbon nanotube architectures were formed through the π-π attractions between them, followed by attaching Fe3O4 nanoparticles onto their surface. The structure and composition of as-prepared ternary nanocomposite were characterized by XRD, FTIR, XPS, SEM, TEM, Raman, TGA, and BET. It was found that the resultant porous graphene oxide/multiwalled carbon nanotube/Fe3O4 ternary nanocomposite with large surface area could effectively prevent the π-π stacking interactions between graphene oxide nanosheets and greatly improve sorption sites on the surfaces. Thus, owing to the unique ternary nanocomposite architecture and synergistic effect among various components, as-prepared ternary nanocomposite exhibited high separation efficiency when they were used to remove the Cu (II) and methylene blue from aqueous solutions. Furthermore, the adsorption isotherms of ternary nanocomposite structures for Cu (II) and methylene blue removal fitted the Langmuir isotherm model. This work demonstrated that the graphene oxide/multiwalled carbon nanotube/Fe3O4 ternary nanocomposite was promising as an efficient adsorbent for heavy metal ions and organic dye removal from wastewater in low concentration.

Kinetics and Mechanism of the Iron(II-Iron(III) Electron-Exchange Reaction in Mixed Solvent Media; Cinetique et Mecanisme de l'Echange d'Electrons entre Fer (II) et Fer (III), dans des Melanges de Solvants; Ikinetika i mekhanizm reaktsii ehlektronnogo obmena zheleza (I) - zheleza (III) v smeshannoj rastvoryayushchej srede; Cinetica y Mecanismo del Intercambio de Electrones Entre Fe{sup II} Y Fe{sup lII} en Mezclas de Disolventes

Energy Technology Data Exchange (ETDEWEB)

Horne, R. A. [Arthur D. Little, Inc. Cambridge, MA (United States)

1965-10-15

The specific reaction rate constants of theFe{sup II}-Fe{sup III} electron-exchange reaction have been measured at various temperatures, acidities, and ionic strengths in water-acetone, water-methanol, and water-ethanol media. The reaction rate markedly diminishes as the water concentration in the last system decreases, approaching zero as the water concentration approaches zero. The activation energy of the exchange is the same in mixed solvent as in aqueous solution. The effective dielectric constant which the reactants ''see'' continues to be that of pure water even in water-ethanol solutions quite dilute in water. Alterations in composition of the solvation sheath of Fe{sup III} in mixed media are reflected in both electron-exchange and spectroscopic measurements. These findings in mixed solvent media support the water-bridging theory of electron exchange. (author) [French] Les constantes de vitesse specifiques de l'echange d'electrons entre Fe{sup II} et Fe{sup III} ont ete mesurees a differentes temperatures et pour differentes acidites et forces ioniques, dans des melanges d'eau et d'acetone, d'eau et de methanol et d'eau et d'ethanol. Dans le dernier systeme, la vitesse d'echange diminue considerablement a mesure que la concentration en eau decroit, et tend vers zero en meme temps que cette concentration. L'energie d'activation de l'echange est la meme dans un melange de solvants et dans une solution aqueuse. La constante dielectrique effective qui intervient entre les corps reagissants reste celle de l'eau pure, meme dans des solutions concentrees d'ethanol dans l'eau. Les changements de composition de la gaine de solvatation de Fe{sup III} dans les melanges se manifestent a la fois dans les mesures de l'echange d'electrons et dans les mesures spectroscopiques. Ces observations viennent confirmer la theorie de l'echange d'electrons fondee sur le pontage par l'eau. (author) [Spanish] El autor ha medido las constantes de velocidad especificas de la reaccion

Marinobacter subterrani, a genetically tractable neutrophilic Fe(II-oxidizing strain isolated from the Soudan Iron Mine

Directory of Open Access Journals (Sweden)

Benjamin Michael Bonis

2015-07-01

Full Text Available We report the isolation, characterization, and development of a robust genetic system for a halophilic, Fe(II-oxidizing bacterium isolated from a vertical borehole originating 714 m below the surface located in the Soudan Iron Mine in northern Minnesota, USA. Sequence analysis of the 16S rRNA gene places the isolate in the genus Marinobacter of the Gammaproteobacteria. The genome of the isolate was sequenced using a combination of short- and long-read technologies resulting in 2 contigs representing a 4.4 Mbp genome. Using genomic information, we used a suicide vector for targeted deletion of specific flagellin genes, resulting in a motility-deficient mutant. The motility mutant was successfully complemented by expression of the deleted genes in trans. Random mutagenesis using a transposon was also achieved. Capable of heterotrophic growth, this isolate represents a microaerophilic Fe(II-oxidizing species for which a system for both directed and random mutagenesis has been established. Analysis of 16S rDNA suggests Marinobacter represents a major taxon in the mine, and genetic interrogation of this genus may offer insight into the structure of deep subsurface communities as well as an additional tool for analyzing nutrient and element cycling in the subsurface ecosystem.

Fe electron transfer and atom exchange in goethite: influence of Al-substitution and anion sorption.

Science.gov (United States)

Latta, Drew E; Bachman, Jonathan E; Scherer, Michelle M

2012-10-02

The reaction of Fe(II) with Fe(III) oxides and hydroxides is complex and includes sorption of Fe(II) to the oxide, electron transfer between sorbed Fe(II) and structural Fe(III), reductive dissolution coupled to Fe atom exchange, and, in some cases mineral phase transformation. Much of the work investigating electron transfer and atom exchange between aqueous Fe(II) and Fe(III) oxides has been done under relatively simple aqueous conditions in organic buffers to control pH and background electrolytes to control ionic strength. Here, we investigate whether electron transfer is influenced by cation substitution of Al(III) in goethite and the presence of anions such as phosphate, carbonate, silicate, and natural organic matter. Results from (57)Fe Mössbauer spectroscopy indicate that both Al-substitution (up to 9%) and the presence of common anions (PO(4)(3-), CO(3)(2-), SiO(4)(4-), and humic acid) does not inhibit electron transfer between aqueous Fe(II) and Fe(III) in goethite under the conditions we studied. In contrast, sorption of a long-chain phospholipid completely shuts down electron transfer. Using an enriched isotope tracer method, we found that Al-substitution in goethite (10%), does, however, significantly decrease the extent of atom exchange between Fe(II) and goethite (from 43 to 12%) over a month's time. Phosphate, somewhat surprisingly, appears to have little effect on the rate and extent of atom exchange between aqueous Fe(II) and goethite. Our results show that electron transfer between aqueous Fe(II) and solid Fe(III) in goethite can occur under wide range of geochemical conditions, but that the extent of redox-driven Fe atom exchange may be dependent on the presence of substituting cations such as Al.

Microcystis aeruginosa-laden water treatment using enhanced coagulation by persulfate/Fe(II), ozone and permanganate: Comparison of the simultaneous and successive oxidant dosing strategy.

Science.gov (United States)

Liu, Bin; Qu, Fangshu; Chen, Wei; Liang, Heng; Wang, Tianyu; Cheng, Xiaoxiang; Yu, Huarong; Li, Guibai; Van der Bruggen, Bart

2017-11-15

In this study, the application of enhanced coagulation with persulfate/Fe(II), permanganate and ozone for Microcystis-laden water treatment was investigated. Two oxidant dosage strategies were compared in terms of the organic removal performance: a simultaneous dosing strategy (SiDS) and a successive dosing strategy (SuDS). To optimize the oxidant species, oxidant doses and oxidant dosage strategy, the zeta potential, floc size and dimension fraction, potassium release and organic removal efficiency during the coagulation of algae-laden water were systematically investigated and comprehensively discussed. Ozonation causes most severe cell lysis and reduces organic removal efficiency because it releases intracellular organics. Moreover, ozonation can cause the release of odor compounds such as 2-methylisoborneol (2-MIB) and geosmin (GSM). With increasing doses, the performance of pollutant removal by coagulation enhanced by persulfate/Fe(II) or permanganate did not noticeably improve, which suggests that a low dosage of persulfate/Fe(II) and permanganate is the optimal strategy to enhance coagulation of Microcystis-laden water. The SiDS performs better than the SuDS because more Microcystis cell lysis occurs and less DOC is removed when oxidants are added before the coagulants. Copyright © 2017 Elsevier Ltd. All rights reserved.

Moessbauer study of FePO4 cathode for lithium- and sodium-ion batteries

International Nuclear Information System (INIS)

Tetsuaki Nishida; Masahiro Tokunaga; Toshiharu Nishizumi; Takafumi Yamamoto; Tomoyuki Shiratsuchi; Shigeto Okada; Jun-ichi Yamaki

2005-01-01

LiFePO 4 of olivine type has attracted much interest as a rare-metal free cathode for lithium-ion battery. The present authors' group has found a low-cost preparation method for new cathode material FePO 4 (P 321 ) from an aqueous solution of metallic iron and P 2 O 5 . A cathode pellet was prepared by mixing FePO 4 , acetylene black (AB) and polytetrafluoroethylene (PTFE) binder at a mass ratio of 70:25:5. Electrochemical cathode performance was investigated under a constant current density of 0.1 mA/cm 2 with a coin-type cell with an anode of metallic Li and Na for Li- and Na-ion batteries, respectively. Moessbauer spectra were measured by a constant accele- ration method with a Moessbauer source of 57 Co(Pd) and an α-Fe foil as a reference of the isomer shift. Moessbauer spectra of the original cathode pellet top left and right) composed of amorphous FePO 4 indicate that all the Fe III atoms have a tetrahedral symmetry. After discharging the Li-(second left) and Na-batteries (second right), all the Fe III were reduced to octahedral Fe II . The reduction of Fe III to Fe II indicates penetration of Li + and Na + into the FePO 4 cathode which accompanies an electron capture; Li + (or Na + ) + Fe III PO 4 + e - = LiFe II PO 4 (or NaFe II PO 4 ) After charging the Li-cell (bottom left), all the Fen atoms were oxidized to tetrahedral Fe III , while 69 % of Fe II was oxidized to Fe III in the Na-ion cell (bottom right) due to a lower cell voltage: 4.0 V. Oxidation of Fe II to Fe III reflects a release of Li + or Na + ions from the FePO 4 cathode to the electrolyte, i.e., an inverse reaction of eq.

The predictors of economic sophistication: media, interpersonal communication and negative economic experiences

NARCIS (Netherlands)

Kalogeropoulos, A.; Albæk, E.; de Vreese, C.H.; van Dalen, A.

2015-01-01

In analogy to political sophistication, it is imperative that citizens have a certain level of economic sophistication, especially in times of heated debates about the economy. This study examines the impact of different influences (media, interpersonal communication and personal experiences) on

Chemical evaluation of HBED/Fe(3+) and the novel HJB/Fe(3+) chelates as fertilizers to alleviate iron chlorosis.

Science.gov (United States)

López-Rayo, Sandra; Hernández, Diana; Lucena, Juan J

2009-09-23

Iron chelates such as ethylenediamine-N,N'-bis(2-hydroxyphenylacetic) acid (o,o-EDDHA) and their analogues are the most efficient soil fertilizers to treat iron chlorosis in plants growing in calcareous soil. A new chelating agent, HJB (N,N'-bis(2-hydroxy-5-methylphenyl)ethylendiamine-N,N'-diacetic acid) may be an alternative to o,o-EDDHA since its synthesis yields a purer product, but its chemical behavior and efficiency as chlorosis corrector should be evaluated. In this research, a known analogous HBED (N,N'-bis(2-hydroxyphenyl)ethylendiamine-N,N'-diacetic acid) has also been considered. First, an ion-pair high performance liquid chromatography (HPLC) method has been tested for the HJB/Fe(3+) and HBED/Fe(3+) determination. The ability of HJB and HBED to maintain Fe in solution has been compared with respect to o,o-EDDHA. Theoretical modelization for HBED and HJB in agronomic conditions has been done after the determination of the protonation and Ca(II), Mg(II), Fe(III), and Cu(II) stability constants for HJB. Also, batch interaction experiments with soils and soil materials have been conducted. According to our results, HJB/Fe(3+) and HBED/Fe(3+) present high stability, even when competing cations (Cu(2+), Ca(2+)) are present, and have low reactivity with soils and soil components. The chelating agent HJB dissolves a higher amount of Fe than o,o-EDDHA, and it seems as effective as o,o-EDDHA in keeping Fe in solution. These results indicate that these chelates may be very efficient products to correct Fe chlorosis, and additional plant experiments should demonstrate plants' ability to assimilate Fe from HJB/Fe(3+) and HBED/Fe(3+).

Redox process catalysed by growing crystal-strengite, FePO4,2H2O, crystallizing from solution with iron(II) and hydroxylamine

Science.gov (United States)

Lundager Madsen, Hans Erik

2014-09-01

In an attempt to grow pure crystals of the iron(II) phosphate vivianite, Fe3(PO4)2,8H2O, from a solution of Mohr's salt, Fe(NH4)2(SO4)2,6H2O, added to a solution of ammonium phosphate, hydroxylammonium chloride, NH3OHCl, was added to the iron(II) stock solution to eliminate oxidation of iron(II) by oxygen from the air. However, the effect turned out to be the opposite of the expected: whereas hydroxylamine reduces iron(III) in bulk solution, it acted as a strong oxidant in the presence of growing iron phosphate crystals, causing the crystallization of the iron(III) phosphate strengite, FePO4,2H2O, as the only solid phase. Evidently the crystal surface catalyses oxidation of iron(II) by hydroxylamine. The usual composite kinetics of spiral growth and surface nucleation was found. The surface-nucleation part yielded edge free energy λ in the range 12-45 pJ/m, virtually independent of temperature and in the range typical for phosphates of divalent metals. The scatter of values for λ presumably arises from contributions from different crystal forms to the overall growth rate. The low mean value points to strong adsorption of iron(II), which is subsequently oxidized at the crystal surface, forming strengite. The state of the system did not tend to thermodynamic equilibrium, but to a metastable state, presumably controlled by the iron(II) rich surface layer of the crystal. In addition to crystal growth, it was possible to measure nucleation kinetics by light scattering (turbidimetry). A point of transition from heterogeneous to homogeneous nucleation was found, and from the results for the homogeneous domain a rather precise value of crystal surface free energy γ=55 mJ/m2 was found. This is a relatively low value as well, indicating that the redox process plays a role already at the nucleation stage.

Precise Wavelengths and Energy Levels for the Spectra of Cr I, Mn I, and Mn III, and Branching Fractions for the Spectra of Fe II and Cr II

Science.gov (United States)

Nave, Gillian

I propose to measure wavelengths and energy levels for the spectra of Cr I, Mn I, and Mn III covering the wavelength range 80 nm to 5500 nm, and oscillator strengths for Fe II and Cr II in the region 120 nm to 2500 nm. I shall also produce intensity calibrated atlases and linelists of the iron-neon and chromium-neon hollow cathode lamps that can be compared with astrophysical spectra. The spectra will be obtained from archival data from spectrometers at NIST and Kitt Peak National Observatory and additional experimental observations as necessary from Fourier transform (FT) and grating spectrometers at NIST. The wavelength uncertainty of the strong lines will be better than 1 part in 10^7. The radiometric calibration of the spectra will be improved in order to reduce the uncertainty of measured oscillator strengths in the near UV region and extend the wavelength range of these measurements down to 120 nm. These will complement and support the measurements of lifetimes and branching fractions by J. E. Lawler in the near UV region. An intensive effort by NIST and Imperial College London that was partly funded by previous NASA awards has resulted in comprehensive analyses of the spectra of Fe II, Cr II and Cu II, with similar analyses of Mn II, Ni II, and Sc II underway. The species included in this proposal will complete the analysis of the first two ionization stages of the elements titanium through nickel using the same techniques, and add the spectrum of Mn III - one of the most important doubly-ionized elements. The elements Cr I and Mn I give large numbers of spectral lines in spectra of cool stars and important absorption lines in the interstellar medium. The spectrum of Mn III is important in chemically peculiar stars and can often only be studied in the UV region. Analyses of many stellar spectra depend on comprehensive analyses of iron-group elements and are hampered by incomplete spectroscopic data. As a result of many decades of work by the group at the

Study of the oxidation-reduction kinetics involved in the Np(V) + Fe(II) in equilibrium Np(IV) + Fe(III) system in nitric acid solutions

International Nuclear Information System (INIS)

Jao, Y.

1975-08-01

Ferrous nitrate-hydrazine is one of the more attractive alternate reactants to the currently used reagent, ferrous sulfamate, for partitioning plutonium from neptunium and uranium. An understanding of the kinetics of the reduction of Np(VI) to Np(IV) by ferrous nitrate-hydrazine is needed before a satisfactory evaluation of the feasibility of this reductant in actinide element separations can be made. The purpose of this work was to study the kinetics and mechanisms of the reduction of Np(V) by Fe(II) and the oxidation of Np(IV) by Fe(III) in 1-2 M nitric acid solutions. The acid concentration range was chosen to include that typically used in the separation of plutonium from neptunium and uranium by solvent extraction with tributylphosphate. The forward and reverse rate constants, hydrogen ion dependence, temperature dependence, ionic strength effects and nitrate ion influence were determined. The proposed reaction mechanisms involve protonation of the NpO 2 + ions and hydroxyoxygenation of Np 4 + ions. (LK)

In situ spectroscopic and solution analyses of the reductive dissolution of Mn02 by Fe(II)

Science.gov (United States)

Villinski, John E.; O'Day, Peggy A.; Corley, Timothy L.; Conklin, Martha H.

2001-01-01

The reductive dissolution of MnO2 by Fe(II) under conditions simulating acid mine drainage (pH 3, 100 mM SO42-) was investigated by utilizing a flow-through reaction cell and synchrotron X-ray absorption spectroscopy. This configuration allows collection of in situ, real-time X-ray absorption near-edge structure (XANES) spectra and bulk solution samples. Analysis of the solution chemistry suggests that the reaction mechanism changed (decreased reaction rate) as MnO2 was reduced and Fe(III) precipitated, primarily as ferrihydrite. Simultaneously, we observed an additional phase, with the local structure of jacobsite (MnFe2O4), in the Mn XANES spectra of reactants and products. The X-ray absorbance of this intermediate phase increased during the experiment, implying an increase in concentration. The presence of this phase, which probably formed as a surface coating, helps to explain the reduced rate of dissolution of manganese(IV) oxide. In natural environments affected by acid mine drainage, the formation of complex intermediate solid phases on mineral surfaces undergoing reductive dissolution may likewise influence the rate of release of metals to solution.

Synthesis of water-dispersible poly-l-lysine-functionalized magnetic Fe3O4-(GO-MWCNTs) nanocomposite hybrid with a large surface area for high-efficiency removal of tartrazine and Pb(II).

Science.gov (United States)

Hu, Dan; Wan, Xiaodong; Li, Xiaohui; Liu, Jianguo; Zhou, Chunhua

2017-12-01

In this study, a novel, effective and environment-friendly methods was used to prepare poly-l-lysine (PLL)-functionalized magnetic Fe 3 O 4 -(GO-MWCNTs) hybrid composite with large surface area and abundant hydroxyl and amino groups. The as-prepared PLL-Fe 3 O 4 -(GO-MWCNTs) nanocomposite was systematically characterized by FT-IR, XRD, TGA, SEM, TEM, VSM and EDX. The PLL-Fe 3 O 4 -(GO-MWCNTs) hybrid composite exhibited excellent adsorption performance for the removal of a dye (tartrazine) and a heave metal (Pb(II)). The result showed that adsorption of Pb(II) reached equilibrium in 30min and adsorption of tartrazine reached equilibrium in approximately 60min. Most importantly, PLL-Fe 3 O 4 -(GO-MWCNTs) hybrid possesses high adsorption capacity, rapid separation, and less time-consuming. The equilibrium adsorption capacity was 1038.42mgg -1 for Pb(II) and 775.19mgg -1 for tartrazine under the optimal conditions. These two pollutants removal were found to obey Langmuir adsorption model, while the kinetics of adsorption followed pseudo-second-order kinetic model. A possible adsorption mechanism has been proposed where the chelation between PLL and Pb(II) or electrostatic interaction between GO and tartrazine. These results demonstrated the potential applications of PLL-Fe 3 O 4 -(GO-MWCNTs) hybrid composite in deep-purification of polluted water. Copyright © 2017 Elsevier B.V. All rights reserved.

Fe-Impregnated Mineral Colloids for Peroxide Activation: Effects of Mineral Substrate and Fe Precursor.

Science.gov (United States)

Li, Yue; Machala, Libor; Yan, Weile

2016-02-02

Heterogeneous iron species at the mineral/water interface are important catalysts for the generation of reactive oxygen species at circumneutral pH. One significant pathway leading to the formation of such species arises from deposition of dissolved iron onto mineral colloids due to changes in redox conditions. This study investigates the catalytic properties of Fe impregnated on silica, alumina, and titania nanoparticles (as prototypical mineral colloids). Fe impregnation was carried out by immersing the mineral nanoparticles in dilute Fe(II) or Fe(III) solutions at pH 6 and 3, respectively, in an aerobic environment. The uptake of iron per unit surface area follows the order of nTiO2 > nAl2O3 > nSiO2 for both types of Fe precursors. Impregnation of mineral particles in Fe(II) solutions results in predominantly Fe(III) species due to efficient surface-mediated oxidation. The catalytic activity of the impregnated solids to produce hydroxyl radical (·OH) from H2O2 decomposition was evaluated using benzoic acid as a probe compound under dark conditions. Invariably, the rates of benzoic acid oxidation with different Fe-laden particles increase with the surface density of Fe until a critical density above which the catalytic activity approaches a plateau, suggesting active Fe species are formed predominantly at low surface loadings. The critical surface density of Fe varies with the mineral substrate as well as the aqueous Fe precursor. Fe impregnated on TiO2 exhibits markedly higher activity than its Al2O3 and SiO2 counterparts. The speciation of interfacial Fe is analyzed with diffuse reflectance UV-vis analysis and interpretation of the data in the context of benzoic oxidation rates suggests that the surface activity of the solids for ·OH generation correlates strongly with the isolated (i.e., mononuclear) Fe species. Therefore, iron dispersed on mineral colloids is a significant form of reactive iron surfaces in the aquatic environment.

Preparation and Eh-pH diagrams of Fe(II)-Fe(III) green rust compounds; hyperfine interaction characteristics and stoichiometry of hydroxy-chloride, -sulphate and -carbonate

International Nuclear Information System (INIS)

Genin, J.-M.R.; Refait, Ph.; Simon, L.; Drissi, S.H.

1998-01-01

Fe(II)-Fe(III) hydroxy-chloride, -sulphate and -carbonate were prepared by oxidation of a ferrous hydroxide precipitate in anion-containing aqueous solutions. The compounds are characterized by monitoring the redox potential E h and the pH of stochiometric suspension vs time with the appropriate concentration ratios. X-ray diffraction allows us to characterize the crystal structure by distinguishing 'green rust one' (GR1) from 'green rust two' (GR2). Since green rusts (GRs) are of a pyroaurite-sjoegrenite-like structure, i.e., consisting of intercalated foreign anions and water molecules in the interlayers between the brucite-like layers of Fe(OH) 2 , their chemical formulae can be determined from the Moessbauer spectra. Three quadrupole doublets are observed: D 1 and D 2 correspond to a ferrous state with isomershift IS of about 1.27 mm s -1 and quadrupole splittings QS of about 2.85 and 2.60 mm s -1 , respectively, whereas D 3 corresponds to a ferric state with IS and QS of about 0.4 mm s -1 . The hyperfine parameters of these doublets are similar from one green rust to another but their intensity ratios vary considerably. Finally, E h and pH equilibrium diagrams of the Fe species in the presence of chloride, sulphate and carbonate anions contained within the water solution are drawn and the thermodynamic conditions of existence and degrees of oxidation of green rusts are discussed

Influence of Ni(II) and Fe(III) complexes of 1,2 dihydroxy 9,10 anthraquinone on the modification in calf thymus DNA upon gamma irradiation

International Nuclear Information System (INIS)

Das, Saurabh; Mandal, Parikshit C.

2009-01-01

Ionizing radiation when allowed to fall upon cells or DNA, the radicals produced modify the base-pair region of the double strands. Radiation-induced double-strand modifications in calf thymus DNA were detected using Ni(II) and Fe(III) complexes of 1,2 dihydroxy 9,10 anthraquinone (DHA). 60 Co was used as the source for γ-radiation and ethidium bromide (EB) as the fluorescent dye for detecting double-strand modifications caused in DNA. Results show that the Fe(III)-DHA complex is more efficient in modifying the base-pair region in double-stranded DNA in comparison to DHA or the Ni(II)-DHA complex

PAUL AND SOPHISTIC RHETORIC: A PERSPECTIVE ON HIS ...

African Journals Online (AJOL)

use of modern rhetorical theories but analyses the letter in terms of the clas- ..... If a critical reader would have had the traditional anti-sophistic arsenal ..... pressions and that 'rhetoric' is mainly a matter of communicating these thoughts.

Moessbauer Study of Electrodeposited Fe/Fe-Oxide Multilayers

International Nuclear Information System (INIS)

Kuzmann, E.; Homonnay, Z.; Klencsar, Z.; Vertes, A.; Lakatos-Varsanyi, M.; Miko, A.; Varga, L.K.; Kalman, E.; Nagy, F.

2005-01-01

Iron has been deposited electrochemically by short current pulses in Na-saccharin containing FeII-chloride and sulphate solution electrolytes. Combined electrochemical techniques with initial pulse plating of iron nanolayer and its subsequent anodic oxidation under potential control have been used for production of Fe/Fe-oxide multilayers. 57Fe CEM spectra of pulse plated iron revealed the presence of a minor doublet attributed mainly to γ-FeOOH in addition to the dominant sextet of α-iron. In the case of anodically oxidized pulse plated iron and of samples after repeated deposition of anodically oxidized pulse plated iron an additional minor doublet, assigned to ferrous chloride, also appears in the Moessbauer spectra. A significant change in the magnetic anisotropy of α-iron was observed with the anodic oxidation. The thickness of the layers were estimated from the CEM spectrum data by a modified computer program of the Liljequist method. The coercive field and the power loss versus frequency data showed that the pulse plated iron cores are good inductive elements up to several kHz frequencies

Manganese(II), iron(II), and mixed-metal metal-organic frameworks based on chains with mixed carboxylate and azide bridges: magnetic coupling and slow relaxation.

Science.gov (United States)

Wang, Yan-Qin; Yue, Qi; Qi, Yan; Wang, Kun; Sun, Qian; Gao, En-Qing

2013-04-15

Mn(II) and Fe(II) compounds derived from azide and the zwitterionic 1-carboxylatomethylpyridinium-4-carboxylate ligand are isomorphous three-dimensional metal-organic frameworks (MOFs) with the sra net, in which the metal ions are connected into anionic chains by mixed (μ-1,1-azide)bis(μ-carboxylate) triple bridges and the chains are cross-linked by the cationic backbones of the zwitterionic ligands. The Mn(II) MOFs display typical one-dimensional antiferromagnetic behavior. In contrast, with one more d electron per metal center, the Fe(II) counterpart shows intrachain ferromagnetic interactions and slow relaxation of magnetization attributable to the single-chain components. The activation energies for magnetization reversal in the infinite- and finite-chain regimes are Δτ1 = 154 K and Δτ2 = 124 K, respectively. Taking advantage of the isomorphism between the Mn(II) and Fe(II) MOFs, we have prepared a series of mixed-metal Mn(II)(1-x)Fe(II)(x) MOFs with x = 0.41, 0.63, and 0.76, which intrinsically feature random isotropic/anisotropic sites and competing antiferromagnetic-ferromagnetic interactions. The materials show a gradual antiferromagnetic-to-ferromagnetic evolution in overall behaviors as the Fe(II) content increases, and the Fe-rich materials show complex relaxation processes that may arise for mixed SCM and spin-glass mechanisms. A general trend is that the activation energy and the blocking temperature increase with the Fe(II) content, emphasizing the importance of anisotropy for slow relaxation of magnetization.

The transformation of ferrihydrite in the presence of trace Fe(II): The effect of the anionic media

International Nuclear Information System (INIS)

Liu Hui; Guo Hui; Li Ping; Wei Yu

2008-01-01

The transformation from ferrihydrite to various iron oxides and iron oxyhydroxides has been given much attention not only in environmental science and geochemistry but also in biology and material science. This laboratory study attempted to investigate Fe(II)-induced transformation of ferrihydrite in sulfate-rich medium. The results indicate that the transformation in sulfate-rich medium differs from that in Cl - medium in the species, the amount and the morphology of products and transformation rate. Lepidocrocite is a main ingredient in the product in Cl - medium at room temperature (RT), while goethite is the only product in SO 4 2- medium at RT. Goethite particles obtained in Cl - medium are star-like but rod-like in SO 4 2- medium. The transformation rate in the latter medium is obviously slower than that in the former medium. The formation of lepidocrocite depends on both the ionic strength of the system and the dissolution rate of ferrihydrite. - Graphical abstract: Fe(II)-induced transformation of ferrihydrite in sulfate-rich medium was studied. Lepidocrocite is a main ingredient in the product in Cl - medium at room temperature (RT), while goethite is the only product in SO 4 2- medium. Goethite particles obtained in Cl - medium are star-like but rod-like in SO 4 2- medium

Reductive dehalogenation by layered iron(II)-iron(III) hydroxides and related iron(II) containing solids

DEFF Research Database (Denmark)

Yin, Weizhao

In the present PhD project, novel synthesis and modifications of layered Fe(II)-Fe(III) hydroxides (green rusts, GRs) were investigated with focus on improved dehalogenation of carbon tetrachloride by using modified green rusts and/or altered reaction conditions. The Ph.D. project has comprised: 1...... sulphate green rust formation by aerial oxidation of FeII or co-precipitation by adding Fe(III) salt to Fe(II). In comparison with traditional green rust synthesis, pure GRs were synthesized in minutes. 2. Enhanced dehalogenation of CT by GR in presence of selected amino acids. In presence of glycine......, chloroform (CF) formation is effectively suppressed: less than 10% of CT is transformed to CF, and more than 90% of dehalogenation products are found to be formic acid and carbon monoxide in presence of 60 mM glycine; while a 80% of CF recovery was obtained without amino acids addition. 3. A “switch...

Rational synthesis of high nuclearity Mo/Fe/S clusters: the reductive coupling approach in the convenient synthesis of (Cl(4)-cat)(2)Mo(2)Fe(6)S(8)(PR(3))(6) [R = Et, (n)Pr, (n)Bu] and the new [(Cl(4)-cat)(2)Mo(2)Fe(2)S(3)O(PEt(3))(3)Cl]-1/2(Fe(PEt(3))(2)(MeCN)(4)) and (Cl(4)-cat)(2)Mo(2)Fe(3)S(5)(PEt(3))(5) clusters.

Science.gov (United States)

Han, J; Koutmos, M; Ahmad, S A; Coucouvanis, D

2001-11-05

A general method for the synthesis of high nuclearity Mo/Fe/S clusters is presented and involves the reductive coupling of the (Et(4)N)(2)[(Cl(4)-cat)MoOFeS(2)Cl(2)] (I) and (Et(4)N)(2)[Fe(2)S(2)Cl(4)] (II) clusters. The reaction of I and II with Fe(PR(3))(2)Cl(2) or sodium salts of noncoordinating anions such as NaPF(6) or NaBPh(4) in the presence of PR(3) (R = Et, (n)Pr, or (n)Bu) affords (Cl(4)-cat)(2)Mo(2)Fe(6)S(8)(PR(3))(6) [R = Et (IIIa), (n)Pr (IIIb), (n)Bu (IIIc)], Fe(6)S(6)(PEt(3))(4)Cl(2) (IV) and (PF(6))[Fe(6)S(8)(P(n)Pr(3))(6)] (V) as byproducts. The isolation of (Et(4)N)[Fe(PEt(3))Cl(3)] (VI), NaCl, and SPEt(3) supports a reductive coupling mechanism. Cluster IV and V also have been synthesized by the reductive self-coupling of compound II. The reductive coupling reaction between I and II by PEt(3) and NaPF(6) in a 1:1 ratio produces the (Et(4)N)(2)[(Cl(4)-cat)Mo(L)Fe(3)S(4)Cl(3)] clusters [L = MeCN (VIIa), THF (VIIb)]. The hitherto unknown [(Cl(4)-cat)(2)Mo(2)Fe(2)S(3)O(PEt(3))(3)Cl](+) cluster (VIII) has been isolated as the 2:1 salt of the (Fe(PEt(3))(2)(MeCN)(4))(2+) cation after the reductive self-coupling reaction of I in the presence of Fe(PEt(3))(2)Cl(2). Cluster VIII crystallizes in the monoclinic space group P2(1)/c with a = 11.098(3) A, b = 22.827(6) A, c = 25.855(6) A, beta = 91.680(4) degrees, and Z = 4. The formal oxidation states of metal atoms in VIII have been assigned as Mo(III), Mo(IV), Fe(II), and Fe(III) on the basis of zero-field Mössbauer spectra. The Fe(PEt(3))(2)(MeCN)(4) cation of VIII is also synthesized independently, isolated as the BPh(4)(-) salt (IX), and has been structurally characterized. The reductive coupling of compound I also affords in low yield the new (Cl(4)-cat)(2)Mo(2)Fe(3)S(5)(PEt(3))(5) cluster (X) as a byproduct. Cluster X crystallizes in the monoclinic space group P2(1)/n with a = 14.811(3) A, b = 22.188(4) A, c = 21.864(4) A, beta = 100.124(3) degrees, and Z = 4 and the structure shows very short Mo-Fe

Kineococcus radiotolerans Dps forms a heteronuclear Mn-Fe ferroxidase center that may explain the Mn-dependent protection against oxidative stress.

Science.gov (United States)

Ardini, Matteo; Fiorillo, Annarita; Fittipaldi, Maria; Stefanini, Simonetta; Gatteschi, Dante; Ilari, Andrea; Chiancone, Emilia

2013-06-01

The ferroxidase center of DNA-binding protein from starved cells (Dps) is a major player in the iron oxidation/detoxification process that leads to a decreased reactive oxygen species production. The possible Mn(II) participation in this process has been studied in Dps from Kineococcus radiotolerans, a radiation-resistant bacterium with a high cytosolic Mn/Fe ratio and a high capacity to survive ionizing and stress conditions. The X-ray structure of recombinant K. radiotolerans Dps loaded with Mn(II) has been solved at 2.0Å resolution. Mn(II) binding to K. radiotolerans Dps and its effect on Fe(II) oxidation have been characterized in spectroscopic measurements. In K. radiotolerans Dps, the Fe-Fe ferroxidase center can have a Mn-Fe composition. Mn(II) binds only at the high affinity, so-called A site, whereas Fe(II) binds also at the low affinity, so-called B site. The Mn-Fe and Fe-Fe centers behave distinctly upon iron oxidation by O2. A site-bound Mn(II) or Fe(II) plays a catalytic role, while B site-bound Fe(II) behaves like a substrate and can be replaced by another Fe(II) after oxidation. When H2O2 is the Fe(II) oxidant, single electrons are transferred to aromatic residues near the ferroxidase center and give rise to intra-protein radicals thereby limiting OH release in solution. The presence of the Mn-Fe center results in significant differences in the development of such intra-protein radicals. Mn(II) bound at the Dps ferroxidase center A site undergoes redox cycling provided the B site contains Fe. The results provide a likely molecular mechanism for the protective role of Mn(II) under oxidative stress conditions as it participates in redox cycling in the hetero-binuclear ferroxidase center. Copyright © 2013 Elsevier B.V. All rights reserved.

Synthesis, physicochemical characterization, DFT calculation and biological activities of Fe(III) and Co(II)-omeprazole complexes. Potential application in the Helicobacter pylori eradication

Science.gov (United States)

Russo, Marcos G.; Vega Hissi, Esteban G.; Rizzi, Alberto C.; Brondino, Carlos D.; Salinas Ibañez, Ángel G.; Vega, Alba E.; Silva, Humberto J.; Mercader, Roberto; Narda, Griselda E.

2014-03-01

The reaction between the antiulcer agent omeprazole (OMZ) with Fe(III) and Co(II) ions was studied, observing a high ability to form metal complexes. The isolated microcrystalline solid complexes were characterized by elemental analysis, X-ray powder diffraction (XRPD), Scanning Electron Microscopy (SEM), magnetic measurements, thermal study, FTIR, UV-Visible, Mössbauer, electronic paramagnetic resonance (EPR), and DFT calculations. The metal-ligand ratio for both complexes was 1:2 determined by elemental and thermal analysis. FTIR spectroscopy showed that OMZ acts as a neutral bidentate ligand through the pyridinic nitrogen of the benzimidazole ring and the oxygen atom of the sulfoxide group, forming a five-membered ring chelate. Electronic, Mössbauer, and EPR spectra together with magnetic measurements indicate a distorted octahedral geometry around the metal ions, where the coordination sphere is completed by two water molecules. SEM and XRPD were used to characterize the morphology and the crystal nature of the complexes. The most favorable conformation for the Fe(III)-OMZ and Co(II)-OMZ complexes was obtained by DFT calculations by using B3LYP/6-31G(d)&LanL2DZ//B3LYP/3-21G(d)&LanL2DZ basis set. Studies of solubility along with the antibacterial activity against Helicobacter pylori for OMZ and its Co(II) and Fe(III) complexes are also reported. Free OMZ and both metal complexes showed antibacterial activity against H. pylori. Co(II)-OMZ presented a minimal inhibitory concentration ˜32 times lower than that of OMZ and ˜65 lower than Fe(III)-OMZ, revealing its promising potential use for the treatment of gastric pathologies associated with the Gram negative bacteria. The morphological changes observed in the cell membrane of the bacteria after the incubation with the metal-complexes were also analyzed by SEM microscopy. The antimicrobial activity of the complexes was proved by the viability test.

Isocratean Discourse Theory and Neo-Sophistic Pedagogy: Implications for the Composition Classroom.

Science.gov (United States)

Blair, Kristine L.

With the recent interest in the fifth century B.C. theories of Protagoras and Gorgias come assumptions about the philosophical affinity of the Greek educator Isocrates to this pair of older sophists. Isocratean education in discourse, with its emphasis on collaborative political discourse, falls within recent definitions of a sophist curriculum.…

A comparative study of dissolution of {alpha}-Fe{sub 2}O{sub 3} and {gamma}-Fe{sub 2}O{sub 3} in DCD formulations

Energy Technology Data Exchange (ETDEWEB)

Ranganathan, S.; Raghavan, P.S.; Gopalan, R. [Madras Christian Coll. (India). Dept. of Chemistry; Srinivasan, M.P.; Narasimhan, S.V.

1998-12-31

The important corrosion products deposited on the surfaces of structural materials such as stainless steel in the primary coolant system of BWRs are haematite in the outer layers and ferrites such as magnetite, nickel ferrite, cobalt ferrite, etc., in the inner layers. Magnetite dissolution by 2, 6 Pyridinedicarboxylic acid (PDCA), Ethylenediaminetetraacetic acid (EDTA) and Nitrolotriacetic acid (NTA) showed that there is an optimum pH of dissolution for each ligand. The leaching of the metal ions from the oxides is controlled in part by reductive dissolution; this is due to the presence of Fe(II)-L complexes generated from the released Fe{sup 2+} ions. The addition of Fe(II)-L with the formulation greatly increases the rate of dissolution. In order to understand the role of Fe{sup 2+} arising from the spinel lattice of Fe{sub 3}O{sub 4} in aiding the dissolution of magnetite, it is appropriate to study the dissolution behaviour of the system like Fe{sub 2}O{sub 3} which is not containing any Fe{sup 2+} in the crystal lattice. The present study has been carried out with {alpha}-Fe{sub 2}O{sub 3} and {gamma}-Fe{sub 2}O{sub 3} in DCD formulation in the presence of ascorbic acid and with the addition of Fe(II)-L as a reductant. (author)

SMEs and new ventures need business model sophistication

DEFF Research Database (Denmark)

Kesting, Peter; Günzel-Jensen, Franziska

2015-01-01

, and Spreadshirt, this article develops a framework that introduces five business model sophistication strategies: (1) uncover additional functions of your product, (2) identify strategic benefits for third parties, (3) take advantage of economies of scope, (4) utilize cross-selling opportunities, and (5) involve...

A sophisticated simulation for the fracture behavior of concrete material using XFEM

Science.gov (United States)

Zhai, Changhai; Wang, Xiaomin; Kong, Jingchang; Li, Shuang; Xie, Lili

2017-10-01

The development of a powerful numerical model to simulate the fracture behavior of concrete material has long been one of the dominant research areas in earthquake engineering. A reliable model should be able to adequately represent the discontinuous characteristics of cracks and simulate various failure behaviors under complicated loading conditions. In this paper, a numerical formulation, which incorporates a sophisticated rigid-plastic interface constitutive model coupling cohesion softening, contact, friction and shear dilatation into the XFEM, is proposed to describe various crack behaviors of concrete material. An effective numerical integration scheme for accurately assembling the contribution to the weak form on both sides of the discontinuity is introduced. The effectiveness of the proposed method has been assessed by simulating several well-known experimental tests. It is concluded that the numerical method can successfully capture the crack paths and accurately predict the fracture behavior of concrete structures. The influence of mode-II parameters on the mixed-mode fracture behavior is further investigated to better determine these parameters.

Factors affecting the Faradaic efficiency of Fe(0) electrocoagulation

NARCIS (Netherlands)

van Genuchten, C.M.; Dalby, K.N.; Ceccato, M.; Stipp, S.L.S.; Dideriksen, K

2017-01-01

Electrocoagulation (EC) using Fe(0) electrodes is a low cost water treatment technology that relies on efficient production of Fe(II) from the electrolytic dissolution of Fe(0) electrodes (i.e. a high Faradaic efficiency). However, the (electro)chemical factors that favor Fe(0) oxidation rather than

Electric dipole f values for Fe II J=9/2->11/2^o transitions

Science.gov (United States)

Beck, Donald R.

2007-06-01

Relativistic configuration-interaction f values have been obtained for all transitions between the lowest 17 J=9/2 and the lowest 27 J=11/2^o levels. The 35 f values >0.01 have an average gauge agreement of 3.6% and generally agree well with the semi-empirical results of Raassen ootnotetextA. J. J. Raassen, ftp://ftp.wins.uva.nl/pub/orth/iron/FeII.E1 (1999).. The near degeneracy of many of the odd levels requires the introduction of small semi-empirical energy shifts ootnotetextD. R. Beck, Phys. Scr. 71, 447 (2005).. A systematic way of estimating radial convergence is discussed.

A luminescent Cd(II)-based metal-organic framework for detection of Fe(III) ions in aqueous solution

Science.gov (United States)

Li, Fen-Fang; Zhu, Miao-Li; Lu, Li-Ping

2018-05-01

A novel Cd((II)-organic framework [Cd(Hcbic)]n (H3cbic = 1-(4-carboxybenz-yl)-1H-benzoim-idazole-5, 6-dicarboxylic acid) was assembled and characterized by X-ray single crystal analysis. The Cd-MOF features one-dimensional left and right-handed double helical chains with screw-pitch of about 4.727 Å and the 4-methyl benzoic acid groups of Hcbic2- ligands in MOF-1 play many ribbons distributing in the two sides of the 2D networks. It is found that MOF-1 shows high selectivity (KSV = 1.8 × 105 L / mol) for Fe3+ ions in water solution with luminescent quenching because of the existence of uncoordinated carboxyl groups within open frameworks, which indicates that MOF-1 is a simple and reliable detection sensing reagent for Fe3+ in practical applications.

Microbial reduction of Fe(III) in the presence of oxygen under low pH conditions

Energy Technology Data Exchange (ETDEWEB)

Kusel, K.; Roth, U.; Drake, H.L. [University of Bayreuth, Bayreuth (Germany)

2002-07-01

In acidic, coal mining lake sediments, facultatively anaerobic Acidiphilium species are probably involved in the reduction of Fe(III). Previous results indicate that these bacteria can co-respire O{sub 2} and Fe(III). In this study, we investigated the capacity of the sediment microbiota to reduce Fe(III) in the presence of O{sub 2} at pH 3. In sediment microcosms with 4% O{sub 2} in the headspace, the concentration of Fe(II) increased at a rate of 1.03 {mu}mol (g wet sediment){sup -1} day{sup -1} within the first 7 days of incubation which was similar to the rate obtained with controls incubated under anoxic conditions. However, in microcosms incubated under air, Fe(II) was consumed after a lag phase of 8 h with a rate of 2.66 {mu}mol (g wet sediment){sup -1} day{sup -1}. Acidiphilium cryptum JF-5, isolated from this sediment, reduced soluble Fe(III) with either 4 or 21% O{sub 2} in the headspace, and concomitantly consumed O{sub 2}. However, the rate of Fe(II) formation normalized for cell density decreased under oxic conditions. Schwertmannite, the predominant Fe(III)-mineral of this sediment, was also reduced by A. cryptum JF-5 under oxic conditions. The rate of Fe(II) formation by A. cryptum JF-5 decreased after transfer from preincubation under air in medium lacking Fe(III). Acidiphilium cryptum JF-5 did not form Fe(II) when preincubated under air and transferred to anoxic medium containing Fe(III) and chloramphenicol, an inhibitor of protein synthesis. These results indicate that: (i) the reduction of Fe(III) can occur at low O{sub 2} concentrations in acidic sediments; (ii) Fe(II) can be oxidized at O{sub 2} concentrations near saturation; and (iii) the enzyme(s) responsible for the reduction of Fe(III) in A. cryptum JF-5 are not constitutive.

Synthesis and Ligand Non-Innocence of Thiolate-Ligated (N4S) Iron(II) and Nickel(II) Bis(imino)pyridine Complexes

Science.gov (United States)

Widger, Leland R.; Jiang, Yunbo; Siegler, Maxime; Kumar, Devesh; Latifi, Reza; de Visser, Sam P.; Jameson, Guy N.L.; Goldberg, David P.

2013-01-01

The known iron(II) complex [FeII(LN3S)(OTf)] (1) was used as starting material to prepare the new biomimetic (N4S(thiolate)) iron(II) complexes [FeII(LN3S)(py)](OTf) (2) and [FeII(LN3S)(DMAP)](OTf) (3), where LN3S is a tetradentate bis(imino)pyridine (BIP) derivative with a covalently tethered phenylthiolate donor. These complexes were characterized by X-ray crystallography, UV-vis, 1H NMR, and Mössbauer spectroscopy, as well as electrochemistry. A nickel(II) analogue, [NiII(LN3S)](BF4) (5), was also synthesized and characterized by structural and spectroscopic methods. Cyclic voltammetric studies showed 1 – 3 and 5 undergo a single reduction process with E1/2 between −0.9 to −1.2 V versus Fc+/Fc. Treatment of 3 with 0.5% Na/Hg amalgam gave the mono-reduced complex [Fe(LN3S)(DMAP)]0 (4), which was characterized by X-ray crystallography, UV-vis, EPR (g = [2.155, 2.057, 2.038]) and Mössbauer (δ = 0.33 mm s−1; ΔEQ = 2.04 mm s−1) spectroscopies. Computational methods (DFT) were employed to model complexes 3 – 5. The combined experimental and computational studies show that 1 – 3 are 5-coordinate, high-spin (S = 2) FeII complexes, whereas 4 is best described as a 5-coordinate, intermediate-spin (S = 1) FeII complex antiferromagnetically coupled to a ligand radical. This unique electronic configuration leads to an overall doublet spin (Stotal = ½) ground state. Complexes 2 and 3 are shown to react with O2 to give S-oxygenated products, as previously reported for 1. In contrast, the mono-reduced 4 appears to react with O2 to give a mixture of S- and Fe-oxygenates. The nickel(II) complex 5 does not react with O2, and even when the mono-reduced nickel complex is produced, it appears to undergo only outer-sphere oxidation with O2. PMID:23992096

Characterization of Fe (III)-reducing enrichment culture and isolation of Fe (III)-reducing bacterium Enterobacter sp. L6 from marine sediment.

Science.gov (United States)

Liu, Hongyan; Wang, Hongyu

2016-07-01

To enrich the Fe (III)-reducing bacteria, sludge from marine sediment was inoculated into the medium using Fe (OH)3 as the sole electron acceptor. Efficiency of Fe (III) reduction and composition of Fe (III)-reducing enrichment culture were analyzed. The results indicated that the Fe (III)-reducing enrichment culture with the dominant bacteria relating to Clostridium and Enterobacter sp. had high Fe (III) reduction of (2.73 ± 0.13) mmol/L-Fe (II). A new Fe (III)-reducing bacterium was isolated from the Fe (III)-reducing enrichment culture and identified as Enterobacter sp. L6 by 16S rRNA gene sequence analysis. The Fe (III)-reducing ability of strain L6 under different culture conditions was investigated. The results indicated that strain L6 had high Fe (III)-reducing activity using glucose and pyruvate as carbon sources. Strain L6 could reduce Fe (III) at the range of NaCl concentrations tested and had the highest Fe (III) reduction of (4.63 ± 0.27) mmol/L Fe (II) at the NaCl concentration of 4 g/L. This strain L6 could reduce Fe (III) with unique properties in adaptability to salt variation, which indicated that it can be used as a model organism to study Fe (III)-reducing activity isolated from marine environment. Copyright © 2015 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Microbial Reduction of Fe(III) in Acidic Sediments: Isolation of Acidiphilium cryptum JF-5 Capable of Coupling the Reduction of Fe(III) to the Oxidation of Glucose

Science.gov (United States)

Küsel, Kirsten; Dorsch, Tanja; Acker, Georg; Stackebrandt, Erko

1999-01-01

To evaluate the microbial populations involved in the reduction of Fe(III) in an acidic, iron-rich sediment, the anaerobic flow of supplemental carbon and reductant was evaluated in sediment microcosms at the in situ temperature of 12°C. Supplemental glucose and cellobiose stimulated the formation of Fe(II); 42 and 21% of the reducing equivalents that were theoretically obtained from glucose and cellobiose, respectively, were recovered in Fe(II). Likewise, supplemental H2 was consumed by acidic sediments and yielded additional amounts of Fe(II) in a ratio of approximately 1:2. In contrast, supplemental lactate did not stimulate the formation of Fe(II). Supplemental acetate was not consumed and inhibited the formation of Fe(II). Most-probable-number estimates demonstrated that glucose-utilizing acidophilic Fe(III)-reducing bacteria approximated to 1% of the total direct counts of 4′,6-diamidino-2-phenylindole-stained bacteria. From the highest growth-positive dilution of the most-probable-number series at pH 2.3 supplemented with glucose, an isolate, JF-5, that could dissimilate Fe(III) was obtained. JF-5 was an acidophilic, gram-negative, facultative anaerobe that completely oxidized the following substrates via the dissimilation of Fe(III): glucose, fructose, xylose, ethanol, glycerol, malate, glutamate, fumarate, citrate, succinate, and H2. Growth and the reduction of Fe(III) did not occur in the presence of acetate. Cells of JF-5 grown under Fe(III)-reducing conditions formed blebs, i.e., protrusions that were still in contact with the cytoplasmic membrane. Analysis of the 16S rRNA gene sequence of JF-5 demonstrated that it was closely related to an Australian isolate of Acidiphilium cryptum (99.6% sequence similarity), an organism not previously shown to couple the complete oxidation of sugars to the reduction of Fe(III). These collective results indicate that the in situ reduction of Fe(III) in acidic sediments can be mediated by heterotrophic Acidiphilium

Microbial reduction of Fe(III) in acidic sediments: isolation of Acidiphilium cryptum JF-5 capable of coupling the reduction of Fe(III) to the oxidation of glucose.

Science.gov (United States)

Küsel, K; Dorsch, T; Acker, G; Stackebrandt, E

1999-08-01

To evaluate the microbial populations involved in the reduction of Fe(III) in an acidic, iron-rich sediment, the anaerobic flow of supplemental carbon and reductant was evaluated in sediment microcosms at the in situ temperature of 12 degrees C. Supplemental glucose and cellobiose stimulated the formation of Fe(II); 42 and 21% of the reducing equivalents that were theoretically obtained from glucose and cellobiose, respectively, were recovered in Fe(II). Likewise, supplemental H(2) was consumed by acidic sediments and yielded additional amounts of Fe(II) in a ratio of approximately 1:2. In contrast, supplemental lactate did not stimulate the formation of Fe(II). Supplemental acetate was not consumed and inhibited the formation of Fe(II). Most-probable-number estimates demonstrated that glucose-utilizing acidophilic Fe(III)-reducing bacteria approximated to 1% of the total direct counts of 4', 6-diamidino-2-phenylindole-stained bacteria. From the highest growth-positive dilution of the most-probable-number series at pH 2. 3 supplemented with glucose, an isolate, JF-5, that could dissimilate Fe(III) was obtained. JF-5 was an acidophilic, gram-negative, facultative anaerobe that completely oxidized the following substrates via the dissimilation of Fe(III): glucose, fructose, xylose, ethanol, glycerol, malate, glutamate, fumarate, citrate, succinate, and H(2). Growth and the reduction of Fe(III) did not occur in the presence of acetate. Cells of JF-5 grown under Fe(III)-reducing conditions formed blebs, i.e., protrusions that were still in contact with the cytoplasmic membrane. Analysis of the 16S rRNA gene sequence of JF-5 demonstrated that it was closely related to an Australian isolate of Acidiphilium cryptum (99.6% sequence similarity), an organism not previously shown to couple the complete oxidation of sugars to the reduction of Fe(III). These collective results indicate that the in situ reduction of Fe(III) in acidic sediments can be mediated by heterotrophic

Adsorption of Cd(II) by Mg–Al–CO{sub 3}- and magnetic Fe{sub 3}O{sub 4}/Mg–Al–CO{sub 3}-layered double hydroxides: Kinetic, isothermal, thermodynamic and mechanistic studies

Energy Technology Data Exchange (ETDEWEB)

Shan, Ran-ran; Yan, Liang-guo, E-mail: yanyu-33@163.com; Yang, Kun; Hao, Yuan-feng; Du, Bin

2015-12-15

Highlights: • The Mg–Al–CO{sub 3}- and magnetic Fe{sub 3}O{sub 4}/Mg–Al–CO{sub 3}–LDH can efficiently remove Cd(II) from aqueous solutions. • The adsorption mechanisms of Cd(II) were discussed in detail. • The adsorption kinetic, isothermal and thermodynamic properties of Cd(II) were studied. • Magnetic Fe{sub 3}O{sub 4}/Mg–Al–CO{sub 3}–LDH can be quickly and easily separated using a magnet. - Abstract: Understanding the adsorption mechanisms of metal cations on the surfaces of solids is important for determining the fate of these metals in water and wastewater treatment. The adsorption kinetic, isothermal, thermodynamic and mechanistic properties of cadmium (Cd(II)) in an aqueous solution containing Mg–Al–CO{sub 3}- and magnetic Fe{sub 3}O{sub 4}/Mg–Al–CO{sub 3}-layered double hydroxide (LDH) were studied. The results demonstrated that the adsorption kinetic and isotherm data followed the pseudo-second-order model and the Langmuir equation, respectively. The adsorption process of Cd(II) was feasible, spontaneous and endothermic in nature. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to explain the adsorption mechanisms. The characteristic XRD peaks and FTIR bands of CdCO{sub 3} emerged in the LDH spectra after Cd(II) adsorption, which indicated that the adsorption of Cd(II) by LDHs occurred mainly via CdCO{sub 3} precipitation, surface adsorption and surface complexation. Furthermore, the magnetic Fe{sub 3}O{sub 4}/Mg–Al–CO{sub 3}-LDH can be quickly and easily separated using a magnet before and after the adsorption process.

Synthesis and structural characterisation of iron(II) and copper(II) diphosphates containing flattened metal oxotetrahedra

Energy Technology Data Exchange (ETDEWEB)

Keates, Adam C. [School of Chemistry, University of Southampton, Southampton, Hampshire SO17 1B,. UK (United Kingdom); Wang, Qianlong [Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY (United Kingdom); Weller, Mark T., E-mail: m.t.weller@bath.ac.uk [Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY (United Kingdom)

2014-02-15

Single crystal and bulk polycrystalline forms of K{sub 2}MP{sub 2}O{sub 7} (M=Fe(II), Cu(II)) have been synthesised and their structures determined from single crystal X-ray diffraction data. Both compounds crystallize in the tetragonal system, space group P-42{sub 1}m. Their structures are formed from infinite sheets of linked oxopolyhedra of the stoichiometry [MP{sub 2}O{sub 7}]{sup 2−} with potassium cations situated between the layers. The MO{sub 4} tetrahedra share oxygen atoms with [P{sub 2}O{sub 7}]{sup 4−} diphosphate groups and the potassium ions have KO{sub 8} square prismatic geometry. In both compounds the M(II) centre has an unusual strongly flattened, tetrahedral coordination to oxygen, as a result of the Jahn–Teller (JT) effect for the high spin d{sup 6} Fe(II) and p-orbital mixing or a second order JT effect for d{sup 9} Cu(II) centres in four fold coordination. The uncommon transition metal ion environments found in these materials are reflected in their optical absorption spectra and magnetism data. - Graphical abstract: The structures of the tetragonal polymorphs of K{sub 2}MP{sub 2}O{sub 7}, M=Cu(II), Fe(II), consist of infinite sheets of stoichiometry [MP{sub 2}O{sub 7}]{sup 2−}, formed from linked pyrophosphate groups and MO{sub 4} tetrahedra, separated by potassium ions. In both compounds the unusual tetrahedral coordination of the M(II) centre is strongly flattened as a result of Jahn–Teller (JT) effects for high spin, d{sup 6} Fe(II) and p-orbital mixing and second-order JT effects for d{sup 9} Cu(II). Display Omitted - Highlights: • Tetrahedral copper and iron(II) coordinated by oxygen. • New layered phosphate structure. • Jahn–Teller and d{sup 10} distorted coordinations.

Synthesis and structural characterisation of iron(II) and copper(II) diphosphates containing flattened metal oxotetrahedra

International Nuclear Information System (INIS)

Keates, Adam C.; Wang, Qianlong; Weller, Mark T.

2014-01-01

Single crystal and bulk polycrystalline forms of K 2 MP 2 O 7 (M=Fe(II), Cu(II)) have been synthesised and their structures determined from single crystal X-ray diffraction data. Both compounds crystallize in the tetragonal system, space group P-42 1 m. Their structures are formed from infinite sheets of linked oxopolyhedra of the stoichiometry [MP 2 O 7 ] 2− with potassium cations situated between the layers. The MO 4 tetrahedra share oxygen atoms with [P 2 O 7 ] 4− diphosphate groups and the potassium ions have KO 8 square prismatic geometry. In both compounds the M(II) centre has an unusual strongly flattened, tetrahedral coordination to oxygen, as a result of the Jahn–Teller (JT) effect for the high spin d 6 Fe(II) and p-orbital mixing or a second order JT effect for d 9 Cu(II) centres in four fold coordination. The uncommon transition metal ion environments found in these materials are reflected in their optical absorption spectra and magnetism data. - Graphical abstract: The structures of the tetragonal polymorphs of K 2 MP 2 O 7 , M=Cu(II), Fe(II), consist of infinite sheets of stoichiometry [MP 2 O 7 ] 2− , formed from linked pyrophosphate groups and MO 4 tetrahedra, separated by potassium ions. In both compounds the unusual tetrahedral coordination of the M(II) centre is strongly flattened as a result of Jahn–Teller (JT) effects for high spin, d 6 Fe(II) and p-orbital mixing and second-order JT effects for d 9 Cu(II). Display Omitted - Highlights: • Tetrahedral copper and iron(II) coordinated by oxygen. • New layered phosphate structure. • Jahn–Teller and d 10 distorted coordinations

The structure of the local interstellar medium. VI. New Mg II, Fe II, and Mn II observations toward stars within 100 pc

International Nuclear Information System (INIS)

Malamut, Craig; Redfield, Seth; Linsky, Jeffrey L.; Wood, Brian E.; Ayres, Thomas R.

2014-01-01

We analyze high-resolution spectra obtained with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope toward 34 nearby stars (≤100 pc) to record Mg II, Fe II, and Mn II absorption due to the local interstellar medium (LISM). Observations span the entire sky, probing previously unobserved regions of the LISM. The heavy ions studied in this survey produce narrow absorption features that facilitate the identification of multiple interstellar components. We detected one to six individual absorption components along any given sight line, and the number of absorbers roughly correlates with the pathlength. This high-resolution near-ultraviolet (NUV) spectroscopic survey was specifically designed for sight lines with existing far-UV (FUV) observations. The FUV spectra include many intrinsically broad absorption lines (i.e., of low atomic mass ions) and are often observed at medium resolution. The LISM NUV narrow-line absorption component structure presented here can be used to more accurately interpret the archival FUV observations. As an example of this synergy, we present a new analysis of the temperature and turbulence along the line of sight toward ε Ind. The new observations of LISM velocity structure are also critical in the interpretation of astrospheric absorption derived from fitting the saturated H I Lyα profile. As an example, we reanalyze the spectrum of λ And and find that this star likely does have an astrosphere. Two stars in the sample that have circumstellar disks (49 Cet and HD141569) show evidence for absorption due to disk gas. Finally, the substantially increased number of sight lines is used to test and refine the three-dimensional kinematic model of the LISM and search for previously unidentified clouds within the Local Bubble. We find that every prediction made by the Redfield and Linsky kinematic model of the LISM is confirmed by an observed component in the new lines of sight.

THE LICK/SDSS LIBRARY. II. [Ca/Fe] AND [Mg/Fe] IN F, G, AND K STARS FROM SDSS-DR7

International Nuclear Information System (INIS)

Franchini, M.; Morossi, C.; Di Marcantonio, P.; Malagnini, M. L.; Chavez, M.

2011-01-01

We analyzed the spectra of 17,600 F, G, and K stars extracted from the seventh Sloan Digital Sky Survey Data Release (SDSS-DR7) database in order to derive ([α/Fe]), [Ca/Fe], and [Mg/Fe] ratios. Particular attention has been devoted to estimating homogeneous and self-consistent atmospheric parameter values, T eff , log g, and [Fe/H], by comparing synthetic and observational Lick/SDSS indices. We present results for the sub-sample of more than 4000 spectra whose overall quality allowed us to derive fairly accurate stellar atmospheric parameter values and, therefore, reliable abundance ratios. A Monte Carlo approach was adopted to evaluate both the errors in the observational Lick/SDSS indices and in the derived parameter estimates. The analysis of the trends of [Ca/Fe] and [Mg/Fe] versus [Fe/H] pointed out that (1) the [Ca/Fe] and [Mg/Fe] ratios increase with decreasing [Fe/H] with different slopes reaching maximum average levels of +0.25 and +0.40 dex at [Fe/H] ≅ -1.75, respectively; (2) our sample contains, at a given [Fe/H], stars characterized by significantly different amounts of α-enhancement, thus belonging to different Galactic populations; and (3) the analyzed sample shows a predominance of thick disk stars for [Fe/H] > - 0.5 and the presence of stars belonging to the h igh-αhalo population for -2.0 < [Fe/H] <-0.5.

Reduction of neptunium(V) and uranium(VI) in bicarbonate solutions by iron(II)

International Nuclear Information System (INIS)

Gogolev, A.V.; Zakharova, E.V.; Rodygina, N.I.; Fedoseev, A.M.; Shilov, V.P.

2006-01-01

Interaction of Np(VI) and Fe(II) compounds in bicarbonate solutions is investigated. Interaction of Np(V) with Fe(II) in the presence of phthalate-ions is studied briefly. Fe(II) compounds reduce Np(V) compounds in saturated with Ar or CO 2 solutions with any bicarbonate-ion concentrations. Chemical reaction kinetics is studied. Reduction of U(VI) by Fe(II) compounds takes place in the case of diluted bicarbonate solutions. UO 2 and FeOOH are products of reaction at raised temperatures [ru

Preservation of Fe Isotope Proxies in the Rock Record

Science.gov (United States)

Johnson, C.; Beard, B.; Valley, J.; Valaas, E.

2005-12-01

Iron isotope variations provide powerful constraints on redox conditions and pathways involved during biogeochemical cycling of Fe in surface and near-surface environments. The relative isotopic homogeneity of igneous rocks and most bulk weathering products contrasts with the significant isotopic variations (4 per mil in 56Fe/54Fe) that accompany oxidation of Fe(II)aq, precipitation of sulfides, and reduction by bacteria. These isotopic variations often reflect intrinsic (equilibrium) Fe isotope fractionations between minerals and aqueous species whose interactions may be directly or indirectly catalyzed by bacteria. In addition, Fe isotope exchange may be limited between reactive Fe pools in low-temperature aqueous-sediment environments, fundamentally reflecting disequilibrium effects. In the absence of significant sulfide, dissimilatory Fe(III) reduction by bacteria produces relatively low 56Fe/54Fe ratios for Fe(II)aq and associated biogenic minerals such as magnetite and siderite. In contrast, Fe(II)aq that exchanges with Fe sulfides (FeS and pyrite) is relatively enriched in 56Fe/54Fe ratios. In modern and ancient environments, anoxic diagenesis tends to produce products that have low 56Fe/54Fe ratios, whereas oxidation of Fe(II)aq from hydrothermal sources tends to produce ferric Fe products that have high 56Fe/54Fe ratios. Redox cycling by bacteria tends to produce reactive ferric Fe reservoirs that have low 56Fe/54Fe ratios. Application of Fe isotopes as a proxy for redox conditions in the ancient rock record depends upon the preservation potential during metamorphism, given the fact that most Archean sedimentary sequences have been subjected to regional greenschist- to granulite-facies metamorphism. The 1.9 Ga banded iron formations (BIFs) of the Lake Superior region that are intruded by large ~1 Ga intrusions (e.g., Duluth gabbro) provide a test of the preservation potential for primary, low-temperature Fe isotope variations in sedimentary rocks. 56Fe/54

Pb(II), Cd(II) and Zn(II) adsorption on low grade manganese ore ...

African Journals Online (AJOL)

Low grade manganese ore (LMO) of Orissa containing 58.37% SiO2, 25.05% MnO2, 8.8% Al2O3, and 5.03% Fe2O3 as the main constituents was taken to study its adsorption behaviour for Pb(II), Cd(II) and Zn(II) from aqueous solutions. The XRD studies showed the crystalline phases to be quartz, ß-MnO2, d-MnO2 and ...

Fe II/Fe III mixed-valence state induced by Li-insertion into the metal-organic-framework Mil53(Fe): A DFT+U study

Science.gov (United States)

Combelles, C.; Ben Yahia, M.; Pedesseau, L.; Doublet, M.-L.

The iron-based metal-organic-framework MIL53(Fe) has recently been tested as a cathode materials for Li-Ion batteries, leading to promising cycling life and rate capability. Despite a poor capacity of 70 mAh g -1 associated with the exchange of almost 0.5Li/Fe, this result is the first evidence of a reversible lithium insertion never observed in a MOF system. In the present study, the MIL53(Fe) redox mechanism is investigated through first-principles DFT+U calculations. The results show that MIL53(Fe) is a weak antiferromagnetic charge transfer insulator at T = 0 K, with iron ions in the high-spin S = 5/2 state. Its reactivity vs elemental lithium is then investigated as a function of lithium composition and distribution over the most probable Li-sites of the MOF structure. The redox mechanism is fully interpreted as a two-step insertion/conversion mechanism, associated with the stabilization of the Fe 3+/Fe 2+ mixed-valence state prior to the complete decomposition of the inorganic-organic interactions within the porous MOF architecture.

[Fe(III)(dmbpy)(CN)4]-: a new building block for designing single-chain magnets.

Science.gov (United States)

Toma, Luminita Marilena; Pasán, Jorge; Ruiz-Pérez, Catalina; Lloret, Francesc; Julve, Miguel

2012-11-28

We herein present the synthesis and magneto-structural study of a new family of heterobimetallic chains of general formula {[Fe(III)(dmbpy)(CN)(4)](2)M(II)(H(2)O)(2)}(n)·pnH(2)O [dmbpy = 4,4'-dimethyl-2,2'-bipyridine; M = Mn (2), Cu (3), Ni (4) and Co (5) with p = 4 (2), 3 (3), 9 (4) and 3.5 (5)] which were prepared by using the mononuclear PPh(4)[Fe(III)(dmbpy)(CN)(4)]·3H(2)O (1) building block (PPh(4)(+) = tetraphenylphosphonium) as a ligand toward fully solvated M(II) ions. The structure of 1 consists of discrete [Fe(III)(dmbpy)(CN)(4)](-) anions, tetraphenylphosphonium cations and noncoordinated water molecules. Complexes 2-5 are isostructural compounds whose structure consists of neutral 4,2-wave like heterobimetallic chains of formula {[Fe(III)(dmbpy)(CN)(4)](2)M(II)(H(2)O)(2)}(n) where the [Fe(III)(dmbpy)(CN)(4)](-) entity adopts a bis-monodentate coordination mode toward trans-[M(II)(H(2)O)(2)] units through two of its four cyanide groups in cis positions. 1 exhibits the magnetic behaviour of magnetically isolated six-coordinate low-spin Fe(III) complexes with an important orbital contribution. 2 behaves as ferrimagnetic Fe(III)(2)Mn(II) chains, whereas 3-5 exhibit intrachain ferromagnetic couplings between the low-spin Fe(III) and either Cu(II) (3), Ni (4) or Co(II) (5) as well as frequency-dependence of the out-of-phase ac susceptibility signals below 3.0 (3), 5.5 (4) and 5.0 K (5). The relaxation time and the energy to reverse the magnetization of 3-5 are related to the anisotropy of the M(II) center and to the intra- and interchain magnetic interactions. Unprecedentedly in the world of cyanide-bearing complexes, 5 exhibits a double slow relaxation of the magnetization.

Atomistic computer simulations of FePt nanoparticles. Thermodynamic and kinetic properties

Energy Technology Data Exchange (ETDEWEB)

Mueller, M.

2007-12-20

In the present dissertation, a hierarchical multiscale approach for modeling FePt nanoparticles by atomistic computer simulations is developed. By describing the interatomic interactions on different levels of sophistication, various time and length scales can be accessed. Methods range from static quantum-mechanic total-energy calculations of small periodic systems to simulations of whole particles over an extended time by using simple lattice Hamiltonians. By employing these methods, the energetic and thermodynamic stability of non-crystalline multiply twinned FePt nanoparticles is investigated. Subsequently, the thermodynamics of the order-disorder transition in FePt nanoparticles is analyzed, including the influence of particle size, composition and modified surface energies by different chemical surroundings. In order to identify processes that reduce or enhance the rate of transformation from the disordered to the ordered state, the kinetics of the ordering transition in FePt nanoparticles is finally investigated by assessing the contributions of surface and volume diffusion. (orig.)

Cognitive ability rivals the effect of political sophistication on ideological voting

DEFF Research Database (Denmark)

Hebbelstrup Rye Rasmussen, Stig

2016-01-01

This article examines the impact of cognitive ability on ideological voting. We find, using a US sample and a Danish sample, that the effect of cognitive ability rivals the effect of the traditionally strongest predicter of ideological voting political sophistication. Furthermore, the results...... are consistent with the effect of cognitive ability being partly mediated by political sophistication. Much of the effect of cognitive ability remains however and is not explained by differences in education or Openness to experience either. The implications of these results for democratic theory are discussed....

Sorption-induced reversible oxidation of Fe(2) at the smectite/water interface under strictly anoxic conditions. A Moessbauer spectroscopy study

Energy Technology Data Exchange (ETDEWEB)

Gehin, A.; Charlet, L. [Laboratoire de Geophysique Interne et Tectonophysique (LGIT), Universite de Grenoble, 38 - Grenoble (France); Gehin, A. [Agence Nationale pour la Gestion des Dechets Radioactifs, ANDRA, 92 - Chatenay Malabry (France); Greneche, J.M. [Laboratoire de Physique de l' Etat Condense, UMR-CNRS 6087, 72 - Le Mans (France); Brendle, J. [Universite de Haute Alsace, Lab. des Materiaux Mineraux (LMM), 68 - Mulhouse (France); Rancourt, D.G. [Ottawa Univ., Dept. of Physics, Ontario (Canada)

2005-07-01

Previous studies of Fe(II) sorption onto montmorillonite have been performed with the mineral extracted from the MX80 bentonite. These studies have shown that Fe(II) can be sorbed onto clay minerals in cation exchange position. The affinity of montmorillonite for Fe(II) and Ca(II) is identical. Fe(II) may also be specifically adsorbed onto montmorillonite clay edges. Moessbauer spectroscopy confirmed the high affinity of clay surfaces for Fe(II) sorption and showed that this sorption is mainly due to a two step mechanism: Fe(II) specific adsorption, followed by oxidation of the Fe(II) sorbed. The identification of the oxidizing agent was prohibited due to the complex chemistry of the natural MX80 montmorillonite. Thus, synthetic iron-free montmorillonite was used (chemical formula: Ca{sub 0.3} (A{sub 1.4}Mg{sub 0.6}) (Si{sub 4}) O{sub 10}(OH){sub 2} ). {sup 57}Fe(II) sorption experiments were conducted in a N{sub 2} atmosphere gloves-box, in strictly anoxic conditions. Solid samples were synthesized in order to confirm the clay high affinity for Fe(II), in absence of structural oxidant, and to have a better comprehension of the sorption mechanism. Moessbauer spectra were recorded for each sample. Whereas no Fe(III) is detected in solution as pH was increased and then, a significant amount of surface sorbed Fe(III) was found to be reversibly produced, which amounts for 0-3% of total Fe in the pre-sorption edge acid region, up to 7% of total Fe when all Fe is sorbed in the neutral to alkaline pH range. From pH {approx_equal} 2 to pH {approx_equal} 7, a sorption edge plateau is observed. In this plateau, the sorbed-Fe(III)/sorbed-Fe ratio increases with pH, up to 45% at pH 7. Moessbauer spectra comparison with ferrous hydroxide, synthesized in the same redox conditions at higher pH, show that this oxidation can not be due to the trace amounts Oz in the suspension. The Moessbauer spectra components of both Fe(II) and Fe(III) appears as paramagnetic doublets: iron has

Cd Mobility in Anoxic Fe-Mineral-Rich Environments - Potential Use of Fe(III)-Reducing Bacteria in Soil Remediation

Science.gov (United States)

Muehe, E. M.; Adaktylou, I. J.; Obst, M.; Schröder, C.; Behrens, S.; Hitchcock, A. P.; Tylsizczak, T.; Michel, F. M.; Krämer, U.; Kappler, A.

2014-12-01

Agricultural soils are increasingly burdened with heavy metals such as Cd from industrial sources and impure fertilizers. Metal contaminants enter the food chain via plant uptake from soil and negatively affect human and environmental health. New remediation approaches are needed to lower soil metal contents. To apply these remediation techniques successfully, it is necessary to understand how soil microbes and minerals interact with toxic metals. Here we show that microbial Fe(III) reduction initially mobilizes Cd before its immobilization under anoxic conditions. To study how microbial Fe(III) reduction influences Cd mobility, we isolated a new Cd-tolerant, Fe(III)-reducing Geobacter sp. from a heavily Cd-contaminated soil. In lab experiments, this Geobacter strain first mobilized Cd from Cd-loaded Fe(III) hydroxides followed by precipitation of Cd-bearing mineral phases. Using Mössbauer spectroscopy and scanning electron microscopy, the original and newly formed Cd-containing Fe(II) and Fe(III) mineral phases, including Cd-Fe-carbonates, Fe-phosphates and Fe-(oxyhydr)oxides, were identified and characterized. Using energy-dispersive X-ray spectroscopy and synchrotron-based scanning transmission X-ray microscopy, Cd was mapped in the Fe(II) mineral aggregates formed during microbial Fe(III) reduction. Microbial Fe(III) reduction mobilizes Cd prior to its precipitation in Cd-bearing mineral phases. The mobilized Cd could be taken up by phytoremediating plants, resulting in a net removal of Cd from contaminated sites. Alternatively, Cd precipitation could reduce Cd bioavailability in the environment, causing less toxic effects to crops and soil microbiota. However, the stability and thus bioavailability of these newly formed Fe-Cd mineral phases needs to be assessed thoroughly. Whether phytoremediation or immobilization of Cd in a mineral with reduced Cd bioavailability are feasible mechanisms to reduce toxic effects of Cd in the environment remains to be

Radiomimeticity of the system H{sub 2}O{sub 2}/Fe(II) on nucleic acid components. Kinetics study; Radiomimeticidad del sistema H{sub 2}O{sub 2}/Fe(II) sobre components de Acidos Nucleicos. Estudio Cinetico

Energy Technology Data Exchange (ETDEWEB)

Cirauqui, R; Mingot, F; Davila, C A

1974-07-01

The kinetic study of the action of a redox system on DNA monomers allowed us to make criticisms on radiomimetic character of this system. Assuming that in both cases, gamma radiolysis of aerated aqueous solutions and action of H{sub 2}O{sub 2} / Fe(II) system in the same conditions, the reactive species is the OH radical, we propose the kinetic expressions that are confirmed by our experimental results. Some of the accepted G-values are corrected in view of our results. Al so these results put in evidence mechanisms of molecular repair after radical attack. (Author) 79 refs.

Arsenic removal with iron(II) and iron(III) in waters with high silicate and phosphate concentrations.

Science.gov (United States)

Roberts, Linda C; Hug, Stephan J; Ruettimann, Thomas; Billah, Morsaline; Khan, Abdul Wahab; Rahman, Mohammad Tariqur

2004-01-01

Arsenic removal by passive treatment, in which naturally present Fe(II) is oxidized by aeration and the forming iron(III) (hydr)oxides precipitate with adsorbed arsenic, is the simplest conceivable water treatment option. However, competing anions and low iron concentrations often require additional iron. Application of Fe(II) instead of the usually applied Fe(III) is shown to be advantageous, as oxidation of Fe(II) by dissolved oxygen causes partial oxidation of As(III) and iron(III) (hydr)oxides formed from Fe(II) have higher sorption capacities. In simulated groundwater (8.2 mM HCO3(-), 2.5 mM Ca2+, 1.6 mM Mg2+, 30 mg/L Si, 3 mg/L P, 500 ppb As(III), or As(V), pH 7.0 +/- 0.1), addition of Fe(II) clearly leads to better As removal than Fe(III). Multiple additions of Fe(II) further improved the removal of As(II). A competitive coprecipitation model that considers As(III) oxidation explains the observed results and allows the estimation of arsenic removal under different conditions. Lowering 500 microg/L As(III) to below 50 microg/L As(tot) in filtered water required > 80 mg/L Fe(III), 50-55 mg/L Fe(II) in one single addition, and 20-25 mg/L in multiple additions. With As(V), 10-12 mg/L Fe(II) and 15-18 mg/L Fe(III) was required. In the absence of Si and P, removal efficiencies for Fe(II) and Fe(III) were similar: 30-40 mg/L was required for As(II), and 2.0-2.5 mg/L was required for As(V). In a field study with 22 tubewells in Bangladesh, passive treatment efficiently removed phosphate, but iron contents were generally too low for efficient arsenic removal.

Viability of thin wall tube forming of ATF FeCrAl

Energy Technology Data Exchange (ETDEWEB)

Maloy, Stuart Andrew [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Aydogan, Eda [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Anderoglu, Osman [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lavender, Curt [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Yamamoto, Yukinori [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2016-09-16

Fabrication of thin walled tubing of FeCrAl alloys is critical to its success as a candidate enhanced accident-tolerant fuel cladding material. Alloys that are being investigated are Generation I and Generation II FeCrAl alloys produced at ORNL and an ODS FeCrAl alloy, MA-956 produced by Special Metals. Gen I and Gen II FeCrAl alloys were provided by ORNL and MA-956 was provided by LANL (initially produced by Special Metals). Three tube development efforts were undertaken. ORNL led the FeCrAl Gen I and Gen II alloy development and tube processing studies through drawing tubes at Rhenium Corporation. LANL received alloys from ORNL and led tube processing studies through drawing tubes at Century Tubing. PNNL led the development of tube processing studies on MA-956 through pilger processing working with Sandvik Corporation. A summary of the recent progress on tube development is provided in the following report and a separate ORNL report: ORNL/TM-2015/478, “Development and Quality Assessments of Commercial Heat Production of ATF FeCrAl Tubes”.

Preparation of iron molybdate catalysts for methanol to formaldehyde oxidation based on ammonium molybdoferrate(II precursor

Directory of Open Access Journals (Sweden)

N.V. Nikolenko

2018-03-01

Full Text Available It was demonstrated that iron molybdate catalysts for methanol oxidation can be prepared using Fe(II as a precursor instead of Fe(III. This would allow for reduction of acidity of preparation solutions as well as elimination of Fe(III oxide impurities which are detrimental for the process selectivity. The system containing Fe(II and Mo(VI species in aqueous solution was investigated using UV–Vis spectroscopy. It was demonstrated that three types of chemical reactions occur in the Fe(II–Mo(VI system: (i formation of complexes between Fe(II and molybdate(VI ions, (ii inner sphere oxidation of coordinated Fe(II by Mo(VI and (iii decomposition of the Fe–Mo complexes to form scarcely soluble Fe(III molybdate, Mo(VI hydrous trioxide and molybdenum blue. Solid molybdoferrate(II prepared by interaction of Fe(II and Mo(VI in solution was characterized by EDXA, TGA, DTA and XRD and a scheme of its thermal evolution proposed. The iron molybdate catalyst prepared from Fe(II precursor was tested in methanol-to-formaldehyde oxidation in a continuous flow fixed-bed reactor to show similar activity and selectivity to the conventional catalyst prepared with the use of Fe(III.

Biogeochemistry of Fe and Tc Reduction and Oxidation in FRC Sediment

International Nuclear Information System (INIS)

John M, Zachara; James K, Fredrickson; Ravi K, Kukkadapu; Steven C, Smith; David W, Kennedy

2004-01-01

The objectives are: (1) To rigorously characterize the distribution of Fe(II) and Fe(III) in FRC sediment. (2) To identify changes to Fe(II)/Fe(III) distribution and concentration resulting from DIRB activity. (3) To determine the dependence of Tc(VII) reduction rate on biogenic Fe(II) and it's forms. (4) To establish tendency of Tc(IV) and biogenic Fe(II) to oxidize and their effects on Tc immobilization. The mineralogic and chemical properties of the pristine, bioreduced, and chemically extracted FRC sediments were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), X-ray microscopy (XRM, at the PNC-CAT beamline at APS), Moessbauer spectroscopy, and scanning and transmission electron microscopy with lattice fringe imaging. Chemical extraction included dithionite-citrate-bicarbonate (DCB), acid ammonium oxalate (AAO), and hydroxylamine hydrochloride (HAH). The FRC sediment was incubated under anoxic conditions with the facultative dissimilatory metal-reducing bacterium Shewanella putrefaciens, strain CN32 in defined aqueous solutions/media with bicarbonate and PIPES buffers for time periods exceeding 75 d. Lactate was used as the electron donor. Aqueous and sorbed Fe(II) (ferrozine assay and 0.5 N HCl extraction) and Mn(II) (ICP-MS and 10 mM CuSO 4 extraction), and pH were monitored to define the reduction progress and extent. The bioreduced materials were characterized using the abovementioned techniques. Bioreduced (pasteurized) sediment or chemically extracted/reduced sediment spiked with Fe(II) was washed with a PIPES buffer/electrolyte solution, and spiked with NaTc(VII)O 4 to yield a concentration of 20 (micro)M. The Tc(VII)-spiked samples were agitated and equilibrated at 25 C and sampled over time to assess the Tc(VII) reduction rate. Selected sediment samples containing 20 (micro)M of reduced Tc [Tc(IV)] were subjected to oxidation by: (1) successive headspace replacements of air, and (2) open system equilibration with air. Removed aqueous

Batch adsorptive removal of Fe(III, Cu(II and Zn(II ions in aqueous and aqueous organic–HCl media by Dowex HYRW2-Na Polisher resin as adsorbents

Directory of Open Access Journals (Sweden)

Abdul-Aleem Soliman Aboul-Magd

2016-09-01

Full Text Available Of the metal ions in tap, Nile, waste and sea water samples and some ores were carried out. Removal of heavy metal ions such as Fe(III, Cd(II, Zn(II, Cu(II, Mn(II, Mg(II, and Pb(II from water and wastewater is obligatory in order to avoid water pollution. Batch shaking adsorption experiments to evaluate the performance of nitric and hydrochloric acid solutions in the removal of metal ions by cation exchange resin at the same conditions for both, such as the effect of initial metal ion concentration, different proportions of some organic solvents, H+-ion concentrations and reaction temperature on the partition coefficients. The metal adsorption for the cation exchanger was found to be significant in different media for both nitric and hydrochloric acids, i.e., the adsorption up take of metal ions presented in this work is very significant depending on the characteristics of ions and on the external concentrations of solute. The presence of low ionic strength or low concentration of acids does have a significant adsorption of metal ions on ion-exchange resin. The results show that the ion exchanger could be employed for the preconcentration, separation and the determination.

Electronic properties of Fe2+ in MTiO3

International Nuclear Information System (INIS)

Ito, A.; Morimoto, S.

1975-01-01

Moessbauer spectra were observed in a temperature range from 4.2 to 300 K for the ilmenite structure compounds MTiO 3 -2 % 57 Fe (M = Mg, Mn-I, Fe, Co, Ni) and for the disordered ilmenite structure compound MnTiO 2 -II-1 % 57 Fe. The Neel temperature and the spin orientation of host materials are tabulated. A well resolved quadrupole doublet was observed for all the samples at temperatures above the respective Neel temperatures. Below the Neel temperature a magnetic structure appeared. The Moessbauer spectra obtained at 4.2 K are presented. The spectra were analyzed on the basis of the well-known Hamiltonian for sup(57m)Fe. Moessbauer parameters obtained are tabulated. Analyzing the spectra at 4.2 K, quadrupole interaction was determined to be negative in MnTiO 3 -II and positive in all other compounds. Hyperfine magnetic field intensities observed a6 4.2 K were 34, 85, 47, 105 and 91 kOe for MnTiO 3 -I, MnTiO 3 -II, FeTiO 3 , CoTiO 3 and NiTiO 3 , respectively. (Z.S.)

Radiomimeticity of the system H2O2/Fe(II) on nucleic acid components. Kinetics study

International Nuclear Information System (INIS)

Cirauqui, R.; Mingot, F.; Davila, C. A.

1974-01-01

The kinetic study of the action of a redox system on DNA monomers allowed us to make criticisms on radiomimetic character of this system. Assuming that in both cases, gamma radiolysis of aerated aqueous solutions and action of H 2 O 2 / Fe(II) system in the same conditions, the reactive species is the OH radical, we propose the kinetic expressions that are confirmed by our experimental results. Some of the accepted G-values are corrected in view of our results. Al so these results put in evidence mechanisms of molecular repair after radical attack. (Author) 79 refs

Towards understanding of magnetization reversal in Nd-Fe-B nanocomposites: analysis by high-throughput micromagnetic simulations

Science.gov (United States)

Erokhin, Sergey; Berkov, Dmitry; Ito, Masaaki; Kato, Akira; Yano, Masao; Michels, Andreas

2018-03-01

We demonstrate how micromagnetic simulations can be employed in order to characterize and analyze the magnetic microstructure of nanocomposites. For the example of nanocrystalline Nd-Fe-B, which is a potential material for future permanent-magnet applications, we have compared three different models for the micromagnetic analysis of this material class: (i) a description of the nanocomposite microstructure in terms of Stoner-Wohlfarth particles with and without the magnetodipolar interaction; (ii) a model based on the core-shell representation of the nanograins; (iii) the latter model including a contribution of superparamagnetic clusters. The relevant parameter spaces have been systematically scanned with the aim to establish which micromagnetic approach can most adequately describe experimental data for this material. According to our results, only the last, most sophisticated model is able to provide an excellent agreement with the measured hysteresis loop. The presented methodology is generally applicable to multiphase magnetic nanocomposites and it highligths the complex interrelationship between the microstructure, magnetic interactions, and the macroscopic magnetic properties.

On the O/Fe versus Fe/H relationship and the progenitors of type I supernovae

International Nuclear Information System (INIS)

Abia, C.; Canal, R.; Isern, J.

1991-01-01

The new observational O/Fe versus Fe/H abundance relationship for halo stars is studied in terms of several models of chemical evolution for the solar neighborhood. Nucleosynthesis products from type I (both Ia and Ib) and Type II SNs are taken into account. The behavior of the O/Fe ratio for halo and disk stars is well reproduced by assuming (1) a lower iron production in SN II than in previous theoretical prescriptions, (2) the coalescence by gravitational wave radiation of two CO white dwarfs as the scenario for type Ia supernovae, and (3) stars in the Wolf-Rayet stage as progenitors of type Ib supernovae. Nevertheless, the best agreement with the observations is obtained by adopting an IMF favoring massive star formation only at very early epochs in the life of the Galaxy. Model predictions from other plausible scenarios for the origin of type I supernovae are also discussed. 41 refs

Proton nuclear magnetic resonance and spectrophotometric studies of nickel(II)-iron(II) hybrid hemoglobins

International Nuclear Information System (INIS)

Shibayama, N.; Inubushi, T.; Morimoto, H.; Yonetani, T.

1987-01-01

Ni(II)-Fe(II) hybrid hemoglobins, α(Fe) 2 β(Ni) 2 and α(Ni) 2 β(Fe) 2 , have been characterized by proton nuclear magnetic resonance with Ni(II) protoporphyrin IX (Ni-PP) incorporated in apoprotein, which serves as a permanent deoxyheme. α(Fe) 2 β(Ni) 2 , α(Ni) 2 β(Fe) 2 , and NiHb commonly show exchangeable proton resonances at 11 and 14 ppm, due to hydrogen-bonded protons in a deoxy-like structure. Upon binding of carbon monoxide (CO) to α(Fe) 2 β(Ni) 2 , these resonances disappear at pH 6.5 to pH 8.5. On the other hand, the complementary hybrid α(Ni) 2 β(Fe-CO) 2 showed the 11 and 14 ppm resonances at low pH. Upon raising pH, the intensities of both resonances are reduced, although these changes are not synchronized. Electronic absorption spectra and hyperfine-shifted proton resonances indicate that the ligation of CO in the β(Fe) subunits induced changes in the coordination and spin states of Ni-PP in the α subunits. In a deoxy-like structure, the coordination of Ni-PP in the α subunits is predominantly in a low-spin (S = 0) four-coordination state, whereas in an oxy-like structure the contribution of a high-spin (S = 1) five-coordination state markedly increased. Ni-PP in the β subunits always takes a high-spin five-coordination state regardless of solution conditions and the state of ligation in the partner α(Fe) subunits. In the β(Ni) subunits, a significant downfield shift of the proximal histidyl N/sub δ/H resonance and a change in the absorption spectrum of Ni-PP were detected, upon changing the quaternary structure of the hybrid. The chemical shifts were analyzed in terms of the E11-Val methyls vs. the porphyrin rings in hybrid Hbs

Surface reaction of SnII on goethite (α-FeOOH): surface complexation, redox reaction, reductive dissolution, and phase transformation.

Science.gov (United States)

Dulnee, Siriwan; Scheinost, Andreas C

2014-08-19

To elucidate the potential risk of (126)Sn migration from nuclear waste repositories, we investigated the surface reactions of Sn(II) on goethite as a function of pH and Sn(II) loading under anoxic condition with O2 level redox state and surface structure were investigated by Sn K edge X-ray absorption spectroscopy (XAS), goethite phase transformations were investigated by high-resolution transmission electron microscopy and selected area electron diffraction. The results demonstrate the rapid and complete oxidation of Sn(II) by goethite and formation of Sn(IV) (1)E and (2)C surface complexes. The contribution of (2)C complexes increases with Sn loading. The Sn(II) oxidation leads to a quantitative release of Fe(II) from goethite at low pH, and to the precipitation of magnetite at higher pH. To predict Sn sorption, we applied surface complexation modeling using the charge distribution multisite complexation approach and the XAS-derived surface complexes. Log K values of 15.5 ± 1.4 for the (1)E complex and 19.2 ± 0.6 for the (2)C complex consistently predict Sn sorption across pH 2-12 and for two different Sn loadings and confirm the strong retention of Sn(II) even under anoxic conditions.

Microbial Reduction of Fe(III) in Acidic Sediments: Isolation of Acidiphilium cryptum JF-5 Capable of Coupling the Reduction of Fe(III) to the Oxidation of Glucose

OpenAIRE

Küsel, Kirsten; Dorsch, Tanja; Acker, Georg; Stackebrandt, Erko

1999-01-01

To evaluate the microbial populations involved in the reduction of Fe(III) in an acidic, iron-rich sediment, the anaerobic flow of supplemental carbon and reductant was evaluated in sediment microcosms at the in situ temperature of 12°C. Supplemental glucose and cellobiose stimulated the formation of Fe(II); 42 and 21% of the reducing equivalents that were theoretically obtained from glucose and cellobiose, respectively, were recovered in Fe(II). Likewise, supplemental H2 was consumed by acid...

A new insight on the core–shell structure of zerovalent iron nanoparticles and its application for Pb(II) sequestration

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yalei, E-mail: zhangyalei@tongji.edu.cn [State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092 (China); Key Laboratory of Yangtze Water Environment for Ministry of Education, Tongji University, Shanghai 200092 (China); Su, Yiming [State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092 (China); Zhou, Xuefei, E-mail: zhouxuefei@tongji.edu.cn [State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092 (China); Dai, Chaomeng [State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092 (China); College of Civil Engineering, Tongji University, Shanghai 200092 (China); Keller, Arturo A. [Bren School of Environmental Science and Management, University of California, Santa Barbara (United States)

2013-12-15

Highlights: • The shell of nZVI is composed of 45.5% Fe(OH){sub 3} and 54.5% FeOOH. • Fe(OH){sub 3} shell suppresses the reduction of Pb(II). • Fe(OH){sub 3} shell greatly promotes the co-precipitation and adsorption of Pb(II). • pH < 4.5 favors Fe dissolution, while pH > 4.5 promotes Pb(II) adsorption. • A reaction between Fe{sup 0} core, Fe(OH){sub 3} and Pb(II) is proposed. -- Abstract: Nanoscale zerovalent iron (nZVI) has shown a high efficacy for removing heavy metals from liquid solution. However, its removal capacity has not been fully explored due to its common shell composition (FeOOH). In this study, a much higher removal capacity of Pb(II) is observed (1667 mg Pb(II)/g Fe), which is over 100% higher than the highest removal capacity of nZVI reported before. High-resolution X-ray photoelectron spectroscopy (HR-XPS) reveals that through restricting the dehydration process of Fe(OH){sub 3}, nZVI can acquire a unique shell, which is composed of 45.5% Fe(OH){sub 3} and 54.5% FeOOH. The presence of Fe(OH){sub 3} suppresses the reduction of Pb(II), but greatly promotes the co-precipitation and adsorption of Pb(II). Combining the ratio of Fe-released to Pb-immobilized and the result of HR-XPS, a reaction between Fe{sup 0} core, Fe(OH){sub 3}, and Pb(II) is proposed. The Fe released from the Fe{sup 0} core leads to the core depletion, observed by transmission electron microscopy (TEM) under high Pb(II) loading. While temperature has little influence on the removal capacity, pH affects the removal capacity greatly. pH < 4.5 favors Fe dissolution, while pH > 4.5 promotes Pb(II) adsorption. Given the high Pb removal capacity via the Fe(OH){sub 3} shell, nZVI can be used to remedy Pb(II) contamination.

Accelerated Removal of Fe-Antisite Defects while Nanosizing Hydrothermal LiFePO4 with Ca(2).

Science.gov (United States)

Paolella, Andrea; Turner, Stuart; Bertoni, Giovanni; Hovington, Pierre; Flacau, Roxana; Boyer, Chad; Feng, Zimin; Colombo, Massimo; Marras, Sergio; Prato, Mirko; Manna, Liberato; Guerfi, Abdelbast; Demopoulos, George P; Armand, Michel; Zaghib, Karim

2016-04-13

Based on neutron powder diffraction (NPD) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), we show that calcium ions help eliminate the Fe-antisite defects by controlling the nucleation and evolution of the LiFePO4 particles during their hydrothermal synthesis. This Ca-regulated formation of LiFePO4 particles has an overwhelming impact on the removal of their iron antisite defects during the subsequent carbon-coating step since (i) almost all the Fe-antisite defects aggregate at the surface of the LiFePO4 crystal when the crystals are small enough and (ii) the concomitant increase of the surface area, which further exposes the Fe-antisite defects. Our results not only justify a low-cost, efficient and reliable hydrothermal synthesis method for LiFePO4 but also provide a promising alternative viewpoint on the mechanism controlling the nanosizing of LiFePO4, which leads to improved electrochemical performances.

Fe4 cluster and a buckled macrocycle complex from the reduction of [(dmgBF2)2Fe(L)2] (L = MeCN, (t)Bu(i)NC).

Science.gov (United States)

Rose, Michael J; Winkler, Jay R; Gray, Harry B

2012-02-20

We report the syntheses, X-ray structures, and reductive electrochemistry of the Fe(II) complexes [(dmgBF(2))(2)Fe(MeCN)(2)] (1; dmg = dimethylglyoxime, MeCN = acetonitrile) and [(dmgBF(2))Fe((t)Bu(i)NC)(2)] (2; (t)Bu(i)NC = tert-butylisocyanide). The reaction of 1 with Na/Hg amalgam led to isolation and the X-ray structure of [(dmgBF(2))(2)Fe(glyIm)] (3; glyIm = glyimine), wherein the (dmgBF(2))(2) macrocyclic frame is bent to accommodate the binding of a bidentate apical ligand. We also report the X-ray structure of a rare mixed-valence Fe(4) cluster with supporting dmg-type ligands. In the structure of [(dmg(2)BF(2))(3)Fe(3)((1)/(2)dmg)(3)Fe(O)(6)] (4), the (dmgBF(2))(2) macrocycle has been cleaved, eliminating BF(2) groups. Density functional theory calculations and electron paramagnetic resonance data are in accordance with a central Fe(III) ion surrounded by three formally Fe(II)dmg(2)BF(2) units.

The Relationship between Logistics Sophistication and Drivers of the Outsourcing of Logistics Activities

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Peter Wanke

2008-10-01

Full Text Available A strong link has been established between operational excellence and the degree of sophistication of logistics organization, a function of factors such as performance monitoring, investment in Information Technology [IT] and the formalization of logistics organization, as proposed in the Bowersox, Daugherty, Dröge, Germain and Rogers (1992 Leading Edge model. At the same time, shippers have been increasingly outsourcing their logistics activities to third party providers. This paper, based on a survey with large Brazilian shippers, addresses a gap in the literature by investigating the relationship between dimensions of logistics organization sophistication and drivers of logistics outsourcing. To this end, the dimensions behind the logistics sophistication construct were first investigated. Results from factor analysis led to the identification of six dimensions of logistics sophistication. By means of multivariate logistical regression analyses it was possible to relate some of these dimensions, such as the formalization of the logistics organization, to certain drivers of the outsourcing of logistics activities of Brazilian shippers, such as cost savings. These results indicate the possibility of segmenting shippers according to characteristics of their logistics organization, which may be particularly useful to logistics service providers.

Lexical Complexity Development from Dynamic Systems Theory Perspective: Lexical Density, Diversity, and Sophistication

Directory of Open Access Journals (Sweden)

Reza Kalantari

2017-10-01

Full Text Available This longitudinal case study explored Iranian EFL learners’ lexical complexity (LC through the lenses of Dynamic Systems Theory (DST. Fifty independent essays written by five intermediate to advanced female EFL learners in a TOEFL iBT preparation course over six months constituted the corpus of this study. Three Coh-Metrix indices (Graesser, McNamara, Louwerse, & Cai, 2004; McNamara & Graesser, 2012, three Lexical Complexity Analyzer indices (Lu, 2010, 2012; Lu & Ai, 2011, and four Vocabprofile indices (Cobb, 2000 were selected to measure different dimensions of LC. Results of repeated measures analysis of variance (RM ANOVA indicated an improvement with regard to only lexical sophistication. Positive and significant relationships were found between time and mean values in Academic Word List and Beyond-2000 as indicators of lexical sophistication. The remaining seven indices of LC, falling short of significance, tended to flatten over the course of this writing program. Correlation analyses among LC indices indicated that lexical density enjoyed positive correlations with lexical sophistication. However, lexical diversity revealed no significant correlations with both lexical density and lexical sophistication. This study suggests that DST perspective specifies a viable foundation for analyzing lexical complexity

A kinetic and ESR investigation of iron(II) oxalate oxidation by hydrogen peroxide and dioxygen as a source of hydroxyl radicals

DEFF Research Database (Denmark)

Park, J S; Wood, P M; Davies, Michael Jonathan

1997-01-01

The reaction of Fe(II) oxalate with hydrogen peroxide and dioxygen was studied for oxalate concentrations up to 20 mM and pH 2-5, under which conditions mono- and bis-oxalate complexes (Fe[II](ox) and Fe[II](ox)2[2-]) and uncomplexed Fe2+ must be considered. The reaction of Fe(II) oxalate...... with hydrogen peroxide (Fe2+ + H2O2 --> Fe3+ + .OH + OH-) was monitored in continuous flow by ESR with t-butanol as a radical trap. The reaction is much faster than for uncomplexed Fe2+ and a rate constant, k = 1 x 10(4) M(-1) s(-1) is deduced for Fe(II)(ox). The reaction of Fe(II) oxalate with dioxygen...... by oxalate. Further ESR studies with DMPO as spin trap reveal that reaction of Fe(II) oxalate with hydrogen peroxide can also lead to formation of the carboxylate radical anion (CO2-), an assignment confirmed by photolysis of Fe(II) oxalate in the presence of DMPO....

Iron(II)-Catalyzed Iron Atom Exchange and Mineralogical Changes in Iron-rich Organic Freshwater Flocs: An Iron Isotope Tracer Study.

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ThomasArrigo, Laurel K; Mikutta, Christian; Byrne, James; Kappler, Andreas; Kretzschmar, Ruben

2017-06-20

In freshwater wetlands, organic flocs are often found enriched in trace metal(loid)s associated with poorly crystalline Fe(III)-(oxyhydr)oxides. Under reducing conditions, flocs may become exposed to aqueous Fe(II), triggering Fe(II)-catalyzed mineral transformations and trace metal(loid) release. In this study, pure ferrihydrite, a synthetic ferrihydrite-polygalacturonic acid coprecipitate (16.7 wt % C), and As- (1280 and 1230 mg/kg) and organic matter (OM)-rich (18.1 and 21.8 wt % C) freshwater flocs dominated by ferrihydrite and nanocrystalline lepidocrocite were reacted with an isotopically enriched 57 Fe(II) solution (0.1 or 1.0 mM Fe(II)) at pH 5.5 and 7. Using a combination of wet chemistry, Fe isotope analysis, X-ray absorption spectroscopy (XAS), 57 Fe Mössbauer spectroscopy and X-ray diffraction, we followed the Fe atom exchange kinetics and secondary mineral formation over 1 week. When reacted with Fe(II) at pH 7, pure ferrihydrite exhibited rapid Fe atom exchange at both Fe(II) concentrations, reaching 76 and 89% atom exchange in experiments with 0.1 and 1 mM Fe(II), respectively. XAS data revealed that it transformed into goethite (21%) at the lower Fe(II) concentration and into lepidocrocite (73%) and goethite (27%) at the higher Fe(II) concentration. Despite smaller Fe mineral particles in the coprecipitate and flocs as compared to pure ferrihydrite (inferred from Mössbauer-derived blocking temperatures), these samples showed reduced Fe atom exchange (9-30% at pH 7) and inhibited secondary mineral formation. No release of As was recorded for Fe(II)-reacted flocs. Our findings indicate that carbohydrate-rich OM in flocs stabilizes poorly crystalline Fe minerals against Fe(II)-catalyzed transformation by surface-site blockage and/or organic Fe(II) complexation. This hinders the extent of Fe atom exchange at mineral surfaces and secondary mineral formation, which may consequently impair Fe(II)-activated trace metal(loid) release. Thus, under short

Iron valence in double-perovskite (Ba,Sr,Ca)2FeMoO6: isovalent substitution effect

International Nuclear Information System (INIS)

Yasukawa, Y.; Linden, J.; Chan, T.S.; Liu, R.S.; Yamauchi, H.; Karppinen, M.

2004-01-01

In the Fe-Mo based B-site ordered double-perovskite, A 2 FeMoO 6.0 , with iron in the mixed-valence II/III state, the valence value of Fe is not precisely fixed at 2.5 but may be fine-tuned by means of applying chemical pressure at the A-cation site. This is shown through a systematic 57 Fe Moessbauer spectroscopy study using a series of A 2 FeMoO 6.0 [A=(Ba,Sr) or (Sr,Ca)] samples with high degree of Fe/Mo order, the same stoichiometric oxygen content and also almost the same grain size. The isomer shift values and other hyperfine parameters obtained from the Moessbauer spectra confirm that Fe remains in the mixed-valence state within the whole range of A constituents. However, upon increasing the average cation size at the A site the precise valence of Fe is found to decrease such that within the A=(Ba,Sr) regime the valence of Fe is closer to II, while within the A=(Sr,Ca) regime it is closer to the actual mixed-valence II/III state. As the valence of Fe approaches II, the difference in charges between Fe and Mo increases, and parallel with this the degree of Fe/Mo order increases. Additionally, for the less-ordered samples an increased tendency of clustering of the antisite Fe atoms is deduced from the Moessbauer data

Microbial reduction of Fe(III) and turnover of acetate in Hawaiian soils.

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Küsel, Kirsten; Wagner, Christine; Trinkwalter, Tanja; Gössner, Anita S; Bäumler, Rupert; Drake, Harold L

2002-04-01

Soils contain anoxic microzones, and acetate is an intermediate during the turnover of soil organic carbon. Due to negligible methanogenic activities in well-drained soils, acetate accumulates under experimentally imposed short-term anoxic conditions. In contrast to forest, agricultural, and prairie soils, grassland soils from Hawaii rapidly consumed rather than formed acetate when incubated under anoxic conditions. Thus, alternative electron acceptors that might be linked to the anaerobic oxidation of soil organic carbon in Hawaiian soils were assessed. Under anoxic conditions, high amounts of Fe(II) were formed by Hawaiian soils as soon as soils were depleted of nitrate. Rates of Fe(II) formation for different soils ranged from 0.01 to 0.31 micromol (g dry weight soil)(-1) h(-1), but were not positively correlated to increasing amounts of poorly crystallized iron oxides. In general, sulfate-reducing and methanogenic activities were negligible. Supplemental acetate was rapidly oxidized to CO2 via the sequential reduction of nitrate and Fe(III) in grassland soil (obtained near Kaena State Park). Supplemental H2 stimulated the formation of Fe(II), but H2-utilizing acetogens appeared to also be involved in the consumption of H2. Approximately 270 micromol Fe(III) (g dry weight soil)(-1) was available for Fe(III)-reducing bacteria, and acetate became a stable end product when Fe(III) was depleted in long-term incubations. Most-probable-number estimates of H2- and acetate-utilizing Fe(III) reducers and of H2-utilizing acetogens were similar. These results indicate that (i) the microbial reduction of Fe(III) is an important electron-accepting process for the anaerobic oxidation of organic matter in Fe(III)-rich Hawaiian soils of volcanic origin, and (ii) acetate, formed by the combined activity of fermentative and acetogenic bacteria, is an important trophic link in anoxic microsites of these soils.

A comparative study of nitrite reduction by synthetic and biogenic Fe(II-III) hydroxysalts green rusts: Evidence for hydroxyl-nitrite green rust formation as an intermediate reaction product.

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Ona-Nguema, G.; Guerbois, D.; Morin, G.; Zhang, Y.; Noel, V.; Brest, J.

2013-12-01

The occurrence of high nitrite concentrations as a result of anthropogenic activities is an important water quality concern as it is highly toxic to human and fauna, and it is used as a nitrogen source for the assimilation process. The toxicity of nitrite is related to its transformation into carcinogenic N-nitroso compounds, which are suspected to be responsible for some gastric cancers, and to its ability to convert the hemoglobin to methaemoglobin what is then unable to fix oxygen and to transport it to the tissues, involving hypoxia and the blue-baby syndrome [1]. To reduce the adverse effect of nitrite on human health and on macroalgal blooms, any process enhancing the transformation of nitrite ions to nitrogen gas is of interest for the remediation of natural environments. To achieve this purpose the use of processes involving Fe(II)-containing minerals could be considered as one of the best options. Green-rusts are mixed Fe(II-III) layered double hydroxides commonly found in anoxic zones of natural environments such as sediments and hydromorphic soils. In such anoxic environments, green rust minerals play an important role in the biogeochemical redox cycling of iron and nitrogen, and can affect the speciation and mobility of many organic and inorganic contaminants. The present study investigates the reduction of nitrite by two synthetic and two biogenic green rusts. On the one hand, Fe(II-III) hydroxychloride and Fe(II-III) hydroxycarbonate green rusts were used as synthetic interlayer forms of GR, which are referred to as ';syn-GR(CO3)' and ';syn-GR(Cl)', respectively. On the other hand, the study was performed with biogenic Fe(II-III) hydroxycarbonate green rusts obtained from the bioreduction of two ferric precursors, either Fe(III)-oxyhydroxycarbonate or lepidocrocite; these biogenic green rusts are referred to as ';bio-GR(CO3)F' and ';bio-GR(CO3)L', respectively. For synthetic green rusts, results showed that the oxidation of both syn-GR(CO3) and syn

Ab Initio f values for Fe II J=9/2 ->9/2^o transitions

Science.gov (United States)

Beck, Donald

2005-05-01

Relativistic configuration interaction f values have been obtained for 264 transitions between the lowest 12 J=9/2 and the 22 J=9/2^o levels. Length and velocity gauges agree to 3.8% for in-shell transitions and 10.0% for shell jump transitions. Two J=9/2^o levels are so nearly degenerate that it was necessary to introduce a semi-empirical correction to produce the correct level ordering. The results are in overall good agreement with the semi-empirical results of Kurucz ootnotetextR. L. Kurucz, http://kurucz.harvard.edu/atoms/2601/ and Raassen ootnotetextA. J. J. Raasen, ftp://ftp.wins.uva.nl/pub/orth/iron/FeII.E1 (1999). An efficient method of including magnetic Breit effects in the energy matrix is presented.

Ferrous Iron Oxidation under Varying pO2 Levels: The Effect of Fe(III)/Al(III) Oxide Minerals and Organic Matter.

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Chen, Chunmei; Thompson, Aaron

2018-01-16

Abiotic Fe(II) oxidation by O 2 commonly occurs in the presence of mineral sorbents and organic matter (OM) in soils and sediments; however, this tertiary system has rarely been studied. Therefore, we examined the impacts of mineral surfaces (goethite and γ-Al 2 O 3 ) and organic matter [Suwannee River fulvic acid (SRFA)] on Fe(II) oxidation rates and the resulting Fe(III) (oxyhydr)oxides under 21 and 1% pO 2 at pH 6. We tracked Fe dynamics by adding 57 Fe(II) to 56 Fe-labeled goethite and γ-Al 2 O 3 and characterized the resulting solids using 57 Fe Mössbauer spectroscopy. We found Fe(II) oxidation was slower at low pO 2 and resulted in higher-crystallinity Fe(III) phases. Relative to oxidation of Fe(II) (aq) alone, both goethite and γ-Al 2 O 3 surfaces increased Fe(II) oxidation rates regardless of pO 2 levels, with goethite being the stronger catalyst. Goethite surfaces promoted the formation of crystalline goethite, while γ-Al 2 O 3 favored nano/small particle or disordered goethite and some lepidocrocite; oxidation of Fe(II) aq alone favored lepidocrocite. SRFA reduced oxidation rates in all treatments except the mineral-free systems at 21% pO 2 , and SRFA decreased Fe(III) phase crystallinity, facilitating low-crystalline ferrihydrite in the absence of mineral sorbents, low-crystalline lepidocrocite in the presence of γ-Al 2 O 3 , but either crystalline goethite or ferrihydrite when goethite was present. This work highlights that the oxidation rate, the types of mineral surfaces, and OM control Fe(III) precipitate composition.

Fe(II)–Al(III) layered double hydroxides prepared by ultrasound-assisted co-precipitation method for the reduction of bromate

International Nuclear Information System (INIS)

Zhong, Yu; Yang, Qi; Luo, Kun; Wu, Xiuqiong; Li, Xiaoming; Liu, Yang; Tang, Wangwang; Zeng, Guangming; Peng, Bo

2013-01-01

Highlights: ► Fe(II)–Al(III) LDHs were synthesized by ultrasound-assisted co-precipitation method. ► The Fe–Al (30 min) exhibited highly reduction reactivity on bromate. ► Pseudo-first-order model described the experimental data well. ► The mechanisms of bromate removal were proposed. -- Abstract: Bromate is recognized as an oxyhalide disinfection byproduct in drinking water. In this paper, Fe(II)–Al(III) layered double hydroxides (Fe–Al LDHs) prepared by the ultrasound-assisted co-precipitation method were used for the reduction of bromate in solution. The Fe–Al LDHs particles were characterized by X-ray diffractometer, scanning electron microscopy and thermogravimetry–differential scanning calorimetry. It was found that ultrasound irradiation assistance promoted the formation of the hydrotalcite-like phase and then improved the removal efficiency of bromate. In addition, the effects of solid-to-solution ratio, contact time, initial bromate concentration, initial pH, coexisting anions on the bromate removal were investigated. The results showed the bromate with an initial concentration of 1.56 μmol/L could be completely removed from solution by Fe–Al LDHs within 120 min. When the initial bromate concentration was 7.81 μmol/L, the Fe–Al LDHs with irradiation time of 30 min exhibited the optimum removal efficiency and the bromate removal capacity (q e ) was 6.80 μmol/g. In addition, the appearance of sulfate and production of bromide were observed simultaneously in this process, which suggested that ion-exchange between sulfate and bromate, and the reduction of bromate to bromide by Fe 2+ were the main mechanisms responsible for the bromate removal by Fe–Al LDHs

A density functional theory study on the active center of Fe-only hydrogenase: characterization and electronic structure of the redox states.

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Liu, Zhi-Pan; Hu, P

2002-05-08

We have carried out extensive density functional theory (DFT) calculations for possible redox states of the active center in Fe-only hydrogenases. The active center is modeled by [(H(CH(3))S)(CO)(CN(-))Fe(p)(mu-DTN)(mu-CO)Fe(d)(CO)(CN(-))(L)](z)() (z is the net charge in the complex; Fe(p)= the proximal Fe, Fe(d) = the distal Fe, DTN = (-SCH(2)NHCH(2)S-), L is the ligand that bonds with the Fe(d) at the trans position to the bridging CO). Structures of possible redox states are optimized, and CO stretching frequencies are calculated. By a detailed comparison of all the calculated structures and the vibrational frequencies with the available experimental data, we find that (i) the fully oxidized, inactive state is an Fe(II)-Fe(II) state with a hydroxyl (OH(-)) group bonded at the Fe(d), (ii) the oxidized, active state is an Fe(II)-Fe(I) complex which is consistent with the assignment of Cao and Hall (J. Am. Chem. Soc. 2001, 123, 3734), and (iii) the fully reduced state is a mixture with the major component being a protonated Fe(I)-Fe(I) complex and the other component being its self-arranged form, Fe(II)-Fe(II) hydride. Our calculations also show that the exogenous CO can strongly bond with the Fe(II)-Fe(I) species, but cannot bond with the Fe(I)-Fe(I) complex. This result is consistent with experiments that CO tends to inhibit the oxidized, active state, but not the fully reduced state. The electronic structures of all the redox states have been analyzed. It is found that a frontier orbital which is a mixing state between the e(g) of Fe and the 2 pi of the bridging CO plays a key role concerning the reactivity of Fe-only hydrogenases: (i) it is unoccupied in the fully oxidized, inactive state, half-occupied in the oxidized, active state, and fully occupied in the fully reduced state; (ii) the e(g)-2 pi orbital is a bonding state, and this is the key reason for stability of the low oxidation states, such as Fe(I)-Fe(I) complexes; and (iii) in the e(g)-2 pi orbital

Improvement of biological nitrogen removal with nitrate-dependent Fe(II) oxidation bacterium Aquabacterium parvum B6 in an up-flow bioreactor for wastewater treatment.

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Zhang, Xiaoxin; Li, Ang; Szewzyk, Ulrich; Ma, Fang

2016-11-01

Aquabacterium parvum strain B6 exhibited efficient nitrate-dependent Fe(II) oxidation ability using nitrate as an electron acceptor. A continuous up-flow bioreactor that included an aerobic and an anoxic section was constructed, and strain B6 was added to the bioreactor as inocula to explore the application of microbial nitrate-dependent Fe(II) oxidizing (NDFO) efficiency in wastewater treatment. The maximum NRE (anoxic section) and TNRE of 46.9% and 79.7%, respectively, could be obtained at a C/N ratio of 5.3:1 in the influent with HRT of 17. Meanwhile, the taxonomy composition of the reactor was assessed, as well. The NDFO metabolism of strain B6 could be expected because of its relatively dominant position in the anoxic section, whereas potential heterotrophic nitrification and aerobic denitrification developed into the prevailing status in the aerobic section after 50days of continuous operation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Study on Formation Mechanism of Fayalite (Fe2SiO4) by Solid State Reaction in Sintering Process

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Wang, Zhongbing; Peng, Bing; Zhang, Lifeng; Zhao, Zongwen; Liu, Degang; Peng, Ning; Wang, Dawei; He, Yinghe; Liang, Yanjie; Liu, Hui

2018-04-01

The sintering behaviors among SiO2, FeS and Fe3O4 were detected to reveal the formation mechanism of Fe2SiO4. The results indicated that the formation mechanism is divided into five steps: (1) migration of O2- induced by S2- under a reducing atmosphere; (2) formation of Fe3O4- β ; (3) migration of Fe(II) into a ferrite cluster structure to gain oxygen and form Fe3- x O4; (4) Fe(II) invaded the silicon atomic position and released Si(IV); and (5) formation of the stable structure of Fe2SiO4 through chemical diffusion between cations of Fe(II) and Si(IV). These findings can provide theoretical support for controlling the process of the recovery of valuable metals in copper slag through the combined roasting modification-magnetic separation process.

From chemolithoautotrophs to electrolithoautotrophs: CO2 fixation by Fe(II)-oxidizing bacteria coupled with direct uptake of electrons from solid electron sources.

Science.gov (United States)

Ishii, Takumi; Kawaichi, Satoshi; Nakagawa, Hirotaka; Hashimoto, Kazuhito; Nakamura, Ryuhei

2015-01-01

At deep-sea vent systems, hydrothermal emissions rich in reductive chemicals replace solar energy as fuels to support microbial carbon assimilation. Until recently, all the microbial components at vent systems have been assumed to be fostered by the primary production of chemolithoautotrophs; however, both the laboratory and on-site studies demonstrated electrical current generation at vent systems and have suggested that a portion of microbial carbon assimilation is stimulated by the direct uptake of electrons from electrically conductive minerals. Here we show that chemolithoautotrophic Fe(II)-oxidizing bacterium, Acidithiobacillus ferrooxidans, switches the electron source for carbon assimilation from diffusible Fe(2+) ions to an electrode under the condition that electrical current is the only source of energy and electrons. Site-specific marking of a cytochrome aa3 complex (aa3 complex) and a cytochrome bc1 complex (bc1 complex) in viable cells demonstrated that the electrons taken directly from an electrode are used for O2 reduction via a down-hill pathway, which generates proton motive force that is used for pushing the electrons to NAD(+) through a bc1 complex. Activation of carbon dioxide fixation by a direct electron uptake was also confirmed by the clear potential dependency of cell growth. These results reveal a previously unknown bioenergetic versatility of Fe(II)-oxidizing bacteria to use solid electron sources and will help with understanding carbon assimilation of microbial components living in electronically conductive chimney habitats.

Interaction of selenite with reduced Fe and/or S species: An XRD and XAS study.

Science.gov (United States)

Finck, Nicolas; Dardenne, Kathy

2016-05-01

In this study, we investigated the interaction between selenite and either Fe((II))aq or S((-II))aq in solution, and the results were used to investigate the interaction between Se((IV))aq and FeS in suspension. The reaction products were characterized by a combination of methods (SEM, XRD and XAS) and the reaction mechanisms were identified. In a first experiment, Se((IV))aq was reduced to Se((0)) by interaction with Fe((II))aq which was oxidized to Fe((III)), but the reaction was only partial. Subsequently, some Fe((III)) produced akaganeite (β-FeOOH) and the release of proton during that reaction decreased the pH. The pH decrease changed the Se speciation in solution which hindered further Se((IV)) reduction by Fe((II))aq. In a second experiment, Se((IV))aq was quantitatively reduced to Se((0)) by S((-II))aq and the reaction was fast. Two sulfide species were needed to reduce one Se((IV)), and the observed pH increase was due to a proton consumption. For both experiments, experimental results are consistent with expectations based on the oxidation reduction potential of the various species. Upon interaction with FeS, Se((IV))aq was reduced to Se((0)) and minute amounts of pyrite were detected, a consequence of partial mackinawite oxidation at surface sulfur sites. These results are of prime importance with respect to safe deep disposal of nuclear waste which contains the long-lived radionuclide (79)Se. This study shows that after release of (79)Se((IV)) upon nuclear waste matrix corrosion, selenite can be reduced in the near field to low soluble Se((0)) by interaction with Fe((II))aq and/or S((-II))aq species. Because the solubility of Se((0)) species is significantly lower than that of Se((IV)), selenium will become much less (bio)available and its migration out of deep HLW repositories may be drastically hindered. Copyright © 2016. Published by Elsevier B.V.

Evolution of the chemistry of Fe bearing waters during CO2 degassing

Science.gov (United States)

Geroni, J.N.; Cravotta, C.A.; Sapsford, D.J.

2012-01-01

The rates of Fe(II) oxidation and precipitation from groundwater are highly pH dependent. Elevated levels of dissolved CO2 can depress pH and cause difficulty in removing dissolved Fe and associated metals during treatment of ferruginous water. This paper demonstrates interdependent changes in pH, dissolved inorganic C species, and Fe(II) oxidation rates that occur as a result of the removal (degassing) of CO2 during aeration of waters discharged from abandoned coal mines. The results of field monitoring of aeration cascades at a treatment facility as well as batchwise aeration experiments conducted using net alkaline and net acidic waters in the UK are combined with geochemical modelling to demonstrate the spatial and temporal evolution of the discharge water chemistry. The aeration cascades removed approximately 67% of the dissolved CO2 initially present but varying the design did not affect the concentration of Fe(II) leaving the treatment ponds. Continued removal of the residual CO2 by mechanical aeration increased pH by as much as 2 units and resulted in large increases in the rates of Fe(II) oxidation and precipitation. Effective exsolution of CO2 led to a reduction in the required lime dose for removal of remaining Fe(II), a very important factor with regard to increasing the sustainability of treatment practices. An important ancillary finding for passive treatment is that varying the design of the cascades had little impact on the rate of CO2 removal at the flow rates measured.

Synthesis of nanometer-sized fayalite and magnesium-iron(II) mixture olivines

Energy Technology Data Exchange (ETDEWEB)

Qafoku, Odeta; Ilton, Eugene S.; Bowden, Mark E.; Kovarik, Libor; Zhang, Xin; Kukkadapu, Ravi K.; Engelhard, Mark H.; Thompson, Christopher J.; Schaef, Herbert T.; McGrail, Bernard Peter; Rosso, Kevin M.; Loring, John S.

2018-04-01

Olivines are divalent orthosilicates with important geologic, biological, and industrial significance and are typically comprised of mixtures of Mg2+ and Fe2+ ranging from forsterite (Mg2SiO4) to fayalite (Fe2SiO4). Investigating the role of Fe(II) in olivine reactivity requires the ability to synthesize olivines that are nanometer-sized, have different percentages of Mg2+ and Fe2+, and have good bulk and surface purity. This article demonstrates a new method for synthesizing nanosized fayalite and Mg-Fe mixture olivines. First, carbonaceous precursors are generated from sucrose, PVA, colloidal silica, Mg2+, and Fe3+. Second, these precursors are calcined in air to burn carbon and create mixtures of Fe(III)-oxides, forsterite, and SiO2. Finally, calcination in reducing CO-CO2 gas buffer leads to Fe(II)-rich olivines. XRD, Mössbauer, and IR analyses verify good bulk purity and composition. XPS indicates that surface iron is in its reduced Fe(II) form, and surface Si is consistent with olivine. SEM shows particle sizes predominately between 50 and 450 nm, and BET surface areas are 2.8-4.2 m2/g. STEM HAADF analysis demonstrates even distributions of Mg and Fe among the available M1 and M2 sites of the olivine crystals. These nanosized Fe(II)-rich olivines are suitable for laboratory studies with in situ probes that require mineral samples with high reactivity at short timescales.

Effects of exogenous pyoverdines on Fe availability and their impacts on Mn(II) oxidation by Pseudomonas putida GB-1

Science.gov (United States)

Lee, Sung-Woo; Parker, Dorothy L.; Geszvain, Kati; Tebo, Bradley M.

2014-01-01

Pseudomonas putida GB-1 is a Mn(II)-oxidizing bacterium that produces pyoverdine-type siderophores (PVDs), which facilitate the uptake of Fe(III) but also influence MnO2 formation. Recently, a non-ribosomal peptide synthetase mutant that does not synthesize PVD was described. Here we identified a gene encoding the PVDGB-1 (PVD produced by strain GB-1) uptake receptor (PputGB1_4082) of strain GB-1 and confirmed its function by in-frame mutagenesis. Growth and other physiological responses of these two mutants and of wild type were compared during cultivation in the presence of three chemically distinct sets of PVDs (siderotypes n°1, n°2, and n°4) derived from various pseudomonads. Under iron-limiting conditions, Fe(III) complexes of various siderotype n°1 PVDs (including PVDGB-1) allowed growth of wild type and the synthetase mutant, but not the receptor mutant, confirming that iron uptake with any tested siderotype n°1 PVD depended on PputGB1_4082. Fe(III) complexes of a siderotype n°2 PVD were not utilized by any strain and strongly induced PVD synthesis. In contrast, Fe(III) complexes of siderotype n°4 PVDs promoted the growth of all three strains and did not induce PVD synthesis by the wild type, implying these complexes were utilized for iron uptake independent of PputGB1_4082. These differing properties of the three PVD types provided a way to differentiate between effects on MnO2 formation that resulted from iron limitation and others that required participation of the PVDGB-1 receptor. Specifically, MnO2 production was inhibited by siderotype n°1 but not n°4 PVDs indicating PVD synthesis or PputGB1_4082 involvement rather than iron-limitation caused the inhibition. In contrast, iron limitation was sufficient to explain the inhibition of Mn(II) oxidation by siderotype n°2 PVDs. Collectively, our results provide insight into how competition for iron via siderophores influences growth, iron nutrition and MnO2 formation in more complex environmental