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1

Bacteriogenic manganese oxides.  

PubMed

Microorganisms control the redox cycling of manganese in the natural environment. Although the homogeneous oxidation of Mn(II) to form manganese oxide minerals is slow, solid MnO(2) is the stable form of manganese in the oxygenated portion of the biosphere. Diverse bacteria and fungi have evolved the ability to catalyze this process, producing the manganese oxides found in soils and sediments. Other bacteria have evolved to utilize MnO(2) as a terminal electron acceptor in respiration. This Account summarizes the properties of Mn oxides produced by bacteria (bacteriogenic MnO(2)) and our current thinking about the biochemical mechanisms of bacterial Mn(II) oxidation. According to X-ray absorption spectroscopy and X-ray scattering studies, the MnO(2) produced by bacteria consists of stacked hexagonal sheets of MnO(6) octahedra, but these particles are extremely small and have numerous structural defects, particularly cation vacancies. The defects provide coordination sites for binding exogenous metal ions, which can be adsorbed to a high loading. As a result, bacterial production of MnO(2) influences the bioavailability of these metals in the natural environment. Because of its high surface area and oxidizing power, bacteriogenic MnO(2) efficiently degrades biologically recalcitrant organic molecules to lower-molecular-mass compounds, spurring interest in using these properties in the bioremediation of xenobiotic organic compounds. Finally, bacteriogenic MnO(2) is reduced to soluble Mn(II) rapidly in the presence of exogenous ligands or sunlight. It can therefore help to regulate the bioavailability of Mn(II), which is known to protect organisms from superoxide radicals and is required to assemble the water-splitting complex in photosynthetic organisms. Bioinorganic chemists and microbiologists have long been interested in the biochemical mechanism of Mn(IV) oxide production. The reaction requires a two-electron oxidation of Mn(II), but genetic and biochemical evidence for several bacteria implicate multicopper oxidases (MCOs), which are only known to engage one-electron transfers from substrate to O(2). In experiments with the exosporium of a Mn(II)-oxidizing Bacillus species, we could trap the one-electron oxidation product, Mn(III), as a pyrophosphate complex in an oxygen-dependent reaction inhibited by azide, consistent with MCO catalysis. The Mn(III) pyrophosphate complex can further act as a substrate, reacting in the presence of the exosporium to produce Mn(IV) oxide. Although this process appears to be unprecedented in biology, it is reminiscent of the oxidation of Fe(II) to form Fe(2)O(3) in the ferritin iron storage protein. However, it includes a critical additional step of Mn(III) oxidation or disproportionation. We shall continue to investigate this biochemically unique process with purified enzymes. PMID:19778036

Spiro, Thomas G; Bargar, John R; Sposito, Garrison; Tebo, Bradley M

2010-01-19

2

Tellurium content of marine manganese oxides and other manganese oxides  

USGS Publications Warehouse

Tellurium in amounts ranging from 5 to 125 parts per million was present in all of 12 samples of manganese oxide nodules from the floor of the Pacific and Indian oceans. These samples represent the first recognized points of high tellurium concentration in a sedimentary cycle. The analyses may lend support to the theory that the minor-element content of seafloor manganese nodules is derived from volcanic emanations.

Lakin, H. W.; Thompson, C. E.; Davidson, D. F.

1963-01-01

3

New layered manganese oxide halides.  

PubMed

The first layered manganese(III) oxide chlorides, Sr2MnO3Cl and Sr4Mn3O8-yCl2, have been synthesised; Sr2MnO3Cl adopts a K2NiF4 type structure with sheets of MnO5 square based pyramids linked through oxygen and separated by SrCl layers; it is the end member of a new family of Ruddlesden-Popper type manganese oxide halides which includes the three-layer member Sr4Mn3O8-yCl2 also reported herein. PMID:12120392

Knee, Christopher S; Weller, Mark T

2002-02-01

4

Neurotoxicity of manganese oxide nanomaterials  

Microsoft Academic Search

Manganese (Mn) toxicity in humans has been observed as manganism, a disease that resembles Parkinson’s disease. The mechanism\\u000a of Mn toxicity and the chemical forms that may be responsible for its neurotoxicity are not well understood. We examined the\\u000a toxicity of Mn oxide nanomaterials in a neuronal precursor cell model, using the MTS assay to evaluate mitochondrial function\\u000a in living

Diana M. Stefanescu; Ali Khoshnan; Paul H. Patterson; Janet G. Hering

2009-01-01

5

High-Performance Manganese Oxide Catalysts for CO Oxidation  

Microsoft Academic Search

The catalytic activity of manganese dioxide samples in oxidation of CO and decomposition of hydrogen peroxide was studied. The promise of manganese dioxide obtained from fluorine-containing electrolytes as a catalyst for carbon monoxide oxidation was considered.

N. D. Ivanova; S. V. Ivanov; E. I. Boldyrev; G. V. Sokol'skii; I. S. Makeeva

2002-01-01

6

40 CFR 721.10201 - Cobalt lithium manganese nickel oxide.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Cobalt lithium manganese nickel oxide. 721.10201...Chemical Substances § 721.10201 Cobalt lithium manganese nickel oxide. (a) Chemical...chemical substance identified as cobalt lithium manganese nickel oxide (PMN...

2013-07-01

7

40 CFR 721.10201 - Cobalt lithium manganese nickel oxide.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Cobalt lithium manganese nickel oxide. 721.10201...Chemical Substances § 721.10201 Cobalt lithium manganese nickel oxide. (a) Chemical...chemical substance identified as cobalt lithium manganese nickel oxide (PMN...

2012-07-01

8

40 CFR 721.10011 - Barium calcium manganese strontium oxide.  

...2014-07-01 false Barium calcium manganese strontium oxide. 721.10011 Section...Substances § 721.10011 Barium calcium manganese strontium oxide. (a) Chemical substance...substance identified as barium calcium manganese strontium oxide (PMN...

2014-07-01

9

40 CFR 721.10201 - Cobalt lithium manganese nickel oxide.  

...2014-07-01 false Cobalt lithium manganese nickel oxide. 721.10201 Section...Substances § 721.10201 Cobalt lithium manganese nickel oxide. (a) Chemical substance...substance identified as cobalt lithium manganese nickel oxide (PMN...

2014-07-01

10

Arsenite Oxidation by a Poorly Crystalline Manganese-Oxide. 2.  

E-print Network

Arsenite Oxidation by a Poorly Crystalline Manganese-Oxide. 2. Results from X-ray Absorption September 23, 2010. Accepted October 1, 2010. Arsenite (AsIII ) oxidation by manganese oxides (Mn-oxides) servestodetoxifyand,undermanyconditions,immobilizearsenic (As) by forming arsenate (AsV ). AsIII oxidation by Mn

Sparks, Donald L.

11

Arsenite Oxidation by a Poorly Crystalline Manganese-Oxide 1.  

E-print Network

Arsenite Oxidation by a Poorly Crystalline Manganese-Oxide 1. Stirred-Flow Experiments B R A N D O September 23, 2010. Accepted October 1, 2010. Manganese-oxides (Mn-oxides) are quite reactive, with respect to arsenite (AsIII ) oxidation. However, studies regarding the pathways of AsIII oxidation, over a range

Sparks, Donald L.

12

Contaminant Transformation by a Biogenic Manganese Oxide  

NASA Astrophysics Data System (ADS)

Biomineralization of manganese by Pseudomonas putida strain MnB1 produces tetravalent manganese oxides that surround the exterior of the bacterial cell. The manganese oxides produced by P. putida transform the herbicide atrazine, a widespread environmental contaminant, by dechlorination, dealkylation and deamination reactions. The transformation reactions catalyzed by biogenic manganese oxide surfaces create a suite of transformation intermediates whose properties, such as aqueous solubility, toxicity and biodegradability, differ dramatically from those of the parent compound. The rates and products of atrazine transformation by biogenic manganese oxide surfaces were examined as functions of temperature and water potential. Air-dry samples of hydrous manganese oxide (? -MnO2) and biogenic manganese oxide were isopiestically equilibrated to -3.10, -0.50 and -0.04 MPa at 40 degrees Celsius and to -0.04 MPa at 20 and 30 degrees Celcius. The concentrations of atrazine and eight transformation intermediates were determined by HPLC. Our results suggest that biogenic manganese oxides may contribute greatly to the detoxification and immobilization of organic contaminants in the environment because of their nanoparticle size, large surface area and high chemical reactivity.

Toner, B. M.; Sposito, G.

2001-12-01

13

Heterogeneous clay-manganese(II) oxidation catalyst  

Microsoft Academic Search

A manganese(II)-Schiff base complex has been heterogenized by its intercalation into clay minerals. The incorporation of the homogeneous manganese(II) complexes in the interlayer space of aluminosilicate mineral is accomplished by a cation exchange process. The obtained clay-manganese(II) composite has been studied by chemical analysis, X-ray diffraction and FT-IR spectroscopy. The new catalytic material has been evaluated as oxidation catalyst. Our

D Gournis; M Louloudi; M. A Karakassides; C Kolokytha; K Mitopoulou; N Hadjiliadis

2002-01-01

14

The Structural Stability of Manganese Oxide Electrodes for Lithium Batteries  

Microsoft Academic Search

Manganese oxides are of interest as insertion electrodes for rechargeable 3 V and 4 V lithium batteries. During discharge, lithium ions are inserted into the manganese oxide host structure with a concomitant reduction of the manganese ions; the reverse process occurs on charge. The cycle life of these batteries is critically dependent on the ability of the manganese oxide structure

Michael M. Thackeray

1997-01-01

15

Battles with Iron: Manganese in Oxidative Stress Protection*  

PubMed Central

The redox-active metal manganese plays a key role in cellular adaptation to oxidative stress. As a cofactor for manganese superoxide dismutase or through formation of non-proteinaceous manganese antioxidants, this metal can combat oxidative damage without deleterious side effects of Fenton chemistry. In either case, the antioxidant properties of manganese are vulnerable to iron. Cellular pools of iron can outcompete manganese for binding to manganese superoxide dismutase, and through Fenton chemistry, iron may counteract the benefits of non-proteinaceous manganese antioxidants. In this minireview, we highlight ways in which cells maximize the efficacy of manganese as an antioxidant in the midst of pro-oxidant iron. PMID:22247543

Aguirre, J. Dafhne; Culotta, Valeria C.

2012-01-01

16

Manganese oxidation model for rivers  

USGS Publications Warehouse

The presence of manganese in natural waters (>0.05 mg/L) degrades water-supply quality. A model was devised to predict the variation of manganese concentrations in river water released from an impoundment with the distance downstream. The model is one-dimensional and was calibrated using dissolved oxygen, biochemical oxygen demand, pH, manganese, and hydraulic data collected in the Duck River, Tennessee. The results indicated that the model can predict manganese levels under various conditions. The model was then applied to the Chattahoochee River, Georgia. Discrepancies between observed and predicted may be due to inadequate pH data, precipitation of sediment particles, unsteady flow conditions in the Chattahoochee River, inaccurate rate expressions for the low pH conditions, or their combinations.

Hess, Glen W.; Kim, Byung R.; Roberts, Philip J.W.

1989-01-01

17

Electrochemical lithium intercalation in nanosized manganese oxides  

Microsoft Academic Search

X-ray amorphous manganese oxides were prepared by reduction of sodium permanganate by lithium iodide in aqueous medium (MnOx-I) and by decomposition of manganese carbonate at moderate temperature (MnOx-C). TEM showed that these materials are not amorphous, but nanostructured, with a prominent spinel substructure in MnOx-C. These materials intercalate lithium with capacities up to 200mAh\\/g at first cycle (potential window 1.8–4.3V)

Pierre Strobel; Céline Darie; F. Thiéry; A. Ibarra-Palos; Maria Bacia; Olivier Proux; Jean-Bruno Soupart

2006-01-01

18

Manganese oxide thin films prepared by nonaqueous sol–gel processing: preferential formation of birnessite  

Microsoft Academic Search

High quality manganese oxide thin films with smooth surfaces and even thicknesses have been prepared with a nonaqueous sol–gel process involving reduction of tetraethylammonium permanganate in methanol. Spin-coated films have been cast onto soft glass, quartz, and Ni foil substrates, with two coats being applied for optimum crystallization. The addition of alkali metal cations as dopants results in exclusive formation

Stanton Ching; Steven M. Hughes; Timothy P. Gray; Eric J. Welch

2004-01-01

19

Efficiency analysis for a manganese-oxide-based thermochemical cycle  

Microsoft Academic Search

A thermochemical cycle for the solar production of hydrogen is proposed. The cycle includes: (1) the conversion of solar to chemical energy by the thermal reduction of manganese(III) oxide to manganese(II) oxide at temperatures below 1900K, (2) the production of hydrogen by reacting manganese(II) oxide with sodium hydroxide, and (3) the separation of manganese oxide from sodium hydroxide by a

M Sturzenegger; P Nüesch

1999-01-01

20

Electrochemical lithium intercalation in disordered manganese oxides  

Microsoft Academic Search

Four highly disordered manganese oxides were prepared by reduction of sodium permanganate by chloride, iodide, hydrogen peroxide or oxalate in aqueous medium containing a large excess of Li+ ions, yielding hydrated oxides with Mn valence in the range 3.80–3.92. Thermogravimetric studies showed that the iodide-reduced oxide can be dehydrated to 92% at 240°C, while the other three ones retain water

A Ibarra Palos; M Anne; P Strobel

2001-01-01

21

Kinetics of Redox Processes in Manganese Oxides  

Microsoft Academic Search

In this work, we studied specific features of redox processes in manganese oxides Mn 2 O 3 and Mn 3 O 4 . The maximal threshold particle size that ensures the irreversible transition of ? -Mn 2 O 3 into hausmannite was determined. In the narrow temperature range of 810— 820¡ë , an overcooled fine powder of hausmannite was found

V. B. Fetisov; A. V. Fetisov; N. V. Korchemkina; L. A. Ovchinnikova; E. A. Pastukhov; A. Ya. Fishman

2002-01-01

22

Manganese oxide cathodes for rechargeable batteries  

NASA Astrophysics Data System (ADS)

Manganese oxides are considered as promising cathodes for rechargeable batteries due to their low cost and low toxicity as well as the abundant natural resources. In this dissertation, manganese oxides have been investigated as cathodes for both rechargeable lithium and alkaline batteries. Nanostructured lithium manganese oxides designed for rechargeable lithium cells have been synthesized by reducing lithium permanganate with methanol or hydrogen in various solvents followed by firing at moderate temperatures. The samples have been characterized by wet-chemical analyses, thermal methods, spectroscopic methods, and electron microscopy. It has been found that chemical residues in the oxides such as carboxylates and hydroxyl groups, which could be controlled by varying the reaction medium, reducing agents, and additives, make a significant influence on the electrochemical properties. The Li/Mn ratio in the material has also been found to be a critical factor in determining the rechargeability of the cathodes. The optimized samples exhibit a high capacity of close to 300 mAh/g with good cyclability and charge efficiency. The high capacity with a lower discharge voltage may make these nanostructured oxides particularly attractive for lithium polymer batteries. The research on the manganese oxide cathodes for alkaline batteries is focused on an analysis of the reaction products generated during the charge/discharge processes or by some designed chemical reactions mimicking the electrochemical processes. The factors influencing the formation of Mn3O4 in the two-electron redox process of delta-MnO2 have been studied with linear sweep voltammetry combined with X-ray diffraction. The presence of bismuth, the discharge rate, and the microstructure of the electrodes are found to affect the formation of Mn3O4, which is known to be electrochemically inactive. A faster voltage sweep and a more intimate mixing of the manganese oxide and carbon in the cathode are found to suppress the formation of Mn3O4. Bismuth has also been found to be beneficial in the one-electron process of gamma-MnO 2 when incorporated into the cathode. The results of a series of chemical reactions reveal that bismuth is blocking some reaction paths leading to the unwanted birnessite or Mn3O4. Barium is also found to play a similar role, but it is less effective than bismuth for the same amount of additive. Optimization of the additives has the potential to make the rechargeable alkaline cells based on manganese oxides to successfully compete with other rechargeable systems due to their low cost, environmental friendliness, and excellent safety features.

Im, Dongmin

23

Pwave Pairing and Colossal Magnetoresistance in Manganese Oxides  

E-print Network

P­wave Pairing and Colossal Magnetoresistance in Manganese Oxides Yong­Jihn Kim y Department that the existing experimental data of most manganese ox­ ides show the frustrated p­wave superconducting paid to the manganese oxides since the observa­ tion of colossal magnetoresistance (CMR). 1\\Gamma4

24

Growth of Manganese Oxide Nanostructures Alters the Layout of  

E-print Network

Growth of Manganese Oxide Nanostructures Alters the Layout of Adhesion on a Carbonate Substrate C H-volume microscopy and a silicon-nitride probe, we measure changes in adhesion when a patchy overgrowth of manganese for advancingthemechanisticmodelingofthefateandtransport of environmental contaminants (11, 12). Manganese oxide (MnOx) nanostructures grown

25

OXIDATION AND SORPTION KINETICS OF ARSENIC ON A POORLY CRYSTALLINE MANGANESE OXIDE  

E-print Network

OXIDATION AND SORPTION KINETICS OF ARSENIC ON A POORLY CRYSTALLINE MANGANESE OXIDE by Brandon J. Lafferty All Rights Reserved #12;OXIDATION AND SORPTION KINETICS OF ARSENIC ON A POORLY CRYSTALLINE MANGANESE OXIDE by Brandon J. Lafferty Approved

Sparks, Donald L.

26

Bacterial Manganese Reduction and Growth with Manganese Oxide as the Sole Electron Acceptor  

Microsoft Academic Search

Microbes that couple growth to the reduction of manganese could play an important role in the biogeochemistry of certain anaerobic environments. Such a bacterium, Alteromonas putrefaciens MR-1, couples its growth to the reduction of manganese oxides only under anaerobic conditions. The characteristics of this reduction are consistent with a biological, and not an indirect chemical, reduction of manganese, which suggest

Charles R. Myers; Kenneth H. Nealson

1988-01-01

27

Thermochemistry of iron manganese oxide spinels  

Microsoft Academic Search

Oxide melt solution calorimetry has been performed on iron manganese oxide spinels prepared at high temperature. The enthalpy of formation of (MnxFe1?x)3O4 at 298K from the oxides, tetragonal Mn3O4 (hausmannite) and cubic Fe3O4 (magnetite), is negative from x=0 to x=0.67 and becomes slightly positive for 0.67

Sophie Guillemet-Fritsch; Alexandra. Navrotsky; Philippe Tailhades; Hervé Coradin; Miaojun Wang

2005-01-01

28

Oxidation state of marine manganese nodules  

USGS Publications Warehouse

Analyses of the bulk oxidation state of marine manganese nodules indicates that more than 98% of the Mn in deep ocean nodules is present as Mn(IV). The samples were collected from three quite different areas: the hemipelagic environment of the Guatemala Basin, the pelagic area of the North Pacific, and seamounts in the central Pacific. Results of the study suggest that todorokite in marine nodules is fully oxidized and has the following stoichiometry: (K, Na, Ca, Ba).33(Mg, Cu, Ni).76Mn5O22(H2O)3.2. ?? 1984.

Piper, D.Z.; Basler, J.R.; Bischoff, J.L.

1984-01-01

29

40 CFR 721.10529 - Cobalt iron manganese oxide, carboxylic acid-modified (generic).  

Code of Federal Regulations, 2013 CFR

... 2013-07-01 false Cobalt iron manganese oxide, carboxylic acid-modified...Substances § 721.10529 Cobalt iron manganese oxide, carboxylic acid-modified...identified generically as cobalt iron manganese oxide, carboxylic...

2013-07-01

30

40 CFR 721.10529 - Cobalt iron manganese oxide, carboxylic acid-modified (generic).  

... 2014-07-01 false Cobalt iron manganese oxide, carboxylic acid-modified...Substances § 721.10529 Cobalt iron manganese oxide, carboxylic acid-modified...identified generically as cobalt iron manganese oxide, carboxylic...

2014-07-01

31

Colloidal Manganese Oxide Precursor to Octahedral Layered, OL-3 Materials  

Microsoft Academic Search

We report the one-pot synthesis of a hexagonal form of a layered manganese oxide material (OL-3) using mild conditions and\\u000a low temperature. The oxidation of an aqueous solution of manganese acetate using tetramethylammonium hydroxide and hydrogen\\u000a peroxide at 4 °C leads to the formation of a colloidal manganese dioxide solution. Colloidal MnO2 was then flocculated using K ions, forming disordered layered

Jason P. Durand; Josanlet C. Villegas; Sinue Gomez-Mower; Oscar Giraldo; Steven L. Suib

2007-01-01

32

Manganese oxide nanowires, films, and membranes and methods of making  

DOEpatents

Nanowires, films, and membranes comprising ordered porous manganese oxide-based octahedral molecular sieves and methods of making the same are disclosed. A method for forming nanowires includes hydrothermally treating a chemical precursor composition in a hydrothermal treating solvent to form the nanowires, wherein the chemical precursor composition comprises a source of manganese cations and a source of counter cations, and wherein the nanowires comprise ordered porous manganese oxide-based octahedral molecular sieves.

Suib, Steven Lawrence (Storrs, CT); Yuan, Jikang (Storrs, CT)

2011-02-15

33

Rates of manganese oxidation in aqueous systems  

USGS Publications Warehouse

The rate of crystal growth of Mn3O4 (hausmannite) and ??MnOOH (feitknechtite) in aerated aqueous manganous perchlorate systems, near 0.01 M in total manganese, was determined at pH levels ranging from 7.00 to 9.00 and at temperatures from 0.5 to 37.4??C. The process is autocatalytic, but becomes psuedo first-order in dissolved Mn2+ activity when the amount of precipitate surface is large compared to the amount of unreacted manganese. Reaction rates determined by titrations using an automated pH-stat were fitted to an equation for precipitate growth. The rates are proportional to surface area of oxide and degree of supersaturation with respect to Mn2+. The oxide obtained at the higher temperature was Mn3O4, but at 0.5?? C only ??MnOOH was formed. At intermediate temperatures, mixtures of these solids were formed. The rate of precipitation of hausmannite is strongly influenced by temperature, and that of feitknechtite much less so. The difference in activation energy may be related to differences in crystal structure of the oxides and the geometry of polymeric hydroxy ion precursors. ?? 1981.

Hem, J.D.

1981-01-01

34

Biological Superoxide In Manganese Oxide Formation  

NASA Astrophysics Data System (ADS)

Manganese (Mn) oxides are among the strongest sorbents and oxidants within the environment, controlling the fate and transport of numerous elements and the degradation of recalcitrant carbon. Both bacteria and fungi mediate the oxidation of Mn(II) to Mn(III/IV) oxides but the genetic and biochemical mechanisms responsible remain poorly understood. Furthermore, the physiological basis for microbial Mn(II) oxidation remains an enigma. We have recently reported that a common marine bacterium (Roseobacter sp. AzwK-3b) oxidizes Mn(II) via reaction with extracellular superoxide (O2-) produced during exponential growth. Here we expand this superoxide-mediated Mn(II) oxidation pathway to fungi, introducing a surprising homology between prokaryotic and eukaryotic metal redox processes. For instance, Stibella aciculosa, a common soil Ascomycete filamentous fungus, precipitates Mn oxides at the base of asexual reproductive structures (synnemata) used to support conidia (Figure 1). This distribution is a consequence of localized production of superoxide (and it's dismutation product hydrogen peroxide, H2O2), leading to abiotic oxidation of Mn(II) by superoxide. Disruption of NADPH oxidase activity using the oxidoreductase inhibitor DPI leads to diminished cell differentiation and subsequent Mn(II) oxidation inhibition. Addition of Cu(II) (an effective superoxide scavenger) leads to a concentration dependent decrease in Mn oxide formation. We predict that due to the widespread production of extracellular superoxide within the fungal and likely bacterial kingdoms, biological superoxide may be an important contributor to the cycling of Mn, as well as other metals (e.g., Hg, Fe). Current and future explorations of the genes and proteins involved in superoxide production and Mn(II) oxidation will ideally lend insight into the physiological and biochemical basis for these processes.

Hansel, C.; Learman, D.; Zeiner, C.; Santelli, C. M.

2011-12-01

35

Isotopic evidence for organic matter oxidation by manganese reduction in the formation of stratiform manganese carbonate ore  

Microsoft Academic Search

Unlike other marine-sedimentary manganese ore deposits, which are largely composed of manganese oxides, the primary ore at Molango (Hidalgo State, Mexico) is exclusively manganese carbonate (rhodochrosite, Mn-calcite, kutnahorite). Stable isotope studies of the carbonates from Molango provide critical new information relevant to the controversy over syngenetic and diagenetic models of stratiform manganese deposit formation. Negative 13 C values for carbonates

Patrick M. Okita; J. Barry Maynard; Elliott C. Spiker; Eric R. Force

1988-01-01

36

Adsorption of B. Subtilis and P. Mendocina Onto Fe-Oxide Coated Quartz and Pure Quartz  

NASA Astrophysics Data System (ADS)

Understanding the controls on bacterial adsorption onto mineral surfaces is crucial in order to model a range of processes, such as contaminant transport, mineral dissolution behavior, and bioremediation techniques. At present, little is known concerning the adsorption behavior of bacteria, even onto some of the most common mineral surfaces present in near-surface environments. In this study, we measured the adsorption of a Gram positive bacterial species (B. subtilis) and a Gram negative species (P. mendocina) onto a quartz sand, and onto an Fe-oxide coated quartz sand, both as functions of time, pH and bacteria:mineral mass ratio. The extent of adsorption was determined by measuring the concentration of free bacteria in the mineral-bacteria systems both before, and after, reaction, using a uv-vis spectrophotometric approach. pH and bacteria:mineral ratio exert strong controls on the extent of bacterial adsorption of both species onto Fe-coated quartz. The extent of adsorption of B. subtilis onto the Fe-coated quartz increases with decreasing pH from close to 0% at pH 10 to a plateau of approximately 80% adsorption between pH 6 and 4. Below pH 4, adsorption of B. subtilis decreases to 50% at pH 2. Adsorption of P. mendocina is similar to that observed for B. subtilis, only it is significantly less extensive under otherwise identical conditions. These adsorption behaviors are in marked contrast to that observed for both species onto the uncoated quartz. There is little to no adsorption of either species onto the uncoated quartz sand over most of the pH range studied. We use a thermodynamic approach to model the adsorption behavior of each species onto the Fe-coated quartz sand, determining equilibrium constants for the dominant adsorption reactions. Our results demonstrate that bacterial adsorption within geologic systems can be strongly dependent on mineralogy, fluid composition, and on the bacterial species present. However, our modeling approach enables the prediction of the extent of adsorption of each bacterial species under a wide range of geologic conditions.

Ams, D.; Fein, J. B.

2002-12-01

37

Bacterial manganese reduction and growth with manganese oxide as the sole electron acceptor  

NASA Technical Reports Server (NTRS)

Microbes that couple growth to the reduction of manganese could play an important role in the biogeochemistry of certain anaerobic environments. Such a bacterium, Alteromonas putrefaciens MR-1, couples its growth to the reduction of manganese oxides only under anaerobic conditions. The characteristics of this reduction are consistent with a biological, and not an indirect chemical, reduction of manganese, which suggest that this bacterium uses manganic oxide as a terminal electron acceptor. It can also utilize a large number of other compounds as terminal electron acceptors; this versatility could provide a distinct advantage in environments where electron-acceptor concentrations may vary.

Myers, Charles R.; Nealson, Kenneth H.

1988-01-01

38

Electron Energy-Loss Safe-Dose Limits for Manganese Valence Measurements in Environmentally Relevant Manganese Oxides  

E-print Network

Electron Energy-Loss Safe-Dose Limits for Manganese Valence Measurements in Environmentally Relevant Manganese Oxides Kenneth J. T. Livi,*, Brandon Lafferty,,§ Mengqiang Zhu,,# Shouliang Zhang, Anne Houssiniere, BP 32229, 44322 Nantes Cedex 3, France *S Supporting Information ABSTRACT: Manganese (Mn) oxides

Sparks, Donald L.

39

Three manganese oxide-rich marine sediments harbor similar communities of acetate-oxidizing manganese-reducing bacteria  

PubMed Central

Dissimilatory manganese reduction dominates anaerobic carbon oxidation in marine sediments with high manganese oxide concentrations, but the microorganisms responsible for this process are largely unknown. In this study, the acetate-utilizing manganese-reducing microbiota in geographically well-separated, manganese oxide-rich sediments from Gullmar Fjord (Sweden), Skagerrak (Norway) and Ulleung Basin (Korea) were analyzed by 16S rRNA-stable isotope probing (SIP). Manganese reduction was the prevailing terminal electron-accepting process in anoxic incubations of surface sediments, and even the addition of acetate stimulated neither iron nor sulfate reduction. The three geographically distinct sediments harbored surprisingly similar communities of acetate-utilizing manganese-reducing bacteria: 16S rRNA of members of the genera Colwellia and Arcobacter and of novel genera within the Oceanospirillaceae and Alteromonadales were detected in heavy RNA-SIP fractions from these three sediments. Most probable number (MPN) analysis yielded up to 106 acetate-utilizing manganese-reducing cells cm?3 in Gullmar Fjord sediment. A 16S rRNA gene clone library that was established from the highest MPN dilutions was dominated by sequences of Colwellia and Arcobacter species and members of the Oceanospirillaceae, supporting the obtained RNA-SIP results. In conclusion, these findings strongly suggest that (i) acetate-dependent manganese reduction in manganese oxide-rich sediments is catalyzed by members of taxa (Arcobacter, Colwellia and Oceanospirillaceae) previously not known to possess this physiological function, (ii) similar acetate-utilizing manganese reducers thrive in geographically distinct regions and (iii) the identified manganese reducers differ greatly from the extensively explored iron reducers in marine sediments. PMID:22572639

Vandieken, Verona; Pester, Michael; Finke, Niko; Hyun, Jung-Ho; Friedrich, Michael W; Loy, Alexander; Thamdrup, Bo

2012-01-01

40

Arsenic mobilization in the critical zone: Oxidation by hydrous manganese oxide Jason S. Fischel, fischjs06@juniata.edu1  

E-print Network

Arsenic mobilization in the critical zone: Oxidation by hydrous manganese oxide GEOC 112 Jason S manganese (Mn) oxides, even in low concentrations, to oxidize trace metals such as arsenic from arsenite [As

Sparks, Donald L.

41

KINETICS AND MECHANISMS OF CHROMIUM(III) OXIDATION AND PRECIPITATION ON MANGANESE OXIDES, IN REAL-TIME AND AT THE  

E-print Network

KINETICS AND MECHANISMS OF CHROMIUM(III) OXIDATION AND PRECIPITATION ON MANGANESE OXIDES, IN REAL(III) OXIDATION AND PRECIPITATION ON MANGANESE OXIDES, IN REAL-TIME AND AT THE MOLECULAR LEVEL by Gautier Landrot

Sparks, Donald L.

42

Solution-based synthesis of manganese oxide cathodes for lithium batteries  

Microsoft Academic Search

With an objective to overcome the cyclability problems of manganese oxides, solution-based procedures are pursued to synthesize metastable manganese oxides. Reduction of permanganate with lithium iodide in an acetonitrile medium followed by heating at 250 C in vacuum gives an amorphous lithium sodium manganese oxyiodide that is intimately mixed with crystalline NaIO. On the other hand, oxidation of manganese acetate

A. Manthiram; J. Kim; S. Choi

2000-01-01

43

The thermal stability of lithium-manganese-oxide spinel phases  

Microsoft Academic Search

The thermal stability of stoichiometric spinel phases in the system Li1+?Mn2-?O4 (0 ? ? ? 0.33) has been investigated by high-temperature powder X-ray diffraction, differential thermal analysis, and thermogravimetric analysis. At elevated temperatures, the lithium-manganese-oxide spinels undergo phase changes by loss of oxygen and lithia (Li2O). The data highlight the importance of temperature control when synthesising lithium-manganese-oxide spinel compounds.

M. M. Thackeray; M. F. Mansuetto; D. W. Dees; D. R. Vissers

1996-01-01

44

Spinel lithium manganese oxide synthesized under a pressurized oxygen atmosphere  

Microsoft Academic Search

Spinel lithium manganese oxide was synthesized via co-precipitation. The prepared lithium manganese oxide powder was further heated at 700°C for 15h under pressurized (3bar) oxygen atmosphere. The resultant exhibited a highly crystalline cubic spinel phase with space group Fd3m, as confirmed by X-ray diffraction. The spinel compound exhibited a slightly smaller lattice constant than a conventional spinel compound, even though

Ki-Soo Lee; Seung-Taek Myung; Hun-Gi Jung; Jung Kyoo Lee; Yang-Kook Sun

2010-01-01

45

Laser microstructuring and annealing processes for lithium manganese oxide cathodes  

Microsoft Academic Search

It is expected that cathodes for lithium-ion batteries (LIB) composed out of nano-composite materials lead to an increase in power density of the LIB due to large electrochemically active surface areas but cathodes made of lithium manganese oxides (Li–Mn–O) suffer from structural instabilities due to their sensitivity to the average manganese oxidation state. Therefore, thin films in the Li–Mn–O system

J. Pröll; R. Kohler; M. Torge; S. Ulrich; C. Ziebert; M. Bruns; H. J. Seifert; W. Pfleging

2011-01-01

46

Higher valency ion substitution into the manganese oxide framework.  

PubMed

A new route for higher valency ion substitution into the manganese oxide (OMS-2) framework is reported. Isomorphously substituted vanadium and niobium OMS-2 were hydrothermally synthesized at 200 degrees C for a period of 2 days. Characterization by XRD, elemental analysis, Raman spectroscopy, and resistivity studies proved that vanadium was incorporated into the manganese oxide structure. The presence of vanadium in the framework changes the electrical properties, making the material very attractive for water sensing applications. PMID:15212514

Polverejan, Mihai; Villegas, Josanlet C; Suib, Steven L

2004-06-30

47

Manganese and iron oxidation by fungi isolated from building stone.  

PubMed

Acid and nonacid generating fungal strains isolated from weathered sandstone, limestone, and granite of Spanish cathedrals were assayed for their ability to oxidize iron and manganese. In general, the concentration of the different cations present in the mineral salt media directly affected Mn(IV) oxide formation, although in some cases, the addition of glucose and nitrate to the culture media was necessary. Mn(II) oxidation in acidogenic strains was greater in a medium containing the highest concentrations of glucose, nitrate, and manganese. High concentrations of Fe(II), glucose, and mineral salts were optimal for iron oxidation. Mn(IV) precipitated as oxides or hydroxides adhered to the mycelium. Most of the Fe(III) remained in solution by chelation with organic acids excreted by acidogenic strains. Other metabolites acted as Fe(III) chelators in nonacidogenic strains, although Fe(III) deposits around the mycelium were also detected. Both iron and manganese oxidation were shown to involve extracellular, hydrosoluble enzymes, with maximum specific activities during exponential growth. Strains able to oxidize manganese were also able to oxidize iron. It is concluded that iron and manganese oxidation reported in this work were biologically induced by filamentous fungi mainly by direct (enzymatic) mechanisms. PMID:24190274

de la Torre, M A; Gomez-Alarcon, G

1994-01-01

48

Manganese and Oxidative Damage in Cucumber  

Microsoft Academic Search

Micronutrients in low or high concentration can affect growth, respiration, photosynthesis, and reproduction in plants. Cucumber (Cucumis sativus, L.) is grown in India in areas low or high in manganese concentration in soils. A study was conducted to investigate the effects of manganese concentration on some metabolic activities affecting developmental responses in cucumber. Seed of cucumber, cv. Sonali, were grown

Rajeev Gopal

2008-01-01

49

Catalytic decomposition of hydrogen peroxide on manganese oxides. IV. Catalytic activities and electrode potentials of platinum-supported manganese oxides  

Microsoft Academic Search

The decomposition of hydrogen peroxide on thin layers of platinum-supported manganese oxides was studied in the stationary and nonstationary regions. The catalytic activities and the electrode potentials of the oxides were simultaneously determined. In the stationary region the surface's oxidation state and structure are independent of the temperature, of the hydrogen peroxide concentration, and of the presence of KCl and

V. A. Sadykov; P. G. Tsyrulnikov

1977-01-01

50

Nano-sized layered aluminium or zinc-manganese oxides as efficient water oxidizing catalysts.  

PubMed

Nano-sized layered aluminium or zinc-manganese oxides were synthesized and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrometry, dynamic light scattering and atomic absorption spectroscopy. These oxides showed efficient water oxidizing activity in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant. Amounts of dissolved manganese, zinc or aluminium, and water oxidation activities of these oxides were reported and compared with other manganese oxides. A mechanism for oxygen evolution and possible roles for zinc or aluminium ions are also proposed. PMID:22565665

Najafpour, Mohammad Mahdi; Pashaei, Babak; Nayeri, Sara

2012-06-21

51

Isotopic evidence for organic matter oxidation by manganese reduction in the formation of stratiform manganese carbonate ore  

Microsoft Academic Search

Unlike other marine-sedimentary manganese ore deposits, which are largely composed of manganese oxides, the primary ore at Molango (Hidalgo State, Mexico) is exclusively manganese carbonate (rhodochrosite, Mn-calcite, kutnahorite). Stable isotope studies of the carbonates from Molango provide critical new information relevant to the controversy over syngenetic and diagenetic models of stratiform manganese deposit formation. Negative δ¹³C values for carbonates from

P. M. Okita; J. B. Maynard; E. C. Spiker; E. R. Force

1988-01-01

52

Effect of enhanced manganese oxidation in the hyporheic zone on basin-scale geochemical mass balance  

E-print Network

Effect of enhanced manganese oxidation in the hyporheic zone on basin-scale geochemical mass) in enhancing microbially mediated oxidation of dissolved manganese (to form manganese precipitates) in a drainage basin contaminated by copper mining. The fate of manganese is of overall importance to water

53

Mineralogical Characterization of Manganese Oxides in Mine Water Treatment Systems  

NASA Astrophysics Data System (ADS)

The removal of manganese(II) from mine water is a significant problem for both operating and abandoned mines across the United States. In many situations, manganese removal represents the most costly aspect of mine water treatment. Active treatment of Mn-containing mine water requires adjustment of pH to 9-10, and results in the abiotic precipitation of manganese oxides (MnOx). After manganese removal, this high pH water must be neutralized before release. Alternatively, passive limestone beds can be used for neutralization of low-pH mine water and subsequent manganese removal. Although limestone beds are effective for Mn removal, the processes involved are not clear (e.g., relative importance of biological Mn(II) oxidation versus surface mediated oxidation) and the characteristics of the manganese "crusts" formed are not well studied. In this field-based study, we have collected natural manganese oxides from two different limestone beds designed to treat mine water from abandoned coal strip mines in Pennsylvania. Samples were collected at different locations in the beds and at different seasons to capture possible variations in mineralogical characteristics. Water samples were also collected to measure the corresponding solution chemistry and revealed that manganese removal was strongly temperature dependent. Solid samples have been examined by scanning and transmission electron microscopy, and by X-ray diffraction. Micro-diffraction XRD has been used to tentatively identify disordered buserite as a predominant mineral in many of these crust samples. Additional characterizations will include particle size distribution and surface charge. Synchroton-based X-ray techniques such as scanning transmission X-ray microscopy (STXM) and X-ray spectroscopy (XAS) may also be pursued.

Tan, H.; Heaney, P.; Post, J.; Burgos, W.

2006-05-01

54

Kinetic Modeling of Oxidation of Antibacterial Agents by Manganese  

E-print Network

with the proposed rate-limiting steps. This new model improves the ability to quantitatively evaluate the kinetics of oxidative transformation of organic contaminants by manganese oxides in well-defined systems. Introduction growth of resistant bacteria and pose adverse health effects to humans (4, 5). Understanding the fate

Huang, Ching-Hua

55

Amorphous manganese oxide remains amorphous upon lithium intercalation and cycling  

Microsoft Academic Search

Lithium intercalation in amorphous manganese oxide, synthesized by a room temperature aqueous oxidation route, is analyzed. As reported before, the material yields a very high intercalation capacity and also shows promising rate capability as cathode for rechargeable lithium batteries. The present study investigates the structure of the material using X-ray powder diffraction conducted on composite cathode pellets at different stages

Xu Jun John; Ye Hui; Jain Gaurav; Yang Jingsi

2004-01-01

56

Chlorobenzene oxidation using ozone over iron oxide and manganese oxide catalysts.  

PubMed

A low-temperature catalytic oxidation of chlorobenzene (CB) has been performed at temperatures of 60-210°C using ozone (O(3)) over iron oxide and manganese oxide, respectively. In the absence of ozone, CB conversion achieved with these two catalysts at 200°C was below 10%. However, addition of 1200 ppm ozone results in a remarkable increase in CB conversion and the conversion reaches 91.7% at 150°C for iron oxide, while 81.5% conversion is achieved with manganese oxide at 90°C. The activation energy of manganese oxide (48 kJ mol(-1)) is higher than that of iron oxide (43 kJ mol(-1)) without ozone. However, as ozone is added, the activation energy is significantly reduced to 20.0 kJ mol(-1) for iron oxide. CO and CO(2) are the only carbon-containing products detected in the effluent gas stream. For the long-term test, no obvious deactivation was found in iron oxide and ozone. However, in the case of manganese oxide and ozone, 3% reduction of CB conversion was observed. Slight deactivation might be attributed to a small amount of reaction byproducts (carboxylic acid species) and residual chloride (MnCl(2)) being deposited on the active sites of the catalysts. PMID:21227575

Wang, Hou Chuan; Liang, Hsu Shang; Chang, Moo Been

2011-02-28

57

Water defluoridation by aluminium oxide-manganese oxide composite material.  

PubMed

In this study, aluminium oxide-manganese oxide (AOMO) composite material was synthesized, characterized, and tested for fluoride removal in batch experiments. AOMO was prepared from manganese(II) chloride and aluminium hydroxide. The surface area of AOMO was found to be 30.7m2/g and its specific density was determined as 2.78 g/cm3. Detailed investigation of the adsorbent by inductively coupled plasma-optical emission spectrometry, inductively coupled plasma-mass spectrometry, and ion chromatography (for sulphate only) showed that it is composed of Al, Mn, SO4, and Na as major components and Fe, Si, Ca, and Mg as minor components. Thermogravimetric analysis was used to study the thermal behaviour of AOMO. X-ray diffraction analysis showed that the adsorbent is poorly crystalline. The point of zero charge was determined as 9.54. Batch experiments (by varying the proportion of MnO, adsorbent dose, contact time, initial F concentration, and raw water pH) showed that fluoride removal efficiency ofAOMO varied significantly with percentage of MnO with an optimum value of about I11% of manganese oxide in the adsorbent. The optimum dose of the adsorbent was 4 g/L which corresponds to the equilibrium adsorption capacity of 4.8 mg F-/g. Both the removal efficiency and adsorption capacity showed an increasing trend with an increase in initial fluoride concentration of the water. The pH for optimum fluoride removal was found to be in the range between 5 and 7. The adsorption data were analysed using the Freundlich, Langmuir, and Dubinirn-Radushkevich models. The minimum adsorption capacity obtained from the non-linear Freundlich isotherm model was 4.94 mg F-/g and the maximum capacity from the Langmuir isotherm method was 19.2mg F-/g. The experimental data of fluoride adsorption on AOMO fitted well to the Freundlich isotherm model. Kinetic studies showed that the adsorption is well described by a non-linear pseudo-second-order reaction model with an average rate constant of 3.1 x 10(-2) g/min mg. It is concluded that AOMO is a highly promising adsorbent for the removal of excess fluoride from drinking water. PMID:24956783

Alemu, Sheta; Mulugeta, Eyobel; Zewge, Feleke; Chandravanshi, Bhagwan Singh

2014-08-01

58

Catalytic Reduction of NO with CO on Active Carbon-Supported Copper, Manganese, and Copper–Manganese Oxides  

Microsoft Academic Search

The catalytic activity of copper, manganese, and copper–manganese oxide catalysts with respect to NO reduction with CO has been investigated in the temperature range 25–300°C. Copper–manganese oxide catalysts with Cu:Mn ratios of 1 : 2 and 1 : 1 where the two metals form spinel-like phases have shown the highest activity. With the three kinds of catalysts NO reduction proceeds

Neli B. Stankova; Mariana S. Khristova; Dimitar R. Mehandjiev

2001-01-01

59

The thermal stability of lithium-manganese-oxide spinel phases  

SciTech Connect

The thermal stability of stoichiometric spinel phases in the system Li{sub 1+{delta}}Mn{sub 2{minus}{delta}}O{sub 4} (0 {le} {delta} {le} 0.33) has been investigated by high-temperature powder X-ray diffraction, differential thermal analysis, and thermogravimetric analysis. At elevated temperatures, the lithium-manganese-oxide spinels undergo phase changes by loss of oxygen and lithia (Li{sub 2}O). The data highlight the importance of temperature control when synthesizing lithium-manganese-oxide spinel compounds.

Thackeray, M.M.; Mansuetto, M.F.; Dees, D.W.; Vissers, D.R. [Argonne National Lab., IL (United States)] [Argonne National Lab., IL (United States)

1996-02-01

60

Electrochemical properties of iodine-containing lithium manganese oxide spinel  

Microsoft Academic Search

Iodine-containing, cation-deficient, lithium manganese oxides (ICCD-LMO) are prepared by reaction of MnO2 with LiI. The MnO2 is completely transformed into spinel-structured compounds with a nominal composition of Li1??Mn2?2?O4Ix. A sample prepared at 800°C, viz. Li0.99Mn1.98O4I0.02, exhibits an initial discharge capacity of 113mAhg?1 with good cycleability and rate capability in the 4-V region. Iodine-containing, lithium-rich lithium manganese oxides (ICLR-LMO) are also

Chi-Hwan Han; Young-Sik Hong; Hyun-Sil Hong; Keon Kim

2002-01-01

61

Synthesis and electrochemistry of a vanadium-pillared manganese oxide  

Microsoft Academic Search

A new manganese dioxide pillared by vanadium oxide species has been synthesized hydrothermally from permanganate. It has the electrochemically active MnO2 layer structure, which has been extensively studied as a battery cathode. The vanadium oxide ions, together with the water molecules, reside in between the oxide sheets; dehydration occurs without structural change. The (VOy)0.1MnO2·nH2O has a rhombohedral structure, with hexagonal

Fan Zhang; Katana Ngala; M. Stanley Whittingham

2000-01-01

62

Np and Pu Sorption to Manganese Oxide Minerals  

SciTech Connect

Manganese oxide minerals are a significant component of the fracture lining mineralogy at Yucca Mountain (Carlos et al., 1993) and within the tuff-confining unit at Yucca Flat (Prothro, 1998), Pahute Mesa (Drellack et al., 1997), and other locations at the Nevada Test Site (NTS). Radionuclide sorption to manganese oxide minerals was not included in recent Lawrence Livermore National Laboratory (LLNL) hydrologic source term (HST) models which attempt to predict the migration behavior of radionuclides away from underground nuclear tests. However, experiments performed for the Yucca Mountain Program suggest that these minerals may control much of the retardation of certain radionuclides, particularly Np and Pu (Triay et al., 1991; Duff et al., 1999). As a result, recent HST model results may significantly overpredict radionuclide transport away from underground nuclear tests. The sorption model used in HST calculations performed at LLNL includes sorption to iron oxide, calcite, zeolite, smectite, and mica minerals (Zavarin and Bruton 2004a; 2004b). For the majority of radiologic source term (RST) radionuclides, we believe that this accounts for the dominant sorption processes controlling transport. However, for the case of Np, sorption is rather weak to all but the iron and manganese oxides (Figure 1). Thus, we can expect to significantly reduce predicted Np transport by accounting for Np sorption to manganese oxides. Similarly, Pu has been shown to be predominantly associated with manganese oxides in Yucca Mountain fractured tuffs (Duff et al., 1999). Recent results on colloid-facilitated Pu transport (Kersting and Reimus, 2003) also suggest that manganese oxide coatings on fracture surfaces may compete with colloids for Pu, thus reducing the effects of colloid-facilitated Pu transport (Figure 1b). The available data suggest that it is important to incorporate Np and Pu sorption to manganese oxides in reactive transport models. However, few data are available for inclusion in our model. A survey of published data found only single-point (Triay et al., 1991; Kersting and Reimus, 2003; Keeney-Kennicutt and Morse, 1984; 1985) and qualitative (Duff et al., 1999; Dyer et al., 2000a; 2000b) Np and Pu sorption information. This report describes recent experiments that quantified the sorption and desorption of Np(V) and Pu(IV) onto three manganese oxide minerals as a function of pH and time. The three manganese oxides (pyrolusite, birnessite, and hollandite) have all been observed on fracture surfaces at Yucca Mountain and are likely to predominate at the NTS. Pyrolusite, birnessite, and hollandite comprise both a range of manganese oxide structure (framework, layered, and tunnel, respectively) and composition and a range of observed manganese oxide mineralogies. The pH range of 3-10 used in these experiments covers the range of pH observed in NTS groundwater (Rose et al., 1997).

Zhao, P; Johnson, M R; Roberts, S K; Zavarin, M

2005-08-30

63

Lithium manganese oxide with excellent electrochemical performance prepared from chemical manganese dioxide for lithium ion batteries  

NASA Astrophysics Data System (ADS)

Chemical manganese dioxide (CMD) is synthesized by the SEDEMA process and adopted as a precursor for lithium manganese oxide with a spinel structure (LMO). LMO is also prepared from electrolytic manganese dioxide (EMD) as a reference for comparison. X-ray diffraction (XRD) shows that CMD is composed of ?-MnO2, and scanning electron microscopy (SEM) with transmission electron microscopy (TEM) shows that the nanorods cover a spherical core with a diameter < 1 ?m. The LMO prepared from CMD shows a much better rate capability and cycle life performance than that from EMD at high temperatures and high current densities. The excellent electrochemical performance is attributed to the structural stability during charge and discharge and the morphology of the LMO, a loose aggregation of the octahedral particles with a uniform size (<1 ?m) and shape, which originated from that of CMD.

Lee, Jae-Won; Kim, Jun-Il; Roh, Kwang Chul

2012-09-01

64

40 CFR 721.4587 - Lithium manganese oxide (LiMn204) (generic name).  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Lithium manganese oxide (LiMn204) (generic...Specific Chemical Substances § 721.4587 Lithium manganese oxide (LiMn204) (generic...chemical substance identified generically as lithium manganese oxide (LiMn204)...

2011-07-01

65

40 CFR 721.4587 - Lithium manganese oxide (LiMn204) (generic name).  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Lithium manganese oxide (LiMn204) (generic...Specific Chemical Substances § 721.4587 Lithium manganese oxide (LiMn204) (generic...chemical substance identified generically as lithium manganese oxide (LiMn204)...

2010-07-01

66

40 CFR 721.4587 - Lithium manganese oxide (LiMn204) (generic name).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Lithium manganese oxide (LiMn204) (generic...Specific Chemical Substances § 721.4587 Lithium manganese oxide (LiMn204) (generic...chemical substance identified generically as lithium manganese oxide (LiMn204)...

2013-07-01

67

40 CFR 721.4587 - Lithium manganese oxide (LiMn204) (generic name).  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Lithium manganese oxide (LiMn204) (generic...Specific Chemical Substances § 721.4587 Lithium manganese oxide (LiMn204) (generic...chemical substance identified generically as lithium manganese oxide (LiMn204)...

2012-07-01

68

75 FR 70583 - Cobalt Lithium Manganese Nickel Oxide; Withdrawal of Significant New Use Rule  

Federal Register 2010, 2011, 2012, 2013

...FRL-8853-2] RIN 2070-AB27 Cobalt Lithium Manganese Nickel Oxide; Withdrawal of...chemical substance identified as cobalt lithium manganese nickel oxide (CAS No. 182442-95-1...withdrawing the rule issued for cobalt lithium manganese nickel oxide (PMN...

2010-11-18

69

40 CFR 721.10008 - Manganese strontium oxide (MnSrO3).  

...2014-07-01 2014-07-01 false Manganese strontium oxide (MnSrO3). 721...Chemical Substances § 721.10008 Manganese strontium oxide (MnSrO3 ). ...The chemical substance identified as manganese strontium oxide (MnSrO3 )...

2014-07-01

70

40 CFR 721.10013 - Manganese yttrium oxide (Mn2YO5).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Manganese yttrium oxide (Mn2YO5). 721.10013...Chemical Substances § 721.10013 Manganese yttrium oxide (Mn2 YO5 ). ...The chemical substance identified as manganese yttrium oxide (Mn2 YO5 )...

2013-07-01

71

40 CFR 721.4587 - Lithium manganese oxide (LiMn204) (generic name).  

...2014-07-01 2014-07-01 false Lithium manganese oxide (LiMn204) (generic name...Chemical Substances § 721.4587 Lithium manganese oxide (LiMn204) (generic name...substance identified generically as lithium manganese oxide (LiMn204)...

2014-07-01

72

40 CFR 721.10008 - Manganese strontium oxide (MnSrO3).  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Manganese strontium oxide (MnSrO3). 721...Chemical Substances § 721.10008 Manganese strontium oxide (MnSrO3 ). ...The chemical substance identified as manganese strontium oxide (MnSrO3 )...

2012-07-01

73

40 CFR 721.10009 - Manganese yttrium oxide (MnYO3).  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Manganese yttrium oxide (MnYO3). 721.10009...Chemical Substances § 721.10009 Manganese yttrium oxide (MnYO3). (a) Chemical...The chemical substance identified as manganese yttrium oxide (MnYO3 ) (PMN...

2010-07-01

74

40 CFR 721.10010 - Barium manganese oxide (BaMnO3).  

...2014-07-01 2014-07-01 false Barium manganese oxide (BaMnO3). 721.10010 Section...Chemical Substances § 721.10010 Barium manganese oxide (BaMnO3 ). (a) Chemical...chemical substance identified as barium manganese oxide (BaMnO3 ) (PMN...

2014-07-01

75

40 CFR 721.10009 - Manganese yttrium oxide (MnYO3).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Manganese yttrium oxide (MnYO3). 721.10009...Chemical Substances § 721.10009 Manganese yttrium oxide (MnYO3 ). (a...The chemical substance identified as manganese yttrium oxide (MnYO3 ) (PMN...

2013-07-01

76

40 CFR 721.10013 - Manganese yttrium oxide (Mn2YO5).  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Manganese yttrium oxide (Mn2YO5). 721.10013...Chemical Substances § 721.10013 Manganese yttrium oxide (Mn2 YO5 ). ...The chemical substance identified as manganese yttrium oxide (Mn2 YO5 )...

2012-07-01

77

40 CFR 721.10010 - Barium manganese oxide (BaMnO3).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Barium manganese oxide (BaMnO3). 721.10010 Section...Chemical Substances § 721.10010 Barium manganese oxide (BaMnO3 ). (a) Chemical...chemical substance identified as barium manganese oxide (BaMnO3 ) (PMN...

2013-07-01

78

40 CFR 721.10010 - Barium manganese oxide (BaMnO3).  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Barium manganese oxide (BaMnO3). 721.10010 Section...Chemical Substances § 721.10010 Barium manganese oxide (BaMnO3). (a) Chemical...chemical substance identified as barium manganese oxide (BaMnO3 ) (PMN...

2010-07-01

79

40 CFR 721.10008 - Manganese strontium oxide (MnSrO3).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Manganese strontium oxide (MnSrO3). 721...Chemical Substances § 721.10008 Manganese strontium oxide (MnSrO3 ). ...The chemical substance identified as manganese strontium oxide (MnSrO3 )...

2013-07-01

80

40 CFR 721.10009 - Manganese yttrium oxide (MnYO3).  

...2014-07-01 2014-07-01 false Manganese yttrium oxide (MnYO3). 721.10009...Chemical Substances § 721.10009 Manganese yttrium oxide (MnYO3 ). (a...The chemical substance identified as manganese yttrium oxide (MnYO3 ) (PMN...

2014-07-01

81

40 CFR 721.10009 - Manganese yttrium oxide (MnYO3).  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Manganese yttrium oxide (MnYO3). 721.10009...Chemical Substances § 721.10009 Manganese yttrium oxide (MnYO3). (a) Chemical...The chemical substance identified as manganese yttrium oxide (MnYO3 ) (PMN...

2011-07-01

82

40 CFR 721.10008 - Manganese strontium oxide (MnSrO3).  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Manganese strontium oxide (MnSrO3). 721...Chemical Substances § 721.10008 Manganese strontium oxide (MnSrO3). (a...The chemical substance identified as manganese strontium oxide (MnSrO3 )...

2010-07-01

83

40 CFR 721.10013 - Manganese yttrium oxide (Mn2YO5).  

...2014-07-01 2014-07-01 false Manganese yttrium oxide (Mn2YO5). 721.10013...Chemical Substances § 721.10013 Manganese yttrium oxide (Mn2 YO5 ). ...The chemical substance identified as manganese yttrium oxide (Mn2 YO5 )...

2014-07-01

84

40 CFR 721.10010 - Barium manganese oxide (BaMnO3).  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Barium manganese oxide (BaMnO3). 721.10010 Section...Chemical Substances § 721.10010 Barium manganese oxide (BaMnO3). (a) Chemical...chemical substance identified as barium manganese oxide (BaMnO3 ) (PMN...

2011-07-01

85

40 CFR 721.10008 - Manganese strontium oxide (MnSrO3).  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Manganese strontium oxide (MnSrO3). 721...Chemical Substances § 721.10008 Manganese strontium oxide (MnSrO3). (a...The chemical substance identified as manganese strontium oxide (MnSrO3 )...

2011-07-01

86

40 CFR 721.10009 - Manganese yttrium oxide (MnYO3).  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Manganese yttrium oxide (MnYO3). 721.10009...Chemical Substances § 721.10009 Manganese yttrium oxide (MnYO3 ). (a...The chemical substance identified as manganese yttrium oxide (MnYO3 ) (PMN...

2012-07-01

87

40 CFR 721.10010 - Barium manganese oxide (BaMnO3).  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Barium manganese oxide (BaMnO3). 721.10010 Section...Chemical Substances § 721.10010 Barium manganese oxide (BaMnO3 ). (a) Chemical...chemical substance identified as barium manganese oxide (BaMnO3 ) (PMN...

2012-07-01

88

40 CFR 721.10013 - Manganese yttrium oxide (Mn2YO5).  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Manganese yttrium oxide (Mn2YO5). 721.10013...Chemical Substances § 721.10013 Manganese yttrium oxide (Mn2YO5). (a...The chemical substance identified as manganese yttrium oxide (Mn2 YO5 )...

2010-07-01

89

40 CFR 721.10013 - Manganese yttrium oxide (Mn2YO5).  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Manganese yttrium oxide (Mn2YO5). 721.10013...Chemical Substances § 721.10013 Manganese yttrium oxide (Mn2YO5). (a...The chemical substance identified as manganese yttrium oxide (Mn2 YO5 )...

2011-07-01

90

Effect of enhanced manganese oxidation in the hyporheic zone on basin-scale geochemical mass balance  

Microsoft Academic Search

We determined the role of the hyporheic zone (the subsurface zone where stream water and shallow groundwater mix) in enhancing microbially mediated oxidation of dissolved manganese (to form manganese precipitates) in a drainage basin contaminated by copper mining. The fate of manganese is of overall importance to water quality in Pinal Creek Basin, Arizona, because manganese reactions affect the transport

Judson W. Harvey; Christopher C. Fuller

1998-01-01

91

Oxidative removal of aqueous steroid estrogens by manganese oxides.  

PubMed

This study investigated the oxidative removal of steroid estrogens from water by synthetic manganese oxide (MnO2) and the factors influencing the reactions. Using 1 x 10(-5)M MnO2 at pH 4, estrone (E1), 17beta-estradiol (E2), estriol (E3) and 17alpha-ethinylestradiol (EE2), all at 4 x 10(-6)M, were rapidly removed within 220 min, indicating the effectiveness of MnO2 as an oxidizing agent towards estrogens. E2 removal increased with decreasing pH over the tested range of 4-8, due most likely to increased oxidizing power of MnO2 and a cleaner reactive surface in acidic solutions. Coexisting metal ions of 0.01 M (Cu(II), Zn(II), Fe(III) and Mn(II)) and Mn(II) released from MnO2 reduction competed with E2 for reactive sites leading to reduced E2 removal. Observed differential suppression on E2 removal may be related to different speciations of metals, as suggested by the MINTEQ calculations, and hence their different adsorptivities on MnO2. By suppressing the metal effect, humic acid substantially enhanced E2 removal. This was attributed to complexation of humic acid with metal ions. With 0.01 M ZnCl2 in solutions containing 1 mg l(-1) humic acid, the binding of humic acid for Zn(II) was determined at 251 mmol g(-1). An in vitro assay using human breast carcinoma MCF-7 cells indicated a near elimination of estrogenic activities without secondary risk of estrogen solutions treated with MnO2. Synthetic MnO2 is therefore a promising chemical agent under optimized conditions for estrogen removal from water. Metal chelators recalcitrant to MnO2 oxidation may be properly used to further enhance the MnO2 performance. PMID:18929389

Xu, Lei; Xu, Chao; Zhao, Meirong; Qiu, Yuping; Sheng, G Daniel

2008-12-01

92

ENVR Dionysios Dionysiou Wednesday, August 22, 2012 261 -Arsenic mobilization in the critical zone: Oxidation by manganese oxide minerals  

E-print Network

: Oxidation by manganese oxide minerals Jason S. Fischel1, fischelj@udel.edu, Matthew H. Fischel1, Brandon J Center, U.S. Army Corps of Engineers, Vicksburg, MS 39180, United States Manganese(IV) oxides are one of the main redox catalysts in the subsurface environment. Their highly reactive surfaces allow manganese (Mn

Sparks, Donald L.

93

Manganese-oxidizing photosynthesis before the rise of cyanobacteria  

E-print Network

Manganese-oxidizing photosynthesis before the rise of cyanobacteria Jena E. Johnsona,1 , Samuel M) The emergence of oxygen-producing (oxygenic) photosynthesis fundamentally transformed our planet; however biological innovation-- the evolution of oxygenic photosynthesis (3, 4). Several bio- chemical attributes

Fischer, Woodward

94

Solid solution of nickel oxide and manganese oxide as negative active material for lithium secondary cells  

Microsoft Academic Search

The solid solution of nickel oxide and manganese oxide has been synthesized successfully by heating Ni1?aMnaOOH at a temperature ranging from 350 to 1000°C in oxygen atmosphere, and investigated as a high-capacity negative active material for lithium secondary cells. The discharge capacity of nickel and manganese oxide solid solution was decreased with increasing heat-treatment temperature. The average discharge potential shifts

Xingjiang Liu; Hideo Yasuda; Masanori Yamachi

2005-01-01

95

Nano-sized manganese oxides as biomimetic catalysts for water oxidation in artificial photosynthesis: a review.  

PubMed

There has been a tremendous surge in research on the synthesis of various metal compounds aimed at simulating the water-oxidizing complex (WOC) of photosystem II (PSII). This is crucial because the water oxidation half reaction is overwhelmingly rate-limiting and needs high over-voltage (approx. 1 V), which results in low conversion efficiencies when working at current densities required for hydrogen production via water splitting. Particular attention has been given to the manganese compounds not only because manganese has been used by nature to oxidize water but also because manganese is cheap and environmentally friendly. The manganese-calcium cluster in PSII has a dimension of about approximately 0.5 nm. Thus, nano-sized manganese compounds might be good structural and functional models for the cluster. As in the nanometre-size of the synthetic models, most of the active sites are at the surface, these compounds could be more efficient catalysts than micrometre (or bigger) particles. In this paper, we focus on nano-sized manganese oxides as functional and structural models of the WOC of PSII for hydrogen production via water splitting and review nano-sized manganese oxides used in water oxidation by some research groups. PMID:22809849

Najafpour, Mohammad Mahdi; Rahimi, Fahimeh; Aro, Eva-Mari; Lee, Choon-Hwan; Allakhverdiev, Suleyman I

2012-10-01

96

Nano-sized manganese oxides as biomimetic catalysts for water oxidation in artificial photosynthesis: a review  

PubMed Central

There has been a tremendous surge in research on the synthesis of various metal compounds aimed at simulating the water-oxidizing complex (WOC) of photosystem II (PSII). This is crucial because the water oxidation half reaction is overwhelmingly rate-limiting and needs high over-voltage (approx. 1 V), which results in low conversion efficiencies when working at current densities required for hydrogen production via water splitting. Particular attention has been given to the manganese compounds not only because manganese has been used by nature to oxidize water but also because manganese is cheap and environmentally friendly. The manganese–calcium cluster in PSII has a dimension of about approximately 0.5 nm. Thus, nano-sized manganese compounds might be good structural and functional models for the cluster. As in the nanometre-size of the synthetic models, most of the active sites are at the surface, these compounds could be more efficient catalysts than micrometre (or bigger) particles. In this paper, we focus on nano-sized manganese oxides as functional and structural models of the WOC of PSII for hydrogen production via water splitting and review nano-sized manganese oxides used in water oxidation by some research groups. PMID:22809849

Najafpour, Mohammad Mahdi; Rahimi, Fahimeh; Aro, Eva-Mari; Lee, Choon-Hwan; Allakhverdiev, Suleyman I.

2012-01-01

97

Transformation from layered to tunnel structures: Synthesis, characterization, and applications of manganese oxide octahedral molecular sieves  

Microsoft Academic Search

Manganese oxide based octahedral molecular sieves (OMS) have been found to have a wide variety of applications as catalysts, absorbents, and battery materials due to their unique structures and physical and chemical properties. OMS materials are made up of manganese oxide octahedral building blocks sharing comers and edges to form tunnel structures. Manganese species in the framework of OMS materials

Guan-Guang Xia

2001-01-01

98

Kinetics of manganese adsorption, desorption, and oxidation in coastal marine sediments  

E-print Network

Kinetics of manganese adsorption, desorption, and oxidation in coastal marine sediments Dominique´bec a` Rimouski, Que´bec, Canada Abstract Ejection of excavated manganese (Mn)-laden particles from disturbances triggers desorption and oxidation of reduced manganese species. These competing reactions

Beaudoin, Georges

99

Manganese oxidation state mediates toxicity in PC12 cells  

SciTech Connect

The role of the manganese (Mn) oxidation state on cellular Mn uptake and toxicity is not well understood. Therefore, undifferentiated PC12 cells were exposed to 0-200 {mu}M Mn(II)-chloride or Mn(III)-pyrophosphate for 24 h, after which cellular manganese levels were measured along with measures of cell viability, function, and cytotoxicity (trypan blue exclusion, medium lactate dehydrogenase (LDH), 8-isoprostanes, cellular ATP, dopamine, serotonin, H-ferritin, transferrin receptor (TfR), Mn-superoxide dismutase (MnSOD), and copper-zinc superoxide dismutase (CuZnSOD) protein levels). Exposures to Mn(III) >10 {mu}M produced 2- to 5-fold higher cellular manganese levels than equimolar exposures to Mn(II). Cell viability and ATP levels both decreased at the highest Mn(II) and Mn(III) exposures (150-200 {mu}M), while Mn(III) exposures produced increases in LDH activity at lower exposures ({>=}50 {mu}M) than did Mn(II) (200 {mu}M only). Mn(II) reduced cellular dopamine levels more than Mn(III), especially at the highest exposures (50% reduced at 200 {mu}M Mn(II)). In contrast, Mn(III) produced a >70% reduction in cellular serotonin at all exposures compared to Mn(II). Different cellular responses to Mn(II) exposures compared to Mn(III) were also observed for H-ferritin, TfR, and MnSOD protein levels. Notably, these differential effects of Mn(II) versus Mn(III) exposures on cellular toxicity could not simply be accounted for by the different cellular levels of manganese. These results suggest that the oxidation state of manganese exposures plays an important role in mediating manganese cytotoxicity.

Reaney, S.H. [Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064 (United States) and Department of Environmental Toxicology, University of California, 1156 High St., Santa Cruz, CA 95064 (United States)]. E-mail: stevereaney@hotmail.com; Smith, D.R. [Department of Environmental Toxicology, University of California, 1156 High St., Santa Cruz, CA 95064 (United States)

2005-06-15

100

Thin film passivation of laser generated 3D micro patterns in lithium manganese oxide cathodes  

NASA Astrophysics Data System (ADS)

The increasing need for long-life lithium-ion batteries requires the further development of electrode materials. Especially on the cathode side new materials or material composites are needed to increase the cycle lifetime. On the one hand, spinel-type lithium manganese oxide is a promising candidate to be used as cathode material due to its non-toxicity, low cost and good thermal stability. On the other hand, the spinel structure suffers from change in the oxidation state of manganese during cycling which is also accompanied by loss of active material into the liquid electrolyte. The general trend is to enhance the active surface area of the cathode in order to increase lithium-ion mobility through the electrode/electrolyte interface, while an enhanced surface area will also promote chemical degradation. In this work, laser microstructuring of lithium manganese oxide thin films was applied in a first step to increase the active surface area. This was done by using 248 nm excimer laser radiation and chromium/quartz mask imaging techniques. In a second step, high power diode laser-annealing operating at a wavelength of 940 nm was used for forming a cubic spinel-like battery phase. This was verified by means of Raman spectroscopy and cyclic voltammetric measurements. In a last step, the laser patterned thin films were coated with indium tin oxide (ITO) layers with a thickness of 10 nm to 50 nm. The influence of the 3D surface topography as well as the ITO thickness on the electrochemical performance was studied by cyclic voltammetry. Post-mortem studies were carried out by using scanning electron microscopy and focused ion beam analysis.

Pröll, J.; Kohler, R.; Bruns, M.; Oberst, V.; Weidler, P. G.; Heißler, S.; Kübel, C.; Scherer, T.; Prang, R.; Seifert, H. J.; Pfleging, W.

2013-03-01

101

Parallel Polarization EPR Characterization of the Mn(III) Center of Oxidized Manganese Superoxide  

E-print Network

Parallel Polarization EPR Characterization of the Mn(III) Center of Oxidized Manganese Superoxide, Maryland 21218 ReceiVed January 22, 1999 ReVised Manuscript ReceiVed March 25, 1999 Manganese superoxide

Miller, Anne-Frances

102

Nano-sized manganese oxide: a proposed catalyst for water oxidation in the reaction of some manganese complexes and cerium(IV) ammonium nitrate.  

PubMed

According to UV-visible spectroscopy, X-ray diffraction spectrometry, dynamic light scattering, Fourier transform infrared spectroscopy, electron paramagnetic resonance spectroscopy, transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy, nano-sized manganese oxides are proposed as active catalysts for water oxidation in the reaction of some manganese complexes and cerium(IV) ammonium nitrate. PMID:22806229

Najafpour, Mohammad Mahdi; Moghaddam, Atefeh Nemati

2012-09-14

103

Synthesis Of Different Phases Of Nano Manganese Oxides And Their Dielectric Behaviour In Chitosan Composites  

Microsoft Academic Search

Nanoscale oxides of transition metals, particularly manganese, are desirable for many applications in designing electric, magnetic and heterogeneous catalytic materials. Manganese oxides exist in different phases, viz. MnO, MnO2, Mn2O3, Mn2O7 and Mn3O4. Using different synthetic routes it is possible to synthesize different phases of manganese oxides. Moreover, composites of these oxides with polymer have the potential to address the

B. A. Harshita; D. Krishna Bhat; Aarti S. Bhatt

2011-01-01

104

Synthesis Of Different Phases Of Nano Manganese Oxides And Their Dielectric Behaviour In Chitosan Composites  

Microsoft Academic Search

Nanoscale oxides of transition metals, particularly manganese, are desirable for many applications in designing electric, magnetic and heterogeneous catalytic materials. Manganese oxides exist in different phases, viz. MnO, MnO2,Mn2O3,Mn2O7 and Mn3O4. Using different synthetic routes it is possible to synthesize different phases of manganese oxides. Moreover, composites of these oxides with polymer have the potential to address the needs of

B. A. Harshita; D. Krishna Bhat; Aarti S. Bhatt

2011-01-01

105

Electrochemical characterization of commercial lithium manganese oxide powders  

Microsoft Academic Search

Five commercial lithium manganese oxide powders have been studied. The XRD spectra showed all samples to exhibit the spinel structure. The composition and morphology were analyzed by Jaeger–Vetter titration and scanning electron microscopy. The lithium intercalation\\/de-intercalation characteristics and the cycleability have been studied using state-of-the-art cells. The morphology of the particles and crystallites, as well as the defect structure of

H. Huang; C. H. Chen; R. C. Perego; E. M. Kelder; L. Chen; J. Schoonman; W. J. Weydanz; D. W. Nielsen

2000-01-01

106

Prismatic cell lithium-ion battery using lithium manganese oxide  

Microsoft Academic Search

Lithium-ion (Li-ion) batteries have demonstrated the ability to fulfill the energy storage needs of many new technologies. The most significant drawbacks of currently available technologies, such as LiCoO 2 based Li-ion cells, is their high cost and significant environmental hazards. Li-ion cells which use a lithium manganese oxide (LiMn2O4) spinel) based cathode material should be much less costly and safer

G. M. Ehrlich; R. M. Hellen; T. B. Reddy

1997-01-01

107

Synthesis of lithium-manganese oxide spinel in hydrothermal conditions  

Microsoft Academic Search

Lithium-manganese oxide spinel LiMn2O4 was synthesized in hydrothermal conditions (400°C, 20 MPa) in the course of thermovaporous treatment mixtures of MnO2 and LiOH\\/or Li2CO3. The conditions of synthesis of the spinel as monophase product were determined. The obtained product has been characterized by means of various physical and chemical methods. The spinel has been used for manufacturing cathodes of rechargeable

G. Panasyuk; I. Voroshilov; G. Boudova; L. Azarova; V. Privalov; V. Minin; A. Skundin; L. Kanevsky; T. Kulova; M. Danchevskaya; Yu. Ivaki

2001-01-01

108

Manganese oxide–carbon composite as supercapacitor electrode materials  

Microsoft Academic Search

Nano-sized manganese oxide (Mn2O3) was incorporated homogeneously in templated mesoporous carbon to prepare Mn2O3–carbon nanocomposites, which were used as supercapacitor electrodes. Cyclic voltammetry was employed to investigate the electrochemical properties of the composite materials in an aqueous electrolyte under different scan rates. Results showed that templated mesoporous carbon with layered graphene domains holds a great promise for high-rate supercapacitor applications.

Li Li Zhang; Tianxin Wei; Wenjuan Wang; X. S. Zhao

2009-01-01

109

A redox-assisted supramolecular assembly of manganese oxide nanotube  

Microsoft Academic Search

In this paper, we report the hydrothermal synthesis of manganese oxide nanotube from an aqueous medium of pH 7, using KMnO4 and MnCl2 as inorganic precursors, polyoxyethylene (10) nonyl phenyl ether (TX-10) a surfactant and acetaldehyde an additive. The characterization of X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and N2 adsorption at 77K (BET) reveals

Li Tao; Cheng-Gao Sun; Mei-Lian Fan; Cai-Juan Huang; Hai-Long Wu; Zi-Sheng Chao; He-Sheng Zhai

2006-01-01

110

New correlated model of colossal magnetoresistive manganese oxides.  

PubMed

A new minimal model is constructed for the doped manganese oxides which exhibit colossal magnetoresistance, involving a broad spin-majority conduction band as well as nearly localized spin-minority electron states. A simple mean-field analysis yields a temperature-dependent hybridized band structure with suppressed carrier weight at the Fermi level. Spin stiffness is complex, indicating strong spin-wave damping. Further investigations are needed to verify the relevance of the proposed model. PMID:20867060

Golosov, D I

2010-05-21

111

Chromium(III) Oxidation by Three Poorly-Crystalline Manganese(IV) Oxides. 1. Chromium(III)-Oxidizing Capacity  

E-print Network

Chromium(III) Oxidation by Three Poorly-Crystalline Manganese(IV) Oxides. 1. Chromium(III)-Oxidizing States *S Supporting Information ABSTRACT: The Cr(III)-oxidizing capacity of three layered poorly in the system, indicated that the Cr(III) oxidation reaction had ceased between 30 min and 1 h under most

Sparks, Donald L.

112

Laser microstructuring and annealing processes for lithium manganese oxide cathodes  

NASA Astrophysics Data System (ADS)

It is expected that cathodes for lithium-ion batteries (LIB) composed out of nano-composite materials lead to an increase in power density of the LIB due to large electrochemically active surface areas but cathodes made of lithium manganese oxides (Li-Mn-O) suffer from structural instabilities due to their sensitivity to the average manganese oxidation state. Therefore, thin films in the Li-Mn-O system were synthesized by non-reactive radiofrequency magnetron sputtering of a spinel lithium manganese oxide target. For the enhancement of the power density and cycle stability, large area direct laser patterning using UV-laser radiation with a wavelength of 248 nm was performed. Subsequent laser annealing processes were investigated in a second step in order to set up a spinel-like phase using 940 nm laser radiation at a temperature of 680 °C. The interaction processes between UV-laser radiation and the material was investigated using laser ablation inductively coupled plasma mass spectroscopy. The changes in phase, structure and grain shape of the thin films due to the annealing process were recorded using Raman spectroscopy, X-ray diffraction and scanning electron microscopy. The structured cathodes were cycled using standard electrolyte and a metallic lithium anode. Different surface structures were investigated and a significant increase in cycling stability was found. Surface chemistry of an as-deposited as well as an electrochemically cycled thin film was investigated via X-ray photoelectron spectroscopy.

Pröll, J.; Kohler, R.; Torge, M.; Ulrich, S.; Ziebert, C.; Bruns, M.; Seifert, H. J.; Pfleging, W.

2011-09-01

113

Diode laser heat treatment of lithium manganese oxide films  

NASA Astrophysics Data System (ADS)

The crystallization of lithium manganese oxide thin films prepared by radio frequency magnetron sputtering on stainless steel substrates under 10 Pa argon pressure is demonstrated by a laser annealing technique. Laser annealing processes were developed as a function of annealing time and temperature with the objective to form an electrochemically active lithium manganese oxide cathode. It is demonstrated, that laser annealing with 940 nm diode laser radiation and an annealing time of 2000 s at 600 °C delivers appropriate parameters for formation of a crystalline spinel-like phase. Characteristic features of this phase could be detected via Raman spectroscopy, showing the characteristic main Raman band at 627 cm-1. Within cyclic voltammetric measurements, the two characteristic redox pairs for spinel lithium manganese oxide in the 4 V region could be detected, indicating that the film was well-crystallized and de-/intercalation processes were reversible. Raman post-analysis of a cycled cathode showed that the spinel-like structure was preserved within the cycling process but mechanical degradation effects such as film cracking were observed via scanning electron microscopy. Typical features for the formation of an additional surface reaction layer could be detected using X-ray photoelectron spectroscopy.

Pröll, J.; Kohler, R.; Mangang, A.; Ulrich, S.; Bruns, M.; Seifert, H. J.; Pfleging, W.

2012-04-01

114

STRUCTURE AND REACTIVITY STUDY OF BIOTIC AND ABIOTIC POORLY CRYSTALLINE MANGANESE OXIDES  

E-print Network

STRUCTURE AND REACTIVITY STUDY OF BIOTIC AND ABIOTIC POORLY CRYSTALLINE MANGANESE OXIDES Rights Reserved #12;STRUCTURE AND REACTIVITY STUDY OF BIOTIC AND ABIOTIC POORLY CRYSTALLINE MANGANESE. Luther, III who inspired me on manganese reaction mechanisms in many helpful discussions, and Dr. Thomas

Sparks, Donald L.

115

Validation of In-Situ Iron-Manganese Oxide Coated Stream Pebbles as Sensors for Arsenic Source Monitoring  

NASA Astrophysics Data System (ADS)

Locating nonpoint source contaminant fluxes can be challenging due to the inherent heterogeneity of source and of the subsurface. Contaminants such as arsenic are a concern for drinking water quality and ecosystem health. Arsenic contamination can be the result of several natural and anthropogenic sources, and therefore it can be difficult to trace and identify major areas of arsenic in natural systems. Identifying a useful source indicator for arsenic is a crucial step for environmental remediation efforts. Previous studies have found iron-manganese oxide coated streambed pebbles as useful source indicators due to their high attraction for heavy metals in water. In this study, pebbles, surface water at baseflow and nearby rocks were sampled from the Pennypack Creek and its tributaries, in southwestern Pennsylvania, to test the ability of coated streambed pebbles as environmental source indicators for arsenic. Quartz pebbles, 5-7 cm in diameter, were sampled to minimize elemental contamination from rock chemistry. In addition, quartz provides an excellent substrate for iron and manganese coatings to form. These coatings were leached from pebbles using 4M nitric acid with 0.1% concentrated hydrochloric acid. Following sample processing, analyses were performed using an ICP-MS and the resulting data were spatially organized using ArcGIS software. Arsenic, iron and manganese concentrations in the leachate are normalized to pebble surface area and each location is reported as a ratio of arsenic to iron and manganese. Results suggest that iron-manganese coated stream pebbles are useful indicators of arsenic location within a watershed.

Blake, J.; Peters, S. C.; Casteel, A.

2013-12-01

116

Manganese ion-assisted assembly of superparamagnetic graphene oxide microbowls  

NASA Astrophysics Data System (ADS)

A facile manganese ion Mn(II)-assisted assembly has been designed to fabricate microbowls by using graphene oxide nanosheets as basic building blocks, which were exfoliated ultrasonically from the oxidized soot powders in deionized water. From the morphology evolution observations of transmission electron microscope and scanning electron microscope, a coordinating-tiling-collapsing manner is proposed to interpret the assembly mechanism based on attractive Van der Waals forces, ?-? stacking, and capillary action. It is interesting to note that the as-prepared microbowls present a room temperature superparamagnetic behavior.

Tian, Zhengshan; Xu, Chunxiang; Li, Jitao; Zhu, Gangyi; Xu, Xiaoyong; Dai, Jun; Shi, Zengliang; Lin, Yi

2014-03-01

117

Lithium-containing manganese dioxide (composite dimensional manganese oxide: CDMO) as positive material for a lithium secondary battery  

NASA Astrophysics Data System (ADS)

Lithium-containing manganese dioxide (CDMO) has been developed as the positive material for lithium secondary batteries. CDMO is prepared from lithium salt and manganese dioxide by heat treatment. It is a composite oxide of ?/?-MnO 2 and Li 2MnO 3. The influence on rechargeability of lithium salts, heat-treatment temperature, and manganese dioxide type has been investigated by conducting cycle tests with flat cells. Lithium hydroxide is more reactive with MnO 2 in the production of Li 2MnO 3 than either Li 2O or Li 2CO 3. The optimum condition for preparing CDMO is to heat treat LiOH and MnO 2 at about 375 °C. CDMO prepared from EMD (electrolytic manganese dioxide) yields a larger and more stable capacity than CDMO prepared from CMD (chemical manganese dioxide). Sodium-free EMD exhibits the largest discharge capacity.

Nohma, T.; Yamamoto, Y.; Nishio, K.; Nakane, I.; Furukawa, N.

118

Alumina-supported manganese oxide catalysts. I. Characterization: Effect of precursor and loading  

Microsoft Academic Search

Alumina-supported manganese oxide catalysts were prepared by two different routes, from Mn acetate and from Mn nitrate, and characterized by temperature-programmed reduction (TPR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and infrared spectroscopy. The characterization studies clearly showed that the two different preparations results in significantly different supported manganese oxide phases. The nitrate precursor resulted primarily in manganese oxide [Mn(III) and

F. Kapteijn; A. D. van Langeveld; J. A. Moulijn; A. Andreieni; M. A. Vuurman; A. M. Turek; J. M. Jehng; I. E. Wachs

1994-01-01

119

Improved cycling performance of bismuth-modified amorphous manganese oxides as cathodes for rechargeable lithium batteries  

Microsoft Academic Search

Bismuth-modified amorphous manganese oxides were synthesized via a room temperature aqueous route. They were galvanostatically tested as intercalation cathodes for rechargeable lithium batteries at 1mAcm?2 between 1.5 and 4.3V. In sharp contrast to severe capacity fading of unmodified amorphous manganese oxide synthesized by the same route, a stable cycling performance of the bismuth-modified amorphous manganese oxide was observed. After an

Jingsi Yang; Terrill B Atwater; Jun John Xu

2005-01-01

120

Constraints on superoxide mediated formation of manganese oxides  

PubMed Central

Manganese (Mn) oxides are among the most reactive sorbents and oxidants within the environment, where they play a central role in the cycling of nutrients, metals, and carbon. Recent discoveries have identified superoxide (O2?) both of biogenic and abiogenic origin as an effective oxidant of Mn(II) leading to the formation of Mn oxides. Here we examined the conditions under which abiotically produced superoxide led to oxidative precipitation of Mn and the solid-phases produced. Oxidized Mn, as both aqueous Mn(III) and Mn(III/IV) oxides, was only observed in the presence of active catalase, indicating that hydrogen peroxide (H2O2), a product of the reaction of O2? with Mn(II), inhibits the oxidation process presumably through the reduction of Mn(III). Citrate and pyrophosphate increased the yield of oxidized Mn but decreased the amount of Mn oxide produced via formation of Mn(III)-ligand complexes. While complexing ligands played a role in stabilizing Mn(III), they did not eliminate the inhibition of net Mn(III) formation by H2O2. The Mn oxides precipitated were highly disordered colloidal hexagonal birnessite, similar to those produced by biotically generated superoxide. Yet, in contrast to the large particulate Mn oxides formed by biogenic superoxide, abiotic Mn oxides did not ripen to larger, more crystalline phases. This suggests that the deposition of crystalline Mn oxides within the environment requires a biological, or at least organic, influence. This work provides the first direct evidence that, under conditions relevant to natural waters, oxidation of Mn(II) by superoxide can occur and lead to formation of Mn oxides. For organisms that oxidize Mn(II) by producing superoxide, these findings may also point to other microbially mediated processes, in particular enzymatic hydrogen peroxide degradation and/or production of organic ligand metabolites, that allow for Mn oxide formation. PMID:24027565

Learman, Deric R.; Voelker, Bettina M.; Madden, Andrew S.; Hansel, Colleen M.

2013-01-01

121

Cathodic behavior of alkali manganese oxides from permanganate  

SciTech Connect

Extensive research is currently underway to find promising candidates for cathode materials in lithium secondary batteries, and a manganese oxide that behaved like the layered LiCoCO{sub 2} would be a prime candidate for this application because of its high free-energy of reaction with lithium and relatively low cost. The reaction of potassium, sodium, and lithium permanganate in water at 170 C leads directly to potassium, sodium, and lithium manganese dioxides, A{sub y}MnO {center_dot} nH{sub 2}O, with a R{bar 3}m rhombohedral structure. These crystalline layered structures after dehydration readily and reversibly react with lithium through an intercalation mechanism. The capacity for lithium is a function of the alkali ion present, and the larger potassium ion maintains the capacity best. For lithium there is a tendency to convert to the spinel structure which leads to loss of capacity.

Chen, R.; Whittingham, M.S. [State Univ. of New York, Binghamton, NY (United States)

1997-04-01

122

Isotopic evidence for organic matter oxidation by manganese reduction in the formation of stratiform manganese carbonate ore  

USGS Publications Warehouse

Unlike other marine-sedimentary manganese ore deposits, which are largely composed of manganese oxides, the primary ore at Molango (Hidalgo State, Mexico) is exclusively manganese carbonate (rhodochrosite, Mn-calcite, kutnahorite). Stable isotope studies of the carbonates from Molango provide critical new information relevant to the controversy over syngenetic and diagenetic models of stratiform manganese deposit formation. Negative ??13C values for carbonates from mineralized zones at Molango are strongly correlated with manganese content both on a whole rock scale and by mineral species. Whole rock ??13C data fall into three groups: high-grade ore = -16.4 to -11.5%.; manganese-rich, sub-ore-grade = -5.2 to 0%.; and unmineralized carbonates = 0 to +2.5%. (PDB). ??18O data show considerable overlap in values among the three groups: +4.8 to -2.8, -5.4 to -0.3%., and -7.4 to +6.2 (PDB), respectively. Isotopic data for individual co-existing minerals suggest a similar separation of ??13C values: ??13C values from calcite range from -1.1 to +0.7%. (PDB), whereas values from rhodochrosite are very negative, -12.9 to -5.5%., and values from kutnahorite or Mn-calcite are intermediate between calcite and rhodochrosite. 13C data are interpreted to indicate that calcite (i.e. unmineralized carbonate) formed from a normal marine carbon reservoir. However, 13C data for the manganese-bearing carbonates suggest a mixed seawater and organic source of carbon. The presence of only trace amounts of pyrite suggests sulfate reduction may have played a minor part in oxidizing organic matter. It is possible that manganese reduction was the predominant reaction that oxidized organic matter and that it released organic-derived CO2 to produce negative ??13C values and manganese carbonate mineralization. ?? 1988.

Okita, P.M.; Maynard, J.B.; Spiker, E. C.; Force, E.R.

1988-01-01

123

First principles calculations for lithiated manganese oxides.  

SciTech Connect

First principles calculations within the local-spin-density-functional theory (LSDFF) framework are presented of densities of electronic states for MnO, LiMnO{sub 2} in the monoclinic and orthorhombic structures, cubic LiMn{sub 2}O{sub 4} spinel and {lambda}-MnO{sub 2} (delithiated spinel), all in antiferromagnetic spin configurations. The changes in energy spectra as the Mn oxidation state varies between 2+ and 4+ are illustrated. Preliminary calculations for Co-doped LiMnO{sub 2} are presented, and the destabilization of a monoclinic relative to a rhombohedral structure is discussed.

Prasad, R.

1998-12-23

124

Kinetics of Chromium(III) Oxidation by Manganese(IV) Oxides Using  

E-print Network

Kinetics of Chromium(III) Oxidation by Manganese(IV) Oxides Using Quick Scanning X-ray Absorption parameters (3). The fate of chromium in soils has been extensively studied (4). Chromium is derived from both(VI) is mobile and more toxic than Cr(III), it is of great environmental concern. Chromium can be found naturally

Sparks, Donald L.

125

Rechargeable 3 V Li cells using hydrated lamellar manganese oxide  

SciTech Connect

The synthesis and the electrochemical features of hydrated lamellar manganese oxides are reported. The authors use the reduction of aqueous permanganate solution by fumaric acid and the oxidation of manganese hydroxide by an aqueous permanganate solution to obtain sol-gel birnessite and classical X-exchanged birnessites (X = Li, Al, Na), respectively. The high oxidation state of Mn associated with the 2D character of the hot lattice allows high specific capacities (150 to 200 Ah/kg) available in the potential range of 4 to 2 V. Interlayer water provides the structural stability of the host lattice required for long cycling. Rechargeable two-electrode Li cells using starved or flooded electrolytes were built with the cathodic materials. The batteries exhibit a satisfactory behavior with a specific capacity of 160 Ah/kg recovered after 30 cycles at the C/20 discharge-charge rate for the sol-gel birnessite. This paper demonstrates an interest in cathodic materials based on oxides containing structural water for use in secondary Li batteries.

Bach, S.; Pereira-Ramos, J.P. [CNRS, Thiais (France). Electrochimie, Catalyse et Synthese Organique; Baffier, N. [CNRS, Paris (France). Chimie Appliquee de l`Etat Solide

1996-11-01

126

Iron and manganese oxide mineralization in the Pacific  

USGS Publications Warehouse

Iron, manganese, and iron-manganese deposits occur in nearly all geomorphologic and tectonic environments in the ocean basins and form by one or more of four processes: (1) hydrogenetic precipitation from cold ambient seawater, (2) precipitation from hydrothermal fluids, (3) precipitation from sediment pore waters that have been modified from bottom water compositions by diagenetic reactions in the sediment column and (4) replacement of rocks and sediment. Iron and manganese deposits occur in five forms: nodules, crusts, cements, mounds and sediment-hosted stratabound layers. Seafloor oxides show a wide range of compositions from nearly pure iron to nearly pure manganese end members. Fe/Mn ratios vary from about 24 000 (up to 58% elemental Fe) for hydrothermal seamount ironstones to about 0.001 (up to 52% Mn) for hydrothermal stratabound manganese oxides from active volcanic arcs. Hydrogenetic Fe-Mn crusts that occur on most seamounts in the ocean basins have a mean Fe/Mn ratio of 0.7 for open-ocean seamount crusts and 1.2 for continental margin seamount crusts. Fe-Mn nodules of potential economic interest from the Clarion-Clipperton Zone have a mean Fe/Mn ratio of 0.3, whereas the mean ratio for nodules from elsewhere in the Pacific is about 0.7. Crusts are enriched in Co, Ni and Pt and nodules in Cu and Ni, and both have significant concentrations of Pb, Zn, Ba, Mo, V and other elements. In contrast, hydrothermal deposits commonly contain only minor trace metal contents, although there are many exceptions, for example, with Ni contents up to 0.66%, Cr to 1.2%, and Zn to 1.4%. Chondrite-normalized REE patterns generally show a positive Ce anomaly and abundant ??REEs for hydrogenetic and mixed hydrogenetic-diagenetic deposits, whereas the Ce anomaly is negative for hydrothermal deposits and ??REE contents are low. However, the Ce anomaly in crusts may vary from strongly positive in East Pacific crusts to slightly negative in West Pacific crusts, which may reflect the redox conditions of seawater. The concentration of elements in hydrogenetic Fe-Mn crusts depends on a wide variety of water column and crust surface characteristics, whereas concentration of elements in hydrothermal oxide deposits depends of the intensity of leaching, rock types leached, and precipitation of sulphides at depth in the hydrothermal system.

Hein, J.R.; Koschinsky, A.; Halbach, P.; Manheim, F. T.; Bau, M.; Kang, J.-K.; Lubick, N.

1997-01-01

127

Thursday, November 8, 2007 -9:15 AM Effects of Environmental Conditions on the Properties of Biogenic Manganese Oxides.  

E-print Network

of Biogenic Manganese Oxides. Mengqiang Zhu, Sanjai Parikh, Matt Ginder-Vogel, and Donald L. Sparks. Plant in the critical zone, have been found to mediate aqueous Mn(II) oxidation to form biogenic manganese oxides (BioMnOx). Microbially mediated BioMnOx are thought to be one of the major sources of manganese oxides in soils. Recent

Sparks, Donald L.

128

Manganese oxide composite electrodes for lithium batteries  

DOEpatents

An activated electrode for a non-aqueous electrochemical cell is disclosed with a precursor of a lithium metal oxide with the formula xLi.sub.2MnO.sub.3.(1-x)LiMn.sub.2-yM.sub.yO.sub.4 for 0

Thackeray, Michael M. (Naperville, IL); Johnson, Christopher S. (Naperville, IL); Li, Naichao (Croton on Hudson, NY)

2007-12-04

129

Manganese oxide composite electrodes for lithium batteries  

DOEpatents

An activated electrode for a non-aqueous electrochemical cell is disclosed with a precursor thereof a lithium metal oxide with the formula xLi.sub.2MnO.sub.3.(1-x)LiMn.sub.2-yM.sub.yO.sub.4 for 0.5

Johnson, Christopher S. (Naperville, IL); Kang, Sun-Ho (Naperville, IL); Thackeray, Michael M. (Naperville, IL)

2009-12-22

130

Thursday, November 8, 2007 -10:50 AM Kinetics of Chromium(III) Oxidation on Manganese Oxides Using Real-Time Molecular Scale Approaches.  

E-print Network

Thursday, November 8, 2007 - 10:50 AM 343-3 Kinetics of Chromium(III) Oxidation on Manganese Oxides, University of Delaware, 152 Townsend Hall, Newark, DE 19717 Manganese oxides are an important soil component

Sparks, Donald L.

131

Sol-gel route to the tunneled manganese oxide cryptomelane  

SciTech Connect

The sol-gel reaction between KMnO{sub 4} and fumaric acid in a 3:1 mole ratio generates a flocculant gel that serves as a precursor to the tunneled manganese oxide, cryptomelane. The elemental composition of sol-gel cryptomelane has been determined to be K{sub 0.12}MnO{sub 2.0-} (H{sub 2}O){sub 0.09}. Further characterization has been performed using powder X-ray diffraction, scanning electron microscopy, and Auger electron spectroscopy. The sol-gel process is heavily dependent on reactant concentration. Solutions that are too concentrated produce the layered manganese oxide birnessite, whereas overly dilute reactions yield mixtures of cryptomelane and Mn{sub 2}O{sub 3}. The preference for cryptomelane over birnessite correlates with low potassium content in the gel. The sol-gel procedure for synthesizing cryptomelane is not easily transferred to the preparation of analogous manganese oxides with different tunnel cations. Reactions that employ permanganates other than KMnO{sub 4} generally yield Mn{sub 2}O{sub 3}, with cryptomelane being a minor product at best. Thermal analyses of cryptomelane gels indicate that calcination proceeds through a series of stages that involve loss of water, loss of residual organics, conversion to cryptomelane, and finally degradation to Mn{sub 3}O{sub 4}. The extraction of potassium ions from sol-gel cryptomelane by various foreign cations is minimal, with the loss of K{sup +} being on the order of 10%. 49 refs., 7 figs., 3 tabs.

Ching, S.; Roark, J.L. [Connecticut College, New London, CT (United States)] [Connecticut College, New London, CT (United States); Duan, N.; Suib, S.L. [Univ. of Connecticut, Storr, CT (United States)] [Univ. of Connecticut, Storr, CT (United States)

1997-03-01

132

Capacity fading of the acid-treated lithium manganese oxides in high-temperature storage  

Microsoft Academic Search

We have studied capacity fadings of acid-treated lithium manganese oxides in high-temperature storage. The amounts of dissolved lithium and manganese ions and consumed acids were determined in the reaction of lithium manganese oxides with acids. Discharge capacities of the acid-treated samples were measured and the small capacity fadings were observed. X-ray diffraction patterns of the acid-treated samples were almost the

Motoharu Saitoh; Shinichiro Yoshida; Hisayuki Yamane; Mitsuru Sano; Miho Fujita; Koichi Kifune; Yoshiki Kubota

2003-01-01

133

Chemical lithium extraction from manganese oxides for lithium rechargeable batteries  

Microsoft Academic Search

Chemical lithium extraction has been carried out on the following manganese oxides: the spinel-type compounds LiMn2O4 and Li(4\\/3)Mn(5\\/3)O4, and the rocksalt-related compound Li2MnO3. Lithium can be partially removed chemically from these compounds without destroying the host framework. Some compounds obtained by this method have been tested as cathodic materials in rechargeable lithium cells. Electrochemical results and X-ray diffraction patterns of

F. Lubin; A. Lecerf; M. Broussely; J. Labat

1991-01-01

134

Lithiated manganese oxide cathodes for rechargeable lithium batteries  

Microsoft Academic Search

Lithiated manganese oxides LixMnyO2 prepared at the low temperature of 400-450°C exhibited significantly different electrochemical properties than the spinel phase, LiMn2O4, formed at 650-850°C. The former was nonstoichiometric and yielded a capacity of ~0.7 LiMn2 unit at ~2.8 V in polymer electrolyte-based Li cells. Its excellent rechargeability was demonstrated by more than 100 charge\\/discharge cycles. Spinel Li2Mn4 was formed by

K. M. Abraham; D. M. Pasquariello; T. H. Hguyen; Z. Jiang; D. Peramunage

1996-01-01

135

Nanostructured lithium nickel manganese oxides for lithium-ion batteries  

Microsoft Academic Search

Nanostructured lithium nickel manganese oxides were investigated as advanced positive electrode materials for lithium-ion batteries designated to power plug-in hybrid electric vehicles and all-electric vehicles. The investigation included material characterization and electrochemical testing. In cell tests, the Li{sub 1.375}Ni{sub 0.25}Mn{sub 0.75}O{sub 2.4375} composition achieved high capacity (210 mAh g¹) at an elevated rate (230 mA g¹), which makes this material

Haixia Deng; Ilias Belharouak; Russel E. Cook; Huiming Wu; Yang-Kook Sun; Khalil Amine

2010-01-01

136

Manganese sulfide formation via concomitant microbial manganese oxide and thiosulfate reduction.  

PubMed

The dissimilatory metal-reducing bacterium, Shewanella oneidensis MR-1 produced ?-MnS (rambergite) nanoparticles during the concurrent reduction of MnO? and thiosulfate coupled to H? oxidation. To investigate effect of direct microbial reduction of MnO? on MnS formation, two MR-1 mutants defective in outer membrane c-type cytochromes (?mtrC/?omcA and ?mtrC/?omcA/?mtrF) were also used and it was determined that direct reduction of MnO? was dominant relative to chemical reduction by biogenic sulfide generated from thiosulfate reduction. Although bicarbonate was excluded from the medium, incubations of strain MR-1 with lactate as the electron donor produced MnCO? (rhodochrosite) as well as MnS in nearly equivalent amounts as estimated by micro X-ray diffraction (micro-XRD) analysis. It was concluded that carbonate released from lactate metabolism promoted MnCO? formation and that Mn(II) mineralogy was strongly affected by carbonate ions even in the presence of abundant sulfide and weakly alkaline conditions expected to favour the precipitation of MnS. Formation of MnS, as determined by a combination of micro-XRD, transmission electron microscopy, energy dispersive X-ray spectroscopy, and selected area electron diffraction analyses was consistent with equilibrium speciation modelling predictions. Biogenic manganese sulfide may be a manganese sink in the Mn biogeochemical cycle in select environments such as deep anoxic marine basins within the Baltic Sea. PMID:21951417

Lee, Ji-Hoon; Kennedy, David W; Dohnalkova, Alice; Moore, Dean A; Nachimuthu, Ponnusamy; Reed, Samantha B; Fredrickson, James K

2011-12-01

137

Water oxidation by manganese oxides formed from tetranuclear precursor complexes: the influence of phosphate on structure and activity.  

PubMed

Two types of manganese oxides have been prepared by hydrolysis of tetranuclear Mn(iii) complexes in the presence or absence of phosphate ions. The oxides have been characterized structurally using X-ray absorption spectroscopy and functionally by O2 evolution measurements. The structures of the oxides prepared in the absence of phosphate are dominated by di-?-oxo bridged manganese ions that form layers with limited long-range order, consisting of edge-sharing MnO6 octahedra. The average manganese oxidation state is +3.5. The structure of these oxides is closely related to other manganese oxides reported as water oxidation catalysts. They show high oxygen evolution activity in a light-driven system containing [Ru(bpy)3](2+) and S2O8(2-) at pH 7. In contrast, the oxides formed by hydrolysis in the presence of phosphate ions contain almost no di-?-oxo bridged manganese ions. Instead the phosphate groups are acting as bridges between the manganese ions. The average oxidation state of manganese ions is +3. This type of oxide has much lower water oxidation activity in the light-driven system. Correlations between different structural motifs and the function as a water oxidation catalyst are discussed and the lower activity in the phosphate containing oxide is linked to the absence of protonable di-?-oxo bridges. PMID:24647521

Shevchenko, Denys; Anderlund, Magnus F; Styring, Stenbjörn; Dau, Holger; Zaharieva, Ivelina; Thapper, Anders

2014-06-28

138

Hydrocarbon oxidation with hydrogen peroxide and pentafluoroiodosylbenzene catalyzed by unusually distorted macrocycle manganese complexes  

Microsoft Academic Search

The highly distorted aza macrocycle manganese complexes as the oxidation catalyst were synthesized newly to achieve more green hydrocarbon oxidation; macrocycle 1 ringed by two bipyridine moieties and macrocycle 3 with two bipyridine and two amide bonds in the ring were prepared, and the catalytic abilities of these macrocycle manganese complexes 2 and 4 were examined. A remarkable result is

Nirei Nakayama; Shinji Tsuchiya; Shojiro Ogawa

2007-01-01

139

Mechanisms and chemistry of dye adsorption on manganese oxides-modified diatomite  

Microsoft Academic Search

The investigations into structural changes which occur during adsorbent modification and the adsorption mechanisms are essential for an effective design of adsorption systems. Manganese oxides were impregnated onto diatomite to form the type known as ?-birnessite. Initial investigations established the effectiveness of manganese oxides-modified diatomite (MOMD) to remove basic and reactive dyes from aqueous solution. The adsorption capacity of MOMD

Mohammad A. Al-Ghouti; Yehya S. Al-Degs; Majeda A. M. Khraisheh; Mohammad N. Ahmad; Stephen J. Allen

2009-01-01

140

Electrochromic properties of electrochemically fabricated nanostructure nickel oxide and manganese oxide films  

Microsoft Academic Search

Thin films of mesoporous lamellar nickel oxides and nanotube manganese oxides were electrochemically fabricated on indium tin oxide (ITO) glass using sodium n-dodecyl sulfate (SDS) as a template agent under different controlled potentials in 10mM Ni(NO3)2 and 100mM MnSO4 solutions. Electrochromic characterization together with the morphological observation by transmission electron microscopy (TEM), structure analysis by X-ray diffraction (XRD) and electron

Takako Yoshino; Kanae Kobayashi; Shingo Araki; Kazuki Nakamura; Norihisa Kobayashi

141

Catalytic asymmetric oxidations using optically active (salen)manganese(III) complexes as catalysts  

Microsoft Academic Search

This review deals with enantioselective one oxygen atom transfer reactions (epoxidation, oxidation of enolates, and oxidation of sulphide to sulphoxides) catlaysed by optically active (salen)manganese(III)complexes. Asymmetric aziridination is also discussed briefly.

Tsutomu Katsuki

1995-01-01

142

Supporting information for Kinetics of Chromium(III) Oxidation by Manganese(IV) Oxides Using Quick Scanning X-Ray Absorption Fine Structure Spectroscopy (Q-XAFS)  

E-print Network

S-1 Supporting information for Kinetics of Chromium(III) Oxidation by Manganese(IV) Oxides Using5-S3) Effect of pH Page S-7: Hydrous Manganese Oxide (HMO) Page S-8: Elemental measurements Page S-8: Literature cited Figure S1: XRD pattern of hydrous manganese oxide. #12;S-2 Figure S2- Chromium pre

Sparks, Donald L.

143

Monday, November 5, 2007 -9:30 AM Real-Time Surface-Chemistry of Arsenite Oxidation by Hydrous Manganese Oxide.  

E-print Network

by Hydrous Manganese Oxide. Matthew Ginder-Vogel and Donald L. Sparks. University of Delaware, 152 Townsend(V)) by manganese(IV) oxide is an important reaction impacting the natural cycling of As. The aresenite species(III) on the surface of manganese oxides has been well characterized; however, the surface chemistry of the oxidation

Sparks, Donald L.

144

Cobalt Alters the Growth of a Manganese Oxide Film Young-Shin Jun and Scot T. Martin*  

E-print Network

Cobalt Alters the Growth of a Manganese Oxide Film Young-Shin Jun and Scot T. Martin* Di in natural waters is partially regulated by interactions with manganese oxide films. In the current work, the effects of aqueous cobalt(II) on manganese oxide film growth are studied by atomic force microscopy

145

UNIVERSITY OF CALIFORNIA, SAN DIEGO Microbial Manganese(II) Oxidation: Biogeochemistry of a Deep-Sea Hydrothermal  

E-print Network

UNIVERSITY OF CALIFORNIA, SAN DIEGO Microbial Manganese(II) Oxidation: Biogeochemistry of a Deep of the Dissertation 9 References 10 II. Manganese(II)-Oxidizing Bacillus Spores in Guaymas Basin Hydrothermal References 38 III. Enzymatic Microbial Manganese(II) Oxidation in the Guaymas Basin Hydrothermal Plume 42

Dick, Christopher

146

Chromite oxidation by manganese oxides in subseafloor basalts and the presence of putative fossilized microorganisms  

PubMed Central

Chromite is a mineral with low solubility and is thus resistant to dissolution. The exception is when manganese oxides are available, since they are the only known naturally occurring oxidants for chromite. In the presence of Mn(IV) oxides, Cr(III) will oxidise to Cr(VI), which is more soluble than Cr(III), and thus easier to be removed. Here we report of chromite phenocrysts that are replaced by rhodochrosite (Mn(II) carbonate) in subseafloor basalts from the Koko Seamount, Pacific Ocean, that were drilled and collected during the Ocean Drilling Program (ODP) Leg 197. The mineral succession chromite-rhodochrosite-saponite in the phenocrysts is interpreted as the result of chromite oxidation by manganese oxides. Putative fossilized microorganisms are abundant in the rhodochrosite and we suggest that the oxidation of chromite has been mediated by microbial activity. It has previously been shown in soils and in laboratory experiments that chromium oxidation is indirectly mediated by microbial formation of manganese oxides. Here we suggest a similar process in subseafloor basalts. PMID:21639896

2011-01-01

147

Chromite oxidation by manganese oxides in subseafloor basalts and the presence of putative fossilized microorganisms.  

PubMed

Chromite is a mineral with low solubility and is thus resistant to dissolution. The exception is when manganese oxides are available, since they are the only known naturally occurring oxidants for chromite. In the presence of Mn(IV) oxides, Cr(III) will oxidise to Cr(VI), which is more soluble than Cr(III), and thus easier to be removed. Here we report of chromite phenocrysts that are replaced by rhodochrosite (Mn(II) carbonate) in subseafloor basalts from the Koko Seamount, Pacific Ocean, that were drilled and collected during the Ocean Drilling Program (ODP) Leg 197. The mineral succession chromite-rhodochrosite-saponite in the phenocrysts is interpreted as the result of chromite oxidation by manganese oxides. Putative fossilized microorganisms are abundant in the rhodochrosite and we suggest that the oxidation of chromite has been mediated by microbial activity. It has previously been shown in soils and in laboratory experiments that chromium oxidation is indirectly mediated by microbial formation of manganese oxides. Here we suggest a similar process in subseafloor basalts. PMID:21639896

Ivarsson, Magnus; Broman, Curt; Holm, Nils G

2011-01-01

148

Structural Study of Poorly Crystalline Layered Manganese Oxides Using the Atomic Pair Distribution Function Technique. Tuesday, November 3, 2009: 11:15 AM  

E-print Network

Structural Study of Poorly Crystalline Layered Manganese Oxides Using the Atomic Pair Distribution, such as ferryhydrite. In this study, we used PDF analysis to investigate structures of manganese oxides. Manganese

Sparks, Donald L.

149

Manganese  

MedlinePLUS

... no RDAs for a nutrient, the Adequate Intake (AI) is used as a guide. The AI is the estimated amount of the nutrient that ... assumed to be adequate. The daily Adequate Intake (AI) levels for manganese are: infants birth to 6 ...

150

Manganese sulfide formation via concomitant microbial manganese oxide and thiosulfate reduction  

SciTech Connect

The dissimilatory metal-reducing bacterium, Shewanella oneidensis MR-1 produced {gamma}-MnS (rambergite) nanoparticles during the concurrent reduction of MnO{sub 2} and thiosulfate coupled to H{sub 2} oxidation. To investigate effect of direct microbial reduction of MnO{sub 2} on MnS formation, two MR-1 mutants defective in outer membrane c-type cytochromes ({Delta}mtrC/{Delta}omcA and {Delta}mtrC/{Delta}omcA/{Delta}mtrF) were also used and it was determined that direct reduction of MnO{sub 2} was dominant relative to chemical reduction by biogenic sulfide generated from thiosulfate reduction. Although bicarbonate was excluded from the medium, incubations of strain MR-1 with lactate as the electron donor produced MnCO{sub 3} (rhodochrosite) as well as MnS in nearly equivalent amounts as estimated by micro X-ray diffraction (micro-XRD) analysis. It was concluded that carbonate released from lactate metabolism promoted MnCO{sub 3} formation and that Mn(II) mineralogy was strongly affected by carbonate ions even in the presence of abundant sulfide and weakly alkaline conditions expected to favor the precipitation of MnS. Formation of MnS, as determined by a combination of micro-XRD, transmission electron microscopy, energy dispersive X-ray spectroscopy, and selected area electron diffraction analyses was consistent with equilibrium speciation modeling predictions. Biogenic manganese sulfide may be a manganese sink in the Mn biogeochemical cycle in select environments such as deep anoxic marine basins within the Baltic Sea.

Lee, Ji-Hoon; Kennedy, David W.; Dohnalkova, Alice; Moore, Dean A.; Nachimuthu, Ponnusamy; Reed, Samantha B.; Fredrickson, Jim K.

2011-12-13

151

Palladium doped manganese dioxide catalysts for low temperature carbon monoxide oxidation  

Microsoft Academic Search

Nano-sized palladium doped manganese dioxide catalysts with varying compositions were prepared by the co-precipitation method. Palladium doped manganese dioxide catalysts show markedly enhanced CO oxidation activity, and CO conversion even at 35°C. Strong interaction occurs between palladium and manganese dioxide which results in high catalytic activity and total CO conversion occurs at a lower temperature. Activity test carried out at

A. V. Salker; R. K. Kunkalekar

2009-01-01

152

Adhesion enhancement of indium tin oxide (ITO) coated quartz optical fibers  

NASA Astrophysics Data System (ADS)

Transparent conductive indium tin oxide (ITO) film was prepared on optical fiber through a multi-step sol-gel process. The influence of annealing temperature on the adhesion of ITO coated optical fibers was studied. Different surface treatments were applied to improve the adhesion between ITO film and quartz optical fiber. Field emission scanning electron microscopy (FE-SEM), X-ray diffraction analysis (XRD), UV-vis spectrophotometer and Avometer were used to characterize the morphology, crystal structure and photo-electric properties. A thermal shock test was used to evaluate the adhesion. The result shows that the adhesion between ITO film and quartz optical fiber can be strongly influenced by the annealing process, and optimal adhesion can be acquired when annealing temperature is 500 °C. Surface treatments of ultrasonic cleaning and the application of surface-active agent have effectively enhanced the adhesion and photo-electric properties of indium tin oxide film coated quartz optical fiber.

Wang, Yihua; Liu, Jing; Wu, Xu; Yang, Bin

2014-07-01

153

Water exchange in manganese-based water-oxidizing catalysts in photosynthetic systems: from the water-oxidizing complex in photosystem II to nano-sized manganese oxides.  

PubMed

The water-oxidizing complex (WOC), also known as the oxygen-evolving complex (OEC), of photosystem II in oxygenic photosynthetic organisms efficiently catalyzes water oxidation. It is, therefore, responsible for the presence of oxygen in the Earth's atmosphere. The WOC is a manganese-calcium (Mn?CaO?(H?O)?) cluster housed in a protein complex. In this review, we focus on water exchange chemistry of metal hydrates and discuss the mechanisms and factors affecting this chemical process. Further, water exchange rates for both the biological cofactor and synthetic manganese water splitting are discussed. The importance of fully unveiling the water exchange mechanism to understand the chemistry of water oxidation is also emphasized here. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy. PMID:24685431

Najafpour, Mohammad Mahdi; Isaloo, Mohsen Abbasi; Eaton-Rye, Julian J; Tomo, Tatsuya; Nishihara, Hiroshi; Satoh, Kimiyuki; Carpentier, Robert; Shen, Jian-Ren; Allakhverdiev, Suleyman I

2014-09-01

154

Volume changes and the technical properties of composites in the spinel-manganese oxide system  

Microsoft Academic Search

Conclusions The volume changes during the oxidation-reduction process of the manganese oxide in the Mg(Al, Cr)2O4-Mn2O3-Mn3O4 system have been studied. The volume changes of the solid phase in this case are not great and are less than those observed in the formation and decomposition of the solid solutions of spinels and hausmannite. In composites of spinels and manganese oxide, the

Yu. D. Kuznetsov; S. A. Suvorov

1982-01-01

155

Nanocrystalline structure and catalytic activity of TiO2 supported manganese oxide catalysts  

Microsoft Academic Search

A series of TiO2 supported manganese oxide catalysts were prepared by wet-impregnation method. Raman spectroscopy was used to characterize the structure and chemical environment of these catalysts as well as manganese oxides. Spectra of different Mn-oxides are presented. It was found that there is strong correlation of the position and the width of E2g mode of anatase at 146 cm-1

Sergey Mamedov; Padmanabha Reddy Ettireddy; Neeraja Ettireddy; Punit Boolchand; Panagiotis G. Smirniotis

2008-01-01

156

Prismatic cell lithium-ion battery using lithium manganese oxide  

SciTech Connect

Lithium-ion (Li-ion) batteries have demonstrated the ability to fulfill the energy storage needs of many new technologies. The most significant drawbacks of currently available technologies, such as LiCoO{sub 2} based Li-ion cells, is their high cost and significant environmental hazards. Li-ion cells which use a lithium manganese oxide (LiMn{sub 2}O{sub 4}) spinel based cathode material should be much less costly and safer than LiCoO{sub 2} based cells. Performance data from prismatic design cells which use a LiMn{sub 2}O{sub 4} based cathode material is presented and shown to meet many military performance criteria. The most significant drawback of this technology, at the present time, is the short cycle life.

Ehrlich, G.M.; Hellen, R.M.; Reddy, T.B. [Yardney Technical Products, Inc., Pawcatuck, CT (United States)

1997-12-01

157

Manganese(III) binding to a pyoverdine siderophore produced by a manganese(II)-oxidizing bacterium  

NASA Astrophysics Data System (ADS)

The possible roles of siderophores (high affinity chelators of iron(III)) in the biogeochemistry of manganese remain unknown. Here we investigate the interaction of Mn(III) with a pyoverdine-type siderophore (PVD MnB1) produced by the model Mn(II)-oxidizing bacterium Pseudomonas putida strain MnB1. PVD MnB1 confirmed typical pyoverdine behavior with respect to: (a) its absorption spectrum at 350-600 nm, both in the absence and presence of Fe(III), (b) the quenching of its fluorescence by Fe(III), (c) the formation of a 1:1 complex with Fe(III), and (d) the thermodynamic stability constant of its Fe(III) complex. The Mn(III) complex of PVD MnB1 had a 1:1 Mn:pvd molar ratio, showed fluorescence quenching, and exhibited a light absorption spectrum (A max = 408-410 nm) different from that of either PVD MnB1-Fe(III) or uncomplexed PVD MnB1. Mn(III) competed strongly with Fe(III) for binding by PVD MnB1 in culture filtrates (pH 8, 4°C). Equilibration with citrate, a metal-binding ligand, did not detectably release Mn from its PVD MnB1 complex at a citrate/PVD MnB1 molar ratio of 830 (pH 8, 4°C), whereas pyrophosphate under the same conditions removed 55% of the Mn from its PVD MnB1 complex. Most of the PVD MnB1-complexed Mn was released by reaction with ascorbate, a reducing agent, or with EDTA, a ligand that is also oxidized by Mn(III). Data on the competition for binding to PVD MnB1 by Fe(III) vs. Mn(III) were used to determine a thermodynamic stability constant (nominally at 4°C) for the neutral species MnHPVD MnB1 (log K = 47.5 ± 0.5, infinite dilution reference state). This value was larger than that determined for FeHPVD MnB1 (log K = 44.6 ± 0.5). This result has important implications for the metabolism, solubility, speciation, and redox cycling of manganese, as well as for the biologic uptake of iron.

Parker, Dorothy L.; Sposito, Garrison; Tebo, Bradley M.

2004-12-01

158

Immobilization of manganese tetraphenylporphyrin on boehmite and its catalysis for aerobic oxidation of cyclohexane  

Microsoft Academic Search

The search for a reusable material as an efficient and economic catalyst for hydrocarbon oxidation is an important field of research. In this study, we investigated the highly effective combination of support and metalloporphyrin provided by manganese tetraphenylporphyrin adsorbed onto a precursor of freshly precipitated aluminium hydroxide, followed by conversion to a manganese porphyrin\\/boehmite compound. This was characterized using FT-IR,

Guan Huang; Shang-Yue Liu; Yong-An Guo; Ai-Ping Wang; Jin Luo; Chun-Cai Cai

2009-01-01

159

A facile manganese dioxide mediated oxidation of primary benzylamines to benzamides.  

PubMed

A high yielding manganese dioxide mediated oxidation of benzylamines to the corresponding amides has been developed under mild reaction conditions. The mechanism for the conversion has been explored by (1)H NMR spectroscopy and the role of both manganese dioxide and molecular sieves in the reaction elucidated. PMID:25098763

Poeschl, A; Mountford, D M

2014-09-28

160

Solid solution of nickel oxide and manganese oxide as negative active material for lithium secondary cells  

NASA Astrophysics Data System (ADS)

The solid solution of nickel oxide and manganese oxide has been synthesized successfully by heating Ni 1- aMn aOOH at a temperature ranging from 350 to 1000 °C in oxygen atmosphere, and investigated as a high-capacity negative active material for lithium secondary cells. The discharge capacity of nickel and manganese oxide solid solution was decreased with increasing heat-treatment temperature. The average discharge potential shifts toward negative as increasing Mn content in the solid solution. Meanwhile, large amount of Mn in the oxide solid solution caused a poor cycleability. The Ni 0.75Mn 0.25O 1.36 obtained by heating its raw material at 600 °C delivered a large discharge capacity over 700 mAh g -1 with a relatively low average discharge potential of 1.69 versus Li/Li +. In addition, the Ni 0.75Mn 0.25O 1.36 gave the best capacity retention of 91% with representative charge-discharge curves even after 22 cycles. According to the results of XRD and high-resolution X-ray fluorescence spectrometer (HRXRF) measurements for the oxide solid solution before and after the first charge, it was clear that an amorphous-like or nano-sized phase was formed during the first electrochemical reduction; all of the nickel and a part of manganese were reduced to metallic state after charge to 0.2 V versus Li/Li +.

Liu, Xingjiang; Yasuda, Hideo; Yamachi, Masanori

161

Prophylactic use of polyvinylpyridine-N-oxide (PVNO) in baboons exposed to quartz dust  

SciTech Connect

Twelve baboons were exposed to a quartz dust cloud. Four of these were also given polyvinylpyridine-N-oxide (PVNO) by aerosol and four received PVNO by aerosol and injection. A prophylactic effect was demonstrated during the course of treatment, but when treatment stopped the silicosis progressed to the same degree of severity as in the untreated animals.

Goldstein, B.; Rendall, R.E.G.

1987-04-01

162

Synthesis and characterization of cobalt-manganese oxides  

NASA Astrophysics Data System (ADS)

Cobalt doped/un-doped manganese oxides materials were synthesized at various doping rates by soft chemical reactions, oxidation-reduction method, which allows generating a metal-mixed oxide. The synthesized materials were characterized using several techniques including chemical analysis, X-rays diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and vibrating sample magnetometer (VSM). The chemical analysis confirmed the presence of cobalt in the samples. XRD patterns reveal mainly a spinel-like structure and SEM micrographs exhibited morphology with fine aggregate of particles. TGA profiles showed weight loss due to loss of water in a first step, followed by a loss of oxygen from the lattice associated with partial reduction of Mn4+ to Mn3+. VSM was used to measure the magnetization as a function of the applied magnetic field at temperatures T=50 and 300 K. Different magnetic behaviors were observed when cobalt percentage changed in the samples. These behaviors are considered to be related to the size of the particles and composition of the materials. Higher coercive field and lesser magnetization were observed for the sample with higher cobalt content.

Valencia, J.; Arias, N. P.; Giraldo, O.; Rosales-Rivera, A.

2012-08-01

163

Photochemical water oxidation by crystalline polymorphs of manganese oxides: structural requirements for catalysis.  

PubMed

Manganese oxides occur naturally as minerals in at least 30 different crystal structures, providing a rigorous test system to explore the significance of atomic positions on the catalytic efficiency of water oxidation. In this study, we chose to systematically compare eight synthetic oxide structures containing Mn(III) and Mn(IV) only, with particular emphasis on the five known structural polymorphs of MnO2. We have adapted literature synthesis methods to obtain pure polymorphs and validated their homogeneity and crystallinity by powder X-ray diffraction and both transmission and scanning electron microscopies. Measurement of water oxidation rate by oxygen evolution in aqueous solution was conducted with dispersed nanoparticulate manganese oxides and a standard ruthenium dye photo-oxidant system. No Ru was absorbed on the catalyst surface as observed by XPS and EDX. The post reaction atomic structure was completely preserved with no amorphization, as observed by HRTEM. Catalytic activities, normalized to surface area (BET), decrease in the series Mn2O3 > Mn3O4 ? ?-MnO2, where the latter is derived from spinel LiMn2O4 following partial Li(+) removal. No catalytic activity is observed from LiMn2O4 and four of the MnO2 polymorphs, in contrast to some literature reports with polydispersed manganese oxides and electro-deposited films. Catalytic activity within the eight examined Mn oxides was found exclusively for (distorted) cubic phases, Mn2O3 (bixbyite), Mn3O4 (hausmannite), and ?-MnO2 (spinel), all containing Mn(III) possessing longer Mn-O bonds between edge-sharing MnO6 octahedra. Electronically degenerate Mn(III) has antibonding electronic configuration e(g)(1) which imparts lattice distortions due to the Jahn-Teller effect that are hypothesized to contribute to structural flexibility important for catalytic turnover in water oxidation at the surface. PMID:23391134

Robinson, David M; Go, Yong Bok; Mui, Michelle; Gardner, Graeme; Zhang, Zhijuan; Mastrogiovanni, Daniel; Garfunkel, Eric; Li, Jing; Greenblatt, Martha; Dismukes, G Charles

2013-03-01

164

Alumina-supported manganese oxide catalysts. I. Characterization: Effect of precursor and loading  

SciTech Connect

Alumina-supported manganese oxide catalysts were prepared by two different routes, from Mn acetate and from Mn nitrate, and characterized by temperature-programmed reduction (TPR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and infrared spectroscopy. The characterization studies clearly showed that the two different preparations results in significantly different supported manganese oxide phases. The nitrate precursor resulted primarily in manganese oxide [Mn(III) and Mn(IV)] microcrystals 2-4 nm in size deposited mainly at the outer region of the alumina particles, while the acetate precursor resulted mainly in a highly dispersed surface manganese oxide phase [Mn(III)], homogeneously distributed throughout the alumina particles. These different states of the manganese oxide are reflected in the reduction properties of the alumina-supported manganese oxide phases (peak positions, sharpness, and extent of reduction). The origin of these differences is related, on the one hand, to the presence of the nitrate, which leads to agglomeration and oxidation of the Mn, and on the other hand, to the ion-exchange mechanism of Mn with surface hydroxyl groups in the acetate preparation route. 46 refs., 9 figs., 2 tabs.

Kapteijn, F.; Langeveld, A.D. van; Moulijn, J.A. [Delft Univ. of Technology (Netherlands)] [Delft Univ. of Technology (Netherlands); Andreieni, A.; Vuurman, M.A. [Univ. of Amsterdam (Netherlands)] [Univ. of Amsterdam (Netherlands); Turek, A.M.; Jehng, J.M.; Wachs, I.E. [Lehigh Univ., Bethlehem, PA (United States)] [Lehigh Univ., Bethlehem, PA (United States)

1994-11-01

165

Nonvolatile transparent manganese oxide thin film resistance random access memory devices  

NASA Astrophysics Data System (ADS)

In this study, the electrical conduction and bipolar switching properties in transparent manganese oxide thin films were investigated and discussed. The as-deposited manganese oxide thin films were prepared by the rf magnetron sputtering method with the rf power of 130 W, chamber pressure of 10 mTorr, substrate temperature of 550 °C, and different oxygen concentrations. To discuss the resistive switching properties of the manganese oxide thin films, the conventional thermal annealing treatment of the manganese oxide thin film resistive random access memory (RRAM) devices were investigated. Finally, the current-voltage characteristics were determined by the ohmic contact and the Poole-Frankel emission conduction method in low/high-voltage regions, respectively.

Chen, Kai-Huang; Huang, Jen-Wei; Cheng, Chien-Min; Lin, Jian-Yang; Wu, Tzung-Shiun

2014-08-01

166

Commercialization of cryptomelane-type manganese oxide (OMS-2) nanowire paper oil sorbent  

E-print Network

Cryptomelane-type Manganese oxide (OMS-2, a group of Octahedral Molecular Sieves) nanowire paper exhibits interesting properties: reversible wettability, oleophilic while being hydrophobic, and high thermal stability. These ...

Soo, Haw Yun

2007-01-01

167

[Hygienic and toxicological safety assessment of nano- and micro-dispersed manganese oxide (III, IV)].  

PubMed

The findings of the experimental study performed within the preliminary hygienic and toxicological assessment of nanodispersed manganese oxide (III, IV), which was endogastrics administered to white nonlinear mice once, showed that, under acute oral exposure to manganese oxide, nanodispersed particles were 2,6-fold more toxic and cumulative (class 3, according to the oral LD50 values) than dispersed solution with micro-sized particles (0.4-592 microm, class 4). Endogactric exposure to nanodispersed solution of manganese oxide (III, IV) in organisme produced such negative health effects as vasodilation and plethora, pathological inclusions and increased cell aggregation, which increased and became more prevalent with higher doses. The prediction of chronic toxicity parameters demonstrated that threshold and NOAEL doses for nanodispersed solution were 1.6 and 0.26 mg/kg, respectively, which are 2.3 times lower than for finely divided solution of manganese oxide (III, IV). PMID:23461167

Za?tseva, N V; Zemlianova, M A; Zvezdin, V N; Saenko, E V; Tarantin, A V; Makhmudov, R R; Lebedinskaia, O V; Melekhin, S V; Akaf'eva, T I

2012-01-01

168

Sodium perxenate permits rapid oxidation of manganese for easy spectrophotometric determination  

NASA Technical Reports Server (NTRS)

Sodium perxenate oxidizes manganese to permanganate almost instantaneously in dilute acid solution and without a catalyst. A solution is prepared by dissolving 200 mg of sodium perxenate in distilled water and diluting to 100 ml.

Bane, R. W.

1967-01-01

169

Rapidly reversible redox transformation in nanophase manganese oxides at room temperature triggered by changes in hydration  

PubMed Central

Chemisorption of water onto anhydrous nanophase manganese oxide surfaces promotes rapidly reversible redox phase changes as confirmed by calorimetry, X-ray diffraction, and titration for manganese average oxidation state. Surface reduction of bixbyite (Mn2O3) to hausmannite (Mn3O4) occurs in nanoparticles under conditions where no such reactions are seen or expected on grounds of bulk thermodynamics in coarse-grained materials. Additionally, transformation does not occur on nanosurfaces passivated by at least 2% coverage of what is likely an amorphous manganese oxide layer. The transformation is due to thermodynamic control arising from differences in surface energies of the two phases (Mn2O3 and Mn3O4) under wet and dry conditions. Such reversible and rapid transformation near room temperature may affect the behavior of manganese oxides in technological applications and in geologic and environmental settings. PMID:24733903

Birkner, Nancy; Navrotsky, Alexandra

2014-01-01

170

Manganese peroxidase-catalyzed oxidative degradation of vanillylacetone.  

PubMed

When 4-(4-hydroxy-3-methoxy-phenyl)-2-butanone (vanillylacetone) was tested for manganese peroxidase (MnP)-catalyzed oxidation, it was found to be degraded with the cleavage of an aromatic ring. Among numerous products of vanillylacetone oxidation, four major ones were purified by thin-layer chromatography and identified using mass spectroscopy (MS) and nuclear magnetic resonance (NMR) analysis. Three of them maintained the aromatic ring structure and were identified as 4-[6,2'-dihydroxy-5,3'-dimethoxy-5'-(3-oxo-butyl)-biphenyl]-butan-2-one, 4-(4-hydroxy-3-methoxyphenyl)-3-buten-2-one, and 4-[6,2'-dihydroxy-5,3'-dimethoxy-5'-(3-oxo-butyl)-biphenyl]-3-buten-2-one. Even though the fourth product could not be purified to a single compound, data from infrared spectroscopy showed that it did not have a benzene ring. From MS and NMR analysis, 3-(3-oxo-butyl)-hexa-2,4-dienedioic acid-1-methyl ester was tentatively suggested as the dominant species. The reaction mechanism was suggested on the basis of the structural information of these products. To our knowledge, this paper is the first report on aromatic ring cleavage of the phenolic compound by MnP. PMID:18472135

Hwang, Sangpill; Lee, Chang-Ha; Ahn, Ik-Sung; Park, Kwangyong

2008-06-01

171

Investigations of lithium manganese oxide materials for lithium-ion batteries  

Microsoft Academic Search

As candidates for cathode materials in lithium-ion batteries, lithium manganese oxides are attractive and competitive. In this work, the feasibility of using a novel manganese oxide with a large-tunnel structure (i.e. todorokite, tunnel size: 3 × 3) as cathode material in lithiumion batteries has been explored. It is found that the initial capacity of todorokite material with Mg2+ in the

Y. Yang; D. Shu; H. Yu; X. Xia; Z. G. Lin

1997-01-01

172

Carbon-supported manganese oxide nanocatalysts for rechargeable lithium–air batteries  

Microsoft Academic Search

Manganese oxide based catalysts were synthesised in the form of nano-particles using a redox reaction of MnSO4 and KMnO4, housed into the pores of a carbon matrix and followed by a thermal treatment. Particle sizes of the manganese oxide nanocatalysts were around 50nm, based on the tunnelling electron microscope measurement. They were uniformly distributed in the carbon matrix, which contributed

H. Cheng; K. Scott

2010-01-01

173

Hydrogen peroxide decomposition on manganese oxide (pyrolusite): Kinetics, intermediates, and mechanism  

Microsoft Academic Search

The objective of this study is the kinetic interpretation of hydrogen peroxide decomposition on manganese oxide (pyrolusite) and the explanation of the reaction mechanism including the hydroperoxide\\/superoxide anion. The decomposition of hydrogen peroxide on manganese oxide at pH 7 was represented by a pseudo first-order model. The maximum value of the observed first-order rates constants (kobs) was 0.741min?1 at 11.8

Si-Hyun Do; Bill Batchelor; Hong-Kyun Lee; Sung-Ho Kong

2009-01-01

174

Selective epoxidation of alkenes with hydrogen peroxide over efficient and recyclable manganese oxides  

Microsoft Academic Search

A series of manganese oxides (MnO, Mn3O4, Mn2O3 and MnO2) were prepared and firstly applied as heterogeneous catalysts for the liquid phase epoxidation of alkenes with 30% H2O2 in bicarbonate solution. Under our experimental conditions, MnO exhibited superior activity for the conversion of styrene to achieve ca. 100% with 92.4% selectivity of epoxide, compared to the other three manganese oxides

Ben Qi; Lan-Lan Lou; Kai Yu; Wenyue Bian; Shuangxi Liu

2011-01-01

175

A new silica-supported manganese chlorin as a biomimetic oxidation catalyst  

Microsoft Academic Search

A new manganese chlorin has been successfully immobilized on a silica matrix by a nucleophilic substitution reaction. The potential application of this new material as a biomimetic oxidation catalyst was tested, using cis-cyclooctene as substrate. Different reaction conditions were studied, including hydrogen peroxide and t-butyl hydroperoxide as oxidants. The new silica-supported manganese chlorin exhibits high catalytic efficiency and a good

Sónia M. G. Pires; Rodrigo De Paula; Mário M. Q. Simões; M. Graça P. M. S. Neves; Isabel C. M. S. Santos; Augusto C. Tomé; José A. S. Cavaleiro

2009-01-01

176

Hawaiian submarine manganese-iron oxide crusts - A dating tool?  

USGS Publications Warehouse

Black manganese-iron oxide crusts form on most exposed rock on the ocean floor. Such crusts are well developed on the steep lava slopes of the Hawaiian Ridge and have been sampled during dredging and submersible dives. The crusts also occur on fragments detached from bedrock by mass wasting, on submerged coral reefs, and on poorly lithified sedimentary rocks. The thickness of the crusts was measured on samples collected since 1965 on the Hawaiian Ridge from 140 dive or dredge localities. Fifty-nine (42%) of the sites were collected in 2001 by remotely operated vehicles (ROVs). The thinner crusts on many samples apparently result from post-depositional breakage, landsliding, and intermittent burial of outcrops by sediment. The maximum crust thickness was selected from each dredge or dive site to best represent crusts on the original rock surface at that site. The measurements show an irregular progressive thickening of the crusts toward the northwest-i.e., progressive thickening toward the older volcanic features with increasing distance from the Hawaiian hotspot. Comparison of the maximum crust thickness with radiometric ages of related subaerial features supports previous studies that indicate a crust-growth rate of about 2.5 mm/m.y. The thickness information not only allows a comparison of the relative exposure ages of two or more features offshore from different volcanoes, but also provides specific age estimates of volcanic and landslide deposits. The data indicate that some of the landslide blocks within the south Kona landslide are the oldest exposed rock on Mauna Loa, Kilauea, or Loihi volcanoes. Crusts on the floors of submarine canyons off Kohala and East Molokai volcanoes indicate that these canyons are no longer serving as channelways for downslope, sediment-laden currents. Mahukona volcano was approximately synchronous with Hilo Ridge, both being younger than Hana Ridge. The Nuuanu landslide is considerably older than the Wailau landslide. The Waianae landslide southwest of Oahu has yielded samples with the greatest manganese-iron oxide crusts (9.5 mm thick) and therefore apparently represents the oldest submarine material yet found in the study area. The submarine volcanic field 100 km southwest of Oahu is apparently younger than the Waianae landslide. ?? 2004 Geological Society of America.

Moore, J.G.; Clague, D.A.

2004-01-01

177

Oxidative damage and neurodegeneration in manganese-induced neurotoxicity  

SciTech Connect

Exposure to excessive manganese (Mn) levels results in neurotoxicity to the extrapyramidal system and the development of Parkinson's disease (PD)-like movement disorder, referred to as manganism. Although the mechanisms by which Mn induces neuronal damage are not well defined, its neurotoxicity appears to be regulated by a number of factors, including oxidative injury, mitochondrial dysfunction and neuroinflammation. To investigate the mechanisms underlying Mn neurotoxicity, we studied the effects of Mn on reactive oxygen species (ROS) formation, changes in high-energy phosphates (HEP), neuroinflammation mediators and associated neuronal dysfunctions both in vitro and in vivo. Primary cortical neuronal cultures showed concentration-dependent alterations in biomarkers of oxidative damage, F{sub 2}-isoprostanes (F{sub 2}-IsoPs) and mitochondrial dysfunction (ATP), as early as 2 h following Mn exposure. Treatment of neurons with 500 {mu}M Mn also resulted in time-dependent increases in the levels of the inflammatory biomarker, prostaglandin E{sub 2} (PGE{sub 2}). In vivo analyses corroborated these findings, establishing that either a single or three (100 mg/kg, s.c.) Mn injections (days 1, 4 and 7) induced significant increases in F{sub 2}-IsoPs and PGE{sub 2} in adult mouse brain 24 h following the last injection. Quantitative morphometric analyses of Golgi-impregnated striatal sections from mice exposed to single or three Mn injections revealed progressive spine degeneration and dendritic damage of medium spiny neurons (MSNs). These findings suggest that oxidative stress, mitochondrial dysfunction and neuroinflammation are underlying mechanisms in Mn-induced neurodegeneration.

Milatovic, Dejan [Vanderbilt University Medical Center, Department of Pediatrics/Pediatric Toxicology, 2215-B Garland Avenue, 11415 MRB IV, Nashville, TN 37232-0414 (United States)], E-mail: dejan.milatovic@vanderbilt.edu; Zaja-Milatovic, Snjezana [Vanderbilt University Medical Center, Department of Pediatrics/Pediatric Toxicology, 2215-B Garland Avenue, 11415 MRB IV, Nashville, TN 37232-0414 (United States); Gupta, Ramesh C. [Murray State University, Breathitt Veterinary Center, Hopkinsville, KY (United States); Yu, Yingchun [Vanderbilt University Medical Center, Department of Pediatrics/Pediatric Toxicology, 2215-B Garland Avenue, 11415 MRB IV, Nashville, TN 37232-0414 (United States); Aschner, Michael [Vanderbilt University Medical Center, Department of Pediatrics/Pediatric Toxicology, 2215-B Garland Avenue, 11415 MRB IV, Nashville, TN 37232-0414 (United States); Pharmacology and the Kennedy Center for Research on Human Development, Nashville, TN (United States)

2009-10-15

178

A functionally stable manganese oxide oxygen evolution catalyst in acid.  

PubMed

First-row metals have been a target for the development of oxygen evolution reaction (OER) catalysts because they comprise noncritical elements. We now report a comprehensive electrochemical characterization of manganese oxide (MnOx) over a wide pH range, and establish MnOx as a functionally stable OER catalyst owing to self-healing, is derived from MnOx redeposition that offsets catalyst dissolution during turnover. To study this process in detail, the oxygen evolution mechanism of MnOx was investigated electrokinetically over a pH range spanning acidic, neutral, and alkaline conditions. In the alkaline pH regime, a ?60 mV/decade Tafel slope and inverse first-order dependence on proton concentration were observed, whereas the OER acidic pH regime exhibited a quasi-infinite Tafel slope and zeroth-order dependence on proton concentration. The results reflect two competing mechanisms: a one-electron one-proton PCET pathway that is dominant under alkaline conditions and a Mn(3+) disproportionation process, which predominates under acidic conditions. Reconciling the rate laws of these two OER pathways with that of MnOx electrodeposition elucidates the self-healing characteristics of these catalyst films. The intersection of the kinetic profile of deposition and that of water oxidation as a function of pH defines the region of kinetic stability for MnOx and importantly establishes that a non-noble metal oxide OER catalyst may be operated in acid by exploiting a self-healing process. PMID:24669981

Huynh, Michael; Bediako, D Kwabena; Nocera, Daniel G

2014-04-23

179

Development and utility of manganese oxides as cathodes in lithiuim batteries.  

SciTech Connect

Manganese oxides have a long history of serving as a cathode in charge storage applications. Electrolytic manganese dioxide (EMD) is widely used in alkaline batteries and MnO{sub 2} originally was part of the Leclanch{acute e} wet cell patented in 1866. Leclanch{acute e} wet cells used a naturally occurring MnO{sub 2} ore with Zn metal as anode and ammonium chloride electrolyte. While there are a vast number of topics to discuss on manganese oxides, in this short paper, two topics researched at Argonne over the last 12 years are highlighted. First, the addition of lithia (Li{sub 2}O) as a stabilizing component in 3 V alpha-MnO{sub 2} is examined. Second, an overview of the evolution of layered-layered composite-structured electrodes derived from the lithium-manganese oxide (Li{sub 2}MnO{sub 3}) layered rock-salt phase is presented.

Johnson, C. S.; Chemical Engineering

2007-01-01

180

Pentacoordinated manganese(III) dihydrosalen complexes as biomimetic oxidation catalysts  

Microsoft Academic Search

A series of seven chiral pentadentate dihydrosalen ligands, carrying an imidazole group as a fifth, axial donor was synthesized in racemic and enantiomerically pure form. All of these ligands afforded mononuclear manganese(III) complexes in good yields. In two cases, the pentacoordination of the manganese ion could be confirmed by X-ray crystallography. The complexes catalyzed the epoxidation of olefins with a

A. Berkessel; M. Frauenkron; T. Schwenkreis; A. Steinmetz; G. Baum; D. Fenske

1996-01-01

181

Effects of FeS on Chromium Oxidation Mediated by Manganese Oxidizers  

SciTech Connect

Reductive immobilization of Cr(VI) has been widely explored as a cost-effective approach for Cr-contaminated site remediation. The long-term stability of the immobilized Cr(III), however, is a concern. Cr(III) is known to be oxidized by Mn oxides chemically and Mn-oxides could be produced through microbially mediated Mn(II) oxidation. This study examined the effect of FeS on Cr(III) oxidation mediated by Pseudomonas putida. The results showed that commercial granular FeS did not affect Cr(III) oxidation in the culture of P. putida with Mn(II), but freshly precipitated FeS slurry inhibited Cr(III) oxidation. A 10 mg/l of FeS did not inhibit the microbial growth, but delayed the production of Mn oxides, thus postponing potential Cr(III) oxidation. In the presence of excessive FeS slurry, both Cr(VI) and Mn oxides were reduced rapidly. The reduced Cr(III) could not be re-oxidized as long as freshly formed FeS was present, even in the presence of the manganese oxidizers.

Wu, Youxian; Deng, Baolin

2004-03-31

182

Lithiated manganese oxide cathodes for rechargeable lithium batteries  

SciTech Connect

Lithiated manganese oxide Li{sub x}Mn{sub y}O{sub z} prepared at the low temperature of 400--450 C exhibited significantly different electrochemical properties than the spinel phase, LiMn{sub 2}O{sub 4}, formed at 650--850 C. The former was non-stoichiometric and yielded a capacity of {approximately} 0.7 Li/Mn{sub 2} unit at {approximately} 2.8 V in polymer electrolyte-based Li cells. Its excellent rechargeability was demonstrated by more than 100 charge/discharge cycles. Spinel LiMn{sub 2}O{sub 4} was formed by heating either a mixture of LiOH and MnO{sub 2} or LiCO{sub 3} and MnCO{sub 3}. The latter reaction yielded micron-sized LiMn{sub 2}O{sub 4}. Its capacity of {approximately} 0.8 Li/LiMn{sub 2}O{sub 4} at {approximately} 4 V was highly reversible. AA-size Li-ion cells with spinel LiMn{sub 2}O{sub 4} exhibited 100 Wh/Kg and 280 Wh/{ell}.

Abraham, K.M.; Pasquariello, D.M.; Nguyen, T.H.; Jiang, Z.; Peramunage, D. [EIC Labs., Inc., Norwood, MA (United States)

1996-11-01

183

Electrochemical quartz crystal microbalance studies of a palladium electrode oxidation in a basic electrolyte solution  

Microsoft Academic Search

Anodic oxidation of Pd in basic solutions (0.1M KOHaq and 0.1M NaOHaq) has been examined via cyclic voltammetry (CV) and an electrochemical quartz crystal microbalance (EQCM). Admittance tests show that Pd(II) layer behaves as a rigid one. The anodic vertex potential influences mass response during formation of the Pd(II) layer. For low anodic vertex potentials, obtained absolute mass per mole

M. Grde?

2009-01-01

184

Morphology of graphite-supported iron-manganese catalyst particles: Formation of hollow spheres during oxidation  

SciTech Connect

Transmission electron microscopy (TEM) and Moessbauer spectroscopy (MES) were used to study the morphology of graphite-supported iron-manganese particles. Following oxidation at 500 K MES showed the iron in the particles to be fully oxidized. TEM showed all the particles to be torroidal in appearance. However, tilting resulting in no change in the apparent dimensions of the particles, yet the apparent distances between particles were sharply reduced. These results suggest the particles are actually spherical. On the basis of these experiments, and similar experiments with reduced particles, a model was developed: Following reduction the particles are spherical and consist of a metallic iron core surrounded by a shell of manganese oxide. During oxidation, iron ions diffuse through the manganese oxide shell to the particle surface. Eventually, this results in the formation of nearly spherical particles with hollow centers, inner shells of iron-manganese spinel, and outer shells of iron oxide. Upon an additional reduction the hollow center remains, but the shells phase segregate into regions of iron metal and manganese oxide.

Chen, A.A.; Vannice, M.A.; Phillips, J. (Pennsylvania State Univ., University Park (USA))

1989-04-01

185

Determination of methylcyclopentadienyl-manganese tricarbonyl by solid phase microextraction-direct thermal desorption-quartz furnace atomic absorption spectrometry  

Microsoft Academic Search

A new procedure that uses a pre-concentration system based on solid phase microextraction (SPME) and detection by quartz furnace-atomic absorption spectrometry after thermal desorption from the microextraction fiber has been proposed for the determination of methylcyclopentadienylmanganese tricarbonyl (MMT) in gasoline and water. Working MMT solutions were prepared in 40 ml amber vials, and sampling was performed by exposing the SPME

Mar??a Sandra Fragueiro; Fausto Alava-Moreno; Isela Lavilla; Carlos Bendicho

2001-01-01

186

Effects of electrochemical-deposition method and microstructure on the capacitive characteristics of nano-sized manganese oxide  

Microsoft Academic Search

The amorphous nano-structured manganese oxide was electrochemically deposited onto a stainless-steel electrode. The structure and surface morphology of the obtained manganese oxide were studied by means of X-ray diffraction analysis and scanning electron microscopy. The capacitive characteristics of the manganese oxide electrodes were investigated by means of cyclic voltammetry and constant current charge–discharge cycling. The morphological and capacitive characteristics of

Takuya Shinomiya; Vinay Gupta; Norio Miura

2006-01-01

187

Preparation and electrochemical performance of composite oxide of alpha manganese dioxide and Li–Mn–O spinel  

Microsoft Academic Search

Nano-sized composite powder which consisted of two manganese-based oxides, alpha manganese dioxide (?-MnO2) and spinel Li–Mn–O, was successfully formed by intergrowth of the spinel phase inside ?-MnO2. This composite oxide was synthesized by precipitation and heat treatment in air; ?-manganese dioxide powder was firstly prepared by oxidative precipitation of Mn(II) with K2S2O8 in an aqueous solution, and then a mixture

Shinichi Komaba; Tomoya Sasaki; Naoaki Kumagai

2005-01-01

188

Abiotic sulfide oxidation via manganese reduction fuels the deep biosphere  

NASA Astrophysics Data System (ADS)

The deep biosphere in marine sediments consists of large populations of metabolically active Bacteria and Archaea [1, 2]. Buried organic carbon is the main energy source for the deep biosphere and is anaerobically oxidized via nitrate-, Mn(IV)-, Fe(III)-, sulfate or carbonate-reduction. Sulfate reduction has been identified as the most important of these processes [3, 4] yet sulfate is typically quantitatively removed from pore waters in the upper few meters of marine sediments. A key question remains: “How is continued metabolic activity maintained in the deep biosphere?”. Buried organic carbon remains as an electron donor but the source of electron acceptors is less clear. Stable isotope compositions of sulfur and oxygen in sulfate are particularly useful in the study of biogeochemical processes and sediment-pore fluid interactions e.g. [5, 6]. Here we use stable sulfur and oxygen isotope compositions to show that the oxidant sulfate is generated by anoxic sulfide oxidation in deeply buried sediments of the Cascadia margin and Blake Ridge and controlled anoxic experiments to constrain the mechanisms involved on this reaction. Pore fluid sulfate in deep Cascadia margin and Blake Ridge sediments contained sulfur with similar isotopic composition to diagenetic sulfide in the sediment and oxygen that was depleted in 18O (in some cases depleted in 18O relative to pore water). Experiments with Mn(IV)-containing oxides confirmed that these can abiotically oxidize iron sulfides and also produce sulfate depleted in 18O relative to water. In another set of anoxic experiments, pyrite was mixed with different Fe(III) minerals. Crucially, experiments with synthesized pure Fe(III) minerals produced no sulfate but identical experiments with natural Fe(III) minerals containing trace Mn did. Sulfate concentrations in solution were stoichiometrically balanced by Mn concentrations, showing trace Mn(IV) in the natural minerals to be the oxidizing agent generating sulfate. Sulfate formed was again depleted in 18O relative to water. Experiments with 18O-labelled water show that all oxygen atoms in the sulfate formed are derived from water molecules, thus the sulfate oxygen isotopic composition represents a true fractionation from water. The depletion of 18O in sulfate relative to water thus acts as a fingerprint for sulfate produced by Mn (IV) reduction. Oxidized manganese stored within the mineral fraction of marine sediments can thus drive abiotic anaerobic sulfide oxidation which, together with microbial sulfate reduction, forms a closed sulfur cycle feeding the deep biosphere in marine sediments. [1] Parkes et al. (2005) Nature 436, 390. [2] Schippers et al. (2005) Nature 433, 861. [3] D’Hondt et al. (2002) Science 295, 2067. [4] D’Hondt et al. (2004) Science 306, 2216. Bottrell et al. (2000) J. Geol. Soc. Lond. 157, 711. [6] Böttcher et al. (2006) Proc. ODP Sci. Res. 201-109, 1.

Bottrell, S.; Böttcher, M. E.; Schippers, A.; Parkes, R.; Raiswell, R.

2009-12-01

189

Gold or silver deposited on layered manganese oxide: a functional model for the water-oxidizing complex in photosystem II.  

PubMed

In this report, gold or silver deposited on layered manganese oxide has been synthesized by a simple method and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrometry, atomic absorption spectroscopy, and energy-dispersive X-ray mapping. The gold deposited on layered manganese oxide showed efficient catalytic activity toward water oxidation in the presence of cerium(IV) ammonium nitrate. The properties associated with this compound suggest it is a functional model for the water-oxidizing complex in photosystem II. PMID:23896796

Najafpour, Mohammad Mahdi; Rahimi, Fahimeh; Sedigh, Davood Jafarian; Carpentier, Robert; Eaton-Rye, Julian J; Shen, Jian-Ren; Allakhverdiev, Suleyman I

2013-11-01

190

Electrochemistry of passive metals modified by manganese oxides deposited by Leptothrix discophora : two-step model verified by ToF-SIMS  

Microsoft Academic Search

We have applied time-of-flight secondary ion mass spectroscopy (ToF-SIMS) to study microbially induced ennoblement of 316L stainless steel and Ti–6Al–4V surfaces exposed to manganese-oxidizing bacteria Leptothrix discophora SP-6. Our observations indicate that manganese biomineralization occurs in two steps: first, the divalent manganese (Mn2+) is oxidized to manganese oxyhydroxide, MnOOH; then the MnOOH is further oxidized to manganese dioxide, MnO2. Both

Xianming Shi; Recep Avci; Zbigniew Lewandowski

2002-01-01

191

Water oxidation catalysed by manganese compounds: from complexes to 'biomimetic rocks'.  

PubMed

One of the most fundamental processes of the natural photosynthetic reaction sequence is the light-driven oxidation of water to molecular oxygen. In vivo, this reaction takes place in the large protein ensemble Photosystem II, where a ?-oxido-Mn(4)Ca- cluster, the oxygen-evolving-complex (OEC), has been identified as the catalytic site for the four-electron/four-proton redox reaction of water oxidation. This Perspective presents recent progress for three strategies which have been followed to prepare functional synthetic analogues of the OEC: (1) the synthesis of dinuclear manganese complexes designed to act as water-oxidation catalysts in homogeneous solution, (2) heterogeneous catalysts in the form of clay hybrids of such Mn(2)-complexes and (3) the preparation of manganese oxide particles of different compositions and morphologies. We discuss the key observations from the studies of such synthetic manganese systems in order to shed light upon the catalytic mechanism of natural water oxidation. Additionally, it is shown how research in this field has recently been motivated more and more by the prospect of finding efficient, robust and affordable catalysts for light-driven water oxidation, a key reaction of artificial photosynthesis. As manganese is an abundant and non-toxic element, manganese compounds are very promising candidates for the extraction of reduction equivalents from water. These electrons could consecutively be fed into the synthesis of "solar fuels" such as hydrogen or methanol. PMID:22068958

Wiechen, Mathias; Berends, Hans-Martin; Kurz, Philipp

2012-01-01

192

Manganese Based Oxidative Technologies For Water/Wastewater Treatment  

E-print Network

and structural properties of ferrites. These laboratory prepared catalysts were thoroughly characterized using XRD, SEM, TEM, HR-TEM, and BET. Their magnetic properties have also been studied. These manganese ferrites offer the potential to enhance hydroxyl...

Desai, Ishan

2013-08-27

193

Electrochemical characteristics of rancieite-type manganese oxide by mechanochemical synthesis  

Microsoft Academic Search

Rancieite-type manganese oxide is synthesized by a mechanochemical method and its electrochemical characteristics as a cathode material for lithium secondary batteries are examined. The discharge capacity increases with milling time up to 45h with a maximum of 274mAhg?1. Further increase in milling time causes a decrease in capacity due to a phase transformation. Lithium insertion into the rancieite-type manganese cathode

Sang-gil Woo; Hansu Kim; Churl Kyung Lee; Hun-Joon Sohn; Tak Kang

2003-01-01

194

Chemistry of a high-oxidation-level manganese porphyrin in aqueous solution  

SciTech Connect

Manganese(III) tetrakis(N-methyl-4-pyridiniumyl)porphyrin (Mn/sup III/P/sup +/) (chloride salt) and other water-soluble manganese(III) porphyrins undergo facile one-electron electrochemical or chemical oxidation in alkaline solution. Best available evidence indicates that the final oxidized species is a manganese(IV) /mu/-oxo dimer, PMn/sup IV/-O-Mn/sup IV/P/sup 2+/. This same species is also produced by the reaction of manganese(II) porphyrin and oxygen. The Mn(IV) /mu/-oxo dimer has limited stability in water returning to 90-94% of the original Mn(III) porphyrin. The rate of this reaction is pH dependent with faster rates at lower pH. Oxygen is not produced during this reduction process. Rather, the reaction involves an unusual disproportionation in which a small percentage of the porphyrin macrocycles supply multiple electrons to rescue the remainder of the oxidized dimer. It was also found that the manganese(IV) dimer reacts rapidly with water-soluble olefins as it also does in aprotic solvent. A mechanism for the disproportionation reaction is discussed with a rate-determining step involving rearrangement of charge within the symmetric dimer to one with both oxidation equivalents on one metalloporphyrin unit, viz., PMn/sup IV/-O-Mn/sup III/P/sup +/ or PMn/sup III/-O-Mn/sup III/P/sup 2+/. This species undergoes nucleophilic attach by water or hydroxide, producing an isoporphyrin or bilirubin type molecule that has many olefinic bonds capable of reaction with remaining Mn(IV) /mu/-oxo dimer. Since coordination by OH/sup /minus// to the manganese center favors the higher manganese(IV) oxidation level, the pH dependence of the disproportionation can be explained by rearrangement within the dimer to a porphyrin-centered oxidation site. 24 references, 3 figures.

Spreer, L.O.; Leone, A.; Maliyackel, A.C.; Otvos, J.W.; Calvin, M.

1988-07-13

195

Porous manganese oxide synthesized through organic-electrolyte templates and their catalytic applications  

SciTech Connect

We report a facile approach to the preparation of porous manganese oxide materials by the organic-electrolyte templates based on strategy. The final products are thoroughly characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectroscopy (ICP-OES), and Brunauer-Emmett-Teller (BET) techniques. The results reveal that porosity (pore size and distribution, surface area) of these manganese oxides has strong relationship with the templates used, which implies a simple way to obtain a series of porous materials. By comparing the catalytic effects of these manganese oxides in oxidation of indene and benzyl alcohol, we find that the pore size and distribution are also crucial to the catalytic properties of these porous materials.

Zhang Wei [CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026 (China); Li Jiangying [Department of Chemistry, University of Science and Technology of China, Hefei 230026 (China); Du Xuemin [CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026 (China); Zhang Zhicheng, E-mail: zczhang@ustc.edu.cn [CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026 (China)

2009-11-15

196

Solution-based synthesis of manganese oxide cathodes for lithium batteries  

SciTech Connect

With an objective to overcome the cyclability problems of manganese oxides, solution-based procedures are pursued to synthesize metastable manganese oxides. Reduction of permanganate with lithium iodide in an acetonitrile medium followed by heating at 250 C in vacuum gives an amorphous lithium sodium manganese oxyiodide that is intimately mixed with crystalline NaIO{sub 3}. On the other hand, oxidation of manganese acetate with lithium or hydrogen peroxide in presence of lithium hydroxide followed by firing at T < 500 C gives the metastable spinel oxides, Li{sub 4}Mn{sub 5}O{sub 12} and Li{sub 2}Mn{sub 4}O{sub 9{minus}{delta}}. The amorphous manganese oxide exhibits excellent cyclability with a capacity >275 mAh/g at 4.3-1.5 V. The presence of NaIO{sub 3} and a unique microstructure are found to play a critical role in the electrochemical properties. Although Li{sub 4}Mn{sub 5}O{sub 12} could be achieved without much oxygen vacancies, Li{sub 2}Mn{sub 4}O{sub 9{minus}{delta}} has significant amount of oxygen vacancies with {delta} > 0.35. Both Li{sub 4}Mn{sub 5}O{sub 12} and Li{sub 2}Mn{sub 4}O{sub 9{minus}{delta}} exhibit capacities around 150 mAh/g with good cyclability in the 3 V region.

Manthiram, A.; Kim, J.; Choi, S.

2000-07-01

197

c-Type cytochromes and manganese oxidation in Pseudomonas putida MnB1  

Microsoft Academic Search

Pseudomonas putida MnB1 is an isolate from an Mn oxide-encrusted pipeline that can oxidize Mn(II) to Mn oxides. The authors used transposon mutagenesis to construct mutants of strain MnB1 that are unable to oxidize manganese, and they characterized some of these mutants. The mutants were divided into three groups: mutants defective in the biogenesis of c-type cytochromes, mutants defective in

RON CASPI; BRADLEY M. TEBO; M. G. Haygood

1998-01-01

198

Determination of uranyl incorporation into biogenic manganese oxides using X-ray absorption spectroscopy and scattering  

USGS Publications Warehouse

Biogenic manganese oxides are common and an important source of reactive mineral surfaces in the environment that may be potentially enhanced in bioremediation cases to improve natural attenuation. Experiments were performed in which the uranyl ion, UO22+ (U(VI)), at various concentrations was present during manganese oxide biogenesis. At all concentrations, there was strong uptake of U onto the oxides. Synchrotron-based extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray diffraction (XRD) studies were carried out to determine the molecular-scale mechanism by which uranyl is incorporated into the oxide and how this incorporation affects the resulting manganese oxide structure and mineralogy. The EXAFS experiments show that at low concentrations (2 mol % U, >4 ??M U(VI) in solution), the presence of U(VI) affects the stability and structure of the Mn oxide to form poorly ordered Mn oxide tunnel structures, similar to todorokite. EXAFS modeling shows that uranyl is present in these oxides predominantly in the tunnels of the Mn oxide structure in a tridentate complex. Observations by XRD corroborate these results. Structural incorporation may lead to more stable U(VI) sequestration that may be suitable for remediation uses. These observations, combined with the very high uptake capacity of the Mn oxides, imply that Mn-oxidizing bacteria may significantly influence dissolved U(VI) concentrations in impacted waters via sorption and incorporation into Mn oxide biominerals. ?? 2006 American Chemical Society.

Webb, S.M.; Fuller, C.C.; Tebo, B.M.; Bargar, J.R.

2006-01-01

199

What are the oxidation states of manganese required to catalyze photosynthetic water oxidation?  

PubMed

Photosynthetic O(2) production from water is catalyzed by a cluster of four manganese ions and a tyrosine residue that comprise the redox-active components of the water-oxidizing complex (WOC) of photosystem II (PSII) in all known oxygenic phototrophs. Knowledge of the oxidation states is indispensable for understanding the fundamental principles of catalysis by PSII and the catalytic mechanism of the WOC. Previous spectroscopic studies and redox titrations predicted the net oxidation state of the S(0) state to be (Mn(III))(3)Mn(IV). We have refined a previously developed photoassembly procedure that directly determines the number of oxidizing equivalents needed to assemble the Mn(4)Ca core of WOC during photoassembly, starting from free Mn(II) and the Mn-depleted apo-WOC complex. This experiment entails counting the number of light flashes required to produce the first O(2) molecules during photoassembly. Unlike spectroscopic methods, this process does not require reference to synthetic model complexes. We find the number of photoassembly intermediates required to reach the lowest oxidation state of the WOC, S(0), to be three, indicating a net oxidation state three equivalents above four Mn(II), formally (Mn(III))(3)Mn(II), whereas the O(2) releasing state, S(4), corresponds formally to (Mn(IV))(3)Mn(III). The results from this study have major implications for proposed mechanisms of photosynthetic water oxidation. PMID:22853909

Kolling, Derrick R J; Cox, Nicholas; Ananyev, Gennady M; Pace, Ron J; Dismukes, G Charles

2012-07-18

200

THE EFFECTS OF IRON(II) ON ARSENIC(III) OXIDATION AND ARSENIC SORPTION/DESORPTION ON MANGANESE OXIDES  

E-print Network

THE EFFECTS OF IRON(II) ON ARSENIC(III) OXIDATION AND ARSENIC SORPTION/DESORPTION ON MANGANESE � 2014 Yun Wu All Rights Reserved #12;THE EFFECTS OF IRON(II) ON ARSENIC(III) OXIDATION AND ARSENIC, Caroline Golt on arsenic speciation and UD Soil Test Lab. I thank all current and previous members

Sparks, Donald L.

201

A very simple method to synthesize nano-sized manganese oxide: an efficient catalyst for water oxidation and epoxidation of olefins.  

PubMed

Nano-sized particles of manganese oxides have been prepared by a very simple and cheap process using a decomposing aqueous solution of manganese nitrate at 100 °C. Scanning electron microscopy, transmission electron microscopy and X-ray diffraction spectrometry have been used to characterize the phase and the morphology of the manganese oxide. The nano-sized manganese oxide shows efficient catalytic activity toward water oxidation and the epoxidation of olefins in the presence of cerium(IV) ammonium nitrate and hydrogen peroxide, respectively. PMID:22858683

Najafpour, Mohammad Mahdi; Rahimi, Fahimeh; Amini, Mojtaba; Nayeri, Sara; Bagherzadeh, Mojtaba

2012-08-28

202

Synthesis of nanostructured manganese oxides from a dipolar binary liquid (water\\/benzene) system and hydrogen storage ability research  

Microsoft Academic Search

A new dipolar binary liquid strategy has been developed to manganese oxide nanostructure’s synthesis, in which different manganese oxide nanostructures have been easily obtained without using any templates or catalysts. It has been found that the reaction temperatures, alkali precipitators’ concentrations and Mn2+ concentrations play a significant role in our dipolar binary liquid technique. This novel approach can be potentially

Hai Men; Peng Gao; Yuzeng Sun; Yujin Chen; Xiaona Wang; Longqiang Wang

2010-01-01

203

New nanocrystalline manganese oxides as cathode materials for lithium batteries : electron microscopy, electrochemical and X-ray absorption studies  

E-print Network

1 New nanocrystalline manganese oxides as cathode materials for lithium batteries : electron: manganese oxide, lithium batteries, nanomaterials Corresponding author: Pierre Strobel, tel. 33 476 887 940, published in "Solid State Ionics 177 (2006) 523" #12;2 2 Introduction Good electrode materials for lithium

Paris-Sud XI, Université de

204

Adsorption behavior of Li + onto nano-lithium ion sieve from hybrid magnesium\\/lithium manganese oxide  

Microsoft Academic Search

Magnesium (II) doped spinel lithium manganese oxide (LMS) was synthesized by soft chemical method and nanosized ion sieve manganese oxide (HMS) was prepared by extracting lithium and magnesium from LMS. The characteristics of HMS were studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, surface areas and determination of pH at the point of zero charge. Experiments were performed

Liyan Tian; Wei Ma; Mei Han

2010-01-01

205

Synthesis and Characterization of a Layered Manganese Oxide: Materials Chemistry for the Inorganic or Instrumental Methods Lab  

ERIC Educational Resources Information Center

A three-week laboratory project involving synthesis and characterization of a layered manganese oxide provides an excellent vehicle for teaching important concepts of inorganic chemistry and instrumental methods related to non-molecular systems. Na-birnessite is an easily prepared manganese oxide with a 7 A interlayer spacing and Na[superscript +]…

Ching, Stanton; Neupane, Ram P.; Gray, Timothy P.

2006-01-01

206

Magnetic phase transition and physical properties of spinel-type nickel manganese oxide  

Microsoft Academic Search

A photo-induced change of the magnetism causes a great interest in the study of the perovskite-type manganese oxides, where the charge-ordered (CO) state with the ordered Mn3+ and Mn4+ alternation is broken by light illumination. We synthesized the powder samples of (Ni1?xMnx)Mn2O4 and Ni(NiyMn2?y)O4 compounds to qualify the function of the photo-induced magnetism in the spinel-type manganese oxide. Structural analysis

Y. Shen; Takahiro Nakayama; Masato Arai; Osami Yanagisawa; Mitusru Izumi

2002-01-01

207

Low-temperature hydrothermal synthesis of spinel-type lithium manganese oxide nanocrystallites  

Microsoft Academic Search

A mild hydrothermal method has been developed to synthesize spinel-type lithium manganese oxide nanocrystallites directly from commercial LiOH, Mn(NO3)2 and H2O2 at 90–110 °C for 8 h. The as-prepared products were characterized by X-ray diffraction (XRD), inductively coupled plasma–atomic emission spectroscopy and chemical analysis. The analysis results indicated that spinel-type lithium manganese oxides with the compositions of Li1+xMn2?xO4?? (0.09?x?0.28, ?<0.05)

Yong Cai Zhang; Hao Wang; Hai Yan Xu; Bo Wang; Hui Yan; Anwar Ahniyaz; Masahiro Yoshimura

2003-01-01

208

Hyperthermia HeLa cell treatment with silica coated manganese oxide nanoparticles  

E-print Network

HeLa tumour cells incubated with ferromagnetic nanoparticles of manganese oxide perovskite La0.56(SrCa)0.22MnO3 were treated with a high frequency alternating magnetic field. The particles were previously coated with silica to improve their biocompatibility. The control assays made with HeLa tumour cells showed that cell survival and growth rate were not affected by the particle internalization in cells, or by the electromagnetic field on cells without nanoparticles. The application of an alternating electromagnetic field to cells incubated with this silica coated manganese oxide induced a significant cellular damage that finally lead to cell death by an apoptotic mechanism.

Villanueva, A; Alonso, JM; Rueda, T; Martínez, A; Crespo, P; Morales, MP; Fernandez, MA Gonzalez; Valdes, J; Rivero, G

2009-01-01

209

Oxidation of unsaturated monoterpenes with hydrogen peroxide catalysed by manganese(III) porphyrin complexes  

Microsoft Academic Search

Oxidation of (+)-3-carene (1), nerol (2) and geraniol (3) by hydrogen peroxide in the presence of catalytic amounts of several manganese(III) porphyrin complexes with electron withdrawing and electron donating groups was examined. The reactions were carried out at room temperature in acetonitrile, using aqueous hydrogen peroxide as oxidant and ammonium acetate as co-catalyst.The oxidation reactions of 3-carene (1) showed high

Rosália R. L Martins; Maria G. P. M. S Neves; Armando J. D Silvestre; Mário M. Q Simões; Artur M. S Silva; Augusto C Tomé; José A. S Cavaleiro; Pietro Tagliatesta; Claudia Crestini

2001-01-01

210

Processes of nickel and cobalt uptake by a manganese oxide forming sediment in Pinal Creek, Globe mining district, Arizona  

USGS Publications Warehouse

A series of column experiments was conducted using manganese oxide coated sediments collected from the hyporheic zone in Pinal Creek (AZ), a metal-contaminated stream, to study the uptake and retention of Mn, Ni, and Co. Experimental variables included the absence (abiotic) and presence (biotic) of active Mn-oxidizing bacteria, the absence and presence of dissolved Mn, and sediment manganese oxide content. Uptake of Mn under biotic conditions was between 8 and 39% higher than under abiotic conditions. Continuous uptake of Mn due to biotic oxidation was evident from extraction of column sediments. Manganese uptake is hypothesized to initially occur as adsorption, which led to subsequent surface and/or microbial oxidation. Complete breakthrough of Ni within 100 pore volumes indicated no process of continuous uptake and was modeled as an equilibrium adsorption process. Nickel uptake in the presence of dissolved Mn was 67-100% reversible. Sediment extractions suggest that Ni uptake occurred through weak and strong adsorption. Continuous uptake of cobalt increased with sediment manganese oxide content, and Co uptake was up to 75% greater under biotic than abiotic conditions. Cobalt uptake was controlled by both existing and newly formed manganese oxides. Only a small amount of Co uptake was reversible (10-25%). XANES spectral analysis indicated that most Co(II) was oxidized to Co(III) and probably incorporated structurally into manganese oxides. Although manganese oxides were the primary phase controlling uptake and retention of Mn, Ni, and Co, the mechanisms varied among the metals.

Kay, J. T.; Conklin, M. H.; Fuller, C. C.; O'Day, P. A.

2001-01-01

211

Reactivity of biogenic manganese oxide for metal sequestration and photochemistry: Computational solid state physics study  

SciTech Connect

Many microbes, including both bacteria and fungi, produce manganese (Mn) oxides by oxidizing soluble Mn(II) to form insoluble Mn(IV) oxide minerals, a kinetically much faster process than abiotic oxidation. These biogenic Mn oxides drive the Mn cycle, coupling it with diverse biogeochemical cycles and determining the bioavailability of environmental contaminants, mainly through strong adsorption and redox reactions. This mini review introduces recent findings based on quantum mechanical density functional theory that reveal the detailed mechanisms of toxic metal adsorption at Mn oxide surfaces and the remarkable role of Mn vacancies in the photochemistry of these minerals.

Kwon, K.D.; Sposito, G.

2010-02-01

212

Oxidation and competitive retention of arsenic between iron- and manganese oxides  

NASA Astrophysics Data System (ADS)

Manganese (Mn) and iron (Fe) oxides are ubiquitous solids in terrestrial systems that have high sorptive capacities for many trace metals, including arsenic (As). Although numerous studies have characterized the effects of As adsorption onto Fe and Mn oxides individually, the fate of arsenic within mixed systems representative of natural environments has not been completely resolved. Here, we examine oxidation and competitive retention of As on goethite and birnessite using a Donnan reactor, where each oxide is isolated by a semi-permeable membrane through which arsenic can migrate. To initiate the Donnan reactor experiments, As(III) was simultaneously added to both chambers. Arsenic(III) injected into the birnessite chamber is rapidly oxidized to As(V) and then slowly redistributes across both chambers, while that added to the goethite chamber undergoes rapid adsorption; the adsorbed As(III) on goethite subsequently undergoes desorption and diffusion into the birnessite chamber followed by oxidation to As(V). With increased reaction time, As(V) is generated and preferentially partitioned onto goethite due to higher adsorption affinity compared to birnessite. Furthermore, the dissolved concentration of As(V) is controlled by the adsorption capacity of the goethite surface, which when saturated, leads to increased aqueous As concentrations; despite an increase in As(V) loading on birnessite with increasing initial As(III) concentration, the resulting aqueous As(V) concentration increase appreciably once the goethite surface is saturated. Our findings show that Mn oxides in soils act as a temporary sorbent of As, but operate primarily as strong oxidants responsible for transformation of As(III) to As(V), which can then strongly adsorb on the surrounding Fe oxide matrix.

Ying, Samantha C.; Kocar, Benjamin D.; Fendorf, Scott

2012-11-01

213

Growth and Dissolution of Iron and Manganese Oxide Films  

SciTech Connect

Growth and dissolution of Fe and Mn oxide films are key regulators of the fate and transport of heavy metals in the environment, especially during changing seasonal conditions of pH and dissolved oxygen. The Fe and Mn are present at much higher concentrations than the heavy metals, and, when Fe and Mn precipitate as oxide films, heavy metals surface adsorb or co-precipitate and are thus essentially immobilized. Conversely, when the Fe and Mn oxide films dissolve, the heavy metals are released to aqueous solution and are thus mobilized for transport. Therefore, understanding the dynamics and properties of Fe and Mn oxide films and thus on the uptake and release of heavy metals is critically important to any attempt to develop mechanistic, quantitative models of the fate, transport, and bioavailablity of heavy metals. A primary capability developed in our earlier work was the ability to grow manganese oxide (MnO{sub x}) films on rhodochrosite (MnCO{sub 3}) substrate in presence of dissolved oxygen under mild alkaline conditions. The morphology of the films was characterized using contact-mode atomic force microscopy. The initial growth began by heteroepitaxial nucleation. The resulting films had maximum heights of 1.5 to 2 nm as a result of thermodynamic constraints. Over the three past years, we have investigated the effects of MnO{sub x} growth on the interactions of MnCO{sub 3} with charged ions and microorganisms, as regulated by the surface electrical properties of the mineral. In 2006, we demonstrated that MnO{sub x} growth could induce interfacial repulsion and surface adhesion on the otherwise neutral MnCO{sub 3} substrate under environmental conditions. Using force-volume microscopy (FVM), we measured the interfacial and adhesive forces on a MnO{sub x}/MnCO{sub 3} surface with a negatively charged silicon nitride tip in a 10-mM NaNO3 solution at pH 7.4. The interfacial force and surface adhesion of MnOx were approximately 40 pN and 600 pN, respectively, whereas those of MnCO{sub 3} were essentially zero. The force differences between MnO{sub x} and MnCO{sub 3} suggest that oxide film growth can focus adsorbates to certain parts of the surface and thereby templating a heterogeneous layout of them. We suspected that the force differences were in part due to the differences in surface electrical properties. In 2007, we investigated two important electrical properties of MnO{sub x} and MnCO{sub 3} surfaces, namely surface potential and ion mobility. Surface potential is a composite quantity that can be linked to the local lattice structure of the reconstructed surface and the adsorption of water layers. The mobile surface ions formed by dissolution can also contribute to surface potential. Using Kelvin probe force microscopy (KPFM) and scanning polarization force microscopy (SPFM), we found that MnOx possessed excess surface potentials of over +200 mV in humid nitrogen and the excess surface potential decreased with increasing relative humidity (i.e., increasing adsorbed water layers on the mineral surface). The dependence of the excess surface potential was attributed to the change of the contributions from mobile ions. These results supported our earlier hypothesis that MnO{sub x} and MnCO{sub 3} had different surface electrical properties. In the third year, we systematically characterized that the change of the electrical double layer (EDL) structure of MnCO{sub 3} surface due to MnO{sub x} growth in aqueous solution and its dependence on pH. The structure of the electrical double layer determines the electrostatic interactions between the mineral surface and charged adsorbates. As described by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the electrostatic force, together with van der Waals interaction, regulates surface adsorption and bacterial attachment. Once adsorbates establish contact with the surface, they must resist hydraulic shear forces through surface adhesion. The adhesion of mineral surfaces is also affected by their electrostatic interactions with adsorbates. To probe the EDL structure, we ap

Scot T. Martin

2008-12-22

214

Adsorption of iron cyanide complexes onto clay minerals, manganese oxide, and soil.  

PubMed

The adsorption characteristics of an iron cyanide complex, soluble Prussian blue KFe(III)[Fe(II)(CN)(6)], were evaluated for representative soil minerals and soil at pH 3.7, 6.4 and 9.7. Three specimen clay minerals (kaolinite, montmorillonite, and illite), two synthesized manganese oxides (birnessite and cryptomelane), and a Drummer soil from Indiana were used as the adsorbents. Surface protonation of variable charge sites increased with decreasing pH yielding positively charged sites on crystal edges and enhancing the attractive force between minerals and iron cyanide complexes. Anion adsorption on clays often is correlated to the metal content of the adsorbent, and a positive relationship was observed between iron or aluminum content and Prussian blue adsorption. Illite had high extractable iron and adsorbed more ferro-ferricyande anion, while kaolinite and montmorillonite had lower extractable iron and adsorbed less. However, less pH effect was observed on the adsorption of iron cyanide to manganese oxides. This may due to the manganese oxide mediated oxidation of ferrocyanide [Fe(II)(CN)(6)(4-)], to ferricyanide [Fe(III)(CN)(6)(3-)], which has a low affinity for manganese oxides. PMID:20665323

Kang, Dong-Hee; Schwab, A Paul; Johnston, C T; Banks, M Katherine

2010-09-01

215

Size and morphology controlled lithium manganese oxide on silica sphere with core-shell structure.  

PubMed

Core-shell structures were prepared from synthesized SiO2-LiMn2O4 with manganese oxide as shell on the silica core by a precipitation method, which allowed control of core structure in terms of thickness and particle size. X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), field emission-transmission electron microscopy (FE-TEM), and energy dispersive spectroscopy (EDS) were used to characterize the SiO2-LiMn2O4. According to FE-SEM images, particle growth was controlled by controlling the amount of manganese precursor and the temperature. The synthesized core-shell structure was composed of silica, lithium silicate, Mn2O3, and the spinel phase of lithium manganese oxide. Electrochemical measurements show that the synthesized core-shell structure has poorer electrochemical performance than that of LiMn2O4. PMID:22629996

Ryu, Seong-Hyeon; Ju, Jeong-Hun; Cho, Sung-Woo; Ryu, Kwang-Sun

2012-02-01

216

Influence of synthesis conditions on the electrochemical properties of nanostructured amorphous manganese oxide cryogels  

NASA Astrophysics Data System (ADS)

Amorphous manganese oxides have received increasing attention in recent years as intercalation cathodes for rechargeable lithium batteries. The sol-gel method is a versatile method for achieving nanostructured amorphous oxides. In this paper, two different sol-gel routes are investigated, where nanostructured amorphous manganese oxide cryogels are obtained via freeze drying Mn(IV) oxide hydrogels formed in situ. In one route the hydrogels are formed by reaction between a solution of sodium permanganate and a solution of disodium fumarate, and in the other route by reaction between a solution of sodium permanganate and solid fumaric acid. Highly homogeneous monolithic manganese oxide hydrogels are obtained from both synthesis routes with precursor concentrations between 0.1 and 0.2 M. The freeze drying method proves to be an efficient method for obtaining nanostructured amorphous manganese oxide cryogels out of the hydrogels. Depending on the synthesis conditions of the hydrogels, the resultant cryogels can yield very high specific capacities for lithium intercalation and excellent rate performance. The cryogel with the best performance exhibits 289 mAh/g at a C/100 rate and 174 mAh/g at a 2 C rate. Strong dependence of electrochemical properties of the cryogels on the synthesis conditions of the parent hydrogels has been observed. The different electrochemical properties are believed to be due to different surface areas and local structures of the cryogels derived from hydrogels synthesized under different conditions. This strong dependence gives rise to the possibility of achieving promising intercalation materials through tailoring the surface area and the local structure of amorphous manganese oxides by adjusting sol-gel synthesis conditions.

Yang, Jingsi; Xu, Jun John

217

Reduction and dissolution of manganese(III) and manganese(IV) oxides by organics. Part 2. Survey of the reactivity of organics  

SciTech Connect

Reduction and dissolution of manganese(III,IV) oxide suspensions by 27 aromatic and nonaromatic compounds resembling natural organics were examined in order to understand the solubilization reaction in nature. At pH 7.2 10/sup -3/ M formate, fumarate, glycerol, lactate, malonate, phthalate, propanol, propionaldehyde, propionate, and sorbitol did not dissolve appreciable amounts of oxide after 3 h of reaction. The following organics did dissolve manganese oxides under these conditions and are listed in order of decreasing reactivity: 3-methoxycatechol approx. catechol approx. 3,4-dihydroxybenzoic acidapprox. ascorbate > 4-nitro-catechol > thiosalicylate > hydroquinone > 2,5-dihydroxybenzoic acid > syringic acid > o-methoxyphenol > vanillic acidapprox. orcinol approx. 3,5-dihydroxybenzoic acid > resorcinol > oxalite approx. pyruvate approx. salicylate. Relative reactivities of organic substrates are discussed in terms of surface complex formation prior to electron transfer. Dissolution of manganese oxides by marine fulvic acid was enhanced by illumination, verifying that the reaction is photocatalyzed.

Stone, A.T.; Morgan, J.J.

1984-01-01

218

The Structure and Properties of Plasma Sprayed Iron Oxide Doped Manganese Cobalt Oxide Spinel Coatings for SOFC Metallic Interconnectors  

Microsoft Academic Search

Manganese cobalt oxide spinel doped with Fe2O3 was studied as a protective coating on ferritic stainless steel interconnects. Chromium alloying causes problems at high\\u000a operation temperatures in such oxidizing conditions where chromium compounds evaporate and poison the cathode active area,\\u000a causing the degradation of the solid oxide fuel cell. In order to prevent chromium evaporation, these interconnectors need\\u000a a protective

Jouni Puranen; Juha Lagerbom; Leo Hyvärinen; Mikko Kylmälahti; Olli Himanen; Mikko Pihlatie; Jari Kiviaho; Petri Vuoristo

2011-01-01

219

Determination of methylcyclopentadienyl-manganese tricarbonyl by solid phase microextraction-direct thermal desorption-quartz furnace atomic absorption spectrometry  

NASA Astrophysics Data System (ADS)

A new procedure that uses a pre-concentration system based on solid phase microextraction (SPME) and detection by quartz furnace-atomic absorption spectrometry after thermal desorption from the microextraction fiber has been proposed for the determination of methylcyclopentadienylmanganese tricarbonyl (MMT) in gasoline and water. Working MMT solutions were prepared in 40 ml amber vials, and sampling was performed by exposing the SPME fiber to the headspace over vigorously stirred samples for 15 min. The analytical performance characteristics of the proposed procedure were as follows: the detection limit for MMT was 0.71 ng ml -1 (as Mn), with a relative standard deviation of 4% for MMT determination of 25 ng ml -1 (as Mn, n=6) while the calibration curve was linear up to 100 ng ml -1 range. The proposed procedure was finally applied to the determination of MMT in gasoline and water samples and non significant differences (Student's t-test) were found between obtained values (using direct calibration and standard additions) and those expected values.

Fragueiro, María. Sandra; Alava-Moreno, Fausto; Lavilla, Isela; Bendicho, Carlos

2001-02-01

220

Synthesis and characterisation of manganese oxides from potassium permanganate and citric acid mixtures  

NASA Astrophysics Data System (ADS)

Reaction of KMnO4 and citric acid at different stoichiometric ratio found to give black precipitate after calcined at 500 %C. The black precipitate are classified as two type of manganese oxides mineral namely as bixbyite and hollandite. IR and XRD data were in agreement with the literature report.

Burhanuddin, Syazwani; Yarmo, Ambar; Yamin, Bohari M.

2013-11-01

221

Heteroepitaxial nucleation and oriented growth of manganese oxide islands on carbonate minerals under aqueous conditions.  

PubMed

Manganese redox cycling and the accompanying dissolution and precipitation reactions are important processes in natural waters. In the present study, Mn2+ (aq) is reacted with O2(aq) at circumneutral pH to form manganese oxide islands on the (1014) surface of MnCO3. The islands grow heteroepitaxially. The effects of the substrate surface morphology, the substrate atomic structure, and the aqueous concentration of Mn2+ are investigated. On terraces, rhombohedral oxide islands form with 90 degrees rotation relative to the crystallographic axis of the underlying carbonate substrate. Although the island heights self-limit between 2 and 3 nm depending on reaction conditions, the islands grow laterally to several square microns before separate islands collide and coalesce. The islands do not grow over substrate steps or down dissolution-pit edges. Comparison studies done with MgCO3 and CaCO3 show that the former also promotes heteroepitaxial growth whereas the latter does not. This difference is explained by the relative bond length mismatch between the structures of the carbonate substrates and the atomic structures of manganese oxides. A free energy model is also presented to explain why the heights of the manganese oxide islands self-limit. Our results provide an improved basis both for the development of predictive models of contaminant fate and transport and for the modeling of hydraulic flow through carbonate aquifers. PMID:15787362

Jun, Young-Shin; Kendall, Treavor A; Martin, Scot T; Friend, Cynthia M; Vlassak, Joost J

2005-03-01

222

Kinetics of manganese oxide reduction from basic slags by carbon dissolved in liquid iron  

Microsoft Academic Search

The reduction of manganese oxide from a basic slag by carbon dissolved in liquid iron is a slow reaction, failing to approach equilibrium closely in 20 hr. Furthermore, the rate of stirring has no apparent effect on the reaction rate. This identifies the rate-controlling step as a chemical reaction at the interface. Only the model for the reaction O 2-

Weldon L. Daines; Robert D. Pehlke

1971-01-01

223

Nanostructural evolution from nanosheets to one-dimensional nanoparticles for manganese oxide  

SciTech Connect

Highlights: ? Nanosheets were transformed to other one-dimensional nanoparticles. ? Nanofibers, nanotubes, nanoribbons, and nanobelts were obtained. ? Nanoparticle morphology can be controlled with organic amines. ? Organic amines act as morphology directing agent. -- Abstract: This paper introduces a novel hydrothermal soft chemical synthesis process for manganese oxide nanostructured particles using two-dimensional manganese oxide nanosheets as precursor. In this process, a birnessite-type manganese oxide with a layered structure was exfoliated into its elementary layer nanosheets, and then the nanosheets were hydrothermally treated to transform the two-dimensional morphology of the nanosheets to one-dimensional nanoparticles. The manganese oxide nanofibers, nanotubes, nanobelts, nanoribbons, and fabric-ribbon-like particles constructed from nanofibers or nanobelts were obtained using this hydrothermal soft chemical process. The nanostructural evolution from the two-dimensional nanosheets to the one-dimensional nanoparticles was characterized by XRD, SEM, TEM, and TG-DTA analysis. The morphology and nanostructure of the products are strongly dependent on the molecular dimension of organic amine cations added in the reaction system. The organic amine cations act as a morphology directing agent in the nanostructural evolution process.

Pan, Hongmei [Department of Preparatory Education, Guangxi University for Nationalities, Daxuexi-Road 188, Nanning, Guangxi 530006 (China)] [Department of Preparatory Education, Guangxi University for Nationalities, Daxuexi-Road 188, Nanning, Guangxi 530006 (China); Kong, Xingang [Department of Advanced Materials Science, Faculty of Engineering, Kagawa University, 2217-20 Hayashi-cho, Takamatsu-shi 761-0396 (Japan)] [Department of Advanced Materials Science, Faculty of Engineering, Kagawa University, 2217-20 Hayashi-cho, Takamatsu-shi 761-0396 (Japan); Wen, Puhong [Department of Chemistry and Chemical Engineering, Baoji University of Arts and Science, 1 Gaoxin Road, Baoji, Shaanxi 721013 (China)] [Department of Chemistry and Chemical Engineering, Baoji University of Arts and Science, 1 Gaoxin Road, Baoji, Shaanxi 721013 (China); Kitayama, Tomonori [Department of Advanced Materials Science, Faculty of Engineering, Kagawa University, 2217-20 Hayashi-cho, Takamatsu-shi 761-0396 (Japan)] [Department of Advanced Materials Science, Faculty of Engineering, Kagawa University, 2217-20 Hayashi-cho, Takamatsu-shi 761-0396 (Japan); Feng, Qi, E-mail: feng@eng.kagawa-u.ac.jp [Department of Advanced Materials Science, Faculty of Engineering, Kagawa University, 2217-20 Hayashi-cho, Takamatsu-shi 761-0396 (Japan)] [Department of Advanced Materials Science, Faculty of Engineering, Kagawa University, 2217-20 Hayashi-cho, Takamatsu-shi 761-0396 (Japan)

2012-09-15

224

Synthesis of Lithium-Manganese-Oxide Spinels: A Study by Thermal Analysis  

Microsoft Academic Search

The synthesis of lithium-manganese-oxide spinels by reaction of Li2CO3 and MnCO3 in air and under nitrogen to Tmax = 600°C has been investigated by thermogravimetric analysis and differential scanning calorimetry. When the reaction is conducted in air, the stoichiometric spinel LiMn2O4 is produced via a series of intermediate \\

M. M. Thackeray; M. H. Rossouw

1994-01-01

225

Hydrothermal Soft Chemical Process for Synthesis of Manganese Oxides with Tunnel Structures  

Microsoft Academic Search

A soft chemical process is used for the synthesis of manganese oxides with tunnel structures. This process comprises two steps: the first step is the preparation of a precursor with layered structure and insertion of templates (structure-directing agents) into its interlayer space by a soft chemical reaction [1], and the second step is the transformation of the template-inserted precursor into

Qi Feng; Kazumichi Yanagisawa; Nakamichi Yamasaki

1998-01-01

226

Investigation of nanostructured iron and manganese oxides as novel intercalation hosts for lithium  

Microsoft Academic Search

Rechargeable lithium battery systems are being pushed to the limits of their performance in modern portable devices, with increasing demands for higher energy and higher power. The intercalation cathode or positive electrode in these batteries is one of the primary bottlenecks in terms of performance. In this thesis, investigation of nanostructured iron and manganese oxide compounds that show immense promise

Gaurav Jain

2005-01-01

227

Nano-sized manganese oxide particles prepared by low-pressure spray pyrolysis using FEAG process  

Microsoft Academic Search

Nano-sized manganese oxide particles were prepared by low-pressure spray pyrolysis using the new type of liquid aerosol generator called as FEAG process. The particles prepared from polymeric precursors spray solution with organic additives had large size, hollow and fractured morphologies due to the gas evolution from the decomposition of the organic additives. The precursor particles with micron size, hollow and

Seo Hee Ju; Yun Chan Kang

2008-01-01

228

SERUM CHEMISTRIES OF COTURNIX JAPONICA GIVEN DIETARY MANGANESE OXIDE (MN3O4)  

EPA Science Inventory

Plasma creatinine and inorganic phosphorus were increased in manganese oxide (Mn3O4)-treated adult male Coturnix quail, but BUN, BUN/creatinine ratio, uric acid, and total calcium were decreased. 2. Serum enzymes (alkaline phosphatase glutamic oxaloacetic transaminase, glutamic p...

229

Manganese-induced oxidative stress in two ontogenetic stages of chamomile and amelioration by nitric oxide.  

PubMed

Impact of manganese (Mn(2+)) excess (100, 500 and 1000 ?M over 7 days) on two ontogenetic stages (7-week-old plants and 7-day-old seedlings) of Matricaria chamomilla was compared. Mn excess depressed growth of seedlings (but not germination) and stimulated oxidative stress (ROS and lipid peroxidation) in both plants and seedlings. Growth inhibition could be evoked by higher Mn uptake and higher translocation factor in seedlings than in plants. Total thiols staining revealed elevation in almost all treatments. In 7-week-old plants, activity of peroxidases increased slightly and rather decreased under high Mn doses. Superoxide rather than hydrogen peroxide contributed to visualized ROS presence. Fluorescence of nitric oxide (NO) showed stimulation in plants but decrease in seedlings. Impact of exogenous nitric oxide donor (sodium nitroprusside/SNP) was therefore tested and results showed amelioration of 1000 ?M Mn-induced oxidative stress in seedlings (decrease in H2O2 and increase in NO content while antioxidative enzyme activities were variably affected) concomitantly with depleted Mn accumulation. It is concluded that NO participates in tolerance to Mn excess but negative effects of the highest SNP dose were also observed. Extensive fluorescence microscopy is also explanatively discussed. PMID:24388509

Ková?ik, Jozef; Babula, Petr; Hedbavny, Josef; Švec, Pavel

2014-02-01

230

Determining the Oxidation States of Manganese in NT2 Cells and Cultured Astrocytes  

SciTech Connect

Excessive brain manganese (Mn) can produce a syndrome called 'manganism', which correlates with loss of striatal dopamine and cell death in the striatum and globus pallidus. The prevalent hypothesis for the cause of this syndrome has been oxidation of cell components by the strong oxidizing agent, Mn{sup 3+}, either formed by oxidation of intracellular Mn{sup 2+} or transported into the cell as Mn{sup 3+}. We have recently used X-ray absorption near edge structure spectroscopy (XANES) to determine the oxidation states of manganese complexes in brain and liver mitochondria and in nerve growth factor (NGF)-induced and non-induced PC12 cells. No evidence was found for stabilization or accumulation of Mn{sup 3+} complexes because of oxidation of Mn{sup 2+} by reactive oxygen species in these tissues. Here we extend these studies of manganese oxidation state to cells of brain origin, human neuroteratocarcinoma (NT2) cells and primary cultures of rat astrocytes. Again we find no evidence for stabilization or accumulation of any Mn{sup 3+} complex derived from oxidation of Mn{sup 2+} under a range of conditions.

Gunter,K.; Aschner, M.; Miller, L.; Eliseev, R.; Salter, J.; Andersen, K.; Gunter, T.

2006-01-01

231

Structural and electrochemical effects of cobalt doping on lithium manganese oxide spinel  

Microsoft Academic Search

Pure LiMn2O4 and lithium manganese oxide spinels with partial replacement of manganese by cobalt up to 20 mole%, LiCoxMn2?xO4, were prepared. The effect of extended cycling on the crystal structure was investigated. A capacity decrease with increasing\\u000a cobalt content was observed in the potential range about 4100 mV vs. Li\\/Li+. Cycling behavior is significantly improved, compared to LiMn2O4. LiCoxMn2?xO4 is

A. Butz; M. Wohlfahrt-Mehrens; R. Oesten; R. A. Huggins

1996-01-01

232

Lattice vibrations of materials for lithium rechargeable batteries III. Lithium manganese oxides  

Microsoft Academic Search

Structural features of several lithiated manganese oxides are studied using Raman scattering (RS) spectroscopy. This local probe is capable to analyse directly the near-neighbour environment of oxygen coordination around manganese and lithium cations. The samples include: orthorhombic and monoclinic LiMnO2, spinel LiMn2O4, monoclinic Li2MnO3, lithiated-spinel Li2Mn2O4, Li-birnessite, LT- and HT-Li0.52MnO2.1, spinel Li4Mn5O12, and Li0.33MnO2. Thus, as a first approach, we

C. M. Julien; M. Massot

2003-01-01

233

Cation-deficient nano-dimensional particle size cobalt–manganese spinel mixed oxides  

Microsoft Academic Search

Cobalt–manganese binary spinel oxides of high-dispersity are synthesized by thermal decomposition of hydroxycarbonate precursors in the limits 0.33?Mn\\/Co?2. The mixed oxides are cation-deficient and contain a high surface concentration of non-stoichiometric oxygen. The oxygen-to-metal surface ratios, determined by ESCA are higher than the stoichiometric value for dioxides. The spinel lattice is tetragonally distorted for atomic ratios Mn\\/Co>1. The samples synthesized

Dimitar G. Klissurski; Ellie L. Uzunova

2003-01-01

234

Relationship between the structural and catalytic properties of mechanosynthesized lithiated manganese oxides  

Microsoft Academic Search

The relationship between the structural and catalytic properties of lithiated spinel manganese oxides was investigated by\\u000a means of X-ray diffraction, Infrared and Xanes spectroscopies, thermogravimetric analysis, and by evaluating two catalytic\\u000a oxidation tests, namely the carbon black combustion and the toluene conversion. Li-Mn-O catalysts were prepared from stoichiometric\\u000a (Li2O + MnO2) mixtures, either by the classical high temperature ceramic method

A. Rougier; S. Soiron; L. Aymard; C. Julien; J. Moscovici; A. Michalowicz; I. Haihal; B. Taouk; G. A. Nazri; J. M. Tarascon

2003-01-01

235

Catalytic decomposition of hydrogen peroxide on manganese oxides. I. Use of the electrode potential method  

Microsoft Academic Search

It has been ascertained by use of electrode potential measurements that the degree of oxidation of the surface of manganese oxides (..beta..-MnOâ, ..beta..-MnâOâ, ..beta..-MnâOâ, and MnO) varies markedly in hydrogen peroxide. Moreover, a rearrangement of the surface layer crystal structure takes place. On prolonged treatment with hydrogen peroxide, an identical steady state of the surface is established for all of

V. A. Sadykov; P. G. Tsyrulnikov

1976-01-01

236

Ion-Exchange Properties of lon-Sieve-Type Manganese Oxides Prepared by Using Different Kinds of Introducing Ions  

Microsoft Academic Search

Three ion-sieve-type manganese oxides, HMnO(Li), HMnO(Na), and HMnO(K), were prepared by acid treatments of Li-, Na-, and K-introduced manganese oxides, respectively. Three oxides were obtained from ?-MnO and the corresponding alkali metal hydroxides by heating at 600°C. The ion-exchange properties of the adsorbents were investigated by pH titration, Kd measurements, and the adsorption of metal ions from seawater. The selectivity

Kenta Ooi; Yoshitaka Miyai; Shunsaku Katoh

1987-01-01

237

Oxidation state of cross-over manganese species on the graphite electrode of lithium-ion cells.  

PubMed

It is well known that Li-ion cells containing manganese oxide-based positive electrodes and graphite-based negative electrodes suffer accelerated capacity fade, which has been attributed to the deposition of dissolved manganese on the graphite electrodes during electrochemical cell cycling. However, the reasons for the accelerated capacity fade are still unclear. This stems, in part, from conflicting reports of the oxidation state of the manganese species in the negative electrode. In this communication, the oxidation state of manganese deposited on graphite electrodes has been probed by X-ray absorption near edge spectroscopy (XANES). The XANES features confirm, unequivocally, the presence of fully reduced manganese (Mn(0)) on the surface of graphite particles. The deposition of Mn(0) on the graphite negative electrode acts as a starting point to understand the consequent electrochemical behavior of these electrodes; possible reasons for the degradation of cell performance are proposed and discussed. PMID:24608259

Gowda, Sanketh R; Gallagher, Kevin G; Croy, Jason R; Bettge, Martin; Thackeray, Michael M; Balasubramanian, Mahalingam

2014-04-21

238

Determination of uranyl incorporation into biogenic manganese oxides using x-ray absorption spectroscopy and scattering.  

PubMed

Biogenic manganese oxides are common and an important source of reactive mineral surfaces in the environment that may be potentially enhanced in bioremediation cases to improve natural attenuation. Experiments were performed in which the uranyl ion, UO2(2+) (U(VI)), at various concentrations was present during manganese oxide biogenesis. At all concentrations, there was strong uptake of U onto the oxides. Synchrotron-based extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray diffraction (XRD) studies were carried out to determine the molecular-scale mechanism by which uranyl is incorporated into the oxide and how this incorporation affects the resulting manganese oxide structure and mineralogy. The EXAFS experiments show that at low concentrations (<0.3 mol % U, <1 microM U(VI) in solution), U(VI) is present as a strong bidentate surface complex. At high concentrations (>2 mol % U, >4 microM U(VI) in solution), the presence of U(VI) affects the stability and structure of the Mn oxide to form poorly ordered Mn oxide tunnel structures, similar to todorokite. EXAFS modeling shows that uranyl is present in these oxides predominantly in the tunnels of the Mn oxide structure in a tridentate complex. Observations by XRD corroborate these results. Structural incorporation may lead to more stable U(VI) sequestration that may be suitable for remediation uses. These observations, combined with the very high uptake capacity of the Mn oxides, imply that Mn-oxidizing bacteria may significantly influence dissolved U(VI) concentrations in impacted waters via sorption and incorporation into Mn oxide biominerals. PMID:16509317

Webb, S M; Fuller, C C; Tebo, B M; Bargar, J R

2006-02-01

239

Element-and site-specific oxidation state and cation distribution in manganese ferrite films by diffraction anomalous fine structure  

E-print Network

Element- and site-specific oxidation state and cation distribution in manganese ferrite films Received 2 April 2008; accepted 9 July 2008; published online 8 August 2008 Epitaxial manganese ferrite.1063/1.2969406 Spinel ferrites represent an important class of materials that provide high permeability, moderate

Haskel, Daniel

240

A study of the kinetics of reductive leaching of manganese oxide ore in aqueous methanol–sulphuric acid medium  

Microsoft Academic Search

Some aspects of the kinetics of reductive leaching of manganese oxide ore in aqueous methanol–sulphuric acid medium have been investigated, looking at the effects of methanol and sulphuric acid concentrations, temperature and particle size on the rate of manganese extraction. Two distinct regions of rate control have been identified. The initial 30 min of reaction were characterised by a weak

F. W. Y Momade; Zs. G Momade

1999-01-01

241

Drinking Water Problems: Iron and Manganese  

E-print Network

concentrations of iron and manganese) Oxidizing filter?manganese greensand or zeolite (use with zeolite coated with manganese oxide. These substances adsorb dis- solved iron and manganese. Synthetic zeolite requires less backwash water and softens water as it removes impurities...

Dozier, Monty; McFarland, Mark L.

2004-02-20

242

Weathering of the Rio Blanco Quartz Diorite, Luquillo Mountains, Puerto Rico: Coupling Oxidation, Dissolution, And Fracturing  

SciTech Connect

In the mountainous Rio Icacos watershed in northeastern Puerto Rico, quartz diorite bedrock weathers spheroidally, producing a 0.2-2 m thick zone of partially weathered rock layers ({approx}2.5 cm thickness each) called rindlets, which form concentric layers around corestones. Spheroidal fracturing has been modeled to occur when a weathering reaction with a positive {Delta}V of reaction builds up elastic strain energy. The rates of spheroidal fracturing and saprolite formation are therefore controlled by the rate of the weathering reaction. Chemical, petrographic, and spectroscopic evidence demonstrates that biotite oxidation is the most likely fracture-inducing reaction. This reaction occurs with an expansion in d (0 0 1) from 10.0 to 10.5 {angstrom}, forming 'altered biotite'. Progressive biotite oxidation across the rindlet zone was inferred from thin sections and gradients in K and Fe(II). Using the gradient in Fe(II) and constraints based on cosmogenic age dates, we calculated a biotite oxidation reaction rate of 8.2 x 10{sup -14} mol biotite m{sup -2} s{sup -1}. Biotite oxidation was documented within the bedrock corestone by synchrotron X-ray microprobe fluorescence imaging and XANES. X-ray microprobe images of Fe(II) and Fe(III) at 2 {micro}m resolution revealed that oxidized zones within individual biotite crystals are the first evidence of alteration of the otherwise unaltered corestone. Fluids entering along fractures lead to the dissolution of plagioclase within the rindlet zone. Within 7 cm surrounding the rindlet-saprolite interface, hornblende dissolves to completion at a rate of 6.3 x 10{sup -13} mol hornblende m{sup -2} s{sup -1}: the fastest reported rate of hornblende weathering in the field. This rate is consistent with laboratory-derived hornblende dissolution rates. By revealing the coupling of these mineral weathering reactions to fracturing and porosity formation we are able to describe the process by which the quartz diorite bedrock disaggregates and forms saprolite. In the corestone, biotite oxidation induces spheroidal fracturing, facilitating the influx of fluids that react with other minerals, dissolving plagioclase and chlorite, creating additional porosity, and eventually dissolving hornblende and precipitating secondary minerals. The thickness of the resultant saprolite is maintained at steady state by a positive feedback between the denudation rate and the weathering advance rate driven by the concentration of pore water O{sub 2} at the bedrock-saprolite interface.

Buss, H.L.; Sak, P.B.; Webb, S.M.; Brantley, S.L.

2009-05-12

243

An Electrochemical Sensor Based on Nanostructured Hollandite-type Manganese Oxide for Detection of Potassium Ions  

PubMed Central

The participation of cations in redox reactions of manganese oxides provides an opportunity for development of chemical sensors for non-electroactive ions. A sensor based on a nanostructured hollandite-type manganese oxide was investigated for voltammetric detection of potassium ions. The detection is based on the measurement of anodic current generated by oxidation of Mn(III) to Mn(IV) at the surface of the electrode and the subsequent extraction of the potassium ions into the hollandite structure. In this work, an amperometric procedure at an operating potential of 0.80 V (versus SCE) is exploited for amperometric monitoring. The current signals are linearly proportional to potassium ion concentration in the range 4.97 × 10?5 to 9.05 × 10?4 mol L?1, with a correlation coefficient of 0.9997. PMID:22399969

Lima, Alex S.; Bocchi, Nerilso; Gomes, Homero M.; Teixeira, Marcos F. S.

2009-01-01

244

The oxidative dechlorination reaction of 2,4,6-trichlorophenol in dilute aqueous suspensions of manganese oxides  

SciTech Connect

Oxidation of 2,4,6-trichlorophenol (TCP) by layered manganese oxides (Na and Co-buserite) in dilute acidified aqueous suspension gives 2,6-dichloro-p-benzoquinone as a major product. This compound is likely to further polymerize and become incorporated into humus like materials. The oxidation rate was higher at lower pH and higher on Na-buserite compared to Co-buserite. TCP reacted at a faster rate than unsubstituted phenol at pH3 and 5.5, which is explained by (a) the lower half-wave potential of TCP compared to phenol; (b) a stronger bond dipole associated with the electronegative halogen, favoring an addition step in nucleophilic substitution; and (c) easier depronation of TCP at the manganese oxide-water interface due to its lower pK[sub a]. IR spectroscopy shows that TCP adsorbs in deprotonated form on the surface of manganese oxide, and it cannot be washed from the surface by water. Nucleophilic attack by addition-elimination is suggested as a mechanism of TCP dechlorination and oxidation.

Ukrainczyk, L.; McBride, M.B. (Cornell Univ., Ithaca, NY (United States). Dept. of Soil, Crop and Atmospheric Sciences)

1993-11-01

245

Uraninite oxidation and dissolution induced by manganese oxide: A redox reaction between two insoluble minerals  

NASA Astrophysics Data System (ADS)

The longevity of subsurface U(IV) produced by reduction of U(VI) during in situ bioremediation can be limited by reoxidation to more mobile U(VI) species. Coupling of the biogeochemical cycles of U and Mn may affect the fate and transport of uranium. Manganese oxides can act as a powerful oxidant that accelerates the oxidative dissolution of UO2. This study investigated the physical and chemical factors controlling the interaction between UO2 and MnO2, which are both poorly soluble minerals. A multi-chamber reactor with a permeable membrane was used to eliminate direct contact of the two minerals while still allowing transport of aqueous species. The oxidation of UO2 was not significantly enhanced by MnO2 if the two solids were physically separated. Complete mixing of MnO2 with UO2 led to a much greater extent and rate of U oxidation. When direct contact is not possible, the reaction slowly progresses through release of soluble U(IV) with its adsorption and oxidation on MnO2. Continuously-stirred tank reactors (CSTRs) were used to quantify the steady-state rates of UO2 dissolution induced by MnO2. MnO2 dramatically promoted UO2 dissolution, but the degree of promotion leveled off once the MnO2:UO2 ratio exceeded a critical value. Substantial amounts of U(VI) and Mn(II) were retained on MnO2 surfaces. The total production of Mn(II) was less than that of U(VI), indicating that the fate of Mn products and their impact on UO2-MnO2 reaction kinetics were complicated and may involve formation of Mn(III) phases. At higher dissolved inorganic carbon concentrations, UO2 oxidation by MnO2 was faster and less U(VI) was adsorbed to MnO2. Such an inverse relationship suggested that U(VI) may passivate MnO2 surfaces. A conceptual model was developed to describe the oxidation rate of UO2 by MnO2. This model is potentially applicable to a broad range of water chemistry conditions and is relevant to other environmental redox processes involving two poorly soluble minerals.

Wang, Zimeng; Lee, Sung-Woo; Kapoor, Pratyul; Tebo, Bradley M.; Giammar, Daniel E.

2013-01-01

246

Improved manganese-oxidizing activity of DypB, a peroxidase from a lignolytic bacterium  

PubMed Central

DypB, a dye-decolorizing peroxidase from the lignolytic soil bacterium Rhodococcus jostii RHA1, catalyzes the peroxide-dependent oxidation of divalent manganese (Mn2+), albeit less efficiently than fungal manganese peroxidases. Substitution of Asn246, a distal heme residue, with alanine, increased the enzyme’s apparent kcat and kcat/Km values for Mn2+ by 80- and 15-fold, respectively. A 2.2 Å resolution X-ray crystal structure of the N246A variant revealed the Mn2+ to be bound within a pocket of acidic residues at the heme edge, reminiscent of the binding site in fungal manganese peroxidase and very different to that of another bacterial Mn2+-oxidizing peroxidase. The first coordination sphere was entirely comprised of solvent, consistent with the variant’s high Km for Mn2+ (17 ± 2 mM). N246A catalyzed the manganese-dependent transformation of hard wood kraft lignin and its solvent-extracted fractions. Two of the major degradation products were identified as 2,6-dimethoxybenzoquinone and 4-hydroxy-3,5-dimethoxybenzaldehyde, respectively. These results highlight the potential of bacterial enzymes as biocatalysts to transform lignin. PMID:23305326

Singh, Rahul; Grigg, Jason C.; Qin, Wei; Kadla, John F.; Murphy, Michael E.P.; Eltis, Lindsay D.

2013-01-01

247

Manganese Oxidation In A Natural Marine Environment- San Antonio Bay  

E-print Network

of Mn4+, which has also been described as a thermodynamic sink (Hem and Lind 1983; Stumm and Morgan 1996; Armstrong 2008). Mn oxides are found in the geologic record associated with other metal oxides such as iron (Fe) and cerium (Ce) (Braun et al... an insoluble oxide (cerianite, CeO2) (Elderfield and Greaves, 1982; Braun et al, 1990). It has been suggested that Ce and Mn oxidation proceed via the same pathway, and each one competitively inhibits the oxidation of the other via kinetic competition...

Neyin, Rosemary Ogheneochuko

2013-04-12

248

Lattice vibrations of manganese oxides. Part I. Periodic structures.  

PubMed

Raman scattering (RS) and Fourier transform-infrared (FT-IR) spectroscopy have been applied to the structural characterisation of manganese dioxides (MDOs). A variety of synthetic battery-grade MDOs are investigated for comparison to the natural phases. The RS and FT-IR spectra are analysed on the basis of the local environment in the MDO structures considering the vibrations of the MnO6 octahedral building the lattices. The vibrational modes of the MnO6 units expand over 400-650 cm(-l) with additional bands in the low-wavelength region. Structural trends are deduced from the comparison of the vibrational spectra of the MDO phases investigated: birnessite, bixbyite, coronadite, groutite, hausmannite, hollandite, manganosite, pyrolusite, ramsdellite, romanechite, spinel, and todorokite. PMID:14747095

Julien, C M; Massot, M; Poinsignon, C

2004-02-01

249

The ability of oxidative stress to mimic quartz-induced chemokine responses is lung cell line-dependent.  

PubMed

Oxidative stress induced by surface-generated radicals has been a dominating hypothesis to explain how mineral particles and fibers trigger cellular responses. However, conflicting studies suggest that the importance of particle-derived formation of reactive oxygen species (ROS) requires further examination. The present study focuses on whether oxidative stress in the form of H(2)O(2)-exposure may mimic the effects of quartz particles on chemokine responses in epithelial lung cells. The results show that H(2)O(2) and quartz exposure induced almost identical levels of CXCL8 (interleukin-8) release in the alveolar epithelial cell line A549, but in the bronchial epithelial cell line BEAS-2B, H(2)O(2)-exposure did not affect CXCL8 release significantly, whereas quartz induced a 16-fold increase. Among 17 different cytokine and chemokine genes H(2)O(2) induced up-regulation of only IL-5 in BEAS-2B cells, while quartz increased the expression of 8 different cytokines and chemokines. In A549 cells, however, there was a moderate but significant correlation between the cytokine/chemokine gene-expression profiles induced by the two agents. Thus, the response to oxidative stress may vary considerably between different lung cell lines. Moreover, the results from the BEAS-2B cells strengthen the notion that non-oxidant initiation mechanisms may also be important to the effects of mineral particles and fibers. PMID:18662758

Ovrevik, Johan; Refsnes, Magne; Schwarze, Per; Låg, Marit

2008-09-26

250

Searching for biosignatures using electron paramagnetic resonance (EPR) analysis of manganese oxides.  

PubMed

Manganese oxide (Mn oxide) minerals from bacterial sources produce electron paramagnetic resonance (EPR) spectral signatures that are mostly distinct from those of synthetic simulants and abiogenic mineral Mn oxides. Biogenic Mn oxides exhibit only narrow EPR spectral linewidths (?500 G), whereas abiogenic Mn oxides produce spectral linewidths that are 2-6 times broader and range from 1200 to 3000 G. This distinction is consistent with X-ray structural observations that biogenic Mn oxides have abundant layer site vacancies and edge terminations and are mostly of single ionic species [i.e., Mn(IV)], all of which favor narrow EPR linewidths. In contrast, abiogenic Mn oxides have fewer lattice vacancies, larger particle sizes, and mixed ionic species [Mn(III) and Mn(IV)], which lead to the broader linewidths. These properties could be utilized in the search for extraterrestrial physicochemical biosignatures, for example, on Mars missions that include a miniature version of an EPR spectrometer. PMID:21970705

Kim, Soon Sam; Bargar, John R; Nealson, Kenneth H; Flood, Beverly E; Kirschvink, Joseph L; Raub, Timothy D; Tebo, Bradley M; Villalobos, Mario

2011-10-01

251

The Role of High Molecular Weight Polyethylene Oxide in Reducing Quartz Gangue Entrainment in Chalcopyrite Flotation by Xanthate Collectors  

NASA Astrophysics Data System (ADS)

Fine particles pose two challenging problems to all mineral processors around the world today. The problems are the inefficient collection of hydrophobic particles (low recovery), and mechanical/hydraulic entrainment of hydrophilic gangue particles (low concentrate grade). Extensive research has been conducted to improve the flotation recovery of fine hydrophobic particles. However, much less effort was made to lower the mechanical/hydraulic entrainment of fine gangue mineral particles. In this study, polyethylene oxide (PEO) was used to flocculate and depress fine quartz particles. Batch flotation results indicated that the addition of low dosages of PEO improved value mineral recovery and concentrate grade in the flotation of artificial mixtures of chalcopyrite/quartz and a commercial Au-Cu sulfide ore sample. It was found that PEO adsorbed on both minerals mainly through hydrogen bonding and caused non-selective flocculation of quartz and chalcopyrite, forming large hetero-aggregates. However, the addition of potassium amyl xanthate (KAX), a specific sulfide mineral collector, adsorbed on chalcopyrite through chemical interaction, replaced PEO and caused the chalcopyrite particles to break away from the hetero-aggregates, forming separate homo-aggregates of quartz and chalcopyrite. The flotation of the chalcopyrite and the depression of the quartz were thus both improved due to the larger sizes of the homo-aggregates compared to the discrete particles. It was also observed that a completely solubilized PEO solution could not flocculate quartz, while a partially solubilized PEO solution was most effective. This was attributed to the better “bridging” functions of the undissolved PEO aggregates when it was partially solubilized. When the PEO was fully solubilized, the individual PEO molecules were probably too flexible and tended to flatten on the adsorbed solid surface and thus could not function as an effective bridging flocculant. Furthermore, it was found that PEO could function as a “collector” for quartz due to its affinity to air-water interface and quartz, and it could increase quartz entrainment when used at high dosages. Selective flocculation and depression of the quartz gangue during chalcopyrite flotation could only be achieved at low PEO dosages. The implication of these observations on how to utilize the polyethylene oxide in industrial flotation was discussed.

Gong, Jihua

252

Mechanism of manganese catalase peroxide disproportionation: determination of manganese oxidation states during turnover.  

PubMed

X-ray absorption near-edge structure (XANES) spectroscopy has been used to determine the oxidation state composition of the Mn site in Mn catalase under turnover conditions. The XANES data are consistent with parallel assignments based on electron paramagnetic resonance (EPR). However, a major advantage of the XANES assignments is that they permit the direct determination of the average oxidation states for derivatives that are EPR silent. In agreement with earlier work [Khangulov, S. V., Barynin, V. V., & Antonyuk-Barynina, S. V. (1990) Biochim. Biophys. Acta 1020, 25-33], these data show that the binuclear Mn site is reduced to Mn(II)/Mn(II) when peroxide is added in the presence of halide inhibitors. In addition, the present data provide the first direct evidence that the reduced enzyme is oxidized if peroxide is added in the absence of inhibitors. Under turnover conditions, the enzyme contains approximately a 2:1 ratio of Mn(II) and Mn(III). Similar results are obtained following incubation with dioxygen. These results are consistent with a Mn(II)/Mn(II)<==>Mn(III)/Mn(III) catalytic cycle and demonstrate that halide inhibition involves trapping the enzyme in the reduced state. PMID:7849009

Waldo, G S; Penner-Hahn, J E

1995-02-01

253

Electrochemical performance of LBO-coated spinel lithium manganese oxide as cathode material for Li-ion battery  

Microsoft Academic Search

Surface treatment of the lithium manganese oxide cathode material coated by lithium borate glass (Li2O–2B2O3) with improved electrochemical cyclability and structural stability was conducted in this study. The lithium manganese oxide powder doped with various weight percentages of LBO glass was calcined to form a fine powder with single spinel phase, exhibiting different particle size, size distribution and morphology. The

Hung-Wei Chan; Jenq-Gong Duh; Shyang-Roeng Sheen

2004-01-01

254

Synthesis and Characterization of a Novel Extracellular Biogenic Manganese Oxide (Bixbyite-like Mn 2 O 3 ) Nanoparticle by Isolated Acinetobacter sp  

Microsoft Academic Search

Recently, manganese oxides have been considered in the environmental remediation, MRI diagnosis and drug and pharmaceutical\\u000a industries. Different numbers of physicochemical and biological methods have been reported for the preparation of nanoscale\\u000a manganese oxides. Although manganese oxide biogenesis by bacterial species has been recognized as the major Mn-oxidizing agent\\u000a in nature, in this research, for first time, we demonstrated the

Baharak Hosseinkhani; Giti Emtiazi

255

Coordination compounds of manganese(II) with polyamines - catalysts of the oxidation of organic dyes by hydrogen peroxide  

SciTech Connect

The peroxidase activity of complexes of manganese(II) with polyamines has been characterized. A comparison of the original and literature data has led to the conclusion that the oxidation of organic substrates having some complexing ability with respect to Manganese(II) in Mn(II)-ligand-H/sub 2/O/sub 2/-S systems takes place according to an inner-sphere ion-molecule mechanism. In cases in which the substrate does not have any complexing ability with respect to Manganese(II), the oxidation process takes place according to an outer-sphere mechanism.

Batyr, D.G.; Isak, V.G.; Kirienko, A.A.; Kharitonov, Yu.Ya.

1987-02-01

256

Low-temperature, manganese oxide-based, thermochemical water splitting cycle  

PubMed Central

Thermochemical cycles that split water into stoichiometric amounts of hydrogen and oxygen below 1,000?°C, and do not involve toxic or corrosive intermediates, are highly desirable because they can convert heat into chemical energy in the form of hydrogen. We report a manganese-based thermochemical cycle with a highest operating temperature of 850?°C that is completely recyclable and does not involve toxic or corrosive components. The thermochemical cycle utilizes redox reactions of Mn(II)/Mn(III) oxides. The shuttling of Na+ into and out of the manganese oxides in the hydrogen and oxygen evolution steps, respectively, provides the key thermodynamic driving forces and allows for the cycle to be closed at temperatures below 1,000?°C. The production of hydrogen and oxygen is fully reproducible for at least five cycles. PMID:22647608

Xu, Bingjun; Bhawe, Yashodhan; Davis, Mark E.

2012-01-01

257

Studies on microbiologically influenced corrosion of SS304 by a novel manganese oxidizer, Bacillus flexus.  

PubMed

A manganese oxidizing bacterium was isolated from the surface of steel scraps and biochemical tests and 16S rRNA sequencing analysis confirmed the isolate as Bacillus flexus. Potentiodynamic polarization curves showed ennoblement of open circuit potential, increased passive current, a lowering of breakdown potential, active re-passivation potential and enhanced cathodic current in the presence of B. flexus. Adhesion studies with B. flexus on SS304 specimens with different surface treatments demonstrated decreased adhesion on passivated and FeCl(3) treated specimens due to the removal of MnS inclusions. The present study provides evidence that surface treatment of stainless steels can reduce adhesion of this manganese oxidizing bacterium and decrease the probability of microbiologically influenced corrosion. PMID:21749279

Anandkumar, B; George, R P; Tamilvani, S; Padhy, N; Mudali, U Kamachi

2011-01-01

258

Kinetics of manganese oxide reduction from basic slags by carbon dissolved in liquid iron  

Microsoft Academic Search

The reduction of manganese oxide from a basic slag by carbon dissolved in liquid iron is a slow reaction, failing to approach\\u000a equilibrium closely in 20 hr. Furthermore, the rate of stirring has no apparent effect on the reaction rate. This identifies\\u000a the rate-controlling step as a chemical reaction at the interface. Only the model for the reactionO\\u000a 2? =O

Weldon L. Daines; Robert D. Pehlke

1971-01-01

259

Persistent alterations in biomarkers of oxidative stress resulting from combined in Utero and neonatal manganese inhalation  

Microsoft Academic Search

Neonatal female and male rats were exposed to airborne manganese sulfate (MnSO4) during gestation and postnatal d 1–18. Three weeks post-exposure, rats were killed and we assessed biochemical end points\\u000a indicative of oxidative stress in five brain regions: cerebellum, hippocampus, hypothalamus, olfactory bulb, and striatum.\\u000a Glutamine synthetase (GS) protein levels, metallothionein (MT) and GS mRNA levels, and total glutathione (GSH)

Keith M. Erikson; David C. Dorman; Lawrence H. Lash; Michael Aschner

2005-01-01

260

Studies on microbiologically influenced corrosion of SS304 by a novel manganese oxidizer, Bacillus flexus  

Microsoft Academic Search

A manganese oxidizing bacterium was isolated from the surface of steel scraps and biochemical tests and 16S rRNA sequencing analysis confirmed the isolate as Bacillus flexus. Potentiodynamic polarization curves showed ennoblement of open circuit potential, increased passive current, a lowering of breakdown potential, active re-passivation potential and enhanced cathodic current in the presence of B. flexus. Adhesion studies with B.

B. Anandkumar; R. P. George; S. Tamilvani; N. Padhy; U. Kamachi Mudali

2011-01-01

261

Lattice vibrations of materials for lithium rechargeable batteries I. Lithium manganese oxide spinel  

Microsoft Academic Search

Raman scattering (RS) and Fourier transform infrared (FTIR) spectroscopy have been applied to the study of local structure of lithium manganese oxides. We report the analysis of the vibrational spectra of spinel LiMn2O4 structure using both the classical group factor analysis (Oh7) and a local environment model. The RS and FTIR spectra are analysed on the basis of LiO4 tetrahedra

C. M. Julien; M. Massot

2003-01-01

262

Improved lithium manganese oxide spinel\\/graphite Li-ion cells for high-power applications  

Microsoft Academic Search

The degradation mechanism of lithium manganese oxide spinel\\/graphite Li-ion cells using LiPF6-based electrolyte was investigated by a Mn-dissolution approach during high-temperature storage, and by ac impedance measurement using a reference electrode-equipped cell. Through these studies, we confirmed that Mn ions were dissolved from the spinel cathode in the electrolyte and were subsequently reduced on the lithiated graphite electrode surface, due

K Amine; J Liu; S Kang; I Belharouak; Y Hyung; D Vissers; G Henriksen

2004-01-01

263

Lattice dynamics and vibrational spectra of lithium manganese oxides: A computer simulation and spectroscopic study  

Microsoft Academic Search

The lattice vibrational modes of spinel-structured lithium manganese oxides have been calculated using atomistic modeling methods. The simulations allow the Raman and infrared spectra of lithiated, fully delithiated, and partially delithiated phases to be assigned for the first time. Calculations for the spinels LiMnâOâ, λ-MnOâ, and Li{sub 0.5}MnâOâ are compared with experimental Raman data measured for thin films of the

Brett Ammundsen; Gary R. Burns; M. Saiful Islam; Hirofumi Kanoh; J. Roziere

1999-01-01

264

Selective ortho-methylation of phenol with methanol over copper manganese mixed-oxide spinel catalysts  

Microsoft Academic Search

Methylation of phenol with methanol as an alkylating agent to produce 2,6-xylenol was investigated over copper manganese mixed oxide spinels, CuxMn3?xO4 (x=0, 0.25, 0.5, 0.75, and 1) prepared through co-precipitation. The catalytic activity strongly depends on the composition, acid–base properties, and structural stability. Various parameters, including catalyst composition, reaction temperature, feed composition, and durability of the catalyst during methylation, were

A. Satyanarayana Reddy; Chinnakonda S. Gopinath; Satyanarayana Chilukuri

2006-01-01

265

Crystal chemistry of non-perovskite manganese oxides - implications for magnetic properties  

Microsoft Academic Search

This paper reviews crystal structures of ternary manganese oxides and their implications for magnetic properties. We point out the critical role of the counter-cation (A) size in driving given stoichiometries to different structure types, in particular AMnO3 compositions to ilmenite or perovskite structure, or A2MnO4 ones to spinel or K2NiF4 type. Mn2+ lies near the size borderline. It occupies the

P. Strobel; A. Ibarra-Palos; M. Pernet; S. Zouari; W. Cheikh-Rouhou; A. Cheikh-Rouhou

2004-01-01

266

X-ray diffraction and impedance spectroscopy studies of lithium manganese oxide spinel  

Microsoft Academic Search

Phase transition in lithium manganese oxide spinel synthesized by sol–gel technique and in samples prepared from commercially available powders of LiMn2O4 (Alfa-Aesar and Sigma–Aldrich) was investigated. In addition to the standard impedance measurements and the X-ray diffraction in Bragg–Brentano geometry, simultaneous measurements of impedance spectrum and X-ray pattern in non-focusing geometry were performed in the temperature range between ?25 and

M. Kope?; D. Lisovytskiy; M. Marzantowicz; J. R. Dygas; F. Krok; Z. Kaszkur; J. Pielaszek

2006-01-01

267

Synthesis and electrochemical studies of manganese oxides with spinel structure in aqueous electrolyte (9 M KOH)  

Microsoft Academic Search

Oxides with spinel structure have received widespread attention as being suitable electrode materials for rechargeable Li-ion batteries. So far they have mostly been synthesized at relatively high temperatures of between 700 and 800 °C. Here, we describe a new synthesis route to LiMn2O4 and manganese dioxides with spinel structure based on the freeze-drying of aqueous solutions and allowing the preparation

H. Schlörb; M. Bungs; W. Plieth

1997-01-01

268

Effect of oxygen non-stoichiometry on the electrochemical performance of lithium manganese oxide spinels  

Microsoft Academic Search

The effect of oxygen non-stoichiometry on the electrochemical performance of lithium manganese oxide spinels is investigated. Spinels with different oxygen contents are obtained from citrate gel synthesis followed by calcination in air in the temperature range 200–850°C. Spinels that were formed at low temperatures are found suitable for 3V applications, whereas those formed at high temperatures perform better at 4V.

A. R Naghash; Jim Y Lee

2001-01-01

269

Performance of lithium-manganese oxide spinel electrodes in a lithium polymer electrolyte cell  

Microsoft Academic Search

The cycling performance of a lithium-manganese oxide spinel (prepared from MnO2 and Li2CO3) has been investigated as a function of preparation temperature in a lithium polymer electrolyte cell. Excellent reversibility and high rate performance have been observed from a spinel phase prepared at 450 C and of general formula Li(x)Mn(2-z)O(4) x = 0.0-1.13, z = 0.0-0.33. This phase has a

W. J. Macklin; R. J. Neat; R. J. Powell

1991-01-01

270

Preparation of lithium manganese oxide fine particles by spray pyrolysis and their electrochemical properties  

Microsoft Academic Search

Highly crystalline nano-sized lithium manganese oxide particles were fabricated by spray pyrolysis. The resultant particles had well-developed facet planes in a transmission electron microscopy (TEM) image and electron diffraction pattern from a single particle also showed clear diffraction spots, indicating that the prepared particles were highly crystalline. The mean crystallite size estimated from X-ray diffraction peaks was ca. 18nm, which

Y. Iriyama; Y. Tachibana; R. Sasasoka; N. Kuwata; T. Abe; M. Inaba; A. Tasaka; K. Kikuchi; J. Kawamura; Z. Ogumi

2007-01-01

271

High resolution electron energy loss spectroscopy of manganese oxides: Application to Mn 3O 4 nanoparticles  

Microsoft Academic Search

Manganese oxides particularly Mn3O4 Hausmannite are currently used in many industrial applications such as catalysis, magnetism, electrochemistry or air contamination. The downsizing of the particle size of such material permits an improvement of its intrinsic properties and a consequent increase in its performances compared to a classical micron-sized material. Here, we report a novel synthesis of hydrophilic nano-sized Mn3O4, a

L. Laffont; P. Gibot

2010-01-01

272

Non-platinum electrocatalysts: Manganese oxide nanoparticle-cobaltporphyrin binary catalysts for oxygen reduction  

Microsoft Academic Search

This study is concerned with the development of non-platinum electrocatalysts for the efficient 4-electron reduction of molecular\\u000a oxygen to water in acidic media. A binary catalyst composed of electrodeposited manganese oxide nanoparticles (nano-MnO\\u000a x\\u000a ) and cobalt porphyrin macro complex (CoP) has been proposed in. The modification of glassy carbon (GC) electrode with CoP\\u000a alone resulted in a significant positive

Mohamed S. El-Deab; Sameh H. Othman; Takeyoshi Okajima; Takeo Ohsaka

2008-01-01

273

Biological water-oxidizing complex: a nano-sized manganese-calcium oxide in a protein environment.  

PubMed

The resolution of Photosystem II (PS II) crystals has been improved using isolated PS II from the thermophilic cyanobacterium Thermosynechococcus vulcanus. The new 1.9 Å resolution data have provided detailed information on the structure of the water-oxidizing complex (Umena et al. Nature 473: 55-61, 2011). The atomic level structure of the manganese-calcium cluster is important for understanding the mechanism of water oxidation and to design an efficient catalyst for water oxidation in artificial photosynthetic systems. Here, we have briefly reviewed our knowledge of the structure and function of the cluster. PMID:22941557

Najafpour, Mohammad Mahdi; Moghaddam, Atefeh Nemati; Yang, Young Nam; Aro, Eva-Mari; Carpentier, Robert; Eaton-Rye, Julian J; Lee, Choon-Hwan; Allakhverdiev, Suleyman I

2012-10-01

274

Sorption of ferric iron from ferrioxamine B to synthetic and biogenic layer type manganese oxides  

NASA Astrophysics Data System (ADS)

Siderophores are biogenic chelating agents produced in terrestrial and marine environments that increase the bioavailability of ferric iron. Recent work has suggested that both aqueous and solid-phase Mn(III) may affect siderophore-mediated iron transport, but scant information appears to be available about the potential roles of layer type manganese oxides, which are relatively abundant in soils and the oligotrophic marine water column. To probe the effects of layer type manganese oxides on the stability of aqueous Fe-siderophore complexes, we studied the sorption of ferrioxamine B [Fe(III)HDFOB +, an Fe(III) chelate of the trihydroxamate siderophore desferrioxamine B (DFOB)] to two synthetic birnessites [layer type Mn(III,IV) oxides] and a biogenic birnessite produced by Pseudomonas putida GB-1. We found that all of these predominantly Mn(IV) oxides greatly reduced the aqueous concentration of Fe(III)HDFOB + at pH 8. Analysis of Fe K-edge EXAFS spectra indicated that a dominant fraction of Fe(III) associated with the Mn(IV) oxides is not complexed by DFOB as in solution, but instead Fe(III) is specifically adsorbed to the mineral structure at multiple sites, thus indicating that the Mn(IV) oxides displaced Fe(III) from the siderophore complex. These results indicate that layer type manganese oxides, including biogenic minerals, may sequester iron from soluble ferric complexes. We conclude that the sorption of iron-siderophore complexes may play a significant role in the bioavailability and biogeochemical cycling of iron in marine and terrestrial environments.

Duckworth, Owen W.; Bargar, John R.; Sposito, Garrison

2008-07-01

275

Siderophore-manganese(III) interactions. I. Air-oxidation of manganese(ll) promoted by desferrioxamine B.  

PubMed

Recent studies suggest that aqueous Mn(ll) complexes, particularly those with non-carboxylated ligands such as microbial siderophores, may be stable in soil and aquatic environments. In this paper, we determine the stability constants for Mn(ll) and Mn(lll) complexes with the common trihydroxamate siderophore, desferrioxamine B (DFOB). Base and redox titrations were conducted to determine DFOB conditional protonation constants and conditional stability constants for 1:1 DFOB complexes with Mn(ll) and Mn(lll). The conditional protonation constants agree well with literature values. We determined stability constants for three Mn(ll)-DFOB species and one Mn(lll)-DFOB species at 25 degrees C in 0.1 M NaCl. The Mn(lll) HDFOB+ complex can be formed readily by air-oxidation of Mn(ll)-DFOB. This reaction exhibits pseudo first-order kinetics with a rate coefficient that can be characterized as the product of oxygen concentration with a linear combination of the concentrations of the three Mn(ll)-DFOB complexes. The second-order rate coefficients appearing in this linear combination are 1 to 2 orders of magnitude smaller than that associated with oxidation of the hydrolytic species Mn(OH)(0)2. The Mn(lll)HDFOB+ complex is stable for pH in the range of 7.0-11.3; but, at pH < 7.0 it decomposes by internal electron transfer, yielding oxidized DFOB products and Mn(ll). For p[H+] > 11.3, the complex degrades by disproportionation, yielding Mn(ll) and solid MnO2. This range of pH stability supports the hypothesis that aqueous Mn(lll) may play a vital role in the biogeochemical cycling of not only manganese, but also other elements, such as carbon, sulfur, nitrogen, oxygen, and redox-active metals. PMID:16173561

Duckworth, Owen W; Sposito, Garrison

2005-08-15

276

Manganese (Mn) Oxidation Increases Intracellular Mn in Pseudomonas putida GB-1  

PubMed Central

Bacterial manganese (Mn) oxidation plays an important role in the global biogeochemical cycling of Mn and other compounds, and the diversity and prevalence of Mn oxidizers have been well established. Despite many hypotheses of why these bacteria may oxidize Mn, the physiological reasons remain elusive. Intracellular Mn levels were determined for Pseudomonas putida GB-1 grown in the presence or absence of Mn by inductively coupled plasma mass spectrometry (ICP-MS). Mn oxidizing wild type P. putida GB-1 had higher intracellular Mn than non Mn oxidizing mutants grown under the same conditions. P. putida GB-1 had a 5 fold increase in intracellular Mn compared to the non Mn oxidizing mutant P. putida GB-1-007 and a 59 fold increase in intracellular Mn compared to P. putida GB-1 ?2665 ?2447. The intracellular Mn is primarily associated with the less than 3 kDa fraction, suggesting it is not bound to protein. Protein oxidation levels in Mn oxidizing and non oxidizing cultures were relatively similar, yet Mn oxidation did increase survival of P. putida GB-1 when oxidatively stressed. This study is the first to link Mn oxidation to Mn homeostasis and oxidative stress protection. PMID:24147089

Banh, Andy; Chavez, Valarie; Doi, Julia; Nguyen, Allison; Hernandez, Sophia; Ha, Vu; Jimenez, Peter; Espinoza, Fernanda; Johnson, Hope A.

2013-01-01

277

Manganese-oxidizing photosynthesis before the rise of cyanobacteria  

PubMed Central

The emergence of oxygen-producing (oxygenic) photosynthesis fundamentally transformed our planet; however, the processes that led to the evolution of biological water splitting have remained largely unknown. To illuminate this history, we examined the behavior of the ancient Mn cycle using newly obtained scientific drill cores through an early Paleoproterozoic succession (2.415 Ga) preserved in South Africa. These strata contain substantial Mn enrichments (up to ?17 wt %) well before those associated with the rise of oxygen such as the ?2.2 Ga Kalahari Mn deposit. Using microscale X-ray spectroscopic techniques coupled to optical and electron microscopy and carbon isotope ratios, we demonstrate that the Mn is hosted exclusively in carbonate mineral phases derived from reduction of Mn oxides during diagenesis of primary sediments. Additional observations of independent proxies for O2—multiple S isotopes (measured by isotope-ratio mass spectrometry and secondary ion mass spectrometry) and redox-sensitive detrital grains—reveal that the original Mn-oxide phases were not produced by reactions with O2, which points to a different high-potential oxidant. These results show that the oxidative branch of the Mn cycle predates the rise of oxygen, and provide strong support for the hypothesis that the water-oxidizing complex of photosystem II evolved from a former transitional photosystem capable of single-electron oxidation reactions of Mn. PMID:23798417

Johnson, Jena E.; Webb, Samuel M.; Thomas, Katherine; Ono, Shuhei; Kirschvink, Joseph L.; Fischer, Woodward W.

2013-01-01

278

Adsorption of ribose nucleotides on manganese oxides with varied mn/o ratio: implications for chemical evolution.  

PubMed

Manganese exists in different oxidation states under different environmental conditions with respect to redox potential. Various forms of manganese oxides, namely, Manganosite (MnO), Bixbyite (Mn(2)O(3)), Hausmannite (Mn(3)O(4)) and Pyrolusite (MnO(2)) were synthesized and their possible role in chemical evolution studied. Adsorption studies of ribose nucleotides (5'-AMP, 5'-GMP, 5'-CMP and 5'-UMP) on these manganese oxides at neutral pH, revealed a higher binding affinity to manganosite (MnO) compared to the other manganese oxides. That manganese oxides having a lower Mn-O ratio show higher binding affinity for the ribonucleotides indirectly implies that such oxides may have provided a surface onto which biomonomers could have been concentrated through selective adsorption. Purine nucleotides were adsorbed to a greater extent compared to the pyrimidine nucleotides. Adsorption data followed Langmuir adsorption isotherms, and X( m ) and K( L ) values were calculated. The nature of the interaction and mechanism was elucidated by infrared spectral studies conducted on the metal-oxide and ribonucleotide-metal-oxide adducts. PMID:21626404

Bhushan, Brij; Shanker, Uma; Kamaluddin

2011-10-01

279

Amorphous manganese-calcium oxides as a possible evolutionary origin for the CaMn? cluster in photosystem II.  

PubMed

In this paper a few calcium-manganese oxides and calcium-manganese minerals are studied as catalysts for water oxidation. The natural mineral marokite is also studied as a catalyst for water oxidation for the first time. Marokite is made up of edge-sharing Mn(3+) in a distorted octahedral environment and eight-coordinate Ca(2+) centered polyhedral layers. The structure is similar to recent models of the oxygen evolving complex in photosystem II. Thus, the oxygen evolving complex in photosystem II does not have an unusual structure and could be synthesized hydrothermally. Also in this paper, oxygen evolution is studied with marokite (CaMn?O?), pyrolusite (MnO?) and compared with hollandite (Ba(0.2)Ca(0.15)K(0.3)Mn(6.9)Al(0.2)Si(0.3)O(16)), hausmannite (Mn?O?), Mn?O?.H?O, Ca Mn?O?.H?O, CaMn?O?.H?O, CaMn?O?.H?O and synthetic marokite (CaMn?O?). I propose that the origin of the oxygen evolving complex in photosystem II resulted from absorption of calcium and manganese ions that were precipitated together in the archean oceans by protocyanobacteria because of changing pH from ~5 to ~8-10. As reported in this paper, amorphous calcium-manganese oxides with different ratios of manganese and calcium are effective catalysts for water oxidation. The bond types and lengths of the calcium and manganese ions in the calcium-manganese oxides are directly comparable to those in the OEC. This primitive structure of these amorphous calcium-manganese compounds could be changed and modified by environmental groups (amino acids) to form the oxygen evolving complex in photosystem II. PMID:20814743

Najafpour, Mohammad Mahdi

2011-06-01

280

Manganese-oxidizing photosynthesis before the rise of cyanobacteria  

NASA Astrophysics Data System (ADS)

The evolution of oxygenic photosynthesis was a singularity that fundamentally transformed our planet's core biogeochemical cycles and changed the redox structure of Earth's surface, crust, and mantle. To date, understanding the evolution of this molecular machinery has largely been derived from comparative biology. Several biochemical innovations enabled water-splitting, including a central photosynthetic pigment with a higher redox potential and coupled photosystems. However the critical photochemical invention was the water oxidizing complex (WOC) of photosystem II, a cubane cluster of four redox-active Mn atoms and a Ca atom bound by oxo bridges, that couple the single electron photochemistry of the photosystem to the four-electron oxidation of water to O2. Transitional forms of the WOC have been postulated, including an Mn-containing catalase-like peptide using an H2O2 donor, or uptake and integration of environmental Mn-oxides. One attractive hypothesis from the perspective of modern photo-assembly of the WOC posits an initial Mn(II)-oxidizing photosystem as a precursor to the WOC (Zubay, 1996; Allen and Martin, 2007). To test these hypotheses, we studied the behavior of the ancient Mn cycle captured by 2415 ± 6 Ma scientific drill cores retrieved by the Agouron Drilling Project through the Koegas Subgroup in Griqualand West, South Africa. This succession contains substantial Mn-enrichments (up to 17 wt.% in bulk). To better understand the petrogenesis and textural context of these deposits, we employed a novel X-ray absorption spectroscopy microprobe to make redox maps of ultra-thin sample sections at a 2?m scale. Coupled to light and electron microscopy and C isotopic measurements, we observe that all of the Mn is present as Mn(II), contained within carbonate minerals produced from early diagenetic reduction of Mn-oxide phases with organic matter. To assay the environmental oxidant responsible for the production of the Mn-oxides we examined two independent techniques sensitive to low levels of environmental O2—multiple sulfur isotopes analyzed using whole-rock IRMS and texture-specific SIMS techniques, and the presence of redox-sensitive detrital grains. Despite the conspicuous oxidation of Mn, both proxies reveal a lack of significant molecular oxygen present in the environment at this time (O2 << 1 ppm). These results provide strong geological support for the idea that an early Mn-oxidizing photosystem once existed as a transitional form prior to the evolution of the WOC of photosystem II and oxygenic photosynthesis. [Refs: Zubay J (1996) Origins of Life on the Earth and in the Cosmos, Academic Press: San Diego. Allen JF, Martin W (2007) Evolutionary biology: Out of thin air, Nature, 445, 610-612.

Johnson, J. E.; Webb, S.; Thomas, K. S.; Ono, S.; Kirschvink, J. L.; Fischer, W. W.

2012-12-01

281

Characterization of structure and electrochemical properties of lithium manganese oxides for lithium secondary batteries hydrothermally synthesized from ?-K x MnO 2  

Microsoft Academic Search

Lithium manganese oxides have attracted much attention as cathode materials for lithium secondary batteries in view of their high capacity and low toxicity. In this study, layered manganese oxide (?-KxMnO2) has been synthesized by thermal decomposition of KMnO4, and four lithium manganese oxide phases have been synthesized for the first time by mild hydrothermal reactions of this material with different

Yanluo Lu; Min Wei; Zhiqiang Wang; D. G. Evans; Xue Duan

2004-01-01

282

Geology, alteration, age, and origin of iron oxide-apatite deposits in Upper Eocene quartz monzonite, Zanjan district, NW Iran  

NASA Astrophysics Data System (ADS)

Iron oxide-apatite deposits are present in Upper Eocene pyroxene-quartz monzonitic rocks of the Zanjan district, northwestern Iran. Mineralization occurred in five stages: (1) deposition of disseminated magnetite and apatite in the host rock; (2) mineralization of massive and banded magnetite ores in veins and stockwork associated with minor brecciation and calcic alteration of host rocks; (3) deposition of sulfide ores together with potassic alteration; (4) formation of quartz and carbonate veins and sericite, chlorite, epidote, silica, carbonate, and tourmaline alteration; and (5) supergene alteration and weathering. U-Pb dating of monazite inclusions in the apatite indicates an age of 39.99 ± 0.24 Ma, which is nearly coeval with the time of emplacement of the host quartz monzonite, supporting the genetic connection. Fluid inclusions in the apatite have homogenization temperatures of about 300 °C and oxygen isotopic compositions of the magnetite support precipitation from magmatic fluids. Late-stage quartz resulted from the introduction of a cooler, less saline, and isotopically depleted fluid. The iron oxide-apatite deposits in the Tarom area of the Zanjan district are typical of a magmatic-hydrothermal origin and are similar to the Kiruna-type deposits with respect to mineral assemblages, fabric and structure of the iron ores, occurrence of the ore bodies, and wall rock alteration.

Nabatian, Ghasem; Ghaderi, Majid; Corfu, Fernando; Neubauer, Franz; Bernroider, Manfred; Prokofiev, Vsevolod; Honarmand, Maryam

2014-02-01

283

Nanophase Manganese Oxides: Chemisorbed Water and Small Particle Size Promote Large Thermodynamically Driven Shifts in Oxidation-Reduction Equilibria  

NASA Astrophysics Data System (ADS)

Manganese oxides are important in terrestrial and Martian settings, and changes in oxidation state (Mn 2+, 3+, 4+) produce different phases. This study focuses on changes in redox energetics at the nanoscale in the Mn-O system with water present. Nanophase hausmannite (Mn3O4), bixbyite (Mn2O3), and pyrolusite (MnO2) were synthesized using minor modifications of previously published methods, stored at room temperature, and then analyzed by powder-XRD, BET surface area measurement, and TGA for total water content. High-temperature oxide-melt drop solution calorimetry was performed on a series of characterized samples with known surface area and water content. The differential heat of water adsorption as a function of coverage was also measured. The surface enthalpies of manganese oxide phases, hausmannite (Mn3O4), bixbyite (Mn2O3), and pyrolusite (MnO2), were determined using the data from high-temperature oxide melt calorimetry and water adsorption calorimetry. Surface energy for the hydrous Mn3O4 tetragonal spinel phase is 0.96±0.08 J/m2, for Mn2O3 cubic phase is 1.29±0.10 J/m2, and for MnO2 cubic rutile phase is 1.64±0.10 J/m2. Surface energy for the anhydrous Mn3O4 is 1.31±0.08 J/m2, for Mn2O3 is 1.57±0.10 J/m2, and for MnO2 is 1.99±0.10 J/m2. Supporting preliminary findings, the spinel phase (hausmannite) has a lower surface energy than bixbyite, while the latter has a smaller surface energy than pyrolusite. We also observed phase changes, some of them rapidly reversible, associated with water adsorption/desorption for the nanophase manganese oxide assemblages. There are geochemical consequences. (1) At the nanoscale, both the pyrolusite/bixbyite and bixbyite/hausmannite equilibria are shifted to higher oxygen fugacity because the reduced phase has the lower surface energy. (2) The ready inter-conversion of phases with different oxidation states under aqueous conditions implies that, after a manganese oxide nanophase forms, it can easily transform to other phases with different oxidation states and water contents and perhaps record changes in environmental conditions after, as well as during, its initial formation.

Birkner, N.; Navrotsky, A.

2011-12-01

284

Directed vapor deposition of lithium manganese oxide films  

Microsoft Academic Search

Electron beam evaporation and sputtering techniques are used to fabricate multilayered thin film structures. However, these techniques suffer several drawbacks resulting from (i) the complex chemistries of the lithiated oxide layers used for the cathode and electrolyte, (ii) the need for precise microstructure control in systems with many metastable phases, and (iii) the low deposition rate and poor material utilization

Sang-Wan Jin

2008-01-01

285

Microbial reduction of manganese oxides - Interactions with iron and sulfur  

NASA Technical Reports Server (NTRS)

Alteromonas putrefaciens (strain MR-1) is capable of rapid Mn(IV) reduction under conditions of neutral pH and temperatures characteristic of the Oneida Lake, New York, sediments from which it was isolated. MR-1 also reduces Fe(3+) to Fe(2+), and disproportionates thiosulfate to sulfide and sulfite; independently, the Fe(2+) and sulfide act as rapid reductants of Mn. The addition of Fe(3+) or thiosulfate to cultures of MR-1 in the presence of oxidized Mn increases the rate and the extent of Mn reduction relative to that observed in the absence of Fe(3+) or thiosulfate. Furthermore, when Fe(3+) and Mn oxides are present conjointly, Fe(2+) does not appear until the reduction of the oxidized Mn is complete. These results demonstrate that the observed rates of Fe(2+) and sulfide production may underestimate the total rates of Fe and sulfate reduction in those environments containing oxidized Mn. These results also demonstrate the potential impact that a single microbe can exert on sediment geochemistry, and provide the basis for preliminary models of the complexity of microbial and geochemical interactions that occur.

Myers, Charles R.; Nealson, Kenneth H.

1988-01-01

286

Secondary cell with orthorhombic alkali metal/manganese oxide phase active cathode material  

DOEpatents

An alkali metal manganese oxide secondary cell is disclosed which can provide a high rate of discharge, good cycling capabilities, good stability of the cathode material, high specific energy (energy per unit of weight) and high energy density (energy per unit volume). The active material in the anode is an alkali metal and the active material in the cathode comprises an orthorhombic alkali metal manganese oxide which undergoes intercalation and deintercalation without a change in phase, resulting in a substantially linear change in voltage with change in the state of charge of the cell. The active material in the cathode is an orthorhombic structure having the formula M.sub.x Z.sub.y Mn.sub.(1-y) O.sub.2, where M is an alkali metal; Z is a metal capable of substituting for manganese in the orthorhombic structure such as iron, cobalt or titanium; x ranges from about 0.2 in the fully charged state to about 0.75 in the fully discharged state, and y ranges from 0 to 60 atomic %. Preferably, the cell is constructed with a solid electrolyte, but a liquid or gelatinous electrolyte may also be used in the cell.

Doeff, Marca M. (Hayward, CA); Peng, Marcus Y. (Cupertino, CA); Ma, Yanping (Albany, CA); Visco, Steven J. (Berkeley, CA); DeJonghe, Lutgard C. (Lafayette, CA)

1996-01-01

287

Oxide Formation Mechanisms in High Manganese Steel Welds  

NASA Astrophysics Data System (ADS)

Oxide inclusions in high-Mn steel welds were analyzed and almost all of which were found to belong to the MnO-Al2O3-SiO2 system. In this study, the inclusions were categorized based on MnS morphology into the following two types: (1) aluminosilicate with a MnS patch, or (2) aluminosilicate with a MnS shell. The most frequently detected was type 1, the formation mechanism of which was investigated using commercially available thermochemical computing software, FactSage™ (ver. 6.3). The thermodynamic calculations predicted that galaxite (MnAl2O4), tephroite (Mn2SiO4), and MnS could precipitate during solidification. However, because of the fast cooling rate in welding processes, galaxite and tephroite phases were unable to fully crystallize, but rather were supercooled as glassy phases. In order to confirm the validity of the thermodynamic calculations, the composition of the observed inclusions was compared with the MnO-SiO2-Al2O3 ternary phase diagram, resulting in remarkably good agreement. Furthermore, it was found that the type of the oxide inclusions was dependent on their location ( i.e., MnS shell- and MnS patch-type oxides were detected at the dendritic core and interdendritic boundary, respectively). Both types of oxides were occasionally found in one oxide, near the interdendritic boundary. This indicates that the morphology variation originates from the redistribution of solute due to fast solidification.

Kim, Dooyoung; Han, Kyutae; Lee, Bongkeun; Han, Ilwook; Park, Joo Hyun; Lee, Changhee

2014-04-01

288

Electrochromic performance, wettability and optical study of copper manganese oxide thin films: Effect of annealing temperature  

NASA Astrophysics Data System (ADS)

In the present work, the nanostructured copper manganese oxide (CMO) thin films were prepared from acetate based sol-gel precursors and deposited on glass and indium tin oxide (ITO) substrates by dip-coating technique. The films were annealed at 300, 400 and 500 °C in ambient atmosphere. The effects of annealing temperature on structural, morphological, wettability, electrochromic and optical properties of CMO thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDX), water contact angle measurement (WCA), cyclic voltammetry (CV) measurements and ultraviolet-visible (UV-vis) spectrophotometery. The presence of mixed oxide phases comprising of copper manganese oxide (CuMn2O4) and manganese oxide at different annealing temperature was confirmed by XRD patterns. The results showed that the Mn3O4 phase has been changed to Mn2O3 when the annealing temperature is increased from 300 to 500 °C. The FESEM images indicated that the granular surface morphology was sensitive to annealing temperature. EDX studies indicated that the thin films contained O, Mn and Cu species. Wettability studies showed that the water contact angle of the nanostructured CMO thin films coated on glass substrates was influenced by the variation of annealing temperature and the surface nature of thin films was changed from hydrophilic to hydrophobic. The results of CVs measurement indicated that the anodic and cathodic charge density and capacitance of all CMO samples decreased with increasing scan rate in potential range of -1-1 eV. Also, the annealed CMO thin film at 500 °C showed better electrochromic performance with respect to other samples at lower scan rate. The thickness, refractive index, extinction coefficient and optical band gap of thin films coated on glass substrates were calculated from reflectance and transmittance spectra using an iterative numerical method. The optical band gap of nanostructured CMO thin films increased with increasing annealing temperature.

Falahatgar, S. S.; Ghodsi, F. E.; Tepehan, F. Z.; Tepehan, G. G.; Turhan, ?.

2014-01-01

289

Spinel lithium manganese oxide nanoparticles: unique molten salt synthesis strategy and excellent electrochemical performances.  

PubMed

As a promising candidate cathode material, spinel lithium manganese oxide nanoparticles were successfully synthesized through a novel molten salt synthesis route at relatively low temperature, using manganese dioxide nanowires as precursor. A variety of techniques were applied to characterize the spinel nanomaterial, including X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscopy, and X-ray photoelectron spectroscopy. The average particle size of the resulting spinel nanoparticles was about 80 nm with narrow distribution. As cathode material for rechargeable lithium ion battery, the electrochemical properties were investigated. All the results show that the electrochemical performances of the homogeneous spinel nanoparticles were improved, which might be ascribed to large specific surface area, fairly narrow size distribution, and the unique synthesis strategy. PMID:19908558

Wang, Xiong; Zhu, Juanjuan; Liu, Yingjie

2009-11-01

290

Fragments of layered manganese oxide are the real water oxidation catalyst after transformation of molecular precursor on clay.  

PubMed

A binuclear manganese molecular complex [(OH2)(terpy)Mn(?-O)2Mn(terpy)(OH2)](3+) (1) is the most prominent structural and functional model of the water-oxidizing Mn complex operating in plants and cyanobacteria. Supported on montmorillonite clay and using Ce(IV) as a chemical oxidant, 1 has been reported to be one of the best Mn-based molecular catalysts toward water oxidation. By X-ray absorption spectroscopy and kinetic analysis of the oxygen evolution reaction, we show that [(OH2)(terpy)Mn(?-O)2Mn(terpy)(OH2)](3+) is transformed into layered type Mn-oxide particles which are the actual water oxidation catalyst. PMID:24798550

Najafpour, M M; Moghaddam, Atefeh N; Dau, Holger; Zaharieva, Ivelina

2014-05-21

291

Abiotic sulfide oxidation via manganese reduction fuels the deep biosphere  

Microsoft Academic Search

The deep biosphere in marine sediments consists of large populations of metabolically active Bacteria and Archaea [1, 2]. Buried organic carbon is the main energy source for the deep biosphere and is anaerobically oxidized via nitrate-, Mn(IV)-, Fe(III)-, sulfate or carbonate-reduction. Sulfate reduction has been identified as the most important of these processes [3, 4] yet sulfate is typically quantitatively

S. Bottrell; M. E. Böttcher; A. Schippers; R. Parkes; R. Raiswell

2009-01-01

292

Tetragonal Distortion of the Oxide Spinels Containing Cobalt and Manganese  

Microsoft Academic Search

The temperature dependences of tetragonal-cubic phase transition of Co-Mn manganites are given; this transition is shown to be of the 1st order. The phase diagram in the usual chemical meaning is shown. The cation distribution of the Co-Mn oxide spinel is measured by Fe-Kalpha radiation; Mn ions tend to occupy B-site preferentially. The lattice parameters of specimens which were quenched

Ikuo Aoki

1962-01-01

293

The Surface Structure of the Proton-Exchanged Lithium Manganese Oxide Spinels and Their Lithium-Ion Sieve Properties  

Microsoft Academic Search

The spinel structure and the valence states of the Mn ions both at the surface and the bulk were characterized for the Li+extracted and inserted manganese oxide spinels. The Li+extraction from the orthorhombic LiMn2O4spinel results in the formation of the cubic spinel, the crystal structure of which is the same as?-MnO2. The LiMn2O4spinel prepared from an electrolytically prepared manganese dioxide

K. Sato; D. M. Poojary; A. Clearfield; M. Kohno; Y. Inoue

1997-01-01

294

Electrochemical properties of spinel-type manganese oxide\\/porous carbon nanocomposite powders in 1 M KOH aqueous solution  

Microsoft Academic Search

Spinel-type manganese oxide\\/porous carbon (Mn3O4\\/C) nanocomposite powders have been simply prepared by a thermal decomposition of manganese gluconate dihydrate under an Ar gas flow at above 600°C. The structure and texture of the Mn3O4\\/C nanocomposite powders are investigated by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) equipped scanning transmission electron microscopy (STEM), transmission electron microscopy (TEM), selected area-electron diffraction (SA-ED),

Tomoki Tsumura; Koichiro Tsumori; Goichi Shimizu; Masahiro Toyoda

295

Green decomposition of organic dyes using octahedral molecular sieve manganese oxide catalysts.  

PubMed

The catalytic degradation of organic dye (methylene blue, MB) has been studied using green oxidation methods (tertiary-butyl hydrogen peroxide, TBHP, as the oxidant with several doped mixed-valent and regular manganese oxide catalysts in water) at room and higher temperatures. These catalysts belong to a class of porous manganese oxides known as octahedral molecular sieves (OMS). The most active catalysts were those of Mo(6+)- and V(5+)-doped OMS. Rates of reaction were found to be first-order with respect to the dye. TBHP has been found to enhance the MB decomposition, whereas H(2)O(2) does not. Reactions were studied at pH 3-11. The optimum pH for these reactions was pH 3. Dye-decomposing activity was proportional to the amount of catalyst used, and a significant increase in catalytic activity was observed with increasing temperature. X-ray diffraction (XRD), energy dispersive spectroscopy (EDX), and thermogravimetric analysis (TGA) studies showed that no changes in the catalyst structure occurred after the dye-degradation reaction. The products as analyzed by electrospray ionization mass spectrometry (ESI-MS) showed that MB was successively decomposed through different intermediate species. PMID:19178167

Sriskandakumar, Thamayanthy; Opembe, Naftali; Chen, Chun-Hu; Morey, Aimee; King'ondu, Cecil; Suib, Steven L

2009-02-26

296

Influence of extractable soil manganese on oxidation capacity of different soils in Korea  

NASA Astrophysics Data System (ADS)

We examined the relationship between soil oxidation capacity and extractable soil manganese, iron oxides, and other soil properties. The Korean soils examined in this study exhibited low to medium Cr oxidation capacities, oxidizing 0.00-0.47 mmol/kg, except for TG-4 soils, which had the highest capacity for oxidizing added Cr(III) [>1.01 mmol/kg of oxidized Cr(VI)]. TG and US soils, with high Mn contents, had relatively high oxidation capacities. The Mn amounts extracted by dithionite-citrate-bicarbonate (DCB) (Mnd), NH2OH·HCl (Mnh), and hydroquinone (Mnr) were generally very similar, except for the YS1 soils, and were well correlated. Only small proportions of either total Mn or DCB-extractable Mn were extracted by NH2OH·HCl and hydroquinone in the YS1 soils, suggesting inclusion of NH2OH·HCl and hydroquinone-resistant Mn oxides, because these extractants are weaker reductants than DCB. No Cr oxidation test results were closely related to total Mn concentrations, but Mnd, Mnh, and Mnr showed a relatively high correlation with the Cr tests ( r = 0.655-0.851; P < 0.01). The concentrations of Mnd and Mnh were better correlated with the Cr oxidation tests than was the Mnr concentration, suggesting that the oxidation capacity of our soil samples can be better explained by Mnd and Mnh than by Mnr. The first component in principal components analysis indicated that extractable soil Mn was a main factor controlling net Cr oxidation in the soils. Total soil Mn, Fe oxides, and the clay fraction are crucial for predicting the mobility of pollutants and heavy metals in soils. The second principal component indicated that the presence of Fe oxides in soils had a significant relationship with the clay fraction and total Mn oxide, and was also related to heavy-metal concentrations (Zn, Cd, and Cu, but not Pb).

Chon, Chul-Min; Kim, Jae Gon; Lee, Gyoo Ho; Kim, Tack Hyun

2008-08-01

297

Metal Inhibition of Growth and Manganese Oxidation in Pseudomonas putida GB-1  

NASA Astrophysics Data System (ADS)

Biogenic manganese oxides (MnO2) are ubiquitous nanoparticulate minerals that contribute to the adsorption of nutrient and toxicant metals, the oxidative degradation of various organic compounds, and the respiration of metal-reducing bacteria in aquatic and terrestrial environments. The formation of these minerals is catalyzed by a diverse and widely-distributed group of bacteria and fungi, often through the enzymatic oxidation of aqueous Mn(II) to Mn(IV). In metal-impacted ecosystems, toxicant metals may alter the viability and metabolic activity of Mn-oxidizing organisms, thereby limiting the conditions under which biogenic MnO2 can form and diminishing their potential as adsorbent materials. Pseudomonas putida GB-1 (P. putida GB-1) is a model Mn-oxidizing laboratory culture representative of freshwater and soil biofilm-forming bacteria. Manganese oxidation in P. putida GB-1 occurs via two single-electron-transfer reactions, involving a multicopper oxidase enzyme found on the bacterial outer membrane surface. Near the onset of the stationary phase of growth, dark brown MnO2 particles are deposited in a matrix of bacterial cells and extracellular polymeric substances, thus forming heterogeneous biomineral assemblages. In this study, we assessed the influence of various transition metals on microbial growth and manganese oxidation capacity in a P. putida GB-1 culture propagated in a nutrient-rich growth medium. The concentration-response behavior of actively growing P. putida GB-1 cells was investigated for Fe, Co, Ni, Cu and Zn at pH ? 6 in the presence and absence of 1 mM Mn. Toxicity parameters such as EC0, EC50 and Hillslope, and EC100 were obtained from the sigmoidal concentration-response curves. The extent of MnO2 formation in the presence of the various metal cations was documented 24, 50, 74 and 104 h after the metal-amended medium was inoculated. Toxicity values were compared to twelve physicochemical properties of the metals tested. Significant correlations were found between EC50 values and reduction potential, electronegativity and the covalent index. Thus, metal toxicity in P. putida GB-1 appears to be modulated by the metals’ propensity to participate in covalent interactions and generate oxidative stress. This study provides a quantitative measure of metal tolerance in P. putida GB-1, as well as operational limits for Mn oxidation in this model system, both of which have important implications for the reactivity of P. putida-MnO2 assemblages formed in metal-impacted ecosystems.

Pena, J.; Sposito, G.

2009-12-01

298

The Structure and Properties of Plasma Sprayed Iron Oxide Doped Manganese Cobalt Oxide Spinel Coatings for SOFC Metallic Interconnectors  

NASA Astrophysics Data System (ADS)

Manganese cobalt oxide spinel doped with Fe2O3 was studied as a protective coating on ferritic stainless steel interconnects. Chromium alloying causes problems at high operation temperatures in such oxidizing conditions where chromium compounds evaporate and poison the cathode active area, causing the degradation of the solid oxide fuel cell. In order to prevent chromium evaporation, these interconnectors need a protective coating to block the chromium evaporation and to maintain an adequate electrical conductivity. Thermal spraying is regarded as a promising way to produce dense and protective layers. In the present work, the ceramic Mn-Co-Fe oxide spinel coatings were produced by using the atmospheric plasma spray process. Coatings with low thickness and low amount of porosity were produced by optimizing deposition conditions. The original spinel structure decomposed because of the fast transformation of solid-liquid-solid states but was partially restored by using post-annealing treatment.

Puranen, Jouni; Lagerbom, Juha; Hyvärinen, Leo; Kylmälahti, Mikko; Himanen, Olli; Pihlatie, Mikko; Kiviaho, Jari; Vuoristo, Petri

2011-01-01

299

The Transparent Conductive Properties of Manganese-Doped Zinc Oxide Films Deposited by Chemical Bath Deposition  

NASA Astrophysics Data System (ADS)

Manganese-doped zinc oxide (Mn-doped ZnO) thin films were prepared using chemical bath deposition (CBD), and the impacts of the manganese dopant concentration on the structure, electrical resistivity, optical transmission, and magnetic properties were investigated using x-ray diffractometry, Hall-effect measurements, ultraviolet-visible-near-infrared (UV-Vis-IR) spectrophotometry, and vibrating sample magnetometry (VSM), respectively. The concentration of the manganese dopant in the ZnO thin film critically impacted the resulting properties, and the 4.0 at.% Mn-doped ZnO film had a resistivity of 5.8 × 10-2 ?cm, transmittance of 75.6% in the visible light range, and bandgap of 3.30 eV when the film was annealed at 600°C in an Ar + H2 atmosphere. Annealing the film could enhance its magnetic properties such that the film had a saturation magnetization of 21.0 emu/cm3 and a coercivity of 45.7 Oe after annealing at 600°C. Because of these electrical, optical, and magnetic properties, Mn-doped thin films are promising for use in spintronic devices.

Fang, J. S.; Luo, W. H.; Hsu, C. H.; Yang, J. C.; Tsai, T. K.

2012-01-01

300

The stabilization of layered manganese oxides for use in rechargeable lithium batteries  

SciTech Connect

The layered structure Li{sub x}TiS{sub 2} and Li{sub x}CoO{sub 2} are excellent reversible cathodes for lithium batteries. However, layered lithium manganese oxides are metastable relative to the spinel form on cycling in lithium batteries. They may be stabilized in the layer form by insertion of larger ions such as potassium in the interlayer region, which minimizes the diffusion of the manganese ions from the MnO{sub 2} blocks. Their low conductivity is an impediment to their use in high rate batteries. Cobalt can be doped into the layered alkali manganese dioxides, M{sub x}Mn{sub 1{minus}y}Co{sub y}O{sub 2} for M = K or Na, during the hydrothermal synthesis from the alkali permanganates. A single phase is obtained up to about 5% mole cobalt. The cobalt doping is found to enhance the conductivity by two orders of magnitude relative to pure K{sub x}MnO{sub 2}.

Whittingham, M.S.; Zavalij, P.; Zhang, F.; Sharma, P.; Moore, G.

2000-07-01

301

Illumina sequencing of fungi associated with manganese oxide deposits in cave systems  

NASA Astrophysics Data System (ADS)

The environmental cycling of manganese (Mn) remains relatively poorly characterized when compared with other metals such as iron. However, fungi have been observed to produce Mn(III/IV) oxides resembling buserite, birnessite, and todorokite on the periphery of vegetative hyphae, hyphal branching points and at the base of fruiting bodies. Recent studies indicate that some of these oxides may be generated by a two-stage reaction with soluble Mn(II) and biogenic reactive oxygen species for some groups of fungi, in particular the Ascomycota. These oxides can provide a versatile protective barrier or aid in the capture of trace metals in the environment, although the exact evolutionary function and trigger is unclear. In this study, two caves in the southern Appalachians, a pristine cave and an anthropogenically impacted cave, were compared by analyzing fungal community assemblages in manganese oxide rich deposits. Quantitative PCR data indicated that fungi are present in a low abundance (<1%) in all locations sampled within the caves. Among amplified DNA sequences retrieved in an 18S rDNA clone library, over 88% were representative of the phylum Basidiomycota (predominantly Agaricomycetes), 2.74% of Ascomycota, 2.28% of Blastocladiomycota and Chytridiomycota, 0.46% of Zygomycota, and 3.65% of Eukarya or Fungi incertae sedis. Using Illumina's MiSeq to sequence amplicons of the fungal ITS1 gene has yielded roughly 100,000-200,000 paired-end reads per sample. These data are currently being analyzed to compare fungal communities before and after induced Mn oxidation in the field. In addition, sites within the pristine cave are being compared with analogous sites in the impacted cave. Culturing efforts have thus far yielded Mn oxide producing members of the orders Glomerales and Pleosporales as well as two Genus incertae sedis (Fungal sp. YECT1, and Fungal sp. YECT3, growing on discarded electrical tape) that do not appear to be closely related to any other known Mn oxidizing fungi.

Zorn, B. T.; Santelli, C. M.; Carmichael, S. K.; Pepe-Ranney, C. P.; Roble, L.; Carmichael, M.; Bräuer, S.

2013-12-01

302

Metalloradical Complexes of Manganese and Chromium Featuring an Oxidatively Rearranged Ligand  

PubMed Central

Redox events involving both metal and ligand sites are receiving increased attention since a number of biological processes direct redox equivalents toward functional residues. Metalloradical synthetic analogs remain scarce and require better definition of their mode of formation and subsequent operation. The trisamido-amine ligand [(RNC6H4)3N]3?, where R is the electron-rich 4-t-BuPh, is employed in this study to generate redox active residues in manganese and chromium complexes. Solutions of [(L1)Mn(II)–THF]? in THF are oxidized by dioxygen to afford [(L1re–1)Mn(III)–(O)2–Mn(III)(L1re–1)]2? as the major product. The rare dinuclear manganese (III,III) core is stabilized by a rearranged ligand that has undergone an one-electron oxidative transformation, followed by retention of the oxidation equivalent as a ? radical in an o-diiminobenzosemiquinonate moiety. Magnetic studies indicate that the ligand-centered radical is stabilized by means of extended antiferromagnetic coupling between the S = ½ radical and the adjacent S = 2 Mn(III) site, as well as between the two Mn(III) centers via the dioxo bridge. Electrochemical and EPR data suggest that this system can store higher levels of oxidation potency. Entry to the corresponding Cr(III) chemistry is achieved by employing CrCl3 to access both [(L1)Cr(III)–THF] and [(L1re–1)Cr(III)–THF(Cl)], featuring the intact and the oxidatively rearranged ligands, respectively. The latter is generated by ligand-centered oxidation of the former compound. The rearranged ligand is perceived to be the product of an one-electron oxidation of the intact ligand to afford a metal-bound aminyl radical that subsequently mediates a radical 1,4-(N-to-N) aryl migration. PMID:18937446

Celenligil-Cetin, Remle; Paraskevopoulou, Patrina; Lalioti, Nikolia; Sanakis, Yiannis; Staples, Richard J.; Rath, Nigam P.; Stavropoulos, Pericles

2009-01-01

303

Coprecipitation and redox reactions of manganese oxides with copper and nickel  

USGS Publications Warehouse

Open-system, continuous-titration experiments have been done in which a slow flux of ???0.02 molar solution of Mn2+ chloride, nitrate, or perchlorate with Cu2+ or Ni2+ in lesser concentrations was introduced into an aerated reactor solution held at constant temperature and at constant pH by a pH-stat titrator that added dilute NaOH. The resulting mixtures of metal oxyhydroxides and their native solutions were aged for periods as long as 2 1/2 years. Fresh and aged precipitates were characterized by chemical analysis, oxidation state determinations, X-ray and electron diffraction, and electron microscopy. The precipitates can be described as mixtures of oxide and oxyhydroxide species, using concepts of equilibrium and nonequilibrium chemical thermodynamics. The metal-ion content of the aged precipitates in systems that contained copper is distributed among three principal components. One of these is a mixed oxide Cu2Mn3O8 in which all Mn is in the 4+ oxidation state. A major component in all precipitates is feitknechtite, ??MnOOH. These forms are supplemented by CuO or by birnessite or ramsdellite forms of MnO2 where stoichiometry and thermodynamic calculations predict them. In systems that contained nickel and manganese, identifiable components included ??MnOOH, Ni(OH)2, and the same two forms of MnO2. The oxidation number of the precipitated manganese increased during aging, and the pH of the supernatant solution decreased. The maximum Mn oxidation number observed was 3.55 in an Mn + Cu precipitate aged for 18 months. Concentrations of Cu2+ and Ni2+ generally decreased to values substantially below those predicted by oxide or hydroxide equilibrium. Scavenging effects of this type are common in natural aqueous systems. ?? 1989.

Hem, J. D.; Lind, C. J.; Roberson, C. E.

1989-01-01

304

Simulation of the surface structure of lithium manganese oxide spinel  

NASA Astrophysics Data System (ADS)

Simulations of the surface structure of low-index surfaces of LiMn2O4 (LMO), a candidate Li-ion battery electrode material, have been performed within the GGA+U approximation, using the VASP code. Surfaces of (001), (110), and (111) orientation were considered, with at least two terminations treated in each case. A slab geometry was employed, with termination-layer vacancies introduced to remove the bulk dipole moment while maintaining ideal stoichiometry. To complement static-structure relaxation calculations, molecular-dynamics simulations were performed to explore the phase space of possible surface reconstructions. A reconstruction is predicted for the Mn-terminated (111) surface, in which the top layers mix in stoichiometric proportions to form an LMO termination layer with square-planar-coordinated Mn. Average surface Mn oxidation states are reduced, relative to the bulk, for all surfaces considered, as a consequence of the lower-energy cost of Jahn-Teller distortion at the surface. Threefold-coordinated surface Mn, found for two terminations, is divalent, which may enhance its vulnerability to dissolution. The Li-terminated (001) surface is lowest in energy, consistent with previous classical-potential simulations for MgAl2O4 that showed the Mg-terminated (001) surface to be lowest in energy.

Benedek, R.; Thackeray, M. M.

2011-05-01

305

Simulation of the surface structure of lithium manganese oxide spinel.  

SciTech Connect

Simulations of the surface structure of low-index surfaces of LiMn{sub 2}O{sub 4} (LMO), a candidate Li-ion battery electrode material, have been performed within the GGA+U approximation, using the VASP code. Surfaces of (001), (110), and (111) orientation were considered, with at least two terminations treated in each case. A slab geometry was employed, with termination-layer vacancies introduced to remove the bulk dipole moment while maintaining ideal stoichiometry. To complement static-structure relaxation calculations, molecular-dynamics simulations were performed to explore the phase space of possible surface reconstructions. A reconstruction is predicted for the Mn-terminated (111) surface, in which the top layers mix in stoichiometric proportions to form an LMO termination layer with square-planar-coordinated Mn. Average surface Mn oxidation states are reduced, relative to the bulk, for all surfaces considered, as a consequence of the lower-energy cost of Jahn-Teller distortion at the surface. Threefold-coordinated surface Mn, found for two terminations, is divalent, which may enhance its vulnerability to dissolution. The Li-terminated (001) surface is lowest in energy, consistent with previous classical-potential simulations for MgAl{sub 2}O{sub 4} that showed the Mg-terminated (001) surface to be lowest in energy.

Benedek, R.; Thackeray, M. M. (Chemical Sciences and Engineering Division)

2011-05-31

306

Oxidative stress involvement in manganese-induced alpha-synuclein oligomerization in organotypic brain slice cultures.  

PubMed

Overexposure to manganese (Mn) has been known to induce neuronal damage. However, little is known of the role that reactive oxygen species (ROS) play in protein aggregation resulting from Mn exposure. The current study investigated whether oxidative stress is involved in manganese-induced alpha-synuclein oligomerization in organotypic brain slices. After application of Mn (0-400?M) for 24h, there was a dose-dependent increase in average percentage of propidium iodide positive (PI(+)) nuclei in slices and levels of lactate dehydrogenase (LDH) in the culture medium. Moreover, the treatment with Mn resulted in a dose-dependent increase in neurocyte apoptosis, ROS level, and decrease in superoxide dismutase (SOD) activity. Mn also caused oxidative damage in cell lipid and protein. At the same time, the exposure of Mn leaded to significantly increase in the expression of alpha-synuclein mRNA and protein. Alpha-synuclein oligomerization occurred in Mn-treated slices, especially on membrane-bound form. It indicated that alpha-synuclein oligomers were more likely to combination cell membranes and resulting in membrane damage. Mn-induced neurocyte damage and alpha-synuclein oligomerization were also partially alleviated by the pretreatment with GSH and aggravated by H2O2 pretreatment. The findings revealed Mn might exert its neurotoxic effects by oxidative stress-mediated alpha-synuclein oligomerization in organotypic brain slices. PMID:23353026

Xu, Bin; Wu, Sheng-Wen; Lu, Chun-Wei; Deng, Yu; Liu, Wei; Wei, Yan-Gang; Yang, Tian-Yao; Xu, Zhao-Fa

2013-03-01

307

Crystal chemistry of non-perovskite manganese oxides - implications for magnetic properties  

NASA Astrophysics Data System (ADS)

This paper reviews crystal structures of ternary manganese oxides and their implications for magnetic properties. We point out the critical role of the counter-cation (A) size in driving given stoichiometries to different structure types, in particular AMnO3 compositions to ilmenite or perovskite structure, or A2MnO4 ones to spinel or K2NiF4 type. Mn2+ lies near the size borderline. It occupies the large site in A2Mn2O7 pyrochlores, contrary to Mn4+, and occupies separate crystallographic sites in known mixed-valent Mn2+-Mn3+ or 4+ oxides. The bond distances, Mn-O-Mn bonding angles and Mn sublattice topology are given for the main A-Mn-O structures. Only the perovskite and K2NiF4 structures give Mn-O-Mn angles near 180°, while these are close to 90° in spinels, to 135° in pyrochlores and marokites. The magnetic properties of non-perovskite manganese oxides are briefly discussed in view of these structural features.

Strobel, P.; Ibarra-Palos, A.; Pernet, M.; Zouari, S.; Cheikh-Rouhou, W.; Cheikh-Rouhou, A.

2004-05-01

308

Nanostructured and layered lithium manganese oxide and method of manufacturing the same  

NASA Technical Reports Server (NTRS)

Nanostructured and layered lithium manganese oxide powders and methods of producing same. The powders are represented by the chemical formula, LixMn1-yMyO2, where 0.5

Singhal, Amit (Inventor); Skandan, Ganesh (Inventor)

2005-01-01

309

Alterations of oxidative stress biomarkers due to in utero and neonatal exposures of airborne manganese  

Microsoft Academic Search

Neonatal rats were exposed to airborne manganese sulfate (MnSO4) (0, 0.05, 0.5, or 1.0 mg Mn\\/m3) during gestation (d 0–19) and postnatal days (PNDs) 1–18. On PND19, rats were killed, and we assessed biochemical end points\\u000a indicative of oxidative stress in five brain regions: cerebellum, hippocampus, hypothalamus, olfactory bulb, and striatum.\\u000a Glutamine synthetase (GS) and tyrosine hydroxylase (TH) protein levels,

Keith M. Erikson; David C. Dorman; Vanessa Fitsanakis; Lawrence H. Lash; Michael Aschner

2006-01-01

310

Microwave-assisted manganese(III) acetate based oxidative cyclizations of alkenes with ?-ketosulfones  

Microsoft Academic Search

The microwave-assisted synthesis of 5-(4-nitrophenyl)-2-phenyl-4-(phenylsulfonyl)-2,3-dihydrofuran (5a) was performed via manganese(III) acetate based oxidative cyclization of 1-(4-nitrophenyl)-2-(phenylsulfonyl)ethanone (3a) with vinylbenzene (4a). This new protocol was applied to four sulfone derivatives (3a–d), using vinylbenzene (4a) and diphenylethene (4b), affording a series of 2,3-dihydrofurans (5a–d, 6a–d) in moderate to good yields (26–55%). Similar methodology, applied on allylbenzene (4c), surprisingly, led to dehydronaphthalene derivatives

Christophe Curti; Maxime D. Crozet; Patrice Vanelle

2009-01-01

311

Synthesis and structural characterization of defect spinels in the lithium-manganese-oxide system  

SciTech Connect

Lithium-manganese-oxides prepared at moderate temperatures are under investigation as insertion electrodes for rechargeable lithium batteries. The structure of two defect-spinel compounds synthesized by the reaction of MnCO[sub 3] and Li[sub 2]CO[sub 3] at 400 C are reported. The cation distribution in the structures were determined by neutron-diffraction to be Li[sub .85][open square][sub .15][sub 8a][Mn[sub 1.74]Li[sub .26

Thackeray, M.M.; Kock, A. de (CSIR, Pretoria (South Africa). Div. of Materials Science and Technology); David, W.I.F. (Rutherford Appleton Lab., Oxfordshire (United Kingdom))

1993-10-01

312

Synthesis and structural characterization of defect spinels in the lithium-manganese-oxide system  

Microsoft Academic Search

Lithium-manganese-oxides prepared at moderate temperatures are under investigation as insertion electrodes for rechargeable lithium batteries. The structure of two defect-spinel compounds synthesized by the reaction of MnCO[sub 3] and Li[sub 2]CO[sub 3] at 400 C are reported. The cation distribution in the structures were determined by neutron-diffraction to be Li[sub .85][open square][sub .15][sub 8a][Mn[sub 1.74]Li[sub .26

M. M. Thackeray; A. de Kock; W. I. F. David

1993-01-01

313

Nano-sized lithium manganese oxide dispersed on carbon nanotubes for energy storage applications  

Microsoft Academic Search

Nano-sized lithium manganese oxide (LMO) dispersed on carbon nanotubes (CNT) has been synthesized successfully via a microwave-assisted hydrothermal reaction at 200°C for 30min using MnO2-coated CNT and an aqueous LiOH solution. The initial specific capacity is 99.4mAh\\/g at a 1.6 C-rate, and is maintained at 99.1mAh\\/g even at a 16 C-rate. The initial specific capacity is also maintained up to

Sang-Bok Ma; Kyung-Wan Nam; Won-Sub Yoon; Seong-Min Bak; Xiao-Qing Yang; Byung-Won Cho; Kwang-Bum Kim

2009-01-01

314

Promotion of the hydrogen peroxide decomposition activity of manganese oxide catalysts  

Microsoft Academic Search

Pure (MnOx), mixed (AyMn1?yOx) and composite ((A,B)yMn1?yOx) manganese oxide based catalysts were prepared, where A is either NiII, CuII, BiIII or CeIV, A and B are various combinations of them, and y=0.4. Subsequently, they were characterized for the crystalline bulk structure by X-ray powder diffractometry, the electron availability by magnetic susceptibility measurements, the surface area by BET-analysis of nitrogen adsorption

Muhammad A Hasan; Mohamed I Zaki; Lata Pasupulety; Kamlesh Kumari

1999-01-01

315

Manganese-doped indium oxide and its application in organic light-emitting diodes  

SciTech Connect

Thin films of manganese-doped indium oxide (IMO) deposited by electron beam evaporation have been investigated as anodes in organic light-emitting diodes (OLEDs). The IMO films have a high work function of 5.35 eV, a desirable surface morphology with an average roughness of 1.1 nm, a high average optical transmittance of 87.2% in the visible region, and a maximum optical transmittance of 92% at 460 nm. It is demonstrated that an IMO anode can effectively improve hole injection at the anode/organic interface, resulting in OLEDs with an increased electroluminescent efficiency.

Liao Yaqin [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Graduate School of Chinese Academy of Sciences, Beijing 100080 (China); Lu Qipeng; Fan Yi; Liu Xingyuan [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China)

2011-07-11

316

Characterization of the manganese oxide produced by pseudomonas putida strain MnB1  

NASA Astrophysics Data System (ADS)

Manganese oxides form typically in natural aqueous environments via Mn(II) oxidation catalyzed by microorganisms, primarily bacteria, but little is known about the structure of the incipient solid-phase products. The Mn oxide produced by a Pseudomonas species representative of soils and freshwaters was characterized as to composition, average Mn oxidation number, and N 2 specific surface area. Electron microscopy, X-ray diffraction, and X-ray absorption near edge structure spectroscopy were applied to complement the physicochemical data with morphological and structural information. A series of synthetic Mn oxides also was analyzed by the same methods to gain better comparative understanding of the structure of the biogenic oxide. The latter was found to be a poorly crystalline layer type Mn(IV) oxide with hexagonal symmetry, significant negative structural charge arising from cation vacancies, and a relatively small number of randomly stacked octahedral sheets per particle. Its properties were comparable to those of ?-MnO 2 (vernadite) and a poorly crystalline hexagonal birnessite ("acid birnessite") synthesized by reduction of permanganate with HCl, but they were very different from those of crystalline triclinic birnessite. Overall, the structure and composition of the Mn oxide produced by P. putida were similar to what has been reported for other freshly precipitated Mn oxides in natural weathering environments, yielding further support to the predominance of biological oxidation as the pathway for Mn oxide formation. Despite variations in the degree of sheet stacking and Mn(III) content, all poorly crystalline oxides studied showed hexagonal symmetry. Thus, there is a need to distinguish layer type Mn oxides with structures similar to those of natural birnessites from the synthetic triclinic variety. We propose designating the unit cell symmetry as an addition to the current nomenclature for these minerals.

Villalobos, Mario; Toner, Brandy; Bargar, John; Sposito, Garrison

2003-07-01

317

Oxidative cleavage of a phenolic diarylpropane lignin model dimer by manganese peroxidase from Phanerochaete chrysosporium  

SciTech Connect

In the presence of Mn{sup II} and H{sub 2}O{sub 2}, homogeneous manganese peroxidase oxidized 1-(3,5-dimethoxy-4-hydroxy phenyl)-2- (4-methoxyphenyl)- 1,3-dihydroxypropane (I) to yield 1-(3,5- dimethoxy-4- hydroxyphenyl)-2- (4-methoxyphenyl)-1-oxo-3- hydroxy propane (II), 2,6-dimethoxy- 1,4-benzoquinone (III), 2,6-dimethoxy- 1,4-dihydroxy benzene (IV), 1-(4-methoxyphenyl)- 1-oxo-2-hydroxyethane (V), 1-(4-methoxyphenyl)- 1,2-dihydroxyethane (VI), syringaldehyde (VIII), and 2-(4-methoxyphenyl)- 3-hydroxypropanal (IX). Chemically prepared manganese(III) malonate catalyzed the same reactions. Oxidation of I in H{sub 2}{sup 18}O under argon resulted in >80% incorporation of {sup 18}O into the phenylglycol VI, the hydroquinone IV, and the quinone III. Oxidation of I in H{sub 2}{sup 18}O under aerobic conditions resulted in 40% incorporation of {sup 18}O into VI but no {sup 18}O incorporation into V. Finally, oxidation of I under {sup 18}O{sub 2} resulted in 89% and 28% incorporation of {sup 18}O into V and VI, respectively. These results are explained by mechanisms involving the one-electron oxidation of the substrate I by enzyme-generated Mn{sup III} to produce a phenoxy radical intermediate I{prime}. Subsequent C{sub {alpha}}-C{sub {beta}} bond cleavage of the radical intermediate yields syringaldehyde (VIII) and a C{sub 6}-C{sub 2} benzylic radical. Syringaldehyde is oxidized by Mn{sup III} in several steps to a cyclohexadiene cation intermediate I{double prime}, which is attacked by water to yield the benzoquinone III. The C{sub 6}-C{sub 2} radical is scavenged by O{sub 2} to form a peroxy radical that decomposes to V and VI. In these reactions, Mn{sup III} generated by manganese peroxidase catalyzes both formation of the substrate phenoxy radical and oxidation of carbon-centered radical intermediates, to yield reactive cations.

Wariishi, Hiroyuki; Valli, K.; Gold, M.H. (Oregon Graduate Center, Beaverton (USA))

1989-07-11

318

The simple preparation of birnessite-type manganese oxide with flower-like microsphere morphology and its remarkable capacity retention  

SciTech Connect

Graphical abstract: Flower-like birnessite-type manganese oxide microspheres with large specific surface area and excellent electrochemical properties have been prepared by a facile hydrothermal method. Highlights: ? Birnessite-type manganese oxide with flower-like microsphere morphology and large specific surface area. ? A facile low-temperature hydrothermal method. ? Novel flower-like microsphere consists of the thin nano-platelets. ? Birnessite-type manganese oxide exhibits an ideal capacitive behavior and excellent cycling stability. -- Abstract: Birnessite-type manganese oxide with flower-like microsphere morphology and large specific surface area has been prepared by hydrothermal treating a mixture solution of KMnO{sub 4} and (NH{sub 4}){sub 2}SO{sub 4} at 90 °C for 24 h. The obtained material is characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N{sub 2} adsorption–desorption. Results indicate that the birnessite-type manganese oxide shows novel flower-like microsphere morphology and a specific surface area of 280 m{sup 2} g{sup ?1}, and the flower-like microsphere consists of the thin nano-platelets. Electrochemical characterization indicates that the prepared material exhibits an ideal capacitive behavior with a capacitance value of 278 F g{sup ?1} in 1 mol L{sup ?1} Na{sub 2}SO{sub 4} aqueous solution at a scan rate of 5 mV s{sup ?1}. Moreover, the prepared manganese oxide electrode shows excellent cycle stability, and the specific capacitance can maintain 98.6% of the initial one after 5000 cycles.

Zhu, Gang; Deng, Lingjuan; Wang, Jianfang; Kang, Liping [Key Laboratory of Applied Surface and Colloid Chemistry (Shaanxi Normal University), Ministry of Education, Xi’an 710062 (China) [Key Laboratory of Applied Surface and Colloid Chemistry (Shaanxi Normal University), Ministry of Education, Xi’an 710062 (China); School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710062 (China); Liu, Zong-Huai, E-mail: zhliu@snnu.edu.cn [Key Laboratory of Applied Surface and Colloid Chemistry (Shaanxi Normal University), Ministry of Education, Xi’an 710062 (China) [Key Laboratory of Applied Surface and Colloid Chemistry (Shaanxi Normal University), Ministry of Education, Xi’an 710062 (China); School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710062 (China)

2012-11-15

319

Mo;ecular Modeling of Biogenic Manganese Oxides Using ab Initio Density Functional Theory  

NASA Astrophysics Data System (ADS)

Layer type manganese oxides with short-range crystalline order (birnessites) are produced by many species of bacteria.Deposits of these oxides form a highly reactive catalytic surface that plays a major role in the destruction and sequestration of organic compounds and metals.Biogenic oxides also contain vacant Mn(IV)sites;these sites,with their associated negative charge, are the probable main cause of the high sorptive reactivity of the oxide surfaces. In order to acquire a deeper understanding of the molecular mechanisms involved in these processes, a model of a biogenic oxide was built and its structure was optimized using the CASTEP three-dimensional periodic system computational package. The resulting crystal structure shows good agreement with EXAFS data from crystals formed by a strain of the common soil and freshwater bacterium, Pseudomonas putida. The greatest challenge in modeling Mn oxides (like other transition metal oxides)comes in dealing with the electronic factors that lead to their magnetic and catalytic properties: they are highly correlated systems where the spin must be taken into account in order to obtain accurate predictions of their properties.

Oconnor, M.; Sposito, G.; Refson, K.

2003-12-01

320

pH-dependent mechanisms of methylene blue reacting with tunneled manganese oxide pyrolusite.  

PubMed

This study examined the reaction of methylene blue (MB) with tunneled manganese oxide pyrolusite regarding pH and reaction time. MB was cleaved through N-demethylation, in which reaction azure B (AB), azure A (AA), azure C (AC), and thionin (TH) were stepwise generated at all tested pH. Pyrolusite predominantly serves as the oxidant in the oxidative degradation of MB at a pH under the pHiep of pyrolusite (4.70) while playing the role of the catalyst at pH higher than pHiep. Among all oxidative products and original MB molecule, TH is the alone compound adsorbed onto the pyrolusite surface at all tested pH. However, the quantity of adsorbed TH increases with pH because of the stronger affinity between the cationic TH molecule and the more negatively charged surface of pyrolusite with pH increasing. Because the lattice oxygen and surface hydroxyl groups form excited oxygen firstly to cause the oxidation of MB, the tunneled pyrolusite with less constrained corner and edge oxygen catalytically promote the oxidation reaction at pH beyond pHiep. The vacancy of the consumed lattice oxygen forms the active sites for the other oxidation and could be replenished by molecular oxygen to complete a catalytic cycle. PMID:22999656

Kuan, Wen-Hui; Chan, Yen-Chuan

2012-11-15

321

Manganese regulation of virulence factors and oxidative stress resistance in Neisseria gonorrhoeae  

PubMed Central

Neisseria gonorrhoeae has evolved a complex and novel network of oxidative stress responses, including defense mechanisms that are dependent on manganese (Mn). We performed systematic analyses at the transcriptomic and proteomic (1D SDS-PAGE and Isotope-Coded Affinity Tag [ICAT]) levels to investigate the global expression changes that take place in a high Mn environment, which results in a Mn-dependent oxidative stress resistance phenotype. These studies revealed that 97 proteins are regulated at the post-transcriptional level under conditions of increased Mn concentration, including proteins involved in virulence (eg. Pilin, a key adhesin), oxidative stress defence (eg. superoxide dismutase), cellular metabolism, protein synthesis, RNA processing and cell division. Mn regulation of inorganic pyrophosphatase (Ppa) indicated the potential involvement of phosphate metabolism in the Mn-dependent oxidative stress defense. A detailed analysis of the role of Ppa and polyphosphate kinase (Ppk) in the gonococcal oxidative stress response revealed that ppk and ppa mutant strains showed increased resistance to oxidative stress. Investigation of these mutants grown with high Mn suggests that phosphate and pyrophosphate are involved in Mn-dependent oxidative stress resistance. PMID:20004262

Wu, Hsing-Ju; Seib, Kate L.; Srikhanta, Yogitha N.; Edwards, Jennifer; Kidd, Stephen P.; Maguire, Tina L .; Hamilton, Amanda; Pan, Kuan-Tin; Hsiao, He-Hsuan; Yao, Chen-Wen; Grimmond, Sean M.; Apicella, Michael A.; McEwan, Alastair G.; Wang, Andrew H-J.; Jennings, Michael P.

2014-01-01

322

Deuterium and lithium-6 MAS NMR studies of manganese oxide electrode materials  

NASA Astrophysics Data System (ADS)

Electrolytic manganese dioxide (EMD) is used world wide as the cathode materials in both lithium and alkaline primary (non-rechargeable) batteries. We have developed deuterium and lithium MAS NMR techniques to study EMD and related manganese oxides and hydroxides, where diffraction techniques are of limited value due to a highly defective nature of the structures. Deuterons in EMD, manganite, groutite, and deuterium-intercalated pyrolusite and ramsdellite were detected by NMR, for the first time, and their locations and motions in the structures were analyzed by applying variable temperature NMR techniques. Discharge mechanisms of EMD in alkaline (aqueous) electrolytes were studied, in conjunction with step potential electrochemical spectroscopic (SPECS) method, and five distinctive discharge processes were proposed. EMD is usually heat-treated at about 300--400°C to remove water to be used in lithium batteries. Details of the effects of heat-treatment, such as structural and compositional changes as a function of heat-treatment temperature, were studied by a combination of MAS NMR, XRD, and thermogravimetric analysis. Lithium local environments in heat-treated EMD (HEMD) that were discharged in lithium cells, were described in terms of related environments found in model compounds pyrolusite and ramsdellite where specific Li + sites were detected by MAS NMR and the hyperfine shift scale method of Grey et al. Acid-leaching of Li2MnO3 represents an approach for synthesizing new or modified manganese oxide electrode materials for lithium rechargeable batteries. Progressive removal of lithium from specific crystallographic sites, followed by a gradual change of the crystal structure, was monitored by a combination of NMR and XRD techniques.

Paik, Younkee

323

Decolorization of methylene blue in layered manganese oxide suspension with H2O2.  

PubMed

Layered birnessite-type manganese oxides (Na-OL-1) were prepared via a redox reaction involving MnO(4)(-) and Mn(2+) under markedly alkaline conditions. According to the XRD analysis, the resulting material exhibited a well-crystallized octahedral layer (OL) structure with several different phases, including ?-MnOOH, ?-MnOOH and ?-Mn(3)O(4). The catalyst was highly effective for the decolorization and degradation of methylene blue (MB) in the presence of H(2)O(2) at neutral pH. The tested MB was completely decolorized in Na-OL-1 suspension by the fraction dosing of H(2)O(2) (556.5mM at the beginning and then 183.8mM at 40 min). Based on the studies of electron spin resonance and the effect of radical scavengers, the (1)O(2) and O(2)(-) were the main reactive oxygen species (ROS) in the reaction. It was found that both oxygen and ROS were generated from the decomposition of H(2)O(2) in Na-OL-1 suspension, wherein the decomposition pathways were proposed. The generation of H(2)O(2) in Na-OL-1 suspension at air atmosphere indicated that the existence of multivalent manganese oxides greatly enhanced the interfacial electron transfer, leading to the high activity of Na-OL-1. PMID:21524842

Zhang, Lili; Nie, Yulun; Hu, Chun; Hu, Xuexiang

2011-06-15

324

Development of a genetic system for a model manganese-oxidizing proteobacterium, Leptothrix discophora SS1.  

PubMed

Understanding the molecular underpinnings of manganese oxidation in Leptothrix discophora SS1 has been hampered by the lack of a genetic system. In this report, we describe the development of a genetic system for L. discophora SS1. The antibiotic sensitivity was characterized, and a procedure for transformation with exogenous DNA via conjugation was developed and optimized, resulting in a maximum transfer frequency of 5.2×10(-1) and a typical transfer frequency of the order of 1×10(-3) transconjugants per donor. Genetic manipulation of L. discophora SS1 was demonstrated by disrupting pyrF via chromosomal integration with a plasmid containing a R6K? origin of replication through homologous recombination. This resulted in resistance to 5-fluoroorotidine, which was abolished by complementation with an ectopically expressed copy of pyrF cloned into pBBR1MCS. This system is expected to be amenable to a systematic genetic analysis of L. discophora SS1, including those genes responsible for manganese oxidation. PMID:25149187

Bocioaga, Daniela; El Gheriany, Iman A; Lion, Leonard W; Ghiorse, William C; Shuler, Michael L; Hay, Anthony G

2014-11-01

325

Covalent hybrid of spinel manganese-cobalt oxide and graphene as advanced oxygen reduction electrocatalysts.  

PubMed

Through direct nanoparticle nucleation and growth on nitrogen doped, reduced graphene oxide sheets and cation substitution of spinel Co(3)O(4) nanoparticles, a manganese-cobalt spinel MnCo(2)O(4)/graphene hybrid was developed as a highly efficient electrocatalyst for oxygen reduction reaction (ORR) in alkaline conditions. Electrochemical and X-ray near-edge structure (XANES) investigations revealed that the nucleation and growth method for forming inorganic-nanocarbon hybrids results in covalent coupling between spinel oxide nanoparticles and N-doped reduced graphene oxide (N-rmGO) sheets. Carbon K-edge and nitrogen K-edge XANES showed strongly perturbed C-O and C-N bonding in the N-rmGO sheet, suggesting the formation of C-O-metal and C-N-metal bonds between N-doped graphene oxide and spinel oxide nanoparticles. Co L-edge and Mn L-edge XANES suggested substitution of Co(3+) sites by Mn(3+), which increased the activity of the catalytic sites in the hybrid materials, further boosting the ORR activity compared with the pure cobalt oxide hybrid. The covalently bonded hybrid afforded much greater activity and durability than the physical mixture of nanoparticles and carbon materials including N-rmGO. At the same mass loading, the MnCo(2)O(4)/N-graphene hybrid can outperform Pt/C in ORR current density at medium overpotentials with stability superior to Pt/C in alkaline solutions. PMID:22280461

Liang, Yongye; Wang, Hailiang; Zhou, Jigang; Li, Yanguang; Wang, Jian; Regier, Tom; Dai, Hongjie

2012-02-22

326

Sodium manganese oxide thin films as cathodes for Na-ion batteries  

SciTech Connect

This paper presents the fabrication and characterization of sodium manganese oxide cathode thin films for rechargeable Na-ion batteries. Layered oxide compounds of nominal compositions Na0.6MnO2 and Na1.0MnO2 have been prepared by radio frequency magnetron sputtering and post-annealing at high temperatures under various conditions. The Na0.6MnO2 thin films possess either a hexagonal or orthorhombic structure while the Na1.0MnO2 films crystallize in a monoclinic structure, as shown by X-ray diffraction and X-ray absorption spectroscopy results. The potential profiles of the film cathodes are characterized by features similar to those measured for the powders and exhibit reversible storage capacities in the range of 50-60 Ah cm-2 m-1, which correspond to about 120-140 mAh g-1, and are maintained over 80 cycles.

Baggetto, Loic [ORNL; Carroll, Kyler J [University of California, San Diego; Unocic, Raymond R [ORNL; Bridges, Craig A [ORNL; Meng, Ying Shirley [University of California, San Diego; Veith, Gabriel M [ORNL

2014-01-01

327

Nano-sized Lithium Manganese Oxide Dispersed on Carbon Nanotubes for Energy Storage Applications  

SciTech Connect

Nano-sized lithium manganese oxide (LMO) dispersed on carbon nanotubes (CNT) has been synthesized successfully via a microwave-assisted hydrothermal reaction at 200 C for 30 min using MnO{sub 2}-coated CNT and an aqueous LiOH solution. The initial specific capacity is 99.4 mAh/g at a 1.6 C-rate, and is maintained at 99.1 mAh/g even at a 16 C-rate. The initial specific capacity is also maintained up to the 50th cycle to give 97% capacity retention. The LMO/CNT nanocomposite shows excellent power performance and good structural reversibility as an electrode material in energy storage systems, such as lithium-ion batteries and electrochemical capacitors. This synthetic strategy opens a new avenue for the effective and facile synthesis of lithium transition metal oxide/CNT nanocomposite.

Bak, S.B.

2009-08-01

328

Oxidation of Reactive Alcohols with Hydrogen Peroxide Catalyzed by Manganese Complexes  

Microsoft Academic Search

\\u000a Abstract  Two manganese-containing catalysts have been employed in the oxidation with hydrogen peroxide of two reactive alcohols (1-phenylethanol\\u000a and glycerol): soluble catalyst [LMn(?-O)3MnL](PF6)2 (1a) and heterogenized catalyst [LMn(?-O)3MnL]2[SiW12O40] (1b) (L is 1,4,7-trimethyl-1,4,7-triazacyclononane, TMTACN). Oxidation of 1-phenylethanol catalyzed by 1a in acetonitrile solution proceeds at room temperature in the presence of a small amount of oxalic acid; the turnover number\\u000a attains 15,000

Georgiy B. Shul’pin; Yuriy N. Kozlov; Lidia S. Shul’pina; Tatyana V. Strelkova; Dalmo Mandelli

2010-01-01

329

Development of novel nonvolatile memory devices using the colossal magnetoresistive oxide praseodymium-calcium-manganese trioxide  

NASA Astrophysics Data System (ADS)

Pr0.7Ca0.3MnO3 (PCMO) manganese oxide belongs in the family of materials known as transition metal oxides. These compounds have received increased attention due to their perplexing properties such as Colossal Magnetoresistance effect, Charge-Ordered phase, existence of phase-separated states etc. In addition, it was recently discovered that short electrical pulses in amplitude and duration are sufficient to induce reversible and non-volatile resistance changes in manganese perovskite oxide thin films at room temperature, known as the EPIR effect. The existence of the EPIR effect in PCMO thin films at room temperature opens a viable way for the realization of fast, high-density, low power non-volatile memory devices in the near future. The purpose of this study is to investigate, optimize and understand the properties of Pr0.7Ca0.3MnO 3 (PCMO) thin film devices and to identify how these properties affect the EPIR effect. PCMO thin films were deposited on various substrates, such as metals, and conducting and insulating oxides, by pulsed laser and radio frequency sputtering methods. Our objective was to understand and compare the induced resistive states. We attempted to identify the induced resistance changes by considering two resistive models to be equivalent to our devices. Impedance spectroscopy was also utilized in a wide temperature range that was extended down to 70K. Fitted results of the temperature dependence of the resistance states were also included in this study. In the same temperature range, we probed the resistance changes in PCMO thin films and we examined whether the phase transitions affect the EPIR effect. In addition, we included a comparison of devices with electrodes consisting of different size and different materials. We demonstrated a direct relation between the EPIR effect and the phase diagram of bulk PCMO samples. A model that could account for the observed EPIR effect is presented.

Papagianni, Christina

330

Applications of manganese oxides based catalyst for the destruction of VOCs  

SciTech Connect

Catalytic oxidation, as a proven control technology, has demonstrated a high level of efficiency in reducing Volatile Organic Compound (VOC`s) at competitive, and in many cases, lower cost than the other thermal incineration methods. Catalytic oxidation is the preferred technology for the destruction of VOC`s in a variety of industries; such as, flexographic printing, metal can coating, contract sterilization and bakeries. A key component of these catalytic systems is the catalyst itself, and transition metal oxide catalysts have demonstrated their advantage and overall superior applicability in numerous installations. The higher VOC destruction efficiencies of these catalysts, particularly for oxygenated VOC`s, allows for a lower temperature of operation making these catalysts an economically attractive alternative based upon the energy savings when compared to noble metal catalysts. Manganese based oxide catalysts are available in either homogenous extruded form or in monolith form, depending upon their application. The performance characteristics - measured as VOC destruction efficiencies - of these catalysts are dependent upon the operating conditions of the catalytic reactor. Reactor configuration and operating conditions; such as, catalyst operating temperature, gas phase linear velocity, contact time of the gas stream with the catalyst, and finally the characteristics of the hydrocarbon, all influence the efficiency of these catalytic systems. Models relating the hydrocarbon destruction efficiencies of these catalysts, as it is affected by these parameters, will be presented. These parametric models allow for comparison of various alternative catalyst strategies to be applied to a VOC destruction situation in the design phase. Data will be presented on a transition metal extruded catalyst, an extended temperature range manganese based catalyst, as well as a monolithic form of the transition metal catalyst.

Singh, N.; Pisarczyk, K.S.; Sigmund, J.J. [Carus Chemical Co., LaSalle, IL (United States)

1997-12-31

331

Influence of Calcium(II) and Chloride on the Oxidative Reactivity of a Manganese(II) Complex of a Cross-Bridged Cyclen Ligand.  

PubMed

Available data from different laboratories have confirmed that both Ca(2+) and Cl(-) are crucial for water oxidation in Photosystem II. However, their roles are still elusive. Using a manganese(II) complex having a cross-bridged cyclen ligand as a model, the influence of Ca(2+) on the oxidative reactivity of the manganese(II) complex and its corresponding manganese(IV) analogue were investigated. It has been found that adding Ca(2+) can significantly improve the oxygenation efficiency of the manganese(II) complex in sulfide oxidation and further accelerate the oxidation of sulfoxide to sulfone. Similar improvements have also been observed for Mg(2+), Sr(2+), and Ba(2+). A new monomeric manganese(IV) complex having two cis-hydroxide ligands has also been isolated through oxidation of the corresponding manganese(II) complex with H2O2 in the presence of NH4PF6. This rare cis-dihydroxomanganese(IV) species has been well characterized by X-ray crystallography, electrochemistry, electron paramagnetic resonance, and UV-vis spectroscopy. Notably, using the manganese(IV) complex as a catalyst demonstrates higher activity than the corresponding manganese(II) complex, and adding Ca(2+) further improves its catalytic efficiency. However, adding Cl(-) decreases its catalytic activity. In electrochemical studies of manganese(IV) complexes with no chloride ligand present, adding Ca(2+) positively shifted the redox potential of the Mn(IV)/Mn(III) couple but negatively shifted its Mn(V)/Mn(IV) couple. In the manganese(II) complex having a chloride ligand, adding Ca(2+) shifted both the Mn(IV)/Mn(III) and Mn(V)/Mn(IV) couples in the negative direction. The revealed oxidative reactivity and redox properties of the manganese species affected by Ca(2+) and Cl(-) may provide new clues to understanding their roles in the water oxidation process of Photosystem II. PMID:25375413

Zhang, Zhan; Coats, Katherine L; Chen, Zhuqi; Hubin, Timothy J; Yin, Guochuan

2014-11-17

332

Manganese oxide-coated redox bars as an indicator for reducing soil conditions  

NASA Astrophysics Data System (ADS)

Field identification of reducing soil conditions is of concern not only for soil pedogenesis but also for nutrient and pollutant dynamics in soils. We manufactured manganese (Mn) oxide-coated polyvinyl chloride (PVC) bars and proved their suitability for identification of reducing soil conditions in both the laboratory and field. Birnessite (?-MnO2) was synthesized according to a recently published method and was coated onto white PVC bars. We used microcosm devices with adjusted redox potentials (EH) to distinguish the onset and intensity of depletion patterns along the Mn oxide-coating and soil column experiments combined with field application to validate the enhanced removal of Mn against Fe oxide-coated bars under anaerobe soil conditions. Field application was performed at a site with shallow and strongly fluctuating water tables where water table depth and soil temperature were monitored. Three microcosm experiments adjusted to oxidizing (EH ~500 mV, pH 7), weakly reducing (EH ~175 mV, pH 7) and moderately reducing conditions (EH ~25 mV, pH 7) showed depending on the EH no, slight, or intense removal of the Mn oxide-coating, respectively. Moreover, the removal of Mn oxide (225 mm2 d-1) in soil column experiments exceeded the removal of Fe oxide (118 mm2 d-1). The enhanced removal of the Mn oxide-coating was also found under anaerobe conditions in field application. Consequently, identifying of reducing conditions in soils by Mn oxide-coated bars is possible. We recommend using this methodology for short-term monitoring, e.g. on weekly basis, since tri- and tetravalent Mn is the preferred electron acceptor compared with trivalent Fe.

Dorau, Kristof; Mansfeldt, Tim

2014-05-01

333

Polyvinylpyrrolidone/reduced graphene oxide nanocomposites thin films coated on quartz crystal microbalance for NO2 detection at room temperature  

NASA Astrophysics Data System (ADS)

Polyvinylpyrrolidone (PVP)/reduced graphene oxide (RGO) nanocomposites are sprayed on quartz crystal microbalance (QCM) for NO2 sensing. The thin films are characterized by Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV-VIS). The experimental results reveal that PVP/RGO sensor exhibits higher sensitivity and shorter recovery time than those of PVP. Besides, the response to 20 ppm NO2 is higher than other gases such as CO, CO2 and NH3 even at 100ppm. When the PVP/RGO sensor is exposed to these gases, the good selectivity to NO2 makes the sensor ideal for NO2 detection.

Huang, Junlong; Xie, Guangzhong; Zhou, Yong; Xie, Tao; Tai, HuiLing; Yang, Guangjin

2014-08-01

334

Thiol-mediated oxidation of nonphenolic lignin model compounds by manganese peroxidase of Phanerochaete chrysosporium  

SciTech Connect

In the presence of Mn{sup II}, H{sub 2}O{sub 2}, and glutathione (GSH), manganese peroxidase oxidized veratryl alcohol (1) to veratraldehyde (4). Anisyl alcohol (2) and benzyl alcohol (3) were also oxidized by this system to their corresponding aldehydes, anisaldehyde (5) and benzaldehyde (6). In the presence of GSH, chemically prepared Mn{sup III} or {gamma}-irradiation also catalyzed the oxidation of 1, 2, and 3 to 4, 5, and 6, respectively. GSH and dithiothreitol rapidly reduced Mn{sup III} to Mn{sup II} in the absence of aromatic substrates and the dithiothreitol was oxidized to its disulfide (4,5-dihydroxyl-1,2-dithiane). These results indicate that the thiol is oxidized by enzyme-generated Mn{sup III} to a thiyl radical. The latter abstracts a hydrogen from the substrate , forming a benzylic radical which reacts with another thiyl radical to yield an intermediate which decomposes to the benzaldehyde product. 51 refs., 5 figs., 2 tabs.

Wariishi, Hiroyuki; Valli, K.; Renganathan, V.; Gold, M.H. (Oregon Graduate Center, Beaverton (United States))

1989-08-25

335

Molecular-Level Processes Governing the Interaction of Contaminants with Iron and Manganese Oxides - Final Report  

SciTech Connect

Many of the inorganic and organic contaminants present in sediments at DOE sites can be altered or destroyed by reduction and oxidation (redox) reactions occurring at mineral surfaces. A fundamental understanding of such redox processes provided by molecular-level studies on structurally and compositionally well-defined mineral surfaces will lead to: (i) improved models of contaminant fate and transport in geochemical systems, and (ii) optimized manipulation of these processes for remediation purposes. To contribute to this understanding, we will study, both experimentally and theoretically, redox processes involving three important contaminants - chromate ion, carbon tetrachloride, and trichloroethene TCE, on the following iron and manganese oxides - hematite, magnetite, maghemite, and pyrolusite. These oxides and their hydroxylated analogs commonly occur as coatings on minerals or as interfaces in the subsurface environment. Single-crystal surfaces of these oxides will be synthesized in carefully controlled fashion by molecular beam epitaxy. These surfaces, as well as high surface are powdered samples of these oxides, will be used in spectroscopic and kinetic experiments in both aqueous and gas phases. Our goal is to identify products and to determine the kinetics and mechanisms of surface-catalyzed redox reaction of Cr(VI) and CR(III), and the reductive dechlorination of carbon tetrachloride and TCE. The combination of theory and experiment will provide the base information needed to scale from the molecular level to the microscopic grain level minerals.

Brown Jr., G. E.; Chambers, S. A.

1999-10-31

336

Stability of manganese-oxide-modified lanthanum strontium cobaltite in the presence of chromia  

NASA Astrophysics Data System (ADS)

In order to restrain the decomposition and conductivity degradation of perovskite-type conductive material in the presence of chromia, manganese oxide modification of lanthanum strontium cobaltite has been studied. La0.7Sr0.3CoO3-? (LSC) and MnO2-modified LSC coatings are applied onto Ni-Cr alloy and exposed to long-term oxidation text to examine their chemical stability. In a LSC coating, chromium species migrating from the Ni-Cr alloy could induce the decomposition of LSC and produce SrCrO4 and Co-Cr spinel oxides. In contrast, in the MnO2-modified LSC, Sr is stable and the low-conductivity phase SrCrO4 phase is rarely seen even the coated alloy has gone through 1000 h of oxidation tests at 800 °C. It highlights that MnO2 modification could greatly improve the stability of LSC under Cr-rich conditions. The study of solid state reactions reveals that the influence of MnO2 is mainly due to the reaction between MnO2 and LSC, instead of the direct reaction between MnO2 and chromium oxides.

Ou, Ding Rong; Cheng, Mojie

2014-12-01

337

Structure of reduced and oxidized manganese superoxide dismutase: a combined computational and experimental approach.  

PubMed

Manganese superoxide dismutases catalyze the disproportionation of the superoxide radical anion to molecular oxygen and hydrogen peroxide. Recently, atomic-resolution crystal structures of the reduced and oxidized enzymes have been reported. They show an active site with the manganese ion bound to one aspartate, three histidine residues, and a solvent molecule. In this paper, we combine crystallographic refinement with quantum mechanical methods to show that the solvent ligand is undoubtedly a water molecule in the reduced state. However, the putative oxidized structure is to a large extent reduced during data collection, so that it contains a mixture of the Mn2+ and Mn3+ structure. The crystal structures show that the Mn-bound solvent molecule accepts a hydrogen bond from the side chain of the conserved Gln-146 residue. If the solvent ligand is water, then this could lead to a steric clash, but it is avoided by the plane of water molecule forming an angle of 72 degrees to the Mn-O bond. Such a conformation is also found outside the enzyme, giving a minimal destabilization of the reduced state. We show by molecular dynamics simulations that the suggested Mn2+-H2O and Mn3+-OH- structures are stable. Moreover, we show that the superoxide substrate may bind both in the first coordination sphere of the Mn ion, opposite to the aspartate ligand, or in the second sphere, close to the conserved Tyr-34 and His-30 residues, approximately 5 A from Mn. However, the second-sphere structures are not stable in long molecular dynamics simulations. We see no difference in the coordination between the reduced and the oxidized states of the enzyme. PMID:16771427

Rulísek, Lubomír; Ryde, Ulf

2006-06-15

338

Purification and Characterization of the Manganese(II) Oxidizing Protein from Erythrobacter sp. SD-21  

NASA Astrophysics Data System (ADS)

The manganese(II) oxidizing protein (Mop) found in the alpha-proteobacterium Erythrobacter sp. SD-21 catalyzes the formation of insoluble Mn(III/IV) oxides from soluble Mn(II). These Mn(III/IV) oxides formed are one of the strongest naturally occurring oxides, next to oxygen, and can be used to adsorb and oxidize toxic chemicals from the surrounding environment. Because of the beneficial use in the treatment of contaminated sources, the mechanism and biochemical properties of this novel enzyme are being studied. Due to low expression levels in the native host strain, purification of Mop has been problematic. To overcome this problem the gene encoding Mop, mopA, was cloned from the native host into a C-terminal histidine tag vector and expressed in Escherichia coli cells. Affinity chromatography under denaturing conditions have been applied in attempts to purify an active Mop. Western blots have confirmed that the protein is being expressed and is at the expected size of 250 kDa. Preliminary characterization on crude extract containing Mop has shown a Km and vmax value of 2453 uM and 0.025 uM min-1, respectively. Heme and pyrroloquinoline quinone can stimulate Mn(II) oxidizing activity, but hydrogen peroxide does not affect activity, despite the sequence similarity to animal heme peroxidase proteins. Research has been shown that calcium is essential for Mop activity. Purifying an active Mn(II) oxidizing protein will allow for a better understanding behind the enigmatic process of Mn(II) oxidation.

Nakama, K. R.; Lien, A.; Johnson, H. A.

2013-12-01

339

Sorption of Ferric Iron from Ferrioxamine B to Synthetic and Biogenic Layer Type Manganese Oxides  

NASA Astrophysics Data System (ADS)

Siderophores are biogenic chelating agents produced in terrestrial and marine environments to increase the bioavailablity of ferric iron. Recent work has suggested that both aqueous and solid-phase Mn(III) may affect siderophore-mediated iron transport, but no information appears to be available about the effect of solid-phase Mn(IV). To probe the effects of predominantly Mn(IV) oxides, we studied the sorption reaction of ferrioxamine B [Fe(III)HDFOB+, an Fe(III) chelate of the trihydroxamate siderophore desferrioxamine B (DFOB)] with two synthetic birnessites [layer type Mn(III, IV) oxides] and a biogenic birnessite produced by Pseudomonas putida MnB1. We found that all of these predominantly Mn(IV) oxides greatly reduced the aqueous concentration of Fe(III)HDFOB+ over at pH 8. After 72 hours equilibration time, the sorption behavior for the synthetic birnessites could be accurately described by a Langmuir isotherm; for the biogenic oxide, a Freundlich isotherm was best utilized to model the sorption data. To study the molecular nature of the interaction between the Fe(III)HDFOB+ complex and the oxide surface, Fe K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy was employed. Analysis of the EXAFS spectra indicated that Fe(III) associated with the Mn(IV) oxides is not complexed by DFOB as in solution, but instead Fe(III) is specifically adsorbed to into the mineral structure at multiple sites with no evidence of DFOB complexation, thus indicating that the Mn(IV) oxides displaced Fe(III) from the siderophore complex. These results indicate that manganese oxides, including biominerals, may strongly sequester iron from soluble ferric complexes and thus may play a significant role in the biogeochemical cycling of iron in marine and terrestrial environments.

Duckworth, O.; John, B.; Sposito, G.

2006-12-01

340

Electronic transport in Lithium Nickel Manganese Oxide, a high-voltage cathode material for Lithium-Ion batteries  

E-print Network

Potential routes by which the energy densities of lithium-ion batteries may be improved abound. However, the introduction of Lithium Nickel Manganese Oxide (LixNi1i/2Mn3/2O4, or LNMO) as a positive electrode material appears ...

Ransil, Alan Patrick Adams

2013-01-01

341

Synthesis and structures of lithium manganese oxide spinel, LiMn 2O 4? ? (0? ??0.27)  

Microsoft Academic Search

Lithium manganese oxides spinels were synthesized under various synthesis conditions and their structures were determined by TOF neutron powder diffraction measurements. Oxygen vacancies exist for the samples synthesized above 800°C, and the amount of vacancies was found to be sensitive to the synthesis conditions. The nearly stoichiometric spinels were synthesized at 750°C in O2 followed by heating at 470°C. The

Ryoji Kanno; Masao Yonemura; Tomoko Kohigashi; Yoji Kawamoto; Mitsuharu Tabuchi; Takashi Kamiyama

2001-01-01

342

In Situ XAS and XRD Studies of Substituted Spinel Lithium Manganese Oxides in the 4-5 V Region  

Microsoft Academic Search

Partial substitution of Mn in lithium manganese oxide spinel materials by Cu and Ni greatly affects the electrochemistry and the phase behavior of the cathode. Substitution with either metal or with a combination of both shortens the 4.2 V plateau and results in higher voltage plateaus. In situ x-ray absorption (XAS) studies indicate that the higher voltage plateaus are related

J. McBreen; S. Mukerjee; X. Q. Yang; X. Sun; Y. Ein-Eli

1998-01-01

343

ADSORPTION OF LEAD FROM A CONTAMINATED SOIL TREATED WITH PHOSPHORUS AND MANGANESE OXIDES BY APRAGUE-DAWLEY RATS  

EPA Science Inventory

In addition to the formation of insoluble lead (Pb) compounds as a mean of reducing Pb bioavalability, adsorption is another potentially important process controlling the bioavailability of Pb in soils. Less attention has been given to manganese (Mn) oxides, even though they are ...

344

Preparation of poly(aniline-co-o-anisidine)-intercalated mesostructured manganese oxide composites by exchange reaction  

SciTech Connect

Layered mesostructured manganese oxide (mesostructured MnO{sub 2}) was synthesized using manganese chloride and lithium hydroxide as the raw materials and cetyltrimethylammonium bromide (CTAB) as the structure-directing agent. Poly(aniline-co-o-anisidine)-intercalated mesostructured MnO{sub 2} composites (P(An-co-oAs)/MnO{sub 2}) were synthesized in an organic solvent through the exchange reaction between the CTAB in MnO{sub 2} gallery and the P(An-co-oAs). The interlayer spacing (I{sub c} values) of mesostructured MnO{sub 2} enlarged from 2.52 to 4.41 nm as the added amount of P(An-co-oAs) increased from 0 to 0.5 g per 0.5 g of mesostructured MnO{sub 2}. The regularity of the layered structure of the composites was firstly decreased due to intercalation of low amounts of P(An-co-oAs). However, with increasing the intercalated amount of P(An-co-oAs) the layered structure of the composites becomes more regular. The electrical conductivity of the composites is 10{sup 2} to 10{sup 3} times higher than that of the mesostructured MnO{sub 2}.

Wang Gengchao [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China)], E-mail: gengchaow@ecust.edu.cn; Yang Zhenyu; Li Xingwei; Li Chunzhong [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Yuan Weikang [UNILAB, State Key Laboratory of Chemical Reaction Engineering, East China University of Science and Technology, Shanghai 200237 (China)

2008-08-04

345

Coprecipitation mechanisms and products in manganese oxidation in the presence of cadmium  

USGS Publications Warehouse

Manganese oxidation products were precipitated in an aerated open-aqueous system where a continuous influx of mixed Mn2+ and Cd2+ solution was supplied and pH was maintained with an automated pH-stat adding dilute NaOH. X-ray diffraction and electron diffraction identified the solids produced as mixtures of Cd2Mn34+O8, Mn2+2Mn4+3O8, MnO2 (ramsdellite), and CdCO3. Mean oxidation numbers of the total precipitated Mn as great as 3.6 were reached during titrations. During subsequent aging in solution, oxidation numbers between 3.8 and 3.9 were reached in some precipitates in less than 40 days. Conditional oxidation rate constants calculated from a crystal-growth equation applied to titration data showed the overall precipitation rate, without considering manganese oxidation state in the precipitate, was increased by a factor of ~4 to ~7 when the mole ratio (Cd/Mn + Cd) of cadmium in the feed solution was 0.40 compared with rate constants for hausmannite (Mn2+Mn23+O4 precipitation under similar conditions but without accessory metals. Kinetic experiments were made to test effects of various Cd/Mn + Cd mole ratios and rates of addition of the feed solution, different temperatures from 5.0 to 35??C, and pH from 8.0 to 9.0. Oxidation rates were slower when the Cd mole ratio was less than 0.40. The rate increased by a factor of ~10 when pH was raised one-half unit. The effect of temperature on the rate constants was also substantial, but the meaning of this is uncertain because the rate of formation of Mn4+ oxide in the absence of Cd or other accessory metals was too slow to be measurable in titration experiments. The increased rate of Mn4+ oxide formation in the presence of Cd2+ can be ascribed to the formation of a labile adsorbed intermediate, CdMn2O4 Int, an analog of hausmannite, formed on precipitate surfaces at the beginning of the oxidation process. The increased lability of this structure, resulting from coordination-chemical behavior of Cd2+ during the titration, causes a rapid second-stage rearrangement and facilitates disproportionation of the Mn3+ ions. The Mn2+ ions thus released provide a positive feedback mechanism that couples the two steps of the conversion of Mn2+ to Mn4+ more closely than is possible when other metal ions besides manganese are not present. During aging of precipitates in contact with solutions, proportions of Cd2Mn3O8 and MnO2 increased at the expense of other precipitate components. ?? 1991.

Hem, J.D.; Lind, C.J.

1991-01-01

346

Quartz crystal microbalance coated with sol–gel-derived indium–tin oxide thin films as gas sensor for NO detection  

Microsoft Academic Search

This paper presents the possibilities and properties of indium–tin oxide (ITO)-covered quartz crystal microbalances (QCM) as a NOx toxic gas sensors. The starting sol–gel solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol (0–20% by weight). The ITO thin films were deposited on the gold electrodes of quartz crystals by spin-coating and annealing

J Zhang; J Hu; Z. Q Zhu; H Gong; S. J O’Shea

2004-01-01

347

Electrochemical and magnetic properties of lithium manganese oxide spinels prepared by oxidation at low temperature of hydrothermally obtained LiMnO 2  

Microsoft Academic Search

Cubic and tetragonally distorted lithium manganese oxide spinels (LiMnO2 + x) were obtained by progressive oxidation of LiMnO2 between 300 and 400 °C. Orthorhombic LiMnO2 was prepared by hydrothermal treatment of either ?-MnOOH or Mn(COOCH3)3 · 2H2O with LiOH · H2O in large excess. The reversible specific capacity for LiMnO2 + x was found to be sensitive to average manganese

Mitsuharu Tabuchi; Kazuaki Ado; Christian Masquelier; Ichiro Matsubara; Hikari Sakaebe; Hiroyuki Kageyama; Hironori Kobayashi; Ryoji Kanno; Osamu Nakamura

1996-01-01

348

Preparation of an electrochemically-formed spinel lithium manganese oxide and its charge–discharge behaviors  

Microsoft Academic Search

Manganese hydroxides were prepared by a cathodic electrochemical precipitation from a manganese nitrate solution. The grass blade-like precipitate, which is ascribed to manganese hydroxide was 20–80?m long and 1–5?m wide and was spread out on a Pt substrate after the electrochemical precipitation. When the electrochemically precipitated manganese hydroxides were kept in an alkali metal hydroxide aqueous solution, such as NaOH,

Katsumi Katakura; Shin-ichi Nishimura; Zempachi Ogumi

2005-01-01

349

Heterologous Expression and Characterization of the Manganese-Oxidizing Protein from Erythrobacter sp. Strain SD21.  

PubMed

The manganese (Mn)-oxidizing protein (MopA) from Erythrobacter sp. strain SD21 is part of a unique enzymatic family that is capable of oxidizing soluble Mn(II). This enzyme contains two domains, an animal heme peroxidase domain, which contains the catalytic site, followed by a C-terminal calcium binding domain. Different from the bacterial Mn-oxidizing multicopper oxidase enzymes, little is known about MopA. To gain a better understanding of MopA and its role in Mn(II) oxidation, the 238-kDa full-length protein and a 105-kDa truncated protein containing only the animal heme peroxidase domain were cloned and heterologously expressed in Escherichia coli. Despite having sequence similarity to a peroxidase, hydrogen peroxide did not stimulate activity, nor was activity significantly decreased in the presence of catalase. Both pyrroloquinoline quinone (PQQ) and hemin increased Mn-oxidizing activity, and calcium was required. The Km for Mn(II) of the full-length protein in cell extract was similar to that of the natively expressed protein, but the Km value for the truncated protein in cell extract was approximately 6-fold higher than that of the full-length protein, suggesting that the calcium binding domain may aid in binding Mn(II). Characterization of the heterologously expressed MopA has provided additional insight into the mechanism of bacterial Mn(II) oxidation, which will aid in understanding the role of MopA and Mn oxidation in bioremediation and biogeochemical cycling. PMID:25172859

Nakama, Katherine; Medina, Michael; Lien, Ahn; Ruggieri, Jordan; Collins, Krystle; Johnson, Hope A

2014-11-01

350

Preparation and catalytic activity of nickel–manganese oxide catalysts with an ilmenite-type structure in the reactions of complete oxidation of hydrocarbons  

Microsoft Academic Search

Mixed nickel–manganese oxides with an ilmenite and spinel structure were investigated in order to elucidate the effect of the crystal structure type and cation coordination on the catalytic performance in the reactions of complete oxidation of ethyl acetate, benzene and carbon monoxide. Highly dispersive and well-crystallized monophase oxides with an ilmenite (NiMnO3) and spinel (NixMn3?xO4) structure were synthesized from homogeneous

D. Mehandjiev; E. Zhecheva; G. Ivanov; R. Ioncheva

1998-01-01

351

Oxidative decomposition of malonic acid as basis for the action of manganese peroxidase in the absence of hydrogen peroxide  

Microsoft Academic Search

Manganese peroxidase (MnP) from the ligninolytic basidiomycetes Phlebia radiata and Nematoloma frowardii was found to decompose malonate oxidatively in the absence of H2O2 in a reaction system consisting of the enzyme, sodium malonate and MnCl2. The enzymatic oxidation resulted in a substantial decrease in malonate concentration and the formation of CO2, oxalate, glyoxylate and formate. Simultaneously with the decomposition of

M. Hofrichter; D. Ziegenhagen; T. Vares; M. Friedrich; M. G. Jäger; W. Fritsche; A. Hatakka

1998-01-01

352

Manganese peroxidase from the basidiomycete Phanerochaete chrysosporium: spectral characterization of the oxidized states and the catalytic cycle  

Microsoft Academic Search

Manganese peroxidase (MnP), an extracellular heme enzyme from the lignin-degrading fungus Phanerochaete chrysosporium, catalyzes the Mn(II)-dependent oxidation of a variety of phenols. Herein, the authors spectroscopically characterize the oxidized states of MnP compounds I, II, and III and clarify the role of Mn in the catalytic cycle of the enzyme. Addition of 1 equiv of HâOâ to the native ferric

Hiroyuki Wariishi; Lakshmi Akileswaran; Michael H. Gold

1988-01-01

353

Tissue Manganese Concentrations in Young Male Rhesus Monkeys following Subchronic Manganese Sulfate Inhalation  

Microsoft Academic Search

High-dose human exposure to manganese results in manganese accumulation in the basal ganglia and dopaminergic neuropa- thology. Occupational manganese neurotoxicity is most frequently linked with manganese oxide inhalation; however, exposure to other forms of manganese may lead to higher body burdens. The objective of this study was to determine tissue manganese con- centrations in rhesus monkeys following subchronic (6 h\\/day,

David C. Dorman; Melanie F. Struve; Marianne W. Marshall; Carl U. Parkinson; R. Arden James; Brian A. Wong

2006-01-01

354

Effects of synthesis temperature and precursor composition on the crystal structure, morphology, and electrode activity of 1D nanostructured manganese oxides  

Microsoft Academic Search

1D nanostructured manganese oxides are prepared by oxidation reaction of precursor LiMn2?xCrxO4 microcrystals under hydrothermal condition. The crystal structure and morphology of the obtained manganese oxides are strongly dependent on the reaction condition and the chemical composition of the precursors. The ?-MnO2 nanowires are prepared by reaction at 120°C, and their aspect ratios decrease with the Cr content in the

In Young Kim; Sun Hee Lee; Hyung-Wook Ha; Tae Woo Kim; Yoon Soo Han; Jin Kyu Kang; Dong Ha Lee; Seong-Ju Hwang

2010-01-01

355

Doubling the capacity of lithium manganese oxide spinel by a flexible skinny graphitic layer.  

PubMed

By coating nanoparticular lithium manganese oxide (LMO) spinel with a few layers of graphitic basal planes, the capacity of the material reached up to 220?mA?h?g(-1) at a cutoff voltage of 2.5?V. The graphitic layers 1)?provided a facile electron-transfer highway without hindering ion access and, more interestingly, 2)?stabilized the structural distortion at the 3?V region reaction. The gain was won by a simple method in which microsized LMO was ball-milled in the presence of graphite with high energy. Vibratory ball milling pulverized the LMO into the nanoscale, exfoliated graphite of less than 10?layers and combined them together with an extremely intimate contact. Ab?initio calculations show that the intrinsically very low electrical conductivity of the tetragonal phase of the LMO is responsible for the poor electrochemical performance in the 3?V region and could be overcome by the graphitic skin strategy proposed. PMID:24706561

Noh, Hyun Kuk; Park, Han-Saem; Jeong, Hu Young; Lee, Sang Uck; Song, Hyun-Kon

2014-05-12

356

Reaction of Formic Acid over Amorphous Manganese Oxide Catalytic Systems: An In Situ Study  

SciTech Connect

The interaction of formic acid with amorphous manganese oxide (AMO) is investigated using in situ photoelectron and infrared spectroscopy techniques. Soft X-ray photoelectron spectroscopy (sXPS) and in situ FTIR illustrate two possible modes of formate bound species at the AMO surface. Two peaks in the IR region from 1340-1390 cm{sup -1} are indicative of formate species bound to the surface in a bidentate configuration. However, a 224 cm{sup -1} band gap between v{sub s}OCO and v{sub as}OCO suggests formate is bound in a bridging configuration. Temperature-programmed desorption studies confirm the formate bound species desorbs as carbon dioxide from the surface at multiple binding sites. At temperatures above 700 K, the presence of K{sup +} {hor_ellipsis} OC complex suggests the bound species interacts at vacant sites related to framework oxygen and cation mobility.

J Durand; S Senanayake; S Suib; D Mullins

2011-12-31

357

Recovery of manganese oxides from spent alkaline and zinc-carbon batteries. An application as catalysts for VOCs elimination.  

PubMed

Manganese, in the form of oxide, was recovered from spent alkaline and zinc-carbon batteries employing a biohydrometallurgy process, using a pilot plant consisting in: an air-lift bioreactor (containing an acid-reducing medium produced by an Acidithiobacillus thiooxidans bacteria immobilized on elemental sulfur); a leaching reactor (were battery powder is mixed with the acid-reducing medium) and a recovery reactor. Two different manganese oxides were recovered from the leachate liquor: one of them by electrolysis (EMO) and the other by a chemical precipitation with KMnO4 solution (CMO). The non-leached solid residue was also studied (RMO). The solids were compared with a MnOx synthesized in our laboratory. The characterization by XRD, FTIR and XPS reveal the presence of Mn2O3 in the EMO and the CMO samples, together with some Mn(4+) cations. In the solid not extracted by acidic leaching (RMO) the main phase detected was Mn3O4. The catalytic performance of the oxides was studied in the complete oxidation of ethanol and heptane. Complete conversion of ethanol occurs at 200°C, while heptane requires more than 400°C. The CMO has the highest oxide selectivity to CO2. The results show that manganese oxides obtained using spent alkaline and zinc-carbon batteries as raw materials, have an interesting performance as catalysts for elimination of VOCs. PMID:23562448

Gallegos, María V; Falco, Lorena R; Peluso, Miguel A; Sambeth, Jorge E; Thomas, Horacio J

2013-06-01

358

Nanostructured dimagnesium manganese oxide (Spinel): Control of size, shape and their magnetic and electro catalytic properties  

SciTech Connect

Tetravalent Mn based ternary oxides are of interest as they are important electrode materials. Dimagnesium manganate (Mg{sub 2}MnO{sub 4}) is one Mn(IV) containing oxide which has been of interest. Nanostructures of the above oxide (spinel) have been obtained by the thermal decomposition of nanostructured metal oxalate precursor at 500 Degree-Sign C. The size and anisotropy of the oxide nanostructures was controlled by choosing appropriate decomposition temperature of the oxalate precursor. Mg{sub 2}MnO{sub 4} nanorods were obtained at low temperature (500 Degree-Sign C), formed by aligned nanoparticles of size{approx}8-10 nm. These nanoparticles show Curie-Weiss behavior with Weiss constant (14 K). Below {approx}50 K there is a small deviation resulting in a negative Weiss constant (-7.36 K) indicating exchange cross over (from ferromagnetic like interactions to antiferromagnetic interactions). The high temperature magnetic moment corresponds to Mn (IV). Electrochemical experiments show that nanostructured Mg{sub 2}MnO{sub 4} is an efficient anode material for oxygen evolution reaction with a current density of 14 mA/cm{sup 2}. The stability of the anode over several cycles of oxidation and reduction is highly encouraging. - Graphical abstract: Nanostructured dimagnesium manganese with efficient electrocatalytic property synthesized by reverse micellar route. Highlights: Black-Right-Pointing-Pointer Mg{sub 2}MnO{sub 4} nanorods were synthesized by reverse micellar route. Black-Right-Pointing-Pointer Anisotropy of oxalate rods retained in oxides nanorods. Black-Right-Pointing-Pointer Nanorods show good catalytic behavior towards oxygen evolution reaction.

Garg, Neha; Menaka [Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi 110016 (India); Ramanujachary, Kandalam V. [Department of Chemistry and Biochemistry, Rowan University, Glassboro, NJ 08028 (United States); Lofland, Samuel E. [Department of Physics and Astronomy, Rowan University, Glassboro, NJ 08028 (United States); Ganguli, Ashok K., E-mail: ashok@chemistry.iitd.ernet.in [Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi 110016 (India)

2013-01-15

359

Manganese doping of magnetic iron oxide nanoparticles: tailoring surface reactivity for a regenerable heavy metal sorbent.  

PubMed

A method for tuning the analyte affinity of magnetic, inorganic nanostructured sorbents for heavy metal contaminants is described. The manganese-doped iron oxide nanoparticle sorbents have a remarkably high affinity compared to the precursor material. Sorbent affinity can be tuned toward an analyte of interest simply by adjustment of the dopant quantity. The results show that following the Mn doping process there is a large increase in affinity and capacity for heavy metals (i.e., Co, Ni, Zn, As, Ag, Cd, Hg, and Tl). Capacity measurements were carried out for the removal of cadmium from river water and showed significantly higher loading than the relevant commercial sorbents tested for comparison. The reduction in Cd concentration from 100 ppb spiked river water to 1 ppb (less than the EPA drinking water limit of 5 ppb for Cd) was achieved following treatment with the Mn-doped iron oxide nanoparticles. The Mn-doped iron oxide nanoparticles were able to load ~1 ppm of Cd followed by complete stripping and recovery of the Cd with a mild acid wash. The Cd loading and stripping is shown to be consistent through multiple cycles with no loss of sorbent performance. PMID:22329500

Warner, Cynthia L; Chouyyok, Wilaiwan; Mackie, Katherine E; Neiner, Doinita; Saraf, Laxmikant V; Droubay, Timothy C; Warner, Marvin G; Addleman, R Shane

2012-02-28

360

Manganese Doping of Magnetic Iron Oxide Nanoparticles: Tailoring Surface Reactivity for a Regenerable Heavy Metal Sorbent  

SciTech Connect

A method for tuning the analyte affinity of magnetic, inorganic nanostructured sorbents for heavy metal contaminants is described. The manganese-doped iron oxide nanoparticle sorbents have a remarkably high affinity compared to the precursor material. Sorbent affinity can be tuned toward an analyte of interest simply by adjustment of the dopant quantity. The results show that following the Mn doping process there is a large increase in affinity and capacity for heavy metals (i.e., Co, Ni, Zn, As, Ag, Cd, Hg, and Tl). Capacity measurements were carried out for the removal of cadmium from river water and showed significantly higher loading than the relevant commercial sorbents tested for comparison. The reduction in Cd concentration from 100 ppb spiked river water to 1 ppb (less than the EPA drinking water limit of 5 ppb for Cd) was achieved following treatment with the Mn-doped iron oxide nanoparticles. The Mn-doped iron oxide nanoparticles were able to load 1 ppm of Cd followed by complete stripping and recovery of the Cd with a mild acid wash. The Cd loading and stripping is shown to be consistent through multiple cycles with no loss of sorbent performance.

Warner, Cynthia L.; Chouyyok, Wilaiwan; Mackie, Katherine E.; Neiner, Doinita; Saraf, Laxmikant; Droubay, Timothy C.; Warner, Marvin G.; Addleman, Raymond S.

2012-02-28

361

Metals, Oxidative Stress and Neurodegeneration: A focus on Iron, Manganese and Mercury  

PubMed Central

Essential metals are crucial for the maintenance of cell homeostasis. Among the 23 elements that have known physiological functions in humans, 12 are metals, including iron (Fe) and manganese (Mn). Nevertheless, excessive exposure to these metals may lead to pathological conditions, including neurodegeneration. Similarly, exposure to metals that do not have known biological functions, such as mercury (Hg), also present great health concerns. This reviews focuses on the neurodegenerative mechanisms and effects of Fe, Mn and Hg. Oxidative stress (OS), particularly in mitochondria, is a common feature of Fe, Mn and Hg toxicity. However, the primary molecular targets triggering OS are distinct. Free cationic iron is a potent pro-oxidant and can initiate a set of reactions that form extremely reactive products, such as OH•. Mn can oxidize dopamine (DA), generating reactive species and also affect mitochondrial function, leading to accumulation of metabolites and culminating with OS. Cationic Hg forms have strong affinity for nucleophiles, such as –SH and –SeH. Therefore, they target critical thiol- and selenol-molecules with antioxidant properties. Finally, we address the main sources of exposure to these metals, their transport mechanisms into the brain, and therapeutic modalities to mitigate their neurotoxic effects. PMID:23266600

Farina, Marcelo; Avila, Daiana Silva; da Rocha, Joao Batista Teixeira

2013-01-01

362

Photochemical Water Oxidation by Crystalline Polymorphs of Manganese Oxides: Structural Requirements for Catalysis  

E-print Network

globally scalable. Among the catalytically more active nonprecious metal oxides are nano- crystalline, and IrO2,, which have the lowest energy losses.1 Bulk metal oxides have long been of interest compositions and disordered structure types.2-4 Among these, the precious metal oxides like RuO2 and IrO2 were

Garfunkel, Eric

363

The oxidation of acid azo dye AY 36 by a manganese oxide containing mine waste.  

PubMed

The oxidative breakdown of acid azo dye acid yellow 36 (AY 36) by a Mn oxide containing mine tailings is demonstrated. The oxidation reaction is pH dependent with the rate of decolorization increasing with decreasing pH. The oxidation reaction mechanism is initiated at the amino moiety and proceeds via successive, one electron transfers from the dye to the Mn oxide minerals. The reaction pathway involves the formation of a number of colorless intermediate products, some of which hydrolyze in a Mn oxide-independent step. Decolorization of the dye is rapid and is observed before the cleavage of the azo-bond, which is a slower process. The terminal oxidation products were observed to be p-benzoquinone and 3-hydroxybenzenesulfonate. The reaction order of the initial decolorization was determined to be pseudo fractional order with respect to pH and pseudo first order with respect to dye concentration and Mn tailings' surface area. PMID:23333488

Clarke, Catherine E; Kielar, Filip; Johnson, Karen L

2013-02-15

364

Superoxide Production by a Manganese-Oxidizing Bacterium Facilitates Iodide Oxidation  

PubMed Central

The release of radioactive iodine (i.e., iodine-129 and iodine-131) from nuclear reprocessing facilities is a potential threat to human health. The fate and transport of iodine are determined primarily by its redox status, but processes that affect iodine oxidation states in the environment are poorly characterized. Given the difficulty in removing electrons from iodide (I?), naturally occurring iodide oxidation processes require strong oxidants, such as Mn oxides or microbial enzymes. In this study, we examine iodide oxidation by a marine bacterium, Roseobacter sp. AzwK-3b, which promotes Mn(II) oxidation by catalyzing the production of extracellular superoxide (O2?). In the absence of Mn2+, Roseobacter sp. AzwK-3b cultures oxidized ?90% of the provided iodide (10 ?M) within 6 days, whereas in the presence of Mn(II), iodide oxidation occurred only after Mn(IV) formation ceased. Iodide oxidation was not observed during incubations in spent medium or with whole cells under anaerobic conditions or following heat treatment (boiling). Furthermore, iodide oxidation was significantly inhibited in the presence of superoxide dismutase and diphenylene iodonium (a general inhibitor of NADH oxidoreductases). In contrast, the addition of exogenous NADH enhanced iodide oxidation. Taken together, the results indicate that iodide oxidation was mediated primarily by extracellular superoxide generated by Roseobacter sp. AzwK-3b and not by the Mn oxides formed by this organism. Considering that extracellular superoxide formation is a widespread phenomenon among marine and terrestrial bacteria, this could represent an important pathway for iodide oxidation in some environments. PMID:24561582

Li, Hsiu-Ping; Daniel, Benjamin; Creeley, Danielle; Grandbois, Russell; Zhang, Saijin; Xu, Chen; Ho, Yi-Fang; Schwehr, Kathy A.; Kaplan, Daniel I.; Santschi, Peter H.; Hansel, Colleen M.

2014-01-01

365

Chemical syntheses of manganese and tantalum oxide octahedral molecular sieves and their structural characterization by powder x-ray diffraction  

NASA Astrophysics Data System (ADS)

This research consists of soft chemical synthesis and structural investigations of manganese and tantalum oxide octahedral molecular sieves. These include the use of sol-gel, hydrothermal and reflux methods for syntheses and the employment of various techniques for characterization, especially the Rietveld analysis of powder X-ray diffraction data for structural refinements. The manganese oxide cryptomelane (K-OMS-2) with a tunnel structure and birnessite layered materials (OL-1) were prepared by the sol gel method. The synthesis consists of reacting MnO4- solutions with fumaric acid or glucose to form a gel, and heating the xerogels at a temperature effective to produce the final manganese oxide materials. These sol-gel methods give many advantages, such as high thermal stabilities of products, over other preparation routes. The synthetic parameters have been optimized to prepare pure K-OMS-2 and OL-1. The crystal structure of K-OMS-2 has been refined by the Rietveld method from in-house powder X-ray diffraction data. The potassium tantalate defect pyrochlores were prepared by hydrothermal methods at a temperature of 200°C. The materials were crystallized from tantalum pentoxide in a potassium hydroxide solution, with a uniform crystal size of about 1 mum. They were ion-exchanged with H+ at low temperatures in a nitric acid solution. A BET surface area of 15 m 2/g was obtained. The structure of this defect pyrochlore and its acid exchanged form were determined by Rietveld refinement from powder X-ray diffraction data. The reflux method was also employed to search for new manganese oxide microporous materials. A ramsdellite material with a 1 x 2 tunnel structure and high surface area of 70 m2/g was prepared. Catalytic oxidations of hexane and cyclohexane with tert-butyl hydroperoxide have shown good activities with this catalyst. This investigation suggests that shape selectivity plays a role in the high catalytic activities of the oxidations of these saturated hydrocarbons.

Duan, Niangao

366

Photochemical oxidation of a manganese(III) complex with oxygen and toluene derivatives to form a manganese(V)-oxo complex.  

PubMed

Visible light photoirradiation of an oxygen-saturated benzonitrile solution of a manganese(III) corrolazine complex [(TBP8Cz)Mn(III)] (1): [TBP8Cz = octakis(p-tert-butylphenyl)corrolazinato(3-)] in the presence of toluene derivatives resulted in formation of the manganese(V)-oxo complex [(TBP8Cz)Mn(V)(O)]. The photochemical oxidation of (TBP8Cz)Mn(III) with O2 and hexamethylbenzene (HMB) led to the isosbestic conversion of 1 to (TBP8Cz)Mn(V)(O), accompanied by the selective oxidation of HMB to pentamethylbenzyl alcohol (87%). The formation rate of (TBP8Cz)Mn(V)(O) increased with methyl group substitution, from toluene, p-xylene, mesitylene, durene, pentamethylbenzene, up to hexamethylbenzene. Deuterium kinetic isotope effects (KIEs) were observed for toluene (KIE = 5.4) and mesitylene (KIE = 5.3). Femtosecond laser flash photolysis of (TBP8Cz)Mn(III) revealed the formation of a tripquintet excited state, which was rapidly converted to a tripseptet excited state. The tripseptet excited state was shown to be the key, activated state that reacts with O2 via a diffusion-limited rate constant. The data allow for a mechanism to be proposed in which the tripseptet excited state reacts with O2 to give the putative (TBP8Cz)Mn(IV)(O2(•-)), which then abstracts a hydrogen atom from the toluene derivatives in the rate-determining step. The mechanism of hydrogen abstraction is discussed by comparison of the reactivity with the hydrogen abstraction from the same toluene derivatives by cumylperoxyl radical. Taken together, the data suggest a new catalytic method is accessible for the selective oxidation of C-H bonds with O2 and light, and the first evidence for catalytic oxidation of C-H bonds was obtained with 10-methyl-9,10-dihydroacridine as a substrate. PMID:24219426

Jung, Jieun; Ohkubo, Kei; Prokop-Prigge, Katharine A; Neu, Heather M; Goldberg, David P; Fukuzumi, Shunichi

2013-12-01

367

Processing of Manganese-Doped [Bi0.5Na0.5]TiO3 Ferroelectrics: Reduction and Oxidation Reactions During Calcination and Sintering  

E-print Network

During Calcination and Sintering Elena Aksel,z Peter Jakes,y Emre Erdem,y Donald M. Smyth,z Andrew calcination at 8001C the manganese functional centers are oxidized to Mn31 . Subsequent to the sintering

McQuade, D. Tyler

368

Biogenic precipitation of manganese oxides and enrichment of heavy metals at acidic soil pH  

NASA Astrophysics Data System (ADS)

The precipitation of biogenic Mn oxides at acidic pH is rarely reported and poorly understood, compared to biogenic Mn oxide precipitation at near neutral conditions. Here we identified and investigated the precipitation of biogenic Mn oxides in acidic soil, and studied their role in the retention of heavy metals, at the former uranium mining site of Ronneburg, Germany. The site is characterized by acidic pH, low carbon content and high heavy metal loads including rare earth elements. Specifically, the Mn oxides were present in layers identified by detailed soil profiling and within these layers pH varied from 4.7 to 5.1, Eh varied from 640 to 660 mV and there were enriched total metal contents for Ba, Ni, Co, Cd and Zn in addition to high Mn levels. Using electron microprobe analysis, synchrotron X-ray diffraction and X-ray absorption spectroscopy, we identified poorly crystalline birnessite (?-MnO2) as the dominant Mn oxide in the Mn layers, present as coatings covering and cementing quartz grains. With geochemical modelling we found that the environmental conditions at the site were not favourable for chemical oxidation of Mn(II), and thus we performed 16S rDNA sequencing to isolate the bacterial strains present in the Mn layers. Bacterial phyla present in the Mn layers belonged to Firmicutes, Actinobacteria and Proteobacteria, and from these phyla we isolated six strains of Mn(II) oxidizing bacteria and confirmed their ability to oxidise Mn(II) in the laboratory. The biogenic Mn oxide layers act as a sink for metals and the bioavailability of these metals was much lower in the Mn layers than in adjacent layers, reflecting their preferential sorption to the biogenic Mn oxide. In this presentation we will report our findings, concluding that the formation of natural biogenic poorly crystalline birnessite can occur at acidic pH, resulting in the formation of a biogeochemical barrier which, in turn, can control the mobility and bioavailability of heavy metals in acidic soil environments.

Mayanna, Sathish; Peacock, Caroline L.; Schäffner, Franziska; Grawunder, Anja; Merten, Dirk; Kothe, Erika; Büchel, Georg

2014-05-01

369

Lithium extraction from orthorhombic lithium manganese oxide and the phase transformation to spinel  

SciTech Connect

Development of rechargeable lithium batteries is limited by a concern regarding their safety. Current efforts are focused on rocking-chair'' cells which avoid the use of metallic lithium electrodes and are therefore potentially far safer than conventional lithium cells. Carbon is the anode material of choice for rocking-chair'' cells as it gives good reversibility, high capacity and low average voltage versus lithium, resulting in high energy density cells. Carbon anodes must be coupled with lithium-rich or discharged cathodes. When the cell is first charged, lithium is transferred from the lithium-rich cathode to the carbon anode. However, not all the lithium can be recovered from the anode on the subsequent discharge; surplus cathode capacity is therefore required in the initial cathode to counteract this loss. Lithium transition-metal oxides are being developed as cathode materials for rocking-chair'' batteries. Lithium manganese oxides, which are cheap and non-toxic, are favored over the lithium-cobalt-oxide, LiCoO[sub 2], and lithium-nickel-oxide, LiNiO[sub 2].Here, orthorhombic LiMnO[sub 2] products, synthesized by the reaction of [gamma]-MnO[sub 2] and LiOH in argon at 600--620 C using carbon as a reducing agent, have been evaluated as electrode materials in lithium cells. Products that contained a minor proportion of a lithiated spinel phase showed greater electrochemical activity than pure LiMnO[sub 2]. On delithiation, LiMnO[sub 2] transforms irreversibly to a spinel-type structure. A mechanism for the orthorhombic Li[sub x]MnO[sub 2]-spinel phase transformation is proposed.

Gummow, R.J.; Liles, D.C.; Thackeray, M.M. (CSIR, Pretoria (South Africa). Div. of Materials Science and Technology)

1993-12-01

370

Manganese peroxidase degrades pristine but not surface-oxidized (carboxylated) single-walled carbon nanotubes.  

PubMed

The transformation of engineered nanomaterials in the environment can significantly affect their transport, fate, bioavailability, and toxicity. Little is known about the biotransformation potential of single-walled carbon nanotubes (SWNTs). In this study, we compared the enzymatic transformation of SWNTs and oxidized (carboxylated) SWNTs (O-SWNTs) using three ligninolytic enzymes: lignin peroxidase, manganese peroxidase (MnP), and laccase. Only MnP was capable of transforming SWNTs, as determined by Raman spectroscopy, near-infrared spectroscopy, and transmission electron microscopy. Interestingly, MnP degraded SWNTs but not O-SWNTs. The recalcitrance of O-SWNTs to enzymatic transformation is likely attributable to the binding of Mn2+ by their surface carboxyl groups at the enzyme binding site, which inhibits critical steps in the MnP catalytic cycle (i.e., Mn2+ oxidation and Mn3+ dissociation from the enzyme). Our results suggest that oxygen-containing surface functionalities do not necessarily facilitate the biodegradation of carbonaceous nanomaterials, as is commonly assumed. PMID:24988479

Zhang, Chengdong; Chen, Wei; Alvarez, Pedro J J

2014-07-15

371

Composite manganese oxide percolating networks as a suspension electrode for an asymmetric flow capacitor.  

PubMed

In this study, we examine the use of a percolating network of metal oxide (MnO2) as the active material in a suspension electrode as a way to increase the capacitance and energy density of an electrochemical flow capacitor. Amorphous manganese oxide was synthesized via a low-temperature hydrothermal approach and combined with carbon black to form composite flowable electrodes of different compositions. All suspension electrodes were tested in static configurations and consisted of an active solid material (MnO2 or activated carbon) immersed in aqueous neutral electrolyte (1 M Na2SO4). Increasing concentrations of carbon black led to better rate performance but at the cost of capacitance and viscosity. Furthermore, it was shown that an expanded voltage window of 1.6 V could be achieved when combining a composite MnO2-carbon black (cathode) and an activated carbon suspension (anode) in a charge balanced asymmetric device. The expansion of the voltage window led to a significant increase in the energy density to ?11 Wh kg(-1) at a power density of ?50 W kg(-1). These values are ?3.5 times and ?2 times better than a symmetric suspension electrode based on activated carbon. PMID:24758221

Hatzell, Kelsey B; Fan, Lei; Beidaghi, Majid; Boota, Muhammad; Pomerantseva, Ekaterina; Kumbur, Emin C; Gogotsi, Yury

2014-06-11

372

Manganese oxide/titania materials for removal of NOx and elemental mercury from flue gas  

SciTech Connect

A novel catalyst for low temperature selective catalytic reduction (SCR) using CO as reductant, MnOx supported on titania, has been shown to be effective for both elemental mercury capture and low temperature SCR. In low temperature (200{sup o}C) SCR trials using an industrially relevant space velocity (50 000 h{sup -1}) and oxygen concentration (2 vol %), nearly quantitative reduction of NOx was obtained using CO as the reductant. Fresh catalyst used as an adsorbent for elemental mercury from an inert atmosphere showed remarkable mercury capture capacity, as high as 17.4 mg/g at 200{sup o}C. The catalyst effectively captured elemental mercury after use in NOx reduction. Mercury capture efficiency was not affected by the presence of water vapor. Mercury capacity was reduced in the presence of SO{sub 2}. Manganese loading and bed temperature, which influence surface oxide composition, were found to be important factors for mercury capture. X-ray photoelectron spectroscopy (XPS) results reveal that the mercury is present in its oxidized form (HgO) in spent catalyst, indicating the participation of lattice oxygen of the catalyst in the reaction. These results suggest that a single-step process integrating low temperature SCR and mercury capture from flue gas might be feasible. 42 refs., 10 figs., 2 tabs.

Lei Ji; Pavani M. Sreekanth; Panagiotis G. Smirniotis; Stephen W. Thiel; Neville G. Pinto [University of Cincinnati, Cincinnati, OH (United States). Department of Chemical & Materials Engineering

2008-07-15

373

Growth of different phases of yttrium manganese oxide thin films by pulsed laser deposition  

SciTech Connect

Various phases of yttrium manganese oxide (YMO) thin films have been synthesized on different substrates from a single target of h-YMnO{sub 3}. It is observed that the phase stability and crystallinity of YMO thin films depend on the substrate used and oxygen partial pressure (OPP). (110) oriented and polycrystalline growth of h-YMnO{sub 3} are observed on the Al{sub 2}O{sub 3} (0001) and NGO (110) substrates respectively, when grown in OPP {approx_equal} 10{sup -6} Torr. While for similar OPP value, growth of mixed phases (h-YMnO{sub 3} and o-YMn{sub 2}O{sub 5}) is observed on Si (001) substrate. Oriented growth of O-YMn{sub 2}O{sub 5} phase film on Si (001) substrate is observed first time, when deposited at OPP value of 225 and 350 mTorr. +3 and mixed oxidation states (+3 and +4) of Mn were confirmed by x-ray photoelectron spectroscopy in pure YMnO{sub 3} phase and YMn{sub 2}O{sub 5} phase respectively.

Kumar, Manish; Choudhary, R. J.; Phase, D. M. [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore, 452001 (India)

2012-06-05

374

Effect of the high pressure on the structure and intercalation properties of lithium–nickel–manganese oxides  

Microsoft Academic Search

Lithium–nickel–manganese oxides (Li1+x(Ni1\\/2Mn1\\/2)1?xO2, x=0 and 0.2), having different cationic distributions and an oxidation state of Ni varying from 2+ to 3+, were formed under a high-pressure (3GPa). The structure and cationic distribution in these oxides were examined by powder X-ray diffraction, infrared (IR) and electron paramagnetic resonance (EPR) in X-band (9.23GHz) and at higher frequencies (95 and 285GHz). Under a

M. Yoncheva; R. Stoyanova; E. Zhecheva; R. Alcántara; G. Ortiz; J. L. Tirado

2007-01-01

375

Effects of synthetic parameters on structure and electrochemical performance of spinel lithium manganese oxide by citric acid-assisted sol–gel method  

Microsoft Academic Search

The spinel lithium manganese oxide cathode materials were prepared by citric acid-assisted sol–gel method at 623–1073K in air. The effects of pH value, raw material, synthesis temperature and time on structure and electrochemical performance of spinel lithium manganese oxide are investigated by X-ray diffraction (XRD), scanning electronic microscope (SEM) and cyclic voltammetry (CV). XRD data results strongly suggest that the

Tingfeng Yi; Changsong Dai; Kun Gao; Xinguo Hu

2006-01-01

376

Multifunctional porous mix-valent manganese oxide nano-materials and ruthenium\\/titanium dioxide for magnetic, electronic, and catalytic applications  

Microsoft Academic Search

This thesis contains two parts: (1) development of porous mixed-valent manganese oxide octahedral molecular sieve (OMS) nano-materials with controlled tunnel structures and muilt-functionalities and (2) application of H 2 adsorption for metal particle size evaluation on TiO2 supported Ru Fischer-Tropsch catalysts. Manganese oxide OMS with different nano-scale tunnel sizes may result in various microporosities for different selective catalysis and separation

Xiongfei Shen

2006-01-01

377

Electrochemical evaluation of the a carbon-paste electrode modified with spinel manganese(IV) oxide under flow conditions for amperometric determination of lithium  

Microsoft Academic Search

The participation of cations in redox reactions of manganese oxides provides an opportunity for development of chemical sensors for non-electroactive ions. This paper describes the amperometric determination of lithium ions using carbon-paste electrode modified with spinel manganese(IV) oxide under flow conditions. Systematic investigations were made to optimize the experimental parameters for lithium sensor by flow injection analysis. The detection was

Paulo A. Raymundo-Pereira; Cibely S. Martin; Marcio F. Bergamini; Nerilso Bocchi; Marcos F. S. Teixeira

2011-01-01

378

Early diagenetic quartz formation at a deep iron oxidation front in the Eastern Equatorial Pacific - A modern analogue for banded iron/chert formations?  

NASA Astrophysics Data System (ADS)

The mechanisms of early diagenetic quartz formation under low-temperature conditions are still poorly understood. In this study we investigated lithified cherts consisting of microcrystalline quartz recovered near the base of a 420 m thick Miocene-Holocene sequence of nannofossil and diatom ooze at a drill site in the Eastern Equatorial Pacific (Ocean Drilling Program Site 1226). Precipitation seems still ongoing based on a sharp depletion in dissolved silica at the depth of the cherts. Also, palaeo-temperatures reconstructed from ?18O values in the cherts are in the range of adjacent porewater temperatures. Opal-A dissolution appears to control silica concentration throughout the sequence, while the solution remains oversaturated with respect to quartz. However, at the depth of the sharp depletion in dissolved silica, quartz is still saturated while the more soluble silica phases are strongly undersaturated. Hence, precipitation of quartz was initiated by an auxiliary process. A process, previously observed to assist in the nucleation of quartz is the adsorption of silica on freshly precipitated iron oxides. Indeed, a deep iron oxidation front is present at 400 m below seafloor, which is caused by upward diffusing nitrate from an oxic seawater aquifer in the underlying oceanic crust. Sequential iron extraction showed a higher content of the adsorbed iron hydroxide fraction in the chert than in the adjacent nannofossil and diatom ooze. X-ray absorption near-edge structure (XANES) spectroscopy revealed that iron in the cherts predominantly occurs in illite and amorphous iron oxide, whereas iron in the nannofossil and diatom ooze occurs mainly in smectite. Mössbauer spectroscopy also indicated the presence of illite that is to 97% oxidized. Two possible mechanisms may be operative during early diagenetic chert formation at iron oxidation fronts: (1) silica precipitation is catalysed by adsorption to freshly precipitated iron oxide surfaces, and (2) porewater silica concentration is locally decreased below opal-A and opal-CT saturation allowing for precipitation of the thermodynamically more stable phase: quartz. This mechanism of chert formation at the iron oxidation front in suboxic zones may explain why early-diagenetic microcrystalline chert only occurs sporadically in modern marine sediments. It may also serve as a modern analogue for the deposition of much more abundant banded iron/chert formations at the time of the great oxidation event around 2.4 Ga BP, which was probably the largest iron oxidation front in Earth's history.

Meister, Patrick; Chapligin, Bernhard; Picard, Aude; Meyer, Hanno; Fischer, Cornelius; Rettenwander, Daniel; Amthauer, Georg; Vogt, Christoph; Aiello, Ivano W.

2014-07-01

379

Oxidation of alkanes and alkenes by iodosylbenzene and hydrogen peroxide catalysed by halogenated manganese porphyrins in homogeneous solution and covalently bound to silica  

Microsoft Academic Search

Manganese(III) 5-(pentafluorophenyl)-10,15,20-tri(2,6-dichlorophenyl)porphyrin, Mn(PFTDCPP), and manganese(II) 2,3,7,8,12,13,17,18-octachloro-5-(pentafluorophenyl)-10,15-20-tri(2,6-dichlorophenyl)porphyrin, Mn(PFTDCCl8PP), have been synthesised and used as catalysts in hydrocarbon oxidations by iodosylbenzene and hydrogen peroxide both in solution and covalently bound to aminopropylated silica. The former shows higher efficiency in the epoxidation of alkenes by iodosylbenzene, whereas the perchlorinated manganese porphyrin is more efficient in the hydroxylation of alkanes by this oxidant. The

Fabio G Doro; John R. Lindsay Smith; Antônio G Ferreira; Marilda D Assis

2000-01-01

380

Effect of Li ion in transition metal sites on electrochemical behavior of layered lithium manganese oxides solid solutions  

Microsoft Academic Search

Two solid solutions of Li[Li1\\/5Ni1\\/10Co1\\/5Mn1\\/2]O2 and Li[Ni1\\/4Co1\\/2Mn1\\/4]O2 compositions were synthesized using a sol–gel method. The solid solutions with layered manganese oxides were both formed with typical hexagonal structure with maintaining the manganese oxidation state of 4+. The electrochemical characterization of the synthesized materials showed a monotonous discharge curve shape without structural transformation to spinel during charge–discharge processes. The Li[Li1\\/5Ni1\\/10Co1\\/5Mn1\\/2]O2 and

K. S Park; M. H Cho; S. J Jin; K. S Nahm; Y. S Hong

2004-01-01

381

Trivalent manganese as an environmentally friendly oxidizing reagent for microwave- and ultrasound-assisted chemical oxygen demand determination  

Microsoft Academic Search

In the present work manganese(III) has been used as oxidant and microwave radiation and ultrasound energy have been assessed to speed up and to improve the efficiency of digestion step for the determination of chemical oxygen demand (COD). Microwave (MW) and ultrasound-assisted COD determination methods have been optimized by means of experimental design and the optimum conditions are: 40psi pressure,

Claudia E. Domini; Lorena Vidal; Antonio Canals

2009-01-01

382

Capacity loss of lithium manganese oxide spinel in LiPFâ\\/ethylene carbonate-dimethyl carbonate electrolytes  

Microsoft Academic Search

The stability of lithium manganese oxide spinel in LiPFâ\\/EC:DMC (ethylene carbonate-dimethyl carbonate) based electrolytes has been investigated at different states of charge and at temperatures between 21 and 55 C. Reversible capacity loss due to reinsertion of lithium takes place at all states of charge and temperature. This reaction can proceed to the extent of inserting more than one Li

Haitao Huang; C. A. Vincent; P. G. Bruce

1999-01-01

383

Low Temperature Synthesis of Nano-Sized Lithium Manganese Oxide Powder by the Sol-Gel Process Using PVA  

Microsoft Academic Search

Lithium manganese oxide (LiMn2O4) powder with spinel structure has been synthesized by a sol-gel method using an aqueous solution of metal nitrates containing polyvinyl alcohol (PVA). The role of PVA and the calcination conditions for the formation of LiMn2O4 have been studied. Homogeneity and reactivity of the precursor powder are enhanced with an increase in the amount of PVA in

Chung-Hsin Lu; Susanta Kumar Saha

2001-01-01

384

Catalytic decomposition of hydrogen peroxide on manganese oxides. II. A study of the kinetics of the decomposition process  

Microsoft Academic Search

The kinetic parameters of the decomposition process of hydrogen peroxide on manganese oxide have been determined in the concentration range 0.03 to 1 N and the temperature range 1.5 to 42°C; the effect of pH on the rate of decomposition has been studied (pH 2 to 10); and the change in catalyst activity upon repeated treatment with the very same

V. A. Sadykov; P. G. Tsyrulnikov

1976-01-01

385

Effect of Copper Oxide and Manganese Oxide on Properties and Low Temperature Degradation of Sintered Y-TZP Ceramic  

NASA Astrophysics Data System (ADS)

The effect of copper oxide (CuO) and manganese oxide (MnO2) co-dopant on the densification behavior of 3 mol% yttria-stabilized zirconia was investigated. Green samples were prepared and sintered in air at temperatures ranging from 1250 to 1500 °C with a short holding time of 12 min. Sintered bodies were characterized to determine the phase stability, bulk density, hardness, fracture toughness, Young's modulus and grain size. In addition, the aging-induced tetragonal to monoclinic phase transformation of the sintered zirconia was evaluated. It was revealed that the addition of CuO-MnO2 co-dopant was beneficial in enhancing the densification and mechanical properties of the ceramic particularly at low temperatures. A high fracture toughness of 5.5 MPam1/2 coupled with high hardness of 14.5 GPa was obtained for co-doped samples sintered at 1350 °C. However, the undoped ceramic exhibited better properties when sintered above 1350 °C. The study also found that the dopants did not prevent grain coarsening and hence did not suppress the aging-induced phase transformation particularly for samples sintered above 1350 °C.

Khan, M. M.; Ramesh, S.; Bang, L. T.; Wong, Y. H.; Ubenthiran, S.; Tan, C. Y.; Purbolaksono, J.; Misran, H.

2014-09-01

386

Translocation of Inhaled Ultrafine Manganese Oxide Particles to the Central Nervous System  

PubMed Central

Background Studies in monkeys with intranasally instilled gold ultrafine particles (UFPs; < 100 nm) and in rats with inhaled carbon UFPs suggested that solid UFPs deposited in the nose travel along the olfactory nerve to the olfactory bulb. Methods To determine if olfactory translocation occurs for other solid metal UFPs and assess potential health effects, we exposed groups of rats to manganese (Mn) oxide UFPs (30 nm; ~ 500 ?g/m3) with either both nostrils patent or the right nostril occluded. We analyzed Mn in lung, liver, olfactory bulb, and other brain regions, and we performed gene and protein analyses. Results After 12 days of exposure with both nostrils patent, Mn concentrations in the olfactory bulb increased 3.5-fold, whereas lung Mn concentrations doubled; there were also increases in striatum, frontal cortex, and cerebellum. Lung lavage analysis showed no indications of lung inflammation, whereas increases in olfactory bulb tumor necrosis factor-? mRNA (~ 8-fold) and protein (~ 30-fold) were found after 11 days of exposure and, to a lesser degree, in other brain regions with increased Mn levels. Macrophage inflammatory protein-2, glial fibrillary acidic protein, and neuronal cell adhesion molecule mRNA were also increased in olfactory bulb. With the right nostril occluded for a 2-day exposure, Mn accumulated only in the left olfactory bulb. Solubilization of the Mn oxide UFPs was < 1.5% per day. Conclusions We conclude that the olfactory neuronal pathway is efficient for translocating inhaled Mn oxide as solid UFPs to the central nervous system and that this can result in inflammatory changes. We suggest that despite differences between human and rodent olfactory systems, this pathway is relevant in humans. PMID:16882521

Elder, Alison; Gelein, Robert; Silva, Vanessa; Feikert, Tessa; Opanashuk, Lisa; Carter, Janet; Potter, Russell; Maynard, Andrew; Ito, Yasuo; Finkelstein, Jacob; Oberdorster, Gunter

2006-01-01

387

Electrochemical characteristics of metal oxide-coated lithium manganese oxide (spinel type)  

Microsoft Academic Search

Metal oxide-coated spinel was investigated with respect to electrochemical characteristics. Metal oxide coating on commercial spinel powder (LiMn2?xMxO4, M=Zr, Nikki, Japan) was carried out using the sol–gel method. Al2O3\\/CuOx-coated spinel exhibited stable cycle performance in the range from 3.0 to 4.4V, and it had lower charge transfer resistance and higher double layer capacitance than bare spinel in later cycles. In

Seung-Won Lee; Kwang-Soo Kim; Ki-Lyoung Lee; Hee-Soo Moon; Hyun-Joong Kim; Byung-Won Cho; Won-Il Cho; Jong-Wan Park

2004-01-01

388

Electrochemical and structural characteristics of metal oxide-coated lithium manganese oxide (spinel type)  

Microsoft Academic Search

The electrochemical and structural characteristics of the metal oxide-coated spinel were investigated in the range of 2.5–4.2V. Metal oxide coating on commercial spinel powder (LiMn2?xMxO4, M=Zr, Nikki, Japan) was carried out using the sol–gel method. Al2O3\\/(PtOx or CuOx)-coated spinel exhibited improved cyclability compared to bare spinel. Impedance analysis results indicated that electrochemical resistance value was not consistent with cycle performance.

Seung-Won Lee; Kwang-Soo Kim; Hee-Soo Moon; Jae-Pil Lee; Hyun-Joong Kim; Byung-Won Cho; Won-Il Cho; Jong-Wan Park

2004-01-01

389

Modeling sorption of divalent metal cations on hydrous manganese oxide using the diffuse double layer model  

USGS Publications Warehouse

Manganese oxides are important scavengers of trace metals and other contaminants in the environment. The inclusion of Mn oxides in predictive models, however, has been difficult due to the lack of a comprehensive set of sorption reactions consistent with a given surface complexation model (SCM), and the discrepancies between published sorption data and predictions using the available models. The authors have compiled a set of surface complexation reactions for synthetic hydrous Mn oxide (HMO) using a two surface site model and the diffuse double layer SCM which complements databases developed for hydrous Fe (III) oxide, goethite and crystalline Al oxide. This compilation encompasses a range of data observed in the literature for the complex HMO surface and provides an error envelope for predictions not well defined by fitting parameters for single or limited data sets. Data describing surface characteristics and cation sorption were compiled from the literature for the synthetic HMO phases birnessite, vernadite and ??-MnO2. A specific surface area of 746 m2g-1 and a surface site density of 2.1 mmol g-1 were determined from crystallographic data and considered fixed parameters in the model. Potentiometric titration data sets were adjusted to a pH1EP value of 2.2. Two site types (???XOH and ???YOH) were used. The fraction of total sites attributed to ???XOH (??) and pKa2 were optimized for each of 7 published potentiometric titration data sets using the computer program FITEQL3.2. pKa2 values of 2.35??0.077 (???XOH) and 6.06??0.040 (???YOH) were determined at the 95% confidence level. The calculated average ?? value was 0.64, with high and low values ranging from 1.0 to 0.24, respectively. pKa2 and ?? values and published cation sorption data were used subsequently to determine equilibrium surface complexation constants for Ba2+, Ca2+, Cd 2+, Co2+, Cu2+, Mg2+, Mn 2+, Ni2+, Pb2+, Sr2+ and Zn 2+. In addition, average model parameters were used to predict additional sorption data for which complementary titration data were not available. The two-site model accounts for variability in the titration data and most metal sorption data are fit well using the pKa2 and ?? values reported above. A linear free energy relationship (LFER) appears to exist for some of the metals; however, redox and cation exchange reactions may limit the prediction of surface complexation constants for additional metals using the LFER. ?? 2003 Elsevier Ltd. All rights reserved.

Tonkin, J.W.; Balistrieri, L.S.; Murray, J.W.

2004-01-01

390

Effect of support on the catalytic activity of manganese oxide catalyts for toluene combustion.  

PubMed

The aim of this work was to study combustion of toluene (1000ppm) over MnO(2) modified with different supports. ?-Al(2)O(3) and ?-Al(2)O(3) obtained from Boehmite, ?-Al(2)O(3) (commercial), SiO(2), TiO(2) and ZrO(2) were used as commercial support materials. In view of potential interest of this process, the influence of support material on the catalytic performance was discussed. The deposition of 9.5MnO(2) was performed by impregnation over support. The catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction and oxidation (TPR/TPO) and thermogravimetric analysis (TGA). The catalytic tests were carried out at atmospheric pressure in a fixed-bed flow reactor. 9.5MnO(2)/?-Al(2)O(3)(B) (synthesized from Boehmite) catalyst exhibits the highest catalytic activity, over which the toluene conversion was up to 90% at a temperature of 289°C. Considering all the characterization and reaction data reported in this study, it was concluded that the manganese state and oxygen species played an important role in the catalytic activity. PMID:22579460

Pozan, Gulin Selda

2012-06-30

391

Layered manganese oxide intergrowth electrodes for rechargeable lithium batteries: Part 1-substitution with Co or Ni  

SciTech Connect

Lithium manganese oxides substituted with nickel or cobalt were characterized electrochemically in lithium cell configurations. The compounds studied were either single-phase layered structures with either primarily O2 or O3 stacking arrangements, or O2/O3 intergrowths, prepared from P2, P3 and P2/P3 sodium-containing precursors, respectively. The stacking arrangements are extremely sensitive to the Na/T. M. (T. M. = transition metal) ratios and the level of substitution. Phase diagrams showing the stability regions of the various arrangements for the Na-Ni-Mn-O system are presented. A possible correlation between vacancies and electrochemical performance is suggested. For high levels of substitution with Ni, fewer defects are possible for materials containing more O3 component and higher discharge capacities can be achieved, but spinel conversion upon cycling also occurs more rapidly as the O3 content increases. Intergrowths show intermediate behavior and represent a potential route towards designing stable, high capacity electrodes.

Dolle, Mickael; Patoux, Sebastien; Doeff, Marca M.

2004-09-08

392

Relationship of crystal structure to interionic interactions in the lithium-manganese spinel oxides  

PubMed

Lithium manganese oxides in the form of cubic spinel phases (space group Fd3m) are formed in a LixMn3-xO4 system for rather limited values of x. Structural investigations by X-ray powder diffraction, applied to the Li-Mn-O compounds, indicate the formation of a second crystalline phase, Li2MnO3 (space group C2/m), with the increasing lithium content. Total Li+ content per unit cell and the cation distribution over a spinel lattice in LixMn3-xO4 have been studied by measurements of integrated intensities of X-ray reflections, and by structure refinement using Rietveld profile analysis. In an attempt to understand the factors affecting cation distribution in the spinel lattice, we applied the computer modelling techniques and investigated the Li+, Mn3+ and Mn4+ ion distribution by calculating the lattice energy, combined with energy minimisation procedures, using the General Utility Lattice Program (GULP), a program designed for simulation of ionic and semi-ionic solids, based on interatomic potential models. PMID:10890371

Piszora; Catlow; Woodley; Wolska

2000-07-01

393

Investigation of nanostructured iron and manganese oxides as novel intercalation hosts for lithium  

NASA Astrophysics Data System (ADS)

Rechargeable lithium battery systems are being pushed to the limits of their performance in modern portable devices, with increasing demands for higher energy and higher power. The intercalation cathode or positive electrode in these batteries is one of the primary bottlenecks in terms of performance. In this thesis, investigation of nanostructured iron and manganese oxide compounds that show immense promise as cathode materials for rechargeable lithium batteries has been conducted. The electrochemical performance of these nanostructured compounds is dramatically superior to their microcrystalline counterparts, with higher specific discharge capacities, improved capacity retention upon charge-discharge cycling and enhanced rate performance. Tied to these promising electrochemical properties are unconventional structural and mechanistic characteristics that have been examined carefully. Higher solid-solubility of lithium in the nanostructured hosts, reduced tendency to undergo phase transformations typically observed in microcrystalline hosts, perfectly reversible lithium intercalation-deintercalation in nanostructured compounds possessing hydroxyl species, are some characteristics illustrated here. The properties exhibited by these materials are dependent upon such structural aspects as lack of long-range order, nano-sized morphology, disordered surface structure and non-stoichiometry. A detailed characterization of these compounds is conducted by studying the local atomic and electronic structures via x-ray absorption spectroscopy (XAS), in conjunction with studying the crystal structure via x-ray diffraction (XRD). The synthesis, electrochemistry, and structural phenomena that possess general relevance to fundamental nanoscale materials science, are highlighted in this work.

Jain, Gaurav

394

Caldimonas manganoxidans gen. nov., sp. nov., a poly(3-hydroxybutyrate)-degrading, manganese-oxidizing thermophile.  

PubMed

A poly(3-hydroxybutyrate) (PHB)-degrading, gram-negative, aerobic bacterium, strain HS(T), was isolated from a hot spring and chemotaxonomically and phylogenetically characterized. The oxidase-positive, weakly catalase-positive, non-pigmented cells (0.6 x 2.6 microm) exhibited a single polar flagellum and accumulated PHB granules. Strain HS(T) was capable of manganese oxidation. Highest growth rate was attained at 50 degrees C. The optimum pH for growth was 7-8. The major respiratory quinone was ubiquinone-8 and major cellular fatty acids were C16:0, C16:1 and C18:1. The G+C content of the DNA was 66.2 mol%. Comparative 16S rDNA analysis indicated that strain HS(T) is related to the Rubrivivax subgroup and the family Comamonadaceae. The nearest phylogenetic relatives were Ideonella dechloratans (92.1% similarity), Leptothrix discophora (93.6%), Roseateles depolymerans (92.4%) and Rubrivivax gelatinosus (92.2%). On the basis of its phylogenetic and phenotypic properties, it is proposed that this isolate be designated Caldimonas manganoxidans gen. nov., sp. nov.; the type strain is HS(T) (= JCM 10698T = IFO 16448T = ATCC BAA-369T). PMID:12054255

Takeda, Minoru; Kamagata, Yoichi; Ghiorse, William C; Hanada, Satoshi; Koizumi, Jun-ichi

2002-05-01

395

A sodium manganese oxide cathode by facile reduction for sodium batteries.  

PubMed

A nonstoichiometric sodium manganese oxide (Na(x)MnO(2+?)) cathode useful for sodium batteries was synthesized by an ambient-temperature strategy that involved facile reduction of aqueous sodium permanganate in sodium iodide and subsequent heat treatment at 600?°C. Combined powder X-ray diffraction and synchrotron X-ray diffraction analyses confirmed the annealed sample to belong to a Na(x)MnO2 phase with a P2-hexagonal structure. The ICP-AES results confirmed the stoichiometry of the sample to be Na0.53MnO(2+?) . Electron microscopy studies revealed the particle size of the electrode to be in the range of a few hundred nanometers. The Na0.53MnO(2+?) cathode delivered an average discharge capacity of 170?mA?h?g(-1) with a stable plateau at 2.1?V for the initial 25?cycles versus sodium. Ex?situ XANES studies confirmed the reversible intercalation of sodium into Na0.53MnO(2+?) and suggested the accommodation of over-stoichiometric Mn(4+) ions to contribute towards the performance of the electrode. PMID:24692202

Song, Jinju; Gim, Jihyeon; Kim, Sungjin; Kang, Jungwon; Mathew, Vinod; Ahn, Docheon; Kim, Jaekook

2014-06-01

396

Solar-thermal Water Splitting Using the Sodium Manganese Oxide Process & Preliminary H2A Analysis  

SciTech Connect

There are three primary reactions in the sodium manganese oxide high temperature water splitting cycle. In the first reaction, Mn2O3 is decomposed to MnO at 1,500°C and 50 psig. This reaction occurs in a high temperature solar reactor and has a heat of reaction of 173,212 J/mol. Hydrogen is produced in the next step of this cycle. This step occurs at 700°C and 1 atm in the presence of sodium hydroxide. Finally, water is added in the hydrolysis step, which removes NaOH and regenerates the original reactant, Mn2O3. The high temperature solar�driven step for decomposing Mn2O3 to MnO can be carried out to high conversion without major complication in an inert environment. The second step to produce H2 in the presence of sodium hydroxide is also straightforward and can be completed. The third step, the low temperature step to recover the sodium hydroxide is the most difficult. The amount of energy required to essentially distill water to recover sodium hydroxide is prohibitive and too costly. Methods must be found for lower cost recovery. This report provides information on the use of ZnO as an additive to improve the recovery of sodium hydroxide.

Todd M. Francis, Paul R. Lichty, Christopher Perkins, Melinda Tucker, Peter B. Kreider, Hans H. Funke, Allan Lewandowski, and Alan W. Weimer

2012-10-24

397

Heavy metals and manganese oxides in the genesee watershed, New York state: effects of geology and land use  

USGS Publications Warehouse

Manganese oxide coatings on gravels from 255 sites on tributary streams in the Genesee River Watershed were analyzed for Mn, Fe, Zn, Cd, Co, Ni, Pb, and Cu. The results were compared with data on bedrock geology, surficial geology and land use, using factor analysis and stepwise multiple regression. All metals except Pb show strong positive correlation with Mn. This association results from the well-known tendency of Mn oxide precipitates to adsorb and incorporate dissolved trace metals. Pb may be present in a separate phase on the gravel surfaces; alternatively Pb abundance may be so strongly influenced by environmental factors that the effect of varying abundance of the carrier phase becomes relatively unimportant. When the effects of varying Mn abundance are allowed for, Pb and to a lesser extent Zn and Cu abundances are seen to be related to commercial, industrial and residential land use. In addition to this pollution effect, all the trace metals, Cd and Ni most strongly, tend to be more abundant in oxide coatings from streams in the forested uplands in the southern part of the area. This probably reflects increased geochemical mobility of the metals in the more acid soils and groundwater of the southern region. A strong Zn anomaly is present in streams draining areas underlain by the Lockport Formation. Oxide coatings in these streams contain up to 5% Zn, originating from disseminated sphalerite in the Lockport and secondary Zn concentrations in the overlying muck soils. The same group of metals, plus calcium and loss on ignition, were determined in the silt and clay (minus 230 mesh) fraction of stream sediments from 129 of the same sites, using a hot nitric acid leach. The amounts of manganese in the sediments are low (average 1020 ppm) and manganese oxides are, at most, of relatively minor significance in the trace-metal geochemistry of these sediments. The bulk of the trace metals in sediment appears to be associated with iron oxides, clays and organic matter. ?? 1981.

Whitney, P. R.

1981-01-01

398

Catalytic oxidation of manganese(II) by multicopper oxidase CueO and characterization of the biogenic Mn oxide.  

PubMed

Manganese(II) contamination is naturally occurring in many groundwater and surface water sources. Moreover, industrial wastewater is also responsible for much of the Mn(II) contamination. Nowadays, Mn(II) contamination has become a serious environmental problem in some regions of the world. To explore a biological approach for removing excessive amounts of aqueous Mn(II) from water, we found a new biocatalyst multicopper oxidase CueO, which was firstly proved to catalyze the oxidation of Mn(II) both in vitro and in vivo. Subsequently, we established a CueO-mediated catalysis system to prepare biogenic Mn oxide (BioMnOx), which was confirmed to be ?-Mn3O4 by X-ray diffraction. This newly prepared BioMnOx consisted of 53.6% Mn(II), 18.4% Mn(III) and 28.0% Mn(IV) characterized by X-ray photoelectron spectroscopy. It exhibited distinct polyhedral structure with nanoparticles of 150-350 nm diameters observed by transmission electron microscopy. Importantly, CueO could remove 35.7% of Mn(II) after a seven-day reaction, and on the other hand, the cueO-overexpressing Escherichia coli strain (ECueO) could also oxidize 58.1% dissolved Mn(II), and simultaneously remove 97.7% Mn(II). Based on these results, we suggest that ECueO strain and CueO enzyme have potential applications on Mn(II) decontamination in water treatment. PMID:24699422

Su, Jianmei; Deng, Lin; Huang, Liangbo; Guo, Shujin; Liu, Fan; He, Jin

2014-06-01

399

Manganese oxides and associated minerals as constituents of dispersed mineralization of metasomatic rocks in the Dukat ore field  

NASA Astrophysics Data System (ADS)

Lithiophorite and coronadite—varieties of vernadite and todorokite—make up finely dispersed colloform mixtures along with minor grains and nanoparticles of aluminosilicates and ore minerals in metasomatic rocks of the Dukat ore field, which were formed in local areas of fluid and hydrothermal-solution discharge at the upper level of the ore-forming system. Fe-vernadite associates with feroxyhyte, magnetite, apatite, K-feldspar, native silver, and acanthite in greisenized granitoids and with epidote, cerianite, plattnerite, and Fe-chlorite in quartz-garnet-chlorite propylites. Todorokite with high Pb, Tl, and Sn contents associates with epidote, albite, bitumen, and native silver in quartz-epidote-chlorite propylites. Al-vernadite, coronadite, and lithiophorite associate with opal, kaolinite, Fe-chlorite, zincite, uraninite, native silver, and acanthite in argillisites. These data allowed us to estimate the conditions of manganese accumulation in the epithermal ore-forming system and deposition conditions of Mn-rich, finely dispersed mineral mixtures in mineralized zones hosted in metasomatic rocks of the ore field.

Filimonova, L. G.; Sivtsov, A. V.; Trubkin, N. V.

2010-08-01

400

Well-ordered organic-inorganic hybrid layered manganese oxide nanocomposites with excellent decolorization performance  

SciTech Connect

Well-ordered organic-inorganic hybrid layered manganese oxide nanocomposites (CTAB-Al-MO) with excellent decolorization performance were prepared through a two-step process. Specifically, the MnO{sub 2} nanosheets were self-assembled in the presence of CTAB, and subsequently pillared with Keggin ions. The obtained CTAB-Al-MO with the basal spacing of 1.59 nm could be stable at 300 Degree-Sign C for 2 h and also possesses high total pore volumes (0.41 cm Superscript-Three g{sup -1}) and high specific BET surface area (161 m{sup 2} g{sup -1}), which is nine times larger than that of the pristine (19 m{sup 2} g{sup -1}). Possible formation process for the highly thermal stable CTAB-Al-MO is proposed here. The decolorization experiments of methyl orange showed that the obtained CTAB-Al-MO exhibit excellent performance in wastewater treatment and the decolorization rate could reach 95% within 5 min. - Graphical Abstract: Well-ordered organic-inorganic hybrid LMO nanocomposites (CTAB-Al-MO) with excellent decolorization performance were prepared through a two-step process. Specifically, the MnO{sub 2} nanosheets were self-assembled by CTAB, and subsequently pillared with Keggin ions. Highlights: Black-Right-Pointing-Pointer A two-step synthesis method was used to prepare the CTAB-Al-MO. Black-Right-Pointing-Pointer The CTAB-Al-MO has the large basal spacing and high specific BET surface area. Black-Right-Pointing-Pointer The thermal stability of the well-ordered CTAB-Al-MO could obviously improve. Black-Right-Pointing-Pointer The CTAB-Al-MO exhibits excellent oxidation and absorption ability to remove organic pollutants.

Zhou, Junli, E-mail: Zhoujunli19851111@163.com [Faculty of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, Guangdong (China)] [Faculty of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, Guangdong (China); Yu, Lin, E-mail: gych@gdut.edu.cn [Faculty of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, Guangdong (China)] [Faculty of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, Guangdong (China); Sun, Ming; Ye, Fei; Lan, Bang; Diao, Guiqiang; He, Jun [Faculty of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, Guangdong (China)] [Faculty of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, Guangdong (China)

2013-02-15

401

Support Information for Kinetic Modeling of Oxidation of Antibacterial Agents by Manganese Oxides  

E-print Network

and k: (a)CIP; (b) CDX. FIGURE S4. Effect of MnO2 loading on Srxn and k: (a) Triclosan; (b) CDX. FIGURE S5. Effect of pH on Srxn and k: (a) CIP; (b) CDX. 1 #12;TABLE S1. Structures and pKa valuesKa (ref) Carbadox (CDX) O N N O O N H N O 9.61 (2) Quinoline N-oxide (QNO) N O Not Applicable Quinoxaline

Huang, Ching-Hua

402

Manganese-Cobalt Mixed Spinel Oxides as Surface Modifiers for Stainless Steel Interconnects of Solid Oxide Fuel Cells  

SciTech Connect

Ferritic stainless steels are promising candidates for interconnect applications in low- and mid-temperature solid oxide fuel cells (SOFCs). A couple of issues however remain for the particular application, including the chromium poisoning due to chromia evaporation, and long-term surface and electrical stability of the scale grown on these steels. Application of a manganese colbaltite spinel protection layer on the steels appears to be an effective approach to solve the issues. For an optimized performance, Mn{sub 1+x}Co{sub 2-x}O{sub 4} (-1 {le} x {le} 2) spinels were investigated against properties relative for protection coating applications on ferritic SOFC interconnects. Overall it appears that the spinels with x around 0.5 demonstrate a good CTE match to ceramic cell components, a relative high electrical conductivity, and a good thermal stability up to 1,250 C. This was confirmed by a long-term test on the Mn{sub 1.5}Co{sub 1.5}O{sub 4} protection layer that was thermally grown on Crofer22 APU, indicating the spinel protection layer not only significantly decreased the contact resistance between a LSF cathode and the stainless steel interconnects, but also inhibited the sub-scale growth on the stainless steels.

Xia, Gordon; Yang, Z Gary; Stevenson, Jeffry W.

2006-11-06

403

Kinetics of Chromium(III) Oxidation by Manganese(IV) Oxides Using Quick X-Ray Absorption Fine Structure Spectroscopy (Q-Thursday, November 5, 2009: 9:30 AM  

E-print Network

Kinetics of Chromium(III) Oxidation by Manganese(IV) Oxides Using Quick X-Ray Absorption Fine, Univ. of Delaware, Newark, DE The rapid kinetics of Cr(III) oxidation on mineral surfaces is poorly understood, yet a significant portion of the oxidation process occurs on rapid time scales. In this study

Sparks, Donald L.

404

Different Arsenate and Phosphate Incorporation Effects on the Nucleation and Growth of Iron(III) (Hydr)oxides on Quartz.  

PubMed

Iron(III) (hydr)oxides play an important role in the geochemical cycling of contaminants in natural and engineered aquatic systems. The ability of iron(III) (hydr)oxides to immobilize contaminants can be related to whether the precipitates form heterogeneously (e.g., at mineral surfaces) or homogeneously in solution. Utilizing grazing incidence small-angle X-ray scattering (GISAXS), we studied heterogeneous iron(III) (hydr)oxide nucleation and growth on quartz substrates for systems containing arsenate and phosphate anions. For the iron(III) only system, the radius of gyration (Rg) of heterogeneously formed precipitates grew from 1.5 to 2.5 (±1.0) nm within 1 h. For the system containing 10(-5) M arsenate, Rg grew from 3.6 to 6.1 (±0.5) nm, and for the system containing 10(-5) M phosphate, Rg grew from 2.0 to 4.0 (±0.2) nm. While the systems containing these oxyanions had more growth, the system containing only iron(III) had the most nucleation events on substrates. Ex situ analyses of homogeneously and heterogeneously formed precipitates indicated that precipitates in the arsenate system had the highest water content and that oxyanions may bridge iron(III) hydroxide polymeric embryos to form a structure similar to ferric arsenate or ferric phosphate. These new findings are important because differences in nucleation and growth rates and particle sizes will impact the number of available reactive sites and the reactivity of newly formed particles toward aqueous contaminants. PMID:25232994

Neil, Chelsea W; Lee, Byeongdu; Jun, Young-Shin

2014-10-21

405

Nanostructured manganese oxide/carbon nanotubes, graphene and graphene oxide as water-oxidizing composites in artificial photosynthesis.  

PubMed

Herein, we report on nano-sized Mn oxide/carbon nanotubes, graphene and graphene oxide as water-oxidizing compounds in artificial photosynthesis. The composites are synthesized by different and simple procedures and characterized by a number of methods. The water-oxidizing activities of these composites are also considered in the presence of cerium(IV) ammonium nitrate. Some composites are efficient Mn-based catalysts with TOF (mmol O2 per mol Mn per second) ~ 2.6. PMID:24898625

Najafpour, Mohammad Mahdi; Rahimi, Fahime; Fathollahzadeh, Maryam; Haghighi, Behzad; Ho?y?ska, Ma?gorzata; Tomo, Tatsuya; Allakhverdiev, Suleyman I

2014-07-28

406

Ab initio molecular dynamics study of manganese porphine hydration and interaction with nitric oxide  

E-print Network

The authors use ab initio molecular dynamics and the density functional theory+U (DFT+U) method to compute the hydration environment of the manganese ion in manganese (II) and manganese (III) porphines (MnP) dispersed in liquid water. These are intended as simple models for more complex water soluble porphyrins, which have important physiological and electrochemical applications. The manganese ion in Mn(II)P exhibits significant out-of-porphine plane displacement and binds strongly to a single H2O molecule in liquid water. The Mn in Mn(III)P is on average coplanar with the porphine plane and forms a stable complex with two H2O molecules. The residence times of these water molecules exceed 15 ps. The DFT+U method correctly predicts that water displaces NO from Mn(III)P-NO, but yields an ambiguous spin state for the MnP(II)-NO complex.

Kevin Leung; Craig J. Medforth

2007-01-23

407

Nanocrystalline lithium–manganese oxide spinels for Li-ion batteries — Sol-gel synthesis and characterization of their structure and selected physical properties  

Microsoft Academic Search

Nanocrystalline lithium–manganese oxide spinels were synthesized by a modified sol-gel method. Simple salts of lithium, manganese and iron were used as starting reagents and citric acid as a complexing agent. The gelled materials turned into nanopowders after the calcination was carried out in air in the 450–700°C temperature range. The combined DSC-TGA measurements have shown important stages of the syntheses.

M. Michalska; L. Lipi?ska; M. Mirkowska; M. Aksienionek; R. Diduszko; M. Wasiucionek

2011-01-01

408

Synthesis and characterization of novel manganese and vanadium oxides as cathodes for lithium rechargeable batteries  

NASA Astrophysics Data System (ADS)

The development of advanced rechargeable lithium batteries depends on cathodes that can reversibly intercalate lithium ions. Intercalation chemistry plays a key role in the electrochemical reduction and oxidation by lithium of many solid electrodes including transition metal compounds. Intercalation compounds such as LixTiS2 and LiCoO2 exhibit some of the ideal characteristics expected of a cathode for advanced batteries. The former shows high rate capability, excellent electronic conductivity and almost perfect reversibility; the latter shows a high voltage suitable for carbon based anodes and good reversibility but an energy density no higher than that of LixTiS2, a prohibitively high cost and an environmental hazard. The spinel LiMn2O4 removes the cost issue but not the others. Thus, much effort has been directed at synthesizing new structures that exhibit enhanced electrochemical activity. Soft chemistry approaches have been applied for this purpose. One such approach is mild hydrothermal reactions which lead to the formation of new metastable transition metal oxides, not accessible by conventional high temperature methods. The nature of the reactants, the pH of the reaction medium, heating temperature and heating duration have dramatic effects on the crystal structure of the phase formed. The mild hydrothermal decomposition of aqueous permanganate solutions has been found to lead to new layered manganese oxides. In the case of alkali permanganates AMnO4, layered birnessite-type compounds are formed with the general formula AxMnO2.nH 2O (A = Li, Na, K). These compounds have R 3¯ m rhombohedral structures analogous to the layered disulfides. The water is reversibly lost on heating, and the compounds readily react with lithium through an intercalation mechanism. The capacity for lithium is a function of the alkali ion present, and the larger potassium ion maintains the capacity best. For the lithium compound, there is a tendency to convert to the spinel structure which leads to loss of capacity. In the case of hydrothermal decomposition of tetramethylammonium permanganate in the presence of nickel, a new structure compound Ni1-xMn1-yO 3 is formed that has a different structure from that of the known ilmenite form. The structure contains empty tunnels into which lithium ions can be intercalated. Reaction of this nickel manganese oxide with n-butyl lithium showed the uptake of 0.91 Li per formula unit. It converts into the known ilmenite form of NiMnO3 at around 400°C. This compound also has interesting magnetic properties. A wide variety of vanadium oxides can be prepared using hydrothermal methods. Organic templates play an important role in directing the structures formed. Although tetramethyl ammonium hydroxide is a widely used organic template, other amines and long chain amine surfactants also yield interesting new structures many of which are layered phases. The hydrothermal reaction of vanadium pentoxide with methylamine leads to a series of new layered vanadium oxides, which differ in structure from the corresponding ones prepared in the presence of the tetramethylammonium ion because of the existence of hydrogen bonding. Methylamine is the first organic to form a double sheet vanadium oxide, (CH3NH3) 0.75V4O10.0.67H2O, with delta-AgxV2O5 structure. (CH 3NH3)V3O7 shows significant buckling of the vanadium oxide layers compared with N(CH3)4V 3O7. Both of these two compounds are monoclinic. (CH 3NH2)2V8O17 has a tetrahedral unit cell and IR shows that the lone pair electrons of nitrogen bond to vanadium. Also, vanadium coordination decreases with an increase in the pH of the reaction medium and hydrogen bonding controls the orientation of the polyhedra in the vanadium sheets, in contrast to the tetramethylammonium ion where the bonding is predominantly ionic.

Chen, Rongji

409

Real-time surface-chemistry of arsenite oxidation by hydrous manganese oxide: Impact of Matthew Ginder-Vogel, mattgv@udel.edu1, Sanjai J. Parikh, sjparikh@udel.edu1, Jason S. Fischel, fischjs06@juniata.edu2, and Donald  

E-print Network

Real-time surface-chemistry of arsenite oxidation by hydrous manganese oxide: Impact of oxyanions, Huntingdon, PA 16652 Arsenite (As(III)) oxidation to arsenate (As(V)) by manganese(IV) oxide is an important to bind more weakly to soils than As(V) does. Heterogeneous oxidation of As(III) on the surface

Sparks, Donald L.

410

Characterization of the Fe-Doped Mixed-Valent Tunnel Structure 2 Manganese Oxide KOMS-2  

SciTech Connect

A sol-gel-assisted combustion method was used to prepare Fe-doped manganese oxide octahedral molecular sieve (Fe-KOMS-2) materials with the cryptomelane structure. Characterization of the nanopowder samples over a wide range of Fe-doping levels (0 {le} Fe/Mn {le} 1/2) was carried out using a variety of experimental techniques. For each sample, Cu K{alpha} XRD and ICP-AES were used to index the cryptomelane structure and determine the elemental composition, respectively. A combination of SEM and TEM images revealed that the morphology changes from nanoneedle to nanorod after Fe doping. Furthermore, TGA scans indicated that the thermal stability is also enhanced with the doping. Anomalous XRD demonstrated that the Fe ions replace the Mn ions in the cryptomelane structure, particularly in the (211) planes, and results in a lattice expansion along the c axis, parallel to the tunnels. Reasonable fits to EXAFS data were obtained using a model based on the cryptomelane structure. Moessbauer spectra for selected Fe-KOMS-2 samples indicated that the Fe is present as Fe{sup 3+} in an octahedral environment similar to Mn in the MnO{sub 6} building blocks of KOMS-2. Magnetization measurements detected a small amount of {gamma}-Fe{sub 2}O{sub 3} second phase (e.g., 0.6 wt % for the Fe/Mn = 1/10 sample), the vast majority of the Fe being in the structure as Fe{sup 3+} in the high-spin state.

Hanson J. C.; Shen X.; Morey A.M.; Liu J.; Ding Y.; Cai J.; Durand J.; Wang Q.; Wen W.; Hines W.A.; Bai J.; Frenkel A.I.; Reiff W.; Aindow M.; Suib S.L.

2011-11-10

411

Immobilization of manganese peroxidase from Lentinula edodes on alkylaminated Emphaze{trademark} AB 1 polymer for generation of Mn{sup 3+} as an oxidizing agent  

Microsoft Academic Search

Manganese peroxidase (MnP) is secreted by white-rot fungi and participates in the degradation of lignin by these organisms. MnP uses HâOâ as an oxidant to oxidize Mn{sup II} to Mn{sup III} as the manganic ion Mn{sup 3+}. The Mn{sup 3+} stabilized by chelation, is a highly reactive nonspecific oxidant capable of oxidizing a variety of toxic organic compounds. Previous attempts

A. C. Grabski; R. R. Burgess; J. K. Rasmussen; P. L. Coleman

1996-01-01

412

Electrochemical generation of manganese(III) and behaviour of the generated oxidant in acetic acid in the presence of perchlorate ions  

Microsoft Academic Search

Summary Research was carried out to determine conditions for the anodic generation of manganese(III) with high current efficiency in solutions of sodium perchlorate in acetic acid, and to examine the behaviour of the oxidant thus generated. The effects of water and acetic anhydride on current efficiency in the generation of the oxidant was also examined. The formal redox potential of

Tibor J. Pastor; Ivan ?iri?

1984-01-01

413

Synthesis of Layered-Type Hydrous Manganese Oxides from Monoclinic-Type LiMnO 2  

NASA Astrophysics Data System (ADS)

Layered-type hydrous manganese oxides MnO 2·0.70H 2O and MnO 2·0.22H 2O with almost the same rod shape morphology as that of the precursor monoclinic-type LiMnO 2 were synthesized. The structural transformations from monoclinic-type LiMnO 2 to a birnessite-type MnO 2·0.70H 2O took place after lithium in LiMnO 2 was extracted with 0.1 mol dm -3 (NH 4) 2S 2O 8 solution without dissolution of manganese. The extraction of lithium from LiMnO 2 with 0.5 mol dm -3 HCl solution followed by the dissolution of manganese formed a trigonal-type MnO 2·0.22H 2O. The maximum ion exchange capacity of MnO 2·0.22H 2O toward alkali metal ions was found to be only 3 mmol/g; the material did not show any ion sieve properties. The pH titration study suggested that the MnO 2·0.22H 2O was a weak acidic adsorbent which was found to be a metastable phase.

Chitrakar, Ramesh; Kanoh, Hirofumi; Kim, Yang-Soo; Miyai, Yoshitaka; Ooi, Kenta

2001-08-01

414

Towards an understanding of thallium isotope fractionation during adsorption to manganese oxides  

NASA Astrophysics Data System (ADS)

We have conducted the first study of Tl isotope fractionation during sorption of aqueous Tl(I) onto the manganese oxide hexagonal birnessite. The experiments had different initial Tl concentrations, amounts of birnessite, experimental durations, and temperatures, but all of them exhibit heavy Tl isotope compositions for the sorbed Tl compared with the solution, which is consistent with the direction of isotope fractionation observed between seawater and natural ferromanganese sediments. However, the magnitude of fractionation in all experiments (? ? 1.0002-1.0015, where ?=205Tl/203Tl/205Tl/203Tl is smaller than observed between seawater and natural sediments (? ? 1.0019-1.0021; Rehkämper et al., 2002, Earth. Planet. Sci. Lett. 197, 65-81). The experimental results display a strong correlation between the concentration of Tl in the resulting Tl-sorbed birnessite and the magnitude of fractionation. This correlation is best explained by sorption of Tl to two sites on birnessite, one with large isotope fractionation and one with little or no isotope fractionation. Previous work (Peacock and Moon, 2012, Geochim. Cosmochim. Acta 84, 297-313) indicates that Tl in natural ferromanganese sediments is oxidized to Tl(III) and adsorbed over Mn vacancy sites in the phyllomanganate sheets of birnessite, and we hypothesize that this site is strongly fractionated from Tl in solution due to the change in oxidation state from aqueous Tl(I). In most experiments, which have orders of magnitude more Tl associated with the solid than in nature, these vacancy sites are probably fully saturated, so various amounts of additional Tl are likely sorbed to either edge sites on the birnessite or triclinic birnessite formed through oxidative ripening of the hexagonal starting material, with unknown oxidation state and little or no isotopic fractionation. Thus each experiment displays isotopic fractionation governed by the proportions of Tl in the fractionated and slightly fractionated sites, and those proportions are controlled by how much total Tl is sorbed per unit of birnessite. In the experiments with the lowest initial Tl concentrations in solution (˜0.15-0.4 ?g/g) and the lowest concentrations of Tl in the resulting Tl-sorbed birnessite (?17 ?g Tl/mg birnessite), we observed the largest isotopic fractionations, and fractionation is inversely proportional to the initial aqueous Tl concentration. Again, this correlation can be explained by the simultaneous occupation of two different sorption sites; vacancy sites that carry isotopically fractionated Tl and a second site carrying slightly fractionated Tl. The fractionation factors observed in nature exceed those in the experiments likely because the Tl concentrations in seawater and in ferromanganese sediments are three to four orders of magnitude lower than in our experiments, and therefore the second slightly fractionated sorption site is not significantly utilized. Temperature (6-40 °C) and experimental duration (3 min-72 h) appear to have little or no effects on isotope behaviour in this system.

Nielsen, Sune G.; Wasylenki, Laura E.; Rehkämper, Mark; Peacock, Caroline L.; Xue, Zichen; Moon, Ellen M.

2013-09-01

415

Microbially-mediated thiocyanate oxidation and manganese cycling control arsenic mobility in groundwater at an Australian gold mine  

NASA Astrophysics Data System (ADS)

Arsenic contamination of groundwater poses a serious environmental and human health problem in many regions around the world. Historical groundwater chemistry data for a Western-Central Victorian gold mine (Australia) revealed a strong inverse correlation between dissolved thiocyanate and iron(II), supporting the interpretation that oxidation of thiocyanate, a major groundwater contaminant by-product of cyanide-based gold leaching, was coupled to reductive dissolution of iron ox(yhydrox)ides in tailings dam sediments. Microbial growth was observed in this study in a selective medium using SCN- as the sole carbon and nitrogen source. The potential for use of SCN- as a tracer of mining contamination in groundwater was evaluated in the context of biological SCN- oxidation potential in the aquifer. Geochemical data also revealed a high positive correlation between dissolved arsenic and manganese, indicating that sorption on manganese-oxides most likely controls arsenic mobility at this site. Samples of groundwater and sediments along a roughly straight SW-NE traverse away from a large mine tailings storage facility, and parallel to the major groundwater flow direction, were analysed for major ions and trace metals. Groundwater from wells approaching the tailings along this traverse showed a nearly five-fold increase (roughly 25-125 ppb) in dissolved arsenic concentrations relative to aqueous Mn(II) concentrations. Thus, equivalent amounts of dissolved manganese released a five-fold difference in the amount of adsorbed arsenic. The interpretation that reductive dissolution of As-bearing MnO2 at the mine site has been mediated by groundwater (or aquifer) microorganisms is consistent with our recovery of synthetic birnessite-reducing enrichment cultures that were inoculated with As-contaminated groundwaters.

Horvath, A. S.; Baldisimo, J. G.; Moreau, J. W.

2010-12-01

416

Structure and surface chemistry of manganese-doped copper-based mixed metal oxides derived from layered double hydroxides  

Microsoft Academic Search

The paper reports data relative to the preparation of a series of manganese-doped copper-based mixed metal oxides under identical conditions by calcination of layered double hydroxides (LDHs) at 773K for 5h. LDHs with Cu2+\\/Zn2+\\/Mn2+\\/Fe3+\\/Al3+ molar ratios in synthesis mixture from 1:1:0:0.3:0.7 to 1:0:1:0.3:0.7 have been synthesized by co-precipitation method. The samples of both the as-synthesized LDHs and the corresponding calcined

Feng Li; Lihong Zhang; David G. Evans; Xue Duan

2004-01-01

417

Search for new manganese-cobalt oxides as positive electrode materials for lithium batteries P. Strobel, J. Tillier, A. Diaz, A. Ibarra-Palos, F. Thiry and J.B. Soupart *  

E-print Network

Search for new manganese-cobalt oxides as positive electrode materials for lithium batteries P new mixed manganese-cobalt oxides for lithium battery positive electrode materials were obtained using material for rechargeable lithium batteries so far. Many efforts are underway to replace part or all cobalt

Boyer, Edmond

418

Mineralogical and elemental description of pacific manganese nodules  

NASA Astrophysics Data System (ADS)

The report is divided into three sections: morphology, mineralogy and elemental composition. The nodule morphology section defines what is considered a nodule for the study, and details the external characteristics and internal structure. Nodule mineralogy is discussed in three sections: manganese minerals, iron oxide minerals, and accessory minerals. The major manganese minerals discussed are todorokite, birnessite, and vernadite. The iron oxide minerals are less well known and include feroxyhyte, goethite, and lepidocrocite. Accessory minerals present include quartz, clays, and other silicates and nonsilicates. A discussion on moisture content is also included. The elemental composition section presents data on 74 elements occurring as cations or anions. Summary data, histograms, and interelement correlation coefficients are presented.

Haynes, B. W.; Law, S. L.; Barron, D. C.

1983-03-01

419

Lithium-manganese-nickel-oxide electrodes with integrated layered-spinel structures for lithium batteries.  

SciTech Connect

A series of lithium-manganese-nickel-oxide compositions that can be represented in three-component notation, xLi[Mn{sub 1.5}Ni{sub 0.5}]O{sub 4} {center_dot} (1-x)(Li{sub 2}MnO{sub 3} {center_dot} Li(Mn{sub 0.5}Ni{sub 0.5})O{sub 2}), in which a spinel component, Li[Mn{sub 1.5}Ni{sub 0.5}]O{sub 4}, and two layered components, Li{sub 2}MnO{sub 3} and Li(Mn{sub 0.5}Ni{sub 0.5})O{sub 2}, are structurally integrated in a highly complex manner, have been evaluated as electrodes in lithium cells for x = 1, 0.75, 0.50, 0.25 and 0. In this series of compounds, which is defined by the Li[Mn{sub 1.5}Ni{sub 0.5}]O{sub 4}{sup -} (Li{sub 2}MnO{sub 3} {center_dot} Li(Mn{sub 0.5}Ni{sub 0.5})O{sub 2}) tie-line in the Li[Mn{sub 1.5}Ni{sub 0.5}]O{sub 4}-Li{sub 2}MnO{sub 3}-Li(Mn{sub 0.5}Ni{sub 0.5})O{sub 2} phase diagram, the Mn:Ni ratio in the spinel and the combined layered Li{sub 2}MnO{sub 3} {center_dot} Li(Mn{sub 0.5}Ni{sub 0.5})O{sub 2} components is always 3:1. Powder X-ray diffraction patterns of the end members and the electrochemical profiles of cells with these electrodes are consistent with those expected for the spinel Li[Mn{sub 1.5}Ni{sub 0.5}]O{sub 4} (x = 1) and for 'composite' Li{sub 2}MnO{sub 3} {center_dot} Li(Mn{sub 0.5}Ni{sub 0.5})O{sub 2} layered electrode structures (x = 0). Electrodes with intermediate values of x exhibit both spinel and layered character and yield extremely high capacities, reaching more than 250 mA h/g with good cycling stability between 2.0 V and 4.95 V vs. Li{sup o} at a current rate of 0.1 mA/cm{sup 2}.

Park, S. H.; Kang, S. H.; Johnson, C. S.; Amine, K.; Thackeray, M. M.; Chemical Engineering

2007-02-01

420

Structural study of biotic and abiotic poorly-crystalline manganese oxides using atomic pair distribution function analysis  

SciTech Connect

Manganese (Mn) oxides are among the most reactive natural minerals and play an important role in elemental cycling in oceanic and terrestrial environments. A large portion of naturally-occurring Mn oxides tend to be poorly-crystalline and/or nanocrystalline, with not fully resolved crystal structures. In this study, the crystal structures of their synthetic analogs including acid birnessite (AcidBir), {delta}-MnO{sub 2}, polymeric MnO{sub 2} (PolyMnO{sub 2}) and a bacteriogenic Mn oxide (BioMnO{sub x}), have been revealed using atomic pair distribution function (PDF) analysis. Results unambiguously verify that these Mn oxides are layered materials. The best models that accurately allow simulation of pair distribution functions (PDFs) belong to the monoclinic C12/m1 space group with a disk-like shape. The single MnO{sub 6} layers in the average structures deviate significantly from hexagonal symmetry, in contrast to the results of previous studies based on X-ray diffraction analysis in reciprocal space. Manganese occupancies in MnO{sub 6} layers are estimated to be 0.936, 0.847, 0.930 and 0.935, for AcidBir, BioMnOx, {delta}-MnO{sub 2} and PolyMnO{sub 2}, respectively; however, occupancies of interlayer cations and water molecules cannot be accurately determined using the models in this study. The coherent scattering domains (CSDs) of PolyMnO{sub 2}, {delta}-MnO{sub 2} and BioMnO{sub x} are at the nanometer scale, comprising one to three MnO{sub 6} layers stacked with a high disorder in the crystallographic c-axis direction. Overall, the results of this study advance our understanding of the mineralogy of Mn oxide minerals in the environment.

Zhu, Mengqiang; Farrow, Christopher L.; Post, Jeffrey E.; Livi, Kenneth J.T.; Billinge, Simon J.L.; Ginder-Vogel, Matthew; Sparks, Donald L. (Delaware); (Columbia); (JHU); (Smithsonian)

2012-03-15

421

Structural Study of Biotic and Abiotic Poorly-crystalline Manganese Oxides Using Atomic Pair Distribution Function Analysis  

SciTech Connect

Manganese (Mn) oxides are among the most reactive natural minerals and play an important role in elemental cycling in oceanic and terrestrial environments. A large portion of naturally-occurring Mn oxides tend to be poorly-crystalline and/or nanocrystalline, with not fully resolved crystal structures. In this study, the crystal structures of their synthetic analogs including acid birnessite (AcidBir), {delta}-MnO{sub 2}, polymeric MnO{sub 2} (PolyMnO{sub 2}) and a bacteriogenic Mn oxide (BioMnO{sub x}), have been revealed using atomic pair distribution function (PDF) analysis. Results unambiguously verify that these Mn oxides are layered materials. The best models that accurately allow simulation of pair distribution functions (PDFs) belong to the monoclinic C12/m1 space group with a disk-like shape. The single MnO{sub 6} layers in the average structures deviate significantly from hexagonal symmetry, in contrast to the results of previous studies based on X-ray diffraction analysis in reciprocal space. Manganese occupancies in MnO{sub 6} layers are estimated to be 0.936, 0.847, 0.930 and 0.935, for AcidBir, BioMnO{sub x}, {delta}-MnO{sub 2} and PolyMnO{sub 2}, respectively; however, occupancies of interlayer cations and water molecules cannot be accurately determined using the models in this study. The coherent scattering domains (CSDs) of PolyMnO{sub 2}, {delta}-MnO{sub 2} and BioMnO{sub x} are at the nanometer scale, comprising one to three MnO{sub 6} layers stacked with a high disorder in the crystallographic c-axis direction. Overall, the results of this study advance our understanding of the mineralogy of Mn oxide minerals in the environment.

Billinge S. J.; Zhu, M.; Farrow, C.L.; Post, J.E.; Livi, K.J.T.; Ginder-Vogel, M.; Sparks, D.L.

2012-03-15

422

Manganese Oxidizing Bacteria in Guaymas Basin Hydrothermal Fluids, Sediments, and Plumes  

Microsoft Academic Search

The active seafloor hydrothermal system at Guaymas Basin in the Gulf of California is unique in that spreading centers are covered with thick sediments, and hydrothermal fluids are injected into a semi-enclosed basin. This hydrothermal activity is the source of a large input of dissolved manganese [Mn(II)] into Guaymas Basin, and the presence of a large standing stock of particulate

G. J. Dick; B. M. Tebo

2002-01-01

423

Chemical approach to a new crystal structure: phase control of manganese oxide on a carbon sphere template.  

PubMed

The stabilization and growth of a non-native structure, hexagonal wurtzite MnO (h-MnO), is explored via kinetic control of manganese precursor on a carbon sphere template. MnO is most stable in the cubic rock-salt structure (c-MnO), and a number of studies have focused on the synthesis and properties of this rock-salt phase. However, h-MnO has not been fully characterized before our work. Prolonged heating at a relatively low temperature yields c-MnO, whereas rapid heating of the reaction mixture at reflux produces h-MnO in the presence of carbon spheres. The effect of benzyl amine concentration on the formation of two different oxidation states (c-MnO and t-Mn3 O4 ) was examined as well. Moreover, the structural stability of the manganese oxides and phase transition of MnO in terms of the wurtzite to rock-salt structural transformation have been investigated. PMID:25303773

Nam, Ki Min; Park, Joon T

2014-12-01

424

Copper doped hollow structured manganese oxide mesocrystals with controlled phase structure and morphology as anode materials for lithium ion battery with improved electrochemical performance.  

PubMed

We develop a facile synthesis route to prepare Cu doped hollow structured manganese oxide mesocrystals with controlled phase structure and morphology using manganese carbonate as the reactant template. It is shown that Cu dopant is homogeneously distributed among the hollow manganese oxide microspherical samples, and it is embedded in the lattice of manganese oxide by substituting Mn(3+) in the presence of Cu(2+). The crystal structure of manganese oxide products can be modulated to bixbyite Mn2O3 and tetragonal Mn3O4 in the presence of annealing gas of air and nitrogen, respectively. The incorporation of Cu into Mn2O3 and Mn3O4 induces a great microstructure evolution from core-shell structure for pure Mn2O3 and Mn3O4 samples to hollow porous spherical Cu-doped Mn2O3 and Mn3O4 samples with a larger surface area, respectively. The Cu-doped hollow spherical Mn2O3 sample displays a higher specific capacity of 642 mAhg(-1) at a current density of 100 mA g(-1) after 100 cycles, which is about 1.78 times improvement compared to that of 361 mA h g(-1) for the pure Mn2O3 sample, displaying a Coulombic efficiency of up to 99.5%. The great enhancement of the electrochemical lithium storage performance can be attributed to the improvement of the electronic conductivity and lithium diffusivity of electrodes. The present results have verified the ability of Cu doping to improve electrochemical lithium storage performances of manganese oxides. PMID:24080017

Li, Qun; Yin, Longwei; Li, Zhaoqiang; Wang, Xuekun; Qi, Yongxin; Ma, Jingyun

2013-11-13

425

Manganese, Metallogenium, and Martian Microfossils  

NASA Technical Reports Server (NTRS)

Manganese could easily be considered an abundant element in the Martian regolith, assuming that the composition of martian meteorites reflects the composition of the planet. Mineralogical analyses of 5 SNC meteorites have revealed an average manganese oxide concentration of 0.48%, relative to the 0.1% concentration of manganese found in the Earth's crust. On the Earth, the accumulation of manganese oxides in oceans, soils, rocks, sedimentary ores, fresh water systems, and hydrothermal vents can be largely attributed to microbial activity. Manganese is also a required trace nutrient for most life forms and participates in many critical enzymatic reactions such as photosynthesis. The wide-spread process of bacterial manganese cycling on Earth suggests that manganese is an important element to both geology and biology. Furthermore, there is evidence that bacteria can be fossilized within manganese ores, implying that manganese beds may be good repositories for preserved biomarkers. A particular genus of bacteria, known historically as Metallogenium, can form star-shaped manganese oxide minerals (called metallogenium) through the action of manganese oxide precipitation along its surface. Fossilized structures that resemble metallogenium have been found in Precambrian sedimentary formations and in Cretaceous-Paleogene cherts. The Cretaceous-Paleogene formations are highly enriched in manganese and have concentrations of trace elements (Fe, Zn, Cu, and Co) similar to modern-day manganese oxide deposits in marine environments. The appearance of metallogenium-like fossils associated with manganese deposits suggests that bacteria may be preserved within the minerals that they form. Additional information is contained in the original extended abstract.

Stein, L. Y.; Nealson, K. H.

1999-01-01

426

Manganese and iron oxide immobilized activated carbons precursor to dead biomasses in the remediation of cadmium-contaminated waters.  

PubMed

The aim of the present investigation was to exploit the high specific surface area of activated carbons in immobilizing the manganese and iron oxides as to obtain a suitable, efficient and cost effective and environment benign wastewater treatment process in the remediation of cadmium-contaminated waters. The manganese and iron oxides were impregnated in situ onto the surface and pores of the activated carbons precursors to the rice hulls and areca nut wastes. The solids were characterized with the help of Fourier transform infrared spectroscopy and X-ray diffraction analytical data, and the BET specific surface area as obtained. The surface morphology of these solids was discussed with the help of scanning electron microscopic images. The activated carbon samples along with the manganese and iron immobilized activated carbons were further employed in the batch and column reactor operations in the remediation of cadmium-contaminated waters. The batch data showed that an increase in sorptive pH from 2.0 to 10.0 and concentration from 1.0 to 20 mg/L favoured the uptake of cadmium by these solids. Moreover, the 1,000 times increase in background electrolyte concentrations NaNO3 caused an insignificant decrease in cadmium uptake by these solids, which inferred that sorbing ions/species were sorbed specifically and forming 'inner-sphere' complexes onto the solid surface. The concentration dependence data were utilized to model various adsorption isotherms and indicated that Freundlich adsorption isotherm was reasonably fitted well. The kinetic data was fitted well to the pseudo-second-order rate equations; hence, the equilibrium sorption capacity was estimated. Furthermore, the dynamic experiments carried out by the column experiments and the breakthrough data were fitted well to the non-linear Thomas equations; accordingly, the loading capacity of the column was estimated. Iron or manganese immobilized activated carbons showed relatively higher loading capacity compared to its precursor activated carbons hence showing its possible implication in the remediation processes. Moreover, among these modified ACs, IIAC showed higher removal capacity than the MIAC solid. PMID:23589235

Lee, Seung-Mok; Lalhmunsiama; Choi, Sang-Il; Tiwari, Diwakar

2013-10-01

427

Bioaccumulation of manganese and its toxicity in feral pigeons (Columba livia) exposed to manganese oxide dust (Mn{sub 3}O{sub 4})  

SciTech Connect

Manganese tetroxide (Mn{sub 3}O{sub 4}) is a product from the combustion of methylcyclopentadienyl manganese tricarbonyl. Exposure to high levels of manganese can lead to serious health effects especially to the central nervous and respiratory systems. Very few studies on the effects of long-term low level exposure to Mn{sub 3}O{sub 4} have been reported. The present study was therefore conducted to examine the bioaccumulation and toxicity of manganese in various organs of feral pigeons (Columba kivia) when exposed to low levels of Mn{sub 3}O{sub 4} via inhalation and hence to find any possible relationship between these two parameters. A total of 22 pigeons was exposed to 239 {micro}g/m{sup 3} of manganese for 7 h/day, 5 days/week for 5, 9, and 13 consecutive weeks. Manganese concentrations in various tissues, e.g., brain (mesencephalon), lung, liver, intestine, pancreas, kidney, muscle, bone, and whole blood, were measured by neutron activation analysis. Various biochemical parameters in blood, e.g., hematocrit, total proteins, glucose, uric acid, alinine aminotransferase, total iron, blood urea nitrogen and triglycerides, were also measured.

Sierra, P.; Chakrabarti, S.; Tounkara, R.; Loranger, S.; Kennedy, G.; Zayed, J. [Univ. of Montreal (Canada)] [Univ. of Montreal (Canada)

1998-11-01

428

Catalytic oxidation of NO with O2 over FeMnOx/TiO2: Effect of iron and manganese oxides loading sequences and the catalytic mechanism study  

NASA Astrophysics Data System (ADS)

FeMnOx/TiO2 with different iron and manganese oxides adding orders were prepared through isovolumetric impregnation and tested for catalytic oxidation of NO with O2. It was found that the sample obtained from one-step impregnation method had better catalytic activity. The excellent activity was attributed to higher surface area, lower crystalline of manganese oxides, abundant Mn3+, Fe3+ and chemisorbed oxygen species on the surface. Furthermore, effects of loading sequences on FeMnOx/TiO2 catalysts were investigated. The study showed that Fe and Mn would affect each other and change the surface physicochemical properties of FeMnOx/TiO2 when they were loaded step-by-step. In addition, the inhibiting effect of H2O on catalytic activity was reversible while the conversion of NO recovered to 40% when SO2 was cut off. XPS analysis between used and fresh catalysts revealed the electron transfer between Fen+ and Mnn+ ions in FeMnOx/TiO2. Possible reaction mechanism was put forward by comprehensive analysis of XPS and FT-IR results.

Zhang, Mengying; Li, Caiting; Qu, Long; Fu, Mengfan; Zeng, Guangming; Fan, Chunzhen; Ma, Jinfeng; Zhan, Fuman

2014-05-01