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1

Interactions of pentachlorophenol with manganese oxide  

SciTech Connect

Abiotic interactions of pentachlorophenol (PCP) on manganese oxide surfaces were investigated to determine the extent of transformation. The optimal pH and ratio of manganese oxide to PCP were determined. Sorption of PCP on manganese oxide surfaces was quantified at optimal conditions. The effectiveness of utilizing manganese oxide to remediate contaminated subsurface environments was investigated.

Cramer, A.; McLean, J.E.; Sims, R.C. [Utah State Univ., Logan, UT (United States). Utah Water Research Lab.

1994-12-31

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

Microbial Formation of Manganese Oxides  

PubMed Central

Microbial manganese oxidation was demonstrated at high Mn2+ concentrations (5 g/liter) in bacterial cultures in the presence of a microalga. The structure of the oxide produced varied depending on the bacterial strain and mode of culture. A nonaxenic, acid-tolerant microalga, a Chlamydomonas sp., was found to mediate formation of manganite (?-MnOOH). Bacteria isolated from associations with crude cultures of this alga grown in aerated bioreactors formed disordered ?-MnO2 from Mn2+ at concentrations of 5 g/liter over 1 month, yielding 3.3 g of a semipure oxide per liter. All algal-bacterial cultures removed Mn2+ from solution, but only those with the highest removal rates formed an insoluble oxide. While the alga was an essential component of the reaction, a Pseudomonas sp. was found to be primarily responsible for the formation of a manganese precipitate. Medium components—algal biomass and urea—showed optima at 5.7 and 10 g/liters, respectively. The scaled-up culture (50 times) gave a yield of 22.3 g (53 mg/liter/day from a 15-liter culture) of semipure disordered ?-MnO2, identified by X-ray diffraction and Fourier transform infrared (FTIR) spectroscopy, and had a manganese oxide O/Mn ratio of 1.92. The Mn(IV) content in the oxide was low (30.5%) compared with that of mined or chemically formed ?-MnO2 (ca. 50%). The shortfall in the bacterial oxide manganese content was due to biological and inorganic contaminants. FTIR spectroscopy, transmission electron microscopy, and electron diffraction studies have identified manganite as a likely intermediate product in the formation of disordered ?-MnO2. PMID:16348459

Greene, Anthony C.; Madgwick, John C.

1991-01-01

4

The effect of manganese on olivine-quartz-orthopyroxene stability  

NASA Astrophysics Data System (ADS)

The effect of manganese on the stability of ferrosilite relative to fayalite + quartz has been experimentally determined to assess its importance to orthopyroxene barometry. Reaction reversals in a piston-cylinder apparatus were obtained to within 0.1-kbar intervals indicating instability of Fs 95Rh 5 below 10.3, 10.9, 11.4, 12.2, 12.9, 13.7 kbar and Fs 90Rh 10 below 9.8, 10.4, 10.9, 11.6, 12.4 and 13.2 kbar at 750, 800, 850, 900, 950 and 1000°C, respectively. Each mole % MnSiO 3 extends the pyroxene stability by approximately 0.12 kbar relative to FeSiO 3. Electron microprobe analyses of run products indicate a small preference of Mn for pyroxene over olivine with KDMn-Fe opx-oliv = 1.2-1.5, similar to values observed for natural pairs. Mössbauer spectra are consistent with a random distribution of Mn between the M1 and M2 sites in the orthopyroxene. These experimental data allow downward revision of pressure estimates based on the orthopyroxene barometer in areas where Mn is a significant component in orthopyroxene.

Bohlen, Steven R.; Boettcher, Arthur L.; Dollase, Wayne A.; Essene, Eric J.

1980-03-01

5

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

6

40 CFR 721.10201 - Cobalt lithium manganese nickel oxide.  

...2014-07-01 2014-07-01 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...

2014-07-01

7

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

8

40 CFR 721.10011 - Barium calcium manganese strontium oxide.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Barium calcium manganese strontium oxide. 721.10011...Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. (a...chemical substance identified as barium calcium manganese strontium oxide (PMN...

2011-07-01

9

40 CFR 721.10011 - Barium calcium manganese strontium oxide.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Barium calcium manganese strontium oxide. 721.10011...Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. (a...chemical substance identified as barium calcium manganese strontium oxide (PMN...

2010-07-01

10

40 CFR 721.10011 - Barium calcium manganese strontium oxide.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Barium calcium manganese strontium oxide. 721.10011...Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. (a...chemical substance identified as barium calcium manganese strontium oxide (PMN...

2012-07-01

11

40 CFR 721.10011 - Barium calcium manganese strontium oxide.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Barium calcium manganese strontium oxide. 721.10011...Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. (a...chemical substance identified as barium calcium manganese strontium oxide (PMN...

2013-07-01

12

40 CFR 721.10011 - Barium calcium manganese strontium oxide.  

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

2014-07-01

13

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.

14

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.

15

Synthesis, characterization, optical and sensing property of manganese oxide nanoparticles  

SciTech Connect

Manganese oxide nanoparticles were prepared by thermal decomposition of manganese oxalate. Manganese oxalate was synthesized by reacting 1:1 mole ratio of manganese acetate and ammonium oxalate along with sodium dodecyl sulfate (SDS). The structural characterization of manganese oxalate and manganese oxide nanoparticles was analyzed by XRD. The XRD spectrum confirms the crystal structure of the manganese oxide and manganese oxalate. In addition, the average grain size, lattice parameter values were also calculated using XRD spectrum. Moreover, the diffraction peaks were broadened due to the smaller size of the particle. The band gap of manganese oxide was calculated from optical absorption, which was carried out by DRS UV-Visible spectroscopy. The morphology of manganese oxide nanoparticles was analyzed by SEM images. The FT-IR analysis confirms the formation of the manganese oxide from manganese oxalate nanoparticles. The electrochemical sensing behavior of manganese oxide nanoparticles were investigated using hydrogen peroxide by cyclic voltammetry.

Manigandan, R.; Suresh, R.; Giribabu, K.; Narayanan, V., E-mail: vnnara@yahoo.co.in [Department of Inorganic Chemistry, University of Madras, Guindy Campus, Chennai 600 025 (India); Vijayalakshmi, L. [Annai Veilankanni's College for Women (Arts and Science), Saidapet, Chennai 600015 (India); Stephen, A. [Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600 025 (India)

2014-01-28

16

Environmental Controls of Biological Manganese Oxidation  

NASA Astrophysics Data System (ADS)

Biological catalysis of manganese oxidation represents an important contribution to global manganese cycling; biological oxidation rates are several orders of magnitude higher than those of abiotic processes. Despite recent genetics advances, ongoing behavioral studies, and a large pool of knowledge regarding manganese chemistry, the links between biology and environmental chemistry remain unresolved. We have performed experiments on batch cultures of Leptothrix discophora SS-1 to explore the physiology of biological manganese oxidation. We have further conducted spectroscopic and microscopic studies of the mechanism as manganese proceeds from the soluble Mn2+ species to the insoluble Mn(III) and Mn(IV) phases. These investigations suggest roles for aqueous chemistry, mineralogy, and microbial physiology in controlling manganese fluxes in metal-rich environments.

Belz, A. P.; Ahn, C. C.; Nealson, K. H.

2001-12-01

17

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

18

Manganese.  

PubMed

Manganese is a very hard, brittle metal, which is used to increase the strength of steel alloys. Absorption from the gastrointestinal tract occurs in the divalent and tetravalent forms. Permanganates, which are strong oxidizing agents, have a +7 valence. The principal organomanganese compound is the anti-knock additive, methylcyclopentadienyl manganese tricarbonyl. Manganese is a ubiquitous constituent of the environment comprising about 0.1% of the earth's crust. For the general population, food is the most important source of manganese with daily intake ranging from 2-9 mg Mn. Combustion of gasoline containing methylcyclopentadienyl manganese tricarbonyl releases submicron particles of Mn3O4 that are potentially respirable. Biomagnification of manganese in the food chain probably does not occur. The lungs and gastrointestinal tract absorb some manganese, but the relative amounts absorbed from each site are not known. Homeostatic mechanisms limit the absorption of manganese from the gastrointestinal tract. Elimination of manganese occurs primarily by excretion into the bile. Animal studies indicate that manganese is an essential co-factor for enzymes, such as hexokinase, superoxide dismutase, and xanthine oxidase. However, no case of manganese deficiency in humans has been identified. Manganism is a central nervous system disease first described in the 1800s following exposure to high concentrations of manganese oxides. Manganese madness was the term used to describe the initial psychiatric syndrome (compulsive behavior, emotional lability, hallucinations). More commonly, these workers developed a Parkinson's-like syndrome. Currently, the risks of exposure to low concentrations of manganese in the industrial and in the environmental settings (e.g., methylcyclopentadienyl manganese tricarbonyl in gasoline) are being evaluated with regards to the development of subclinical neuropsychological changes. The American Conference of Governmental and Industrial Hygienists recently lowered the TLV-TWA for manganese compounds and inorganic manganese compounds to 0.2 mg Mn/m3. PMID:10382563

Barceloux, D G

1999-01-01

19

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.

20

Manganese oxide reduction as a form of anaerobic respiration  

Microsoft Academic Search

Some instances of bacterial manganese oxide reduction observed in nature and under laboratory conditions are a form of respiration. Anaerobiosis is not a necessary condition for its occurrence, although anaerobic reduction of manganese oxide which is inhibited by air has been reported. It is the kind of manganese reducing microorganism involved which determines whether anaerobic conditions are required. In at

Henry L. Ehrlich

1987-01-01

21

Manganese  

SciTech Connect

Manganese (Mn) is a hard, brittle, gray-white transition metal, with the most numerous oxidation states of the elements in the first series of the Periodic Table. Since the manganese atom can donate up to seven electrons from its outer two shells, manganese compounds exist with valences from -3 to +7, the most common being +2, +4, and +7. Due to its sulfur-fixing, deoxidizing, and alloying properties, as well as its low cost, the principal commercial application for manganese is in iron and steel production. Manganese is also employed in non-ferrous metallurgy, batteries and chemical processes. Although potentially harmful to the respiratory and nervous systems, manganese is an essential element for animals and humans, and a micronutrient for plants.

Major-Sosias, M.A.

1996-10-01

22

Manganese Dependent Anaerobic Oxidation of Methane  

NASA Astrophysics Data System (ADS)

Understanding the anaerobic oxidation is not only important for understanding hydrocarbon degradation but it also important for understanding the global carbon cycle. The anaerobic oxidation of methane (AOM) is a large sink for methane consuming 5-20% of today's methane flux (Valentine and Reeburgh, 2000), yet the requirements for this process are not well understood. It has been suggested that no other electron acceptors other than sulfate can be used in the AOM (Nauhaus, 2005). However, our new data suggests that manganese, in the form of birnessite, can be used as an electron acceptor instead of sulfate (Beal et al., in prep). Methane seep sediment from the Eel River Basin, CA was incubated with methane, 13C-labeled methane, and carbon dioxide. Because the net result of the AOM is the production of carbon dioxide from methane, the rate of the AOM in each of the incubations can be determined by measuring the incorporation of 13C in the carbon dioxide. Using this method, it was found that cultures incubated with nitrate showed inhibition of the AOM, while cultures incubated with iron gave inconclusive results. The only positive results that were found for alternate electron acceptors are the incubations that were given manganese and no sulfate, which showed methane oxidation. Further, when more manganese was injected into these incubations, the rate of AOM increased. Preliminary analysis of the microbial population using terminal restriction fragment length polymorphism (TRFLP) targeting the mcr gene showed an unidentified organism in these cultures. Future work with TRFLP, as well as clone libraries, will help to identify the organisms responsible for this process. Nauhaus, K., 2005, Environmental regulation of the anaerobic oxidation of methane: a comparison of ANME-I and ANME-II communities: Environmental microbiology, v. 7, p. 98. Valentine, D.L., and Reeburgh, W.S., 2000, New perspectives on anaerobic methane oxidation: Environmental Microbiology, v. 2, p. 477-484.

Beal, E.; House, C.

2007-12-01

23

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

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

2014-07-01

24

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

Code of Federal Regulations, 2013 CFR

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

2013-07-01

25

75 FR 70665 - Proposed Significant New Use Rule for Cobalt Lithium Manganese Nickel Oxide  

Federal Register 2010, 2011, 2012, 2013

...Proposed Significant New Use Rule for Cobalt Lithium Manganese Nickel Oxide AGENCY...for the chemical substance identified as cobalt lithium manganese nickel oxide (CAS No...for the chemical substance identified as cobalt lithium manganese nickel oxide...

2010-11-18

26

Formation of manganese oxides by bacterially generated superoxide  

NASA Astrophysics Data System (ADS)

Manganese oxide minerals are among the strongest sorbents and oxidants in the environment. The formation of these minerals controls the fate of contaminants, the degradation of recalcitrant carbon, the cycling of nutrients and the activity of anaerobic-based metabolisms. Oxidation of soluble manganese(II) ions to manganese(III/IV) oxides has been primarily attributed to direct enzymatic oxidation by microorganisms. However, the physiological reason for this process remains unknown. Here we assess the ability of a common species of marine bacteria-Roseobacter sp. AzwK-3b-to oxidize manganese(II) in the presence of chemical and biological inhibitors. We show that Roseobacter AzwK-3b oxidizes manganese(II) by producing the strong and versatile redox reactant superoxide. The oxidation of manganese(II), and concomitant production of manganese oxides, was inhibited in both the light and dark in the presence of enzymes and metals that scavenge superoxide. Oxidation was also inhibited by various proteases, enzymes that break down bacterial proteins, confirming that the superoxide was bacterially generated. We conclude that bacteria can oxidize manganese(II) indirectly, through the enzymatic generation of extracellular superoxide radicals. We suggest that dark bacterial production of superoxide may be a driving force in metal cycling and mineralization in the environment.

Learman, D. R.; Voelker, B. M.; Vazquez-Rodriguez, A. I.; Hansel, C. M.

2011-02-01

27

Thermochemistry of iron manganese oxide spinels  

SciTech Connect

Oxide melt solution calorimetry has been performed on iron manganese oxide spinels prepared at high temperature. The enthalpy of formation of (Mn{sub x}Fe{sub 1-x}){sub 3}O{sub 4} at 298K from the oxides, tetragonal Mn{sub 3}O{sub 4} (hausmannite) and cubic Fe{sub 3}O{sub 4} (magnetite), is negative from x=0 to x=0.67 and becomes slightly positive for 0.670.6) spinels of intermediate compositions. The enthalpies of formation are discussed in terms of three factors: oxidation-reduction relative to the end-members, cation distribution, and tetragonality. A combination of measured enthalpies and Gibbs free energies of formation in the literature provides entropies of mixing. {delta}S{sub mix}, consistent with a cation distribution in which all trivalent manganese is octahedral and all other ions are randomly distributed for x>0.5, but the entropy of mixing appears to be smaller than these predicted values for x<0.4.

Guillemet-Fritsch, Sophie [Centre InterUniversitaire de Recherche et d'Ingenierie des Materiaux (CIRIMAT/LCMIE), Universite Paul Sabatier, Ba-hat timent 2R1, 118, route de Narbonne, 31062 Toulouse, Cedex 04 (France); Navrotsky, Alexandra [Thermochemistry Facility and NEAT ORU, University of California at Davis, One Shields Avenue, Davis, CA 95616-877 (United States)]. E-mail: anavrotsky@ucdavis.edu; Tailhades, Philippe [Centre InterUniversitaire de Recherche et d'Ingenierie des Materiaux (CIRIMAT/LCMIE), Universite Paul Sabatier, Ba-hat timent 2R1, 118, route de Narbonne, 31062 Toulouse, Cedex 04 (France); Coradin, Herve [Centre InterUniversitaire de Recherche et d'Ingenierie des Materiaux (CIRIMAT/LCMIE), Universite Paul Sabatier, Ba-hat timent 2R1, 118, route de Narbonne, 31062 Toulouse, Cedex 04 (France); Wang Miaojun [Thermochemistry Facility and NEAT ORU, University of California at Davis, One Shields Avenue, Davis, CA 95616-877 (United States)

2005-01-15

28

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

29

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

30

Pwave Pairing and Colossal Magnetoresistance in Manganese Oxides  

E-print Network

P­wave Pairing and Colossal Magnetoresistance in Manganese Oxides Yong­Jihn Kim y Department understood in terms of the p­wave pairing. In addition, colossal magnetoresistance (CMR) is natu­ rally paid to the manganese oxides since the observa­ tion of colossal magnetoresistance (CMR). 1\\Gamma4

31

[Ferrous-manganese oxidizing bacteria from the nature water].  

PubMed

Glass slides were hanged into a canal to acquire the ferrous-manganese oxidizing bacteria settled bio-film. Two isolated methods for ferrous-manganese oxidizing bacteria with special iron-manganese oxidizing matrix from the bio-film were tested. Element component of bacteria product and sheath structure of bacteria were analyzed. With two methods, plate cultivation and the novel semi-solid in situ cultivation method, strains belong to Family Leptothrix were isolated. XRF showed that the amorphous iron and manganese were two major metal elements of the precipitation formed by one strain of Leptothrix spp.. Through the microscope observation, one strain of Family Leptothrix was determined to form branch-like structured sheath, while another strain formed spider web-like structured sheath. Those isolated bacteria provide model strains for future testing of FISH probe and PCR primer of ferrous-manganese oxidizing bacteria. PMID:18763517

Qin, Song-yan; Ma, Fang; Huang, Peng

2008-06-01

32

Catalytic oxidation of chlorobenzene on supported manganese oxide catalysts  

Microsoft Academic Search

Total oxidation of chlorinated aromatics on supported manganese oxide catalysts was investigated. The catalysts have been prepared by wet impregnation method and characterized by XRD and TPR. Among the catalysts with the supports of TiO2, Al2O3 and SiO2, titania-supported catalyst (MnOx\\/TiO2) gives the highest catalytic activity. MnOx\\/TiO2 (Mn loading, 1.9wt.%) shows the total oxidation of chlorobenzene at about 400°C. The

Yan Liu; Mengfei Luo; Zhaobin Wei; Qin Xin; Pinliang Ying

2001-01-01

33

Oxidative stress involves in astrocytic alterations induced by manganese.  

PubMed

It is hypothesized that manganese neurotoxicity could be secondary to a diminution of cellular protective and scavenger mechanisms. Since manganese is known to be sequestered in glial cells, we investigated possible neurotoxic mechanisms involving astrocytes in vitro. Astrocytes differentiated into process-bearing stellate cells in response to manganese treatment. Manganese concentration dependently decreased cellular DNA synthesis, glial fibrillary acidic protein expression, energy production, antioxidant capacity, and glutamate transporter activity. In contrast, manganese increased glutamine synthetase protein expression and cytokine-stimulated interleukin 6 mRNA expression. Under the concentration of 0.1 mM, manganese chloride caused no significant astrocyte death even up to 48 h after treatment. That is, these astrocytic alterations proceeded before the onset of cell demise. As a possible mediator of manganese-derived alterations, we determined intracellular redox state in astrocytes. Manganese time-dependently changed intracellular redox potential into oxidized state. The influx of manganese and its resultant oxidative stress was essential to most of the alterations, except for the action on stellation. Astrocytes are central component of the brain's antioxidant defense. Therefore, the observations suggest that dysfunction of astrocytes possibly involved in neurotoxic action of manganese. PMID:12009774

Chen, Chun-Jung; Liao, Su-Lan

2002-05-01

34

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

35

Available manganese oxides in neutral and alkaline soils  

Microsoft Academic Search

Summary The available higher oxides of manganese in neutral and alkaline soils are estimated by first treating with alcoholic quinol, then washing with alcohol, and finally extracting with semi-molar calcium nitrate. Healthy soils contain from 20 to 50 p.p.m. of manganese so extractable.

L. H. P. Jones; G. W. Leeper

1951-01-01

36

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

37

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

PubMed

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 10(6) 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

2012-11-01

38

Structural Characterization of Biogenic Manganese Oxides Produced in Sea Water  

NASA Astrophysics Data System (ADS)

Manganese oxides have been coined as the "scavengers of the sea" and play important roles in both marine and freshwater systems. Natural manganese oxide nanoparticles and grain coatings are ubiquitous in the environment and profoundly impact the quality of sediments via their ability to degrade and sequester contaminants. These oxides are believed to form dominantly via oxidation of Mn(II) by marine and freshwater bacteria and have extremely high sorptive capacities for heavy metals. We have used XANES, EXAFS, and synchrotron (SR)-XRD techniques to study biogenic manganese oxides produced by spores of the marine Bacillus sp., strain SG-1 in seawater as a function of reaction time under fully in-situ conditions. The primary biogenic solid-phase Mn oxide product is a hexagonal layered phyollomanganate with an oxidation state similar to that in delta-MnO2. XRD data show the biooxides to have a phyllomanganate 10 basal plane spacing, suggesting the interlayer is hydrated and contains calcium. As the experiment continues, the initial biooxide changes to show triclinic symmetry. Fits to these EXAFS spectra suggest the octahedral layers have low Mn octahedral site vacancies in the lattice and the latyers bend to accommodate Jahn-Teller distortions creating the change in symmetry. The oxides observed in this study as models of Mn(II) bio-oxidation may be representative of the most abundant manganese oxide phase suspended in the oxic and sub-oxic zones of the oceanic water column.

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

2003-12-01

39

Manganese-oxidizing bacteria mediate the degradation of 17?-ethinylestradiol.  

PubMed

Manganese (II) and manganese-oxidizing bacteria were used as an efficient biological system for the degradation of the xenoestrogen 17?-ethinylestradiol (EE2) at trace concentrations. Mn(2+)-derived higher oxidation states of Mn (Mn(3+), Mn(4+)) by Mn(2+)-oxidizing bacteria mediate the oxidative cleavage of the polycyclic target compound EE2. The presence of manganese (II) was found to be essential for the degradation of EE2 by Leptothrix discophora, Pseudomonas putida MB1, P. putida MB6 and P. putida MB29. Mn(2+)-dependent degradation of EE2 was found to be a slow process, which requires multi-fold excess of Mn(2+) and occurs in the late stationary phase of growth, implying a chemical process taking place. EE2-derived degradation products were shown to no longer exhibit undesirable estrogenic activity. PMID:21261871

Sabirova, Julia S; Cloetens, L F F; Vanhaecke, L; Forrez, I; Verstraete, Willy; Boon, N

2008-11-01

40

Synthesis of manganese oxide supported on mesoporous titanium oxide: Influence of the block copolymer  

NASA Astrophysics Data System (ADS)

Manganese oxides supported on mesoporous titanium oxides were synthesized via a sol-gel route using block copolymer self-assembly. The oxides were characterized by X-ray diffraction, infrared spectroscopy, thermal analyses, nitrogen adsorption/desorption, electron microscopy and electronic paramagnetic resonance. A mesoporous anatase containing amorphous manganese oxide particles could be obtained with a 0.2 Mn:Ti molar ratio. At higher manganese loading (0.5 Mn:Ti molar ratio), segregation of crystalline manganese oxide occurred. The influence of block copolymer and manganese salt on the oxide structure was discussed. The evolution of the textural and structural characteristics of the materials upon hydrothermal treatment was also investigated.

Schmit, F.; Bois, L.; Chiriac, R.; Toche, F.; Chassagneux, F.; Besson, M.; Descorme, C.; Khrouz, L.

2015-01-01

41

Energetic basis of catalytic activity of layered nanophase calcium manganese oxides for water oxidation  

PubMed Central

Previous measurements show that calcium manganese oxide nanoparticles are better water oxidation catalysts than binary manganese oxides (Mn3O4, Mn2O3, and MnO2). The probable reasons for such enhancement involve a combination of factors: The calcium manganese oxide materials have a layered structure with considerable thermodynamic stability and a high surface area, their low surface energy suggests relatively loose binding of H2O on the internal and external surfaces, and they possess mixed-valent manganese with internal oxidation enthalpy independent of the Mn3+/Mn4+ ratio and much smaller in magnitude than the Mn2O3-MnO2 couple. These factors enhance catalytic ability by providing easy access for solutes and water to active sites and facile electron transfer between manganese in different oxidation states. PMID:23667149

Birkner, Nancy; Nayeri, Sara; Pashaei, Babak; Najafpour, Mohammad Mahdi; Casey, William H.; Navrotsky, Alexandra

2013-01-01

42

Acetone Oxidation using Ozone on Manganese Oxide Catalysts  

SciTech Connect

Supported manganese oxide catalysts were prepared by the impregnation of alumina foam blocks washcoated with alumina and silica. The manganese content based on the weight of the washcoats was 10 wt % calculated as MnO{sub 2}. Fourier transform profiles of the Mn K-edge EXAFS spectra for these samples gave three distinctive peaks at 0.15, 0.25, and 0.32 nm and were close to the profiles of Mn{sub 3}O{sub 4} and {beta}-MnO{sub 2}. The number of surface active sites was determined through oxygen chemisorption measurements at a reduction temperature (T{sub red} = 443 K) obtained from temperature-programmed reduction (TPR) experiments. Acetone catalytic oxidation was studied from room temperature to 573 K, and was found to be highly accelerated by the use of ozone on both catalysts with substantial reductions in the reaction temperature. The only carbon-containing product detected was CO{sub 2}. The alumina-supported catalyst was found to be more active than the silica-supported catalyst in acetone and ozone conversion, with higher turnover frequencies (TOFs) for both reactions. The pressure drop through the foam was low and increased little (0.003 kPa/10 000 h{sup -1}) with space velocity. In situ steady-state Raman spectroscopy measurements during the acetone catalytic oxidation reaction showed the presence of an adsorbed acetone species with a C-H bond at 2930 cm{sup -1} and a peroxide species derived from ozone with an O-O bond at 890 cm{sup -1}.

Xi,Y.; Reed, C.; Lee, Y.; Oyama, S.

2005-01-01

43

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

44

Electrodeposition of manganese and molybdenum mixed oxide thin films and their charge storage properties.  

PubMed

Manganese and molybdenum mixed oxides in a thin film form were deposited anodically on a platinum substrate by cycling the electrode potential between 0 and +1.0 V vs Ag/AgCl in aqueous manganese(II) solutions containing molybdate anion (MoO(4)2-). A possible mechanism for the film formation is as follows. First, electrooxidation of Mn2+ ions with H2O yields Mn oxide and protons. Then, the protons being accumulated near the electrode surface react with MoO(4)2- to form polyoxomolybdate through a dehydrated condensation reaction (by protonation and dehydration). The condensed product coprecipitates with the Mn oxide. Cyclic voltammetry of the Mn/Mo oxide film-coated electrode in aqueous 0.5 M Na2SO4 solution exhibited a pseudocapacitive behavior with higher capacitance and better rate capability than that of the pure Mn oxide prepared similarly, most likely as a result of an increase in electrical conductivity of the film. Electrochemical quartz crystal microbalance and X-ray photoelectron spectroscopy clearly demonstrated that the observed pseudocapacitive behavior results from reversible extraction/insertion of hydrated protons to balance the charge upon oxidation/reduction of Mn3+/Mn4+ in the film. PMID:15952841

Nakayama, Masaharu; Tanaka, Akihiro; Sato, Yoshimine; Tonosaki, Tsuyoshi; Ogura, Kotaro

2005-06-21

45

Carbothermal Reduction of Manganese Oxide in Different Gas Atmospheres  

NASA Astrophysics Data System (ADS)

Carbothermal reduction of manganese oxides was studied in hydrogen, helium, and argon at different temperatures and carbon-to-manganese oxide ratios. Isothermal and temperature programmed carbothermal reduction experiments were conducted in a fixed bed reactor in a vertical tube furnace, with on-line monitoring of gas composition by the CO-CO2 infrared sensor. The extent of reduction was calculated using the off-gas composition and LECO oxygen contents in the reduced samples. In all gas atmospheres, the reaction rate increased with temperature. The reduction rate of manganese oxide in hydrogen was higher than in helium, and in helium higher than in argon. This was attributed to the involvement of hydrogen in the reduction process and the difference in CO and CO2 diffusion coefficients in helium and argon.

Kononov, Ring; Ostrovski, Oleg; Ganguly, Samir

2008-10-01

46

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...Chemical Substances § 721.10010 Barium manganese oxide (BaMnO3 ). (a...The chemical substance identified as barium manganese oxide (BaMnO3 )...

2013-07-01

47

40 CFR 721.10010 - Barium manganese oxide (BaMnO3).  

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

2014-07-01

48

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...Chemical Substances § 721.10010 Barium manganese oxide (BaMnO3 ). (a...The chemical substance identified as barium manganese oxide (BaMnO3 )...

2012-07-01

49

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...Chemical Substances § 721.10010 Barium manganese oxide (BaMnO3). (a...The chemical substance identified as barium manganese oxide (BaMnO3 )...

2011-07-01

50

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...Chemical Substances § 721.10010 Barium manganese oxide (BaMnO3). (a...The chemical substance identified as barium manganese oxide (BaMnO3 )...

2010-07-01

51

40 CFR 721.10013 - Manganese yttrium oxide (Mn2YO5).  

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Manganese yttrium oxide (Mn2YO5). 721.10013 Section 721...Substances § 721.10013 Manganese yttrium oxide (Mn2YO5). (a) Chemical substance...substance identified as manganese yttrium oxide (Mn2 YO5 ) (PMN...

2011-07-01

52

40 CFR 721.10013 - Manganese yttrium oxide (Mn2YO5).  

...2014-07-01 false Manganese yttrium oxide (Mn2YO5). 721.10013 Section 721...Substances § 721.10013 Manganese yttrium oxide (Mn2 YO5 ). (a) Chemical substance...substance identified as manganese yttrium oxide (Mn2 YO5 ) (PMN...

2014-07-01

53

40 CFR 721.10009 - Manganese yttrium oxide (MnYO3).  

...2014-07-01 false Manganese yttrium oxide (MnYO3). 721.10009 Section 721...Substances § 721.10009 Manganese yttrium oxide (MnYO3 ). (a) Chemical substance...substance identified as manganese yttrium oxide (MnYO3 ) (PMN P-00-1122;...

2014-07-01

54

40 CFR 721.10009 - Manganese yttrium oxide (MnYO3).  

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Manganese yttrium oxide (MnYO3). 721.10009 Section 721...Substances § 721.10009 Manganese yttrium oxide (MnYO3 ). (a) Chemical substance...substance identified as manganese yttrium oxide (MnYO3 ) (PMN P-00-1122;...

2012-07-01

55

40 CFR 721.10008 - Manganese strontium oxide (MnSrO3).  

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Manganese strontium oxide (MnSrO3). 721.10008 Section 721...Substances § 721.10008 Manganese strontium oxide (MnSrO3). (a) Chemical substance...substance identified as manganese strontium oxide (MnSrO3 ) (PMN P-00-1121;...

2011-07-01

56

Joining of highly aluminum-doped lanthanum strontium manganese oxide with tetragonal zirconia by plastic deformation  

E-print Network

Joining of highly aluminum-doped lanthanum strontium manganese oxide with tetragonal zirconia February 2008; accepted 24 March 2008 Abstract Aluminum-doped lanthanum strontium manganese oxide, La0.77Sr at the interface. © 2008 Elsevier B.V. All rights reserved. Keywords: Lanthanum strontium aluminum manganese oxide

Dutta, Prabir K.

57

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

58

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

59

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

...2014-07-01 2014-07-01 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)...

2014-07-01

60

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

61

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

62

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

63

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 name...Chemical Substances § 721.4587 Lithium manganese oxide (LiMn204) (generic name...substance identified generically as lithium manganese oxide (LiMn204)...

2010-07-01

64

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

65

76 FR 47996 - Cobalt Lithium Manganese Nickel Oxide; Significant New Use Rule  

Federal Register 2010, 2011, 2012, 2013

...EPA-HQ-OPPT-2009-0922; FRL-8878-2] RIN 2070-AB27 Cobalt Lithium Manganese Nickel Oxide; Significant...for the chemical substance identified as cobalt lithium manganese nickel oxide (CAS No...for the chemical substance identified as cobalt lithium manganese nickel oxide...

2011-08-08

66

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

Federal Register 2010, 2011, 2012, 2013

...EPA-HQ-OPPT-2009-0922; FRL-8853-2] RIN 2070-AB27 Cobalt Lithium Manganese Nickel Oxide; Withdrawal...for the chemical substance identified as cobalt lithium manganese nickel oxide (CAS No...EPA is withdrawing the rule issued for cobalt lithium manganese nickel oxide (PMN...

2010-11-18

67

Local Structure Analysis of Strontium Sorption to Hydrous Manganese Oxide.  

PubMed

To develop mechanistic models of contaminant distribution processes, we conducted an X-ray absorption fine structure analysis of strontium sorption to hydrous manganese oxide (HMO). Sr K-edge measurements were performed at 298, 220, and 77 K, and at sample loadings from 10(-4) to 10(-2) mol Sr/g HMO. Results from fitting the first shell in the sorbed samples indicate that strontium is surrounded by 10-12 oxygen atoms at an average distance of 2.58 Å. This coordination environment is consistent with the strontium atom remaining hydrated upon sorption to the oxide, where in water hydrated strontium has approximately 9 atoms of oxygen at 2.62 Å. Furthermore, the temperature dependence of the strontium-oxygen bond also suggests physical adsorption due to the large contribution of the dynamic component of the Debye Waller factor. Although second-shell data are consistent with either 3 manganese atoms at 4.12 Å or 6 strontium atoms at 3.88 Å, both the near-edge and fine structure data for the manganese K-edge indicate that the local coordination environment of the manganese ion remains intact as a function of time or strontium sorption. Furthermore, the local structure of amorphous manganese oxide is highly ordered. Copyright 2000 Academic Press. PMID:10727353

Axe; Tyson; Trivedi; Morrison

2000-04-15

68

Arsenic transport and partitioning within manganese- and iron-oxide rich aggregated sediments  

NASA Astrophysics Data System (ADS)

Manganese and iron oxides are ubiquitous phases in terrestrial environments that have high sorptive capacities for arsenic. Although numerous studies have characterized the effects of As adsorption onto Fe and Mn oxides individually, the fate of arsenic within mixed (competitive) systems representative of natural environments is unresolved. Here, we investigate As dynamics in an aerobic aggregate composed of ferrihydrite and birnessite coated quartz sand fused by an agarose polymer. Mn and Fe oxide coated sands, having pre-adsorbed As(V), are cast into cohesive spheres and inoculated with Shewanella sp. ANA-3, a bacterial strain capable of reducing As(V) and Mn(IV) and Fe(III) oxides. Arsenic(III) produced by bacterial reduction of As(V) within the aggregate diffuses to the aggregate exterior (proximal to aerated solutes), where it is re-oxidized to As(V) by Mn-oxides; following oxidation, As(V) is repartitioned onto the Fe oxides. X-ray fluorescence microprobe analysis was used to map the spatial distribution of As(III) and As(V) within the aggregate, after which ?-XANES was used to confirm arsenic oxidation state within the mapped areas. These results illustrate the dynamic interplay of biogeochemical transformation, physical heterogeneity, and mixed mineralogy representative of field systems on the fate of arsenic.

Ying, S. C.; Masue-Slowey, Y.; Fendorf, S. E.

2009-12-01

69

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

70

Comparison of the oxidation resistances of yttrium implanted low manganese and low manganese–carbon steels at high temperature  

Microsoft Academic Search

Yttrium implanted and unimplanted low manganese and low manganese–carbon steel samples were analyzed at T=700°C and under an oxygen partial pressure PO2=0.04 Pa for 24 h to show the yttrium implantation effect on sample high temperature oxidation resistances. Sample oxidation weight gains were studied by thermogravimetry and structural analyses were performed by in-situ high temperature X-ray diffraction (XRD) with the

E. Caudron; H Buscail

2000-01-01

71

Distributions of Manganese, Iron, and Manganese-Oxidizing Bacteria In Lake Superior Sediments of Different Organic Carbon Content  

NASA Technical Reports Server (NTRS)

Profiles of oxygen, soluble and particulate manganese and iron, organic carbon and nitrogen were examined in Lake Superior sediment cores, along with the distribution and abundance of heterotrophic and manganese oxidizing bacteria. Analyses were performed using cores collected with the submersible Johnson Sea Link II. Three cores, exhibiting a range of organic carbon content, were collected from the deepest basin in Lake Superior and the north and south ends of the Caribou trough, and brought to the surface for immediate analysis. Minielectrode profiles of oxygen concentration of the three cores were carried out using a commercially available minielectrode apparatus. Oxygen depletion to less than 1% occurred within 4 cm of the surface for two of the cores, but not until approximately 15 cm for the core from the south basin of the Caribou trough. The three cores exhibited very different profiles of soluble, as well as leachable, manganese and iron, suggesting different degrees of remobilization of these metals in the sediments. Vertical profiles of viable bacteria and Mn oxidizing bacteria, determined by plating and counting, showed that aerobic (and facultatively aerobic) heterotrophic bacteria were present at the highest concentrations near the surface and decreased steadily with depth, while Mn oxidizing bacteria were concentrations primarily at and above the oxic/anoxic interface. Soluble manganese in the pore waters, along with abundant organic carbon, appeared to enhance the presence of manganese oxidizing bacteria, even below the oxic/anoxic interface. Profiles of solid-phase leachable manganese suggested a microbial role in manganese reprecipitation in these sediments.

Richardson, Laurie L.; Nealson, Kenneth H.

1989-01-01

72

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, are disclosed. A single crystal ultra-long nanowire includes an ordered porous manganese oxide-based octahedral molecular sieve, and has an average length greater than about 10 micrometers and an average diameter of about 5 nanometers to about 100 nanometers. A film comprises a microporous network comprising a plurality of single crystal nanowires in the form of a layer, wherein a plurality of layers is stacked on a surface of a substrate, wherein the nanowires of each layer are substantially axially aligned. A free standing membrane comprises a microporous network comprising a plurality of single crystal nanowires in the form of a layer, wherein a plurality of layers is aggregately stacked, and wherein the nanowires of each layer are substantially axially aligned.

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

2008-10-21

73

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

74

Giant magnetoresistance of manganese oxides with a layered perovskite structure  

Microsoft Academic Search

MANGANESE oxides with the cubic perovskite structure (typified by LaMnO3) have stimulated considerable interest because of their magnetoresistive properties1-9 they exhibit extremely large changes in electrical resistance in response to applied magnetic fields, a property that is of technological relevance for the development of magnetic memory and switching devices. But for such applications to be viable, great improvements will be

Y. Moritomo; A. Asamitsu; H. Kuwahara; Y. Tokura

1996-01-01

75

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) Department of Plant and Soil Sciences and the Center for Critical Zone Research, University of Delaware, 152 manganese (Mn) oxides, even in low concentrations, to oxidize trace metals such as arsenic from arsenite [As

Sparks, Donald L.

76

Nonequilibrium models for predicting forms of precipitated manganese oxides  

USGS Publications Warehouse

Manganese oxides precipitated by bubbling air through 0.01 molar solutions of MnCl2, Mn(NO3)2, MnSO4, or Mn(ClO4)2 at a constantly maintained pH of 8.5 to 9.5 at temperatures of 25??C or higher consisted mainly of hausmannite, Mn3O4. At temperatures near 0??C, but with other conditions the same, the product is feitknechtite, ??MnOOH, except that if the initial solution is MnSO4 and the temperature is near 0??C the product is a mixture of manganite, ??MnOOH and groutite, ??MnOOH. All these oxides are metastable in aerated solution and alter by irreversible processes to more highly oxidized species during aging. A two-step nonequilibrium thermodynamic model predicts that the least stable species, ??MnOOH, should be most readily converted to MnO2. Some preparations of ??MnOOH aged in their native solution at 5??C attained a manganese oxidation state of +3.3 or more after 7 months. Hausmannite aged at 25??C altered to ??MnOOH. The latter is more stable than a or ??MnOOH, and manganese oxidation states above 3.0 were not reached in hausmannite precipitates during 4 months of aging. Initial precipitation of MnCO3 rather than a form of oxide is likely only where oxygen availability is very low. Composition of solutions and oxidation state and morphology of solids were determined during the aging process by chemical analyses, X-ray and electron diffraction and transmission electron micrographs. ?? 1983.

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

1983-01-01

77

Manganese oxidation induced by water table fluctuations in a sand column.  

PubMed

On-off cycles of production wells, especially in bank filtration settings, cause oscillations in the local water table, which can deliver significant amounts of dissolved oxygen (DO) to the shallow groundwater. The potential for DO introduced in this manner to oxidize manganese(II) (Mn(II)), mediated by the obligate aerobe Pseudomonas putida GB-1, was tested in a column of quartz sand fed with anoxic influent solution and subject to 1.3 m water table changes every 30-50 h. After a period of filter ripening, 100 ?M Mn was rapidly removed during periods of low water table and high dissolved oxygen concentrations. The accumulation of Mn in the column was confirmed by XRF analysis of the sand at the conclusion of the study, and both measured net oxidation rates and XAS analysis suggest microbial oxidation as the dominant process. The addition of Zn, which inhibited GB-1 Mn oxidation but not its growth, interrupted the Mn removal process, but Mn oxidation recovered within one water table fluctuation. Thus transient DO conditions could support microbially mediated Mn oxidation, and this process could be more relevant in shallow groundwater than previously thought. PMID:22126514

Farnsworth, Claire E; Voegelin, Andreas; Hering, Janet G

2012-01-01

78

Manganese ion-assisted assembly of superparamagnetic graphene oxide microbowls  

SciTech Connect

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 [State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096 (China); School of Chemistry and Chemical Engineering, Pingdingshan University, Pingdingshan 467000 (China); Xu, Chunxiang, E-mail: xcxseu@seu.edu.cn; Li, Jitao; Zhu, Gangyi; Xu, Xiaoyong; Dai, Jun; Shi, Zengliang; Lin, Yi [State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096 (China)

2014-03-24

79

Constraints on superoxide mediated formation of manganese oxides.  

PubMed

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 ([Formula: see text]) 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 [Formula: see text] 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

80

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

81

Migration of Mn cations in delithiated lithium manganese oxides.  

PubMed

Li2MnO3 is an integrated component in lithium-manganese-rich nickel manganese cobalt oxides, and the conversion of Li2MnO3 to a spinel-like structure after electrochemical activation has been associated with the continuous potential decay of the material. Delithiated Li2MnO3 and delithiated LiMn2O4 were used as model materials to investigate the mechanism of forming the spinel-like structure. An in situ high-energy X-ray diffraction technique was used to trace the structural change of materials at elevated temperatures, a procedure to mimic the structural transformation during the normal cycling of batteries. It was also found that the migration of Mn atoms from the octahedral sites to tetrahedral sites is the key step for phase transformation from a monoclinic structure to a spinel structure. PMID:25162360

Kan, Yongchun; Hu, Yuan; Lin, Chi-Kai; Ren, Yang; Sun, Yang-Kook; Amine, Khalil; Chen, Zonghai

2014-10-14

82

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

83

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.

84

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

85

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

86

Manganese  

MedlinePLUS

... the body, including processing of cholesterol, carbohydrates, and protein. It might also be involved in bone formation. ... the effectiveness of some antibiotics. To avoid this interaction, take manganese supplements at least one hour after ...

87

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

88

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

89

Calcium manganese(IV) oxides: biomimetic and efficient catalysts for water oxidation.  

PubMed

CaMnO(3) and Ca(2)Mn(3)O(8) were synthesized and characterized by SEM, XRD, FTIR and BET. Both oxides showed oxygen evolution activity in the presence of oxone, cerium(IV) ammonium nitrate and H(2)O(2). Oxygen evolution from water during irradiation with visible light (? > 400 nm) was also observed upon adding these manganese oxides to an aqueous solution containing tris(2,2'-bipyridyl) ruthenium(II), as photosensitizer, and chloro pentaammine cobalt(III) chloride, as electron acceptor, in an acetate buffer. The amounts of dissolved manganese and calcium from CaMnO(3) and Ca(2)Mn(3)O(8) in the oxygen evolving reactions were reported and compared with other (calcium) manganese oxides. Proposed mechanisms of oxygen evolution and proposed roles for the calcium ions are also considered. PMID:22382465

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

2012-04-28

90

Reaction of lincosamide antibiotics with manganese oxide in aqueous solution.  

PubMed

Lincosamides are among the most frequently detected antibacterial agents in effluents from wastewater treatment plants and surface runoff at agricultural production systems. Little is known about their transformations in the environment. This study revealed that manganese oxide caused rapid and extensive decomposition of clindamycin and lincomycin in aqueous solution. The reactions occurred mainly at the pyranose ring of lincosamides, initially by formation of complexes with Mn and cleavage of the ether linkage, leading to the formation of a variety of degradation products via subsequent hydrolytic and oxidative reactions. The results of LC-MS/MS and FTIR analysis confirm cleavage of the C-O-C bond in the pyranose ring, formation of multiple carbonyl groups, and transformation of the methylthio moiety to sulfur oxide. The overall transformation was controlled by interactions of cationic species of lincosamides with MnO(2) surfaces. The presence of electrolytes (i.e., NaCl, CaCl(2), and MnCl(2)) and dissolved organic matter in aqueous solution, and increase of solution pH, diminished lincosamide binding to MnO(2) hence reducing the rate and magnitude of the transformations. Results from this study indicate that manganese dioxides in soils and sediments could contribute to the decomposition of lincosamide antibiotics released into the environment. PMID:20476766

Chen, Wan-Ru; Ding, Yunjie; Johnston, Cliff T; Teppen, Brian J; Boyd, Stephen A; Li, Hui

2010-06-15

91

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

92

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

93

Manganese Oxidation by Bacterial Isolates from the Indian Ridge System  

Microsoft Academic Search

The abundance and activity of culturable manganese-oxidizing bacteria were assessed from near-bottom water samples of the\\u000a tectonically active Carlsberg Ridge. Retrievable counts as colony forming units (CFU) on dilute nutrient agar medium (dilNA\\u000a = 2 gm l?1 nutrient broth+2% agar) and on dilNA supplemented with 1, 2 and 3 mM MnCl2·4H2O were in the order of 106 CFU  l?1. Retrievability of heterotrophs ranged

Sheryl Oliveira Fernandes; K. P. Krishnan; V. D. Khedekar; P. A. Loka Bharathi

2005-01-01

94

Synchrotron-Based Studies of Manganese Oxide Biomineralization  

NASA Astrophysics Data System (ADS)

Natural Mn oxide colloids and grain coatings are ubiquitous in the environment and profoundly impact the quality of soils and soil solutions via their ability to degrade and sequester contaminants. These oxides are generated via oxidation of Mn(II) by freshwater and marine bacteria and have extremely high sorptive capacities for heavy metals. Mn oxides readily oxidize a variety of recalcitrant organic and inorganic compounds. The mechanism(s) and products of bacterial Mn(II) oxidtion are therefore believed to have deep and wide-ranging roles in the environmental cycling of trace metals, organics, and carbon. We have utilized X-ray absorption spectroscopy (XAS) and synchrotron-based in-situ transmission XRD (SR-XRD) to probe the structure of fully hydrated biogenic manganese oxides produced by spores of the marine bacterium, Bacillus spp., strain SG-1. Biogenic oxides were produced in the absence and then presence of co-metal solutes Co(II), which have high affinities for Mn oxides, but present contrasting redox proerties and coordination chemistries, thus providing greater probe capability. The primary biogenic product is a poorly crystalline solid similar to delta MnO2 in which Mn has an oxidation state close to 4+. The structure of the oxide is analogous to acid birnessite, but with fewer layer vacancies and greater local order around Mn(IV). Co(II) is oxidizied to Co(III) and incorporated at Mn(IV) sites in the octahedral layer. The presence of Co(III) alters the stability and structure of the host Mn oxides. This observation, combined with the very high sorptive capacity of the Mn oxides, imply that bacteria can exert tremendous influence over Co cycling in impacted waters via Mn oxide biomineralization.

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

2002-12-01

95

Occurrence of manganese-oxidizing microorganisms and manganese deposition during biofilm formation on stainless steel in a brackish surface water.  

PubMed

Abstract Biofilm formation on 316L stainless steel was investigated in a pilotscale flow-through system fed with brackish surface water using an alternating flow/stagnation/flow regime. Microbial community analysis by denaturing gradient gel electrophoresis and sequencing revealed the presence of complex microbial ecosystems consisting of, amongst others, Leptothrix-related manganese-oxidizing bacteria in the adjacent water, and sulfur-oxidizing, sulfate-reducing and slime-producing bacteria in the biofilm. Selective plating of the biofilm indicated the presence of high levels of manganese-oxidizing microorganisms, while microscopic and chemical analyses of the biofilm confirmed the presence of filamentous manganese-precipitating microorganisms, most probably Leptothrix species. Strong accumulation of iron and manganese occurred in the biofilm relative to the adjacent water. No evidence of selective colonization of the steel surface or biocorrosion was found over the experimental period. The overall results of this study highlight the potential formation of complex microbial biofilm communities in flow-through systems thriving on minor concentrations of manganese. PMID:19709183

Kielemoes, Jan; Bultinck, Isabelle; Storms, Hedwig; Boon, Nico; Verstraete, Willy

2002-01-01

96

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

97

Structure and Oxidation State of Silica-Supported Manganese Oxide Catalysts and Reactivity for Acetone Oxidation with Ozone  

SciTech Connect

Silica-supported manganese oxide catalysts with loadings of 3, 10, 15, and 20 wt % (as MnO{sub 2}) were characterized with use of X-ray absorption spectroscopy and X-ray diffraction (XRD). The edge positions in the X-ray absorption spectra indicated that the oxidation state for the manganese decreased with increasing metal oxide loading from a value close to that of Mn{sub 2}O{sub 3} (+3) to a value close to that of Mn{sub 3}O{sub 4} (+2 2/3). The XRD was consistent with these results as the diffractograms for the supported catalysts of higher manganese oxide loading matched those of a Mn{sub 3}O{sub 4} reference. The reactivity of the silica-supported manganese oxide catalysts in acetone oxidation with ozone as an oxidant was studied over the temperature range of 300 to 600 K. Both oxygen and ozone produced mainly CO{sub 2} as the product of oxidation, but in the case of ozone the reaction temperature and activation energy were significantly reduced. The effect of metal oxide loading was investigated, and the activity for acetone oxidation was greater for a 10 wt % MnO{sub x}/SiO{sub 2} catalyst sample compared to a 3 wt % MnO{sub x}/SiO{sub 2} sample.

Reed,C.; Lee, Y.; Oyama, S.

2006-01-01

98

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 Summer 2010 Copyright 2010 Gautier Landrot All Rights Reserved #12;KINETICS AND MECHANISMS OF CHROMIUM

Sparks, Donald L.

99

Oxidation of As(III) by Hydrous Manganese Oxide: Effect of Carbonate  

Microsoft Academic Search

The mobility of arsenic in aquatic environment is largely governed by its speciation and adsorption on the surfaces of minerals. Hydrous manganese oxide (HMO) plays an important role in redox transformation of arsenic in aquatic environment and is available for remedy of groundwater with high arsenic concentration. Carbonate is often present as major anion in groundwater and its influence on

Zhixi Zhao; Shanlin Zhao; Yongfeng Jia

2011-01-01

100

Manganese oxide minerals: Crystal structures and economic and environmental significance  

PubMed Central

Manganese oxide minerals have been used for thousands of years—by the ancients for pigments and to clarify glass, and today as ores of Mn metal, catalysts, and battery material. More than 30 Mn oxide minerals occur in a wide variety of geological settings. They are major components of Mn nodules that pave huge areas of the ocean floor and bottoms of many fresh-water lakes. Mn oxide minerals are ubiquitous in soils and sediments and participate in a variety of chemical reactions that affect groundwater and bulk soil composition. Their typical occurrence as fine-grained mixtures makes it difficult to study their atomic structures and crystal chemistries. In recent years, however, investigations using transmission electron microscopy and powder x-ray and neutron diffraction methods have provided important new insights into the structures and properties of these materials. The crystal structures for todorokite and birnessite, two of the more common Mn oxide minerals in terrestrial deposits and ocean nodules, were determined by using powder x-ray diffraction data and the Rietveld refinement method. Because of the large tunnels in todorokite and related structures there is considerable interest in the use of these materials and synthetic analogues as catalysts and cation exchange agents. Birnessite-group minerals have layer structures and readily undergo oxidation reduction and cation-exchange reactions and play a major role in controlling groundwater chemistry. PMID:10097056

Post, Jeffrey E.

1999-01-01

101

Complete oxidation of acetone over manganese oxide catalysts supported on alumina- and zirconia-pillared clays  

Microsoft Academic Search

The complete oxidation of acetone has been studied over a series of manganese oxide catalysts supported on the unpillared and the Al- and Zr-pillared forms of two natural clays of the smectite class (a montmorillonite and a saponite). The temperatures required for total combustion of acetone over the several catalysts ranged from 610 to 660K at the relatively low WMn\\/Fin

L. M Gand??a; M. A Vicente; A Gil

2002-01-01

102

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(VI) in the soil of contaminated sites. 1. INTRODUCTION Chromium can be found at very high concentrations 2.7 million times higher than the chromium mean concentration in natural waters,2 in a soil near

Sparks, Donald L.

103

Overcharging manganese oxides: Extracting lithium beyond Mn 4+  

NASA Astrophysics Data System (ADS)

It has been demonstrated previously that Li may be removed electrochemically from Mn containing oxides beyond the maximum oxidation state of 4+ for Mn in an octahedral oxygen environment. Here we present a comparison of such overcharge behavior in a series of different layered lithium manganese oxides including Li 2MnO 3, Li x[Mn 1 - yLi y]O 2, ( y ? 0.2), and Li[Ni xLi 1/3 - 2 x/3 Mn 2/3 - x/3 ]O 2 (0 ? x ? 0.5). We show that there are two competing mechanisms by which electrochemical extraction of lithium can occur in Mn (4+) systems. In the first Li removal is accompanied by O 2- loss (effective removal of Li 2O) whilst the second involves oxidation of the non-aqueous electrolyte thus generating H + ions which exchange for Li +. At 30 °C the first mechanism is dominant in all examples studied, whilst at 55 °C the proton exchange mechanism becomes more important. At 30 °C H + exchange is more prevalent in Li 2MnO 3 than in the other two cases. The preference for O loss in the Mn/Ni system may be understood in terms of the ease with which MnO 2 will lose oxygen.

Armstrong, A. R.; Robertson, A. D.; Bruce, P. G.

104

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

105

Resistive switching properties of manganese oxide nanoparticles with hexagonal shape  

NASA Astrophysics Data System (ADS)

Uniformly sized hexagonal shaped manganese oxide (MnO) nanoparticles were chemically synthesized. The bipolar resistive switching characteristics were investigated in the Ti/MnO/Pt structure. The nanoparticles were assembled as close-packed monolayer with a thickness of 30 nm by dip-coating and annealing procedures. The bipolar resistive switching behaviors in Ti/MnO/Pt device could be caused by the formation and rupture of conductive filaments in the nanoparticles. The temperature dependence of resistance was discussed. The resistance of HRS presented a negative temperature dependence at high temperature, indicating a typical semiconducting behavior. The resistance of LRS increased with the elevated temperature exhibiting a metallic state. Ohmic conduction, space charge limited conduction (SCLC), and Schottky conduction have been investigated for the conduction and switching mechanism.

Hu, Quanli; Park, Mira; Abbas, Yawar; Kim, Jai Soon; Yoon, Tae-Sik; Choi, Young Jin; Kang, Chi Jung

2015-01-01

106

Chemical lithium extraction from manganese oxides for lithium rechargeable batteries  

NASA Astrophysics Data System (ADS)

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 cycled cathodes are presented. Electrochemical insertion/extraction of Li(+) ions occurs with tetragonal/cubic distortion in the spinel framework, whereas Li(+) ions can move in compounds having the rocksalt structure, without significant modification of the X-ray patterns.

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

1991-03-01

107

Manganese oxide microswitch for electronic memory based on neural networks  

NASA Technical Reports Server (NTRS)

A solid-state, resistance tailorable, programmable-once, binary, nonvolatile memory switch based on manganese oxide thin films is reported. MnO(x) exhibits irreversible memory switching from conducting (on) to insulating (off) state, with the off and on resistance ratio of greater than 10,000. The switching mechanism is current-triggered chemical transformation of a conductive MnO(2-Delta) to an insulating Mn2O3 state. The energy required for switching is of the order of 4-20 nJ/sq micron. The low switching energy, stability of the on and off states, and tailorability of the on state resistance make these microswitches well suited as programmable binary synapses in electronic associative memories based on neural network models.

Ramesham, R.; Daud, T.; Moopenn, A.; Thakoor, A. P.; Khanna, S. K.

1989-01-01

108

The Wettability of a Multi-Component DNAPL on Quartz and Iron Oxide Sands  

NASA Astrophysics Data System (ADS)

Dense nonaqueous phase liquids (DNAPLs) released to the subsurface often contain a variety of chemical constituents, via either co-disposal or intentional modification to increase their industrial efficacy. These additional constituents are often surface active compounds (surfactants)that partition to soil surfaces. The role that these surface active compounds that sorb to soil surfaces have on DNAPL migration is still poorly understood despite an increasing amount of work in the area. Most studies have focused on the role surface active chemicals play in altering the wettability of quartz sands. This research aims to extend the understanding of multi-component DNAPL transport to other porous media and under a variety of pH conditions. Specifically, the objective of this study was to compare the changes in the wettability of quartz and iron oxide sands in a tetrachloroethylene (PCE)/water system spiked with dodecylamine, a representative cationic surfactant. Wettability was assessed through: (i) contact angles measured on representative quartz and iron oxide-coated plates as well as (ii) contact angles measured directly on sands using an Axial Drop Symmetrical Analyzer apparatus; and (iii) capillary pressure-saturation relationships obtained via multi-step outflow experiments. In addition, two-dimensional sandbox experiments explored the influences of iron oxide and quartz sands on multicomponent DNAPL migration. Results suggest that quartz and iron oxide-coated sands exhibit different wetting characteristics under similar subsurface conditions.

Molnar, I.; O'Carroll, D.; Gerhard, J.

2009-05-01

109

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

110

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

111

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

112

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

113

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

114

Selective synthesis of manganese oxide nanostructures for electrocatalytic oxygen reduction.  

PubMed

This work presents two points with respect to manganese oxide (MnO(x)) nanomaterials: their controllable synthesis with desired phases and shapes together with their applications as catalysts for oxygen reduction and Al/air batteries. Solid MnO(x) with crystalline phases of MnOOH, Mn(2)O(3), and MnO(2) as well as shapes of the sphere, wire, rod, and particle were prepared through a simple one-pot hydrothermal route. Selective preparation was achieved by adjusting the surfactant concentration that controls simultaneously the growth thermodynamic and dynamic parameters of MnO(x) nanocrystals. Electrochemical investigations show that the obtained Mn(2)O(3) nanowires, which possess a large aspect ratio and preferentially exposed (222) crystal surfaces, exhibit remarkable catalytic activity (comparable to Pt/C counterparts) toward the electroreduction of oxygen in alkaline media. The tailored MnO(x) nanostructures may find prospective applications as low-cost catalysts for alkaline fuel cells and metal/air batteries. PMID:20353237

Cheng, Fangyi; Shen, Jian; Ji, Weiqiang; Tao, Zhanliang; Chen, Jun

2009-02-01

115

Experimental evaluation of the effects of quench rate and quartz surface area on homogeneous mercury oxidation  

SciTech Connect

This paper presents a mercury oxidation data set suitable for validation of fundamental kinetic models of mercury chemistry and for mechanism development. Experimental facilities include a mercury reactor fitted with a 300-W, quartz-glass burner and a quartz reaction chamber. While operated with a temperature profile representative of a typical boiler, a residence time of 6 s was achieved. Participating reacting species (chlorine, mercury) were introduced through the burner to produce a radical pool representative of real combustion systems. Speciated mercury measurements were performed using a Tekran 2537A Analyzer coupled with a conditioning system. Homogeneous mercury reactions involving chlorine have been investigated under two different temperature profiles producing quench rates of -210 K/s and -440 K/s. The larger quench rate produced 52% greater total oxidation than the lower quench at chlorine concentrations of 200 ppm. The effect of reactor surface area on oxidation was also investigated. The quartz surfaces interacted with mercury only in the presence of chlorine and their overall effect was to weakly inhibit oxidation. The extent of oxidation was predicted using a detailed kinetic model. The model predicted the effects of quench rate and chlorine concentration shown in experimentation. 12 refs., 5 figs., 3 tabs.

Andrew Fry; Brydger Cauch; Geoffrey D. Silcox; JoAnn S. Lighty; Constance L. Senior [University of Utah, Salt Lake City, UT (United States). Department of Chemical Engineering

2007-07-01

116

Quartz and Hydrous Iron Oxides from the Bee Bluff Structure of South Texas  

NASA Astrophysics Data System (ADS)

There is substantial information showing that the Bee Bluff structure is an impact site and that a residual crater can be identified. The thin hard cap of Carrizo Sandstone, Indio fm calcareous silt and a thin layer of iron-rich siltstone leads to impact processes in which the high pressure release wave proceeds promptly upward leading to a trapping of metamorphic products at the impact interface, a `bottom-up' pressure release. Release of water from goethite binder in the sandstone and from the iron-rich siltstone results in supersaturated steam in mixtures with iron and quartz compounds. Samples with quartz and hydrous iron oxide features are examined with optical microscopy, SEM, EDX and XRD. A quartz grain is found with a well defined PDF set. There is widespread amorphous quartz including lechatleriete. Nanocrystals of ?-goethite in the acicular form are common. A condensation sphere from the `Uvalde Crater Rosetta Stone' shows a complex mixture of hematite, goethite, and alpha quartz with a trace of trydimite. Numerous samples are yet to be analyzed. The crater appears to have features that can serve as an Earth analog to Mars craters. A companion paper in the present proceedings summarizes prior work, adds new site detail, reports impact-loading analysis, and describes overall features of impactite samples from the site.

Graham, R. A.; Martin, M.; Thadhani, N. N.; Morosin, B.

2006-07-01

117

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

E-print Network

are coatings of manganese oxides. Oxide coatings provide a surface for metal adsorption5-8 and a medium. The film is grown on the (101h4) surface of rhodochrosite (MnCO3). In the presence of O2(aq) and at circumneutral pH, film growth begins as manganese oxide islands that expand laterally across the surface

118

Effect of oxide formation mechanisms on lead adsorption by biogenic manganese (hydr)oxides, iron (hydr)oxides, and their mixtures.  

PubMed

The effects of iron and manganese (hydr)oxide formation processes on the trace metal adsorption properties of these metal (hydr)oxides and their mixtures was investigated by measuring lead adsorption by iron and manganese (hydr)oxides prepared by a variety of methods. Amorphous iron (hydr)oxide formed by fast precipitation at pH 7.5 exhibited greater Pb adsorption (gamma(max) = 50 mmol of Pb/mol of Fe at pH 6.0) than iron (hydr)oxide formed by slow, diffusion-controlled oxidation of Fe(II) at pH 4.5-7.0 or goethite. Biogenic manganese(III/IV) (hydr)oxide prepared by enzymatic oxidation of Mn(II) by the bacterium Leptothrix discophora SS-1 adsorbed five times more Pb (per mole of Mn) than an abiotic manganese (hydr)oxide prepared by oxidation of Mn(II) with permanganate, and 500-5000 times more Pb than pyrolusite oxides (betaMnO2). X-ray crystallography indicated that biogenic manganese (hydr)oxide and iron (hydr)oxide were predominantly amorphous or poorly crystalline and their X-ray diffraction patterns were not significantly affected by the presence of the other (hydr)oxide during formation. When iron and manganese (hydr)oxides were mixed after formation, or for Mn biologically oxidized with iron(III) (hydr)oxide present, observed Pb adsorption was similar to that expected for the mixture based on Langmuir parameters for the individual (hydr)oxides. These results indicate that interactions in iron/manganese (hydr)oxide mixtures related to the formation process and sequence of formation such as site masking, alterations in specific surface area, or changes in crystalline structure either did not occur or had a negligible effect on Pb adsorption by the mixtures. PMID:11871557

Nelson, Yarrow M; Lion, Leonard W; Shuler, Michael L; Ghiorse, William C

2002-02-01

119

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

120

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

121

Synthesis of highly monodisperse porous manganese oxide spheres using a butyric acid microemulsion.  

PubMed

Porous manganese oxide spheres form readily from a reaction between KMnO4 and n-butanol in aqueous butyric acid under ambient conditions. Spheres have uniform size, tuneable diameters and high surface areas. The material is an active catalyst for the oxidation of isopropanol to acetone. PMID:25531308

Ching, Stanton; Richter, Ian J; Tutunjian, Kathryn A; Kriz, David A; Kovic, Yumi

2015-01-20

122

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

123

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

124

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

125

Manganese oxide helices, rings, strands, and films, and methods for their preparation  

DOEpatents

Methods for the preparation of mixed-valence manganese oxide compositions with quaternary ammonium ions are described. The compositions self-assemble into helices, rings, and strands without any imposed concentration gradient. These helices, rings, and strands, as well as films having the same composition, undergo rapid ion exchange to replace the quaternary ammonium ions with various metal ions. And the metal-ion-containing manganese oxide compositions so formed can be heat treated to form semi-conducting materials with high surface areas.

Suib, Steven L. (Storrs, CT); Giraldo, Oscar (Storrs, CT); Marquez, Manuel (Wheeling, IL); Brock, Stephanie (Detroit, MI)

2003-01-07

126

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

127

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

NASA Astrophysics Data System (ADS)

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 emerging dielectric technologies. In the present work, using manganese chloride and hydrazine hydrate, Mn3O4 and Mn2O3 nanoparticles were successfully synthesized by conventional and hydrothermal method respectively. The variation in the formation of the different phases has been discussed. The nanoparticles were well characterized by X-ray Diffraction and using the Debye Scherrer formula, the average size of Mn3O4 and Mn2O3 nanoparticles were calculated to be 35 nm and 25 nm respectively. Using solution casting method, nanocomposites of chitosan/Mn3O4 were prepared and their electrochemical properties were studied using electrochemical impedance spectroscopy. It was observed that with increase in the content of nano oxides, the conductivity of the films increased. Also, the variation in the permittivity of these samples with respect to frequency was studied. The results suggest that the composites have a fair chance to be used in energy storage devices.

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

2011-10-01

128

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

129

Manganese is required for oxidative metabolism in unstressed Bradyrhizobium japonicum cells  

PubMed Central

Recent studies of Mn2+ transport mutants indicate that manganese is essential for unstressed growth in some bacterial species, but is required primarily for induced stress responses in others. A Bradyrhizobium japonicum mutant defective in the high affinity Mn2+ transporter gene mntH has a severe growth phenotype under manganese limitation, suggesting a requirement for the metal under unstressed growth. Here, we found that activities of superoxide dismutase and the glycolytic enzyme pyruvate kinase were deficient in an mntH strain grown under manganese limitation. We identified pykM as the only pyruvate kinase-encoding gene based on deficiency in activity of a pykM mutant, rescue of the growth phenotype with pyruvate, and pyruvate kinase activity of purified recombinant PykM. PykM is unusual in that it required Mn2+ rather than Mg2+ for high activity, and that neither fructose 1,6-bisphosphate nor AMP was a positive allosteric effector. The mntH-dependent superoxide dismutase is encoded by sodM, the only expressed superoxide dismutase-encoding gene under unstressed growth conditions. An mntH mutant grew more slowly on pyruvate under manganese-limited conditions than did a pykM sodM double mutant, implying additional manganese-dependent processes. The findings implicate roles for manganese in key steps in unstressed oxidative metabolism in B. japonicum. PMID:22463793

Hohle, Thomas H.; O’Brian, Mark R.

2012-01-01

130

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

131

Plasma-electrolytic formation, composition and catalytic activity of manganese oxide containing structures on titanium  

NASA Astrophysics Data System (ADS)

In the present work, we report the data about formation of TiO 2-rutile or TiO 2 and Mn 2O 3, Mn 3O 4 containing oxide structures on titanium in aqueous electrolytes by means of plasma-electrolytic deposition. The layers formed are characterized by X-ray diffraction, electron probe microanalysis and scanning electron microscopy methods. The PEO coatings on titanium formed in sodium tetraborate solution contain the TiO 2 stabile rutile modification that is important when utilizing such a structure as a catalyst carrier. Manganese acetate adding into the electrolyte leads to formation of layers that contain Mn 2O 3, Mn 3O 4 and TiO 2-rutile in outer region. The manganese content in the surface layer depends on the formation conditions as well as on manganese acetate concentration in the electrolyte. Catalytic activity of the layers in CO ? CO 2 reaction is studied in the static and flow conditions. The manganese-containing layers obtained possess the catalytic activity in CO ? CO 2 oxidation reaction at the temperature range of 250-350 °C. The catalytic activity depends on the concentration and surface distribution of manganese as well as on the layers morphology.

Rudnev, V. S.; Vasilyeva, M. S.; Kondrikov, N. B.; Tyrina, L. M.

2005-12-01

132

Manganese oxide micro-supercapacitors with ultra-high areal capacitance  

NASA Astrophysics Data System (ADS)

A symmetric micro-supercapacitor is constructed by electrochemically depositing manganese oxide onto micro-patterned current collectors. High surface-to-volume ratio of manganese oxide and short diffusion distance between electrodes give an ultra-high areal capacitance of 56.3 mF cm-2 at a current density of 27.2 ?A cm-2.A symmetric micro-supercapacitor is constructed by electrochemically depositing manganese oxide onto micro-patterned current collectors. High surface-to-volume ratio of manganese oxide and short diffusion distance between electrodes give an ultra-high areal capacitance of 56.3 mF cm-2 at a current density of 27.2 ?A cm-2. Electronic supplementary information (ESI) available: Experimental procedures; optical images of micro-supercapacitors; areal capacitances of samples M-0.3C, M-0.6C and M-0.9C; illustration of interdigital finger electrodes; Nyquist plot of Co(OH)2 deposited on micro-electrodes. See DOI: 10.1039/c3nr00210a

Wang, Xu; Myers, Benjamin D.; Yan, Jian; Shekhawat, Gajendra; Dravid, Vinayak; Lee, Pooi See

2013-05-01

133

Structural stability of lithium manganese oxides S. K. Mishra and G. Ceder  

E-print Network

of magnetism on the Li intercalation potential, an important property for rechargeable Li batteries. S0163. These materials can therefore be applied on the cathode side of a rechargeable Li battery where Li is stored- rial of choice in rechargeable batteries.4,5 Lithiated manganese oxides are also interesting from

Ceder, Gerbrand

134

IMPACT OF WATER CHEMISTRY ON MANGANESE REMOVAL DURING OXIDATION/FILTRATION TREATMENT  

EPA Science Inventory

This is a poster showing the purpose and setup of our pilot plant experiments with manganese filtration. The focus is on the differences, effectiveness, and problems with using chlorine and potassium permanganate in oxidation/filtration. The poster will show the results and findi...

135

Structural study of biotic and abiotic poorly-crystalline manganese oxides using atomic  

E-print Network

Structural study of biotic and abiotic poorly-crystalline manganese oxides using atomic pair structures. In this study, the crystal structures of their synthetic analogs includ- ing acid birnessite using atomic pair distribution function (PDF) analysis. Results unambiguously verify that these Mn

Sparks, Donald L.

136

Manganese Peroxidase Degrades Pristine but Not Surface-Oxidized (Carboxylated) Single-Walled Carbon Nanotubes  

E-print Network

about the biotransformation potential of single-walled carbon nanotubes (SWNTs). In this study, we, and mechanical properties.1 Single-walled carbon nanotubes (SWNTs) are particularly attractive for potentialManganese Peroxidase Degrades Pristine but Not Surface-Oxidized (Carboxylated) Single-Walled Carbon

Alvarez, Pedro J.

137

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

138

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

139

Manganese oxide/graphene aerogel composites as an outstanding supercapacitor electrode material.  

PubMed

Graphene aerogels (GA), prepared with an organic sol-gel process, possessing a high specific surface area of 793?m(2) ?g(-1) , a high pore volume of 3?cm(3) ?g(-1) , and a large average pore size of 17?nm, were applied as a support for manganese oxide for supercapacitor applications. The manganese oxide was electrochemically deposited into the highly porous GA to form MnO2 /GA composites. The composites, at a high manganese oxide loading of 61?wt.?%, exhibited a high specific capacitance of 410?F?g(-1) at 2?mV?s(-1) . More importantly, the high rate specific capacitances measured at 1000?mV?s(-1) for these composites were two-fold higher than those obtained with samples prepared in the absence of the GA support. The specific capacitance retention ratio, based on the specific capacitance obtained at 25?mV?s(-1) , was maintained high, at 85?%, even at the high scan rate of 1000?mV?s(-1) , in contrast with the significantly lower value of 67?% for the plain manganese oxide sample. For the cycling stability, the specific capacitance of the composite electrode decayed by only 5?% after 50,000 cycles at 1000?mV?s(-1) . The success of this MnO2 /GA composite may be attributed to the structural advantages of high specific surface areas, high pore volumes, large pore sizes, and three-dimensionally well-connected network of the GA support. These structural advantages made possible the high mass loading of the active material, manganese oxide, large amounts of electroactive surfaces for the superficial redox events, fast mass-transfer within the porous structure, and well-connected conductive paths for the involved charge transport. PMID:24327570

Wang, Chun-Chieh; Chen, Hsuan-Ching; Lu, Shih-Yuan

2014-01-01

140

Efficient Oxidative Methyl Esterification of Aldehydes By Silica-supported Manganese Complex: Clean and Recyclable Catalyst  

Microsoft Academic Search

An oxidative methyl esterification of aldehydes was carried out using hydrogen peroxide as oxidant and silica supported manganese complex as catalyst. The catalyst was prepared by grafting method and characterized by surface area analysis by the BET method, elemental and thermogravimetric analyses, FT-IR, C-CPMAS spectral studies and atomic absorption spectrometry technique (AAS). The work-up procedure is very simple and products

R. K. Sharma; Chetna Sharma

2010-01-01

141

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

E-print Network

.F. Abstract New nanostructured manganese oxi-iodides were prepared by redox reaction of sodium permanganate black incorporated directly in the aqueous reaction medium at the synthesis stage, or on samples with a single-phase lithium intercalation reaction with simultaneous manganese oxidation-reduction. Keywords

Paris-Sud XI, Université de

142

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

143

Effect of Structure on the Storage Characteristics of ManganeseOxide Electrode Materials  

SciTech Connect

Eleven types of manganese-containing electrode materialswere subjected to long-term storage at 55oC in 1M LiPF6 ethylenecarbonate/dimethyl carbonate (EC/DMC) solutions. The amount of manganesedissolution observed depended upon the sample surface area, the averageMn oxidation state, the structure, and substitution levels of themanganese oxide. In some cases, structural changes such as solvateformation were exacerbated by the high temperature storage, andcontributed to capacity fading upon cycling even in the absence ofsignificant Mn dissolution. The most stable materials appear to beTi-substituted tunnel structures and mixed metal layered oxides with Mnin the +4 oxidation state.

Park, Yong Joon; Doeff, Marca M.

2006-01-31

144

Oxidant-induced DNA damage by quartz in alveolar epithelial cells  

Microsoft Academic Search

Respirable quartz has recently been classified as a human carcinogen. Although, studies with quartz using naked DNA as a target suggest that formation of oxyradicals by particles may play a role in the DNA-damaging properties of quartz, it is not known whether this pathway is important for DNA damage in the target cells for quartz carcinogenesis, i.e. alveolar epithelial cells.

Roel P. F. Schins; Ad M. Knaapen; Gonca D. Cakmak; Tingming Shi; Christel Weishaupt; Paul J. A. Borm

2002-01-01

145

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

146

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

NASA Astrophysics Data System (ADS)

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 below 400 °C are composed from spherical-shaped particles with diameters in the nano-scale range 6-12 nm. Reduction of the binary spinel oxides with hydrogen proceeds in multiple steps that correspond to the reduction steps Co(III)?Co(II); Co(II)?Co reduction and Mn(IV), Mn(III)?Mn(II). In the temperature range 100-1200 °C reduction to metallic manganese has not been observed.

Klissurski, Dimitar G.; Uzunova, Ellie L.

2003-05-01

147

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 capable of oxidizing chromium(III) to the more hazardous and mobile chromium(VI). Although the kinetics of chromium oxidation by Mn-oxides have been studied, the calculated rate parameters are apparent since

Sparks, Donald L.

148

Tailoring structural, optical and magnetic properties of spinel type cobalt oxide (Co3O4) by manganese doping  

NASA Astrophysics Data System (ADS)

To study the effects of manganese doping on structural, optical and magnetic properties of spinel type cobalt oxide (Co3O4) system, manganese ions were doped at different concentrations (5-20%) using co-precipitation method. Crystalline nature and phase purity of the prepared materials were investigated using XRD, FTIR and XPS measurements. Manganese ions played a major role in reducing crystallite size and introducing macro/micro-strains in the doped compounds. Surface morphology of the materials examined using FESEM images confirmed the role played by manganese ion in restraining particle growth. Manganese doping was further confirmed using EDS and XPS elemental analysis. From the XPS studies, manganese concentration in the doped samples were identified to be close to the initial doping percentage (MnxCo3-xO4; x=4.61%, 8.25%, 14.13% and 18.10%). Presence of three types of manganese ions was revealed from the XPS study. Pair of absorption bands centered at 440 nm and 720 nm characteristic of spinel type cobalt oxide was observed for all the prepared materials. Micro- and macro-strains induced by manganese doping have created localized density of states reducing band energy gaps in the doped materials. Mn2+ ions replacing Co2+ ions in the tetrahedral site have enhanced the weak ferromagnetism observed for pristine cobalt oxide. Saturation magnetization, coercivity and remanent magnetization was found to increase with Mn2+ concentration.

Naveen, A. Nirmalesh; Selladurai, Subramanian

2015-01-01

149

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

150

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

151

Electroless preparation and ASAXS microstructural analysis of pseudocapacitive carbon manganese oxide supercapacitor electrodes.  

PubMed

Anomalous small angle X-Ray scattering (ASAXS) has been utilized as a non-invasive, integral tool to access the structural properties of carbon xerogel-manganese oxide electrodes with nanometer resolution. As these electrodes constitute the elementary functional units in supercapacitors and as their microstructure governs the macroscopic electrical performance, it is essential to gain a detailed morphological understanding of the underlying carbon particle scaffold coated with manganese oxide. We demonstrate that, in this regard, ASAXS provides a powerful technique and in combination with a theoretical core-shell model enables a quantitative estimation of the relevant structural parameters. As a result, we determined the thicknesses of the solution deposited MnO2-shells to range between 3 to 26 nm depending on the carbon particle size and thus on their effective surface area. By our core-shell modeling we conclude the revealed manganese oxide coatings on the carbon support to be rather thick, but nevertheless to show a high uniformity in thickness. At 1.8+-0.2 to 2.2+-0.1 gcm-3 the related effective MnO2-densities of the shells are about 30 % lower than the corresponding bulk density of 3.0 gcm-3. This mainly originates from a substructure within the shell, whose growth is controlled by a pronounced reduction of the manganese precursor during layer formation. Finally, the presented ASAXS data are complemented by SEM and N2 sorption measurements, proving not only qualitatively the proposed flake-like MnO2-surface morphology but also confirming quantitatively the manganese shell thickness, complementary, on a local scale. PMID:25453192

Weber, Christian; Reichenauer, Gudrun; Pflaum, Jens

2014-12-01

152

Redox-responsive degradable honeycomb manganese oxide nanostructures as effective nanocarriers for intracellular glutathione-triggered drug release.  

PubMed

Redox-responsive degradable honeycomb manganese oxide (hMnO2) nanostructures consisting of some lamellar MnO2 platelets were established as a new class of drug carriers for intracellular glutathione-triggered drug release. PMID:25421350

He, Dinggeng; He, Xiaoxiao; Wang, Kemin; Yang, Xue; Yang, Xiaoxiao; Zou, Zhen; Li, Xuecai

2015-01-14

153

Correction: Sacrificial template-directed synthesis of mesoporous manganese oxide architectures with superior performance for organic dye adsorption  

NASA Astrophysics Data System (ADS)

Correction for `Sacrificial template-directed synthesis of mesoporous manganese oxide architectures with superior performance for organic dye adsorption' by Lunhong Ai et al., Nanoscale, 2012, 4, 5401-5408.

Ai, Lunhong; Yue, Haitao; Jiang, Jing

2014-10-01

154

Manganese oxide/carbon yolk-shell nanorod anodes for high capacity lithium batteries.  

PubMed

Transition metal oxides have attracted much interest for their high energy density in lithium batteries. However, the fast capacity fading and the low power density still limit their practical implementation. In order to overcome these challenges, one-dimensional yolk-shell nanorods have been successfully constructed using manganese oxide as an example through a facile two-step sol-gel coating method. Dopamine and tetraethoxysilane are used as precursors to obtain uniform polymer coating and silica layer followed by converting into carbon shell and hollow space, respectively. As anode material for lithium batteries, the manganese oxide/carbon yolk-shell nanorod electrode has a reversible capacity of 660 mAh/g for initial cycle at 100 mA/g and exhibits excellent cyclability with a capacity of 634 mAh/g after 900 cycles at a current density of 500 mA/g. An enhanced capacity is observed during the long-term cycling process, which may be attributed to the structural integrity, the stability of solid electrolyte interphase layer, and the electrochemical actuation of the yolk-shell nanorod structure. The results demonstrate that the manganese oxide is well utilized with the one-dimensional yolk-shell structure, which represents an efficient way to realize excellent performance for practical applications. PMID:25490409

Cai, Zhengyang; Xu, Lin; Yan, Mengyu; Han, Chunhua; He, Liang; Hercule, Kalele Mulonda; Niu, Chaojiang; Yuan, Zefan; Xu, Wangwang; Qu, Longbing; Zhao, Kangning; Mai, Liqiang

2015-01-14

155

Phenolic mediators enhance the manganese peroxidase catalyzed oxidation of recalcitrant lignin model compounds and synthetic lignin.  

PubMed

Fungal oxidative enzymes, such as peroxidases and laccases, are the key catalysts in lignin biodegradation in vivo, and consequently provide an important source for industrial ligninolytic biocatalysts. Recently, it has been shown that some syringyl-type phenolics have potential as industrial co-oxidants or mediators, in laccase-catalyzed modification of lignocellulosic material. We have now studied the effect of such mediators with ligninolytic peroxidases on oxidation of the most recalcitrant lignin model compounds. We found that they are able to enhance the manganese peroxidase (MnP) catalyzed oxidation reactions of small non-phenolic compounds, veratryl alcohol and veratrylglycerol ?-guaiacyl ether (adlerol), which are not usually oxidized by manganese peroxidases alone. In these experiments we compared two peroxidases from white-rot fungi, MnP from Phlebia sp. Nf b19 and versatile peroxidase (VP) from Bjerkandera adusta under two oxidation conditions: (i) the Mn(III) initiated mediated oxidation by syringyl compounds and (ii) the system involving MnP-dependent lipid peroxidation, both with production of (hydrogen) peroxides in situ to maintain the peroxidase catalytic cycle. It was found that both peroxidases produced ?-carbonyl oxidation product of veratryl alcohol in clearly higher yields in reactions mediated by phenoxy radicals than in lipid-peroxyl radical system. The oxidation of adlerol, on the other hand, was more efficient in lipid-peroxidation-system. VP was more efficient than MnP in the oxidation of veratryl alcohol and showed its lignin peroxidase type activity in the reaction conditions indicated by some cleavage of C?-C?-bond of adlerol. Finally, the mediator assisted oxidation conditions were applied in the oxidation of synthetic lignin (DHP) and the structural analysis of the oxidized polymers showed clear modifications in the polymer outcome, e.g. the oxidation resulted in reduced amount of aliphatic hydroxyls indicated by (31)P NMR. PMID:25108071

Nousiainen, Paula; Kontro, Jussi; Manner, Helmiina; Hatakka, Annele; Sipilä, Jussi

2014-11-01

156

Regulating proton-coupled electron transfer for efficient water splitting by manganese oxides at neutral pH  

PubMed Central

Manganese oxides have been extensively investigated as model systems for the oxygen-evolving complex of photosystem II. However, most bioinspired catalysts are inefficient at neutral pH and functional similarity to the oxygen-evolving complex has been rarely achieved with manganese. Here we report the regulation of proton-coupled electron transfer involved in water oxidation by manganese oxides. Pyridine and its derivatives, which have pKa values intermediate to the water ligand bound to manganese(II) and manganese(III), are used as proton-coupled electron transfer induction reagents. The induction of concerted proton-coupled electron transfer is demonstrated by the detection of deuterium kinetic isotope effects and compliance of the reactions with the libido rule. Although proton-coupled electron transfer regulation is essential for the facial redox change of manganese in photosystem II, most manganese oxides impair these regulatory mechanisms. Thus, the present findings may provide a new design rationale for functional analogues of the oxygen-evolving complex for efficient water splitting at neutral pH. PMID:24977746

Yamaguchi, Akira; Inuzuka, Riko; Takashima, Toshihiro; Hayashi, Toru; Hashimoto, Kazuhito; Nakamura, Ryuhei

2014-01-01

157

Weathering of the Rio Blanco quartz diorite, Luquillo Mountains, Puerto Rico: Coupling oxidation, dissolution, and fracturing  

USGS Publications Warehouse

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 (???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 ??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 A??, 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 ?? 10-14 mol biotite m-2 s-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 ??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 ?? 10-13 mol hornblende m-2 s-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 O2 at the bedrock-saprolite interface. ?? 2008 Elsevier Ltd. All rights reserved.

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

2008-01-01

158

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

159

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

160

Hybrid ternary rice paper-manganese oxide-carbon nanotube nanocomposites for flexible supercapacitors  

NASA Astrophysics Data System (ADS)

Modern portable electronic devices create a strong demand for flexible energy storage devices. Paper based nanocomposites are attractive as sustainable materials for such applications. Here, we directly explored the hydroxyl chemistry of cellulose fibers to synthesize hybrid ternary nanocomposites, comprised of rice paper, single-walled carbon nanotubes (SWCNTs) and manganese oxide nanoparticles. The functional groups on cellulose fibers can react with adsorbed permanganate ions, resulting in uniform deposition of manganese oxide nanoparticles. SWCNTs coated on top of manganese oxide nanoparticles form a highly conductive network connecting individual manganese oxide particles. By using the hybrid ternary composites as electrodes, the assembled two-electrode supercapacitors demonstrated high capacitance (260.2 F g-1), energy (9.0 W h kg-1), power (59.7 kW kg-1), and cycle stability (12% drop after 3000 cycles). In addition, the nanocomposites show good strength and excellent mechanical flexibility, and their capacitance shows negligible changes after bending more than 100 times. These findings suggest that opportunities exist to further explore the rich chemistry of cellulose fibers for innovative energy applications.Modern portable electronic devices create a strong demand for flexible energy storage devices. Paper based nanocomposites are attractive as sustainable materials for such applications. Here, we directly explored the hydroxyl chemistry of cellulose fibers to synthesize hybrid ternary nanocomposites, comprised of rice paper, single-walled carbon nanotubes (SWCNTs) and manganese oxide nanoparticles. The functional groups on cellulose fibers can react with adsorbed permanganate ions, resulting in uniform deposition of manganese oxide nanoparticles. SWCNTs coated on top of manganese oxide nanoparticles form a highly conductive network connecting individual manganese oxide particles. By using the hybrid ternary composites as electrodes, the assembled two-electrode supercapacitors demonstrated high capacitance (260.2 F g-1), energy (9.0 W h kg-1), power (59.7 kW kg-1), and cycle stability (12% drop after 3000 cycles). In addition, the nanocomposites show good strength and excellent mechanical flexibility, and their capacitance shows negligible changes after bending more than 100 times. These findings suggest that opportunities exist to further explore the rich chemistry of cellulose fibers for innovative energy applications. Electronic supplementary information (ESI) available: Chemical structures of functional groups on cellulose fibers, the surface water wettability of rice paper, CV curves of supercapacitors at different scan rates, galvanostatic charge-discharge curves of supercapacitors at different current densities, TGA profiles of the SWCNT-MnO2-paper composites synthesized at different temperatures, TEM images of MnO2 particles deposited on rice paper at different temperatures, photographs of supercapacitors under different bending test conditions, and a video of bending and folding the SWCNT-MnO2-paper composites. See DOI: 10.1039/c3nr03010e

Jiang, Wenchao; Zhang, Kaixi; Wei, Li; Yu, Dingshan; Wei, Jun; Chen, Yuan

2013-10-01

161

Synthesis of carbon microspheres loaded with manganese oxide as air cathode in alkaline media  

NASA Astrophysics Data System (ADS)

Carbon microspheres with large surface have been synthesized from sucrose in H2SO4 solution by reflux-calcinations method. The catalyst of the manganese oxide loaded on carbon microspheres surface demonstrates significant catalytic activity for the oxygen reduction reaction in alkaline media and the mechanism of oxygen reduction is a 2e pathway. It shows an enhanced efficiency for electrochemical properties on active surface and apparent exchange current density 0.649 mA cm-2 (comes from the Tafel plots) for oxygen reduction reaction. This enhancement results from the large reaction area of the 7.32 wt.% manganese oxide loaded on carbon microspheres as well as the porous structures between this composite, which can significantly promote the efficient diffusion.

Gao, Hailing; Li, Zhenya; Qin, Xue

2014-02-01

162

Oxidation of antimony (III) by amorphous iron and manganese oxyhydroxides  

Microsoft Academic Search

Amorphous forms of natural and synthetic Fe oxyhydroxides and synthetic Mn oxyhydroxides were used to study the oxidation of antimonite, Sb(III), at different pH values. Sb species were measured by differential pulse adsorptive stripping voltametry (DPACSV). The oxidation of Sb(III) to Sb(V) was always rapid and completed after a few days following pseudo-first order rate laws. A slightly slower oxidation

Nelson Belzile; Yu-Wei Chen; Zijian Wang

2001-01-01

163

Structural and Chemical Effects of Lithium Extraction in Spinel Manganese Oxides  

Microsoft Academic Search

XAFS of the manganese K-edge in Linz04 has allowed the chemical and structural effects of lithium exh-action and reinsertion to be characterised and attributed to oxidation-reduction processes. Structural information in the experimental data at low k, as well as that relating to scatterers beyond the first two coordination shells, can be accurately analysed using ab inirio curved-wave multiple scattering simulations.

B. Arnmundsen; D. J. Jones; J. Rozikre

164

Controlled synthesis and characterization of layered manganese oxide nanostructures with different morphologies  

Microsoft Academic Search

Layered manganese oxide nanostructures with different morphologies, such as nanowire bundles, cotton agglomerates, and platelikes\\u000a were successfully fabricated by a simple and template-free hydrothermal method based on a reaction of KMnO4 and KOH solutions with different concentrations. The obtained nanowire bundles were assembled by nanowires with diameters\\u000a of 10 to 200 nm and lengths up to 5–10 ?m. The cotton agglomerates were

Naicai Xu; Zong-Huai Liu; Xiangrong Ma; Shanfeng Qiao; Jiaqi Yuan

2009-01-01

165

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

166

Calmagite dye oxidation using in situ generated hydrogen peroxide catalysed by manganese(II) ions.  

PubMed

Hydrogen peroxide (H(2)O(2)) generated from the manganese(II) catalysed reduction of dioxygen has been shown to efficiently oxidize Calmagite (3-hydroxy-4-(2-hydroxy-5-methylphenylazo)naphthalene-1-sulfonic acid) in aqueous solution at pH 8.0 and 20 +/- 1 degrees C with de-protonated Tiron (1,2-dihydroxybenzene-3,5-disulfonate, disodium salt) acting as an essential co-ligand. PMID:17985017

Sheriff, Tippu S; Cope, Steven; Ekwegh, Mmaezi

2007-11-28

167

Binder-free manganese oxide/carbon nanomaterials thin film electrode for supercapacitors.  

PubMed

A ternary thin film electrode was created by coating manganese oxide onto a network composed of single-walled carbon nanotubes and single-walled carbon nanohorns. The electrode exhibited a porous structure, which is a promising architecture for supercapacitors applications. The maximum specific capacitances of 357 F/g for total electrode at 1 A/g were achieved in 0.1 M Na(2)SO(4) aqueous solution. PMID:21988200

Wang, Ning; Wu, Chuxin; Li, Jiaxin; Dong, Guofa; Guan, Lunhui

2011-11-01

168

Oxidation of titanium, manganese, iron, and niobium silicides: Marker experiments  

NASA Astrophysics Data System (ADS)

The mechanism of atomic transport inside the silicide during thermal oxidation of silicide layers on Si substrates has been analyzed by means of inert gas markers implanted in TiSi2, Mn11Si19, FeSi2, and NbSi2. Oxidation was carried out in dry oxygen. The marker displacement reveals that the growth of metal-free SiO2 over the first three of these compounds occurs via the reverse motion of metal atoms, from the silicide/oxide to the silicon/silicide interface, rather than through the direct diffusion of Si atoms from the substrate to the oxide. Moreover, analysis of the marker position indicates that the total amount of Si between the marker and the free surface decreases during oxidation, as had been previously observed in the oxidation of NiSi2, CoSi2, and CrSi2. Although this could occur via the formation and evaporation of SiO, it is believed that the loss of Si is due to the motion of Si atoms, also in the ``reverse'' direction as for the metal atoms, across the silicide layer. The experiment conducted with NbSi2 shows that this silicide oxidizes via the direct motion of Si from the substrate to the oxide as anticipated. With TiSi2 the initial state of oxidation occurs as described, but the experimental observations imply that thick oxide layers grow via the direct motion of Si from the substrate to the oxide.

Stolt, L.; Thomas, O.; d'Heurle, F. M.

1990-11-01

169

Chemical fluxes and origin of a manganese carbonate-oxide-silicate deposit in bedded chert  

USGS Publications Warehouse

Lens-like rhodochrosite-rich bodies within interbedded chert and shale are associated with basalt and/or graywacke in ophiolitic and orogenic zones. The Buckeye manganese mine in the Franciscan Complex of the California Coast Ranges is associated with metagraywacke. Despite blueschist-facies metamorphism, this deposit preserves the compositions and some textural features of its sedimentary protoliths. For this reason, it is a suitable deposit with which to compare more intensely altered deposits, or deposits originating in different paleoenvironments. Six Mn-rich and three Mn-poor minerals form monomineralic layers and mixtures: rhodochrosite, gageite, Mn-oxides (hausmannite, braunite), divalent Mn-silicates (caryopilite, taneyamalite), chlorite, quartz (metachert) and aegirine-augite. The Mn-rich protoliths have high Mn/Fe combined with relatively low concentrations of Ca, Al, Ti, Co, Ni, Cu, Th and REE. REE patterns of various protoliths are distinct. Rhodochrosite and gageite layers are depleted (seawater ?? 5 ?? 104) and flat, whereas patterns of metachert and the Mn-silicate-rich layers mimic the patterns of metashale and metagraywacke (seawater ?? 106). Hausmannite layers have flat patterns (seawater ?? 7 ?? 104) whereas braunite-rich layers are more enriched (seawater ?? 2 ?? 105) and show a distinct positive Ce anomaly. Factor analysis reveals components and fluxes attributed to sub-seafloor fluids (Ni, As, Zn, Sb, W, Mn), seawater (Mg, Au, V, Mo), detritus and veins (Ca, Ba, Sr). Silica is negatively correlated with the sub-seafloor factor. The observed variances indicate that water from the sediment column mixed with seawater, that deposition occurred near the sediment-seawater interface before mixtures of subsurface fluid and seawater homogenized, and that the system was not entirely closed during metamorphism. The variations in REE enrichment can be related to kinetics of deposition: rhodochrosite and gageite were precipitated most rapidly, and therefore were the protoliths that most effectively diluted the REE-rich background resulting from fine clastic material (derived from distal turbidites). The variation of the Ce anomaly and U/Th among diverse lithologies and the differences in Mn oxidation states are consistent with progressive dilution of reduced subsurface fluids with oxidized seawater. By this scheme, rhodochrosite, gageite and hausmannite were deposited from the most reduced fluids, braunite from intermediate mixtures, and Mn-silicates from the sub-seafloor fluids most diluted with fresh seawater. Comparison of the Buckeye with other lens-like and sheet-like deposits having high Mn/Fe and containing Mn3+ and/or Mn2+ suggests that each had three essential fluxes: a sub-seafloor source of Mn, a local source of very soluble silica and a source of relatively fresh, oxygenated water. Additional fluxes, such as clastics, appear to be more characteristic of the paleoenvironment than the three essential fluxes. ?? 1992.

Huebner, J.S.; Flohr, M.J.K.; Grossman, J.N.

1992-01-01

170

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

171

Adsorption of Ribose Nucleotides on Manganese Oxides with Varied Mn/O Ratio: Implications for Chemical Evolution  

NASA Astrophysics Data System (ADS)

Manganese exists in different oxidation states under different environmental conditions with respect to redox potential. Various forms of manganese oxides, namely, Manganosite (MnO), Bixbyite (Mn2O3), Hausmannite (Mn3O4) and Pyrolusite (MnO2) 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.

Bhushan, Brij; Shanker, Uma; Kamaluddin

2011-10-01

172

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

173

Manganese (Mn) oxidation increases intracellular Mn in Pseudomonas putida GB-1.  

PubMed

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

174

Manganese oxide phases and morphologies: A study on calcination temperature and atmospheric dependence.  

PubMed

Manganese oxides are one of the most important groups of materials in energy storage science. In order to fully leverage their application potential, precise control of their properties such as particle size, surface area and Mn (x) (+) oxidation state is required. Here, Mn3O4 and Mn5O8 nanoparticles as well as mesoporous ?-Mn2O3 particles were synthesized by calcination of Mn(II) glycolate nanoparticles obtained through an economical route based on a polyol synthesis. The preparation of the different manganese oxides via one route facilitates assigning actual structure-property relationships. The oxidation process related to the different MnO x species was observed by in situ X-ray diffraction (XRD) measurements showing time- and temperature-dependent phase transformations occurring during oxidation of the Mn(II) glycolate precursor to ?-Mn2O3 via Mn3O4 and Mn5O8 in O2 atmosphere. Detailed structural and morphological investigations using transmission electron microscopy (TEM) and powder XRD revealed the dependence of the lattice constants and particle sizes of the MnO x species on the calcination temperature and the presence of an oxidizing or neutral atmosphere. Furthermore, to demonstrate the application potential of the synthesized MnO x species, we studied their catalytic activity for the oxygen reduction reaction in aprotic media. Linear sweep voltammetry revealed the best performance for the mesoporous ?-Mn2O3 species. PMID:25671151

Augustin, Matthias; Fenske, Daniela; Bardenhagen, Ingo; Westphal, Anne; Knipper, Martin; Plaggenborg, Thorsten; Kolny-Olesiak, Joanna; Parisi, Jürgen

2015-01-01

175

Manganese oxide phases and morphologies: A study on calcination temperature and atmospheric dependence  

PubMed Central

Summary Manganese oxides are one of the most important groups of materials in energy storage science. In order to fully leverage their application potential, precise control of their properties such as particle size, surface area and Mnx + oxidation state is required. Here, Mn3O4 and Mn5O8 nanoparticles as well as mesoporous ?-Mn2O3 particles were synthesized by calcination of Mn(II) glycolate nanoparticles obtained through an economical route based on a polyol synthesis. The preparation of the different manganese oxides via one route facilitates assigning actual structure–property relationships. The oxidation process related to the different MnOx species was observed by in situ X-ray diffraction (XRD) measurements showing time- and temperature-dependent phase transformations occurring during oxidation of the Mn(II) glycolate precursor to ?-Mn2O3 via Mn3O4 and Mn5O8 in O2 atmosphere. Detailed structural and morphological investigations using transmission electron microscopy (TEM) and powder XRD revealed the dependence of the lattice constants and particle sizes of the MnOx species on the calcination temperature and the presence of an oxidizing or neutral atmosphere. Furthermore, to demonstrate the application potential of the synthesized MnOx species, we studied their catalytic activity for the oxygen reduction reaction in aprotic media. Linear sweep voltammetry revealed the best performance for the mesoporous ?-Mn2O3 species.

Fenske, Daniela; Bardenhagen, Ingo; Westphal, Anne; Knipper, Martin; Plaggenborg, Thorsten; Kolny-Olesiak, Joanna; Parisi, Jürgen

2015-01-01

176

Kinetics and spectroscopic observations of atrazine dealkylation on manganese oxides  

SciTech Connect

Abiotic transformations of organic pollutants are often neglected in remediation scenarios but nonetheless can contribute significantly to detoxification. Mn oxide minerals are capable of degrading organic pollutants adsorbed to their surfaces by both redox and proton-promoted mechanisms. Concurrently with calorimetric, gas-pressure, chromatographic, and ESR methods, we used ICP, DRS, DRIFT, and FTIR spectroscopies to investigate atrazine degradation on three Mn oxides. We found that N-dealkylation can occur abiotically, leading to the formation of deethylatrazine and deisopropylatrazine. The Mn extractability after degradation of atrazine was highly dependent on the Mn oxide. Extractable Mn increased with time for cryptomelane, was constant for pyrolusite, and remained very low for birnessite. The extractable Mn is Mn(II). UV signatures of atrazine by-products were different from one another and were used to trace degradation products at the Mn oxide surface. Mechanistic interpretation of the in situ reaction kinetics and thermodynamics will be discussed.

Malengreau, N.; Sposito, G. [Lawrence Berkeley National Lab., CA (United States); Cheney, M.A. [Rutgers Univ., New Brunswick, NJ (United States); Crowley, D.E. [Univ. of California, Riverside, CA (United States)

1997-12-31

177

Oxidation of bisphenol F (BPF) by manganese dioxide  

Microsoft Academic Search

Bisphenol F (BPF), an environmental estrogen, is used as a monomer in plastic industry and its environmental fate and decontamination are emerging concern. This study focused on the kinetics, influencing factors and pathways of its oxidation by MnO2. At pH 5.5, about 90% of BPF was oxidized in 20min in a solution containing 100?M MnO2 and 4.4?M BPF. The reaction

Zhijiang Lu; Kunde Lin; Jay Gan

2011-01-01

178

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

179

Characterization of Manganese Oxide Precipitates from Appalachian Coal Mine Mine Drainage Treatment Systems  

SciTech Connect

The removal of Mn(II) from coal mine drainage (CMD) by chemical addition/active treatment can significantly increase treatment costs. Passive treatment for Mn removal involves promotion of biological oxidative precipitation of manganese oxides (MnO{sub x}). Manganese(II) removal was studied in three passive treatment systems in western Pennsylvania that differed based on their influent Mn(II) concentrations (20-150 mg/L), system construction ({+-}inoculation with patented Mn(II)-oxidizing bacteria), and bed materials (limestone vs. sandstone). Manganese(II) removal occurred at pH values as low as 5.0 and temperatures as low as 2 C, but was enhanced at circumneutral pH and warmer temperatures. Trace metals such as Zn, Ni and Co were removed effectively, in most cases preferentially, into the MnO{sub x} precipitates. Based on synchrotron radiation X-ray diffraction and Mn K-edge extended X-ray absorption fine structure spectroscopy, the predominant Mn oxides at all sites were poorly crystalline hexagonal birnessite, triclinic birnessite and todorokite. The surface morphology of the MnOx precipitates from all sites was coarse and 'sponge-like' composed of nm-sized lathes and thin sheets. Based on scanning electron microscopy (SEM), MnO{sub x} precipitates were found in close proximity to both prokaryotic and eukaryotic organisms. The greatest removal efficiency of Mn(II) occurred at the one site with a higher pH in the bed and a higher influent total organic C (TOC) concentration (provided by an upstream wetland). Biological oxidation of Mn(II) driven by heterotrophic activity was most likely the predominant Mn removal mechanism in these systems. Influent water chemistry and Mn(II) oxidation kinetics affected the relative distribution of MnOx mineral assemblages in CMD treatment systems.

Tan, H.; Zhang, G; Heaney, P; Webb, S; Burgos, W

2010-01-01

180

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

181

c-Type Cytochromes and Manganese Oxidation in Pseudomonas putida MnB1  

PubMed Central

Pseudomonas putida MnB1 is an isolate from an Mn oxide-encrusted pipeline that can oxidize Mn(II) to Mn oxides. We used transposon mutagenesis to construct mutants of strain MnB1 that are unable to oxidize manganese, and we characterized some of these mutants. The mutants were divided into three groups: mutants defective in the biogenesis of c-type cytochromes, mutants defective in genes that encode key enzymes of the tricarboxylic acid cycle, and mutants defective in the biosynthesis of tryptophan. The mutants in the first two groups were cytochrome c oxidase negative and did not contain c-type cytochromes. Mn(II) oxidation capability could be recovered in a c-type cytochrome biogenesis-defective mutant by complementation of the mutation. PMID:9758766

Caspi, Ron; Tebo, Bradley M.; Haygood, M. G.

1998-01-01

182

Ion beam studies on reactive DC sputtered manganese doped indium tin oxide thin films  

NASA Astrophysics Data System (ADS)

Indium based transparent conducting oxides doped with magnetic elements have been studied intensively in recent years with a view to develop novel ferromagnetic semiconductors for spin-based electronics. In the present work, we have grown manganese doped indium tin oxide (Mn:ITO) thin films, onto Si and Si/SiO 2 substrates by DC reactive sputtering of a composite target containing indium-tin alloy and manganese, in a gas mixture of oxygen and argon. Glancing angle X-ray diffraction (GXRD) studies reveal the polycrystalline nature of the films. Magnetic measurements carried out using vibrating sample magnetometer (VSM) suggest that the films are ferromagnetic at room temperature, with a saturation magnetization of ˜22.8 emu/cm 3. The atomic percentages of In, Sn, Mn and O, as estimated using Rutherford backscattering spectrometry (RBS) are 37.0, 4.0, 1.6 and 57.4, respectively. RBS measurements reveal that the interface of the films with Si substrate has a ˜30 nm thick intermediate layer. This layer consists of oxygen, silicon, indium, tin and manganese, in the ratio 1:0.56:0.21:0.07:0.03, indicative of diffusion of elements across the interface. The films on Si/SiO 2, on the other hand, have a sharp interface.

Sarath Kumar, S. R.; Malar, P.; Osipowicz, Thomas; Banerjee, S. S.; Kasiviswanathan, S.

2008-04-01

183

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

184

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{minus}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. 11 figs.

Doeff, M.M.; Peng, M.Y.; Ma, Y.; Visco, S.J.; DeJonghe, L.C.

1996-09-24

185

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

186

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

187

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

188

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

189

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

E-print Network

Monday, November 5, 2007 - 9:30 AM 91-1 Real-Time Surface-Chemistry of Arsenite Oxidation by Hydrous Manganese Oxide. Matthew Ginder-Vogel and Donald L. Sparks. University of Delaware, 152 Townsend Hall, Dept of Plant and Soil Sciences, Newark, DE 19716 Arsenite (As(III)) oxidation to arsenate (As

Sparks, Donald L.

190

Manganese oxides: parallels between abiotic and biotic structures.  

PubMed

A large number of microorganisms are responsible for the oxidation of Mn(2+)((aq)) to insoluble Mn(3+/4+) oxides (MnO(x)()) in natural aquatic systems. This paper reports the structure of the biogenic MnO(x)(), including a quantitative analysis of cation vacancies, formed by the freshwater bacterium Leptothrix discophora SP6 (SP6-MnO(x)()). The structure and the morphology of SP6-MnO(x)() were characterized by transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), including full multiple-scattering analysis, and powder X-ray diffraction (XRD). The biogenic precipitate consists of nanoparticles that are approximately 10 nm by 100 nm in dimension with a fibrillar morphology that resembles twisted sheets. The results dem-onstrate that this biogenic MnO(x)() is composed of sheets of edge-sharing of Mn(4+)O(6) octahedra that form layers. The detailed analysis of the EXAFS spectra indicate that 12 +/- 4% of the Mn(4+) layer cation sites in SP6-MnO(x)() are vacant, whereas the analysis of the XANES suggests that the average oxidation state of Mn is 3.8 +/- 0.3. Therefore, the average chemical formula of SP6-MnO(x)() is M(n)()(+)(y)()Mn(3+)(0.12)[ square(0.12)Mn(4+)(0.88)]O(2).zH(2)O, where M(n)()(+)(y)() represents hydrated interlayer cations, square(0.12) represents Mn(4+) cation vacancies within the layer, and Mn(3+)(0.12) represents hydrated cations that occupy sites above/below these cation vacancies. PMID:16925437

Saratovsky, Ian; Wightman, Peter G; Pastén, Pablo A; Gaillard, Jean-François; Poeppelmeier, Kenneth R

2006-08-30

191

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

192

Nanocrystalline todorokite-like manganese oxide produced by bacterial catalysis.  

PubMed

We describe the characterization of an unknown and difficult to identify but geochemically and environmentally significant MnOx structure produced by a freshwater bacterium, Leptothrix discophora SP-6, using combined transmission electron microscopy (TEM), extended X-ray absorption fine structure (EXAFS), and UV Raman spectroscopy. The large surface-to-volume ratio of the needle-shaped nanocrystalline MnO2 formed around the bacterial cells coupled to the porous, zeolite-like structure has the potential to catalyze reactions and oxidize and adsorb metals. PMID:14624570

Kim, Hack-Sung; Pastén, Pablo A; Gaillard, Jean-François; Stair, Peter C

2003-11-26

193

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

194

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

195

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

196

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

197

Study of quartz crystal microbalance NO2 sensor coated with sputtered indium tin oxide film  

NASA Astrophysics Data System (ADS)

A study of NO2 gas sorption ability of thin indium tin oxide (ITO) deposited on 16 MHz quartz crystal microbalance (QCM) is presented. ITO films are grown by RF sputtering of indium/tin target with weight proportion 95:5 in oxygen environment. The ITO films have been characterized by X-ray photoelectron spectroscopy measurements. The ITO surface composition in atomic % is defined to be: In-40.6%, Sn-4.3% and O-55%. The thickness and refractive index of the films are determined by ellipsometric method. The frequency shift of QCM-ITO is measured at different NO2 concentrations. The QCM-ITO system becomes sensitive at NO2 concentration >= 500 ppm. The sorbed mass for each concentration is calculated according the Sauerbrey equation. The results indicated that the 1.09 ng of the gas is sorbed into 150 nm thick ITO film at 500 ppm NO2 concentration. When the NO2 concentration increases 10 times the calculated loaded mass is 5.46 ng. The sorption process of the gas molecules is defined as reversible. The velocity of sorbtion /desorption processes are studied, too. The QCM coated with thin ITO films can be successfully used as gas sensors for detecting NO2 in the air at room temperature.

Georgieva, V.; Aleksandrova, M.; Stefanov, P.; Grechnikov, A.; Gadjanova, V.; Dilova, T.; Angelov, Ts

2014-12-01

198

Pathogenic prion protein is degraded by a manganese oxide mineral found in soils  

USGS Publications Warehouse

Prions, the aetiological agents of transmissible spongiform encephalopathies, exhibit extreme resistance to degradation. Soil can retain prion infectivity in the environment for years. Reactive soil components may, however, contribute to the inactivation of prions in soil. Members of the birnessite family of manganese oxides (MnO2) rank among the strongest natural oxidants in soils. Here, we report the abiotic degradation of pathogenic prion protein (PrPTSE) by a synthetic analogue of naturally occurring birnessite minerals. Aqueous MnO2 suspensions degraded the PrPTSE as evidenced by decreased immunoreactivity and diminished ability to seed protein misfolding cyclic amplification reactions. Birnessite-mediated PrPTSE degradation increased as a solution's pH decreased, consistent with the pH-dependence of the redox potential of MnO2. Exposure to 5.6 mg MnO2 ml-1 (PrPTSE:MnO2=1 : 110) decreased PrPTSE levels by ???4 orders of magnitude. Manganese oxides may contribute to prion degradation in soil environments rich in these minerals. ?? 2009 SGM.

Russo, F.; Johnson, C.J.; McKenzie, D.; Aiken, J.M.; Pedersen, J.A.

2009-01-01

199

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

200

Bright blue photoluminescence from a mixed tin and manganese oxide xerogel prepared via sol—hydrothermal—gel process  

NASA Astrophysics Data System (ADS)

A new blue photoluminescent material, a mixed tin and manganese oxide xerogel, is prepared via sol—hydrothermal—gel process assisted by citric acid. The composition xerogel exhibits strong blue emission at room temperature, with an emission maximum at 434 nm under short (234 nm) or long-wavelength (343 nm) ultraviolet excitation. The photoluminescent excitation spectrum of the mixed tin and manganese oxide xerogel, monitored at an intensity maximum wavelength of 434 nm of the emission, consists of two excitation peaks at 234 nm and 343 nm. With heat treatment temperature increasing from 110 °C to 200 °C, the blue emission intensity increases remarkably, whereas it is almost completely quenched after being treated at 300 °C. The carbon impurities in the mixed tin and manganese oxide xerogel, confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, should be responsible for the bright blue photoluminescence.

Xiang, Xia; Cheng, Xiao-Feng; He, Shao-Bo; Yuan, Xiao-Dong; Zheng, Wan-Guo; Li, Zhi-Jie; Liu, Chun-Ming; Zhou, Wei-Lie; Zu, Xiao-Tao

2011-12-01

201

Trace metal-rich Quaternary hydrothermal manganese oxide and barite deposit, Milos Island, Greece  

USGS Publications Warehouse

The Cape Vani Mn oxide and barite deposit on Milos Island offers an excellent opportunity to study the three-dimensional characteristics of a shallow-water hydrothermal system. Milos Island is part of the active Aegean volcanic arc. A 1 km long basin located between two dacitic domes in northwest Milos is filled with a 35-50 m thick section of Quaternary volcaniclastic and pyroclastic rocks capped by reef limestone that were hydrothermally mineralized by Mn oxides and barite. Manganese occurs as thin layers, as cement of sandstone and as metasomatic replacement of the limestone, including abundant fossil shells. Manganese minerals include chiefly ?-MnO2, pyrolusite and ramsdellite. The MnO contents for single beds range up to 60%. The Mn oxide deposits are rich in Pb (to 3.4%), BaO (to 3.1%), Zn (to 0.8%), As (to 0.3%), Sb (to 0.2%) and Ag (to 10 ppm). Strontium isotopic compositions of the Mn oxide deposits and sulphur isotopic compositions of the associated barite show that the mineralizing fluids were predominantly sea water. The Mn oxide deposit formed in close geographical proximity to sulphide-sulphate-Au-Ag deposits and the two deposit types probably formed from the same hydrothermal system. Precipitation of Mn oxide took place at shallow burial depths and was promoted by the mixing of modified sea water (hydrothermal fluid) from which the sulphides precipitated at depth and sea water that penetrated along faults and fractures in the Cape Vani volcaniclastic and tuff deposits. The hydrothermal fluid was formed from predominantly sea water that was enriched in metals leached from the basement and overlying volcanogenic rocks. The hydrothermal fluids were driven by convection sustained by heat from cooling magma chambers. Barite was deposited throughout the time of Mn oxide mineralization, which occurred in at least two episodes. Manganese mineralization occurred by both focused and diffuse flow, the fluids mineralizing the beds of greatest porosity and filling dilatational fractures along with barite.

Hein, J.R.; Stamatakis, G.; Dowling, J.S.

2000-01-01

202

Effect of bacterial adsorption on low frequency electrical properties of clean quartz sands and iron-oxide coated sands  

NASA Astrophysics Data System (ADS)

Low frequency electrical measurements (0.1-1000 Hz) were conducted to investigate the adsorption effect of Pseudomonas aeruginosa cells onto clean quartz sands and iron-oxide coated sands. The clean quartz sands showed a gradual increase in the microbial adsorption to mineral grains, concurrent with an increase of 13% in the imaginary conductivity component (?''). However, iron-oxide coated sands (20-100% by weight) showed a rapid increase in microbial adsorption with ?'' reaching a maximum of 37 % for the 80-100% iron coated sands. No significant changes were observed in the real conductivity component (?') due to microbial adsorption. A power law dependency was observed between the adsorbed cells and ?''. We suggest that the polarization results from the increase in the surface roughness and surface area of the grain due to bacteria sorption. These results suggest that low frequency electrical measurements can play an important role in assessing microbial transport in subsurface environments.

Abdel Aal, Gamal; Atekwana, Estella; Radzikowski, Sylvia; Rossbach, Silvia

2009-02-01

203

An electrochemical quartz crystal impedance study on cystine precipitation onto an Au electrode surface during cysteine oxidation in aqueous solution  

Microsoft Academic Search

Electrochemical quartz crystal impedance studies on l-cysteine oxidation in aqueous solutions were conducted. The precipitation of electrogenerated species on the Au electrode surface was found in acetic and phosphate buffers. Changes in the equivalent circuit parameters, resonant frequencies and half peak width of the conductance spectra (?fG1\\/2) obtained simultaneously during electrochemical experiments were discussed. Significant changes in the motional resistance

Qingji Xie; Youyu Zhang; Yu Yuan; Yanghui Guo; Xiangjun Wang; Shouzhuo Yao

2000-01-01

204

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

SciTech Connect

Highlights: • Manganese oxides were synthesized using spent batteries as raw materials. • Spent alkaline and zinc–carbon size AA batteries were used. • A biohydrometallurgical process was employed to bio-lixiviate batteries. • Manganese oxides were active in the oxidation of VOCs (ethanol and heptane). - Abstract: 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 KMnO{sub 4} solution (CMO). The non-leached solid residue was also studied (RMO). The solids were compared with a MnO{sub x} synthesized in our laboratory. The characterization by XRD, FTIR and XPS reveal the presence of Mn{sub 2}O{sub 3} in the EMO and the CMO samples, together with some Mn{sup 4+} cations. In the solid not extracted by acidic leaching (RMO) the main phase detected was Mn{sub 3}O{sub 4}. 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 CO{sub 2}. 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.

Gallegos, María V., E-mail: plapimu@yahoo.com.ar [Pla.Pi.Mu-Planta Piloto Multipropósito, (CICPBA-UNLP) Cno. Centenario y 505, M.B. Gonnet, Buenos Aires (Argentina); Falco, Lorena R., E-mail: mlfalco@quimica.unlp.edu.ar [Pla.Pi.Mu-Planta Piloto Multipropósito, (CICPBA-UNLP) Cno. Centenario y 505, M.B. Gonnet, Buenos Aires (Argentina); Peluso, Miguel A., E-mail: apelu@quimica.unlp.edu.ar [Centro de Investigación y Desarrollo en Ciencias Aplicadas, “Dr. J. Ronco” CINDECA (CONICET CCT La Plata), 47 N°257, La Plata, Buenos Aires (Argentina); Sambeth, Jorge E., E-mail: sambeth@quimica.unlp.edu.ar [Centro de Investigación y Desarrollo en Ciencias Aplicadas, “Dr. J. Ronco” CINDECA (CONICET CCT La Plata), 47 N°257, La Plata, Buenos Aires (Argentina); Thomas, Horacio J. [Pla.Pi.Mu-Planta Piloto Multipropósito, (CICPBA-UNLP) Cno. Centenario y 505, M.B. Gonnet, Buenos Aires (Argentina)

2013-06-15

205

Competing magnetic phases in mixed-valent manganese oxide perovskites  

NASA Astrophysics Data System (ADS)

Measurement of specific heat Cp(T) below 300K of melt-grown samples of La1-xCaxMnO3 (0?x?0.3) and R0.7A0.3MnO3 (R=rare-earth,A=alkaline-earth) with room-temperature tolerance factor 0.950?t?0.996 have been supplemented by transport and magnetic measurements. Comparison of the phase diagram of La1-xCaxMnO3 with that of La1-xSrxMnO3 and the evolution with t of the R0.7A0.3MnO3 family illustrate the sensitivity to t of the crossover from localized to itinerant behavior of the ? -bonding electrons and support the model of two magnetic phases in the crossover compositional range that has been used to account for the colossal magnetoresistance (CMR) phenomenon found in these oxides. A vanishing of the specific-heat anomaly at the Curie temperature Tc and the magnetic data at crossover are typical of a spin glass, and a broad hump in Cp(T) below a Th>Tc , where there is no anomaly at the Tc signal ferromagnetic ordering within isolated pockets of a hole-rich, conductive O* minority phase at Th . On cooling through TN of the antiferromagnetic matrix, the spins freeze at a spin-glass temperature Tg in zero magnetic field H if the ferromagnetic phase does not percolate; the ferromagnetic phase grows in an applied H , and a modest H converts the spin glass to a bulk ferromagnet with a Curie temperature Tc?Tg , where the ferromagnetic phase grows to beyond percolation. As x increases in La1-xCaxMnO3 , a ferromagnetic-insulator O? phase having a charge ordering and a different orbital ordering than the parent O' phase percolates below a Tg?Tc , and the minority O' phase remains paramagnetic until it becomes antiferromagnetic below a TM

Liu, G.-L.; Zhou, J.-S.; Goodenough, J. B.

2004-12-01

206

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

207

Stress response to cadmium and manganese in Paracentrotus lividus developing embryos is mediated by nitric oxide.  

PubMed

Increasing concentrations of contaminants, often resulting from anthropogenic activities, have been reported to occur in the marine environment and affect marine organisms. Among these, the metal ions cadmium and manganese have been shown to induce developmental delay and abnormalities, mainly reflecting skeleton elongation perturbation, in the sea urchin Paracentrotus lividus, an established model for toxicological studies. Here, we provide evidence that the physiological messenger nitric oxide (NO), formed by l-arginine oxidation by NO synthase (NOS), mediates the stress response induced by cadmium and manganese in sea urchins. When NO levels were lowered by inhibiting NOS, the proportion of abnormal plutei increased. Quantitative expression of a panel of 19 genes involved in stress response, skeletogenesis, detoxification and multidrug efflux processes was followed at different developmental stages and under different conditions: metals alone, metals in the presence of NOS inhibitor, NO donor and NOS inhibitor alone. These data allowed the identification of different classes of genes whose metal-induced transcriptional expression was directly or indirectly mediated by NO. These results open new perspectives on the role of NO as a sensor of different stress agents in sea urchin developing embryos. PMID:25181703

Migliaccio, Oriana; Castellano, Immacolata; Romano, Giovanna; Palumbo, Anna

2014-11-01

208

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

209

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

210

Electrochemical impedance spectroscopy studies of lithium diffusion in doped manganese oxide  

SciTech Connect

Cathode performance is critical to lithium ion rechargeable battery performance; effects of doping lithium manganese oxide cathode materials on cathode performance are being investigated. In this paper, Li diffusion in Al-doped LiMn{sub 2}O{sub 4} was studied and found to be controlled by the quantity of Al dopant. Electrochemical cycling was conducted at 0.5mA/cm{sub 2}; electrochemical impedance spectra were taken at open circuit potential, with impedance being measured at 65 kHz-0.01 Hz. As the Al dopant level was increased, the Li diffusion rate decreased; this was attributed to the decreased lattice parameter of the doped oxide.

Johnson, B.J.; Doughty, D.H.; Voigt, J.A.; Boyle, T.J.

1996-06-01

211

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

212

In Situ X-ray Absorption Study of a Layered Manganese-chromium Oxide-based Cathode Material  

SciTech Connect

We have investigated the electronic and atomic structure of a manganese-chromium-based layered oxide material Li[Li{sub 0.2}Cr{sub 0.4}Mn{sub 0.4}]O{sub 2} during electrochemical cycling using in situ X-ray absorption spectroscopy. Our results indicate that charge compensation in the cathode material is achieved by the oxidation/reduction of octahedral Cr(III) ions to tetrahedral Cr(VI) ions during delithiation/lithiation. Manganese ions are present predominantly in the Mn(IV) oxidation state and do not appear to actively participate in the charge compensation process. To accommodate the large changes in coordination symmetry of the Cr(III) and Cr(VI) ions, the chromium ions have to move between the regular octahedral sites in the R{bar 3}m-like lattice to interstitial tetrahedral sites during the charge/discharge process. The highly reversible (at least after the first charge) three-electron oxidation/reductions and the easy mobility of the chromium between octahedral and tetrahedral sites are very unusual and interesting. Equally interesting is the fact that chromium is the active metal undergoing oxidation/reduction rather than manganese. Our results also suggest that in the local scale manganese and chromium ions are not evenly distributed in the as-prepared material, but are present in separate domains of Mn and Cr-rich regions.

Balasubramanian, M.; McBreen, J; Davidson, I; Whitfield, P; Kargina, I

2010-01-01

213

SOLUBLE MANGANESE REMOVAL BY POROUS MEDIA FILTRATION  

Microsoft Academic Search

Filtration experiments were conducted to investigate soluble manganese removal in granular media filtration; sand, manganese oxide coated sand (MOCS), sand + MOCS (1:1) and granular activated carbon (GAC) were used as filter media. Manganese removal, manganese oxide accumulation, turbidity removal, and regeneration of MOCS under various conditions were examined. Soluble manganese removal by the MOCS column was rapid and efficient;

J. Kim; S. Jung

2008-01-01

214

Photoassisted dissolution of a colloidal manganese oxide in the presence of fulvic acid  

SciTech Connect

The dissolution of a synthesized manganese dioxide by a well-characterized fulvic acid has been investigated over a range of reactant concentrations, pH, and illumination conditions, as have components of the overall dissolution process including fulvic acid and manganous ion adsorption to the oxide surface. The dissolution process is satisfactorily described by an initial rapid formation of a surface-located precursor complex followed by a slower intramolecular electron-transfer step resulting in Mn(II) formation at the oxide surface. Illumination by 365-nm light enhances the rate of electron transfer significantly, with an increase in first-order reduction rate constant from 0.31 min/sup -1/ (dark) to 0.55 min/sup -1/ (light at pH 4.00 and from 0.53 min/sup -1/ (dark) to 1.23 min/sup -1/ (light) at pH 7.10. Depending on the affinity of the oxide surface for manganous ion, a portion of the Mn(II) produced at the oxide surface will be rapidly released to solution, resulting in dissolution of the oxide.

Walte, T.D.; Wrigley, I.C.; Szymczak, R.

1988-07-01

215

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 ...

216

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

217

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

218

Understanding the role of manganese dioxide in the oxidation of phenolic compounds by aqueous permanganate.  

PubMed

Recent studies have shown that manganese dioxide (MnO2) can significantly accelerate the oxidation kinetics of phenolic compounds such as triclosan and chlorophenols by potassium permanganate (Mn(VII)) in slightly acidic solutions. However, the role of MnO2 (i.e., as an oxidant vs catalyst) is still unclear. In this work, it was demonstrated that Mn(VII) oxidized triclosan (i.e., trichloro-2-phenoxyphenol) and its analogue 2-phenoxyphenol, mainly generating ether bond cleavage products (i.e., 2,4-dichlorophenol and phenol, respectively), while MnO2 reacted with them producing appreciable dimers as well as hydroxylated and quinone-like products. Using these two phenoxyphenols as mechanistic probes, it was interestingly found that MnO2 formed in situ or prepared ex situ greatly accelerated the kinetics but negligibly affected the pathways of their oxidation by Mn(VII) at acidic pH 5. The yields (R) of indicative products 2,4-dichlorophenol and phenol from their respective probes (i.e., molar ratios of product formed to probe lost) under various experimental conditions were quantified. Comparable R values were obtained during the treatment by Mn(VII) in the absence vs presence of MnO2. Meanwhile, it was confirmed that MnO2 could accelerate the kinetics of Mn(VII) oxidation of refractory nitrophenols (i.e., 2-nitrophenol and 4-nitrophenol), which otherwise showed negligible reactivity toward Mn(VII) and MnO2 individually, and the effect of MnO2 was strongly dependent upon its concentration as well as solution pH. These results clearly rule out the role of MnO2 as a mild co-oxidant and suggest a potential catalytic effect on Mn(VII) oxidation of phenolic compounds regardless of their susceptibility to oxidation by MnO2. PMID:25437924

Jiang, Jin; Gao, Yuan; Pang, Su-Yan; Lu, Xue-Ting; Zhou, Yang; Ma, Jun; Wang, Qiang

2015-01-01

219

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

220

Imidazolium or guanidinium/layered manganese (III, IV) oxide hybrid as a promising structural model for the water-oxidizing complex of Photosystem II for artificial photosynthetic systems.  

PubMed

Photosystem II is responsible for the light-driven biological water-splitting system in oxygenic photosynthesis and contains a cluster of one calcium and four manganese ions at its water-oxidizing complex. This cluster may serve as a model for the design of artificial or biomimetic systems capable of splitting water into oxygen and hydrogen. In this study, we consider the ability of manganese oxide monosheets to self-assemble with organic compounds. Layered structures of manganese oxide, including guanidinium and imidazolium groups, were synthesized and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrometry, and atomic absorption spectroscopy. The compounds can be considered as new structural models for the water-oxidizing complex of Photosystem II. The overvoltage of water oxidation for the compounds in these conditions at pH = 6.3 is ~0.6 V. These compounds may represent the first step to synthesize a hybrid of guanidinium or imidazole together with manganese as a biomimetic system for the water-oxidizing complex of Photosystem II. PMID:23543329

Najafpour, Mohammad Mahdi; Tabrizi, Mahmoud Amouzadeh; Haghighi, Behzad; Eaton-Rye, Julian J; Carpentier, Robert; Allakhverdiev, Suleyman I

2013-11-01

221

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

222

Highly Efficient Oxidation of Secondary Alcohols to Ketones Catalyzed by Manganese Complexes of N4 Ligands with H2O2.  

PubMed

The manganese complex Mn(S-PMB)(CF3SO3)2 was proven to be highly efficient in the catalytic oxidation of several benzylic and aliphatic secondary alcohols with H2O2 as the oxidant and acetic acid as the additive. A maximum turnover number of 4700 was achieved in the alcohol oxidation. In addition, the Hammett analysis unveiled the electrophilic nature of this manganese catalyst with N4 ligand. PMID:25513725

Shen, Duyi; Miao, Chengxia; Xu, Daqian; Xia, Chungu; Sun, Wei

2015-01-01

223

THEORETICAL TECHNIQUE FOR DETERMINING THE CUMULATIVE IMPACT OF IRON AND MANGANESE OXIDATION IN STREAMS RECEIVING COAL-MINE DISCHARGE.  

USGS Publications Warehouse

Two U. S. Geological Survey computer programs are modified and linked to predict the cumulative impact of iron and manganese oxidation in coal-mine discharge on the dissolved-chemical quality of a receiving stream. The coupled programs calculate the changes in dissolved-iron, dissolved-manganese, and dissolved-oxygen concentrations, and the pH of surface water downstream from the discharge. The cumulative impact of representative discharges from several coal mines on stream quality in a small watershed in southwestern Indiana was simulated to determine the effectiveness and sensitivity of the coupled programs.

Bobay, Keith E.; Banaszak, Konrad J.

1985-01-01

224

Mesoporous iron–manganese oxides for sulphur mustard and soman degradation  

SciTech Connect

Graphical abstract: Display Omitted Highlights: ? New nanodispersive materials based on Fe and Mn oxides for degradations of warfare agents. ? The best activities for the degradation of sulphur mustard (97.9% in 64 min) and soman (97.9% in 64 min). ? One pot synthesis with friendly transformed to industrial conditions. -- Abstract: Substituted iron(III)–manganese(III, IV) oxides, ammonio-jarosite and birnessite, were prepared by a homogeneous hydrolysis of potassium permanganate and iron(III) sulphate with 2-chloroacetamide and urea, respectively. Synthesised oxides were characterised using Brunauer–Emmett–Teller (BET) surface area and Barrett–Joiner–Halenda porosity (BJH), X-ray diffraction (XRD), infrared spectroscopy (IR), Raman spectroscopy and scanning electron microscopy (SEM). The oxides were taken for an experimental evaluation of their reactivity against sulphur mustard (HD) and soman (GD). When ammonio-jarosite formation is suppressed by adding urea to the reaction mixture, the reaction products are mixtures of goethite, schwertmannite and ferrihydrite, and their degradation activity against soman considerably increases. The best activities for the degradation of sulphur mustard (97.9% in 64 min) and soman (97.9% in 64 min) were observed for FeMn{sub 7}5 with 32.6 wt.% Fe (36.8 wt.% Mn) and FeMn{sub 3}7U with 60.8 wt.% Fe (10.1 wt.% Mn) samples, respectively.

Štengl, Václav, E-mail: stengl@iic.cas.cz [Department of Solid State Chemistry, Institute of Inorganic Chemistry AS CR, v.v.i., 250 68 ?ež (Czech Republic) [Department of Solid State Chemistry, Institute of Inorganic Chemistry AS CR, v.v.i., 250 68 ?ež (Czech Republic); J.E. Purkyn? University in Ústí nad Labem, Faculty of Environment, 400 96 Ústí nad Labem (Czech Republic); Grygar, TomᚠMatys [Department of Solid State Chemistry, Institute of Inorganic Chemistry AS CR, v.v.i., 250 68 ?ež (Czech Republic) [Department of Solid State Chemistry, Institute of Inorganic Chemistry AS CR, v.v.i., 250 68 ?ež (Czech Republic); J.E. Purkyn? University in Ústí nad Labem, Faculty of Environment, 400 96 Ústí nad Labem (Czech Republic); Bludská, Jana [Department of Solid State Chemistry, Institute of Inorganic Chemistry AS CR, v.v.i., 250 68 ?ež (Czech Republic)] [Department of Solid State Chemistry, Institute of Inorganic Chemistry AS CR, v.v.i., 250 68 ?ež (Czech Republic); Opluštil, František; N?mec, Tomᚠ[Military Technical Institute of Protection Brno, Vesla?ská 230, 628 00 Brno (Czech Republic)] [Military Technical Institute of Protection Brno, Vesla?ská 230, 628 00 Brno (Czech Republic)

2012-12-15

225

Surface characteristics and in vitro biocompatibility of a manganese-containing titanium oxide surface  

NASA Astrophysics Data System (ADS)

This study investigated the surface characteristics and in vitro biocompatibility of a titanium (Ti) oxide layer incorporating the manganese ions (Mn) obtained by hydrothermal treatment with the expectation of utilizing potent integrin-ligand binding enhancement effect of Mn for future applications as an endosseous implant surface. The surface characteristics were evaluated by scanning electron microscopy, thin-film X-ray diffractometry, X-ray photoelectron spectroscopy, optical profilometry and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The in vitro biocompatibility of the Mn-containing Ti oxide surface was evaluated in comparison with untreated bare Ti using a mouse calvaria-derived osteoblastic cell line (MC3T3-E1). The hydrothermal treatment produced a nanostructured Mn-incorporated Ti oxide layer approximately 0.6 ?m thick. ICP-AES analysis demonstrated that the Mn ions were released from the hydrothermally treated surface into the solution. Mn incorporation notably decreased cellular attachment, spreading, proliferation, alkaline phosphatase activity, and osteoblast phenotype gene expression compared with the bare Ti surface (p < 0.05). The results indicate that the Mn-incorporation into the surface Ti oxide layer has no evident beneficial effects on osteoblastic cell function, but instead, actually impaired cell behavior.

Park, Jin-Woo; Kim, Youn-Jeong; Jang, Je-Hee

2011-11-01

226

Tremendous effect of the morphology of birnessite-type manganese oxide nanostructures on catalytic activity.  

PubMed

The octahedral layered birnessite-type manganese oxide (OL-1) with the morphologies of nanoflowers, nanowires, and nanosheets were prepared and characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric/differential scanning calorimetry (TG/DSC), Brunnauer-Emmett-Teller (BET), inductively coupled plasma (ICP), and X-ray photoelectron spectroscopy (XPS). The OL-1 nanoflowers possess the highest concentration of oxygen vacancies or Mn(3+), followed by the OL-1 nanowires and nanosheets. The result of catalytic tests shows that the OL-1 nanoflowers exhibit a tremendous enhancement in the catalytic activity for benzene oxidation as compared to the OL-1 nanowires and nanosheets. Compared to the OL-1 nanosheets, the OL-1 nanoflowers demonstrate an enormous decrease (?T(50) = 274 °C; ?T(90) > 248 °C) in reaction temperatures T50 and T90 (corresponding to 50 and 90% benzene conversion, respectively) for benzene oxidation. The origin of the tremendous effect of morphology on the catalytic activity for the nanostructured OL-1 catalysts is experimentally and theoretically studied via CO temperature-programmed reduction (CO-TPR) and density functional theory (DFT) calculation. The tremendous catalytic enhancement of the OL-1 nanoflowers compared to the OL-1 nanowires and nanosheets is attributed to their highest surface area as well as their highest lattice oxygen reactivity due to their higher concentration of oxygen vacancies or Mn(3+), thus tremendously improving the catalytic activity for the benzene oxidation. PMID:25140618

Hou, Jingtao; Li, Yuanzhi; Mao, Mingyang; Ren, Lu; Zhao, Xiujian

2014-09-10

227

Degradation of ciprofloxacin by cryptomelane-type manganese(III/IV) oxides.  

PubMed

The objective of this study is to investigate and understand the oxidizing properties of a manganese oxide, specifically synthetic cryptomelane (KMn(8)O(16)) and its derivatives, in aqueous solution. Ciprofloxacin (CIP), a commonly used fluoroquinolone antibiotic, was used as the probe. Synthetic cryptomelane, known as octahedral molecular sieves (OMS-2), was synthesized, and its derivatives were prepared by adding transition metal oxides, V(2)O(5) or MoO(3), as dopants during synthesis. The solids were characterized by x-ray powder diffraction (XRD), SEM-energy-dispersive spectrometry (SEM-EDX), x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectra (FTIR), Raman spectra, and N(2)-Brunauer-Emmett-Teller method. Degradation of CIP by different doped OMS-2 was carried out. Process conditions were optimized using response surface methodology (RSM). XRD patterns indicated the crystal phase of regular and doped OMS-2 as the cryptomelane type. Presence of the dopants in doped cryptomelane was confirmed by SEM-EDX and XPS. FTIR and Raman results suggested that the dopants were substituted into the framework in place of manganese. SEM images, XRD analysis, and surface area analysis of doped OMS-2 indicated decreased particle size, decreased crystallinity, and increased surface area compared to regular OMS-2. Higher oxidizing reactivity of doped OMS-2 was also observed with increased CIP removal rates from aqueous solution. The enhancement of reactivity may be due to the increase of surface areas. Nine percent Mo/OMS-2, the most effective oxidant of all synthesized derivatives, was selected for optimization study. Favorable treatment conditions were obtained using RSM at pH 3 with molar ratio [9 % Mo/OMS-2]/[CIP] ? 50. Under such conditions, more than 90 % CIP can be removed in 30 min. The degradation kinetics was modeled by a modified first order rate with introduction of a retardation factor-? (R (2) > 0.98). Analysis of degradation products indicated that oxidation takes place mainly on the piperazine ring of CIP. PMID:22723249

Xiao, Xiao; Sun, Sheng-Peng; McBride, Murray B; Lemley, Ann T

2013-01-01

228

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

229

Impact of surfactant-induced wettability alterations on DNAPL invasion in quartz and iron oxide-coated sand systems.  

PubMed

Dense non-aqueous phase liquids (DNAPLs) present in the subsurface may contain surface active compounds that impact DNAPL migration and distribution. While a number of studies have revealed the role surface active compounds play in altering the wettability of quartz sand, few have considered the implications for other minerals common to contaminated sites. This study extends understanding of DNAPL/surfactant wettability to iron oxide surfaces. Specifically, quartz and iron oxide-coated sands in a tetrachloroethene (PCE)/water system containing the organic base (an organic molecule that acts as a base) dodecylamine (DDA) were compared at a variety of scales. Wettability of the minerals' surfaces, and the impact of wettability on capillary resistance to DNAPL entry, were assessed as a function of pH through: (i) advancing and receding contact angles, (ii) primary drainage capillary pressure-saturation experiments, and (iii) small, two-dimensional, flow cell experiments. The work revealed that, at neutral pH and under identical boundary capillary pressures, DNAPL invaded quartz sand but not iron oxide-coated sand; however, at low pH, DNAPL invaded both sands equally. These differences were demonstrated to be due to wettability alterations associated with the strength of attractive forces between DDA and the mineral surface, dictated by the isolectric point of the minerals and system pH. Observed differences in DNAPL invasion behavior were consistent with measured intrinsic contact angles and P(c)-S relationships, the latter requiring scaling by the operative contact angle inside the porous medium for a meaningful comparison. This study suggests that the distribution of minerals (and, more specifically, their isoelectric points), as well as the aqueous phase pH at a given site, may have a significant impact on the DNAPL source zone architecture. PMID:20880604

Molnar, Ian L; O'Carroll, Denis M; Gerhard, Jason I

2011-01-25

230

Structure-property relationships in manganese oxide--mesoporous silica nanoparticles used for T1-weighted MRI and simultaneous anti-cancer drug delivery.  

PubMed

The extremely low longitudinal relaxivity (r(1)) of manganese oxide has severely impeded their substitution for cytotoxic gadolinium-based contrast agents for safe clinical magnetic resonance imaging (MRI). Here, we report on a synthetic strategy of chemical oxidation/reduction reaction in-situ in mesopores, followed by hydrogen reduction, for the fabrication of non-toxic manganese oxide/MSNs-based MRI-T(1) contrast agents with highly comparable imaging performance to commercial Gd-based agents. This strategy involves a "soft-templating" process to prepare mesoporous silica nanoparticles, in-situ reduction of MnO(4)(-) by the "soft templates" in mesopores and heat treatment under reducing atmosphere, to disperse manganese oxide nanoparticles within mesopores. This special nanostructure combines the merits of nanopores for maximum manganese paramagnetic center accessibility for water molecules for enhanced MRI performance and encapsulation/sustained release/intracellular delivery of drugs. The synthesized manganese oxide/MSNs were successfully assessed as a high performance contrast agent for MRI-T(1) both in intro and in vivo, and meanwhile, was also demonstrated as an effective anti-cancer drug delivery (doxorubicin) vehicle, therefore, a family of manganese-based theranostics was successfully demonstrated based on the manganese oxide/MSNs composite. PMID:22177841

Chen, Yu; Chen, Hangrong; Zhang, Shengjian; Chen, Feng; Sun, Shikuan; He, Qianjun; Ma, Ming; Wang, Xia; Wu, Huixia; Zhang, Lingxia; Zhang, Linlin; Shi, Jianlin

2012-03-01

231

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

232

In depth analysis of apoptosis induced by silica coated manganese oxide nanoparticles in vitro.  

PubMed

Manganese oxide nanoparticles (MnO NPs) have been regarded as a new class of T1-positive contrast agents. The cytotoxicity of silica coated MnO NPs (MnO@SiO2 NPs) was investigated in human cervical carcinoma cells (HeLa) and mouse fibroblast cells (L929). The changes of cell viability, cell morphology, cellular oxidative stress, mitochondrial membrane potential and cell cycle induced by MnO@SiO2 NPs were evaluated. Compared to HeLa cells, L929 cells showed lower cell viability, more strongly response to oxidative stress and higher percentage in the G2/M phase of cell cycle. The appearance of sub-G1 peak, double staining with Annexin V-FITC/PI and the increase of Caspase-3 activity further confirmed apoptosis should be the major form of cell death. Moreover, the apoptotic pathway was clarified as follows. Firstly, reactive oxygen species (ROS) is generated induced by MnO@SiO2 NPs, then p53 is activated followed by an increase in the bax and a decrease in the bcl-2, ultimately leading to G2/M phase arrest, increasing the activity of caspase-3 and inducing apoptosis. PMID:25464291

Yu, Chao; Zhou, Zhiguo; Wang, Jun; Sun, Jin; Liu, Wei; Sun, Yanan; Kong, Bin; Yang, Hong; Yang, Shiping

2015-02-11

233

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

234

The effect of different metal ions between nanolayers of manganese oxide on water oxidation.  

PubMed

Here, we used a strategy to answer to the question that whether Ca(II) ion is specific for water oxidation or not? In the procedure, first we synthesized layered Mn oxides with K(I) between layers and then replaced K(I) by Ca(II), K(I), Mg(II), La(III) or Ni(II). We proposed that Ca(II), K(I), Mg(II), La(III) and Ni(II), between layers are important to form efficient water-oxidizing catalyst, but not specific in water oxidation. However, Cu(II) ions decrease water-oxidizing activity of layered Mn oxides. The result is important to find critical factors in water oxidation by low-cost and environmentally friendly nanolayered Mn oxides. PMID:25463674

Najafpour, Mohammad Mahdi; Isaloo, Mohsen Abbasi; Ghobadi, Mohadeseh Zarei; Amini, Emad; Haghighi, Behzad

2014-12-01

235

Photochemical Oxidation of a Manganese(III) Complex with Oxygen and Toluene Derivatives to Form a Manganese(V)-Oxo Complex  

PubMed Central

Visible light photoirradiation of an oxygen-saturated benzonitrile solution of a manganese(III) corrolazine complex [(TBP8Cz)MnIII (1): [TBP8Cz = octakis(p-tert-butylphenyl)corrolazinato3?] in the presence of toluene derivatives resulted in formation of the manganese(V)-oxo complex [(TBP8Cz)MnV(O)]. The photochemical oxidation of (TBP8Cz)MnIII with O2 and hexamethylbenzene (HMB) led to the isosbestic conversion of 1 to (TBP8Cz)MnV(O), accompanied by the selective oxidation of HMB to pentamethylbenzyl alcohol (87%). The formation rate of (TBP8Cz)MnV(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)MnIII 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)MnIV(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

2013-01-01

236

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

237

Weathering of the Rio Blanco quartz diorite, Luquillo Mountains, Puerto Rico: Coupling oxidation, dissolution, and fracturing  

Microsoft Academic Search

In the mountainous Rio Icacos watershed in northeastern Puerto Rico, quartz diorite bedrock weathers spheroidally, producing a 0.2–2m thick zone of partially weathered rock layers (?2.5cm thickness each) called rindlets, which form concentric layers around corestones. Spheroidal fracturing has been modeled to occur when a weathering reaction with a positive ?V of reaction builds up elastic strain energy. The rates

Heather L. Buss; Peter B. Sak; Samuel M. Webb; Susan L. Brantley

2008-01-01

238

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

239

Understanding the role of gold nanoparticles in enhancing the catalytic activity of manganese oxides in water oxidation reactions.  

PubMed

The Earth-abundant and inexpensive manganese oxides (MnOx ) have emerged as an intriguing type of catalysts for the water oxidation reaction. However, the overall turnover frequencies of MnOx catalysts are still much lower than that of nanostructured IrO2 and RuO2 catalysts. Herein, we demonstrate that doping MnOx polymorphs with gold nanoparticles (AuNPs) can result in a strong enhancement of catalytic activity for the water oxidation reaction. It is observed that, for the first time, the catalytic activity of MnOx /AuNPs catalysts correlates strongly with the initial valence of the Mn centers. By promoting the formation of Mn(3+) species, a small amount of AuNPs (<5?%) in ?-MnO2 /AuNP catalysts significantly improved the catalytic activity up to 8.2 times in the photochemical and 6 times in the electrochemical system, compared with the activity of pure ?-MnO2 . PMID:25284796

Kuo, Chung-Hao; Li, Weikun; Pahalagedara, Lakshitha; El-Sawy, Abdelhamid M; Kriz, David; Genz, Nina; Guild, Curtis; Ressler, Thorsten; Suib, Steven L; He, Jie

2015-02-16

240

Curcumin protects against cytotoxic and inflammatory effects of quartz particles but causes oxidative DNA damage in a rat lung epithelial cell line  

SciTech Connect

Chronic inhalation of high concentrations of respirable quartz particles has been implicated in various lung diseases including lung fibrosis and cancer. Generation of reactive oxygen species (ROS) and oxidative stress is considered a major mechanism of quartz toxicity. Curcumin, a yellow pigment from Curcuma longa, has been considered as nutraceutical because of its strong anti-inflammatory, antitumour and antioxidant properties. The aim of our present study was to investigate whether curcumin can protect lung epithelial cells from the cytotoxic, genotoxic and inflammatory effects associated with quartz (DQ12) exposure. Electron paramagnetic resonance (EPR) measurements using the spin-trap DMPO demonstrated that curcumin reduces hydrogen peroxide-dependent hydroxyl-radical formation by quartz. Curcumin was also found to reduce quartz-induced cytotoxicity and cyclooxygenase 2 (COX-2) mRNA expression in RLE-6TN rat lung epithelial cells (RLE). Curcumin also inhibited the release of macrophage inflammatory protein-2 (MIP-2) from RLE cells as observed upon treatment with interleukin-1 beta (IL-1{beta}) and tumour necrosis factor-alpha (TNF{alpha}). However, curcumin failed to protect the RLE cells from oxidative DNA damage induced by quartz, as shown by formamidopyrimidine glycosylase (FPG)-modified comet assay and by immunocytochemistry for 8-hydroxydeoxyguanosine. In contrast, curcumin was found to be a strong inducer of oxidative DNA damage itself at non-cytotoxic and anti-inflammatory concentrations. In line with this, curcumin also enhanced the mRNA expression of the oxidative stress response gene heme oxygenase-1 (ho-1). Curcumin also caused oxidative DNA damage in NR8383 rat alveolar macrophages and A549 human lung epithelial cells. Taken together, these observations indicate that one should be cautious in considering the potential use of curcumin in the prevention or treatment of lung diseases associated with quartz exposure.

Li Hui; Berlo, Damien van; Shi Tingming [Institut fuer umweltmedizinische Forschung (IUF) at the Heinrich-Heine-University Duesseldorf gGmbH, Auf'm Hennekamp 50, 40225 Duesseldorf (Germany); Speit, Guenter [Institute of Human Genetics, University of Ulm (Germany); Knaapen, Ad M. [Department of Health Risk Analysis and Toxicology, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), University of Maastricht (Netherlands); Borm, Paul J.A. [Institut fuer umweltmedizinische Forschung (IUF) at the Heinrich-Heine-University Duesseldorf gGmbH, Auf'm Hennekamp 50, 40225 Duesseldorf (Germany); Centre for Expertise in Life Sciences, Zuyd University, Heerlen (Netherlands); Albrecht, Catrin [Institut fuer umweltmedizinische Forschung (IUF) at the Heinrich-Heine-University Duesseldorf gGmbH, Auf'm Hennekamp 50, 40225 Duesseldorf (Germany); Schins, Roel P.F. [Institut fuer umweltmedizinische Forschung (IUF) at the Heinrich-Heine-University Duesseldorf gGmbH, Auf'm Hennekamp 50, 40225 Duesseldorf (Germany)], E-mail: roel.schins@uni-duesseldorf.de

2008-02-15

241

Manganese Oxidation State as a Cause of Irritant Patch Test Reactions  

PubMed Central

Background Manganese chloride (MnCl2) 2.5% is included in the extended metals patch test series to evaluate patients for contact hypersensitivity to this metal salt. Objectives The objective of this study was to prospectively determine the rate of allergic and irritant patch test reactions to MnCl2 (Mn(II)), Mn2O3 (Mn(III)), and KMnO4 (Mn(VII)) in a cohort of patients undergoing patch testing. Methods Fifty-eight patients were patch tested with MnCl2, Mn2O3, and KMnO4, each at 2.5% in petrolatum. Patch readings were taken at 48, and 72 or 96 hours, and scored using standard methods. Cultured monolayers of keratinocytes (KCs) were exposed to MnCl2, Mn2O3, and KMnO4 in aqueous culture medium, and cell survival and cytokine release were studied. Conclusions MnCl2 caused irritant patch test reactions in 41% of the cohort, whereas Mn2O3 and KMnO4 caused a significantly lower rate of irritant reactions (both 3%). No allergic morphologies were observed. Similarly, in cultured KC monolayers, only MnCl2 was cytotoxic to KC and induced tumor necrosis factor ? release. The oxidation state of manganese used for patch testing affects the irritancy of this metal salt, as Mn(II) caused an unacceptably high rate of irritant reactions in a cohort of patients. In vitro studies confirmed these clinical data, as only Mn(II) was cytotoxic to cultured monolayers of KC. PMID:24603521

Shallcross, Laurie; Ritchie, Simon; Harberts, Erin; Tammaro, Antonella; Gaitens, Joanna; Gaspari, Anthony A.

2015-01-01

242

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

243

Growth of manganese oxide nanostructures alters the layout of adhesion on a carbonate substrate.  

PubMed

Nanostructures grown under natural conditions can modify the layout of adhesion on mineral surfaces. Using force-volume microscopy and a silicon-nitride probe, we measure changes in adhesion when a patchy overgrowth of manganese oxide nanostructures forms on the surface of rhodochrosite. For the most part, the observations show that the adhesive force to the nanostructures is dominated by van-der-Waals attraction. Measurements made across an area of the surface provide a frequency distribution of adhesive forces, and the mode of this distribution is 166 pN at pH 5.0, increasing to a maximum of 692 pN at pH 7.1, followed by a decrease to 275 pN at pH 9.7. At a few sampling locations over some nanostructures, electrostatic repulsion overtakes van-der-Waals attraction and thus results in negative adhesive forces (i.e., repulsion). Local roughness causes this effect. In comparison to the oxide nanostructures, the exposed rhodochrosite substrate has negligible adhesive force with the probe over the same pH range, suggesting both weak van-der-Waals attraction and weak electrostatic repulsion over this pH range. The quantitative mapping of adhesive force applied more generally to the study of other nanostructures can lead to an improved mechanistic understanding of how nanostructure growth influences contaminant immobilization and bacterial attachment. PMID:19673293

Na, Chongzheng; Martin, Scot T

2009-07-01

244

Removal of phosphorus by a composite metal oxide adsorbent derived from manganese ore tailings.  

PubMed

The selective adsorption of phosphate (P) from wastewater is a promising method for controlling eutrophication in water bodies. In this study, an adsorbent of composite metal oxides (CMOMO) was synthesized from manganese ore tailings by the process of digestion-oxidation-coprecipitation. CMOMO was characterized using several methods, and its adsorption behaviors for phosphate were investigated. Based on the results from SEM and BET analysis, CMOMO exhibited a rough surface and a large surface area (307.21 m(2)/g). According to the results of EDAX, XRD and XPS, its main constituents were determined to be amorphous FeOOH, MnO(2) and AlOOH. The kinetic data were best fit using the Elovich model due to its complicate composites. The maximal adsorption capacity of P would increase with elevated temperatures. Additionally, it was found that the P removal efficiency decreased with an increase of pH (4-10) or a decrease of ion strength (1-0.01 M). The coexisting anions had little effects on phosphate removal, implying the specific adsorption of P by CMOMO. Furthermore, the desorption and reuse results indicated that this adsorbent could be regenerated using alkali solutions. PMID:22464586

Liu, Ting; Wu, Kun; Zeng, Lihua

2012-05-30

245

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

SciTech Connect

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 LiMn{sub 2}O{sub 4}, {lambda}-MnO{sub 2}, and Li{sub 0.5}Mn{sub 2}O{sub 4} are compared with experimental Raman data measured for thin films of the oxides coated on a platinum electrode. The appearance of a number of new bands in the Raman spectrum of LiMn{sub 2}O{sub 4} following partial extraction of lithium is shown to result from local lowering of the symmetry and Raman activation of modes which are optically inactive or only infrared active in LiMn{sub 2}O{sub 4}. The results support a model for the Li{sub 0.5}Mn{sub 2}O{sub 4} lattice in which the lithium ions are ordered. The deformation vibrations of lattice hydroxyl defects in {lambda}-MnO{sub 2} have also been calculated; comparison of the calculated and experimental vibrational data supports a model in which hydroxyl species are localized at octahedral Mn vacancies.

Ammundsen, B. [Univ. Montpellier 2 (France). Lab. des Agregats Moleculaires et Materiaux Inorganiques] [Univ. Montpellier 2 (France). Lab. des Agregats Moleculaires et Materiaux Inorganiques; [Victoria Univ. of Wellington (New Zealand). School of Chemical and Physical Sciences; Burns, G.R. [Victoria Univ. of Wellington (New Zealand). School of Chemical and Physical Sciences] [Victoria Univ. of Wellington (New Zealand). School of Chemical and Physical Sciences; Islam, M.S. [Univ. of Surrey, Guildford (United Kingdom). Dept. of Chemistry] [Univ. of Surrey, Guildford (United Kingdom). Dept. of Chemistry; Kanoh, Hirofumi [Shikoku National Industrial Research Inst., Takamatsu (Japan)] [Shikoku National Industrial Research Inst., Takamatsu (Japan); Roziere, J. [Univ. Montpellier 2 (France). Lab des Agregats Moleculaires et Materiaux Inorganiques] [Univ. Montpellier 2 (France). Lab des Agregats Moleculaires et Materiaux Inorganiques

1999-06-24

246

Solubilisation effect of spent wash on oxide-ores of manganese and iron.  

PubMed

Samples of iron ore (haematite) and manganese ore (pyrolusite) of known compositions were equilibrated with aliquots of analysed sample of spent wash. The concentrations of iron(II), iron(III), complexed iron, manganese(II) ions and complexed Mn-ions were determined after increasing durations. One litre of the spent wash was found to extract out 141 mg of total iron and 161 mg of total manganese. In case of iron, the predominance was of iron(II) (92%), whereas in case of manganese it was of the complexed form (95%). PMID:24202955

Pervez, S; Pandey, G S

1991-09-01

247

Inhibition of Cell Growth and Sensitization to Oxidative Damage by Overexpression of Manganese Superoxide Dismutase in Rat Glioma Cells1  

Microsoft Academic Search

The effects of overexpression of human manganese superoxide dismutase (MnSOD) on cell proliferation and response to oxidative stress in rat glioma cells were studied. MnSOD-overexpressing cells had a 2- to 14-fold increase in MnSOD activity, but did not have consistent changes in the activities of CuZnSOD, catalase, or glutathione peroxidase. Cells with more than a 5-fold increase in MnSOD activity

Weixiong Zhong; Larry W. Oberley; Terry D. Oberley; Tao Yan; Frederick E. Domann

1996-01-01

248

Structural, optical, photocatalytic and antibacterial activity of zinc oxide and manganese doped zinc oxide nanoparticles  

NASA Astrophysics Data System (ADS)

Polycrystalline ZnO doped with Mn (5 and 10 at%) was prepared by the co-precipitation method. The effect of Mn doping on the photocatalytic, antibacterial activities and the influence of doping concentration on structural, optical properties of nanoparticles were studied. Structural and optical properties of the particles elucidated that the Mn 2+ ions have substituted the Zn 2+ ions without changing the Wurtzite structure of ZnO. The optical spectra showed a blue shift in the absorbance spectrum with increasing dopant concentration. The photocatalytic activities of ZnO powders were evaluated by measuring the degradation of methylene blue (MB) in water under the UV region. It was found that undoped ZnO bleaches MB much faster than manganese doped ZnO upon its exposure to the UV light. The potential toxicity of nanosized ZnO and Mn doped ZnO were investigated using both Gram positive and Gram negative bacteria as test organisms. The results showed that Mn doped ZnO nanoparticles enhanced the antibacterial activity than ZnO nanoparticles.

Rekha, K.; Nirmala, M.; Nair, Manjula G.; Anukaliani, A.

2010-08-01

249

Protective effects of manganese(II) chloride on hyaluronan degradation by oxidative system ascorbate plus cupric chloride.  

PubMed

The degradation of several high-molar-mass hyaluronan samples was investigated in the presence of ascorbic acid itself and further by an oxidative system composed of ascorbic acid plus transition metal ions, i.e. Fe(II) or Cu(II) ions. The latter oxidative system imitates conditions in a joint synovial fluid during early phase of acute joint inflammation and can be used as a model for monitoring oxidative degradation of hyaluronan under pathophysiological conditions. The system Cu(II) plus ascorbate (the Weissberger oxidative system) resulted in a more significant decrease of hyaluronan molar mass compared to the oxidative system Fe(II) plus ascorbate. Addition of manganese(II) chloride was found to decrease the rate of the oxidative damage of hyaluronan initiated by ascorbate itself and by the Weissberger system. PMID:21217868

Valachová, Katarína; Kogan, Grigorij; Gemeiner, Peter; Soltés, Ladislav

2010-03-01

250

Protective effects of manganese(II) chloride on hyaluronan degradation by oxidative system ascorbate plus cupric chloride  

PubMed Central

The degradation of several high-molar-mass hyaluronan samples was investigated in the presence of ascorbic acid itself and further by an oxidative system composed of ascorbic acid plus transition metal ions, i.e. Fe(II) or Cu(II) ions. The latter oxidative system imitates conditions in a joint synovial fluid during early phase of acute joint inflammation and can be used as a model for monitoring oxidative degradation of hyaluronan under pathophysiological conditions. The system Cu(II) plus ascorbate (the Weissberger oxidative system) resulted in a more significant decrease of hyaluronan molar mass compared to the oxidative system Fe(II) plus ascorbate. Addition of manganese(II) chloride was found to decrease the rate of the oxidative damage of hyaluronan initiated by ascorbate itself and by the Weissberger system. PMID:21217868

Valachová, Katarína; Kogan, Grigorij; Gemeiner, Peter; Šoltés, Ladislav

2010-01-01

251

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.

2014-12-01

252

Carbon nanotube-assisted electrodeposition. Part I: Battery performance of manganese oxide films electrodeposited at low current densities  

NASA Astrophysics Data System (ADS)

In electrochemical synthesis of manganese oxide, current density has a substantial influence on redox behavior, but less effect on the film morphology. Here we report that a small amount (even not detectable by electron microscopy) of carbon nanotubes can significantly affect the film growth pathway. Although, the galvanostatic syntheses of manganese oxide were similar in the absence and presence of carbon nanotubes, the morphological structures are totally different. This difference is also valid for electrochemical behavior in favor of the formation of a single redox couple. The influence of carbon nanotubes on potentiodynamic electrodeposition of manganese oxide was also similar, leading to the appearance of a strong redox couple without any noticeable capacitive behavior. It should be emphasized that this influence is only valid for the experimental condition under consideration (i.e., low current densities), and electrodeposition at higher current densities in the presence of carbon nanotubes may strengthen the capacitive behavior in favor of supercapacitors (as discussed in the second part). The interesting point is that this tiny additive can predominantly control the electrochemical properties of the system under consideration: supercapacitor or battery.

Eftekhari, Ali; Molaei, Foroogh

2015-01-01

253

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; Oberdörster, Günter

2006-01-01

254

Removal and Recovery of Toxic Silver Ion Using Deep-Sea Bacterial Generated Biogenic Manganese Oxides  

PubMed Central

Products containing silver ion (Ag+) are widely used, leading to a large amount of Ag+-containing waste. The deep-sea manganese-oxidizing bacterium Marinobacter sp. MnI7-9 efficiently oxidizes Mn2+ to generate biogenic Mn oxide (BMO). The potential of BMO for recovering metal ions by adsorption has been investigated for some ions but not for Ag+. The main aim of this study was to develop effective methods for adsorbing and recovering Ag using BMO produced by Marinobacter sp. MnI7-9. In addition, the adsorption mechanism was determined using X-ray photoelectron spectroscopy analysis, specific surface area analysis, adsorption kinetics and thermodynamics. The results showed that BMO had a higher adsorption capacity for Ag+ compared to the chemical synthesized MnO2 (CMO). The isothermal absorption curves of BMO and CMO both fit the Langmuir model well and the maximum adsorption capacities at 28°C were 8.097 mmol/g and 0.787 mmol/g, for BMO and CMO, respectively. The change in enthalpy (?H?) for BMO was 59.69 kJ/mol indicating that it acts primarily by chemical adsorption. The change in free energy (?G?) for BMO was negative, which suggests that the adsorption occurs spontaneously. Ag+ adsorption by BMO was driven by entropy based on the positive ?S? values. The Ag+ adsorption kinetics by BMO fit the pseudo-second order model and the apparent activation energy of Ea is 21.72 kJ/mol. X-ray photoelectron spectroscopy analysis showed that 15.29% Ag+ adsorbed by BMO was transferred to Ag(0) and meant that redox reaction had happened during the adsorption. Desorption using nitric acid and Na2S completely recovered the Ag. The results show that BMO produced by strain MnI7-9 has potential for bioremediation and reutilization of Ag+-containing waste. PMID:24312566

Pei, Yuanjun; Chen, Xiao; Xiong, Dandan; Liao, Shuijiao; Wang, Gejiao

2013-01-01

255

New divalent manganese complex with pyridine carboxylate N-oxide ligand: Synthesis, structure and magnetic properties  

NASA Astrophysics Data System (ADS)

Two new manganese complexes, [Mn 3( L1) 4(NO 3) 2] n ( 1, H L1=nicotinate N-oxide acid) and [Mn L2Cl] n ( 2, H L2=isonicotinate N-oxide acid)], have been hydrothermally synthesized and characterized by elemental analysis, IR and single-crystal X-ray diffraction. In 1, the L1 ligands take two different coordinated modes bridging four and three Mn II ions. The nitrate anions take chelating coordination modes, leading one type of the Mn II ions as a 4-connected node. The whole net can be viewed as a 3, 4, 6-connected 4-nodal net with Schläfli notation {4 3}2{4 4; 6 2}4{4 6; 6 6; 8 3}. Complex 2 has a honeycomb layer mixed bridged by chlorine, N-oxide and carboxylate. The adjacent layers are linked by the phenyl ring of L2 ligand, giving a 3D framework with a {3 4; 5 4} {3 2;4;5 6;6 6} 4, 6-connect net. Magnetic studies indicate that 1 is an antiferromagnet with low-dimensional characteristic, in which a - J1J1J2- coupled alternating chain is predigested. Fitting the data of 1 gives the best parameters J1=-2.77, J2=-0.67 cm -1. The magnetic properties of complex 2 represent the character of the 2D honeycomb layer with the J1=-2.05 and J2=0.55 cm -1, which results in a whole antiferromagnetic state.

Liu, Fu-Chen; Xue, Min; Wang, Hai-Chao; Ou-Yang, Jie

2010-09-01

256

Oxidation of arsenate(III) with manganese oxides in water treatment  

Microsoft Academic Search

Arsenate(III) is the more toxic form of inorganic arsenic and its removal from drinking water is less effective as compared to arsenate(V). Arsenate(III) persists in aerated water, even at high pH, but is easily oxidized by managanese dioxides. The oxidation of As(III) follows a second order rate law with respect to As(III). The reaction rate is effected by the initial

Wolfgang Driehaus; Reiner Seith; Martin Jekel

1995-01-01

257

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

258

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

259

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

260

The Influence of Manganese Oxide on the Sintering Behavior of Yttria Tetragonal Zirconia  

SciTech Connect

The sintering behavior of yttria-stabilized zirconia, with the influence of small additions of MnO{sub 2}(up to 1 wt %) sintered over the temperature range from 1250 deg. C to 1500 deg. C was investigated. It was found that the mechanical properties of Y-TZP were dependent on the dopant amount and sintering temperature. The results revealed that relative densities above 97.5% of theoretical (i.e. >5.95 Mgm{sup -3}) could be obtained in Y-TZPs sintered at low temperatures, 1250 deg. C and 1300 deg. C, with the additions of {<=}0.3 wt% MnO{sub 2}. In comparison to the undoped samples, the additions of up to 1 wt%MnO{sub 2} and for sintering up to 1350 deg. C was found to be beneficial in enhancing the Vickers hardness of the ceramic. The fracture toughness of Y-TZP however, was found to increase only in the 1 wt% MnO{sub 2}-doped samples when sintered above 1400 deg. C. The relation between the measured mechanical properties is discussed with the emphasis on the role of the manganese oxide.

Meenaloshini, S.; Amiriyan, M.; Sankar, U.; Tolouei, R.; Ramesh, S. [Ceramics Technology Laboratory, University Tenaga Nasional, 43009 Kajang Selangor (Malaysia)

2011-01-17

261

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

262

Iron and manganese in oxide minerals and in glasses: preliminary consideration of Eh buffering potential at Yucca Mountain, Nevada  

SciTech Connect

The tuffs of Yucca Mountain at the Nevada Test Site are currently under investigation as a possible deep burial site for high-level radioactive waste disposal. One of the main concerns is the effect of oxidizing groundwater on the transport of radionuclides. Rock components that may affect the oxygen content of groundwater include Fe-Ti oxides, Mn oxides, and glasses that contain ferrous iron. Some phenocryst Fe-Ti oxides at Yucca Mountain are in reduced states, whereas groundmass Fe-Ti oxides have been oxidized to hematite, rutile, and pseudobrookite (Fe{sup 3+}-bearing phases) exclusively. Estimates of Fe{sup 2+}-bearing oxides indicate that less than 0.33 vol% phenocrysts is available to act as solid buffering agents of Eh. Of this percentage, significant amounts of Fe-Ti oxides are isolated from effective interaction with groundwater because they occur in densely welded, devitrified tuffs that have low interstitial permeability. Manganese oxides occur primarily along fractures in the ash-flow tuffs. Because the Mn oxides are concentrated along the same pathways (fractures) where transport has occurred in the past, these small volume percentages could act as buffers. However, the oxidation states of actual Mn-oxide phases are high (Mn{sup 4+}), and these minerals have virtually no potential for reducing groundwater Eh. Manganese oxides may even act as oxidizing agents. However, regardless of their poor capabilities as reducing agents, the Mn oxides could be important as sorbents of heavy metals at Yucca Mountain. The lack of accessible, pristine Fe-Ti oxides and the generally high oxidation states of Mn oxides seem to rule out these oxides as Eh buffers of the Yucca Mountain groundwater system. Reduction of ferrous iron within glassy tuffs may have some effect on Eh, but further study is needed. At present it is prudent to assume that minerals and glasses have little or no capacity for reducing oxygen-rich groundwater at Yucca Mountain. 25 refs., 3 figs., 12 tabs

Caporuscio, F.A.; Vaniman, D.T.

1985-04-01

263

Revisiting the coordination chemistry for preparing manganese oxide nanocrystals in the presence of oleylamine and oleic acid  

NASA Astrophysics Data System (ADS)

By pyrolyzing manganese(ii) acetate in 1-octadecene in the presence of oleylamine and oleic acid, manganese oxide nanocrystals were prepared. It was observed that both MnO and Mn3O4 nanocrystals were simultaneously formed by quickly heating the reaction mixture up to 250 °C, while a preheating procedure carried out at 100 °C led to uniform MnO nanocubes that developed into eight-arm MnO nanocrystals upon prolonged reaction. To understand the mechanisms for forming these two different kinds of manganese oxide nanocrystals, i.e., Mn3O4 and MnO, the coordination between oleic acid/oleylamine and Mn2+ was investigated. The detailed investigations suggest that Mn2+-oleylamine coordination is kinetically driven and favorable for the formation of Mn3O4 nanocrystals due to the relatively low electronegativity of N from oleylamine, while Mn2+-oleate coordination is thermodynamically driven and can prevent the central metal ion (Mn2+) from being oxidized owing to the relatively high electronegativity of O from the oleate ligand. Following these new insights, by properly balancing the coordination of oleic acid and oleylamine to Mn2+, the selective synthesis of MnO and Mn3O4 nanocrystals with uniform shapes was successfully achieved.By pyrolyzing manganese(ii) acetate in 1-octadecene in the presence of oleylamine and oleic acid, manganese oxide nanocrystals were prepared. It was observed that both MnO and Mn3O4 nanocrystals were simultaneously formed by quickly heating the reaction mixture up to 250 °C, while a preheating procedure carried out at 100 °C led to uniform MnO nanocubes that developed into eight-arm MnO nanocrystals upon prolonged reaction. To understand the mechanisms for forming these two different kinds of manganese oxide nanocrystals, i.e., Mn3O4 and MnO, the coordination between oleic acid/oleylamine and Mn2+ was investigated. The detailed investigations suggest that Mn2+-oleylamine coordination is kinetically driven and favorable for the formation of Mn3O4 nanocrystals due to the relatively low electronegativity of N from oleylamine, while Mn2+-oleate coordination is thermodynamically driven and can prevent the central metal ion (Mn2+) from being oxidized owing to the relatively high electronegativity of O from the oleate ligand. Following these new insights, by properly balancing the coordination of oleic acid and oleylamine to Mn2+, the selective synthesis of MnO and Mn3O4 nanocrystals with uniform shapes was successfully achieved. Electronic supplementary information (ESI) available: (1) TEM image and corresponding SAED pattern of the tiny particles shown in Fig. 1b; (2) TEM images of the branched nanoparticles (Fig. 1e) showing a self-organized superstructure; (3) TEM image and the electron diffraction pattern of the particles obtained by heating the Mn(Ac)2 in oleylamine at 100 °C for 540 min; (4) TEM image and the electron diffraction pattern of the particles obtained from the second reference experiment; (5) Temporal evolution of size and size distribution of manganese oxide nanocrystals shown in Fig. 5 and Fig. 6. See DOI: 10.1039/c4nr00761a

Zhang, Hongwei; Jing, Lihong; Zeng, Jianfeng; Hou, Yi; Li, Zhen; Gao, Mingyuan

2014-05-01

264

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

265

Normal Cellular Prion Protein Protects against Manganese-induced Oxidative Stress and Apoptotic Cell Death  

PubMed Central

The normal prion protein is abundantly expressed in the CNS, but its biological function remains unclear. The prion protein has octapeptide repeat regions that bind to several divalent metals, suggesting that the prion proteins may alter the toxic effect of environmental neurotoxic metals. In the present study, we systematically examined whether prion protein modifies the neurotoxicity of manganese (Mn) by comparing the effect of Mn on mouse neural cells expressing prion protein (PrPC -cells) and prion-knockout (PrPKO -cells). Exposure to Mn (10 ?M-1 mM) for 24 hr produced a dose-dependent cytotoxic response in both PrPC -cells and PrPKO -cells. Interestingly, PrPC -cells (EC50 117.6?M) were more resistant to Mn-induced cytotoxicity, as compared to PrPKO -cells (EC50 59.9?M), suggesting a protective role for PrPC against Mn neurotoxicity. Analysis of intracellular Mn levels showed less Mn accumulation in PrPC -cells as compared to PrPKO -cells. Furthermore, Mn-induced mitochondrial depolarization and ROS generation were significantly attenuated in PrPC -cells as compared to PrPKO -cells. Measurement of antioxidant status revealed similar basal levels of glutathione (GSH) in PrPC -cells and PrPKO -cells; however, Mn treatment caused greater depletion of GSH in PrPKO -cells. Mn-induced mitochondrial depolarization and ROS production were followed by time- and dose-dependent activation of the apoptotic cell death cascade involving caspase-9 and -3. Notably, DNA fragmentation induced by both Mn treatment and oxidative stress-inducer hydrogen peroxide (100?M) was significantly suppressed in PrPC -cells as compared to PrPKO -cells. Together, these results demonstrate that prion protein interferes with divalent metal Mn uptake and protects against Mn-induced oxidative stress and apoptotic cell death. PMID:17483122

Choi, Christopher J.; Anantharam, Vellareddy; Saetveit, Nathan J.; Houk, Robert. S.; Kanthasamy, Arthi; Kanthasamy, Anumantha G.

2012-01-01

266

New strategy to enhance phosphate removal from water by hydrous manganese oxide.  

PubMed

Hydrous manganese oxide (HMO) is generally negatively charged at circumneutral pH and cannot effectively remove anionic pollutants such as phosphate. Here we proposed a new strategy to enhance HMO-mediated phosphate removal by immobilizing nano-HMO within a polystyrene anion exchanger (NS). The resultant nanocomposite HMO@NS exhibited substantially enhanced phosphate removal in the presence of sulfate, chloride, and nitrate at greater levels. This is mainly attributed to the pHpzc shift from 6.2 for the bulky HMO to 10.5 for the capsulated HMO nanoparticles, where HMO nanoparticles are positively charged at neutral pH. The ammonium groups of NS also favor phosphate adsorption through the Donnan effect. Cyclic column adsorption experiment indicated that the fresh HMO@NS could treat 460 bed volumes (BV) of a synthetic influent (from the initial concentration of 2 mg P[PO4(3-)]/L to 0.5 mg P[PO4(3-)]/L), while only 80 BV for NS. After the first time of regeneration by NaOH-NaCl solution, the capacity of HMO@NS was lowered to ? 300 BV and then kept constant for the subsequent 5 runs, implying the presence of both the reversible and irreversible adsorption sites of nano-HMO. Additional column adsorption feeding with a real bioeffluent further validated great potential of HMO@NS in advanced wastewater treatment. This study may provide an alternative approach to expand the usability of other metal oxides in water treatment. PMID:24730751

Pan, Bingcai; Han, Feichao; Nie, Guangze; Wu, Bing; He, Kai; Lu, Lv

2014-05-01

267

Synthesis of Layered-Type Hydrous Manganese Oxides from Monoclinic-Type LiMnO 2  

Microsoft Academic Search

Layered-type hydrous manganese oxides MnO2·0.70H2O and MnO2·0.22H2O with almost the same rod shape morphology as that of the precursor monoclinic-type LiMnO2 were synthesized. The structural transformations from monoclinic-type LiMnO2 to a birnessite-type MnO2·0.70H2O took place after lithium in LiMnO2 was extracted with 0.1 mol dm?3 (NH4)2S2O8 solution without dissolution of manganese. The extraction of lithium from LiMnO2 with 0.5 mol

Ramesh Chitrakar; Hirofumi Kanoh; Yang-Soo Kim; Yoshitaka Miyai; Kenta Ooi

2001-01-01

268

Intense photo- and tribo-luminescence of three tetrahedral manganese(ii) dihalides with chelating bidentate phosphine oxide ligand.  

PubMed

Three air-stable tetrahedral manganese(ii) dihalide complexes [MnX2(DPEPO)] (DPEPO = bis[2-(diphenylphosphino)phenyl]ether oxide; X = Cl, Br and I) were prepared. All of the obtained compounds were structurally characterized by single-crystal X-ray diffraction analyses, which reveal that they crystallize in centrosymmetric space groups and feature an isolated mononuclear structure with Mn(2+) in a tetrahedral environment. Interestingly, these complexes show excellent photoluminescent performance in neat solid form, with the highest total quantum yield (?total) of up to 70% recorded for the dibromide complex. Intense green flashes of light could be observed by the naked eye when rubbing the manganese(ii) complexes. PMID:25597698

Chen, Jun; Zhang, Qing; Zheng, Fa-Kun; Liu, Zhi-Fa; Wang, Shuai-Hua; Wu, A-Qing; Guo, Guo-Cong

2015-02-01

269

Comparison of Functions for Evaluating the Effect of Fe and Al Oxides on the Particle Size Distribution of Kaolin and Quartz  

Microsoft Academic Search

Although it is generally agreed that Fe and A1 can act to bind soil particles, their relative efficiencies as aggregants are still disputed. In this work, the aggregating efficiencies of both aged and non-aged Fe and AI oxides precipitated on kaolin or quartz substrates were characterized by comparing their effects on particle size distributions (PSD), To facilitate comparison of PSD

M. Arias; E. LOPEZ; M. T. BARRAL

1997-01-01

270

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

271

One-dimensional manganese-cobalt oxide nanofibres as bi-functional cathode catalysts for rechargeable metal-air batteries.  

PubMed

Rechargeable metal-air batteries are considered a promising energy storage solution owing to their high theoretical energy density. The major obstacles to realising this technology include the slow kinetics of oxygen reduction and evolution on the cathode (air electrode) upon battery discharging and charging, respectively. Here, we report non-precious metal oxide catalysts based on spinel-type manganese-cobalt oxide nanofibres fabricated by an electrospinning technique. The spinel oxide nanofibres exhibit high catalytic activity towards both oxygen reduction and evolution in an alkaline electrolyte. When incorporated as cathode catalysts in Zn-air batteries, the fibrous spinel oxides considerably reduce the discharge-charge voltage gaps (improve the round-trip efficiency) in comparison to the catalyst-free cathode. Moreover, the nanofibre catalysts remain stable over the course of repeated discharge-charge cycling; however, carbon corrosion in the catalyst/carbon composite cathode degrades the cycling performance of the batteries. PMID:25563733

Jung, Kyu-Nam; Hwang, Soo Min; Park, Min-Sik; Kim, Ki Jae; Kim, Jae-Geun; Dou, Shi Xue; Kim, Jung Ho; Lee, Jong-Won

2015-01-01

272

One-dimensional manganese-cobalt oxide nanofibres as bi-functional cathode catalysts for rechargeable metal-air batteries  

NASA Astrophysics Data System (ADS)

Rechargeable metal-air batteries are considered a promising energy storage solution owing to their high theoretical energy density. The major obstacles to realising this technology include the slow kinetics of oxygen reduction and evolution on the cathode (air electrode) upon battery discharging and charging, respectively. Here, we report non-precious metal oxide catalysts based on spinel-type manganese-cobalt oxide nanofibres fabricated by an electrospinning technique. The spinel oxide nanofibres exhibit high catalytic activity towards both oxygen reduction and evolution in an alkaline electrolyte. When incorporated as cathode catalysts in Zn-air batteries, the fibrous spinel oxides considerably reduce the discharge-charge voltage gaps (improve the round-trip efficiency) in comparison to the catalyst-free cathode. Moreover, the nanofibre catalysts remain stable over the course of repeated discharge-charge cycling; however, carbon corrosion in the catalyst/carbon composite cathode degrades the cycling performance of the batteries.

Jung, Kyu-Nam; Hwang, Soo Min; Park, Min-Sik; Kim, Ki Jae; Kim, Jae-Geun; Dou, Shi Xue; Kim, Jung Ho; Lee, Jong-Won

2015-01-01

273

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

NASA Astrophysics Data System (ADS)

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, KOH and LiOH, the respective alkali metal ion was incorporated into the precipitate. Fiber-like nano-structured spinel-LiMn 2O 4 crystals 200 nm in diameter were obtained on a substrate by the calcination of the Li incorporated precipitate at 750 °C without any additives. The electrochemically-formed spinel-LiMn 2O 4 showed well-shaped CVs, even in higher scan rates. These behaviors are ascribed to the crystal size and shape of the processed spinel-LiMn 2O 4.

Katakura, Katsumi; Nishimura, Shin-ichi; Ogumi, Zempachi

274

PROGRESS REPORT. TRANSURANIC INTERFACIAL REACTION STUDIES ON MANGANESE OXIDE HYDROXIDE MINERAL SURFACES  

EPA Science Inventory

Several DOE sites have been contaminated by transuranic radionuclide (TRU) discharges including neptunium and plutonium. Their interaction with the surrounding geological media can affect the transport and remediation of these radionuclides in the environment. Manganese based min...

275

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

276

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

277

Microarray genomic profile of mitochondrial and oxidant response in Manganese Chloride treated PC12 cells  

PubMed Central

Environmental or occupational exposure to high levels of manganese (Mn) can lead to manganism, a symptomatic neuro-degenerative disorder similar to idiopathic Parkinson’s disease. The underlying mechanism of Mn neurotoxicity remains unclear. In this study, we evaluate the primary toxicological events associated with MnCl2 toxicity in rat PC12 cells using whole genome cDNA microarray, RT-PCR, western blot and functional studies. The results show that a sub-lethal dose range (38–300 µM MnCl2) initiated slight metabolic stress evidenced by heightened glycolytic rate and induction of enolase / aldolase - gene expression. The largest shift observed in the transcriptome was MnCl2 induction of heme-oxygenase 1 (HO-1) [7.7 fold, p <0.001], which was further corroborated by RT-PCR and western blot studies. Concentrations in excess of 300 µM corresponded to dose dependent loss of cell viability which was associated with enhanced production of H2O2 concomitant to elevation of of gene expression for diverse antioxidant enzymes; biliverdin reductase, arsenite inducible RNA associated protein, dithiolethione-inducible gene-1 (DIG-1) and .thioredoxin reductase 1. Moreover, Mn initiated significant reduction of gene expression of mitochondrial glutaryl-coenzyme A dehydrogenase (GCDH) -, an enzyme involved with glutaric acidemia, oxidative stress, lipid peroxidation and striatal degeneration observed in association with severe dystonic dyskinetic movement disorder. Future research will be required to elucidate a defined role for HO-1 and GCDH in Mn toxicity. PMID:22281203

Taka, Equar; Mazzio, Elizabeth; Soliman, Karam FA; Reams, R. Renee

2012-01-01

278

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

279

Theoretical technique for predicting the cumulative impact of iron and manganese oxidation in streams receiving discharge from coal mines  

USGS Publications Warehouse

Two U.S. Geological Survey computer programs are modified and linked to predict the cumulative impact of iron and manganese oxidation in coal-mine discharge water on the dissolved chemical quality of a receiving stream. The coupled programs calculate the changes in dissolved iron, dissolved manganese, and dissolved oxygen concentrations; alkalinity; and, pH of surface water downstream from the point of discharge. First, the one-dimensional, stead-state stream, water quality program uses a dissolved oxygen model to calculate the changes in concentration of elements as a function of the chemical reaction rates and time-of-travel. Second, a program (PHREEQE) combining pH, reduction-oxidation potential, and equilibrium equations uses an aqueous-ion association model to determine the saturation indices and to calculate pH; it then mixes the discharge with a receiving stream. The kinetic processes of the first program dominate the system, whereas the equilibrium thermodynamics of the second define the limits of the reactions. A comprehensive test of the technique was not possible because a complete set of data was unavailable. However, the cumulative impact of representative discharges from several coal mines on stream quality in a small watershed in southwestern Indiana was simulated to illustrate the operation of the technique and to determine its sensitivity to changes in physical, chemical, and kinetic parameters. Mine discharges averaged 2 cu ft/sec, with a pH of 6.0, and concentrations of 7.0 mg/L dissolved iron, 4.0 mg/L dissolved manganese, and 8.08 mg/L dissolved oxygen. The receiving stream discharge was 2 cu ft/sec, with a pH of 7.0, and concentrations of 0.1 mg/L dissolved iron, 0.1 mg/L dissolved manganese, and 8.70 mg/L dissolved oxygen. Results of the simulations indicated the following cumulative impact on the receiving stream from five discharges as compared with the effect from one discharge: 0.30 unit decrease in pH, 1.82 mg/L increase in dissolved iron, 1.50 mg/L increase in dissolved manganese, and 0.24 mg/L decrease in dissolved oxygen concentration. (Author 's abstract)

Bobay, Keith E.

1986-01-01

280

Graphene-Based Hybrids with Manganese Oxide Polymorphs as Tailored Interfaces for Electrochemical Energy Storage: Synthesis, Processing, and Properties  

NASA Astrophysics Data System (ADS)

Technological progress is determined to a greater extent by developments of novel materials or new combinations of known materials with different dimensionality and diverse functionality. In this work, we report on the synthesis and characterization of graphene-based hybrid nanomaterials coupled with transition-metal oxide polymorphs (nano/micro-manganese oxides, i.e., ?-MnO2 [Mn(IV)] and Mn3O4 [Mn(II, III)]). This lays the groundwork for high-performance electrochemical electrodes for alternative energy devices owing to their higher specific capacitance, wide operational potential window and stability through charge-discharge cycling, environmentally benignity, cost-effectiveness, easy processing, and reproducibility on a larger scale. To accomplish this, we strategically designed these hybrids by direct anchoring or physical adsorption of ?-MnO2 and Mn3O4 on variants of graphene, namely graphene oxide and its reduced form, via mixing dispersions of the constituents under mild ultrasonication and drop-casting, resulting in four different combinations. This facile approach affords strong chemical/physical attachment and is expected to result in coupling between the pseudocapacitive transition-metal oxides and supercapacitive nanocarbons showing enhanced activity/reactivity and reasonable areal density of tailored interfaces. We used a range of complementary analytical characterization tools to determine the structure and physical properties, such as scanning electron microscopy combined with energy-dispersive x-ray spectroscopy, atomic force microscopy, x-ray diffraction, resonance Raman spectroscopy combined with elemental Raman mapping, and transmission electron microscopy in conjunction with selected-area electron diffraction. All of these techniques reveal surface morphology, local (lattice dynamical) and average structure, and local charge transfer due to the physically (or chemically) adsorbed manganese oxide of synthesized hybrids that helps to establish microscopic structure-property-function correlations highlighting the surface structure and interfaces to further investigate their electrochemical supercapacitor properties.

Gupta, S.; van Meveren, M. M.; Jasinski, J.

2015-01-01

281

Electrical transport properties of manganese containing pyrochlore type semiconducting oxides using impedance analyses  

SciTech Connect

Graphical abstract: DC conductivity variation of CaCe{sub 1?x}Mn{sub x}SnNbO{sub 7??} (x = 0, 0.2, 0.4 and 0.6) with inverse of temperature. Variation of conductivity with Mn concentration at 600 °C is shown in the inset. Display Omitted Highlights: ? We have observed that the structural ordering as well as grain size increase with Mn substitution. ? Impedance analysis proved that a correlated barrier hopping type conduction mechanism is involved in the materials. ? Activation energy as well as electrical conductivity increases with increase in Mn substitution. ? Localization of electrons associated with Mn{sup 2+} and structural ordering are the key factors for the increased activation energy with Mn substitution. ? All the materials showed good NTC thermistor properties. -- Abstract: A new series of manganese containing pyrochlore type semiconducting oxides CaCe{sub 1?x}Mn{sub x}SnNbO{sub 7??} (x = 0, 0.2, 0.4 and 0.6) have been synthesized to study the effect of Mn substitution on the structure, microstructure and electrical properties of these samples. X-ray diffraction and scanning electron microscopy studies revealed an increase of structural ordering and grain size respectively with increase of Mn substitution. Rietveld analysis and Raman spectroscopy were also employed to corroborate the XRD results. The bulk resistance measurements with temperature exhibit negative temperature coefficient behavior. The impedance analysis of the samples revealed a non-Debye type relaxation existed in the materials. The ac conductivity variation with temperature and frequency indicates a correlated barrier hopping type conduction mechanism in these materials. The barrier height and the intersite separation for hopping influence the electrical conductivity of these samples and are found to be a function of localization of electrons associated with the Mn{sup 2+} ions and the unit cell volume respectively. The Mn substitution increases both electrical conductivity and activation energy contrastingly. This unusual behavior has been explained by correlating the structure, microstructure, defect states, electron localization and intersite separation with the conductivity data of the samples.

Sumi, S. [Materials and Minerals Division, National Institute for Interdisciplinary Science and Technology (NIIST), Trivandrum 695 019 (India)] [Materials and Minerals Division, National Institute for Interdisciplinary Science and Technology (NIIST), Trivandrum 695 019 (India); Prabhakar Rao, P., E-mail: padala_rao@yahoo.com [Materials and Minerals Division, National Institute for Interdisciplinary Science and Technology (NIIST), Trivandrum 695 019 (India); Mahesh, S.K. [Materials and Minerals Division, National Institute for Interdisciplinary Science and Technology (NIIST), Trivandrum 695 019 (India)] [Materials and Minerals Division, National Institute for Interdisciplinary Science and Technology (NIIST), Trivandrum 695 019 (India); Koshy, Peter [Mount Zion College of Engineering for Women, Chengannur 689 521 (India)] [Mount Zion College of Engineering for Women, Chengannur 689 521 (India)

2012-12-15

282

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-Mn3O4) 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

283

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

284

Identifying active surface phases for metal oxide electrocatalysts: a study of manganese oxide bi-functional catalysts for oxygen reduction and water oxidation catalysis.  

PubMed

Progress in the field of electrocatalysis is often hampered by the difficulty in identifying the active site on an electrode surface. Herein we combine theoretical analysis and electrochemical methods to identify the active surfaces in a manganese oxide bi-functional catalyst for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). First, we electrochemically characterize the nanostructured ?-Mn(2)O(3) and find that it undergoes oxidation in two potential regions: initially, between 0.5 V and 0.8 V, a potential region relevant to the ORR and, subsequently, between 0.8 V and 1.0 V, a potential region between the ORR and the OER relevant conditions. Next, we perform density function theory (DFT) calculations to understand the changes in the MnO(x) surface as a function of potential and to elucidate reaction mechanisms that lead to high activities observed in the experiments. Using DFT, we construct surface Pourbaix and free energy diagrams of three different MnO(x) surfaces and identify 1/2 ML HO* covered Mn(2)O(3) and O* covered MnO(2), as the active surfaces for the ORR and the OER, respectively. Additionally, we find that the ORR occurs through an associative mechanism and that its overpotential is highly dependent on the stabilization of intermediates through hydrogen bonds with water molecules. We also determine that OER occurs through direct recombination mechanism and that its major source of overpotential is the scaling relationship between HOO* and HO* surface intermediates. Using a previously developed Sabatier model we show that the theoretical predictions of catalytic activities match the experimentally determined onset potentials for the ORR and the OER, both qualitatively and quantitatively. Consequently, the combination of first-principles theoretical analysis and experimental methods offers an understanding of manganese oxide oxygen electrocatalysis at the atomic level, achieving fundamental insight that can potentially be used to design and develop improved electrocatalysts for the ORR and the OER and other important reactions of technological interest. PMID:22990481

Su, Hai-Yan; Gorlin, Yelena; Man, Isabela C; Calle-Vallejo, Federico; Nørskov, Jens K; Jaramillo, Thomas F; Rossmeisl, Jan

2012-10-28

285

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

286

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

287

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

288

Manganese metallurgy review. Part II: Manganese separation and recovery from solution  

Microsoft Academic Search

Various methods for manganese separation and recovery from solution are reviewed, which are potentially applicable to leach solutions of secondary manganese sources, particularly nickel laterite waste effluents. The main methods include solvent extraction, sulfide precipitation, ion exchange, hydroxide precipitation and oxidative precipitation. These methods are briefly compared and assessed for both purification of manganese solutions and recovery of manganese from

Wensheng Zhang; Chu Yong Cheng

2007-01-01

289

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. of Delaware, Bear, DE (4)Univ. of Delaware, Newark, DE The atomic pair distribution function (PDF) is a powerful technique to analyze crystal structures of nanoparticulate, poorly crystalline and amorphous

Sparks, Donald L.

290

Oxidation of aniline and other primary aromatic amines by manganese dioxide  

SciTech Connect

This investigation evaluated the redox reaction between a manganese dioxide, {sigma}-MnO{sub 2}, and anilines and other aromatic reductants in aqueous suspensions at pH values ranging from 3.7 to 6.5. The reaction with manganese dioxide may represent a pathway for transformation of aniline and other primary aromatic amines in acidic mineralogical and soil/water environments in the absence of oxygen and substantial microbial activity. The reaction rate with aniline is pH-dependent, increasing with decreasing pH, and first order with respect to {sigma}-MnO{sub 2} and organic solute. Aniline and p-toluidine are demonstrated to be 2-equiv reductants, as is believed to be the case for the other aromatic solutes considered in this study, including the substituted anilines, and hydroquinone and catechol and their alkyl substituents. Ring-bound nitrogen-containing aromatic solutes (methylimidazole, quinoline, and 5,5-dimethylhydantion) were unreactive with manganese dioxide at pH 6.4. The order of the reactivity of para-substituted anilines was methoxy >> methyl > chloro > carboxy >> nitro; the relative reactivity of these compounds correlated with the solute's half-wave potential and Hammett constant.

Laha, S.; Luthy, R.G. (Carnegie Mellon Univ., Pittsburgh, PA (USA))

1990-03-01

291

Characterization of High-Velocity Solution Precursor Flame-Sprayed Manganese Cobalt Oxide Spinel Coatings for Metallic SOFC Interconnectors  

NASA Astrophysics Data System (ADS)

A modified high-velocity oxy-fuel spray (HVOF) thermal spray torch equipped with liquid feeding hardware was used to spray manganese-cobalt solutions on ferritic stainless steel grade Crofer 22 APU substrates. The HVOF torch was modified in such a way that the solution could be fed axially into the combustion chamber through 250- and 300-?m-diameter liquid injector nozzles. The solution used in this study was prepared by diluting nitrates of manganese and cobalt, i.e., Mn(NO3)2·4H2O and Co(NO3)2·6H2O, respectively, in deionized water. The as-sprayed coatings were characterized by X-ray diffraction and field-emission scanning electron microscopy operating in secondary electron mode. Chemical analyses were performed on an energy dispersive spectrometer. Coatings with remarkable density could be prepared by the novel high-velocity solution precursor flame spray (HVSPFS) process. Due to finely sized droplet formation in the HVSPFS process and the use of as delivered Crofer 22 APU substrate material having very low substrate roughness ( R a < 0.5 ?m), thin and homogeneous coatings, with thicknesses lower than 10 ?m could be prepared. The coatings were found to have a crystalline structure equivalent to MnCo2O4 spinel with addition of Co-oxide phases. Crystallographic structure was restored back to single-phase spinel structure by heat treatment.

Puranen, Jouni; Laakso, Jarmo; Kylmälahti, Mikko; Vuoristo, Petri

2013-06-01

292

Surface structure of the proton-exchanged lithium manganese oxide spinels and their lithium-ion sieve properties  

SciTech Connect

The spinel structure and the valence states of the Mn ions both at the surface and the bulk were characterized for the Li{sup +} extracted and inserted manganese oxide spinels. The Li{sup +} extraction from the orthorhombic LiMn{sub 2}O{sub 4} spinel results in the formation of the cubic spinel, the crystal structure of which is the same as {lambda}-MnO{sub 2}. The LiMn{sub 2}O{sub 4} spinel prepared from an electrolytically prepared manganese dioxide is converted to HMn{sub 2}O{sub 4} on dilute acid treatment. X-ray photoelectron spectroscopic analysis revealed that the valence state of the surface Mn ions remains unchanged during the Li{sup +} extraction and insertion, which indicates an occurrence of the Li{sup +}-H{sup +} ion exchange reaction at the surface irrespective of the solution pH. The Fourier transform infrared photoacoustic spectra of the Li{sup +} extracted spinel demonstrated the existence of the surface hydroxyl groups, which is considered to be associated with the vacant 8a tetrahedral sites in the spinel structure. Based on the thermal stability of the surface hydroxyl groups and the bulk hydroxyl groups, the Li{sup +} extracted spinel structure is discussed in relation to its lithium-ion sieve property.

Sato, K.; Poojary, D.M.; Clearfield, A. [Texas A & M Univ., College Station, TX (United States)] [Texas A & M Univ., College Station, TX (United States); Kohno, M.; Inoue, Y. [Nagaoka Univ. of Technology, Niigata (Japan)] [Nagaoka Univ. of Technology, Niigata (Japan)

1997-06-01

293

Manganese reduction/oxidation reaction on graphene composites as a reversible process for storing enormous energy at a fast rate  

E-print Network

Oxygen reduction/evolution reaction (ORR/OER) is a basic process for fuel cells or metal air batteries. However, ORR/OER generally requires noble metal catalysts and suffers from low solubility (10-3 molar per liter) of O2, low kinetics rate (10-6 cm2/s) and low reversibility. We report a manganese reduction/oxidation reaction (MRR/MOR) on graphene/MnO2 composites, delivering a high capacity (4200 mAh/g), fast kinetics (0.0024 cm2/s, three orders higher than ORR/OER), high solubility (three orders than O2), and high reversibility (100%). We further use MRR/MOR to invent a rechargeable manganese ion battery (MIB), which delivers an energy density of 1200 Wh/Kg (several times of lithium ion battery), a fast charge ability (3 minutes), and a long cycle life (10,000 cycles). MRR/MOR renders a new class of energy conversion or storage systems with a very high energy density enabling electric vehicles run much more miles at one charge.

Chen, Yanyi; Shi, Shan; Li, Jia; Kang, Feiyu; Wei, Chunguang

2014-01-01

294

Structural, optical, and magnetic studies of manganese-doped zinc oxide hierarchical microspheres by self-assembly of nanoparticles  

NASA Astrophysics Data System (ADS)

In this study, a series of manganese [Mn]-doped zinc oxide [ZnO] hierarchical microspheres [HMSs] are prepared by hydrothermal method only using zinc acetate and manganese acetate as precursors and ethylene glycol as solvent. X-ray diffraction indicates that all of the as-obtained samples including the highest Mn (7 mol%) in the crystal lattice of ZnO have a pure phase (hexagonal wurtzite structure). A broad Raman spectrum from as-synthesized doping samples ranges from 500 to 600 cm-1, revealing the successful doping of paramagnetic Mn2+ ions in the host ZnO. Optical absorption analysis of the samples exhibits a blueshift in the absorption band edge with increasing dopant concentration, and corresponding photoluminescence spectra show that Mn doping suppresses both near-band edge UV emission and defect-related blue emission. In particular, magnetic measurements confirm robust room-temperature ferromagnetic behavior with a high Curie temperature exceeding 400 K, signifying that the as-formed Mn-doped ZnO HMSs will have immense potential in spintronic devices and spin-based electronic technologies.

Hao, Yao-Ming; Lou, Shi-Yun; Zhou, Shao-Min; Yuan, Rui-Jian; Zhu, Gong-Yu; Li, Ning

2012-02-01

295

Structural, optical, and magnetic studies of manganese-doped zinc oxide hierarchical microspheres by self-assembly of nanoparticles  

PubMed Central

In this study, a series of manganese [Mn]-doped zinc oxide [ZnO] hierarchical microspheres [HMSs] are prepared by hydrothermal method only using zinc acetate and manganese acetate as precursors and ethylene glycol as solvent. X-ray diffraction indicates that all of the as-obtained samples including the highest Mn (7 mol%) in the crystal lattice of ZnO have a pure phase (hexagonal wurtzite structure). A broad Raman spectrum from as-synthesized doping samples ranges from 500 to 600 cm-1, revealing the successful doping of paramagnetic Mn2+ ions in the host ZnO. Optical absorption analysis of the samples exhibits a blueshift in the absorption band edge with increasing dopant concentration, and corresponding photoluminescence spectra show that Mn doping suppresses both near-band edge UV emission and defect-related blue emission. In particular, magnetic measurements confirm robust room-temperature ferromagnetic behavior with a high Curie temperature exceeding 400 K, signifying that the as-formed Mn-doped ZnO HMSs will have immense potential in spintronic devices and spin-based electronic technologies. PMID:22296968

2012-01-01

296

Tunable T1 and T2 contrast abilities of manganese-engineered iron oxide nanoparticles through size control  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate the tunable T1 and T2 contrast abilities of engineered iron oxide nanoparticles with high performance for liver contrast-enhanced magnetic resonance imaging (MRI) in mice. To enhance the diagnostic accuracy of MRI, large numbers of contrast agents with T1 or T2 contrast ability have been widely explored. The comprehensive investigation of high-performance MRI contrast agents with controllable T1 and T2 contrast abilities is of high importance in the field of molecular imaging. In this study, we synthesized uniform manganese-doped iron oxide (MnIO) nanoparticles with controllable size from 5 to 12 nm and comprehensively investigated their MRI contrast abilities. We revealed that the MRI contrast effects of MnIO nanoparticles are highly size-dependent. By controlling the size of MnIO nanoparticles, we can achieve T1-dominated, T2-dominated, and T1-T2 dual-mode MRI contrast agents with much higher contrast enhancement than the corresponding conventional iron oxide nanoparticles.In this paper, we demonstrate the tunable T1 and T2 contrast abilities of engineered iron oxide nanoparticles with high performance for liver contrast-enhanced magnetic resonance imaging (MRI) in mice. To enhance the diagnostic accuracy of MRI, large numbers of contrast agents with T1 or T2 contrast ability have been widely explored. The comprehensive investigation of high-performance MRI contrast agents with controllable T1 and T2 contrast abilities is of high importance in the field of molecular imaging. In this study, we synthesized uniform manganese-doped iron oxide (MnIO) nanoparticles with controllable size from 5 to 12 nm and comprehensively investigated their MRI contrast abilities. We revealed that the MRI contrast effects of MnIO nanoparticles are highly size-dependent. By controlling the size of MnIO nanoparticles, we can achieve T1-dominated, T2-dominated, and T1-T2 dual-mode MRI contrast agents with much higher contrast enhancement than the corresponding conventional iron oxide nanoparticles. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr02680b

Huang, Guoming; Li, Hui; Chen, Jiahe; Zhao, Zhenghuan; Yang, Lijiao; Chi, Xiaoqin; Chen, Zhong; Wang, Xiaomin; Gao, Jinhao

2014-08-01

297

A high-capacity, low-cost layered sodium manganese oxide material as cathode for sodium-ion batteries.  

PubMed

A layered sodium manganese oxide material (NaMn3 O5 ) is introduced as a novel cathode materials for sodium-ion batteries. Structural characterizations reveal a typical Birnessite structure with lamellar stacking of the synthetic nanosheets. Electrochemical tests reveal a particularly large discharge capacity of 219 mAh g(-1) in the voltage rang of 1.5-4.7 V vs. Na/Na(+) . With an average potential of 2.75 V versus sodium metal, layered NaMn3 O5 exhibits a high energy density of 602 Wh kg(-1) , and also presents good rate capability. Furthermore, the diffusion coefficient of sodium ions in the layered NaMn3 O5 electrode is investigated by using the galvanostatic intermittent titration technique. The results greatly contribute to the development of room-temperature sodium-ion batteries based on earth-abundant elements. PMID:24919424

Guo, Shaohua; Yu, Haijun; Jian, Zelang; Liu, Pan; Zhu, Yanbei; Guo, Xianwei; Chen, Mingwei; Ishida, Masayoshi; Zhou, Haoshen

2014-08-01

298

Design, synthesis, and characterization of materials for controlled line deposition, environmental remediation, and doping of porous manganese oxide material  

NASA Astrophysics Data System (ADS)

This thesis covers three topics: (1) coatings formed from sol-gel phases, (2) environmental remediation, and (3) doping of a porous manganese oxide. Synthesis, characterization, and application were investigated for each topic. Line-formations were formed spontaneously by self-assembly from vanadium sol-gels and other metal containing solutions on glass substrates. The solutions were prepared by the dissolution of metal oxide or salt in water. A more straightforward method is proposed than used in previous work. Analyses using optical microscopy, atomic force microscopy, scanning electron microscopy, energy-dispersive X-ray analysis, and infrared spectroscopy showed discreet lines whose deposition could be controlled by varying the concentration. A mechanism was developed from the observed results. Microwave heating, the addition of graphite rods, and oxidants, can enhance HCB remediation from soil. To achieve remediation, a TeflonRTM vessel open to the atmosphere along with an oxidant, potassium persulfate (PerS) or potassium hydroxide, along with uncoated or aluminum oxide coated, graphite rods were heated in a research grade microwave oven. Microwave heating was used to decrease the heating time, and graphite rods were used to increase the absorption of the microwave energy by providing thermal centers. The results showed that the percent HCB removed was increased by adding graphite rods and oxidants. Tungsten, silver, and sulfur were investigated as doping agents for K--OMS-2. The synthesis of these materials was carried out with a reflux method. The doping of K--OMS-2 led to changes in the properties of a tungsten doped K--OMS-2 had an increased resistivity, the silver doped material showed improved epoxidation of trans-stilbene, and the addition of sulfur produced a paper-like material. Rietveld refinement of the tungsten doped K--OMS-2 showed that the tungsten was doped into the framework.

Calvert, Craig A.

299

One-step through-mask electrodeposition of a porous structure composed of manganese oxide nanosheets with electrocatalytic activity for oxygen reduction  

SciTech Connect

Potentiostatic electrolysis of a mixed aqueous solution of Bu{sub 4}NBr and MnSO{sub 4} at +1.0 V (vs. Ag/AgCl) on Pt electrode led to the oxidation of Br{sup -} and Mn{sup 2+} ions. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and X-ray diffraction (XRD) revealed that this anodic process was followed by the deposition of insulating crystals of bromide salt of Bu{sub 4}N{sup +} and the subsequent formation of layered manganese oxide in the interstitial spaces of the bromide grains already grown. Dissolution of the bromide crystals in water left a well-dispersed porous texture composed of manganese oxide nanosheets. The resulting MnO{sub x}-modified electrode exhibited a larger catalytic current for the reduction of oxygen in alkaline solution, compared to the bare Pt electrode.

Fukuda, Masaki; Iida, Chihiro [Department of Applied Chemistry, Yamaguchi University, 2-16-1 Tokiwadai, Ube 755-8611 (Japan); Nakayama, Masaharu, E-mail: nkymm@yamaguchi-u.ac.jp [Department of Applied Chemistry, Yamaguchi University, 2-16-1 Tokiwadai, Ube 755-8611 (Japan)

2009-06-03

300

Degradation of lithium ion batteries employing graphite negatives and nickel-cobalt-manganese oxide + spinel manganese oxide positives: Part 2, chemical-mechanical degradation model  

NASA Astrophysics Data System (ADS)

Capacity fade is reported for 1.5 Ah Li-ion batteries containing a mixture of Li-Ni-Co-Mn oxide (NCM) + Li-Mn oxide spinel (LMO) as positive electrode material and a graphite negative electrode. The batteries were cycled at a wide range of temperatures (10 °C-46 °C) and discharge currents (0.5C-6.5C). The measured capacity losses were fit to a simple physics-based model which calculates lithium inventory loss from two related mechanisms: (1) mechanical degradation at the graphite anode particle surface caused by diffusion-induced stresses (DIS) and (2) chemical degradation caused by lithium loss to continued growth of the solid-electrolyte interphase (SEI). These two mechanisms are coupled because lithium is consumed through SEI formation on newly exposed crack surfaces. The growth of crack surface area is modeled as a fatigue phenomenon due to the cyclic stresses generated by repeated lithium insertion and de-insertion of graphite particles. This coupled chemical-mechanical degradation model is consistent with the observed capacity loss features for the NCM + LMO/graphite cells.

Purewal, Justin; Wang, John; Graetz, Jason; Soukiazian, Souren; Tataria, Harshad; Verbrugge, Mark W.

2014-12-01

301

Natural manganese oxide: Combined analytical approach for solid characterization and arsenic retention  

NASA Astrophysics Data System (ADS)

To understand the retention of As on a natural manganese sand, the structural, textural and chemical properties of the solid were first investigated by combining scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron-energy-loss spectroscopy (EELS), X-ray diffraction (XRD), BET N 2 gas adsorption, diffuse reflectance Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis. Manganese sand could be mainly described as a mixture of a phyllomanganate, lithiophorite [(Al,Li)MnO 2(OH) 2], and pyrolusite (MnO 2). Iron particle, kaolinite and gibbsite type-phases were also observed. Particles organization led to the presence of a mesoporosity with pore diameters ranging from 100 to 200 Å and a specific surface area of 23 m 2 g -1. Contact with an As(V) solution (0.67 mmol L -1) led to an average fractional surface coverage of 0.4. Both As (V) and (III) were present on the surface of the sand in a 1:1 ratio. As(V) was sorbed on lithiophorite-type particles through surface complexation type reaction. As(III) was thought to result from As(V) reduction mechanism on iron particles.

Ouvrard, S.; de Donato, Ph.; Simonnot, M. O.; Begin, S.; Ghanbaja, J.; Alnot, M.; Duval, Y. B.; Lhote, F.; Barres, O.; Sardin, M.

2005-06-01

302

Oxidative aliphatic C-H fluorination with manganese catalysts and fluoride ion  

PubMed Central

Fluorination is a reaction that is useful in improving the chemical stability and changing the binding affinity of biologically active compounds. The protocol described here can be used to replace aliphatic, C(sp3)-H hydrogen in small molecules with fluorine. Notably, isolated methylene groups and unactivated benzylic sites are accessible. The method uses readily available manganese porphyrin and manganese salen catalysts and various fluoride ion reagents, including silver fluoride (AgF), tetrabutylammonium fluoride and triethylamine trihydrofluoride (TREAT·HF), as the source of fluorine. Typically, the reactions afford 50–70% yield of mono-fluorinated products in one step. Two representative examples, the fragrance component celestolide and the nonsteroidal anti-inflammatory drug ibuprofen, are described; they produced useful isolated quantities (250–300 mg, ~50% yield) of fluorinated material over periods of 1–8 h. The procedures are performed in a typical fume hood using ordinary laboratory glassware. No special precautions to rigorously exclude water are required. PMID:24177292

Liu, Wei; Huang, Xiongyi; Groves, John T

2014-01-01

303

Multivariate data analysis approach to understand magnetic properties of perovskite manganese oxides  

SciTech Connect

Here we apply statistical multivariate data analysis techniques to obtain some insights into the complex structure-property relations in antiferromagnetic (AFM) and ferromagnetic (FM) manganese perovskite systems, AMnO{sub 3}. The 131 samples included in the present analyses are described by 21 crystal-structure or crystal-chemical (CS/CC) parameters. Principal component analysis (PCA), carried out separately for the AFM and FM compounds, is used to model and evaluate the various relationships among the magnetic properties and the various CS/CC parameters. Moreover, for the AFM compounds, PLS (partial least squares projections to latent structures) analysis is performed so as to predict the magnitude of the Neel temperature on the bases of the CS/CC parameters. Finally, so-called PLS-DA (PLS discriminant analysis) method is employed to find out the most influential/characteristic CS/CC parameters that differentiate the two classes of compounds from each other. - Graphical abstract: Statistical multivariate data analysis techniques are applied to detect structure-property relations in antiferromagnetic (AFM) and ferromagnetic (FM) manganese perovskites. For AFM compounds, partial least squares projections to latent structures analysis predict the magnitude of the Neel temperature on the bases of structural parameters only. Moreover, AFM and FM compounds are well separated by means of so-called partial least squares discriminant analysis method.

Imamura, N. [Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Laboratory of Inorganic Chemistry, Department of Chemistry, Helsinki University of Technology, FI-02015 TKK (Finland); Mizoguchi, T. [Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Yamauchi, H. [Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Laboratory of Inorganic Chemistry, Department of Chemistry, Helsinki University of Technology, FI-02015 TKK (Finland); Karppinen, M. [Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Laboratory of Inorganic Chemistry, Department of Chemistry, Helsinki University of Technology, FI-02015 TKK (Finland)], E-mail: maarit.karppinen@tkk.fi

2008-05-15

304

Oxidative aliphatic C-H fluorination with manganese catalysts and fluoride ion.  

PubMed

Fluorination is a reaction that is useful in improving the chemical stability and changing the binding affinity of biologically active compounds. The protocol described here can be used to replace aliphatic, C(sp(3))-H hydrogen in small molecules with fluorine. Notably, isolated methylene groups and unactivated benzylic sites are accessible. The method uses readily available manganese porphyrin and manganese salen catalysts and various fluoride ion reagents, including silver fluoride (AgF), tetrabutylammonium fluoride and triethylamine trihydrofluoride (TREAT·HF), as the source of fluorine. Typically, the reactions afford 50-70% yield of mono-fluorinated products in one step. Two representative examples, the fragrance component celestolide and the nonsteroidal anti-inflammatory drug ibuprofen, are described; they produced useful isolated quantities (250-300 mg, ~50% yield) of fluorinated material over periods of 1-8 h. The procedures are performed in a typical fume hood using ordinary laboratory glassware. No special precautions to rigorously exclude water are required. PMID:24177292

Liu, Wei; Huang, Xiongyi; Groves, John T

2013-12-01

305

Degradation of lithium ion batteries employing graphite negatives and nickel-cobalt-manganese oxide + spinel manganese oxide positives: Part 1, aging mechanisms and life estimation  

NASA Astrophysics Data System (ADS)

We examine the aging and degradation of graphite/composite metal oxide cells. Non-destructive electrochemical methods were used to monitor the capacity loss, voltage drop, resistance increase, lithium loss, and active material loss during the life testing. The cycle life results indicated that the capacity loss was strongly impacted by the rate, temperature, and depth of discharge (DOD). Lithium loss and active electrode material loss were studied by the differential voltage method; we find that lithium loss outpaces active material loss. A semi-empirical life model was established to account for both calendar-life loss and cycle-life loss. For the calendar-life equation, we adopt a square root of time relation to account for the diffusion limited capacity loss, and an Arrhenius correlation is used to capture the influence of temperature. For the cycle life, the dependence on rate is exponential while that for time (or charge throughput) is linear.

Wang, John; Purewal, Justin; Liu, Ping; Hicks-Garner, Jocelyn; Soukazian, Souren; Sherman, Elena; Sorenson, Adam; Vu, Luan; Tataria, Harshad; Verbrugge, Mark W.

2014-12-01

306

Melatonin inhibits manganese-induced motor dysfunction and neuronal loss in mice: involvement of oxidative stress and dopaminergic neurodegeneration.  

PubMed

Excessive manganese (Mn) induces oxidative stress and dopaminergic neurodegeneration. However, the relationship between them during Mn neurotoxicity has not been clarified. The purpose of this study was to investigate the probable role of melatonin (MLT) against Mn-induced motor dysfunction and neuronal loss as a result of antagonizing oxidative stress and dopaminergic neurodegeneration. Mice were randomly divided into five groups as follows: control, MnCl2, low MLT?+?MnCl2, median MLT?+?MnCl2, and high MLT?+?MnCl2. Administration of MnCl2 (50 mg/kg) for 2 weeks significantly induced hypokinesis, dopaminergic neurons degeneration and loss, neuronal ultrastructural damage, and apoptosis in the substantia nigra and the striatum. These conditions were caused in part by the overproduction of reactive oxygen species, malondialdehyde accumulation, and dysfunction of the nonenzymatic (GSH) and enzymatic (GSH-Px, superoxide dismutase, quinone oxidoreductase 1, glutathione S-transferase, and glutathione reductase) antioxidative defense systems. Mn-induced neuron degeneration, astrocytes, and microglia activation contribute to the changes of oxidative stress markers. Dopamine (DA) depletion and downregulation of DA transporter and receptors were also found after Mn administration, this might also trigger motor dysfunction and neurons loss. Pretreatment with MLT prevented Mn-induced oxidative stress and dopaminergic neurodegeneration and inhibited the interaction between them. As a result, pretreatment with MLT significantly alleviated Mn-induced motor dysfunction and neuronal loss. In conclusion, Mn treatment resulted in motor dysfunction and neuronal loss, possibly involving an interaction between oxidative stress and dopaminergic neurodegeneration in the substantia nigra and the striatum. Pretreatment with MLT attenuated Mn-induced neurotoxicity by means of its antioxidant properties and promotion of the DA system. PMID:24969583

Deng, Yu; Jiao, Congcong; Mi, Chao; Xu, Bin; Li, Yuehui; Wang, Fei; Liu, Wei; Xu, Zhaofa

2015-02-01

307

Manganese oxide-based multifunctionalized mesoporous silica nanoparticles for pH-responsive MRI, ultrasonography and circumvention of MDR in cancer cells.  

PubMed

Nano-biotechnology has been introduced into cancer theranostics by engineering a new generation of highly versatile hybrid mesoporous composite nanocapsules (HMCNs) for manganese-based pH-responsive dynamic T(1)-weighted magnetic resonance imaging (MRI) to efficiently respond and detect the tumor acidic microenvironment, which was further integrated with ultrasonographic function based on the intrinsic unique hollow nanostructures of HMCNs for potentially in vitro and in vivo dual-modality cancer imaging. The manganese oxide-based multifunctionalization of hollow mesoporous silica nanoparticles was achieved by an in situ redox reaction using mesopores as the nanoreactors. Due to the dissolution nature of manganese oxide nanoparticles under weak acidic conditions, the relaxation rate r(1) of manganese-based mesoporous MRI-T(1) contrast agents (CAs) could reach 8.81 mM(-1)s(-1), which is a 11-fold magnitude increase compared to the neutral condition, and is almost two times higher than commercial Gd(III)-based complex agents. This is also the highest r(1) value ever reported for manganese oxide nanoparticles-based MRI-T(1) CAs. In addition, the hollow interiors and thin mesoporous silica shells endow HMCNs with the functions of CAs for efficient in vitro and in vivo ultrasonography under both harmonic- and B-modes. Importantly, the well-defined mesopores and large hollow interiors of HMCNs could encapsulate and deliver anticancer agents (doxorubicin) intracellularly to circumvent the multidrug resistance (MDR) of cancer cells and restore the anti-proliferative effect of drugs by nanoparticle-mediated endocytosis process, intracellular drug release and P-gp inhibition/ATP depletion in cancer cells. PMID:22789722

Chen, Yu; Yin, Qi; Ji, Xiufeng; Zhang, Shengjian; Chen, Hangrong; Zheng, Yuanyi; Sun, Yang; Qu, Haiyun; Wang, Zheng; Li, Yaping; Wang, Xia; Zhang, Kun; Zhang, Linlin; Shi, Jianlin

2012-10-01

308

An aqueous method for the controlled manganese (Mn(2+)) substitution in superparamagnetic iron oxide nanoparticles for contrast enhancement in MRI.  

PubMed

Despite the success in the use of superparamagnetic iron oxide nanoparticles (SPION) for various scientific applications, its potential in biomedical fields has not been exploited to its full potential. In this context, an in situ substitution of Mn(2+) was performed in SPION and a series of ferrite particles, MnxFe1-xFe2O4 with a varying molar ratio of Mn(2+)?:?Fe(2+) where 'x' varies from 0-0.75. The ferrite particles obtained were further studied in MRI contrast applications and showed appreciable enhancement in their MRI contrast properties. Manganese substituted ferrite nanocrystals (MnIOs) were synthesized using a novel, one-step aqueous co-precipitation method based on the use of a combination of sodium hydroxide and trisodium citrate (TSC). This approach yielded the formation of highly crystalline, superparamagnetic MnIOs with good control over their size and bivalent Mn ion crystal substitution. The presence of a TSC hydrophilic layer on the surface facilitated easy dispersion of the materials in an aqueous media. Primary characterizations such as structural, chemical and magnetic properties demonstrated the successful formation of manganese substituted ferrite. More significantly, the MRI relaxivity of the MnIOs improved fourfold when compared to SPION crystals imparting high potential for use as an MRI contrast agent. Further, the cytocompatibility and blood compatibility evaluations demonstrated excellent cell morphological integrity even at high concentrations of nanoparticles supporting the non-toxic nature of nanoparticles. These results open new horizons for the design of biocompatible water dispersible ferrite nanoparticles with good relaxivity properties via a versatile and easily scalable co-precipitation route. PMID:25586703

Ereath Beeran, Ansar; Nazeer, Shaiju S; Fernandez, Francis Boniface; Muvvala, Krishna Surendra; Wunderlich, Wilfried; Anil, Sukumaran; Vellappally, Sajith; Ramachandra Rao, M S; John, Annie; Jayasree, Ramapurath S; Harikrishna Varma, P R

2015-01-28

309

In-situ X-Ray Absorption Spectroscopy (XAS) Investigation of a Bifunctional Manganese Oxide Catalyst with High Activity for Electrochemical Water Oxidation and Oxygen Reduction  

PubMed Central

In-situ x-ray absorption spectroscopy (XAS) is a powerful technique that can be applied to electrochemical systems, with the ability to elucidate the chemical nature of electrocatalysts under reaction conditions. In this study, we perform in-situ XAS measurements on a bifunctional manganese oxide (MnOx) catalyst with high electrochemical activity for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Using x-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS), we find that exposure to an ORR-relevant potential of 0.7 V vs. RHE produces a disordered Mn3II,III,IIIO4 phase with negligible contributions from other phases. After the potential is increased to a highly anodic value of 1.8 V vs. RHE, relevant to the OER, we observe an oxidation of approximately 80% of the catalytic thin film to form a mixed MnIII,IV oxide, while the remaining 20% of the film consists of a less oxidized phase, likely corresponding to unchanged Mn3II,III,IIIO4. XAS and electrochemical characterization of two thin film catalysts with different MnOx thicknesses reveals no significant influence of thickness on the measured oxidation states, at either ORR or OER potentials, but demonstrates that the OER activity scales with film thickness. This result suggests that the films have porous structure, which does not restrict electrocatalysis to the top geometric layer of the film. As the portion of the catalyst film that is most likely to be oxidized at the high potentials necessary for the OER is that which is closest to the electrolyte interface, we hypothesize that the MnIII,IV oxide, rather than Mn3II,III,IIIO4, is the phase pertinent to the observed OER activity. PMID:23758050

Benck, Jesse D.; Gul, Sheraz; Webb, Samuel M.; Yachandra, Vittal K.; Yano, Junko; Jaramillo, Thomas F.

2013-01-01

310

In situ X-ray absorption spectroscopy investigation of a bifunctional manganese oxide catalyst with high activity for electrochemical water oxidation and oxygen reduction.  

PubMed

In situ X-ray absorption spectroscopy (XAS) is a powerful technique that can be applied to electrochemical systems, with the ability to elucidate the chemical nature of electrocatalysts under reaction conditions. In this study, we perform in situ XAS measurements on a bifunctional manganese oxide (MnOx) catalyst with high electrochemical activity for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Using X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), we find that exposure to an ORR-relevant potential of 0.7 V vs RHE produces a disordered Mn3(II,III,III)O4 phase with negligible contributions from other phases. After the potential is increased to a highly anodic value of 1.8 V vs RHE, relevant to the OER, we observe an oxidation of approximately 80% of the catalytic thin film to form a mixed Mn(III,IV) oxide, while the remaining 20% of the film consists of a less oxidized phase, likely corresponding to unchanged Mn3(II,III,III)O4. XAS and electrochemical characterization of two thin film catalysts with different MnOx thicknesses reveals no significant influence of thickness on the measured oxidation states, at either ORR or OER potentials, but demonstrates that the OER activity scales with film thickness. This result suggests that the films have porous structure, which does not restrict electrocatalysis to the top geometric layer of the film. As the portion of the catalyst film that is most likely to be oxidized at the high potentials necessary for the OER is that which is closest to the electrolyte interface, we hypothesize that the Mn(III,IV) oxide, rather than Mn3(II,III,III)O4, is the phase pertinent to the observed OER activity. PMID:23758050

Gorlin, Yelena; Lassalle-Kaiser, Benedikt; Benck, Jesse D; Gul, Sheraz; Webb, Samuel M; Yachandra, Vittal K; Yano, Junko; Jaramillo, Thomas F

2013-06-12

311

Complete oxidation of solid phase sulfides by manganese and bacteria in anoxic marine sediments  

SciTech Connect

During the physical or biological reworking of surficial marine sediments, metal oxides are often brought into contact with both solid and dissolved sulfides. Experiments simulating these mixing processes demonstrate that in natural sediments Mn-oxides can completely oxidize solid phase sulfides to SO{sup =}{sub 4} under anoxic conditions. The major source of sulfur is probably acid volatile sulfide. Minerals containing Mn{sup +4} are apparently more effective than Mn{sup +3} in driving the oxidation. There is slight or no evidence for complete sulfide oxidation by Fe-oxides under similar conditions. The reaction is inhibited by DNP (dinitrophenol) and Azide, implying biological mediation by a group of chemolithotrophic bacteria such as the thiobacilli, having a well-organized cytochrome system, oxidative phosphorylation coupled with sulfide oxidation, and possibly autotrophic CO{sub 2} fixation. Lack of sensitivity to chlorate suggests that a NO{sup {minus}}{sub 3} reductase complex is not involved. Because of metal reduction and the overall stoichiometry of reaction, this sulfide oxidation causes a rise in pH in contrast to oxidation by O{sub 2}. Alkalinity is also simultaneously depleted by Mn, Ca carbonate precipitation. Both manganoan kutnahorite and manganoan calcite are observed to form rapidly (days) during Mn reduction. The oxidation of sulfides by Mn-oxides is likely to be important, but highly variable, in organic-rich shelf sediments and environments such as hydrothermal vents where sulfidic plumes contact oxidized metals. A substantial proportion of sedimentary sulfide may be oxidized and Mn reduced by this pathway, particularly in bioturbated sediments. The relative roles of lithotrophic (S) and heterotrophic (C) Mn-reduction in marine sediments are presently unknown.

Aller, R.C.; Rude, P.D. (State Univ. of New York, Stony Brook (USA))

1988-03-01

312

Complete oxidation of solid phase sulfides by manganese and bacteria in anoxic marine sediments  

NASA Astrophysics Data System (ADS)

During the physical or biological reworking of surficial marine sediments, metal oxides are often brought into contact with both solid and dissolved sulfides. Experiments simulating these mixing processes demonstrate that in natural sediments Mn-oxides can completely oxidize solid phase sulfides to SO 4- under anoxic conditions. The major source of sulfur is probably acid volatile sulfide. Minerals containing Mn +4 are apparently more effective than Mn +3 in driving the oxidation. There is slight or no evidence for complete sulfide oxidation by Fe-oxides under similar conditions. The reaction is inhibited by DNP (dinitrophenol) and azide, implying biological mediation by a group of chemolithotrophic bacteria such as the thiobacilli, having a well-organized cytochrome system, oxidative phosphorylation coupled with sulfide oxidation, and possibly aulolrophic CO 2 fixation. Lack of sensitivity to chlorate suggests that a No 3- reductase complex is not involved. Because of metal reduction and the overall stoichiometry of reaction, this sulfide oxidation causes a rise in pH in contrast to oxidation by O 2. Alkalinity is also simultaneously depeleted by Mn, Ca carbonate precipitation. Both manganoan kutnahorite and manganoan calcite are observed to form rapidly (days) during Mn reduction. The oxidation of sulfides by Mn-oxides is likely to be important, but highly variable, in organic-rich shelf sediments and environments such as hydrothermal vents where sulfidic plumes contact oxidized metals. A substantial Proportion of sedimentary sulfide may be oxidized and Mn reduced by this pathway, particularly in bioturbated sediments. The relative roles of lithotrophic (S) and heterotrophic (C) Mn-reduction in marine sediments are presently unknown.

Aller, Robert C.; Rude, Peter D.

1988-03-01

313

Single pot synthesis of pyridine-N-oxide based polymeric complexes of cadmium and manganese: Crystal structure and luminescence property  

NASA Astrophysics Data System (ADS)

Two new polymeric complexes of cadmium(II) and manganese(II) with Pyridine-N-oxide (pyo) mediated by thiocyanate and dicyanamide (dca) anions have been synthesized and characterized by X-ray single crystal structure analysis. The structural analyses reveal that complexes [Cd(pyo)2(SCN)2]n (1) and [Mn(pyo)2(dca)2]n (2) [where, pyo = pyridine-N-oxide; dca = dicyanamide] are 2D coordination polymers. In complex 1 hexa-coordinated Cd(II) centers posses distorted octahedral coordination environments. Each Cd(II) is coordinated by four SCN- in end to end fashion forming a zigzag chain and two pyo monodentate ligands bridge two adjacent Cd(II) centers leading to a two-dimensional sheet structure. In complex 2 hexa-coordinated Mn(II) centers posses octahedral coordination environments. The coordination polymer constitute a 2D polymeric sheet and has a (4, 4) grid network architecture Successive stacking of coordination polymeric sheets are enforced by inter layer OH⋯O and OH⋯N hydrogen bonding. The luminescence properties of these two polynuclear complexes in solid state were studied and complex 1 exhibits higher luminescence intensity than 2.

Mondal, Sandip; Guha, Averi; Suresh, Eringathodi; Jana, Atish Dipankar; Banerjee, Arpita

2012-12-01

314

Preparation of highly active manganese oxides supported on functionalized MWNTs for low temperature NOx reduction with NH3  

NASA Astrophysics Data System (ADS)

Manganese oxide catalysts (MnOx) supported on functionalized multi-walled carbon nanotubes (FMWNTs) for low temperature selective catalytic reduction (LTSCR) of nitrogen oxides (NOx) with NH3 in the presence of excess O2 were prepared by the incipient wetness impregnation method. These catalysts were characterized by N2 adsorption, Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and H2-temperature programmed reduction (H2-TPR) methods. The effects of reaction temperature, MnOx loading, calcination temperature and calcination time were investigated. The presence of surface nitrate species under moderate calcination conditions may play a favorable role in the LTSCR of NOx with NH3. Under the reaction conditions of 200 °C, 1 bar, NO = NH3 = 900 ppm, O2 = 5 vol%, GHSV = 30,000 h-1 and 12 wt% MnOx, NOx conversion and N2 selectivity were 97% and 99.5%, respectively. The SCR activity was reduced in the presence of 100 ppm SO2 and 2.5 vol% H2O from 97% to 92% within 6 h at 200 °C, however such an effect was shown to be reversible by exposing the catalyst to a helium flow for 2 h at 350 °C due to thermal decomposition of ammonium sulphate salts.

Pourkhalil, Mahnaz; Moghaddam, Abdolsamad Zarringhalam; Rashidi, Alimorad; Towfighi, Jafar; Mortazavi, Yadollah

2013-08-01

315

Characterization of a mitochondrial manganese superoxide dismutase gene from Apis cerana cerana and its role in oxidative stress.  

PubMed

Mitochondrial manganese superoxide dismutase (mMnSOD) plays a vital role in the defense against reactive oxygen species (ROS) in eukaryotic mitochondria. In this study, we isolated and identified a mMnSOD gene from Apis cerana cerana, which we named AccSOD2. Several putative transcription factor-binding sites were identified within the 5'-flanking region of AccSOD2, which suggests that AccSOD2 may be involved in organismal development and/or environmental stress responses. Quantitative real-time PCR analysis showed that AccSOD2 is highly expressed in larva and pupae during different developmental stages. In addition, the expression of AccSOD2 could be induced by cold (4 °C), heat (42 °C), H2O2, ultraviolet light (UV), HgCl2, and pesticide treatment. Using a disc diffusion assay, we provide evidence that recombinant AccSOD2 protein can play a functional role in protecting cells from oxidative stress. Finally, the in vivo activities of AccSOD2 were measured under a variety of stressful conditions. Taken together, our results indicate that AccSOD2 plays an important role in cellular stress responses and anti-oxidative processes and that it may be of critical importance to honeybee survival. PMID:24269344

Jia, Haihong; Sun, Rujiang; Shi, Weina; Yan, Yan; Li, Han; Guo, Xingqi; Xu, Baohua

2014-01-01

316

Geology, Geochemistry and Re-Os systematics of manganese deposits from the Santa Rosalía Basin and adjacent areas in Baja California Sur, México  

NASA Astrophysics Data System (ADS)

The manganese ores in the Santa Rosalía region, western Mexico, are mainly stratiform horizons or mantos, constrained to the initial stages of sedimentary cycles of the Miocene Boléo Formation. The manganese mineralization is generally restricted to isolated paleo-basins and related to NW-SE faults formed during the early stages of the opening of the Gulf of California. Jasper, Fe, and Mn oxides associated to the NW-SE structures may represent feeder zones for the mineralized system. The manganese oxide minerals include pyrolusite, cryptomelane, todorokite, hollandite, jacobsite, and pyrochroite. Trace elements in the manganese ores indicate a hydrothermal origin for the deposits of the Santa Rosalía area. Rare earth elements (REE) patterns obtained for manganese minerals from the Lucifer and El Gavilán deposits also support a hydrothermal origin, whereas the middle REE enrichment observed in samples from the Boléo district indicates mixing between hydrothermal and hydrogenous sources. Osmium and rhenium concentrations of the manganese minerals range between 33-173 ppt and 0.14-89 ppb, respectively. The initial 187Os/188Os ratios in the manganese oxides from Lucifer and the Boléo district range between 0.43 to 0.51 and 0.70 to 0.74, respectively. These ratios are different from seawater at 7 Ma (0.84-0.89), which suggests important contributions of osmium from underlying rocks such as the Miocene volcanic rocks and the Cretaceous quartz-monzonite basement. Field evidence, manganese oxide mineralogy coupled with major and trace element geochemistry and Re-Os systematics support a hydrothermal origin for the manganese deposits from the Santa Rosalía region. The ore deposition style indicates an exhalative-intraformational environment restricted to isolated basins in a diagenetic stage related to the initial evolution of the Gulf of California.

Del Rio Salas, R.; Ruiz, J.; Ochoa-Landín, L.; Noriega, O.; Barra, F.; Meza-Figueroa, D.; Paz-Moreno, F.

2008-06-01

317

PerR-Regulated Manganese Ion Uptake Contributes to Oxidative Stress Defense in an Oral Streptococcus  

PubMed Central

Metal homeostasis plays a critical role in antioxidative stress. Streptococcus oligofermentans, an oral commensal facultative anaerobe lacking catalase activity, produces and tolerates abundant H2O2, whereas Dpr (an Fe2+-chelating protein)-dependent H2O2 protection does not confer such high tolerance. Here, we report that inactivation of perR, a peroxide-responsive repressor that regulates zinc and iron homeostasis in Gram-positive bacteria, increased the survival of H2O2-pulsed S. oligofermentans 32-fold and elevated cellular manganese 4.5-fold. perR complementation recovered the wild-type phenotype. When grown in 0.1 to 0.25 mM MnCl2, S. oligofermentans increased survival after H2O2 stress 2.5- to 23-fold, and even greater survival was found for the perR mutant, indicating that PerR is involved in Mn2+-mediated H2O2 resistance in S. oligofermentans. Mutation of mntA could not be obtained in brain heart infusion (BHI) broth (containing ?0.4 ?M Mn2+) unless it was supplemented with ?2.5 ?M MnCl2 and caused 82 to 95% reduction of the cellular Mn2+ level, while mntABC overexpression increased cellular Mn2+ 2.1- to 4.5-fold. Thus, MntABC was identified as a high-affinity Mn2+ transporter in S. oligofermentans. mntA mutation reduced the survival of H2O2-pulsed S. oligofermentans 5.7-fold, while mntABC overexpression enhanced H2O2-challenged survival 12-fold, indicating that MntABC-mediated Mn2+ uptake is pivotal to antioxidative stress in S. oligofermentans. perR mutation or H2O2 pulsing upregulated mntABC, while H2O2-induced upregulation diminished in the perR mutant. This suggests that perR represses mntABC expression but H2O2 can release the suppression. In conclusion, this work demonstrates that PerR regulates manganese homeostasis in S. oligofermentans, which is critical to H2O2 stress defenses and may be distributed across all oral streptococci lacking catalase. PMID:24487543

Wang, Xinhui; Dong, Xiuzhu

2014-01-01

318

Determining the Role of Multicopper Oxidases in Manganese(II) Oxidation by Marine Bacillus Spores  

NASA Astrophysics Data System (ADS)

Bacteria play an important role in the environmental cycling of Mn by oxidizing soluble Mn(II) and forming insoluble Mn(III/IV) oxides. These biogenic Mn oxides are renowned for their strong sorptive and oxidative properties, which control the speciation and availability of many metals and organic compounds. A wide variety of bacteria are known to catalyze the oxidation of Mn(II); one of the most frequently isolated types are Bacillus species that oxidize Mn(II) only as metabolically dormant spores. We are using genetic and biochemical methods to study the molecular mechanisms of this process in these organisms. mnxG, a gene related to the multicopper oxidase (MCO) family of enzymes, is required for Mn(II) oxidation in the model organism, Bacillus sp. strain SG-1. Mn(II)-oxidizing activity can be detected in crude protein extracts of the exosporium and as a discrete band in SDS-PAGE gels, however previous attempts to purify or identify this Mn(II)-oxidizing enzyme have failed. A direct link between the Mn(II)-oxidizing enzyme and the MCO gene suspected to encode it has never been made. We used genetic and biochemical methods to investigate the role of the MCO in the mechanism of Mn(II) oxidation. Comparative analysis of the mnx operon from several diverse Mn(II)-oxidizing Bacillus spores revealed that mnxG is the most highly conserved gene in the operon, and that copper binding sites are highly conserved. As with Mn(II) oxidases from other organisms, heterologous expression of the Bacillus mnxG in E. coli did not yield an active Mn(II) oxidase. Purifying sufficient quantities of the native Mn(II) oxidase from Bacillus species for biochemical characterization has proven difficult because the enzyme does not appear to be abundant, and it is highly insoluble. We were able to partially purify the Mn(II) oxidase, and to analyze the active band by in-gel trypsin digestion followed by tandem mass spectrometry (MS/MS). MS/MS spectra provided a conclusive match to mnxG, suggesting that this MCO directly catalyzes the oxidation of Mn(II) and the precipitation of Mn(IV) oxide, which represents a novel reaction for a MCO. MS/MS analysis of bands identified by in-gel activity assays is a powerful method of identifying novel enzymes responsible for geochemical processes.

Dick, G. J.; Tebo, B. M.

2005-12-01

319

Thermal chemistry of Mn{sub 2}(CO){sub 10} during deposition of thin manganese films on silicon oxide and on copper surfaces  

SciTech Connect

The surface chemistry of dimanganese decacarbonyl on the native oxide of Si(100) wafers was characterized with the aid of x-ray photoelectron spectroscopy. Initial experiments in a small stainless-steel reactor identified a narrow range of temperatures, between approximately 445 and 465 K, in which the deposition of manganese could be achieved in a self-limiting fashion, as is desirable for atomic layer deposition. Deposition at higher temperatures leads to multilayer growth, but the extent of this Mn deposition reverses at even higher temperatures (about 625 K), and also ifhydrogen is added to the reaction mixture. Extensive decarbonylation takes place below room temperature, but limited C-O bond dissociation and carbon deposition are still seen after high exposures at 625 K. The films deposited at low ({approx}450 K) temperatures are mostly in the form of MnO, but at 625 K that converts to a manganese silicate, and upon higher doses a manganese silicide forms at the SiO{sub 2}/Si(100) interface as well. No metallic manganese could be deposited with this precursor on either silicon dioxide or copper surfaces.

Qin Xiangdong; Sun Huaxing; Zaera, Francisco [Department of Chemistry, University of California, Riverside, California 92521 (United States)

2012-01-15

320

Atomistic Simulation Study of Lithium Manganese Oxides for Li-Ion Batteries  

NASA Astrophysics Data System (ADS)

Simulated amorphisation recrystallisation (A+R) technique has been successfully used to generate models of various nano-forms of the complex manganese dioxides [1]. We apply the method to study lithium insertion into the nano - spheres, sheets, rods and porous structures of the binary MnO2. The variation of mechanical properties and microstructural features with lithium concentration are investigated. The bulk ternary Li2MnO3 provides structural integrity for lithium-ion battery cathodes and is electrochemically inactive. The nanocrystalline Li2MnO3 has a structure similar to that of the bulk, but shows different lithium intercalation properties [2]. We simulated such a nanophase by the A+R method, and the resulting microstructures provide insights into the origins of the electrochemical activity which renders it suitable for battery electrodes. [4pt] [1]. T.X.T. Sayle, R.R. Maphanga, P.E. Ngoepe, and D.C. Sayle, J. Am. Chem. Soc., 131, 6161, (2009).[0pt] [2]. G. Jain, J. Yang, M. Balasubramanian and J,J. Xu, Chem. Mater. 17, 3850, (2005)

Ngoepe, Phuti; Kgatwane, Kenneth; Maphanga, Rapela; Sayle, Thi; Sayle, Dean

2011-03-01

321

Oxidation state of manganese in zinc pyrophosphate: Probed by luminescence and EPR studies  

SciTech Connect

Zn{sub 2}P{sub 2}O{sub 7}: Mn was synthesized by wet chemical route and characterized by X-ray diffraction (XRD), photoluminescence (PL) and electron paramagnetic resonance (EPR) techniques. Photoluminescence spectrum shows two bands, one at 500 nm (green emission), which is attributed to the {sup 4}T{sub 1}({sup 4}G)-{sup 6}A{sub 1}({sup 6}S) transition of Mn{sup 2+} and other centered at 686 nm (red emission) is attributed to the electronic transition between {sup 2}E and {sup 4}A{sub 2} of Mn{sup 4+} accompanied with vibronic transitions. EPR spectroscopic studies also confirmed the presence of both Mn2+ and Mn4+ ions in zinc pyrophosphate with difference in the number of fine transitions and g values (Mn{sub 4+}, S=3/2, three fine transitions and g < 2.00; Mn{sup 2+} S=5/2, five fine transitions and g=2.00).Mn{sup 2+} is attributed to presence of Mn at 6-ccordinated Zn{sup 2+} site whereas Mn{sup 4+} is due to presence substitution of Mn{sup 4+} at Zn{sup 2+} site thereby invoking charge compensation by presence of interstitial oxygen ions around Mn{sup 4+} ion or due to substitution of manganese at distorted 5-coordinated zinc site.

Gupta, Santosh K., E-mail: santoshg@barc.gov.in; Kadam, R. M., E-mail: santoshg@barc.gov.in; Natarajan, V., E-mail: santoshg@barc.gov.in; Godbole, S. V., E-mail: santoshg@barc.gov.in [Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

2014-04-24

322

Biodiesel Synthesis Catalyzed by Transition Metal Oxides: Ferric-Manganese Doped Tungstated/ Molybdena Nanoparticle Catalyst.  

PubMed

The solid acid Ferric-manganese doped tungstated/molybdena nananoparticle catalyst was prepared via impregnation reaction followed by calcination at 600? for 3 h. The characterization was done using X-ray diffraction (XRD), Raman spectroscopy, thermal gravimetric analysis (TGA), temperature programmed desorption of NH3 (TPD-NH3), X-ray fluorescence (XRF), Transmission electron microscope (TEM) and Brunner-Emmett-Teller surface area measurement (BET). Moreover, dependence of biodiesel yield on the reaction variables such as the reaction temperature, catalyst loading, as well as molar ratio of methanol/oil and reusability were also appraised. The catalyst was reused six times without any loss in activity with maximum yield of 92.3% ±1.12 achieved in the optimized conditions of reaction temperature of 200?; stirring speed of 600 rpm, 1:25 molar ratio of oil to alcohol, 6 % w/w catalyst loading as well as 8 h as time of the reaction. The fuel properties of WCOME's were evaluated, including the density, kinematic viscosity, pour point, cloud point and flash point whereas all properties were compared with the limits in the ASTM D6751 standard. PMID:25492234

Alhassan, Fatah Hamid; Rashid, Umer; Taufiq-Yap, Yun Hin

2014-12-10

323

Enzymatic Manganese(II) Oxidation by Metabolically Dormant Spores of Diverse Bacillus Species  

PubMed Central

Bacterial spores are renowned for their longevity, ubiquity, and resistance to environmental insults, but virtually nothing is known regarding whether these metabolically dormant structures impact their surrounding chemical environments. In the present study, a number of spore-forming bacteria that produce dormant spores which enzymatically oxidize soluble Mn(II) to insoluble Mn(IV) oxides were isolated from coastal marine sediments. The highly charged and reactive surfaces of biogenic metal oxides dramatically influence the oxidation and sorption of both trace metals and organics in the environment. Prior to this study, the only known Mn(II)-oxidizing sporeformer was the marine Bacillus sp. strain SG-1, an extensively studied bacterium in which Mn(II) oxidation is believed to be catalyzed by a multicopper oxidase, MnxG. Phylogenetic analysis based on 16S rRNA and mnxG sequences obtained from 15 different Mn(II)-oxidizing sporeformers (including SG-1) revealed extensive diversity within the genus Bacillus, with organisms falling into several distinct clusters and lineages. In addition, active Mn(II)-oxidizing proteins of various sizes, as observed in sodium dodecyl sulfate-polyacrylamide electrophoresis gels, were recovered from the outer layers of purified dormant spores of the isolates. These are the first active Mn(II)-oxidizing enzymes identified in spores or gram-positive bacteria. Although extremely resistant to denaturation, the activities of these enzymes were inhibited by azide and o-phenanthroline, consistent with the involvement of multicopper oxidases. Overall, these studies suggest that the commonly held view that bacterial spores are merely inactive structures in the environment should be revised. PMID:11823231

Francis, Chris A.; Tebo, Bradley M.

2002-01-01

324

Manganese oxidation in pH and O2 microenvironments produced by phytoplankton  

NASA Technical Reports Server (NTRS)

This paper reports on the oxidation of Mn(II) by pure cultures of Chlorella. It is shown that these cultures establish strong microgradients of pH and O2 concentration due to their photosynthetic activity, and it is demonstrated that Mn oxidation in the pelagic zone of Oneida Lake, New York, is limited to a microzone of high pH and O2 associated with the near-surface aggregates of phytoplankton cells. The data suggest that visible light is important in catalyzing Mn oxidation by driving the photosynthetic removal of CO2 with concomitant increases in pH.

Richardson, Laurie L.; Aguilar, Carmen; Nealson, Kenneth H.

1988-01-01

325

Synthesis and Microstructural Characterization of Manganese Oxide Electrodes for Application as Electrochemical Supercapacitors  

NASA Astrophysics Data System (ADS)

The aim of this thesis work was to synthesize Mn-based oxide electrodes with high surface area structures by anodic electrodeposition for application as electrochemical capacitors. Rod-like structures provide large surface areas leading to high specific capacitances. Since templated electrosynthesis of rods is not easy to use in practical applications, it is more desirable to form rod-like structures without using any templates. In this work, Mn oxide electrodes with rod-like structures (˜1.5 µm in diameter) were synthesized from a solution of 0.01 M Mn acetate under galvanostatic control without any templates, on Au coated Si substrates. The electrochemical properties of the synthesized nanocrystalline electrodes were investigated to determine the effect of morphology, chemistry and crystal structure on the corresponding electrochemical behavior of Mn oxide electrodes. Mn oxides prepared at different current densities showed a defective antifluoritetype crystal structure. The rod-like Mn oxide electrodes synthesized at low current densities (5 mAcm.2) exhibited a high specific capacitance due to their large surface areas. Also, specific capacity retention after 250 cycles in an aqueous solution of 0.5 M Na2SO4 at 100 mVs -1 was about 78% of the initial capacity (203 Fg-1 ). To improve the electrochemical capacitive behavior of Mn oxide electrodes, a sequential approach and a one-step method were adopted to synthesize Mn oxide/PEDOT electrodes through anodic deposition on Au coated Si substrates from aqueous solutions. In the former case, free standing Mn oxide rods (about 10 µm long and less than 1.5 µm in diameter) were first synthesized, then coated by electro-polymerization of a conducting polymer (PEDOT) giving coaxial rods. The one-step, co-electrodeposition method produced agglomerated Mn oxide/PEDOT particles. The electrochemical behavior of the deposits depended on the morphology and crystal structure of the fabricated electrodes, which were affected by the composition and pH of the electrolyte, temperature, current density and polymer deposition time. Mn oxide/PEDOT coaxial core/shell rods consisted of MnO2 with an antifluorite-type structure coated with amorphous PEDOT. The Mn oxide/PEDOT coaxial core/shell electrodes prepared by the sequential method showed significantly better specific capacity and redox performance properties relative to both uncoated Mn oxide rods and co- electrodeposited Mn oxide/PEDOT electrodes. The best specific capacitance for Mn oxide/PEDOT rods produced sequentially was ˜295 F g-1 with ˜92% retention after 250 cycles in 0.5 M Na2SO4 at 100 mV s-1. To further improve the electrochemical capacitive behavior of Mn oxide electrodes, Co-doped and Fe-doped Mn oxide electrodes with a rod-like morphology and antifluorite-type crystal structure were synthesized by anodic electrodeposition, on Au coated Si substrates, from dilute solutions of Mn acetate and Co sulphate and Mn acetate and Fe chloride. Also, Mn-Co oxide/PEDOT coaxial core/shell rods were synthesized by applying a shell of PEDOT on Mn-Co oxide electrodes. Mn-Co oxide/PEDOT electrodes consisted of MnO2, with partial Co 2+ and Co3+ ion substitution for Mn4+, and amorphous PEDOT. Mn-Fe oxide electrodes consisted of MnO2, with partial Fe2+ and Fe3+ ion substitution for Mn4+. Electrochemical analysis showed that the capacitance values for all deposits increased with increasing scan rate to 100 mVs -1, and then decreased after 100 mVs-1. The Mn-Co oxide/PEDOT electrodes showed improved specific capacity and electrochemical cyclability relative to uncoated Mn-Co oxides and Mn-Fe oxides. Mn-Co oxide/PEDOT electrodes with rod-like structures had high capacitances (up to 310 Fg -1) at a scan rate of 100 mVs-1 and maintained their capacitance after 500 cycles in 0.5 M Na2SO4 (91% retention). Capacitance reduction for the deposits was mainly due to the loss of Mn ions by dissolution in the electrolyte solution. To better understand the nucleation and growth mechanisms of Mn oxide electrodes, the effects of supersaturation ratio on the

Babakhani, Banafsheh

326

Redox processes at surfaces of manganese oxide and their effects on aqueous metal ions  

USGS Publications Warehouse

Mn oxides precipitated from aerated solutions of Mn2+ by raising the pH are reported in various publications to have the approximate composition Mn3O4 or MnOOH. These oxyhydroxides in turn can disproportionate to Mn2+ and MnO2 resulting in a substantial decrease in equilibrium Mn solubility. The disproportionation can catalyze the oxidation of Mn2+ and other metals by facilitating electron-transfer processes. Diversion of some electron transfers from Mn species to other metal ions can greatly decrease the equilibrium solubility of Co, Pb, Ni and some other elements in the presence of mixed-valence Mn oxides. Some scavenging and coprecipitation effects involving Mn oxides may be attributable to redox processes. Equilibrium solubilities for Mn, Co and Pb are summarized in four graphs. ?? 1978.

Hem, J.D.

1978-01-01

327

Distribution and speciation of trace elements in iron and manganese oxide cave deposits  

SciTech Connect

Fe and Mn oxide minerals control the distribution and speciation of heavy metals and trace elements in soils and aquatic systems through chemical mechanisms involving adsorption, incorporation, and electron transfer. The Pautler Cave System in Southwest Illinois, an analog to other temperate carbonate-hosted karst systems, contains Fe and Mn oxide minerals that form in multiple depositional environments and have high concentrations of associated trace elements. Synchrotron-based micro-scanning X-ray fluorescence ({mu}-SXRF) shows unique spatial distributions of Fe, Mn, and trace elements in mineral samples. Profile maps of Mn oxide cave stream pebble coatings show Fe- and As-rich laminations, indicating dynamic redox conditions in the cave stream. {mu}-SXRF maps demonstrate that Ni, Cu, and Zn correlate primarily with Mn whereas As correlates with both Mn and Fe; As is more enriched in the Fe phase. Zn is concentrated in the periphery of Mn oxide stream pebble coatings, and may be an indication of recent anthropogenic surface activity. X-ray absorption fine structure spectroscopy measurements reveal that As(V) occurs as surface complexes on Mn and Fe oxides whereas Zn(II) associated with Mn oxides is adsorbed to the basal planes of phyllomanganates in a tetrahedral coordination. Co(III) and Se(IV) are also observed to be associated with Mn oxides. The observation of Fe, Mn, and trace element banding in Mn oxide cave stream pebble coatings suggests that these materials are sensitive to and document aqueous redox conditions, similar to ferromanganese nodules in soils and in marine and freshwater sediments. Furthermore, speciation and distribution measurements indicate that these minerals scavenge trace elements and limit the transport of micronutrients and contaminants in karst aquifer systems while also potentially recording changes in anthropogenic surface activity and land-use.

Frierdich, Andrew J.; Catalano, Jeffrey G. (WU)

2012-10-24

328

Thermodynamic analysis of the reaction of vanadium oxides with oxides of sodium, potassium, calcium, barium, and manganese  

Microsoft Academic Search

The current global structure of iron and vanadium production is based on the processing of titanomagnetites to obtain, successively, hot metal, steel, vanadium converter slag, and vanadium oxide. In Russia, the production of vanadium oxide has been repeatedly improved. In 1936, at Chusov Metallurgical Plant (now OAO Chusovskoi Metallurgicheskii Zavod), sylvinite was used. In 1978, it was replaced by soda,

V. V. Vdovin; A. I. Edil’baev; V. A. Kozlov; A. A. Karpov; V. A. Spitsyn; A. Zh. Terlikbaeva; A. A. Pechenkina

2007-01-01

329

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

E-print Network

ENVR Dionysios Dionysiou Wednesday, August 22, 2012 261 - Arsenic mobilization in the critical zone. Lafferty2, Donald L. Sparks1. (1) Department of Plant and Soil Sciences and the Center for Critical Zone) oxides to oxidize trace metals such as arsenic from the mobile and toxic arsenite [As(III)], to a less

Sparks, Donald L.

330

Electrochemical and structural characterization of titanium-substituted manganese oxides based on Na0.44MnO2  

SciTech Connect

A series of titanium-substituted manganese oxides, Li{sub x}Ti{sub y}Mn{sub 1-y}O{sub 2} (y = 0.11, 0.22, 0.33, 0.44, and 0.55) with the Na{sub 0.44}MnO{sub 2} structure were prepared from Na{sub x}Ti{sub y}Mn{sub 1-y}O{sub 2} (x {approx} 0.44) precursors. The electrochemical characteristics of these compounds, which retain the unique double-tunnel structure during ion exchange, were examined in lithium/polymer electrolyte cells operating at 85 C. All of the substituted cathode materials intercalated lithium reversibly, with Li{sub x}Ti{sub 0.22}Mn{sub 0.78}O{sub 2} exhibiting the highest capacity in polymer cells, about 10-20% greater than that of unsubstituted Li{sub x}MnO{sub 2} made from Na{sub 0.44}MnO{sub 2}. In common with Li{sub x}MnO{sub 2}, the Ti-substituted materials exhibited good capacity retention over one hundred or more cycles, with some compositions exhibiting a fade rate of less than 0.03% per cycle.

Doeff, Marca M.; Richardson, Thomas J.; Hwang, Kwang-Taek

2004-03-01

331

Electrochemical deposition of nanostructured manganese oxide on hierarchically porous graphene-carbon nanotube structure for ultrahigh-performance electrochemical capacitors  

NASA Astrophysics Data System (ADS)

A 3D graphene sheet-carbon nanotube (GS-CNT) structure with a good wetting property, high porosity, and large surface area is homogeneously deposited with active amorphous manganese oxide (a-MnOx) by potentiodynamic deposition. The flowery a-MnOx nanostructure with ultra-slender petals (ca. 5-8 nm) on the framework of hierarchically porous GS-CNT matrix not only enables nearly full utilization of a-MnOx but also retains sufficient conductivity and porosity for the high-rate charge-discharge application. The use of a-MnOx on the 3D GS-CNT material produces a specific capacitance of MnOx of 1200 F g-1 which is much-higher than that of a pure a-MnOx electrode (CS,Mn = 233 F g-1). The specific energy and specific power of a-MnOx/GS-CNT are respectively as high as 46.2 Wh kg-1 and 33.2 kW kg-1, revealing that our work conceptually provides a way to produce porous structures composed of graphene, carbon nanotubes, and various electroactive materials for high-performance energy storage devices.

Li, Shin-Ming; Wang, Yu-Sheng; Yang, Shin-Yi; Liu, Chia-Hong; Chang, Kuo-Hsin; Tien, Hsi-Wen; Wen, Niann-Tsyr; Ma, Chen-Chi M.; Hu, Chi-Chang

2013-03-01

332

One-pot synthesis of manganese oxide-carbon composite microspheres with three dimensional channels for Li-ion batteries  

NASA Astrophysics Data System (ADS)

The fabrication of manganese oxide-carbon composite microspheres with open nanochannels and their electrochemical performance as anode materials for lithium ion batteries are investigated. Amorphous-like Mn3O4 nanoparticles embedded in a carbon matrix with three-dimensional channels are fabricated by one-pot spray pyrolysis. The electrochemical properties of the Mn3O4 nanopowders are also compared with those of the Mn3O4-C composite microspheres possessing macropores resembling ant-cave networks. The discharge capacity of the Mn3O4-C composite microspheres at a current density of 500 mA g-1 is 622 mA h g-1 after 700 cycles. However, the discharge capacity of the Mn3O4 nanopowders is as low as 219 mA h g-1 after 100 cycles. The Mn3O4-C composite microspheres with structural advantages and high electrical conductivity have higher initial discharge and charge capacities and better cycling and rate performances compared to those of the Mn3O4 nanopowders.

Ko, You Na; Park, Seung Bin; Choi, Seung Ho; Kang, Yun Chan

2014-08-01

333

Catalytic degradation of Acid Orange 7 by manganese oxide octahedral molecular sieves with peroxymonosulfate under visible light irradiation.  

PubMed

In this paper, the photodegradation of Acid Orange 7 (AO7) in aqueous solutions with peroxymonosulfate (PMS) was studied with manganese oxide octahedral molecular sieves (OMS-2) as the catalyst. The activities of different systems including OMS-2 under visible light irradiation (OMS-2/Vis), OMS-2/PMS and OMS-2/PMS/Vis were evaluated. It was found that the efficiency of OMS-2/PMS was much higher than that of OMS-2/Vis and could be further enhanced by visible light irradiation. The catalyst also exhibited stable performance for multiple runs. Results from ESR and XPS analyses suggested that the highly catalytic activity of the OMS-2/PMS/Vis system possible involved the activation of PMS to sulfate radicals meditated by the redox pair of Mn(IV)/Mn(III) and Mn(III)/Mn(II), while in the OMS-2/PMS system, only the redox reaction between Mn(IV)/Mn(III) occurred. Several operational parameters, such as dye concentration, catalyst load, PMS concentration and solution pH, affected the degradation of AO7. PMID:25528234

Duan, Lian; Sun, Binzhe; Wei, Mingyu; Luo, Shilu; Pan, Fei; Xu, Aihua; Li, Xiaoxia

2015-03-21

334

YREE sorption on hydrous manganese oxide (MnOx) in 0.5 M NaCl  

NASA Astrophysics Data System (ADS)

Cerium is the only member of the yttrium and rare earth element (YREE) series that can be oxidized in natural waters from Ce(III) to less soluble Ce(IV), causing anomalous sorption behavior with respect to its strictly trivalent YREE neighbors. Sedimentary Ce anomaly records have been interpreted in terms of episodic shifts in the bottom water oxygenation of the paleo-ocean. However, Ce anomalies also form due to catalytic Ce oxidation on certain sorbent surfaces regardless of ambient redox conditions, thus creating a ‘preformed’ signal that may instead reflect variations in the composition of settling particles. We investigate YREE sorption in 0.5 M NaCl on mixtures of three major components of marine particulate matter: Fe and Mn oxides, and algal debris. Here we report our results for one pure endmember, hydrous manganese oxide (MnOx). Batch experiments with freshly prepared MnOx were conducted under nitrogen atmosphere, to prevent aerobic Ce oxidation and YREE complexation with carbonate, over a range of pH (4-8) at 25.0±0.1°C. After at least 6 hours of equilibration at each pH, solution samples were filtered to 0.22 ?m and dissolved YREE concentrations analyzed by ICP-MS to determine their solid/solution distribution coefficient, K. Under the same experimental conditions, log K increases less steeply with pH for MnOx than for hydrous ferric oxide (HFO). This may result from the lower pHzpc of MnOx as well as its higher tendency than HFO to form bidentate edge-sharing YREE surface complexes, as determined by others using X-ray Absorption Fine Structure (XAFS) spectroscopy. A non-electrostatic surface complexation model is being developed to further elucidate these findings. Preferential Ce sorption, implying catalytic Ce oxidation at the mineral-water interface, was observed on MnOx but never on HFO or organic surfaces, in agreement with prior research. This may be related to the generally higher Gibbs free energy gain associated with oxidation reactions in which MnOx is the electron acceptor, although some large organic ligands, such as siderophores, have also been reported to catalyze Ce(III) oxidation. The enhanced Ce removal in anoxic 0.5 M NaCl solutions increases with pH from about 10- to 100-fold relative to the other YREEs, which show comparatively little fractionation among themselves. Sedimentary Ce anomalies are therefore unlikely to provide a reliable and lasting record of bottom water oxygenation when Mn oxides are an important constituent of settling particles and their interpretation as a proxy of paleo-redox conditions should be undertaken with appropriate caution.

Marshall, K. S.; Schijf, J.

2010-12-01

335

Hydrogen and formate oxidation coupled to dissimilatory reduction of iron or manganese by Alteromonas putrefaciens  

USGS Publications Warehouse

The ability of Alteromonas putrefaciens to obtain energy for growth by coupling the oxidation of various electron donors to dissimilatory Fe(III) or Mn(IV) reduction was investigated. A. putrefaciens grew with hydrogen, formate, lactate, or pyruvate as the sole electron donor and Fe(III) as the sole electron acceptor. Lactate and pyruvate were oxidized to acetate, which was not metabolized further. With Fe(III) as the electron acceptor, A. putrefaciens had a high affinity for hydrogen and formate and metabolized hydrogen at partial pressures that were 25-fold lower than those of hydrogen that can be metabolized by pure cultures of sulfate reducers or methanogens. The electron donors for Fe(III) reduction also supported Mn(IV) reduction. The electron donors for Fe(III) and Mn(IV) reduction and the inability of A. putrefaciens to completely oxidize multicarbon substrates to carbon dioxide distinguish A. putrefaciens from GS-15, the only other organism that is known to obtain energy for growth by coupling the oxidation of organic compounds to the reduction of Fe(III) or Mn(IV). The ability of A. putrefaciens to reduce large quantities of Fe(III) and to grow in a defined medium distinguishes it from a Pseudomonas sp., which is the only other known hydrogen-oxidizing, Fe(III)-reducing microorganism. Furthermore, A. putrefaciens is the first organism that is known to grow with hydrogen as the electron donor and Mn(IV) as the electron acceptor and is the first organism that is known to couple the oxidation of formate to the reduction of Fe(III) or Mn(IV). Thus, A. putrefaciens provides a much needed microbial model for key reactions in the oxidation of sediment organic matter coupled to Fe(III) and Mn(IV) reduction.

Lovley, D.R.; Phillips, E.J.P.; Lonergan, D.J.

1989-01-01

336

Mobilization of manganese by basalt associated Mn(II)-oxidizing bacteria from the Indian Ridge System.  

PubMed

The Indian Ridge System basalt bearing Mn-oxide coatings had todorokite as the major and birnesite as the minor mineral. We posit that microorganisms associated with these basalts participate in the oxidation of Mn and contribute to mineral deposition. We also hypothesized that, the Mn-oxidizing microbes may respond reversibly to pulses of fresh organic carbon introduced into the water column by mobilizing the Mn in Mn-oxides. To test these two hypotheses, we enumerated the number of Mn-oxidizers and -reducers and carried out studies on the mobilization of Mn by microbial communities associated with basalt. In medium containing 100 ?M Mn(2+), 10(3) colony forming units (CFU) were recovered with undetectable number of reducers on Mn-oxide amended medium, suggesting that the community was more oxidative. Experiments were then conducted with basalt fragments at 4±2 °C in the presence 'G(+)' and absence 'G(-)' of glucose (0.1%). Controls included set-ups, some of which were poisoned with 15 mM azide and the others of which were heat-killed. The mobilization of Mn in the presence of glucose was 1.76 ?g g(-1) d(-1) and in the absence, it was 0.17 ?g g(-1) d(-1) after 150 d. Mn mobilization with and without added glucose was 13 and 4 times greater than the corresponding azide treated controls. However, rates in 'G(+)' were 16 times and 'G(-)' 24 times more than the respective heat killed controls. The corresponding total counts in the presence of added glucose increased from 1.63×10(6) to 6.71×10(7) cells g(-1) and from 1.41×10(7) to 3.52×10(7) cells g(-1) in its absence. Thus, the addition of glucose as a proxy for organic carbon changed the community's response from Mn(II)-oxidizing to Mn(IV)-reducing activity. The results confirm the participation of Mn oxidizing bacteria in the mobilization of Mn. Identification of culturable bacteria by 16S rRNA gene analysis showed taxonomic affiliations to Bacillus, Exiguobacterium, Staphylococcus, Brevibacterium and Alcanivorax sp. PMID:24183631

Sujith, P P; Mourya, B S; Krishnamurthi, S; Meena, R M; Loka Bharathi, P A

2014-01-01

337

Relationship of manganese-iron oxides and associated heavy metals to grain size in stream sediments  

USGS Publications Warehouse

The distribution of ammonium citrate-leachable lead, zinc and cadmium among size fractions in stream sediments is strongly influenced by the presence of hydrous Mn-Fe oxides in the form of coatings on sediment grains. Distribution curves showing leachable metals as a function of particle size are given for eight samples from streams in New York State. These show certain features in common; in particular two concentrations of metals, one in the finest fractions, and a second peak in the coarse sand and gravel fraction. The latter can be explained as a result of the increasing prevalence and thickness of oxide coatings with increasing particle size, with the oxides serving as collectors for the heavy metals. The distribution of Zn and Cd in most of the samples closely parallels that of Mn; the distribution of Pb is less regular and appears to be related to Fe in some samples and Mn in others. The concentration of metals in the coarse fractions due to oxide coatings, combined with the common occurrence of oxide deposition in streams of glaciated regions, raises the possibility of using coarse materials for geochemical surveys and environmental heavy-metal studies. ?? 1975.

Whitney, P.R.

1975-01-01

338

Electronic structures of iron(III) and manganese(IV) (hydr)oxide minerals: Thermodynamics of photochemical reductive dissolution in aquatic environments  

NASA Astrophysics Data System (ADS)

Sunlight-induced reduction and dissolution of colloidal Fe-Mn (hydr)oxide minerals yields elevated concentrations of Fe 2+ and Mn 2+ in natural waters. Since these elements may be biolimiting micronutrients, photochemical reactions might play a significant role in biogeochemical cycles. Reductive photodissolution of Fe (hydr)oxide minerals may also release sorbed metals. The reactivity of Fe-Mn (hydr)oxide minerals to sunlight-induced photochemical dissolution is determined by the electronic structure of the mineral-water interface. In this work, oxygen K-edge absorption and emission spectra were used to determine the electronic structures of iron(III) (hydr)oxides (hematite, goethite, lepidocrocite, akaganeite and schwertmannite) and manganese(IV) oxides (pyrolusite, birnessite, cryptomelane). The band gaps in the iron(III) (hydr)oxide minerals are near 2.0-2.5 eV; the band gaps in the manganese (IV) oxide phases are 1.0-1.8 eV. Using published values for the electrochemical flat-band potential for hematite together with experimental pH pzc values for the (hydr)oxides, it is possible to predict the electrochemical potentials of the conduction and valence bands in aqueous solutions as a function of pH. The band potentials enable semiquantitative predictions of the susceptibilities of these minerals to photochemical dissolution in aqueous solutions. At pH 2 (e.g., acid-mine waters), photoreduction of iron(III) (hydr)oxides could yield millimolal concentrations of aqueous Fe 2+ (assuming surface detachment of Fe 2+ is not rate limiting). In seawater (pH 8.3), however, the direct photo-reduction of colloidal iron(III) (hydr)oxides to give nanomolal concentrations of dissolved, uncomplexed, Fe 2+ is not thermodynamically feasible. This supports the hypothesis that the apparent photodissolution of iron(III) (hydr)oxides in marines systems results from Fe 3+ reduction by photochemically produced superoxide. In contrast, the direct photoreduction of manganese oxides should be energetically feasible at pH 2 and 8.3.

Sherman, David M.

2005-07-01

339

Kinetics of chromium(II) oxidation to chromium(VI) by reaction with manganese dioxide  

Microsoft Academic Search

The kinetics of oxidation of aqueous Cr(III) to Cr(VI) by reaction with pyrolusite (..beta..-MnOâ(s)) were studied in aerated and deaerated solutions at 27°C for pH 3.0-10.1, for 10\\/sup -4.7\\/-10\\/sup -3.4\\/ M Cr(III), and as a function of ..beta..-MnOâ(s) surface area to assess the possible effects on Cr transport in industrial waste materials. The oxidation of aqueous Cr(III) is not appreciably

L. Edmond Eary; Dhanpat Rai

1987-01-01

340

Photo-catalytic oxidation of a di-nuclear manganese centre in an engineered bacterioferritin 'reaction centre'.  

PubMed

Photosynthesis involves the conversion of light into chemical energy through a series of electron transfer reactions within membrane-bound pigment/protein complexes. The Photosystem II (PSII) complex in plants, algae and cyanobacteria catalyse the oxidation of water to molecular O2. The complexity of PSII has thus far limited attempts to chemically replicate its function. Here we introduce a reverse engineering approach to build a simple, light-driven photo-catalyst based on the organization and function of the donor side of the PSII reaction centre. We have used bacterioferritin (BFR) (cytochrome b1) from Escherichia coli as the protein scaffold since it has several, inherently useful design features for engineering light-driven electron transport. Among these are: (i.) a di-iron binding site; (ii.) a potentially redox-active tyrosine residue; and (iii.) the ability to dimerise and form an inter-protein heme binding pocket within electron tunnelling distance of the di-iron binding site. Upon replacing the heme with the photoactive zinc-chlorin e6 (ZnCe6) molecule and the di-iron binding site with two manganese ions, we show that the two Mn ions bind as a weakly coupled di-nuclear Mn2II,II centre, and that ZnCe6 binds in stoichiometric amounts of 1:2 with respect to the dimeric form of BFR. Upon illumination the bound ZnCe6 initiates electron transfer, followed by oxidation of the di-nuclear Mn centre possibly via one of the inherent tyrosine residues in the vicinity of the Mn cluster. The light dependent loss of the MnII EPR signals and the formation of low field parallel mode Mn EPR signals are attributed to the formation of MnIII species. The formation of the MnIII is concomitant with consumption of oxygen. Our model is the first artificial reaction centre developed for the photo-catalytic oxidation of a di-metal site within a protein matrix which potentially mimics water oxidation centre (WOC) photo-assembly. PMID:19409368

Conlan, Brendon; Cox, Nicholas; Su, Ji-Hu; Hillier, Warwick; Messinger, Johannes; Lubitz, Wolfgang; Dutton, P Leslie; Wydrzynski, Tom

2009-09-01

341

The inhibitory effect of manganese on acetylcholinesterase activity enhances oxidative stress and neuroinflammation in the rat brain  

PubMed Central

Background Manganese (Mn) is a naturally occurring element and an essential nutrient for humans and animals. However, exposure to high levels of Mn may cause neurotoxic effects. The pathological mechanisms associated with Mn neurotoxicity are poorly understood, but several reports have established it is mediated, at least in part, by oxidative stress. Objectives The present study was undertaken to test the hypothesis that a decrease in acetylcholinesterase (AChE) activity mediates Mn-induced neurotoxicity. Methods Groups of 6 rats received 4 or 8 intraperitoneal (i.p.) injections of 25 mg MnCl2/kg/day, every 48 hours. Twenty-four hours after the last injection, brain AChE activity and the levels of F2-isoprostanes (F2-IsoPs) and F4-neuroprostanes (F4-NPs) (biomarkers of oxidative stress), as well as prostaglandin E2 (PGE2) (biomarker of neuroinflammation) were analyzed. Results The results showed that after either 4 or 8 Mn doses, brain AChE activity was significantly decreased (p<0.05), to 60 ± 16 % and 55 ± 13 % of control levels, respectively. Both treated groups exhibited clear signs of neurobehavioral toxicity, characterized by a significant (p<0.001) decrease in ambulation and rearings in open-field. Furthermore, Mn treatment caused a significant increase (p<0.05) in brain F2-IsoPs and PGE2 levels, but only after 8 doses. In rats treated with 4 Mn doses, a significant increase (p<0.05) in brain F4-NPs levels was found. To evaluate cellular responses to oxidative stress, we assessed brain nuclear factor-erythroid 2 p45-related factor 2 (Nrf2) and Mn-superoxide dismutase (Mn-SOD, SOD2) protein expression levels. A significant increase in Mn-SOD protein expression (p<0.05) and a trend towards increased Nrf2 protein expression was noted in rat brains after 4 Mn doses vs. the control group, but the expression of these proteins was decreased after 8 Mn doses. Taken together, these results suggest that the inhibitory effect of Mn on AChE activity promotes increased neuronal oxidative stress and neuroinflammatory biomarkers. PMID:22154916

Santos, Dinamene; Milatovic, Dejan; Andrade, Vanda; Camila, Batoreu M.; Aschner, Michael; Marreilha dos Santos, A.P.

2011-01-01

342

Patterns of sheath elongation, cell proliferation, and manganese(II) oxidation in Leptothrix cholodnii.  

PubMed

Leptothrix cholodnii is a Mn(II)-oxidizing and sheath-forming member of the class ?-Proteobacteria. Its sheath is a microtube-like filament that contains a chain of cells. From a chemical perspective, the sheath can be described as a supermolecule composed of a cysteine-rich polymeric glycoconjugate, called thiopeptidoglycan. However, the mechanism that controls the increase in sheath length is unknown. In this study, we attempted to detect sheath elongation through microscopic examination by using conventional reagents. Selective fluorescent labeling of preexisting or newly formed regions of the sheath was accomplished using combinations of biotin-conjugated maleimide, propionate-conjugated maleimide, and a fluorescent antibiotin antibody. Epifluorescence microscopy indicated that the sheath elongates at the terminal regions. On the bases of this observation, we assumed that the newly secreted thiopeptidoglycan molecules are integrated into the preexisting sheath at its terminal ends. Successive phase-contrast microscopy revealed that all cells proliferate at nearly the same rate regardless of their positions within the sheath. Mn(II) oxidation in microcultures was also examined with respect to cultivation time. Results suggested that the deposition of Mn oxides is notable in the aged regions. The combined data reveal the spatiotemporal relationships among sheath elongation, cell proliferation, and Mn oxide deposition in L. cholodnii. PMID:22392226

Takeda, Minoru; Kawasaki, Yuta; Umezu, Takuto; Shimura, Shoichi; Hasegawa, Makoto; Koizumi, Jun-ichi

2012-08-01

343

ROLE OF IRON AND MANGANESE OXIDES IN BIOSOLIDS AND BIOSOLIDS-AMENDED SOILS ON METAL BINDING  

EPA Science Inventory

Biosolids contain high levels of Fe, Mn, and Al. Surfaces of freshly precipitated metal oxides, especially Fe and Mn, are known to be highly active sites for most dissolved metal ion species. We nw have metal sorption/desorption data that illustrate the importance of Fe and Mn fr...

344

Mechanism, decomposition pathway and new evidence for self-healing of manganese oxides as efficient water oxidizing catalysts: new insights.  

PubMed

The electrochemical water-oxidation reaction usually requires a catalyst to reduce the overpotential and Earth-abundant catalysts, like MnO2, are attracting much attention. Here we use chemometric analysis, EPR and UV-Vis spectroscopies to track Mn(II) and MnO4(-) byproducts to the reaction of a MnO2 film in the presence of cerium(IV) ammonium nitrate. Permanganate ion is involved in at least two key reactions: it may oxidize water to O2 or can combine with Mn(II) to remake MnO2 solid. We propose mechanisms for water oxidation and present a self-healing process for this reaction. PMID:23982587

Najafpour, Mohammad Mahdi; Kompany-Zareh, Mohsen; Zahraei, Ali; Jafarian Sedigh, Davood; Jaccard, Hugues; Khoshkam, Maryam; Britt, R David; Casey, William H

2013-10-28

345

Photosystem II Like Water Oxidation Mechanism in a Bioinspired Tetranuclear Manganese Complex.  

PubMed

The synthesis of Mn-based catalysts to mimic the structural and catalytic properties of the oxygen-evolving complex in photosystem II is a long-standing goal for researchers. An interesting result in this field came with the synthesis of a Mn complex that enables water oxidation driven by the mild single-electron oxidant [Ru(bpy)3](3+). On the basis of hybrid density functional calculations, we herein propose a water oxidation mechanism for this bioinspired Mn catalyst, where the crucial O-O bond formation proceeds from the formal Mn4(IV,IV,IV,V) state by direct coupling of a Mn(IV)-bound terminal oxyl radical and a di-Mn bridging oxo group, a mechanism quite similar to the presently leading suggestion for the natural system. Of importance here is that the designed ligand is shown to be redox-active and can therefore store redox equivalents during the catalytic transitions, thereby alleviating the redox processes at the Mn centers. PMID:25486382

Liao, Rong-Zhen; Kärkäs, Markus D; Lee, Bao-Lin; Åkermark, Björn; Siegbahn, Per E M

2015-01-01

346

Electrochemical Quartz Crystal Microbalance Studies of Electron Addition at Nanocrystalline Tin Oxide/Water and Zinc Oxide/Water Interfaces: Evidence for  

E-print Network

Oxide/Water and Zinc Oxide/Water Interfaces: Evidence for Band-Edge-Determining Proton Uptake Buford I at nanocrystalline zinc oxide/ water and tin oxide/water interfaces is similarly accompanied by uptake of charge intercalation is a general mode of reactivity for metal oxide semiconductors. Finally, the new observations

347

A nano-sized manganese oxide in a protein matrix as a natural water-oxidizing site.  

PubMed

The purpose of this review is to present recent advances in the structural and functional studies of water-oxidizing center of Photosystem II and its surrounding protein matrix in order to synthesize artificial catalysts for production of clean and efficient hydrogen fuel. PMID:24560883

Najafpour, Mohammad Mahdi; Ghobadi, Mohadeseh Zarei; Haghighi, Behzad; Tomo, Tatsuya; Carpentier, Robert; Shen, Jian-Ren; Allakhverdiev, Suleyman I

2014-08-01

348

Stability of beta MnOOH and manganese oxide deposition from springwater.  

USGS Publications Warehouse

beta MnOOH is precipitated preferentially (with respect to Mn3O4) at T near 0oC when Mn2+ is oxidized in aerated aqueous solutions. Upon aging in solutions open to the atmosphere, a slurry of beta MnOOH tends to disproportionate to form MnO2 and Mn2+. In such aged solutions, Mn2+ and H+ activities can be constant, and both the oxidation reaction Mn2+ + 1/4O2(aq) + 3/2H2O rt arrow beta MnOOH(c) + 2H+ and the disproportionation reaction 2beta MnOOH(c) + 2H+ rt arrow MnO2(c) + Mn2+ + 2H2O can have positive reaction affinities. It is not possible for both reactions to be in thermodynamic equilibrium in the same system unless oxygen is almost completely absent. A value for 028DELTA Gof of -129.8 + or - 0.6 kcal/mol was obtained for beta MnOOH from experimental data by assuming that the reaction affinity for the oxidation reaction is equal to that for the disproportionation, and a value of -129.8 + or - 0.5 kcal/mol was determined by measuring the redox potentials for the postulated half-reaction MnO2(c) + H+ + e- rt arrow beta MnOOH(c) at 0o, 5o, and 15oC and extrapolating to 25oC. Both these values are consistent with laboratory observations that beta MnOOH is less stable than gamma MnOOH or Mn3O4 at 25oC. Analytical data for Mn-depositing springwater samples are consistent with a non-equilibrium model involving disproportionation of either beta MnOOH or Mn3O4. (Authors' abstract)-T.R.

Hem, J.D.; Roberson, C.E.; Fournier, R.B.

1982-01-01

349

Manganese Complexes: Diverse Metabolic Routes to Oxidative Stress Resistance in Prokaryotes and Yeast  

PubMed Central

Abstract Significance: Antioxidant enzymes are thought to provide critical protection to cells against reactive oxygen species (ROS). However, many organisms can fully compensate for the loss of such enzymatic defenses by accumulating metabolites and Mn2+, which can form catalytic Mn-antioxidants. Accumulated metabolites can direct reactivity of Mn2+ with superoxide and specifically shield proteins from oxidative damage. Recent Advances: There is mounting evidence that Mn-Pi (orthophosphate) complexes act as potent scavengers of superoxide in all three branches of life. Moreover, it is evident that Mn2+ in complexes with carbonates, peptides, nucleosides, and organic acids can also form catalytic Mn-antioxidants, pointing to diverse metabolic routes to oxidative stress resistance. Critical Issues: What conditions favor utility of Mn-metabolites versus enzymatic means for removing ROS? Mn2+-metabolite defenses are critical for preserving the activity of repair enzymes in Deinococcus radiodurans exposed to intense radiation stress, and in Lactobacillus plantarum, which lacks antioxidant enzymes. In other microorganisms, Mn-antioxidants can serve as an auxiliary protection when enzymatic antioxidants are insufficient or fail. These findings of a critical role of Mn-antioxidants in the survival of prokaryotes under oxidative stress parallel the trends developing for the simple eukaryote Saccharomyces cerevisiae. Future Directions: Phosphates, peptides and organic acids are just a snapshot of the types of anionic metabolites that promote such reactivity of Mn2+. Their probable roles in pathogen defense against the host immune response and in ROS-mediated signaling pathways are also areas that are worthy of serious investigation. Moreover, it is clear that these protective chemical processes can be harnessed for practical purposes. Antioxid. Redox Signal. 19, 933–944. PMID:23249283

2013-01-01

350

Azide groups in higher oxidation state manganese cluster chemistry: from structural aesthetics to single-molecule magnets.  

PubMed

This Forum Article overviews the recent amalgamation of two long-established areas, manganese/oxo coordination cluster chemistry involving the higher Mn(II)/Mn(IV) oxidation states and transition-metal azide (N(3)(-)) chemistry. The combination of azide and alkoxide- or carboxylate-containing ligands in Mn chemistry has led to a variety of new polynuclear clusters, high-spin molecules, and single-molecule magnets, with metal nuclearities ranging from Mn(4) to Mn(32) and with ground-state spin values as large as S = 83/2. The organic bridging/chelating ligands are discussed separately as follows: (i) pyridyl alkoxides [the anions of 2-(hydroxymethyl)pyridine (hmpH), 2,6-pyridinedimethanol (pdmH(2)), and the gem-diol form of di-2-pyridyl ketone (dpkdH(2))]; (ii) non-pyridyl alkoxides [the anions of 1,1,1-tris(hydroxymethyl)ethane (thmeH(3)), triethanolamine (teaH(3)), and N-methyldiethanolamine (mdaH(2))]; (iii) other alcohols [the anions of 2,6-dihydroxymethyl-4-methylphenol (LH(3)) and Schiff bases]; (iv) pyridyl monoximes/dioximes [the anions of methyl-2-pyridyl ketone oxime (mpkoH), phenyl-2-pyridyl ketone oxime (ppkoH), and 2,6-diacetylpyridine dioxime (dapdoH(2))]; (v) non-pyridyl oximes [the anions of salicylaldoxime (saoH(2)) and its derivatives R-saoH(2)]. The large structural diversity of the resulting complexes stems from the combined ability of the azide and organic ligands to adopt a variety of ligation and bridging modes. The combined work demonstrates the synthetic novelty that arises when azide is used in conjunction with alcohol-based chelates, the aesthetic beauty of the resulting molecules, and the often fascinating magnetic properties that these compounds possess. This continues to emphasize the extensive and remarkable ability of Mn chemistry to satisfy a variety of different tastes. PMID:19364123

Stamatatos, Theocharis C; Christou, George

2009-04-20

351

Biodistribution and acute toxicity of a nanofluid containing manganese iron oxide nanoparticles produced by a mechanochemical process.  

PubMed

Superparamagnetic iron oxide nanoparticles are candidate contrast agents for magnetic resonance imaging and targeted drug delivery. Biodistribution and toxicity assessment are critical for the development of nanoparticle-based drugs, because of nanoparticle-enhanced biological reactivity. Here, we investigated the uptake, in vivo biodistribution, and in vitro and in vivo potential toxicity of manganese ferrite (MnFe2O4) nanoparticles, synthesized by an original high-yield, low-cost mechanochemical process. Cultures of murine Balb/3T3 fibroblasts were exposed for 24, 48, or 72 hours to increasing ferrofluid concentrations. Nanoparticle cellular uptake was assessed by flow-cytometry scatter-light measurements and microscopy imaging after Prussian blue staining; cytotoxicity was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and colony-forming assays. After a single intravenous injection, in vivo nanoparticle biodistribution and clearance were evaluated in mice by Mn spectrophotometric determination and Prussian blue staining in the liver, kidneys, spleen, and brain at different posttreatment times up to 21 days. The same organs were analyzed for any possible histopathological change. The in vitro study demonstrated dose-dependent nanoparticle uptake and statistically significant cytotoxic effects from a concentration of 50 ?g/mL for the MTT assay and 20 ?g/mL for the colony-forming assay. Significant increases in Mn concentrations were detected in all analyzed organs, peaking at 6 hours after injection and then gradually declining. Clearance appeared complete at 7 days in the kidneys, spleen, and brain, whereas in the liver Mn levels remained statistically higher than in vehicle-treated mice up to 3 weeks postinjection. No evidence of irreversible histopathological damage to any of the tested organs was observed. A comparison of the lowest in vitro toxic concentration with the intravenously injected dose and the administered dose of other ferrofluid drugs currently in clinical practice suggests that there might be sufficient safety margins for further development of our formulation. PMID:24790434

Bellusci, Mariangela; La Barbera, Aurelio; Padella, Franco; Mancuso, Mariateresa; Pasquo, Alessandra; Grollino, Maria Giuseppa; Leter, Giorgio; Nardi, Elisa; Cremisini, Carlo; Giardullo, Paola; Pacchierotti, Francesca

2014-01-01

352

Shewanella-mediated Biosynthesis of Manganese Oxide Micro-/Nanocubes as Efficient Electrocatalysts for the Oxygen Reduction Reaction.  

PubMed

Developing efficient electrocatalysts for the oxygen reduction reaction (ORR) is critical for promoting the widespread application of fuel cells and metal-air batteries. Here, we develop a biological low-cost, ecofriendly method for the synthesis of Mn2 O3 micro-/nanocubes by calcination of MnCO3 precursors in an oxygen atmosphere. Microcubic MnCO3 precursors with an edge length of 2.5??m were fabricated by dissimilatory metal-reducing Shewanella loihica PV-4 in the presence of MnO4 (-) as the sole electron acceptor under anaerobic conditions. After calcining the MnCO3 precursors at 500 and 700?°C, porous Mn2 O3 -500 and Mn2 O3 -700 also showed microcubic morphology, while their edge lengths decreased to 1.8??m due to thermal decomposition. Moreover, the surfaces of the Mn2 O3 microcubes were covered by granular nanoparticles with average diameters in the range of 18-202?nm, depending on the calcination temperatures. Electrochemical measurements demonstrated that the porous Mn2 O3 -500 micro-/nanocubes exhibit promising catalytic activity towards the ORR in an alkaline medium, which should be due to a synergistic effect of the overlapping molecular orbitals of oxygen/manganese and the hierarchically porous structures that are favorable for oxygen absorption. Moreover, these Mn2 O3 micro-/nanocubes possess better stability than commercial Pt/C catalysts and methanol-tolerance property in alkaline solution. Thus the Shewanella-mediated biosynthesis method we provided here might be a new strategy for the preparation of various transition metal oxides as high-performance ORR electrocatalysts at low cost. PMID:25425435

Jiang, Congcong; Guo, Zhaoyan; Zhu, Ying; Liu, Huan; Wan, Meixiang; Jiang, Lei

2015-01-01

353

Kinetics and mechanism of the manganese(II) catalysed Calmagite dye oxidation using in situ generated hydrogen peroxide.  

PubMed

The kinetics and mechanism for the bleaching of Calmagite (H3CAL, 3-hydroxy-4-(2-hydroxy-5-methylphenylazo)naphthalene-1-sulfonic acid) in aqueous solution at pH 8.00 and 23 ± 1 °C using in situ generated H2O2 is described. Complete mineralisation of H3CAL results with turnover frequencies (TOF = moles of H3CAL bleached per mole of manganese per hour) of 40 h(-1). The monohydroxy azo dyes Me-H2CAL, Orange G and Orange II are not bleached which indicates that a requirement of dye bleaching is the coordination of the dye to the Mn centre. Spectroscopic studies show the formation of Mn(CAL)2 and Mn(CAL) species but in the presence of Tiron (1,2-dihydroxybenzene-3,5-disulfonate, disodium salt, monohydrate, Na2TH2·H2O), [Mn(CAL)(T)] is formed. It is proposed that a Mn(III)-hydroperoxide species is generated, [Mn(O2H)(CAL)(TQ)] from the in situ generated H2O2, where TQ represents the o-quinone form of Tiron, and this is the active species in the bleaching of coordinated CAL; the formation of this hydroperoxide species is supported by UV/VIS and ESI-MS data. The formation of a Mn(III) species is supported by EPR studies which also show some evidence for the presence of a labile d(5) Mn(II) species in the presence of the reducing substrate hydroxylamine (NH2OH). This would enable rapid ligand exchange for both in situ H2O2 generation and dye bleaching to occur; there is no evidence for the presence of Mn(IV)=O species. The virtue of low local concentrations of in situ generated H2O2 is shown to be important in preventing over oxidation of the catalyst and thus contributing to a robust catalytic system. PMID:23440053

Sheriff, Tippu S; Cope, Steven; Varsani, Dhimal S

2013-04-28

354

The destruction of dichloroethane over a gamma-alumina supported manganese oxide catalyst.  

PubMed

Halogenated VOCs emissions are associated to a wide range of industrial processes; for instance, dichloroethane (DCEA) is mainly used in metal degreasing processes and known to be hazardous to the environment and public health. The effects of operating parameters on the catalytic incineration of DCEA over the Mn(2)O(3)/gamma-Al(2)O(3) catalyst were performed in this study. The results show that conversion of DCEA increases as inlet temperature and oxygen concentration increase, and decreases with the increases of DCEA concentration and space velocity. The effects of O(2) and DCEA content in carrier gas on the catalytic reaction rate are also observed. Experimental results indicate that the oxidation kinetic behavior of DCEA with the catalyst can be expressed by using the rate expression of the power rate law. The experimental results are compared with those predicted from the kinetic model. The products and reactants distributions from the oxidation of DCEA over Mn(2)O(3)/gamma-Al(2)O(3) were observed. The results show that the DCEA conversion starts from 15% at 450K and rises to 100% in the 700-800K ranges and the CO(2) yield is complete (100%) in the same temperature ranges. HCl and Cl(2) are the other main products with little halogenated VOC intermediates. PMID:20227177

Tseng, Ting Ke; Wang, Ling; Ho, Chiun Teh; Chu, Hsin

2010-06-15

355

High Valent Manganese and Cobalt Complexes of Oxidatively Robust Nitrogen and Oxygen Donor Ligands.  

NASA Astrophysics Data System (ADS)

The focus of this thesis is to extend the range of ligands that satisfy the Collins criteria through a program of organic synthesis, and to apply the resulting high valent metal ligand complexes to the solution of current problems in structural inorganic chemistry, solid state chemistry (with a particular emphasis on magnetic interactions in solids) and to homogeneous and heterogeneous catalysis. Notable achievements along these directions to date are: (i) A streamlined synthesis of diamide dialkoxide and diamide diphenoxide acyclic ligands which allows for a wide range of both electron withdrawing and electron donating substituents to be incorporated into the ligand framework. (ii) The first example of a LMn(V)O species stable enough to be crystallographically characterized was obtained, utilizing the acyclic ligands of (i). (iii) Catalytic O-atom transfer oxidations utilizing acyclic ligands from (i) have been performed. Planar Co(III) complexes of these ligands can catalyze O-atom transfers, ^1 with 30-50 turnovers, including enantioselective ones,^2 implicating that the ligands remain at least partially intact during the catalytic process. (iv) Unusual magnetic ordering has been observed in an infinite linear chain of S = 2 LMn(III) centers, in collaboration with Edmund P. Day. (v) Ferromagnetic exchange has been obtained in a ((LCo(III)) _3Co(II)) ^{-} complex^4 Magnetic model building in collaboration with Gordon Yee and Emile Bominaar has led to an understanding of the magnetic data suitable for publication.^5 (vi) Adaptation of a range of electronic substituents (see (i)) into a macrocyclic framework^7 allows for the preparation of hydrolytically and oxidatively stable high valent metal complexes. The presence of a range of electronic substituents further allows redox potentials for a single (LM) ^{rm n+}/(LM) ^{(rm n+1)+ } oxidation process to be tuned over a range that spans ca. 1 V. (vii) Initial linear syntheses for these macrocycles involved the use of organic azide intermediates. (viii) A new macrocyclic switching ligand has been synthesized utilizing (vii), that allows H^{+} or other lewis acids to act at the secondary site as electron withdrawing groups from the metal. In the structurally characterized switching (Co(III)( kappa^4-L)) ^{ -} complex, there is a bidentate switching site consisting of a pyridine-N and an adjacent amide-O donor. It has been found that the cobalt(II) derivative (CO(II)(kappa^4-L)) ^{-} readily reduces O _2 by an outer sphere (presumably by 1 e ^{-}) process. (ix) Robust homogeneous metalloredox-active oxidants are an important strategic goal for primary pollution prevention, or what is often called "green chemistry". Use of (vii) provides access to quantities of a macrocyclic ligand, that is derivatized in such a way that it can be attached to a solid polymer support. (x) C-H bond activation has been observed in iron systems^{15} in collaboration with Mike Bartos (the principal investigator) where use of (vii) has allowed quantities of ligand to be synthesized and burned in reaction chemistry with nitriles and oxidants. (xi) Macrocyclic ligands with organic solubilizing groups have been prepared utilizing (vii) and metal complexes with substantial alkane solubility result. (Abstract shortened by UMI.).

Gordon-Wylie, Scott Wallace

1995-01-01

356

Water-soluble colloidal manganese dioxide as an oxidant for L-tyrosine in the absence and presence of non-ionic surfactant TX-100.  

PubMed

Water-soluble colloidal manganese dioxide has been used to oxidize L-tyrosine in aqueous-acidic medium. The kinetics of the reaction was studied in the absence and presence of non-ionic surfactant (TX-100) using a spectrophotometric technique. As the reaction was fast under pseudo-first-order conditions ([L-tyrosine]>[MnO(2)]), the rate constants as a function of [L-tyrosine], [MnO(2)], [HClO(4)] and temperature were obtained under second-order conditions. The rate of the reaction increased and decreased with the increase in [L-tyrosine] and [MnO(2)], respectively. Perchloric acid, sodium pyrophosphate and sodium fluoride showed catalytic effect. The effect of externally added manganese(II) sulphate is complex. It is not possible to predict the exact dependence of the rate constants on manganese(II) concentration, which has a series of reactions with other reactants. The reaction is inhibited by the non-ionic surfactant TX-100. Activation parameters have been evaluated using Arrhenius and Eyring equations. Based on observed kinetic results, a probable mechanism for the reaction has been proposed which corresponds to fast adsorption of the reductant and hydrogen ion on the surface of colloidal MnO(2) followed by one-step two-electron transfer rate limiting process. PMID:19570658

Altaf, Mohammad; Akram, Mohd; Kabir-ud-Din

2009-10-15

357

The synthesis, characterization of oxidized multi-walled carbon nanotubes, and application to surface acoustic wave quartz crystal gas sensor  

Microsoft Academic Search

Intermetallic alloy catalysts had been prepared by the polyol method, and used for the growth of the individual- or bundle-shaped multi-walled carbon nanotubes (MWCNTs) by thermal chemical vapor deposition method. The purified MWCNTs catalyzed by Mg28-Ni68-Mo4 alloy catalyst were oxidized with the nitric acid\\/hydrogen peroxide solution (volume ratio=2\\/1) to generate carboxylic acid groups. The oxidized MWCNTs (MWCNT-COOH) were further modified

Hao-Lin Hsu; Jih-Mirn Jehng; Yuh Sung; Li-Chun Wang; Sang-Ren Yang

2008-01-01

358

Ferromagnetism of manganese-doped indium tin oxide films deposited on polyethylene naphthalate substrates  

SciTech Connect

Mn-doped indium tin oxide (ITO) films were deposited on polyethylene naphthalate (PEN) substrates using radio-frequency magnetron sputtering. The magnetic, electrical, and optical properties of the films deposited on PEN substrates were investigated by comparing with the properties of films grown on glass substrates at the same growth conditions. Thin films on PEN substrates exhibited low electrical resistivity of the order of 10{sup -4} {omega} cm and high optical transmittance between 75% and 90% in the visible region. Ferromagnetic hysteresis loops were observed at room temperature for the samples grown on PEN substrates. Mn-doped ITO films can be one of the most promising candidates of transparent ferromagnetic materials for flexible spintronic devices.

Nakamura, Toshihiro; Isozaki, Shinichi; Tanabe, Kohei; Tachibana, Kunihide [Department of Electronic Science and Engineering, Kyoto University, Kyotodaigaku-Katsura, Nishikyo-ku, Kyoto 615-8510 (Japan)

2009-04-01

359

Spinel manganese-nickel-cobalt ternary oxide nanowire array for high-performance electrochemical capacitor applications.  

PubMed

Aligned spinel Mn-Ni-Co ternary oxide (MNCO) nanowires are synthesized by a facile hydrothermal method. As an electrode of supercapacitors, the MNCO nanowire array on nickel foam shows an outstanding specific capacitance of 638 F g(-1) at 1 A g(-1) and excellent cycling stability. This exceptional performance benefits from its nanowire architecture, which can provide large reaction surface area, fast ion and electron transfer, and good structural stability. Furthermore, an asymmetric supercapacitor (ASC) with high energy density is assembled successfully by employing the MNCO nanowire array as positive electrode and carbon black as negative electrode. The excellent electrochemical performances indicate the promising potential application of the ASC device in the energy storage field. PMID:25247606

Li, Lu; Zhang, Yongqi; Shi, Fan; Zhang, Yijun; Zhang, Jiaheng; Gu, Changdong; Wang, Xiuli; Tu, Jiangping

2014-10-22

360

Synthesis and characterization of lithium nickel manganese oxides and their delithiated phases  

Microsoft Academic Search

Single phases of layered LiNi0.5Mn0.5O2 structure (a=2.89A?, c=14.30A?) with the LiNiO2 structure and cubic Li0.4Ni0.3Mn0.3O (a=4.15A?) with the NiO structure were synthesized by calcination of mixed oxide (NiMnO3) and LiOH·H2O. The optimum calcination temperatures were 1000°C in air for LiNi0.5Mn0.5O2 and 700°C in nitrogen for Li0.4Ni0.3Mn0.3O. To our knowledge, the Li0.4Ni0.3Mn0.3O material has not been reported in the literature so

Ramesh Chitrakar; Shuji Kasaishi; Aya Umeno; Kohji Sakane; Norio Takagi; Yang-Soo Kim; Kenta Ooi

2002-01-01

361

Development and application of 16S rRNA-targeted probes for detection of iron- and manganese-oxidizing sheathed bacteria in environmental samples.  

PubMed

Comparative sequence analysis of the 16S rRNA genes from several Leptothrix and Sphaerotilus strains led to the design of an oligonucleotide probe (PS-1) based on a sequence within the hypervariable region 1 specific for four Leptothrix strains and for one of the four Sphaerotilus natans strains examined. Another probe (PSP-6) was based on a sequence within the hypervariable region 2. PSP-6 was specific for one of the two evolutionary lineages previously described for Leptothrix spp. (P. L. Siering and W. C. Ghiorse, Int. J. Syst. Bacteriol. 46:173-182, 1996). Fluorescein-labeled oligonucleotide probes were synthesized, and their specificity for fluorescence in situ hybridization identification was confirmed by a laser scanning microscopy technique (W. C. Ghiorse, D. N. Miller, R. L. Sandoli, and P. L. Siering, Microsc. Res. Tech. 33:73-86, 1996) to compare whole-cell hybridizations of closely related bacteria. Probe specificity was also tested in dot blot against total RNA isolated from four Leptothrix strains, four Sphaerotilus strains, and 15 other members of the class Proteobacteria. When the probes were tested on samples from the Sapsucker Woods wetland habitat where Leptothrix spp. are thought to play a role in manganese and iron oxidation, positive signals were obtained from several sheathed filamentous bacteria including some that were morphologically similar to previously isolated strains of "Leptothrix discophora." Other unknown filamentous sheathed bacteria also gave strong positive signals. This work provides a foundation for future studies correlating the presence of members of the Leptothrix-Sphaerotilus group of sheathed bacteria with manganese and iron oxidation activity in habitats where biological iron and manganese oxidation are important environmental processes. PMID:9023942

Siering, P L; Ghiorse, W C

1997-02-01

362

Development and application of 16S rRNA-targeted probes for detection of iron- and manganese-oxidizing sheathed bacteria in environmental samples.  

PubMed Central

Comparative sequence analysis of the 16S rRNA genes from several Leptothrix and Sphaerotilus strains led to the design of an oligonucleotide probe (PS-1) based on a sequence within the hypervariable region 1 specific for four Leptothrix strains and for one of the four Sphaerotilus natans strains examined. Another probe (PSP-6) was based on a sequence within the hypervariable region 2. PSP-6 was specific for one of the two evolutionary lineages previously described for Leptothrix spp. (P. L. Siering and W. C. Ghiorse, Int. J. Syst. Bacteriol. 46:173-182, 1996). Fluorescein-labeled oligonucleotide probes were synthesized, and their specificity for fluorescence in situ hybridization identification was confirmed by a laser scanning microscopy technique (W. C. Ghiorse, D. N. Miller, R. L. Sandoli, and P. L. Siering, Microsc. Res. Tech. 33:73-86, 1996) to compare whole-cell hybridizations of closely related bacteria. Probe specificity was also tested in dot blot against total RNA isolated from four Leptothrix strains, four Sphaerotilus strains, and 15 other members of the class Proteobacteria. When the probes were tested on samples from the Sapsucker Woods wetland habitat where Leptothrix spp. are thought to play a role in manganese and iron oxidation, positive signals were obtained from several sheathed filamentous bacteria including some that were morphologically similar to previously isolated strains of "Leptothrix discophora." Other unknown filamentous sheathed bacteria also gave strong positive signals. This work provides a foundation for future studies correlating the presence of members of the Leptothrix-Sphaerotilus group of sheathed bacteria with manganese and iron oxidation activity in habitats where biological iron and manganese oxidation are important environmental processes. PMID:9023942

Siering, P L; Ghiorse, W C

1997-01-01

363

High-performance binder-free supercapacitor electrode by direct growth of cobalt-manganese composite oxide nansostructures on nickel foam  

NASA Astrophysics Data System (ADS)

A facile approach composed of hydrothermal process and annealing treatment is proposed to directly grow cobalt-manganese composite oxide ((Co,Mn)3O4) nanostructures on three-dimensional (3D) conductive nickel (Ni) foam for a supercapacitor electrode. The as-fabricated porous electrode exhibits excellent rate capability and high specific capacitance of 840.2 F g-1 at the current density of 10 A g-1, and the electrode also shows excellent cycling performance, which retains 102% of its initial discharge capacitance after 7,000 cycles. The fabricated binder-free hierarchical composite electrode with superior electrochemical performance is a promising candidate for high-performance supercapacitors.

Jiang, Shulan; Shi, Tielin; Long, Hu; Sun, Yongming; Zhou, Wei; Tang, Zirong

2014-09-01

364

Surface chemistry of coated lithium manganese nickel oxide thin film cathodes studied by XPS  

SciTech Connect

The effect of coating high voltage LiMn1.5Ni0.5O4 spinel cathode thin films with three metal oxide thin layers is discussed. The changes in surface chemistry of the electrodes are measured by X-ray photoelectron spectroscopy. ZnO is found to decompose during the first charge whereas Al2O3 and ZrO2 are stable for more than 100 cycles. ZrO2, however, importantly limits the available Li storage capacity of the electrochemical reaction due to poorer kinetics. Al2O3 offers the best results in term of capacity retention. Upon cycling, the evidence of a signal at 75.4 eV in the Al2p binding energy spectrum indicates the partial conversion of Al2O3 into Al2O2F2. Moreover, the continuous formation of PEO , esters and LixPOyFz compounds on the surface of the electrodes is found for all coating materials.

Baggetto, Loic [ORNL] [ORNL; Dudney, Nancy J [ORNL] [ORNL; Veith, Gabriel M [ORNL] [ORNL

2013-01-01

365

Reflections on Small Molecule Manganese Models that Seek to Mimic Photosynthetic Water Oxidation Chemistry  

PubMed Central

Recent advances in the study of the Oxygen Evolving Complex (OEC) of Photosystem II (PSII) include structural information attained from several X-ray crystallographic (XRD) and spectroscopic (XANES and EXAFS) investigations. The possible structural features gleaned from these studies have enabled synthetic chemists to design more accurate model complexes, which in turn, offer better insight into the possible pathways used by PSII to drive photosynthetic water oxidation catalysis. Mononuclear model compounds have been used to advance the knowledge base regarding the physical properties and reactivity of high-valent (MnIV or MnV) complexes. Such investigations have been especially important in regard to the manganyl (MnIV=O or MnV?O) species, as there are no reports, to date, of any structural characterized multinuclear model compounds that incorporate such a functionality. Dinuclear and trinuclear model compounds have also been thoroughly studied in attempts to draw further comparison to the physical properties observed in the natural system and to design systems of catalytic relevance. As the reactive center of the OEC has been shown to contain an oxo-Mn4Ca cluster, exact structural models necessitate a tetranuclear Mn core. The number of models that make use of Mn4 clusters has risen substantially in recent years, and these models have provided evidence to support and refute certain mechanistic proposals. Further work is needed to adequately address the rationale for Ca (and Cl) in the OEC and to determine the sequence of events that lead to O2 evolution. PMID:19081816

Mullins, Christopher S.

2008-01-01

366

MANGANESE IN NARRAGANSETT BAY  

EPA Science Inventory

Concentrations of dissolved manganese and particulate manganese and aluminum were determined in samples from Narragansett Bay, Rhode Island, and its surrounding rivers. Total manganese is approximately conservative, but dissolved and particulate manganese are not. Desorption may ...

367

Stability of amorphous hydrous manganese oxide in contrasting soils and implications for its use in chemical stabilization of metals/metalloids in contaminated soil environments  

NASA Astrophysics Data System (ADS)

Amorphous manganese oxides are known to be efficient sorbents in soils and thus useful in remediation technologies. A novel amorphous hydrous manganese oxide (HMO) was prepared by a modified procedure generally used for birnessite synthesis. Its long-term stability in view of possible applications for chemical stabilization of metals/metalloids in polluted soils was evaluated. HMO was sealed in experimental bags prepared from polyamide fabric (pore size 1 um) and placed in the pots containing 200 g of soil. Three contrasting soils were used (two cambisols with pH values of 4.2 and 5.4, respectively, and a chernozem with a pH of 7.3). Each pot was equipped with a rhizon pore water sampler and the water content was maintained at 80% WHC throughout the experiment. HMO and pore waters were sampled after 1, 7, 15, 30, 45, 60, 75 and 90 days of incubation. Up to 113 mg Mn/L was released into pore water at the beginning of the experiment in more acidic soils indicating a slight dissolution of HMO surfaces. Manganese release into the pore water stabilized after 15 days in agreement with mass loss measurements. Mass loss decreased again after 60 days of the incubation for the neutral soil due to the formation of secondary rhodochrosite (MnCO3) detected on the HMO surfaces by X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). The efficiency of HMO for trace metal retention in soils (e.g., Zn) slightly decreased after 60 days, probably due to the mineralogical transformation of the sorbent leading to decrease of binding surfaces. Nevertheless, only approximately 10% of HMO dissolved after 90 days of experiment showing that this sorbent can be relatively stable in the studied soils. Its binding capacity for metals/metalloids should be further tested in soils with elevated contaminant concentrations.

Ettler, V.; Knytl, V.; Komarek, M.; Della Puppa, L.; Mihaljevic, M.; Sebek, O.

2012-04-01

368

Oxidative induction of pro-inflammatory cytokine formation by human monocyte-derived macrophages following exposure to manganese in vitro.  

PubMed

Abstract Manganese (as Mn(2+)), a superoxide dismutase mimetic, catalyzes the formation of the relatively stable membrane-permeable reactive oxygen species (ROS) hydrogen peroxide (H2O2), a mediator of intracellular redox signaling in immune and inflammatory cells. The goal of this study was to investigate the potential for Mn(2+), via its pro-oxidative properties, to activate production of pro-inflammatory cytokines/chemokines IL-1?, IL-6, IL-8, IFN?, TNF?, and G-CSF by human monocyte-derived macrophages in vitro. For these studies, the cells were isolated from peripheral blood mononuclear leukocytes and matured to generate a population of large CD14/CD16 co-expressing cells. The monocyte-derived macrophages were then exposed to bacterial lipopolysaccharide (LPS, 1??g/ml) or MnCl2 (25-100??M)-alone or in combination-for 24?h at 37?°C, after which cell-free supernatants were analyzed using a multiplex cytokine assay procedure. Exposure of the cells to LPS caused modest statistically insignificant increases in cytokine production; MnCl2 caused dose-related increases in production of all six cytokines (achieving statistical significance of p?

Mokgobu, Matlou I; Cholo, Moloko C; Anderson, Ronald; Steel, Helen C; Motheo, Maraki P; Hlatshwayo, Thembani N; Tintinger, Gregory R; Theron, Annette J

2015-01-01

369

Copper-manganese mixed oxides: CO2-selectivity, stable, and cyclic performance for chemical looping combustion of methane.  

PubMed

Chemical looping combustion (CLC) is a key technology for oxy-fuel combustion with inherent separation of CO2 from a flue gas, in which oxygen is derived from a solid oxygen carrier. Multi-cycle CLC performance and the product selectivity towards CO2 formation were achieved using mixed oxide of Cu and Mn (CuMn2O4) (Fd3[combining macron]m, a = b = c = 0.83 nm) as an oxygen carrier. CuMn2O4 was prepared by the co-precipitation method followed by annealing at 900 °C using copper(II) nitrate trihydrate and manganese(II) nitrate tetrahydrate as metal precursors. CuMn2O4 showed oxygen-desorption as well as reducibility at elevated temperatures under CLC conditions. The lattice of CuMn2O4 was altered significantly at higher temperature, however, it was reinstated virtually upon cooling in the presence of air. CuMn2O4 was reduced to CuMnO2, Mn3O4, and Cu2O phases at the intermediate stages, which were further reduced to metallic Cu and MnO upon the removal of reactive oxygen from their lattice. CuMn2O4 showed a remarkable activity towards methane combustion reaction at 750 °C. The reduced phase of CuMn2O4 containing Cu and MnO was readily reinstated when treated with air or oxygen at 750 °C, confirming efficient regeneration of the oxygen carrier. Neither methane combustion efficiency nor oxygen carrying capacity was altered with the increase of CLC cycles at any tested time. The average oxygen carrying capacity of CuMn2O4 was estimated to be 114 mg g(-1), which was not altered significantly with the repeated CLC cycles. Pure CO2 but no CO, which is one of the possible toxic by-products, was formed solely upon methane combustion reaction of CuMn2O4. CuMn2O4 shows potential as a practical CLC material both in terms of multi-cycle performance and product selectivity towards CO2 formation. PMID:25110101

Mungse, Pallavi; Saravanan, Govindachetty; Uchiyama, Tomoki; Nishibori, Maiko; Teraoka, Yasutake; Rayalu, Sadhana; Labhsetwar, Nitin

2014-09-28

370

Porous cobalt-manganese oxide nanocubes derived from metal organic frameworks as a cathode catalyst for rechargeable Li-O2 batteries  

NASA Astrophysics Data System (ADS)

The development of cathode catalysts with a porous structure is essential to design Li-O2 batteries with a high rate performance and good cycle stability. Herein, spinel-type porous cobalt-manganese oxide (Co-Mn-O) nanocubes derived from metal organic frameworks were employed as an electrocatalyst in a Li-O2 battery. The battery with the porous Co-Mn-O nanocubes electrode showed a low overpotential and enhanced capacity. The synergistic effects of large specific surface area, porous structure, and the high electrocatalytic activity of the porous Co-Mn-O nanocubes electrode endowed the Li-O2 battery with a good rate performance and excellent cycle stability up to 100 cycles.The development of cathode catalysts with a porous structure is essential to design Li-O2 batteries with a high rate performance and good cycle stability. Herein, spinel-type porous cobalt-manganese oxide (Co-Mn-O) nanocubes derived from metal organic frameworks were employed as an electrocatalyst in a Li-O2 battery. The battery with the porous Co-Mn-O nanocubes electrode showed a low overpotential and enhanced capacity. The synergistic effects of large specific surface area, porous structure, and the high electrocatalytic activity of the porous Co-Mn-O nanocubes electrode endowed the Li-O2 battery with a good rate performance and excellent cycle stability up to 100 cycles. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05865h

Zhang, Jian; Wang, Liangjun; Xu, Leilei; Ge, Xiaoming; Zhao, Xiao; Lai, Min; Liu, Zhaolin; Chen, Wei

2014-12-01

371

Carbon nanotube-assisted electrodeposition. Part II: Superior pseudo-capacitive behavior of manganese oxide film electrodeposited at high current densities  

NASA Astrophysics Data System (ADS)

A practical approach for controlling the morphology and electrochemical properties of electroactive materials is proposed. In this study, manganese oxide films were galvanostatically deposited in the presence of a small amount of carbon nanotube (CNT). The resulting film cannot be considered as a CNT-based nanocomposite, as no CNT is detected by electron microscopy. However, the manganese oxide electrodeposited delivers an excellent pseudo-capacitive behavior to be used as a superior supercapacitor. The samples prepared by applying a current density of 3.0 mA cm-2 showed a specific capacitance of 280 F g-1. As it seems that the capacitance of this electrode is related to the chemisorption of the alkali cation, an extremely high specific capacitance of 434 F g-1 was achieved in a saturated medium of Li electrolyte. This high specific capacitance can be attributed to a bulk process. The presence of carbon nanotubes results in the formation of nanostructured films which provide a better accessibility for capacitive behavior. Although the exact mechanism for this phenomenon is still vague, the presence of carbon nanotubes (probably as a solid charge carrier) close to the electrode surface is apparently responsible for a different pathway for the electrodeposition process.

Eftekhari, Ali; Molaei, Foroogh

2015-01-01

372

Elimination of Manganese(II,III) Oxidation in Pseudomonas putida GB-1 by a Double Knockout of Two Putative Multicopper Oxidase Genes  

PubMed Central

Bacterial manganese(II) oxidation impacts the redox cycling of Mn, other elements, and compounds in the environment; therefore, it is important to understand the mechanisms of and enzymes responsible for Mn(II) oxidation. In several Mn(II)-oxidizing organisms, the identified Mn(II) oxidase belongs to either the multicopper oxidase (MCO) or the heme peroxidase family of proteins. However, the identity of the oxidase in Pseudomonas putida GB-1 has long remained unknown. To identify the P. putida GB-1 oxidase, we searched its genome and found several homologues of known or suspected Mn(II) oxidase-encoding genes (mnxG, mofA, moxA, and mopA). To narrow this list, we assumed that the Mn(II) oxidase gene would be conserved among Mn(II)-oxidizing pseudomonads but not in nonoxidizers and performed a genome comparison to 11 Pseudomonas species. We further assumed that the oxidase gene would be regulated by MnxR, a transcription factor required for Mn(II) oxidation. Two loci met all these criteria: PputGB1_2447, which encodes an MCO homologous to MnxG, and PputGB1_2665, which encodes an MCO with very low homology to MofA. In-frame deletions of each locus resulted in strains that retained some ability to oxidize Mn(II) or Mn(III); loss of oxidation was attained only upon deletion of both genes. These results suggest that PputGB1_2447 and PputGB1_2665 encode two MCOs that are independently capable of oxidizing both Mn(II) and Mn(III). The purpose of this redundancy is unclear; however, differences in oxidation phenotype for the single mutants suggest specialization in function for the two enzymes. PMID:23124227

McCarthy, James K.; Tebo, Bradley M.

2013-01-01

373

On Manganese in Sea and Fresh Waters  

Microsoft Academic Search

Chemical and spectrographic analyses have shown that the sea contains a variable quantity of manganese, ranging between 1 ~d 10 mg.jm.3 (Thomp- son & Wilson, 1935; Noddack & Noddack, 1940), while river waters contain some 500 to 1000 mg.jm.3 (Twenhofel, 1938). These 'estimates include manganese in solution and that present as particulate or colloidal oxides soluble in concentrated hydrochloric acid.

H. W. Harvey

1949-01-01

374

Induction of oxidative stress and inflammatory cytokines by manganese chloride in cultured T98G cells, human brain glioblastoma cell line  

Microsoft Academic Search

Manganese, an essential trace nutrient in human beings, has been widely used in the steel industry to improve hardness, stiffness, and strength. With the increased applications of manganese compounds, discharge into the environment has rapidly increased and may exert adverse effects on human health. In this study, manganese toxicity was investigated using cultured T98G cells, which are derived from human

Eun-Jung Park

2010-01-01

375

Porous cobalt-manganese oxide nanocubes derived from metal organic frameworks as a cathode catalyst for rechargeable Li-O2 batteries.  

PubMed

The development of cathode catalysts with a porous structure is essential to design Li-O2 batteries with a high rate performance and good cycle stability. Herein, spinel-type porous cobalt-manganese oxide (Co-Mn-O) nanocubes derived from metal organic frameworks were employed as an electrocatalyst in a Li-O2 battery. The battery with the porous Co-Mn-O nanocubes electrode showed a low overpotential and enhanced capacity. The synergistic effects of large specific surface area, porous structure, and the high electrocatalytic activity of the porous Co-Mn-O nanocubes electrode endowed the Li-O2 battery with a good rate performance and excellent cycle stability up to 100 cycles. PMID:25429438

Zhang, Jian; Wang, Liangjun; Xu, Leilei; Ge, Xiaoming; Zhao, Xiao; Lai, Min; Liu, Zhaolin; Chen, Wei

2014-12-11

376

Heterogeneous catalytic ozonation of biologically pretreated Lurgi coal gasification wastewater using sewage sludge based activated carbon supported manganese and ferric oxides as catalysts.  

PubMed

Sewage sludge of biological wastewater treatment plant was converted into sewage sludge based activated carbon (SBAC) with ZnCl? as activation agent, which supported manganese and ferric oxides as catalysts (including SBAC) to improve the performance of ozonation of real biologically pretreated Lurgi coal gasification wastewater. The results indicated catalytic ozonation with the prepared catalysts significantly enhanced performance of pollutants removal and the treated wastewater was more biodegradable and less toxic than that in ozonation alone. On the basis of positive effect of higher pH and significant inhibition of radical scavengers in catalytic ozonation, it was deduced that the enhancement of catalytic activity was responsible for generating hydroxyl radicals and the possible reaction pathway was proposed. Moreover, the prepared catalysts showed superior stability and most of toxic and refractory compounds were eliminated at successive catalytic ozonation runs. Thus, the process with economical, efficient and sustainable advantages was beneficial to engineering application. PMID:24907577

Zhuang, Haifeng; Han, Hongjun; Hou, Baolin; Jia, Shengyong; Zhao, Qian

2014-08-01

377

High-performance binder-free supercapacitor electrode by direct growth of cobalt-manganese composite oxide nansostructures on nickel foam  

PubMed Central

A facile approach composed of hydrothermal process and annealing treatment is proposed to directly grow cobalt-manganese composite oxide ((Co,Mn)3O4) nanostructures on three-dimensional (3D) conductive nickel (Ni) foam for a supercapacitor electrode. The as-fabricated porous electrode exhibits excellent rate capability and high specific capacitance of 840.2 F g-1 at the current density of 10 A g-1, and the electrode also shows excellent cycling performance, which retains 102% of its initial discharge capacitance after 7,000 cycles. The fabricated binder-free hierarchical composite electrode with superior electrochemical performance is a promising candidate for high-performance supercapacitors. PMID:25258611

2014-01-01

378

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

SciTech Connect

Hexavalent chromium is a highly toxic contaminant that has been introduced into aquifers and shallow sediments and soils via many anthropogenic activities. Hexavalent chromium contamination is a problem or potential problem in the shallow subsurface at several DOE sites, including Hanford, Idaho National Laboratory, Los Alamos National Laboratory and the Oak Ridge Reservation (DOE, 2008). To accurately quantify the fate and transport of hexavalent chromium at DOE and other contaminated sites, robust geochemical models, capable of correctly predicting changes in chromium chemical form resulting from chemical reactions occurring in subsurface environments are needed. One important chemical reaction that may greatly impact the bioavailability and mobility of hexavalent chromium in the subsurface is chemical binding to the surfaces of particulates, termed adsorption or surface complexation. Quantitative thermodynamic surface complexation models have been derived that can correctly calculate hexavalent chromium adsorption on well-characterized materials over ranges in subsurface conditions, such pH and salinity. However, models have not yet been developed for hexavalent chromium adsorption on many important constituents of natural soils and sediments, such as clay minerals. Furthermore, most of the existing thermodynamic models have been developed for relatively simple, single solid systems and have rarely been tested for the complex mixtures of solids present in real sediments and soils. In this study, the adsorption of hexavalent chromium was measured as a function of pH (3-10), salinity (0.001 to 0.1 M NaNO3), and partial pressure of carbon dioxide(0-5%) on a suite of naturally-occurring solids including goethite (FeOOH), hydrous manganese oxide (MnOOH), hydrous ferric oxide (Fe(OH)3), ?-alumina (Al2O3), kaolinite (Al2Si2O5(OH)4), and montmorillonite (Na3(Al, Mg)2Si4O10(OH)2?nH2O). The results show that all of these materials can bind substantial quantities of hexavalent chromium, especially at low pH. Unexpectedly, experiments with the clay minerals kaolinite and montmorillonite suggest that hexavalent chromium may interact with these solids over much longer periods of time than expected. Furthermore, hexavalent chromium may irreversibly bind to these solids, perhaps because of oxidation-reduction reactions occurring on the surfaces of the clay minerals. More work should be done to investigate and quantify these chemical reactions. Experiments conducted with mixtures of goethite, hydrous manganese oxide, hydrous ferric oxide, ?-alumina, montmorillonite and kaolinite demonstrate that it is possible to correctly predict hexavalent chromium binding in the presence of multiple minerals using thermodynamic models derived for the simpler systems. Further, these models suggest that of the six solid considered in this study, goethite is typically the solid to which most of the hexavalent chromium will bind. Experiments completed with organic-rich and organic-poor natural sediments demonstrate that in organic-rich substrates, organic matter is likely to control uptake of the hexavalent chromium. The models derived and tested in this study for hexavalent chromium binding to ?-alumina, hydrous manganese oxide, goethite, hydrous ferric oxide and clay minerals can be used to better predict changes in hexavalent chromium bioavailability and mobility in contaminated sediments and soils.

Koretsky, Carla [Western Michigan University] [Western Michigan University

2013-11-29

379

In situ high-pressure synchrotron X-ray powder diffraction study of tunnel manganese oxide minerals: hollandite, romanechite, and todorokite  

NASA Astrophysics Data System (ADS)

In situ high-pressure synchrotron X-ray powder diffraction study of three tunnel manganese oxide minerals (hollandite with 2 × 2 MnO6 octahedra tunnels, romanechite with 2 × 3 tunnels, and todorokite with 3 × 3 tunnels) was performed using a diamond anvil cell and nominally penetrating alcohol and water mixture as a pressure-transmitting medium up to ~8 GPa. Bulk moduli (B 0) calculated using Murnaghan's equation of state are inversely proportional to the size of the tunnel, i.e., 134(4) GPa for hollandite (I2/m), 108(2) GPa for romanechite (C2/m), and 67(5) GPa for todorokite (P2/m). On the other hand, axial compressibilities show different elastic anisotropies depending on the size of the tunnel, i.e., ?0a (a/a 0) = -0.00066(3) GPa-1, ?0b (b/b 0) = 0.00179(8) GPa-1, ?0c (c/c 0) = 0.00637(4) GPa-1 [c > b > a] for hollandite; ?0a (a/a 0) = 0.00485(4) GPa-1, ?0b (b/b 0) = 0.0016(1) GPa-1, ?0c (c/c 0) = 0.00199(8) GPa-1 [a > c > b] for romanechite; and ?0a (a/a 0) = 0.00826(9) GPa-1, ?0b (b/b 0) = 0.0054(1) GPa-1, ?0c (c/c 0) = 0.00081(8) GPa-1 [a > b > c] for todorokite. Overall, the degree of tunnel distortion increases with increasing pressure and correlates with the size of the tunnel, which is evidenced by the gradual increases in the monoclinic ? angles up to 3 GPa of 0.62°, 0.8°, and 1.15° in hollandite, romanechite, and todorokite, respectively. The compression of tunnel manganese oxides is related to the tunnel distortion and the size of the tunnel.

Hwang, Gil Chan; Post, Jeffrey E.; Lee, Yongjae

2015-01-01

380

Siderophore-mediated oxidation of Ce and fractionation of HREE by Mn (hydr)oxide-coprecipitation and sorption on MnO2: Experimental evidence for negative Ce-anomalies in abiogenic manganese precipitates  

NASA Astrophysics Data System (ADS)

We conducted experiments with Rare Earths and Yttrium (REY), where the REY were sorbed on synthetic manganese dioxide as well as on coprecipitating manganese (hydr)oxide in the presence and absence of the siderophore desferrioxamine-B (DFOB). Siderophores are a group of globally abundant biogenic complexing agents which are excreted by plants and bacteria to enhance the bioavailability of Fe in oxic environments. The model siderophore used in this study, DFOB, is a hydroxamate siderophore occurring in almost all environmental settings with concentrations in the nanomolar to millimolar range and is one of the most thoroughly studied siderophores. In the absence of siderophores and other organic ligands, trivalent Ce is usually surface-oxidized to tetravalent Ce during sorption onto manganese (hydr)oxides. Such Mn precipitates, therefore, often show positive Ce anomalies, whereas the ambient solutions exhibit negative Ce anomalies (Ohta and Kawabe, 2001). In marked contrast, however, REY sorption in the presence of DFOB produces negative Ce anomalies in the Mn precipitates and a distinct and characteristic positive Ce anomaly in the residual siderophore-bearing solution. Furthermore, the heavy REY with ionic radii larger than the radius of Sm are also almost completely prevented from sorption onto the Mn solid phases. Sorption of REY onto Mn (hydr)oxides in the presence of DFOB creates a distinct and pronounced fractionation of Ce and the heavy REY from the light and middle REY. Apart from Ce, which is oxidized in solution by the siderophore, the distribution of the other REY mimics the stability constants for multi-dentate complexes of REY with DFOB, as determined by Christenson & Schijf (2011). Heavier REY are forming stronger complexes (and are hence better "protected" from sorption) than light REY, excluding Ce. Preferential partitioning of Ce into the liquid phase during the precipitation of Mn (hydr)oxides has only rarely been described for natural Mn (hydr)oxides (e.g., Tanaka et al., 2010, Loges et al., 2012). Our experimental results demonstrate that biogenic organic ligands such as hydroxamate siderophores, may produce solutions with positive Ce anomaly (Bau et al., 2013) and may even counteract the surface oxidation of Ce on Mn (hydr)oxides. References Bau, M., Tepe, N., Mohwinkel, D., 2013. Siderophore-promoted transfer of rare earth elements and iron from volcanic ash into glacial meltwater, river and ocean water. Earth Planet. Sci. Lett. 364, 30-36. Christenson E. A. and Schijf J. (2011) Stability of YREE complexes with the trihydroxamate siderophore desferrioxamine B at seawater ionic strength. Geochim. Cosmochim. Acta 75, 7047-7062. Loges, A., Wagner, T., Barth, M., Bau, M., Göb, S., and Markl, G. 2012. Negative Ce anomalies in Mn oxides: The role of Ce4+ mobility during water-mineral interaction. Geochimica and Cosmochimica Acta 86, 296-317 Ohta A. and Kawabe I. (2001) REE (III) adsorption onto Mn dioxide (delta-MnO2) and Fe oxyhydroxide: Ce(III) oxidation by delta-MnO2. Geochim. Cosmochim. Acta 65, 695-703. Tanaka K., Tani Y., Takahashi Y., Tanimizu M., Suzuki Y., Kozai N. and Ohnuki T. (2010) A specific Ce oxidation process during sorption of rare earth elements on biogenic Mn oxide produced by Acremonium sp. strain KR21-2. Geochim. Cosmochim. Acta 74, 5463-5477.

Krämer, Dennis; Tepe, Nathalie; Bau, Michael

2014-05-01

381

Culture-Independent Identification of Manganese-Oxidizing Genes from Deep-Sea Hydrothermal Vent Chemoautotrophic Ferromanganese Microbial Communities Using a Metagenomic Approach  

NASA Astrophysics Data System (ADS)

Microbial activity has long been recognized as being important to the fate of manganese (Mn) in hydrothermal systems, yet we know very little about the organisms that catalyze Mn oxidation, the mechanisms by which Mn is oxidized or the physiological function that Mn oxidation serves in these hydrothermal systems. Hydrothermal vents with thick ferromanganese microbial mats and Mn oxide-coated rocks observed throughout the Pacific Ring of Fire are ideal models to study the mechanisms of microbial Mn oxidation, as well as primary productivity in these metal-cycling ecosystems. We sampled ferromanganese microbial mats from Vai Lili Vent Field (Tmax=43°C) located on the Eastern Lau Spreading Center and Mn oxide-encrusted rhyolytic pumice (4°C) from Niua South Seamount on the Tonga Volcanic Arc. Metagenomic libraries were constructed and assembled from these samples and key genes known to be involved in Mn oxidation and carbon fixation pathways were identified in the reconstructed genomes. The Vai Lili metagenome assembled to form 121,157 contiguous sequences (contigs) greater than 1000bp in length, with an N50 of 8,261bp and a total metagenome size of 593 Mbp. Contigs were binned using an emergent self-organizing map of tetranucleotide frequencies. Putative homologs of the multicopper Mn-oxidase MnxG were found in the metagenome that were related to both the Pseudomonas-like and Bacillus-like forms of the enzyme. The bins containing the Pseudomonas-like mnxG genes are most closely related to uncultured Deltaproteobacteria and Chloroflexi. The Deltaproteobacteria bin appears to be an obligate anaerobe with possible chemoautotrophic metabolisms, while the Chloroflexi appears to be a heterotrophic organism. The metagenome from the Mn-stained pumice was assembled into 122,092 contigs greater than 1000bp in length with an N50 of 7635 and a metagenome size of 385 Mbp. Both forms of mnxG genes are present in this metagenome as well as the genes encoding the putative Mn oxidases McoA and MopA. The greater diversity of Mn oxidase pathways in this metagenome suggests a more diverse Mn oxidizing microbial community in the cold pumice sample. Key enzymes for four of the six known carbon fixation pathways (the Calvin Cycle, the reductive TCA cycle, the Wood-Ljungdahl pathway, and the 3-hydroxypropionate/4-hydroxybutyrate Cycle) were also identified in both samples indicating primary production occurs via a diverse community of carbon fixing organisms. Together, these samples contain active, diverse populations of Mn oxidizing bacteria living in association with microbial communities supported by chemoautotrophic carbon fixation.

Davis, R.; Tebo, B. M.

2013-12-01

382

Biomineralisation of manganese on titanium surfaces exposed to seawater.  

PubMed

A 2-year long study was carried out to isolate and characterise various bacterial species present in the biofilm formed on titanium surfaces exposed to seawater and to assess the manganese oxidizing potential of the marine isolates. The amount of manganese present in the biofilm was also measured using atomic absorption spectrometry (AAS). The results showed that titanium was susceptible to biofouling. More than 50% of the culturable marine bacterial isolates were capable of bringing about oxidation of Mn(II). All these manganese oxidizing bacteria were heterotrophic. Autotrophic manganese oxidizing bacteria such as Leptothrix was not isolated in the present study. The AAS results confirmed that the manganese content in the biofilms increased with increasing exposure time. Hence, the study indicates that the titanium surfaces when exposed to seawater were colonised by a large number of heterotrophic bacteria, which have the ability of bringing about biomineralisation of manganese. PMID:18568665

Gopal, Judy; Muraleedharan, P; Sarvamangala, H; George, R P; Dayal, R K; Tata, B V R; Khatak, H S; Natarajan, K A

2008-01-01

383

Beneficiation and agglomeration process to utilize low-grade ferruginous manganese ore fines  

Microsoft Academic Search

Characterisation, beneficiation and agglomeration studies were carried out to develop a utilization strategy for typical Indian low grade manganese ore fines. The major mineral phases found are pyrolusite, hematite, goethite, clay, feldspar and quartz. QEMSCAN and Sink–Float studies suggested that 40% of manganese minerals are in liberated form, whereas 30% are locked with iron minerals. Classification followed by two-stage high

Veerendra Singh; Tamal K. Ghosh; Y. Ramamurthy; Vilas Tathavadkar

2011-01-01

384

Concretionary manganese-iron oxides in streams and their usefulness as a sample medium for geochemical prospecting  

USGS Publications Warehouse

Correlation studies of 400 samples of sieved stream sediments and 325 samples of fluvial, concretionary Mn-Fe oxides from Maine resulted in the separation of elements into the following categories: (1) elements not scavenged by Mn-Fe oxides - B, Cr, K, Mg, Rb, Sc, Ti, V, and Zr; (2) elements probably not scavenged by Mn-Fe oxides - Ag, Be, Ca, Ga, La, Sb, and Y; (3) elements scavenged weakly by Mn-Fe oxides - Cu, Mo, Pb, and Sr; (4) elements scavenged strongly by Mn oxides - Ba, Cd, Co, Ni, Tl, and Zn; and (5) elements scavenged strongly by Fe oxides - As and In. Studies of the scavenged elements showed that the deviation from the mean is characteristically greater in oxide samples as compared to sieved sediments from the same locality. However, a significant increase in contrast between anomalous and background localities, when oxides are the sample medium, more than offsets the disadvantage of data scatter. The use of oxides as a sampling medium clearly and significantly accentuates anomalous localities. In general, non-ratioed data on oxides give very nearly the same results as data consisting of scavenged elements ratioed to Mn and Fe. However, ratioed data expand the geographic area of specific anomalies. Cd and Zn consistently show strong correlations with concretionary Mn-Fe oxides, but their concentrations in the oxides do not generally show as much contrast between anomalous and background localities as do Cu, Mo, and Pb. These latter elements are strongly scavenged where rocks are mineralized. ?? 1976.

Nowlan, G.A.

1976-01-01

385

The impact of partial manganese superoxide dismutase (SOD2)-deficiency on mitochondrial oxidant stress, DNA fragmentation and liver injury during acetaminophen hepatotoxicity  

SciTech Connect

Acetaminophen (APAP) hepatotoxicity is the most frequent cause of acute liver failure in many countries. The mechanism of cell death is initiated by formation of a reactive metabolite that binds to mitochondrial proteins and promotes mitochondrial dysfunction and oxidant stress. Manganese superoxide dismutase (SOD2) is a critical defense enzyme located in the mitochondrial matrix. The objective of this investigation was to evaluate the functional consequences of partial SOD2-deficiency (SOD2+/-) on intracellular signaling mechanisms of necrotic cell death after APAP overdose. Treatment of C57Bl/6J wild type animals with 200 mg/kg APAP resulted in liver injury as indicated by elevated plasma alanine aminotransferase activities (2870 {+-} 180 U/L) and centrilobular necrosis at 6 h. In addition, increased tissue glutathione disulfide (GSSG) levels and GSSG-to-GSH ratios, delayed mitochondrial GSH recovery, and increased mitochondrial protein carbonyls and nitrotyrosine protein adducts indicated mitochondrial oxidant stress. In addition, nuclear DNA fragmentation (TUNEL assay) correlated with translocation of Bax to the mitochondria and release of apoptosis-inducing factor (AIF). Furthermore, activation of c-jun-N-terminal kinase (JNK) was documented by the mitochondrial translocation of phospho-JNK. SOD2+/- mice showed 4-fold higher ALT activities and necrosis, an enhancement of all parameters of the mitochondrial oxidant stress, more AIF release and more extensive DNA fragmentation and more prolonged JNK activation. Conclusions: the impaired defense against mitochondrial superoxide formation in SOD2+/- mice prolongs JNK activation after APAP overdose and consequently further enhances the mitochondrial oxidant stress leading to exaggerated mitochondrial dysfunction, release of intermembrane proteins with nuclear DNA fragmentation and more necrosis.

Ramachandran, Anup; Lebofsky, Margitta [Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, 3901 Rainbow Blvd, MS 1018, Kansas City, KS 66160 (United States); Weinman, Steven A. [Department of Medicine and Microbiology and Immunology, University of Kansas Medical Center, Kansas City, KS 66160 (United States); Jaeschke, Hartmut, E-mail: hjaeschke@kumc.edu [Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, 3901 Rainbow Blvd, MS 1018, Kansas City, KS 66160 (United States)

2011-03-15

386

Stability and Rate Capability of Al Substituted Lithium-Rich High-Manganese Content Oxide Materials for Li-Ion Batteries  

SciTech Connect

The structures, electrochemical properties and thermal stability of Al-substituted lithium-excess oxides, Li{sub 1.2}Ni{sub 0.16} Mn{sub 0.56}Co{sub 0.08-y}Al{sub y}O{sub 2} (y = 0, 0.024, 0.048, 0.08), are reported, and compared to the stoichiometric compounds, LiNi{sub z}Mn{sub z}Co{sub 1-2z}O{sub 2}. A solid solution was found up to at least y = 0.06. Aluminum substitution improves the poor thermal stability while preserving the high energy density of lithium-excess oxides. However, these high manganese compositions are inferior to the lithium stoichiometric materials, LiNi{sub z}Mn{sub z}Co{sub 1-2z}O{sub 2} (z = 0.333, 0.4), in terms of both power and thermal stability.

Li, Zheng; Chernova, Natasha A.; Feng, Jijun; Upreti, Shailesh; Omenya, Fredrick; Whittingham, M. Stanley (SUNY-Binghamton)

2012-03-15

387

Biogeochemical cycling of manganese in Oneida Lake, New York: whole lake studies of manganese  

NASA Technical Reports Server (NTRS)

Oneida Lake, New York is a eutrophic freshwater lake known for its abundant manganese nodules and a dynamic manganese cycle. Temporal and spatial distribution of soluble and particulate manganese in the water column of the lake were analyzed over a 3-year period and correlated with other variables such as oxygen, pH, and temperature. Only data from 1988 are shown. Manganese is removed from the water column in the spring via conversion to particulate form and deposited in the bottom sediments. This removal is due to biological factors, as the lake Eh/pH conditions alone can not account for the oxidation of the soluble manganese Mn(II). During the summer months the manganese from microbial reduction moves from the sediments to the water column. In periods of stratification the soluble Mn(II) builds up to concentrations of 20 micromoles or more in the bottom waters. When mixing occurs, the soluble Mn(II) is rapidly removed via oxidation. This cycle occurs more than once during the summer, with each manganese atom probably being used several times for the oxidation of organic carbon. At the end of the fall, whole lake concentrations of manganese stabilize, and remain at about 1 micromole until the following summer, when the cycle begins again. Inputs and outflows from the lake indicate that the active Mn cycle is primarily internal, with a small accumulation each year into ferromanganese nodules located in the oxic zones of the lake.

Aguilar, C.; Nealson, K. H.

1998-01-01

388

Quartz Crystal Clocks  

NASA Technical Reports Server (NTRS)

General Time Corporation, under contract to NASA, developed a quartz crystal for obtaining a stable time base from which all mission times could be derived. This later became basis of consumer clocks and watches with accuracy of one minute a year, watches useful in timing sports events as well as general use. When quartz is electrically stimulated it can vibrate millions of times a second. Since timepieces use a vibrating body to keep up time, incredibly fast vibration of a quartz crystal--up to 4,194,304 beats a second opened a new horizon in accuracy.

1976-01-01

389

Geodynamic and climate controls in the formation of Mio-Pliocene world-class oxidized cobalt and manganese ores in the Katanga province, DR Congo  

NASA Astrophysics Data System (ADS)

The Katanga province, Democratic Republic of Congo, hosts world-class cobalt deposits accounting for ~50% of the world reserves. They originated from sediment-hosted stratiform copper and cobalt sulfide deposits within Neoproterozoic metasedimentary rocks. Heterogenite, the main oxidized cobalt mineral, is concentrated as “cobalt caps” along the top of silicified dolomite inselbergs. The supergene cobalt enrichment process is part of a regional process of residual ore formation that also forms world-class “manganese cap” deposits in western Katanga, i.e., the “black earths” that are exploited by both industrial and artisanal mining. Here, we provide constraints on the genesis and the timing of these deposits. Ar-Ar analyses of oxidized Mn ore and in situ U-Pb SIMS measurements of heterogenite yield Mio-Pliocene ages. The Ar-Ar ages suggest a multi-phase process, starting in the Late Miocene (10-5 Ma), when the metal-rich substratum was exposed to the action of meteoric fluids, due to major regional uplift. Further oxidation took place in the Pliocene (3.7-2.3 Ma) and formed most of the observed deposits under humid conditions: Co- and Mn-caps on metal-rich substrata, and coeval Fe laterites on barren areas. These deposits formed prior to the regional shift toward more arid conditions in Central Africa. Arid conditions still prevailed during the Quaternary and resulted in erosion and valley incision, which dismantled the metal-bearing caps and led to ore accumulation in valleys and along foot slopes.

Decrée, Sophie; Deloule, Étienne; Ruffet, Gilles; Dewaele, Stijn; Mees, Florias; Marignac, Christian; Yans, Johan; de Putter, Thierry

2010-10-01

390

Induced oxidative stress and activated expression of manganese superoxide dismutase during hepatitis C virus replication: role of JNK, p38 MAPK and AP-1.  

PubMed Central

Activation of cellular kinases and transcription factors mediates the early phase of the cellular response to chemically or biologically induced stress. In the present study we investigated the oxidant/antioxidant balance in Huh-7 cells expressing the HCV (hepatitis C virus) subgenomic replicon, and observed a 5-fold increase in oxidative stress during HCV replication. We used MnSOD (manganese-superoxide dismutase) as an indicator of the cellular antioxidant response, and found that its activity, protein levels and promoter activity were significantly increased, whereas Cu/ZnSOD was not affected. The oxidative stress-induced protein kinases p38 MAPK (mitogen-activated protein kinase) and JNK (c-Jun N-terminal kinase) were activated in the HCV repliconcontaining cells and in Huh-7 cells transduced with Ad-NS5A [a recombinant adenovirus encoding NS5A (non-structural protein 5A)], coupled with a 4-5-fold increase in AP-1 (activator protein-1) DNA binding. Ava.1 cells, which encode a replication-defective HCV replicon, showed no significant changes in MnSOD, p38 MAPK or JNK activity. The AP-1 inhibitors dithiothreitol and N -acetylcysteine, as well as a dominant negative AP-1 mutant, significantly reduced AP-1 activation, demonstrating that this activation is oxidative stress-related. Exogenous NS5A had no effect on AP-1 activation in vitro, suggesting that NS5A acts at the upstream targets of AP-1 involving p38 MAPK and JNK signalling cascades. AP-1-dependent gene expression was increased in HCV subgenomic replicon-expressing Huh-7 cells. MnSOD activation was blocked by inhibitors of JNK (JNKI1) and p38 MAPK (SB203580), but not by an ERK (extracellular-signal-regulated kinase) inhibitor (U0126), in HCV-replicating and Ad-NS5A-transduced cells. Our results demonstrate that cellular responses to oxidative stress in HCV subgenomic replicon-expressing and Ad-NS5A-transduced cells are regulated by two distinct signalling pathways involving p38 MAPK and JNK via AP-1 that is linked to increased oxidative stress and therefore to an increased antioxidant MnSOD response. PMID:14670077

Qadri, Ishtiaq; Iwahashi, Mieko; Capasso, Juan M; Hopken, Matthew W; Flores, Sonia; Schaack, Jerome; Simon, Francis R

2004-01-01

391

Protective effects of manganese(II) chloride on hyaluronan degradation by oxidative system ascorbate plus cupric chloride  

Microsoft Academic Search

The degradation of several high-molar-mass hyaluronan samples was investigated in the presence of ascorbic acid itself and further by an oxidative system composed of ascorbic acid plus transition metal ions, i.e. Fe(II) or Cu(II) ions. The latter oxidative system imitates conditions in a joint synovial fluid during early phase of acute joint inflammation and can be used as a model

Katarína Valachová; Grigorij Kogan; Peter Gemeiner; Ladislav Šoltés

2010-01-01

392

Mesoporous Silica-Coated Hollow Manganese Oxide Nanoparticles as Positive T1 Contrast Agents for Labeling and MRI Tracking of Adipose-Derived Mesenchymal Stem Cells  

PubMed Central

Mesoporous silica-coated hollow manganese oxide (HMnO@mSiO2) nanoparticles were developed as a novel T1 magnetic resonance imaging (MRI) contrast agent. We hypothesized that the mesoporous structure of the nanoparticle shell enables optimal access of water molecules to the magnetic core, and consequently, an effective longitudinal (R1) relaxation enhancement of water protons, which value was measured to be 0.99 (mM?1s?1) at 11.7 T. Adipose-derived mesenchymal stem cells (MSCs) were efficiently labeled using electroporation, with much shorter T1 values as compared to direct incubation without electroporation, which was also evidenced by signal enhancement on T1-weighted MR images in vitro. Intracranial grafting of HMnO@mSiO2-labeled MSCs enabled serial MR monitoring of cell transplants over 14 days. These novel nanoparticles may extend the arsenal of currently available nanoparticle MR contrast agents by providing positive contrast on T1-weighted images at high magnetic field strengths. PMID:21314118

2011-01-01

393

Controllable synthesis of spinel lithium nickel manganese oxide cathode material with enhanced electrochemical performances through a modified oxalate co-precipitation method  

NASA Astrophysics Data System (ADS)

A spinel lithium nickel manganese oxide (LiNi0.5Mn1.5O4) cathode material is synthesized with a modified oxalate co-precipitation method by controlling pH value of the precursor solution and introducing excessive Li source in the precursor. All the samples synthesized through this method are of Fd3m phase with a small amount of P4332 phase. It is found that pH value of the precursor solution considerably affects the morphology, stoichiometry and crystallographic structure of the target material, thereby resulting in different amounts of Mn3+ (i.e., different degree of disorder). 5% excessive Li source in the precursor may compensate for the lithium loss during the high-temperature sintering process and eliminate the LixNi1-xO impurity phase. Under the optimized synthesis conditions, the obtained high-purity LiNi0.5Mn1.5O4 spinel exhibits enhanced electrochemical performances. A reversible capacity of ca. 140 mAh g-1 can be delivered at 0.1C and the electrode retains 106 mAh g-1 at 10C rate. When cycled at 0.2C, a capacity retention of more than 98% is obtained in the initial 50 electrochemical cycles.

Liu, Hongmei; Zhu, Guobin; Zhang, Li; Qu, Qunting; Shen, Ming; Zheng, Honghe

2015-01-01

394

The manganese site of the photosynthetic water-splitting enzyme  

SciTech Connect

As the originator of the oxygen in our atmosphere, the photosynthetic water-splitting enzyme of chloroplasts is vital for aerobic life on the earth. It has a manganese cluster at its active site, but it is poorly understood at the molecular level. Polarized synchrotron radiation was used to examine the x-ray absorption of manganese in oriented chloroplasts. The manganese site, in the resting (S{sub 1}) state, is an asymmetric cluster, which probably contains four manganese atoms, with interatomic separations of 2.7 and 3.3 angstroms; the vector formed by the 3.3-angstrom manganese pair is oriented perpendicular to the membrane plane. Comparisons with model compounds suggest that the cluster contains bridging oxide or hydroxide ligands connecting the manganese atoms, perhaps with carboxylate bridges connecting the 3.3-angstrom manganese pair. 24 refs., 2 figs., 1 tab.

George, G.N.; Prince, R. (Exxon Research and Engineering Co., Annandale, NJ (USA)); Cramer, S.P. (Schlumberger-Doll Research, Ridgefield, CT (USA))

1989-02-10

395

Artificial Neural Network Modelling of Photodegradation in Suspension of Manganese Doped Zinc Oxide Nanoparticles under Visible-Light Irradiation  

PubMed Central

The artificial neural network (ANN) modeling of m-cresol photodegradation was carried out for determination of the optimum and importance values of the effective variables to achieve the maximum efficiency. The photodegradation was carried out in the suspension of synthesized manganese doped ZnO nanoparticles under visible-light irradiation. The input considered effective variables of the photodegradation were irradiation time, pH, photocatalyst amount, and concentration of m-cresol while the efficiency was the only response as output. The performed experiments were designed into three data sets such as training, testing, and validation that were randomly splitted by the software's option. To obtain the optimum topologies, ANN was trained by quick propagation (QP), Incremental Back Propagation (IBP), Batch Back Propagation (BBP), and Levenberg-Marquardt (LM) algorithms for testing data set. The topologies were determined by the indicator of minimized root mean squared error (RMSE) for each algorithm. According to the indicator, the QP-4-8-1, IBP-4-15-1, BBP-4-6-1, and LM-4-10-1 were selected as the optimized topologies. Among the topologies, QP-4-8-1 has presented the minimum RMSE and absolute average deviation as well as maximum R-squared. Therefore, QP-4-8-1 was selected as final model for validation test and navigation of the process. The model was used for determination of the optimum values of the effective variables by a few three-dimensional plots. The optimum points of the variables were confirmed by further validated experiments. Moreover, the model predicted the relative importance of the variables which showed none of them was neglectable in this work. PMID:25538962

Abdollahi, Yadollah; Sairi, Nor Asrina; Amin Matori, Khamirul; Fard Masoumi, Hamid Reza

2014-01-01

396

Processes of zinc attenuation by biogenic manganese oxides forming in the hyporheic zone of Pinal Creek, Arizona.  

PubMed

The distribution and speciation of Zn sorbed to biogenic Mn oxides forming in the hyporheic zone of Pinal Creek, AZ, was investigated using extended X-ray absorption fine structure (EXAFS) and microfocused synchrotron X-ray fluorescence (?SXRF) mapping, and chemical extraction. ?SXRF and chemical extractions show that contaminant Zn co-varied with Mn in streambed sediment grain coatings. Bulk and microfocused EXAFS spectra of Zn in the biogenic Mn oxide coating are indicative of Zn forming triple-corner-sharing inner-sphere complexes over octahedral vacancies in the Mn oxide sheet structure. Zn desorbed in response to the decrease in pH in batch experiments and resulted in near-equal dissolved Zn at each pH over a 10-fold range in the solid/solution ratio. The geometry of sorbed Zn was unchanged after 50% desorption at pH 5, indicating that desorption is not controlled by dissolution of secondary Zn phases. In summary, these findings support the idea that Zn attenuation in Pinal Creek is largely controlled by sorption to microbial Mn oxides forming in the streambed during hyporheic exchange. Sorption to biogenic Mn oxides is likely an important process of Zn attenuation in circum-neutral pH reaches of many acid-mine drainage contaminated streams when dissolved Mn is present. PMID:24460038

Fuller, Christopher C; Bargar, John R

2014-02-18

397

Processes of zinc attenuation by biogenic manganese oxides forming in the hyporheic zone of Pinal Creek, Arizona  

USGS Publications Warehouse

The distribution and speciation of Zn sorbed to biogenic Mn oxides forming in the hyporheic zone of Pinal Creek, AZ, was investigated using extended X-ray absorption fine structure (EXAFS) and microfocused synchrotron X-ray fluorescence (?SXRF) mapping, and chemical extraction. ?SXRF and chemical extractions show that contaminant Zn co-varied with Mn in streambed sediment grain coatings. Bulk and microfocused EXAFS spectra of Zn in the biogenic Mn oxide coating are indicative of Zn forming triple-corner-sharing inner-sphere complexes over octahedral vacancies in the Mn oxide sheet structure. Zn desorbed in response to the decrease in pH in batch experiments and resulted in near-equal dissolved Zn at each pH over a 10-fold range in the solid/solution ratio. The geometry of sorbed Zn was unchanged after 50% desorption at pH 5, indicating that desorption is not controlled by dissolution of secondary Zn phases. In summary, these findings support the idea that Zn attenuation in Pinal Creek is largely controlled by sorption to microbial Mn oxides forming in the streambed during hyporheic exchange. Sorption to biogenic Mn oxides is likely an important process of Zn attenuation in circum-neutral pH reaches of many acid-mine drainage contaminated streams when dissolved Mn is present.

Fuller, Christopher C.; Bargar, John R.

2014-01-01

398

Near-infrared light activated release of nitric oxide from designed photoactive manganese nitrosyls: strategy, design, and potential as NO donors.  

PubMed

Two new manganese complexes derived from the pentadentate ligand N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-quinoline-2-carboxamide, PaPy2QH, where H is dissociable proton), namely, [Mn(PaPy2Q)(NO)]ClO4 (2) and [Mn(PaPy2Q)(OH)]ClO4 (3), have been synthesized and structurally characterized. The Mn(III) complex [Mn(PaPy2Q)(OH)]ClO4 (3), though insensitive to dioxygen, reacts with nitric oxide (NO) to afford the nitrosyl complex [Mn(PaPy2Q)(NO)]ClO4 (2) via reductive nitrosylation. This diamagnetic {Mn-NO}6 nitrosyl exhibits nuNO at 1725 cm-1 and is highly soluble in water, with lambdamax at 500 and 670 nm. Exposure of solutions of 2 to near-infrared (NIR) light (810 nm, 4 mW) results in bleaching of the maroon solution and detection of free NO by an NO-sensitive electrode. The quantum yield of 2 (Phi = 0.694 +/- 0.010, lambdairr = 550 nm, H2O) is much enhanced over the first generation {Mn-NO}6 nitrosyl derived from analogous polypyridine ligand, namely, [Mn(PaPy3)(NO)]ClO4 (1, Phi = 0.385 +/- 0.010, lambdairr = 550 nm, H2O), reported by this group in a previous account. Although quite active in the visible range (500-600 nm), 1 exhibits very little photoactivity under NIR light. Both 1 and 2 have been incorporated into sol-gel (SG) matrices to obtain nitrosyl-polymer composites 1.SG and 2.SG. The NO-donating capacities of the polyurethane-coated hybrid materials 1.HM and 2.HM have been determined. 2.HM has been used to transfer NO to reduced myoglobin with 780 nm light. The various strategies for synthesizing photosensitive metal nitrosyls have been discussed to establish the merits of the present approach. The results of the present study confirm that proper ligand design is a very effective way to isolate photoactive manganese nitrosyls that could be used to deliver NO to biological targets under the control of NIR light. PMID:18335935

Eroy-Reveles, Aura A; Leung, Yvonne; Beavers, Christine M; Olmstead, Marilyn M; Mascharak, Pradip K

2008-04-01

399

Role of manganese oxides in the exposure of mute swans (Cygnus olor) to Pb and other elements in the Chesapeake Bay, USA  

USGS Publications Warehouse

The aims of this study are to estimate exposure of waterfowl to elements in contaminated sediments in the Chesapeake Bay and to consider the potential role of Mn in influencing bioavailability and exposure. Mute swans living on the Aberdeen Proving Ground were collected and samples of swan digesta were analyzed and compared to samples of feces collected from mute swans living at a nearby reference site. Sediments from the proving ground had elevated concentrations of Cu, S, Se, Zn, As, Co, Cr, Hg and Pb, but concentrations of only the first four of these elements were elevated in swan digesta. Sediments from the proving ground had an elevated mean concentration of total As, about seven times the concentration at the reference site, but the swans from that site were not ingesting more As than were reference swans. Swans at both sites were feeding on submerged aquatic vegetation and ingested about 4% sediment at the proving ground and about 5% sediment at the reference site. None of the concentrations detected in the digesta or livers of the swans was considered toxic, although the concentrations of Cu and Se were high compared to those concentrations reported in other waterfowl. A remarkably high mean concentration of Mn (6900 mg/kg, dry weight) detected in the feces of the reference swans was attributed to the deposition of manganese oxides on vegetation. The ingestion of Pb by swans at the reference site was correlated with Mn and Fe concentrations, rather than with markers of sediment ingestion. The Pb was presumably scavenged by Mn and Fe oxides from the water and deposited on the surface of vegetation. Under some environmental chemical conditions, this route of exposure for Pb is more important than sediment ingestion, which w