The Experts below are selected from a list of 222 Experts worldwide ranked by ideXlab platform
Asfaw Zegeye - One of the best experts on this subject based on the ideXlab platform.
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Biogenic Mineral Precipitation during Antimony bearing Ferrihydrite bioreduction
2017Co-Authors: Asfaw Zegeye, Crosby Chang, Mustapha Abdelmoula, Thomas HauetAbstract:Fe(III) oxide such as ferrihydrite are ubiquitous in sediments and soils and due to their large surface area and reactive surface properties, they can be important sorbents of metal and metalloid such as antimony (Sb). Sorption and co-precipitation are considered to be the predominant processes by which most of the metals are scavenged by iron oxides, although co-precipitation appears to be more efficient for the removal of metals from solution. However, co-precipitated metals can be released to the surrounding environment as a direct or indirect consequence of dissimilatory iron reduction (DIR), which is a microbial reduction process of geochemical importance in natural systems. Even if DIR is often implicated in the remobilization of metals, the subsequent bio-Mineralization processes can lead to their sequestration into secondary Mineral products. Therefore, the aim of our study was to investigate Sb behavior during DIR. Sb-bearing ferrihydrites, with variable Sb/(Fe+Sb) molar ratios, were synthezised by coprecipitation and incubated with an iron reducing bacteria, Shewanella oneidensis MR1. Chemical analysis were undertaken to monitor the rate and the extent of the bioreduction and the mobilisation of Sb. Mössbauer analysis were carried out to characterize the bulk cation properties of the Biogenic Minerals at different temperatures. The spectra were fitted to obtain degrees of oxidation of iron and therefore it's Mineralogical signature. Measurements of the magnetization with respect to applied magnetic field were also carried out at room and low temperature and coercivity, saturation magnetization and remanence data obtained from hysteresis loops. The results revealed that the presence of Sb impacted the extent of reduction but no significant difference was measured in the rate of Fe(III) reduction. Although, the precipitaion of Biogenic magnetite was evidenced independently of the intial Sb/(Fe+Sb) molar ratios, the Biogenic magnetites displayed variable structural and magnetic properties implying an incorporation of Sb in their crystallographic structure.
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BioMineralization and fate of the FeII-FeIII hydroxy salt green rust vs. magnetite
2012Co-Authors: Frédéric Jorand, Asfaw Zegeye, Anne-sophie Sergent, Paul-philippe Rémy, Bruno Lartiges, Khalil HannaAbstract:It is well known that iron oxide reduction by Shewanella spp. bacteria promotes the formation of FeII bearing Minerals, such as the mixed FeII-FeIII hydroxysalt green rusts (GRs), in anaerobic conditions. Although the microbial-promoted generation of GRs is widely demonstrated, the mechanisms and factors governing the GR formation as the main secondary iron Mineral at the expense of other products in lab-scale investigations or environmental systems are largely unknown. As GR is an effective reductant for several contaminants the mechanism controlling the formation routes of GR merit investigation, from both the environmental and engineering points of view. Some factors such as cellular material (i.e. autoclaved cells and/or bacterial polymers), synthetic anionic polymers or oxyanions have been identified to control the route of the GR Mineralization as secondary Mineral at the expense of other products such as magnetite. The arrangement mode of the heterogeneous aggregates resulting from the interactions between bacterial cells , iron oxide particles and polymers was suggested to influence the routes of formation of secondary iron Minerals by limiting the diffusion of reactive species and thus creating favorable microenvironment for GR formation. In these aggregates, the electron transfer from cells to iron oxides is supported by organic electron shuttles. On the other hand, anionic polymers, colloidal and aqueous silicates were found to also influence the nature of the secondary iron Minerals through the stabilization of the G R crystals. The e results indicate clearly that the bacterial cells d rive indirectly the nature of the secondary FeII-bearing Mineral. Moreover, they give new insights into the understanding of the mechanisms of « Biogenic » Mineral formation based on the electron transfers from bacteria towards iron oxides. Finally, this work contributes to our understanding of the processes leading to green rust formation in environmental systems, such as soils or aquatic systems bio films , in which a very high cell density can be found at a micro-scale level, associated to exo-cellular polymers and natural silica Mineral composites .
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in situ monitoring of lepidocrocite bioreduction and magnetite formation by reflection mossbauer spectroscopy
American Mineralogist, 2011Co-Authors: Asfaw Zegeye, Khalil Hanna, Mustapha Abdelmoula, Muhammad Usman, Christian RubyAbstract:The miniaturized Mossbauer spectrometer (MIMOS II) was used to monitor in situ the Mineralogical transformation of lepidocrocite (γ-FeOOH) in a Shewanella putrefaciens culture under anaerobic conditions using methanoate as the electron source. Magnetite was the only Biogenic Mineral formed during the course of the incubation. The analysis of the Biogenic Mineral by transmission electron microscopy (TEM) revealed cubic-shaped crystals with a relatively homogeneous grain size of about 50 nm. After one day of incubation, the departure from stoichiometry, δ, of the biogenerated magnetite was very low (δ ~ 0.025) and rapidly reached values close to zero. Such low values of δ were not obtained for magnetite synthesized inorganically when Fe 3+ in the form of γ-FeOOH was reacted with stoichiometric quantities of soluble Fe 2+ and OH − . The experimental setup used in this study could be replicated in field experiments when assessing the formation of magnetite in modern geological settings as its formation is suspected to be caused by a strong bacterial activity.
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In situ monitoring of lepidocrocite bioreduction and magnetite formation by reflection Mössbauer spectroscopy
American Mineralogist, 2011Co-Authors: Asfaw Zegeye, Khalil Hanna, Mustapha Abdelmoula, Muhammad Usman, Christian RubyAbstract:The miniaturized Mossbauer spectrometer (MIMOS II) was used to monitor in situ the Mineralogical transformation of lepidocrocite (γ-FeOOH) in a Shewanella putrefaciens culture under anaerobic conditions using methanoate as the electron source. Magnetite was the only Biogenic Mineral formed during the course of the incubation. The analysis of the Biogenic Mineral by transmission electron microscopy (TEM) revealed cubic-shaped crystals with a relatively homogeneous grain size of about 50 nm. After one day of incubation, the departure from stoichiometry, δ, of the biogenerated magnetite was very low (δ ~ 0.025) and rapidly reached values close to zero. Such low values of δ were not obtained for magnetite synthesized inorganically when Fe 3+ in the form of γ-FeOOH was reacted with stoichiometric quantities of soluble Fe 2+ and OH − . The experimental setup used in this study could be replicated in field experiments when assessing the formation of magnetite in modern geological settings as its formation is suspected to be caused by a strong bacterial activity.
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In situ monitoring of lepidocrocite bio-reduction and magnetite formation by reflexion Mössbauer spectroscopy
American Mineralogist, 2011Co-Authors: Asfaw Zegeye, Khalil Hanna, Mustapha Abdelmoula, Muhammad Usman, Christian RubyAbstract:The miniaturized Mössbauer spectrometer (MIMOS II) was used to monitor in situ the Mineralogical transformation of lepidocrocite (δ-FeOOH) in a Shewanella putrefaciens culture under anaerobic conditions using methanoate as the electron source. Magnetite was the only Biogenic Mineral formed during the course of the incubation. The analysis of the Biogenic Mineral by transmission electron microscopy (TEM) revealed cubic-shaped crystals with a relatively homogeneous grain size of about 50 nm. After one day of incubation, the departure from stoichiometry, δ, of the biogenerated magnetite was very low (δ∼0.025) and rapidly reached values close to zero. Such low values of δwere not obtained for magnetite synthesized inorganically when Fe3+ in the form of δ-FeOOH was reacted with stoichiometric quantities of soluble Fe2+ and OH-. The experimental setup used in this study could be replicated in field experiments when assessing the formation of magnetite in modern geological settings as its formation is suspected to be caused by a strong bacterial activity.
Christian Ruby - One of the best experts on this subject based on the ideXlab platform.
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In situ monitoring of lepidocrocite bioreduction and magnetite formation by reflection Mössbauer spectroscopy
American Mineralogist, 2011Co-Authors: Asfaw Zegeye, Khalil Hanna, Mustapha Abdelmoula, Muhammad Usman, Christian RubyAbstract:The miniaturized Mossbauer spectrometer (MIMOS II) was used to monitor in situ the Mineralogical transformation of lepidocrocite (γ-FeOOH) in a Shewanella putrefaciens culture under anaerobic conditions using methanoate as the electron source. Magnetite was the only Biogenic Mineral formed during the course of the incubation. The analysis of the Biogenic Mineral by transmission electron microscopy (TEM) revealed cubic-shaped crystals with a relatively homogeneous grain size of about 50 nm. After one day of incubation, the departure from stoichiometry, δ, of the biogenerated magnetite was very low (δ ~ 0.025) and rapidly reached values close to zero. Such low values of δ were not obtained for magnetite synthesized inorganically when Fe 3+ in the form of γ-FeOOH was reacted with stoichiometric quantities of soluble Fe 2+ and OH − . The experimental setup used in this study could be replicated in field experiments when assessing the formation of magnetite in modern geological settings as its formation is suspected to be caused by a strong bacterial activity.
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in situ monitoring of lepidocrocite bioreduction and magnetite formation by reflection mossbauer spectroscopy
American Mineralogist, 2011Co-Authors: Asfaw Zegeye, Khalil Hanna, Mustapha Abdelmoula, Muhammad Usman, Christian RubyAbstract:The miniaturized Mossbauer spectrometer (MIMOS II) was used to monitor in situ the Mineralogical transformation of lepidocrocite (γ-FeOOH) in a Shewanella putrefaciens culture under anaerobic conditions using methanoate as the electron source. Magnetite was the only Biogenic Mineral formed during the course of the incubation. The analysis of the Biogenic Mineral by transmission electron microscopy (TEM) revealed cubic-shaped crystals with a relatively homogeneous grain size of about 50 nm. After one day of incubation, the departure from stoichiometry, δ, of the biogenerated magnetite was very low (δ ~ 0.025) and rapidly reached values close to zero. Such low values of δ were not obtained for magnetite synthesized inorganically when Fe 3+ in the form of γ-FeOOH was reacted with stoichiometric quantities of soluble Fe 2+ and OH − . The experimental setup used in this study could be replicated in field experiments when assessing the formation of magnetite in modern geological settings as its formation is suspected to be caused by a strong bacterial activity.
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In situ monitoring of lepidocrocite bio-reduction and magnetite formation by reflexion Mössbauer spectroscopy
American Mineralogist, 2011Co-Authors: Asfaw Zegeye, Khalil Hanna, Mustapha Abdelmoula, Muhammad Usman, Christian RubyAbstract:The miniaturized Mössbauer spectrometer (MIMOS II) was used to monitor in situ the Mineralogical transformation of lepidocrocite (δ-FeOOH) in a Shewanella putrefaciens culture under anaerobic conditions using methanoate as the electron source. Magnetite was the only Biogenic Mineral formed during the course of the incubation. The analysis of the Biogenic Mineral by transmission electron microscopy (TEM) revealed cubic-shaped crystals with a relatively homogeneous grain size of about 50 nm. After one day of incubation, the departure from stoichiometry, δ, of the biogenerated magnetite was very low (δ∼0.025) and rapidly reached values close to zero. Such low values of δwere not obtained for magnetite synthesized inorganically when Fe3+ in the form of δ-FeOOH was reacted with stoichiometric quantities of soluble Fe2+ and OH-. The experimental setup used in this study could be replicated in field experiments when assessing the formation of magnetite in modern geological settings as its formation is suspected to be caused by a strong bacterial activity.
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Kinetic and Thermodynamic Analysis During Dissimilatory γ-FeOOH Reduction: Formation of Green Rust 1 and Magnetite
Geomicrobiology Journal, 2007Co-Authors: Asfaw Zegeye, Christian Ruby, Frédéric JorandAbstract:In laboratory experiments, lepidocrocite reduction by the dissimilatory iron reducing bacteria, Shewanella putrefaciens, is known to generate extra-cellular iron (II-III) Minerals as green rust (GR) or magnetite. However, the parameters controlling the formation of these Minerals remain unclear. In order to identify these parameters, reduction experiments were designed to obtain either GR or magnetite with methanoate as electron source and lepidocrocite (γ-FeOOH) as the electron acceptor. The Mineral products were monitored by XRD analyses, and the rate of reduction and Eh/pH evolution were assessed during GR and magnetite formation. The only difference between the two conditions lies with the inoculum size: magnetite is systematically produced by the treatments containing the lowest cell density (5 × 10 CFU mL) and GR1(CO3 ) precipitated in the highest cell density (2 × 10 CFU mL). We showed that 100 μ M of anthraquinone 2,6 disulfonate (AQDS) did not influence the nature of the Biogenic Minerals. In addition, based on thermodynamic calculations, we observed that the Eh/pH paths in the Pourbaix diagram depend on the nature of the Minerals formed, i.e. GR1(CO3 ) or Fe3O4. However, the Pourbaix diagram cannot be used to forecast unambiguously the nature of these Minerals. We propose that a close association of bacterial cells and γ-FeOOH particles occurs during the Fe(III) Mineral reduction. We hypothesis that this aggregation influences the bio-reduction rate and is related to the nature of the Biogenic Mineral precipitated in the reduction media.
Lia Addadi - One of the best experts on this subject based on the ideXlab platform.
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the transient phase of amorphous calcium carbonate in sea urchin larval spicules the involvement of proteins and magnesium ions in its formation and stabilization
Advanced Functional Materials, 2003Co-Authors: P C Hamilton, Fred H Wilt, Steve Weiner, Lia AddadiAbstract:Amorphous calcium carbonate (ACC) is a precursor phase of calcite in the formation of the sea urchin larval spicule. The goal of this research is to study the formation and stabilization mode of this transient phase. We first characterized the Mineralogy of the spicules from the sea urchin Strongylocentrotus purpuratus. We then examined the role of the macromolecules extracted from the spicules at different growth stages in the formation of transient ACC in vitro.The Biogenic amorphous transient phase is shown to be both structurally and compositionally different from the known stable ACC phases. It does not contain bound water, and is thus the first dehydrated ACC phase to be detected. The macromolecules that were extracted at early stages of spicule growth, when the amorphous content of the Biogenic Mineral is high, induced the formation of transient ACC in vitro in the presence of magnesium ions. In contrast, the macromolecules extracted at a later stage, when the spicules are completely crystalline, induced the formation of single crystals of low magnesian calcite. We therefore deduce that the macromolecules from the sea urchin larval spicules together with magnesium ions, mediate the transient formation of ACC as a precursor to calcite. These observations may well provide novel ideas for improved materials synthesis.
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factors involved in the formation of amorphous and crystalline calcium carbonate a study of an ascidian skeleton
Journal of the American Chemical Society, 2002Co-Authors: Joanna Aizenberg, Gretchen Lambert, Steve Weiner, Lia AddadiAbstract:The majority of invertebrate skeletal tissues are composed of the most stable crystalline polymorphs of CaCO3, calcite, and/or aragonite. Here we describe a composite skeletal tissue from an ascidian in which amorphous and crystalline calcium carbonate coexist in well-defined domains separated by an organic sheath. Each Biogenic Mineral phase has a characteristic Mg content (5.9 and 1.7 mol %, respectively) and concentration of intraMineral proteins (0.05 and 0.01 wt %, respectively). Macromolecular extracts from various Biogenic amorphous calcium carbonate (ACC) skeletons are typically glycoproteins, rich in glutamic acid and hydroxyamino acids. The proteins from the crystalline calcitic phases are aspartate-rich. Macromolecules extracted from Biogenic ACC induced the formation of stabilized ACC and/or inhibited crystallization of calcite in vitro. The yield of the synthetic ACC was 15−20%. The presence of Mg facilitated the stabilization of ACC: the protein content in synthetic ACC was 0.12 wt % in the...
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Factors Involved in the Formation of Amorphous and Crystalline Calcium Carbonate: A Study of an Ascidian Skeleton
2002Co-Authors: Joanna Aizenberg, Gretchen Lambert, Steve Weiner, Lia AddadiAbstract:Abstract: The majority of invertebrate skeletal tissues are composed of the most stable crystalline polymorphs of CaCO3, calcite, and/or aragonite. Here we describe a composite skeletal tissue from an ascidian in which amorphous and crystalline calcium carbonate coexist in well-defined domains separated by an organic sheath. Each Biogenic Mineral phase has a characteristic Mg content (5.9 and 1.7 mol %, respectively) and concentration of intraMineral proteins (0.05 and 0.01 wt %, respectively). Macromolecular extracts from various Biogenic amorphous calcium carbonate (ACC) skeletons are typically glycoproteins, rich in glutamic acid and hydroxyamino acids. The proteins from the crystalline calcitic phases are aspartate-rich. Macromolecules extracted from Biogenic ACC induced the formation of stabilized ACC and/or inhibited crystallization of calcite in vitro. The yield of the synthetic ACC was 15-20%. The presence of Mg facilitated the stabilization of ACC: the protein content in synthetic ACC was 0.12 wt % in the absence of Mg and 0.07 wt % in the presence of Mg (the Mg content in the precipitate was 8.5 mol %). In contrast, the macromolecules extracted from the calcitic layer induced the formation of calcite crystals with modified morphology similar to that expressed by the original Biogenic calcite. We suggest that specialized macromolecules and magnesium ions may cooperate in the stabilization of intrinsically unstable amorphous calcium carbonate and in the formation of complex ACC/calcite tissues in vivo
Mustapha Abdelmoula - One of the best experts on this subject based on the ideXlab platform.
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Biogenic Mineral Precipitation during Antimony bearing Ferrihydrite bioreduction
2017Co-Authors: Asfaw Zegeye, Crosby Chang, Mustapha Abdelmoula, Thomas HauetAbstract:Fe(III) oxide such as ferrihydrite are ubiquitous in sediments and soils and due to their large surface area and reactive surface properties, they can be important sorbents of metal and metalloid such as antimony (Sb). Sorption and co-precipitation are considered to be the predominant processes by which most of the metals are scavenged by iron oxides, although co-precipitation appears to be more efficient for the removal of metals from solution. However, co-precipitated metals can be released to the surrounding environment as a direct or indirect consequence of dissimilatory iron reduction (DIR), which is a microbial reduction process of geochemical importance in natural systems. Even if DIR is often implicated in the remobilization of metals, the subsequent bio-Mineralization processes can lead to their sequestration into secondary Mineral products. Therefore, the aim of our study was to investigate Sb behavior during DIR. Sb-bearing ferrihydrites, with variable Sb/(Fe+Sb) molar ratios, were synthezised by coprecipitation and incubated with an iron reducing bacteria, Shewanella oneidensis MR1. Chemical analysis were undertaken to monitor the rate and the extent of the bioreduction and the mobilisation of Sb. Mössbauer analysis were carried out to characterize the bulk cation properties of the Biogenic Minerals at different temperatures. The spectra were fitted to obtain degrees of oxidation of iron and therefore it's Mineralogical signature. Measurements of the magnetization with respect to applied magnetic field were also carried out at room and low temperature and coercivity, saturation magnetization and remanence data obtained from hysteresis loops. The results revealed that the presence of Sb impacted the extent of reduction but no significant difference was measured in the rate of Fe(III) reduction. Although, the precipitaion of Biogenic magnetite was evidenced independently of the intial Sb/(Fe+Sb) molar ratios, the Biogenic magnetites displayed variable structural and magnetic properties implying an incorporation of Sb in their crystallographic structure.
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in situ monitoring of lepidocrocite bioreduction and magnetite formation by reflection mossbauer spectroscopy
American Mineralogist, 2011Co-Authors: Asfaw Zegeye, Khalil Hanna, Mustapha Abdelmoula, Muhammad Usman, Christian RubyAbstract:The miniaturized Mossbauer spectrometer (MIMOS II) was used to monitor in situ the Mineralogical transformation of lepidocrocite (γ-FeOOH) in a Shewanella putrefaciens culture under anaerobic conditions using methanoate as the electron source. Magnetite was the only Biogenic Mineral formed during the course of the incubation. The analysis of the Biogenic Mineral by transmission electron microscopy (TEM) revealed cubic-shaped crystals with a relatively homogeneous grain size of about 50 nm. After one day of incubation, the departure from stoichiometry, δ, of the biogenerated magnetite was very low (δ ~ 0.025) and rapidly reached values close to zero. Such low values of δ were not obtained for magnetite synthesized inorganically when Fe 3+ in the form of γ-FeOOH was reacted with stoichiometric quantities of soluble Fe 2+ and OH − . The experimental setup used in this study could be replicated in field experiments when assessing the formation of magnetite in modern geological settings as its formation is suspected to be caused by a strong bacterial activity.
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In situ monitoring of lepidocrocite bioreduction and magnetite formation by reflection Mössbauer spectroscopy
American Mineralogist, 2011Co-Authors: Asfaw Zegeye, Khalil Hanna, Mustapha Abdelmoula, Muhammad Usman, Christian RubyAbstract:The miniaturized Mossbauer spectrometer (MIMOS II) was used to monitor in situ the Mineralogical transformation of lepidocrocite (γ-FeOOH) in a Shewanella putrefaciens culture under anaerobic conditions using methanoate as the electron source. Magnetite was the only Biogenic Mineral formed during the course of the incubation. The analysis of the Biogenic Mineral by transmission electron microscopy (TEM) revealed cubic-shaped crystals with a relatively homogeneous grain size of about 50 nm. After one day of incubation, the departure from stoichiometry, δ, of the biogenerated magnetite was very low (δ ~ 0.025) and rapidly reached values close to zero. Such low values of δ were not obtained for magnetite synthesized inorganically when Fe 3+ in the form of γ-FeOOH was reacted with stoichiometric quantities of soluble Fe 2+ and OH − . The experimental setup used in this study could be replicated in field experiments when assessing the formation of magnetite in modern geological settings as its formation is suspected to be caused by a strong bacterial activity.
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In situ monitoring of lepidocrocite bio-reduction and magnetite formation by reflexion Mössbauer spectroscopy
American Mineralogist, 2011Co-Authors: Asfaw Zegeye, Khalil Hanna, Mustapha Abdelmoula, Muhammad Usman, Christian RubyAbstract:The miniaturized Mössbauer spectrometer (MIMOS II) was used to monitor in situ the Mineralogical transformation of lepidocrocite (δ-FeOOH) in a Shewanella putrefaciens culture under anaerobic conditions using methanoate as the electron source. Magnetite was the only Biogenic Mineral formed during the course of the incubation. The analysis of the Biogenic Mineral by transmission electron microscopy (TEM) revealed cubic-shaped crystals with a relatively homogeneous grain size of about 50 nm. After one day of incubation, the departure from stoichiometry, δ, of the biogenerated magnetite was very low (δ∼0.025) and rapidly reached values close to zero. Such low values of δwere not obtained for magnetite synthesized inorganically when Fe3+ in the form of δ-FeOOH was reacted with stoichiometric quantities of soluble Fe2+ and OH-. The experimental setup used in this study could be replicated in field experiments when assessing the formation of magnetite in modern geological settings as its formation is suspected to be caused by a strong bacterial activity.
Edith Joseph - One of the best experts on this subject based on the ideXlab platform.
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Bacterial iron reduction and Biogenic Mineral formation for the stabilisation of corroded iron objects.
Scientific reports, 2018Co-Authors: Wafa M. Kooli, Lucrezia Comensoli, Julien Maillard, Monica Albini, Arnaud Gelb, Pilar Junier, Edith JosephAbstract:Exploiting bacterial metabolism for the stabilisation of corroded iron artefacts is a promising alternative to conventional conservation-restoration methods. Bacterial iron reduction coupled to Biogenic Mineral formation has been shown to promote the conversion of reactive into stable corrosion products that are integrated into the natural corrosion layer of the object. However, in order to stabilise iron corrosion, the formation of specific Biogenic Minerals is essential. In this study, we used the facultative anaerobe Shewanella loihica for the production of stable Biogenic iron Minerals under controlled chemical conditions. The Biogenic formation of crystalline iron phosphates was observed after iron reduction in a solution containing Fe(III) citrate. When the same biological treatment was applied on corroded iron plates, a layer composed of iron phosphates and iron carbonates was formed. Surface and cross-section analyses demonstrated that these two stable corrosion products replaced 81% of the reactive corrosion layer after two weeks of treatment. Such results demonstrate the potential of a biological treatment in the development of a stabilisation method to preserve corroded iron objects.
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Soluble and Solid Iron Reduction Assays with Desulfitobacterium hafniense
BIO-PROTOCOL, 2018Co-Authors: Lucrezia Comensoli, Wafa M. Kooli, Julien Maillard, Pilar Junier, Edith JosephAbstract:There is a pressing need to develop sustainable and efficient methods to protect and stabilize iron objects. To develop a conservation-restoration method for corroded iron objects, this bio-protocol presents the steps to investigate reductive dissolution of ferric iron and Biogenic production of stabilizing ferrous iron Minerals in the strict anaerobe Desulfitobacterium hafniense (strains TCE1 and LBE). We investigated iron reduction using three different Fe(III) sources: Fe(III)-citrate (a soluble phase), akaganeite (solid iron phase), and corroded coupons. This protocol describes a method that combines spectrophotometric quantification of the complex Fe(II)-Ferrozine® with Mineral characterization by scanning electron microscopy and Raman spectroscopy. These three methods allow assessing reductive dissolution of ferric iron and Biogenic Mineral production as a promising alternative for the development of an innovative sustainable method for the stabilization of corroded iron
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Use of Bacteria To Stabilize Archaeological Iron
Applied and environmental microbiology, 2017Co-Authors: Lucrezia Comensoli, Julien Maillard, Monica Albini, Pilar Junier, Frederic Sandoz, Edith JosephAbstract:Iron artifacts are common among the findings of archaeological excavations. The corrosion layer formed on these objects requires stabilization after their recovery, without which the destruction of the item due to physicochemical damage is likely. Current technologies for stabilizing the corrosion layer are lengthy and generate hazardous waste products. Therefore, there is a pressing need for an alternative method for stabilizing the corrosion layer on iron objects. The aim of this study was to evaluate an alternative conservation-restoration method using bacteria. For this, anaerobic iron reduction leading to the formation of stable iron Minerals in the presence of chlorine was investigated for two strains of Desulfitobacterium hafniense (strains TCE1 and LBE). Iron reduction was observed for soluble Fe(III) phases as well as for akaganeite, the most troublesome iron compound in the corrosion layer of archaeological iron objects. In terms of Biogenic Mineral production, differential efficiencies were observed in assays performed on corroded iron coupons. Strain TCE1 produced a homogeneous layer of vivianite covering 80% of the corroded surface, while on the coupons treated with strain LBE, only 10% of the surface was covered by the same Mineral. Finally, an attempt to reduce iron on archaeological objects was performed with strain TCE1, which led to the formation of both Biogenic vivianite and magnetite on the surface of the artifacts. These results demonstrate the potential of this biological treatment for stabilizing archaeological iron as a promising alternative to traditional conservation-restoration methods. IMPORTANCE Since the Iron Age, iron has been a fundamental material for the building of objects used in everyday life. However, due to its reactivity, iron can be easily corroded, and the physical stability of the object built is at risk. This is particularly true for archaeological objects on which a potentially unstable corrosion layer is formed during the time the object is buried. After excavation, changes in environmental conditions (e. g., higher oxygen concentration or lower humidity) alter the stability of the corrosion layer and can lead to the total destruction of the object. In this study, we demonstrate the feasibility of an innovative treatment based on bacterial iron reduction and Biogenic Mineral formation to stabilize the corrosion layer and protect these objects.