Arsenite adsorption on goethite at elevated temperatures

International Nuclear Information System (INIS)

Kersten, Michael; Vlasova, Nataliya

2009-01-01

Experimental closed-system ΔT acid-base titrations between 10 deg. C and 75 deg. C were used to constrain a temperature-dependent 1-pK basic Stern model of the goethite surface complexation reactions. Experimental data for the temperature dependence of pH PZC determined by the one-term Van't Hoff extrapolation yield a value for goethite surface protonation enthalpy of -49.6 kJ mol -1 in good agreement with literature data. Batch titration data between 10 deg. C and 75 deg. C with arsenite concentrations between 10 μM and 100 μM yield adsorption curves, which increases with pH, peak at a pH of 9, and decrease at higher pH values. The slope of this bend becomes steeper with increasing temperature. A 1-pK charge distribution model in combination with a basic Stern layer option could be established for the pH-dependent arsenite adsorption. Formation of two inner-sphere bidentate surface complexes best matched the experimental data in agreement with published EXAFS spectroscopic information. The temperature behaviour of the thus derived intrinsic equilibrium constants can be well represented by the linear Van't Hoff logK T int vs. 1/T plot. Adsorption of arsenite on the goethite surface is exothermic (negative Δ r H 298 values) and therefore becomes weaker with increasing temperature. Application of the new constants with the aqueous speciation code VMINTEQ predicts that the As(III) concentration in presence of goethite sorbent decreases by 10 times once the hydrothermal solution is cooled from 99 deg. C to 1 deg. C. The model curve matches data from a natural thermal water spring system. The increase of adsorption efficiency for As along the temperature gradient may well serve as an additional process to prevent ecosystem contamination by As-rich water seepage from geothermal energy generation facilities

Molecular Interactions of Plutonium(VI) with Synthetic Manganese-Substituted Goethite

Energy Technology Data Exchange (ETDEWEB)

Hu, Yung-Jin; Schwaiger, Luna Kestrel; Booth, Corwin H.; Kukkadapu, Ravi K.; Cristiano, Elena; Kaplan, Daniel; Nitsche, Heino

2010-03-09

Plutonium(VI) sorption on the surface of well-characterized synthetic manganese-substituted goethite minerals (Fe1-xMnxOOH) was studied using X-ray absorption spectroscopy. We chose to study the influence of manganese as a minor component in goethite, because goethite rarely exists as a pure phase in nature. Manganese X-ray absorption near-edge structure measurements indicated that essentially all the Mn in the goethite existed as Mn(III), even though Mn was added during mineral synthesis as Mn(II). Importantly, energy dispersive X-ray analysis demonstrated that Mn did not exist as discrete phases and that it was homogeneously mixed into the goethite to within the limit of detection of the method. Furthermore, Mössbauer spectra demonstrated that all Fe existed as Fe(III), with no Fe(II) present. Plutonium(VI) sorption experiments were conducted open to air and no attempt was made to exclude carbonate. The use of X-ray absorption spectroscopy allows us to directly and unambiguously measure the oxidation state of plutonium in situ at the mineral surface. Plutonium X-ray absorption near-edge structure measurements carried out on these samples showed that Pu(VI) was reduced to Pu(IV) upon contact with the mineral. This reduction appears to be strongly correlated with mineral solution pH, coinciding with pH transitions across the point of zero charge of the mineral. Furthermore, extended X-ray absorption fine structure measurements show evidence of direct plutonium binding to the metal surface as an inner-sphere complex. This combination of extensive mineral characterization and advanced spectroscopy suggests that sorption of the plutonium onto the surface of the mineral was followed by reduction of the plutonium at the surface of the mineral to form an inner-sphere complex. Because manganese is often found in the environment as a minor component associated with major mineral components, such as goethite, understanding the molecular-level interactions of plutonium with

(U-Th)/He geochronology of goethite and the origin and evolution of cangas

Science.gov (United States)

Monteiro, Hevelyn S.; Vasconcelos, Paulo M.; Farley, Kenneth A.; Spier, Carlos A.; Mello, Claudio L.

2014-04-01

(U-Th)/He geochronology of 147 grains of goethite cements extracted from ferruginous duricrusts (cangas) developed on banded iron-formations from the Quadrilátero Ferrífero region, Minas Gerais, Brazil, records a history of protracted mineral dissolution-reprecipitation that started at ca. 48.1 ± 4.8 Ma and continues intermittently until the Present. A large majority of the samples (more than 30%) are younger than 2 Ma, revealing active mineral dissolution-reprecipitation in the recent past. Within cangas, goethite cements are younger near the surface and become progressively older towards the bottom of the weathering profile, indicating that iron is more effectively cycled in the parts of the weathering profile more strongly affected by biogenic activity. (U-Th)/He geochronology of 14 goethite grains from saprolites in the same profiles yield results ranging from 55.3 ± 5.5 to 25.7 ± 2.6 Ma. For a single weathering profile, goethite cements from cangas are invariably younger than goethite grains from the underlying saprolite, indicating that the duricrust and the saprolite behave as independent and separate systems responding to different environmental controls. Thorium shows conservative behaviour during goethite dissolution-reprecipitation, and it is enriched towards the surface of the weathering profile. Uranium, on the other hand, is preferentially leached from the surface into the saprolite or out of the weathering profile. Recurrent goethite dissolution-reprecipitation lends great textural complexities to cangas, but it is also responsible for its capacity to reheal when physically disrupted. This self-healing property accounts for canga’s role in armoring banded iron-formation landscapes.

Solid-phase photocatalytic degradation of polystyrene plastic with goethite modified by boron under UV-vis light irradiation

International Nuclear Information System (INIS)

Liu Guanglong; Zhu Duanwei; Zhou Wenbing; Liao Shuijiao; Cui Jingzhen; Wu Kang; Hamilton, David

2010-01-01

A novel photodegradable polyethylene-boron-goethite (PE-B-goethite) composite film was prepared by embedding the boron-doped goethite into the commercial polyethylene. The goethite catalyst was modified by boron in order to improve its photocatalytic efficiency under the ultraviolet and visible light irradiation. Solid-phase photocatalytic degradation of the PE-B-goethite composite film was carried out in an ambient air at room temperature under ultraviolet and visible light irradiation. The properties of composite films were compared with those of the pure PE films and the PE-goethite composite films through performing weight loss monitoring, scanning electron microscope (SEM) analysis, FT-IR spectroscopy and X-ray photoelectron spectroscopy (XPS). The photo-induced degradation of PE-B-goethite composite films was higher than that of the pure PE films and the PE-goethite composite films under the UV-irradiation, while there has been little change under the visible light irradiation. The weight loss of the PE-B-goethite (0.4 wt.%) composite film reached 12.6% under the UV-irradiation for 300 h. The photocatalytic degradation mechanism of the composite films was briefly discussed.

Structure analysis of cation selective Cr-goethite as protective rust of weathering steel

International Nuclear Information System (INIS)

Konishi, Hiroyuki; Mizuki, Jun'ichiro; Yamashita, Masato; Uchida, Hitoshi

2005-01-01

We have performed extended X-ray absorption fine structure (EXAFS) analysis for artificial Cr-goethite to elucidate the local structure around Cr in Cr-goethite. The spectra were obtained using synchrotron radiation X-rays at the Photon Factory in Tsukuba. The first shell contributions were isolated by Fourier filtering EXAFS data, and the inverse Fourier transformed single-shell data were analyzed using a curve fitting method. The results show that Cr is coordinated with (7±1)O 2- ions. The protective characteristics of the Cr-goethite protective rust layer on weathering steel can be interpreted in terms of the O 2- coordination around Cr 3+ resulting in the creation of negative fixed charge in the Cr-goethite particles. (author)

Goethite promoted biodegradation of 2,4-dinitrophenol under nitrate reduction condition.

Science.gov (United States)

Tang, Ting; Yue, Zhengbo; Wang, Jin; Chen, Tianhu; Qing, Chengsong

2018-02-05

Iron oxide may interact with other pollutants in the aquatic environments and further influence their toxicity, transport and fate. The current study was conducted to investigate the biodegradation of 2,4-dinitrophenol (2,4-DNP) in the presence of iron oxide of goethite under anoxic condition using nitrate as the electron acceptor. Experiment results showed that the degradation rate of 2,4-DNP was improved by goethite. High performance liquid chromatography-mass spectra analysis results showed that goethite promoted degradation and transformation of 2,4-diaminophenol and 2-amino-4-nitrophenol (2-nitro-4-aminophenol). Microbial community analysis results showed that the abundance of Actinobacteria, which have the potential ability to degrade PAHs, was increased when goethite was available. This might partially explain the higher degradation of 2,4-DNP. Furthermore, another bacterium of Desulfotomaculum reducens which could reduce soluble Fe(III) and nitrate was also increased. Results further confirmed that nanomaterials in the aquatic environment will influence the microbial community and further change the transformation process of toxic pollutants. Copyright © 2017 Elsevier B.V. All rights reserved.

Goethite (U–Th)/He geochronology and precipitation mechanisms during weathering of basalts

OpenAIRE

Riffel, Silvana B.; Vasconcelos, Paulo M.; Carmo, Isabela O.; Farley, Kenneth A.

2016-01-01

(U–Th)/He geochronology of 33 goethite grains from in situ ferruginous duricrusts overlying the Paraná flood basalt in the Guarapuava region, Paraná, Brazil, reveals ages ranging from 3.6 ± 0.4 to 0.4 ± 0.1 Ma. Thirty-one grains from detrital fragments of ferruginous duricrust yield ages in the 6.2 ± 0.6 to 0.7 ± 0.1 Ma range. The results show that goethites from detrital blocks are generally older than those from the in situ ferruginous layers and that all the goethites from the Guarapuava s...

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.

Arsenite adsorption on goethite at elevated temperatures

Energy Technology Data Exchange (ETDEWEB)

Kersten, Michael [Environmental Geochemistry Group, Institute of Geosciences, Johannes Gutenberg-University, Mainz 55099 (Germany)], E-mail: kersten@uni-mainz.de; Vlasova, Nataliya [Environmental Geochemistry Group, Institute of Geosciences, Johannes Gutenberg-University, Mainz 55099 (Germany)

2009-01-15

Experimental closed-system {delta}T acid-base titrations between 10 deg. C and 75 deg. C were used to constrain a temperature-dependent 1-pK basic Stern model of the goethite surface complexation reactions. Experimental data for the temperature dependence of pH{sub PZC} determined by the one-term Van't Hoff extrapolation yield a value for goethite surface protonation enthalpy of -49.6 kJ mol{sup -1} in good agreement with literature data. Batch titration data between 10 deg. C and 75 deg. C with arsenite concentrations between 10 {mu}M and 100 {mu}M yield adsorption curves, which increases with pH, peak at a pH of 9, and decrease at higher pH values. The slope of this bend becomes steeper with increasing temperature. A 1-pK charge distribution model in combination with a basic Stern layer option could be established for the pH-dependent arsenite adsorption. Formation of two inner-sphere bidentate surface complexes best matched the experimental data in agreement with published EXAFS spectroscopic information. The temperature behaviour of the thus derived intrinsic equilibrium constants can be well represented by the linear Van't Hoff logK{sub T}{sup int} vs. 1/T plot. Adsorption of arsenite on the goethite surface is exothermic (negative {delta}{sub r}H{sub 298} values) and therefore becomes weaker with increasing temperature. Application of the new constants with the aqueous speciation code VMINTEQ predicts that the As(III) concentration in presence of goethite sorbent decreases by 10 times once the hydrothermal solution is cooled from 99 deg. C to 1 deg. C. The model curve matches data from a natural thermal water spring system. The increase of adsorption efficiency for As along the temperature gradient may well serve as an additional process to prevent ecosystem contamination by As-rich water seepage from geothermal energy generation facilities.

Thermal treatment of natural goethite: Thermal transformation and physical properties

Energy Technology Data Exchange (ETDEWEB)

Liu, Haibo [Laboratory for Nanomineralogy and Environmental Material, School of Resources and Environmental Engineering, Hefei University of Technology (China); School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology (Australia); Chen, Tianhu, E-mail: chentianhu@hfut.edu.cn [Laboratory for Nanomineralogy and Environmental Material, School of Resources and Environmental Engineering, Hefei University of Technology (China); Zou, Xuehua; Qing, Chengsong [Laboratory for Nanomineralogy and Environmental Material, School of Resources and Environmental Engineering, Hefei University of Technology (China); Frost, Ray L., E-mail: r.frost@qut.edu.au [School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology (Australia)

2013-09-20

Highlights: • We have characterized the thermal transformation of natural goethite. • The heated products showed a topotactical relationship to the original mineral. • The N2 adsorption isotherm provided the variation of surface area and pore size distribution with temperature. • The significant increase in surface area was attributed to the formation of regularly arranged slit-shaped micropores. • The hematite derived from heating goethite has application as an adsorbent and catalyst. - Abstract: XRD (X-ray diffraction), XRF (X-ray fluorescence), TG (thermogravimetry), FT-IES (Fourier transform infrared emission spectroscopy), FESEM (field emission scanning electron microscope), TEM (transmission electron microscope) and nitrogen–adsorption–desorption analysis were used to characterize the composition and thermal evolution of the structure of natural goethite. The in situ FT-IES demonstrated the start temperature (250 °C) of the transformation of natural goethite to hematite and the thermodynamic stability of protohematite between 250 and 600 °C. The heated products showed a topotactic relationship to the original mineral based on SEM analysis. Finally, the nitrogen–adsorption–desorption isotherm provided the variation of surface area and pore size distribution as a function of temperature. The surface area displayed a remarkable increase up to 350 °C, and then decreased above this temperature. The significant increase in surface area was attributed to the formation of regularly arranged slit-shaped micropores running parallel to elongated direction of hematite microcrystal. The main pore size varied from 0.99 nm to 3.5 nm when heating temperature increases from 300 to 400 °C. The hematite derived from heating goethite possesses high surface area and favors the possible application of hematite as an adsorbent as well as catalyst carrier.

Thermal treatment of natural goethite: Thermal transformation and physical properties

International Nuclear Information System (INIS)

Liu, Haibo; Chen, Tianhu; Zou, Xuehua; Qing, Chengsong; Frost, Ray L.

2013-01-01

Highlights: • We have characterized the thermal transformation of natural goethite. • The heated products showed a topotactical relationship to the original mineral. • The N2 adsorption isotherm provided the variation of surface area and pore size distribution with temperature. • The significant increase in surface area was attributed to the formation of regularly arranged slit-shaped micropores. • The hematite derived from heating goethite has application as an adsorbent and catalyst. - Abstract: XRD (X-ray diffraction), XRF (X-ray fluorescence), TG (thermogravimetry), FT-IES (Fourier transform infrared emission spectroscopy), FESEM (field emission scanning electron microscope), TEM (transmission electron microscope) and nitrogen–adsorption–desorption analysis were used to characterize the composition and thermal evolution of the structure of natural goethite. The in situ FT-IES demonstrated the start temperature (250 °C) of the transformation of natural goethite to hematite and the thermodynamic stability of protohematite between 250 and 600 °C. The heated products showed a topotactic relationship to the original mineral based on SEM analysis. Finally, the nitrogen–adsorption–desorption isotherm provided the variation of surface area and pore size distribution as a function of temperature. The surface area displayed a remarkable increase up to 350 °C, and then decreased above this temperature. The significant increase in surface area was attributed to the formation of regularly arranged slit-shaped micropores running parallel to elongated direction of hematite microcrystal. The main pore size varied from 0.99 nm to 3.5 nm when heating temperature increases from 300 to 400 °C. The hematite derived from heating goethite possesses high surface area and favors the possible application of hematite as an adsorbent as well as catalyst carrier

Goethite Bench-scale and Large-scale Preparation Tests

Energy Technology Data Exchange (ETDEWEB)

Josephson, Gary B.; Westsik, Joseph H.

2011-10-23

The Hanford Waste Treatment and Immobilization Plant (WTP) is the keystone for cleanup of high-level radioactive waste from our nation's nuclear defense program. The WTP will process high-level waste from the Hanford tanks and produce immobilized high-level waste glass for disposal at a national repository, low activity waste (LAW) glass, and liquid effluent from the vitrification off-gas scrubbers. The liquid effluent will be stabilized into a secondary waste form (e.g. grout-like material) and disposed on the Hanford site in the Integrated Disposal Facility (IDF) along with the low-activity waste glass. The major long-term environmental impact at Hanford results from technetium that volatilizes from the WTP melters and finally resides in the secondary waste. Laboratory studies have indicated that pertechnetate ({sup 99}TcO{sub 4}{sup -}) can be reduced and captured into a solid solution of {alpha}-FeOOH, goethite (Um 2010). Goethite is a stable mineral and can significantly retard the release of technetium to the environment from the IDF. The laboratory studies were conducted using reaction times of many days, which is typical of environmental subsurface reactions that were the genesis of this new process. This study was the first step in considering adaptation of the slow laboratory steps to a larger-scale and faster process that could be conducted either within the WTP or within the effluent treatment facility (ETF). Two levels of scale-up tests were conducted (25x and 400x). The largest scale-up produced slurries of Fe-rich precipitates that contained rhenium as a nonradioactive surrogate for {sup 99}Tc. The slurries were used in melter tests at Vitreous State Laboratory (VSL) to determine whether captured rhenium was less volatile in the vitrification process than rhenium in an unmodified feed. A critical step in the technetium immobilization process is to chemically reduce Tc(VII) in the pertechnetate (TcO{sub 4}{sup -}) to Tc(Iv)by reaction with the

Rate constants and mechanisms for the crystallization of Al nano-goethite under environmentally relevant conditions

Science.gov (United States)

Bazilevskaya, Ekaterina; Archibald, Douglas D.; Martínez, Carmen Enid

2012-07-01

Mobile inorganic and organic nanocolloidal particles originate-from and interact-with bulk solid phases in soil and sediment environments, and as such, they contribute to the dynamic properties of environmental systems. In particular, ferrihydrite and (nano)goethite are the most abundant of nanocolloidal Fe oxy(hydr)oxides in these environments. We therefore investigated the ferrihydrite to goethite phase transformation using experimental reaction conditions that mimicked environmental conditions where the formation of nanocolloidal Fe oxy(hydr)oxides may occur: slow titration of dilute solutions to pH 5 at 25 °C with and without 2 mol% Al. Subsequently, the rate constants from 54-d nano-goethite aging/crystallization experiments at 50 °C were determined using aliquots pulled for vibrational spectroscopy (including multivariate curve resolution, MCR, analyses of infrared spectra) and synchrotron-based X-ray diffraction (XRD). We also present a mechanistic model that accounts for the nano-goethite crystallization observed by the aforementioned techniques, and particle structural characteristics observed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). In contrast to the common assumption that metastable ferrihydrite precipitates first, before it transforms to goethite, the presence of characteristic infrared bands in freshly synthesized nanoparticle suspensions indicate goethite can precipitate directly from solution under environmentally relevant conditions: low Fe concentration, ambient temperature, and pH maintained at 5. However, the presence of 2 mol% Al prevented direct goethite precipitation. Rate constants obtained by fitting the contributions from the MCR-derived goethite-like component to the OH-stretching region were (7.4 ± 1.1) × 10-7 s-1 for 0% Al and (4.2 ± 0.4) × 10-7 s-1 for 2 mol% Al suspensions. Rate constants derived from intensities of OH-bending infrared vibrations (795 and 895 cm-1) showed similar values

Synthesis and characterization of a nanocomposite of goethite nanorods and reduced graphene oxide for electrochemical capacitors

International Nuclear Information System (INIS)

Shou Qingliang; Cheng Jipeng; Zhang Li; Nelson, Bradley J.; Zhang Xiaobin

2012-01-01

We report a one-step synthesis of a nanocomposite of goethite (α-FeOOH) nanorods and reduced graphene oxide (RGO) using a solution method in which ferrous cations serve as a reducing agent of graphite oxide (GO) to graphene and a precursor to grow goethite nanorods. As-prepared goethite nanorods have an average length of 200 nm and a diameter of 30 nm and are densely attached on both sides of the RGO sheets. The electrochemical properties of the nanocomposite were characterized by cyclic voltammetry (CV) and chronopotentiometry (CP) charge–discharge tests. The results showed that goethite/RGO composites have a high electrochemical capacitance of 165.5 F g −1 with an excellent recycling capability making the material promising for electrochemical capacitors. - Graphical abstract: The reduced graphene oxide sheets are decorated with goethite nanorods. The as-prepared composite exhibits a high electrochemical capacitance with good recycling capability, which is promising for supercapacitor applications. Higlights: ► Ferrous ions act as reductant of graphite oxide and precursor of goethite nanorods. ► Goethite nanorods are attached on both sides of the reduced graphene oxide sheets. ► Composite exhibits a high specific capacitance and a good recycling capability. ► Composite is promising for supercapacitor applications.

In situ preparation of magnetic nanocomposites of goethite in a styrene-maleimide copolymer template

International Nuclear Information System (INIS)

Sepulveda-Guzman, S.; Perez-Camacho, O.; Rodriguez-Fernandez, O.; Garcia-Zamora, M.

2005-01-01

Magnetic composites were prepared by in situ precipitation of α-FeOOH (goethite) using a new styrene-co-N-4 carboxybutylmaleimide cross-linked copolymer as template. Thermogravimetric analysis showed iron oxide content in the composites up to 45%. The iron oxide phase was identified as goethite by X-ray diffraction analysis. Transmission electron microscopy revealed that the crosslinking extent of polymeric templates affected both the shape and dimension of the goethite particles, and consequently, the magnetic behavior of the polymer/iron oxide composites

Facet-Dependent Oxidative Goethite Growth As a Function of Aqueous Solution Conditions.

Science.gov (United States)

Strehlau, Jennifer H; Stemig, Melissa S; Penn, R Lee; Arnold, William A

2016-10-04

Nitroaromatic compounds are groundwater pollutants that can be degraded through reactions with Fe(II) adsorbed on iron oxide nanoparticles, although little is known about the evolving reactivity of the minerals with continuous pollutant exposure. In this work, Fe(II)/goethite reactivity toward 4-chloronitrobenzene (4-ClNB) as a function of pH, organic matter presence, and reactant concentrations was explored using sequential-spike batch reactors. Reaction rate constants were smaller with lower pH, introduction of organic matter, and diluted reactant concentrations as compared to a reference condition. Reaction rate constants did not change with the number of 4-ClNB spikes for all reaction conditions. Under all conditions, oxidative goethite growth was demonstrated through X-ray diffraction, magnetic characterization, and transmission electron microscopy. Nonparametric statistics were applied to compare histograms of lengths and widths of goethite nanoparticles as a function of varied solution conditions. The conditions that slowed the reaction also resulted in statistically shorter and wider particles than for the faster reactions. Additionally, added organic matter interfered with particle growth on the favorable {021} faces to a greater extent, with statistically reduced rate of growth on the tip facets and increased rate of growth on the side facets. These data demonstrate that oxidative growth of goethite in aqueous systems is dependent on major groundwater variables, such as pH and the presence of organic matter, which could lead to the evolving reactivity of goethite particles in natural environments.

Outer Sphere Adsorption of Pb(II)EDTA on Goethite

Energy Technology Data Exchange (ETDEWEB)

Bargar, John R

1999-07-16

FTIR and EXAFS spectroscopic measurements were performed on Pb(II)EDTA adsorbed on goethite as functions of pH (4-6), Pb(II)EDTA concentration (0.11 {micro}M - 72 {micro}M), and ionic strength (16 {micro}M - 0.5M). FTIR measurements show no evidence for carboxylate-Fe(III) bonding or protonation of EDTA at Pb:EDTA = 1:1. Both FTIR and EXAFS measurements suggest that EDTA acts as a hexadentate ligand, with all four of its carboxylate and both amine groups bonded to Pb(II). No evidence was observed for inner-sphere Pb(II)-goethite bonding at Pb:EDTA = 1:1. Hence, the adsorbed complexes should have composition Pb(II)EDTA{sup 2{minus}}. Since substantial uptake of PbEDTA(II){sup 2{minus}} occurred in the samples, we infer that Pb(II)EDTA{sup 2{minus}} adsorbed as outer-sphere complexes and/or as complexes that lose part of their solvation shells and hydrogen bond directly to goethite surface sites. We propose the term ''hydration-sphere'' for the latter type of complexes because they should occupy space in the primary hydration spheres of goethite surface functional groups, and to distinguish this mode of sorption from common structural definitions of inner- and outer-sphere complexes. The similarity of Pb(II) uptake isotherms to those of other divalent metal ions complexed by EDTA suggests that they too adsorb by these mechanisms. The lack of evidence for inner-sphere EDTA-Fe(III) bonding suggests that previously proposed metal-ligand - promoted dissolution mechanisms should be modified, specifically to account for the presence of outer-sphere precursor species.

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

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

Water adsorption on goethite: Application of multilayer adsorption models

Science.gov (United States)

Hatch, C. D.; Tumminello, R.; Meredith, R.

2016-12-01

Adsorbed water on the surface of atmospheric mineral dust has recently been shown to significantly affect the ability of mineral dust aerosol to act as cloud condensation nuclei. We have studied water adsorption as a function of relative humidity (RH) on goethite (α-FeO(OH)), a common component of atmospheric mineral dust. The goethite surface area and particle size was determined using BET analysis and with N2 as an adsorbate and scanning electron microscopy, respectively. Water adsorption on the sample was monitored using horizontal attenuated total reflectance Fourier transform infrared (HATR-FTIR) spectroscopy equipped with a flow cell. Water content was determined using Beer's law and the optical constants for bulk water. The results were analyzed using Type II adsorption isotherms to model multilayer adsorption, including BET (Brunauer, Emmet and Teller), FHH (Frenkel, Halsey and Hill) and Freundlich. BET fits to experimental data provide parameters of monolayer coverage, while the FHH and Freundlich isotherms provide insights into multilayer adsorption mechanisms. Results indicate that goethite contains 5% H2O by mass at 50% RH, which increases to 12% by mass at 90% RH. Adsorption parameters and experimental results will be presented.

Mineral transformations associated with goethite reduction by Methanosarcina barkeri

Science.gov (United States)

Liu, D.; Wang, Hongfang; Dong, H.; Qiu, X.; Dong, X.; Cravotta, C.A.

2011-01-01

To investigate the interaction between methanogens and iron-containing minerals in anoxic environments, we conducted batch culture experiments with Methanosarcina barkeri in a phosphate-buffered basal medium (PBBM) to bioreduce structural Fe(III) in goethite with hydrogen as the sole substrate. Fe(II) and methane concentrations were monitored over the course of the bioreduction experiments with wet chemistry and gas chromatography, respectively. Subsequent mineralogical changes were characterized with X-ray diffraction (XRD) and scanning electron microscopy (SEM). In the presence of an electron shuttle anthraquinone-2,6-disulfonate (AQDS), 30% Fe(III) in goethite (weight basis) was reduced to Fe(II). In contrast, only 2% Fe(III) (weight basis) was bioreduced in the absence of AQDS. Most of the bioproduced Fe(II) was incorporated into secondary minerals including dufr??nite and vivianite. Our data implied a dufr??nite-vivianite transformation mechanism where a metastable dufr??nite transformed to a more stable vivianite over extended time in anaerobic conditions. Methanogenesis was greatly inhibited by bioreduction of goethite Fe(III). These results have important implications for the methane flux associated with Fe(III) bioreduction and ferrous iron mineral precipitation in anaerobic soils and sediments. ?? 2011 Elsevier B.V.

Dispersions of Goethite Nanorods in Aprotic Polar Solvents

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Delphine Coursault

2017-10-01

Full Text Available Colloidal suspensions of anisotropic nanoparticles can spontaneously self-organize in liquid-crystalline phases beyond some concentration threshold. These phases often respond to electric and magnetic fields. At lower concentrations, usual isotropic liquids are observed but they can display very strong Kerr and Cotton-Mouton effects (i.e., field-induced particle orientation. For many examples of these colloidal suspensions, the solvent is water, which hinders most electro-optic applications. Here, for goethite (α-FeOOH nanorod dispersions, we show that water can be replaced by polar aprotic solvents, such as N-methyl-2-pyrrolidone (NMP and dimethylsulfoxide (DMSO, without loss of colloidal stability. By polarized-light microscopy, small-angle X-ray scattering and electro-optic measurements, we found that the nematic phase, with its field-response properties, is retained. Moreover, a strong Kerr effect was also observed with isotropic goethite suspensions in these polar aprotic solvents. Furthermore, we found no significant difference in the behavior of both the nematic and isotropic phases between the aqueous and non-aqueous dispersions. Our work shows that goethite nanorod suspensions in polar aprotic solvents, suitable for electro-optic applications, can easily be produced and that they keep all their outstanding properties. It also suggests that this solvent replacement method could be extended to the aqueous colloidal suspensions of other kinds of charged anisotropic nanoparticles.

Gallium isotope fractionation during Ga adsorption on calcite and goethite

Science.gov (United States)

Yuan, Wei; Saldi, Giuseppe D.; Chen, JiuBin; Vetuschi Zuccolini, Marino; Birck, Jean-Louis; Liu, Yujie; Schott, Jacques

2018-02-01

Gallium (Ga) isotopic fractionation during its adsorption on calcite and goethite was investigated at 20 °C as a function of the solution pH, Ga aqueous concentration and speciation, and the solid to solution ratio. In all experiments Ga was found to be enriched in light isotopes at the solid surface with isotope fractionation △71Gasolid-solution up to -1.27‰ and -0.89‰ for calcite and goethite, respectively. Comparison of Ga isotopic data of this study with predictions for 'closed system' equilibrium and 'Rayleigh fractionation' models indicates that the experimental data are consistent with a 'closed system' equilibrium exchange between the fluid and the solid. The results of this study can be interpreted based on Ga aqueous speciation and the structure of Ga complexes formed at the solid surfaces. For calcite, Ga isotope fractionation is mainly triggered by increased Ga coordination and Ga-O bond length, which vary respectively from 4 and 1.84 Å in Ga(OH)4- to 6 and 1.94 Å in the >Ca-O-GaOH(OH2)4+ surface complex. For goethite, despite the formation of Ga hexa-coordinated >FeOGa(OH)20 surface complexes (Ga-O distances of 1.96-1.98 Å) both at acid and alkaline pH, a similar extent of isotope fractionation was found at acid and alkaline pH, suggesting that Ga(OH)4- is preferentially adsorbed on goethite for all investigated pH conditions. In addition, the observed decrease of Ga isotope fractionation magnitude observed with increasing Ga surface coverage for both calcite and goethite is likely related to the formation of Ga surface polymers and/or hydroxides with reduced Ga-O distances. This first study of Ga isotope fractionation during solid-fluid interactions suggests that the adsorption of Ga by oxides, carbonates or clay minerals could yield significant Ga isotope fractionation between secondary minerals and surficial fluids including seawater. Ga isotopes thus should help to better characterize the surficial biogeochemical cycles of gallium and its

Protonation of Different Goethite Surfaces - Unified Models for NaNO3 and NaCl Media

International Nuclear Information System (INIS)

Lutzenkirchen, Johannes; Boily, Jean-Francois F.; Gunneriusson, Lars; Lovgren, L.; Sjojberg, S.

2008-01-01

Acid-base titration data for two goethites samples in sodium nitrate and sodium chloride media are discussed. The data are modeled based on various surface complexation models in the framework of the MUlti SIte Complexation (MUSIC) model. Various assumptions with respect to the goethite morphology are considered in determining the site density of the surface functional groups. The results from the various model applications are not statistically significant in terms of goodness of fit. More importantly, various published assumptions with respect to the goethite morphology (i.e. the contributions of different crystal planes and their repercussions on the ''overall'' site densities of the various surface functional groups) do not significantly affect the final model parameters. The simultaneous fit of the chloride and nitrate data results in electrolyte binding constants, which are applicable over a wide range of electrolyte concentrations including mixtures of chloride and nitrate. Model parameters for the high surface area goethite sample are in excellent agreement with parameters that were independently obtained by another group on different goethite titration data sets

A study of selenium and tin sorption on granite and goethite

International Nuclear Information System (INIS)

Ticknor, K.V.; McMurry, J.

1996-01-01

Sensitivity analyses based on an illustrative performance assessment case study of a disposal concept for nuclear fuel waste have shown that radioisotopes of Se and Sn could have a significant effect on cumulative radioactive dose if they were to be transported through the geosphere without retardation. Static batch sorption methods, coupled with 2 n factorial experimental designs, were used to determine the extent to which Se and Sn can be sorbed by granite and goethite as a function of total dissolved solids concentration, (TDS), natural fulvic acid concentration as dissolved organic carbon, [DOC], pH and, for the studies with Se, the Se concentration, [Se]. Aqueous speciation and the saturation indices of solubility-controlling solid phases were estimated using the speciation code HARPHRQ with the HATCHES thermodynamic database. The experimental results indicated that Se sorption on granite was low and not affected by changes in [DOC] or [TDS]. Increased [Se] and increased pH decreased sorption. For Se sorption on goethite, the pH range was narrow but indicated that sorption decreased as pH increased. Increased [TDS] and [Se] lowered sorption on goethite, but changes in (DOC] had no effect on sorption. For Sn, increased pH, [TDS] and [DOC] decreased sorption on granite. For Sn sorption on goethite, increased [DOC] resulted in decreased sorption, but differences in [TDS] and pH had little consistent effect on sorption. (author)

The effect of water content on the magnetic and structural properties of goethite

International Nuclear Information System (INIS)

Betancur, J.D.; Barrero, C.A.; Greneche, J.M.; Goya, G.F.

2004-01-01

We have studied the effect of water content on the magnetic and structural properties of goethite. For that purpose, four samples were prepared using two different hydrothermal methods, one of them is derived on the Fe(II) precursors and the other one from Fe(III) precursors. The samples were characterized by X-ray diffraction (XRD), TGA, BET, FTIR, Moessbauer spectrometry at RT, 77 and 4.2 K and ZFC and FC curves. The results suggest that the goethites from the Fe(II) precursors are less crystalline, have higher water contents and do not show magnetic ordered structure at RT in comparison to the goethites from the Fe(III) precursors. The goethites from the last systems exhibit good crystallinity, low water content and magnetic ordering at room temperature. Our results suggest that both structural and adsorbed water contents reduce the magnetic hyperfine field at 4.2 K. A linear correlation with regression coefficient of 0.91 between the saturation hyperfine field and both the structural hydroxyl content and the surface area could be derived

Removal of caffeine from water by combining dielectric barrier discharge (DBD plasma with goethite

Directory of Open Access Journals (Sweden)

Jian Wang

2017-07-01

Full Text Available In this research, dielectric barrier discharge plasma was developed to cooperate with goethite for removing caffeine in aqueous solution. Goethite was characterized by X-ray diffraction and scanning electron microscopy. The effects of input power, initial concentration and catalysts concentration on the removal efficiency of caffeine were evaluated. Furthermore, the degradation pathways of caffeine were also discussed preliminarily. In the case of caffeine concentration at 50 mg L−1, the degradation efficiency of caffeine was improved from 41% to 94% after 24 min on the conditions of input power of 75 W by combining goethite catalysts (2.5 g L−1, while the energy efficiency could be enhanced 1.6–2.3 times compared to the single DBD reactor. The reaction mechanism experiments demonstrated that attack by hydroxyl radical and ozone was the main degradation process of caffeine in aqueous solution. These studies also provided a theoretical and practical basis for the application of DBD-goethite in treatment of caffeine from water.

Control of Earth-like magnetic fields on the transformation of ferrihydrite to hematite and goethite.

Science.gov (United States)

Jiang, Zhaoxia; Liu, Qingsong; Dekkers, Mark J; Barrón, Vidal; Torrent, José; Roberts, Andrew P

2016-07-26

Hematite and goethite are the two most abundant iron oxides in natural environments. Their formation is controlled by multiple environmental factors; therefore, their relative concentration has been used widely to indicate climatic variations. In this study, we aimed to test whether hematite and goethite growth is influenced by ambient magnetic fields of Earth-like values. Ferrihydrite was aged at 95 °C in magnetic fields ranging from ~0 to ~100 μT. Our results indicate a large influence of the applied magnetic field on hematite and goethite growth from ferrihydrite. The synthesized products are a mixture of hematite and goethite for field intensities fields favour hematite formation by accelerating ferrimagnetic ferrihydrite aggregation. Additionally, hematite particles growing in a controlled magnetic field of ~100 μT appear to be arranged in chains, which may be reduced to magnetite keeping its original configuration, therefore, the presence of magnetic particles in chains in natural sediments cannot be used as an exclusive indicator of biogenic magnetite. Hematite vs. goethite formation in our experiments is influenced by field intensity values within the range of geomagnetic field variability. Thus, geomagnetic field intensity could be a source of variation when using iron (oxyhydr-)oxide concentrations in environmental magnetism.

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.

Sorption of radionickel to goethite: Effect of water quality parameters and temperature

International Nuclear Information System (INIS)

Baowei Hu; ShaoXing University, ShaoXing; Wen Cheng; Hui Zhang; Guodong Sheng; Chinese Academy of Sciences, Hefei

2010-01-01

In this work, sorption of Ni(II) from aqueous solution to goethite as a function of various water quality parameters and temperature was investigated. The results indicated that the pseudo-second-order rate equation fitted the kinetic sorption well. The sorption of Ni(II) to goethite was strongly dependent on pH and ionic strength. A positive effect of HA/FA on Ni(II) sorption was found at pH 8.0. The Langmuir, Freundlich, and D-R models were applied to simulate the sorption isotherms at three different temperatures of 293.15 K, 313.15 K and 333.15 K. The thermodynamic parameters (ΔH 0 , ΔS 0 and ΔG 0 ) were calculated from the temperature dependent sorption, and the results indicated that the sorption was endothermic and spontaneous. At low pH, the sorption of Ni(II) was dominated by outer-sphere surface complexation or ion exchange with Na + /H + on goethite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. (author)

Lead and selenite adsorption at water-goethite interfaces from first principles

Science.gov (United States)

Leung, Kevin; Criscenti, Louise J.

2017-09-01

The complexation of toxic and/or radioactive ions on to mineral surfaces is an important topic in geochemistry. We apply periodic-boundary-conditions density functional theory (DFT) molecular dynamics simulations to examine the coordination of Pb(II), SeO_32- , and their contact ion pairs to goethite (1 0 1) and (2 1 0) surfaces. The multitude of Pb(II) adsorption sites and possibility of Pb(II)-induced FeOH deprotonation make this a complex problem. At surface sites where Pb(II) is coordinated to three FeO and/or FeOH groups, and with judicious choices of FeOH surface group protonation states, the predicted Fe-Pb distances are in good agreement with EXAFS measurements. Trajectories where Pb(II) is in part coordinated to only two surface Fe-O groups exhibit larger fluctuations in Pb-O distances. Pb(II)/SeO_32- contact ion pairs are at least metastable on goethite (2 1 0) surfaces if the SeO_32- has a monodentate Se-O-Fe bond. Our DFT-based molecular dynamics calculations are a prerequisite for calculations of finite temperature equilibrium binding constants of Pb(II) and Pb(II)/SeO_32- ion pairs to goethite adsorption sites.

The transformation of ferrihydrite into goethite or hematite, revisited

International Nuclear Information System (INIS)

Cudennec, Yannick; Lecerf, Andre

2006-01-01

During the oxidation of iron, poorly crystallized phases are firstly formed: 2- and 6-line ferrihydrite, which presents for the last phase, a similarity with wustite FeO but also with hematite α-Fe 2 O 3 . Crystallization increases with time and the solid phase obtained is dependent on temperature and pH. Obviously, high temperature favours the formation of the oxide hematite α-Fe 2 O 3 . As for the pH factor, it is more complicated. Low and high values of pH (2-5 and 10-14) favour the formation of goethite α-FeOOH, while obtaining hematite is favoured at neutral pH (values around 7). Goethite or hematite are obtained either through a dissolution-crystallization process or in the solid state, through a topotactic transformation. Given the structural relationships observed between ferrihydrite and wustite and hematite, it is allowed to think that a structural continuity could exist between wustite Fe (1- x ) O and hematite via ferrihydrite

Goethite surface reactivity: III. Unifying arsenate adsorption behavior through a variable crystal face - Site density model

Science.gov (United States)

Salazar-Camacho, Carlos; Villalobos, Mario

2010-04-01

We developed a model that describes quantitatively the arsenate adsorption behavior for any goethite preparation as a function of pH and ionic strength, by using one basic surface arsenate stoichiometry, with two affinity constants. The model combines a face distribution-crystallographic site density model for goethite with tenets of the Triple Layer and CD-MUSIC surface complexation models, and is self-consistent with its adsorption behavior towards protons, electrolytes, and other ions investigated previously. Five different systems of published arsenate adsorption data were used to calibrate the model spanning a wide range of chemical conditions, which included adsorption isotherms at different pH values, and adsorption pH-edges at different As(V) loadings, both at different ionic strengths and background electrolytes. Four additional goethite-arsenate systems reported with limited characterization and adsorption data were accurately described by the model developed. The adsorption reaction proposed is: lbond2 FeOH +lbond2 SOH +AsO43-+H→lbond2 FeOAsO3[2-]…SOH+HO where lbond2 SOH is an adjacent surface site to lbond2 FeOH; with log K = 21.6 ± 0.7 when lbond2 SOH is another lbond2 FeOH, and log K = 18.75 ± 0.9, when lbond2 SOH is lbond2 Fe 2OH. An additional small contribution of a protonated complex was required to describe data at low pH and very high arsenate loadings. The model considered goethites above 80 m 2/g as ideally composed of 70% face (1 0 1) and 30% face (0 0 1), resulting in a site density for lbond2 FeOH and for lbond2 Fe 3OH of 3.125/nm 2 each. Below 80 m 2/g surface capacity increases progressively with decreasing area, which was modeled by considering a progressively increasing proportion of faces (0 1 0)/(1 0 1), because face (0 1 0) shows a much higher site density of lbond2 FeOH groups. Computation of the specific proportion of faces, and thus of the site densities for the three types of crystallographic surface groups present in

Carbonate adsorption onto goethite as a function of pH and ionic strength

International Nuclear Information System (INIS)

Rundberg, R.S.; Albinsson, Y.

1991-01-01

The adsorption of carbonate onto geothite was studied as a function of both pH and ionic strength (NaClO 4 electrolyte) using 14 C tracer. The pH ranged from 2.5 to 11.6. The ionic strength was controlled by varying the NaClO 4 concentration and ranged from 0.01 to 0.1 molar. The results indicate that carbonate is adsorbed on goethite as primarily an inner-sphere complex at pH values above the point of zero charge. This is inferred from the lack of dependence on ionic strength in the adsorption of carbonate. Below the point of zero charge carbonate is adsorbed by an additional outer-sphere mechanism. An adsorption isotherm was measured at pH 7.0 with an electrolyte concentration of 0.01M. Deconvolution of the isotherm proved that at least two sorption mechanisms exist. These mechanisms lead to large distribution coefficients at low pH. Thereby making the complete removal and exclusion of carbonate from an aqueous goethite system difficult, for the purpose of characterizing a ''clean'' goethite surface

Competitive adsorption and photodegradation of salicylate and oxalate on goethite

Czech Academy of Sciences Publication Activity Database

Krýsa, J.; Jirkovský, Jaromír; Bajt, O.; Mailhot, G.

2011-01-01

Roč. 161, č. 1 (2011), s. 221-227 ISSN 0920-5861 R&D Projects: GA MŠk 1M0577 Institutional research plan: CEZ:AV0Z40400503 Keywords : goethite * oxalate * salicylate Subject RIV: CG - Electrochemistry Impact factor: 3.407, year: 2011

In situ ATR FTIR studies of SO4 adsorption on goethite in the presence of copper ions.

Science.gov (United States)

Beattie, D A; Chapelet, J K; Gräfe, M; Skinner, W M; Smith, E

2008-12-15

Despite the existence of many single ion sorption studies on iron and aluminum oxides, fewer studies have been reported that describe cosorption reactions. In this work, we present an in situ ATR FTIR study of synergistic adsorption of sulfate (SO4) and copper (Cu) on goethite, which is representative of the minerals and ions present in mine wastes, acid sulfate soils, and other industrial and agricultural settings. Sulfate adsorption was studied as a function of varying pH, and as a function of increasing concentration in the absence and presence of Cu. The presence of Cu ions in solution had a complex effect on the ability of SO4 ions to be retained on the goethite surface with increasing pH, with complete desorption occurring near pH 7 and 9 in the absence and presence of Cu, respectively. In addition, Cu ions altered the balance of inner vs outer sphere adsorbed SO4. The solid phase partitioning of SO4 at pH 3 and pH 5 was elevated by the presence of Cu; in both cases Cu increased the affinity of SO4 for the goethite surface. Complementary ex situ sorption edge studies of Cu on goethite in the absence and presence of SO4 revealed that the Cu adsorption edge shifted to lower pH (6.3 --> 5.6) in the presence of SO4, consistent with a decrease of the electrostatic repulsion between the goethite surface and adsorbing Cu. Based on the ATR FTIR and bulk sorption data we surmise that the cosorption products of SO4 and Cu at the goethite-water interface were not in the nature of ternary complexes under the conditions studied here. This information is critical for the evaluation of the onset of surface precipitates of copper-hydroxy sulfates as a function of pH and solution concentration.

Loading and Light Degradation Characteristics of B t Toxin on Nano goethite: A Potential Material for Controlling the Environmental Risk of B t Toxin

International Nuclear Information System (INIS)

Zhou, X.; She, Ch.; She, Ch.; Liu, H.

2015-01-01

Transgenic B t-modified crops release toxins into soil through root exudate s and upon decomposition of residues. The fate of these toxins in soil has not been yet clearly elucidated. Nano goethite was found to have a different influence on the lifetime and identicalness activity of B t toxin. The aim of this study was to elucidate the adsorption characteristics of B t toxin on nano goethite and its activity changes before and after adsorption. The adsorption of toxin on nano goethite reached equilibrium within 5 h, and the adsorption isotherm of B t toxin on nano goethite conformed to the Langmuir equation (). In the range of ph from 6.0 to 8.0, larger adsorption occurred at lower ph value. The toxin adsorption decreased with the temperature between 10 and 50 degree. The results of Ftir, XRD, and SEM indicated that toxin did not influence the structure of nano goethite and the adsorption of toxin only on the surface of nano goethite. The LC_5_0 value for bound toxin was higher than that of free toxin, and the nano goethite greatly accelerated the degradation of toxin by ultraviolet irradiation. The above results suggested that nano goethite is a potential material for controlling the environmental risk of toxin released by Bt transgenic plants

Structural properties and hyperfine characterization of Sn-substituted goethites

Energy Technology Data Exchange (ETDEWEB)

Larralde, A.L. [INQUIMAE, Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina); Ramos, C.P. [Departamento de Fisica de la Materia Condensada, GIyA - CAC - CNEA, Av. Gral. Paz 1499 (1650), San Martin, Bs. As. (Argentina); Arcondo, B. [Departamento de Fisica, Facultad de Ingenieria, Universidad de Buenos Aires, Av. Paseo Colon 850 (C1063ACV), Bs. As. (Argentina); Tufo, A.E. [INQUIMAE, Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina); Saragovi, C. [Departamento de Fisica de la Materia Condensada, GIyA - CAC - CNEA, Av. Gral. Paz 1499 (1650), San Martin, Bs. As. (Argentina); Sileo, E.E., E-mail: sileo@qi.fcen.uba.ar [INQUIMAE, Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina)

2012-04-16

Highlights: Black-Right-Pointing-Pointer Pure and tin-doped goethites were synthesized from Sn(II) solutions at ambient pressure and 70 Degree-Sign C. Black-Right-Pointing-Pointer The Rietveld refinement of PXRD data indicated that Sn partially substituted the Fe(III) ions. Black-Right-Pointing-Pointer The substitution provoked unit cell expansion, and a distortion of the coordination polyhedron. Black-Right-Pointing-Pointer {sup 119}Sn Moessbauer spectroscopy revealed that Sn(II) is incorporated as Sn(IV). Black-Right-Pointing-Pointer {sup 57}Fe Moessbauer spectroscopy showed a lower magnetic coupling as tin concentration increased. - Abstract: Tin-doped goethites obtained by a simple method at ambient pressure and 70 Degree-Sign C were characterized by inductively coupled plasma atomic emission spectrometry, scanning electron microscopy, Rietveld refinement of powder X-ray diffraction data, and {sup 57}Fe and {sup 119}Sn Moessbauer spectroscopy. The particles size and the length to width ratios decreased with tin-doping. Sn partially substituted the Fe(III) ions provoking unit cell expansion and increasing the crystallinity of the particles with enlarged domains that grow in the perpendicular and parallel directions to the anisotropic broadening (1 1 1) axis. Intermetallic E, E Prime and DC distances also change although the variations are not monotonous, indicating different variations in the coordination polyhedron. In general, the Sn-substituted samples present larger intermetallic distances than pure goethite, and the greatest change is shown in the E Prime distance which coincides with the c-parameter. {sup 119}Sn Moessbauer spectroscopy revealed that Sn(II) is incorporated as Sn(IV) in the samples. On the other hand, Fe(II) presence was not detected by {sup 57}Fe Moessbauer spectroscopy, suggesting the existence of vacancies in the Sn-doped samples. A lower magnetic coupling is also evidenced from the average magnetic hyperfine field values obtained as tin

Reductive Dissolution of Goethite and Hematite by Reduced Flavins

Energy Technology Data Exchange (ETDEWEB)

Shi, Zhi; Zachara, John M.; Wang, Zheming; Shi, Liang; Fredrickson, Jim K.

2013-10-02

The abiotic reductive dissolution of goethite and hematite by the reduced forms of flavin mononucleotide (FMNH2) and riboflavin (RBFH2), electron transfer mediators (ETM) secreted by the dissimilatory iron-reducing bacterium Shewanella, was investigated under stringent anaerobic conditions. In contrast to the rapid redox reaction rate observed for ferrihydrite and lepidocrocite (Shi et al., 2012), the reductive dissolution of crystalline goethite and hematite was slower, with the extent of reaction limited by the thermodynamic driving force at circumneutral pH. Both the initial reaction rate and reaction extent increased with decreasing pH. On a unit surface area basis, goethite was less reactive than hematite between pH 4.0 and 7.0. AH2DS, the reduced form of the well-studied synthetic ETM anthraquinone-2,6-disulfonate (AQDS), yielded higher rates than FMNH2 under most reaction conditions, despite the fact that FMNH2 was a more effective reductant than AH2DS for ferryhydrite and lepidocrocite. Two additional model compounds, methyl viologen and benzyl viologen, were investigated under similar reaction conditions to explore the relationship between reaction rate and thermodynamic properties. Relevant kinetic data from the literature were also included in the analysis to span a broad range of half-cell potentials. Other conditions being equal, the surface area normalized initial reaction rate (ra) increased as the redox potential of the reductant became more negative. A non-linear, parabolic relationship was observed between log ra and the redox potential for eight reducants at pH 7.0, as predicted by Marcus theory for electron transfer. When pH and reductant concentration were fixed, log ra was positively correlated to the redox potential of four Fe(III) oxides over a wide pH range, following a non-linear parabolic relationship as well.

Acid base properties of a goethite surface model: A theoretical view

Science.gov (United States)

Aquino, Adelia J. A.; Tunega, Daniel; Haberhauer, Georg; Gerzabek, Martin H.; Lischka, Hans

2008-08-01

Density functional theory is used to compute the effect of protonation, deprotonation, and dehydroxylation of different reactive sites of a goethite surface modeled as a cluster containing six iron atoms constructed from a slab model of the (1 1 0) goethite surface. Solvent effects were treated at two different levels: (i) by inclusion of up to six water molecules explicitly into the quantum chemical calculation and (ii) by using additionally a continuum solvation model for the long-range interactions. Systematic studies were made in order to test the limit of the fully hydrated cluster surfaces by a monomolecular water layer. The main finding is that from the three different types of surface hydroxyl groups (hydroxo, μ-hydroxo, and μ 3-hydroxo), the hydroxo group is most active for protonation whereas μ- and μ 3-hydroxo sites undergo deprotonation more easily. Proton affinity constants (p Ka values) were computed from appropriate protonation/deprotonation reactions for all sites investigated and compared to results obtained from the multisite complexation model (MUSIC). The approach used was validated for the consecutive deprotonation reactions of the [Fe(H 2O) 6] 3+ complex in solution and good agreement between calculated and experimental p Ka values was found. The computed p Ka for all sites of the modeled goethite surface were used in the prediction of the pristine point of zero charge, pH PPZN. The obtained value of 9.1 fits well with published experimental values of 7.0-9.5.

Interaction between calcium and phosphate adsorption on goethite.

Science.gov (United States)

Rietra, R P; Hiemstra, T; van Riemsdijk, W H

2001-08-15

Quantitatively, little is known about the ion interaction processes that are responsible for the binding of phosphate in soil, water, and sediment, which determine the bioavailability and mobility of phosphate. Studies have shown that metal hydroxides are often responsible for the binding of PO4 in soils and sediments, but the binding behavior of PO4 in these systems often differs significantly from adsorption studies on metal hydroxides in laboratory. The interaction between PO4 and Ca adsorption was studied on goethite because Ca can influence the PO4 adsorption equilibria. Since adsorption interactions are very difficult to discriminate from precipitation reactions, conditions were chosen to prevent precipitation of Ca-PO4 solids. Adsorption experiments of PO4 and Ca, individually and in combination, show a strong interaction between adsorbed Ca and PO4 on goethite for conditions below the saturation index of apatite. It is shown that it is possible to predict the adsorption and interaction of PO4 and Ca on electrostatic arguments using the model parameter values derived from the single-ion systems and without invoking ternary complex formation or precipitation. The model enables the prediction of the Ca-PO4 interaction for environmentally relevant calcium and phosphate concentrations.

Investigating sorption on iron-oxyhydroxide soil minerals by solid-state NMR spectroscopy: a 6Li MAS NMR study of adsorption and absorption on goethite

DEFF Research Database (Denmark)

Nielsen, Ulla Gro; Paik, Younkee; Julmis, Keinia

2005-01-01

High-resolution 2H MAS NMR spectra can be obtained for nanocrystalline particles of goethite (alpha-FeOOH, particle size approximately 4-10 nm) at room temperature, facilitating NMR studies of sorption under environmentally relevant conditions. Li sorption was investigated as a function of pH, th...... on the goethite surface. Even larger Li hyperfine shifts (289 ppm) were observed for Li+-exchanged goethite, which contains lithium ions in the tunnels of the goethite structure, confirming the Li assignment of the 145 ppm Li resonance to the surface sites. Udgivelsesdato: 2005-Oct-6...

Equilibrium isotherms, kinetics, and thermodynamics studies for congo red adsorption using calcium alginate beads impregnated with nano-goethite.

Science.gov (United States)

Munagapati, Venkata Subbaiah; Kim, Dong-Su

2017-07-01

The present study is concerned with the batch adsorption of congo red (CR) from an aqueous solution using calcium alginate beads impregnated with nano-goethite (CABI nano-goethite) as an adsorbent. The optimum conditions for CR removal were determined by studying operational variables viz. pH, adsorbent dose, contact time, initial dye ion concentration and temperature. The CABI nano-goethite was characterized by Fourier transform infrared spectroscopy (FTIR), X- ray diffraction (XRD) and Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) analysis. The CR sorption data onto CABI nano-goethite were described using Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm models. The results show that the best fit was achieved with the Langmuir isotherm model. The maximum adsorption capacity (181.1mg/g) of CR was occurred at pH 3.0. Kinetic studies showed that the adsorption followed a pseudo-second-order model. Desorption experiments were carried out to explore the feasibility of regenerating the adsorbent and the adsorbed CR from CABI nano-goethite. The best desorbing agent was 0.1M NaOH with an efficiency of 94% recovery. The thermodynamic parameters ΔG°, ΔH°, and ΔS° for the CR adsorption were determined by using adsorption capacities at five different temperatures (293, 303, 313, 323 and 303K). Results show that the adsorption process was endothermic and favoured at high temperature. Copyright © 2017 Elsevier Inc. All rights reserved.

Oxidative C-H activation of amines using protuberant lychee-like goethite

Science.gov (United States)

Goethite with protuberant lychee morphology has been synthesized that accomplishes C-H activation of N-methylanilines to generate α-aminonitriles; the catalyst takes oxygen from air and uses it as a cooxidant in the process. Inspired by nature, we aspired to design a protocol for...

Surface complexation of carbonate on goethite: IR spectroscopy, structure & charge distribution

NARCIS (Netherlands)

Hiemstra, T.; Rahnemaie, R.; Riemsdijk, van W.H.

2004-01-01

The adsorption of carbonate on goethite has been evaluated, focussing on the relation between the structure of the surface complex and corresponding adsorption characteristics, like pH dependency and proton co-adsorption. The surface structure of adsorbed CO3-2 has been assessed with (1) a

Interactions between goethite particles subjected to heat treatment

DEFF Research Database (Denmark)

Madsen, Daniel Esmarch; Hansen, Mikkel Fougt; Koch, C.B.

2008-01-01

We have studied the effect of heating on the magnetic properties of particles of nanocrystalline goethite by use of Mossbauer spectroscopy. Heating at 150 degrees C for 24 h leads to a change in the quadrupole shift in the low-temperature spectra, indicating a rotation of the sublattice...... magnetization directions. Fitting of quantiles, derived from the asymmetrically broadened spectra between 80 and 300 K, to the superferromagnetism model indicates that this change is due to a stronger magnetic coupling between the particles....

Reconstructing Holocene hematite and goethite variations in the Indus Canyon to trace changes in the Asian monsoon system

Science.gov (United States)

Koehler, Cornelia; Clift, Peter; Pressling, Nicola; Limmer, David; Giosan, Liviu; Tabrez, Ali

2010-05-01

In order to study Holocene Asian monsoon variations, we reconstructed changes in chemical weathering by examining sediments from the Indus Canyon. During the late Holocene, the Asian monsoon system had periods of high and low intensities that influenced the civilisations living in its realm. For example, the demise of the Harappan civilisation has been linked to a weakened monsoon system around 4 ka. The sediments in the Indus Canyon, which originate from the River Indus and its Himalayan tributaries, provide an ideal, natural environmental archive of the South Asian monsoon system. In order to investigate the alternation between arid and humid monsoonal climatic conditions, variations are traced using the magnetic minerals hematite and goethite, which form under distinct environmental conditions: goethite is stable under humid conditions, whereas hematite forms from the dehydration of goethite under arid conditions. The two minerals are characterised and quantified using environmental magnetic measurements, as well as diffuse reflectance spectrometry. Combining both approaches will enable us to reconstruct variations in chemical weathering over time. Furthermore, because this is governed by temperature and the availability of moisture, our weathering record will allow us to understand monsoon variability during the Holocene and test whether summer rain intensity has been decreasing in SW Asia since 8 ka. In addition, the multi-component analysis of colour reflectance spectra identifies different mineral components including hematite/goethite, clay mineral mixtures, calcite and organics. We will present our results from the multi-sensor core logger equipped with a Minolta spectrometer, measuring both magnetic susceptibility and the optical properties of the split sediment cores. Initial results indicate the presence of hematite and goethite in the sediment. There is an increasing hematite content up the cores, indicating an aridification trend during the Holocene

The adsorption and dissociation of water molecule on goethite (010) surface: A DFT approach

Energy Technology Data Exchange (ETDEWEB)

Zhou, Long, E-mail: shuweixia@ouc.edu.cn [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, College of Chemistry and Chemical Engineering (China); Xiu, Fangyuan [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, College of Chemistry and Chemical Engineering (China); Qiu, Meng [Qingdao Institute of Bioenergy and Bioprocess Technology (China); Xia, Shuwei; Yu, Liangmin [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, College of Chemistry and Chemical Engineering (China)

2017-01-15

Graphical abstract: The optimized structure of hydrated goethite (010) surface with medium water coverage (water density about 6.7 H{sub 2}O/nm{sup 2}). - Highlights: • Stable adsorption and dissociation structure of H{sub 2}O on goethite (010) surface was investigated by DFT. • Reasonable path for water dissociation was proposed by transitional state analysis. • The mechanism of water adsorption on goethite and binding nature were revealed by PDOS. - Abstract: Using density functional theory (DFT) calculation, we investigate the configuration, stability and electronic properties of fresh cleaved (010) goethite surface (Pnma) and this surface exposed to water monolayer at low, medium and high coverage. Water is predicted to be chemisorbed to the surface, together with the surface reconstruction. The interaction energy of the most stable configuration of both low and medium coverage per water molecule is almost the same (−1.17 eV), while that of high coverage is much lower (less than 1.03 eV). It indicates that highly hydrated surface is less stable. PDOS analysis reveals the adsorption of H{sub 2}O is due to the formation of Fe−O bond, caused by overlapping of Fe's 3d and O's 2p orbitals. Dissociation processes at low and medium water coverage are non-spontaneous; while at high coverage, it can undertake spontaneously both thermodynamically and dynamically. The dissociation paths of all three water coverage are the similar. The proton from one adsorbed water is likely to dissociate to bind to the vicinal surface μ{sub 3}−O as an intermediate product; the proton belonged to μ{sub 3}−O transferred to the neighbor surface μ{sub 2}−O as the dissociative configuration.

Microstructure, Interaction Mechanisms, and Stability of Binary Systems Containing Goethite and Kaolinite

NARCIS (Netherlands)

Wei, S.Y.; Tan, W.F.; Zhao, W.; Yu, Y.T.; Liu, F.; Koopal, L.K.

2012-01-01

Goethite and kaolinite are ubiquitous in natural environments. In soils they are often cemented together as a binary association, which has a significant influence on the structure and properties of soils. In this study, the mineralogy (using X-ray diffraction [XRD], thermal analyses, and infrared

Inner- and outer-sphere complexation of ions at the goethite-solution interface

NARCIS (Netherlands)

Rahnemaie, R.; Hiemstra, T.; Riemsdijk, van W.H.

2006-01-01

Formation of inner- and outer-sphere complexes of environmentally important divalent ions on the goethite surface was examined by applying the charge distribution CD model for inner- and outer-sphere complexation. The model assumes spatial charge distribution between the surface (0-plane) and the

Influence of the goethite (α-FeOOH) surface on the stability of distorted PuO{sub 2} and PuO{sub 2-x} phases

Energy Technology Data Exchange (ETDEWEB)

Taylor, Sandra D.; Becker, Udo [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Earth and Environmental Sciences; Powell, Brian A. [Clemson Univ., Anderson, SC (United States). Environmental Engineering and Earth Science Dept.

2016-07-01

Experiments by [Powell, B. A., Dai, Z. R., Zavarin, M., Zhao, P. H., Kersting, A. B.: Stabilization of plutonium nano-colloids by epitaxial distortion on mineral surfaces. Environ. Sci. Technol. 45, 2698 (2011).] deduced the heteroepitaxial growth of a bcc Pu{sub 4}O{sub 7} phase when sorbed onto goethite from d-spacing measurements obtained from selected-area electron diffraction (SAED) patterns. The structural and/or chemical modification of Pu(IV) oxide (PO) nanocolloids upon sorption to goethite, in turn, affects colloidal-transport of Pu in the subsurface. In this study, molecular simulations were applied to investigate mechanisms affecting the formation of non-fcc PO phases and to understand the influence of goethite in stabilizing the non-fcc PO phase. Analyses of the structure, chemistry, and formation energetics for several bulk PuO{sub 2} and PuO{sub 2-x} phases, using ab initio methods, show that the formation of a non-fcc PO can occur from the lattice distortion (LD) of fcc PuO{sub 2} upon sorption and formation of a PO-goethite interface. To strain and non-uniformly distort the PuO{sub 2} lattice to match that of the goethite substrate at ambient conditions would require 88 kJ/mol Pu{sub 4}O{sub 8}. The formation of a hypostoichiometric PuO{sub 2-x} phase, such as the experimentally-deduced bcc, Ia anti 3 Pu{sub 4}O{sub 7} phase, requires more O-poor conditions and/or high energetic inputs (> +365 kJ/mol Pu{sub 4}O{sub 7} at O-rich conditions). Empirical methods were also applied to study the effect of lattice distortion on sorption energetics and adsorbate particle growth using simple heterointerfaces between cubic salts, where KCl clusters (notated as KCl{sub LD}) of varying size and lattice mismatch (LM) were sorbed to a NaCl cluster. When the lattice of a KCl{sub LD} cluster has <15% LM with that of a NaCl substrate, the sorption of KCl{sub LD} onto NaCl is exothermic (<-80 kJ/mol) and the KCl{sub LD} cluster can reach sizes of ∝2-5 nm on the Na

Fungal biomineralization of montmorillonite and goethite to short-range-ordered minerals

Science.gov (United States)

Li, Huan; Hu, Shuijin; Polizzotto, Matthew L.; Chang, Xiaoli; Shen, Qirong; Ran, Wei; Yu, Guanghui

2016-10-01

Highly reactive nano-scale minerals, e.g., short-range-ordered minerals (SROs) and other nanoparticles, play an important role in soil carbon (C) retention. Yet, the mechanisms that govern biomineralization from bulk minerals to highly reactive nano-scale minerals remain largely unexplored, which critically hinders our efforts toward managing nano-scale minerals for soil C retention. Here we report the results from a study that explores structural changes during Aspergillus fumigatus Z5 transformation of montmorillonite and goethite to SROs. We examined the morphology and structure of nano-scale minerals, using high-resolution transmission electron microscopy, time-resolved solid-state 27Al and 29Si NMR, and Fe K-edge X-ray absorption fine structure spectroscopy combined with two dimensional correlation spectroscopy (2D COS) analysis. Our results showed that after a 48-h cultivation of montmorillonite and goethite with Z5, new biogenic intracellular and extracellular reactive nano-scale minerals with a size of 3-5 nm became abundant. Analysis of 2D COS further suggested that montmorillonite and goethite were the precursors of the dominant biogenic nano-scale minerals. Carbon 1s near edge X-ray absorption fine structure (NEXAFS) spectra and their deconvolution results demonstrated that during fungus Z5 growth, carboxylic C (288.4-289.1 eV) was the dominant organic group, accounting for approximately 34% and 59% in the medium and aggregates, respectively. This result suggested that high percentage of the production of organic acids during the growth of Z5 was the driving factor for structural changes during biomineralization. This is, to the best of our knowledge, the first report of the structural characterization of nano-scale minerals by 2D COS, highlighting its potential to elucidate biomineralization pathways and thus identify the precursors of nano-scale minerals.

Fluoride adsorption on goethite in relation to different types of surface sites

NARCIS (Netherlands)

Hiemstra, T.; Riemsdijk, van W.H.

2000-01-01

Metal (hydr)oxides have different types of surface groups. Fluoride ions have been used as a probe to assess the number of surface sites. We have studied the F− adsorption on goethite by measuring the F− and H interaction and F− adsorption isotherms. Fluoride ions exchange against singly coordinated

Surface complexation of selenite on goethite: MO/DFT geometry and charge distribution

NARCIS (Netherlands)

Hiemstra, T.; Rietra, R.P.J.J.; Riemsdijk, van W.H.

2007-01-01

The adsorption of selenite on goethite (alpha-FeOOH) has been analyzed with the charge distribution (CD) and the multi-site surface complexation (MUSIC) model being combined with an extended Stem (ES) layer model option. The geometry of a set of different types of hydrated iron-selenite complexes

Oxidation of a Dimethoxyhydroquinone by Ferrihydrite and Goethite Nanoparticles: Iron Reduction versus Surface Catalysis.

Science.gov (United States)

Krumina, Lelde; Lyngsie, Gry; Tunlid, Anders; Persson, Per

2017-08-15

Hydroquinones are important mediators of electron transfer reactions in soils with a capability to reduce Fe(III) minerals and molecular oxygen, and thereby generating Fenton chemistry reagents. This study focused on 2,6-dimethoxy hydroquinone (2,6-DMHQ), an analogue to a common fungal metabolite, and its reaction with ferrihydrite and goethite under variable pH and oxygen concentrations. Combined wet-chemical and spectroscopic analyses showed that both minerals effectively oxidized 2,6-DMHQ in the presence of oxygen. Under anaerobic conditions the first-order oxidation rate constants decreased by one to several orders of magnitude depending on pH and mineral. Comparison between aerobic and anaerobic results showed that ferrihydrite promoted 2,6-DMHQ oxidation both via reductive dissolution and heterogeneous catalysis while goethite mainly caused catalytic oxidation. These results were in agreement with changes in the reduction potential (E H ) of the Fe(III) oxide/Fe(II) aq redox couple as a function of dissolved Fe(II) where E H of goethite was lower than ferrihydrite at any given Fe(II) concentration, which makes ferrihydrite more prone to reductive dissolution by the 2,6-DMBQ/2,6-DMHQ redox couple. This study showed that reactions between hydroquinones and iron oxides could produce favorable conditions for formation of reactive oxygen species, which are required for nonenzymatic Fenton-based decomposition of soil organic matter.

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.

Hierarchical paramecium-like hollow and solid Au/Pt bimetallic nanostructures constructed using goethite as template

Science.gov (United States)

Liu, Wei; Repo, Eveliina; Heikkilä, Mikko; Leskelä, Markku; Sillanpää, Mika

2010-10-01

Novel hollow and solid paramecium-like hierarchical Au/Pt bimetallic nanostructures were constructed using goethite as template via a seed-mediated growth method. Transmission electron microscopy (TEM), ξ-potential measurement, UV-vis spectroscopy, energy dispersive x-ray spectroscopy (EDS), ICP-AES measurement, x-ray powder diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) were utilized to systematically characterize the bimetallic nanostructures. It is found that the core structure of the paramecium-like bimetallic nanomaterial is closely related to reducing agent. When ascorbic acid is used as reducing agent, goethite serves as in situ sacrificed template and hollow paramecium-like bimetallic structure is obtained. When NH2OH·HCl is used, solid nanostructure with preserved goethite core is produced. Heating the reaction solution is necessary to obtain the paramecium-like morphology with rough interconnected Pt cilia shell. The thickness of Pt cilia layer can be controlled by adjusting the molar ratio of H2PtCl6 to Au nanoseeds. The overgrowth of the rough Pt cilia is proposed to be via an autocatalytic and three-dimensional heterogeneous nucleation process first through flower-like morphology. Both the hollow and solid hierarchical paramecium-like Au/Pt bimetallic nanostructures show good catalytic activities.

Hierarchical paramecium-like hollow and solid Au/Pt bimetallic nanostructures constructed using goethite as template

International Nuclear Information System (INIS)

Liu Wei; Repo, Eveliina; Sillanpaeae, Mika; Heikkilae, Mikko; Leskelae, Markku

2010-01-01

Novel hollow and solid paramecium-like hierarchical Au/Pt bimetallic nanostructures were constructed using goethite as template via a seed-mediated growth method. Transmission electron microscopy (TEM), ξ-potential measurement, UV-vis spectroscopy, energy dispersive x-ray spectroscopy (EDS), ICP-AES measurement, x-ray powder diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) were utilized to systematically characterize the bimetallic nanostructures. It is found that the core structure of the paramecium-like bimetallic nanomaterial is closely related to reducing agent. When ascorbic acid is used as reducing agent, goethite serves as in situ sacrificed template and hollow paramecium-like bimetallic structure is obtained. When NH 2 OH·HCl is used, solid nanostructure with preserved goethite core is produced. Heating the reaction solution is necessary to obtain the paramecium-like morphology with rough interconnected Pt cilia shell. The thickness of Pt cilia layer can be controlled by adjusting the molar ratio of H 2 PtCl 6 to Au nanoseeds. The overgrowth of the rough Pt cilia is proposed to be via an autocatalytic and three-dimensional heterogeneous nucleation process first through flower-like morphology. Both the hollow and solid hierarchical paramecium-like Au/Pt bimetallic nanostructures show good catalytic activities.

Hierarchical paramecium-like hollow and solid Au/Pt bimetallic nanostructures constructed using goethite as template

Energy Technology Data Exchange (ETDEWEB)

Liu Wei; Repo, Eveliina; Sillanpaeae, Mika [Laboratory of Applied Environmental Chemistry, University of Eastern Finland, Patteristonkatu 1, FI-50100 Mikkeli (Finland); Heikkilae, Mikko; Leskelae, Markku, E-mail: weiliuzk@yahoo.cn, E-mail: mika.sillanpaa@uef.fi [Laboratory of Inorganic Chemistry, Department of Chemistry, University of Helsinki, PO Box 55 (A.I. Virtasen aukio 1), FI-00014, Helsinki (Finland)

2010-10-01

Novel hollow and solid paramecium-like hierarchical Au/Pt bimetallic nanostructures were constructed using goethite as template via a seed-mediated growth method. Transmission electron microscopy (TEM), {xi}-potential measurement, UV-vis spectroscopy, energy dispersive x-ray spectroscopy (EDS), ICP-AES measurement, x-ray powder diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) were utilized to systematically characterize the bimetallic nanostructures. It is found that the core structure of the paramecium-like bimetallic nanomaterial is closely related to reducing agent. When ascorbic acid is used as reducing agent, goethite serves as in situ sacrificed template and hollow paramecium-like bimetallic structure is obtained. When NH{sub 2}OH{center_dot}HCl is used, solid nanostructure with preserved goethite core is produced. Heating the reaction solution is necessary to obtain the paramecium-like morphology with rough interconnected Pt cilia shell. The thickness of Pt cilia layer can be controlled by adjusting the molar ratio of H{sub 2}PtCl{sub 6} to Au nanoseeds. The overgrowth of the rough Pt cilia is proposed to be via an autocatalytic and three-dimensional heterogeneous nucleation process first through flower-like morphology. Both the hollow and solid hierarchical paramecium-like Au/Pt bimetallic nanostructures show good catalytic activities.

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

Effects of Organic Acids on Adsorption of Cadmium onto Kaolinite, Goethite, and Bayerite

Institute of Scientific and Technical Information of China (English)

无

2006-01-01

Effects of organic acids (oxalic, acetic, and citric) on adsorption characteristics of Cadmium (Cd) on soil clay minerals(kaolinite, goethite, and bayerite) were studied under different concentrations and different pH values. Although the types of organic acids and minerals were different, the effects of the organic acids on the adsorption of Cd on the minerals were similar, i.e., the amount of adsorbed Cd with an initial solution pH of 5.0 and initial Cd concentration of 35 mg L-1increased with increasing concentration of the organic acid in solution at lower concentrations, and decreased at higher concentrations. The percentage of Cd adsorbed on the minerals in the presence of the organic acids increased considerably with increasing pH of the solution. Meanwhile, different Cd adsorption in the presence of the organic acids, due to different properties on both organic acids and clay minerals, on kaolinite, goethite, or bayerite for different pHs or organic acid concentrations was found.

Synthesis and characterization of boehmite γ-AIOOH and goethite α-FeOOH

International Nuclear Information System (INIS)

Corral C, N. G.; Granados C, F.

2009-01-01

The aluminum oxy-hydroxides (boehmite) and of iron (goethite) were synthesized by means of the Sol-Gel and oxidative hydrolysis methods, to be employees as adsorbent materials of the present Cd 2+ in aqueous solution. The synthesized materials were characterized by means of X-ray diffraction, infrared analysis and scanning electron microscopy, to identify their purity, elementary chemical composition and morphology. (Author)

Transformation of goethite/ferrihydrite to hematite and maghemite under temperate humid conditions in Denmark

Science.gov (United States)

Nørnberg, P.; Finster, K.; Gunnlaugsson, H. P.; Jensen, S. K.; Merrison, J. P.; Vendelboe, A. L.

2012-04-01

At a number of sandy soil sites in Mid Jutland, Denmark, with iron content of 1-2%, very red spots (Munsell colour: dusky red 10R 3/4) of a few square meters are found. These spots are most likely due to burning events. After the fire ashes raised pH. This dispersed silt and clay size soil particles which were then transported with seepage water down into lower soil horizons. These particles contain hematite and maghemite due to influence of the fire. However, a long-standing unresolved question is how hematite and maghemite can also be present along with goethite and ferrihydrite, in the same geographical region, and in extended areas with high iron content (8-40 %) in the topsoil. Hematite and particularly maghemite would normally not be expected to form under the temperate humid Danish climate, but be interpreted as the result of high temperature as found in tropical regions or as seen in soils exposed to fire. The high iron content most likely has its origin in pyrite dissolution in top of the groundwater zone in deeper Miocene deposits. From there Fe2+ is brought to the surface by the groundwater, and in wells oxidized by meeting the atmosphere and precipitated as two line ferrihydrite. This is later transformed into goethite. However, along with these two minerals hematite and maghemite are present in the topsoil around the well area. Forest fires would be a likely explanation to the hematite and maghemite. But a body of evidence argues against these sites having been exposed to fire. 1) The pH in the topsoil is 3.6 - 4.8 and thus not raised by ashes. 2) No charcoal is present. 3) There is no indication of fire outside the high iron content areas. 4) Goethite is present along with hematite and maghemite in microparticles, and the mineralogical zonation produced in a forest fire is not seen. The natural sites contain a uniform mixture of goethite/ferrihydrite, hematite and maghemite down to 20 cm depth. An experimental forest fire left charcoal and ashes at

Nano size crystals of goethite, α-FeOOH: Synthesis and thermal transformation

International Nuclear Information System (INIS)

Christensen, Axel Norlund; Jensen, Torben R.; Bahl, Christian R.H.; DiMasi, Elaine

2007-01-01

An aqueous suspension of amorphous iron(III) hydroxide was kept at room temperature (298 K) for 23 years. During this period of time the pH of the liquid phase changed from 4.3 to 2.85, and nano size crystals of goethite, α-FeOOH crystallised from the amorphous iron(III) hydroxide. Transmission electron microscopy (TEM) investigations, Moessbauer spectra, and powder X-ray diffraction using Co Kα radiation showed that the only iron containing crystalline phase present in the recovered product was α-FeOOH. The size of these nano particles range from 10 to 100 nm measured by TEM. The thermal decomposition of α-FeOOH was investigated by time-resolved in situ synchrotron radiation powder X-ray diffraction and the data showed that the sample of α-FeOOH transformed to α-Fe 2 O 3 in the temperature range 444-584 K. A quantitative phase analysis shows the increase in scattered X-ray intensity from α-Fe 2 O 3 to follow the decrease of intensity from α-FeOOH in agreement with the topotactic phase transition. - Graphical abstract: Nano size crystals of goethite, α-FeOOH formed from amorphous iron(III) hydroxide after 23 years, and transforms faster to α-Fe 2 O 3 upon heating

Degradation and Mineralization of Phenol Compounds with Goethite Catalyst and Mineralization Prediction Using Artificial Intelligence

Science.gov (United States)

Tisa, Farhana; Davoody, Meysam; Abdul Raman, Abdul Aziz; Daud, Wan Mohd Ashri Wan

2015-01-01

The efficiency of phenol degradation via Fenton reaction using mixture of heterogeneous goethite catalyst with homogeneous ferrous ion was analyzed as a function of three independent variables, initial concentration of phenol (60 to 100 mg /L), weight ratio of initial concentration of phenol to that of H2O2 (1: 6 to 1: 14) and, weight ratio of initial concentration of goethite catalyst to that of H2O2 (1: 0.3 to 1: 0.7). More than 90 % of phenol removal and more than 40% of TOC removal were achieved within 60 minutes of reaction. Two separate models were developed using artificial neural networks to predict degradation percentage by a combination of Fe3+ and Fe2+ catalyst. Five operational parameters were employed as inputs while phenol degradation and TOC removal were considered as outputs of the developed models. Satisfactory agreement was observed between testing data and the predicted values (R2 Phenol = 0.9214 and R2TOC= 0.9082). PMID:25849556

Degradation and mineralization of phenol compounds with goethite catalyst and mineralization prediction using artificial intelligence.

Directory of Open Access Journals (Sweden)

Farhana Tisa

Full Text Available The efficiency of phenol degradation via Fenton reaction using mixture of heterogeneous goethite catalyst with homogeneous ferrous ion was analyzed as a function of three independent variables, initial concentration of phenol (60 to 100 mg /L, weight ratio of initial concentration of phenol to that of H2O2 (1: 6 to 1: 14 and, weight ratio of initial concentration of goethite catalyst to that of H2O2 (1: 0.3 to 1: 0.7. More than 90 % of phenol removal and more than 40% of TOC removal were achieved within 60 minutes of reaction. Two separate models were developed using artificial neural networks to predict degradation percentage by a combination of Fe3+ and Fe2+ catalyst. Five operational parameters were employed as inputs while phenol degradation and TOC removal were considered as outputs of the developed models. Satisfactory agreement was observed between testing data and the predicted values (R2Phenol = 0.9214 and R2TOC= 0.9082.

Sulfate adsorption on goethite

Energy Technology Data Exchange (ETDEWEB)

Rietra, R P.J.J.; Hiemstra, T; Riemsdijk, W.H. van

1999-10-15

Recent spectroscopic work has suggested that only one surface species of sulfate is dominant on hematite. Sulfate is therefore a very suitable anion to test and develop adsorption models for variable charge minerals. The authors have studied sulfate adsorption on goethite covering a large range of sulfate concentrations, surface coverages, pH values, and electrolyte concentrations. Four different techniques were used to cover the entire range of conditions. For characterization at low sulfate concentrations, below the detection limit of sulfate with ICP-AES, the authors used proton-sulfate titrations at constant pH. Adsorption isotherms were studied for the intermediate sulfate concentration range. Acid-base titrations in sodium sulfate and electromobility were used for high sulfate concentrations. All the data can be modeled with one adsorbed species if it is assumed that the charge of adsorbed sulfate is spatially distributed in the interface. The charge distribution of sulfate follows directly from modeling the proton-sulfate adsorption stoichoimemtry sine this stoichiometry is independent of the intrinsic affinity constant of sulfate. The charge distribution can be related to the structure of the surface complex by use of the Pauling bond valence concept and is in accordance with the microscopic structure found by spectroscopy. The intrinsic affinity constant follows from the other measurements. Modeling of the proton-ion stoichoimetry with the commonly used 2-pK models, where adsorbed ions are treated as point charges, is possible only if at least two surface species for sulfate are used.

Cu2+ and Ca2+ adsorption to goethite in the presence of fulvic acids

NARCIS (Netherlands)

Weng, L.P.; Riemsdijk, van W.H.; Hiemstra, T.

2008-01-01

The interaction between copper ions (Cu2+), Strichen fulvic acid (FA), and goethite has been studied with batch experiments in the pH range of 3¿11. Similar systems with Ca2+ have been studied previously and are used here for comparison. Depending on the pH and Cu2+ loading, the binding of Cu ions

Modeling the adsorption of hydrogen, sodium, chloride and phthalate on goethite using a strict charge-neutral ion-exchange theory.

Science.gov (United States)

Schulthess, Cristian P; Ndu, Udonna

2017-01-01

Simultaneous adsorption modeling of four ions was predicted with a strict net charge-neutral ion-exchange theory and its corresponding equilibrium and mass balance equations. An important key to the success of this approach was the proper collection of all the data, particularly the proton adsorption data, and the inclusion of variable concentrations of conjugate ions from the experimental pH adjustments. Using IExFit software, the ion-exchange model used here predicted the competitive retention of several ions on goethite by assuming that the co-adsorption or desorption of all ions occurred in the correct stoichiometries needed to maintain electroneutrality. This approach also revealed that the retention strength of Cl- ions on goethite increases in the presence of phthalate ions. That is, an anion-anion enhancement effect was observed. The retention of Cl- ions was much weaker than phthalate ions, and this also resulted in a higher sensitivity of the Cl- ions toward minor variations in the surface reactivity. The proposed model uses four goethite surface sites. The drop in retention of phthalate ions at low pH was fully described here as resulting from competitive Cl- reactions, which were introduced in increasing concentrations into the matrix as the conjugate base to the acid added to lower the pH.

Adsorption of Nucleic Acid/Protein Supramolecular Complexes on Goethite: The Influence of Solution Interactions on Behavior at the Solution-Mineral Interface

Science.gov (United States)

Schmidt, M.; Martinez, C. E.

2017-12-01

Adsorption of biomolecule rich supramolecular complexes onto mineral surfaces plays an important role in the development of organo-mineral associations in soils. In this study, a series of supramolecular complexes of a model nucleic acid (deoxyribonucleic acid (DNA)) and protein (bovine serum albumin (BSA)) are synthesized, characterized and exposed to goethite to probe their adsorption behavior. To synthesize DNA/BSA complexes, a fixed DNA concentration (0.1 mg/mL) was mixed with a range of BSA concentrations (0.025-0.5 mg/mL) in 5 mM KCl at pH=5.0. Circular dichroism spectroscopy demonstrates strong, cooperative, Hill-type binding between DNA and BSA (Ka= 4.74 x 105 M-1) with DNA saturation achieved when BSA concentration reaches 0.4 mg/mL. Dynamic light scattering measurements of DNA/BSA complexes suggest binding accompanies disruption of DNA-DNA intermolecular electrostatic repulsion, resulting in a decrease of the DNA slow relaxation mode with increasing amount of BSA. Zeta potential measurements show increasing amounts of BSA lead to a reduction of negative charge on DNA/BSA complexes, in line with light scattering results. In situ attenuated total reflectance Fourier transform infrared spectroscopic studies of adsorption of DNA/BSA complexes onto goethite show that complexation of BSA with DNA appears to hinder direct coordination of DNA backbone phosphodiester groups with goethite, relative to DNA by itself. Furthermore, increasing amount of BSA (up to 0.4 mg/mL) in DNA/BSA complexes enhances DNA adsorption, possibly as a result of reduced repulsion between adsorbed DNA helices. When BSA concentration exceeds 0.4 mg/mL, a decrease in adsorbed DNA is observed. We hypothesize that this discrepancy in behavior between systems with BSA concentrations below and above saturation of DNA is caused by initial fast adsorption of loosely associated BSA on goethite, restricting access to goethite surface sites. Overall, these results highlight the impact of solution

Cosmogenic 3He in hematite and goethite from Brazilian "canga" duricrust demonstrates the extreme stability of these surfaces

Science.gov (United States)

Shuster, David L.; Farley, Kenneth A.; Vasconcelos, Paulo M.; Balco, Greg; Monteiro, Hevelyn S.; Waltenberg, Kathryn; Stone, John O.

2012-05-01

Helium isotopes were measured in hematite and goethite samples from several lateritiric duricrusts (canga) developed on banded iron formations. These samples uniformly have high 3He concentrations which must arise from long periods of cosmic ray exposure. From coexisting phases from the Quadrilátero Ferrífero in east central Brazil, we determined the ratio of cosmogenic 3He in hematite to that of 21Ne in quartz to be 3.96 ± 0.19. Combined with best current estimates of the 21Ne production rate in quartz, this ratio implies a sea-level high latitude (SLHL) 3He production rate in hematite of 68.1 ± 8.1 atoms/g/yr; from the chemical composition we estimate the 3He production rate in goethite to be ~ 5% higher. We use these production rate estimates to interpret 3He concentrations measured in goethite and hematite from a ~ 10 m depth profile collected from a surface canga in Carajás, in the Amazon basin of Brazil. We find that the Carajás canga has experienced a very low rate of surface erosion (~ 0.16-0.54 m/Myr) over at least the last few millions of years. This iron-rich canga surface is remarkably resistant to erosion despite its location in a wet tropical environment. Details of the depth profile suggest that despite its stability, the canga has also been internally dynamic (translocation of material; solution and reprecipitation) over million-year timescales.

Aluminum Coprecipitates with Fe (hydr)oxides: Does Isomorphous Substitution of Al3plus for Fe3plus in Goethite Occur

Energy Technology Data Exchange (ETDEWEB)

E Bazilevskaya; D Archibald; M Aryanpour; J Kubicki; C Martinez

2011-12-31

Iron (hydr)oxides are common in natural environments and typically contain large amounts of impurities, presumably the result of coprecipitation processes. Coprecipitation of Al with Fe (hydr)oxides occurs, for example, during alternating reduction-oxidation cycles that promote dissolution of Fe from Fe-containing phases and its re-precipitation as Fe-Al (hydr)oxides. We used chemical and spectroscopic analyses to study the formation and transformation of Al coprecipitates with Fe (hydr)oxides. In addition, periodic density functional theory (DFT) computations were performed to assess the structural and energetic effects of isolated or clustered Al atoms at 8 and 25 mol% Al substitution in the goethite structure. Coprecipitates were synthesized by raising the pH of dilute homogeneous solutions containing a range of Fe and Al concentrations (100% Fe to 100% Al) to 5. The formation of ferrihydrite in initial suspensions with {<=}20 mol% Al, and of ferrihydrite and gibbsite in initial suspensions with {>=}25 mol% Al was confirmed by infrared spectroscopic and synchrotron-based X-ray diffraction analyses. While base titrations showed a buffer region that corresponded to the hydrolysis of Fe in initial solutions with {<=}25 mol% Al, all of the Al present in these solutions was retained by the solid phases at pH 5, thus indicating Al coprecipitation with the primary Fe hydroxide precipitate. In contrast, two buffer regions were observed in solutions with 30 mol% Al (at pH {approx}2.25 for Fe{sup 3+} and at pH {approx}4 for Al{sup 3+}), suggesting the formation of Fe and Al (hydr)oxides as two separate phases. The Al content of initial coprecipitates influenced the extent of ferrihydrite transformation and of its transformation products as indicated by the presence of goethite, hematite and/or ferrihydrite in aged suspensions. DFT experiments showed that: (i) optimized unit cell parameters for Al-substituted goethites (8 and 25 Mol% Al) in clustered arrangement (i.e., the

Miocene weathering environments in Western Australia-Inferences from the abundance and 13C/12C of Fe(CO3)OH in CID goethite

Science.gov (United States)

Fritz, Tyler O.; Yapp, Crayton J.

2018-04-01

The channel iron deposits (CID) of the Hamersley Province in Western Australia are dominated by pedogenic goethite/hematite-rich ooids and pisoids that were transported to, and deposited in, the meandering channels of Miocene rivers. Information about the Miocene weathering environments that produced the Fe(III) oxides is archived in the mole fraction (X) and δ13C of the Fe(CO3)OH component in solid solution in oolitic CID goethite (α-FeOOH). Values of X and δ13C were measured for 12 oolitic goethite samples from different depths in two cores drilled in CID of the Robe Formation of Mesa J. The weighted-average plateau values of X ranged from 0.0098 to 0.0334, which suggest ambient CO2 concentrations that ranged from ∼50,000 ppm V to perhaps as much as ∼200,000 ppm V at the time of goethite crystallization. In a vadose zone characterized by in situ production of CO2 with steady-state Fickian diffusive transport of the gas, such concentrations would correspond to modeled soil respiration rates (Q) ranging from about 10 to 30 mmol/m2/h. Values for Q of about 10 mmol/m2/h are reported for soils in modern tropical forests with MAP ≥ ∼2000 mm. However, model-derived values of Q that exceed 15 mmol/m2/h are larger than observed in modern systems. This could indicate that some of the CID goethites crystallized in conditions that were phreatic or near phreatic rather than vadose. The δ13C values of the Fe(CO3)OH component in these 12 CID samples ranged from -24.0‰ to -22.3‰, which are among the most negative measured to date. If they reflect steady-state diffusive transport of CO2 in vadose environments, the soil CO2 would have been derived from a source with δ13C values that ranged from ∼-31‰ to -29‰. If, on the other hand, the goethites crystallized in a nearly phreatic environment that was moderately acidic, the inferred δ13C of the ancient CO2 source would have been about -27.6‰ to -25.8‰. In either case, the δ13C values point to in situ

Structure of titanium-doped goethite rust

International Nuclear Information System (INIS)

Nakayama, Takenori; Ishikawa, Tatsuo; Konno, Toyohiko J.

2005-01-01

To investigate the influence of titanium addition on the formation and structure of goethite (α-FeOOH) rust which is one of main corrosion products of weathering steel, the artificially synthesized α-FeOOH rusts were prepared by hydrolysis of aqueous solutions of Fe(III) containing Ti(IV) at different atomic ratios (Ti/Fe) in the range 0-0.1. The obtained rusts particles were observed by TEM. Characterization by XRD, N 2 absorption, Moessbauer spectroscopy was also done. TEM observation revealed that the α-FeOOH rust particle size increased with the increase of Ti/Fe, and that Ti-enriched poorly crystalline particles were formed around the rust particles. XRD confirmed that the crystallite size increased with the increase of Ti/Fe, while the XRD peaks decreased in intensity. Specific surface area obtained by N 2 absorption increased with the increase of Ti/Fe. It is deduced from the obtained results that the addition of Ti(IV) increases the crystallite size of α-FeOOH, and produces double domain particles consisting of the particle core and a porous poorly crystalline shell. It is thought that such unique rust structure produced by titanium addition contributes to the protective properties of rust layer of the weathering steel

Iron Isotopes in Spherical Hematite and Goethite Concretions from the Navajo Sandstone (Utah, USA): A Prospective Study for "Martian Blueberries"

Science.gov (United States)

Busigny, V.; Dauphas, N.

2006-03-01

Iron isotopes of terrestrial hematite and goethite concretions provide clues on fluid transport, reservoir sizes, redox variations and biotic versus abiotic processes. This opens several avenues of research for future work on Martian blueberries.

Ab Initio Molecular Dynamics of Uranium Incorporated in Goethite (α-FeOOH): Interpretation of X-ray Absorption Spectroscopy of Trace Polyvalent Metals.

Science.gov (United States)

Kerisit, Sebastien; Bylaska, Eric J; Massey, Michael S; McBriarty, Martin E; Ilton, Eugene S

2016-11-21

Incorporation of economically or environmentally consequential polyvalent metals into iron (oxyhydr)oxides has applications in environmental chemistry, remediation, and materials science. A primary tool for characterizing the local coordination environment of such metals, and therefore building models to predict their behavior, is extended X-ray absorption fine structure spectroscopy (EXAFS). Accurate structural information can be lacking yet is required to constrain and inform data interpretation. In this regard, ab initio molecular dynamics (AIMD) was used to calculate the local coordination environment of minor amounts of U incorporated in the structure of goethite (α-FeOOH). U oxidation states (VI, V, and IV) and charge compensation schemes were varied. Simulated trajectories were used to calculate the U L III -edge EXAFS function and fit experimental EXAFS data for U incorporated into goethite under reducing conditions. Calculations that closely matched the U EXAFS of the well-characterized mineral uraninite (UO 2 ), and constrained the S 0 2 parameter to be 0.909, validated the approach. The results for the U-goethite system indicated that U(V) substituted for structural Fe(III) in octahedral uranate coordination. Charge balance was achieved by the loss of one structural proton coupled to addition of one electron into the solid (-1 H + , +1 e - ). The ability of AIMD to model higher energy states thermally accessible at room temperature is particularly relevant for protonated systems such as goethite, where proton transfers between adjacent octahedra had a dramatic effect on the calculated EXAFS. Vibrational effects as a function of temperature were also estimated using AIMD, allowing separate quantification of thermal and configurational disorder. In summary, coupling AIMD structural modeling and EXAFS experiments enables modeling of the redox behavior of polyvalent metals that are incorporated in conductive materials such as iron (oxyhydr)oxides, with

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.

Synthesis and super capacitance of goethite/reduced graphene oxide for supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Xu, Huan; Hu, Zhongai, E-mail: zhongai@nwnu.edu.cn; Lu, Ailian; Hu, Yingying; Li, Li; Yang, Yuying; Zhang, Ziyu; Wu, Hongying

2013-08-15

We report a one-step fabrication of α-iron oxyhydroxide/reduced graphene oxide (α-FeOOH/rGO) composites, in which the ferrous sulfate (FeSO{sub 4}·7H{sub 2}O) are used as the iron raw and reducing agent to grow goethite (α-FeOOH) and reduce graphite oxide (GO) to rGO in the same time. The morphology, composition and microstructure of the as-obtained samples are systematically characterized by thermogravimetric (TG) analysis, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and FT-IR. Moreover, their electrochemical properties are investigated using cyclic voltammetry and galvanostatic charge/discharge techniques. The specific capacitance of 452 F g{sup −1} is obtained at a specific current of 1 A g{sup −1} when the mass ratio of α-FeOOH to rGO is up to 80.3:19.7. In addition, the α-FeOOH/rGO composite electrodes exhibit the excellent rate capability (more than 79% retention at 10 A g{sup −1} relative to 1 A g{sup −1}) and well cycling stability (13% capacitance decay after 1000 cycles). These results suggest the importance and great potential of α-FeOOH/rGO composites in the applications of high-performance energy-storage. - Graphical abstract: α-FeOOH loaded on rGO sheets reveals excellent super-capacitive performance. Display Omitted - Highlights: • A one-step synthesis of the environmentally friendly electrode material is designed. • Ferrous sulfate is used as both iron raw source of goethite and reductant of GO. • α-FeOOH nanorods loaded on rGO sheets arrange into a raft-like array. • The resultant composite exhibits high specific capacitance and long cycling stability.

Synthesis and super capacitance of goethite/reduced graphene oxide for supercapacitors

International Nuclear Information System (INIS)

Xu, Huan; Hu, Zhongai; Lu, Ailian; Hu, Yingying; Li, Li; Yang, Yuying; Zhang, Ziyu; Wu, Hongying

2013-01-01

We report a one-step fabrication of α-iron oxyhydroxide/reduced graphene oxide (α-FeOOH/rGO) composites, in which the ferrous sulfate (FeSO 4 ·7H 2 O) are used as the iron raw and reducing agent to grow goethite (α-FeOOH) and reduce graphite oxide (GO) to rGO in the same time. The morphology, composition and microstructure of the as-obtained samples are systematically characterized by thermogravimetric (TG) analysis, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and FT-IR. Moreover, their electrochemical properties are investigated using cyclic voltammetry and galvanostatic charge/discharge techniques. The specific capacitance of 452 F g −1 is obtained at a specific current of 1 A g −1 when the mass ratio of α-FeOOH to rGO is up to 80.3:19.7. In addition, the α-FeOOH/rGO composite electrodes exhibit the excellent rate capability (more than 79% retention at 10 A g −1 relative to 1 A g −1 ) and well cycling stability (13% capacitance decay after 1000 cycles). These results suggest the importance and great potential of α-FeOOH/rGO composites in the applications of high-performance energy-storage. - Graphical abstract: α-FeOOH loaded on rGO sheets reveals excellent super-capacitive performance. Display Omitted - Highlights: • A one-step synthesis of the environmentally friendly electrode material is designed. • Ferrous sulfate is used as both iron raw source of goethite and reductant of GO. • α-FeOOH nanorods loaded on rGO sheets arrange into a raft-like array. • The resultant composite exhibits high specific capacitance and long cycling stability

Do goethite surfaces really control the transport and retention of multi-walled carbon nanotubes in chemically heterogeneous porous media?

Science.gov (United States)

Transport and retention behavior of multiwalled carbon nanotubes (MWCNTs) was studied in mixtures of negatively charged quartz sand (QS) and positively charged goethite-coated sand (GQS) to assess the role of chemical heterogeneity. The linear equilibrium sorption model provided a good description o...

Transformation of Goethite to Hematite Nanocrystallines by High Energy Ball Milling

Directory of Open Access Journals (Sweden)

O. M. Lemine

2014-01-01

Full Text Available α-Fe2O3 nanocrystallines were prepared by direct transformation via high energy ball milling treatment for α-FeOOH powder. X-ray diffraction, Rietveld analysis, TEM, and vibrating sample magnetometer (VSM are used to characterize the samples obtained after several milling times. Phase identification using Rietveld analysis showed that the goethite is transformed to hematite nanocrystalline after 40 hours of milling. HRTEM confirm that the obtained phase is mostly a single-crystal structure. This result suggested that the mechanochemical reaction is an efficient way to prepare some iron oxides nanocrystallines from raw materials which are abundant in the nature. The mechanism of the formation of hematite is discussed in text.

Liberation of Adsorbed and Co-Precipitated Arsenic from Jarosite, Schwertmannite, Ferrihydrite, and Goethite in Seawater

Directory of Open Access Journals (Sweden)

Rodrigo Alarcón

2014-07-01

Full Text Available Sea level rise is able to change the geochemical conditions in coastal systems. In these environments, transport of contaminants can be controlled by the stability and adsorption capacity of iron oxides. The behavior of adsorbed and co-precipitated arsenic in jarosite, schwertmannite, ferrihydrite, and goethite in sea water (common secondary minerals in coastal tailings was investigated. The aim of the investigation was to establish As retention and transport under a marine flood scenario, which may occur due to climate change. Natural and synthetic minerals with co-precipitated and adsorbed As were contacted with seawater for 25 days. During this period As, Fe, Cl, SO4, and pH levels were constantly measured. The larger retention capability of samples with co-precipitated As, in relation with adsorbed As samples, reflects the different kinetics between diffusion, dissolution, and surface exchange processes. Ferrihydrite and schwertmannite showed good results in retaining arsenic, although schwertmannite holding capacity was enhanced due its buffering capacity, which prevented reductive dissolution throughout the experiment. Arsenic desorption from goethite could be understood in terms of ion exchange between oxides and electrolytes, due to the charge difference generated by a low point-of-zero-charge and the change in stability of surface complexes between synthesis conditions and natural media.

ATR-FTIR and density functional theory study of the structures, energetics, and vibrational spectra of phosphate adsorbed onto goethite.

Science.gov (United States)

Kubicki, James D; Paul, Kristian W; Kabalan, Lara; Zhu, Qing; Mrozik, Michael K; Aryanpour, Masoud; Pierre-Louis, Andro-Marc; Strongin, Daniel R

2012-10-16

Periodic plane-wave density functional theory (DFT) and molecular cluster hybrid molecular orbital-DFT (MO-DFT) calculations were performed on models of phosphate surface complexes on the (100), (010), (001), (101), and (210) surfaces of α-FeOOH (goethite). Binding energies of monodentate and bidentate HPO(4)(2-) surface complexes were compared to H(2)PO(4)(-) outer-sphere complexes. Both the average potential energies from DFT molecular dynamics (DFT-MD) simulations and energy minimizations were used to estimate adsorption energies for each configuration. Molecular clusters were extracted from the energy-minimized structures of the periodic systems and subjected to energy reminimization and frequency analysis with MO-DFT. The modeled P-O and P---Fe distances were consistent with EXAFS data for the arsenate oxyanion that is an analog of phosphate, and the interatomic distances predicted by the clusters were similar to those of the periodic models. Calculated vibrational frequencies from these clusters were then correlated with observed infrared bands. Configurations that resulted in favorable adsorption energies were also found to produce theoretical vibrational frequencies that correlated well with experiment. The relative stability of monodentate versus bidentate configurations was a function of the goethite surface under consideration. Overall, our results show that phosphate adsorption onto goethite occurs as a variety of surface complexes depending on the habit of the mineral (i.e., surfaces present) and solution pH. Previous IR spectroscopic studies may have been difficult to interpret because the observed spectra averaged the structural properties of three or more configurations on any given sample with multiple surfaces.

Sequestration of uranium on fabricated aluminum co-precipitated with goethite (Al-FeOOH)

Energy Technology Data Exchange (ETDEWEB)

Sun, Yubing; Yang, Shubin; Wang, Qi; Wang, Xiangke [Chinese Academy of Science, Hefei (China). Key Laboratory of Novel Thin Film Solar Cells; Alsaedi, Ahmad [King Abdulaziz Univ., Jeddah (Saudi Arabia). Nonlinear Analysis and Applied Mathematics (NAAM) Research Group

2014-11-01

Aluminum co-precipitated with goethites (Al-FeOOHs) are ubiquitous within (sub)-surface environments, which are considered one of the most important sinks for radionuclide pollution management. Accordingly, various mole ratios Al-FeOOH were synthesized and characterized by XRD, FT-IR, TEM, specific surface area and potentiometric acid-base titration. According to XRD and TEM images, the morphology of Al-FeOOH was transformed from acicular-like goethite to cotton-like gibbsite with increasing Al content. The adsorption and sequential desorption of U(VI) on Al-FeOOHs were conducted by batch techniques under N{sub 2} conditions. The batch adsorption results showed that the adsorption of U(VI) on Al-FeOOHs slightly increased at pH < 4.0, then the significant increase of U(VI) adsorption was observed at pH from 4.0 to 7.0, whereas the suppressed adsorption at pH > 8.0 was due to the electrostatic repulsion between negative charge surface and negative carbonato-complexes. The adsorption of U(VI) on Al-FeOOHs was independent of ionic strength at pH > 5.0, indicating that the inner-sphere surface complexation predominated their adsorption behaviors, whereas U(VI) adsorption on Al-FeOOH could be the outer-sphere surface/cation exchange reaction. The sequential extraction texts showed that the desorption of U(VI) from Al-FeOOHs decreased with increasing Al content. These findings highlighted the effect of Al content on the sequestration and immobilization of U(VI) onto Al-FeOOHs from (sub)-surface environments in pollution management.

Comparison of the mineralogical effects of an experimental forest fire on a goethite/ferrihydrite soil with a topsoil that contains hematite, maghemite and goethite

DEFF Research Database (Denmark)

Nørnberg, Per; Vendelboe, Anders Lindblad; Gunnlaugsson, Haraldur Pall

2009-01-01

as the result of high temperature as found after forest fires. However, a body of evidence argues against these sites having been exposed to fire. In an attempt to get closer to an explanation of this Fe mineralogy, an experimental forest fire was produced. The results showed a clear mineralogical zonation down...... to 10 cm depth. This was not observed at the natural sites, which contained a mixture of goethite/ferrihydrite, hematite and maghemite down to 20 cm depth. The experimental forest fire left charcoal and ashes at the topsoil, produced high pH and decreased organic matter content, all of which...... is in contrast to the natural sites. The conclusion from this work is that the mineralogy of these sites is not consistent with exposure to forest fire, but may instead result from long-term transformation in a reducing environment, possibly involving microbiology....

Transformation of goethite/ferrihydrite to hematite and maghemite under temperate humid conditions in Denmark

DEFF Research Database (Denmark)

Nørnberg, Per; Finster, Kai; Gunnlaugsson, Haraldur Pall

2012-01-01

At a number of sandy soil sites in Mid Jutland, Denmark, with iron content of 1-2%, very red spots (Munsell colour: dusky red 10R 3/4) of a few square meters are found. These spots are most likely due to burning events. After the fire ashes raised pH. This dispersed silt and clay size soil...... particles which were then transported with seepage water down into lower soil horizons. These particles contain hematite and maghemite due to influence of the fire. However, a long-standing unresolved question is how hematite and maghemite can also be present along with goethite and ferrihydrite...

Coating a polystyrene well-plate surface with synthetic hematite, goethite and aluminium hydroxide for cell mineral adhesion studies in a controlled environment

International Nuclear Information System (INIS)

Pouran, Hamid M.; Banwart, Steve A.; Romero-Gonzalez, Maria

2014-01-01

Highlights: • Hematite, goethite and aluminium hydroxide were synthesized and characterize. • Polystyrene cell culture well plates were coated with the synthetic metal oxides. • The coated well plates proven to be completely identical to the synthetic minerals. • The coating method is compatible with what occurs in aquifers with metal oxides. • This method provides a key experimental part for cell mineral adhesion studies. - Abstract: Iron and aluminium oxides are available in many climatic regions and play a vital role in many environmental processes, including the interactions of microorganisms in contaminated soils and groundwater with their ambient environment. Indigenous microorganisms in contaminated environments often have the ability to degrade or transform those contaminants, a concept that supports an in situ remediation approach and uses natural microbial populations in order to bio-remediate polluted sites. These metal oxides have a relatively high pH-dependent surface charge, which makes them good candidates for studying mineral–bacterial adhesion. Given the importance of understanding the reactions that occur at metal oxide and bacterial cell interfaces and to investigate this phenomenon further under well-characterized conditions, some of the most common iron and aluminium oxides; hematite, goethite and aluminium hydroxide, were synthesized and characterized and a coating method was developed to coat polystyrene well-plates as a surface exposable to bacterial adhesion with these minerals (non-treated polystyrene-12 well-plates which are used for cell cultures). The coating process was designed in a way that resembles naturally coated surfaces in aquifers. Hematite, Fe 2 O 3 , was synthesized from acidic FeCl 3 solution, while goethite, FeOOH, and aluminium hydroxide, Al(OH) 3 , were prepared from an alkaline solution of Fe(NO 3 ) 3 and Al(NO 3 ) 3 . They were further characterized using X-ray diffraction (XRD), Fourier transform infrared

Enhanced photoanisotropic response in azopolymer doped with elongated goethite nanoparticles

International Nuclear Information System (INIS)

Nedelchev, L; Nazarova, D; Berberova, N; Mateev, G; Kostadinova, D; Mariño-Fernández, R; Salgueiriño, V; Schmool, D

2016-01-01

We present a study of the photoinduced birefringence in nanocomposite films of an azopolymer (PAZO) doped with goethite (a-FeOOH, a characteristic antiferromagnetic material) nanoparticles (NPs). The NPs had an elongated shape with a size 15×150 nm, i.e., a ratio of 1:10. Samples were prepared with different concentrations of the NPs in the azopolymer varying from 0% (undoped azopolymer film) to 15 wt %. An unusual dependence of the birefringence on the concentration was observed - two peaks of enhancement at 1 % and at 10 % concentration. Our previous studies on ZnO and SiO 2 NP have indicated only one peak of increase at low concentrations - 0.5 wt % and 2 wt %, respectively. This effect could be related to the elongated shape of the nanoparticles and the presence of two characteristic NPs sizes - 15 and 150 nm. Moreover, the birefringence increase for the samples with 10 wt % NPs concentration (compared with the non-doped samples) was rather significant - nearly 70%. (paper)

Simultaneous sequestration of uranyl and arsenate at the goethite/water interface

International Nuclear Information System (INIS)

Fang Yuan; Yawen Cai; Shitong Yang; Zhiyong Liu; Lanhua Chen; Yue Lang; Shuao Wang; Xiangke Wang; Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Suzhou; North China Electric Power University, Beijing

2017-01-01

This study highlights the simultaneous sequestration of U(VI) and arsenate at the goethite/water interface. The uptake trends and speciation of these two components were related with molar arsenate/U(VI) ratio, solution pH, contact order and aging time. A metastable [UO_2(H_2AsO_4)_2·H_2O] was observed after 3 days and then this solid completely transformed into Na_2(UO_2AsO_4)_2·3H_2O after 7 days. The disodium ethylenediamine tetraacetate ligand gave rise to the complete dissolution of Na_2(UO_2AsO_4)_2·3H_2O phase and the release of U(VI) and arsenate back into the solution. The experimental findings facilitated us better comprehend the migration and fate of coexisting U(VI) and arsenate in the aquatic environment. (author)

D/H of late Miocene meteoric waters in Western Australia: Paleoenvironmental conditions inferred from the δD of (U-Th)/He-dated CID goethite

Science.gov (United States)

Yapp, Crayton J.; Shuster, David L.

2017-09-01

Nineteen (U-Th)/He ages were determined for eight samples from a core drilled in an ore-grade channel iron deposit (CID) of the Robe Pisolite (Robe Formation) of Mesa J in Western Australia. With one exception, uncorrected ages of the analyzed aliquots range from 6.7(±0.4) Ma to 30.2(±3.1) Ma, while molar ratios of Th/U range from 0.42 to 5.06. The exception is an aliquot with an apparent age of 2.7 Ma and Th/U of 5.70. A three-component mixing model involving one generation of goethite and two generations of hematite suggests that the age of crystallization of the oolitic goethites is ∼7(±1) Ma. If so, the goethites have effectively been closed systems for ∼7 million years and should preserve a stable hydrogen isotope record of late Miocene rainfall in the vicinity of Mesa J. Cenozoic movement of the Australian continent had placed Mesa J and environs in the subtropics at a paleolatitude of about 29 °S during the late Miocene. Al-adjusted δD values of oolitic goethite in the eight CID samples range from -153‰ to -146‰ and imply that the δD of the late Miocene meteoric waters ranged from -61‰ to -53‰, with an average of -56‰. These relatively negative δD values might indicate that near-coastal, late Miocene rain was derived primarily from summer-season tropical cyclones with storm tracks that extended into the subtropics of western Australia. The postulated late Miocene tropical cyclones would have occurred more often and/or exhibited greater intensity at a paleolatitude of 29 °S than is the case for modern sites at approximately 30 °S on the west coast of Australia (e.g., Perth). Higher fluxes of meteoric water in the Miocene summers would have facilitated dissolution and removal of BIF-sourced silica with concomitant enrichment in oxidized Fe. Moreover, wetter late Miocene summers could have promoted multiple cycles of microbially mediated dissolution and recrystallization of Fe(III) oxides in the aerobic systems. The oolitic textures may

Unraveling climatic changes from intraprofile variation in oxygen and hydrogen isotopic composition of goethite and kaolinite in laterites: An integrated study from Yaou, French Guiana

Energy Technology Data Exchange (ETDEWEB)

Girard, J.P.; Freyssinet, P.; Chazot, G.

2000-02-01

An integrated study of O and H isotopes in the latertic profile of Yaou, French Guiana, was undertaken to investigate the usefulness of stable isotopes as tracers of climatic changes in continental environments. The studied profile is composed of a 27 m thick saprolite, mostly developed in the past under wet-and-dry tropical climate in association with a duricrust, overlain by a 3 m thick yellow latosol formed more recently under present equatorial hot and humid climate. {delta}{sup 18}O-{delta}D values determined for weathering goethite (pseudomorphs after pyrite) and kaolinite (microcrystalline clay groundmass) throughout the 30 m deep profile reflect formation temperatures consistent with present (25 C) and realistic past climatic temperatures (20 C--30 C), indicating that weathering minerals formed in isotopic equilibrium with their genetic environment and were not subjected to significant isotope exchange after formation. A distinct shift downward from low to high {delta}{sup 18}O-{delta}D values occurs around 20 m depth in the saprolite. It is interpreted as recording the change from the past tropical to the present equatorial climate. Goethite and kaolinite in the 5--10 m thick saprolite interval immediately above the active basement weathering front are in isotopic equilibrium with modern water and must have formed under present equatorial-humid conditions. In contrast, goethite and kaolinite found higher up on the saprolite and in the duricrust formed in the past under tropical wet and dry climate from waters distinctly depleted in {sup 18}O and D relative to modern water. The marked depletion of paleo-meteoric water at Yaou most likely reflects a more contrasted or monsoonal character of the ancient tropical climate. The present study shows that ancient weathering minerals in lateritic profiles preserve their {delta}{sup 18}O-{delta}D values and carry a time signal. The time signal is best expressed in minerals formed rapidly at the weathering front and

Silicic acid competes for dimethylarsinic acid (DMA) immobilization by the iron hydroxide plaque mineral goethite.

Science.gov (United States)

Kersten, Michael; Daus, Birgit

2015-03-01

A surface complexation modeling approach was used to extend the knowledge about processes that affect the availability of dimethylarsinic acid (DMA) in the soil rhizosphere in presence of a strong sorbent, e.g., Fe plaques on rice roots. Published spectroscopic and molecular modeling information suggest for the organoarsenical agent to form bidentate-binuclear inner-sphere surface complexes with Fe hydroxides similar to the inorganic As oxyanions. However, since also the ubiquitous silicic acid oxyanion form the same bidentate binuclear surface complexes, our hypothesis was that it may have an effect on the adsorption of DMA by Fe hydroxides in soil. Our experimental batch equilibrium data show that DMA is strongly adsorbed in the acidic pH range, with a steep adsorption edge in the circumneutral pH region between the DMA acidity constant (pKa=6.3) and the point of zero charge value of the goethite adsorbent (pHpzc=8.6). A 1-pK CD-MUSIC surface complexation model was chosen to fit the experimental adsorption vs. pH data. The same was done for silicic acid batch equilibrium data with our goethite adsorbent. Both model parameters for individual DMA and silicic acid adsorption were then merged into one CD-MUSIC model to predict the binary DMA+Si adsorption behavior. Silicic acid (500 μM) was thus predicted by the model to strongly compete for DMA with up to 60% mobilization of the latter at a pH6. This model result could be verified subsequently by experimental batch equilibrium data with zero adjustable parameters. The thus quantified antagonistic relation between DMA and silicic acid is discussed as one of factors to explain the increase of the DMA proportion in rice grains as observed upon silica fertilization of rice fields. Copyright © 2014 Elsevier B.V. All rights reserved.

Influence of silicate ions on the formation of goethite from green rust in aqueous solution

International Nuclear Information System (INIS)

Kwon, Sang-Koo; Kimijima, Ken'ichi; Kanie, Kiyoshi; Suzuki, Shigeru; Muramatsu, Atsushi; Saito, Masatoshi; Shinoda, Kozo; Waseda, Yoshio

2007-01-01

We investigated the influence of silicate ions on the formation of goethite converted from hydroxysulphate green rust, which was synthesized by neutralizing mixed solution of Fe 2 (SO 4 ) 3 and FeSO 4 with NaOH solution, by O 2 in an aqueous solution. The pH and oxidation-reduction potential of the suspension and the Fe and Si concentrations in supernatant solutions were analyzed. X-ray diffraction results for the solid particles formed during the conversion were consistent with the results of the solution analyses. The results indicated that silicate ions suppressed the conversion from green rust to α-FeOOH and distorted the linkages of FeO 6 octahedral units in the α-FeOOH structure

Effect of interactions between Co(2+) and surface goethite layer on the performance of α-FeOOH coated hollow fiber ceramic ultrafiltration membranes.

Science.gov (United States)

Zhu, Zhiwen; Zhu, Li; Li, Jianrong; Tang, Jianfeng; Li, Gang; Hsieh, Yi-Kong; Wang, TsingHai; Wang, Chu-Fang

2016-03-15

The consideration of water energy nexus inspires the environmental engineering community to pursue a more sustainable strategy in the wastewater treatment. One potential response would be to enhance the performance of the low-pressure driven filtration system. To reach this objective, it is essential to have a better understanding regarding the surface interaction between the target substance and the surface of membrane. In this study, the hollow fiber ceramic membranes were coated with a goethite layer in order to enhance the Co(2+) rejection. Experimental results indicate that higher Co(2+) rejections are always accompanied with the significant reduction in the permeability. Based on the consideration of electroviscous effect, the surface interactions including the induced changes in viscosity, pore radius and Donnan effect in the goethite layer are likely responsible for the pH dependent behaviors in the rejection and permeability. These results could be valuable references to develop the filtration system with high rejection along with acceptable degree of permeability in the future. Copyright © 2015 Elsevier Inc. All rights reserved.

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

Science.gov (United States)

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

Study of the radium sorption/desorption on goethite

International Nuclear Information System (INIS)

Bassot, S.; Stammose, D.; Mallet, C.; Lefebvre, C.; Ferreux, J.-M.

2000-01-01

The oxi-hydroxides, present at trace level in uranium mill tailings, are responsible of about 70% of the 226 radium sorption, half being fixed on crystallized forms. This radionuclide (half time=1622y), present at high level (50 to 100kBq.kg -1 ), can be released in groundwater, involving a possible contamination of the food chain (actual concentration limit=0.37Bq.1 -1 ). So, it is very important to point out the mechanisms of the radium sorption/desorption on crystallized oxi-hydroxides as a function of chemical conditions of the system. The radium sorption on synthetic goethite α-FeOOH has been studied as a function of contact time, initial radium activity, pH, sodium and calcium concentrations. The results show that, after one hour of contact time (necessary to reach equilibrium), the radium sorption increases widely in a pH range 6-7. The increase of Na + concentration is without influence on the radium sorption, indicating the low interactions between sodium and surface sites. At the opposite, the presence of calcium in solution decreases widely the radium sorption, that indicates a competition between calcium and radium for the same kind of sorption sites of the oxi-hydroxide surface. The percentage of radium desorbed increases widely with time, from 1 to 120h and becomes constant at a time higher than 120h. This long equilibrium time for desorption in comparison with sorption one can be explain by a local evolution of the sorption sites of the solid, which become less accessible for the solution in contact. (author)

Elementary and isotopic geochemistry of vein goethite in laterite-gossanic crusts from the Igarape Bahia gold mine (Carajas, Brazil)

International Nuclear Information System (INIS)

Costa, Marcondes Lima da; Schumann, Thomas; Poellmann, Herbert

1996-01-01

The lateritic crusts of the gold mine from the Igarape Bahia, in Carajas, situated at Para state, Brazil, present themselves frequently sectioned by the goethite sub-vertical veins. The veins have the following measures: until 10 cm of thickness and more than 6 m of length. This work aims to characterize the textural, mineralogical and chemical aspects of these veins, in order to understand its evolution, mainly the relation with the laterites and its geological importance, including the aspects referents to the mineral prospecting. (author)

Variabilidade de goethita e hematita via dissolução redutiva em solos de região tropical e subtropical Goethite and hematite variability via reductive dissolution in soils from tropical and subtropical regions

Directory of Open Access Journals (Sweden)

Alberto Vasconcellos Inda Junior

2005-12-01

combinou baixa substituição por Al3+ e alta ASE. A caracterização de populações heterogêneas de goethita pode ampliar a utilização deste óxido como indicador de processos pedogênicos em solos poligenéticos, bem como contribuir para um melhor entendimento do comportamento químico e físico desses solos.Iron oxides from 22 soil samples (19 from argillic B horizons; one from a plinthic B horizon; one from a cambic horizon and one from a C horizon were subjected to selective dissolution with sodium dithionite-citrate-bicarbonate at 20 ºC in time intervals of 5 to 3,840 minutes. Mean coherence lengths (MCL, specific surface area (SSA and iron by aluminum substitution (Al3+-substitution of goethite and hematite in untreated sub-samples and in selected sub-samples treated during selective dissolution were estimated by X ray diffraction analysis (XRD. The control of remaining goethite and hematite phases after each time interval of selective dissolution was carried out by differential X ray diffraction (DXRD. The crystal dissolution kinetics was described by segmentation of the iron dissolution curve as a time function at the intervals where dissolution occurred linearly. Dissolution rates of each linear segment were obtained by the angular coefficient of the straight line of each linear segment. In the latossolic goethitic samples, this methodology discriminated different phases of goethite (heterogeons populations regarding Al3+-substitution, MCL and SSA, making possible to classify goethite stability degrees (low, medium, high, and very high stability. Goethite samples from young pedogenic environments and latossolic hematitic samples were characterized by higher crystal homogeneity, which were classified as being of low and medium stability. In goethitic samples, crystal proportion with high stability (high Al3+-substitution and crystallinity in each population showed positive association with gibbisite proportion compared to caulinite in the samples. Hematite

Nano size crystals of goethite, α-FeOOH: Synthesis and thermal transformation

Science.gov (United States)

Christensen, Axel Nørlund; Jensen, Torben R.; Bahl, Christian R. H.; DiMasi, Elaine

2007-04-01

An aqueous suspension of amorphous iron(III) hydroxide was kept at room temperature (298 K) for 23 years. During this period of time the pH of the liquid phase changed from 4.3 to 2.85, and nano size crystals of goethite, α-FeOOH crystallised from the amorphous iron(III) hydroxide. Transmission electron microscopy (TEM) investigations, Mössbauer spectra, and powder X-ray diffraction using Co K α radiation showed that the only iron containing crystalline phase present in the recovered product was α-FeOOH. The size of these nano particles range from 10 to 100 nm measured by TEM. The thermal decomposition of α-FeOOH was investigated by time-resolved in situ synchrotron radiation powder X-ray diffraction and the data showed that the sample of α-FeOOH transformed to α-Fe 2O 3 in the temperature range 444-584 K. A quantitative phase analysis shows the increase in scattered X-ray intensity from α-Fe 2O 3 to follow the decrease of intensity from α-FeOOH in agreement with the topotactic phase transition.

Unraveling climatic changes from intra-profile variation in oxygen and hydrogen isotopic composition of goethite and kaolinite in laterites: An integrated study from Yaou, French Guiana

Science.gov (United States)

Girard, Jean-Pierre; Freyssinet, Philippe; Chazot, Gilles

2000-02-01

An integrated study of O and H isotopes in the lateritic profile of Yaou, French Guiana, was undertaken to investigate the usefulness of stable isotopes as tracers of climatic changes in continental environments. The studied profile is composed of a 27 m thick saprolite, mostly developed in the past under wet-and-dry tropical climate in association with a duricrust, overlain by a 3 m thick yellow latosol formed more recently under present equatorial hot and humid climate. δ 18O-δD values determined for weathering goethite (pseudomorphs after pyrite) and kaolinite (microcrystalline clay groundmass) throughout the 30 m deep profile reflect formation temperatures consistent with present (25°C) and realistic past climatic temperatures (20°C-30°C), indicating that weathering minerals formed in isotopic equilibrium with their genetic environment and were not subjected to significant isotope exchange after formation. A distinct shift downward (2‰ for δ 18O, 15‰ for δD) from low to high δ 18O-δD values occurs around 20 m depth in the saprolite. It is interpreted as recording the change from the past tropical to the present equatorial climate. Goethite and kaolinite in the 5-10 m thick saprolite interval immediately above the active basement weathering front are in isotopic equilibrium with modern water and must have formed under present equatorial-humid conditions. In contrast, goethite and kaolinite found higher up in the saprolite and in the duricrust formed in the past under tropical wet and dry climate from waters distinctly depleted in 18O and D relative to modern water. The marked depletion of paleo-meteoric water at Yaou most likely reflects a more contrasted or "monsoonal" character of the ancient tropical climate. The present study shows that ancient weathering minerals in lateritic profiles preserve their δ 18O-δD values and carry a time signal. The time signal is best expressed in minerals formed rapidly at the weathering front and not subjected

Mineralogical effects of an experimental forest fire on a goethite/ferrihydrite soil - an attempt to solve the presence of hematite and maghemite in topsoils in a temperate region

Science.gov (United States)

Nørnberg, Per; Vendelboe, Anders L.; Gunnlaugsson, Haraldur P.; Merrison, Jonathan P.; Finster, Kai; Jensen, Svend K.

2010-05-01

Isolated soil spots, a few square metres in size, as red as Munsell colour 10R ¾ are found in Denmark. These spots are well known as places that have been exposed to fire. However, a long-standing unresolved puzzle is the presence of extended areas with high iron content (8-40 %) where goethite and ferrihydrite are present in the topsoil along with hematite and maghemite. Hematite and particularly maghemite would normally not be expected to occur under the temperate humid Danish climate, but be interpreted as the result of high temperature as found in tropical areas or after forest fires. However, a body of evidence argues against these sites having been exposed to fire. In an attempt to get closer to an explanation of this iron mineralogy, an experimental forest fire was produced. The results showed a clear mineralogical zonation down to 10 cm depth. This was not observed at the natural sites, which contained a uniform mixture of goethite/ferrihydrite, hematite and maghemite down to 20 cm depth. The experimental forest fire furthermore left charcoal and ashes at the topsoil, produced high pH and decreased organic matter content, all of which is in contrast to the natural sites. Physical and chemical date as well as XRD, Mössbauer spectroscopic data and TEM micrographs from the sites will be presented. The conclusion from this work is that the mineralogy of these sites is not consistent with exposure to fire, but may rather result from long term transformation within a reducing environment, possibly involving microorganisms. References: Nørnberg, P., Vendelboe, A.L., Gunnlaugsson, H.P., Merrison, J.P., Finster, K., Jensen, S.K. 2009 Mineralogy after an experimental forest fire on Quaternary soil goethite, compared with a hematite, maghemite, goethite containing topsoil. Clay Minerals, 44, 239-247. Nørnberg, P., Gunnlaugsson, H.P., Merrison, J.P., Vendelboe, A.L. 2009: Salten Skov I: A Martian dust analogue. Planetary and Space Science, 57, 628-631. Nørnberg, P

Surface complexation modelling: Experiments on sorption of nickel on quartz, goethite and kaolinite and preliminary tests on sorption of thorium on quartz

Energy Technology Data Exchange (ETDEWEB)

Puukko, E.; Hakanen, M. [Univ. of Helsinki (Finland). Dept. of Chemistry. Lab. of Radiochemistry

1997-09-01

The aim of the work was to study the sorption behaviour of Ni on quartz, goethite and kaolinite at different pH levels and in different electrolyte solutions of different strength. In addition preliminary experiments were made to study the sorption of thorium on quartz. The MUS quartz and Nilsiae quartz were analysed for MnO{sub 2} by neutron activation analysis (NAA) and the experimental results were modelled with the HYDRAQL computer model. 9 refs.

The influence of temperature on selenate adsorption by goethite

Energy Technology Data Exchange (ETDEWEB)

Kersten, M.; Vlasova, N. [Mainz Univ. (Germany). Geosciences Inst.

2013-08-01

Acid-base batch titration data up to 75 C were used to constrain a temperature-dependent 1-pK basic Stern model of the surface protonation reactions of goethite. Experimental data for the temperature dependence of pH{sub PZC} (as determined using the two-term Van't Hoff extrapolation) yielded a negative value of -44.9 kJ/mol for the surface protonation enthalpy, and therefore a shift of the zero point of charge towards lower pH values with increasing temperature. Batch titrations at selenate concentrations of between 10 and 100 {mu}M showed an increased degree of adsorption in the acidic pH range, which appeared to be sensitive to the ionic strength of the solution. The selenate adsorption edges shifted towards more acidic pH values with increasing temperature. A 1-pK charge distribution multi-site surface complexation (CD-MUSIC) model was applied, assuming the formation of an outer-spheric surface complex together with an inner-spheric one, in agreement with published spectroscopic information. The temperature behaviour of the intrinsic equilibrium constants were well represented by a linear Van't Hoff log K vs. 1/T plot, from which negative enthalpy values could be derived for both adsorption reactions. The adsorption of the selenate was therefore exothermic and became weaker with increasing temperature. The bidentate inner-spheric complex was more sensitive to rises in temperature (-70 kJ/mol), compared to the outer-spheric complex (-36 kJ/mol). The latter ultimately became the dominating adsorption process at the highest temperature studied. (orig.)

The influence of temperature on selenate adsorption by goethite

International Nuclear Information System (INIS)

Kersten, M.; Vlasova, N.

2013-01-01

Acid-base batch titration data up to 75 C were used to constrain a temperature-dependent 1-pK basic Stern model of the surface protonation reactions of goethite. Experimental data for the temperature dependence of pH PZC (as determined using the two-term Van't Hoff extrapolation) yielded a negative value of -44.9 kJ/mol for the surface protonation enthalpy, and therefore a shift of the zero point of charge towards lower pH values with increasing temperature. Batch titrations at selenate concentrations of between 10 and 100 μM showed an increased degree of adsorption in the acidic pH range, which appeared to be sensitive to the ionic strength of the solution. The selenate adsorption edges shifted towards more acidic pH values with increasing temperature. A 1-pK charge distribution multi-site surface complexation (CD-MUSIC) model was applied, assuming the formation of an outer-spheric surface complex together with an inner-spheric one, in agreement with published spectroscopic information. The temperature behaviour of the intrinsic equilibrium constants were well represented by a linear Van't Hoff log K vs. 1/T plot, from which negative enthalpy values could be derived for both adsorption reactions. The adsorption of the selenate was therefore exothermic and became weaker with increasing temperature. The bidentate inner-spheric complex was more sensitive to rises in temperature (-70 kJ/mol), compared to the outer-spheric complex (-36 kJ/mol). The latter ultimately became the dominating adsorption process at the highest temperature studied. (orig.)

Comments on the paper 'Sorption of radionickel to goethite: effect of water quality parameters and temperature' by Hu et al

International Nuclear Information System (INIS)

Yuh-Shan Ho

2011-01-01

Recently, Hu et al. [1]. published a paper with the above title. In section 'Effect of contact time', the authors stated, 'In order to study the sorption rate constant of Ni(II) to goethite, the pseudo-second-order rate equation was used to fit the kinetic sorption of Ni(II) to goethite' and referred to two self-citations published in 2008 and 2010 respectively [2, 3]. In fact, this kinetic model has already been published first in 1996 [4], and a modified model was presented in the following years to correct a mistake in the 1996 paper [5-7]. However the mistake in the model was duplicated by other researchers [8, 9]. In order to stop the proliferation of the mistake a comment has been made [10]. This type of error could be avoided if authors have had paid more attentions to details about the model from the original paper [11]. Accuracy in citing references is very important for the transmission of scientific knowledge. Citation errors reflect poorly on authors who republish original ideas that were already published. Hopefully, the identification of this type of problems will lead to improved accuracy in referencing [12]. Authors should make serious efforts to check the accuracy of references cited in their manuscripts as well as to read the original article before quoting it rather than citing from abstracts or cross-references [13]. It is recommended that more attention should be paid in preparing bibliographies and in checking quoted references [14]. (author)

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.

Nanocrack Formation in Hematite through the Dehydration of Goethite and the Carbon Infiltration from Biotar

Directory of Open Access Journals (Sweden)

Yoshiaki Kashiwaya

2010-01-01

Full Text Available The cracks in nano-order are generated and propagated when the combined water is released during the dehydration. If the nanopore can be utilized for a reaction site, the overall reaction can be extremely accelerated. On the other hand, it is well known that woody biomass is an attractive alternative fuel for the reduction of CO2 emission. However, the process of biomass pyrolysis is disturbed by the tar which causes a clogging in gas tubing system. Hata et al. found that the tar was consumed almost 100% in the iron ore layer having nanocrack or nanopore. The nanocracks formed in hematite crystals after dehydration of goethite were about 4 nm in width, which is in excellent agreement with the result of BET measurement. When the carbon deposited from tar into the nanocracks, reduction reactions were occurred simultaneously. The deposited carbons completely infilled into the nanocracks and the void in the sample.

Response to the comments of Y. S. Ho to the paper 'Sorption of radionickel to goethite. Effect of water quality parameters and temperature'

International Nuclear Information System (INIS)

Baowei Hu; ShaoXing University, ShaoXing, Zhejiang; Wen Cheng; Hui Zhang; Guodong Sheng; Chinese Academy of Sciences, Hefei

2011-01-01

In our published paper entitled 'Sorption of radionickel to goethite: effect of water quality parameters and temperature' published in JRNC 285 (2010) 389-398 [1], the sorption of radionickel to goethite as affected by various environmental conditions such as pH, humic substances, ionic strength and temperature on radionickel sorption has been investigated by using batch technique. The sorption mechanism of radionickel on goethite was discussed according to the experimental data and the fitting results of sorption isotherms by Langmuir, Freundlich and D-R models. Kinetic sorption data was fitted by a pseudo-second-order rate equation. Ho et al. firstly reported the pseudo-second-order rate equation [2, 3], and then further developed this frame work in their following works [4, 5]. In our previous research, we had ever cited the original paper about the sorption isotherms such as Langmuir or Freundlich models. However, the reviewers gave the comments that the models had been widely used and it was not necessary for us to cite the original paper about the sorption isotherm. Similar condition can be also observed for carbon nanotubes that there are a lot of papers about carbon nanotubes not citing the original paper reported by Iijima [6]. In our published paper [1], we think that the pseudo-second-order rate equation has been widely applied and the equation is now a famous model to fit the sorption kinetic data. However, it is essential for us to cite all the relative references accurately so as to transmit scientific knowledge more effectively. We are so sorry to the fact that the original papers [2, 3] were not cited in our published paper [1], but it is not meant to show the disrespect to the author Ho [2]. In our future work, we wish to cite the papers published by Ho whose work are interesting and useful to simulate the sorption kinetic data of metal ions at solid-water interfaces. The physicochemical behavior of radionickel in environment is quite important to

Adsorption of Pb(II) ions present in aqueous solution on the oxy hydroxides: boehmite (γ-AIOOH), goethite (α-FeOOH) and manganite (γ-MnOOH)

International Nuclear Information System (INIS)

Arreola L, J. E.

2013-01-01

Boehmite, goethite and manganite were synthesized by different methods and characterized using X-ray diffraction (XRD), infrared spectroscopy (IR), thermogravimetric study , N 2 physisorption measurements, scanning electron microscopy (Sem), semiquantitative elemental analysis (EDS), as well as additional studies were determined the surface active sites concentration and zero point of charge. Furthermore, we studied the Pb(II) ion adsorption capacity present in aqueous solution on these synthesized materials by batch-type experiments at room temperature, as a function of contact time between the phases liquid-solid system (adsorption kinetics), initial concentration of the adsorbate (adsorption isotherms), ph and temperature. The adsorption equilibrium time of adsorption processes in these studied systems was found at 60 minutes for boehmite and 30 minutes for goethite and manganite respectively after contacting the solid-liquid phase systems. The adsorption capacity of the lead ions on these adsorbent materials depended of lead concentration, ph and temperature of the systems. Were evaluated lead adsorption capacities in these materials to different contact times using an initial concentration of 20 mg/L of Pb(II) ions at ph = 4, the results of three systems were adjusted to second pseudo kinetic model order. With respect to the study of the adsorbate concentration effect, boehmite-Pb(II) and goethite-Pb(II) systems were adjusted to Langmuir isotherm model which proposes that the adsorption is carried out in a monolayer, moreover manganite-Pb(II) system was adjusted Temp kin isotherm model, which assumes that the adsorption heat of all the molecules in the layer decreases linearly with coverage due to adsorbent-adsorbate interactions and adsorption is characterized by a uniform distribution of the binding energies. Were studied the ph effect of Pb(II) ions solution on the adsorption capacity of such adsorbents, it was found that as the ph increases lead solution

Reversibility of sorption of plutonium-239 onto hematite and goethite colloids

International Nuclear Information System (INIS)

Lu, N.; Cotter, C.R.; Kitten, H.D.; Bentley, J.; Triay, I.R.

1998-01-01

Laboratory batch sorption experiments were conducted to evaluate: (1) sorption of plutonium-239 ( 239 Pu) on different iron oxide colloids (hematite and geothite), (2) sorption kinetics of colloidal Pu(IV) and soluble Pu(V) onto these two colloids, and (3) desorption of colloidal Pu(IV) and soluble Pu(V) from 239 Pu-loaded colloids as a function of time. Natural groundwater and carbonate-rich synthetic groundwater were used in this study. To examine the possible influence of bicarbonate on 239 Pu sorption, an additional set of experiments was conducted in sodium nitrate (NaNO 3 ) solutions under carbon dioxide free environments. Our results show that colloidal Pu(IV) as well as soluble Pu(V) was rapidly adsorbed by hematite and goethite colloids in both natural and synthetic groundwater. The amount of 239 Pu adsorbed by both iron oxide colloids in synthetic groundwater was higher than in natural groundwater. The presence of carbonate did not influence the sorption of 239 Pu. While sorption of soluble Pu(V) is a slow process, sorption of colloidal Pu(IV) occurs rapidly. Desorption of Pu from iron oxide colloids is much slower than the sorption processes. Our findings suggest that different sorption and desorption behaviors of 239 Pu by iron oxide colloids in groundwater may facilitate the transport of 239 Pu along potential flowpaths from the areas contaminated by radionuclide and release to the accessible environment. (orig.)

Method for Transformation of Weakly Magnetic Minerals (Hematite, Goethite into Strongly Magnetic Mineral (Magnetite to Improve the Efficiency of Technologies for Oxidized Iron Ores Benefication

Directory of Open Access Journals (Sweden)

Ponomarenko, O.

2015-03-01

Full Text Available A new method for relatively simple transformation of weakly magnetic minerals (goethite (α-FeOOH and hematite (α-Fe2O3 into strongly magnetic mineral (magnetite (Fe3O4 was developed. It was shown, that transformation of structure and magnetic characteristics of go ethite and hematite are realized in the presence of starch at relatively low temperatures (in the range of 300—600 °С. Obtained results open up new possibilities for development of effective technologies for oxidized iron ore beneficiation.

Neptunium redox behavior and sorption onto goethite and hematite in the presence of humic acids with different hydroquinone content

International Nuclear Information System (INIS)

Khasanova, A.B.; Kalmykov, St.N.; Perminova, I.V.; Clark, S.B.

2007-01-01

The effect of humic acids (HA) on neptunium redox behavior and sorption onto hematite, α-Fe 2 O 3 , and goethite, α-FeOOH, colloids was established in batch sorption experiments that were carried out in broad pH interval. The sorption isotherms were provided for two samples of HA: commercial sample of leonardite humic acid and its hydroquinone-enriched derivative obtained using formaldehyde copolycondensation. The distribution of Np fitted the distribution of hydroquinone-enriched HA at low pH values in case of both solids while the influence of parent HA on Np sorption was negligible. This is due to Np(V) reduction upon interaction with hydroquinone-enriched derivative having higher reducing capacity compared to the parent HA. The order of components addition was found to be significant for Np retention

Colloidal behavior of goethite nanoparticles modified with humic acid and implications for aquifer reclamation

Energy Technology Data Exchange (ETDEWEB)

Tiraferri, Alberto; Saldarriaga Hernandez, Laura Andrea; Bianco, Carlo; Tosco, Tiziana; Sethi, Rajandrea, E-mail: rajandrea.sethi@polito.it [Politecnico di Torino, Department of Land, Environment, and Infrastructure Engineering (DIATI) (Italy)

2017-03-15

Nanosized colloids of iron oxide adsorb heavy metals, enhance the biodegradation of contaminants, and represent a promising technology to clean up contaminated aquifers. Goethite particles for aquifer reclamation were recently synthesized with a coating of humic acids to reduce aggregation. This study investigates the stability and the mobility in porous media of this material as a function of aqueous chemistry, and it identifies the best practices to maximize the efficacy of the related remediation. Humic acid-coated nanogoethite (hydrodynamic diameter ∼90 nm) displays high stability in solutions of NaCl, consistent with effective electrosteric stabilization. However, particle aggregation is fast when calcium is present and, to a lesser extent, also in the presence of magnesium. This result is rationalized with complexation phenomena related to the interaction of divalent cations with humic acid, inducing rapid flocculation and sedimentation of the suspensions. The calcium dose, i.e., the amount of calcium ions with respect to solids in the dispersion, is the parameter governing stability. Therefore, more concentrated slurries may be more stable and mobile in the subsurface than dispersions of low particle concentration. Particle concentration during field injection should be thus chosen based on concentration and proportion of divalent cations in groundwater.

Development of Surface Complexation Models of Cr(VI) Adsorption on Soils, Sediments and Model Mixtures of Kaolinite, Montmorillonite, γ-Alumina, Hydrous Manganese and Ferric Oxides and Goethite

Energy Technology Data Exchange (ETDEWEB)

Koretsky, Carla [Western Michigan University

2013-11-29

Hexavalent chromium is a highly toxic contaminant that has been introduced into aquifers and shallow sediments and soils via many anthropogenic activities. Hexavalent chromium contamination is a problem or potential problem in the shallow subsurface at several DOE sites, including Hanford, Idaho National Laboratory, Los Alamos National Laboratory and the Oak Ridge Reservation (DOE, 2008). To accurately quantify the fate and transport of hexavalent chromium at DOE and other contaminated sites, robust geochemical models, capable of correctly predicting changes in chromium chemical form resulting from chemical reactions occurring in subsurface environments are needed. One important chemical reaction that may greatly impact the bioavailability and mobility of hexavalent chromium in the subsurface is chemical binding to the surfaces of particulates, termed adsorption or surface complexation. Quantitative thermodynamic surface complexation models have been derived that can correctly calculate hexavalent chromium adsorption on well-characterized materials over ranges in subsurface conditions, such pH and salinity. However, models have not yet been developed for hexavalent chromium adsorption on many important constituents of natural soils and sediments, such as clay minerals. Furthermore, most of the existing thermodynamic models have been developed for relatively simple, single solid systems and have rarely been tested for the complex mixtures of solids present in real sediments and soils. In this study, the adsorption of hexavalent chromium was measured as a function of pH (3-10), salinity (0.001 to 0.1 M NaNO3), and partial pressure of carbon dioxide(0-5%) on a suite of naturally-occurring solids including goethite (FeOOH), hydrous manganese oxide (MnOOH), hydrous ferric oxide (Fe(OH)3), γ-alumina (Al2O3), kaolinite (Al2Si2O5(OH)4), and montmorillonite (Na3(Al, Mg)2Si4O10(OH)2-nH2O). The results show that all of these materials can bind substantial quantities of

Application of surface complexation modelling: Nickel sorption on quartz, manganese oxide, kaolinite and goethite, and thorium on silica

International Nuclear Information System (INIS)

Olin, M.; Lehikoinen, J.

1997-12-01

The study is a follow-up to a previous modelling task on mechanistic sorption. The experimental work has been carried out at the Laboratory of Radiochemistry, University of Helsinki (HYRL), and the sorption modelling was performed using the HYDRAQL code. Parameters taken from the open literature were employed in the modelling phase. The thermodynamic data for aqueous solutions were extracted from the EQ3/6 database and subsequently modified for HYDRAQL where necessary. The experimental data were obtained from five different experiments, four of which concerned the adsorption of nickel. The first experimental system was a mixture of Nilsiae quartz and manganese dioxide. In the second experiment, quartz was equilibrated with a fresh and saline groundwater simulant instead of an electrolyte solution. The third and fourth experiments dealt with nickel adsorption from an electrolyte solution onto goethite and kaolinite surfaces respectively. In the fifth experiment, adsorption of thorium onto a quartz surface was investigated

Hybrid Films Based on a Bridged Silsesquioxane Doped with Goethite and Montmorillonite Nanoparticles as Sorbents of Wastewater Contaminants

Directory of Open Access Journals (Sweden)

Carolina V. Waiman

2016-01-01

Full Text Available The synthesis and characterization of silsesquioxane (SSO films with pendant dodecyl groups and doped with goethite (Gt or montmorillonite (MMT nanoparticles were carried out and the new materials tested as sorbents of diverse contaminants. The synthetic method used yielded SSO films with the inorganic substrates homogeneously distributed within the polymeric matrices. The new materials were characterized by SEM, FTIR, XRD, and DSC and tested to evaluate their capability for adsorbing metallic cations, organic dyes, and phosphate, frequent contaminants of industrial effluents. All films were found suitable for removing metallic cations. Results also showed that the SSO films undoped and doped with Gt are primarily apt for anionic compounds removal. Although the SSO films doped with MMT are capable of removing cationic contaminants from aqueous samples, the stiffness of the SSO matrix hinders MMT properties as an adsorbent. The possibility of dispersing nanoparticulate systems in the stable and chemically inert SSO matrices simplifies their application for contaminant removal, particularly because it makes the separation process of the absorbed pollutant from the treated medium easier.

Adsorption of hydroxamate siderophores and EDTA on goethite in the presence of the surfactant sodium dodecyl sulfate

Directory of Open Access Journals (Sweden)

Xu Jide

2009-06-01

Full Text Available Abstract Siderophore-promoted iron acquisition by microorganisms usually occurs in the presence of other organic molecules, including biosurfactants. We have investigated the influence of the anionic surfactant sodium dodecyl sulfate (SDS on the adsorption of the siderophores DFOB (cationic and DFOD (neutral and the ligand EDTA (anionic onto goethite (α-FeOOH at pH 6. We also studied the adsorption of the corresponding 1:1 Fe(III-ligand complexes, which are products of the dissolution process. Adsorption of the two free siderophores increased in a similar fashion with increasing SDS concentration, despite their difference in molecule charge. In contrast, SDS had little effect on the adsorption of EDTA. Adsorption of the Fe-DFOB and Fe-DFOD complexes also increased with increasing SDS concentrations, while adsorption of Fe-EDTA decreased. Our results suggest that hydrophobic interactions between adsorbed surfactants and siderophores are more important than electrostatic interactions. However, for strongly hydrophilic molecules, such as EDTA and its iron complex, the influence of SDS on their adsorption seems to depend on their tendency to form inner-sphere or outer-sphere surface complexes. Our results demonstrate that surfactants have a strong influence on the adsorption of siderophores to Fe oxides, which has important implications for siderophore-promoted dissolution of iron oxides and biological iron acquisition.

Reactive transport of uranyl: fixation mode on silica and goethite; experiments in columns and closed reactors; simulations

International Nuclear Information System (INIS)

Gabriel, U.

1998-01-01

Uranium contaminated areas are found in mine waste disposal sites, former military areas, etc. The present study focuses on the identification or mechanisms which may lead contaminated soils to become a sudden potential threat to surface and ground waters. Mechanisms were studied on model material at two levels. On the molecular scale, the complexation of uranyl at trace metal concentrations was investigated with amorphous silica. Complexation is shown to occur via the formation of surface complexes, characterised by different time-resolved laser-induced luminescence spectra and life times and stoichiometry. On the macro-scale the transport behaviour of uranyl in a cristobalite-goethite-carbonate-uranyl system was investigated with laboratory column and batch experiments. Uranium mobility was found to be controlled by the interaction between physical transport and a reversible, rate-controlled, fixation reaction. Sorption was shown to be an ensemble of competing solution and surface complexation reactions, leading to an apparent non-linear (Langmuir-like) adsorption isotherm. Finally the impact of a sudden change in background geochemistry was studied. Conditions leading to a dramatic mobilization of uranium from mildly contaminated systems were experimentally identified. Maximal uranyl concentration are controlled by the total extractable uranyl in the system and limited by uranyl solubility. Evolution of the background geochemical conditions is thus an important part of contaminated sites risk assessment. (author)

Optical filter based on Fabry-Perot structure using a suspension of goethite nanoparticles as electro-optic material

Science.gov (United States)

Abbas, Samir; Dupont, Laurent; Dozov, Ivan; Davidson, Patrick; Chanéac, Corinne

2018-02-01

We have investigated the feasibility of optical tunable filters based on a Fabry-Perot etalon that uses a suspension of goethite (α-FeOOH) nanorods as electro-optic material for application in optical telecommunications in the near IR range. These synthetic nanoparticles have a high optical anisotropy that give rise to a very strong Kerr effect in their colloidal suspensions. Currently, these particles are dispersed in aqueous solvent, with pH2 to ensure the colloidal electrostatic stability. However, the high conductivity of these suspensions requires using high-frequency electric fields (f > 1 MHz), which brings about a high power consumption of the driver. To decrease the field frequency, we have changed the solvent to ethylene glycol which has a lower electrical conductivity than the aqueous solvent. We have built a Fabry-Perot cell, filled with this colloidal suspension in the isotropic phase, and showed that a phase shift of 14 nm can be obtained in a field of 3V/μm. Therefore, the device can operate as a tunable filter. A key advantage of this filter is that it is, by principle, completely insensitive to the polarization of the input light. However, several technological issues still need to be solved, such as ionic contamination of the suspension from the blocking layers, and dielectrophoretic and thermal effects.

Adsorption Equilibrium and Kinetics at Goethite-Water and Related Interfaces

Energy Technology Data Exchange (ETDEWEB)

Katz, Lynn Ellen [Univ. of Texas, Austin, TX (United States)

2017-04-15

This research study is an important component of a broader comprehensive project, “Geochemistry of Interfaces: From Surfaces to Interlayers to Clusters,” which sought to identify and evaluate the critical molecular phenomena at metal-oxide interfaces that control many geochemical and environmental processes. The primary goal of this research study was to better understand and predict adsorption of metal ions at mineral/water surfaces. Macroscopic data in traditional batch experiments was used to develop predictive models that characterize sorption in complex systems containing a wide range of background solution compositions. Our studies focused on systems involving alkaline earth metal (Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺) and heavy metal (Hg²⁺, Co²⁺, Cd²⁺, Cu²⁺, Zn²⁺, Pb²⁺) cations. The anions we selected for study included Cl^-, NO₃^-, ClO₄^-, SO₄^2-, CO₃^2- and SeO₃^2- and the background electrolyte cations we examined included (Na⁺, K⁺, Rb⁺ and Cs⁺) because these represent a range of ion sizes and have varying potentials for forming ion-pairs or ternary complexes with the metal ions studied. The research led to the development of a modified titration congruency approach for estimating site densities for mineral oxides such as goethite. The CD-MUSIC version of the surface complexation modeling approach was applied to potentiometric titration data and macroscopic adsorption data for single-solute heavy metals, oxyanions, alkaline earth metals and background electrolytes over a range of pH and ionic strength. The model was capable of predicting sorption in bi-solute systems containing multiple cations, cations and oxyanions, and transition metal cations and alkaline earth metal ions. Incorporation of ternary

Spectral variations in rocks and soils containing ferric iron hydroxide and(or) sulfate minerals as seen by AVIRIS and laboratory spectroscopy

Science.gov (United States)

Rockwell, Barnaby W.

2004-01-01

Analysis of Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data covering the Big Rock Candy Mountain area of the Marysvale volcanic field, west-central Utah, identified abundant rocks and soils bearing jarosite, goethite, and chlorite associated with volcanic rocks altered to propylitic grade during the Miocene (2321 Ma). Propylitically-altered rocks rich in pyrite associated with the relict feeder zones of convecting, shallow hydrothermal systems are currently undergoing supergene oxidation to natrojarosite, kaolinite, and gypsum. Goethite coatings are forming at the expense of jarosite where most pyrite has been consumed through oxidation in alluvium derived from pyrite-bearing zones. Spectral variations in the goethite-bearing rocks that resemble variations found in reference library samples of goethites of varying grain size were observed in the AVIRIS data. Rocks outside of the feeder zones have relatively low pyrite content and are characterized by chlorite, epidote, and calcite, with local copper-bearing quartz-calcite veins. Iron-bearing minerals in these rocks are weathering directly to goethite. Laboratory spectral analyses were applied to samples of iron-bearing rock outcrops and alluvium collected from the area to determine the accuracy of the AVIRIS-based mineral identification. The accuracy of the iron mineral identification results obtained by analysis of the AVIRIS data was confirmed. In general, the AVIRIS analysis results were accurate in identifying medium-grained goethite, coarse-grained goethite, medium- to coarse-grained goethite with trace jarosite, and mixtures of goethite and jarosite. However, rock fragments from alluvial areas identified as thin coatings of goethite with the AVIRIS data were found to consist mainly of medium- to coarse-grained goethite based on spectral characteristics in the visible and near-infrared. To determine if goethite abundance contributed to the spectral variations observed in goethite-bearing rocks

Influence of temperature on pentavalent Np Sorption and desorption onto Goethite, Montmorillonite

International Nuclear Information System (INIS)

Vial, M.A.; Sherman, C; Czerwinski, K.R.; Reed, D.

2002-01-01

H 6) distinguished two sorption processes, a fast one attributable to the sorption of NpO 2 + on the easily accessible outer surface of Na-montmorillonite and a slow one assigned to the sorption of the interlayer surface. They found similar results for the sorption on magnetite and hematite [3J, with a fast sorption attributable to sorption on the surface and noncrystal phases of Fe oxides for magnetite and hematite in both acidic and alkaline solutions, and a slow sorption representing sorption into the crystal phase of magnetic in both acidic and alkaline solutions and that of hematite in an acidic solution. Nakayama et al. [4J did some investigations at 30 degree C and found that sorption on goethite was strong above pH 6 while it occurred for hematite and magnetite only above pH 9

Adsorption of Pb(II) ions present in aqueous solution on the oxy hydroxides: boehmite (γ-AIOOH), goethite (α-FeOOH) and manganite (γ-MnOOH); Adsorcion de iones Pb(II) presentes en solucion acuosa sobre los oxihidroxidos: boehmita (γ-AlOOH), goetita (α-FeOOH) y manganita (γ-MnOOH)

Energy Technology Data Exchange (ETDEWEB)

Arreola L, J. E.

2013-07-01

Boehmite, goethite and manganite were synthesized by different methods and characterized using X-ray diffraction (XRD), infrared spectroscopy (IR), thermogravimetric study , N{sub 2} physisorption measurements, scanning electron microscopy (Sem), semiquantitative elemental analysis (EDS), as well as additional studies were determined the surface active sites concentration and zero point of charge. Furthermore, we studied the Pb(II) ion adsorption capacity present in aqueous solution on these synthesized materials by batch-type experiments at room temperature, as a function of contact time between the phases liquid-solid system (adsorption kinetics), initial concentration of the adsorbate (adsorption isotherms), ph and temperature. The adsorption equilibrium time of adsorption processes in these studied systems was found at 60 minutes for boehmite and 30 minutes for goethite and manganite respectively after contacting the solid-liquid phase systems. The adsorption capacity of the lead ions on these adsorbent materials depended of lead concentration, ph and temperature of the systems. Were evaluated lead adsorption capacities in these materials to different contact times using an initial concentration of 20 mg/L of Pb(II) ions at ph = 4, the results of three systems were adjusted to second pseudo kinetic model order. With respect to the study of the adsorbate concentration effect, boehmite-Pb(II) and goethite-Pb(II) systems were adjusted to Langmuir isotherm model which proposes that the adsorption is carried out in a monolayer, moreover manganite-Pb(II) system was adjusted Temp kin isotherm model, which assumes that the adsorption heat of all the molecules in the layer decreases linearly with coverage due to adsorbent-adsorbate interactions and adsorption is characterized by a uniform distribution of the binding energies. Were studied the ph effect of Pb(II) ions solution on the adsorption capacity of such adsorbents, it was found that as the ph increases lead

The Search for Hesperian Organic Matter on Mars: Pyrolysis Studies of Sediments Rich in Sulfur and Iron.

Science.gov (United States)

Lewis, James M T; Najorka, Jens; Watson, Jonathan S; Sephton, Mark A

2018-04-01

Jarosite on Mars is of significant geological and astrobiological interest, as it forms in acidic aqueous conditions that are potentially habitable for acidophilic organisms. Jarosite can provide environmental context and may host organic matter. The most common extraction technique used to search for organic compounds on the surface of Mars is pyrolysis. However, thermal decomposition of jarosite releases oxygen into pyrolysis ovens, which degrades organic signals. Jarosite has a close association with the iron oxyhydroxide goethite in many depositional/diagenetic environments. Hematite can form by dehydration of goethite or directly from jarosite under certain aqueous conditions. Goethite and hematite are significantly more amenable than jarosite for pyrolysis experiments employed to search for organic matter. Analysis of the mineralogy and organic chemistry of samples from a natural acidic stream revealed a diverse response for organic compounds during pyrolysis of goethite-rich layers but a poor response for jarosite-rich or mixed jarosite-goethite samples. Goethite units that are associated with jarosite, but do not contain jarosite themselves, should be targeted for organic detection pyrolysis experiments on Mars. These findings are extremely timely, as exploration targets for Mars Science Laboratory include Vera Rubin Ridge (formerly known as "Hematite Ridge"), which may have formed from goethite precursors. Key Words: Mars-Pyrolysis-Jarosite-Goethite-Hematite-Biosignatures. Astrobiology 18, 454-464.

Ferrous Iron Oxidation under Varying pO2 Levels: The Effect of Fe(III)/Al(III) Oxide Minerals and Organic Matter.

Science.gov (United States)

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.

(ajst) the influence of ph and adsorbent

African Journals Online (AJOL)

goethite sorbed a little more metal ion than the natural goethite. This was attributed ... was greatly governed by pH with nearly 100% adsorption of Pb occurring at initial pH of 5. Generally, Pb was ... extensively study and applied for the removal of heavy .... Goethite has variable surface charge characteristics, which gave it a ...

Mineralogy of the clay fraction of alfisols in two slope curvatures: IV - spatial correlation with physical properties

Directory of Open Access Journals (Sweden)

Livia Arantes Camargo

2013-04-01

Full Text Available Although the influence of clay mineralogy on soil physical properties has been widely studied, spatial relationships between these features in Alfisols have rarely been examined. The purpose of this work was to relate the clay minerals and physical properties of an Alfisol of sandstone origin in two slope curvatures. The crystallographic properties such as mean crystallite size (MCS and width at half height (WHH of hematite, goethite, kaolinite and gibbsite; contents of hematite and goethite; aluminium substitution (AS and specific surface area (SSA of hematite and goethite; the goethite/(goethite+hematite and kaolinite/(kaolinite+gibbsite ratios; and the citrate/bicarbonate/dithionite extractable Fe (Fe d were correlated with the soil physical properties through Pearson correlation coefficients and cross-semivariograms. The correlations found between aluminium substitution in goethite and the soil physical properties suggest that the degree of crystallinity of this mineral influences soil properties used as soil quality indicators. Thus, goethite with a high aluminium substitution resulted in large aggregate sizes and a high porosity, and also in a low bulk density and soil penetration resistance. The presence of highly crystalline gibbsite resulted in a high density and micropore content, as well as in smaller aggregates. Interpretation of the cross-semivariogram and classification of landscape compartments in terms of the spatial dependence pattern for the relief-dependent physical and mineralogical properties of the soil proved an effective supplementary method for assessing Pearson correlations between the soil physical and mineralogical properties.

Paleomagnetism and tectonics of the Jura arcuate mountain belt in France and Switzerland

Science.gov (United States)

Gehring, Andreas U.; Keller, Peter; Heller, Friedrich

1991-02-01

Goethite and hematite in ferriferous oolitic beds of Callovian age from the Jura mountains (Switzerland, France) carry either pre- and/or post-tectonic magnetization. The frequent pre-tectonic origin of goethite magnetization indicates a temperature range during formation of the arcuate Jura mountain belt below the goethite Néel temperature of about 100°C. The scatter of the pre-tectonic paleomagnetic directions ( D = 11.5° E, I = 55.5°; α95 = 4.7) which reside both in goethite and hematite, provides strong evidence that the arcuate mountain belt was shaped without significant rotation. The paleomagnetic results support tectonic thin-skinned models for the formation of the Jura mountain belt.

Iron Oxides of Mars: Evidence for Contemporary Weathering

Science.gov (United States)

Huguenin, R. L.

1985-01-01

Reflectance spectra of Mars were analyzed using a multiple high order derivative spectroscopy technique. Among the results of the analysis was the presence of suites of bands in each of the spectra that can be attributed to Fe(3e) phases. Several of the spectra contained bands that are very close to the band positions in the laboratory spectra of goethite, an hexagonal hydrated ferric oxide. Spectra of other areas showed absorption bands that were within 3% of the positions for hematite, and hexagonal close packed unhydrated Fe203. Remaining areas showed bands that are intermediate in position to the goethite and hematite bands, suggesting that there may be mixtures of goethite and hematite, and/or intermediate (partially dehydrated goethite) phases present in those areas. Both bright areas and dark areas showed suites of goethite bands and hematite bands, and there does not therefore appear to be a correlation with albedo. The areas that showed the goethite bands are, however, within zones of ongoing or historically frequent dust cloud activity, and the areas with the hematite bands were outside of the zones of frequent dust cloud activity. This suggests the possiblility that the more hydrated phase may occur within a mobile dust component.

Bacillus subtilis biofilm development in the presence of soil clay minerals and iron oxides.

Science.gov (United States)

Ma, Wenting; Peng, Donghai; Walker, Sharon L; Cao, Bin; Gao, Chun-Hui; Huang, Qiaoyun; Cai, Peng

2017-01-01

Clay minerals and metal oxides, as important parts of the soil matrix, play crucial roles in the development of microbial communities. However, the mechanism underlying such a process, particularly on the formation of soil biofilm, remains poorly understood. Here, we investigated the effects of montmorillonite, kaolinite, and goethite on the biofilm formation of the representative soil bacteria Bacillus subtilis . The bacterial biofilm formation in goethite was found to be impaired in the initial 24 h but burst at 48 h in the liquid-air interface. Confocal laser scanning microscopy showed that the biofilm biomass in goethite was 3-16 times that of the control, montmorillonite, and kaolinite at 48 h. Live/Dead staining showed that cells had the highest death rate of 60% after 4 h of contact with goethite, followed by kaolinite and montmorillonite. Atomic force microscopy showed that the interaction between goethite and bacteria may injure bacterial cells by puncturing cell wall, leading to the swarming of bacteria toward the liquid-air interface. Additionally, the expressions of abrB and sinR , key players in regulating the biofilm formation, were upregulated at 24 h and downregulated at 48 h in goethite, indicating the initial adaptation of the cells to minerals. A model was proposed to describe the effects of goethite on the biofilm formation. Our findings may facilitate a better understanding of the roles of soil clays in biofilm development and the manipulation of bacterial compositions through controlling the biofilm in soils.

2015 Progress Report/July 2016: Iron Oxide Redox Transformation Pathways: The Bulk Electrical Conduction Mechanism

Energy Technology Data Exchange (ETDEWEB)

Scherer, Michelle M. [Univ. of Iowa, Iowa City, IA (United States); Rosso, Kevin M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2016-07-25

Despite decades of research on the reactivity and stable isotope properties of Fe oxides, the ability to describe the redox behavior of Fe oxides in the environment is still quite limited. This is due, in large part, to the analytical and spatial complexities associated with studying microscopic processes at the Fe oxide-water interface. This project had the long-term vision of filling this gap by developing a detailed understanding of the relationship between interfacial ET processes, surface structure and charge, and mineral semiconducting properties. We focused on the Fe(III)-oxides and oxyhydroxides because of their geochemical preponderance, versatility in synthesis of compositionally, structurally, and morphologically tailored phases, and because they are amenable to a wide range of surface and bulk properties characterization. In particular, reductive transformation of phases such as hematite (α-Fe₂O₃) and goethite (α-FeOOH) in aqueous solution can serve as excellent model systems for studies of electron conduction processes, as well as provide valuable insights into effect of nanoscale conductive materials on contaminant fate at DOE sites. More specifically, the goal of the Iowa component of this project was to use stable Fe isotope measurements to simultaneously measure isotope specific oxidation states and concentrations of Fe at the hematite-water and goethite-water interface. This work builds on our previous work where we used an innovative combination of ⁵⁷Fe Mössbauer spectroscopy and high precision isotope ratio measurements (MC-ICP-MS) to probe the dynamics of the reaction of aqueous Fe(II) with goethite. Mössbauer spectroscopy detects ⁵⁷Fe only among all other Fe isotopes and we have capitalized on this to spectroscopically demonstrate Fe(II)-Fe(III) electron transfer between sorbed Fe(II) and Fe(III) oxides (Handler, et al., 2009; Gorski, et al. 2010; Rosso et al., 2010). By combining the M�

Heteroaggregation of graphene oxide with minerals in aqueous phase.

Science.gov (United States)

Zhao, Jian; Liu, Feifei; Wang, Zhenyu; Cao, Xuesong; Xing, Baoshan

2015-03-03

Upon release into waters, sediments, and soils, graphene oxide (GO) may interact with fine mineral particles. We investigated the heteroaggregation of GO with different minerals, including montmorillonite, kaolinite, and goethite, in aqueous phase. GO significantly enhanced the dispersion of positively charged goethite (>50%) via heteroaggregation, while there was no interaction between GO and negatively charged montmorillonite or kaolinite. Electrostatic attraction was the dominant force in the GO-goethite heteroaggregation (pH 4.0-8.5), and the dissolved Fe ions (formation of multilayered GO-goethite complex with high configurational stability. These findings are useful for understanding the interaction of GO with mineral surfaces, and potential fate and toxicity of GO under natural conditions in aquatic environments, as well as in soils and sediments.

Abdus-Salam and Ikudayisi (10)

African Journals Online (AJOL)

DELL

Instrumental characterization such as Fourier Transform Infrared (FTIR) for ... The nano-sizer also revealed a near nano-size for the synthesized goethite ... Keywords: Iron oxy-hydroxide, Goethite, Date-palm seeds, Particle nano-sizer, BET.

Molecular modeling studies of oleate adsorption on iron oxides

International Nuclear Information System (INIS)

Rath, Swagat S.; Sinha, Nishant; Sahoo, Hrushikesh; Das, Bisweswar; Mishra, Barada Kanta

2014-01-01

Graphical abstract: - Highlights: • Plane wave periodic DFT study of oleate-iron oxide interaction. • Magnetite-oleate complex is more stable than hematite and goethite. • Flotation recovery of magnetite is more compared to the other two oxides. - Abstract: Comparative studies of oleate interaction with hematite, magnetite and goethite using density functional calculations are presented. The approach is illustrated by carrying out geometric optimization of oleate on the stable and most exposed planes of hematite, magnetite, and goethite. Interaction energies for oleate-mineral surface have been determined, based on which, magnetite is found to be forming the most stable complex with oleate. Trend as obtained from the quantum chemical calculations has been validated by contact angle measurements and flotation studies on hematite, magnetite and goethite with sodium oleate at different pH and collector concentrations

Molecular modeling studies of oleate adsorption on iron oxides

Energy Technology Data Exchange (ETDEWEB)

Rath, Swagat S. [CSIR-Institute of Minerals and Materials Technology, Bhubaneswar (India); Sinha, Nishant [Accelrys K.K, Bengaluru (India); Sahoo, Hrushikesh [CSIR-Institute of Minerals and Materials Technology, Bhubaneswar (India); Das, Bisweswar, E-mail: bdas@immt.res.in [CSIR-Institute of Minerals and Materials Technology, Bhubaneswar (India); Mishra, Barada Kanta [CSIR-Institute of Minerals and Materials Technology, Bhubaneswar (India)

2014-03-01

Graphical abstract: - Highlights: • Plane wave periodic DFT study of oleate-iron oxide interaction. • Magnetite-oleate complex is more stable than hematite and goethite. • Flotation recovery of magnetite is more compared to the other two oxides. - Abstract: Comparative studies of oleate interaction with hematite, magnetite and goethite using density functional calculations are presented. The approach is illustrated by carrying out geometric optimization of oleate on the stable and most exposed planes of hematite, magnetite, and goethite. Interaction energies for oleate-mineral surface have been determined, based on which, magnetite is found to be forming the most stable complex with oleate. Trend as obtained from the quantum chemical calculations has been validated by contact angle measurements and flotation studies on hematite, magnetite and goethite with sodium oleate at different pH and collector concentrations.

Cd(II), Cu(II)

African Journals Online (AJOL)

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Depending on the way goethite was pretreated with oxalic acid, affinity for Cd(II) varied ...... Effects and mechanisms of oxalate on Cd(II) adsorption on goethite at different ... precipitation, surfactant mediation, hydrothermal and micro-emulsion.

Spectroscopic study of the final protective corrosion product on weathering steel

International Nuclear Information System (INIS)

Yamashita, M.; Misawa, T.

1998-01-01

Recent progress in understanding the structure and properties of final protective rust layer on weathering steel and its application for structural steels is shown based on the data obtained mainly by spectroscopic characterization. The main constituent of the weathering steel rust layer is changed with exposure period from γ- FeOOH (less than a few years) via, amorphous substance (several years), to α-FeOOH goethite phase (decades). The corrosion rate of the weathering steel decreased with this phase transformation. The final protective rust layer possesses the structure of α- (Fe 1 - X p Cr x)O OH, Cr substitute goethite; the crystal size decreases with its Cr-content. It is shown that the Cr content in the Cr-substituted goethite increases gradiently with reaching the rust/steel interface. This increase in the Cr content and resultant aggregation of fine crystals lead a densely packed Cr-substituted goethite rust layers which provides higher protective ability for atmospheric corrosives. It is found that the Cr-substituted goethite possesses the cation selective ability at the vicinity of the rust/steel interface where the Cr content can be estimated approximately 5-10 mass %. Thus, the final protective rust layer of the Cr-substituted goethite impedes the penetration of aggressive corrosive anions such as Cl - and SO 4 2- , besides the physically prevention effect of its densely aggregated structure for corrosive penetration. It is found that Cr 2 (SO 4 ) 3 is effective for obtaining the final protective rust layer in a short period. SO 4 2 accelerates rust formation and Cr 3- substitutes goethite crystal lattice point at the initial stage of corrosion; resultantly the rust layer formed suppresses dissolution of the steel even in the severe environment. (Author)

Comparison study on transformation of iron oxyhydroxides: Based on theoretical and experimental data

International Nuclear Information System (INIS)

Lu Bin; Guo Hui; Li Ping; Liu Hui; Wei Yu; Hou Denglu

2011-01-01

We have investigated the catalytic transformation of ferrihydrite, feroxyhyte, and lepidocrocite in the presence of Fe(II). In this paper, the transformation from akaganeite and goethite to hematite in the presence of trace Fe(II) was studied in detail. The result indicates that trace Fe(II) can accelerate the transformation of akaganeite and goethite. Compared with the transformation of other iron oxyhydroxides (e.g., ferrihydrite, feroxyhyte, lepidocrocite, and akaganeite), a complete transformation from goethite to hematite was not observed in the presence of Fe(II). On the basis of our earlier and present experimental results, the transformation of various iron oxyhydroxides was compared based on their thermodynamic stability, crystalline structure, transformation mechanism, and transformation time. - Graphical abstract: The transformation of various iron oxyhydroxides in the presence of trace Fe(II) was compared based on experimental results, thermodynamic stability, crystalline structure, and transformation mechanism. Highlights: → Fe(II) can accelerate the transformation from akaganeite to hematite. → Small particles of goethite can transform to hematite in the presence of Fe(II). → Some hematite particles were found to be embedded within the crystal of goethite. → The relationship between structure and transformation mechanism was revealed.

X-ray diffraction analysis of rust layer on a weathering steel bridge with surface treatment using synchrotron radiation

International Nuclear Information System (INIS)

Yamashita, Masato; Hara, Shuichi; Kamimura, Takayuki; Miyuki, Hideaki; Sato, Masugu

2007-01-01

We have examined the structure of rust layer formed on a weathering steel bridge, to which the surface treatment, employing the effect of Cr 2 (SO 4 ) 3 sophisticatedly designed to form the protective goethite (α-FeOOH) rust layer which contains a certain amount of Cr, Cr-goethite, was applied in 1996, using X-ray diffraction at SPring-8 synchrotron radiation facility. It was shown that the formation of α-FeOOH was promoted and/or crystal growth of γ-FeOOH was suppressed by the surface treatment. The increase in the protective ability index (PAI) of the rust layer indicates that the protective goethite was predominantly formed under the effect of the surface treatment. In conclusion, it can be said that the surface treatment worked well to promote the formation of the protective goethite rust layer on the weathering steel bridge during the 10-year exposure. (author)

Nanostructure of protective rust layer on weathering steel examined using synchrotron radiation x-rays

International Nuclear Information System (INIS)

Yamashita, Masato; Uchida, Hitoshi; Konishi, Hiroyuki; Mizuki, Jun'ichiro

2004-01-01

The X-ray absorption fine structure (XAFS) spectrum of pure goethite around the Fe K absorption edge and that of the protective rust layer formed on weathering steel exposed for 17 years in an atmospheric environment around the Cr K edge, have been examined using synchrotron radiation X-rays. It was found that the rust layer on the weathering steel mainly consisted of Cr-goethite. By examining the fine structure at the Cr K edge and the Fe K edge, we concluded that Cr 3+ in the rust layer is coordinated with O 2- and is positioned in the double chains of vacant sites in the network of FeO 3 (OH) 3 octahedra in the goethite crystal. This Cr 3+ site indicates that the protective effect of the rust layer is due to the dense aggregation of fine crystals of Cr-goethite with cation selectivity. (author)

Mineralogy of the clay fraction of Alfisols in two slope curvatures: III - spatial variability

Directory of Open Access Journals (Sweden)

Livia Arantes Camargo

2013-04-01

Full Text Available A good knowledge of the spatial distribution of clay minerals in the landscape facilitates the understanding of the influence of relief on the content and crystallographic attributes of soil minerals such as goethite, hematite, kaolinite and gibbsite. This study aimed at describing the relationships between the mineral properties of the clay fraction and landscape shapes by determining the mineral properties of goethite, hematite, kaolinite and gibbsite, and assessing their dependence and spatial variability, in two slope curvatures. To this end, two 100 × 100 m grids were used to establish a total of 121 regularly spaced georeferenced sampling nodes 10 m apart. Samples were collected from the layer 0.0-0.2 m and analysed for iron oxides, and kaolinite and gibbsite in the clay fraction. Minerals in the clay fraction were characterized from their X-ray diffraction (XRD patterns, which were interpreted and used to calculate the width at half height (WHH and mean crystallite dimension (MCD of iron oxides, kaolinite, and gibbsite, as well as aluminium substitution and specific surface area (SSA in hematite and goethite. Additional calculations included the goethite and hematite contents, and the goethite/(goethite+hematite [Gt/(Gt+Hm] and kaolinite/(kaolinite+gibbsite [Kt/(Kt+Gb] ratios. Mineral properties were established by statistical analysis of the XRD data, and spatial dependence was assessed geostatistically. Mineralogical properties differed significantly between the convex area and concave area. The geostatistical analysis showed a greater number of mineralogical properties with spatial dependence and a higher range in the convex than in the concave area.

On the reaction of iron oxides and oxyhydroxides with tannic and phosphoric acid and their mixtures

Energy Technology Data Exchange (ETDEWEB)

Beltran, J. J., E-mail: jjbj08@yahoo.com; Novegil, F. J.; Garcia, K. E.; Barrero, C. A. [Universidad de Antioquia, Sede de Investigacion Universitaria, Grupo de Estado Solido, Instituto de Fisica (Colombia)

2010-01-15

The actions of tannic acid, phosphoric acid and their mixture on lepidocrocite, goethite, superparamagnetic goethite, akaganeite, magnetite, hematite and maghemite for 1 day and 1 month were explored. It was found that these acids form iron tannates and phosphates. Lepidocrocite and magnetite were the iron phases more easily transformed with the mixture of the acids after 1 month of reaction, whereas hematite was the most resistant phase. In the case of goethite, our results suggest that in order to understand properly the action of these acids, we have to take into account its stoichiometry, surface area and degree of crystallinity.

Effect of solution chemistry on the adsorption of perfluorooctane sulfonate onto mineral surfaces.

Science.gov (United States)

Tang, Chuyang Y; Shiang Fu, Q; Gao, Dawen; Criddle, Craig S; Leckie, James O

2010-04-01

Perfluorooctane sulfonate (PFOS) is an emergent contaminant of substantial environmental concerns, yet very limited information has been available on PFOS adsorption onto mineral surfaces. PFOS adsorption onto goethite and silica was investigated by batch adsorption experiments under various solution compositions. Adsorption onto silica was only marginally affected by pH, ionic strength, and calcium concentration, likely due to the dominance of non-electrostatic interactions. In contrast, PFOS uptake by goethite increased significantly at high [H+] and [Ca2+], which was likely due to enhanced electrostatic attraction between the negatively charged PFOS molecules and positively charged goethite surface. The effect of pH was less significant at high ionic strength, likely due to electrical double layer compression. PFOS uptake was reduced at higher ionic strength for a strongly positively charged goethite surface (pH 3), while it increased for a weakly charged surface (pH 7 and 9), which could be attributed to the competition between PFOS-surface electrostatic attraction and PFOS-PFOS electrostatic repulsion. A conceptual model that captures PFOS-surface and PFOS-PFOS electrostatic interactions as well as non-electrostatic interaction was also formulated to understand the effect of solution chemistry on PFOS adsorption onto goethite and silica surfaces. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

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.

Effects of Si as alloying element on corrosion resistance of weathering steel

International Nuclear Information System (INIS)

Mejía Gómez, J.A.; Antonissen, J.; Palacio, C.A.; De Grave, E.

2012-01-01

Highlights: ► Weathering steels with different concentrations of Si as alloying element were exposed to laboratory atmospheric conditions. ► The iron oxides formed as corrosion products were characterized and analyzed by XRD, TEM and Mössbauer spectroscopy. ► Silicon affects the corrosion resistance of weathering steels. ► Silicon promotes the formation of goethite as corrosion product with small particle size. - Abstract: The corrosion resistance in saline conditions of weathering steel with different concentrations of Si (1, 2 and 3 wt.%) exposed to dip dry tests (simulating wet/dry cycles of atmospheric corrosion) was studied by weight loss, X-ray diffraction, Mössbauer spectroscopy and transmission electron microscopy. The results showed that the steels exhibit better corrosion performance with increasing Si concentration. The formation of Fe-oxides such as goethite, lepidocrocite and magnetite was observed. Superparamagnetic goethite is the dominant phase in the rust developed on the Si steels, indicating that Si favors the formation of goethite with small particle size.

An Integrated Experimental-Modelling Procedure Applied to the Design of a Field Scale Goethite Nanoparticle Injection for the Remediation of Contaminated Sites

Science.gov (United States)

Bianco, C.; Tosco, T.; Sethi, R.

2017-12-01

Nanoremediation is a promising in-situ technology for the reclamation of contaminated aquifers. It consists in the subsurface injection of a reactive colloidal suspension for the in-situ treatment of pollutants. The overall success of this technology at the field scale is strictly related to the achievement of an effective and efficient emplacement of the nanoparticles (NP) inside the contaminated area. Mathematical models can be used to support the design of nanotechnology-based remediation by effectively assessing the expected NP mobility at the field scale. Several analytical and numerical tools have been developed in recent years to model the transport of NPs in simplified geometry and boundary conditions. The numerical tool MNMs was developed by the authors of this work to simulate colloidal transport in 1D Cartesian and radial coordinates. A new modelling tool, MNM3D (Micro and Nanoparticle transport Model in 3D geometries), was also proposed for the simulation of injection and transport of NP suspensions in generic complex scenarios. MNM3D accounts for the simultaneous dependency of NP transport on water ionic strength and velocity. The software was developed to predict the NP mobility at different stages of a nanoremediation application, from the design stage to the prediction of the long-term fate after injection. In this work an integrated experimental-modelling procedure is applied to support the design of a field scale injection of goethite NPs carried out in the framework of the H2020 European project Reground. Column tests are performed at different injection flowrates using natural sand collected at the contaminated site as porous medium. The tests are interpreted using MNMs to characterize the NP mobility and derive the constitutive equations describing the suspension behavior in the natural porous medium. MNM3D is then used to predict NP behavior during the field scale injection and to assess the long-term mobility of the injected slurry. Finally

Surface complexation modeling of the effects of phosphate on uranium(VI) adsorption

Energy Technology Data Exchange (ETDEWEB)

Romero-Gonzalez, M.R.; Cheng, T.; Barnett, M.O. [Auburn Univ., AL (United States). Dept. of Civil Engeneering; Roden, E.E. [Wisconsin Univ., Madison, WI (United States). Dept. of Geology and Geophysics

2007-07-01

Previous published data for the adsorption of U(VI) and/or phosphate onto amorphous Fe(III) oxides (hydrous ferric oxide, HFO) and crystalline Fe(III) oxides (goethite) was examined. These data were then used to test the ability of a commonly-used surface complexation model (SCM) to describe the adsorption of U(VI) and phosphate onto pure amorphous and crystalline Fe(III) oxides and synthetic goethite-coated sand, a surrogate for a natural Fe(III)-coated material, using the component additivity (CA) approach. Our modeling results show that this model was able to describe U(VI) adsorption onto both amorphous and crystalline Fe(III) oxides and also goethite-coated sand quite well in the absence of phosphate. However, because phosphate adsorption exhibits a stronger dependence on Fe(III) oxide type than U(VI) adsorption, we could not use this model to consistently describe phosphate adsorption onto both amorphous and crystalline Fe(III) oxides and goethite-coated sand. However, the effects of phosphate on U(VI) adsorption could be incorporated into the model to describe U(VI) adsorption to both amorphous and crystalline Fe(III) oxides and goethite-coated sand, at least for an initial approximation. These results illustrate both the potential and limitations of using surface complexation models developed from pure systems to describe metal/radionuclide adsorption under more complex conditions. (orig.)

Surface complexation modeling of the effects of phosphate on uranium(VI) adsorption

International Nuclear Information System (INIS)

Romero-Gonzalez, M.R.; Cheng, T.; Barnett, M.O.; Roden, E.E.

2007-01-01

Previous published data for the adsorption of U(VI) and/or phosphate onto amorphous Fe(III) oxides (hydrous ferric oxide, HFO) and crystalline Fe(III) oxides (goethite) was examined. These data were then used to test the ability of a commonly-used surface complexation model (SCM) to describe the adsorption of U(VI) and phosphate onto pure amorphous and crystalline Fe(III) oxides and synthetic goethite-coated sand, a surrogate for a natural Fe(III)-coated material, using the component additivity (CA) approach. Our modeling results show that this model was able to describe U(VI) adsorption onto both amorphous and crystalline Fe(III) oxides and also goethite-coated sand quite well in the absence of phosphate. However, because phosphate adsorption exhibits a stronger dependence on Fe(III) oxide type than U(VI) adsorption, we could not use this model to consistently describe phosphate adsorption onto both amorphous and crystalline Fe(III) oxides and goethite-coated sand. However, the effects of phosphate on U(VI) adsorption could be incorporated into the model to describe U(VI) adsorption to both amorphous and crystalline Fe(III) oxides and goethite-coated sand, at least for an initial approximation. These results illustrate both the potential and limitations of using surface complexation models developed from pure systems to describe metal/radionuclide adsorption under more complex conditions. (orig.)

Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

Science.gov (United States)

Moskowitz, Bruce M; Reynolds, Richard L.; Goldstein, Harland L.; Beroquo, Thelma; Kokaly, Raymond F.; Bristow, Charlie S

2016-01-01

Atmospheric mineral dust can influence climate and biogeochemical cycles. An important component of mineral dust is ferric oxide minerals (hematite and goethite) which have been shown to influence strongly the optical properties of dust plumes and thus affect the radiative forcing of global dust. Here we report on the iron mineralogy of dust-source samples from the Bodélé Depression (Chad, north-central Africa), which is estimated to be Earth’s most prolific dust producer and may be a key contributor to the global radiative budget of the atmosphere as well as to long-range nutrient transport to the Amazon Basin. By using a combination of magnetic property measurements, Mössbauer spectroscopy, reflectance spectroscopy, chemical analysis, and scanning electron microscopy, we document the abundance and relative amounts of goethite, hematite, and magnetite in dust-source samples from the Bodélé Depression. The partition between hematite and goethite is important to know to improve models for the radiative effects of ferric oxide minerals in mineral dust aerosols. The combination of methods shows (1) the dominance of goethite over hematite in the source sediments, (2) the abundance and occurrences of their nanosize components, and (3) the ubiquity of magnetite, albeit in small amounts. Dominant goethite and subordinate hematite together compose about 2% of yellow-reddish dust-source sediments from the Bodélé Depression and contribute strongly to diminution of reflectance in bulk samples. These observations imply that dust plumes from the Bodélé Depression that are derived from goethite-dominated sediments strongly absorb solar radiation. The presence of ubiquitous magnetite (0.002–0.57 wt%) is also noteworthy for its potentially higher solubility relative to ferric oxide and for its small sizes, including PM bioavailability to marine and terrestrial ecosystems.

Retention of actinide and fission products by poly-mineral solid phases

International Nuclear Information System (INIS)

Peynet, Vincent

2003-01-01

This research thesis first reports available knowledge on reactivity of mineral surfaces (notably the thermodynamic modelling of their retention properties) and discusses the different approaches proposed in the literature regarding the prediction of retention of an element on an adsorbent mixing. It also proposes a synthesis of publications on retention properties of montmorillonite, goethite and calcite with respect to elements with high or very low concentrations. Then, the author reports a characterization of solids in terms of ion exchanger theory. Results are used for traces of caesium, americium and selenium. He finally reports measurement results of traces of elements by montmorillonite / goethite and montmorillonite / calcite binary mixings, or by montmorillonite / goethite / calcite ternary mixings

Seasonal variations of ochreous precipitates in mine effluents in Finland

International Nuclear Information System (INIS)

Kumpulainen, Sirpa; Carlson, Liisa; Raeisaenen, Marja-Liisa

2007-01-01

Ochreous precipitate and water samples were collected from the surroundings of seven closed sulphide mines in Finland. In the Hammaslahti Zn-Cu-Au mine, Otravaara pyrite mine and Paroistenjaervi Cu-W-As mine, the collection was repeated in different seasons to study mineralogical and geochemical variations of precipitates. The sampling was done in 1999-2002 from the ditches and drainage ponds of the tailings and waste rock piles that are susceptible to seasonal changes. Mineralogy of the precipitates was evaluated by X-ray diffraction (XRD) and infrared spectroscopy (IR), and precipitate geochemistry was examined by selective extractions. Schwertmannite (Fe 8 O 8 (OH) 6 SO 4 ) was the most typical Fe hydroxide mineral found. Goethite was almost as common as schwertmannite, was often poorly ordered, and contained up to 10 wt.% of SO 4 . Goethite and schwertmannite were commonly found as mixtures, and they occurred in similar pH and SO 4 concentrations. Ferrihydrite (nominally Fe 5 HO 8 . 4H 2 O) was typically found in areas not influenced by acid mine drainage, and also in acid mine waters with high organic matter or As content. Jarosite (KFe 3 (SO 4 ) 2 (OH) 6 ) was found only in one site. In addition, some gypsum (CaSO 4 . 2H 2 O) and aluminous sulphate precipitates (presumably basaluminite, Al 4 (SO 4 )(OH) 10 . 5H 2 O) were identified. Selective extractions showed that acid extracts Fe tot /S tot -ratios of schwertmannite and goethite samples were similar, but the ratio of oxalate-extractable to total Fe, Fe ox /Fe tot , of goethite samples were lower than those of the schwertmannite samples. Only Al, Si and As were bound to precipitates in substantial amounts, up to several wt.%. In schwertmannites and goethites, Al, Cu, Co, Mn and Zn were mostly structural, substituting for Fe in an Fe oxyhydroxide structure or bound to surface adsorption sites in pores limited by diffusion. In ferrihydrites, heavy metals were also partly bound in adsorbed form dissolving in

Use of Infrared spectroscopy for the akaganeite identification 3. NACE Latin American Corrosion Congress and the 6. Ibero-American Congress of Corrosion and Protection

International Nuclear Information System (INIS)

Parra, A.; Martinez, L.; Mondragon, M.A.; Castano, V.

1998-01-01

It is now knew that 1020 and 750 bands belong to lepidocrocite phase; 890 and 790 are goethite bands. The akaganeite is identified in the 840 band; but when it is in a small quantity, its spectra is opaque by the goethite. It is considered that this type of IR analysis, is ideal to identify the lepidocrocite and goethite not so for the akaganeite. In order to identify and to quantify the akaganeite it is used the X-ray spectroscopy and Moessbauer, moreover to identify the akaganeite with Moessbauer analysis, which is realized at low temperature. However, if the quantity of akaganeite is significant the infrared spectra will be very clear for the 840 band that is characteristic of the akaganeite. (Author)

Use of Infrared spectroscopy for the akaganeite identification 3. NACE Latin American Corrosion Congress and the 6. Ibero-American Congress of Corrosion and Protection; Uso de la espectroscopia IR para la identificacion de la kaganeita

Energy Technology Data Exchange (ETDEWEB)

Parra, A.; Martinez, L. [Instituto de Fisica, UNAM, A.P. 48-3, C.P. 62251, Cuernavaca, Morelos, Mexico (Mexico); Mondragon, M.A.; Castano, V. [Instituto de Fisica, UNAM, Mexico D.F. (Mexico)

1998-12-31

It is now knew that 1020 and 750 bands belong to lepidocrocite phase; 890 and 790 are goethite bands. The akaganeite is identified in the 840 band; but when it is in a small quantity, its spectra is opaque by the goethite. It is considered that this type of IR analysis, is ideal to identify the lepidocrocite and goethite not so for the akaganeite. In order to identify and to quantify the akaganeite it is used the X-ray spectroscopy and Moessbauer, moreover to identify the akaganeite with Moessbauer analysis, which is realized at low temperature. However, if the quantity of akaganeite is significant the infrared spectra will be very clear for the 840 band that is characteristic of the akaganeite. (Author)

Spatial distribution of crystalline corrosion products formed during corrosion of stainless steel in concrete

Energy Technology Data Exchange (ETDEWEB)

Serdar, Marijana [Department of Materials, Faculty of Civil Engineering, University of Zagreb, 10000 Zagreb (Croatia); Meral, Cagla [Middle East Technical University, Department of Civil Engineering, Ankara (Turkey); Kunz, Martin [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Bjegovic, Dubravka [Department of Materials, Faculty of Civil Engineering, University of Zagreb, 10000 Zagreb (Croatia); Wenk, Hans-Rudolf [Department of Earth and Planetary Science, University of California, Berkeley, CA 94720 (United States); Monteiro, Paulo J.M., E-mail: monteiro@ce.berkeley.edu [Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720 (United States)

2015-05-15

The mineralogy and spatial distribution of nano-crystalline corrosion products that form in the steel/concrete interface were characterized using synchrotron X-ray micro-diffraction (μ-XRD). Two types of low-nickel high-chromium reinforcing steels embedded into mortar and exposed to NaCl solution were investigated. Corrosion in the samples was confirmed by electrochemical impedance spectroscopy (EIS). μ-XRD revealed that goethite (α-FeOOH) and akaganeite (β-FeOOH) are the main iron oxide–hydroxides formed during the chloride-induced corrosion of stainless steel in concrete. Goethite is formed closer to the surface of the steel due to the presence of chromium in the steel, while akaganeite is formed further away from the surface due to the presence of chloride ions. Detailed microstructural analysis is shown and discussed on one sample of each type of steel. - Highlights: • Synchrotron micro-diffraction used to map the distribution of crystalline phases. • Goethite and akaganeite are the main corrosion products during chloride induced corrosion in mortar. • Layers of goethite and akaganeite are negatively correlated. • EDS showed Cr present in corrosion products identified by SEM.

Spatial distribution of crystalline corrosion products formed during corrosion of stainless steel in concrete

International Nuclear Information System (INIS)

Serdar, Marijana; Meral, Cagla; Kunz, Martin; Bjegovic, Dubravka; Wenk, Hans-Rudolf; Monteiro, Paulo J.M.

2015-01-01

The mineralogy and spatial distribution of nano-crystalline corrosion products that form in the steel/concrete interface were characterized using synchrotron X-ray micro-diffraction (μ-XRD). Two types of low-nickel high-chromium reinforcing steels embedded into mortar and exposed to NaCl solution were investigated. Corrosion in the samples was confirmed by electrochemical impedance spectroscopy (EIS). μ-XRD revealed that goethite (α-FeOOH) and akaganeite (β-FeOOH) are the main iron oxide–hydroxides formed during the chloride-induced corrosion of stainless steel in concrete. Goethite is formed closer to the surface of the steel due to the presence of chromium in the steel, while akaganeite is formed further away from the surface due to the presence of chloride ions. Detailed microstructural analysis is shown and discussed on one sample of each type of steel. - Highlights: • Synchrotron micro-diffraction used to map the distribution of crystalline phases. • Goethite and akaganeite are the main corrosion products during chloride induced corrosion in mortar. • Layers of goethite and akaganeite are negatively correlated. • EDS showed Cr present in corrosion products identified by SEM

Reactive transport model of the formation of oxide-type Ni-laterite profiles (Punta Gorda, Moa Bay, Cuba)

Science.gov (United States)

Domènech, Cristina; Galí, Salvador; Villanova-de-Benavent, Cristina; Soler, Josep M.; Proenza, Joaquín A.

2017-10-01

Oxide-type Ni-laterite deposits are characterized by a dominant limonite zone with goethite as the economically most important Ni ore mineral and a thin zone of hydrous Mg silicate-rich saprolite beneath the magnesium discontinuity. Fe, less soluble, is mainly retained forming goethite, while Ni is redeposited at greater depth in a Fe(III) and Ni-rich serpentine (serpentine II) or in goethite, where it adsorbs or substitutes for Fe in the mineral structure. Here, a 1D reactive transport model, using CrunchFlow, of Punta Gorda oxide-type Ni-laterite deposit (Moa Bay, Cuba) formation is presented. The model reproduces the formation of the different laterite horizons in the profile from an initial, partially serpentinized peridotite, in 106 years, validating the conceptual model of the formation of this kind of deposits in which a narrow saprolite horizon rich in Ni-bearing serpentine is formed above peridotite parent rock and a thick limonite horizon is formed over saprolite. Results also confirm that sorption of Ni onto goethite can explain the weight percent of Ni found in the Moa goethite. Sensitivity analyses accounting for the effect of key parameters (composition, dissolution rate, carbonate concentration, quartz precipitation) on the model results are also presented. It is found that aqueous carbonate concentration and quartz precipitation significantly affects the laterization process rate, while the effect of the composition of secondary serpentine or of mineral dissolution rates is minor. The results of this reactive transport modeling have proven useful to validate the conceptual models derived from field observations.

Surface complexation modeling of groundwater arsenic mobility: Results of a forced gradient experiment in a Red River flood plain aquifer, Vietnam

Science.gov (United States)

Jessen, Søren; Postma, Dieke; Larsen, Flemming; Nhan, Pham Quy; Hoa, Le Quynh; Trang, Pham Thi Kim; Long, Tran Vu; Viet, Pham Hung; Jakobsen, Rasmus

2012-12-01

Three surface complexation models (SCMs) developed for, respectively, ferrihydrite, goethite and sorption data for a Pleistocene oxidized aquifer sediment from Bangladesh were used to explore the effect of multicomponent adsorption processes on As mobility in a reduced Holocene floodplain aquifer along the Red River, Vietnam. The SCMs for ferrihydrite and goethite yielded very different results. The ferrihydrite SCM favors As(III) over As(V) and has carbonate and silica species as the main competitors for surface sites. In contrast, the goethite SCM has a greater affinity for As(V) over As(III) while PO43- and Fe(II) form the predominant surface species. The SCM for Pleistocene aquifer sediment resembles most the goethite SCM but shows more Si sorption. Compiled As(III) adsorption data for Holocene sediment was also well described by the SCM determined for Pleistocene aquifer sediment, suggesting a comparable As(III) affinity of Holocene and Pleistocene aquifer sediments. A forced gradient field experiment was conducted in a bank aquifer adjacent to a tributary channel to the Red River, and the passage in the aquifer of mixed groundwater containing up to 74% channel water was observed. The concentrations of As (SCM correctly predicts desorption for As(III) but for Si and PO43- it predicts an increased adsorption instead of desorption. The goethite SCM correctly predicts desorption of both As(III) and PO43- but failed in the prediction of Si desorption. These results indicate that the prediction of As mobility, by using SCMs for synthetic Fe-oxides, will be strongly dependent on the model chosen. The SCM based on the Pleistocene aquifer sediment predicts the desorption of As(III), PO43- and Si quite superiorly, as compared to the SCMs for ferrihydrite and goethite, even though Si desorption is still somewhat under-predicted. The observation that a SCM calibrated on a different sediment can predict our field results so well suggests that sediment based SCMs may be a

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

Consideration of Nuclear Criticality When Directly Disposing Highly Enriched Spent Nuclear Fuel in Unsaturated Tuff - I: Nuclear Criticality Constraints

International Nuclear Information System (INIS)

Rechard, Rob P.; Sanchez, Lawrence C.; Trellue, Holly R.

2003-01-01

This paper presents the mass, concentration, and volume required for a critical event to occur in homogeneous mixtures of fissile material and various other geologic materials. The fissile material considered is primarily highly enriched uranium spent fuel; however, 239 Pu is considered in some cases. The non-fissile materials examined are those found in the proposed repository area at Yucca Mountain, Nevada: volcanic tuff, iron rust, concrete, and naturally occurring water. For 235 U, the minimum critical solid concentration for tuff was 5 kg/m 3 (similar to sandstone), and in goethite, 45 kg/m 3 . The critical mass of uranium was sensitive to a number of factors, such as moisture content and fissile enrichment, but had a minimum, assuming almost 100% saturation and >20% enrichment, of 18 kg in tuff as Soddyite (or 9.5 kg as UO 2 ) and 7 kg in goethite. For 239 Pu, the minimum critical solid concentration for tuff was 3 kg/m 3 (similar to sandstone); in goethite, 20 kg/m 3 . The critical mass of plutonium was also sensitive to a number of factors, but had a minimum, assuming 100% saturation and 80-90% enrichment, of 5 kg in tuff and 6 kg in goethite

Study of the in-situ thermal transformations of Limonite used as pigment coming from Peru; Estudio in-situ de la transformacion termica de limonita utilizada como pigmento procedente de Peru

Energy Technology Data Exchange (ETDEWEB)

Romero-Gomez, P.; Gonzalez, J. C.; Bustamente, A.; Ruiz-conde, A.; Sanchez-Soto, P. J.

2013-06-01

It has been performed a kinetic study of the thermal transformation of Limonite [FeO(OH).nH{sub 2}O] by thermal gravimetric analysis (TGA), thermal X-ray Diffraction (XRD) and {mu}-Raman spectroscopy. The mineral was extracted from the Taraco District, Huancane Province, Puno region (Peru). Powdered XRD identify goethite phase as the main mineralogical component besides quartz. It was subjected to in-situ thermal treatment in the range of temperatures 100 to 500 degree centigrade in air and an inert atmosphere (nitrogen). The goethite phase remains stable from room temperature until 200 degree centigrade. From 250 degree centigrade there is a phase transformation {alpha}-FeO(OH) {yields}{alpha}-Fe{sub 2}O{sub 3} with 8 wt % weight loss and a chromatic change, i.e., the change of the hydroxylated goethite phase (yellow) to oxided hematite phase (red), as evidenced by the TGA and evolution of the XRD profiles. Moreover, the {mu}-Raman spectra of the in-situ thermal treatment corroborate that there is a transition at 290 degree centigrade by the transformation of the characteristic Raman bands of the goethite to hematite phase, in the frequency range from 200 to 1800cm{sup -}1. (Author) 11 refs.

Controls on chemistry and diagenesis of naturally occurring iron-oxide phases

Energy Technology Data Exchange (ETDEWEB)

Nancy W. Hinman; J. Michelle Kotler; Beizhan Yan; Aaron Tenesch; Richard V. Morris; Daphne L. Stoner; Jill R. Scott

2009-07-01

The purposes of this study were to (i) document chemical and mineralogical compositions in two naturally acidic drainages over a 1 m soil profile, (ii) document organic and inorganic signatures representative of past chemical or biological processes in the soils, and (iii) determine whether mineralogical and chemical differences are a consequence of differences in original composition, depositional conditions, or diagenesis. Two sites were studied: Paymaster Creek in the Heddleston Mining District near Lincoln, Montana and the New World Mining District near Cooke City, Montana. The oldest deposits at both naturally acidic sites pre-date human mining activity by several thousand years, although there is recent human activity at both sites. Both sites have streams with high dissolved Fe and moderately low pH and actively accumulate schwertmannite on streambeds. Soil deposits away from the streambed at Paymaster Creek contained goethite with adsorbed sulfate, but no schwertmannite, suggesting either that the original conditions precluded schwertmannite precipitation or that diagenesis occurred rapidly converting the schwertmannite to goethite. The New World Mining District site showed the expected profile, which is a gradual transition from schwertmannite- and goethite-bearing soils to goethite-only soils. Concentrations of Cr, As and other trace elements shown to retard diagenesis were higher at the New World site than at the Paymaster site.

Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

Science.gov (United States)

Moskowitz, Bruce M; Reynolds, Richard L.; Goldstein, Harland L.; Beroquo, Thelma; Kokaly, Raymond F.; Bristow, Charlie S

2016-01-01

Atmospheric mineral dust can influence climate and biogeochemical cycles. An important component of mineral dust is ferric oxide minerals (hematite and goethite) which have been shown to influence strongly the optical properties of dust plumes and thus affect the radiative forcing of global dust. Here we report on the iron mineralogy of dust-source samples from the Bodélé Depression (Chad, north-central Africa), which is estimated to be Earth’s most prolific dust producer and may be a key contributor to the global radiative budget of the atmosphere as well as to long-range nutrient transport to the Amazon Basin. By using a combination of magnetic property measurements, Mössbauer spectroscopy, reflectance spectroscopy, chemical analysis, and scanning electron microscopy, we document the abundance and relative amounts of goethite, hematite, and magnetite in dust-source samples from the Bodélé Depression. The partition between hematite and goethite is important to know to improve models for the radiative effects of ferric oxide minerals in mineral dust aerosols. The combination of methods shows (1) the dominance of goethite over hematite in the source sediments, (2) the abundance and occurrences of their nanosize components, and (3) the ubiquity of magnetite, albeit in small amounts. Dominant goethite and subordinate hematite together compose about 2% of yellow-reddish dust-source sediments from the Bodélé Depression and contribute strongly to diminution of reflectance in bulk samples. These observations imply that dust plumes from the Bodélé Depression that are derived from goethite-dominated sediments strongly absorb solar radiation. The presence of ubiquitous magnetite (0.002–0.57 wt%) is also noteworthy for its potentially higher solubility relative to ferric oxide and for its small sizes, including PM iron apportionment is estimated at about 33% in ferric oxide minerals, 1.4% in magnetite, and 65% in ferric silicates. Structural iron in clay

Evidence of biogeochemical processes in iron duricrust formation

Science.gov (United States)

Levett, Alan; Gagen, Emma; Shuster, Jeremiah; Rintoul, Llew; Tobin, Mark; Vongsvivut, Jitraporn; Bambery, Keith; Vasconcelos, Paulo; Southam, Gordon

2016-11-01

Canga is a moderately hard iron-rich duricrust primarily composed of goethite as a result of the weathering of banded iron formations. Canga duricrusts lack a well-developed soil profile and consequently form an innate association with rupestrian plants that may become ferruginised, contributing to canga possessing macroscopic biological features. Examination of polished canga using a field emission scanning electron microscope (FE-SEM) revealed the biological textures associated with canga extended to the sub-millimetre scale in petrographic sections and polished blocks. Laminae that formed by abiotic processes and regions where goethite cements were formed in association with microorganisms were observed in canga. Biological cycling of iron within canga has resulted in two distinct forms of microbial fossilisation: permineralisation of multispecies biofilms and mineralisation of cell envelopes. Goethite permineralised biofilms frequently formed around goethite-rich kaolinite grains in close proximity to goethite bands and were composed of micrometre-scale rod-shaped, cocci and filamentous microfossils. In contrast, the cell envelopes immobilised by authigenic iron oxides were primarily of rod-shaped microorganisms, were not permineralised and occurred in pore spaces within canga. Complete mineralisation of intact rod-shaped casts and the absence of permineralisation suggested mineralised cell envelopes may represent fossilised iron-oxidising bacteria in the canga ecosystem. Replication of these iron-oxidising bacteria appeared to infill the porous regions within canga. Synchrotron-based Fourier transform infrared (FTIR) microspectroscopy demonstrated that organic biomarkers were poorly preserved with only weak bands indicative of aliphatic methylene (CH2) associated with permineralised microbial biofilms. High resolution imaging of microbial fossils in canga that had been etched with oxalic acid supported the poor preservation of organic biomarkers within canga

Chemical speciation and adsorption behavior of plutonium in natural waters

International Nuclear Information System (INIS)

Sanchez, A.L.

1983-01-01

Dissolved Pu profiles in two partially anoxic basins--Saanich Inlet, an intermittently anoxic marine fiord in Vancouver Island, British Columbia, and Soap Lake, a saline, alkaline lake in eastern Washington state, revealed minimum concentrations at the O 2 /H 2 S interface. The Pu concentrations in the anoxic waters of Saanich Inlet were less than the surface concentrations; however, in Soap Lake, a 15- to 50-fold increase in Pu concentration in the anoxic monimolimnion correlated with large increases in the major ions, total alkalinity, and dissolved organic carbon. Laboratory experiments were designed to investigate the effects of pH, ionic strength, dissolved organic carbon, and carbonate ions on the adsorption of tracer amounts of Pu IV and Pu V. The Pu-goethite adsorption system provided the data base for developing a thermodynamic model of Pu interaction with an oxide surface and with dissolved ligands, using the MINEQL computer program. Pu IV and Pu V interacted very differently with goethite, which is consistent with their different hydrolytic character. A reduction of Pu V to Pu IV occurred on the goethite surface and also on montmorillonite and silica gel, suggesting that redox transformations are an important aspect of Pu adsorption. Increases in ionic strength (up to 3 M NaCl or NaNO 3 ) did not affect Pu IV or V adsorption. In the presence of dissolved organic carbon (DOC), Pu V reduction to Pu IV occurred in solution. Pu IV adsorption on goethite decreased only 30% in the presence of 240 ppm of natural DOC from Soap Lake; however, carbonate anions inhibited Pu IV adsorption on goethite at the alkalinity levels (1500 meq/L total alkalinity, 0.57 M CO 3 =) measured for Soap Lake monimolimnion waters

A study of selenium and tin sorption on granite and geothite

International Nuclear Information System (INIS)

Ticknor, K.V.; McMurry, J.

1996-01-01

Sensitivity analyses based on an illustrative performance assessment case study of a disposal concept for nuclear fuel waste have shown that radioisotopes of Se and Sn could have a significant effect on cumulative radioactive dose if they were to be transported through the geosphere without retardation. Static batch sorption methods, coupled with 2 n factorial experimental designs, were used to determine the extent to which Se and Sn can be sorbed by granite and goethite as a function of total dissolved solids concentration, [TDS], natural fulvic acid concentration as dissolved organic carbon, [DOC], pH and, for the studies with Se, the Se concentration, [Se]. Aqueous speciation and the saturation indices of solubility-controlling solid phases were estimated using the speciation code HARPHRQ with the HATCHES thermodynamic database. The experimental results indicated that Se sorption on granite was, low and not affected by changes in [DOC] or [TDS]. Increased [Se] and increased pH decreased sorption. For Se sorption on goethite, the pH range was narrow but indicated that sorption decreased as pH increased. Increased [TDS] and [Se] lowered sorption on goethite, but changes in [DOC] had no effect on sorption. For Sn, increased pH, [TDS] and [DOC] decreased sorption on granite. For Sn sorption on goethite, increased [DOC] resulted in decreased sorption, but differences in [TDS] and pH had little consistent effect on sorption. (orig.)

Effects of humic acid on adsorption of actinide elements on rocks and others

Energy Technology Data Exchange (ETDEWEB)

Ohashi, Masakazu; Sato, Seichi; Ohashi, Hiroshi [Hokkaido Univ., Sapporo (Japan). Faculty of Engineering; Sakamoto, Yoshiaki; Nagao, Seiya; Onuki, Toshihiko; Senoo, Muneaki

1996-01-01

Since the transfer rates of radionuclides are reduced by their adsorption to rocks and soils, it is essential to elucidate the adsorption process for safety assessment of their geological disposal. In this study, adsorption of Np(V) to goethite, one of the widely distributed minerals was investigated as functions of pH and humic acid concentration. The surface charge density of goethite was determined and the zero charge point was 6.2 for synthesized and 6.4 for natural goethite. Since the point for humic acid was 4.5, adsorption sites for humic acid were reduced as the increase of negative charge density above pH6, resulting in a decrease in its adsorption rate. Np(V) adsorption to goethite was raised by the presence of humic acid in the range of 0-10ppm because the surface charge on the rock was shifted to negative by the adsorption of humic acid, resulting in easy adsorption of NpO{sub 2}{sup +}, which is stable in the condition below pH 9.5. On the other hand, humic acid adsorption was saturated at a concentration higher than 50 ppm, but its content in the solution would increase. Thus, it was thought that Np(V)-humic acid complex becomes more stable, resulting in the decrease in Np(V) adsorption rate. (M.N.)

Microcalorimetric and potentiometric titration studies on the adsorption of copper by extracellular polymeric substances (EPS), minerals and their composites.

Science.gov (United States)

Fang, Linchuan; Huang, Qiaoyun; Wei, Xing; Liang, Wei; Rong, Xinming; Chen, Wenli; Cai, Peng

2010-08-01

Equilibrium adsorption experiments, isothermal titration calorimetry and potentiometric titration techniques were employed to investigate the adsorption of Cu(II) by extracellular polymeric substances (EPS) extracted from Pseudomonas putida X4, minerals (montmorillonite and goethite) and their composites. Compared with predicted values of Cu(II) adsorption on composites, the measured values of Cu(II) on EPS-montmorillonite composite increased, however, those on EPS-goethite composite decreased. Potentiometric titration results also showed that more surface sites were observed on EPS-montmorillonite composite and less reactive sites were found on EPS-goethite composite. The adsorption of Cu(II) on EPS molecules and their composites with minerals was an endothermic reaction, while that on minerals was exothermic. The positive values of enthalpy change (Delta H) and entropy change (DeltaS) for Cu(II) adsorption on EPS and mineral-EPS composites indicated that Cu(II) mainly interacts with carboxyl and phosphoryl groups as inner-sphere complexes on EPS molecules and their composites with minerals. (c) 2010 Elsevier Ltd. All rights reserved.

The effect of soil mineral phases on the abiotic degradation of selected organic compounds. Final report, June 31, 1990--December 31, 1994

Energy Technology Data Exchange (ETDEWEB)

Sandhu, S.S.

1994-12-31

Funds were received from the United States Department of Energy to study the effects of soil mineral phases on the rates of abiotic degradation of tetraphenylborate (TPB) and diphenylboronic acid (DPBA). In addition to kaolinite and montmorillonite clay minerals, the role of goethite, corundum, manganite, and rutile in the degradation of organoborates was also evaluated. The effects of DPBA, argon, molecular dioxygen (O{sub 2}), temperature, and organic matter on the degradation of organoborates were also measured. The results indicated that TPB and DPBA degraded rapidly on the mineral surfaces. The initial products generated from the degradation of TPB were DPBA and biphenyl; however, further degradation resulted in the formation of phenylboric acid and phenol which persisted even after TPB disappeared. The data also showed that the rate of TPB degradation was faster in kaolinite, a 1:1 clay mineral, than in montmorillonite, a double layer mineral. The initial degradation of TPB by corundum was much higher than goethite, manganite and rutile. However, no further degradation by this mineral was observed where as the degradation of TPB continued by goethite and rutile minerals. Over all, the degradation rate of TPB was the highest for goethite as compared to the other metal oxide minerals. The degradation of TPB and DPBA was a redox reaction where metals (Fe, Al, Ti, Mn) acted as Lewis acids. DPBA and argon retarded the TPB degradation where as molecular oxygen organic matter and temperature increased the rate of TPB disappearance.

Irreversible Sorption of Contaminants During Ferrihydrite Transformation

International Nuclear Information System (INIS)

Anderson, H.L.; Arthur, S.E.; Brady, P.V.; Cygan, R.T.; Nagy, K.L.; Westrich, H.R.

1999-01-01

A better understanding of the fraction of contaminants irreversibly sorbed by minerals is necessary to effectively quantify bioavailability. Ferrihydrite, a poorly crystalline iron oxide, is a natural sink for sorbed contaminants. Contaminants may be sorbed/occluded as ferrihydrite precipitates in natural waters or as it ages and transforms to more crystalline iron oxides such as goethite or hematite. Laboratory studies indicate that Cd, Co, Cr, Cu, Ni, Np, Pb, Sr, U, and Zn are irreversibly sorbed to some extent during the aging and transformation of synthetic ferrihydrite. Barium, Ra and Sr are known to sorb on ferrihydrite in the pH range of 6 to 10 and sorb more strongly at pH values above its zero point of charge (pH> 8). We will review recent literature on metal retardation, including our laboratory and modeling investigation of Ba (as an analogue for Ra) and Sr adsorption/resorption, during ferrihydrite transformation to more crystalline iron oxides. Four ferrihydrite suspensions were aged at pH 12 and 50 C with or without Ba in 0.01 M KN03 for 68 h or in 0.17 M KN03 for 3424 h. Two ferrihydrite suspensions were aged with and without Sr at pH 8 in 0.1 M KN03 at 70C. Barium or Sr sorption, or resorption, was measured by periodically centrifuging suspension subsamples, filtering, and analyzing the filtrate for Ba or Sr. Solid subsamples were extracted with 0.2 M ammonium oxalate (pH 3 in the dark) and with 6 M HCl to determine the Fe and Ba or Sr attributed to ferrihydrite (or adsorbed on the goethite/hematite stiace) and the total Fe and Ba or Sr content, respectively. Barium or Sr occluded in goethite/hematite was determined by the difference between the total Ba or Sr and the oxalate extractable Ba or Sr. The percent transformation of ferrihydrite to goethite/hematite was estimated from the ratio of oxalate and HC1 extractable Fe. All Ba was retained in the precipitates for at least 20 h. Resorption of Ba reached a maximum of 7 to 8% of the Ba2+ added for

Impact of Bioreduction on Remobilization of Adsorbed Cadmium on Iron Minerals in Anoxic Condition.

Science.gov (United States)

Ghorbanzadeh, Nasrin; Lakzian, Amir; Halajnia, Akram; Choi, Ui-Kyu; Kim, Ki-Hyun; Kim, Jong-Oh; Kurade, Mayur; Jeon, Byong-Hun

2017-06-01

  The impact of bioreduction on the remobilization of adsorbed cadmium Cd(II) on minerals, including hematite, goethite, and two iron(III)-rich clay minerals nontronites (NAU-1 and NAU-2) under anoxic conditions was investigated. Langmuir isotherm equation better described the sorption of Cd(II) onto the all minerals. The maximum adsorption capacity was 6.2, 18.1, 3.6, and 4 mg g-1 for hematite, goethite, NAU-1 and NAU-2, respectively. The desorption of Cd(II) was due to the production of Fe(II) as a result of bioreduction of structural Fe(III) in the minerals by Shewanella putrefaciens. The bioreduction of Cd(II)-loaded Fe(III) minerals was negligible during the initial 5 days followed by a rapid increase up to 20 days. The amount of Cd(II) in solution phase at the end of 30 days increased up to 0.07 mmol L-1 for hematite, NAU-1, and NAU-2 and 0.02 mmol L-1 for goethite. The X-ray diffraction study showed negligible changes in bioreduced minerals phases.

Evolution and alteration in situ of a massive iron duricrust in Central Africa

Science.gov (United States)

Bitom, Dieudonné; Volkoff, Boris; Abossolo-Angue, Monique

2003-08-01

A soil sequence with iron duricrust is described in an area covered by tropical rain forest in South Cameroon. The dismantling of the iron duricrust is documented through a close observation of a soft duricrust, which corresponds to a transitional stage in the degradation of a massive iron duricrust into a loose nodular horizon. In the initial massive and hematitic duricrust, nodular shapes are progressively formed. The nodules and the internodular matrix remain hematitic. The internodular matrix undergoes goethitization and a pronounced deferruginisation before loosening; the primary structure of the iron duricrust is maintained, however, due to internodular bridges, relics of internodular matrix which escaped the process of goethitization. The iron is gradually released from these hematitic bridges, which become softer. This leads to the collapse of the initial structures of the iron duricrust and to the formation of a loose nodular material with a clayey matrix containing kaolinite and goethite. Many loose nodular horizons, which are found all over Central Africa, may have been formed by such alteration of a former iron duricrust.

On the Origin of Bastnaesite-(La,Nd,Y in the Nissi (Patitira Bauxite Laterite Deposit, Lokris, Greece

Directory of Open Access Journals (Sweden)

Sofia Kalatha

2017-03-01

Full Text Available A detailed geochemical study and a thorough mineralogical description of the rare-earth elements (REE-minerals and associated minerals were carried out in two vertical profiles of approximately 4 m length, from the Nissi (Patitira bauxite laterite deposit, Lokris, Greece, characterized by the presence of goethite in small sizes resembling bacterial cell coated by goethite and a significant REE enrichment. The enrichment of the REE concentrated in bastnaesite-group minerals, the intergrowths between REE-minerals and Al–Ni–silicates with significant sulfur contents and their association with goethite microtextures interpreted as bacteriomorphic, indicate REE remobilization along with iron bio-leaching and re-precipitation on karstified limestone. In addition to the previous-reported hydroxylbastnaesites, a (La,Nd,Y(CO3F member of the bastnaesite-group associated with Al–Ni–silicates were identified, the stability of which may reflect the dependence on the source rocks and the local variations of pH-Eh. Interaction between downward percolating water and carbonate rocks seems to be a very effective mechanism for REE fluorocarbonates deposition under alkaline and reducing conditions.

Transport of contaminants from energy-process-waste leachates through subsurface soils and soil components: laboratory experiments

International Nuclear Information System (INIS)

Wangen, L.E.; Stallings, E.A.; Walker, R.D.

1982-08-01

The subsurface transport and attenuation of inorganic contaminants common to a variety of energy process waste leachates are being studied using laboratory column methods. Anionic species currently being emphasized are As, B, Mo, and Se. Transport of the cations Cd and Ni is also being studied. The solid adsorbents consist of three soil mineral components (silica sand, kaolinite, and goethite), and four subsurface soils (a dunal sand, an oxidic sandy clay loam, an acidic clay loam, and an alkaline clay loam). Breakthrough patterns of these species from packed soil columns are followed by monitoring eluent concentrations vs time under carefully controlled laboratory conditions. This report describes the experimental methods being used, the results of preliminary batch adsorption studies, and the results of column experiments completed through calendar year 1981. Using column influent concentrations of about 10 mg/l, adsorption (mmoles/100 g) has been determined from the eluent volume corresponding to 50% breakthrough. On silica sand, kaolinite, dunal sand, and goethite, respectively, these are 2.0 x 10 -4 , 0.020, 0.013, and 0.31 for cadmium, 4.4 x 10 -4 , 0.039, 0.020, and 0.98 for nickel. On kaolinite, dunal sand, and goethite, respectively, adsorption values (mmoles/100 g) are As (0.24, 0.019, and 20.5), B (0.041, 0.0019, and 1.77), Mo (0.048, 0.0010, and 5.93), and Se (0.029, 0.00048, and 1.30). Arsenic is the most highly adsorbed contaminant species and goethite has the largest adsorption capacity of the adsorbents

Moessbauer spectroscopy study of a mineral sample from Oshno Hill, District of Chavin de Pariarca, Huanuco Region, Peru

International Nuclear Information System (INIS)

Bustamante, A.; Lovera, D.; Quille, R.; Arias, A. V.; Quinones, J.

2010-01-01

The analysis by X-ray diffraction of a mining sample collected from Oshno hill, which is located in the District of Chavin de Pariarca, Huamalies Province, Huanuco, Peru, indicates the presence of lepidocrocite (γ-FeOOH) and goethite (α-FeOOH). The room temperature Moessbauer spectrum (MS) doublet with broad lines displays hyperfine parameters corresponding to the presence of particles of iron hydroxides smaller than 100 A in a superparamagnetic regime. The measurement of a MS at 4.2 K allowed confirming the presence of goethite and lepidocrocite (with average magnetic fields of 49.21 T and 44.59 T, respectively).

Nanocrystallinity induced by heating

DEFF Research Database (Denmark)

Mørup, Steen; Meaz, T.M.; Bender Koch, C.

1997-01-01

Samples of akaganeite (beta-FeOOH) and goethite (alpha-FeOOH) have been studied after heating at various temperatures up to 800 C. X-ray diffraction and Mossbauer spectroscopy measurements showed that slightly below the temperatures at which the samples transform to hematite (alpha-Fe2O3) the oxy......Samples of akaganeite (beta-FeOOH) and goethite (alpha-FeOOH) have been studied after heating at various temperatures up to 800 C. X-ray diffraction and Mossbauer spectroscopy measurements showed that slightly below the temperatures at which the samples transform to hematite (alpha-Fe2O3...

Remediation of ultra low level of transuranics from potable water using hybrid materials

International Nuclear Information System (INIS)

Singhal, R.K.; Basu, H.; Reddy, A.V.R.

2015-01-01

In case of nuclear accidents like Daiichi Nuclear Power Plant (NPP) Fukushima, Japan (11 March, 2011) and nuclear accidents like Chernobyl, USSR (March, 1986), where large amount of activity spread in public domain necessitate the need of development of new material which can efficiently remove transuranic from potable water without disturbing its water quality. Three different types of natural sorbents were developed using natural siliceous material, sodium alginate and impregnation of goethite in alginate matrix. Experiments were carried out for decontamination of americium and plutonium by using Calcium Alginate (Cal-Alg) and Goethite impregnated Cal-Alg (Geo-Cal-Alg) respectively

EPR in characterization of seeds paramagnetic species

International Nuclear Information System (INIS)

Luiz, A.P.C.; Mauro, M.F.F.L.; Portugal, K.O.; Barbana, V.M.; Guedes, C.L.B.; Mauro, E. di; Carneiro, C.E.A.; Zaia, D.A.M.; Prete, C.E.C.

2011-01-01

Full text. In Brazil, since 1970s, renewable fuel programs has been developed in order to replace petroleum. Today a program that has been discussed is the bio diesel, which intend to replace diesel fuel, fossil oil, to bio diesel, renewal fuel. As seeds are the basis for production of oil and consequently processed into bio diesel, the goal of this work is to characterize and compare paramagnetic species present in the seeds by Electron Paramagnetic Resonance (EPR). Samples used in this study were seeds of sorghum, barley, corn, peanuts, soy beans, cotton, wheat, oats, mustard, rice, sunflower and turnip. Some paramagnetic species present in soil was also investigated as goethite (FeOOH), hematite (Fe 2 O 3 ), magnetite (Fe 3 O 4 ), and ferrihydrite (Fe 5 HO 8 · 4H 2 O), since, these species present in appreciable quantities in the soil can be present in the seeds and analyzed for comparison. The characterization of these species is essential to understand the EPR seeds spectra. Each sample is placed in a thin quartz tube 4 mm in diameter, and it is inserted into the cavity of the spectrometer at room temperature, at low temperature (77 K) and variable temperature using liquid nitrogen flow and hot flow through a compressor air. It was used as standard Mg O:Mn 2+ , which is also inserted into the cavity. Shortly after the potency is regulated, frequency, amplitude and sweep the field. The spectroscopic analysis by EPR X-band (∼ 9:5GHz), were performed at the Fluorescence and Electron Paramagnetic Resonance Laboratory, Exact Sciences Center, State University of Londrina, Parana state, Brazil, through an EPR spectrometer JEOL brand (JES-PE-3X). In the EPR spectra, spectroscopic factor or g factor and line width were determined in paramagnetic species. Studies from several seeds with EPR technique detected in all of them presence of same complex of Fe 3+ present in the goethite at g ∼ 2, and in the seeds exist free radicals at g = 2:004, at room temperature

Prediction of metal sorption in soils

International Nuclear Information System (INIS)

Westrich, Henry R.; Anderson, Harold L. Jr.; Arthur, Sara E.; Brady, Patrick V.; Cygan, Randall T.; Liang, Jianjie; Zhang, Pengchu; Yee, N.

2000-01-01

Radionuclide transport in soils and groundwaters is routinely calculated in performance assessment (PA) codes using simplified conceptual models for radionuclide sorption, such as the K D approach for linear and reversible sorption. Model inaccuracies are typically addressed by adding layers of conservativeness (e.g., very low K D 's), and often result in failed transport predictions or substantial increases in site cleanup costs. Realistic assessments of radionuclide transport over a wide range of environmental conditions can proceed only from accurate, mechanistic models of the sorption process. They have focused on the sorption mechanisms and partition coefficients for Cs + , Sr 2+ and Ba 2+ (analogue for Ra 2+ ) onto iron oxides and clay minerals using an integrated approach that includes computer simulations, sorption/desorption measurements, and synchrotron analyses of metal sorbed substrates under geochemically realistic conditions. Sorption of Ba 2+ and Sr 2+ onto smectite is strong, pH-independent, and fully reversible, suggesting that cation exchange at the interlayer basal sites controls the sorption process. Sr 2+ sorbs weakly onto geothite and quartz, and is pH-dependent. Sr 2+ sorption onto a mixture of smectite and goethite, however, is pH- and concentration dependent. The adsorption capacity of montmorillonite is higher than that of goethite, which may be attributed to the high specific surface area and reaction site density of clays. The presence of goethite also appears to control the extent of metal desorption. In-situ, extended X-ray absorption fine structure (EXAFS) spectroscopic measurements for montmorillonite and goethite show that the first shell of adsorbed Ba 2+ is coordinated by 6 oxygens. The second adsorption shell, however, varies with the mineral surface coverage of adsorbed Ba 2+ and the mineral substrate. This suggests that Ba 2+ adsorption on mineral surfaces involves more than one mechanism and that the stability of sorbed

EPR in characterization of seeds paramagnetic species

Energy Technology Data Exchange (ETDEWEB)

Luiz, A.P.C.; Mauro, M.F.F.L.; Portugal, K.O.; Barbana, V.M.; Guedes, C.L.B.; Mauro, E. di; Carneiro, C.E.A.; Zaia, D.A.M.; Prete, C.E.C. [Universidade Estadual de Londrina (UEL), PR (Brazil)

2011-07-01

Full text. In Brazil, since 1970s, renewable fuel programs has been developed in order to replace petroleum. Today a program that has been discussed is the bio diesel, which intend to replace diesel fuel, fossil oil, to bio diesel, renewal fuel. As seeds are the basis for production of oil and consequently processed into bio diesel, the goal of this work is to characterize and compare paramagnetic species present in the seeds by Electron Paramagnetic Resonance (EPR). Samples used in this study were seeds of sorghum, barley, corn, peanuts, soy beans, cotton, wheat, oats, mustard, rice, sunflower and turnip. Some paramagnetic species present in soil was also investigated as goethite (FeOOH), hematite (Fe{sub 2}O{sub 3}), magnetite (Fe{sub 3}O{sub 4}), and ferrihydrite (Fe{sub 5}HO{sub 8} {center_dot} 4H{sub 2}O), since, these species present in appreciable quantities in the soil can be present in the seeds and analyzed for comparison. The characterization of these species is essential to understand the EPR seeds spectra. Each sample is placed in a thin quartz tube 4 mm in diameter, and it is inserted into the cavity of the spectrometer at room temperature, at low temperature (77 K) and variable temperature using liquid nitrogen flow and hot flow through a compressor air. It was used as standard Mg O:Mn{sup 2+}, which is also inserted into the cavity. Shortly after the potency is regulated, frequency, amplitude and sweep the field. The spectroscopic analysis by EPR X-band ({approx} 9:5GHz), were performed at the Fluorescence and Electron Paramagnetic Resonance Laboratory, Exact Sciences Center, State University of Londrina, Parana state, Brazil, through an EPR spectrometer JEOL brand (JES-PE-3X). In the EPR spectra, spectroscopic factor or g factor and line width were determined in paramagnetic species. Studies from several seeds with EPR technique detected in all of them presence of same complex of Fe{sup 3+} present in the goethite at g {approx} 2, and in the seeds

Mineralogy of the clay fraction of alfisols in two slope curvatures: IV - spatial correlation with physical properties Mineralogia da fração argila de um argissolo em curvaturas do relevo: II - correlação especial com atributos físicos

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Livia Arantes Camargo

2013-04-01

Full Text Available Although the influence of clay mineralogy on soil physical properties has been widely studied, spatial relationships between these features in Alfisols have rarely been examined. The purpose of this work was to relate the clay minerals and physical properties of an Alfisol of sandstone origin in two slope curvatures. The crystallographic properties such as mean crystallite size (MCS and width at half height (WHH of hematite, goethite, kaolinite and gibbsite; contents of hematite and goethite; aluminium substitution (AS and specific surface area (SSA of hematite and goethite; the goethite/(goethite+hematite and kaolinite/(kaolinite+gibbsite ratios; and the citrate/bicarbonate/dithionite extractable Fe (Fe d were correlated with the soil physical properties through Pearson correlation coefficients and cross-semivariograms. The correlations found between aluminium substitution in goethite and the soil physical properties suggest that the degree of crystallinity of this mineral influences soil properties used as soil quality indicators. Thus, goethite with a high aluminium substitution resulted in large aggregate sizes and a high porosity, and also in a low bulk density and soil penetration resistance. The presence of highly crystalline gibbsite resulted in a high density and micropore content, as well as in smaller aggregates. Interpretation of the cross-semivariogram and classification of landscape compartments in terms of the spatial dependence pattern for the relief-dependent physical and mineralogical properties of the soil proved an effective supplementary method for assessing Pearson correlations between the soil physical and mineralogical properties.A influência da mineralogia da fração argila nos atributos físicos do solo é reportada na literatura; porém, as relações espaciais entre esses atributos são escassas em se tratando de Argissolos. O objetivo deste trabalho foi avaliar a correlação espacial entre os minerais da fra

Synthesis of Minerals with Iron Oxide and Hydroxide Contents as a Sorption Medium to Remove Arsenic from Water for Human Consumption

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Sofia Garrido-Hoyos

2015-12-01

Full Text Available Arsenic has been classified as a toxic and carcinogenic chemical element. It therefore presents a serious environmental problem in different regions of the country and the world. In the present work, two adsorbent media were developed and evaluated to remove arsenic from water in the Pájaro Verde mine shaft, Huautla, Tlaquiltenango, Morelos. The media were synthesized and characterized, obtaining a surface area of 43.04 m2·g−1 for the goethite and 2.44 m2·g−1 for silica sand coated with Fe(III. To conduct the sorption kinetics and isotherms, a 23 factorial design was performed for each medium in order to obtain the optimal conditions for the factors of arsenic concentration, pH and mass of the adsorbent. The best results were obtained for goethite, with a removal efficiency of 98.61% (C0 of As(V 0.360 mg·L−1, and an effluent concentration of 0.005 mg·L−1, a value that complies with the modified Official Mexican Standard NOM-127-SSA1-1994 [1] and WHO guidelines (2004 [2]. The kinetic equation that best fit the experimental data was the pseudo-second-order, resulting in the highest values for the constants for synthetic goethite, with a rate constant sorption of 4.019·g·mg−1·min−1. With respect to the sorption isotherms, both media were fitted to the Langmuir-II linear model with a sorption capacity (qm of 0.4822 mg·g−1 for goethite and 0.2494 mg·g−1 for silica sand coated with Fe(III.

Synthesis of Minerals with Iron Oxide and Hydroxide Contents as a Sorption Medium to Remove Arsenic from Water for Human Consumption.

Science.gov (United States)

Garrido-Hoyos, Sofia; Romero-Velazquez, Lourdes

2015-12-23

Arsenic has been classified as a toxic and carcinogenic chemical element. It therefore presents a serious environmental problem in different regions of the country and the world. In the present work, two adsorbent media were developed and evaluated to remove arsenic from water in the Pájaro Verde mine shaft, Huautla, Tlaquiltenango, Morelos. The media were synthesized and characterized, obtaining a surface area of 43.04 m²·g(-1) for the goethite and 2.44 m²·g(-1) for silica sand coated with Fe(III). To conduct the sorption kinetics and isotherms, a 2³ factorial design was performed for each medium in order to obtain the optimal conditions for the factors of arsenic concentration, pH and mass of the adsorbent. The best results were obtained for goethite, with a removal efficiency of 98.61% (C₀ of As(V) 0.360 mg·L(-1)), and an effluent concentration of 0.005 mg·L(-1), a value that complies with the modified Official Mexican Standard NOM-127-SSA1-1994 [1] and WHO guidelines (2004) [2]. The kinetic equation that best fit the experimental data was the pseudo-second-order, resulting in the highest values for the constants for synthetic goethite, with a rate constant sorption of 4.019·g·mg(-1)·min(-1). With respect to the sorption isotherms, both media were fitted to the Langmuir-II linear model with a sorption capacity (qm) of 0.4822 mg·g(-1) for goethite and 0.2494 mg·g(-1) for silica sand coated with Fe(III).

Moessbauer and XRD Comparative Study of Host Rock and Iron Rich Mineral Samples from Paz del Rio Iron Ore Mineral Mine in Colombia

International Nuclear Information System (INIS)

Fajardo, M.; Perez Alcazar, G. A.; Moreira, A. M.; Speziali, N. L.

2004-01-01

A comparative study between the host rock and the iron rich mineral samples from the Paz del Rio iron ore mineral mine in Colombia was performed using X-ray diffraction and Moessbauer spectroscopy. Diffraction results of the iron rich mineral sample show that goethite, hematite, quartz, kaolinite and siderite are the main phases, and that a small amount of illite is also present. By Moessbauer spectroscopy at room temperature (RT) the presence of all the above mentioned phases was detected except quartz as well as an additional presence of small amount of biotite. The goethite, which appears as four sextets with hyperfine fields of 33.5, 30.5, 27.5 and 18.5 T, respectively, is the majority phase. This result shows the different grades of formation of this oxyhydroxide. The Moessbauer spectrum of this sample at 80 K presents the same phases obtained at RT without any superparamagnetic effect. In this case the goethite appears as two sextets. Diffraction results of the host rock sample show a large amount of quartz and kaolinite and small amounts of illite and biotite, whereas by Moessbauer spectroscopy illite, kaolinite and biotite were detected.

Sequestration of non-pure carbon dioxide streams in iron oxyhydroxide-containing saline repositories

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Garcia, S.; Rosenbauer, Robert J.; Palandri, James L.; Maroto-Valer, M. Mercedes

2012-01-01

Iron oxyhydroxide, goethite (α-FeOOH), was evaluated as a potential formation mineral reactant for trapping CO2 in a mineral phase such as siderite (FeCO3), when a mixture of CO2-SO 2 flue gas is injected into a saline aquifer. Two thermodynamic simulations were conducted, equilibrating a CO2-SO2 fluid mixture with a NaCl-brine and Fe-rich rocks at 150 °C and 300 bar. The modeling studies evaluated mineral and fluid composition at equilibrium and the influence of pH buffering in the system. Results show siderite precipitates both in the buffered and unbuffered system; however, the presence of an alkaline pH buffer enhances the stability of the carbonate. Based on the model, an experiment was designed to compare with thermodynamic predictions. A CO2-SO2 gas mixture was reacted in 150 ml of NaCl-NaOH brine containing 10 g of goethite at 150 °C and 300 bar for 24 days. Mineralogical and brine chemistry confirmed siderite as the predominant reaction product in the system. Seventy-six mg of CO2 are sequestered in siderite per 10 g of goethite.

Seismic slip recorded in tourmaline fault mirrors from Elba Island (Italy)

Science.gov (United States)

Viti, C.; Brogi, A.; Liotta, D.; Mugnaioli, E.; Spiess, R.; Dini, A.; Zucchi, M.; Vannuccini, G.

2016-05-01

This paper reports the first example of fault mirrors developed in an unusual protolith, consisting of tourmaline crystals with interstitial goethite. The deformation mechanisms active in the fault zone have been investigated from the outcrop to the nanoscale, aiming to identify possible traces of frictional heating at seismic slip rate, as observed for other fault mirrors in different protoliths. The investigation revealed the superposition of two main deformational stages. The first was dominated by brittle processes and produced a cataclastic/ultracataclastic principal slip zone, a few mm thick; the second was associated with seismic slip and produced a sharp discontinuity (the principal slip surface) within the cataclastic/ultracataclastic zone. The mirror-like coating, a few microns thick, occurs on the principal slip surface, and is characterized by 1) absence of interstitial goethite; 2) occurrence of truncated tourmaline crystals; 3) highly variable grain size, from 200 μm to 200 nm; 4) tourmaline close packing with interlobate grain boundaries, and 5) tourmaline random crystallographic orientation. Micro and nanostructural investigations indicate the occurrence of thermally-activated processes, involving both interstitial goethite and tourmaline. In particular, close to the principal slip surface, goethite is completely decomposed, and produced an amorphous porous material, with local topotactic recrystallization of hematite. Tourmaline clasts are typically characterized by strongly lobate boundaries, indicative of reaction and partial decomposition at grain boundaries. TEM observations revealed the occurrence of tourmaline nanograins, a few tens of nm in size, characterized by rounded shape and fading amorphous boundaries, that cannot be obtained by brittle processes. Lastly, the peculiar interlobate microstructure of the mirror surface is interpreted as the result of grain boundary recrystallization processes taking place by deformation at high

Why magnetite is not the only indicator of past rainfall in the Chinese loess plateau?

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Guo, Xuelian; Banerjee, Subir K.; Wang, Ronghua; Zhao, Guoyong; Song, Hong; Lü, Bin; Li, Qian; Liu, Xiuming

2018-03-01

The study investigates the magnetic mineralogy of paleosol S5 from Xifeng (XF), Linyou (LY) and Baoji (BJ) sections with increasing annual precipitation from north to the south on the Chinese Loess Plateau. Paleosol S5 samples from these three localities are further prepared as magnetic extracts and separation residues. Low temperature magnetic measurements including field cooled and zero field cooled (FC/ZFC) remanence, in-phase magnetic susceptibility, thermal remanent magnetization and room temperature saturation isothermal remanence magnetization (RTSIRM), with X-ray diffraction measurements are carried out for all magnetic extracts and separation residues samples. The asymmetric rounded `hump' in cooling curves on RTSIRM and the `tilted' Verwey transition on ZFC/FC curves suggest that partially oxidized magnetite is the dominant magnetic contributor, not pure maghemite or magnetite. Furthermore, The Verwey transitions on cooling curves slightly decrease and the increased slope of `tilted' Verwey transition on ZFC remanence curves show that the degree of oxidation of magnetite between localities increases in the order XF-LY-BJ. Hard isothermal remanent magnetization, X-ray diffraction data and the difference of magnetization in warming curves of RTSIRM suggest that both hematite concentration in magnetic extracts and goethite concentration in separation residues increase from XF to BJ. Frequency dependent susceptibility and ZFC/FC curves show that BJS5 layer formed under high paleoprecipitation has less superparamagnetic (SP) but more single domain to pseudo-single domain particles, because SP maghemite was dissolved and transformed into goethite by temporary water-logging. The increase in hematite concentration is interpreted as due to SP maghemite oxidation or original goethite dehydration within dry soil environment. Therefore, transformation of maghemite to goethite in waterlogged phases of the S5 paleosol led to the loss of magnetization.

The Corrosion of High Performance Steel in Adverse Environments

International Nuclear Information System (INIS)

Cook, Desmond C.

2005-01-01

The corrosion products that have formed on weathering steel bridges exposed to different weather conditions in the United States have been evaluated. They have been analyzed by spectroscopic techniques to determine the relationship between protective and non-protective rust coatings, and their relationship to the exposure conditions. Bridges constructed recently using High Performance Steel, as well as older bridges built with Type A588B weathering steel, were evaluated for corrosion performance of the rust coatings. In locations where the steel is subjected to regular wet-dry cycling, where the surface is wet for less than about 20% of the time, a protective patina starts to form after a few months exposure, and continues to an adherent, impervious coating after a decade. The protective patina is characterized by the formation of only goethite and lepidocrocite. The goethite makes up about 80% of the rust, and itself consists of a nanophase component, 40%, or infrequent drying cycles (regions close to waterways, fog or having high humidity), the weathering steel forms a rust coating that consists of a large amount of maghemite, and goethite that contains very little of the nanophase component. The rust coating ex-foliates from the steel and is not protective. Under exposure conditions in which chlorides are deposited onto the weathering steel surface (marine or de-icing salt locations), the protective patina also does not form. Instead, the rust coating consists of a large fraction of akaganeite that forms at the expense of the lepidocrocite and nanophase goethite. The bridges exposed to high chloride concentrations, 1.5 wt%, and therefore having no protective patina, have corrosion rates measured to be 6 times larger than expected for weathering steel with the protective patina

Mössbauer and XRD studies of Roman amphorae buried in the sea for two millennia

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Wagner, F. E.; Wagner, U.; Häusler, W.; Costa, B. F. O.; Blot, J.-Y.; Silva, A. J. M.; Bombico, S.

2016-12-01

During the years 2004-2007 many Roman amphora sherds were found in the sea near Cortiçais, off the southern coast of the Peniche peninsula on the Atlantic coast of Portugal. The amphorae are of the Haltern 70 type and stem from a shipwreck that has been dated to the time of the emperor Augustus, between about 15 BC and 15 AD. They were produced in the Roman Province of Baetica in the south of Spain and used to transport wine and other staple foods by sea to other Roman settlements. We have studied several fragments of these amphorae by 57Fe Mössbauer spectroscopy and X-ray diffraction in order to look for changes in the ceramic material caused by two millennia of exposure to sea water. For comparison Mössbauer data on a Haltern 70 type amphora handle excavated on land at the site of Castro do Vieito in the north of Portugal were used. The fragments on which we report here are a body sherd and two handles. The sherds show a visible layer structure. The different layers were studied separately. The Mössbauer spectra of the buff surface layers indicate that up to about 60 % of the iron is present as very fine goethite particles, which are superparamagnetic at RT but exhibit magnetically split spectra at 4.2 K. Their blocking temperature is around or even below 50 K. The goethite is too fine grained to be detected by X-ray diffraction. Re-firing experiments confirm the presence of goethite, which is found to convert to hematite between 300 and 600 ∘C. The results show that the iron in the silicate matrix of the ceramic material converts to goethite under the prolonged influence of the sea water, mainly in the outermost several millimetres and apparently depending on the nature of the ceramic material.

Mineralogy, morphology, and textural relationships in coatings on quartz grains in sediments in a quartz-sand aquifer

Science.gov (United States)

Zhang, Shouliang; Kent, Douglas B.; Elbert, David C.; Shi, Zhi; Davis, James A.; Veblen, David R.

2011-01-01

Mineralogical studies of coatings on quartz grains and bulk sediments from an aquifer on Western Cape Cod, Massachusetts, USA were carried out using a variety of transmission electron microscopy (TEM) techniques. Previous studies demonstrated that coatings on quartz grains control the adsorption properties of these sediments. Samples for TEM characterization were made by a gentle mechanical grinding method and focused ion beam (FIB) milling. The former method can make abundant electron-transparent coating assemblages for comprehensive and quantitative X-ray analysis and the latter technique protects the coating texture from being destroyed. Characterization of the samples from both a pristine area and an area heavily impacted by wastewater discharge shows similar coating textures and chemical compositions. Major constituents of the coating include Al-substituted goethite and illite/chlorite clays. Goethite is aggregated into well-crystallized domains through oriented attachment resulting in increased porosity. Illite/chlorite clays with various chemical compositions were observed to be mixed with goethite aggregates and aligned sub-parallel to the associated quartz surface. The uniform spatial distribution of wastewater-derived phosphorus throughout the coating from the wastewater-contaminated site suggests that all of the coating constituents, including those adjacent to the quartz surface, are accessible to groundwater solutes. Both TEM characterization and chemical extraction results indicate there is a significantly greater amount of amorphous iron oxide in samples from wastewater discharge area compared to those from the pristine region, which might reflect the impact of redox cycling of iron under the wastewater-discharge area. Coating compositions are consistent with the moderate metal and oxy-metalloid adsorption capacities, low but significant cation exchange capacities, and control of iron(III) solubility by goethite observed in reactive transport

Mössbauer and XRD studies of Roman amphorae buried in the sea for two millennia

International Nuclear Information System (INIS)

Wagner, F. E.; Wagner, U.; Häusler, W.; Costa, B. F. O.; Blot, J.-Y.; Silva, A. J. M.; Bombico, S.

2016-01-01

During the years 2004–2007 many Roman amphora sherds were found in the sea near Cortiçais, off the southern coast of the Peniche peninsula on the Atlantic coast of Portugal. The amphorae are of the Haltern 70 type and stem from a shipwreck that has been dated to the time of the emperor Augustus, between about 15 BC and 15 AD. They were produced in the Roman Province of Baetica in the south of Spain and used to transport wine and other staple foods by sea to other Roman settlements. We have studied several fragments of these amphorae by "5"7Fe Mössbauer spectroscopy and X-ray diffraction in order to look for changes in the ceramic material caused by two millennia of exposure to sea water. For comparison Mössbauer data on a Haltern 70 type amphora handle excavated on land at the site of Castro do Vieito in the north of Portugal were used. The fragments on which we report here are a body sherd and two handles. The sherds show a visible layer structure. The different layers were studied separately. The Mössbauer spectra of the buff surface layers indicate that up to about 60 % of the iron is present as very fine goethite particles, which are superparamagnetic at RT but exhibit magnetically split spectra at 4.2 K. Their blocking temperature is around or even below 50 K. The goethite is too fine grained to be detected by X-ray diffraction. Re-firing experiments confirm the presence of goethite, which is found to convert to hematite between 300 and 600 "∘C. The results show that the iron in the silicate matrix of the ceramic material converts to goethite under the prolonged influence of the sea water, mainly in the outermost several millimetres and apparently depending on the nature of the ceramic material.

Why magnetite is not the only indicator of past rainfall in the Chinese Loess Plateau?

Science.gov (United States)

Guo, Xuelian; Banerjee, Subir K.; Wang, Ronghua; Zhao, Guoyong; Song, Hong; Lü, Bin; Li, Qian; Liu, Xiuming

2018-06-01

This study investigates the magnetic mineralogy of palaeosol S5 from Xifeng (XF), Linyou (LY) and Baoji (BJ) sections with increasing annual precipitation from north to the south on the Chinese Loess Plateau. Palaeosol S5 samples from these three localities are further prepared as magnetic extracts and separation residues. Low-temperature magnetic measurements including field cooled and zero field cooled (FC/ZFC) remanence, in-phase magnetic susceptibility, thermal remanent magnetization and room temperature saturation isothermal remanence magnetization (RTSIRM), with X-ray diffraction measurements are carried out for all magnetic extracts and separation residues samples. The asymmetric rounded `hump' in cooling curves on RTSIRM and the `tilted' Verwey transition on ZFC/FC curves suggest that partially oxidized magnetite is the dominant magnetic contributor, not pure maghemite or magnetite. Furthermore, The Verwey transitions on cooling curves slightly decrease and the increased slope of `tilted' Verwey transition on ZFC remanence curves show that the degree of oxidation of magnetite between localities increases in the order XF-LY-BJ. Hard isothermal remanent magnetization, X-ray diffraction data and the difference of magnetization in warming curves of RTSIRM suggest that both hematite concentration in magnetic extracts and goethite concentration in separation residues increase from XF to BJ. Frequency-dependent susceptibility and ZFC/FC curves show that BJS5 layer formed under high palaeoprecipitation has less superparamagnetic (SP) but more single domain to pseudo-single domain particles, because SP maghemite was dissolved and transformed into goethite by temporary waterlogging. The increase in hematite concentration is interpreted as due to SP maghemite oxidation or original goethite dehydration within dry soil environment. Therefore, transformation of maghemite to goethite in waterlogged phases of the S5 palaeosol led to the loss of magnetization.

Different weathering stages indicated by the magnetization of limestones: An example from the southeast Pyrenees, Spain

Science.gov (United States)

Keller, P.; Gehring, A. U.

1992-06-01

Paleomagnetic and structural data from the Pedraforca thrust sheet in the southeast Pyrenees show that the chemical weathering of the late Cretaceous limestones is a multistage process. The first weathering stage, of latest Eocene to early Oligocene age, is indicated by a chemical remanent magnetization carried by hematite. The formation of hematite as the dominant weathering product suggests a subtropical climate in northeast Spain during this period. The second weathering stage is indicated by the presence of goethite, which carries a chemical remanent magnetization parallel to the present earth field. This suggests formation of the goethite since the late Pleistocene under cooler climatic conditions similar to the present-day climate in the Pyrenees.

OCHRE PRECIPITATES AND ACID MINE DRAINAGE IN A MINE ENVIRONMENT

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BRANISLAV MÁŠA

2012-03-01

Full Text Available This paper is focused to characterize the ochre precipitates and the mine water effluents of some old mine adits and settling pits after mining of polymetallic ores in Slovakia. It was shown that the mine water effluents from two different types of deposits (adits; settling pits have similar composition and represent slightly acidic sulphate water (pH in range 5.60-6.05, sulphate concentration from 1160 to 1905 g.dm-3. The ochreous precipitates were characterized by methods of X-ray diffraction analysis (XRD, scanning electron microscopy (SEM and B.E.T. method for measuring the specific surface area and porosity. The dominant phases were ferrihydrite with goethite or goethite with lepidocrocide.

Rust in the Apollo 16 rocks. [hydration and oxidation processes in lunar environment

Science.gov (United States)

Taylor, L. A.; Mao, H. K.; Bell, P. M.

1973-01-01

Apollo 16 samples of all four rock types and from all stations contain evidence for hydration and oxidation - i.e., the presence of hydrated iron oxide, probably goethite. Rock 66095 contains native FeNi grains with a characteristic intergrowth of schreibersite and, to lesser extents, of cohenite. Troilite also contains sphalerite. The goethite contains 1.5-4.6 wt.% chlorine and occurs mainly on the edges of FeNi metal, causing a rust color in the cracks and space around the native metal grains, which also contain abundant chlorine. This observation suggests the presence of lawrencite (FeCl2), a phase that deliquesces and oxidizes very rapidly upon exposure to water or to a moist atmosphere.

Calculation of Site-specific Carbon-isotope Fractionation in Pedogenic Oxide Minerals

Energy Technology Data Exchange (ETDEWEB)

Rustad, James R.; Zarzycki, Piotr

2008-07-29

Ab initio molecular dynamics and quantum chemistry techniques are used to calculate the structure, vibrational frequencies, and carbon-isotope fractionation factors of the carbon dioxide component [CO2(m)] of soil (oxy)hydroxide minerals goethite, diaspore, and gibbsite. We have identified two possible pathways of incorporation of CO2(m) into (oxy)hydroxide crystal structures: one in which the C4+ substitutes for four H+ [CO2(m)A] and another in which C4+ substitutes for (Al3+,Fe3+) + H+ [CO2(m)B]. Calculations of isotope fractionation factors give large differences between the two structures, with the CO2(m)A being isotopically lighter than CO2(m)B by ≈10 per mil in the case of gibbsite and nearly 20 per mil in the case of goethite. The reduced partition function ratio of CO2(m)B structure in goethite differs from CO2(g) by <1 per mil. The predicted fractionation for gibbsite is >10 per mil higher, close to those measured for calcite and aragonite. The surprisingly large difference in the carbon-isotope fractionation factor between the CO2(m)A and CO2(m)B structures within a given mineral suggests that the isotopic signatures of soil (oxy)hydroxide could be heterogeneous.

Iron concretions in Brazilian Soils. 2. Mineralogical characterization

International Nuclear Information System (INIS)

Fontes, M.R.; Silva, E.G. da

1985-01-01

The mineralogy of six concretionary material from several pedological domains in Brazil were examined by x-ray diffratometry analysis and room temperature (RT) 57 Fe Moessbauer Spectroscopy. In two samples (from 'Quadrilatero Ferrifero' and Itaituba, in the state of Para) hematite was the predominant mineralogical phase, while in the other samples, from Chapada do Apodi (State of Rio Grande do Norte), Calciolandia (State of Minas Gerais), and Vicosa (State of Minas Gerais), goethite appeared as the main occurring mineral, in the (hydr) oxide crystallized fraction. The goethitic character was related to the manganese content in the concretions. The Moessbauer patterns exhibited superparamagnetic relaxation effects, although a six line hyperfine magnetic splitting, and a central doublet appeared at least in three cases. Exceptionally, in the two samples from Chapada do Apodi the six line pattern collapsed completely, and only a central doublet remained. The hyperfine magnetic field was drastically reduced both by particle size and isomorphically substituted aluminum in the iron oxide structure, probably, of Al-hematites. From the Moessbauer parameters, Al-goethite seemed to be present only in the sample from Vicosa, although it should be emphasized that the RT measurements do not always permit access to the hyperfine strucutre in this kind of material, as a result of small size particle effects. (Author) [pt

Iron Oxide Minerals in Atmospheric Dust and Source Sediments-Studies of Types and Properties to Assess Environmental Effects

Science.gov (United States)

Reynolds, R. L.; Goldstein, H. L.; Moskowitz, B. M.; Till, J. L.; Flagg, C.; Kokaly, R. F.; Munson, S.; Landry, C.; Lawrence, C. R.; Hiza, M. M.; D'Odorico, P.; Painter, T. H.

2011-12-01

Ferric oxide minerals in atmospheric dust can influence atmospheric temperatures, accelerate melting of snow and ice, stimulate marine phytoplankton productivity, and impact human health. Such effects vary depending on iron mineral type, size, surface area, and solubility. Generally, the presence of ferric oxides in dust is seen in the red, orange, or yellow hues of plumes that originate in North Africa, central and southwest Asia, South America, western North America, and Australia. Despite their global importance, these minerals in source sediments, atmospheric dust, and downwind aeolian deposits remain poorly described with respect to specific mineralogy, particle size and surface area, or presence in far-traveled aerosol compounds. The types and properties of iron minerals in atmospheric dust can be better understood using techniques of rock magnetism (measurements at 5-300 K), Mössbauer and high-resolution visible and near-infrared reflectance spectroscopy; chemical reactivity of iron oxide phases; and electron microscopy for observing directly the ferric oxide coatings and particles. These studies can elucidate the diverse environmental effects of iron oxides in dust and can help to identify dust-source areas. Dust-source sediments from the North American Great Basin and Colorado Plateau deserts and the Kalahari Desert, southern Africa, were used to compare average reflectance values with a magnetic parameter (hard isothermal remanent magnetization, HIRM) for ferric oxide abundance. Lower reflectance values correspond strongly with higher HIRM values, indicating that ferric oxides (hematite or goethite, or both) contribute to absorption of solar radiation in these sediments. Dust deposited to snow cover of the San Juan Mountains (Colorado) and Wasatch Mountains (Utah) was used to characterize dust composition compared with properties of sediments exposed in source-areas identified from satellite retrievals. Results from multiple methods indicate that

Controls on Fe reduction and mineral formation by a subsurface bacterium

Science.gov (United States)

Glasauer, Susan; Weidler, Peter G.; Langley, Sean; Beveridge, Terry J.

2003-04-01

The reductive dissolution of FeIII (hydr)oxides by dissimilatory iron-reducing bacteria (DIRB) could have a large impact on sediment genesis and Fe transport. If DIRB are able to reduce FeIII in minerals of high structural order to carry out anaerobic respiration, their range could encompass virtually every O 2-free environment containing FeIII and adequate conditions for cell growth. Previous studies have established that Shewanella putrefaciens CN32, a known DIRB, will reduce crystalline Fe oxides when initially grown at high densities in a nutrient-rich broth, conditions that poorly model the environments where CN32 is found. By contrast, we grew CN32 by batch culture solely in a minimal growth medium. The stringent conditions imposed by the growth method better represent the conditions that cells are likely to encounter in their natural habitat. Furthermore, the expression of reductases necessary to carry out dissimilatory Fe reduction depends on the method of growth. It was found that under anaerobic conditions CN32 reduced hydrous ferric oxide (HFO), a poorly crystalline FeIII mineral, and did not reduce suspensions containing 4 mM FeIII in the form of poorly ordered nanometer-sized goethite (α-FeOOH), well-ordered micron-sized goethite, or nanometer-sized hematite (α-Fe 2O 3) crystallites. Transmission electron microscopy (TEM) showed that all minerals but the micron-sized goethite attached extensively to the bacteria and appeared to penetrate the outer cellular membrane. In the treatment with HFO, new FeII and FeIII minerals formed during reduction of HFO-Fe in culture medium containing 4.0 mmol/L P i (soluble inorganic P), as observed by TEM with energy-dispersive X-ray spectroscopy, selected area electron diffraction, and X-ray diffraction. The minerals included magnetite (Fe 3O 4), goethite, green rust, and vivianite [Fe 3(PO 4) 2 · 8H 2O]. Vivianite appeared to be the stable end product and the mean coherence length was influenced by the rate of Fe

Crystallization of -type hexagonal ferrites from mechanically

Indian Academy of Sciences (India)

Crystallization of -type hexagonal ferrites from mechanically activated mixtures of barium carbonate and goethite ... Abstract. -type hexagonal ferrite precursor was prepared by a soft mechanochemical ... Bulletin of Materials Science | News.

Insight into the product film formed on Ni-advanced weathering steel in a tropical marine atmosphere

Science.gov (United States)

Wu, Wei; Cheng, Xuequn; Hou, Huaxing; Liu, Bo; Li, Xiaogang

2018-04-01

The product film formed on Ni-advanced weathering steel in a tropical marine environment was investigated in detail through outdoor exposure by using diverse surface analysis techniques combined with electrochemical impedance spectroscopy and scanning kelvin probe measurements. The results showed that the product film was mainly composed of nanophasic goethite in the inner layer and maghemite, akaganeite, and hematite in the outer layer. Moreover, the resistance to atmospheric corrosion gradually increased from the outermost product film to the innermost film. Ni was significantly enriched in the inner layer in the form of the spinel phase NiFe2O4, which transformed lepidocrocite to fine-grained goethite, withstood the invasion of chloridion, and improved the corrosion potential of the product film in a tropical marine atmosphere.

Synthesis, Characterization, and Evaluation of Boron-Doped Iron Oxides for the Photocatalytic Degradation of Atrazine under Visible Light

Directory of Open Access Journals (Sweden)

Shan Hu

2012-01-01

Full Text Available Photocatalytic degradation of atrazine by boron-doped iron oxides under visible light irradiation was investigated. In this work, boron-doped goethite and hematite were successfully prepared by sol-gel method with trimethylborate as boron precursor. The powders were characterized by XRD, UV-vis diffuse reflectance spectra, and porosimetry analysis. The results showed that boron doping could influence the crystal structure, enlarge the BET surface area, improve light absorption ability, and narrow their band-gap energy. The photocatalytic activity of B-doped iron oxides was evaluated in the degradation of atrazine under the visible light irradiation, and B-doped iron oxides showed higher atrazine degradation rate than that of pristine iron oxides. Particularly, B-doped goethite exhibited better photocatalytic activity than B-doped hematite.

Physical-chemical modeling of elements' behavior in mixing sea and fresh waters of minor rivers in the White Sea catchment area.

Science.gov (United States)

Maksimova, Victoria V; Mazukhina, Svetlana I; Cherepanova, Tatiana A; Gorbacheva, Tamara T

2017-07-29

The physical-chemical stage of marginal filters in minor rivers of the White Sea catchment area by the example of the Umba River, flowing to Kandalaksha Gulf, has been explored. Application of the method of physical-chemical modeling on the basis of field data allowed establishing migration forms of a number of elements in the "river-sea" system and deposition of solid phases when mixing waters. The mixing of river and sea water is accompanied by the sedimentation of predominantly goethite, hydromuscovite, and hydroxylapatite. Sediments in mixing river and sea waters were found to be mainly composed by goethite, hydromuscovite, and hydroxylapatite. The research has added to the knowledge of the role of the abiotic part in the marginal filters of small rivers in the Arctic.

Interaction between calcium and phosphate adsorption on goethite

NARCIS (Netherlands)

Rietra, R.P.J.J.; Hiemstra, T.; Riemsdijk, van W.H.

2001-01-01

Quantitatively, little is known about the ion interaction processes that are responsible for the binding of phosphate in soil, water, and sediment, which determine the bioavailability and mobility of phosphate. Studies have shown that metal hydroxides are often responsible for the binding of PO4 in

The impact of particle size, relative humidity, and sulfur dioxide on iron solubility in simulated atmospheric marine aerosols.

Science.gov (United States)

Cartledge, Benton T; Marcotte, Aurelie R; Herckes, Pierre; Anbar, Ariel D; Majestic, Brian J

2015-06-16

Iron is a limiting nutrient in about half of the world's oceans, and its most significant source is atmospheric deposition. To understand the pathways of iron solubilization during atmospheric transport, we exposed size segregated simulated marine aerosols to 5 ppm sulfur dioxide at arid (23 ± 1% relative humidity, RH) and marine (98 ± 1% RH) conditions. Relative iron solubility increased as the particle size decreased for goethite and hematite, while for magnetite, the relative solubility was similar for all of the fine size fractions (2.5-0.25 μm) investigated but higher than the coarse size fraction (10-2.5 μm). Goethite and hematite showed increased solubility at arid RH, but no difference (p > 0.05) was observed between the two humidity levels for magnetite. There was no correlation between iron solubility and exposure to SO2 in any mineral for any size fraction. X-ray absorption near edge structure (XANES) measurements showed no change in iron speciation [Fe(II) and Fe(III)] in any minerals following SO2 exposure. SEM-EDS measurements of SO2-exposed goethite revealed small amounts of sulfur uptake on the samples; however, the incorporated sulfur did not affect iron solubility. Our results show that although sulfur is incorporated into particles via gas-phase processes, changes in iron solubility also depend on other species in the aerosol.

Oligomerization of glycine and alanine catalyzed by iron oxides: implications for prebiotic chemistry.

Science.gov (United States)

Shanker, Uma; Bhushan, Brij; Bhattacharjee, G; Kamaluddin

2012-02-01

Iron oxide minerals are probable constituents of the sediments present in geothermal regions of the primitive earth. They might have adsorbed different organic monomers (amino acids, nucleotides etc.) and catalyzed polymerization processes leading to the formation of the first living cell. In the present work we tested the catalytic activity of three forms of iron oxides (Goethite, Akaganeite and Hematite) in the intermolecular condensation of each of the amino acids glycine and L-alanine. The effect of zinc oxide and titanium dioxide on the oligomerization has also been studied. Oligomerization studies were performed for 35 days at three different temperatures 50, 90 and 120°C without applying drying/wetting cycling. The products formed were characterized by HPLC and ESI-MS techniques. All three forms of iron oxides catalyzed peptide bond formation (23.2% of gly2 and 10.65% of ala2). The reaction was monitored every 7 days. Formation of peptides was observed to start after 7 days at 50°C. Maximum yield of peptides was found after 35 days at 90°C. Reaction at 120°C favors formation of diketopiperazine derivatives. It is also important to note that after 35 days of reaction, goethite produced dimer and trimer with the highest yield among the oxides tested. We suggest that the activity of goethite could probably be due to its high surface area and surface acidity.

Atomic force microscopy measurements of bacterial adhesion and biofilm formation onto clay-sized particles

Science.gov (United States)

Huang, Qiaoyun; Wu, Huayong; Cai, Peng; Fein, Jeremy B.; Chen, Wenli

2015-01-01

Bacterial adhesion onto mineral surfaces and subsequent biofilm formation play key roles in aggregate stability, mineral weathering, and the fate of contaminants in soils. However, the mechanisms of bacteria-mineral interactions are not fully understood. Atomic force microscopy (AFM) was used to determine the adhesion forces between bacteria and goethite in water and to gain insight into the nanoscale surface morphology of the bacteria-mineral aggregates and biofilms formed on clay-sized minerals. This study yields direct evidence of a range of different association mechanisms between bacteria and minerals. All strains studied adhered predominantly to the edge surfaces of kaolinite rather than to the basal surfaces. Bacteria rarely formed aggregates with montmorillonite, but were more tightly adsorbed onto goethite surfaces. This study reports the first measured interaction force between bacteria and a clay surface, and the approach curves exhibited jump-in events with attractive forces of 97 ± 34 pN between E. coli and goethite. Bond strengthening between them occurred within 4 s to the maximum adhesion forces and energies of −3.0 ± 0.4 nN and −330 ± 43 aJ (10−18 J), respectively. Under the conditions studied, bacteria tended to form more extensive biofilms on minerals under low rather than high nutrient conditions. PMID:26585552

Arsenic release and geochemical evolution of groundwater in an alluvial aquitard, West Bengal, India.

Science.gov (United States)

Desbarats, A. J.; Pal, T.; Mukherjee, P. K.; Beckie, R. D.

2017-12-01

According to the World Health Organization, contamination of groundwater by geogenic arsenic (As) represents the largest mass poisoning in history. At a field site in West Bengal, India, the source of As affecting a shallow aquifer was traced to silty sediments filling an abandoned river meander. Along with As-bearing phases, these sediments also contain 0.46 % organic carbon. The release of As within the channel fill is investigated using a geochemical mass balance model supported by detailed field observations of aqueous chemistry, sequential extraction analyses of sediment chemistry, and analyses of sediment mineralogy. The model explores the evolution of groundwater chemistry along a flow path extending from its recharge point in an abandoned channel pond, through the channel-fill sequence, to the underlying aquifer. Variations in groundwater composition within the host sediments are explained in terms of mineral weathering driven by organic carbon decay. The model yields reaction coefficients expressing amounts of minerals (and gases) reacting or precipitating along the flow path. Arsenic and phosphorus cycles appear closely linked as these species are hosted by goethite, Fe-rich chlorite, and vivianite. Arsenic is released through the rapid reductive dissolution of goethite and the slower weathering of chlorite. Concomitantly, some As is sequestered in precipitating vivianite. These competing processes reach equilibrium deeper in the channel-fill sequence as groundwater As concentrations stabilize. Using groundwater residence time in channel fill obtained from a numerical flow model and the calculated reaction coefficients, rates of organic carbon oxidation, goethite dissolution, and net As release are estimated at 1.15 mmol C L-1 a-1, 0.18 mmol L-1 a-1, and 4.57 10-4 mmol L-1 a-1, respectively. Fine-grained yet slightly permeable deposits such as channel-fill silts containing reactive organic carbon and As-bearing goethite and phyllosilicates are localized

In situ treatment of arsenic contaminated groundwater by aquifer iron coating: Experimental study.

Science.gov (United States)

Xie, Xianjun; Wang, Yanxin; Pi, Kunfu; Liu, Chongxuan; Li, Junxia; Liu, Yaqing; Wang, Zhiqiang; Duan, Mengyu

2015-09-15

In situ arsenic removal from groundwater by an aquifer iron coating method has great potential to be a cost effective and simple groundwater remediation technology, especially in rural and remote areas where groundwater is used as the main water source for drinking. The in situ arsenic removal technology was first optimized by simulating arsenic removal in various quartz sand columns under anoxic conditions. The effectiveness was then evaluated in an actual high-arsenic groundwater environment. The arsenic removal mechanism by the coated iron oxide/hydroxide was investigated under different conditions using scanning electron microscopy (SEM)/X-ray absorption spectroscopy, electron probe microanalysis, and Fourier transformation infrared spectroscopy. Aquifer iron coating method was developed via a 4-step alternating injection of oxidant, iron salt and oxygen-free water. A continuous injection of 5.0 mmol/L FeSO4 and 2.5 mmol/L NaClO for 96 h can form a uniform goethite coating on the surface of quartz sand without causing clogging. At a flow rate of 7.2 mL/min of the injection reagents, arsenic (as Na2HAsO4) and tracer fluorescein sodium to pass through the iron-coated quartz sand column were approximately at 126 and 7 column pore volumes, respectively. The retardation factor of arsenic was 23.0, and the adsorption capacity was 0.11 mol As per mol Fe. In situ arsenic removal from groundwater in an aquifer was achieved by simultaneous injections of As(V) and Fe(II) reagents. Arsenic fixation resulted from a process of adsorption/co-precipitation with fine goethite particles by way of bidentate binuclear complexes. Therefore, the study results indicate that the high arsenic removal efficiency of the in situ aquifer iron coating technology likely resulted from the expanded specific surface area of the small goethite particles, which enhanced arsenic sorption capability and/or from co-precipitation of arsenic on the surface of goethite particles. Copyright © 2015

Mössbauer and XRD studies of Roman amphorae buried in the sea for two millennia

Energy Technology Data Exchange (ETDEWEB)

Wagner, F. E., E-mail: fwagner@tum.de; Wagner, U.; Häusler, W. [Technical University of Munich, Physics Department E15 (Germany); Costa, B. F. O. [University of Coimbra, CFisUC, Physics Department (Portugal); Blot, J.-Y. [Universidade Nova de Lisboa, CHAMFCSH (Portugal); Silva, A. J. M. [University of Coimbra, FCT/Centro de Estudos Arqueológicos das Universidades de Coimbra e do Porto (Portugal); Bombico, S. [University of Evora, CIDEHUS (Portugal)

2016-12-15

During the years 2004–2007 many Roman amphora sherds were found in the sea near Cortiçais, off the southern coast of the Peniche peninsula on the Atlantic coast of Portugal. The amphorae are of the Haltern 70 type and stem from a shipwreck that has been dated to the time of the emperor Augustus, between about 15 BC and 15 AD. They were produced in the Roman Province of Baetica in the south of Spain and used to transport wine and other staple foods by sea to other Roman settlements. We have studied several fragments of these amphorae by {sup 57}Fe Mössbauer spectroscopy and X-ray diffraction in order to look for changes in the ceramic material caused by two millennia of exposure to sea water. For comparison Mössbauer data on a Haltern 70 type amphora handle excavated on land at the site of Castro do Vieito in the north of Portugal were used. The fragments on which we report here are a body sherd and two handles. The sherds show a visible layer structure. The different layers were studied separately. The Mössbauer spectra of the buff surface layers indicate that up to about 60 % of the iron is present as very fine goethite particles, which are superparamagnetic at RT but exhibit magnetically split spectra at 4.2 K. Their blocking temperature is around or even below 50 K. The goethite is too fine grained to be detected by X-ray diffraction. Re-firing experiments confirm the presence of goethite, which is found to convert to hematite between 300 and 600 {sup ∘}C. The results show that the iron in the silicate matrix of the ceramic material converts to goethite under the prolonged influence of the sea water, mainly in the outermost several millimetres and apparently depending on the nature of the ceramic material.

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

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

Formation of iron oxides in soils developed under natural fires and slash-and-burn based agriculture in a monsoonal climate (Chittagong Hill Tracts, Bangladesh)

International Nuclear Information System (INIS)

Bender Koch, C.; Borggaard, O. K.; Gafur, A.

2005-01-01

Fire-induced mineral transformations have been investigated in composite mineral grains separated from the coarse sand fractions (400-2,000 μm) from Ultisols developed in the Chittagong Hill Tracts (Bangladesh). Magnetic and colour based separation (into light brown, dark red, and magnetic, dark red classes) were used to select the grains that were studied by Moessbauer spectroscopy. Aluminium substituted goethite (α-FeOOH) dominates the light brown particles. Fire transform the goethite into a poorly crystalline hematite (α-Fe 2 O 3 ) dominating in the dark red particles. In the dark red, magnetic grains a recrystallized hematite dominates, but small amounts of maghemite (γ-Fe 2 O 3 ) are also present. The latter is indicated by comparing the line intensities in spectra measurement with and without an external magnetic field.

Development of the Facility for Transformation of Magnetic Characteristics of Weakly Magnetic Oxidized Iron Ores Related to Improvement of Technologies for Iron Ore Concentrate Production

Directory of Open Access Journals (Sweden)

Ponomarenko, O.M.

2016-01-01

Full Text Available New facility for continuous registration of iron ore magnetization depending on temperature by heating of iron ores upon reducing conditions was created. Facility allows to register the processes of transformation of weakly magnetic minerals into strongly magnetic ones under the influence of reducing agents and temperature, as well as to determine the Curie temperature of the minerals. Using created facility it was shown, that heating of goethite and hematite in the presence of 4 % of starch in the temperature range of 300—650 °С leads to significant increase of magnetization of the samples. X-Ray diffraction confirmed that under indicated conditions the structure of hematite and goethite is transformed into magnetite structure. Obtained results open up new possibilities for the development of effective technologies for oxidized iron ore beneficiation.

Atmospheric corrosion of mild steel in Oman

International Nuclear Information System (INIS)

Gismelseed, Abbasher; Al-Harthi, S. H.; Elzain, M.; Al-Rawas, A. D.; Yousif, A.; Al-Saadi, S.; Al-Omari, I.; Widatallah, H.; Bouziane, K.

2006-01-01

A systematic study has been made of the initial corrosion products which form on mild steel capons exposed near the coastal region of Oman and at some industrial areas. The phases and compositions of the products formed at different periods of exposure were examined by using Moessbauer spectroscopy (295 and 78 K) and X-ray diffraction (XRD) techniques. The results show that lepidocorcite and maghemite are early corrosion products and goethite starts to form after 2 months of metal exposure to the atmosphere. Akaganeite is an early corrosion product but it forms in marine environments only, which reflects the role of chlorine effect in the atmosphere. The 12 months coupons showed the presence of goethite, lepidocorcite and maghemite, but no akaganeite being seen in the products of one of the studied areas.

Atmospheric corrosion of mild steel in Oman

Energy Technology Data Exchange (ETDEWEB)

Gismelseed, Abbasher, E-mail: abbasher@squ.edu.om; Al-Harthi, S. H.; Elzain, M.; Al-Rawas, A. D.; Yousif, A.; Al-Saadi, S.; Al-Omari, I.; Widatallah, H.; Bouziane, K. [College of Science, Department of Physics (Oman)

2006-01-15

A systematic study has been made of the initial corrosion products which form on mild steel capons exposed near the coastal region of Oman and at some industrial areas. The phases and compositions of the products formed at different periods of exposure were examined by using Moessbauer spectroscopy (295 and 78 K) and X-ray diffraction (XRD) techniques. The results show that lepidocorcite and maghemite are early corrosion products and goethite starts to form after 2 months of metal exposure to the atmosphere. Akaganeite is an early corrosion product but it forms in marine environments only, which reflects the role of chlorine effect in the atmosphere. The 12 months coupons showed the presence of goethite, lepidocorcite and maghemite, but no akaganeite being seen in the products of one of the studied areas.

Aquifer geochemistry at potential aquifer storage and recovery sites in coastal plain aquifers in the New York city area, USA

Science.gov (United States)

Brown, C.J.; Misut, P.E.

2010-01-01

The effects of injecting oxic water from the New York city (NYC) drinking-water supply and distribution system into a nearby anoxic coastal plain aquifer for later recovery during periods of water shortage (aquifer storage and recovery, or ASR) were simulated by a 3-dimensional, reactive-solute transport model. The Cretaceous aquifer system in the NYC area of New York and New Jersey, USA contains pyrite, goethite, locally occurring siderite, lignite, and locally varying amounts of dissolved Fe and salinity. Sediment from cores drilled on Staten Island and western Long Island had high extractable concentrations of Fe, Mn, and acid volatile sulfides (AVS) plus chromium-reducible sulfides (CRS) and low concentrations of As, Pb, Cd, Cr, Cu and U. Similarly, water samples from the Lloyd aquifer (Cretaceous) in western Long Island generally contained high concentrations of Fe and Mn and low concentrations of other trace elements such as As, Pb, Cd, Cr, Cu and U, all of which were below US Environmental Protection Agency (USEPA) and NY maximum contaminant levels (MCLs). In such aquifer settings, ASR operations can be complicated by the oxidative dissolution of pyrite, low pH, and high concentrations of dissolved Fe in extracted water.The simulated injection of buffered, oxic city water into a hypothetical ASR well increased the hydraulic head at the well, displaced the ambient groundwater, and formed a spheroid of injected water with lower concentrations of Fe, Mn and major ions in water surrounding the ASR well, than in ambient water. Both the dissolved O2 concentrations and the pH of water near the well generally increased in magnitude during the simulated 5-a injection phase. The resultant oxidation of Fe2+ and attendant precipitation of goethite during injection provided a substrate for sorption of dissolved Fe during the 8-a extraction phase. The baseline scenario with a low (0.001M) concentration of pyrite in aquifer sediments, indicated that nearly 190% more water

Detection of low concentrations of fine-grained iron oxides by voltammetry of microparticles

Czech Academy of Sciences Publication Activity Database

Oorschot van, I. H. M.; Grygar, Tomáš; Dekkers, M. J.

2001-01-01

Roč. 193, 3-4 (2001), s. 631-642 ISSN 0012-821X Institutional research plan: CEZ:AV0Z4032918 Keywords : hematite * goethite * analysis Subject RIV: CA - Inorganic Chemistry Impact factor: 2.700, year: 2001

Rapid preparation of α-FeOOH and α-Fe{sub 2}O{sub 3} nanostructures by microwave heating and their application in electrochemical sensors

Energy Technology Data Exchange (ETDEWEB)

Marinho, J.Z.; Montes, R.H.O. [Universidade Federal de Uberlândia, Instituto de Química, 38400-902 Uberlândia, MG (Brazil); Moura, A.P. de; Longo, E.; Varela, J.A. [Universidade Estadual Paulista, Instituto de Química, 14800-900 Araraquara, SP (Brazil); Munoz, R.A.A. [Universidade Federal de Uberlândia, Instituto de Química, 38400-902 Uberlândia, MG (Brazil); Lima, R.C., E-mail: rclima@iqufu.ufu.br [Universidade Federal de Uberlândia, Instituto de Química, 38400-902 Uberlândia, MG (Brazil)

2014-01-01

Graphical abstract: - Highlights: • Simple microwave method leads to the rapid formation of the goethite and hematite. • Homogenous nucleation and growth of particles are controlled by synthesis time. • Modified electrode with α-FeOOH nanoplates improved the electrochemical response. • The sample is directly heated by microwaves and its crystallization is accelerated. • Fe{sup 3+} nanostructures are promising for development of electrochemical sensors. - Abstract: α-FeOOH (goethite) and α-Fe{sub 2}O{sub 3} (hematite) nanostructures have been successfully synthesized using the microwave-assisted hydrothermal (MAH) method and by the rapid burning in a microwave oven of the as-prepared goethite, respectively. The orthorhombic α-FeOOH to rhombohedralα-Fe{sub 2}O{sub 3} structural transformation was observed by X-ray diffraction (XRD) and Raman spectroscopy results. Plates-like α-FeOOH prepared in 2 min and rounded and quasi-octahedral shaped α-Fe{sub 2}O{sub 3} particles obtained in 10 min were observed using field emission gun scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The use of microwave heating allowed iron oxides to be prepared with shorter reaction times when compared to other synthesis methods. α-FeOOH nanoplates were incorporated into graphite-composite electrodes, which presented electrocatalytic properties towards the electrochemical oxidation of ascorbic acid in comparison with unmodified electrodes. This result demonstrates that such α-FeOOH nanostructures are very promising chemical modifiers for the development of improved electrochemical sensors.

A Moessbauer Spectral Study of the Hull Steel and Rusticles Recovered from the Titanic

Energy Technology Data Exchange (ETDEWEB)

Long, Gary J., E-mail: glong@umr.edu; Hautot, Dimitri [University of Missouri-Rolla, Department of Chemistry (United States); Grandjean, Fernande; Vandormael, D. [University of Liege, Institute of Physics, B5 (Belgium); Leighly, H. P. [University of Missouri-Rolla, Department of Metallurgical Engineering (United States)

2004-09-15

The recent recovery of steel from the Titanic has permitted a 295 K conversion electron Moessbauer spectral study of the Titanic hull plate steel oriented with the gamma-ray direction either perpendicular or parallel to the microstructural banding directions. The two spectra reveal virtually identical average orientations of the magnetization close to the plane of the plate. The hyperfine parameters are virtually identical to those of {alpha}-iron, a finding which agrees with the chemical analysis which reveals at most 0.21 wt% carbon corresponding to 3 wt% of cementite in pearlite. A 4.2 to 295 K transmission Moessbauer spectral study of the rusticles reveals small particles of geothite undergoing superparamagnetic relaxation with a blocking temperature of ca. 300 K. In addition approximately two percent of the Moessbauer spectral absorption area corresponds to a quadrupole doublet with hyperfine parameters typical of green rust. The identified iron containing components in therusticles agree with the powder X-ray diffraction results which reveal the predominant presence of small particles of poorly crystallized goethite and traces of quartz and green rust. An average size of 20{+-}5 nm for the goethite particles is obtained from both the average hyperfine field and the broadening of the X-ray diffraction peaks. The magnetic anisotropy constant of the goethite particles deduced from the hyperfine field and the particle size is 8x10{sup 3} J/m{sup 3}.

Effect of initial pH and temperature of iron salt solutions on formation of magnetite nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Gnanaprakash, G. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Mahadevan, S. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Jayakumar, T. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Kalyanasundaram, P. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Philip, John [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India)]. E-mail: philip@igcar.gov.in; Raj, Baldev [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India)

2007-05-15

We report the effect of initial pH and temperature of iron salt solutions on formation of magnetite (Fe{sub 3}O{sub 4}) nanoparticles during co-precipitation. We synthesized nanoparticles by keeping the initial pH at 0.7, 1.5, 3.0, 4.7, 5.7, 6.7 for two different temperatures of 30 and 60 deg. C. When the initial pH (prior to alkali addition) of the salt solution was below 5, the nanoparticles formed were 100% spinel iron oxide. Average size of the magnetite particles increases with initial pH until ferrihydrite is formed at a pH of 3 and the size remains the same till 4.7 pH. The percentage of goethite formed along with non-stoichiometric magnetite was 35 and 78%, respectively, when the initial pH of the solution was 5.7 and 6.7. As the reaction temperature was increased to 60 deg. C, maintaining a pH of 6.7, the amount of goethite increased from 78 to 100%. These results show that the initial pH and temperature of the ferrous and ferric salt solution before initiation of the precipitation reaction are critical parameters controlling the composition and size of nanoparticles formed. We characterize the samples using X-ray diffraction, transmission electron microscopy and vibrating sample magnetometer. The results of the present work provide the right conditions to synthesis pure magnetite nanoparticles, without goethite impurities, through co-precipitation technique for ferrofluid applications.

Rapid preparation of α-FeOOH and α-Fe2O3 nanostructures by microwave heating and their application in electrochemical sensors

International Nuclear Information System (INIS)

Marinho, J.Z.; Montes, R.H.O.; Moura, A.P. de; Longo, E.; Varela, J.A.; Munoz, R.A.A.; Lima, R.C.

2014-01-01

Graphical abstract: - Highlights: • Simple microwave method leads to the rapid formation of the goethite and hematite. • Homogenous nucleation and growth of particles are controlled by synthesis time. • Modified electrode with α-FeOOH nanoplates improved the electrochemical response. • The sample is directly heated by microwaves and its crystallization is accelerated. • Fe 3+ nanostructures are promising for development of electrochemical sensors. - Abstract: α-FeOOH (goethite) and α-Fe 2 O 3 (hematite) nanostructures have been successfully synthesized using the microwave-assisted hydrothermal (MAH) method and by the rapid burning in a microwave oven of the as-prepared goethite, respectively. The orthorhombic α-FeOOH to rhombohedralα-Fe 2 O 3 structural transformation was observed by X-ray diffraction (XRD) and Raman spectroscopy results. Plates-like α-FeOOH prepared in 2 min and rounded and quasi-octahedral shaped α-Fe 2 O 3 particles obtained in 10 min were observed using field emission gun scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The use of microwave heating allowed iron oxides to be prepared with shorter reaction times when compared to other synthesis methods. α-FeOOH nanoplates were incorporated into graphite-composite electrodes, which presented electrocatalytic properties towards the electrochemical oxidation of ascorbic acid in comparison with unmodified electrodes. This result demonstrates that such α-FeOOH nanostructures are very promising chemical modifiers for the development of improved electrochemical sensors

Adsorption Mechanisms of Trivalent Gold onto Iron Oxy-Hydroxides: From the Molecular Scale to the Model

International Nuclear Information System (INIS)

Cances, Benjamin; Benedetti, Marc; Farges, Francois; Brown, Gordon E. Jr.

2007-01-01

Gold is a highly valuable metal that can concentrate in iron-rich exogenetic horizons such as laterites. An improved knowledge of the retention mechanisms of gold onto highly reactive soil components such as iron oxy-hydroxides is therefore needed to better understand and predict the geochemical behavior of this element. In this study, we use EXAFS information and titration experiments to provide a realistic thermochemical description of the sorption of trivalent gold onto iron oxy-hydroxides. Analysis of Au LIII-edge XAFS spectra shows that aqueous Au(III) adsorbs from chloride solutions onto goethite surfaces as inner-sphere square-planar complexes (Au(III)(OH,Cl)4), with dominantly OH ligands at pH > 6 and mixed OH/Cl ligands at lower pH values. In combination with these spectroscopic results, Reverse Monte Carlo simulations were used to constraint the possible sorption sites on the surface of goethite. Based on this structural information, we calculated sorption isotherms of Au(III) on Fe oxy-hydroxides surfaces, using the CD-MUSIC (Charge Distribution - MUlti SIte Complexation) model. The various Au(III)-sorbed species were identified as a function of pH, and the results of these EXAFS+CD-MUSIC models are compared with titration experiments. The overall good agreement between the predicted and measured structural models shows the potential of this combined approach to better model sorption processes of transition elements onto highly reactive solid surfaces such as goethite and ferrihydrite

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.

Visible-near infrared point spectrometry of drill core samples from Río Tinto, Spain: results from the 2005 Mars Astrobiology Research and Technology Experiment (MARTE) drilling exercise.

Science.gov (United States)

Sutter, Brad; Brown, Adrian J; Stoker, Carol R

2008-10-01

Sampling of subsurface rock may be required to detect evidence of past biological activity on Mars. The Mars Astrobiology Research and Technology Experiment (MARTE) utilized the Río Tinto region, Spain, as a Mars analog site to test dry drilling technologies specific to Mars that retrieve subsurface rock for biological analysis. This work examines the usefulness of visible-near infrared (VNIR) (450-1000 nm) point spectrometry to characterize ferric iron minerals in core material retrieved during a simulated Mars drilling mission. VNIR spectrometry can indicate the presence of aqueously precipitated ferric iron minerals and, thus, determine whether biological analysis of retrieved rock is warranted. Core spectra obtained during the mission with T1 (893-897 nm) and T2 (644-652 nm) features indicate goethite-dominated samples, while relatively lower wavelength T1 (832-880 nm) features indicate hematite. Hematite/goethite molar ratios varied from 0 to 1.4, and within the 880-898 nm range, T1 features were used to estimate hematite/goethite molar ratios. Post-mission X-ray analysis detected phyllosilicates, which indicates that examining beyond the VNIR (e.g., shortwave infrared, 1000-2500 nm) will enhance the detection of other minerals formed by aqueous processes. Despite the limited spectral range of VNIR point spectrometry utilized in the MARTE Mars drilling simulation project, ferric iron minerals could be identified in retrieved core material, and their distribution served to direct core subsampling for biological analysis.

Profile characterization of soil developed on pelitic rocks from the Bambui Group through chemical analysis, X-ray diffraction and Moessbaur spectroscopy

International Nuclear Information System (INIS)

Almeida Barbosa, L.C. de.

1986-07-01

Five sample from a Red-yellow latosol developed on pelitic rocks from the Bambui Group, located close to Paraopeba, state of Minas Gerais, Brazil, were collected and studied. The sample with color patterns varying from yellowish (sample SL11; 0.3m depth), in superficial horizons, to reddish (SL12; 1.0m) in intermediate profile positions, and various shades (SL14A and SL14V; 3.0m), in deeper horizons, were studied through Moessbauer spectroscopy in order to characterize, in detail, the ferruginous species present. The total iron content within the soil is practically constant in relation to the depth. Yet, the hematite/goethite content ratio varies within the expected sequence according to the color. A linear relationship was observed between the reddish intensity and the hematite content of the argillaceous fraction. The hematite contents are proportionally less in the SL14A sample, apparently due to deficient drainage in the past, and in the SL11 sample, due to organic matter effects. This latter sample is also characterized by at least two goethite populations: one with 20% mol replacing aluminum and another with certainly more than 30% mol. In to explan this difference, three hypothesis were elaborated. The most suitable one suggests that the goethite is destroyed and formed again through the soil column, in response to pedo environmental changes closer to the surface. (D.J.M.) [pt

Stability of dispersions in polar organic media. I. Electrostatic stabilization

NARCIS (Netherlands)

Rooy, N. de; Bruyn, P.L. de; Overbeek, J.Th.G.

Electrostatically stabilized sols of silver, silver iodide, α-goethite, and copper phthalocyanine in methanol, ethanol, isopropanol, and acetone have been prepared and characterized. Coagulation concentrations with electrolytes of various charge numbers have been determined in water, in organic

Gas-Liquid Precipitation of water dissolved heavy metal ions using hydrogen sulfide gas

NARCIS (Netherlands)

Al Tarazi, M.Y.M.

2004-01-01

Precipitation of solids promoted by gas-liquid reactions is applied in many industrial processes such as the production of ammonium phosphate, ammonium sulphate, barium carbonate, calcium carbonate, calcium fluoride, ypsum (calcium sulphate), goethite, sodium bicarbonate, strontium carbonate and

Super gene alternation of magnetite and pyrite and the role of their alternation products in the fixation of uranium from the circulating media. Vol. 3

Energy Technology Data Exchange (ETDEWEB)

El-Gemmizi, M A [Nuclear Materials Authority, Cairo, (Egypt)

1996-03-01

In most of the Egyptian altered radioactive granites, highly magnetic heavy particles were found to be radioactive. They are a mixture of several iron oxide minerals which are products of super gene alternation of the preexisting hypo gene iron-bearing minerals especially magnetite and pyrite. The end products of this super gene alternation are mainly hydrated iron oxide minerals limonite and/or goethite. During the alternation, deformation and defects in the mineral structure took place, thereby promoting diffusion of the substitutional and interstitial ions (uranium) towards these sites. The mechanism of the alternation of the hypo gene iron-bearing minerals, magnetite and pyrite to form the secondary mineral hematite, limonite and goethite; and the role of these secondary minerals in fixing uranium from the circulating media, and as indicators to the radioactivity of the host rocks are discussed. 2 figs.

Study of the dehydroxylation in the hydrated ferric oxide named limonite

International Nuclear Information System (INIS)

Palacios, P.R.; Bustamante, A.; De Los Santos Valladares, L.; Gonzalez, J.C.

2012-01-01

We completed the previous characterization of the compound named limonite (FeO[OH].nH 2 O) with the analysis of thermal behavior at temperatures from ambient to 1000 o C, as well as their chemical analysis through the measurements of energy dispersive X-ray and the study in the infrared region in energy range from 600 to 4000 cm -1 . The results show a sharp endotherm peak around 264 o C, it corresponds to the structure change of the orthorhombic goethite (Pbnm) to rhombohedra hematite (R3c). Moreover, we found three inflexion points in the percentage of mass loss at temperatures of 50, 190 and 290 o C. These changes are closely related to the deshydroxylation of limonite to goethite, α-FeO(OH), phases and subsequently to hematite, α-Fe 2 O 3 . (author).

Super gene alternation of magnetite and pyrite and the role of their alternation products in the fixation of uranium from the circulating media. Vol. 3

International Nuclear Information System (INIS)

El-Gemmizi, M.A.

1996-01-01

In most of the Egyptian altered radioactive granites, highly magnetic heavy particles were found to be radioactive. They are a mixture of several iron oxide minerals which are products of super gene alternation of the preexisting hypo gene iron-bearing minerals especially magnetite and pyrite. The end products of this super gene alternation are mainly hydrated iron oxide minerals limonite and/or goethite. During the alternation, deformation and defects in the mineral structure took place, thereby promoting diffusion of the substitutional and interstitial ions (uranium) towards these sites. The mechanism of the alternation of the hypo gene iron-bearing minerals, magnetite and pyrite to form the secondary mineral hematite, limonite and goethite; and the role of these secondary minerals in fixing uranium from the circulating media, and as indicators to the radioactivity of the host rocks are discussed. 2 figs

Surface complexation modeling of groundwater arsenic mobility: Results of a forced gradient experiment in a Red River flood plain aquifer, Vietnam

DEFF Research Database (Denmark)

Jessen, Søren; Postma, Dieke; Larsen, Flemming

2012-01-01

, suggesting a comparable As(III) affinity of Holocene and Pleistocene aquifer sediments. A forced gradient field experiment was conducted in a bank aquifer adjacent to a tributary channel to the Red River, and the passage in the aquifer of mixed groundwater containing up to 74% channel water was observed......Three surface complexation models (SCMs) developed for, respectively, ferrihydrite, goethite and sorption data for a Pleistocene oxidized aquifer sediment from Bangladesh were used to explore the effect of multicomponent adsorption processes on As mobility in a reduced Holocene floodplain aquifer......(III) while PO43− and Fe(II) form the predominant surface species. The SCM for Pleistocene aquifer sediment resembles most the goethite SCM but shows more Si sorption. Compiled As(III) adsorption data for Holocene sediment was also well described by the SCM determined for Pleistocene aquifer sediment...

METHYLENE BLUE ADSORPTION FROM GLYCEROL SOLUTION ...

African Journals Online (AJOL)

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The recognition of the presence of two habits of goethite was indicated by. Atkinson et ... The growth of certain face may be preferred over the other and the ... A Genesis II Fourier Transform infrared spectrometer was used to record the spectra.

In situ treatment of arsenic contaminated groundwater by aquifer iron coating: Experimental study

Energy Technology Data Exchange (ETDEWEB)

Xie, Xianjun, E-mail: xjxie@cug.edu.cn [State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, 430074 Wuhan (China); Wang, Yanxin, E-mail: yx.wang@cug.edu.cn [State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, 430074 Wuhan (China); Pi, Kunfu [State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, 430074 Wuhan (China); Liu, Chongxuan [State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, 430074 Wuhan (China); Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Li, Junxia; Liu, Yaqing; Wang, Zhiqiang; Duan, Mengyu [State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, 430074 Wuhan (China)

2015-09-15

In situ arsenic removal from groundwater by an aquifer iron coating method has great potential to be a cost effective and simple groundwater remediation technology, especially in rural and remote areas where groundwater is used as the main water source for drinking. The in situ arsenic removal technology was first optimized by simulating arsenic removal in various quartz sand columns under anoxic conditions. The effectiveness was then evaluated in an actual high-arsenic groundwater environment. The arsenic removal mechanism by the coated iron oxide/hydroxide was investigated under different conditions using scanning electron microscopy (SEM)/X-ray absorption spectroscopy, electron probe microanalysis, and Fourier transformation infrared spectroscopy. Aquifer iron coating method was developed via a 4-step alternating injection of oxidant, iron salt and oxygen-free water. A continuous injection of 5.0 mmol/L FeSO{sub 4} and 2.5 mmol/L NaClO for 96 h can form a uniform goethite coating on the surface of quartz sand without causing clogging. At a flow rate of 7.2 mL/min of the injection reagents, arsenic (as Na{sub 2}HAsO{sub 4}) and tracer fluorescein sodium to pass through the iron-coated quartz sand column were approximately at 126 and 7 column pore volumes, respectively. The retardation factor of arsenic was 23.0, and the adsorption capacity was 0.11 mol As per mol Fe. In situ arsenic removal from groundwater in an aquifer was achieved by simultaneous injections of As(V) and Fe(II) reagents. Arsenic fixation resulted from a process of adsorption/co-precipitation with fine goethite particles by way of bidentate binuclear complexes. Therefore, the study results indicate that the high arsenic removal efficiency of the in situ aquifer iron coating technology likely resulted from the expanded specific surface area of the small goethite particles, which enhanced arsenic sorption capability and/or from co-precipitation of arsenic on the surface of goethite particles

Role of iron species in the photo-transformation of phenol in artificial and natural seawater

International Nuclear Information System (INIS)

Calza, Paola; Massolino, Cristina; Pelizzetti, Ezio; Minero, Claudio

2012-01-01

The role played by iron oxides (goethite and akaganeite) and iron(II)/(III) species as photo-sensitizers toward the transformation of organic matter was examined in saline water using phenol as a model molecule. The study was carried out in NaCl 0.7 M solution at pH 8, artificial (ASW) and natural (NSW) seawater, in a device simulating solar light spectrum and intensity. Under illumination phenol decomposition occurs in all the investigated cases. Conversely, dark experiments show that no reaction takes place, implying that phenol transformation is a light- activated process. Following the addition of Fe(II) ions to aerated solutions, Fe(II) is easily oxidized to Fe(III) and hydrogen peroxide is formed. Regardless of the addition of Fe(II) or Fe(III) ions, photo-activated degradation is mediated by Fe(III) species. Several (and different) hydroxylated and halogenated intermediates were identified. In ASW, akaganeite promotes the formation of ortho and para chloro derivatives (2- and 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol), while goethite induces the formation of 3-chlorophenol and bromophenols. Conversely, Fe(II) or Fe(III) addition causes the formation of 3- and 4-chlorophenol and 2,3- or 3,4-dichlorophenol. 4-Bromophenol was only identified when irradiating Fe(II) spiked solutions. Natural seawater sampled in the Gulf of Trieste, Italy, has been spiked with phenol and irradiated. Phenol photo-induced transformation in NSW mediated by natural photosensitizers occurs and leads to the formation of numerous halophenols, condensed products and nitrophenols. When NSW is spiked with phenol and iron oxides, Fe(II) or Fe(III), halophenols production is enhanced. A close analogy exists between Fe(III), Fe(II)/goethite in ASW and NSW products. Different halophenols production in the natural seawater samples depends on Fe(II)/goethite (above all for 3-chlorophenol, 2,3-dichlorophenol and 4-bromophenol formation) and on Fe(III) colloidal species (3

Sorption of a branched nonylphenol isomer and perfluorooctanoic acid on geosorbents and carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Li, Chengliang

2011-10-13

As metabolites of organic surfactants, both nonylphenol (NP) and perfluorooctanoic acid (PFOA) are toxic and ubiquitous in the environment. Their sorption on soils and sediments is of importance for their fate and transport in the environment. Especially in China, there is still a lack of consolidated knowledge on the sorption behavior of NP and PFOA on geosorbents such as Yangtze River sediments. Thus, the present thesis investigates the sorption of a branched NP isomer [4-(1-ethyl-1, 3-dimethylpentyl) phenol] (NP111) and PFOA on Yangtze River sediments and their model components, i.e. a clay mineral (illite), metal oxides (goethite and {delta}-Al{sub 2}O{sub 3}) and organic matter (isolated from Yangtze River sediments and commercial organic matter) by both batch and dialysis techniques. NP111 is the most environmentally relevant NP isomer and its fate in the environment is unknown. Because PFOA is weakly adsorbed on geosorbents, multi-walled carbon nanotubes (MWCNTs) were studied as promising adsorbents. One of the MWCNTs studied contained traces of metal catalyst on the outer surface. Sorption isotherms of NP111 and PFOA on the sediments and their model components were fitted well by the Freundlich model. Sorption of NP111 on the sediments depended largely on their organic carbon content, resulting in organic carbon-normalized sorption coefficient (K{sub OC}) values between 6.3 x 10{sup 3} and 1.1 x 10{sup 4} L kg{sup -1}. The sorption of NP111 on {delta}-Al{sub 2}O{sub 3} and illite was comparable to that on sediments, but significantly lower than that on goethite. In contrast, the sorption of PFOA on the sediments was significantly lower. The affinity of PFOA to goethite and {delta}-Al{sub 2}O{sub 3} was slightly higher than to the sediments, but it was negligible to natural organic matter and illite. The results suggest that the organic carbon content of the sediments plays a dominant role in the sorption of NP111, whereas goethite acts as a potential sink

In situ treatment of arsenic contaminated groundwater by aquifer iron coating: Experimental study

International Nuclear Information System (INIS)

Xie, Xianjun; Wang, Yanxin; Pi, Kunfu; Liu, Chongxuan; Li, Junxia; Liu, Yaqing; Wang, Zhiqiang; Duan, Mengyu

2015-01-01

In situ arsenic removal from groundwater by an aquifer iron coating method has great potential to be a cost effective and simple groundwater remediation technology, especially in rural and remote areas where groundwater is used as the main water source for drinking. The in situ arsenic removal technology was first optimized by simulating arsenic removal in various quartz sand columns under anoxic conditions. The effectiveness was then evaluated in an actual high-arsenic groundwater environment. The arsenic removal mechanism by the coated iron oxide/hydroxide was investigated under different conditions using scanning electron microscopy (SEM)/X-ray absorption spectroscopy, electron probe microanalysis, and Fourier transformation infrared spectroscopy. Aquifer iron coating method was developed via a 4-step alternating injection of oxidant, iron salt and oxygen-free water. A continuous injection of 5.0 mmol/L FeSO 4 and 2.5 mmol/L NaClO for 96 h can form a uniform goethite coating on the surface of quartz sand without causing clogging. At a flow rate of 7.2 mL/min of the injection reagents, arsenic (as Na 2 HAsO 4 ) and tracer fluorescein sodium to pass through the iron-coated quartz sand column were approximately at 126 and 7 column pore volumes, respectively. The retardation factor of arsenic was 23.0, and the adsorption capacity was 0.11 mol As per mol Fe. In situ arsenic removal from groundwater in an aquifer was achieved by simultaneous injections of As(V) and Fe(II) reagents. Arsenic fixation resulted from a process of adsorption/co-precipitation with fine goethite particles by way of bidentate binuclear complexes. Therefore, the study results indicate that the high arsenic removal efficiency of the in situ aquifer iron coating technology likely resulted from the expanded specific surface area of the small goethite particles, which enhanced arsenic sorption capability and/or from co-precipitation of arsenic on the surface of goethite particles. - Highlights: �

Iron oxides as a cause of GPR reflections

NARCIS (Netherlands)

van Dam, R.L.; Schlager, W.; Dekkers, M.; Huisman, J.A.

2002-01-01

Iron oxides frequently occur as secondary precipitates in both modern and ancient sediments and may form bands or irregular patterns. We show from time-domain reflectometry (TDR) field studies that goethite iron-oxide precipitates significantly lower the electromagnetic wave velocity of sediments.

Assessment of the BCR sequential extraction procedure for thallium fractionation using synthetic mineral mixtures

Czech Academy of Sciences Publication Activity Database

Vaněk, A.; Grygar, Tomáš; Chrastný, V.; Tejnecký, V.; Drahota, Petr; Komárek, M.

2010-01-01

Roč. 176, 1-3 (2010), s. 913-918 ISSN 0304-3894 Institutional research plan: CEZ:AV0Z4032918; CEZ:AV0Z30130516 Keywords : Metal * Sequential extraction * Goethite * Ferrihydrite * Birnessite * Illite Subject RIV: DD - Geochemistry Impact factor: 3.723, year: 2010

Phosphorites from the error seamount, Northern Arabian Sea

Digital Repository Service at National Institute of Oceanography (India)

Rao, V.P

are algal foraminiferal limestones of shallow water origin. X-ray diffraction study shows that calcite is the dominant mineral followed by francolite, fluorite and goethite. P 2O5 concentration of the phosphorite varies between 18.0 and 21.5%. It appears...

Modeling selenate adsorption behavior on oxides, clay minerals, and soils using the triple layer model

Science.gov (United States)

Selenate adsorption behavior was investigated on amorphous aluminum oxide, amorphous iron oxide, goethite, clay minerals: kaolinites, montmorillonites, illite, and 18 soil samples from Hawaii, and the Southwestern and the Midwestern regions of the US as a function of solution pH. Selenate adsorpti...

Spatial distribution of crystalline corrosion products formed during corrosion of stainless steel in concrete

KAUST Repository

Serdar, Marijana

2015-05-01

© 2015 Elsevier Ltd All rights reserved. The mineralogy and spatial distribution of nano-crystalline corrosion products that form in the steel/concrete interface were characterized using synchrotron X-ray micro-diffraction (μ-XRD). Two types of low-nickel high-chromium reinforcing steels embedded into mortar and exposed to NaCl solution were investigated. Corrosion in the samples was confirmed by electrochemical impedance spectroscopy (EIS). μ-XRD revealed that goethite (α-FeOOH) and akaganeite (β-FeOOH) are the main iron oxide-hydroxides formed during the chloride-induced corrosion of stainless steel in concrete. Goethite is formed closer to the surface of the steel due to the presence of chromium in the steel, while akaganeite is formed further away from the surface due to the presence of chloride ions. Detailed microstructural analysis is shown and discussed on one sample of each type of steel.

An X-ray diffraction study of corrosion products from low carbon steel

International Nuclear Information System (INIS)

Morales, A. L.

2003-01-01

It was found in earlier work a decrease in the corrosion rate from low carbon steel when it was subjected to the action of a combined pollutant concentration (SO 4 ''2-=10''-4 M+Cl=1.5x 10''-3 M). It was also found that large magnetic content of the rust was related to higher corrosion rates. In the present study corrosion products are further analyzed by means of X-ray diffraction to account for composition changes during the corrosion process. it is found that lepidocrocite and goethite are the dominant components for the short-term corrosion in all batches considered while for log-term corrosion lepidocrite and goethite dominates if the corrosion rates is low and magnetite dominates if the corrosion rate is high. The mechanism for decreasing the corrosion rate is related to the inhibition of magnetite production at this particular concentration. (Author) 15 refs

Spatial distribution of crystalline corrosion products formed during corrosion of stainless steel in concrete

KAUST Repository

Serdar, Marijana; Meral, Cagla; Kunz, Martin; Bjegovic, Dubravka; Wenk, Hans-Rudolf; Monteiro, Paulo J.M.

2015-01-01

© 2015 Elsevier Ltd All rights reserved. The mineralogy and spatial distribution of nano-crystalline corrosion products that form in the steel/concrete interface were characterized using synchrotron X-ray micro-diffraction (μ-XRD). Two types of low-nickel high-chromium reinforcing steels embedded into mortar and exposed to NaCl solution were investigated. Corrosion in the samples was confirmed by electrochemical impedance spectroscopy (EIS). μ-XRD revealed that goethite (α-FeOOH) and akaganeite (β-FeOOH) are the main iron oxide-hydroxides formed during the chloride-induced corrosion of stainless steel in concrete. Goethite is formed closer to the surface of the steel due to the presence of chromium in the steel, while akaganeite is formed further away from the surface due to the presence of chloride ions. Detailed microstructural analysis is shown and discussed on one sample of each type of steel.

Mineralogy and crystal chemistry of iron in the Timan bauxite and products of their technological processing

Science.gov (United States)

Kotova, O.; Silaev, V.; Lutoev, V.; Vakhrushev, A.

2016-04-01

Mineralogical and geochemical features of two series of samples of typical bauxites from two deposits of Middle Timan mining area (Vezhayu-Vorykva and Svetlinskoe) were studied. The phase composition of ferrous bauxites generally is boehmite, hematite, ultradisperse low-ordered goethite and berthierine. In a boehmite and kaolinite structural impurity of iron to 10%, and in the iron oxidehydroxides aluminum impurity is revealed. On iron content bauxites are subdivided into three mineral types for which quantitative data on valence states of ions of iron and proportions of their distribution last on nonequivalent structural positions in hematite, goethite and berthierine are obtained. Noble metals (Ag, Au, Ir, Rh, Pd) concentrating in bauxites are revealed for the first time. Obtained data can lead to decrease of power consumption during aluminum production and high quality ceramics, to provide production of valuable iron oxide, and also to minimize the ecological harm from accumulation of bauxite wastes.

Novel environmentally friendly synthesis of superparamagnetic magnetite nanoparticles using mechanochemical effect

International Nuclear Information System (INIS)

Iwasaki, Tomohiro; Kosaka, Kazunori; Watano, Satoru; Yanagida, Takeshi; Kawai, Tomoji

2010-01-01

A novel method for synthesizing superparamagnetic magnetite nanoparticles in water system via coprecipitation under an environmentally friendly condition has been developed. In this method, an almost neutral suspension containing ferrous hydroxide and goethite is used as the starting suspension and subjected to a ball-milling treatment. The product was characterized by transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, dynamic light scattering, superconducting quantum interference device magnetometry, and Moessbauer spectroscopy. The mechanochemical effect generated by the ball-milling treatment promoted the reaction between ferrous hydroxide and goethite even at room temperature, resulting in the formation of homogeneous magnetite nanoparticles. Simultaneously, it also contributed to crystallize the formed magnetite nanoparticles while inhibiting the particle growth. This resulted in the formation of ultrafine magnetite nanoparticles of about 10 nm having a single crystal structure. This method could provide ferromagnetic magnetite nanoparticles with superparamagnetism under the moderate condition without neither heating nor any additives such as surfactant and organic solvent.

Corrosion of steel in carbonated media: The oxidation processes of chukanovite (Fe2(OH)2CO3)

International Nuclear Information System (INIS)

Azoulay, I.; Rémazeilles, C.; Refait, Ph.

2014-01-01

Highlights: • Oxidation of chukanovite does not lead to carbonated green rust. • Both lepidocrocite and goethite can result from the oxidation of chukanovite. • Violent oxidation of chukanovite by hydrogen peroxide leads to a Fe(III) oxycarbonate. • Chukanovite crystal structure withstands a partial oxidation of Fe(II) to Fe(III). - Abstract: The oxidation of aqueous suspensions of chukanovite (Fe 2 (OH) 2 CO 3 ) obtained by mixing NaOH, FeCl 2 and Na 2 CO 3 solutions was studied. The reaction was monitored by recording the pH and the redox potential of a platinum electrode immersed in the suspension. The precipitate was analyzed at various oxidation stages by infrared spectroscopy. The end products were also characterized by X-ray diffraction. The oxidation by air of the suspensions leads to lepidocrocite and goethite without formation of an intermediate green rust compound. Violent oxidation of chukanovite by hydrogen peroxide leads to a Fe(III) oxycarbonate with a crystal structure closely related to that of chukanovite

Effect of dissimilatory Fe(III) reducers on bio-reduction and nickel-cobalt recovery from Sukinda chromite-overburden.

Science.gov (United States)

Esther, Jacintha; Panda, Sandeep; Behera, Sunil K; Sukla, Lala B; Pradhan, Nilotpala; Mishra, Barada K

2013-10-01

The effect of an adapted dissimilatory iron reducing bacterial consortium (DIRB) towards bio-reduction of Sukinda chromite overburden (COB) with enhanced recovery of nickel and cobalt is being reported for the first time. The remarkable ability of DIRB to utilize Fe(III) as terminal electron acceptor reducing it to Fe(II) proved beneficial for treatment of COB as compared to previous reports for nickel leaching. XRD studies showed goethite as the major iron-bearing phase in COB. Under facultative anaerobic conditions, goethite was reduced to hematite and magnetite with the exposure of nickel oxide. FESEM studies showed DIRB to be associated with COB through biofilm formation with secondary mineral precipitates of magnetite deposited as tiny globular clusters on the extra polymeric substances. The morphological and mineralogical changes in COB, post DIRB application, yielded a maximum of 68.5% nickel and 80.98% cobalt in 10 days using 8M H2SO4. Copyright © 2013 Elsevier Ltd. All rights reserved.

Raman microscopy and x-ray fluorescence analysis of pigments on medieval and Renaissance Italian manuscript cuttings.

Science.gov (United States)

Burgio, Lucia; Clark, Robin J H; Hark, Richard R

2010-03-30

Italian medieval and Renaissance manuscript cuttings and miniatures from the Victoria and Albert Museum were analyzed by Raman microscopy to compile a database of pigments used in different periods and different Italian regions. The palette identified in most manuscripts and cuttings was found to include lead white, gypsum, azurite, lazurite, indigo, malachite, vermilion, red lead, lead tin yellow (I), goethite, carbon, and iron gall ink. A few of the miniatures, such as the historiated capital "M" painted by Gerolamo da Cremona and the Petrarca manuscript by Bartolomeo Sanvito, are of exceptional quality and were analyzed extensively; some contained unusual materials. The widespread usage of iron oxides such as goethite and hematite as minor components of mixtures with azurite is particularly notable. The use of a needle-shaped form of iron gall ink as a pigment rather than a writing material was established by both Raman microscopy and x-ray fluorescence spectroscopy for the Madonna and Child by Franco de' Russi.

Apatite-brannerite-pitchblende association in hydrothermal quartz veins

International Nuclear Information System (INIS)

Brodin, B.V.; Mel'nikova, A.M.; Osipov, B.S.; Pavlov, E.G.

1976-01-01

A study into the vein quartz mineralization confined to the tectonic zones of crush and silicification in sedimentary-igneous rocks of the lower Paleozoic has been made. The physicochemical characteristics of minerals were studied by way of optical and electron microscopy, chemical, laser-microspectral and X-ray structural analyses, microprobing and alpha-microradiography. 3 mineral associations have been discriminated, representative of the sequence of hydrothermal mineralization. An unusual parogenesis of pitchblende and brannerite with apatite, xenotime and more recent goethite has been revealed. The results are indicative of a medium-low-temperature hydrothermal process occurring at the final stages of formation of uraniferrous quartz veins. By composition and mineralization sequence, the latters are close to low- and medium-temperature uranium-quartz-chlorite-hydromica formations with apatite, coffinite, brannerite and pitchblende. The weak initial metamictization of goethite in veins 80 to 100 million years old is due to the radioactive effect of the submicroscopic radioactive mineral impurity on the crystalline lattice

The effect of sulfide on the aerobic corrosion of carbon steel in near-neutral pH saline solutions

International Nuclear Information System (INIS)

Sherar, B.W.A.; Keech, P.G.; Shoesmith, D.W.

2013-01-01

Highlights: ► The corrosion rate is low when steel is exposed to anaerobic conditions (pH = 8.9). ► An anaerobic to aerobic corrosion with sulfide switch increases the corrosion rate. ► Aerobic exposure induces the formation of goethite-covered tubercles. ► Continual sulfide exposure leads to the slow conversion of goethite to mackinawite. - Abstract: Severe corrosion damage may occur when gas transmission pipelines are exposed, at disbonded coating locations, to trapped waters containing sulfide followed by secondary exposure to air. Aerobic corrosion with sulfide was investigated in a long-term corrosion experiment in which corrosion was monitored by measurement of the corrosion potential and polarization resistance obtained from linear polarization resistance measurements. The properties and composition of the corrosion product deposits formed were determined using scanning electron microscopy, energy dispersive X-ray analysis, and Raman spectroscopy. A switch from aerobic to aerobic-with-sulfide corrosion doubles the relative corrosion rate.

Field sludge characterization obtained from inner of pipelines

Energy Technology Data Exchange (ETDEWEB)

Nava, N.; Sosa, E.; Alamilla, J.L. [Instituto Mexicano del Petroleo, Programa de Integridad de Ductos, Eje Central Lazaro Cardenas Norte 152, San Bartolo Atepehuacan, C.P. 07730 (Mexico); Knigth, C. [PEMEX Refinacion, Avenida Marina Nacional 329, Edificio B-2, Piso 11, C.P. 11311 (Mexico); Contreras, A. [Instituto Mexicano del Petroleo, Programa de Integridad de Ductos, Eje Central Lazaro Cardenas Norte 152, San Bartolo Atepehuacan, C.P. 07730 (Mexico)], E-mail: acontrer@imp.mx

2009-11-15

Physicochemical characterization of sludge obtained from refined hydrocarbons transmission pipeline was carried out through Moessbauer spectroscopy and X-ray diffraction. The Moessbauer and X-ray patterns indicate the presence of corrosion products composed of different iron oxide and sulfide phases. Hematite ({alpha}-Fe{sub 2}O{sub 3}), magnetite (Fe{sub 3}O{sub 4}), maghemite ({gamma}-Fe{sub 2}O{sub 3}), magnetic and superparamagnetic goethite ({alpha}-FeOOH), pyrrhotite (Fe{sub 1-x}S), akaganeite ({beta}-FeOOH), and lepidocrocite ({gamma}-FeOOH) were identified as corrosion products in samples obtained from pipeline transporting Magna and Premium gasoline. For diesel transmission pipeline, hematite, magnetite, and magnetic goethite were identified. Corrosion products follow a simple reaction mechanism of steel dissolution in aerated aqueous media at a near-neutral pH. Chemical composition of the corrosion products depends on H{sub 2}O and sulfur inherent in fluids (traces). These results can be useful for decision-making with regard to pipeline corrosion control.

Occurrence and mineralogy of ferruginous bauxites along the eastern seaboard of South Africa

International Nuclear Information System (INIS)

Fitzpatrick, R.W.

1983-01-01

The distribution of ferruginous bauxites along the eastern seaboard of South Africa is shown in a small-scale map and their genesis is briefly described. The aluminium oxide, iron oxide, primary slightly-altered iron and titanium oxides and layer silicate minerals in some typical ferruginous bauxites from the eastern seaboard of South Africa have been investigated by X-ray powder diffraction (XRD), infra-red spectroscopy (IR), thin section, electron optical (SEM and TEM) and chemical extraction analysis. The dominant aluminium oxide mineral is well-crystalline gibbsite. Traces of boehmite were identified in some samples. The dominant iron oxide mineral is finely-divided goethite containing from 20 to 25 mole per cent AIO(OH), this being the mineral which gives the bauxites their characteristic yellowish colour. The reddish bauxites also contain finely-divided Al-substituted hematite which masks the colour of the goethite. The aluminium incorporated in the iron oxide structures is not recoverable by the normal Bayer Process

Interaction of aromatic amines with iron oxides: implications for prebiotic chemistry.

Science.gov (United States)

Shanker, Uma; Singh, Gurinder; Kamaluddin

2013-06-01

The interaction of aromatic amines (aniline, p-chloroaniline, p-toludine and p-anisidine) with iron oxides (goethite, akaganeite and hematite) has been studied. Maximum uptake of amines was observed around pH 7. The adsorption data obtained at neutral pH were found to follow Langmuir adsorption. Anisidine was found to be a better adsorbate probably due to its higher basicity. In alkaline medium (pH > 8), amines reacted on goethite and akaganeite to give colored products. Analysis of the products by GC-MS showed benzoquinone and azobenzene as the reaction products of aniline while p-anisidine afforded a dimer. IR analysis of the amine-iron oxide hydroxide adduct suggests that the surface acidity of iron oxide hydroxides is responsible for the interaction. The present study suggests that iron oxide hydroxides might have played a role in the stabilization of organic molecules through their surface activity and in prebiotic condensation reactions.

Dissolution of Fe(III) (hydr) oxides by metal-EDTA complexes

Science.gov (United States)

Ngwack, Bernd; Sigg, Laura

1997-03-01

The dissolution of Fe(III)(hydr)oxides (goethite and hydrous ferric oxide) by metal-EDTA complexes occurs by ligand-promoted dissolution. The process is initiated by the adsorption of metal-EDTA complexes to the surface and is followed by the dissociation of the complex at the surface and the release of Fe(III)EDTA into solution. The dissolution rate is decreased to a great extent if EDTA is complexed by metals in comparison to the uncomplexed EDTA. The rate decreases in the order EDTA CaEDTA ≫ PbEDTA > ZnEDTA > CuEDTA > Co(II)EDTA > NiEDTA. Two different rate-limiting steps determine the dissolution process: (1) detachment of Fe(III) from the oxide-structure and (2) dissociation of the metal-EDTA complexes. In the case of goethite, step 1 is slower than step 2 and the dissolution rates by various metals are similar. In the case of hydrous ferric oxide, step 2 is rate-limiting and the effect of the complexed metal is very pronounced.

(ajst) the potential for gold mineralisation

African Journals Online (AJOL)

were formed by mineralising fluids that intruded the country rock through already existing NW-trending fractures. The fluids also altered the country rock leading to the formation of secondary minerals like chlorite, sericite, epidote, zoisite, calcite, sphene and goethite. The major ore minerals are pyrite, magnetite and ilmenite.

Solid-Phase Fe Speciation along the Vertical Redox Gradients in Floodplains using XAS and Mössbauer Spectroscopies

Energy Technology Data Exchange (ETDEWEB)

Chen, Chunmei [Department; Kukkadapu, Ravi K. [Environmental; Lazareva, Olesya [Department; Sparks, Donald L. [Department

2017-06-30

Properties of Fe minerals are poorly understood in natural soils and sediments with variable redox conditions. In this study, we combined 57Fe Mössbauer and Fe K-edge X-ray absorption spectroscopic techniques to assess solid-phase Fe speciation along the vertical redox gradients of floodplain profiles, which exhibited a succession of oxic, anoxic and suboxic-oxic zones with increasing depth along the vertical profiles. The anoxic conditions at the intermediate horizon (55-80 cm) of the eastern floodplain resulted in extensive depletion of Fe(III)-oxides including both ferrihydrite and goethite, concurrent with a corresponding reduction of phyllosilicates(PS)-Fe(III) to PS-Fe(II). In addition, the anoxic conditions increased the crystallinity of Fe(III)-oxides in this reduced zone, relative to the oxic zones. In the most reduced intermediate sediments at 80-120cm of the western floodplain, the anoxic conditions drove the complete reductive dissolution of Fe(III) oxides, as well as the greatest reduction (48-55%) in PS-Fe(III). In both oxic near-surface horizon and oxic-suboxic gravel aquifers beneath the soil horizons, Fe(III)-oxides were mainly present as ferrihydrite with a less amount of goethite, which preferentially occurred as nanogoethite or Al/Si-substituted goethite. Ferrihydrite with varying crystallinity or impurities such as organic matter, Al or Si, persisted under suboxic-oxic conditions in the floodplain. This study indicates that vertical redox gradients exert a major control on the quantity and speciation of Fe(III) oxides as well as the oxidation state of structural Fe in PS, which could significantly affect nutrient cycling and carbon (de)stabilization.

Photostabilization of the herbicide norflurazon microencapsulated with ethylcellulose in the soil-water system

Energy Technology Data Exchange (ETDEWEB)

Sopena, Fatima, E-mail: fsopenav@irnase.csic.es [Institute of Natural Resources and Agrobiology (CSIC), Reina Mercedes 10, Apdo 1052, 41080 Seville, ES (Spain); Villaverde, Jaime; Maqueda, Celia; Morillo, Esmeralda [Institute of Natural Resources and Agrobiology (CSIC), Reina Mercedes 10, Apdo 1052, 41080 Seville, ES (Spain)

2011-11-15

Highlights: {yields} Herbicide photodegradation studies using ethylcellulose-microencapsulated formulations (ECF) in soil and water. {yields} Greater herbicide photo-protection observed from EFC than from its commercial form. {yields} Photo-protective effect due to the gradual herbicide release and the presence of ethylcellulose. {yields} Herbicide photo-stability conditioned by soil colloidal components, especially by goethite and humic acids. {yields} EFC could reduce the field herbicide losses by photolysis. - Abstract: Ethylcellulose-microencapsulated formulations (ECFs) of norflurazon have been shown to reduce leaching, maintaining a threshold concentration in the topsoil than the commercial formulation (CF). Since photodegradation contributes to field dissipation of norflurazon, the objective of the present work was to study if such formulations can also protect from its photodescomposition. For this purpose, aqueous solutions of CF and ECFs, containing the most important soil components (goethite, humic and fulvic acids and montmorillonite) were tested. To get a more realistic approach, studies in soil were also performed. The results were well explained by a simple first order model. DT{sub 50} value was 3 h for CF under irradiation, which was considerably lower than those corresponding to the systems where ECF was used (35 h for ECF; 260 h for ECF-goethite; 53 h for ECF-humic acids; 33 h for ECF-montmorillonite; and 28 h for ECF-fulvic acids). ECF protected against photodegradation in both aqueous solution and soil due to the gradual release of the herbicide, which reduced the herbicide available to be photodegraded. These lab-scale findings proved that ECF could reduce the herbicide dosage, minimizing its photolysis, which would be especially advantageous during the first hours after foliar and soil application.

Combined Application of QEM-SEM and Hard X-ray Microscopy to Determine Mineralogical Associations and Chemcial Speciation of Trace Metals

Energy Technology Data Exchange (ETDEWEB)

M Grafe; M Landers; R Tappero; P Austin; B Gan; A Grabsch; C Klauber

2011-12-31

We describe the application of quantitative evaluation of mineralogy by scanning electron microscopy in combination with techniques commonly available at hard X-ray microprobes to define the mineralogical environment of a bauxite residue core segment with the more specific aim of determining the speciation of trace metals (e.g., Ti, V, Cr, and Mn) within the mineral matrix. Successful trace metal speciation in heterogeneous matrices, such as those encountered in soils or mineral residues, relies on a combination of techniques including spectroscopy, microscopy, diffraction, and wet chemical and physical experiments. Of substantial interest is the ability to define the mineralogy of a sample to infer redox behavior, pH buffering, and mineral-water interfaces that are likely to interact with trace metals through adsorption, coprecipitation, dissolution, or electron transfer reactions. Quantitative evaluation of mineralogy by scanning electron microscopy coupled with micro-focused X-ray diffraction, micro-X-ray fluorescence, and micro-X-ray absorption near edge structure (mXANES) spectroscopy provided detailed insights into the composition of mineral assemblages and their effect on trace metal speciation during this investigation. In the sample investigated, titanium occurs as poorly ordered ilmenite, as rutile, and is substituted in iron oxides. Manganese's spatial correlation to Ti is closely linked to ilmenite, where it appears to substitute for Fe and Ti in the ilmenite structure based on its mXANES signature. Vanadium is associated with ilmenite and goethite but always assumes the +4 oxidation state, whereas chromium is predominantly in the +3 oxidation state and solely associated with iron oxides (goethite and hematite) and appears to substitute for Fe in the goethite structure.

Adsorption and desorption of Cu2+ on paddy soil aggregates pretreated with different levels of phosphate.

Science.gov (United States)

Dai, Jun; Wang, Wenqin; Wu, Wenchen; Gao, Jianbo; Dong, Changxun

2017-05-01

Interactions between anions and cations are important for understanding the behaviors of chemical pollutants and their potential risks in the environment. Here we prepared soil aggregates of a yellow paddy soil from the Taihu Lake region, and investigated the effects of phosphate (P) pretreatment on adsorption-desorption of Cu 2+ of soil aggregates, free iron oxyhydrates-removed soil aggregates, goethite, and kaolinite with batch adsorption method. The results showed that Cu 2+ adsorption was reduced on the aggregates pretreated with low concentrations of P, and promoted with high concentrations of P, showing a V-shaped change. Compared with the untreated aggregates, the adsorption capacity of Cu 2+ was reduced when P application rates were lower than 260, 220, 130 and 110mg/kg for coarse, clay, silt and fine sand fractions, respectively. On the contrary, the adsorption capacity of Cu 2+ was higher on P-pretreated soil aggregates than on the control ones when P application rates were greater than those values. However, the desorption of Cu 2+ was enhanced at low levels of P, but suppressed at high levels of P, displaying an inverted V-shaped change over P adsorption. The Cu 2+ adsorption by the aggregate particles with and without P pretreatments was well described by the Freundlich equation. Similar results were obtained on P-pretreated goethite. However, such P effects on Cu 2+ adsorption-desorption were not observed on kaolinite and free iron oxyhydrates-removed soil aggregates. The present results indicate that goethite is one of the main soil substances responsible for the P-induced promotion and inhibition of Cu 2+ adsorption. Copyright © 2016. Published by Elsevier B.V.

Petrography, Geochemistry and Proposed Genesis of Ordovician Oolitic Iron Formation Members of the Lashkarak Formation, Eastern Alborz

International Nuclear Information System (INIS)

Maghsoudloo Mahalli, M.; Shafiei Bafti, B.

2016-01-01

Mineralogical characteristics combined with geochemical data show that anomalous values of Fe in studied carbonate argillite formations with respect to common sedimentary rocks are related to the abundance of iron-bearing oolites as oxides such as hematite and goethite, and the clay mineral chamosite. Based on Fe, Mg and Ca concentrations, oolitic iron formations can be divided into low-grade and high-grade iron formations. The former is characterized by chamosite and calcite, whereas the latter consists ofhematite and calcite. This research, along with available paleo-geographic and sedimentological information suggests that the iron for the formation of iron oolites was available from normal sea water and Fe could be carried as clastic particles along with clays or coating of clay particles derived from weathering and erosion of shales from adjacent land. High contents of K and Si in oolitic iron horizons, the presence of detrital zircon, quartz and clay minerals within oolites and also in the matrix of these rocks confirm the proposed model and show the important role of Fe-bearing clay minerals in the genesis of the primary chamositic oolites in an environment with p H=5-9 and medium-weak redox conditions (Maynard, 1983; Maynard, 1986). The abundance of hematite relative to goethite in the Fe-oolites, dense and elliptical oolites as well as the frequent occurrence of calcite veinlets cutting oolite beds has been attributed to diagenetic processes and the modification of chamosite and goethite to hematite. Our findings indicate that the studied members can be classified as low-grade oolitic iron formation (average 21 wt.% Fe) which do not have economic importance at present.

Mineralogical Characterization of The Alteration Facies at Gabal El-Missikat Area, Central Eastern Desert, Egypt

International Nuclear Information System (INIS)

El-Sherif, A.M.

2013-01-01

The present study deals with the petrographical, mineralogical and geochemical characteristics of the alteration facies zones recognized around the shear zone at Gabal El-Missikat area, Central Eastern Desert, Egypt. Petrographically, the fresh granitic samples are composed mainly of quartz, K-feldspars (microcline and microcline perthite), plagioclase, biotite. The secondary minerals are sericite, kaolinite, muscovite, chlorite and epidote as well as zircon, apatite, fluorite, titanite and iron oxides as accessory minerals. Two alteration facies zones are recognized and namely as propylitic and advanced argillic. The propylitic facies zone is composed mainly of sericite with minor kaolinite, muscovite, quartz, relics of plagioclases, chlorite and rare epidote as well as zircon, hematite, goethite, magnetite, ilmenite, ilmenorutile, rutile, titanite, apatite, columbite and fluorite and secondary uranium minerals, the advanced argillic facies zone is composed mainly of kaolinite with minor sericite, quartz, muscovite, chlorite and rare epidote as well as zircon, hematite, goethite, magnetite, ilmenite, ilmenorutile, rutile, titanite, apatite and garnet of spessartine type as accessory minerals. The identified minerals in the studied two alteration facies zones can be grouped into three mineral groups which are: the primary minerals (pyrite, magnetite, galena, columbite and gold), the secondary minerals (uranophane, kasolite and wulfenite) and the gangue minerals (anhydrite, barite, celestine, hematite, goethite and fluorite). The identified mineral assemblage of the studied propylitic alteration facies zone may be attributed to strongly alkaline hydrothermal solutions at ph value of more than 7 with temperature varying between 350 and 450°C, while the advanced argillic alteration facies zone is essentially associated with strongly acidic hydrothermal solutions at ph value less than 7 with temperature varying between 150 and 400°C

Photostabilization of the herbicide norflurazon microencapsulated with ethylcellulose in the soil-water system

International Nuclear Information System (INIS)

Sopena, Fatima; Villaverde, Jaime; Maqueda, Celia; Morillo, Esmeralda

2011-01-01

Highlights: → Herbicide photodegradation studies using ethylcellulose-microencapsulated formulations (ECF) in soil and water. → Greater herbicide photo-protection observed from EFC than from its commercial form. → Photo-protective effect due to the gradual herbicide release and the presence of ethylcellulose. → Herbicide photo-stability conditioned by soil colloidal components, especially by goethite and humic acids. → EFC could reduce the field herbicide losses by photolysis. - Abstract: Ethylcellulose-microencapsulated formulations (ECFs) of norflurazon have been shown to reduce leaching, maintaining a threshold concentration in the topsoil than the commercial formulation (CF). Since photodegradation contributes to field dissipation of norflurazon, the objective of the present work was to study if such formulations can also protect from its photodescomposition. For this purpose, aqueous solutions of CF and ECFs, containing the most important soil components (goethite, humic and fulvic acids and montmorillonite) were tested. To get a more realistic approach, studies in soil were also performed. The results were well explained by a simple first order model. DT 50 value was 3 h for CF under irradiation, which was considerably lower than those corresponding to the systems where ECF was used (35 h for ECF; 260 h for ECF-goethite; 53 h for ECF-humic acids; 33 h for ECF-montmorillonite; and 28 h for ECF-fulvic acids). ECF protected against photodegradation in both aqueous solution and soil due to the gradual release of the herbicide, which reduced the herbicide available to be photodegraded. These lab-scale findings proved that ECF could reduce the herbicide dosage, minimizing its photolysis, which would be especially advantageous during the first hours after foliar and soil application.

In Vitro Enzymatic Reduction Kinetics of Mineral Oxides by Membrane Fractions from Shewanella oneidensis MR-1

International Nuclear Information System (INIS)

Ruebush, S.; Icopini, G.; Brantley, S.; Tien, M.

2006-01-01

This study documents the first example of in vitro solid-phase mineral oxide reduction by enzyme-containing membrane fractions. Previous in vitro studies have only reported the reduction of aqueous ions. Total membrane (TM) fractions from iron-grown cultures of Shewanella oneidensis MR-1 were isolated and shown to catalyze the reduction of goethite, hematite, birnessite, and ramsdellite/pyrolusite using formate. In contrast, nicotinamide adenine dinucleotide (NADH) and succinate cannot function as electron donors. The significant implications of observations related to this cell-free system are: (i) both iron and manganese mineral oxides are reduced by the TM fraction, but aqueous U(VI) is not; (ii) TM fractions from anaerobically grown, but not aerobically grown, cells can reduce the mineral oxides; (iii) electron shuttles and iron chelators are not needed for this in vitro reduction, documenting conclusively that reduction can occur by direct contact with the mineral oxide; (iv) electron shuttles and EDTA stimulate the in vitro Fe(III) reduction, documenting that exogenous molecules can enhance rates of enzymatic mineral reduction; and (v) multiple membrane components are involved in solid-phase oxide reduction. The membrane fractions, consisting of liposomes of cytoplasmic and outer membrane segments, contain at least 100 proteins including the enzyme that oxidizes formate, formate dehydrogenase. Mineral oxide reduction was inhibited by the addition of detergent Triton X-100, which solubilizes membranes and their associated proteins, consistent with the involvement of multiple electron carriers that are disrupted by detergent addition. In contrast, formate dehydrogenase activity was not inhibited by Triton X-100. The addition of anthraquinone-2,6-disulfonate (AQDS) and menaquinone-4 was unable to restore activity; however, menadione (MD) restored 33% of the activity. The addition of AQDS and MD to reactions without added detergent increased the rate of goethite

Multifunctional Silver Coated E-33/Iron Oxide Water Filters: Inhibition of Biofilm Growth and Arsenic Removal

Science.gov (United States)

Bayoxide® E33 (E-33, Goethite) is a widely used commercial material for arsenic adsorption. It is a mixture of iron oxyhydroxide and oxides. E-33 is primarily used to remove arsenic from water and to a lesser extent, other anions, but generally lacks multifunctuality. It is a non...

Influence of Ni-dopant on the properties of synthetic goethite

International Nuclear Information System (INIS)

Krehula, Stjepko; Music, Svetozar; Popovic, Stanko

2005-01-01

The influence of Ni-dopant on the properties of α-FeOOH was investigated by XRD, FT-IR, 57 Fe Moessbauer spectroscopy and transmission electron microscopy. α-FeOOH was synthesized at a highly alkaline pH by precipitation from the FeCl 3 solution with the addition of tetramethylammonium hydroxide and autoclaving at 160 o C. The samples doped with Ni 2+ ions were precipitated in the same way, but in the presence of varying concentrations of NiCl 2 . Solid solutions, having the structure of α-FeOOH, were observed in samples with the Ni/Fe ratio up to 0.05. Upon increasing the amount of Ni-dopant the XRD lines were gradually broadened. The sample with the ratio Ni/Fe=0.10 showed NiFe 2 O 4 , besides the dominant phase having the structure type of α-FeOOH. Shifts of IR bands at 892 and 796cm -1 were not observed in all samples doped with Ni. For the ratio Ni/Fe=0.10, the IR bands centered at 631 and 404cm -1 were significantly broadened. RT Moessbauer spectrum of undoped α-FeOOH and Ni-doped α-FeOOH showed distributions of hyperfine magnetic fields. B hf decreased from 35.1T for an undoped α-FeOOH to 32.1T for α-FeOOH containing Ni 2+ ions (Ni/Fe=0.05). The saturation of the α-FeOOH structure with Ni 2+ ions in amounts higher than ∼5mol% was also observed by Moessbauer spectroscopy. The particle size (length) of acicular α-FeOOH particles with a maximum in the interval 180-220nm was slightly decreased with Ni-doping, but the distribution of the length/width ratio showed no change, having a maximum at 4-5. TEM photographs additionally showed small populations of cubic-shaped or pseudocubic particles of ∼10nm in size for the ratio Ni/Fe=0.05 and about 10-20nm in size for the ratio Ni/Fe=0.10. These particles were assigned to NiFe 2 O 4

Geometry, charge distribution, and surface speciation of phosphate on goethite.

NARCIS (Netherlands)

Rahnemaie, R.; Hiemstra, T.; Riemsdijk, van W.H.

2007-01-01

The surface speciation of phosphate has been evaluated with surface complexation modeling using an interfacial charge distribution (CD) approach based on ion adsorption and ordering of interfacial water. In the CD model, the charge of adsorbed ions is distributed over two electrostatic potentials in

On the crystalline structures of iron oxides formed during the removal process of iron in water

International Nuclear Information System (INIS)

Cho, Bongyeon; Fujita, Kenji; Oda, Katsuro; Ino, Hiromitsu

1993-01-01

The iron oxide samples collected from both filtration and batch reactors were analysed by X-ray diffraction and Moessbauer spectroscopy. In the filtration of water containing iron, the oxidized form of iron was determined to be ferrihydrite. In contrast, in the batch experiment without filtration, iron was oxidized to microcrystalline goethite. (orig.)

Iron oxide mineralogy in late Miocene red beds from La Gloria, Spain: rock-magnetic, voltammetric and Vis spectroscopy analyses

Czech Academy of Sciences Publication Activity Database

Grygar, Tomáš; Dědeček, Jiří; Kruiver, P. P.; Dekkers, M. J.; Bezdička, Petr; Schneeweiss, Oldřich

2003-01-01

Roč. 53, č. 2 (2003), s. 115-132 ISSN 0341-8162 R&D Projects: GA MŠk LN00A028 Institutional research plan: CEZ:AV0Z4040901; CEZ:AV0Z4032918 Keywords : Fe oxide s * goethite * hematite Subject RIV: CA - Inorganic Chemistry Impact factor: 1.083, year: 2003

An updated astronomical time scale for the Plio-Pleistocene deposits from South China Sea and new insights into Asian monsoon evolution

NARCIS (Netherlands)

Ao, H.; Dekkers, M.J.; Qin, L.; Xiao, G.

2011-01-01

Here we present an improved astronomical timescale since 5 Ma as recorded in the ODP Site 1143 in the southern South China Sea, using a recently published Asian summer monsoon record (hematite to goethite content ratio, Hm/Gt) and a parallel benthic δ18O record. Correlation of the benthic δ18O

Highway pavement failure induced by poor soil geotechnical ...

African Journals Online (AJOL)

X-ray diffraction studies showed the presence of abundant kaolinite peaks and a subdued goethite peak without any trace of montmorrilonite. The presence of excess fines in the pavement construction materials (soils) contributed to the failure of the highway pavement at this locality. The low CBR value is also a noted cause ...

Solid-Phase Fe Speciation along the Vertical Redox Gradients in Floodplains using XAS and Mössbauer Spectroscopies.

Science.gov (United States)

Chen, Chunmei; Kukkadapu, Ravi K; Lazareva, Olesya; Sparks, Donald L

2017-07-18

Properties of Fe minerals are poorly understood in natural soils and sediments with variable redox conditions. In this study, we combined 57 Fe Mössbauer and Fe K-edge X-ray absorption spectroscopic (XAS) techniques to assess solid-phase Fe speciation along the vertical redox gradients of floodplains, which exhibited a succession of oxic, anoxic, and suboxic-oxic zones with increasing depth along the vertical profiles. The incised stream channel is bounded on the east by a narrow floodplain and a steep hillslope, and on the west by a broad floodplain. In the eastern floodplain, the anoxic conditions at the intermediate horizon (55-80 cm) coincided with lower Fe(III)-oxides (particularly ferrihydrite), in concurrence with a greater reduction of phyllosilicates(PS)-Fe(III) to PS-Fe(II), relative to the oxic near-surface and sandy gravel layers. In addition, the anoxic conditions in the eastern floodplain coincided with increased crystallinity of goethite, relative to the oxic layers. In the most reduced intermediate sediments at 80-120 cm of the western floodplain, no Fe(III)-oxides were detected, concurrent with the greatest PS-Fe(III) reduction (PS-Fe(II)/Fe(III) ratio ≈ 1.2 (Mössbauer) or 0.8 (XAS)). In both oxic near-surface horizon and oxic-suboxic gravel aquifers beneath the soil horizons, Fe(III)-oxides were mainly present as ferrihydrite with a much less amount of goethite, which preferentially occurred as nanogoethite or Al/Si-substituted goethite. Ferrihydrite with varying crystallinity or impurities such as organic matter, Al or Si, persisted under suboxic-oxic conditions in the floodplain. This study indicates that vertical redox gradients exert a major control on the quantity and speciation of Fe(III) oxides as well as the oxidation state of structural Fe in PS, which could significantly affect nutrient cycling and carbon (de)stabilization.

Magnetic fabrics and fluid flow directions in hydrothermal systems. A case study in the Chaillac Ba-F-Fe deposits (France)

Science.gov (United States)

Sizaret, Stanislas; Chen, Yan; Chauvet, Alain; Marcoux, Eric; Touray, Jean Claude

2003-02-01

This study presents a possible use of anisotropy of magnetic susceptibility (AMS) to describe the mineralizing process in hydrothermal systems. Ba-F-Fe-rich deposits within the Chaillac Basin are on the southern border of the Paris Basin. In these deposits hydrothermal textures and tectonic structures have been described in veins, sinters, and sandstone cemented by hydrothermal goethite. 278 oriented cores from 24 sites have been collected in these formations. In addition, a lateritic duricrust superimposed on the hydrothermal formation has been sampled. Rock magnetic investigations show that the principal magnetic carrier is goethite for the hydrothermal mineralization and for the laterite level. The AMS measurements show distinguishable behaviors in the different mineralogical and geological contexts. The K1 magnetic lineation (maximum axis) is strongly inclined for the vertical veins. For the horizontally mineralized sinters, the magnetic lineation is almost horizontal with an azimuth similar to the sedimentary flow direction. The AMS of goethite-rich sandstone close to the veins shows strongly inclined K1 as they are probably influenced by the vertical veins; however, when the distance from the vein is larger than 1 m, the AMS presents rather horizontal K1 directions, parallel to the sedimentary flow. The laterite has a foliation dominance of AMS with vertically well-grouped K3 axes and scattered K1 and K2 axes. Field structural observations suggest that the ore deposit is mainly controlled by EW extension tectonics associated with NS trending normal faults. Combining the AMS results on the deposit with vein textures and field data a model is proposed in which AMS results are interpreted in terms of hydrothermal fluid flow. This work opens a new investigation field to constrain hydrodynamic models using the AMS method. Textural study combined with efficient AMS fabric measurements should be used for systematic investigation to trace flow direction in fissures

The colour of ochres explained by their composition

International Nuclear Information System (INIS)

Elias, M.; Chartier, C.; Prevot, G.; Garay, H.; Vignaud, C.

2006-01-01

The first purpose of this paper is to underline a relevant colorimetric co-ordinate characterizing the colour of ochres within their extremely wide range, from pale yellow to dark red. The second purpose is to link together quantitatively the variations of this colorimetric co-ordinate and the various chemical compositions of the samples, mainly hematite, goethite and white pigments. A group of 30 modern ochres and a group of 20 ancient ochres have been investigated. All these natural pigments have been commercialized. Diffuse reflectance spectrometry allows to calculate the colorimetric co-ordinates in the CIE-L * a * b * space and the position of the absorption band of each sample. Physico-chemical analysis has been obtained by quantitative X-ray diffraction, scanning and transmitting electronic microscopy and particle-size analysis by laser diffraction. The positive a * co-ordinate (redness) has been underlined, for the first time, to be the only relevant colorimetric parameter to characterize the colour of the ochres. Its variations are quantitatively connected to the shift of the absorption band due to the charge transfer between the ligand (OH - or O 2- ) and the Fe 3+ ion contained in goethite and/or hematite. For ochres containing both hematite and goethite, the a * co-ordinate linearly increases with the relative amount of hematite while the absorption band progressively shifts towards the high wavelengths. Such a linear shift of the absorption band has never been underlined before. For ochres containing only one iron oxide, a * linearly decreases with the amount of white pigments, whatever the nature of the white charges. Moreover, this study gives the opportunity to show that only the nature, the amount and the size distribution of the white charges allow to discriminate the ochres according to their geographic origin

Fate of Lu(III) sorbed on 2-line ferrihydrite at pH 5.7 and aged for 12 years at room temperature. I: insights from ICP-OES, XRD, ESEM, AsFlFFF/ICP-MS, and EXAFS spectroscopy.

Science.gov (United States)

Finck, Nicolas; Bouby, Muriel; Dardenne, Kathy

2018-01-31

Two-line ferrihydrite (2LFh) was aged for 12 years under ambient conditions and sheltered from light in the presence of Lu(III) used as surrogate for trivalent actinides. 2LFh aging produced hematite rhombohedra with overgrown acicular goethite particles. Analysis of the homogeneous suspension by asymmetrical flow field-flow fractionation (AsFlFFF) coupled to ICP-MS indicated that particles have a mean hydrodynamic diameter of about 140 nm and the strong correlation of the Fe and Lu fractograms hinted at a structural association of the lanthanide with the solid phase(s). Unfortunately, recoveries were low and thus results cannot be considered representative of the whole sample. The suspension was centrifuged and X-ray absorption spectroscopy (XAS) at the Lu L 3 -edge on the settled particles indicated that Lu(III) is sixfold coordinated by oxygen atoms, pointing to a retention by structural incorporation within particles. This result is consistent with AsFlFFF results on the same suspension without centrifugation. The detection of next nearest Fe and O atoms were consistent with the structure of goethite, ruling out incorporation within hematite. After centrifugation of the suspension, only nanoparticulate needle-like particles, very likely goethite, could be detected in the supernatant by ESEM. AsFlFFF data of the supernatant were comparable to that obtained for the homogeneous suspension, whereas XAS indicated that Lu(III) is predominantly present as dissolved species in the supernatant. Results from both techniques can be interpreted as a major fraction of Lu present as aqueous ions and a minor fraction as structurally incorporated. Findings from this study are corroborated by STEM-HAADF data and results from DFT calculations in a companion paper.

Avaliação de procedimentos de extração dos óxidos de ferro pedogênicos com ditionito-citrato-bicarbonato de sódio Evaluation of pedogenic iron oxide extraction procedures with sodium dithionite-citrate-bicarbonate

Directory of Open Access Journals (Sweden)

A. V. Inda Junior

2003-12-01

Full Text Available Em 20 amostras hematíticas e goethíticas de horizontes B latossólicos, uma de B plíntico, uma de B incipiente e uma de saprolito, foram avaliados dois procedimentos de extração de óxidos de ferro pedogênicos (Fe d por ditionito-citrato-bicarbonato de sódio (DCB. O procedimento a 80 ºC (DCB80 extraiu aproximadamente 90 % do Fe d na primeira extração e praticamente a totalidade do mesmo na segunda extração, sendo mais efetivo que o procedimento a temperatura ambiente (DCB20, o qual teve sua eficiência reduzida com o aumento da substituição isomórfica de Fe3+ por Al3+ na goethita. A substituição isomórfica de Fe3+ por Al3+ na goethita determinada por DCB80 superestimou os valores determinados por DRX conforme aumentaram as extrações. Em amostras hematíticas, esta estimativa foi prejudicada pela presença de maghemita que dissolveu juntamente com a hematita.Pedogenic iron oxides (Fe d were quantified in 22 hematitic and goethitic soil samples (19 from oxic horizons; one from a plinthic horizon; one from a cambic horizon; one from saprolite by use of two extraction procedures with sodium dithionite-citrate-bicarbonate (DCB. Approximately ninety percent of the Fe d content was extracted at the first extraction by the DCB80 procedure. This procedure was more effective at extracting Fe d than the DCB20, whose efficiency decreased with increasing Al3+-substitution in goethite. Compared with the DRX analysis, Al3+-substitution in goethite determined by the DCB80 procedure was superestimated. Maghemite masked Al3+-substitution estimates in hematite from hematitic samples.

Effectiveness of various sorbents and biological oxidation in the removal of arsenic species from groundwater

NARCIS (Netherlands)

Corsini, A.; Cavalca, L.; Muyzer, G.; Zaccheo, P.

2014-01-01

The AsIII and AsV adsorption capacity of biochar, chabazite, ferritin-based material, goethite and nano zero-valent iron was evaluated in artificial systems at autoequilibrium pH (i.e. MilliQ water without adjusting the pH) and at approximately neutral pH (i.e. TRIS-HCl, pH 7.2). At autoequilibrium

A dimorphic magnetorheological fluid with improved oxidation and chemical stability under oscillatory shear

Czech Academy of Sciences Publication Activity Database

Sedlačík, M.; Pavlínek, V.; Vyroubal, R.; Peer, Petra; Filip, Petr

2013-01-01

Roč. 22, č. 3 (2013) ISSN 0964-1726 R&D Projects: GA ČR GA202/09/1626 Grant - others:GA MŠk(CZ) ED2.1.00/03.0111 Institutional support: RVO:67985874 Keywords : goethites * magnetorheological fluids * MR fluids * tetraethylorthosilicate (TEOS) Subject RIV: BK - Fluid Dynamics Impact factor: 2.449, year: 2013

Migration behavior of naturally occurring radionuclides at the Nopal I uranium deposit, Chihuahua, Mexico

Science.gov (United States)

Prikryl, James D.; Pickett, David A.; Murphy, William M.; Pearcy, English C.

1997-04-01

Oxidation of pyrite at the Nopal I uranium deposit, Peña Blanca district, Chihuahua, Mexico has resulted in the formation of Fe-oxides/hydroxides. Anomalous U concentrations (i.e. several hundred to several thousand ppm) measured in goethite, hematite, and amorphous Fe-oxyhydroxides in a major fracture that crosscuts the deposit and the absence of U minerals in the fracture suggest that U was retained during secondary mineral growth or sorbed on mineral surfaces. Mobilization and transport of U away from the deposit is suggested by decreasing U concentrations in fracture-infilling materials and in goethite and hematite with distance from the deposit. Greater than unity {234U}/{238U} activity ratios measured in fracture-infilling materials indicate relatively recent ( < 1 Ma) U uptake from fluids that carried excess 234U. Systematic decreases in {234U}/{238U} activity ratios of fracture materials with distance from the deposit suggest a multistage mobilization process, such as remobilization of U from 234U-enriched infill minerals or differential or diminished transport of U-bearing solutions containing excess 234U.

Effect of in situ soil amendments on arsenic uptake in successive harvests of ryegrass (Lolium perenne cv Elka) grown in amended As-polluted soils

International Nuclear Information System (INIS)

Hartley, William; Lepp, Nicholas W.

2008-01-01

Several iron-bearing additives, selected for their potential ability to adsorb anions, were evaluated for their effectiveness in attenuation of arsenic (As) in three soils with different sources of contamination. Amendments used were lime, goethite (α-FeOOH) (crystallised iron oxide) and three iron-bearing additives, iron grit, Fe II and Fe III sulphates plus lime, applied at 1% w/w. Sequential extraction schemes conducted on amended soils determined As, Cu, Zn and Ni fractionation. Plant growth trials using perennial ryegrass (Lolium perenne var. Elka) assessed shoot As uptake. This was grown in the contaminated soils for 4 months, during which time grass shoots were successively harvested every 3 weeks. Goethite increased biomass yields, but clear differences were observed in As transfer rates with the various iron oxides. In conclusion, whilst Fe-oxides may be effective in situ amendments, reducing As bioavailability, their effects on plant growth require careful consideration. Soil-plant transfer of As was not completely halted by any amendment. - Arsenic attenuation is illustrated using Fe-based amendments, their efficacy providing different indicators of success

Some antarctic soil cores from Wood Bay characterised by Moessbauer spectroscopy

International Nuclear Information System (INIS)

Bertelle, M.; Leotta, G.; Calogero, S.; Constantinescu, S.; Oddone, M.

1999-01-01

Marine, lacustrine and terrestrial soil cores, sampled in a restricted area of Wood Bay in Antarctica, were characterised by 57 Fe Moessbauer spectroscopy. The results of X-ray diffraction and instrumental neutron activation analysis are shortly discussed too. The soils, formed by mechanical disaggregation and weathering of rocks of volcanic origin from Mt. Melbourne, consist of alkaline feldspars, olivines, augitic clinopyroxenes, and iron oxides such as haematite, goethite, and magnetite. Lacustrine and terrestrial soils are richer in clinopyroxenes whereas marine soils are richer in olivines. This finding shows that the soils retain a content in olivines and clinopyroxenes comparable to that found in the parent lava outcropped from Mt. Melbourne volcano. The soils appear at the initial stage of weathering. Two main weathering effects are observed: 1. atmospheric oxygen determines the oxidation of the iron(II) present in olivines and clinopyroxenes and the neo-formed iron(III) is mainly retained in silicate sites as structural iron(III); 2. a part of magnetite, present as a primary constituent of the volcanic rocks, is oxidised to bulk haematite and goethite. (authors)

Influence of hydrology on heavy metal speciation and mobility in a Pb-Zn mine tailing

International Nuclear Information System (INIS)

Kovacs, Elza; Dubbin, William E.; Tamas, Janos

2006-01-01

Among the inorganic toxicants of greatest concern in mine tailings, Pb, Zn, Cu, Cd and As figure prominently due to their abundance and potential toxicity. Here we report on their biolability and solid-phase speciation in two sediment cores subject to variable hydrological regimes at an abandoned pyritic mine tailing. The oxic conditions of well-drained sediments induced pyrite oxidation and the subsequent liberation of H + , SO 4 2- and considerable quantities of Fe(III), which precipitated as goethite. Solubility of Pb, Zn, Cu and Cd was closely coupled to pH and goethite presence. Metal lability was particularly low in zones of neutralization, formed by the accumulation of calcite, first carried then deposited by percolating waters in both saturated and unsaturated cores. We conclude that differential hydrology induces variable heavy metal speciation and biolability in Pb-Zn mine tailings, and suggest that site-specific risk assessments must account for past and present hydrological regimes. - Variable hydrology influences heavy metal speciation and mobility, and the formation of neutralization zones, in a Pb-Zn mine tailing

Methylene blue adsorption from glycerol solution onto the acicular ...

African Journals Online (AJOL)

The mechanism of methylene blue adsorption onto the surface of synthetic acicular habit of α-goethite from glycerol solution has been studied through batch experiment at 25, 30 and 35 0C in a glass cell of minimal dead volume. To describe the adsorption results, an attempt was made to fit the data to the Langmuir, ...

Moessbauer study of rock paintings from Minas Gerais (Brazil)

International Nuclear Information System (INIS)

Costa, G.M. da; Jesus Filho, M.F. de; Cruz Souza, L.A.

1991-01-01

Four samples of a wall containing rock paintings have been studied by Moessbauer spectroscopy in combination with optical microscopy analysis and X-ray diffraction. Hematite and goethite were identified as the pigments responsible for the colors and the mineral tinsleyite, as the principal component of a light pink layer that is present in some parts of the wall. (orig.)

Mini-review: The Morphology, Mineralogy and Microbiology of Accumulated Iron Corrosion Products

Science.gov (United States)

2014-03-11

including the morphology, mineralogy , microbiology and the mecha- nisms for formation. Use of descriptive terms to denote specific iron corrosion product...RESPONSIBLE PERSON 19b. TELEPHONE NUMBER (Include area code) 11-03-2014 Journal Article Mini-review: the morphology, mineralogy and microbiology of...oxides/ hydroxides with a preponderance of α-FeOOH (goethite) and accumulation of metals. Bacteria, particularly iron-oxidizing and sulfatereducing

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

Energy Technology Data Exchange (ETDEWEB)

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.

2010-09-30

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.

Monosilicate adsorption by ferrihydrite and goethite at pH 3-6

DEFF Research Database (Denmark)

Hansen, Hans Christian Bruun; Raben-Lange, B.; Raulund-Rasmussen, Karsten

1994-01-01

The constant capacitance model and the Elovich equation were combined in the following mathematical expression enabling calculation of the amount of silicic acid adsorbed by iron oxides as a function of the Si concentration, pH, soil:solution ratio, and reaction time: [GRAPHICS] K(a1) is the prot......The constant capacitance model and the Elovich equation were combined in the following mathematical expression enabling calculation of the amount of silicic acid adsorbed by iron oxides as a function of the Si concentration, pH, soil:solution ratio, and reaction time: [GRAPHICS] K(a1...

The interaction of boron with goethite: Experiments and CD-MUSIC modeling

NARCIS (Netherlands)

Goli, E.; Rahnemaie, R.; Hiemstra, T.; Malakouti, M.J.

2011-01-01

Boron (B) is an essential element for plants and animals growth that interacts with mineral surfaces regulating its bioavailability and mobility in soils, sediments, and natural ecosystems. The interaction with mineral surfaces is quite important because of a narrow range between boron deficiency

Adsorption, Aggregation, and Deposition Behaviors of Carbon Dots on Minerals.

Science.gov (United States)

Liu, Xia; Li, Jiaxing; Huang, Yongshun; Wang, Xiangxue; Zhang, Xiaodong; Wang, Xiangke

2017-06-06

The increased production of carbon dots (CDs) and the release and accumulation of CDs in both surface and groundwater has resulted in the increasing interest in their research. To assess the environmental behavior of CDs, the interaction between CDs and goethite was studied under different environmental conditions. Electrokinetic characterization of CDs suggested that the ζ-potential and size distribution of CDs were affected by pH and electrolyte species, indicating that these factors influenced the stability of CDs in aqueous solutions. Traditional Derjaguin-Landau-Verwey-Overbeek theory did not fit well the aggregation process of CDs. Results of the effects of pH and ionic strength suggested that electronic attraction dominated the aggregation of CDs. Compared with other minerals, hydrogen-bonding interactions and Lewis acid-base interactions contributed to the aggregation of CDs, in addition to van der Waals and electrical double-layer forces. Adsorption isotherms and microscopic Fourier transformed infrared spectroscopy indicated that chemical bonds were formed between CDs and goethite. These findings are useful to understand the interaction of CDs with minerals, as well as the potential fate and toxicity of CDs in the natural environment, especially in soils and sediments.

Occurrence and Characterization Microstructure of Iron Impurities in Halloysite.

Science.gov (United States)

Liu, Rong; Yan, Chunjie; Wang, Hongquan; Xiao, Guoqi; Tu, Dong

2015-09-01

The quality of the clays and over all halloysite are mostly associated with minor amounts of ferruginous impurities content, since this element gives an undesirable reddish color to the halloysite mineral. Hence, finding out the modes of occurrence of iron in halloysite is of prime importance in the value addition and optimum utilization of halloysite. In order to analyze the occurrence of iron impurities in halloysite, Transmission Electron Microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were combined with wet chemical analysis methods to study the low-grade halloysite. The results indicated that the mineral phases of iron impurities in the concentrates are mainly composed of amounts of magnetite, goethite and hematite. Two types of occurrences for iron impurities have been found. One is single crystalline mineral consist in the halloysite, which contains three different phases of Goethite FeO(OH) (44.75%), Magnetite Fe3O4 (27.43%) and Hematite Fe2O3 (31.96%). The other is amorphous Fe-Al-Si glial materials. This study is of significance in the theoretical research on the halloysite mineralogy and in the developmental practice of halloysite in coal measures.

Mineralogical and crystallochemical transformations originated from thermal essays on ferruginous kaolinitic clays; Transformacoes mineralogicas e cristaloquimicas decorrentes dos ensaios termais em argilas cauliniticas ferruginosas

Energy Technology Data Exchange (ETDEWEB)

Ferreira, M.M.; Varajao, A.F.D.C.; Morales-Carrera, A.M.; Peralta-Sanchez, M.G.; Costa, G.M. da, E-mail: angelica@degeo.ufop.br [Universidade Federal de Ouro Preto, Campus Universitario, Morro do Cruzeiro s/n, Ouro Preto, MG (Brazil)

2012-01-15

Mineralogical and crystallochemical transformations of representative ferruginous kaolinitic clay samples were investigated in specimens burned at 800, 1000 and 1200 deg C. X-ray diffraction and differential thermal and thermogravimetric analyses showed that kaolinite was the predominant mineral in the raw samples. The Moessbauer spectroscopy results showed that the high iron content (22.5 wt.%), as determined by X-ray fluorescence, is related to the presence of goethite (18 wt.%) and hematite (16 wt.%). However, after Fe was extracted using a dithionite-citrate system buffered with sodium bicarbonate, a residue of this element (Fe{sup 3+} and Fe{sup 2+}) was found in the structure of the kaolinite. The sintering process showed the destruction of kaolinite, as well as the transformation of the goethite into hematite, the crystals growing as the temperature increases. The hematite crystal size at 1200 deg C is five times larger than in the raw sample. The mullite formation at 1000 deg C is comprised of a solid solution of Fe{sub 2}O{sub 3} and Al{sub 2}O{sub 3},which results in a resistant product with a higher thermal stability (author)

A New Tool for Separating the Magnetic Mineralogy of Complex Mineral Assemblages from Low Temperature Magnetic Behavior

Directory of Open Access Journals (Sweden)

France Lagroix

2017-07-01

Full Text Available One timeless challenge in rock magnetic studies, inclusive of paleomagnetism and environmental magnetism, is decomposing a sample's bulk magnetic behavior into its individual magnetic mineral components. We present a method permitting to decompose the magnetic behavior of a bulk sample experimentally and at low temperature avoiding any ambiguities in data interpretation due to heating-induced alteration. A single instrument is used to measure the temperature dependence of remanent magnetizations and to apply an isothermal demagnetization step at any temperature between 2 and 400 K. The experimental method is validated on synthetic mixtures of magnetite, hematite, goethite as well as on natural loess samples where the contributions of magnetite, goethite, hematite and maghemite are successfully isolated. The experimental protocol can be adapted to target other iron bearing minerals relevant to the rock or sediment under study. One limitation rests on the fact that the method is based on remanent magnetizations. Consequently, a quantitative decomposition of absolute concentration of individual components remains unachievable without assumptions. Nonetheless, semi-quantitative magnetic mineral concentrations were determined on synthetic and natural loess/paleosol samples in order to validate and test the method as a semi-quantitative tool in environmental magnetism studies.

Detailed characterization and preliminary adsorption model for materials for an intermediate-scale reactive-transport experiment

International Nuclear Information System (INIS)

Ward, D.B.; Bryan, C.R.

1994-01-01

An experiment involving migration of fluid and tracers (Li, Br, Ni) through a 6-m-high x 3-m-dia caisson Wedron 510 sand, is being carried out for Yucca Mountain Site Characterization Project. Sand's surface chemistry of the sand was studied and a preliminary surface-complexation model of Ni adsorption formulated for transport calculations. XPS and leaching suggest that surface of the quartz sand is partially covered by thin layers of Fe-oxyhydroxide and Ca-Mg carbonate and by flakes of kaolinite. Ni adsorption by the sand is strongly pH-dependent, showing no adsorption at pH 5 and near-total adsorption at pH 7. Location of adsorption edge is independent of ionic strength and dissolved Ni concentration; it is shifted to slightly lower pH with higher pCO2 and to slightly higher pH by competition with Li. Diminished adsorption at alkiline pH with higher pCO2 implies formation of dissolved Ni-carbonato complexes. Ni adsorption edges for goethite and quartz, two components of the sand were also measured. Ni adsorption on pure quartz is only moderately pH-dependent and differs in shape and location from that of the sand, whereas Ni adsorption by goethite is strongly pH-dependent. A triple-layer surface-complexation model developed for goethite provides a good fit to the Ni-adsorption curve of the sand. Based on this model, the apparent surface area of the Fe-oxyhydroxide coating is estimated to be 560 m 2 /g, compatible with its occurrence as amorphous Fe-oxyhydroxide. Potentiometric titrations on sand also differ from pure quartz and suggest that effective surface area of sand may be much greater than that measured by N 2 -BET gas adsorption. Attempts to model the adsorption of bulk sand in terms of properties of pure end member components suggest that much of the sand surface is inert. Although the exact Ni adsorption mechanisms remain ambiguous, this preliminary adsorption model provides an initial set of parameters that can be used in transport calculations

Weathering of the New Albany Shale, Kentucky, USA: I. Weathering zones defined by mineralogy and major-element composition

Science.gov (United States)

Tuttle, M.L.W.; Breit, G.N.

2009-01-01

Comprehensive understanding of chemical and mineralogical changes induced by weathering is valuable information when considering the supply of nutrients and toxic elements from rocks. Here minerals that release and fix major elements during progressive weathering of a bed of Devonian New Albany Shale in eastern Kentucky are documented. Samples were collected from unweathered core (parent shale) and across an outcrop excavated into a hillside 40 year prior to sampling. Quantitative X-ray diffraction mineralogical data record progressive shale alteration across the outcrop. Mineral compositional changes reflect subtle alteration processes such as incongruent dissolution and cation exchange. Altered primary minerals include K-feldspars, plagioclase, calcite, pyrite, and chlorite. Secondary minerals include jarosite, gypsum, goethite, amorphous Fe(III) oxides and Fe(II)-Al sulfate salt (efflorescence). The mineralogy in weathered shale defines four weathered intervals on the outcrop-Zones A-C and soil. Alteration of the weakly weathered shale (Zone A) is attributed to the 40-a exposure of the shale. In this zone, pyrite oxidization produces acid that dissolves calcite and attacks chlorite, forming gypsum, jarosite, and minor efflorescent salt. The pre-excavation, active weathering front (Zone B) is where complete pyrite oxidation and alteration of feldspar and organic matter result in increased permeability. Acidic weathering solutions seep through the permeable shale and evaporate on the surface forming abundant efflorescent salt, jarosite and minor goethite. Intensely weathered shale (Zone C) is depleted in feldspars, chlorite, gypsum, jarosite and efflorescent salts, but has retained much of its primary quartz, illite and illite-smectite. Goethite and amorphous FE(III) oxides increase due to hydrolysis of jarosite. Enhanced permeability in this zone is due to a 14% loss of the original mass in parent shale. Denudation rates suggest that characteristics of Zone C

Biological versus mineralogical chromium reduction: potential for reoxidation by manganese oxide.

Science.gov (United States)

Butler, Elizabeth C; Chen, Lixia; Hansel, Colleen M; Krumholz, Lee R; Elwood Madden, Andrew S; Lan, Ying

2015-11-01

Hexavalent chromium (Cr(vi), present predominantly as CrO4(2-) in water at neutral pH) is a common ground water pollutant, and reductive immobilization is a frequent remediation alternative. The Cr(iii) that forms upon microbial or abiotic reduction often co-precipitates with naturally present or added iron (Fe), and the stability of the resulting Fe-Cr precipitate is a function of its mineral properties. In this study, Fe-Cr solids were formed by microbial Cr(vi) reduction using Desulfovibrio vulgaris strain RCH1 in the presence of the Fe-bearing minerals hematite, aluminum substituted goethite (Al-goethite), and nontronite (NAu-2, Clay Minerals Society), or by abiotic Cr(vi) reduction by dithionite reduced NAu-2 or iron sulfide (FeS). The properties of the resulting Fe-Cr solids and their behavior upon exposure to the oxidant manganese (Mn) oxide (birnessite) differed significantly. In microcosms containing strain RCH1 and hematite or Al-goethite, there was significant initial loss of Cr(vi) in a pattern consistent with adsorption, and significant Cr(vi) was found in the resulting solids. The solid formed when Cr(vi) was reduced by FeS contained a high proportion of Cr(iii) and was poorly crystalline. In microcosms with strain RCH1 and hematite, Cr precipitates appeared to be concentrated in organic biofilms. Reaction between birnessite and the abiotically formed Cr(iii) solids led to production of significant dissolved Cr(vi) compared to the no-birnessite controls. This pattern was not observed in the solids generated by microbial Cr(vi) reduction, possibly due to re-reduction of any Cr(vi) generated upon oxidation by birnessite by active bacteria or microbial enzymes. The results of this study suggest that Fe-Cr precipitates formed in groundwater remediation may remain stable only in the presence of active anaerobic microbial reduction. If exposed to environmentally common Mn oxides such as birnessite in the absence of microbial activity, there is the potential

Interfacial reactions between humic-like substances and lateritic clay: application to the preparation of "geomimetic" materials.

Science.gov (United States)

Goure-Doubi, Herve; Martias, Céline; Lecomte-Nana, Gisèle Laure; Nait-Ali, Benoît; Smith, Agnès; Thune, Elsa; Villandier, Nicolas; Gloaguen, Vincent; Soubrand, Marilyne; Konan, Léon koffi

2014-11-15

The aim of this study was to understand the mechanisms responsible for the strengthening of "geomimetic" materials, especially the chemical bonding between clay and humic substances. The mineral matter is lateritic clay which mainly consists in kaolinite, goethite, hematite and quartz. The other starting products are fulvic acid (FA) and lime. The preparation of these geomimetic materials is inspired from the natural stabilization of soils by humic substances occurring over thousands of years. The present process involves acidic and alkaline reactions followed by a curing period of 18days at 60°C under a water saturated atmosphere. The acceleration of the strengthening process usually observed in soils makes this an original process for treatment of soils. The consolidation of the "geomimetic" materials could result from two major phenomena: (i) chemical bonding at the interface between the clay particles and iron compounds and the functional groups of the fulvic acid, (ii) a partial dissolution of the clay grains followed by the precipitation of the cementitious phases, namely calcium silicate hydrates, calcium aluminate hydrates and mixed calcium silicum and aluminum hydrates. Indeed, the decrease of the BET specific area of the lateritic clay after 24 h of reaction with FA added to the structural reorganization observed between 900 and 1000°C in the "geomimetic" material, and to the results of adsorption measurements, confirm the formation of organo-ferric complexes. The presence of iron oxides in clay, in the form of goethite, appears to be another parameter in favor of a ligand exchange process and the creation of binding bridges between FA and the mineral matter. Indeed all faces of goethite are likely to be involved in complexation reactions whereas in lateritic clay only lateral faces could be involved. The results of the adsorption experiments realized at a local scale will improve our understandings about the process of adsorption of FA on lateritic

Estudio del efecto de la adición de distintos mineralizadores en la síntesis cerámica del pigmento rosa coral de hierro-circón

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Llusar, M.

1999-06-01

Full Text Available The addition of several mineralizing agents (alkaline or alkaline-earth halides, KNO3, etc. in the traditional ceramic synthesis of the “coral pink” iron-zircon (Fe-ZrSiO4 ceramic pigment has been analysed, using two different Fe precursors (sulphate and goethite. FeSO4.7H2O employment as Fe precursor allows us to obtain a better reddish colour than with goethite (FeO(OH. Results let us to classify the studied mineralisers in two major groups: i primary or zircon-forming mineralisers, which activate somehow zircon formation with a good occlusion efficiency of hematite into the zircon matrix (NaF, NaCl and BaF2 when using FeSO4 and Na2SiF6 and NaAl3F6 with goethite,. and ii secondary or modifying mineralisers, that have a collateral effect on the pigment synthesis regulating both hematite crystallisation and occlusion (KNO3, Na2SiF6 and NaAl3F6 with FeSO4 and KI and KNO3 with goethite. With regard to the color yield, those compositions mineralised with the binary systems NaF-Na2SiF6, NaF-NaAl3F6 and NaF-KNO3 have been found to develop the best red color.

Se ha analizado el efecto de la adición de distintos agentes mineralizadores (haluros alcalinos y alcalino-térreos, KNO3, etc. en la síntesis cerámica tradicional del pigmento rosa coral de hierro-circón (Fe-ZrSiO4, usando dos precursores diferentes para el hierro (sulfato y goetita. El empleo de FeSO4.7H2O como fuente de hierro permite obtener mejores coloraciones rojizas que con goetita (FeO(OH. Los resultados obtenidos permiten clasificar a los distintos mineralizadores ensayados en dos grandes grupos: i mineralizadores primarios o “formadores de circón”, los cuales permiten activar el desarrollo del circón con una buena eficiencia en el encapsulamiento de la hematita en los cristales de circón (NaF, NaCl y BaF2 con FeSO4, y Na2SiF6 y NaAl3F6 con goetita, y ii mineralizadores “secundarios o coadyuvantes”, con un efecto colateral sobre la síntesis del pigmento

The correlation between accelerated and field corrosion tests performed in carbon steel and weathering steel coupons, coated and non-coated

International Nuclear Information System (INIS)

Antunes, Renato Altobelli

2002-01-01

The performance of four different organic coating systems applied to carbon and weathering steel coupons has been assessed in this investigation. applied on the surface of carbon steel and weathering steel coupons. The coupons have been evaluated using five different tests, three field tests and two accelerated tests. The field tests were carried out at three atmospheric stations, located at COSIPA in Cubatao-SP, at Alto da Serra in Cubatao-SP and at Paula Souza in Sao Paulo city. The accelerated tests consisted of (a) exposure to alternate cycles of ultraviolet radiation/condensation combined with salt spray cycles (UVCON combined with Salt Spray) and of (b) exposure to alternate cycles of ultraviolet radiation/condensation combined with the Prohesion test. The performance of the coatings was assessed by visual observation and photographs, using a method based on ASTM D-610, ASTM D-714 and ASTM-1654 standards to rank them. The oxide phases formed on the surfaces of the non-coated specimens of carbon and weathering steels, exposed to the same tests performed with the coated specimens, were identified using three different techniques: X-ray diffraction, Raman microscopy and Moessbauer spectroscopy. In the field tests, the specimens have been exposed for 1, 2, 3, 6 and 9 months. In the accelerated ones, the results were obtained after 1340 hours (4 cycles) test. The main component identified in all the specimens collected from the field tests and from the UVCON combined with the Prohesion test was lepidocrocite (γ-FeOOH). Goethite (α-FeOOH ) and magnetite (Fe 3 O 4 ) were identified as the other two main phases present in ali the specimens. In the UVCON combined with Salt Spray test, the dominant phase was magnetite, followed by goethite and lepidocrocite. The morphology of the rust formed on the specimens was examined by scanning electron microscopy (SEM). Structures corresponding to goethite and lepidocrocited were recognized on ali specimens, except those

The correlation between accelerated and field corrosion tests performed in carbon steel and weathering steel coupons, coated and non-coated; Correlacao entre ensaios acelerados e ensaios de campo em corpos-de-provas de aco carbono e aco patinavel, sem e com revestimento

Energy Technology Data Exchange (ETDEWEB)

Antunes, Renato Altobelli

2002-07-01

The performance of four different organic coating systems applied to carbon and weathering steel coupons has been assessed in this investigation. applied on the surface of carbon steel and weathering steel coupons. The coupons have been evaluated using five different tests, three field tests and two accelerated tests. The field tests were carried out at three atmospheric stations, located at COSIPA in Cubatao-SP, at Alto da Serra in Cubatao-SP and at Paula Souza in Sao Paulo city. The accelerated tests consisted of (a) exposure to alternate cycles of ultraviolet radiation/condensation combined with salt spray cycles (UVCON combined with Salt Spray) and of (b) exposure to alternate cycles of ultraviolet radiation/condensation combined with the Prohesion test. The performance of the coatings was assessed by visual observation and photographs, using a method based on ASTM D-610, ASTM D-714 and ASTM-1654 standards to rank them. The oxide phases formed on the surfaces of the non-coated specimens of carbon and weathering steels, exposed to the same tests performed with the coated specimens, were identified using three different techniques: X-ray diffraction, Raman microscopy and Moessbauer spectroscopy. In the field tests, the specimens have been exposed for 1, 2, 3, 6 and 9 months. In the accelerated ones, the results were obtained after 1340 hours (4 cycles) test. The main component identified in all the specimens collected from the field tests and from the UVCON combined with the Prohesion test was lepidocrocite ({gamma}-FeOOH). Goethite ({alpha}-FeOOH ) and magnetite (Fe{sub 3}O{sub 4}) were identified as the other two main phases present in ali the specimens. In the UVCON combined with Salt Spray test, the dominant phase was magnetite, followed by goethite and lepidocrocite. The morphology of the rust formed on the specimens was examined by scanning electron microscopy (SEM). Structures corresponding to goethite and lepidocrocited were recognized on ali specimens

Geothermometry obtained from the calcite twin and fluid inclusions in barite (Irankuh Pb-Zn deposit, Southwest of Isfahan)

OpenAIRE

Alijan Aftabi; Hengameh Hosseini-Dinani

2017-01-01

The Irankuh mining district is located 20 km southwest of Isfahan and is geologically situated in Sanandaj - Sirjan zone and the lower Cretaceous sequence of Isfahan-Malayer ore mineralization area. The ore minerals are emplaced in the faulted contact of Jurassic shale and Cretaceous carbonates and include pyrite, galena, sphalerite, calcite, barite, dolomite, quartz as well as minor marcasite, smithsonite, cerussite, gypsum, malachite, hematite and goethite. The mineralization is mainly occu...

ETUDE DE LA DISTRIBUTION DES CATIONS ECHANGEABLES

African Journals Online (AJOL)

SEI Joseph

anastomosés. La caractérisation pétro-sédimentologique révèle la présence de certains minéraux tels que : quartz, hématite, biotite, sillimanite, scheelite, goethite, limonite, manganèse, pyroxène et tourmaline. Les grès auraient un ciment hémato-manganeux. Aussi, les sables sont moyennement classés. Ces sables ont.

A role for iron and oxygen chemistry in preserving soft tissues, cells and molecules from deep time

OpenAIRE

Schweitzer, Mary H.; Zheng, Wenxia; Cleland, Timothy P.; Goodwin, Mark B.; Boatman, Elizabeth; Theil, Elizabeth; Marcus, Matthew A.; Fakra, Sirine C.

2014-01-01

The persistence of original soft tissues in Mesozoic fossil bone is not explained by current chemical degradation models. We identified iron particles (goethite-αFeO(OH)) associated with soft tissues recovered from two Mesozoic dinosaurs, using transmission electron microscopy, electron energy loss spectroscopy, micro-X-ray diffraction and Fe micro-X-ray absorption near-edge structure. Iron chelators increased fossil tissue immunoreactivity to multiple antibodies dramatically, suggesting a ro...

Moessbauer, X-ray fluorescence and paleomagnetic studies of deep-sea sediments from Peru Basin: two million years of sedimentation history

International Nuclear Information System (INIS)

Drodt, M.; Trautwein, A.X.; Dekkers, M.J.

1996-01-01

Sediment cores with different sub-bottom depths (I: 45 cm and II: 700 cm) from the Peru Basin have been investigated. From the depth profile of the relative amount of Fe(II) a redox zone is obtained which correlates with the organic carbon flux into the sediment (core I). Moessbauer parameters suggest that the iron in the sediments is mainly contained in clay minerals and to varying extent also in goethite

针铁矿催化氧化溴酚生成羟基多溴联苯醚和溴代二英%Formation of hydroxylated polybrominated diphenyl ethers and polychlorinated dibenzo-p-dioxins via goethite-catalyzed oxidation of bromophenols

Institute of Scientific and Technical Information of China (English)

孙粉玲; 丁佳锋; 周时洋; 林坤德

2015-01-01

探究了针铁矿催化转化溴酚（2，4⁃DBP或2，4，6⁃TBP）生成羟基化多溴联苯醚（HO⁃PBDEs）和溴代二噁英（ PBDD／Fs）的可能性．结果表明，针铁矿可以在常温和干反应条件下有效地催化转化溴酚化合物生成HO⁃PBDEs和PBDD／Fs．反应16 d，97．3％的2，4⁃DBP被针铁矿氧化转化，其中2．4％被转化为2′⁃OH⁃BDE⁃68，2．8％被转化为2，2′⁃OH⁃BB⁃80，0．2％被转化1，3，8⁃TrBDD，0．4％被转化为2，4，6，8⁃TeBDF．同样的反应时间内，98．7％的2，4，6⁃TBP被针铁矿氧化转化，反应产物可能为2′⁃OH⁃BDE⁃121、4′⁃OH⁃BDE⁃121、1，3，6，8⁃TeBDD和1，3，7，9⁃TeBDD．根据检测到的产物，提出了针铁矿氧化转化溴酚的可能途径．%The formation of hydroxylated polybrominated diphenyl ethers ( HO⁃PBDEs ) and brominated dibenzo⁃p⁃dioxins, dibenzofurans ( PBDD/Fs ) from goethite⁃catalyzed oxidation of bromophenols ( BPs, e. g., 2, 4⁃DBP and 2, 4, 6⁃TBP ) was investigated. Results showed that goethite readily catalyzed the conversion of 2,4⁃DBP and 2,4,6⁃TBP to HO⁃PBDEs and PBDD/Fs under dry conditions and at ambient temperature. In 16 d, 97.3%of 2,4⁃DBP was converted and the yields of 2′⁃OH⁃BDE⁃68, 2,2′⁃OH⁃BB⁃80, 1,3,8⁃TrBDD and 2,4,6,8⁃TeBDF were 2.4%, 2.8%, 0.2% and 0. 4%, respectively. Similarly, 98. 7% of 2,4,6⁃TBP was transformed and the possible reaction products were 2′⁃OH⁃BDE⁃121, 4′⁃OH⁃BDE⁃121, 1,3,6,8⁃TBDD and 1,3,7,9⁃TBDD. The possible formation pathways for the goethite⁃catalyzed oxidation of bromophenols were proposed.

Impact of uranyl-calcium-carbonato complexes on uranium(VI) adsorption to synthetic and natural sediments.

Science.gov (United States)

Stewart, Brandy D; Mayes, Melanie A; Fendorf, Scott

2010-02-01

Adsorption on soil and sediment solids may decrease aqueous uranium concentrations and limit its propensity for migration in natural and contaminated settings. Uranium adsorption will be controlled in large part by its aqueous speciation, with a particular dependence on the presence of dissolved calcium and carbonate. Here we quantify the impact of uranyl speciation on adsorption to both goethite and sediments from the Hanford Clastic Dike and Oak Ridge Melton Branch Ridgetop formations. Hanford sediments were preconditioned with sodium acetate and acetic acid to remove carbonate grains, and Ca and carbonate were reintroduced at defined levels to provide a range of aqueous uranyl species. U(VI) adsorption is directly linked to UO(2)(2+) speciation, with the extent of retention decreasing with formation of ternary uranyl-calcium-carbonato species. Adsorption isotherms under the conditions studied are linear, and K(d) values decrease from 48 to 17 L kg(-1) for goethite, from 64 to 29 L kg (-1) for Hanford sediments, and from 95 to 51 L kg(-1) for Melton Branch sediments as the Ca concentration increases from 0 to 1 mM at pH 7. Our observations reveal that, in carbonate-bearing waters, neutral to slightly acidic pH values ( approximately 5) and limited dissolved calcium are optimal for uranium adsorption.

Source and Fate of Inorganic Soil Contamination Around the Abandoned Phillips Sulfide Mine Hudson Highlands New York

Energy Technology Data Exchange (ETDEWEB)

S Gilchrist; A Gates; E Elzinga; M Gorring; z Szabo

2011-12-31

The abandoned Phillips sulfide mine in the critical Highlands watershed in New York has been shown to produce strongly acidic mine drainage (AMD) with anomalous metal contaminants in first-order streams that exceeded local water standards by up to several orders of magnitude (Gilchrist et al., 2009). The metal-sulfide-rich tailings also produce contaminated soils with pH < 4, organic matter < 2.5% and trace metals sequestered in soil oxides. A geochemical transect to test worst-case soil contamination showed that Cr, Co and Ni correlated positively with Mn, (r = 0.72, r = 0.89, r = 0.80, respectively), suggesting Mn-oxide sequestration and that Cu and Pb correlated with Fe (r = 0.76, r = 0.83, respectively), suggesting sequestration in goethite. Ubiquitous, yellow coating on the mine wastes, including jarosite and goethite, is a carrier of the metals. Geochemical and {mu}-SXRF analyses determined Cu to be the major soil contaminant, {mu}-SXRF also demonstrated that the heterogeneous nature of the soil chemistry at the micro-meter scale is self-similar to those in the bulk soil samples. Generally metals decreased, with some fluctuations, rapidly downslope through suspension of fines and dissolution in AMD leaving the area of substantial contamination << 0.5 km from the source.

Moessbauer Characterization of Magnetite/Polyaniline Magnetic Nanocomposite

International Nuclear Information System (INIS)

Rodriguez, Anselmo F. R.; Faria, Fernando S. E. D. V.; Lopez, Jorge L.; Mesquita, Antonio G. G.; Coaquira, Jose A. H.; Oliveira, Aderbal C.; Morais, Paulo C.; Azevedo, Ricardo B.; Araujo, Ana C. V. de; Alves, Severino Jr.; Azevedo, Walter M. de

2010-01-01

Aniline surface coated Fe 3 O 4 nanoparticles have been successfully synthesized by UV irradiation varying the time and the acid media (HCl, HNO 3 , or H 2 SO 4 ). The synthesized material represents a promising platform for application in nerve regeneration. XRD patterns are consistent with the crystalline structure of magnetite. Nevertheless, for UV irradiation times longer than 2 h, extra XRD lines reveal the presence of goethite. The mean crystallite size of uncoated particles is estimated to be 25.4 nm, meanwhile that size is reduced to 19.9 nm for the UV irradiated sample in HCl medium for 4 h. Moessbauer spectra of uncoated nanoparticles reveal the occurrence of thermal relaxation at room temperature, while the 77 K-Moessbauer spectrum suggests the occurrence of electron localization effects similar to that expected in bulk magnetite. The Mossbauer spectra of UV irradiated sample in HCl medium during 4 h, confirms the presence of the goethite phase. For this sample, the thermal relaxation is more evident, since the room temperature spectrum shows larger spectral area for the nonmagnetic component due to the smaller crystallite size. Meanwhile, the 77 K-Moessbauer spectrum suggests the absence of the electron localization effect above 77 K.

Effect of the oxidation rate and Fe(II) state on microbial nitrate-dependent Fe(III) mineral formation

Science.gov (United States)

Senko, John M.; Dewers , Thomas A.; Krumholz, Lee R.

2005-01-01

A nitrate-dependent Fe(II)-oxidizing bacterium was isolated and used to evaluate whether Fe(II) chemical form or oxidation rate had an effect on the mineralogy of biogenic Fe(III) (hydr)oxides resulting from nitrate-dependent Fe(II) oxidation. The isolate (designated FW33AN) had 99% 16S rRNA sequence similarity to Klebsiella oxytoca. FW33AN produced Fe(III) (hydr)oxides by oxidation of soluble Fe(II) [Fe(II)sol] or FeS under nitrate-reducing conditions. Based on X-ray diffraction (XRD) analysis, Fe(III) (hydr)oxide produced by oxidation of FeS was shown to be amorphous, while oxidation of Fe(II)sol yielded goethite. The rate of Fe(II) oxidation was then manipulated by incubating various cell concentrations of FW33AN with Fe(II)sol and nitrate. Characterization of products revealed that as Fe(II) oxidation rates slowed, a stronger goethite signal was observed by XRD and a larger proportion of Fe(III) was in the crystalline fraction. Since the mineralogy of Fe(III) (hydr)oxides may control the extent of subsequent Fe(III) reduction, the variables we identify here may have an effect on the biogeochemical cycling of Fe in anoxic ecosystems.

Chemical state analysis of iron(III) compounds precipitated homogeneously from solutions containing urea by means of Moessbauer spectrometry and x-ray diffractometry

International Nuclear Information System (INIS)

Ujihira, Yusuke; Ohyabu, Matashige; Murakami, Tetsuro; Horie, Tsuyoshi.

1978-01-01

Chemical states of iron(III) compounds, precipitated homogeneously by heating the iron(III) salt solution at 363 K in the presence of urea, was studied by means of Moessbauer spectrometry and X-ray diffractometry. The pH-time relation of urea hydrolysis revealed that the precipitation process from homogeneous solution is identical to the hydrolysis of iron(III) ion at pH around 2 under the homogeneous supply of OH - ion, which is generated by hydrolysis of urea. Accordingly, iron(III) oxide hydroxide or similar compounds to the hydrolysis products of iron(III) ion was precipitated by the precipitation from homogeneous solution methods. Akaganeite (β-FeOOH) was crystallized from 0.1 M iron(III) chloride solution. Goethite(α-FeOOH) and hematite(α-Fe 2 O 3 ) was precipitated from 0.1 M iron(III) nitrate solution, vigorous liberation of OH - ion favoring the crystallization of hematite. The addition of chloride ion to the solution resulted in the formation of akaganeite. Basic salt of iron sulfate[NH 4 Fe 3 (OH) 6 (SO 4 ) 2 ] and goethite were formed from 0.1 M iron(III) sulfate solution, the former being obtained in the more moderate condition of the urea hydrolysis ( 363 K). (author)

Non-Destructive Multi-Analytical Approach to Study the Pigments of Wall Painting Fragments Reused in Mortars from the Archaeological Site of Pompeii (Italy

Directory of Open Access Journals (Sweden)

Domenico Miriello

2018-03-01

Full Text Available During the excavations carried out in Via di Mercurio (Regio VI, 9, 3 in Pompeii, in 2015, some red, green, black, and brown wall painting fragments were found in the preparatory layer of an ancient pavement which was probably built after the 62 AD earthquake. These fragments, derived from the rubble, were used as coarse aggregate to prepare the mortar for building the pavement. The wall painting fragments are exceptionally well preserved, which is an uncommon occurrence in the city of Pompeii. However, as they were enclosed in the mortar, the wall painting fragments were protected from the high temperatures (probably ranging between 180 °C and 380 °C produced by the eruption in 79 AD. The pigmented outer surface of each sample was analyzed using a non-destructive multi-analytical approach, by combining spectrophotometric colorimetry and portable X-ray fluorescence with micro-Raman spectroscopy. The compositional characterization of the samples revealed the presence of cuprorivaite, goethite, and celadonite in the green pigments; hematite in the red pigments; goethite in the brown pigment; and charcoal in the black pigment. These data probably provide us with the most “faithful picture” of the various red, green, black, and brown pigments used in Pompeii prior to the 79 AD eruption.

Sorptive Uptake Studies of an Aryl-Arsenical with Iron Oxide Composites on an Activated Carbon Support

Directory of Open Access Journals (Sweden)

Jae H. Kwon

2014-03-01

Full Text Available Sorption uptake kinetics and equilibrium studies for 4-hydroxy-3-nitrobenzene arsonic acid (roxarsone was evaluated with synthetic magnetite (Mag-P, commercial magnetite (Mag-C, magnetite 10%, 19%, and 32% composite material (CM-10, -19, -32 that contains granular activated carbon (GAC, and synthetic goethite at pH 7.00 in water at 21 °C for 24 h. GAC showed the highest sorptive removal of roxarsone and the relative uptake for each sorbent material with roxarsone are listed in descending order as follows: GAC (471 mg/g > goethite (418 mg/g > CM-10 (377 mg/g CM-19 (254 mg/g > CM-32 (227 mg/g > Mag-P (132 mg/g > Mag-C (29.5 mg/g. The As (V moiety of roxarsone is adsorbed onto the surface of the iron oxide/oxyhydrate and is inferred as inner-sphere surface complexes; monodentate-mononuclear, bidentate-mononuclear, and bidentate-binuclear depending on the protolytic speciation of roxarsone. The phenyl ring of roxarsone provides the primary driving force for the sorptive interaction with the graphene surface of GAC and its composites. Thus, magnetite composites are proposed as multi-purpose adsorbents for the co-removal of inorganic and organic arsenicals due to the presence of graphenic and iron oxide active adsorption sites.

On the Rust Products Formed on Weathering and Carbon Steels Exposed to Chloride in Dry-Wet Cyclical Processes

International Nuclear Information System (INIS)

Garcia, K. E.; Morales, A. L.; Barrero, C. A.; Greneche, J. M.

2005-01-01

The rust products formed on weathering and carbon steels exposed to dry-wet cyclical processes in different chloride-rich solutions are carefully examined by means of different techniques. Special emphasis is given to the methodology of analysis of the data using 300 K and 77 K Moessbauer spectrometry and X-ray diffraction. The rust that is loosely bound to the metal surface and that it is lost during the corrosion process, for both types of steel, was found to be composed of lepidocrocite, superparamagnetic goethite, hematite, and traces of akaganeite. On the other hand, the adherent rust, which is differentiated as scraped and hit according to the way it is obtained, from both steels was found to be composed of akaganeite, spinel phase, goethite exhibiting broad distribution of particle sizes and lepidocrocite. The relative abundances of rust components for both steels were very similar, suggesting similar corrosion processes. Mass loss measurements show that the corrosion rates increases with increasing the chloride concentration. The presence of large quantities of spinel phase and akaganeite are a consequence of a corrosion process under the influence of very high chloride concentrations. Our results are useful for assessing the behavior of weathering steels where the levels of chlorides are high or in contact with sea water.

The Fate of Lipid Biosignatures in a Mars-Analogue Sulfur Stream.

Science.gov (United States)

Tan, Jonathan; Lewis, James M T; Sephton, Mark A

2018-05-15

Past life on Mars will have generated organic remains that may be preserved in present day Mars rocks. The most recent period in the history of Mars that retained widespread surface waters was the late Noachian and early Hesperian and thus possessed the potential to sustain the most evolved and widely distributed martian life. Guidance for investigating late Noachian and early Hesperian rocks is provided by studies of analogous acidic and sulfur-rich environments on Earth. Here we report organic responses for an acid stream containing acidophilic organisms whose post-mortem remains are entombed in iron sulphates and iron oxides. We find that, if life was present in the Hesperian, martian organic records will comprise microbial lipids. Lipids are a potential sizeable reservoir of fossil carbon on Mars, and can be used to distinguish between different domains of life. Concentrations of lipids, and particularly alkanoic or "fatty" acids, are highest in goethite layers that reflect high water-to-rock ratios and thus a greater potential for habitability. Goethite can dehydrate to hematite, which is widespread on Mars. Mars missions should seek to detect fatty acids or their diagenetic products in the oxides and hydroxides of iron associated with sulphur-rich environments.

Composite structure of wood cells in petrified wood

International Nuclear Information System (INIS)

Nowak, Jakub; Florek, Marek; Kwiatek, Wojciech; Lekki, Janusz; Chevallier, Pierre; Zieba, Emil; Mestres, Narcis; Dutkiewicz, E.M.; Kuczumow, Andrzej

2005-01-01

Special kinds of petrified wood of complex structure were investigated. All the samples were composed of at least two different inorganic substances. The original cell structure was preserved in each case. The remnants of the original biological material were detected in some locations, especially in the cell walls. The complex inorganic structure was superimposed on the remnant organic network. The first inorganic component was located in the lumena (l.) of the cells while another one in the walls (w.) of the cells. The investigated arrangements were as follows: calcite (l.)-goethite-hematite (w.)-wood from Dunarobba, Italy; pyrite (l.)-calcite (w.)-wood from Lukow, Poland; goethite (l.)-silica (w.)-wood from Kwaczala, Poland. The inorganic composition was analysed and spatially located by the use of three spectral methods: electron microprobe, X-ray synchrotron-based microprobe, μ-PIXE microprobe. The accurate mappings presenting 2D distribution of the chemical species were presented for each case. Trace elements were detected and correlated with the distribution of the main elements. In addition, the identification of phases was done by the use of μ-Raman and μ-XRD techniques for selected and representative points. The possible mechanisms of the described arrangements are considered. The potential synthesis of similar structures and their possible applications are suggested

Composite structure of wood cells in petrified wood

Energy Technology Data Exchange (ETDEWEB)

Nowak, Jakub [Department of Chemistry, Catholic University of Lublin, 20-718 Lublin (Poland); Florek, Marek [Department of Chemistry, Catholic University of Lublin, 20-718 Lublin (Poland); Kwiatek, Wojciech [Institute of Nuclear Physics, Department of Nuclear Spectroscopy, 31-342 Cracow (Poland); Lekki, Janusz [Institute of Nuclear Physics, Department of Nuclear Spectroscopy, 31-342 Cracow (Poland); Chevallier, Pierre [LPS, CEN Saclay et LURE, Universite Paris-Sud, Bat 209D, F-91405 Orsay (France); Zieba, Emil [Department of Chemistry, Catholic University of Lublin, 20-718 Lublin (Poland); Mestres, Narcis [Institut de Ciencia de Materials de Barcelona (ICMAB), Campus de la UAB, E-08193-Bellaterra (Spain); Dutkiewicz, E.M. [Institute of Nuclear Physics, Department of Nuclear Spectroscopy, 31-342 Cracow (Poland); Kuczumow, Andrzej [Department of Chemistry, Catholic University of Lublin, 20-718 Lublin (Poland)

2005-04-28

Special kinds of petrified wood of complex structure were investigated. All the samples were composed of at least two different inorganic substances. The original cell structure was preserved in each case. The remnants of the original biological material were detected in some locations, especially in the cell walls. The complex inorganic structure was superimposed on the remnant organic network. The first inorganic component was located in the lumena (l.) of the cells while another one in the walls (w.) of the cells. The investigated arrangements were as follows: calcite (l.)-goethite-hematite (w.)-wood from Dunarobba, Italy; pyrite (l.)-calcite (w.)-wood from Lukow, Poland; goethite (l.)-silica (w.)-wood from Kwaczala, Poland. The inorganic composition was analysed and spatially located by the use of three spectral methods: electron microprobe, X-ray synchrotron-based microprobe, {mu}-PIXE microprobe. The accurate mappings presenting 2D distribution of the chemical species were presented for each case. Trace elements were detected and correlated with the distribution of the main elements. In addition, the identification of phases was done by the use of {mu}-Raman and {mu}-XRD techniques for selected and representative points. The possible mechanisms of the described arrangements are considered. The potential synthesis of similar structures and their possible applications are suggested.

Underestimation of phosphorus fraction change in the supernatant after phosphorus adsorption onto iron oxides and iron oxide-natural organic matter complexes.

Science.gov (United States)

Yan, Jinlong; Jiang, Tao; Yao, Ying; Wang, Jun; Cai, Yuanli; Green, Nelson W; Wei, Shiqiang

2017-05-01

The phosphorus (P) fraction distribution and formation mechanism in the supernatant after P adsorption onto iron oxides and iron oxide-humic acid (HA) complexes were analyzed using the ultrafiltration method in this study. With an initial P concentration of 20mg/L (I=0.01mol/L and pH=7), it was shown that the colloid (1kDa-0.45μm) component of P accounted for 10.6%, 11.6%, 6.5%, and 4.0% of remaining total P concentration in the supernatant after P adsorption onto ferrihydrite (FH), goethite (GE), ferrihydrite-humic acid complex (FH-HA), goethite-humic acid complex (GE-HA), respectively. The oxide aggregates was the main mechanism for the formation of the colloid P in the supernatant. And colloidal adsorbent particles co-existing in the supernatant were another important reason for it. Additionally, dissolve organic matter dissolved from iron oxide-HA complexes could occupy large adsorption sites of colloidal iron causing less colloid P in the supernatant. Ultimately, we believe that the findings can provide a new way to deeply interpret the geochemical cycling of P, even when considering other contaminants such as organic pollutants, heavy metal ions, and arsenate at the sediment/soil-water interface in the real environment. Copyright © 2016. Published by Elsevier B.V.

Some antarctic lacustrine sediments from northern Victoria Land investigation by Moessbauer spectroscopy, INNA and XRD

International Nuclear Information System (INIS)

Stievano, L.; Bertelle, M.; Leotta, G.; Calogero, S.; Constantinescu, S.; Oddone, M.

1999-01-01

Fifteen lacustrine sediments, sampled during the 1994-1995 Austral summer in Northern Victoria Land (Antarctica), were characterised by 57 Fe Moessbauer spectroscopy, instrumental neutron activation analysis and X-ray diffraction. These sediments are related to the intrusive rocks from Granite Harbour, to the metamorphic rocks of the Complex of Wilson Terrane and the volcanic rocks from Mc Murdo. The samples contain quartz, alkaline feldspars, plagioclases, amphiboles, biotite, chlorite and muscovite except for the sediments of volcanic origin that contain alkaline feldspars, plagioclases and pyroxenes. The paramagnetic components of the Moessbauer spectra were assigned mainly to the iron sides in biotites except for those displayed from the sediments of volcanic origin assigned mainly to pyroxenes. Moessbauer spectra at room temperature do not display magnetic ordering except for those of the sediments of volcanic origin containing bulk magnetite, hematite and goethite. Moessbauer spectra collected at the liquid helium temperature always exhibit magnetic ordering. This spectral difference has been attributed to the different dimensions of the iron oxide particles in the sediments. The scarce weathering involves a partial transformation of magnetite in hematite and goethite in the sediment of volcanic origin. In the remaining sediments a partial hydrolysis of biotite together with a partial oxidation of iron (II) retained in silicates is present. (authors)

Caracterización estructural de vidrios con altos contenidos de óxidos de hierro obtenidos a partir de un residuo de la hidrometalurgia del zinc

OpenAIRE

Romero, M.; Rincón, J. María; Mûsik, S.; Kozhukharov, W.

1997-01-01

It has been carried out the structural characterization of high oxide content glasses obtained by melting of a goethite industrial waste from the zinc hydrometallurgy with other raw materials as dolomite and glass cullet. The structural characterization has been carried out by X-Ray Diffraction (XRD), X-Ray Diffraction by Amorphous Dispersion (RDF) and Mossbauer spectroscopy. It has been determined the interatomic distance, the oxidation state and the coordination of iron atoms in these glass...

Extraction of metals from liquid effluent using modified inorganic ion exchangers

International Nuclear Information System (INIS)

Hudson, M.J.

1993-01-01

Inorganic ion exchangers such as goethite, titanium (IV) oxide; silica and zeolites have been modified to examine the extraction of ruthenium; technetium and cobalt from liquid effluent. In addition, tin (IV) hydrogenphosphate and antimony hydrogenphosphate have been also examined in the modified and unmodified forms. It has been shown that some of the above reagents are able to remove the required metal ions from aqueous solution at the trace and mg L -1 levels. (author)

Caracterização de óxidos de ferro de solos do ambiente tabuleiros costeiros Characterizing iron oxides from coastal and central plain soils

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Marcelo Metri Correa

2008-06-01

apresentou correlação com algumas propriedades cristalográficas das goethitas dos solos estudados, mostrando-se ser uma técnica promissora para o estudo dos óxidos de ferro.There have been several papers in the literature studying the genesis and consequences of particles cohesion in Argisols (Ultisols and Latosols (Oxisols from the Brazilian Inner and Coastal Plains. Just a few, however, provide insights into the clay fraction mineralogy, specially, the iron oxides complete characterization. The objective of this study was to investigate the chemical and crystallographic characteristics of iron oxides in red and yellow soils derived from the sediments of the Barreiras Formation or Pre-Cambrian rocks in the region of the coastal and central plateaus of several Brazilian states. The following research procedures were used: X-ray diffraction analyses in iron oxide-concentrated samples; successive extractions with CBD, and ammonium oxalate extraction in clay samples; spectral characterization by DRS; estimation of the crystallographic properties of goethite; quantification of isomorphic substitution of Fe for Al; and electronic transmission microscopy. According to the results, the following conclusions were drawn: (a goethite was the predominant iron oxide in all soils, even in those with 2.5YR hues, of which the hematite value was below 2.5 dag kg-1 clay; (b the values of the isomorphic Fe substitution by Al were 3 to 6 times higher for goethites than for hematites. These values did not agree with those estimated by mathematical models proposed in the scientific literature, which indicates the need for further studies of the relationships between crystallographic parameters of natural goethites and their chemical properties; (c the results obtained by X ray diffractometry and chemical dissolution analysis revealed that the goethites in the soils differ from those cited, to date, in the literature; (d the position of the bands obtained in the spectra of the diffuse

Estudio in-situ de la transformación térmica de limonita utilizada como pigmento procedente de Perú

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Romero-Gómez, P.

2013-06-01

Full Text Available It has been performed a kinetic study of the thermal transformation of Limonite [FeO(OH.nH2O] by thermal gravimetric analysis (TGA, thermal X-ray Diffraction (XRD and μ-Raman spectroscopy. The mineral was extracted from the Taraco District, Huancané Province, Puno region (Peru. Powdered XRD identify goethite phase as the main mineralogical component besides quartz. It was subjected to in-situ thermal treatment in the range of temperatures 100 to 500 ºC in air and an inert atmosphere (nitrogen. The goethite phase remains stable from room temperature until 200 ºC. From 250ºC there is a phase transformation α-FeO(OH → α-Fe2O3 with 8 wt % weight loss and a chromatic change, i.e., the change of the hydroxylated goethite phase (yellow to oxided hematite phase (red, as evidenced by the TGA and evolution of the XRD profiles. Moreover, the μ-Raman spectra of the in-situ thermal treatment corroborate that there is a transition at 290 ºC by the transformation of the characteristic Raman bands of the goethite to hematite phase, in the frequency range from 200 to 1800cm-1.Se ha realizado un estudio cinético de la transformación térmica de limonita [FeO(OH.nH2O] mediante análisis térmico gravimétrico (TGA, termodifracción de rayos X (DRX y espectroscopía μ-Raman. La muestra estudiada fue extraída de un yacimiento en el distrito de Taraco, provincia de Huancané, Región de Puno (Perú. La técnica DRX en polvo identificó la fase goetita como el principal componente mineralógico, además de cuarzo. La muestra se sometió a un tratamiento térmico in-situ en un intervalo de temperaturas de 100 a 500 °C en atmósfera de aire e inerte (nitrógeno y se estudió por DRX. Los resultados han mostrado que la fase goetita permanece estable desde la temperatura ambiente hasta 200 °C. A partir de los 250 °C se produce una transformación de fase α-FeO(OH → α-Fe2O3 con un cambio cromático, es decir, el paso de la fase hidroxilada goetita

From iron(III) precursor to magnetite and vice versa

International Nuclear Information System (INIS)

Gotic, M.; Jurkin, T.; Music, S.

2009-01-01

The syntheses of nanosize magnetite particles by wet-chemical oxidation of Fe 2+ have been extensively investigated. In the present investigation the nanosize magnetite particles were synthesised without using the Fe(II) precursor. This was achieved by γ-irradiation of water-in-oil microemulsion containing only the Fe(III) precursor. The corresponding phase transformations were monitored. Microemulsions (pH ∼ 12.5) were γ-irradiated at a relatively high dose rate of ∼22 kGy/h. Upon 1 h of γ-irradiation the XRD pattern of the precipitate showed goethite and unidentified low-intensity peaks. Upon 6 h of γ-irradiation, reductive conditions were achieved and substoichiometric magnetite (∼Fe 2.71 O 4 ) particles with insignificant amount of goethite particles found in the precipitate. Hydrated electrons (e aq - ), organic radicals and hydrogen gas as radiolytic products were responsible for the reductive dissolution of iron oxide in the microemulsion and the reduction Fe 3+ → Fe 2+ . Upon 18 h of γ-irradiation the precipitate exhibited dual behaviour, it was a more oxidised product than the precipitate obtained after 6 h of γ-irradiation, but it contained magnetite particles in a more reduced form (∼Fe 2.93 O 4 ). It was presumed that the reduction and oxidation processes existed as concurrent competitive processes in the microemulsion. After 18 h of γ-irradiation the pH of the medium shifted from the alkaline to the acidic range. The high dose rate of ∼22 kGy/h was directly responsible for this shift to the acidic range. At a slightly acidic pH a further reduction of Fe 3+ → Fe 2+ resulted in the formation of more stoichiometric magnetite particles, whereas the oxidation conditions in the acidic medium permitted the oxidation Fe 2+ → Fe 3+ . The Fe 3+ was much less soluble in the acidic medium and it hydrolysed and recrystallised as goethite. The γ-irradiation of the microemulsion for 25 h at a lower dose rate of 16 kGy/h produced pure

Arsenic in Holocene aquifers of the Red River floodplain, Vietnam: Effects of sediment-water interactions, sediment burial age and groundwater residence time

Science.gov (United States)

Sø, Helle Ugilt; Postma, Dieke; , Mai Lan, Vi; Pham, Thi Kim Trang; Kazmierczak, Jolanta; Dao, Viet Nga; Pi, Kunfu; Koch, Christian Bender; Pham, Hung Viet; Jakobsen, Rasmus

2018-03-01

Water-sediment interactions were investigated in arsenic contaminated Holocene aquifers of the Red River floodplain, Vietnam, in order to elucidate the origin of the spatial variability in the groundwater arsenic concentration. The investigated aquifers are spread over an 8 × 13 km field area with sediments that varied in burial age from V) redox couple was found in disequilibrium with the other redox couples. Using the pe calculated from the CH4/CO2 redox couple we show that the groundwater has a reducing potential towards Fe-oxides ranging from ferrihydrite to poorly crystalline goethite, but not for well crystalline goethite or hematite. Hematite and poorly crystalline goethite were identified as the Fe-oxides present in the sediments. Reductive dissolution experiments identify two phases releasing Fe(II); one rapidly dissolving that also contains As and a second releasing Fe(II) more slowly but without As. The initial release of Fe and As occurs at a near constant As/Fe ratio that varied from site to site between 1.2 and 0.1 mmol As/mol Fe. Siderite (FeCO3) is the main sink for Fe(II), based on saturation calculations as well as the identification of siderite in the sediment. Most of the carbonate incorporated in siderite originates from the dissolution of sedimentary CaCO3. Over time the CaCO3 content of the sediments diminishes and FeCO3 appears instead. No specific secondary phases that incorporate arsenite could be identified. Alternatively, the amount of arsenic mobilized during the dissolution of reactive phases can be contained in the pool of adsorbed arsenite. Combining groundwater age with aquifer sediment age allows the calculation of the total number of pore volumes flushed through the aquifer. Comparison with groundwater chemistry shows the highest arsenic concentration to be present within the first 200 pore volumes flushed through the aquifer. These results agree with reactive transport modeling combining a kinetic description of reductive

Clay mineral facies and lateritization in basalts of the southeastern Parana Basin, Brazil

International Nuclear Information System (INIS)

Oliveira, M.T.G. de; Formoso, M.L.L.; Trescases, J.J.; Meunier, A.

1998-01-01

Seventeen samples from two lateritic profiles, each with five facies, were studied. These profiles occur on the old planation surface of the plateau basalts of the southern part of ParanáBasin, Brazil. Optical microscopy, X-ray diffraction, electron microprobe, Mössbauer spectroscopy and Fourier Transform Infrared Spectra were used to obtain information about the nature and chemical composition of each weathering facies. In addition, scanning electron microscopy and analyses of clay minerals were performed to detect microcrystalline environmental changes. Both profiles have two major parts: a loose red-clay latosol separated from an underlying mottled clay and an alterite facies; a stone line may or may not be present between the latosol and the underlying units. In both profiles the latosol consists principally of kaolinite, hematite and goethite. Two alterite facies, shaped by differential weathering, are also present in the lower profile: a halloysite–nontronite clayey matrix with a well developed fissure system occurs in the argillaceous alterite and a network of Al–goethite aggregates is typical of the highly porous cortex of the boulder alterite that is found in the stone line and below it. Gibbsite has crystallized in the large pores of porphyritic boulder alterite but is absent in the small pores of the subaphyric boulder alterite. Clay minerals observed in fissures include halloysite associated with goethite and manganese oxides. The basalt has hydrothermal green-clays (mixed layers and trioctahedral smectites) that formed between primary plagioclase, pyroxene and Ti–magnetite crystals while fresh corestones of the boulder alterite have cryptocrystalline iron-rich material. The study of these profiles shows one principal evolutionary trend for clay minerals. This trend is from smectite and mixed layers that form green clays in altered bedrock at the base of the profile to an intermediate association of nontronite and halloysite in the argillaceous

Mössbauer spectroscopic studies on the iron forms of deep-sea sediments

Science.gov (United States)

Drodt, M.; Trautwein, A. X.; König, I.; Suess, E.; Koch, C. Bender

Mössbauer spectroscopy was applied to characterize the valence states Fe(II) and Fe(III) in sedimentary minerals from a core of the Peru Basin. The procedure in unraveling this information includes temperature-dependent measurements from 275 K to very low temperature (300 mK) in zero-field and also at 4.2 K in an applied field (up to 6.2 T) and by mathematical procedures (least-squares fits and spectral simulations) in order to resolve individual spectral components. The depth distribution of the amount of Fe(II) is about 11% of the total Fe to a depth of 19 cm with a subsequent steep increase (within 3 cm) to about 37%, after which it remains constant to the lower end of the sediment core (at about 40 cm). The steep increase of the amount of Fe(II) defines a redox boundary which coincides with the position where the tan/green color transition of the sediment occurs. The isomer shifts and quadrupole splittings of Fe(II) and Fe(III) in the sediment are consistent with hexacoordination by oxygen or hydroxide ligands as in oxide and silicate minerals. Goethite and traces of hematite are observed only above the redox boundary, with a linear gradient extending from about 20% of the total Fe close to the sediment surface to about zero at the redox boundary. The superparamagnetic relaxation behavior allows to estimate the order of magnitude for the size of the largest goethite and hematite particles within the particle-site distribution, e.g. 170 Å and 50 Å, respectively. The composition of the sediment spectra recorded at 300 mK in zero-field, apart from the contributions due to goethite and hematite, resembles that of the sheet silicates smectite, illite and chlorite, which have been identified as major constituents of the sediment in the clay-mineral iron is redox sensitive. It is proposed that the color change of the sediment at the redox boundary from tan to green is related to the increase of Fe(II)-Fe(III) pairs in the layer silicates, because of the

Microbial Composition in Decomposing Pine Litter Shifts in Response to Common Soil Secondary Minerals

Science.gov (United States)

Welty-Bernard, A. T.; Heckman, K.; Vazquez, A.; Rasmussen, C.; Chorover, J.; Schwartz, E.

2011-12-01

A range of environmental and biotic factors have been identified that drive microbial community structure in soils - carbon substrates, redox conditions, mineral nutrients, salinity, pH, and species interactions. However, soil mineralogy has been largely ignored as a candidate in spite of recent studies that indicate that minerals have a substantial impact on soil organic matter stores and subsequent fluxes from soils. Given that secondary minerals and organic colloids govern a soil's biogeochemical activity due to surface area and electromagnetic charge, we propose that secondary minerals are a strong determinant of the communities that are responsible for process rates. To test this, we created three microcosms to study communities during decomposition using pine forest litter mixed with two common secondary minerals in soils (goethite and gibbsite) and with quartz as a control. Changes in bacterial and fungal communities were tracked over the 154-day incubation by pyrosequencing fragments of the bacterial 16S and fungal 18S rRNA genes. Ordination using nonmetric multidimensional scaling showed that bacterial communities separated on the basis of minerals. Overall, a single generalist - identified as an Acidobacteriaceae isolate - dominated all treatments over the course of the experiment, representing roughly 25% of all communities. Fungal communities discriminated between the quartz control alone and mineral treatments as a whole. Again, several generalists dominated the community. Coniochaeta ligniaria dominated communities with abundances ranging from 29 to 40%. The general stability of generalist populations may explain the similarities between treatment respiration rates. Variation between molecular fingerprints, then, were largely a function of unique minor members with abundances ranging from 0.01 to 8%. Carbon availability did not surface as a possible mechanism responsible for shifts in fingerprints due to the relatively large mass of needles in the

Moessbauer spectroscopy of iron in clay minerals

International Nuclear Information System (INIS)

Raclavsky, K.; Sitek, J.; Lipka, J.

1975-01-01

Selected pure clay minerals predominantly of Czechoslovak origin were studied, such as montmorillonite, nontronite, beidellite, glauconite, seladonite, illite, vermiculite, saponite, palygorskite, goethite. Moessbauer measurements were performed at room temperature with a 57 Co in Pd source. The spectra were fitted by the least square method. The parameters of the measured Moessbauer spectra are given. The values of isomer shifts, quadrupole splittings and line widths were obtained with an error of +- 0.03 mm/sec. (Z.S.)

Structural characterization of hog iron oxide content glasses obtained from zinc hydrometallurgy wastes

International Nuclear Information System (INIS)

Romero, M.; Rincon, J.M.; Musik, S.; Kozhujharov, W.

1997-01-01

It has been carried out the structural characterization of high oxide content glasses obtained by melting of a goethite industrial waste from the zinc hydrometallurgy with other raw materials as dolomite and glass cullet. The structural characterization has been carried out by X-ray Diffraction (XRD), X-Ray Diffraction by Amorphous Dispersion (RDF) and Mossbauer spectroscopy. It has been determined the interatomic distance, the oxidation state and the coordination of iron atoms in these glasses. (Author) 16 refs

Mineralogical, micromorphological and geochemical transformations in the initial steps of the weathering process of charnockite from the Caparaó Range, southeastern Brazil

Science.gov (United States)

Soares, Caroline Cibele Vieira; Varajão, Angélica Fortes Drummond Chicarino; Varajão, César Augusto Chicarino; Boulangé, Bruno

2014-12-01

X-ray diffraction (XRD), X-ray Fluorescence (XRF), optical microscopy, Scanning Electron Microscopy coupled with Energy Dispersive Spectrometry (SEM-EDS) and Electron Probe micro-analyser (EPMA) and Wavelength-Dispersive Spectroscopy (WDS) were conducted on charnockite from the Caparaó Suite and its alteration cortex to determine the mineralogical, micromorphological and geochemical transformations resulting from the weathering process. The hydrolysis of the charnockite occurred in different stages, in accordance with the order of stability of the minerals with respect to weathering: andesine/orthopyroxene, pargasite and alkali feldspar. The rock modifications had begun with the formation of a layer of incipient alteration due to the percolation of weathering solutions first in the pressure relief fractures and then in cleavage and mineral edges. The iron exuded from ferromagnesian minerals precipitated in the intermineral and intramineral discontinuities. The layer of incipient alteration evolves into an inner cortex where the plagioclase changes into gibbsite by direct alitisation, the ferromagnesian minerals initiate the formation of goethitic boxworks with kaolinitic cores, and the alkali feldspar initiates indirect transformation into gibbsite, forming an intermediate phase of illite and kaolinite. In the outer cortex, mostly traces of alkali feldspar remain, and they are surrounded by goethite and gibbsite as alteromorphics, characterising the formation of the isalteritic horizon that occurs along the slope and explains the bauxitization process at the Caparaó Range, SE Brazil.

Assessing mine drainage pH from the color and spectral reflectance of chemical precipitates

Science.gov (United States)

Williams, D.J.; Bigham, J.M.; Cravotta, C.A.; Traina, S.J.; Anderson, J.E.; Lyon, J.G.

2002-01-01

The pH of mine impacted waters was estimated from the spectral reflectance of resident sediments composed mostly of chemical precipitates. Mine drainage sediments were collected from sites in the Anthracite Region of eastern Pennsylvania, representing acid to near neutral pH. Sediments occurring in acidic waters contained primarily schwertmannite and goethite while near neutral waters produced ferrihydrite. The minerals comprising the sediments occurring at each pH mode were spectrally separable. Spectral angle difference mapping was used to correlate sediment color with stream water pH (r2=0.76). Band-center and band-depth analysis of spectral absorption features were also used to discriminate ferrihydrite and goethite and/or schwertmannite by analyzing the 4T1??? 6A1 crystal field transition (900-1000 nm). The presence of these minerals accurately predicted stream water pH (r2=0.87) and provided a qualitative estimate of dissolved SO4 concentrations. Spectral analysis results were used to analyze airborne digital multispectral video (DMSV) imagery for several sites in the region. The high spatial resolution of the DMSV sensor allowed for precise mapping of the mine drainage sediments. The results from this study indicate that airborne and space-borne imaging spectrometers may be used to accurately classify streams impacted by acid vs. neutral-to-alkaline mine drainage after appropriate spectral libraries are developed.

Hydrogeochemical and mineralogical characteristics related to heavy metal attenuation in a stream polluted by acid mine drainage:A case study in Dabaoshan Mine, China

Institute of Scientific and Technical Information of China (English)

Huarong Zhao; Beicheng Xia; Jianqiao Qin; Jiaying Zhang

2012-01-01

Dabaoshan Mine,the largest mine in south China,has been developed since the 1970s.Acid mine drainage (AMD) discharged from the mine has caused severe environmental pollution and human health problems.In this article,chemical characteristics,mineralogy of ocher precipitations and heavy metal attenuation in the AMD are discussed based on physicochemical analysis,mineral analysis,sequential extraction experiments and hydrogeochemistry.The AMD chemical characteristics were determined from the initial water composition,water-rock interactions and dissolved sulfide minerals in the mine tailings.The waters,affected and unaffected by AMD,were Ca-SO4 and Ca-HCO3 types,respectively.The affected water had a low pH,high SO42- and high heavy metal content and oxidation as determined by the Fe2+/Fe3+ couple.Heavy metal and SO42- contents of Hengshi River water decreased,while pH increased,downstream.Schwertmannite was the major mineral at the waste dump,while goethite and quartz were dominant at the tailings dam and streambed.Schwertmannite was transformed into goethite at the tailings dam and streambed.The sulfate ions of the secondary minerals changed from bidentate- to monodentate-complexes downstream.Fe-Mn oxide phases of Zn,Cd and Pb in sediments increased downstream.However,organic matter complexes of Cu in sediments increased further away from the tailings.Fe3+ mineral precipitates and transformations controlled the AMD water chemistry.

Klimt artwork (Part II): material investigation by backscattering Fe-57 Mössbauer- and Raman- spectroscopy, SEM and p-XRF

Energy Technology Data Exchange (ETDEWEB)

Costa, B. F. O. [University of Coimbra, CFisUC, Physics Department (Portugal); Lehmann, R.; Wengerowsky, D. [Leibniz Universität Hannover, Institut für Anorganische Chemie (Germany); Blumers, M. [Joh. Gutenberg-Universität Mainz, Institut für Anorganische Chemie und Analytische Chemie (Germany); Sansano, A.; Rull, F. [Unidad Asociada UVA-CSIC Centro de Astrobiologia (Spain); Schmidt, H.-J. [Leibniz Universität Hannover, Institut für Anorganische Chemie (Germany); Dencker, F. [Hochschule Hannover, Fakultät II-Maschinenbau und Bioverfahrenstechnik (Germany); Niebur, A. [Technische Universität Dresden, Institut für Physikalische Chemie (Germany); Klingelhöfer, G. [Joh. Gutenberg-Universität Mainz, Institut für Anorganische Chemie und Analytische Chemie (Germany); Sindelar, R. [Hochschule Hannover, Fakultät II-Maschinenbau und Bioverfahrenstechnik (Germany); Renz, F., E-mail: renz@acd.uni-hannover.de [Leibniz Universität Hannover, Institut für Anorganische Chemie (Germany)

2016-12-15

In a rediscovered Klimt-artwork “Trompetender Putto” material tests have been conducted. We report studies on different points of the painting. The spots are of different colors, mainly taken in spots of the painting not restaurated. MIMOS II Fe-57 Mössbauer spectroscopy revealed mainly haematite and nano particle oxides in red and red/brown colors. Brown colors also contain crystallized goethite. In brown/ochre colors the same pigments as in brown colors are observed, but there is less quantity of goethite and more quantity of haematite. The green colors show Fe-rich clays, like celadonite or glauconite and or lepidocrocite as main component. Raman spectroscopy revealed cinnabar in red colors of the Scarf; and massicot in brown/ochre points, i.e. in the Left Wing of the “Putto”. With scanning electron microscopy, various layers of the original and of overpainting could be recognized. The investigations of sample 1 show three layers of colored materials, which were identified as zinc-white, cinnabar and galena as well as carbon compounds. In sample 2 four layers could be detected. These are identified (bottom to top) as gypsum and lead-white (layer 1), zinc-white (layer 2), lead-white and cinnabar (layer 3) and titanium-white (layer 4). The elementary composition was examined with the portable X-ray-fluorescence analysis for qualitative manner at different points.

Adsorption of guanidinium collectors on aluminosilicate minerals - a density functional study.

Science.gov (United States)

Nulakani, Naga Venkateswara Rao; Baskar, Prathab; Patra, Abhay Shankar; Subramanian, Venkatesan

2015-10-07

In this density functional theory based investigation, we have modelled and studied the adsorption behaviour of guanidinium cations and substituted (phenyl, methoxy phenyl, nitro phenyl and di-nitro phenyl) guanidinium cationic collectors on the basal surfaces of kaolinite and goethite. The adsorption behaviour is assessed in three different media, such as gas, explicit water and pH medium, to understand the affinity of GC collectors to the SiO4 tetrahedral and AlO6 octahedral surfaces of kaolinite. The tetrahedral siloxane surface possesses a larger binding affinity to GC collectors than the octahedral sites due to the presence of surface exposed oxygen atoms that are active in the intermolecular interactions. Furthermore, the inductive electronic effects of substituted guanidinium cations also play a key role in the adsorption mechanism. Highly positive cations result in a stronger electrostatic interaction and preferential adsorption with the kaolinite surfaces than low positive cations. Computed interaction energies and electron densities at the bond critical points suggest that the adsorption of guanidinium cations on the surfaces of kaolinite and goethite is due to the formation of intra/inter hydrogen bonding networks. Also, the electrostatic interaction favours the high adsorption ability of GC collectors in the pH medium than gas phase and water medium. The structures and energies of GC collectors pave an intuitive view for future experimental studies on mineral flotation.

Evidence of synsedimentary microbial activity and iron deposition in ferruginous crusts of the Late Cenomanian Utrillas Formation (Iberian Basin, central Spain)

Science.gov (United States)

García-Hidalgo, José F.; Elorza, Javier; Gil-Gil, Javier; Herrero, José M.; Segura, Manuel

2018-02-01

Ferruginous sandstones and crusts are prominent sedimentary features throughout the continental (braided)-coastal siliciclastic (estuarine-tidal) wedges of the Late Cenomanian Utrillas Formation in the Iberian Basin. Crust types recognized are: Ferruginous sandy crusts (Fsc) with oxides-oxyhydroxides (hematite and goethite) concentrated on sandstone tops presenting a fibro-radial internal structure reminding organic structures that penetrate different mineral phases, suggesting the existence of bacterial activity in crust development; Ferruginous muddy crusts (Fmc) consisting of wavy, laminated, microbial mats, being composed mainly of hematite. On the other hand, a more dispersed and broader mineralization included as Ferruginous sandstones with iron oxides and oxyhydroxides (hematite and goethite) representing a limited cement phase on these sediments. The presence of microbial remains, ferruginous minerals, Microbially-induced sedimentary structures, microbial laminites and vertebrate tracks preserved due to the presence of biofilms suggest firstly a direct evidence of syn-depositional microbial activity in these sediments; and, secondly, that iron accumulation and ferruginous crusts development occurred immediately after deposition of the host, still soft sediments. Ferruginous crusts cap sedimentary cycles and they represent the gradual development of hard substrate conditions, and the development of a discontinuity surface at the top of the parasequence sets, related to very low sedimentary rates; the overlying sediments record subsequent flooding of underlying shallower environments; crusts are, consequently, interpreted as boundaries for these higher-order cycles in the Iberian Basin.

Research on atmospheric corrosion of steel using synchrotron radiation

International Nuclear Information System (INIS)

Yamashita, M.; Uchida, H.; Konishi, H.; Mizuki, J.

2004-01-01

Correlation between local structure around Cr in the protective rust layer on weathering steel and protective performance of the rust layer is presented as an example of corrosion research using synchrotron radiation which has recently been applied in various research fields as a useful tool. In addition, in situ observation of initial process of rust formation on steel is also mentioned. It was pointed out by considering the X-ray absorption fine structure spectra that the nanostructure of the protective rust layer on weathering steel primarily comprises of small Cr-goethite crystals containing surface adsorbed and/or intergranular CrO x 3-2X complex anions. This CrO x 3-2X explains the protective performance of the rust layer originated by dense aggregation of fine crystals with cation selectivity of the Cr-goethite. It is very advantageous to employ white X-rays for in situ observation of rusting process of a carbon steel covered with electrolyte thin films because rust structure might change very quickly. This in situ observation revealed the effect of ion species on the change in rust phase during wet/dry repeating. It can be said that application of synchrotron radiation on corrosion research is so useful to understand the nanostructure of surface oxides which closely relate to corrosion behavior of metals and alloys. (author)

Clogging of water supply wells in alluvial aquifers by mineral incrustations, central Serbia

Directory of Open Access Journals (Sweden)

Majkić-Dursun Brankica

2015-01-01

Full Text Available The formation of incrustations on public water supply well screens reduces their performance considerably. The incrustations increase hydraulic losses, reduce the capacity of the well and screen, affect the quality of the pumped water and increase maintenance costs. In alluvial environments, the most common deposits are iron and manganese hydroxides. However, the rates of formation, compositions and levels of crystallization vary, depending on the geochemical characteristics of the alluvial environment, the microbiological characteristics of the groundwater and the abstraction method. Samples of 15 incrustations were collected from wells that tap shallow alluvial aquifers and were found to be dominated by iron. XRD analyses detected low-crystalline ferrihydrite and manganese hydroxide in the samples collected from the water supply source at Trnovče (Velika Morava alluvial. The incrustations from the Belgrade Groundwater Source revealed the presence of ferrihydrite and a substantial amount of goethite α-FeOOH. Apart from goethite, greigite (Fe3S4 was detected in three samples, while one sample additionally contained bernalite Fe(OH3 and monoclinic sulfur S8. Among carbonates, only siderite was detected. Iron oxidizing bacteria generally catalyze deposition processes in wells, while sulfate reducing bacteria (SRB play a role in the biogenic formation of greigite. Determining the nature of the deposited material allows better selection of rehabilitation chemicals and procedure. [Projekat Ministarstva nauke Republike Srbije, br. TR37014

Sorption of nuclides on organic colloids and their migration through porous media. 3

International Nuclear Information System (INIS)

Nagasaki, Shinya

2004-03-01

The environmental behaviors of actinide and heavy metal ions depend on their speciation. Especially, the binding of these ions to natural colloids such as natural organic materials (NOMs) and metal (hydr)oxides (OXs) are of great importance in soil and aquatic systems. Therefore, for the reliable risk assessment and the remediation of the contaminated environment it is necessary to develop chemical thermodynamical models that ca predict the speciation of metal ions in the presence of natural colloids. The binding behavior of metal ions to natural colloids is complicated because of their heterogeneous nature and the interaction between different natural colloids (ex. the adsorption of NOM on OXs) which change the site density available for metal ions and the electrostatic potential in solid/water interfacial region. In the previous report, we explained how the metal binding to heterogeneous surfaces can be modeled and showed the modeling results of the copper binding to humic acid by the NICA-Donnan model. This report concentrates on two topic: (1) the modeling of the copper binding to goethite, one of representative metal (hydr)oxides, by the CD-MUSIC model and (2) the influence of the adsorption of humic acid on goethite upon the proton binding to their mixture. The recent progress in the modeling of the ternary system (metal ions/NOMs/OXs) is also introduced at the end of the report. (author)

Enhanced⁹⁹Tc retention in glass waste form using Tc(IV)-incorporated Fe minerals

OpenAIRE

Um, W; Luksic, SA; Wang, G; Saslow, S; Kim, DS; Schweiger, MJ; Soderquist, CZ; Bowden, ME; Lukens, WW; Kruger, AA

2017-01-01

© 2017 Elsevier B.V. Technetium ( 99 Tc) immobilization by doping into iron oxide mineral phases may alleviate the problems with Tc volatility during vitrification of nuclear waste. Because reduced Tc, Tc(IV), substitutes for Fe(III) in the crystal structure by a process of Tc reduction from Tc(VII) to Tc(IV) followed by co-precipitation of Fe oxide minerals, two Tc-incorporated Fe minerals (Tc-goethite and Tc-magnetite/maghemite) were prepared and tested for Tc retention in glass melt sample...

Can Dynamic Bubble Templating Play a Role in Corrosion Product Morphology?

Science.gov (United States)

2012-02-01

FeOOH (goethite) with moderate amounts of metallic luster Fe304 (magnetite), and trace amounts of CaC03 (calcite). In addition, the core was marbled ...cathodically produced gas bubbles (i.e., H2). By physically separating the anode and cathode. Stone and Goldstein26 generated tubular structures electro...D.A. Stone , RE. Goldstein. Proc. MatL Acad. Set U.S-A. 101 (2004): p. 11537. G. Butler, H.C.K. Ison, Nature 182 (1958): p. 1229. B. McEnaney. D.C

Functionality of the iron oxides

International Nuclear Information System (INIS)

Castano, J.G.; Arroyave, C.

1998-01-01

Some iron oxides have a great scientific and technological possibilities, not only for their importance in the present, but also for their great potential in the development of the future technologies. They have adequate properties to carry out several functions. They are plentiful in the nature and their synthetic obtention is not complex. This paper shows five of them (hematite, magnetite, maghemite, goethite and akaganeite) and their utilization in fields like chemical industry, biotechnology medicine, new materials and electromagnetism. (Author) 77 refs

Characterization of the corrosion products formed on mild steel in acidic medium with N-octadecylpyridinium bromide as corrosion inhibitor

Energy Technology Data Exchange (ETDEWEB)

Nava, N., E-mail: tnava@imp.mx; Likhanova, N. V. [Direccion de Investigacion y Posgrado, Instituto Mexicano del Petroleo (Mexico); Olivares-Xometl, O. [Benemerita Universidad Autonoma de Puebla, Facultad de Ingenieria Quimica (Mexico); Flores, E. A. [Direccion de Investigacion y Posgrado, Instituto Mexicano del Petroleo (Mexico); Lijanova, I. V. [CIITEC, Instituto Politecnico Nacional (Mexico)

2011-11-15

The characterization of the corrosion products formed on mild steel SAE 1018 after 2 months exposure in aqueous sulfuric acid with and without corrosion inhibitor N-octadecylpyridinium bromide has been carried out by means of transmission {sup 57}Fe Moessbauer spectroscopy and X-ray powder diffraction (XRD). The major constituent of the rust formed in this environment without corrosion inhibitor is goethite ({alpha}-FeOOH). The samples with N-octadecylpyridinium bromide contain rozenite and large amounts of melanterite in the corrosion layers.

Sorption of pesticides to aquifer minerals

DEFF Research Database (Denmark)

Clausen, Liselotte; Fabricius, Ida Lykke

2000-01-01

This paper summarizes results from a work were the sorption of five pesticides on seven minerals were studied in order to quantify the adsorption to different mineral surfaces. Investigated mineral phases are: quartz, calcite, kaolinite, a-alumina, and three iron oxides (2-line ferrihydrite......, goethite, lepidocrocite). Selected pesticides are: atrazine, isoproturon, mecoprop, 2,4-D, and bentazone. The results demonstrate that pesticides adsorb to pure mineral surfaces. However, the size of the adsorption depends on the type of pesticide and the type of mineral....

Electron paramagnetic resonance (EPR) in characterization of rocks and minerals

Energy Technology Data Exchange (ETDEWEB)

Valezi, D.F.; Mauro, E. di [Universidade Estadual de Londrina (UEL), PR (Brazil). Centro de Ciencias Exatas. Lab. de Fluorescencia e Ressonaancia Paramagnetica Eletronica (LAFLURPE); Zaia, D.A.M.; Carneiro, C.E.A. [Universidade Estadual de Londrina (UEL), PR (Brazil). Centro de Ciencias Exatas. Dept. de Quimica; Costa, A.C.S. da [Universidade Estadual de Maringa (UEM), PR (Brazil). Centro de Ciencias Agrarias. Dept. de Agronomia

2011-07-01

Full text. his work is based on the study of several stones and minerals from the Parana state, Brazil. They were analyzed by the Electron Paramagnetic Resonance (EPR) technique. The measurements were made on a spectrometer JEOL (JES-PE-3X), operating on X-band and at room temperature, with the exception of the mineral Goethite, which was measured with temperature variation. In all the samples were determined spectroscopic factors (or g factor) and line widths of paramagnetic species. A great number of the samples showed in their spectra, the presence of iron complexes. Phyllite and shale showed a resonance signal with approximately g = 2, and line width with about 1000 Gauss, which indicates the presence of the hematite mineral hematite in these rocks. Shale and coal samples showed the presence of free radical, it was identified as a very intense signal, centered at about g = 2.003. Phyllite sample showed in its spectra a resonance signal between the third and fourth line of the g marker (Mg O:Mn{sup 2+}) used in the measurements, and also a signal at g = 4.3, these characteristics may indicate the presence of Kaolinite in the sample. Limestone showed a signal with line width of about 600 Gauss, centered around g = 2, this signal is probably due to a mixture of ferrihydrite and some other compound, besides the presence of manganese, displaying a spectra with its six peculiar lines, due to hyperfine splitting. The two different types of limestone presented a overlap of two distinct spectra lines for the manganese, in the first limestone sample, rich in calcite, the existence of these different spectra is a result of the manganese substitution in a single site with different orientations of the calcite; the other limestone sample, this one abundant in dolomite, the existence of these different spectra is the result of the manganese substitution in different dolomite sites, taking the place of calcium and or of the magnesium. Now, we are focusing our research in the

Iron oxide minerals in dust of the Red Dawn event in eastern Australia, September 2009

Science.gov (United States)

Reynolds, Richard L.; Cattle, Stephen R.; Moskowitz, Bruce M.; Goldstein, Harland L.; Yauk, Kimberly; Flagg, Cody B.; Berquó, Thelma S.; Kokaly, Raymond F.; Morman, Suzette A.; Breit, George N.

2014-01-01

Iron oxide minerals typically compose only a few weight percent of bulk atmospheric dust but are important for potential roles in forcing climate, affecting cloud properties, influencing rates of snow and ice melt, and fertilizing marine phytoplankton. Dust samples collected from locations across eastern Australia (Lake Cowal, Orange, Hornsby, and Sydney) following the spectacular “Red Dawn” dust storm on 23 September 2009 enabled study of the dust iron oxide assemblage using a combination of magnetic measurements, Mössbauer spectroscopy, reflectance spectroscopy, and scanning electron microscopy. Red Dawn was the worst dust storm to have hit the city of Sydney in more than 60 years, and it also deposited dust into the Tasman Sea and onto snow cover in New Zealand. Magnetization measurements from 20 to 400 K reveal that hematite, goethite, and trace amounts of magnetite are present in all samples. Magnetite concentrations (as much as 0.29 wt%) were much higher in eastern, urban sites than in western, agricultural sites in central New South Wales (0.01 wt%), strongly suggesting addition of magnetite from local urban sources. Variable temperature Mössbauer spectroscopy (300 and 4.2 K) indicates that goethite and hematite compose approximately 25–45% of the Fe-bearing phases in samples from the inland sites of Orange and Lake Cowal. Hematite was observed at both temperatures but goethite only at 4.2 K, thereby revealing the presence of nanogoethite (less than about 20 nm). Similarly, hematite particulate matter is very small (some of it d < 100 nm) on the basis of magnetic results and Mössbauer spectra. The degree to which ferric oxide in these samples might absorb solar radiation is estimated by comparing reflectance values with a magnetic parameter (hard isothermal remanent magnetization, HIRM) for ferric oxide abundance. Average visible reflectance and HIRM are correlated as a group (r2 = 0.24), indicating that Red Dawn ferric oxides have

Fe K-edge XANES of Maya blue pigment

Science.gov (United States)

Río, M. Sánchez del; Sodo, A.; Eeckhout, S. G.; Neisius, T.; Martinetto, P.; Dooryhée, E.; Reyes-Valerio, C.

2005-08-01

The utilization of techniques used in Materials Science for the characterization of artefacts of interest for cultural heritage is getting more and more attention nowadays. One of the products of the ancient Maya chemistry is the "Maya blue" pigment, made with natural indigo and palygorskite. This pigment is different from any other pigment used in other parts of the world. It is durable and acid-resistant, and still keeps many secrets to scientists even though it has been studied for more than 50 years. Although the pigment is basically made of palygorskite Si8(Mg2Al2)O20(OH)2(OH2)4.4H2O and an organic colourant (indigo: C16H10N2O2), a number of other compounds have been found in previous studies on archaeological samples, like other clays and minerals, iron nanoparticles, iron oxides, impurities of transition metals (Cr, Mn, Ti, V), etc. We measured at the ESRF ID26 beamline the Fe K-edge XANES spectra of the blue pigment in ancient samples. They are compared to XANES spectra of Maya blue samples synthesized under controlled conditions, and iron oxides usually employed as pigments (hematite and goethite). Our results show that the iron found in ancient Maya blue pigment is related to the Fe exchanged in the palygorskite clay. We did not find iron in metallic form or goethite in archaeological Maya blue.

Fe K-edge XANES of Maya blue pigment

International Nuclear Information System (INIS)

Rio, M. Sanchez del; Sodo, A.; Eeckhout, S.G.; Neisius, T.; Martinetto, P.; Dooryhee, E.; Reyes-Valerio, C.

2005-01-01

The utilization of techniques used in Materials Science for the characterization of artefacts of interest for cultural heritage is getting more and more attention nowadays. One of the products of the ancient Maya chemistry is the 'Maya blue' pigment, made with natural indigo and palygorskite. This pigment is different from any other pigment used in other parts of the world. It is durable and acid-resistant, and still keeps many secrets to scientists even though it has been studied for more than 50 years. Although the pigment is basically made of palygorskite Si 8 (Mg 2 Al 2 )O 20 (OH) 2 (OH 2 ) 4 .4H 2 O and an organic colourant (indigo: C 16 H 10 N 2 O 2 ), a number of other compounds have been found in previous studies on archaeological samples, like other clays and minerals, iron nanoparticles, iron oxides, impurities of transition metals (Cr, Mn, Ti, V), etc. We measured at the ESRF ID26 beamline the Fe K-edge XANES spectra of the blue pigment in ancient samples. They are compared to XANES spectra of Maya blue samples synthesized under controlled conditions, and iron oxides usually employed as pigments (hematite and goethite). Our results show that the iron found in ancient Maya blue pigment is related to the Fe exchanged in the palygorskite clay. We did not find iron in metallic form or goethite in archaeological Maya blue

Evolution of nanoscale zero-valent iron (nZVI) in water: Microscopic and spectroscopic evidence on the formation of nano- and micro-structured iron oxides

Energy Technology Data Exchange (ETDEWEB)

Liu, Airong, E-mail: liuairong@tongji.edu.cn; Liu, Jing; Han, Jinhao; Zhang, Wei-xian, E-mail: zhangwx@tongji.edu.cn

2017-01-15

Highlights: • A comprehensive study of corrosion products for nZVI under both oxic and anoxic conditions is performed. • Under anoxic conditions, the oxidation products contain a mixture of wustite (FeO), goethite (α-FeOOH) and akaganeite (β-FeOOH). • Under oxic conditions, the final products are mainly crystalline lepidocrocite (γ-FeOOH) with acicular-shaped structures. • Morphological and structural evolution of nZVI under both oxic and anoxic conditions are substantially different. - Abstract: Knowledge on the transformation of nanoscale zero-valent iron (nZVI) in water is essential to predict its surface chemistry including surface charge, colloidal stability and aggregation, reduction and sorption of organic contaminants, heavy metal ions and other pollutants in the environment. In this work, transmission electronic microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy are applied to study the compositional and structural evolution of nZVI under oxic and anoxic conditions. Under anoxic conditions, the core–shell structure of nZVI is well maintained even after 72 h, and the corrosion products usually contain a mixture of wustite (FeO), goethite (α-FeOOH) and akaganeite (β-FeOOH). Under oxic conditions, the core–shell structure quickly collapses to flakes or acicular-shaped structures with crystalline lepidocrocite (γ-FeOOH) as the primary end product. This work provides detailed information and fills an important knowledge gap on the physicochemical characteristics and structural evolution of engineered nanomaterials in the environment.

Sorption and redox reactions of As(III) and As(V) within secondary mineral coatings on aquifer sediment grains.

Science.gov (United States)

Singer, David M; Fox, Patricia M; Guo, Hua; Marcus, Matthew A; Davis, James A

2013-10-15

Important reactive phenomena that affect the transport and fate of many elements occur at the mineral-water interface (MWI), including sorption and redox reactions. Fundamental knowledge of these phenomena are often based on observations of ideal mineral-water systems, for example, studies of molecular scale reactions on single crystal faces or the surfaces of pure mineral powders. Much less is understood about MWI in natural environments, which typically have nanometer to micrometer scale secondary mineral coatings on the surfaces of primary mineral grains. We examined sediment grain coatings from a well-characterized field site to determine the causes of rate limitations for arsenic (As) sorption and redox processes within the coatings. Sediments were obtained from the USGS field research site on Cape Cod, MA, and exposed to synthetic contaminated groundwater solutions. Uptake of As(III) and As(V) into the coatings was studied with a combination of electron microscopy and synchrotron techniques to assess concentration gradients and reactive processes, including electron transfer reactions. Transmission electron microscopy (TEM) and X-ray microprobe (XMP) analyses indicated that As was primarily associated with micrometer- to submicrometer aggregates of Mn-bearing nanoparticulate goethite. As(III) oxidation by this phase was observed but limited by the extent of exposed surface area of the goethite grains to the exterior of the mineral coatings. Secondary mineral coatings are potentially both sinks and sources of contaminants depending on the history of a contaminated site, and may need to be included explicitly in reactive transport models.

Corrosion of non-irradiated UAl{sub x}-Al fuel in the presence of clay pore solution. A quantitative XRD secondary phase analysis applying the DDM method

Energy Technology Data Exchange (ETDEWEB)

Neumann, Andreas [Halle-Wittenberg Univ. (Germany). Dept. of Mineralogy and Geochemistry; RWTH Aachen Univ. (Germany). Inst. of Crystallography; Klinkenberg, Martina; Curtius, Hildegard [Forschungszentrum Juelich GmbH (Germany). Inst. of Energy and Climate Research, IEK-6 Nuclear Waste Management

2017-04-01

Corrosion experiments with non-irradiated metallic UAl{sub x}-Al research reactor fuel elements were carried out in autoclaves to identify and quantify the corrosion products. Such compounds, considering the long-term safety assessment of final repositories, can interact with the released inventory and this constitutes a sink for radionuclide migration in formation waters. Therefore, the metallic fuel sample was subjected to clay pore solution to investigate its process of disintegration by analyzing the resulting products and the remnants, i.e. the secondary phases. Due to the fast corrosion rate a full sample disintegration was observed within the experimental period of 1 year at 90 C. The obtained solids were subdivided into different grain size fractions and prepared for analysis. The elemental analysis of the suspension showed that, uranium and aluminum are concentrated in the solids, whereas iron was mainly dissolved. Non-ambient X-ray diffraction (XRD) combined with the derivative difference minimization (DDM) method was applied for the qualitative and quantitative phase analysis (QPA) of the secondary phases. Gypsum and hemihydrate (bassanite), residues of non-corroded nuclear fuel, hematite, and goethite were identified. The quantitative phase analysis showed that goethite is the major crystalline phase. The amorphous content exceeded 80 wt% and hosted the uranium. All other compounds were present to a minor content. The obtained results by XRD were well supported by complementary scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis.

Sorption of organic chemicals at biogeochemical interfaces - calorimetric measurements

Science.gov (United States)

Krüger, J.; Lang, F.; Siemens, J.; Kaupenjohann, M.

2009-04-01

Biogeochemical interfaces in soil act as sorbents for organic chemicals, thereby controlling the degradation and mobility of these substances in terrestrial environments. Physicochemical properties of the organic chemicals and the sorbent determine sorptive interactions. We hypothesize that the sorption of hydrophobic organic chemicals ("R-determined" chemicals) is an entropy-driven partitioning process between the bulk aqueous phase and biogeochemical interface and that the attachment of more polar organic chemicals ("F-determined" chemicals) to mineral surfaces is due to electrostatic interactions and ligand exchange involving functional groups. In order to determine thermodynamic parameters of sorbate/sorbent interactions calorimetric titration experiments have been conducted at 20˚ C using a Nanocalorimeter (TAM III, Thermometric). Solutions of different organic substances ("R-determined" chemicals: phenanthrene, bisphenol A, "F-determined" chemicals: MCPA, bentazone) with concentrations of 100 mol l-1 were added to suspensions of pure minerals (goethite, muscovite, and kaolinite and to polygalacturonic acid (PGA) as model substance for biofilms in soil. Specific surface, porosity, N and C content, particle size and point of zero charge of the mineral were analyzed to characterize the sorbents. The obtained heat quantities for the initial injection of the organic chemicals to the goethite were 55 and 71 J for bisphenol A and phenanthrene ("R-determined representatives") and 92 and 105 J for MCPA and bentazone ("F-determined" representatives). Further experiments with muscovite, kaolinite and PGA are in progress to determine G and H of the adsorption process.

Studies of mineralogy and geochemistry of Rare Earth Elements in permo-Triassic Bauxite deposit, Northeast of Bukan, North West of Iran

International Nuclear Information System (INIS)

Abedini, A.; Calagari, A. A.; Hadjalilu, B.; Jahangiri, A.

2008-01-01

Bauxite deposit of Permo-Triassic age in northeast of Bukan was developed stratiformly along the boundary between Ruteh and Elika formations, and includes four distinct rock units. This deposit was affected by tectonic and morphological processes. Mineralogical and geochemical investigations showed that during weathering processes, two mechanisms of ferrugenization and deferrugenization played crucial role in formation of minerals such as Diaspora, boehmite, hematite, goethite, kaolinite, pyrophyllite, clinochlore, illite, montmorillonite, anatase, rutile, albite, sanidine, quartz, and calcite in this deposit. By taking notice of field evidence and of mineralogical and geochemical data, the basalts (whose remnants are still present along the contact of this deposit with carbonate bedrock) are the potential parent rock of this deposit. The distribution pattern of rare earth elements (normalized to chondrite and basaltic parent rock) along with anomaly variations of Eu, Ce, and (La/Yb) N indicates differentiation of LREEs from HREEs during bauxitization processes. Further geochemical considerations indicate that the concentrations of LREEs were occurred by hematite, goethite, manganese oxides, cerianite, and secondary phosphates (rhabdophane, vitusite, gorceixite, monazite) and of HREEs by clay minerals; rutile, anatase, zircon, euxenite, and fergusonite. Incorporation of the results obtained from mineralogical and geochemical investigations suggests that in addition to factors such as p H of weathering solutions, ionic potential, composition of the parent rock, and fixation by residual minerals, adsorption processes also played crucial role in enrichment of rare earth elements during moderate to intense lateritization in the study area

Magnetic enhancement and softening of fault gouges during seismic slip: Laboratory observation and implications

Science.gov (United States)

Yang, T.; Chen, J.; Dekkers, M. J.

2017-12-01

Anomalous rock magnetic properties have been reported in slip zones of many previous earthquakes (e.g., the 1995 Kobe earthquake, Japan; the 1999 Chi-Chi earthquake, Taiwan, and the 2008 Wenchuan earthquake, China). However, it is unclear whether short-duration frictional heating can actually induce such rock magnetic anomalies in fault zones; identification of this process in natural fault zones is not that straightforward. A promising approach to solve this problem is to conduct high-velocity friction (HVF) experiments that reproduce seismic fault movements and frictional heating in a simulated fault zone. Afterwards natural fault zones can be analyzed with renewed insight. Our HVF experiments on fault gouges that are simulating large amounts of earthquake slip, show significant magnetic enhancement and softening of sheared gouges. Mineral magnetic measurements reveal that magnetite was formed due to thermal decomposition of smectite during the HVF experiment on the paramagnetic fault gouge. Also, goethite was transformed to intermediate magnetite during the HVF experiment on the goethite-bearing fault gouge. Magnetic susceptibility, saturation remanence and saturation magnetization of sheared samples are linearly increasing with and strongly depend on the temperature rise induced by frictional heating; in contrast, coecivities are decreasing with increasing temperature. Thus, frictional heating can induce thermal decomposition/transformation during short-duration, high-velocity seismic slip, leading to magnetic enhancement and softening of a slip zone. Mineral magnetic methods are suited for diagnosing earthquake slip and estimating the temperature rise of co-seismic frictional heating.

Adsorption and co-adsorption of graphene oxide and Ni(II) on iron oxides: A spectroscopic and microscopic investigation.

Science.gov (United States)

Sheng, Guodong; Huang, Chengcai; Chen, Guohe; Sheng, Jiang; Ren, Xuemei; Hu, Baowei; Ma, Jingyuan; Wang, Xiangke; Huang, Yuying; Alsaedi, Ahmed; Hayat, Tasawar

2018-02-01

Graphene oxide (GO) may strongly interact with toxic metal ions and mineral particles upon release into the soil environment. We evaluated the mutual effects between GO and Ni (Ni(II)) with regard to their adsorption and co-adsorption on two minerals (goethite and hematite) in aqueous phase. Results indicated that GO and Ni could mutually facilitate the adsorption of each other on both goethite and hematite over a wide pH range. Addition of Ni promoted GO co-adsorption mainly due to the increased positive charge of minerals and cation-π interactions, while the presence of GO enhanced Ni co-adsorption predominantly due to neutralization of positive charge and strong interaction with oxygen-containing functional groups on adsorbed GO. Increasing adsorption of GO and Ni on minerals as they coexist may thus reduce their mobility in soil. Extended X-ray absorption fine structure (EXAFS) spectroscopy data revealed that GO altered the microstructure of Ni on minerals, i.e., Ni formed edge-sharing surface species (at R Ni-Fe ∼3.2 Å) without GO, while a GO-bridging ternary surface complexes (at R Ni-C ∼2.49 Å and R Ni-Fe ∼4.23 Å) was formed with GO. These findings improved the understanding of potential fate and toxicity of GO as well as the partitioning processes of Ni ions in aquatic and soil environments. Copyright © 2017 Elsevier Ltd. All rights reserved.

Synthesis of Minerals with Iron Oxide and Hydroxide Contents as a Sorption Medium to Remove Arsenic from Water for Human Consumption

OpenAIRE

Garrido-Hoyos, Sofia; Romero-Velazquez, Lourdes

2015-01-01

Arsenic has been classified as a toxic and carcinogenic chemical element. It therefore presents a serious environmental problem in different regions of the country and the world. In the present work, two adsorbent media were developed and evaluated to remove arsenic from water in the Pájaro Verde mine shaft, Huautla, Tlaquiltenango, Morelos. The media were synthesized and characterized, obtaining a surface area of 43.04 m2·g−1 for the goethite and 2.44 m2·g−1 for silica sand coated with Fe(II...

SON68 glass alteration enhanced by magnetite

Energy Technology Data Exchange (ETDEWEB)

Godon, Nicole; Gin, Stephane; Rebiscoul, Diane; Frugier, Pierre [CEA, DEN-Marcoule, F30207, Bagnols-sur-Ceze (France)

2013-07-01

This paper reports experimental and modeling results of SON68 glass / magnetite interactions while in contact with synthetic groundwater from a clay environment. It is shown that magnetite enhances glass alteration, first by the sorption of Si released from the glass onto magnetite surfaces, then by a second process that could be the precipitation of an iron silicate mineral or the transformation of magnetite into a more reactive phase like hematite or goethite. This study globally suggests a detrimental effect of magnetite on the long-term durability of nuclear glass in geological disposal conditions. (authors)

The assessment of pellicular anion-exchange resins for the determination of anions by ion chromatography

International Nuclear Information System (INIS)

Pohlandt, C.

1981-01-01

Because pellicular anion-exchange resins suitable for the determination, by ion chromatography, of anions with alkaline eluents were unavailable in South Africa at the inception of this work, an attempt was made to prepare such resins. In this study it is shown that the pellicular resins produced are more efficient than the surface-aminated resins used previously. The simultaneous separation and determination of five common anions is demonstrated. The method was applied to the analysis of uranium leach liquors, effluent samples, and a solid sample of ferric oxide (goethite)

Phurcalite: a rare secondary calcium uranium phosphate mineral from Putholi, Chittaurgarh District, Rajasthan

International Nuclear Information System (INIS)

Singh, Yamuna; Singh, K.D.P.; Bhatt, A.K.

1999-01-01

X-ray powder diffraction data are presented for phurcalite [Ca 2 (UO 2 ) 3 (PO 4 ) 2 (OH) 4 , 4H 2 O], with orthorhombic symmetry, a very rare, yellow coloured, secondary uranium mineral, from Putholi (24 o 57' 45 : 74 o 38' 30). The host rock is quartzite which contains fluoroapatite, pyrite, goethite, hematite, magnetite, chlorite and mica as accessory minerals. Measured cell parameters of the phurcalite are : a = 17.3416 A, b=16.1138 A and c =13.5491 A, with a cell volume of 3786.16 A. (author)

Characterization of the precipitates formed during the denitration of simulated HRLW

International Nuclear Information System (INIS)

Music, S.; Ristic, M.; Popovic, S.

1989-01-01

The denitration of several chemical compositions of simulated highly radioactive liquid waste (HRLW) was performed using formic acid as reducing agent. Precipitates formed during the denitration of simulated HRLW were analyzed using x-ray diffraction and 57 Fe Moessbauer spectroscopy. Goethite and amorphous fractions were the principal phases in these precipitates. It was found that the chemical composition of HRLW and the experimental conditions of denitration had more influence on the crystal formation and the particle size than on the phase composition of the precipitates. (author) 27 refs.; 6 figs.; 6 tabs

A Moessbauer and Electrochemical Characterization of the Corrosion Products Formed from Marine and Marine-Antartic Environments

Energy Technology Data Exchange (ETDEWEB)

Ohanian, M.; Caraballo, R.; Dalchiele, E. A.; Quagliata, E. [Instituto de Ingenieria Quimica, Facultad de Ingenieria (Uruguay)

2003-06-15

Corrosion products formed on low alloy steel under two marine environments are characterised. Both environments are classified as C4 according to the ISO 9223 Standard. The corrosion products are identified and their relative proportion is determined by Moessbauer spectroscopy (transmission geometry). Free potentials of corrosion are measured to evaluate the activity of their surfaces. Structural characterisation by XRD were performed on selected samples. It is concluded that the principal phases are goethite, lepidocrocite, ferrihidrite and maghemite. The relative amount of each of them changes with time and with the atmospheric dynamics of each environment.

A Moessbauer and Electrochemical Characterization of the Corrosion Products Formed from Marine and Marine-Antartic Environments

International Nuclear Information System (INIS)

Ohanian, M.; Caraballo, R.; Dalchiele, E. A.; Quagliata, E.

2003-01-01

Corrosion products formed on low alloy steel under two marine environments are characterised. Both environments are classified as C4 according to the ISO 9223 Standard. The corrosion products are identified and their relative proportion is determined by Moessbauer spectroscopy (transmission geometry). Free potentials of corrosion are measured to evaluate the activity of their surfaces. Structural characterisation by XRD were performed on selected samples. It is concluded that the principal phases are goethite, lepidocrocite, ferrihidrite and maghemite. The relative amount of each of them changes with time and with the atmospheric dynamics of each environment.

An 57Fe Mössbauer study of three Australian L5 ordinary-chondrite meteorites: dating Kinclaven–001

International Nuclear Information System (INIS)

Cadogan, J. M.; Rebbouh, L.; Mills, J. V. J.; Bland, P. A.

2013-01-01

Three L5-type ordinary chondrite meteorites recovered from the Nullarbor Region of Western Australia were studied by 57 Fe Mössbauer spectroscopy: Kinclaven–001, Camel Donga–007 and Gunnadorah–002. The relative amounts of the various Fe-bearing phases including the primary minerals (Olivine, Pyroxene, Troilite and Fe-Ni metal) and the ferric alteration products (Goethite, Maghemite/Magnetite) were obtained to determine the percentage of iron converted to Fe 3 +  by weathering processes. These data allow us to estimate the terrestrial age of Kinclaven–001 at 1,700 ± 1,300 yrs

Litology and possibilities of comprehensive using modern alluvium Dnieper

Directory of Open Access Journals (Sweden)

Ivanchenko V. V.

2015-09-01

Full Text Available Studied mineralogy of bottom sediments of the Lower Dnieper. The identified minerals zirconium, rare earths (monazite, titanium, grenades, etc., is finding gold, silver and diamonds. In addition to typical detrital grains tumors installed component authigenic sediment - pyrite, marcasite, carbonates, goethite. The observed constant presence of particles of sludge, slag, refractory, metallurgical graphite, spinel, glass and ore balls - indicators of anthropogenic pollution. Search interest with gold, zircon, ilmenite, rutile, monazite, diamond. When passing extraction can be used light fraction minerals: quartz, kaolinite and other clay minerals and mushlevyy detritus and limestone.

Fe K-edge XANES of Maya blue pigment

Energy Technology Data Exchange (ETDEWEB)

Rio, M. Sanchez del [ESRF, Experiments Division, B.P. 220, F-38043, Grenoble Cedex (France)]. E-mail: srio@esrf.fr; Sodo, A. [ESRF, Experiments Division, B.P. 220, F-38043, Grenoble Cedex (France); Eeckhout, S.G. [ESRF, Experiments Division, B.P. 220, F-38043, Grenoble Cedex (France); Neisius, T. [ESRF, Experiments Division, B.P. 220, F-38043, Grenoble Cedex (France); Martinetto, P. [Laboratoire de Cristallographie, CNRS, Grenoble B.P. 166, F-38042, Grenoble Cedex 09 (France); Dooryhee, E. [Laboratoire de Cristallographie, CNRS, Grenoble B.P. 166, F-38042, Grenoble Cedex 09 (France); Reyes-Valerio, C. [INAH, Mexico DF (Mexico)

2005-08-15

The utilization of techniques used in Materials Science for the characterization of artefacts of interest for cultural heritage is getting more and more attention nowadays. One of the products of the ancient Maya chemistry is the 'Maya blue' pigment, made with natural indigo and palygorskite. This pigment is different from any other pigment used in other parts of the world. It is durable and acid-resistant, and still keeps many secrets to scientists even though it has been studied for more than 50 years. Although the pigment is basically made of palygorskite Si{sub 8}(Mg{sub 2}Al{sub 2})O{sub 20}(OH){sub 2}(OH{sub 2}){sub 4}.4H{sub 2}O and an organic colourant (indigo: C{sub 16}H{sub 10}N{sub 2}O{sub 2}), a number of other compounds have been found in previous studies on archaeological samples, like other clays and minerals, iron nanoparticles, iron oxides, impurities of transition metals (Cr, Mn, Ti, V), etc. We measured at the ESRF ID26 beamline the Fe K-edge XANES spectra of the blue pigment in ancient samples. They are compared to XANES spectra of Maya blue samples synthesized under controlled conditions, and iron oxides usually employed as pigments (hematite and goethite). Our results show that the iron found in ancient Maya blue pigment is related to the Fe exchanged in the palygorskite clay. We did not find iron in metallic form or goethite in archaeological Maya blue.

Study of solution speciation, soil retention and soil-plant transfer of zirconium; Etude de la speciation en solution, de la retention dans les sols et du transfert sol-plante du zirconium

Energy Technology Data Exchange (ETDEWEB)

Ferrand, E

2005-12-15

Within the framework of the risks prevention policy of Andra, the radioactive zirconium introduction ({sup 93}Zr and {sup 95}Zr) into the environment could be carried out starting from the nuclear waste whose storage is envisaged in deep geological layers. Thus, the goal of this study was to evaluate the parameters and phenomena influencing speciation (various chemical forms) and the soil-plant transfer of zirconium. Experiments of adsorption/desorption of zirconium with different ligands likely to be present in soils (goethite and humic acid) and with two soils, with contrasted characteristics, close to the underground research laboratory of Andra (Meuse) were carried out. These results of adsorption were then confronted with those obtained by the MUSIC and NICA-DONNAN models carried out using the computer code ECOSAT. Zr presents a strong affinity for the two types of soils and the soils constituents. Specific interactions of internal sphere type with the goethite were highlighted using the model. Soil-solution partition coefficients, or K{sub d}, values increase with pH and contact time. Various types of edible plants, pea (Pisum sativum L.) and tomato (Lycopersicon esculentum L cv. St Pierre) were cultivated in hydroponic conditions and in soils spiked with various sources of Zirconium. The maximum zirconium contents are mainly measured in the roots of the plants. The soil-plant transfer factors measured during these experiments show a weak bioavailability of zirconium. An influence of speciation on Zr bioavailability is however highlighted. Some chemical forms, such as oxychloride or acetate, are more easily mobilized than others by the plant. (author)

Study of solution speciation, soil retention and soil-plant transfer of zirconium

International Nuclear Information System (INIS)

Ferrand, E.

2005-12-01

Within the framework of the risks prevention policy of Andra, the radioactive zirconium introduction ( 93 Zr and 95 Zr) into the environment could be carried out starting from the nuclear waste whose storage is envisaged in deep geological layers. Thus, the goal of this study was to evaluate the parameters and phenomena influencing speciation (various chemical forms) and the soil-plant transfer of zirconium. Experiments of adsorption/desorption of zirconium with different ligands likely to be present in soils (goethite and humic acid) and with two soils, with contrasted characteristics, close to the underground research laboratory of Andra (Meuse) were carried out. These results of adsorption were then confronted with those obtained by the MUSIC and NICA-DONNAN models carried out using the computer code ECOSAT. Zr presents a strong affinity for the two types of soils and the soils constituents. Specific interactions of internal sphere type with the goethite were highlighted using the model. Soil-solution partition coefficients, or K d , values increase with pH and contact time. Various types of edible plants, pea (Pisum sativum L.) and tomato (Lycopersicon esculentum L cv. St Pierre) were cultivated in hydroponic conditions and in soils spiked with various sources of Zirconium. The maximum zirconium contents are mainly measured in the roots of the plants. The soil-plant transfer factors measured during these experiments show a weak bioavailability of zirconium. An influence of speciation on Zr bioavailability is however highlighted. Some chemical forms, such as oxychloride or acetate, are more easily mobilized than others by the plant. (author)

Concentrations of inorganic arsenic in groundwater, agricultural soils and subsurface sediments from the middle Gangetic plain of Bihar, India.

Science.gov (United States)

Kumar, Manoj; Ramanathan, A L; Rahman, Mohammad Mahmudur; Naidu, Ravi

2016-12-15

Concentrations of inorganic forms [arsenite, As(III) and arsenate, As(V) of arsenic (As) present in groundwater, agricultural soils and subsurface sediments located in the middle Gangetic plain of Bihar, India were determined. Approximately 73% of the groundwater samples (n=19) show As(III) as the dominant species while 27% reveals As(V) was the dominant species. The concentration of As(III) in agricultural soil samples varies from not detectable to 40μg/kg and As(V) was observed as the major species (ranging from 1050 to 6835μg/kg) while the total As concentration varied from 3528 to 14,690μg/kg. Total extracted concentration of As was higher in the subsurface sediments (range 9119-20,056μg/kg in Methrapur and 4788-19,681μg/kg in Harail Chapar) than the agricultural soil, indicating the subsurface sediment as a source of As. Results of X-ray diffraction (XRD) and environmental scanning electron microscope (ESEM) revealed the presence of hematite and goethite throughout the vertical section below while magnetite was observed only in the upper oxidized layer at Methrapur and Harail Chapar. Alteration of Fe-oxides and presence of fibrous goethite indicating presence of diagenetic sediment. Siderite plays a crucial role as sinks to the As in subsurface sediments. The study also concluded that decomposition of organic matter present in dark and grey sections promote the redox conditions and trigger mobilization of As into groundwater. Copyright © 2016 Elsevier B.V. All rights reserved.

Synthesis and properties of iridium-doped hematite ({alpha}-Fe{sub 2}O{sub 3})

Energy Technology Data Exchange (ETDEWEB)

Krehula, Stjepko, E-mail: krehul@irb.hr [Division of Materials Chemistry, Ruder Boskovic Institute, P.O. Box 180, HR-10002 Zagreb (Croatia); Stefanic, Goran [Division of Materials Chemistry, Ruder Boskovic Institute, P.O. Box 180, HR-10002 Zagreb (Croatia); Zadro, Kreso [Department of Physics, Faculty of Science, University of Zagreb, Bijenicka 32, 10000 Zagreb (Croatia); Kratofil Krehula, Ljerka [Faculty of Chemical Engineering and Technology, University of Zagreb, Marulicev trg 19, 10000 Zagreb (Croatia); Marcius, Marijan; Music, Svetozar [Division of Materials Chemistry, Ruder Boskovic Institute, P.O. Box 180, HR-10002 Zagreb (Croatia)

2012-12-25

Highlights: Black-Right-Pointing-Pointer Ir-doped hematites were prepared by heating Ir-doped goethites. Black-Right-Pointing-Pointer Ir-doping in hematite led to an increase in unit cell and a decrease in crystallite size. Black-Right-Pointing-Pointer Ir-doping significantly affected magnetic, infrared and UV-Vis properties of hematite. Black-Right-Pointing-Pointer The Morin transition temperature increased with an increase in Ir-doping. Black-Right-Pointing-Pointer Ir ions brought about changes in the size and shape of the formed hematite particles. - Abstract: The effect of the incorporation of Ir{sup 3+} ions on the properties of {alpha}-Fe{sub 2}O{sub 3} formed by dehydroxylation of {alpha}-FeOOH was investigated using X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), {sup 57}Fe Moessbauer, UV-Vis-NIR and FT-IR spectroscopies, SQUID magnetometer, field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS). Pure and Ir-doped hematite samples were obtained by heating of pure and Ir-doped goethites ({alpha}-FeOOH) formed by precipitation from mixed Fe(III)-Ir(III) chloride solutions in a highly alkaline medium. The incorporation of Ir{sup 3+} ions into the {alpha}-Fe{sub 2}O{sub 3} structure led to changes in unit-cell dimensions, crystallinity, particle size and shape, as well as changes in the magnetic, infrared and UV-Vis properties. An increase in the temperature of the Morin transition with an increase in Ir-doping was observed by Moessbauer spectroscopy and magnetic measurements.

Inhibitory Effect of Dissolved Silica on the H2O2 Decomposition by Iron(III) and Manganese(IV) Oxides: Implications for H2O2-based In Situ Chemical Oxidation

Science.gov (United States)

Pham, Anh Le-Tuan; Doyle, Fiona M.; Sedlak, David L.

2011-01-01

The decomposition of H2O2 on iron minerals can generate •OH, a strong oxidant that can transform a wide range of contaminants. This reaction is critical to In Situ Chemical Oxidation (ISCO) processes used for soil and groundwater remediation, as well as advanced oxidation processes employed in waste treatment systems. The presence of dissolved silica at concentrations comparable to those encountered in natural waters decreases the reactivity of iron minerals toward H2O2, because silica adsorbs onto the surface of iron minerals and alters catalytic sites. At circumneutral pH values, goethite, amorphous iron oxide, hematite, iron-coated sand and montmorillonite that were pre-equilibrated with 0.05 – 1.5 mM SiO2 were significantly less reactive toward H2O2 decomposition than their original counterparts, with the H2O2 loss rates inversely proportional to the SiO2 concentration. In the goethite/H2O2 system, the overall •OH yield, defined as the percentage of decomposed H2O2 producing •OH, was almost halved in the presence of 1.5 mM SiO2. Dissolved SiO2 also slows the H2O2 decomposition on manganese(IV) oxide. The presence of dissolved SiO2 results in greater persistence of H2O2 in groundwater, lower H2O2 utilization efficiency and should be considered in the design of H2O2-based treatment systems. PMID:22129132

The fate of arsenic adsorbed on iron oxides in the presence of arsenite-oxidizing bacteria.

Science.gov (United States)

Zhang, Zhennan; Yin, Naiyi; Du, Huili; Cai, Xiaolin; Cui, Yanshan

2016-05-01

Arsenic (As) is a redox-active metalloid whose toxicity and mobility in soil depend on its oxidation state. Arsenite [As(III)] can be oxidized by microbes and adsorbed by minerals in the soil. However, the combined effects of these abiotic and biotic processes are not well understood. In this study, the fate of arsenic in the presence of an isolated As(III)-oxidizing bacterium (Pseudomonas sp. HN-1, 10(9) colony-forming units (CFUs)·ml(-1)) and three iron oxides (goethite, hematite, and magnetite at 1.6 g L(-1)) was determined using batch experiments. The total As adsorption by iron oxides was lower with bacteria present and was higher with iron oxides alone. The total As adsorption decreased by 78.6%, 36.0% and 79.7% for goethite, hematite and magnetite, respectively, due to the presence of bacteria. As(III) adsorbed on iron oxides could also be oxidized by Pseudomonas sp. HN-1, but the oxidation rate (1.3 μmol h(-1)) was much slower than the rate in the aqueous phase (96.2 μmol h(-1)). Therefore, the results of other studies with minerals only might overestimate the adsorptive capacity of solids in natural systems; the presence of minerals might hinder As(III) oxidation by microbes. Under aerobic conditions, in the presence of iron oxides and As(III)-oxidizing bacteria, arsenic is adsorbed onto iron oxides within the adsorption capacity, and As(V) is the primary form in the solid and aqueous phases. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of pH on the Structural and Magnetic Properties of Magnetite Nanoparticles Synthesised by Co-Precipitation

International Nuclear Information System (INIS)

Ramadan, W.; Kareem, M.; Hannoyer, B.; Saha, Sh.

2011-01-01

Magnetite, Fe3O4, nanoparticles were synthesized using co-precipitation aqueous method at room temperature and at different pH, from 8 to 12.5. The pH value was found to influence greatly the resulting phases and has no significant effect on the particle size. In all cases, magnetite was found to be the main phase but the contribution of Goethite phase was identified clearly with the increase in pH. Significant reduction in saturation magnetization was evident. Structural and magnetic properties of the nanoparticles were examined using; XRD, TEM, Raman Spectroscopy and SQUID. (author)

Óxidos de ferro e suas aplicações em processos catalíticos: uma revisão

Directory of Open Access Journals (Sweden)

Luiz C. A. Oliveira

2013-01-01

Full Text Available A review of most of the reported studies on the use of iron oxides as catalyst in specific processes, namely Haber-Bosch reaction, Fischer-Tropsch synthesis, Fenton oxidation and photolytic molecular splitting of water to produce gaseous hydrogen, was carried out. An essential overview is thus presented, intending to address the fundamental meaning, as well as the corresponding chemical mechanisms, and perspectives on new technological potentialities of natural and synthetic iron oxides, more specifically hematite (α-Fe2O3, goethite (α-FeOOH, magnetite (Fe3O4 and maghemite (γ-Fe2O3, in heterogeneous catalysis.

Identification of Pigments in Colored Layers of a Painting by Raman Spectroscopy

Science.gov (United States)

Petrova, O. I.; Pankin, D. V.; Povolotckaia, A. V.; Borisov, E. V.; Beznosova, M. O.; Krivul'ko, T. A.; Kurochkin, A. V.

2017-12-01

Using the method of Raman spectroscopy the pigment composition is investigated of, and the brushwork technique used in, the original layer of a 19th century painting is established. It is an overdoor worked, presumably, by Antoine Jean-Etienne Faivre. It is established that the artist used the following pigments: cinnabar and dyes on the basis of goethite and hematite (for red, yellow-orange, and brown shades), ultramarine and Prussian blue (for blue shades), and Emerald green and a mixture of blue and yellow shades (to obtain a green color). It is determined that white lead was used a primer.

Influence of kinetics on the determination of the surface reactivity of oxide suspensions by acid-base titration.

Science.gov (United States)

Duc, M; Adekola, F; Lefèvre, G; Fédoroff, M

2006-11-01

The effect of acid-base titration protocol and speed on pH measurement and surface charge calculation was studied on suspensions of gamma-alumina, hematite, goethite, and silica, whose size and porosity have been well characterized. The titration protocol has an important effect on surface charge calculation as well as on acid-base constants obtained by fitting of the titration curves. Variations of pH versus time after addition of acid or base to the suspension were interpreted as diffusion processes. Resulting apparent diffusion coefficients depend on the nature of the oxide and on its porosity.

Óxidos de ferro e suas aplicações em processos catalíticos: uma revisão Iron oxides and their applications in catalytic processes: a review

Directory of Open Access Journals (Sweden)

Luiz C. A. Oliveira

2013-01-01

Full Text Available A review of most of the reported studies on the use of iron oxides as catalyst in specific processes, namely Haber-Bosch reaction, Fischer-Tropsch synthesis, Fenton oxidation and photolytic molecular splitting of water to produce gaseous hydrogen, was carried out. An essential overview is thus presented, intending to address the fundamental meaning, as well as the corresponding chemical mechanisms, and perspectives on new technological potentialities of natural and synthetic iron oxides, more specifically hematite (α-Fe2O3, goethite (α-FeOOH, magnetite (Fe3O4 and maghemite (γ-Fe2O3, in heterogeneous catalysis.

Moessbauer investigations of itmid

International Nuclear Information System (INIS)

Mrayed, Y.S.; Ellid, M.S.; Fallagh, F.A.

1996-01-01

A sample of itmid available commercially was obtained and investigated using 57 Fe Moessbauer spectroscopy, atomic absorption, X-ray fluorescence. The Moessbauer spectra showed the presence hematite (alpha-Fe 2 O 3 ), goethite (alpha-FeOOH), and a third phase which has a six-line spectrum with the following parameters : Isomer shift (gamma= 0.52 mm/s), magnetic field (H=290 kOe). After conducting a series of reduction and calcination to the itmid sample and with the aid of atomic absorption and X-ray fluorescence results the third phase was identified as the iron sulfide compound FeS. 3 figs., 3 tabs

Development of a reactive force field for iron-oxyhydroxide systems.

Science.gov (United States)

Aryanpour, Masoud; van Duin, Adri C T; Kubicki, James D

2010-06-03

We adopt a classical force field methodology, ReaxFF, which is able to reproduce chemical reactions, and train its parameters for the thermodynamics of iron oxides as well as energetics of a few iron redox reactions. Two parametrizations are developed, and their results are compared with quantum calculations or experimental measurements. In addition to training, two test cases are considered: the lattice parameters of a selected set of iron minerals, and the molecular dynamics simulation of a model for alpha-FeOOH (goethite)-water interaction. Reliability and limitations of the developed force fields in predicting structure and energetics are discussed.

Ecotoxicity testing and environmental risk assessment of iron nanomaterials for sub-surface remediation – Recommendations from the FP7 project NanoRem

DEFF Research Database (Denmark)

Hjorth, Rune; Coutris, Claire; Nguyen, Nhung

2017-01-01

engineered Fe nanomaterials, specifically, Nano-Goethite, Trap-Ox Fe-zeolites, Carbo-Iron® and FerMEG12, developed within the European FP7 project NanoRem for sub-surface remediation towards a test battery consisting of eight ecotoxicity tests on bacteria (V. fisheri, E. coli), algae (P. subcapitata...... milled nZVI (FerMEG12), showed no toxicity in the test battery when tested in concentrations up to 100 mg/L, which is the cutoff for hazard labeling in chemicals regulation in Europe. However it should be noted that Fe nanomaterials proved challenging to test adequately due to their turbidity...

Moessbauer Spectroscopic Study of a Mural Painting from Morgadal Grande, Mexico

International Nuclear Information System (INIS)

Kuno, A.; Matsuo, M.; Soto, A. Pascual; Tsukamoto, K.

2004-01-01

In this study, 57 Fe Moessbauer spectroscopy has been applied to fragments of a mural painting excavated at Morgadal Grande, Mexico, to characterize the pigments used. A sextet attributable to hematite (α-Fe 2 O 3 ) was clearly detected in the red fragments. The spectra of orange fragments showed a doublet attributable to paramagnetic high-spin Fe 3+ , which presumably originates from goethite (α-FeOOH) exhibiting superparamagnetic relaxation due to its small particle size. The blue fragments contained little iron. The scattered X-ray Moessbauer spectra revealed that the thickness of the pigments was larger than 20 μm.

From Desert to Dessert: Why Australian Dust Matters.

Science.gov (United States)

Hunter, K. A.; Mackie, D. S.; Boyd, P. W.; McTainsh, G. H.

2006-12-01

The growth of some types of phytoplankton in several parts of the world ocean, including much of the Southern Ocean, is limited by the supply of iron. Large Australian dust storms uplift, transport and abrade soils, to produce aeolian dust that is a significant source iron to the Southern Ocean. Atmospheric processes that enhance the dissolution of iron from aeolian dusts are of interest and have been studied for material from major dust producing regions like the Sahara, Gobi and Australian deserts; the reported solubility of iron from aeolian dusts ranges from <0.01% to 80%. The characteristic red soils, sands and dusts from Australia are generally believed to consist of quartz grains with a coating of fine grains and crystals of iron oxides, primarily hematite and goethite. The precise mineralogy of soil and dust grain coatings is poorly understood and it also not well known how the coatings are altered during uplift and transport to the ocean. Current models to understand the processes operating during the transport and atmospheric processing of dust include some generalisations and simplifications that are not always warranted and our work has shown the overlooked complexity of the system. Models for aeolian-iron dissolution based on Northern Hemisphere data commonly include the pollutants SOx and NOx. The modern Southern Hemisphere is less polluted and thus resembles past environmental systems. The dissolution of iron from soils of the Saharan, Gobi and Australian deserts in the presence of protons only (i.e. without SOx and NOx) occurs in two phases. The first, faster phase, representing up to 20% of total iron is via a surface-controlled mechanism. The rate determining variable is the exposed surface area of the iron oxides and not the size of the underlying quartz grain. The second, slower, phase of dissolution occurs via the transport-controlled formation of a leached layer. During the simulated aeolian abrasion of Australian soils from dust producing

Dynamics of colloidal systems of magnetic nanoparticles under influence of magnetic fields investigated by XPCS

International Nuclear Information System (INIS)

Schavkan, Alexander

2017-05-01

This thesis investigates structural properties and the underlying microscopic dynamics of suspensions of α-FeOOH goethite platelets in water under the influence of magnetic fields. Goethite particles show unusual physical properties and a rich phase diagram, which makes their suspensions an object of high interest for research in the area of ''smart nanoparticles''. Five nanoparticle concentrations were chosen such that different liquid crystal phases could be studied. The suspensions of platelets of these chosen concentrations were exposed to magnetic fields of varying strength. Small angle X-ray scattering and X-ray photon correlation spectroscopy data were taken and evaluated. The appearing phases and phase transitions were studied as a function of concentration and applied magnetic field. For this purpose, order parameters, ellipticity, radial and azimuthal peak positions and widths of scattering features were investigated to clarify the structural properties in detail. For the analysis of the underlying dynamics, the relaxation rates and the shape of measured time correlation functions were evaluated. The results show that with increasing magnetic field a partial realignment of the platelets occurs. This realignment is connected to the magnetic properties of the particles. The dynamics of the corresponding phases revealed a dependence on the concentration of nanoparticles in the suspension. At a concentration of c=20 vol% the transition from the nematic to the anti-nematic phase traverses a mixed state. The nematic and anti-nematic phases show ballistic motion and very similar properties, even though a realignment of the particles from an orientation with the long axis parallel to the applied magnetic field in the nematic phase to an orientation with the long axis perpendicular to the magnetic field in the anti-nematic phase occurs. The mixed state of 20 vol%-suspension exhibits a diffusive motion of the particles and different characteristics. A significant

Dynamics of colloidal systems of magnetic nanoparticles under influence of magnetic fields investigated by XPCS

Energy Technology Data Exchange (ETDEWEB)

Schavkan, Alexander

2017-05-15

This thesis investigates structural properties and the underlying microscopic dynamics of suspensions of α-FeOOH goethite platelets in water under the influence of magnetic fields. Goethite particles show unusual physical properties and a rich phase diagram, which makes their suspensions an object of high interest for research in the area of ''smart nanoparticles''. Five nanoparticle concentrations were chosen such that different liquid crystal phases could be studied. The suspensions of platelets of these chosen concentrations were exposed to magnetic fields of varying strength. Small angle X-ray scattering and X-ray photon correlation spectroscopy data were taken and evaluated. The appearing phases and phase transitions were studied as a function of concentration and applied magnetic field. For this purpose, order parameters, ellipticity, radial and azimuthal peak positions and widths of scattering features were investigated to clarify the structural properties in detail. For the analysis of the underlying dynamics, the relaxation rates and the shape of measured time correlation functions were evaluated. The results show that with increasing magnetic field a partial realignment of the platelets occurs. This realignment is connected to the magnetic properties of the particles. The dynamics of the corresponding phases revealed a dependence on the concentration of nanoparticles in the suspension. At a concentration of c=20 vol% the transition from the nematic to the anti-nematic phase traverses a mixed state. The nematic and anti-nematic phases show ballistic motion and very similar properties, even though a realignment of the particles from an orientation with the long axis parallel to the applied magnetic field in the nematic phase to an orientation with the long axis perpendicular to the magnetic field in the anti-nematic phase occurs. The mixed state of 20 vol%-suspension exhibits a diffusive motion of the particles and different

Use of airborne multispectral scanner data to map alteration related to roll-front uranium migration

International Nuclear Information System (INIS)

Peters, D.C.

1983-01-01

Computer-enhanced airborne multispectral scanner (MSS) images have been used to detect and map red oxidized alteration related to roll-front uranium migration in the southern Powder River basin, Wyoming. Information in the 0.4- to 1.1-μm spectral region was used to produce a color ratio composite image, upon which the red-altered areas can be differentiated. The red-altered and incipiently altered sandstones result from the migration of a roll-front (or geochemical cell) through the sandstone in the direction of the hydrologic gradient. Most uranium deposits in the Powder River basin occur at the boundary between this oxidized sandstone and reduced sandstone. Therefore, the ability to detect and map this alteration reliably can provide important information about the potential for uranium mineralization down gradient from the altered areas, at the surface in an area of interest. Spectral reflectance studies indicate that a shift in the absorption band edge from 0.52 μm (for goethitic sandstone) to 0.58 μm (for hematitic sandstone) and an intensification of an absorption band at 0.85 μm (for hematitic sandstone) are the bases for identifying the red-altered sandstone as green anomalous areas on the color ratio composite image. Some of the incipiently altered sandstone also appears green, whereas unaltered material and white-altered sandstone appear as blue to cyan colors. Therefore, the composite image is useful in discriminating hematitic sandstone from goethitic sandstone. At high densities (>65%), vegetation masks the sandstones on the color ratio composite image. Artemisia tridentata (sage) and Stipa comata (grass) are the species that have the greatest individual effect on the image

Red and yellow ochres from the archaeological site Pedra do Cantagalo I, in Piripiri, Piauí, Brazil

Energy Technology Data Exchange (ETDEWEB)

Duarte Cavalcante, Luis Carlos, E-mail: cavalcanteufpi@yahoo.com.br; Sousa Bezerra da Silva, Heralda Kelis [Federal University of Piauí (UFPI), Center of Natural Sciences (Brazil); Fabris, José Domingos [Federal University of Minas Gerais (UFMG), Department of Chemistry – ICEx (Brazil); Ardisson, José Domingos [Center for the Development of the Nuclear Technology (CDTN) (Brazil)

2017-11-15

The archaeological site Pedra do Cantagalo I is a sandstone shelter displaying rupestrian inscriptions. It is located in the rural area of the municipality of Piripiri, in the northern region of the Piauí state, Brazil. The site was found as being originally decorated with more than 1,900 prehistoric rupestrian paintings, along with engravings, lithics, ceramic fragments and mineral pigments forming reddish and yellowish ochres. Materials of these ochres, collected from recent excavations in this archaeological site, were analyzed by energy dispersive X-ray fluorescence (EDXRF); backscattering and transmission {sup 57}Fe-Mössbauer spectroscopy at 298 K and 25 K and powder X-ray diffraction (XRD), in an effort to assess the chemical and mineralogical characteristics of these sources of pigments that composed the ancient paint materials of the site. The iron contents (expressed as Fe {sub 2}O{sub 3}) for the reddish ochres were found to range from ∼60 to ∼68 mass%; for the yellowish ochres the corresponding content was ∼34 mass%, as determined by EDXRF. From the Mössbauer spectra for these red ochre samples, hematite (αFe {sub 2}O{sub 3}) or a mixture of hematite and goethite (αFeOOH) were identified. Actually, the spectra at room temperature for the yellow ochres are rather complex, as it is usual for most soil clay materials. At least part of the intense central doublet was assumed to be from superparamagnetic iron oxides in very small particles. The Mössbauer patterns at 25 K allowed confirming this assumption, as the superparamagnetic relaxation effects were virtually suppressed; the spectral contributions due to goethite could be thus more easily separated.

Batch and column studies of adsorption of Li, Ni and Br by a reference sand for contaminant transport experiments

International Nuclear Information System (INIS)

Seigel, M.D.; Ward, D.B.; Bryan, C.R.

1995-09-01

A processed quartz sand (Wedron 510), mined from the St. Peter sandstone, has been characterized by a variety of chemical and physical methods for use as a reference porous media in transport model validation experiments. Wedron 510 sand was used in an intermediate-scale experiment involving migration of Ni, Li and Br through a 6-m high x 3-m diameter caisson. Ni and Li adsorption/desorption, and Li/Ni site-competition experiments yielded information on the importance of the trace mineral phases to adsorption of Li and Ni by the sand. The presence of an iron hydroxide coating similar to goethite on the sand grains is suggested by visual observation and leaching experiments. Kaolinite was identified by SEM and XRD as a significant trace mineral phase in the sand and occurs as small particles coating the sand grains. Quartz, the predominant constituent of the sand by weight, does not appear to contribute significantly to the adsorption properties of the sand. Qualitatively, the adsorption properties of the sand can be adequately modeled as a two-mineral system (goethite and kaolinite). The studies described in this report should provide a basis for understanding transport of Ni, Li and Br through porous media similar to the reference sand. Techniques were developed for obtaining parameter values for surface complexation and kinetic adsorption models for the sand and its mineral components. These constants can be used directly in coupled hydrogeochemical transport codes. The techniques should be useful for characterization of other natural materials and elements in high-level nuclear waste in support of coupled hydrogeochemical transport calculations for Yucca Mountain

Red and yellow ochres from the archaeological site Pedra do Cantagalo I, in Piripiri, Piauí, Brazil

Science.gov (United States)

Duarte Cavalcante, Luis Carlos; da Silva, Heralda Kelis Sousa Bezerra; Fabris, José Domingos; Ardisson, José Domingos

2017-11-01

The archaeological site Pedra do Cantagalo I is a sandstone shelter displaying rupestrian inscriptions. It is located in the rural area of the municipality of Piripiri, in the northern region of the Piauí state, Brazil. The site was found as being originally decorated with more than 1,900 prehistoric rupestrian paintings, along with engravings, lithics, ceramic fragments and mineral pigments forming reddish and yellowish ochres. Materials of these ochres, collected from recent excavations in this archaeological site, were analyzed by energy dispersive X-ray fluorescence (EDXRF); backscattering and transmission 57Fe-Mössbauer spectroscopy at 298 K and 25 K and powder X-ray diffraction (XRD), in an effort to assess the chemical and mineralogical characteristics of these sources of pigments that composed the ancient paint materials of the site. The iron contents (expressed as Fe 2 O 3) for the reddish ochres were found to range from ˜60 to ˜68 mass%; for the yellowish ochres the corresponding content was ˜34 mass%, as determined by EDXRF. From the Mössbauer spectra for these red ochre samples, hematite ( αFe 2 O 3) or a mixture of hematite and goethite ( αFeOOH) were identified. Actually, the spectra at room temperature for the yellow ochres are rather complex, as it is usual for most soil clay materials. At least part of the intense central doublet was assumed to be from superparamagnetic iron oxides in very small particles. The Mössbauer patterns at 25 K allowed confirming this assumption, as the superparamagnetic relaxation effects were virtually suppressed; the spectral contributions due to goethite could be thus more easily separated.

Fe atom exchange between aqueous Fe2+ and magnetite.

Science.gov (United States)

Gorski, Christopher A; Handler, Robert M; Beard, Brian L; Pasakarnis, Timothy; Johnson, Clark M; Scherer, Michelle M

2012-11-20

The reaction between magnetite and aqueous Fe(2+) has been extensively studied due to its role in contaminant reduction, trace-metal sequestration, and microbial respiration. Previous work has demonstrated that the reaction of Fe(2+) with magnetite (Fe(3)O(4)) results in the structural incorporation of Fe(2+) and an increase in the bulk Fe(2+) content of magnetite. It is unclear, however, whether significant Fe atom exchange occurs between magnetite and aqueous Fe(2+), as has been observed for other Fe oxides. Here, we measured the extent of Fe atom exchange between aqueous Fe(2+) and magnetite by reacting isotopically "normal" magnetite with (57)Fe-enriched aqueous Fe(2+). The extent of Fe atom exchange between magnetite and aqueous Fe(2+) was significant (54-71%), and went well beyond the amount of Fe atoms found at the near surface. Mössbauer spectroscopy of magnetite reacted with (56)Fe(2+) indicate that no preferential exchange of octahedral or tetrahedral sites occurred. Exchange experiments conducted with Co-ferrite (Co(2+)Fe(2)(3+)O(4)) showed little impact of Co substitution on the rate or extent of atom exchange. Bulk electron conduction, as previously invoked to explain Fe atom exchange in goethite, is a possible mechanism, but if it is occurring, conduction does not appear to be the rate-limiting step. The lack of significant impact of Co substitution on the kinetics of Fe atom exchange, and the relatively high diffusion coefficients reported for magnetite suggest that for magnetite, unlike goethite, Fe atom diffusion is a plausible mechanism to explain the rapid rates of Fe atom exchange in magnetite.

Metal ion binding to iron oxides

Science.gov (United States)

Ponthieu, M.; Juillot, F.; Hiemstra, T.; van Riemsdijk, W. H.; Benedetti, M. F.

2006-06-01

The biogeochemistry of trace elements (TE) is largely dependent upon their interaction with heterogeneous ligands including metal oxides and hydrous oxides of iron. The modeling of TE interactions with iron oxides has been pursued using a variety of chemical models. The objective of this work is to show that it is possible to model the adsorption of protons and TE on a crystallized oxide (i.e., goethite) and on an amorphous oxide (HFO) in an identical way. Here, we use the CD-MUSIC approach in combination with valuable and reliable surface spectroscopy information about the nature of surface complexes of the TE. The other objective of this work is to obtain generic parameters to describe the binding of the following elements (Cd, Co, Cu, Ni, Pb, and Zn) onto both iron oxides for the CD-MUSIC approach. The results show that a consistent description of proton and metal ion binding is possible for goethite and HFO with the same set of model parameters. In general a good prediction of almost all the collected experimental data sets corresponding to metal ion binding to HFO is obtained. Moreover, dominant surface species are in agreement with the recently published surface complexes derived from X-ray absorption spectroscopy (XAS) data. Until more detailed information on the structure of the two iron oxides is available, the present option seems a reasonable approximation and can be used to describe complex geochemical systems. To improve our understanding and modeling of multi-component systems we need more data obtained at much lower metal ion to iron oxide ratios in order to be able to account eventually for sites that are not always characterized in spectroscopic studies.

Fe-Ni-bearing serpentines from the saprolite horizon of Caribbean Ni-laterite deposits: new insights from thermodynamic calculations

Science.gov (United States)

Villanova-de-Benavent, Cristina; Domènech, Cristina; Tauler, Esperança; Galí, Salvador; Tassara, Santiago; Proenza, Joaquín A.

2017-10-01

Fe-Ni-bearing serpentine from the saprolite horizon is the main Ni ores in hydrous silicate-type Ni laterites and formed by chemical weathering of partially serpentinized ultramafic rocks under tropical conditions. During lateritization, Mg, Si, and Ni are leached from the surface and transported downwards. Fe2+ is oxidized to Fe3+ and fixed as insoluble Fe-oxyhydroxides (mostly goethite) that incorporate Ni. This Ni is later leached from goethite and incorporated in secondary serpentine and garnierite. As a result, a serpentine-dominated saprolite horizon forms over the ultramafic protolith, overlapped by a Fe-oxyhydroxide-dominated limonite horizon. The serpentine from the protolith (serpentine I) is of hydrothermal origin and yields similar Ni (0.10-0.62 wt.% NiO) and lower Fe (mostly 1.37-5.81 wt.% FeO) concentrations than the primary olivine. In contrast, Fe-Ni-bearing serpentine from the saprolite (serpentine II) shows significantly higher and variable Fe and Ni contents, typically ranging from 2.23 to 15.59 wt.% Fe2O3 and from 1.30 to 7.67 wt.% NiO, suggesting that serpentine get enriched in Fe and Ni under supergene conditions. This study presents detailed mineralogical, textural, and chemical data on this serpentine II, as well as new insights by thermodynamic calculations assuming ideal solution between Fe-, Ni- and Mg-pure serpentines. The aim is to assess if at atmospheric pressure and temperature Fe-Ni-bearing serpentine can be formed by precipitation. Results indicate that the formation of serpentine II under atmospheric pressure and temperature is thermodynamically supported, and pH, Eh, and the equilibrium constant of the reaction are the parameters that affect the results more significantly.

Recovery of iron oxides from acid mine drainage and their application as adsorbent or catalyst.

Science.gov (United States)

Flores, Rubia Gomes; Andersen, Silvia Layara Floriani; Maia, Leonardo Kenji Komay; José, Humberto Jorge; Moreira, Regina de Fatima Peralta Muniz

2012-11-30

Iron oxide particles recovered from acid mine drainage represent a potential low-cost feedstock to replace reagent-grade chemicals in the production of goethite, ferrihydrite or magnetite with relatively high purity. Also, the properties of iron oxides recovered from acid mine drainage mean that they can be exploited as catalysts and/or adsorbents to remove azo dyes from aqueous solutions. The main aim of this study was to recover iron oxides with relatively high purity from acid mine drainage to act as a catalyst in the oxidation of dye through a Fenton-like mechanism or as an adsorbent to remove dyes from an aqueous solution. Iron oxides (goethite) were recovered from acid mine drainage through a sequential precipitation method. Thermal treatment at temperatures higher than 300 °C produces hematite through a decrease in the BET area and an increase in the point of zero charge. In the absence of hydrogen peroxide, the solids adsorbed the textile dye Procion Red H-E7B according to the Langmuir model, and the maximum amount adsorbed decreased as the temperature of the thermal treatment increased. The decomposition kinetics of hydrogen peroxide is dependent on the H(2)O(2) concentration and iron oxides dosage, but the second-order rate constant normalized to the BET surface area is similar to that for different iron oxides tested in this and others studies. These results indicate that acid mine drainage could be used as a source material for the production of iron oxide catalysts/adsorbents, with comparable quality to those produced using analytical-grade reagents. Copyright © 2012 Elsevier Ltd. All rights reserved.

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...

Mineralogy and fluid inclusion studies in kalchoye Copper- gold deposit, East of Esfahan

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Rezvan Mehvary

2009-09-01

Full Text Available Kalchoye Copper-gold deposit is located about 110 kilometers east of Esfahan province and within the Eocene volcano sedimentary rocks. Sandy tuff and andesite lava are important members of this complex.The form of mineralization in area is vein and veinlet and quartz as the main gangue phase. The main ore minerals are chalcopyrite, chalcocite, galena and weathered minerals such as goethite, iron oxides, malachite and azurite. Studies in area indicate that ore mineralization Kalchoye is low sulfide, quartz type of hydrothermal ore deposits and results of thermometry studies on quartz minerals low- medium fluid with low potential mineralization is responsible for mineralization in this area.

Moessbauer studies on some Argentinian soil: mollisols from Bahia Blanca

International Nuclear Information System (INIS)

Saragovi, C.; Venegas, R.

1994-01-01

Clay fractions of a Mollisol sample as is, treated with ammonium oxalate (AO), with dithionite-citrate-bicarbonate (DCB) and with dithionite-ethilene-diamine- tetraacetic acid (D-EDTA) methods, were studied. Illite-montmorillonites together with hematites, goethites and maghemites, all of the Al-substituted and with a wide range of sizes, were identified. It is found that the AO attack extracts little iron, whereas the other two attacks extract the magnetic signal. Furthermore, the DCB attack facilitates the reduction of the Fe 3+ ions, while the D-EDTA method does not. Instead, this attack extracts more clay mineral Fe ions. A comparison with large grain soil samples is made. (orig.)

Materials to be used for radionuclide transport experiments (milestones SPL3A1M4)

International Nuclear Information System (INIS)

Viani, B.

1998-02-01

Experiments to determine the effect of canister corrosion products on the transport of radionuclides will be undertaken using the FE(III) oxides goethite and hematite as proxies for the expected corrosion envelope that will form as a result of alteration of the corrosion allowance overpack prior to the breaching of the waste container. Samples of ESF invert concrete that have been crushed, or left intact but fractured, and that have been subjected to hydrothermal alteration will be used to determine the effect of cementitious materials on transport of radionuclides. A mixture of CaCO 3 , Si0 2 , and aggregate will be used as a proxy for completely carbonated concrete

Pigmentos de pinturas rupestres pré-históricas do sítio Letreiro do Quinto, Pedro II, Piauí, Brasil

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Tetisuelma Leal Alves

2011-01-01

Full Text Available The Letreiro do Quinto rock shelter is located in the rural area of the city of Pedro II, Piauí, Brazil. The sandstone walls of the shelter are covered with prehistoric rupestrian paintings, painted in patterns of yellow and light and dark red hues. The chemical-mineralogical characterization of the prehistoric pigments was made with energy dispersive spectroscopy, scanning electron microscopy, energy dispersive X-ray fluorescence and 57Fe transmission Mössbauer spectroscopy at 110 K. Results confirm the occurrence of hematite- and goethite-rich ochres and also that the pigment layers are indeed made of a mixture of clay minerals mixed with iron oxides.

Analysis of traditional Tibetan pills

Science.gov (United States)

Cesnek, Martin; Štefánik, Milan; Miglierini, Marcel; Kmječ, Tomáš; Sklenka, L'ubomír

2017-11-01

Traditional Tibetan medicine starts to be a very popular complementary medicine in USA and Europe. These pills contain many elements essential for the human body. However, they might also contain heavy metals such as mercury, iron, arsenic, etc. This paper focuses on elemental composition of two Tibetan pills and investigation of forms of iron in them. X-ray fluorescence spectroscopy and neutron activation analysis identified the presence of several heavy metals such as mercury, iron and copper. Mőssbauer spectroscopy revealed the possible presence of α - F e 2 O 3(hematite) and α - F e O O H(goethite) in both of the investigated samples.

Non-destructive and in situ analysis of Egyptian wall paintings by X-ray diffraction and X-ray fluorescence portable systems

International Nuclear Information System (INIS)

Pages-Camagna, S.; Laval, E.; Vigears, D.; Duran, A.

2010-01-01

The concurrence and complementarities of obtained images under various wavelengths and the elemental and structural analyses provided by XRF and XRD, using portable non-invasive systems, have allowed for obtaining accurate data about the employed pictorial technique in two Egyptian wall paintings dating from the New Kingdom. Thus, compounds such as Egyptian blue, Egyptian green, goethite, jarosite, hematite, calcite, anhydrite or huntite have been detected in the paintings. The performance of the measurements by the different techniques and its contribution to the knowledge of the materials are discussed. They notably give a clue on the origin of arsenic compounds, unexpectedly detected in some decors. (orig.)

Mössbauer studies on some Argentinian soil: Mollisols from Bahia Blanca

Science.gov (United States)

Saragovi, C.; Labenski, F.; Duhalde, S. M.; Acebal, S.; Venegas, R.

1994-12-01

Clay fractions of a Mollisol sample as is, treated with ammonium oxalate (AO), with dithionite-citrate-bicarbonate (DCB) and with dithionite-ethilene-diamine-tetraacetic acid (D-EDTA) methods, were studied. Illite-montmorillonites together with hematites, goethites and maghemites, all of the AI-substituted and with a wide range of sizes, were identified. It is found that the AO attack extracts little iron, whereas the other two attacks extract the magnetic signal. Furthermore, the DCB attack facilitates the reduction of the Fe3+ ions, while the D-EDTA method does not. Instead, this attack extracts more clay mineral Fe ions. A comparison with large grain soil samples is made.

Influence of silicon on local structure and morphology of γ-FeOOH and α-FeOOH particles

International Nuclear Information System (INIS)

Kwon, Sang-Koo; Shinoda, Kozo; Suzuki, Shigeru; Waseda, Yoshio

2007-01-01

The extended X-ray absorption fine structure (EXAFS) method was used for investigating the local structures of lepidocrocite and goethite with and without silicon. The structure and morphology of these particles were investigated using X-ray diffraction and transmission electron microscopy, respectively. The bonding structure was examined by Fourier transform infrared spectroscopy (FT-IR). When silicon species was added, the structure and morphology changed while the linkage of FeO 6 octahedral units was distorted. The FT-IR spectra revealed the formation of the Fe-O-Si bond in particles containing silicate ions, and the characteristic bond affects the local structure and morphology of the particles

Moessbauer investigations of itmid

Energy Technology Data Exchange (ETDEWEB)

Mrayed, Y S; Ellid, M S; Fallagh, F A [Physics and material Science Department, Tajoura Nuclear Research Center, Tripoli, (Libyan Arab Jamahiriya)

1997-12-31

A sample of itmid available commercially was obtained and investigated using{sup 57} Fe Moessbauer spectroscopy, atomic absorption, X-ray fluorescence. The Moessbauer spectra showed the presence hematite (alpha-Fe{sub 2} O{sub 3}), goethite (alpha-FeOOH), and a third phase which has a six-line spectrum with the following parameters : Isomer shift (gamma= 0.52 mm/s), magnetic field (H=290 kOe). After conducting a series of reduction and calcination to the itmid sample and with the aid of atomic absorption and X-ray fluorescence results the third phase was identified as the iron sulfide compound FeS. 3 figs., 3 tabs.

Formation of secondary minerals in a lysimeter approach - A mineral-microbe interaction

Science.gov (United States)

Schäffner, F.; Merten, D.; De Giudici, G.; Beyer, A.; Akob, D. M.; Ricci, P. C.; Küsel, K.; Büchel, G.

2012-04-01

Heavy metal contamination of large areas due to uranium mining operations poses a serious long-term environmental problem. In the Ronneburg district (eastern Thuringia, Germany), leaching of low grade uranium bearing ores (uranium content metals, especially Cd, Ni, Co, Cu and Zn due to a residual contamination even after remediation efforts. To reveal the processes of secondary mineral precipitation in the field a laboratory lysimeter approach was set up under in situ-like conditions. Homogenized soil from the field site and pure quartz sand were used as substrates. In general, in situ measurements of redox potentials in the substrates showed highly oxidizing conditions (200-750 mV). Water was supplied to the lysimeter from below via a mariottés bottle containing contaminated groundwater from the field. Evaporation processes were allowed, providing a continuous flow of water. This led to precipitation of epsomite and probably aplowite on the top layer of substrate, similar to what is observed in field investigations. After 4 weeks, the first iron and manganese bearing secondary minerals became visible. Soil water samples were used to monitor the behaviour of metals within the lysimeter. Saturation indices (SI) for different secondary minerals were calculated with PHREEQC. The SI of goethite showed oversaturation with respect to the soil solution. SEM-EDX analyses and IR spectroscopy confirmed the formation of goethite. Geochemical data revealed that goethite formation was mainly dominated by Eh/pH processes and that heavy metals, e.g. Zn and U, could be enriched in this phase. Although Eh/pH data does not support formation of manganese minerals, Mn(II)-oxidizing bacteria (MOB) could be isolated from field soil samples, supporting the fact that microorganisms may influence this natural attenuation process. Laser ablation ICP-MS data reveal accumulation of manganese in MOB biomass on Mn(II)-containing agar plates. Furthermore, it was possible to show the importance

Legacy of the California Gold Rush: Environmental geochemistry of arsenic in the southern Mother Lode Gold District

Science.gov (United States)

Savage, K.S.; Bird, D.K.; Ashley, R.P.

2000-01-01

Gold mining activity in the Sierra Nevada foothills, both recently and during the California Gold Rush, has exposed arsenic-rich pyritic rocks to weathering and erosion. This study describes arsenic concentration and speciation in three hydrogeologic settings in the southern Mother Lode Gold District: mineralized outcrops and mine waste rock (overburden); mill tailings submerged in a water reservoir; and lake waters in this monomictic reservoir and in a monomictic lake developing within a recent open-pit mine. These environments are characterized by distinct modes of rock-water interaction that influence the local transport and fate of arsenic. Arsenic in outcrops and waste rock occurs in arsenian pyrite containing an average of 2 wt% arsenic. Arsenic is concentrated up to 1300 ppm in fine-grained, friable iron-rich weathering products of the arsenian pyrite (goethite, jarosite, copiapite), which develop as efflorescences and crusts on weathering outcrops. Arsenic is sorbed as a bidentate complex on goethite, and substitutes for sulfate in jarosite. Submerged mill tailings obtained by gravity core at Don Pedro Reservoir contain arsenic up to 300 ppm in coarse sand layers. Overlying surface muds have less arsenic in the solid fraction but higher concentrations in porewaters (up to 500 ??g/L) than the sands. Fine quartz tailings also contain up to 3.5 ppm mercury related to the ore processing. The pH values in sediment porewaters range from 3.7 in buried gypsum-bearing sands and tailings to 7 in the overlying lake sediments. Reservoir waters immediately above the cores contain up to 3.5 ??g/L arsenic; lake waters away from the submerged tailings typically contain less than 1 ??g/L arsenic. Dewatering during excavation of the Harvard open-pit mine produced a hydrologic cone of depression that has been recovering toward the pre-mining groundwater configuration since mining ended in 1994. Aqueous arsenic concentrations in the 80 m deep pit lake are up to 1000 ??g

Abiotic versus biotic iron mineral transformation studied by a miniaturized backscattering Mössbauer spectrometer (MIMOS II), X-ray diffraction and Raman spectroscopy

Science.gov (United States)

Markovski, C.; Byrne, J. M.; Lalla, E.; Lozano-Gorrín, A. D.; Klingelhöfer, G.; Rull, F.; Kappler, A.; Hoffmann, T.; Schröder, C.

2017-11-01

Searching for biomarkers or signatures of microbial transformations of minerals is a critical aspect for determining how life evolved on Earth, and whether or not life may have existed in other planets, including Mars. In order to solve such questions, several missions to Mars have sought to determine the geochemistry and mineralogy on the Martian surface. This research includes the two miniaturized Mössbauer spectrometers (MIMOS II) on board the Mars Exploration Rovers Spirit and Opportunity, which have detected a variety of iron minerals on Mars, including magnetite (Fe2+Fe3+2O4) and goethite (α-FeO(OH)). On Earth, both minerals can derive from microbiological activity (e.g. through dissimilatory iron reduction of ferrihydrite by Fe(III)-reducing bacteria). Here we used a lab based MIMOS II to characterize the mineral products of biogenic transformations of ferrihydrite to magnetite by the Fe(III)-reducing bacteria Geobacter sulfurreducens. In combination with Raman spectroscopy and X-ray diffraction (XRD), we observed the formation of magnetite, goethite and siderite. We compared the material produced by biogenic transformations to abiotic samples in order to distinguish abiotic and biotic iron minerals by techniques that are or will be available onboard Martian based laboratories. The results showed the possibility to distinguish the abiotic and biotic origin of the minerals. Mossbauer was able to distinguish the biotic/abiotic magnetite with the interpretation of the geological context (Fe content mineral assemblages and accompanying minerals) and the estimation of the particle size in a non-destructive way. The Raman was able to confirm the biotic/abiotic principal peaks of the magnetite, as well as the organic principal vibration bands attributed to the bacteria. Finally, the XRD confirmed the particle size and mineralogy.

Electron transfer capacity dependence of quinone-mediated Fe(III) reduction and current generation by Klebsiella pneumoniae L17.

Science.gov (United States)

Li, Xiaomin; Liu, Liang; Liu, Tongxu; Yuan, Tian; Zhang, Wei; Li, Fangbai; Zhou, Shungui; Li, Yongtao

2013-06-01

Quinone groups in exogenous electron shuttles can accelerate extracellular electron transfer (EET) from bacteria to insoluble terminal electron acceptors, such as Fe(III) oxides and electrodes, which are important in biogeochemical redox processes and microbial electricity generation. However, the relationship between quinone-mediated EET performance and electron-shuttling properties of the quinones remains incompletely characterized. This study investigates the effects of a series of synthetic quinones (SQs) on goethite reduction and current generation by a fermenting bacterium Klebsiella pneumoniae L17. In addition, the voltammetric behavior and electron transfer capacities (ETCs) of SQ, including electron accepting (EAC) and donating (EDC) capacities, is also examined using electrochemical methods. The results showed that SQ can significantly increase both the Fe(III) reduction rates and current outputs of L17. Each tested SQ reversibly accepted and donated electrons as indicated by the cyclic voltammograms. The EAC and EDC results showed that Carmine and Alizarin had low relative capacities of electron transfer, whereas 9,10-anthraquinone-2,6-disulfonic acid (AQDS), 2-hydroxy-1,4-naphthoquinone (2-HNQ), and 5-hydroxy-1,4-naphthoquinone (5-HNQ) showed stronger relative ETC, and 9,10-anthraquinone-2-carboxylic acid (AQC) and 9,10-anthraquinone-2-sulfonic acid (AQS) had high relative ETC. Enhancement of microbial goethite reduction kinetics and current outputs by SQ had a good linear relationship with their ETC, indicating that the effectiveness of quinone-mediated EET may be strongly dependent on the ETC of the quinones. Therefore, the presence of quinone compounds and fermenting microorganisms may increase the diversity of microbial populations that contribute to element transformation in natural environments. Moreover, ETC determination of different SQ would help to evaluate their performance for microbial EET under anoxic conditions. Copyright © 2013 Elsevier

Study characteristics of new concrete mixes and their mechanical, physical, and gamma radiation attenuation features

Energy Technology Data Exchange (ETDEWEB)

El-Samrah, Moamen G.; Abdel-Rahman, Mohamed A.E. [Nuclear Engineering Department, Military Technical College Kobry El-kobbah, Cairo (Egypt); Kany, Amr M.I. [Physics Department, Faculty of Science, Al-Azhar University, Cairo (Egypt)

2018-02-01

Ordinary concrete and those of different compositions are regarded as suitable material in many applications concerning with gamma and neutron radiation shielding purposes. They are widely used in nuclear power plant, medical facilities, nuclear shelters, and for radioactive materials transportation as well as storage of radioactive wastes. In this study four different concrete mixes were prepared with the following different types of coarse aggregates: dolomite, barite, goethite, and steel slag. The effect of changes in the fine aggregates, selected to be 50 % local sand and 50 % limonite with addition of 10 % silica fume (SF) and 10 % fly ash (FA) by replacement of the total cement weight, on the performance of the samples was also investigated. To examine the performance of such samples for radiation shielding applications, a set of physical, mechanical, and radiation attenuation properties was studied and compared with those of ordinary concrete. This investigation includes compressive strength, slump test, bulk density, ultrasonic pulse velocity test, and gamma rays attenuation measurements for the different samples. A verification of the experimental results concerning the radiation attenuation measurements was performed using WinXcom program (Version 3.1). The experimental results revealed that all concrete mixes; goethite-limonite concrete (G.L), barite-limonite concrete (B.L), steel slag-limonite concrete (S.L) and dolomite concrete (D.C) have good physical and mechanical properties that successfully satisfying them as high performance concretes. In addition the barite-limonite and the steel slag-limonite have the higher γ-ray attenuation coefficients at low and high energy range and hence have a better radiation shielding. The obtained results from WinXcom program calculations showed a good agreement with the experimental results concerning γ-ray attenuation measurements for the studied concrete mixes. (copyright 2018 WILEY-VCH Verlag GmbH and Co. KGa

Microstructural characterisation and corrosion performance of old railway girder bridge steel and modern weathering structural steel

International Nuclear Information System (INIS)

Tewary, N.K.; Kundu, A.; Nandi, R.; Saha, J.K.; Ghosh, S.K.

2016-01-01

Highlights: • Microstructure and corrosion performance are compared for two structural steels. • Microstructure evolution shows primarily ferrite-pearlite in both the steels. • Steels show higher corrosion rate in 1% HCl solution than in 3.5% NaCl solution. • The corrosion products show the presence of oxide, hydroxide and oxy-hydroxides. • The corroded surface reveals morphologies like flowery, cotton balls and rosette. - Abstract: A comparison on microstructure and corrosion performance has been made between the two structural steels used in old railway girder bridge (Sample A) and modern grades of weathering structural steel (Sample B). The microstructures, viewed under optical microscope and scanning electron microscope (SEM), show mainly ferrite-pearlite phase constituents in both the steels, A and B. The phase fraction analysis shows higher amount of pearlite in steel A compared to that of steel B. The grain size of steel A is larger than that of steel B under identical processing condition. The immersion corrosion test in 3.5% NaCl shows that the corrosion rate of steel A increases with time, while the same for steel B decreases with time. On the other hand, corrosion test in 1% HCl shows that the corrosion rate of both steel A and B is higher as compared to that of NaCl which always decreases with time. The XRD analysis of corrosion products show the presence of many oxides, hydroxide and oxy-hydroxide like Lepidocrocite (γ-FeOOH), Goethite (α-FeOOH), Akaganeite (β-FeOOH), Magnetite (Fe_3O_4) and Maghemite (γ-Fe_2O_3) in both the steels. The SEM images of corroded surfaces reveal different morphologies like flowery, cotton balls and rosette etc. which indicate that the corrosion products primarily contain Lepidocrocite (γ-FeOOH), Goethite (α-FeOOH) and Akaganeite (β-FeOOH).

The influence of time on the magnetic properties of late Quaternary periglacial and alluvial surface and buried soils along the Delaware River, USA

Directory of Open Access Journals (Sweden)

Gary E Stinchcomb

2014-08-01

Full Text Available Magnetic susceptibility of soils has been used as a proxy for rainfall, but other factors can contribute to magnetic enhancement in soils. Here we explore influence of century- to millennial-scale duration of soil formation on periglacial and alluvial soil magnetic properties by assessing three terraces with surface and buried soils ranging in exposure ages from <0.01 to ~16 kyrs along the Delaware River in northeastern USA. The A and B soil horizons have higher Xlf, Ms, and S-ratios compared to parent material, and these values increase in a non-linear fashion with increasing duration of soil formation. Magnetic remanence measurements show a mixed low- and high-coercivity mineral assemblage likely consisting of goethite, hematite and maghemite that contributes to the magnetic enhancement of the soil. Room-temperature and low-temperature field-cooled and zero field-cooled remanence curves confirm the presence of goethite and magnetite and show an increase in magnetization with increasing soil age. These data suggest that as the Delaware alluvial soils weather, the concentration of secondary ferrimagnetic minerals increase in the A and B soil horizons. We then compared the time-dependent Xlf from several age-constrained buried alluvial soils with known climate data for the region during the Quaternary. Contradictory to most studies that suggest a link between increases in magnetic susceptibility and high moisture, increased magnetic enhancement of Delaware alluvial soils coincides with dry climate intervals. Early Holocene enhanced soil Xlf (9.5 – 8.5 ka corresponds with a well-documented cool-dry climate episode. This relationship is probably related to less frequent flooding during dry intervals allowing more time for low-coercive pedogenic magnetic minerals to form and accumulate, which resulted in increased Xlf. Middle Holocene enhanced Xlf (6.1 – 4.3 ka corresponds with a transitional wet/dry phase and a previously documented incision

Listvenite logging on D/V CHIKYU: Hole BT1B, Oman Drilling Project

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Kelemen, P. B.; Beinlich, A.; Morishita, T.; Greenberger, R. N.; Johnson, K. T. M.; Lafay, R.; Michibayashi, K.; Harris, M.; Phase I Science Party, T. O. D. P.

2017-12-01

Listvenite, quartz-carbonate altered ultramafic rock containing minor fuchsite (Cr-muscovite) forms by complete carbonation of peridotite and is thus an attractive objective for carbon mitigation studies. However, reaction controls and evolution of listvenite are still enigmatic. Here we present the first results of Phase 1 of the ICDP (International Continental Drilling Program) Oman Drilling Project and subsequent core logging using the analytical facilities on board the research vessel D/V CHIKYU. Hole BT1B contains 300 m of continuous drill core intersecting alluvium, listvenite-altered serpentinite, serpentinite, ophicarbonate and the underlying metamorphic sole of the Semail ophiolite, Oman. The drill core has been systematically investigated by visual core description, thin section petrography, X-ray fluorescence core logging, X-ray diffractometry, visible-shortwave infrared imaging spectroscopy and X-ray Computer Tomography. Our observations show that listvenite is highly variable in texture and color on the mm to m scale. Listvenite was visually categorized into 5 principal color groups: the dominant dark red (47 %), light red (19 %), orange (14 %), pale (2 %) and green (16 %). The presence of hematite/goethite results in dark reddish, red and orange hues. Light grey or pale colored listvenite lacks hematite and/or goethite veins and may represent the `true' listvenite. Green listvenite is characterized by the presence of cm-sized quartz-fuchsite intergrowths. Five zones of serpentinite, which vary in thickness between several tens of cm and 4 m, are intercalated within the massive listvenite of Hole BT1B. Gradational listvenite-serpentinite transition zones contain the ophicarbonate assemblage (magnesite + serpentine) and sometimes additional talc, representing intermediate carbonation reaction progress. Preservation of the former mesh texture and bastite after orthopyroxene in the listvenite suggest that the listvenite precursor had already been

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.

Weathering process in Sør Rondane Mountains, East Antarctica

Science.gov (United States)

Kanamaru, T.; Suganuma, Y.; Oiwane, H.; Miura, M.; Okuno, J.; Hayakawa, H.

2016-12-01

Weathering process under the hyper-arid and hypothermal environment is a key to understand the geomorphogic process and landscape evolution in Antarctica and on Mars. A nunber of studies have focused on weathering process of basaltic rocks in Antarctica, however, the nature of the weathering process of plutonic type rock, a common rock type on the Earth, have been less focused and remain unclear. Here, we report the physical/chemical weathering process of the granitic rocks obtained from Dronning Maud Land in East Antarctica based on a multiplicity of petrological approaches. Loss on Ignition (LOI) and major element composition of the crust and core of the rock samples indicate that chemical weathering process in this area seems to be very limited. The microscopic observations and laser-Raman micro spectroscopy for thin sections from the crust and core indicate that goethite grains are formed mainly in the vein around the crust, which is consistent with the higher Fe3+/Fe2+ contrast from the core to crust. A negative correlation between the rock hardness and color strength index (CSI) values also indicate that crust of rock samples tend to less hard than core due to cracking of the rock samples and following goethite formation. On the other hand, EPMA analysis indicates that original Fe-Ti oxide grains in the core of rock samples are damaged by weathering, and altered to hematite, and to non-stoichiometric Fe-Ti compound associated with ilmenite grans in case of the higher relative height samples. These reveal that the weathering process of the plutonic rocks under the hyper-cold and hypothermal environment are mainly controlled by oxidation, including iron hydroxide formation in the veins formed by mechanical distraction, and Fe-Ti oxide alteration in rock interior.

Phase and Chemical Composition Analysis on Neolithic Painted Ceramics Sherds Using Synchrotron Radiation X-Ray Powder Diffraction (SRXPD)

International Nuclear Information System (INIS)

Constantinescu, B.

2003-01-01

Full text: Synchrotron Radiation X-ray Powder Diffraction studies were performed at the wiggler beamline 1711 of MAX II Synchrotron accelerator from Lund, Sweden, in the frame of EU FPV Access to Large Scale Facilities programme. Diffraction data were collected using radiation of wavelength 1.36 A, which was detected by a Brucker system with a Smart 1000 CCD detector. The main goal of our studies was to distinguish different clays and mineral pigments of various Neolithic pottery-producing centres on Romanian territory in relation with possible inter-regional trade route connections. As main results we can mention: - identification of black pigment composition from Cucuteni (Northern Moldavia), Ariusd (South-Eastern Transylvania) and Cris-Starcevo (Oltenia) type pottery (VI - IV Millennia B. Chr.) as a combination of jacobsite, bixbyite (Manganese oxides), magnetite and goethite (Iron oxides) originary from North Moldova mineral deposits of Iacobeni (150 km up on the river Bistritza from analyzed Cucuteni archaeological sites), and as a combination of pyrolusite, magnetite and hematite for Cris-Starcevo samples, probably from local clay (enriched in Mn-Fe oxides) - identification of white pigment composition as calcite (CaCO3) for Cris- Starcevo culture sites from Central Transylvania (from the local abundant chalk deposits) and as calcium silicates mixed with illite (K, H2))Al2[(H2O, OH)2]AlSi3O10 for Cucuteni culture sites - identification of read-brown pigment composition as various mixtures of hematite - goethite - magnetite, all of local provenance - identification of all examined sherds as having local provenance for the clay The main conclusion is that during Neolithic period, the pottery workshops, largely extended on Romanian territory, used local clays but traded black mineral pigments across the Carpathian mountains (Cucuteni and Ariusd areas are separated by these mountains by easily crossed by passes along small rivers)

Discovery of jarosite within the Mawrth Vallis region of Mars: Implications for the geologic history of the region

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Farrand, W. H.; Glotch, T.D.; Rice, J. W.; Hurowitz, J.A.; Swayze, G.A.

2009-01-01

Analysis of visible to near infrared reflectance data from the MRO CRISM hyperspectral imager has revealed the presence of an ovoid-shaped landform, approximately 3 by 5 km in size, within the layered terrains surrounding the Mawrth Vallis outflow channel. This feature has spectral absorption features consistent with the presence of the ferric sulfate mineral jarosite, specifically a K-bearing jarosite (KFe3(SO4)2(OH)6). Terrestrial jarosite is formed through the oxidation of iron sulfides in acidic environments or from basaltic precursor minerals with the addition of sulfur. Previously identified phyllosilicates in the Mawrth Vallis layered terrains include a basal sequence of layers containing Fe-Mg smectites and an upper set of layers of hydrated silica and aluminous phyllosilicates. In terms of its fine scale morphology revealed by MRO HiRISE imagery, the jarosite-bearing unit has fracture patterns very similar to that observed in Fe-Mg smectite-bearing layers, but unlike that observed in the Al-bearing phyllosilicate unit. The ovoid-shaped landform is situated in an east-west bowl-shaped depression superposed on a north sloping surface. Spectra of the ovoid-shaped jarosite-bearing landform also display an anomalously high 600 nm shoulder, which may be consistent with the presence of goethite and a 1.92 ??m absorption which could indicate the presence of ferrihydrite. Goethite, jarosite, and ferrihydrite can be co-precipitated and/or form through transformation of schwertmannite, both processes generally occurring under low pH conditions (pH 2-4). To date, this location appears to be unique in the Mawrth Vallis region and could represent precipitation of jarosite in acidic, sulfur-rich ponded water during the waning stages of drying. ?? 2009 Elsevier Inc. All rights reserved.

Multiproxy analysis of a new terrestrial and a marine Cretaceous-Paleogene (K-Pg) boundary site from New Zealand

Science.gov (United States)

Ferrow, Embaie; Vajda, Vivi; Koch, Christian Bender; Peucker-Ehrenbrink, Bernhard; Willumsen, Pi Suhr

2011-01-01

An integrated study of palynology, Mössbauer spectroscopy, mineralogy and osmium isotopes has led to the detection of the first K-Pg boundary clay layer in a Southern Hemisphere terrestrial setting. The K-Pg boundary layer was independently identified at centimetre resolution by all the above mentioned methods at the marine K-Pg boundary site of mid-Waipara and the terrestrial site of Compressor Creek (Greymouth coal field), New Zealand. Mössbauer spectroscopy shows an anomaly of Fe-containing particles in both K-Pg boundary sections: jarosite at mid-Waipara and goethite at Compressor Creek. This anomaly coincides with a turnover in vegetation indicated by an interval dominated by fern spores and extinction of key pollen species in both sections. In addition to the terrestrial floristic changes, the mid-Waipara section reveals a turnover in the dinoflagellate assemblages and the appearance of global earliest Danian index species. Geochemical data reveal relatively small iridium enrichments in the boundary layers of 321 pg/g at mid-Waipara and 176 pg/g at Compressor Creek. Unradiogenic 187Os/ 188Os values of the boundary clay reveal the presence of a significant extraterrestrial component. We interpret the accumulation of Fe nano-phases at the boundary as originating from both the impactor and the crystalline basement target rock. The goethite and jarosite are interpreted as secondary phases formed by weathering and diagenesis. The primary phases were probably controlled by the initial composition of the vapor plume and condensation kinetics rather than condensation thermodynamics. This investigation indicates that identification of Fe in nano-phases by Mössbauer spectroscopy is an accurate and cost-effective method for identifying impact event horizons and it efficiently complements widely used biostratigraphic and geochemical methods.

Mineralogical and particulate morphological characterization of geophagic clayey soils from Botswana

Directory of Open Access Journals (Sweden)

Georges-Ivo Ekosse

2012-12-01

Full Text Available This study focused on determining the minerals composition and particle morphology of geophagic clayey soils from Botswana in order to infer on how they could influence human health. Six representative geophagic clayey soils from Botswana were mineralogically characterized using X-ray powder diffractometry (XRPD, optical microscopy, and environmental scanning electron microscopy (ESEM. Results of identified mineral phases revealed quartz (SiO2 as the most dominant in all samples constituting close to 70 wt %; followed by goethite (FeO.OH having a mean concentration of 9 wt%, and kaolinite (Al2Si2O5(OH4 with a mean concentration of 8 wt%. Other minerals present were smectite ((Na,Ca(Al,Mg6(Si4O103(OH6-n(H2O, mica (AB2-3(Al,SiSi3O10(F,OH2, feldspar (Na/K(AlSi3O8 and hematite (Fe2O3. The quartz particles were generally coarse; and angular to very angular in morphology. Due to ions present in goethite, kaolinite, and smectite, these minerals impact positively on properties of geophagic clayey soils and could possibly influence human health when consumed. The quartz particles could negatively affect dental enamel as a result of mastication; and cause abrasion of the walls of the gastro-intestinal tract which may lead to rupturing. Although the studied clayey soils could have potential to provide medicinal benefits to the consumer, there is need for beneficiation exercise to be conducted to reduce the coarse angular particles contained in them. It is therefore necessary for constructive efforts to be directed at beneficiating geophagic materials which will render them safe for human consumption.DOI: http://dx.doi.org/10.4314/bcse.v26i3.6

Study of archaeological iron objects by PGAA, Mössbauer spectroscopy and X-ray diffraction

International Nuclear Information System (INIS)

Wagner, F. E.; Gebhard, R.; Häusler, W.; Wagner, U.; Albert, P.; Hess, H.; Révay, Z.; Kudejová, P.; Kleszcz, K.

2016-01-01

Archaeological iron objects often corrode rapidly after their excavation, even though they have survived long times of burial in the ground. Chlorine that accumulates during burial is thought to play a major role in this destructive post-excavation corrosion. It is therefore important for the conservation of such objects to determine the chlorine content in a non-destructive manner and, if necessary, to remove the chlorine from the artefacts by appropriate methods. Such methods are leaching in alkaline solutions or heating in a reducing atmosphere at temperatures up to 800 "∘C. We have studied the efficiency of the heating method using prompt gamma activation analysis (PGAA) for monitoring the Cl content and Mössbauer spectroscopy at room temperature (RT) and 4.2 K as well as X-ray diffraction to study the mineralogical transformations of the rust layers. The heat treatments were performed a N_2/H_2 (90/10) mixture at temperatures up to 750 "∘C. As test specimens sections of iron rods from the Celtic oppidum of Manching (Bavaria) were used. The initial Cl contents of the pieces varied in the range of several hundred ppm, referring to the iron mass. Annealing for 24 h at 350, 550 and 750 "∘C was found to reduce the Cl contents of the specimens, to about 70, 30 and 15 % of the original values, respectively. The rust consists mainly of goethite with admixtures of magnetite, lepidocrocite and akaganeite, which is thought to be a major carrier of chlorine, probably together with iron chlorides. Much of the goethite is so fine-grained that it does not split magnetically at RT. Annealing converts the rust mainly to maghemite at 350 "∘C, to magnetite at 550 "∘C and to wüstite plus magnetite and metallic iron at 750 "∘C. Pure akaganeite behaves in nearly the same manner.

Study of archaeological iron objects by PGAA, Mössbauer spectroscopy and X-ray diffraction

Science.gov (United States)

Wagner, F. E.; Gebhard, R.; Häusler, W.; Wagner, U.; Albert, P.; Hess, H.; Révay, Z.; Kudejová, P.; Kleszcz, K.

2016-12-01

Archaeological iron objects often corrode rapidly after their excavation, even though they have survived long times of burial in the ground. Chlorine that accumulates during burial is thought to play a major role in this destructive post-excavation corrosion. It is therefore important for the conservation of such objects to determine the chlorine content in a non-destructive manner and, if necessary, to remove the chlorine from the artefacts by appropriate methods. Such methods are leaching in alkaline solutions or heating in a reducing atmosphere at temperatures up to 800 ∘C. We have studied the efficiency of the heating method using prompt gamma activation analysis (PGAA) for monitoring the Cl content and Mössbauer spectroscopy at room temperature (RT) and 4.2 K as well as X-ray diffraction to study the mineralogical transformations of the rust layers. The heat treatments were performed a N2/H2 (90/10) mixture at temperatures up to 750 ∘C. As test specimens sections of iron rods from the Celtic oppidum of Manching (Bavaria) were used. The initial Cl contents of the pieces varied in the range of several hundred ppm, referring to the iron mass. Annealing for 24 h at 350, 550 and 750 ∘C was found to reduce the Cl contents of the specimens, to about 70, 30 and 15 % of the original values, respectively. The rust consists mainly of goethite with admixtures of magnetite, lepidocrocite and akaganeite, which is thought to be a major carrier of chlorine, probably together with iron chlorides. Much of the goethite is so fine-grained that it does not split magnetically at RT. Annealing converts the rust mainly to maghemite at 350 ∘C, to magnetite at 550 ∘C and to wüstite plus magnetite and metallic iron at 750 ∘C. Pure akaganeite behaves in nearly the same manner.

Arsenate reduction and mobilization in the presence of indigenous aerobic bacteria obtained from high arsenic aquifers of the Hetao basin, Inner Mongolia

International Nuclear Information System (INIS)

Guo, Huaming; Liu, Zeyun; Ding, Susu; Hao, Chunbo; Xiu, Wei; Hou, Weiguo

2015-01-01

Intact aquifer sediments were collected to obtain As-resistant bacteria from the Hetao basin. Two strains of aerobic As-resistant bacteria (Pseudomonas sp. M17-1 and Bacillus sp. M17-15) were isolated from the aquifer sediments. Those strains exhibited high resistances to both As(III) and As(V). Results showed that both strains had arr and ars genes, and led to reduction of dissolved As(V), goethite-adsorbed As(V), scorodite As(V) and sediment As(V), in the presence of organic carbon as the carbon source. After reduction of solid As(V), As release was observed from the solids to solutions. Strain M17-15 had a higher ability than strain M17-1 in reducing As(V) and promoting the release of As. These results suggested that the strains would mediate As(V) reduction to As(III), and thereafter release As(III), due to the higher mobility of As(III) in most aquifer systems. The processes would play an important role in genesis of high As groundwater. - Highlights: • Two strains of As-resistant bacteria were isolated from high As aquifer sediment. • The strains (M17–1 and M17-15) had an As tolerance under oxic conditions. • The strains had arr and ars genes, and reduced both dissolved As(V) and solid As(V). • Reduction of solid As(V) resulted in As release into solutions. • M17-15 had a higher ability in reducing As(V) and promoting As release than M17-1. - Indigenous aerobic bacteria from the high-As aquifer sediment had arr and ars genes and led to reduction of dissolved As(V), goethite-adsorbed As(V), scorodite As(V) and sedimentary As

One step facile synthesis of ferromagnetic magnetite nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Suppiah, Durga Devi; Abd Hamid, Sharifah Bee, E-mail: sharifahbee@um.edu.my

2016-09-15

The ferromagnetic properties of magnetite (Fe{sub 3}O{sub 4}) were influenced by the nanoparticle size, hence importance were given to the synthesis method. This paper clearly shows that magnetite nanoparticles were successfully synthesized by employing one step controlled precipitation method using a single salt (Iron(II) sulfate) iron precursor. The acquired titration curve from this method provides vital information on the possible reaction mechanism leading to the magnetite (Fe{sub 3}O{sub 4}) nanoparticles formation. Goethite (α-FeOOH) was obtained at pH 4, while the continuous addition of hydroxyl ions (OH{sup −}) forms iron hydroxides (Fe(OH){sub 2}). This subsequently reacts with the goethite, producing magnetite (Fe{sub 3}O{sub 4}) at pH 10. Spectroscopy studies validate the magnetite phase existence while structural and morphology analysis illustrates cubic shaped magnetite with an average size of 35 nm was obtained. The synthesized magnetite might be superparamagnetic though lower saturation magnetization (67.5 emu/g) measured at room temperature as compared to bulk magnetite. However the nanoparticles surface anisotropy leads to higher remanence (12 emu/g) and coercivity (117.7 G) making the synthesized magnetite an excellent candidate to be utilized in recording devices. The understanding of the magnetite synthesis mechanism can not only be used to achieve even smaller magnetite nanoparticles but also to prepare different types of iron oxides hydroxides using different iron precursor source. - Highlights: • Magnetite strong magnetism properties make it versatile in various applications including biomedical and electromagnetic materials. • Sulfate (SO{sub 4}{sup 2−}) anion plays a major role in the structure control of iron oxide during synthesis. • Phase pure magnetite nanoparticles with high magnetism properties can be obtained using a single salt (SO{sub 4}{sup 2−}) method.

Evaluating the oxidation of shale during hydraulic fracturing using SEM-EDS and spectrocolorimetry

Science.gov (United States)

Tan, X. Y.; Nakashima, S.

2017-12-01

During hydraulic fracturing (fracking) for shale gas/oil extraction, oxygen is introduced into deep oxygen-poor environments, and Fe2+-bearing minerals in rocks can be oxidized thus leading to the degradation of rock quality. Akita diatomaceous shale is considered to be one of the source rocks for oil and gas fields in northwestern Japan. Outcrops of Akita shale often show presence of jarosite (Fe sulfate: yellow) and/or goethite (Fe hydroxide: brown to orange) as oxidation products of pyrite (FeS2). Several series of oxidation experiments of Akita shale under dry, humid, and wet conditions were conducted at temperatures of around 30 oC and 50oC for 30-40 days. Portable color spectro-colorimeters were used to monitor color changes of the rock surfaces every hour. SEM-EDS, UV-Vis, and Raman spectroscopic analyses were performed on the rock sample surface to examine the chemical and mineralogical compositions of Akita shale before and after the dry, humid, and wet experiments. In SEM-EDS analyses before the humid experiment, Fe and S containing phases show their atomic ratio close to 1:2 indicating that this is pyrite (FeS2). After the experiment, the ratio changed to around 1:1 suggesting a conversion from pyrite (FeS2) to mackinawite-like mineral (FeS). In addition, the formation of Ca sulfate (possibly gypsum: CaSO4.2H2O) and goethite-like Fe hydroxide were identified which were not present initially. Therefore, oxidation pathways of iron sulfide (pyrite: FeS2) via FeS to sulfate is confirmed by our humid experiments around 30oC on Akita shale. These oxidation processes might occur during the fracking of shale within relatively short time periods associated with precipitation of sulfates and hydroxides. Therefore, further studies are needed for their effects on rock properties and gas/oil production.

The Mineralogic Transformation of Ferrihydrite Induced by Heterogeneous Reaction with Bioreduced Anthraquinone Disulfonate (AQDS) and the Role of Phosphate

Energy Technology Data Exchange (ETDEWEB)

Zachara, John M.; Kukkadapu, Ravi K.; Peretyazhko, Tetyana; Bowden, Mark E.; Wang, Chong M.; Kennedy, David W.; Moore, Dean A.; Arey, Bruce W.

2011-10-12

Anthraquinone-2-6-disulfonate (AQDS) enhances electron donor utilization and mineral product crystallization in studies of Fe(III) oxide reductive mineralization by metal reducing bacteria (MRB) through heterogeneous redox reaction. In spite of the strong effect of AQDS in these systems, little information exits on its direct role in reductive mineralization. To provide such insights, bioreduced AQDS (AH2DS; dihydro-anthraquinone) was reacted with a 2-line, Si-substituted ferrihydrite under anoxic conditions at neutral pH in PIPES buffer. Phosphate (P) and bicarbonate (C); common adsorptive oxyanions and media/buffer components known to effect ferrihydrite mineralization; and Fe(II)aq (as a catalytic mineralization agent) were used in comparative experiments. Heterogeneous AH2DS oxidation coupled with Fe(III) reduction occurred within 0.13-1 day, with mineralogic transformation occurring thereafter. The product suite included lepidocrocite, goethite, and/or magnetite, with proportions varing with reductant:oxidant ratio (r:o) and the presence of P or C. Lepidocrocite was the primary product at low r:o in the absence of P or C, with evidence for multiple formation pathways. P inhibited reductive recrystallization, while C promoted goethite formation. Stoichiometric magnetite was the sole product at higher r:o in the absence and presence of P. Lepidocrocite was the primary mineralization product in the Fe(II)aq system, with magnetite observed at near equal amounts when Fe(II) was high [Fe(II)/Fe(III)]=0.5 and P was absent. P had a greater effect on reductive mineralization in the Fe(II)aq system, while AQDS was more effective than Fe(II)aq in promoting magnetite formation. The direct AH2DS-driven reductive reaction pathway produced mineral products that were different from AH2DS-ferrihydite-MRB systems, particularly in presence of P.

Long-term atmospheric corrosion of mild steel

International Nuclear Information System (INIS)

Fuente, D. de la; Diaz, I.; Simancas, J.; Chico, B.; Morcillo, M.

2011-01-01

Research highlights: → Atmospheric corrosion rate stabilises after the first 4-6 years of exposure. → Great compaction of the rust layers in rural and urban atmospheres. → Corrosion (in rural and urban) deviates from common behaviour of bilogarithmic law. → Typical structures of lepidocrocite, goethite and akaganeite are identified. → Formation of hematite (industrial atmosphere) and ferrihydrite (marine atmosphere). - Abstract: A great deal of information is available on the atmospheric corrosion of mild steel in the short, mid and even long term, but studies of the structure and morphology of corrosion layers are less abundant and generally deal with those formed in just a few years. The present study assesses the structure and morphology of corrosion product layers formed on mild steel after 13 years of exposure in five Spanish atmospheres of different types: rural, urban, industrial and marine (mild and severe). The corrosion layers have been characterised by X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). Long-term corrosion is seen to be more severe in the industrial and marine atmospheres, and less so in the rural and urban atmospheres. In all cases the corrosion rate is seen to decrease with exposure time, stabilising after the first 4-6 years of exposure. The most relevant aspects to be noted are (a) the great compaction of the rust layers formed in the rural and urban atmospheres, (b) the formation of hematite and ferrihydrite phases (not commonly found) in the industrial and marine atmospheres, respectively and (c) identification of the typical morphological structures of lepidocrocite (sandy crystals and flowery plates), goethite (cotton balls structures) and akaganeite (cotton balls structures and cigar-shaped crystals).

Mineralogical anomalies and their influences on elemental geochemistry of the main workable coal beds from the Dafang Coalfield, Guizhou, China

Science.gov (United States)

Dai, S.; Ren, D.; Li, D.; Chou, C.-L.; Luo, K.

2006-01-01

Mineralogy and geochemistry of the No. 11 Coal bed were investigated by using inductively-coupled plasma mass spectrometry (ICP-MS), X-ray fluorescence (XRF), scanning electron microscopy equipped with energy-dispersive X-ray (SEM-EDX), sequential chemical extraction procedure (SCEP), and optical microscopy. The results show that the No. 11 Coal bed has very high contents of veined quartz (Vol. 11.4%) and veined ankerite (Vol. 10.2 %). The veined ankerite was generally coated by goethite and the veined quartz embraced chalcopyrite, sphalerite, and selenio-galena. In addition, a trace amount of kaolinite was filled in the veins. These seven minerals often occur in the same veins. The formation temperatures of the veined ankerite and quartz are 85??C and 180??C respectively, indicating their origins of iron-rich calcic and siliceous low-temperature hydrothermal fluids in different epigenetic periods. Studies have also found that the veined quartz probably formed earlier than the veined ankerite, and at least three distinct ankerite formation stages were observed by the ration of Ca/Sr and Fe/Mn of ankerite. The mineral formation from the early to late stage is in order of sulfide, quartz, kaolinite, ankerite, and goethite. The veined ankerite is the dominant source of Mn, Cu, Ni, Pb, and Zn, which are as high as 0.09%, 74.0 ??g/g, 33.6 ??g/g, 185 ??g/g, and 289 ??g/g in this coal seam, respectively. However, the veined quartz is the main carrier of Pd, Pt, and Ir, which are 1.57 ??g/g, 0.15 ??g/g, and 0.007 ??g/g in this coal seam, respectively. In addition, chalcopyrite, sphalerite, and selenio-galena of hydrothermal origin were determined in the veined quartz, and these three sulfide minerals are also important carriers of Cu, Zn and Pb in the No. 11 Coal bed.

Discovery of jarosite within the Mawrth Vallis region of Mars: Implications for the geologic history of the region

Science.gov (United States)

Farrand, William H.; Glotch, Timothy D.; Rice, James W.; Hurowitz, Joel A.; Swayze, Gregg A.

2009-12-01

Analysis of visible to near infrared reflectance data from the MRO CRISM hyperspectral imager has revealed the presence of an ovoid-shaped landform, approximately 3 by 5 km in size, within the layered terrains surrounding the Mawrth Vallis outflow channel. This feature has spectral absorption features consistent with the presence of the ferric sulfate mineral jarosite, specifically a K-bearing jarosite (KFe 3(SO 4) 2(OH) 6). Terrestrial jarosite is formed through the oxidation of iron sulfides in acidic environments or from basaltic precursor minerals with the addition of sulfur. Previously identified phyllosilicates in the Mawrth Vallis layered terrains include a basal sequence of layers containing Fe-Mg smectites and an upper set of layers of hydrated silica and aluminous phyllosilicates. In terms of its fine scale morphology revealed by MRO HiRISE imagery, the jarosite-bearing unit has fracture patterns very similar to that observed in Fe-Mg smectite-bearing layers, but unlike that observed in the Al-bearing phyllosilicate unit. The ovoid-shaped landform is situated in an east-west bowl-shaped depression superposed on a north sloping surface. Spectra of the ovoid-shaped jarosite-bearing landform also display an anomalously high 600 nm shoulder, which may be consistent with the presence of goethite and a 1.92 μm absorption which could indicate the presence of ferrihydrite. Goethite, jarosite, and ferrihydrite can be co-precipitated and/or form through transformation of schwertmannite, both processes generally occurring under low pH conditions (pH 2-4). To date, this location appears to be unique in the Mawrth Vallis region and could represent precipitation of jarosite in acidic, sulfur-rich ponded water during the waning stages of drying.

Ion sorption onto hydrous ferric oxides: Effect on major element fluid chemistry at Aespoe, Sweden

International Nuclear Information System (INIS)

Bruton, C.J.; Viani, B.E.

1996-06-01

The observed variability of fluid chemistry at the Aespoe Hard Rock Laboratory is not fully described by conservative fluid mixing models. Ion exchange may account for some of the observed discrepancies. It is also possible that variably charged solids such as oxyhydroxides of Fe can serve as sources and sinks of anions and cations through surface complexation. Surface complexation reactions on hydrous ferric oxides involve sorption of both cations and anions. Geochemical modeling of the surface chemistry of hydrous ferric oxides (HFOs) in equilibrium with shallow HBH02 and deep KA0483A waters shows that HFOs can serve as significant, pH-sensitive sources and sinks for cations and anions. Carbonate sorption is favored especially at below-neutral pH. A greater mass of carbonate is sorbed onto HFO surfaces than is contained in the fluid when 10 g goethite, used as a proxy for HFOs, is in contact with 1 kg H 2 O. The masses of sorbent required to significantly impact fluid chemistry through sorption/desorption reactions seem to be reasonable when compared to the occurrences of HFOs at Aespoe. Thus, it is possible that small changes in fluid chemistry can cause significant releases of cations or anions from HFOs into the fluid phase or, alternately, result in uptake of aqueous species onto HFO surfaces. Simulations of the mixing of shallow HBH02 and native KA0483A waters in the presence of a fixed mass of goethite show that surface complexation does not cause the concentrations of Ca, Sr, and SO 4 to deviate from those that are predicted using conservative mixing models. Results for HCO 3 are more difficult to interpret and cannot be addressed adequately at this time

Morphological study and thermal analysis of surface modified α-FeOOH via in situ polymerization of methyl methacrylate

International Nuclear Information System (INIS)

Han Yaoxing; Ma Xinsheng; Cao Hongming; Zhang Haiying; Wu Qiufang

2004-01-01

Considering the interfacial characteristics of goethite (α-FeOOH, iron oxide yellow), the in situ polymerization of methyl methacrylate was employed to modify the surfaces of α-FeOOH pigments in aqueous slurry. The scanning electron micrographs indicated that the poly(methyl methacrylate) anchored on the surfaces of the particle homogeneously. From this study, it was found that one of the key requirements in the synthesis of the α-FeOOH-PMMA composite was to enhance interfacial compatibility between inorganic particles and organic monomer. Moreover, polymer-treated α-FeOOH particles were easily dispersed in organic medium to form a stable colloid and the heat resistance of α-FeOOH particles was improved

Oxidation of organic compounds in wastewater from the humid processing of coffee berries

International Nuclear Information System (INIS)

Goncalves, Maraisa; Guerreiro, Mario Cesar; Oliveira, Luiz Carlos Alves; Rocha, Cristian Luciana da

2008-01-01

Materials based on pure iron oxide and impregnated with niobia (Nb 2 O 5 ) were prepared. Their catalytic activities were tested on the oxidation of compounds present in the wastewater from the processing of coffee berries. Particularly caffeine and catechol were tested. The oxidation reactions were carried out with the following systems: UV/H 2 O 2 ; photo-Fenton and heterogeneous Fenton. All materials were characterized with X-ray diffraction, Moessbauer and infrared spectroscopy. Iron was mainly in the forms of goethite and maghemite. The oxidation kinetics were monitored by UV-vis and the oxidation products were monitored by mass spectrometry. The photo-Fenton reaction presented highest oxidation efficiency, removing 98% of all caffeine and catechol contents. (author)

Crystal chemistry and Moessbauer spectroscopic analysis of clays around Riyadh for brick industry

Energy Technology Data Exchange (ETDEWEB)

Khalil, Mutasim I., E-mail: mkhalil@ksu.edu.sa [King Saud University, Department of Chemistry, College of Science (Saudi Arabia)

2013-04-15

A total of 30 clay samples were collected from the area around Riyadh city, Saudi Arabia. A complete chemical analysis was carried out using different techniques. X-ray diffraction studies showed that the clay samples were mainly of the smectite group with traces of the kaolinite one. The samples studied were classified as nontronite clay minerals. One of the clay fraction has been studied by Moessbauer spectroscopy as raw clay fraction and after being fired at 950-1,000 Degree-Sign C. The Moessbauer spectra showed accessory iron compounds in the form of hematite and goethite. The structural iron contents disintegrate on firing transforming into magnetic iron oxide and a paramagnetic small particles iron oxide.

Sedimentary uranium deposit of the Ipora/Amorinopolis region, state of Goias, Brazil

International Nuclear Information System (INIS)

Fernandes, S.M.; Leonardos, O.H.

1984-01-01

The uranium mineralization is chiefly found within arkosic sandstones at the base of the Devonian Ponta Grossa Formation. The ore is tabular and concordant with the bedding, the controls being simultaneously litho-stratigraphical and biochemical. Narrow permeable horizons of arkosic sandstone lie between impermeable shale and siltstone layers. Within the permeable horizon, the fossil remains (probably brachiopods) are replaced by uranium minerals. The oxidized iron minerals may have acted as to insulate and preserve the secondary soluble uranium minerals. The mineral paragenesis is represented by renardite, meta - autunite I, fourmarierite, Koninckite, ranquilite, meta-uranocircite II, barite, apatite, calophane, wavelite, varscite, an unnamed uranium mineral, quartz, calcedony, goethite, lepidocrocite and hematite. (Author) [pt

Mineralogical aspects of the laterites of Maicuru

International Nuclear Information System (INIS)

Lemos, V.P.; Costa, M.C. da

1989-01-01

This paper presents the prelimary mineralogical data of the weathering materials derived from the alkaline-ultramafic-carbonatitic Maicuru complex, State of Para. These material include several minerals species: iron, titanium and aluminium oxides/hydroxides as aluminous goethite, geothite, hematite, maghemite, lepidocrocite, anatase; and gibbsite; clay minerals of the smectite, chlorite, vermiculite and kaolinite groups and interstratified chlorite-smectite, mica-vermiculite, vermiculite-chlorite and Kaolinite-smectite; and aluminous phosphates of the crandalite group, wardite, augelite, senegalite, wavelite and variscite. The principal characteristics of these minerals were obtained by X-ray diffraction, optical methods, electron probe microanalysis, energy dispersive scanning electron microscope, X-ray fluorescence, atomic absorption, inductively coupled plasma-ICP source spectrometry and colorimetric methods. (author) [pt

IN SITU URANIUM STABILIZATION BY MICROBIAL METABOLITES

Energy Technology Data Exchange (ETDEWEB)

Turick, C; Anna Knox, A; Chad L Leverette,C; Yianne Kritzas, Y

2006-11-29

Soil contaminated with U was the focus of this study in order to develop in-situ, U bio-immobilization technology. We have demonstrated microbial production of a metal chelating biopolymer, pyomelanin, in U contaminated soil from the Tims Branch area of the Department of Energy (DOE) Savannah River Site (SRS) as a result of tyrosine amendments. Bacterial densities of pyomelanin producers were >106 cells/g wet soil. Pyomelanin demonstrated U chelating and mineral binding capacities at pH 4 and 7. In laboratory studies, in the presence of goethite or illite, pyomelanin enhanced U sequestration by these minerals. Tyrosine amended soils in field tests demonstrated increased U sequestration capacity following pyomelanin production up to 13 months after tyrosine treatments.

Service life prediction for 50-year-old buildings in marine environments

Directory of Open Access Journals (Sweden)

Agustín Sánchez-Deza

2018-03-01

Full Text Available Steel reinforcing bars are often coated with rusts formed during service in reinforced concrete (RC structures. Rust layers growing on steel rebars induce expansive stresses and cause cracking on cover concrete. This study uses steel corrosion rate results measured on reinforced concrete buildings of more than 50 years of age located in marine environments and considers the pressure generated by the volume expansion of corrosion product layers to calculate the service life of the RC structures using a numerical simulation, estimating the time to corrosion cracking of the concrete cover. Akaganeite, goethite, lepidocrocite, hematite, magnetite and maghemite were identified by X-ray diffraction as crystalline phase constituents of the rust layers.

Drenagem interna como fator de diferenciação de Latossolos do Distrito Federal The internal drainage as a differentiation factor in Oxisols of Distrito Federal, Brazil

Directory of Open Access Journals (Sweden)

Patrícia Maurício Campos

2010-03-01

, the water-table oscillation was monitored using 2.5-m depth observation wells, during one year. The studied Oxisols were considered chemically and physically similar. However, they differed as to morphological and mineralogical characterization, with the presence of concretionary horizons and goethite in the LVA. Goethite stability in this soils was influenced by the water-table oscillation. The presence of concretionry horizons in LVA caused an internal drainage deficiency, which resulted in lower saturated hydraulic conductivity and lower variation of the water-table levels. Therefore, LVA soils show lower agricultural potential than LV ones, in Distrito Federal. Oxisols physicohydric characteristics have little influence on soil diagnostic attributes, except for iron oxides mineralogy, which show increased contents of goethite in low internal drainage conditions.

Short Range-Ordered Minerals: Insight into Aqueous Alteration Processes on Mars

Science.gov (United States)

Ming, Douglas W.; Morris, R. V.; Golden, D. C.

2011-01-01

Short range-ordered (SRO) aluminosilicates (e.g., allophane) and nanophase ferric oxides (npOx) are common SRO minerals derived during aqueous alteration of basaltic materials. NpOx refers to poorly crystalline or amorphous alteration products that can be any combination of superparamagnetic hematite and/or goethite, akaganeite, schwertmannite, ferrihydrite, iddingsite, and nanometer-sized ferric oxide particles that pigment palagonitic tephra. Nearly 30 years ago, SRO phases were suggested as alteration phases on Mars based on similar spectral properties for altered basaltic tephra on the slopes of Mauna Kea in Hawaii and Martian bright regions measured by Earth-based telescopes. Detailed characterization of altered basaltic tephra on Mauna Kea have identified a variety of alteration phases including allophane, npOx, hisingerite, jarosite, alunite, hematite, goethite, ferrihydrite, halloysite, kaolinite, smectite, and zeolites. The presence of npOx and other Fe-bearing minerals (jarosite, hematite, goethite) was confirmed by the M ssbauer Spectrometer onboard the Mars Exploration Rovers. Although the presence of allophane has not been definitely identified on Mars robotic missions, chemical analysis by the Spirit and Opportunity rovers and thermal infrared spectral orbital measurements suggest the presence of allophane or allophane-like phases on Mars. SRO phases form under a variety of environmental conditions on Earth ranging from cold and arid to warm and humid, including hydrothermal conditions. The formation of SRO aluminosilicates such as allophane (and crystalline halloysite) from basaltic material is controlled by several key factors including activity of water, extent of leaching, Si activity in solution, and available Al. Generally, a low leaching index (e.g., wet-dry cycles) and slightly acidic to alkaline conditions are necessary. NpOx generally form under aqueous oxidative weathering conditions, although thermal oxidative alteration may occasional be

Analytical Study of the Materials Used in Mural Paintings in the Love Chamber of El Sakakeny Palace

Directory of Open Access Journals (Sweden)

Kholod Khairy Salama

2017-07-01

Full Text Available In the present study, a comprehensive investigation has been undertaken into mural paintings dating to the 19 th century and painted by Italian students. They were initially located in El Sakakeny Palace in El Sakakeny Square in Egypt. The analytical instruments used for investigation were Optical Microscopy, Scanning Electron Microscopy with EDX, X-Ray diffraction and Fourier Transform Infrared coupled with Attenuated Total Reflectance (FTIR-ATR. The analysis revealed that the pigments used in the mural paintings were hematite, litharge, zincate, gold oxide, Goethite (brown ochre and malachite mixed with linseed oil or animal glue. The original ground layer comprises zincate with gypsum. The medium used in the ground layer is animal glue and the support is limestone.

Oxidation of organic compounds in wastewater from the humid processing of coffee berries; Materiais a base de oxido de ferro para oxidacao de compostos presentes no efluente da despolpa do cafe

Energy Technology Data Exchange (ETDEWEB)

Goncalves, Maraisa; Guerreiro, Mario Cesar; Oliveira, Luiz Carlos Alves; Rocha, Cristian Luciana da [Universidade Federal de Lavras, MG (Brazil). Dept. de Quimica]. E-mail: guerrero@ufla.br

2008-07-01

Materials based on pure iron oxide and impregnated with niobia (Nb{sub 2}O{sub 5}) were prepared. Their catalytic activities were tested on the oxidation of compounds present in the wastewater from the processing of coffee berries. Particularly caffeine and catechol were tested. The oxidation reactions were carried out with the following systems: UV/H{sub 2}O{sub 2}; photo-Fenton and heterogeneous Fenton. All materials were characterized with X-ray diffraction, Moessbauer and infrared spectroscopy. Iron was mainly in the forms of goethite and maghemite. The oxidation kinetics were monitored by UV-vis and the oxidation products were monitored by mass spectrometry. The photo-Fenton reaction presented highest oxidation efficiency, removing 98% of all caffeine and catechol contents. (author)

Magnetic interactions between nanoparticles

DEFF Research Database (Denmark)

Mørup, Steen; Hansen, Mikkel Fougt; Frandsen, Cathrine

2010-01-01

We present a short overview of the influence of inter-particle interactions on the properties of magnetic nanoparticles. Strong magnetic dipole interactions between ferromagnetic or ferrimagnetic particles, that would be superparamagnetic if isolated, can result in a collective state...... of nanoparticles. This collective state has many similarities to spin-glasses. In samples of aggregated magnetic nanoparticles, exchange interactions are often important and this can also lead to a strong suppression of superparamagnetic relaxation. The temperature dependence of the order parameter in samples...... of strongly interacting hematite nanoparticles or goethite grains is well described by a simple mean field model. Exchange interactions between nanoparticles with different orientations of the easy axes can also result in a rotation of the sub-lattice magnetization directions....

Raman spectroscopic analysis of real samples: Brazilian bauxite mineralogy

Science.gov (United States)

Faulstich, Fabiano Richard Leite; Castro, Harlem V.; de Oliveira, Luiz Fernando Cappa; Neumann, Reiner

2011-10-01

In this investigation, Raman spectroscopy with 1064 and 632.8 nm excitation was used to investigate real mineral samples of bauxite ore from mines of Northern Brazil, together with Raman mapping and X-rays diffraction. The obtained results show clearly that the use of microRaman spectroscopy is a powerful tool for the identification of all the minerals usually found in bauxites: gibbsite, kaolinite, goethite, hematite, anatase and quartz. Bulk samples can also be analysed, and FT-Raman is more adequate due to better signal-to-noise ratio and representativity, although not efficient for kaolinite. The identification of fingerprinting vibrations for all the minerals allows the acquisition of Raman-based chemical maps, potentially powerful tools for process mineralogy applied to bauxite ores.

The Moessbauer spectroscopy in the characterization of atmospheric corrosion products

International Nuclear Information System (INIS)

Hernandez Torres, D.; Leiva Ronda, P.; Gomez, J.; Ronda, M.

1996-01-01

A study of corrosion products on mild steel formed after 1 and 5 years exposure in two industrial coastal weathering stations in the Bay from Matanzas City, Cuba, has been carried out. Structural analysis was conducted using mainly transmission Moessbauer Spectroscopy and the X-ray diffraction as complementary technique. The main phases found in the specimen exposed to high chloride containing environment were: lepidocrocite (γ- FeOOH), goethite (α- FeOOH) and magnetite concentration was the lowest, the phases found were γ- FeOOH and α- FeOOH, and the phase transformation proposed was γ- FeOOh -> α- Fe-OOH. In this station were found also amorphous corrosion products. There amorphous phases could be responsible for the lowest levels of corrosion on steel in this station

The Moessbauer spectroscopy in the characterization of atmospheric corrosion products; La espectroscopia Moessbauer en la caracterizacion de productos de corrosion atmosferica

Energy Technology Data Exchange (ETDEWEB)

Hernandez Torres, D; Leiva Ronda, P [Centro de Estudios Aplicados al Desarrollo Nuclear (CEADEN), La Habana (Cuba); Gomez, J; Ronda, M [Centro de Investigaciones del Petroleo, La Habana (Cuba)

1996-07-01

A study of corrosion products on mild steel formed after 1 and 5 years exposure in two industrial coastal weathering stations in the Bay from Matanzas City, Cuba, has been carried out. Structural analysis was conducted using mainly transmission Moessbauer Spectroscopy and the X-ray diffraction as complementary technique. The main phases found in the specimen exposed to high chloride containing environment were: lepidocrocite ({gamma}- FeOOH), goethite ({alpha}- FeOOH) and magnetite concentration was the lowest, the phases found were {gamma}- FeOOH and {alpha}- FeOOH, and the phase transformation proposed was {gamma}- FeOOh -> {alpha}- Fe-OOH. In this station were found also amorphous corrosion products. There amorphous phases could be responsible for the lowest levels of corrosion on steel in this station.

Radiolytic formation of iron oxyhydroxide nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Sutherland, T.; Wren, J.C., E-mail: tsuther4@uwo.ca [The Univ. of Western Ontario, London, ON (Canada)

2014-07-01

The formation of iron oxyhydroxide nanoparticles under gamma irradiation of ferrous ion solutions is a process in the infancy of its understanding. Herein we present work to probe the mechanism by which these nanoparticles are formed. These results can be used to better understand the activity transport processes occurring within a reactor environment which may pose both environmental and safety concerns. Initial ferrous concentrations and solution pH were modified and found to have little effect on final particle size and composition. The nanoparticles were formed in the presence of scavengers and it was found that hydroxyl radicals promote the particle formation while solvated electrons diminish it. Post-synthesis heating was found to shift the initially-formed lepidocrocite particles towards a mixture of goethite and maghemite. (author)

Co-binding of pharmaceutical compounds at mineral surfaces: Molecular investigations of dimer formation at goethite/water interfaces

OpenAIRE

Xu , Jing; Marsac , Rémi; Costa , Dominique; Cheng , Wei; Wu , Feng; Boily , Jean-François; Hanna , Khalil

2017-01-01

International audience; The emergence of antibiotic and anti-inflammatory agents in aquatic and terrestrial systems is becoming a serious threat to human and animal health worldwide. Because pharmaceutical compounds rarely exist individually in nature, interactions between various compounds can have unforeseen effects on their binding to mineral surfaces. This work demonstrates this important possibility for the case of two typical antibiotic and anti-inflammatory agents (nalidixic acid (NA) ...

Enhanced permanganate in situ chemical oxidation through MnO2 particle stabilization: evaluation in 1-D transport systems.

Science.gov (United States)

Crimi, Michelle; Quickel, Mark; Ko, Saebom

2009-02-27

In situ chemical oxidation using permanganate is an increasingly employed approach to organic contaminant remediation at hazardous waste sites. Manganese dioxide (MnO2) particles form as a by-product of the reaction of permanganate with contaminants and naturally-reduced subsurface materials. These particles are of interest because they have the potential to deposit in the subsurface and impact the flow regime in/around permanganate injection, including the well screen, filter pack, and the surrounding subsurface formation. Control of these particles can allow for improved oxidant injection and transport, and contact between the oxidant and contaminants of concern. Sodium hexametaphosphate (HMP) has previously been identified as a promising aid to stabilize MnO2 in solution when included in the oxidizing solution, increasing the potential to inhibit particle deposition and impact subsurface flow. The goal of the experimental studies described herein was to investigate the ability of HMP to prevent particle deposition in transport studies using four different types of porous media. Permanganate was delivered to a contaminant source zone (trichloroethylene) located within four different media types with variations in sand, clay, organic carbon, and iron oxides (as goethite) content. Deposition of MnO2 within the columns was quantified with distance from the source zone. Experiments were repeated in replicate columns with the inclusion of HMP directly with the oxidant delivery solution, and MnO2 deposition was again quantified. While total MnO2 deposition within the 60 cm columns did not change significantly with the addition of HMP, deposition within the contaminant source zone decreased by 25-85%, depending on the specific media type. The greatest differences in deposition were observed in the goethite-containing and clay-containing columns. Columns containing these two media types experienced completely plugged flow in the oxidant-only delivery systems; however

Potential Remobilization of Toxic Anions during Reduction of Arsenated and Chromated Schwertmannite by the Dissimilatory Fe(III)-Reducing Bacterium Acidiphilium cryptum JF-5

International Nuclear Information System (INIS)

Regenspurg, Simona; Goessner, Anita; Peiffer, Stefan; Kuesel, Kirsten

2002-01-01

Schwertmannite, an iron(III)-oxyhydroxysulfate formed in acidic mining-impacted stream or lake waters often contaminated with toxic elements like arsenate or chromate, is able to incorporate high amounts of these oxyanions. Detoxification of the water might be achieved if precipitated arsenated or chromated schwertmannite is fixed in the sediment. However, under reduced conditions, reductive dissolution of iron oxides mediated by the activity of Fe(III)-reducing bacteria might mobilize arsenate and chromate again. In this study, the reduction of synthesized arsenated or chromated schwertmannite by the acidophilic Fe(III)-reducer Acidiphilium cryptum JF-5, isolated from an acidic mining-impacted sediment, was investigated. In TSB medium at pH 2.7 with glucose as electron donor, A. cryptum JF-5 reduced about 10% of the total Fe(III) present in pure synthetic schwertmannite but only 5% of Fe(III) present in arsenated schwertmannite. In contrast to sulfate that was released during the reductive dissolution of pure schwertmannite, arsenate was not released during the reduction of arsenated schwertmannite probably due to the high surface complexation constant of arsenate and Fe(III). In medium containing chromated schwertmannite, no Fe(II) was formed, and no glucose was consumed indicating that chromate might have been toxic to cells of A. cryptum JF-5. Both As(V) or Cr(VI) could not be utilized as electron acceptor by A. cryptum JF-5. A comparison between autoclaved (121 o C for 20 min) and non-autoclaved schwertmannite samples demonstrated that nearly 100%of the bound sulfate was released during heating, and FTIR spectra indicated a transformation of schwertmannite to goethite. This structural change was not observed with autoclaved arsenated or chromated schwertmannite. These results suggest that the mobility of arsenate and chromate is not enhanced by the activity of acidophilic Fe(III)-reducing bacteria in mining-impacted sediments. In contrast, the presence of

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

Genesis and classification of soils developed on gabbro in the high reliefs of Maroua region, North Cameroon

Directory of Open Access Journals (Sweden)

Désiré Tsozué

2017-04-01

Full Text Available The purpose of this work was to examine the genesis, properties and classification of soils resulting from the weathering of gabbro rock in the high reliefs of Maroua in the Far North Region of Cameroon. The studied soils were ~ 2 m thick, made of four horizons which consisted of coarse saprolite, fine saprolite, loose loamy clayey horizon and humiferous horizon. From petrographical view point, at the bottom of the soil profile, the preservation of the bedrock structure was marked by numerous remnants of altered plagioclases shapes. The groundmass was characterized by a double spaced fine, ranging to equal, enaulic c/f related distribution pattern. It was yellowish, characterized by weakly separated granular microstructure in the fine saprolite and had a speckled and cloudy limpidity in the loose loamy clayey horizon. Secondary minerals consisted of montmorilonite, kaolinite, goethite, quartz, gibbsite, lepidocrocite, sepiolite, feldspar and calcite. Globally, Si/Al ratio ranged between 2.85 and 3.24. The chemical index of alteration ranged from 50.95 to 55.27 % while the mineralogical index of alteration values were between 1.90 and 10.54 %. Physicochemically, soil pH varied from slightly acidic to slightly above neutral. Soil organic carbon contents were low to very low. Exchangeable bases contents were high, mostly represented by Ca2+ and Mg2+. The CEC of soils and the CEC of clay were also high, ranging respectively between 53.68 and 82.88 cmol(+.kg-1, and 116.80 and 181.38 cmol(+.kg-1. The studied soils were classified as dystric haplustepts clayey isohyperthermic. They were developed in situ by the collapse of primary mineral structures from the bottom of the coarse saprolite, due to leaching as a result of bisiallitisation and monosiallitisation. This is accompanied by a progressive ferruginization of materials, confirmed by the densification under the microscope of goethitic brown veil from the base to the loamy clay horizon and the

Tracing the fate of sulfamethoxazole and its metabolites in subsurface: conceptualization and modelling

Science.gov (United States)

Rodriguez-Escales, Paula; Sanchez-Vila, Xavier

2016-04-01

The degradation of low adsorptive SMX in subsurface porous media is spatially and temporally variable. It depends on various environmental factors such as in situ redox potential, availability of nutrients, local soil characteristics, and temperature. Its degradation is better under anoxic conditions and by co-metabolism processes. In this work, we first develop a conceptual model of degradation of SMX under different redox conditions (denitrification and iron reducing conditions), characterizing the metabolite formation in each condition, and second, we construct a mathematical model that allows reproducing different experiments of SMX degradation reported in the literature. The model was validated using the experimental data from Barbieri et al. (2012), Nödler et al. (2012) and Mohatt et al. (2011). The model reproduces the reversible degradation of SMX under the presence of nitrous acid as an intermediate product of denitrification (it is the conjugate acid of nitrite), as well as, the metabolite formation (4-nitro-SMX and desamino SMX). In those experiments degradation was mediated by the transient formation of a diazonium cation, which was considered responsible of the substitution of the amine radical by a nitro radical, forming the 4-nitro-SMX. On the other hand, both the diazonium compound and the methanol present in the experiment produced a deamination in the SMX, producing desamino-SMX. The formation of these metabolites was unstable and they were retransformed to SMX. Concerning the iron conditions, SMX was degraded due to the oxidation of iron (Fe2+), which was previously oxidized from goethite due to the degradation of a pool of labile organic carbon. As the oxidation of iron occurred on the goethite surface, the best model to reproduce the SMX reduction was a power law rate. Our work is an attempt to properly formulate the degradation process of an emerging compound considering the real degradation mechanisms, rather than using an upscaled black

Influence of uranyl speciation and iron oxides on uranium biogeochemical redox reactions

Energy Technology Data Exchange (ETDEWEB)

Stewart, B.D.; Amos, R.T.; Nico, P.S.; Fendorf, S.

2010-03-15

Uranium is a pollutant of concern to both human and ecosystem health. Uranium's redox state often dictates its partitioning between the aqueous- and solid-phases, and thus controls its dissolved concentration and, coupled with groundwater flow, its migration within the environment. In anaerobic environments, the more oxidized and mobile form of uranium (UO{sub 2}{sup 2+} and associated species) may be reduced, directly or indirectly, by microorganisms to U(IV) with subsequent precipitation of UO{sub 2}. However, various factors within soils and sediments may limit biological reduction of U(VI), inclusive of alterations in U(VI) speciation and competitive electron acceptors. Here we elucidate the impact of U(VI) speciation on the extent and rate of reduction with specific emphasis on speciation changes induced by dissolved Ca, and we examine the impact of Fe(III) (hydr)oxides (ferrihydrite, goethite and hematite) varying in free energies of formation on U reduction. The amount of uranium removed from solution during 100 h of incubation with S. putrefaciens was 77% with no Ca or ferrihydrite present but only 24% (with ferrihydrite) and 14% (no ferrihydrite) were removed for systems with 0.8 mM Ca. Imparting an important criterion on uranium reduction, goethite and hematite decrease the dissolved concentration of calcium through adsorption and thus tend to diminish the effect of calcium on uranium reduction. Dissimilatory reduction of Fe(III) and U(VI) can proceed through different enzyme pathways, even within a single organism, thus providing a potential second means by which Fe(III) bearing minerals may impact U(VI) reduction. We quantify rate coefficients for simultaneous dissimilatory reduction of Fe(III) and U(VI) in systems varying in Ca concentration (0 to 0.8 mM), and using a mathematical construct implemented with the reactive transport code MIN3P, we reveal the predominant influence of uranyl speciation, specifically the formation of uranyl

Study of the corrosion products formed on carbon steels in the tropical atmosphere of Panama

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Jaén, J. A.

2003-12-01

Full Text Available Mössbauer spectroscopy and X-ray powder diffraction (in selected samples have been used to characterize corrosion products on carbon steels after atmospheric exposure to the tropical Panamanian locations of Panama and Colon, classified according to ISO 9223 as C3 and C5, respectively. Goethite (α-FeOOH of intermediate particle size (20-100 nm, lepidocrocite (γ-FeOOH, a spinel phase consisting of non-stoichiometric magnetite (Fe_3-xO₄ and/or maghemite (γ-Fe₂O₃ and nano-sized particles were identified in the corrosion products. The spinel phase is related to short term atmospheric exposure transforms in time to other corrosion products. The corrosion resistance increased with fraction of goethite following a saturation-type behavior.

Se caracterizaron los productos de corrosión de aceros al carbono expuestos a las atmósferas tropicales panameñas localizadas en Panamá y Colón, mediante el uso de la espectroscopia Mössbauer y difracción de rayos-X (en muestras seleccionadas. Las atmósferas se clasifican como C3 y C5, respectivamente, de acuerdo a la norma ISO 9223. Se lograron identificar los compuestos goethita (α-FeOOH de tamaño de partícula intermedio (20-100 nm, lepidocrocita (γ-FeOOH, una fase de espinela consistente en magnetita no estequiométrica (Fe_3-xO₄ y/o maghemita (γ-Fe₂O₃, y nanopartículas. La fase de espinela se puede correlacionar con exposiciones cortas a la atmósfera, transformándose en el tiempo en otros productos de corrosión. La resistencia a la corrosión se incrementa con la cantidad de goethita siguiendo una conducta de saturación.

Mineral weathering in acid saprolites from subtropical, southern Brazil Intemperismo subtropical de minerais em saprolitos ácidos do Sul do Brasil

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Celso Augusto Clemente

2007-12-01

Full Text Available Because weathering of minerals releases chemical elements into the biogeochemical cycle, characterization of their weathering products helps to better model groundwater quality, formation of secondary minerals and nutrient flux through the trophic chain. Based on microscopic and elemental analyses, weathering of riodacite from Serra Geral formation was characterized and weathering paths proposed. Three weathering paths of plagioclase phenocrystals were identified: plagioclase to gibbsite (Pg1; plagioclase to gels and gibbsite (Pg2; and plagioclase to gels, gibbsite and kaolinite (Pg3. Pyroxenes weathered to smectite and goethite (Py1, or to goethite and gibbsite (Py2, and magnetite weathered directly into iron oxides. Rock matrix comprises 90% of rock volume, and weathered to kaolinite and gibbsite, which explains why these minerals were the most abundant in the weathering products of these saprolites.O intemperismo de minerais primários disponibiliza elementos químicos no ciclo biogeoquímico, que por sua vez influencia a qualidade da água subterrânea, formação de minerais secundários e o fluxo de nutrientes na cadeia trófica. Com base na análise microscópica e elemental, o intemperismo de riodacito da formação Serra Geral foi caracterizado e mecanismos de intemperismo propostos. Três processos principais de intemperismo de fenocristais de plagioclásios foram identificados: plagioclásio para gibbsita (Pg1; plagioclásio para gel e gibbsita (Pg2, e plagioclásio para gel, gibbsita e caulinita (Pg3. Piroxênios intemperizaram-se para esmectita e goetita (Py1, ou para goethita e gibbsita (Py2, e magnetita intemperizou-se para óxidos de ferro. A matriz da rocha compõe 90% do volume total, e intemperiza-se para caulinita e gibbsita, o que explica a abundância destes minerais nos produtos de intemperismo destes saprolitos.

Genesis of the gossan at the Las Cruces Ore Deposit (SW Spain). Groundwater-Rock Interaction.

Science.gov (United States)

Scheiber, L.; Ayora, C.; Vázquez-Suñé, E.; Soler, A.

2016-12-01

The Las Cruces deposit has sparked an interest in the scientific community due to the exceptional genesis and mineralogical composition. The original gossan formed by goethite and hematite has been replaced by siderite and galena rock. The current gossan composition is as the result of the interaction of groundwater that circulates through the Niebla-Posadas aquifer and a gossan formed by Fe-oxyhydroxides. The groundwater conditions promoted the reductive dissolution of Pb-bearing goethite by the organic matter degradation and the formation of siderite and galena. Hydrochemical and isotopic characteristics of groundwater endorses this hypothesis. Thus, negative Eh values, the existence of H2S and the tendency to light sulfate isotope values show the reducing conditions of groundwater. The key role of the organic matter degradation is marked by the high ammonium, boron and dissolved organic carbon (DOC) concentrations together the light δ13C values, both in groundwater and siderite. The siderite precipitation is confirmed by the high pH values (up to 10), the low amount of Fe (<10ppb) and the thermodynamic calculations. The Fe-oxyhydroxides are a high adsorption capacity which is capable of absorbing metals as arsenic, lead and antimony. The reductive dissolution of these minerals involves the release of these metal to groundwater. Then, the groundwater rich in sulfur and an excess of lead produce the galena precipitation. The likeness between the δ34S values, both the gossan and groundwater, reveals that the sulfur of the galena come from the currently groundwater. A reactive transport model confirm that the present day groundwater flux and composition is able to form the siderite rock in less than 1Ma, with no external supply of reactants. The limiting factor of the process is the Dissolved Organic Carbon (DOC) concentration in groundwater, i.e., higher concentrations would decrease the formation time, whereas the result is not sensitive to flow conditions.

Study of archaeological iron objects by PGAA, Mössbauer spectroscopy and X-ray diffraction

Energy Technology Data Exchange (ETDEWEB)

Wagner, F. E., E-mail: fwagner@tum.de [Technische Universität München, Physik- Department E15 (Germany); Gebhard, R. [Archäologische Staatssammlung München (Germany); Häusler, W.; Wagner, U. [Technische Universität München, Physik- Department E15 (Germany); Albert, P.; Hess, H. [Archäologische Staatssammlung München (Germany); Révay, Z.; Kudejová, P.; Kleszcz, K. [Technische Universität München, Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II) (Germany)

2016-12-15

Archaeological iron objects often corrode rapidly after their excavation, even though they have survived long times of burial in the ground. Chlorine that accumulates during burial is thought to play a major role in this destructive post-excavation corrosion. It is therefore important for the conservation of such objects to determine the chlorine content in a non-destructive manner and, if necessary, to remove the chlorine from the artefacts by appropriate methods. Such methods are leaching in alkaline solutions or heating in a reducing atmosphere at temperatures up to 800 {sup ∘}C. We have studied the efficiency of the heating method using prompt gamma activation analysis (PGAA) for monitoring the Cl content and Mössbauer spectroscopy at room temperature (RT) and 4.2 K as well as X-ray diffraction to study the mineralogical transformations of the rust layers. The heat treatments were performed a N{sub 2}/H{sub 2} (90/10) mixture at temperatures up to 750 {sup ∘}C. As test specimens sections of iron rods from the Celtic oppidum of Manching (Bavaria) were used. The initial Cl contents of the pieces varied in the range of several hundred ppm, referring to the iron mass. Annealing for 24 h at 350, 550 and 750 {sup ∘}C was found to reduce the Cl contents of the specimens, to about 70, 30 and 15 % of the original values, respectively. The rust consists mainly of goethite with admixtures of magnetite, lepidocrocite and akaganeite, which is thought to be a major carrier of chlorine, probably together with iron chlorides. Much of the goethite is so fine-grained that it does not split magnetically at RT. Annealing converts the rust mainly to maghemite at 350 {sup ∘}C, to magnetite at 550 {sup ∘}C and to wüstite plus magnetite and metallic iron at 750 {sup ∘}C. Pure akaganeite behaves in nearly the same manner.

Testing the Prediction of Iron Alteration Minerals on Low Albedo Asteroids

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Jarvis, K. S.; Vilas, Faith; Howell, E.; Kelley, M.; Cochran, A.

1999-01-01

Absorption features centered near 0.60 - 0.65 and 0.80 - 0.90 micron were identified in the spectra of three low-albedo main-belt (165, 368, 877) and two low-albedo outer-belt (225, 334) asteroids (Vilas et al., Icarus, v. 109,274,1994). The absorption features were attributed to charge transfer transitions in iron alteration minerals such as goethite, hematite, and jarosite, all products of aqueous alteration. Concurrently, Jarvis et al. (LPSC XXIV, 715, 1993) presented additional spectra of low-albedo asteroids that had absorption features centered near 0.60 - 0.65 micron without the longer wavelength feature. Since these two features in iron oxides originate from the same ground state, and the longer wavelength feature requires less energy to exist, the single shorter wavelength feature cannot be caused by the iron alteration minerals. In addition, spectra of minerals such as hematite and goethite show a rapid increase in reflectance beginning near 0.5 micron absent in the low-albedo asteroid spectra. The absence of this rise has been attributed to its suppresion from opaques in the surface material. Spectra on more than one night were available for only one of these five asteroids, 225 Henrietta, and showed good repeatability of the 0.65-micron feature. We have acquired additional spectra of all five asteroids in order to test the repeatability of the 0.65-micron feature, and the presence and repeatability of the features centered near 0.8 - 0.9 micron. We specifically will test the possibility that longer wavelength features could be caused by incomplete removal of telluric water. Asteroid 877 Walkure is a member of the Nysa-Hertha family, and will be compared to spectra of other members of that family. Data were acquired in 1996 and 1999 on the 2.1-m telescope with a facility cassegrain spectrograph, McDonald Observatory, Univ. Of Texas, and the 1.5-m telescope with facility cassegrain spectrograph at CTIO. This research is supported by the NASA Planetary

Moessbauer studies of impactites from Huamalies province in Huanuco Region

International Nuclear Information System (INIS)

Bustamante, A.; Espinoza, S.; Morales, G.; Scorzelli, R. B.

2005-01-01

This report is about the X-ray diffraction and Moessbauer studies of three impactite samples denominated PMe-8, PMe-9 and PMe-11 from Huamalies Province in Huanuco Region, Peru. When terrestrial rocks are submitted to pressures higher than 60 GP, the majority is completely melted, forming a kind of glass called impactites. X-ray diffraction indicates the presence of quartz as the principal mineralogical phase in all samples. The 57 Fe Moessbauer spectra at room temperature of samples PMe-8 and PMe-9 show broadened spectra that were fitted using a distribution model. The most probable field of the magnetic component is 34 T, corresponding to the presence of small particles of goethite, confirmed by the 4.2 K spectrum. For the sample PMe-11, the MS showed the presence of well crystallized hematite.

BET measurements: Outgassing of minerals

DEFF Research Database (Denmark)

Clausen, Liselotte; Fabricius, Ida Lykke

2000-01-01

Outgassing minerals at elevated temperatures prior to BET measurements can lead to phase changes, especially in the case of amorphous and poorly crystalline materials. In order to evaluate the applicability of the BET method when low outgassing temperatures are required, selected aquifer minerals...... were outgassed at different temperatures and for different times. The studied minerals are 2-line ferrihydrite, goethite, lepidocrocite, quartz, calcite, ®-alumina, and kaolinite. The results demonstrate that measured specific surface areas of iron oxides are strongly dependent on outgassing conditions...... because the surface area increased by 170% with increasing temperature. In the poorly crystalline minerals, phase changes caused by heating were observed at temperatures lower than 100±C. Therefore low outgassing temperatures are preferable for minimizing phase changes. As demonstrated in this study...

EPR spectroscopy can help with paint pigment provenance

International Nuclear Information System (INIS)

Troup, G.J.; Hutton, D.R.

2000-01-01

Full text: The microwave magnetic spectroscopic technique EPR can be used to determine the presence of paramagnetic impurities in paint pigments, and the purity of composition regarding the main colourant. Hence EPR can help determine provenance of pigments, just as it can for gemstones. Specimens of Lapis Lazuli (synthetic, Afghanistan, Chile, Greenland) showed quite recognisably different spectra, at room temperature, in a Varian E-12 X-band spectrometer (9.1 GHz frequency). Similarly, specimens of yellow ochre, two imported into Australia, one North Australian, another 95% pure Goethite, showed recognisably different spectra. The North Australian one uniquely gave a known radiation damage signal from quartz, perhaps to be expected, given the abundance of radioactive ores in the region. Further samples have been obtained and the results from these will be reported

Análise de pinturas rupestres do Abrigo do Janelão (Minas Gerais por microscopia raman

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Dalva Lúcia A. de Faria

2011-01-01

Full Text Available Rock art paintings from Abrigo do Janelão (Minas Gerais, Brazil were non-destructively investigated by Raman Microscopy, aiming at the identification of materials used, their interaction and degradation. This technique is particularly tailored for heterogeneous samples and allows unequivocal identification of the substances present in the investigated sample. Pigments, were identified together with products of microbiological degradation; no binders were detected. White pigment was identified as calcite (CaCO3, whereas charcoal was used as black, goethite (α-FeOOH as yellow and hematite (α-Fe2O3 as red. Whewellite (CaC2O4.H2O and weddelite (CaC2O4.2H2O were detected and their origin was assigned to degradation products from microbiological activity.

New Insights in the Long-Term Atmospheric Corrosion Mechanisms of Low Alloy Steel Reinforcements of Cultural Heritage Buildings

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Marie Bouchar

2017-06-01

Full Text Available Reinforcing clamps made of low alloy steel from the Metz cathedral and corroded outdoors during 500 years were studied by OM, FESEM/EDS, and micro-Raman spectroscopy. The corrosion product layer is constituted of a dual structure. The outer layer is mainly constituted of goethite and lepidocrocite embedding exogenous elements such as Ca and P. The inner layer is mainly constituted of ferrihydrite. The behaviour of the inner layer under conditions simulating the wetting stage of the RH wet/dry atmospheric corrosion cycle was observed by in situ micro-Raman spectroscopy. The disappearance of ferrihydrite near the metal/oxide interface strongly suggests a mechanism of reductive dissolution caused by the oxidation of the metallic substrate and was observed for the first time in situ on an archaeological system.

Characterization of Corrosion Products on Carbon Steel Exposed to Natural Weathering and to Accelerated Corrosion Tests

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Renato Altobelli Antunes

2014-01-01

Full Text Available The aim of this work was to compare the corrosion products formed on carbon steel plates submitted to atmospheric corrosion in urban and industrial atmospheres with those formed after accelerated corrosion tests. The corrosion products were characterized by X-ray diffraction, Mössbauer spectroscopy, and Raman spectroscopy. The specimens were exposed to natural weathering in both atmospheres for nine months. The morphologies of the corrosion products were evaluated using scanning electron microscopy. The main product found was lepidocrocite. Goethite and magnetite were also found on the corroded specimens but in lower concentrations. The results showed that the accelerated test based on the ASTM B117 procedure presented poor correlation with the atmospheric corrosion tests whereas an alternated fog/dry cycle combined with UV radiation exposure provided better correlation.

Selective Dissolution Techniques, X-Ray Diffraction and Moessbauer Spectroscopy Studies of Forms of Fe in Particle-Size Fractions of an Entic Haplustoll

International Nuclear Information System (INIS)

Acebal, S. G.; Aguirre, M. E.; Santamaria, R. M.; Mijovilovich, A.; Petrick, S.; Saragovi, C.

2003-01-01

Particle-size fractions (o = mean diameter, 5-2 μm, 2-1 μm, and 57 Fe Moessbauer spectroscopy (MS). Quartz, feldspar, smectite, illite and interstratified illite-smectite are the dominant minerals whereas Fe oxides and oxy-hydroxides are present in low concentration but increase as particle size decreases. Poorly crystallized oxides (highly Al-substituted hematite and goethite) amounts are lower, comparable to or slightly higher than the hematite amounts in the o 5-2 μm, 2-1 μm and 3+ and Fe 2+ are associated to the clay minerals and/or hydroxyl-interlayered 2:1 type material present; part of this Fe 3+ is located in the hydroxy-interlayers its amount being higher in the smallest fraction. Any possible changes after the PY and NaOH treatments were not detected by MS.

Evaluation of the Cerro Solo nuclear ore, province of Chubut. Geological characteristics of the deposit and of the basin. Pt. 2

International Nuclear Information System (INIS)

Benitez, A.F.; Fuente, A.; Maloberti, A.; Landi, V.A.; Bianchi, R.E.; Marveggio de Bianchi, N.; Gayone, M.R.

1993-01-01

The Cerro Solo uranium ore deposit, is located 420 km west from Trelew city, Chubut province, in the extra-andean. The geologic environment belongs to the northwest edge portion of the intracratonic San Jorge Gulf Basin. The uraniferous district is named Pichinanes Ridge district. The mineralization lies 25 to 130 m depth, and is hosted by Los Adobes formation aged Aptian-Albian, made up by conglomerates, sandstones, coarse-sandstones and less abundant siltstones and claystones. The Cerro Solo ore deposit that belongs to the sandstone type-uranium occurrences are lenticular or tabular shaped, associated with organic material and pyrite, generally roughly parallel to the bedding (Trend-Type). The uranium minerals are uraninite and coffinite associated with organic material and pyrite, and frequently hematite, goethite, calcite, siderite and barite are observed. (Author)

Clay mineralogy in different geomorphic surfaces in sugarcane areas

Science.gov (United States)

Camargo, L.; Marques, J., Jr.

2012-04-01

The crystallization of the oxides and hydroxides of iron and aluminum and kaolinite of clay fraction is the result of pedogenetic processes controlled by the relief. These minerals have influence on the physical and chemical attributes of soil and exhibit spatial dependence. The pattern of spatial distribution is influenced by forms of relief as the geomorphic surfaces. In this sense, the studies aimed at understanding the relationship between relief and the distribution pattern of the clay fraction attributes contribute to the delineation of specific areas of management in the field. The objective of this study was to evaluate the spatial distribution of oxides and hydroxides of iron and aluminum and kaolinite of clay fraction and its relationship with the physical and chemical attributes in different geomorphic surfaces. Soil samples were collected in a transect each 25 m (100 samples) and in the sides of the same (200 samples) as well as an area of 500 ha (1 sample each six hectare). Geomorphic surfaces (GS) in the transect were mapped in detail to support mapping the entire area. The soil samples were taken to the laboratory for chemical, physical, and mineralogical analysis, and the pattern of spatial distribution of soil attributes was obtained by statistics and geostatistics. The GS I is considered the oldest surface of the study area, with depositional character, and a slope ranging from 0 to 4%. GS II and III are considered to be eroded, and the surface II plan a gentle slope that extends from the edge of the surface until the beginning of I and III. The crystallographic characteristics of the oxides and hydroxides of iron and aluminum and kaolinite showed spatial dependence and the distribution pattern corresponding to the limits present of the GS in the field. Surfaces I and II showed the best environments to the degree of crystallinity of hematite and the surface III to the greatest degree of crystallinity of goethite agreeing to the pedoenvironment

High-Resolution Mineralogical Characterization and Biogeochemical Modeling of Uranium Reduction Pathways at the NABIR Field-Research Center

International Nuclear Information System (INIS)

David R. Veblen; Chen Zhu; Lee Krumholz; Claudine Stirling; Emma-Kate Potter; Alex N. Halliday

2004-01-01

The effectiveness and feasibility of bioremediation at the field scale cannot be fully assessed until the mechanisms of immobilization and U speciation in the solid matrix are resolved. However, characterization of the immobilized U and its valence states is extremely difficult, because microbially mediated mineral precipitates are generally nanometer (nm)-sized, poorly crystalline, or amorphous. We are developing combined field emission gun--scanning electron microscopy (FEG-SEM, at Indiana University) and FEG transmission electron microscopy (TEM, at Hopkins) to detect and isolate uranium containing phases; (1) method developments for TEM sample preparations and parallel electron energy loss spectroscopy (EELS) determination of uranium valence; and (2) to determine the speciation, fate, reactivity, valence states of immobilized uranium, using the state-of-the-art 300-kV, FEG-TEM. We have obtained preliminary results on contaminated sediments from Area 3 at the Oak Ridge Field Research Center (FRC). TEM results show that the sediments contain numerous minerals, including quartz, mica/clay (muscovite and/or illite), rutile, ilmenite, zircon, and an Al-Sr-Ce-Ca phosphate mineral, none of which contain uranium above the EDS detection limit. Substantial U (up to ∼2 wt.%) is, however, clearly associated with two materials: (1) the Fe oxyhydroxide and (2) clots of a chemically complex material that is likely a mixture of several nm-scale phases. The Fe oxyhydroxide was identified as goethite from its polycrystalline SAED pattern and EDS analysis showing it to be very Fe-rich; the aggregate also displays one of several morphologies that are common for goethite. U is strongly sorbed to goethite in the FRC sediment, and the ubiquitous association with phosphorous suggests that complexes containing both U and P may play an important role in that sorption. Results from bulk analysis and SEM had previously demonstrated the association of U with Fe and thus suggested that U

UV, visible, and near-IR reflectivity data for magnetic soils/rocks from Brazil

Science.gov (United States)

Vempati, R. K.; Morris, R. V.; Lauer, H. V., Jr.; Coey, J. M. D.

1991-01-01

The objective is to obtain UV, visible, and near-IR reflectivity spectra for several magnetic Brazilian soils/rocks and compare them to corresponding data for Mars to see if these materials satisfy both magnetic and spectral constraints for Mars. Selected physical properties of the magnetic Brazilian soils/rocks are presented. In general, the spectral features resulting from ferric crystal-field transitions are much better defined in the spectra of the magnetic Brazilian soils/rocks than in Martian spectral data. Presumably, this results from a relatively higher proportion of crystalline ferric oxides for the former. The apparent masking of the spectral signature of maghemite by hematite or goethite for the Brazilian samples implies the magnetic and spectral constraints for Mars can be decoupled. That is, maghemite may be present in magnetically-significant but optically-insignificant amounts compared to crystalline hematite.

Comparative study of ceramic blocks for masonry produced in Paraiba and Rio Grande do Norte

International Nuclear Information System (INIS)

Santos, R.C. dos; Melo, O.B. de; Macedo, R.S. de; Silva, B.J. da; Goncalves, W.P.; Santana, L.N.L.

2011-01-01

The aim of this study to analyze the properties of ceramic blocks produced by the states of Paraiba and Rio Grande do Norte. For this, the raw materials used in the fabrication of these blocks were characterized using the techniques of chemical, granulometry and mineralogical analysis and determination of the plasticity index of mixture ceramic. The properties of the ceramic blocks were determined by evaluating the geometric and visual characteristics and determining the water absorption and compressive strength, according to technical recommendations ABNT NBR 15270. It can be observed that samples have chemical compositions with a predominance of SiO 2 and Al 2 O 3 and Fe 2 O 3 and they are composed of mica, kaolinite, quartz, feldspar and goethite. It was also noted that all blocks showed compressive strength less than 1.5 MPa. (author)

Study of Dronino Iron Meteorite Weathering in Clay Sand Using Mössbauer Spectroscopy

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Grigoriy A. Yakovlev

2016-06-01

Full Text Available Weathering products of two fragments of Dronino iron ungrouped meteorite found in the wet and drier clay sand were studied using X-ray diffraction and Mössbauer spectroscopy with a high velocity resolution. The products of metal oxidation in the internal and external surface layers were different for both fragments. The weathering products in fragment found in the wet clay sand contain magnetite (Fe3O4, maghemite (γ-Fe2O3, goethite (α-FeOOH and probably ferrihydrite (5Fe2O3∙9H2O while those in fragment found in drier clay sand contained ferric hydrous oxides (FeOOH and siderite (FeCO3 mainly. Concretions found near the first fragment contain ferric hydrous oxides (FeOOH mainly. This work is licensed under a Creative Commons Attribution 4.0 International License.

Mineral chemistry in inerted layers of red mud from Hydro Alunorte

International Nuclear Information System (INIS)

Pinheiro, Erika Raiol; Fernandez, Oscar Jesus Choque; Costa, Josivaldo Chaves

2016-01-01

In this study were carried out the mineral chemistry variations in samples of the different depths and deposition time of the red mud solids from Hydro ALUNORTE Para. Red mud samples were analyzed by X-ray diffraction and fluorescence. The predominant chemical compositions are: iron, sodium and titanium oxides, residual alumina and silica. Similar phases along the profiles layers are similar and are represented by hematite, anatase, goethite, sodalite and quartz. Sometimes occur calcite, zircon, cristobalite and gypsum. The iron percentage increases in the deeper layers as well as the residual silica and alumina decrease with depth. The titanium oxide had constant. The pH of the samples ranged from 9.9 to 11. The predominant size particles are < 74 micrometers. The study shows the possibility of working with this residue in other applicability observing its characteristics. (author)

Geochemical modelling of the sorption of tetravalent radioelements

International Nuclear Information System (INIS)

Bond, K.A.; Tweed, C.J.

1991-05-01

The results of an experimental study of the sorption of a range of tetravalent radioelements, plutonium (IV), tin (IV), thorium(IV) and uranium(IV), onto clay at pH8 and pH11 have been successfully simulated using a triple layer sorption model. The model has been incorporated into HARPHRQ, a geochemical program based on PHREEQE. The model has been parameterised using data for sorption onto ferric oxyhydroxide and goethite. The effects of hydroxycarboxylic acids on the sorption process have also been investigated experimentally. It was generally observed that in the presence of 2x10 -3 M gluconate, sorption was reduced by up two orders of magnitude. The model has satisfactorily simulated these lower sorptivities, through assuming competing sorption and complexation reactions. This work, therefore, further confirms the need to take account of such organic materials in safety assessment modelling. (author)

Methods of soil organic carbon determination in Brazilian savannah soils

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Juliana Hiromi Sato

2014-08-01

Full Text Available Several methods exist for determining soil organic carbon, and each one has its own advantages and limitations. Consequently, a comparison of the experimental results obtained when these methods are employed is hampered, causing problems in the comparison of carbon stocks in soils. This study aimed at evaluating the analytical procedures used in the determination of carbon and their relationships with soil mineralogy and texture. Wet combustion methods, including Walkley-Black, Mebius and Colorimetric determination as well as dry combustion methods, such as Elemental and Gravimetric Analysis were used. Quantitative textural and mineralogical (kaolinite, goethite and gibbsite analyses were also carried out. The wet digestion methods underestimated the concentration of organic carbon, while the gravimetric method overestimated. Soil mineralogy interfered with the determination of carbon, with emphasis on the gravimetric method that was greatly influenced by gibbsite.

OPAQUE MINERAL CONTENT OF DUTLUCA VOLCANICS (BURHANİYE - BALIKESİR: THE EFFECT OF HYDROTHERMAL ALTERATION ON THESE MINERALS

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Şükrü KOÇ

2016-12-01

Full Text Available Dutluca volcanics, which are known as Hallaçlar Formation in regional scale in the study area (Kurshens- ky, 1976, are composed of hydrothermally altered andesite and basaltic andesite. In these rocks, sulfidic minerals such as pyrite, enargite and chalcosine, and oxide and hydroxide minerals such as magnetite, hematite and goethite were detected as opaque minerals. The presence of enargite in opaque mineral para- genesis, and the changes observed in structures and textures of opaque and silicate minerals indicate that examined volcanics have been altered by highly sulfidic hydrothermal solutions. During the hydrothermal alteration process, which indicates at least in two phases, a diffuse pyritization rich in H S in reducing conditions and enargite mineral, which is known as pathfinder minerals in such processes, formed in the first phase. Later on; the extensive martitization developed in oxidizing conditions.

Iron oxides in acid mine drainage environments and their association with bacteria

Energy Technology Data Exchange (ETDEWEB)

Ferris, F G; Tazaki, K; Fyfe, W S

1989-01-20

A variety of iron oxides were identified by X-ray diffraction in sediments receiving acid drainage from mine tailing and coal refuse impoundments. Small amounts of goethite and hematite were found in the sediment samples. However, the major iron oxide species was ferrihydrite which gave diffuse diffraction bands at angles corresponding to d2.5, 2.2 and 1.5 Angstrom. Main core line binding energies in Fe (2p) and O (1s) X-ray photoelectron spectra were consistent with the hydrous nature and predominance of ferrihydrite. Electron microscopy and energy-dispersive X-ray spectroscopy also showed that individual bacterial cells promoted the development of iron oxide mineralization. The bacterial associated iron oxides were similar to those in the bulk sediment samples, and exhibited structures conforming to the presence of chemisorbed sulfate or silicate anions. 23 refs., 3 figs.

Ecological interactions in Cloudina from the Ediacaran of Brazil: implications for the rise of animal biomineralization.

Science.gov (United States)

Becker-Kerber, Bruno; Pacheco, Mírian Liza Alves Forancelli; Rudnitzki, Isaac Daniel; Galante, Douglas; Rodrigues, Fabio; Leme, Juliana de Moraes

2017-07-14

At the Ediacaran/Cambrian boundary, ecosystems witnessed an unparalleled biological innovation: the appearance of shelled animals. Here, we report new paleoecological and paleobiological data on Cloudina, which was one of the most abundant shelled animals at the end of the Ediacaran. We report the close association of Cloudina tubes with microbial mat textures as well as organic-rich material, syndepositional calcite and goethite cement between their flanges, thus reinforcing the awareness of metazoan/microorganism interactions at the end of the Ediacaran. The preservation of in situ tubes suggests a great plasticity of substrate utilization, with evidence of different life modes and avoidance behavior. Geochemical analysis revealed walls composed of two secondary laminae and organic sheets. Some walls presented boreholes that are here described as predation marks. Taken together, these data add further information regarding the structuring of shelled animal communities in marine ecosystems.

Mineral chemistry in inerted layers of red mud from Hydro Alunorte; Quimica-mineral das camadas inertizadas em lama vermelha da Hydro Alunorte

Energy Technology Data Exchange (ETDEWEB)

Pinheiro, Erika Raiol; Fernandez, Oscar Jesus Choque; Costa, Josivaldo Chaves, E-mail: raiolerika@hotmail.com [Instituto Federal de Educacao, Ciencia e Tecnologia do Para (IFPA), Belem, PR (Brazil)

2016-07-01

In this study were carried out the mineral chemistry variations in samples of the different depths and deposition time of the red mud solids from Hydro ALUNORTE Para. Red mud samples were analyzed by X-ray diffraction and fluorescence. The predominant chemical compositions are: iron, sodium and titanium oxides, residual alumina and silica. Similar phases along the profiles layers are similar and are represented by hematite, anatase, goethite, sodalite and quartz. Sometimes occur calcite, zircon, cristobalite and gypsum. The iron percentage increases in the deeper layers as well as the residual silica and alumina decrease with depth. The titanium oxide had constant. The pH of the samples ranged from 9.9 to 11. The predominant size particles are < 74 micrometers. The study shows the possibility of working with this residue in other applicability observing its characteristics. (author)

Iron oxide and hydroxide precipitation from ferrous solutions and its relevance to Martian surface mineralogy

International Nuclear Information System (INIS)

Posey-Dowty, J.; Moskowitz, B.; Crerar, D.; Hargraves, R.; Tanenbaum, L.

1986-01-01

Experiments were performed to examine if the ubiquitousness of a weak magnetic component in all Martian surface fines tested with the Viking Landers can be attributed to ferric iron precipitation in aqueous solution under oxidizing conditions at neutral pH. Ferrous solutions were mixed in deionized water and various minerals were added to separate liquid samples. The iron-bearing additives included hematite, goethite, magnetite, maghemite, lepidocrocite and potassium bromide blank at varying concentrations. IR spectroscopic scans were made to identify any precipitates resulting from bubbling oxygen throughout the solutions; the magnetic properties of the precipitates were also examined. The data indicated that the lepidocrocite may have been preferentially precipitated, then aged to maghemite. The process would account for the presumed thin residue of maghemite on the present Martian surface, long after abundant liquid water on the Martian surface vanished. 40 references

Iron oxide and hydroxide precipitation from ferrous solutions and its relevance to Martian surface mineralogy

Science.gov (United States)

Posey-Dowty, J.; Moskowitz, B.; Crerar, D.; Hargraves, R.; Tanenbaum, L.

1986-01-01

Experiments were performed to examine if the ubiquitousness of a weak magnetic component in all Martian surface fines tested with the Viking Landers can be attributed to ferric iron precipitation in aqueous solution under oxidizing conditions at neutral pH. Ferrous solutions were mixed in deionized water and various minerals were added to separate liquid samples. The iron-bearing additives included hematite, goethite, magnetite, maghemite, lepidocrocite and potassium bromide blank at varying concentrations. IR spectroscopic scans were made to identify any precipitates resulting from bubbling oxygen throughout the solutions; the magnetic properties of the precipitates were also examined. The data indicated that the lepidocrocite may have been preferentially precipitated, then aged to maghemite. The process would account for the presumed thin residue of maghemite on the present Martian surface, long after abundant liquid water on the Martian surface vanished.

Mineralogical and geochemical features of the coarse saprolite developed on orthogneiss in the SW of Yaoundé, South Cameroon

Science.gov (United States)

Ndjigui, P.-D.; Badinane, M. F. B.; Nyeck, B.; Nandjip, H. P. K.; Bilong, P.

2013-03-01

A petrological investigation was performed in the coarse saprolite on orthogneiss in Yaoundé (South Cameroon) using combined whole rock geochemical (XRF, ICP-MS) and mineralogical (XRD, SEM) techniques. The orthogneiss has high contents in SiO2 (61.56 wt.%), Ba (916 ppm) and REE (209 ppm), moderate content in Al2O3 (14.34 wt.%) and negative Eu anomaly (Eu/Eu* = 0.68). The weathering leads to the formation of three main constituents in the coarse saprolite: (i) the loose materials (∼85 vol.%) are basically clayey silty with relic structure. They are composed of kaolinite, quartz and goethite. The loose materials have high contents in SiO2 (56-64.83 wt.%) and Al2O3 (21.48-23.96 wt.%), and moderate contents in V (163-236 ppm), Ba (95-340 ppm) and Zr (160-313 ppm). The REE content is low (∼49-169 ppm) relative to the parent rock with LREE-enrichment (LREE/HREE ∼ 7-17). Positive Ce anomaly (Ce/Ce* ∼ 3.35) is observed in the white veins and slight positive Eu anomalies (Eu/Eu* ∼ 1.2-1.4) are noted in all loose samples. The (La/Yb)N ratios (∼0.8-1.5) indicate high REE-fractionation. The mass balance calculation reveals the depletion of several elements except Al, Ti, Sc, Y, Th, Sb and Hf; (ii) the iron duricrust (∼10 vol.%) is located at the bottom and the top of the horizon. The mineral assemblage is dominated by hematite and goethite. The upper iron duricrust has high contents in Fe2O3 (45.60 wt.%) and Cr (1641 ppm), moderate contents in V (459 ppm) and Zn (143 ppm), and low REE content (47 ppm) with low LREE/HREE ratio (4.28). The upper iron duricrust is more enriched in Fe2O3 (53.26 wt.%) than the lower one. Vanadium, Cr and Zr have high contents relative to other trace elements. The REE content is low (39 ppm) as well as the LREE/HREE ratio (2.94). The iron duricrust has negative Ce anomalies (Ce/Ce* ∼ 0.66-0.69) and very low (La/Yb)N ratios (0.1-0.3). Several elements reported in the iron duricrust are highly leached except Fe, Cr, Zn, Sc, V, Pb, Zr

Sulfide oxidation and the natural attenuation of arsenic and trace metals in the waste rocks of the abandoned Seobo tungsten mine, Korea

International Nuclear Information System (INIS)

Lee, Pyeong-koo; Kang, Min-Ju; Choi, Sang-Hoon; Touray, Jean-Claude

2005-01-01

Mineralogical examinations were performed to characterize the formation of secondary minerals and natural removal process of dissolved As and trace metals (Pb, Zn and Cu) from sulfide oxidation. Laboratory-based leaching tests were also conducted to determine whether the concentrations of As and trace metals in the leachates from waste-rock materials and contaminated soil could be affected by the presence acids such as acid rainwater or acid mine drainage. Waste-rock materials and contaminated soil were compared by 4-day leaching tests using HNO 3 solutions of increasing acidity (0.00001-0.1mole/L). Mineralogical studies of the waste rocks confirmed the presence of Fe-(oxy)hydroxides (e.g. goethite), jarosite, elemental S, Fe-sulfates, amorphous Fe-As phases, anglesite and covellite as secondary minerals. These secondary minerals act as mineralogical scavengers of dissolved trace metals, SO 4 2- and acidity released by sulfide oxidation. Arsenic was attenuated by the adsorption on Fe-(oxy)hydroxides and/or the formation of an amorphous Fe-As phase, with a Fe/As ratio=1 (maybe scorodite: FeAsO 4 .2H 2 O). Electron probe microanalyses data showed that the Fe-(oxy)hydroxides had high concentrations of Pb (up to 21wt%), with appreciable amounts of As (up to 7.7wt%), Zn (up to 4.6wt%) and Cu (up to 2.5wt%) indicating that dissolved metals were co-precipitated and adsorbed onto Fe-(oxy)hydroxides, Fe(Mn)-hydroxides and Fe-sulfates. The results of the leaching experiments within the pH-range 3.5-5.0 indicated that acidic rainstorms may leach minor amounts of Pb (ca. 1.7-4.0% of total), Zn (ca. 0.8-2.2% of total), Cu (ca. 0.0-0.2% of total) and As (ca. 0.02-0.1% of total) from waste rocks, including the dissolution of soluble secondary minerals previously formed during prolonged dry periods, while dissolution of these elements was negligible from the contaminated soil. In the pH-range 1.0-3.0, the leaching of Pb (ca. 2.4-31% of total) and As (ca. 0.1-5.8% of total) from

Examination of Technetium Transport Through Soils Under Contrasting Redox Conditions: Batch and Column Work

Science.gov (United States)

Dozier, R.; Montgomery, D.; Wylie, E. M.; Dogan, M.; Moysey, S. M.; Powell, B. A.; Martinez, N. E.

2015-12-01

Experiments were performed under various reducing conditions to evaluate the transport behavior of technetium-99 (99Tc) in the presence of sandy clay loam soil from the Savannah River Site (SRS) and goethite, magnetite, and iron sulfide, which were selected for their increasing reducing potential. The experiments were conducted to investigate how redox reaction equilibria and rates affect the overall mobility of 99Tc as it transitions between the mobile Tc(VII) and immobile Tc(IV). Under oxygen-rich conditions, batch sorption isotherms measured for TcO4- across the concentration range 0.5 to 50 μg/L were linear with distribution coefficients (Kd) of 0.78 mL/g or lower, with decreasing sorption for goethite, magnetite, and iron sulfide, respectively. Addition of Na2S resulted in a marked increase in apparent 99Tc sorption to the solid phase, with Kd of 43 mL/g, 35 mL/g, and 29 mL/g, following the same mineral trend as previously. The increased Kd values are possibly due to reduction of Tc(VII) to Tc(IV), resulting in the formation of TcO2(s). SRS soil batch sorption isotherms measured for TcO4- across the same concentration range were also linear, with Kd of 0.7 mL/g for unadjusted pH, 5.1 mL/g for pH of around 6, and 6.7 mL/g for pH of around 4. Kinetic batch sorption tests showed less than 10% 99Tc sorption in an oxidizing environment and greater than 95% sorption in a reducing environment, with both reactions occurring on the order of minutes. In contrast, desorption experiments initiated by transferring the samples from a reducing environment (0.1% H2(g)/99.9% N2(g)) to atmospheric conditions resulted in a slow desorption step on the order of days. Column experiments conducted with the SRS sands indicate a retardation factor of 1.17 for 99Tc under oxygen rich conditions. Additional column experiments are being conducted to evaluate 99Tc transport dependencies on transitions between oxygen rich and poor conditions.

Effect of ionic strength on barium transport in porous media

Science.gov (United States)

Ye, Zi; Prigiobbe, Valentina

2018-02-01

Hydraulic fracturing (or fracking) is a well stimulation technique used to extract resources from a low permeability formation. Currently, the most common application of fracking is for the extraction of oil and gas from shale. During the operation, a large volume of brine, rich in hazardous chemicals, is produced. Spills of brine from wells or pits might negatively impact underground water resources and, in particular, one of the major concerns is the migration of radionuclides, such as radium (Ra2+), into the shallow subsurface. However, the transport behaviour of Ra2+ through a reactive porous medium under conditions typical of a brine, i.e., high salinity, is not well understood, yet. Here, a study on the transport behaviour of barium (Ba2+, congener of radium) through a porous medium containing a common mineral such as goethite (FeO(OH)) is presented. Batch and column flood tests were carried out at conditions resembling the produced brine, i.e., large values of ionic strength (I), namely, 1 to 3 mol/kg. The measurements were described with the triple layer surface complexation model coupled with the Pitzer activity coefficient method and a reactive transport model, in the case of the transport tests. The experimental results show that the adsorption of Ba2+ onto FeO(OH) increases with pH but decreases with I and it becomes negligible at the brine conditions. Moreover, even if isotherms show adsorption at large I, at the same conditions during transport, Ba2+ travels without retardation through the FeO(OH) porous medium. The triple layer model agrees very well with all batch data but it does not describe well the transport tests in all cases. In particular, the model cannot match the pH measurements at large I values. This suggests that the chemical reactions at the solid-liquid interface do not capture the mechanism of Ba2+ adsorption onto FeO(OH) at large salinity. Finally, this study suggests that barium, and potentially its congeners, namely, radium

Age of the Xalnene Ash, Central Mexico and Archeological Implications

Science.gov (United States)

Renne, P. R.; Feinberg, J. M.; Waters, M. R.; Cabrales, J. A.; Castillo, P. O.; Campa, M. P.; Knight, K. B.

2005-12-01

Human footprints ~40 ka old have been reported from the Toloquilla quarry near Valsequillo Reservoir, ca. 15 km south of the city of Puebla in central Mexico (http://www.mexicanfootprints.co.uk/default.htm). If correct, this would be important evidence for early peopling of the Americas. The indentations interpreted as footprints and other ichnofossils occur on the surface of an indurated basaltic lapilli tuff within a several meter thick sequence of thinly bedded (1-10 cm) tuffs of similar character, lacking paleosols, erosional features or interlayered sediments, informally known as the Xalnene ash. A sample was collected at 18°55.402` N latitude and 098°09.375` W longitude from the surface on which the purported footprints occur. Lapilli were separated and analyzed by incremental heating 40Ar/39Ar methods, yielding 9 indistinguishable plateau ages averaging 1.30 ±0.03 Ma (2σ) for single lapilli (N=6) and multiple lapilli (N=3) subsamples. Though some minor discordance (presumably due to 39Ar recoil) is manifest in 5 of the age spectra, all plateaux comprise >60% of the 39Ar released and 4 or more consecutive steps. Paleomagnetic data from azimuthally unoriented bulk samples of 11.25 cm3 reveal a reverse polarity (I = -32.1°) thermoremanent component carried by titanomagnetite and a normal polarity component carried by goethite. Measurements on individual matrix-free lapilli lack the goethite component, which is presumed to be associated with the clay-rich cement. Consistency of the reverse component implies deposition of the lapilli at supra-Curie temperatures, with no postdepositional reworking. Reverse polarity is consistent with deposition during chron C1r.2r (1.77 to 1.07 Ma) as indicated by the 40Ar/39Ar data. If the features observed on the tuff are indeed footprints, their 1.3 Ma antiquity would be truly remarkable, predating by far any other evidence for human presence in the Americas and in fact predating the evolutionary emergence of Homo sapiens

Modelling sulfamethoxazole degradation under different redox conditions

Science.gov (United States)

Sanchez-Vila, X.; Rodriguez-Escales, P.

2015-12-01

Sulfamethoxazole (SMX) is a low adsorptive, polar, sulfonamide antibiotic, widely present in aquatic environments. Degradation of SMX in subsurface porous media is spatially and temporally variable, depending on various environmental factors such as in situ redox potential, availability of nutrients, local soil characteristics, and temperature. It has been reported that SMX is better degraded under anoxic conditions and by co-metabolism processes. In this work, we first develop a conceptual model of degradation of SMX under different redox conditions (denitrification and iron reducing conditions), and second, we construct a mathematical model that allows reproducing different experiments of SMX degradation reported in the literature. The conceptual model focuses on the molecular behavior and contemplates the formation of different metabolites. The model was validated using the experimental data from Barbieri et al. (2012) and Mohatt et al. (2011). It adequately reproduces the reversible degradation of SMX under the presence of nitrite as an intermediate product of denitrification. In those experiments degradation was mediated by the transient formation of a diazonium cation, which was considered responsible of the substitution of the amine radical by a nitro radical, forming the 4-nitro-SMX. The formation of this metabolite is a reversible process, so that once the concentration of nitrite was back to zero due to further advancement of denitrification, the concentration of SMX was fully recovered. The forward reaction, formation of 4-nitro SMX, was modeled considering a kinetic of second order, whereas the backward reaction, dissociation of 4-nitro-SMX back to the original compound, could be modeled with a first order degradation reaction. Regarding the iron conditions, SMX was degraded due to the oxidation of iron (Fe2+), which was previously oxidized from goethite due to the degradation of a pool of labile organic carbon. As the oxidation of iron occurred on the

Effects of soluble flavin on heterogeneous electron transfer between surface-exposed bacterial cytochromes and iron oxides

Energy Technology Data Exchange (ETDEWEB)

Wang, Zheming; Shi, Zhi; Shi, Liang; White, Gaye F.; Richardson, David J.; Clarke, Thomas A.; Fredrickson, Jim K.; Zachara, John M.

2015-08-25

Dissimilatory iron-reducing bacteria can utilize insoluble Fe(Mn)-oxides as a terminal electron acceptor under anaerobic conditions. For Shewanella species specifically, some evidence suggests that iron reduction is associated with the secretion of flavin mononucleotide (FMN) and riboflavin that are proposed to mediate electron transfer (Marsili et al., 2008). In this work, we used methyl viologen (MV•+)-encapsulated, porin-cytochrome complex (MtrCAB) embedded liposomes (MELs) as a synthetic model of the Shewanella outer membrane to investigate the proposed mediating behavior of secreted flavins. The reduction kinetics of goethite, hematite and lepidocrocite (200 µM) by MELs ([MV•+] ~ 42 µM and MtrABC ≤ 1 nM) were determined in the presence FMN at pH 7.0 in N2 atmosphere by monitoring the concentrations of MV•+ and FMN through their characteristic UV-visible absorption spectra. Experiments were performed where i) FMN and Fe(III)-oxide were mixed and then reacted with the reduced MELs and ii) FMN was reacted with the reduced MELs followed by addition of Fe(III)-oxide. The redox reactions proceeded in two steps: a fast step that was completed in a few seconds, and a slower one lasting over 400 seconds. For all three Fe(III)-oxides, the initial reaction rate in the presence of a low concentration of FMN (≤ 1 µM) was at least a factor of five faster than those with MELs alone, and orders of magnitude faster than those by FMNH2, suggesting that FMN may serve as a co-factor that enhances electron transfer from outer-membrane c-cytochromes to Fe(III)-oxides. The rate and extent of the initial reaction followed the order of lepidocrocite > hematite > goethite, the same as their reduction potentials, implying thermodynamic control on reaction rate. However, at higher FMN concentrations (> 1 µM), the reaction rates for both steps decreased and varied inversely with FMN concentration, indicating that FMN inhibited the MEL to Fe(III)-oxide electron transfer

Mineralogical and geochemical characterization of weathering profiles developed on mylonites in the Fodjomekwet-Fotouni section of the Cameroon Shear Zone (CSZ), West Cameroon

Science.gov (United States)

Tematio, P.; Tchaptchet, W. T.; Nguetnkam, J. P.; Mbog, M. B.; Yongue Fouateu, R.

2017-07-01

The mineralogical and geochemical investigation of mylonitic weathering profiles in Fodjomekwet-Fotouni was done to better trace the occurrence of minerals and chemical elements in this area. Four representative soil profiles were identified in two geomorphological units (upland and lowland) differentiating three weathering products (organo-mineral, mineral and weathered materials). Weathering of these mylonites led to some minerals association such as vermiculite, kaolinite, goethite, smectite, halloysite, phlogopite and gibbsite. The minerals in a decreasing order of abundance are: quartz (24.2%-54.8%); kaolinite (8.4%-36.0%); phlogopite (5.5%-21.9%); goethite (7.8%-16.1%); vermiculite (6.7%-15.7%); smectite (10.2%-11.9%); gibbsite (9.0%-11.8%) and halloysite (5.6%-11.5%) respectively. Patterns of chemical elements allow highlighting three behaviors (enriched elements, depleted elements and elements with complex behavior), depending on the landscape position of the profiles. In the upland weathering products, K, Cr and REEs are enriched; Ca, Mg, Na, Mn, Rb, S and Sr are depleted while Si, Al, Fe, Ti, Ba, Co, Cu, Ga, Mo, Nb, Ni, Pb, Sc, V, Y, Zn and Zr portray a complex behavior. Contrarily, the lowland weathering profiles enriched elements are Fe, Ti, Co, Cr, Cu, V, Zr, Pr, Sm, Tb, Dy, Er and Yb; while depleted elements are Ca, Mg, K, Na, Mn, Ba, Ga, S, Sr, Y, Zn, La, Ce and Nd; and Si, Al, Mo, Nb, Ni, Pb, Rb, Sc evidenced complex behaviors. In all the studied weathering products, the REEs fractionation was also noticeable with a landscape-position dependency, showing light REEs (LREEs) enrichment in the upland areas and heavy REEs (HREEs) in lowland areas. SiO2, Al2O3 and Fe2O3 are positively correlated with most of the traces and REEs (Co, Cu, Nb, Ni, Mo, Pb, Sc, V, Zn, Zr, La, Ce, Sm, Tb, Dy, Er, Yb), pointing to the fact that they may be incorporated into newly formed clay minerals and oxides. Ba, Cr, Ga, Rb, S, Sr, Y, Pr and Nd behave like alkalis and