WorldWideScience

Sample records for biogenic manganese oxide

  1. Crystal and fine structural transformation of Heat-treated biogenic manganese oxide

    Czech Academy of Sciences Publication Activity Database

    Kimura, N.; Hashimoto, H.; Miyata, N.; Nishina, Y.; Kusano, Y.; Ikeda, Y.; Nakanishi, Y.; Fujii, T.; Šafařík, Ivo; Šafaříková, Miroslava; Takada, J.

    2013-01-01

    Roč. 60, č. 3 (2013), s. 92-98 ISSN 0532-8799 R&D Projects: GA MŠk(CZ) LH11111 Institutional support: RVO:67179843 Keywords : microorganisms * biogenic manganese oxides * phase transitions * nano-sheets * microstructures Subject RIV: EH - Ecology, Behaviour

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

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, K.D.; Sposito, G.

    2010-02-01

    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.

  3. Diclofenac and 2‐anilinophenylacetate degradation by combined activity of biogenic manganese oxides and silver

    Science.gov (United States)

    Meerburg, Francis; Hennebel, Tom; Vanhaecke, Lynn; Verstraete, Willy; Boon, Nico

    2012-01-01

    Summary The occurrence of a range of recalcitrant organic micropollutants in our aquatic environment has led to the development of various tertiary wastewater treatment methods. In this study, biogenic manganese oxides (Bio‐MnOx), biogenic silver nanoparticles (Bio‐Ag0) and ionic silver were used for the oxidative removal of the frequently encountered drug diclofenac and its dechlorinated form, 2‐anilinophenylacetate (APA). Diclofenac was rapidly degraded during ongoing manganese oxidation by Pseudomonas putida MnB6. Furthermore, whereas preoxidized Bio‐MnOx, Bio‐Ag0 and Ag+ separately did not show any removal capacity for diclofenac, an enhanced removal occurred when Bio‐MnOx and silver species were combined. Similar results were obtained for APA. Finally, a slow removal of diclofenac but more rapid APA degradation was observed when silver was added to manganese‐free P. putida biomass. Combining these results, three mechanisms of diclofenac and APA removal could be distinguished: (i) a co‐metabolic removal during active Mn2+ oxidation by P. putida; (ii) a synergistic interaction between preoxidized Bio‐MnOx and silver species; and (iii) a (bio)chemical process by biomass enriched with silver catalysts. This paper demonstrates the use of P. putida for water treatment purposes and is the first report of the application of silver combined with biogenic manganese for the removal of organic water contaminants. PMID:22221449

  4. Biogenic precipitation of manganese oxides and enrichment of heavy metals at acidic soil pH

    Science.gov (United States)

    Mayanna, Sathish; Peacock, Caroline L.; Schäffner, Franziska; Grawunder, Anja; Merten, Dirk; Kothe, Erika; Büchel, Georg

    2014-05-01

    The precipitation of biogenic Mn oxides at acidic pH is rarely reported and poorly understood, compared to biogenic Mn oxide precipitation at near neutral conditions. Here we identified and investigated the precipitation of biogenic Mn oxides in acidic soil, and studied their role in the retention of heavy metals, at the former uranium mining site of Ronneburg, Germany. The site is characterized by acidic pH, low carbon content and high heavy metal loads including rare earth elements. Specifically, the Mn oxides were present in layers identified by detailed soil profiling and within these layers pH varied from 4.7 to 5.1, Eh varied from 640 to 660 mV and there were enriched total metal contents for Ba, Ni, Co, Cd and Zn in addition to high Mn levels. Using electron microprobe analysis, synchrotron X-ray diffraction and X-ray absorption spectroscopy, we identified poorly crystalline birnessite (δ-MnO2) as the dominant Mn oxide in the Mn layers, present as coatings covering and cementing quartz grains. With geochemical modelling we found that the environmental conditions at the site were not favourable for chemical oxidation of Mn(II), and thus we performed 16S rDNA sequencing to isolate the bacterial strains present in the Mn layers. Bacterial phyla present in the Mn layers belonged to Firmicutes, Actinobacteria and Proteobacteria, and from these phyla we isolated six strains of Mn(II) oxidizing bacteria and confirmed their ability to oxidise Mn(II) in the laboratory. The biogenic Mn oxide layers act as a sink for metals and the bioavailability of these metals was much lower in the Mn layers than in adjacent layers, reflecting their preferential sorption to the biogenic Mn oxide. In this presentation we will report our findings, concluding that the formation of natural biogenic poorly crystalline birnessite can occur at acidic pH, resulting in the formation of a biogeochemical barrier which, in turn, can control the mobility and bioavailability of heavy metals in

  5. Activated carbon doped with biogenic manganese oxides for the removal of indigo carmine.

    Science.gov (United States)

    Hu, Yichen; Chen, Xiao; Liu, Zhiqiang; Wang, Gejiao; Liao, Shuijiao

    2016-01-15

    Indigo carmine (IC) is one of the oldest, most important, and highly toxic dyes which is released from the effluents of many industries and results in serious pollution in water. In this study, the biogenic Mn oxides were activated by NaOH and then heated for 3 h at 350 °C to produce activated carbon doped with Mn oxide (Bio-MnOx-C), which were produced by culturing Mn (II)-oxidizing bacterial strain MnI7-9 in liquid A medium at 28 °C with 10 mmol/L MnCl2. Bio-MnOx-C was characterized by SEM, TEM, IR, XPS, XRD, etc. It contained C, O, and Mn which comprised Mn (IV) and Mn (III) valence states at a ratio of 3.81:1. It had poorly crystalline ε-MnO2 with a specific surface area of 130.94 m(2)/g. A total of 0.1 g Bio-MnOx-C could remove 45.95 g IC from 500 mg/L IC solution after 0.5 h contact time. IC removal by Bio-MnOx-C included a rapid oxidation reaction and the removal reaction followed second-order kinetic equation. These results confirmed that Bio-MnOx-C could be a potential material for wastewater remediation. Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. Spatially Resolved Characterization of Biogenic Manganese Oxide Production within a Bacterial Biofilm

    Science.gov (United States)

    Toner, Brandy; Fakra, Sirine; Villalobos, Mario; Warwick, Tony; Sposito, Garrison

    2005-01-01

    Pseudomonas putida strain MnB1, a biofilm-forming bacterial culture, was used as a model for the study of bacterial Mn oxidation in freshwater and soil environments. The oxidation of aqueous Mn+2 [Mn+2(aq)] by P. putida was characterized by spatially and temporally resolving the oxidation state of Mn in the presence of a bacterial biofilm, using scanning transmission X-ray microscopy (STXM) combined with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at the Mn L2,3 absorption edges. Subsamples were collected from growth flasks containing 0.1 and 1 mM total Mn at 16, 24, 36, and 48 h after inoculation. Immediately after collection, the unprocessed hydrated subsamples were imaged at a 40-nm resolution. Manganese NEXAFS spectra were extracted from X-ray energy sequences of STXM images (stacks) and fit with linear combinations of well-characterized reference spectra to obtain quantitative relative abundances of Mn(II), Mn(III), and Mn(IV). Careful consideration was given to uncertainty in the normalization of the reference spectra, choice of reference compounds, and chemical changes due to radiation damage. The STXM results confirm that Mn+2(aq) was removed from solution by P. putida and was concentrated as Mn(III) and Mn(IV) immediately adjacent to the bacterial cells. The Mn precipitates were completely enveloped by bacterial biofilm material. The distribution of Mn oxidation states was spatially heterogeneous within and between the clusters of bacterial cells. Scanning transmission X-ray microscopy is a promising tool for advancing the study of hydrated interfaces between minerals and bacteria, particularly in cases where the structure of bacterial biofilms needs to be maintained. PMID:15746332

  7. The generation of biogenic manganese oxides and its application in the removal of As(III) in groundwater.

    Science.gov (United States)

    Liang, Guannan; Yang, Yu; Wu, Simiao; Jiang, Yonghai; Xu, Yunfeng

    2017-07-01

    The generation of biogenic manganese oxides (BMnOx) by Microbacterium sp. CSA40, and As(III) removal efficiency and mechanism by BMnOx were investigated in this study. The propagation and growth of Microbacterium sp. CSA40 was conducted in half-strength Luria Broth with 10 mg/L Mn(II), then high concentration of Microbacterium sp. CSA40 was added to PYG medium making its OD600 = 0.9 ± 0.05 for BMnOx generation. The initial Mn(II) concentrations, excessively oligotrophic condition, and pH had great influence on generation of BMnOx by Microbacterium sp. CSA40. An appropriate Mn(II) concentration (50 mg/L) was obtained for generation of BMnOx, and higher or lower Mn(II) concentration would interfere Mn(II) oxidization performance. Mn(II) oxidation ability performed best in weak alkaline conditions and would be restricted in an excessively oligotrophic condition. As(III) oxidization and As(V) adsorption proceed simultaneously by BMnOx, what is more, more than 90% of total As was removed by 0.5 g/L BMnOx. During the application process, no Mn(II) was released in the solution, that is, BMnOx retained its ability for Mn(II) oxidization caused by activity of Microbacterium sp. CSA40. Therefore, BMnOx would be a pollution-free, cost-effective, and high-efficiency material for As(III) treatment in groundwater.

  8. Biogenic manganese oxide nanoparticle formation by a multimeric multicopper oxidase Mnx

    Energy Technology Data Exchange (ETDEWEB)

    Romano, Christine A.; Zhou, Mowei; Song, Yang; Wysocki, Vicki H.; Dohnalkova, Alice C.; Kovarik, Libor; Paša-Tolić, Ljiljana; Tebo, Bradley M.

    2017-09-29

    Bacteria that produce Mn oxides are extraordinarily skilled engineers of nanomaterials that contribute significantly to global biogeochemical cycles. Their enzyme-based reaction mechanisms may be genetically tailored for environmental remediation applications or bioenergy production. However, significant challenges exist for structural characterization of the enzymes responsible for biomineralization. The active Mn oxidase, Mnx, in Bacillus sp. PL-12 is a complex composed of a multicopper oxidase (MCO), MnxG, and two accessory proteins MnxE and MnxF. MnxG shares sequence similarity with other, structurally characterized MCOs. However, MnxE and MnxF have no similarity to any characterized proteins. The ~200 kDa complex has been recalcitrant to crystallization, so its structure is unknown. In this study, native mass spectrometry defines the subunit topology and copper binding of the Mnx complex, while high resolution electron microscopy visualizes the protein and nascent Mn oxide minerals. These data provide critical structural information for conceptualizing how Mnx produces nanoparticulate Mn oxides.

  9. Synthesis and characterization of a novel extracellular biogenic manganese oxide (bixbyite-like Mn₂O₃) nanoparticle by isolated Acinetobacter sp.

    Science.gov (United States)

    Hosseinkhani, Baharak; Emtiazi, Giti

    2011-09-01

    Recently, manganese oxides have been considered in the environmental remediation, MRI diagnosis and drug and pharmaceutical industries. Different numbers of physicochemical and biological methods have been reported for the preparation of nanoscale manganese oxides. Although manganese oxide biogenesis by bacterial species has been recognized as the major Mn-oxidizing agent in nature, in this research, for first time, we demonstrated the process which used to produce bixbyite-like Mn(2)O(3) nanoparticles by isolated aerobic bacterium from Persian Gulf water. The 16SRNA sequencing showed that this isolate belong to a gram-negative Acinetobacter which produced nano Mn-oxide crystal particle. Characterization of complement morphology, size and chemical structure of these particles were determined by TEM, SEM, EDAX, XRD and FTIR. The data showed that this bacterium could produce nanosized extracellular bixbyite-like Mn(2)O(3) which depend on enzymatic pathway.

  10. Biogenic Mn-Oxides in Subseafloor Basalts.

    Science.gov (United States)

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

    2015-01-01

    The deep biosphere of the subseafloor basalts is recognized as a major scientific frontier in disciplines like biology, geology, and oceanography. Recently, the presence of fungi in these environments has involved a change of view regarding diversity and ecology. Here, we describe fossilized fungal communities in vugs in subseafloor basalts from a depth of 936.65 metres below seafloor at the Detroit Seamount, Pacific Ocean. These fungal communities are closely associated with botryoidal Mn oxides composed of todorokite. Analyses of the Mn oxides by Electron Paramagnetic Resonance spectroscopy (EPR) indicate a biogenic signature. We suggest, based on mineralogical, morphological and EPR data, a biological origin of the botryoidal Mn oxides. Our results show that fungi are involved in Mn cycling at great depths in the seafloor and we introduce EPR as a means to easily identify biogenic Mn oxides in these environments.

  11. Biomimetic Water-Oxidation Catalysts: Manganese Oxides.

    Science.gov (United States)

    Kurz, Philipp

    2016-01-01

    The catalytic oxidation of water to molecular oxygen is a key process for the production of solar fuels. Inspired by the biological manganese-based active site for this reaction in the enzyme Photosystem II, researchers have made impressive progress in the last decades regarding the development of synthetic manganese catalysts for water oxidation. For this, it has been especially fruitful to explore the many different types of known manganese oxides MnOx. This chapter first offers an overview of the structural, thermodynamic, and mechanistic aspects of water-oxidation catalysis by MnOx. The different test systems used for catalytic studies are then presented together with general reactivity trends. As a result, it has been possible to identify layered, mixed Mn (III/IV)-oxides as an especially promising class of bio-inspired catalysts and an attempt is made to give structure-based reasons for the good performances of these materials. In the outlook, the challenges of catalyst screenings (and hence the identification of a "best MnOx catalyst") are discussed. There is a great variety of reaction conditions which might be relevant for the application of manganese oxide catalysts in technological solar fuel-producing devices, and thus catalyst improvements are currently still addressing a very large parameter space. Nonetheless, detailed knowledge about the biological catalyst and a solid experimental basis concerning the syntheses and water-oxidation reactivities of MnOx materials have been established in the last decade and thus this research field is well positioned to make important contributions to solar fuel research in the future.

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

    Science.gov (United States)

    Manigandan, R.; Suresh, R.; Giribabu, K.; Vijayalakshmi, L.; Stephen, A.; Narayanan, V.

    2014-01-01

    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.

  13. Constraints on superoxide mediated formation of manganese oxides

    Directory of Open Access Journals (Sweden)

    Deric R. Learman

    2013-09-01

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

  14. Manganese oxide nanoparticles, methods and applications

    Science.gov (United States)

    Abruna, Hector D.; Gao, Jie; Lowe, Michael A.

    2017-08-29

    Manganese oxide nanoparticles having a chemical composition that includes Mn.sub.3O.sub.4, a sponge like morphology and a particle size from about 65 to about 95 nanometers may be formed by calcining a manganese hydroxide material at a temperature from about 200 to about 400 degrees centigrade for a time period from about 1 to about 20 hours in an oxygen containing environment. The particular manganese oxide nanoparticles with the foregoing physical features may be used within a battery component, and in particular an anode within a lithium battery to provide enhanced performance.

  15. Silver manganese oxide electrodes for lithium batteries

    Science.gov (United States)

    Thackeray, Michael M.; Vaughey, John T.; Dees, Dennis W.

    2006-05-09

    This invention relates to electrodes for non-aqueous lithium cells and batteries with silver manganese oxide positive electrodes, denoted AgxMnOy, in which x and y are such that the manganese ions in the charged or partially charged electrodes cells have an average oxidation state greater than 3.5. The silver manganese oxide electrodes optionally contain silver powder and/or silver foil to assist in current collection at the electrodes and to improve the power capability of the cells or batteries. The invention relates also to a method for preparing AgxMnOy electrodes by decomposition of a permanganate salt, such as AgMnO4, or by the decomposition of KMnO4 or LiMnO4 in the presence of a silver salt.

  16. Mixed iron-manganese oxide nanoparticles

    NARCIS (Netherlands)

    Lai, Jriuan; Shafi, Kurikka V.P.M.; Ulman, Abraham; Loos, Katja; Yang, Nan-Loh; Cui, Min-Hui; Vogt, Thomas; Estournès, Claude; Locke, Dave C.

    2004-01-01

    Designing nanoparticles for practical applications requires knowledge and control of how their desired properties relate to their composition and structure. Here, we present a detailed systematic study of mixed iron-manganese oxide nanoparticles, showing that ultrasonication provides the high-energy

  17. Mesoporous manganese oxide for warfare agents degradation

    Czech Academy of Sciences Publication Activity Database

    Štengl, Václav; Králová, Daniela; Opluštil, F.; Němec, T.

    2012-01-01

    Roč. 156, JULY (2012), s. 224-232 ISSN 1387-1811 R&D Projects: GA MPO FI-IM5/231 Institutional research plan: CEZ:AV0Z40320502; CEZ:AV0Z40500505 Keywords : homogeneous hydrolysis * chloroacetamide * manganese(IV) oxide * warfare agents Subject RIV: CA - Inorganic Chemistry Impact factor: 3.365, year: 2012

  18. Quantifying the Global Marine Biogenic Nitrogen Oxides Emissions

    Science.gov (United States)

    Su, H.; Wang, S.; Lin, J.; Hao, N.; Poeschl, U.; Cheng, Y.

    2017-12-01

    Nitrogen oxides (NOx) are among the most important molecules in atmospheric chemistry and nitrogen cycle. The NOx over the ocean areas are traditionally believed to originate from the continental outflows or the inter-continental shipping emissions. By comparing the satellite observations (OMI) and global chemical transport model simulation (GEOS-Chem), we suggest that the underestimated modeled atmospheric NO2 columns over biogenic active ocean areas can be possibly attributed to the biogenic source. Nitrification and denitrification in the ocean water produces nitrites which can be further reduced to NO through microbiological processes. We further report global distributions of marine biogenic NO emissions. The new added emissions improve the agreement between satellite observations and model simulations over large areas. Our model simulations manifest that the marine biogenic NO emissions increase the atmospheric oxidative capacity and aerosol formation rate, providing a closer link between atmospheric chemistry and ocean microbiology.

  19. Nanostructured manganese oxides as highly active water oxidation catalysts: a boost from manganese precursor chemistry.

    Science.gov (United States)

    Menezes, Prashanth W; Indra, Arindam; Littlewood, Patrick; Schwarze, Michael; Göbel, Caren; Schomäcker, Reinhard; Driess, Matthias

    2014-08-01

    We present a facile synthesis of bioinspired manganese oxides for chemical and photocatalytic water oxidation, starting from a reliable and versatile manganese(II) oxalate single-source precursor (SSP) accessible through an inverse micellar molecular approach. Strikingly, thermal decomposition of the latter precursor in various environments (air, nitrogen, and vacuum) led to the three different mineral phases of bixbyite (Mn2 O3 ), hausmannite (Mn3 O4 ), and manganosite (MnO). Initial chemical water oxidation experiments using ceric ammonium nitrate (CAN) gave the maximum catalytic activity for Mn2 O3 and MnO whereas Mn3 O4 had a limited activity. The substantial increase in the catalytic activity of MnO in chemical water oxidation was demonstrated by the fact that a phase transformation occurs at the surface from nanocrystalline MnO into an amorphous MnOx (1oxidizing agent. Photocatalytic water oxidation in the presence of [Ru(bpy)3 ](2+) (bpy=2,2'-bipyridine) as a sensitizer and peroxodisulfate as an electron acceptor was carried out for all three manganese oxides including the newly formed amorphous MnOx . Both Mn2 O3 and the amorphous MnOx exhibit tremendous enhancement in oxygen evolution during photocatalysis and are much higher in comparison to so far known bioinspired manganese oxides and calcium-manganese oxides. Also, for the first time, a new approach for the representation of activities of water oxidation catalysts has been proposed by determining the amount of accessible manganese centers. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Modeling Manganese Sorption and Surface Oxidation During Filtration

    OpenAIRE

    Bierlein, Kevin Andrew

    2012-01-01

    Soluble manganese (Mn) is a common contaminant in drinking water sources. High levels of Mn can lead to aesthetic water quality problems, necessitating removal of Mn during treatment to minimize consumer complaints. Mn may be removed during granular media filtration by the â natural greensand effect,â in which soluble Mn adsorbs to manganese oxide-coated (MnOx(s)) media and is then oxidized by chlorine, forming more manganese oxide. This research builds on a previous model developed by Mer...

  1. Formation of Nano-crystalline Todorokite from Biogenic Mn Oxides

    Energy Technology Data Exchange (ETDEWEB)

    Feng, X.; Zhu, M; Ginder-Vogel, M; Ni, C; Parikh, S; Sparks, D

    2010-01-01

    Todorokite, as one of three main Mn oxide phases present in oceanic Mn nodules and an active MnO{sub 6} octahedral molecular sieve (OMS), has garnered much interest; however, its formation pathway in natural systems is not fully understood. Todorokite is widely considered to form from layer structured Mn oxides with hexagonal symmetry, such as vernadite ({delta}-MnO{sub 2}), which are generally of biogenic origin. However, this geochemical process has not been documented in the environment or demonstrated in the laboratory, except for precursor phases with triclinic symmetry. Here we report on the formation of a nanoscale, todorokite-like phase from biogenic Mn oxides produced by the freshwater bacterium Pseudomonas putida strain GB-1. At long- and short-range structural scales biogenic Mn oxides were transformed to a todorokite-like phase at atmospheric pressure through refluxing. Topotactic transformation was observed during the transformation. Furthermore, the todorokite-like phases formed via refluxing had thin layers along the c* axis and a lack of c* periodicity, making the basal plane undetectable with X-ray diffraction reflection. The proposed pathway of the todorokite-like phase formation is proposed as: hexagonal biogenic Mn oxide {yields} 10-{angstrom} triclinic phyllomanganate {yields} todorokite. These observations provide evidence supporting the possible bio-related origin of natural todorokites and provide important clues for understanding the transformation of biogenic Mn oxides to other Mn oxides in the environment. Additionally this method may be a viable biosynthesis route for porous, nano-crystalline OMS materials for use in practical applications.

  2. Self-assembled manganese oxide structures through direct oxidation

    KAUST Repository

    Zhao, Chao

    2012-12-01

    The morphology and phase of self-assembled manganese oxides during different stages of thermal oxidation were studied. Very interesting morphological patterns of Mn oxide films were observed. At the initial oxidation stage, the surface was characterized by the formation of ring-shaped patterns. As the oxidation proceeded to the intermediate stage, concentric plates formed to relax the compressive stress. Our experimental results gave a clear picture of the evolution of the structures. We also examined the properties of the structures. © 2012 Elsevier B.V.

  3. Biological Superoxide In Manganese Oxide Formation

    Science.gov (United States)

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

    2011-12-01

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

  4. Microwave Production of Manganese from Manganese (IV) Oxide ...

    African Journals Online (AJOL)

    This work investigates the production of manganese metal from MnO2 by microwave irradiation using postconsumer polypropylene (PP) as reductant. Reagent grade MnO2 was first calcined to Mn3O4 followed by reduction with pulverised PP in a domestic microwave oven (Pioneer, Model PM-25 L, 1000 W, 2.45 GHz) in a ...

  5. Microwave Production of Manganese from Manganese (IV) Oxide ...

    African Journals Online (AJOL)

    Michael O. Mensah

    2015-12-02

    Dec 2, 2015 ... This work investigates the production of manganese metal from MnO2 by microwave irradiation using postconsumer polypropylene (PP) as reductant. Reagent grade MnO2 was first calcined to Mn3O4 followed by reduction with pulverised PP in a domestic microwave oven (Pioneer, Model PM-25 L, 1000 ...

  6. Fingerprinting Bacterial and Fungal Manganese Oxidation via Stable Oxygen Isotopes of Manganese Oxides

    Science.gov (United States)

    Sutherland, K. M.; Wankel, S. D.; Hansel, C. M.

    2016-12-01

    Manganese (Mn) oxides are a ubiquitous mineralogical component of surface Earth and Mars. Mn(III/IV) oxides are potent environmental sorbents and oxidants that play a crucial role in the fate of organic matter. The processes by which Mn(II) oxidation occurs in natural systems are poorly understood, but a number of studies have implicated microogranisms as the primary agents of Mn(II) oxidation in terrestrial and marine environments. The ability of microorganisms to oxidize Mn(II) to Mn(III/IV) oxides transcends the boundaries of biological domain, with an abundance of well-characterized prokaryotes as well as eukaryotic fungi with the ability to oxidize Mn(II) to Mn(III/IV) oxides. Biological Mn(II) oxidation proceeds directly through enzymatic activity or indirectly through the production of reactive oxygen species. Building upon earlier research suggesting that stable oxygen isotope fractionation could be used to fingerprint unique Mn(II)-oxidizing organisms or distinct oxidation pathways, here we use culture-based studies of Mn(II)-oxidizing bacteria and fungi to determine the kinetic oxygen isotope effects associated with Mn(II) oxidation. Since the oxygen molecules in Mn(III/IV) oxides are comprised of oxygen from both precursor water and molecular oxygen, we used a two-fold approach to constrain isotope fractionation with respect to each oxygen source. We used open system oxidation experiments using oxygen-18 labeled water in parallel with closed system Rayleigh distillation oxidation experiments to fully constrain isotope fractionation associated with oxygen atom incorporation during Mn(II) oxidation. Our results suggest commonalities among fractionation factors from groups of Mn(II)-oxidizing organisms that have similar oxidation mechanisms. These results suggest that stable oxygen isotopes of Mn(III/IV) oxides have the potential to distinguish between Mn(II) oxidation pathways in nature, providing a way to determine which groups of Mn(II) oxidizers may be

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

    Science.gov (United States)

    Myers, Charles R.; Nealson, Kenneth H.

    1988-01-01

    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.

  8. 40 CFR 721.10011 - Barium calcium manganese strontium oxide.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Barium calcium manganese strontium... Specific Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as barium calcium...

  9. Supported lipid bilayers as templates to design manganese oxide ...

    Indian Academy of Sciences (India)

    Abstract. This work reports on the preparation of nanoclusters of manganese oxide using biotemplating techniques. Supported lipid bilayers (SLBs) on quartz using cationic lipid [Dioctadecyldimethylammonium bromide (DOMA)] and mixed systems with neutral phospholipids dipalmitoyl phosphatidylcholine (DPPC) and.

  10. Manganese and iron oxidation by fungi isolated from building stone.

    Science.gov (United States)

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

    1994-01-01

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

  11. Efficient determination of average valence of manganese in manganese oxides by reaction headspace gas chromatography.

    Science.gov (United States)

    Xie, Wei-Qi; Gong, Yi-Xian; Yu, Kong-Xian

    2017-08-18

    This work investigates a new reaction headspace gas chromatographic (HS-GC) technique for efficient quantifying average valence of manganese (Mn) in manganese oxides. This method is on the basis of the oxidation reaction between manganese oxides and sodium oxalate under the acidic condition. The carbon dioxide (CO 2 ) formed from the oxidation reaction can be quantitatively analyzed by headspace gas chromatography. The data showed that the reaction in the closed headspace vial can be completed in 20min at 80°C. The relative standard deviation of this reaction HS-GC method in the precision testing was within 1.08%, the relative differences between the new method and the reference method (titration method) were no more than 5.71%. The new HS-GC method is automated, efficient, and can be a reliable tool for the quantitative analysis of average valence of manganese in the manganese oxide related research and applications. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Manganese Oxides Resembling Microbial Fabrics and Their Implications for Recognizing Inorganically Preserved Microfossils.

    Science.gov (United States)

    Muscente, A D; Czaja, Andrew D; Tuggle, James; Winkler, Christopher; Xiao, Shuhai

    2018-03-01

    In the search for microfossils of early life on Earth, the demonstration of biogenicity is paramount. Traditionally, only syngenetic structures with cellular elaboration, hollow sheaths/cell walls, and indigenous kerogen have been considered bona fide fossils. Recent reports of inorganically preserved microfossils represent a shift from this practice. Such a shift, if accompanied by a robust set of biogenicity criteria, could have profound implications for the identification of biosignatures on early Earth and extraterrestrial bodies. Here, we reaffirm the conventional criteria by examining aggregates of inorganic filaments from the Pilbara region of Western Australia. These aggregates are preserved in bedded chert, and the filaments measure up to 1 μm in diameter and 100 μm in length. The aggregates superficially resemble kerogenous microbial fabrics and mycelial organisms. However, the filaments consist of manganese oxide, lack cellular elaboration, and show no evidence for hollow sheaths or cell walls. We conclude that the filaments are fibrous minerals of abiotic origin. The similarities between these pseudofossils and some filamentous fossils highlight the need for strict application of the conventional criteria for recognizing microfossils. In the absence of kerogen, morphologically simple structures should, at least, show evidence of cellular features to be considered bona fide fossils. Key Words: Fossil-Manganese oxide-Pilbara-Precambrian-Pseudofossil. Astrobiology 18, 249-258.

  13. Biological Oxidation of DCE through Manganese Addition

    Science.gov (United States)

    2008-08-01

    elevated manganese in groundwater. At high levels of manganese exposure, usually as a dust, neurotoxicity can result with ataxia, increase anxiety...The final volume of groundwater, including amendments, was 140 mL. Bottles were sealed with Teflon stoppers and aluminum seals effectively...sealed with Teflon stoppers and aluminum seals, effectively trapping an anaerobic headspace, and incubated at 15ºC. A background control

  14. Enhanced biogenic emissions of nitric oxide and nitrous oxide following surface biomass burning

    Science.gov (United States)

    Anderson, Iris C.; Levine, Joel S.; Poth, Mark A.; Riggan, Philip J.

    1988-01-01

    Recent measurements indicate significantly enhanced biogenic soil emissions of both nitric oxide (NO) and nitrous oxide (N2O) following surface burning. These enhanced fluxes persisted for at least six months following the burn. Simultaneous measurements indicate enhanced levels of exchangeable ammonium in the soil following the burn. Biomass burning is known to be an instantaneous source of NO and N2O resulting from high-temperature combustion. Now it is found that biomass burning also results in significantly enhanced biogenic emissions of these gases, which persist for months following the burn.

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

    Science.gov (United States)

    Pena, J.; Sposito, G.

    2009-12-01

    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

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

    Science.gov (United States)

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

    2013-01-01

    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

  17. Permanganate-based synthesis of manganese oxide nanoparticles in ferritin

    Science.gov (United States)

    Olsen, Cameron R.; Smith, Trevor J.; Embley, Jacob S.; Maxfield, Jake H.; Hansen, Kameron R.; Peterson, J. Ryan; Henrichsen, Andrew M.; Erickson, Stephen D.; Buck, David C.; Colton, John S.; Watt, Richard K.

    2017-05-01

    This paper investigates the comproportionation reaction of MnII with {{{{MnO}}}4}- as a route for manganese oxide nanoparticle synthesis in the protein ferritin. We report that {{{{MnO}}}4}- serves as the electron acceptor and reacts with MnII in the presence of apoferritin to form manganese oxide cores inside the protein shell. Manganese loading into ferritin was studied under acidic, neutral, and basic conditions and the ratios of MnII and permanganate were varied at each pH. The manganese-containing ferritin samples were characterized by transmission electron microscopy, UV/Vis absorption, and by measuring the band gap energies for each sample. Manganese cores were deposited inside ferritin under both the acidic and basic conditions. All resulting manganese ferritin samples were found to be indirect band gap materials with band gap energies ranging from 1.01 to 1.34 eV. An increased UV/Vis absorption around 370 nm was observed for samples formed under acidic conditions, suggestive of MnO2 formation inside ferritin.

  18. Factors affecting radium removal using mixed iron-manganese oxides

    Energy Technology Data Exchange (ETDEWEB)

    Mott, H.V. Singh, S.; Kondapally, V.R. (South Dakota School of Mines and Technology, Rapid City, SD (United States))

    1993-10-01

    Batch experiments confirmed that sorption of radium by a mixed iron-manganese oxide solid phase shows promise for treating radium-contaminated water. The capacities of these mixed oxides for sorption of radium depend on the composition of the solid phase, the pH of the aqueous solution, and the presence of competing cations. The removal of the oxide-radium complexes from aqueous suspension by manganese greensand filtration was also investigated. It was found that influent radium concentrations of 100 pCi/L were reduced to 2--9 pCi/L by this process. Additional study of the fate of radium in manganese greensand filters is recommended before this procedure is used for drinking water treatment.

  19. A redox-assisted supramolecular assembly of manganese oxide nanotube

    International Nuclear Information System (INIS)

    Tao Li; Sun Chenggao; Fan Meilian; Huang Caijuan; Wu Hailong; Chao Zisheng; Zhai Hesheng

    2006-01-01

    In this paper, we report the hydrothermal synthesis of manganese oxide nanotube from an aqueous medium of pH 7, using KMnO 4 and MnCl 2 as inorganic precursors, polyoxyethylene (10) nonyl phenyl ether (TX-10) a surfactant and acetaldehyde an additive. The characterization of X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and N 2 adsorption at 77 K (BET) reveals that the synthesized manganese oxide nanotube has a mesopore size of ca. 3.65 nm and a wall thickness of ca. 12 nm, with the wall being composed of microporous crystals of monoclinic manganite. The X-ray photoelectron spectroscopy (XPS) result demonstrates a decrease of the binding energy of the Mn 3+ in the manganese oxide nanotube, which may be related to both the nanotubular morphology and the crystalline pore wall. A mechanism of a redox-assisted supramolecular assembly, regulated by acetaldehyde, is postulated

  20. Factors affecting radium removal using mixed iron-manganese oxides

    International Nuclear Information System (INIS)

    Mott, H.V. Singh, S.; Kondapally, V.R.

    1993-01-01

    Batch experiments confirmed that sorption of radium by a mixed iron-manganese oxide solid phase shows promise for treating radium-contaminated water. The capacities of these mixed oxides for sorption of radium depend on the composition of the solid phase, the pH of the aqueous solution, and the presence of competing cations. The removal of the oxide-radium complexes from aqueous suspension by manganese greensand filtration was also investigated. It was found that influent radium concentrations of 100 pCi/L were reduced to 2--9 pCi/L by this process. Additional study of the fate of radium in manganese greensand filters is recommended before this procedure is used for drinking water treatment

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

    Energy Technology Data Exchange (ETDEWEB)

    Schmit, F. [Laboratoire des Multimatériaux et Interfaces, UMR CNRS 5615, Bât. Berthollet, Université Claude Bernard—Lyon 1, 43 Bd 11 novembre 1918, 69622 Villeurbanne (France); IRCELYON, Institut de recherches sur la catalyse et l’environnement de Lyon (UMR 5256 CNRS/Université Lyon 1), Lyon (France); Bois, L., E-mail: laurence.bois@univ-lyon1.fr [Laboratoire des Multimatériaux et Interfaces, UMR CNRS 5615, Bât. Berthollet, Université Claude Bernard—Lyon 1, 43 Bd 11 novembre 1918, 69622 Villeurbanne (France); Chiriac, R.; Toche, F.; Chassagneux, F. [Laboratoire des Multimatériaux et Interfaces, UMR CNRS 5615, Bât. Berthollet, Université Claude Bernard—Lyon 1, 43 Bd 11 novembre 1918, 69622 Villeurbanne (France); Besson, M.; Descorme, C. [IRCELYON, Institut de recherches sur la catalyse et l’environnement de Lyon (UMR 5256 CNRS/Université Lyon 1), Lyon (France); Khrouz, L. [ENS LYON Laboratoire de Chimie (LR6, site Monod), 46, allée d’Italie, 69364 Lyon Cedex 07 (France)

    2015-01-15

    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. - Graphical abstract: One-pot amorphous MnO{sub 2} supported on mesoporous anataseTiO{sub 2}. - Highlights: • Mesoporous manganese titanium oxides were synthesized using block copolymer. • Block copolymers form complexes with Mn{sup 2+} from MnCl{sub 2}. • With block copolymer, manganese oxide can be dispersed around the titania crystallites. • With Mn(acac){sub 2}, manganese is dispersed inside titania. • MnOOH crystallizes outside mesoporous titania during hydrothermal treatment.

  2. Ambient Gas-Particle Partitioning of Tracers for Biogenic Oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Isaacman-VanWertz, Gabriel; Yee, Lindsay D.; Kreisberg, Nathan M.; Wernis, Rebecca; Moss, Joshua A.; Hering, Susanne V.; de Sa, Suzanne; Martin, Scot T.; Alexander, Mikaela L.; Palm, Brett B.; Hu, Weiwei; Campuzano-Jost, Pedro; Day, Douglas; Jimenez, Jose L.; Riva, Matthieu; Surratt, Jason D.; Viegas, Juarez; Manzi, Antonio; Edgerton, Eric S.; Baumann, K.; Souza, Rodrigo A.; Artaxo, Paulo; Goldstein, Allen H.

    2016-08-23

    Exchange of atmospheric organic compounds between gas and particle phases is important in the production and chemistry of particle-phase mass but is poorly understood due to a lack of simultaneous measurements in both phases of individual compounds. Measurements of particle- and gas phase organic compounds are reported here for the southeastern United States and central Amazonia. Polyols formed from isoprene oxidation contribute 8% and 15% on average to particle-phase organic mass at these sites but are also observed to have substantial gas-phase concentrations contrary to many models that treat these compounds as nonvolatile. The results of the present study show that the gas-particle partitioning of approximately 100 known and newly observed oxidation products is not well explained by environmental factors (e.g., temperature). Compounds having high vapor pressures have higher particle fractions than expected from absorptive equilibrium partitioning models. These observations support the conclusion that many commonly measured biogenic oxidation products may be bound in low-volatility mass (e.g., accretion products, inorganic organic adducts) that decomposes to individual compounds on analysis. However, the nature and extent of any such bonding remains uncertain. Similar conclusions are reach for both study locations, and average particle fractions for a given compound are consistent within similar to 25% across measurement sites.

  3. 75 FR 70665 - Proposed Significant New Use Rule for Cobalt Lithium Manganese Nickel Oxide

    Science.gov (United States)

    2010-11-18

    ... Proposed Significant New Use Rule for Cobalt Lithium Manganese Nickel Oxide AGENCY: Environmental... as cobalt lithium manganese nickel oxide (CAS No. 182442-95-1) which was the subject of... section 5(a)(2) of TSCA for the chemical substance identified as cobalt lithium manganese nickel oxide...

  4. 40 CFR 721.10010 - Barium manganese oxide (BaMnO3).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Barium manganese oxide (BaMnO3). 721... Substances § 721.10010 Barium manganese oxide (BaMnO3). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as barium manganese oxide (BaMnO3) (PMN P-00...

  5. Bentonite Modification with Manganese Oxides and Its Characterization

    Czech Academy of Sciences Publication Activity Database

    Dolinská, S.; Schütz, T.; Znamenáčková, I.; Lovás, M.; Vaculíková, Lenka

    2015-01-01

    Roč. 35, č. 1 (2015), s. 213-218 ISSN 1640-4920 Institutional support: RVO:68145535 Keywords : bentonite * natrification * manganese oxide Subject RIV: CB - Analytical Chemistry, Separation http://www.potopk.com.pl/Full_text/2015_full/IM%202-2015-a35.pdf

  6. SSZ-13-supported manganese oxide catalysts for low temperature ...

    Indian Academy of Sciences (India)

    YONGZHOU YE

    Meanwhile, the NOx conversion rate remained greater than 90% at. 450. ◦. C. The Mn/SSZ-13 ... oxygen, a high amorphous MnO2 content, and greatest number of strong Lewis acid sites, which are beneficial to the adsorption of NH3, and may ..... manganese oxides provide better SCR activity.33 The. NH3-SCR activity of ...

  7. Manganese

    Science.gov (United States)

    ... growth in children who have low levels of manganese.Weak bones (osteoporosis). Taking manganese by mouth in combination with calcium, zinc, and ... and protein. It might also be involved in bone formation.

  8. Observation of ferromagnetic semiconductor behavior in manganese-oxide doped graphene

    Directory of Open Access Journals (Sweden)

    Chang-Soo Park

    2014-08-01

    Full Text Available We have doped manganese-oxide onto graphene by an electrochemical method. Graphene showed a clear ferromagnetic semiconductor behavior after doping of manganese-oxide. The manganese-oxide doped graphene has a coercive field (Hc of 232 Oe at 10 K, and has the Curie temperature of 270 K from the temperature-dependent resistivity using transport measurement system. The ferromagnetism of manganese-oxide doped graphene attributes to the double-exchange from the coexistence of Mn3+ and Mn4+ on the surface of graphene. In addition, the semiconducting behavior is caused by the formation of manganese-oxide on graphene.

  9. Determination of the oxidizing capacity of manganese ores.

    Science.gov (United States)

    Prasad, R

    1974-09-01

    An accurate method is described for determining the amount of active oxygen in manganese ores, based on the oxidation-reduction reaction between the ore and arsenic(III) in presence of ammonium molybdate, followed by the back-titration of excess of arsenic(III) with cerium(IV), using osmium tetroxide as catalyst and Disulphine Blue V as indicator. A survey has been made of the applicability of this method to various pyrolusite ores containing less than 0.2% phosphorus. Aluminium(III), copper(II), iron(III), manganese(II), and molybdenum(VI) do not interfere. Up to 30% phosphorus(V) causes no interference.

  10. Manganese oxide/graphene oxide composites for high-energyaqueous asymmetric electrochemical capacitors

    CSIR Research Space (South Africa)

    Jafta, CJ

    2013-11-01

    Full Text Available A high-energy aqueous asymmetric electrochemical capacitor was developed using manganese diox-ide ( -MnO2)/graphene oxide (GO) nanocomposites. The nanostructured -MnO2was prepared frommicron-sized commercial electrolytic manganese dioxide (EMD) via...

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

    Science.gov (United States)

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

    2012-10-07

    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.

  12. Manganese oxidation state mediates toxicity in PC12 cells

    International Nuclear Information System (INIS)

    Reaney, S.H.; Smith, D.R.

    2005-01-01

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

  13. Characterization of carbon nanomaterial formation and manganese oxide reactivity

    Science.gov (United States)

    Shumlas, Samantha Lyn

    Characterization of a material's surface, structural and physical properties is essential to understand its chemical reactivity. Control over these properties helps tailor a material to a particular application of interest. The research presented in this dissertation focuses on characterizing a synthetic method for carbon nanomaterials and the determination of structural properties of manganese oxides that contribute to its reactivity for environmental chemistry. In particular, one research effort was focused on the tuning of synthetic parameters towards the formation of carbon nanomaterials from gaseous methane and gaseous mixtures containing various mixtures of methane, argon and hydrogen. In a second research effort, photochemical and water oxidation chemistry were performed on the manganese oxide, birnessite, to aid in the remediation of arsenic from the environment and provide more options for alternative energy catalysts, respectively. (Abstract shortened by ProQuest.).

  14. Characterization of Synthetic and Natural Manganese Oxides as Martian Analogues

    Science.gov (United States)

    Fox, V. K.; Arvidson, R. E.; Jolliff, B. L.; Carpenter, P. K.; Catalano, J. G.; Hinkle, M. A. G.; Morris, R. V.

    2015-01-01

    Recent discoveries of highly concentrated manganese oxides in Gale Crater and on the rim of Endeavour Crater by the Mars Science Laboratory Curiosity and Mars Exploration Rover Opportunity, respectively, imply more highly oxidizing aqueous conditions than previously recognized. Manganese oxides are a significant environmental indicator about ancient aqueous conditions, provided the phases can be characterized reliably. Manganese oxides are typically fine-grained and poorly crystalline, making the mineral structures difficult to determine, and they generally have very low visible reflectance with few distinctive spectral features in the visible to near infrared, making them a challenge for interpretation from remote sensing data. Therefore, these recent discoveries motivate better characterization using methods available on Mars, particularly visible to near infrared (VNIR) spectroscopy, X-ray diffractometry (XRD), and compositional measurements. Both rovers have complementary instruments in this regard. Opportunity is equipped with its multispectral visible imager, Pancam, and an Alpha Particle X-ray Spectrometer (APXS), and Curiosity has the multispectral Mastcam, ChemCam (laser-induced breakdown spectroscopy and passive spectroscopy), and APXS for in situ characterization, and ChemMin (XRD) for collected samples.

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

    Science.gov (United States)

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

    2012-01-01

    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

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

    Science.gov (United States)

    Suib, Steven Lawrence [Storrs, CT; Yuan, Jikang [Storrs, CT

    2008-10-21

    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.

  17. In Situ Atom Probe Deintercalation of Lithium-Manganese-Oxide.

    Science.gov (United States)

    Pfeiffer, Björn; Maier, Johannes; Arlt, Jonas; Nowak, Carsten

    2017-04-01

    Atom probe tomography is routinely used for the characterization of materials microstructures, usually assuming that the microstructure is unaltered by the analysis. When analyzing ionic conductors, however, gradients in the chemical potential and the electric field penetrating dielectric atom probe specimens can cause significant ionic mobility. Although ionic mobility is undesirable when aiming for materials characterization, it offers a strategy to manipulate materials directly in situ in the atom probe. Here, we present experimental results on the analysis of the ionic conductor lithium-manganese-oxide with different atom probe techniques. We demonstrate that, at a temperature of 30 K, characterization of the materials microstructure is possible without measurable Li mobility. Also, we show that at 298 K the material can be deintercalated, in situ in the atom probe, without changing the manganese-oxide host structure. Combining in situ atom probe deintercalation and subsequent conventional characterization, we demonstrate a new methodological approach to study ionic conductors even in early stages of deintercalation.

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

    Science.gov (United States)

    Richardson, Laurie L.; Nealson, Kenneth H.

    1989-01-01

    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.

  19. Electrical characterization of a laminar manganese oxide type birnessite

    International Nuclear Information System (INIS)

    Arias, N. P.; Becerra, M. E.; Giraldo, O.

    2015-01-01

    This paper records the characterization of a manganese oxide synthesized by solid state routes which is analogous to natural mineral called birnessite. The analysis of X-ray diffraction and average oxidation state of manganese show that the material has a lamellar structure containing manganese in oxidation states (+4) and (+3). The results of electron microscopy along with surface area and pore size measurements reveal the presence of micro and meso pores in the material. Impedance spectroscopy suggests that high frequency electrical conduction occurs in the volume and on the border of the aggregates; in contrast, ionic conductivity at low frequencies was associated with potassium ions located in the interlaminar region. Ac conductivity values at low frequencies were 1.599 x 10 -6 Ω -1 cm -1 and 6.416 x 10 -5 Ω -1 cm -1 at high frequencies. These values are associated with an increased probability of electron jumping as frequency increases. These findings contribute to the understanding of electrical conduction processes and provides important information about its potential applications. As a result, this research will prove relevant in the field of batteries, super capacitors and heterogeneous catalysis, among others. (Author)

  20. Bio-templated synthesis of lithium manganese oxide microtubes and their application in Li+ recovery

    International Nuclear Information System (INIS)

    Yu, Qianqian; Sasaki, Keiko; Hirajima, Tsuyoshi

    2013-01-01

    Highlights: • Biogenic birnessite was used to synthesize microtube-type Li + ion sieve. • The biomineral facilitates LMO formation at a lower temperature. • HMO-MT with high Li + uptake capacity was obtained. • Temperature effects on properties of HMO-MTs were studied. -- Abstract: Microbial transformations, a primary pathway for the Mn oxides formation in nature, provide potential for material-oriented researchers to fabricate new materials. Using Mn oxidizing fungus Paraconiothyrium sp. WL-2 as a bio-oxidizer as well as a bio-template, a special lithium ion sieve with microtube morphology was prepared through a solid-state transformation. Varying the calcination temperature from 300 to 700 °C was found to influence sample properties and consequently, the adsorption of Li + . Lithium manganese oxide microtube (LMO-MTs) calcined at different temperatures as well as their delithiated products (HMO-MTs) were characterized by X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Calcination temperatures affect not only the content but also the crystal structure of LMO spinel, which is important in Li + adsorption. The optimized sample was obtained after calcination at 500 °C for 4 h, which shows higher Li + adsorption capacity than particulate materials

  1. Acclimation of a marine microbial consortium for efficient Mn(II) oxidation and manganese containing particle production

    International Nuclear Information System (INIS)

    Zhou, Hao; Pan, Haixia; Xu, Jianqiang; Xu, Weiping; Liu, Lifen

    2016-01-01

    Highlights: • An efficient Mn(II) oxidation marine sediments microbial community was obtained. • High-throughput sequencing indicated new Mn(II) oxidation associated genus. • Na 3 MnPO 4 CO 3 and MnCO 3 were synthesized by the consortium. • Consortium exhibited Mn(II) oxidation performance over a range of harsh conditions. - Abstract: Sediment contamination with metals is a widespread concern in the marine environment. Manganese oxidizing bacteria (MOB) are extensively distributed in various environments, but a marine microbial community containing MOB is rarely reported. In this study, a consortium of marine metal-contaminated sediments was acclimated using Mn(II). The shift in community structure was determined through high-throughput sequencing. In addition, the consortium resisted several harsh conditions, such as toxic metals (1 mM Cu(II) and Fe(III)), and exhibited high Mn(II) oxidation capacities even the Mn(II) concentration was up to 5 mM. Meanwhile, biogenic Mn containing particles were characterized by scanning electron microscope (SEM), X-ray powder diffraction (XRD), and N 2 adsorption/desorption. Dye removal performance of the Mn containing particles was assayed using methylene blue, and 20.8 mg g −1 adsorption capacity was obtained. Overall, this study revealed several new genera associated with Mn(II) oxidation and rare biogenic Na 3 MnPO 4 CO 3. Results suggested the complexity of natural microbe-mediated Mn transformation.

  2. Manganese Oxidation by Bacteria: Biogeochemical Aspects

    Digital Repository Service at National Institute of Oceanography (India)

    Sujith, P.P.; LokaBharathi, P.A.

    to oxygen in the aquatic environment and therefore control the fate of several elements. Mn oxidizing bacteria have a suit of enzymes that not only help to scavenge Mn but also other associated elements, thus playing a crucial role in biogeochemical cycles...

  3. Highly Conductive One-Dimensional Manganese Oxide Wires by Coating with Graphene Oxides

    Science.gov (United States)

    Tojo, Tomohiro; Shinohara, Masaki; Fujisawa, Kazunori; Muramatsu, Hiroyuki; Hayashi, Takuya; Ahm Kim, Yoong; Endo, Morinobu

    2012-10-01

    Through coating with graphene oxides, we have developed a chemical route to the bulk production of long, thin manganese oxide (MnO2) nanowires that have high electrical conductivity. The average diameter of these hybrid nanowires is about 25 nm, and their average length is about 800 nm. The high electrical conductivity of these nanowires (ca. 189.51+/-4.51 µS) is ascribed to the homogeneous coating with conductive graphene oxides as well as the presence of non-bonding manganese atoms. The growth mechanism of the nanowires is theoretically supported by the initiation of morphological conversion from graphene oxide to wrapped structures through the formation of covalent bonds between manganese and oxygen atoms at the graphene oxide edge.

  4. An engineered polypeptide around nano-sized manganese-calcium oxide: copying plants for water oxidation.

    Science.gov (United States)

    Najafpour, Mohammad Mahdi; Ghobadi, Mohadeseh Zarei; Sarvi, Bahram; Haghighi, Behzad

    2015-09-14

    Synthesis of new efficient catalysts inspired by Nature is a key goal in the production of clean fuel. Different compounds based on manganese oxide have been investigated in order to find their water-oxidation activity. Herein, we introduce a novel engineered polypeptide containing tyrosine around nano-sized manganese-calcium oxide, which was shown to be a highly active catalyst toward water oxidation at low overpotential (240 mV), with high turnover frequency of 1.5 × 10(-2) s(-1) at pH = 6.3 in the Mn(III)/Mn(IV) oxidation range. The compound is a novel structural and efficient functional model for the water-oxidizing complex in Photosystem II. A new proposed clever strategy used by Nature in water oxidation is also discussed. The new model of the water-oxidizing complex opens a new perspective for synthesis of efficient water-oxidation catalysts.

  5. Manganese

    Science.gov (United States)

    Cannon, William F.; Kimball, Bryn E.; Corathers, Lisa A.; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

    2017-12-19

    Manganese is an essential element for modern industrial societies. Its principal use is in steelmaking, where it serves as a purifying agent in iron-ore refining and as an alloy that converts iron into steel. Although the amount of manganese consumed to make a ton of steel is small, ranging from 6 to 9 kilograms, it is an irreplaceable component in the production of this fundamental material. The United States has been totally reliant on imports of manganese for many decades and will continue to be so for at least the near future. There are no domestic reserves, and although some large low-grade resources are known, they are far inferior to manganese ores readily available on the international market. World reserves of manganese are about 630 million metric tons, and annual global consumption is about 16 million metric tons. Current reserves are adequate to meet global demand for several decades. Global resources in traditional land-based deposits, including both reserves and rocks sufficiently enriched in manganese to be ores in the future, are much larger, at about 17 billion metric tons. Manganese resources in seabed deposits of ferromanganese nodules and crusts are larger than those on land and have not been fully quantified. No production from seabed deposits has yet been done, but current research and development activities are substantial and may bring parts of these seabed resources into production in the future. The advent of economically successful seabed mining could substantially alter the current scenario of manganese supply by providing a large new source of manganese in addition to traditional land-based deposits.From a purely geologic perspective, there is no global shortage of proven ores and potential new ores that could be developed from the vast tonnage of identified resources. Reserves and resources are very unevenly distributed, however. The Kalahari manganese district in South Africa contains 70 percent of the world’s identified resources

  6. Synthesis of iron oxide/manganese oxide composite particles and their magnetic properties

    Science.gov (United States)

    Ullrich, Aladin; Hohenberger, Stefan; Özden, Ayberk; Horn, Siegfried

    2014-08-01

    We have investigated the synthesis and structural as well as magnetic properties of composite nanoparticles, including core-shell particles, consisting of iron and manganese oxides. The synthesis is based on thermal decomposition of suitable metal oleates in a high boiling solvent. Seed particles are used to avoid homogeneous nucleation and to initiate the formation of heterogeneous systems. The as-synthesized particles were characterized by energy filtered transmission electron microscopy (EFTEM) and SQUID magnetometry. The synthesized nanoparticles had diameters between 10 and 20 nm and consisted of manganese oxide and iron oxide.

  7. From molecular to colloidal manganese vanadium oxides for water oxidation catalysis.

    Science.gov (United States)

    Schwarz, Benjamin; Forster, Johannes; Anjass, Montaha H; Daboss, Sven; Kranz, Christine; Streb, Carsten

    2017-10-19

    The spontaneous, sonication-driven conversion of a molecular manganese vanadium oxide water oxidation catalyst, (n-Bu 4 N) 3 [Mn 4 V 4 O 17 (OAc) 3 ] × 3H 2 O, into colloidal manganese vanadium oxide particles (average particle size ca. 70 nm) together with their stability and chemical water oxidation activity is reported. The nanoparticulate metal oxide colloid (approximate composition: VMn 5 O 10 ·ca. 6H 2 O·ca. 0.2nBu 4 N + ) is formed spontaneously when the molecular precursor is sonicated in water. The particles show water oxidation activity when combined with Ce IV as the oxidant, are stable even under highly acidic reaction conditions and can be recovered and reused.

  8. Study of nitric oxide catalytic oxidation on manganese oxides-loaded activated carbon at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    You, Fu-Tian [Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen (China); University of Chinese Academy of Sciences, Beijing (China); Yu, Guang-Wei, E-mail: gwyu@iue.ac.cn [Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen (China); Wang, Yin, E-mail: yinwang@iue.ac.cn [Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen (China); Xing, Zhen-Jiao [Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen (China); Liu, Xue-Jiao; Li, Jie [Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen (China); University of Chinese Academy of Sciences, Beijing (China)

    2017-08-15

    Highlights: • Loading manganese oxides on activated carbon effectively promotes NO oxidation. • NO adsorption-desorption on activated carbon is fundamental to NO oxidation. • A high Mn{sup 4+}/Mn{sup 3+} ratio contributes to NO oxidation by promoting lattice O transfer. - Abstract: Nitric oxide (NO) is an air pollutant that is difficult to remove at low concentration and low temperature. Manganese oxides (MnO{sub x})-loaded activated carbon (MLAC) was prepared by a co-precipitation method and studied as a new catalyst for NO oxidation at low temperature. Characterization of MLAC included X-ray diffraction (XRD), scanning electron microscopy (SEM), N{sub 2} adsorption/desorption and X-ray photoelectron spectroscopy (XPS). Activity tests demonstrated the influence of the amount of MnO{sub x} and the test conditions on the reaction. MLAC with 7.5 wt.% MnO{sub x} (MLAC003) exhibits the highest NO conversion (38.7%) at 1000 ppm NO, 20 vol.% O{sub 2}, room temperature and GHSV ca. 16000 h{sup −1}. The NO conversion of MLAC003 was elevated by 26% compared with that of activated carbon. The results of the MLAC003 activity test under different test conditions demonstrated that NO conversion is also influenced by inlet NO concentration, inlet O{sub 2} concentration, reaction temperature and GHSV. The NO adsorption-desorption process in micropores of activated carbon is fundamental to NO oxidation, which can be controlled by pore structure and reaction temperature. The activity elevation caused by MnO{sub x} loading is assumed to be related to Mn{sup 4+}/Mn{sup 3+} ratio. Finally, a mechanism of NO catalytic oxidation on MLAC based on NO adsorption-desorption and MnO{sub x} lattice O transfer is proposed.

  9. Nanorods of manganese oxides: Synthesis, characterization and catalytic application

    Science.gov (United States)

    Yang, Zeheng; Zhang, Yuancheng; Zhang, Weixin; Wang, Xue; Qian, Yitai; Wen, Xiaogang; Yang, Shihe

    2006-03-01

    Single-crystalline nanorods of β-MnO 2, α-Mn 2O 3 and Mn 3O 4 were successfully synthesized via the heat-treatment of γ-MnOOH nanorods, which were prepared through a hydrothermal method in advance. The calcination process of γ-MnOOH nanorods was studied with the help of Thermogravimetric analysis and X-ray powder diffraction. When the calcinations were conducted in air from 250 to 1050 °C, the precursor γ-MnOOH was first changed to β-MnO 2, then to α-Mn 2O 3 and finally to Mn 3O 4. When calcined in N 2 atmosphere, γ-MnOOH was directly converted into Mn 3O 4 at as low as 500 °C. Transmission electron microscopy (TEM) and high-resolution TEM were also used to characterize the products. The obtained manganese oxides maintain the one-dimensional morphology similar to the precursor γ-MnOOH nanorods. Further experiments show that the as-prepared manganese oxide nanorods have catalytic effect on the oxidation and decomposition of the methylene blue (MB) dye with H 2O 2.

  10. Hydrothermal synthesis of nanostructured spinel lithium manganese oxide

    Science.gov (United States)

    Liu, Zhanqiang; Wang, Wen-lou; Liu, Xianming; Wu, Minchang; Li, Dan; Zeng, Zhen

    2004-04-01

    Nanostructured spherical spinel lithium manganese oxide (LiMnO) with about 200 nm in diameter was synthesized for the first time by mild hydrothermal method. The formation of the nanostructured spheres was through self-assembly of the nanoparticles and nanobelts. The influence of the reaction temperature and the time of formation of the nanostructures have been systematically studied. The thermal stability of the nanostructures has been examined by heating-treatment at different temperatures. Powder X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, thermogravimetric analysis and inductively coupled plasma-atomic emission spectroscopy were used to characterize the products.

  11. Manganese oxides-based composite electrodes for supercapacitors

    Science.gov (United States)

    Su, Dongyun; Ma, Jun; Huang, Mingyu; Liu, Feng; Chen, Taizhou; Liu, Chao; Ni, Hongjun

    2017-06-01

    In recent, nanostructured transition metal oxides as a new class of energy storage materials have widely attracted attention due to its excellent electrochemical performance for supercapacitors. The MnO2 based transition metal oxides and their composite electrode materials were focused in the review for supercapacitor applications. The researches on different nanostructures of manganese oxides such as Nano rods, Nano sheets, nanowires, nanotubes and so on have been discovered in recent years, together with brief explanations of their properties. Research on enhancing materials’ properties by designing combination of different materials on the micron or Nano scale is too limited, and therefore we discuss the effects of different components’ sizes and their synergy on the performance. Moreover, the low-cost and large-scale fabrication of flexible supercapacitors with high performance (high energy density and cycle stability) have been pointed out and studied.

  12. Photoinduced oxidation of a water-soluble manganese(III) porphyrin

    Science.gov (United States)

    Maliyackel, Anthony C.; Otvos, John W.; Spreer, Larry O.; Calvin, Melvin

    1986-01-01

    The photoinduced oxidation of tetra(N-methyl-4-pyridyl)porphyrinmanganese(III) has been achieved in homogeneous solution. The manganese porphyrin was used as an electron donor in a three-component system with tris-(2,2′-bipyridine)ruthenium(II) as the photosensitizer and chloropentaamminecobalt(III) as the electron acceptor. The photooxidized manganese porphyrin is unstable in aqueous solution, reverting to the starting manganese(III) porphyrin. The oxidation of manganese(III) porphyrin and the subsequent reduction of the oxidized porphyrin can be cycled repeatedly. PMID:16593699

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

    Science.gov (United States)

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

    2014-06-28

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

  14. Population structure of manganese-oxidizing bacteria in stratified soils and properties of manganese oxide aggregates under manganese-complex medium enrichment.

    Directory of Open Access Journals (Sweden)

    Weihong Yang

    Full Text Available Manganese-oxidizing bacteria in the aquatic environment have been comprehensively investigated. However, little information is available about the distribution and biogeochemical significance of these bacteria in terrestrial soil environments. In this study, stratified soils were initially examined to investigate the community structure and diversity of manganese-oxidizing bacteria. Total 344 culturable bacterial isolates from all substrata exhibited Mn(II-oxidizing activities at the range of 1 µM to 240 µM of the equivalent MnO2. The high Mn(II-oxidizing isolates (>50 mM MnO2 were identified as the species of phyla Actinobacteria, Firmicutes and Proteobacteria. Seven novel Mn(II-oxidizing bacterial genera (species, namely, Escherichia, Agromyces, Cellulomonas, Cupriavidus, Microbacterium, Ralstonia, and Variovorax, were revealed via comparative phylogenetic analysis. Moreover, an increase in the diversity of soil bacterial community was observed after the combined enrichment of Mn(II and carbon-rich complex. The phylogenetic classification of the enriched bacteria represented by predominant denaturing gradient gel electrophoresis bands, was apparently similar to culturable Mn(II-oxidizing bacteria. The experiments were further undertaken to investigate the properties of the Mn oxide aggregates formed by the bacterial isolates with high Mn(II-oxidizing activity. Results showed that these bacteria were closely encrusted with their Mn oxides and formed regular microspherical aggregates under prolonged Mn(II and carbon-rich medium enrichment for three weeks. The biotic oxidation of Mn(II to Mn(III/IV by these isolates was confirmed by kinetic examinations. X-ray diffraction assays showed the characteristic peaks of several Mn oxides and rhodochrosite from these aggregates. Leucoberbelin blue tests also verified the Mn(II-oxidizing activity of these aggregates. These results demonstrated that Mn oxides were formed at certain amounts under the

  15. 75 FR 70583 - Cobalt Lithium Manganese Nickel Oxide; Withdrawal of Significant New Use Rule

    Science.gov (United States)

    2010-11-18

    ... 2070-AB27 Cobalt Lithium Manganese Nickel Oxide; Withdrawal of Significant New Use Rule AGENCY... chemical substance identified as cobalt lithium manganese nickel oxide (CAS No. 182442-95-1), which was the..., subpart D. In accordance with 40 CFR 721.160(c)(3)(ii), EPA is withdrawing the rule issued for cobalt...

  16. 76 FR 47996 - Cobalt Lithium Manganese Nickel Oxide; Significant New Use Rule

    Science.gov (United States)

    2011-08-08

    ... Safety and Health Administration (OSHA) Permissible Exposure Level (PEL) of 0.1 mg/m\\3\\ for nickel. The... 2070-AB27 Cobalt Lithium Manganese Nickel Oxide; Significant New Use Rule AGENCY: Environmental... lithium manganese nickel oxide (CAS No. 182442-95-1), which was the subject of premanufacture notice (PMN...

  17. The mechanism of water oxidation catalyzed by nanolayered manganese oxides: New insights.

    Science.gov (United States)

    Najafpour, Mohammad Mahdi; Abbasi Isaloo, Mohsen

    2015-11-01

    Herein we consider the mechanism of water oxidation by nanolayered manganese oxide in the presence of cerium(IV) ammonium nitrate. Based on membrane-inlet mass spectrometry results, the rate of H2((18))O exchange of μ-O groups on the surface of the nanolayered Mn-K oxide, and studies on water oxidation in the presence of different ratios of acetonitrile/water we propose a mechanism for water oxidation by nanolayered Mn oxides in the presence of cerium(IV) ammonium nitrate. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Adsorption behavior of lithium from seawater using manganese oxide adsorbent

    International Nuclear Information System (INIS)

    Wajima, Takaaki; Munakata, Kenzo; Uda, Tatsuhiko

    2012-01-01

    The deuterium-tritium (D-T) fusion reactor system is expected to provide the main source of electricity in the future. Large amounts of lithium will be required, dependent on the reactor design concept, and alternative resources should be found to provide lithium inventories for nuclear fusion plants. Seawater has recently become an attractive source of this element and the separation and recovery of lithium from seawater by co-precipitation, solvent extraction and adsorption have been investigated. Amongst these techniques, the adsorption method is suitable for recovery of lithium from seawater, because certain inorganic ion-exchange materials, especially spinel-type manganese oxides, show extremely high selectivity for the lithium ion. In this study, we prepared a lithium adsorbent (HMn 2 O 4 ) by elution of spinel-type lithium di-manganese-tetra-oxide (LiMn 2 O 4 ) and examined the kinetics of the adsorbent for lithium ions in seawater using a pseudo-second-order kinetic model. The intermediate, LiMn 2 O 4 , can be synthesized from LiOH·H 2 O and Mn 3 O 4 , from which the lithium adsorbent can subsequently be prepared via acid treatment., The adsorption kinetics become faster and the amount of lithium adsorbed on the adsorbent increases with increasing solution temperature. The thermodynamic values, ΔG 0 , ΔH 0 and ΔS 0 , indicate that adsorption is an endothermic and spontaneous process. (author)

  19. Magnetically-modified natural biogenic iron oxides for organic xenobiotics removal

    Czech Academy of Sciences Publication Activity Database

    Šafařík, Ivo; Filip, J.; Horská, Kateřina; Nowakova, M.; Tuček, J.; Šafaříková, Miroslava; Hashimoto, H.; Takada, J.; Zbořil, R.

    2015-01-01

    Roč. 12, č. 2 (2015), s. 673-682 ISSN 1735-1472 R&D Projects: GA MŠk(CZ) LH11111; GA MŠk LH12190 Institutional support: RVO:67179843 Keywords : Biogenic iron oxides * Leptothrix ochracea * Magnetic fluid * Magnetic adsorbents * Xenobiotics Subject RIV: EI - Biotechnology ; Bionics Impact factor: 2.344, year: 2015

  20. Modeling the viscosity of silicate melts containing manganese oxide

    Directory of Open Access Journals (Sweden)

    Kim Wan-Yi

    2013-01-01

    Full Text Available Our recently developed model for the viscosity of silicate melts is applied to describe and predict the viscosities of oxide melts containing manganese oxide. The model requires three pairs of adjustable parameters that describe the viscosities in three systems: pure MnO, MnO-SiO2 and MnO-Al2O3-SiO2. The viscosity of other ternary and multicomponent silicate melts containing MnO is then predicted by the model without any additional adjustable model parameters. Experimental viscosity data are reviewed for melts formed by MnO with SiO2, Al2O3, CaO, MgO, PbO, Na2O and K2O. The deviation of the available experimental data from the viscosities predicted by the model is shown to be within experimental error limits.

  1. Biogenic Fabrication of Iron/Iron Oxide Nanoparticles and Their Application

    OpenAIRE

    Siddiqi, Khwaja Salahuddin; ur Rahman, Aziz; Tajuddin,; Husen, Azamal

    2016-01-01

    Enshrined in this review are the biogenic fabrication and applications of coated and uncoated iron and iron oxide nanoparticles. Depending on their magnetic properties, they have been used in the treatment of cancer, drug delivery system, MRI, and catalysis and removal of pesticides from potable water. The polymer-coated iron and iron oxide nanoparticles are made biocompatible, and their slow release makes them more effective and lasting. Their cytotoxicity against microbes under aerobic/anae...

  2. Biotic manganese oxidation coupled with methane oxidation using a continuous-flow bioreactor system under marine conditions.

    Science.gov (United States)

    Kato, Shingo; Miyazaki, Masayuki; Kikuchi, Sakiko; Kashiwabara, Teruhiko; Saito, Yumi; Tasumi, Eiji; Suzuki, Katsuhiko; Takai, Ken; Cao, Linh Thi Thuy; Ohashi, Akiyoshi; Imachi, Hiroyuki

    2017-10-01

    Biogenic manganese oxides (BioMnOx) can be applied for the effective removal and recovery of trace metals from wastewater because of their high adsorption capacity. Although a freshwater continuous-flow system for a nitrifier-based Mn-oxidizing microbial community for producing BioMnOx has been developed so far, a seawater continuous-flow bioreactor system for BioMnOx production has not been established. Here, we report BioMnOx production by a methanotroph-based microbial community by using a continuous-flow bioreactor system. The bioreactor system was operated using a deep-sea sediment sample as the inoculum with methane as the energy source for over 2 years. The BioMnOx production became evident after 370 days of reactor operation. The maximum Mn oxidation rate was 11.4 mg L -1 day -1 . An X-ray diffraction analysis showed that the accumulated BioMnOx was birnessite. 16S rRNA gene-based clone analyses indicated that methanotrophic bacterial members were relatively abundant in the system; however, none of the known Mn-oxidizing bacteria were detected. A continuous-flow bioreactor system coupled with nitrification was also run in parallel for 636 days, but no BioMnOx production was observed in this bioreactor system. The comparative experiments indicated that the methanotroph-based microbial community, rather than the nitrifier-based community, was effective for BioMnOx production under the marine environmental conditions.

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

    Science.gov (United States)

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

    2004-12-01

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

  4. A magnetic route to measure the average oxidation state of mixed-valent manganese in manganese oxide octahedral molecular sieves (OMS).

    Science.gov (United States)

    Shen, Xiong-Fei; Ding, Yun-Shuang; Liu, Jia; Han, Zhao-Hui; Budnick, Joseph I; Hines, William A; Suib, Steven L

    2005-05-04

    A magnetic route has been applied for measurement of the average oxidation state (AOS) of mixed-valent manganese in manganese oxide octahedral molecular sieves (OMS). The method gives AOS measurement results in good agreement with titration methods. A maximum analysis deviation error of +/-7% is obtained from 10 sample measurements. The magnetic method is able to (1) confirm the presence of mixed-valent manganese and (2) evaluate AOS and the spin states of d electrons of both single oxidation state and mixed-valent state Mn in manganese oxides. In addition, the magnetic method may be extended to (1) determine AOS of Mn in manganese oxide OMS with dopant "diamagnetic" ions, such as reducible V5+ (3d0) ions, which is inappropriate for the titration method due to interference of redox reactions between these dopant ions and titration reagents, such as KMnO4, (2) evaluate the dopant "paramagnetic" ions that are present as clusters or in the OMS framework, and (3) determine AOS of other mixed-valent/single oxidation state ion systems, such as Mo3+(3d3)-Mo4+(3d2) systems and Fe3+ in FeCl3.

  5. Study of nitric oxide catalytic oxidation on manganese oxides-loaded activated carbon at low temperature

    Science.gov (United States)

    You, Fu-Tian; Yu, Guang-Wei; Wang, Yin; Xing, Zhen-Jiao; Liu, Xue-Jiao; Li, Jie

    2017-08-01

    Nitric oxide (NO) is an air pollutant that is difficult to remove at low concentration and low temperature. Manganese oxides (MnOx)-loaded activated carbon (MLAC) was prepared by a co-precipitation method and studied as a new catalyst for NO oxidation at low temperature. Characterization of MLAC included X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption/desorption and X-ray photoelectron spectroscopy (XPS). Activity tests demonstrated the influence of the amount of MnOx and the test conditions on the reaction. MLAC with 7.5 wt.% MnOx (MLAC003) exhibits the highest NO conversion (38.7%) at 1000 ppm NO, 20 vol.% O2, room temperature and GHSV ca. 16000 h-1. The NO conversion of MLAC003 was elevated by 26% compared with that of activated carbon. The results of the MLAC003 activity test under different test conditions demonstrated that NO conversion is also influenced by inlet NO concentration, inlet O2 concentration, reaction temperature and GHSV. The NO adsorption-desorption process in micropores of activated carbon is fundamental to NO oxidation, which can be controlled by pore structure and reaction temperature. The activity elevation caused by MnOx loading is assumed to be related to Mn4+/Mn3+ ratio. Finally, a mechanism of NO catalytic oxidation on MLAC based on NO adsorption-desorption and MnOx lattice O transfer is proposed.

  6. Acclimation of a marine microbial consortium for efficient Mn(II) oxidation and manganese containing particle production

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Hao, E-mail: zhouhao@dlut.edu.cn [Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Food and Environment, Dalian University of Technology, Panjin 124221 (China); Pan, Haixia [Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Food and Environment, Dalian University of Technology, Panjin 124221 (China); Xu, Jianqiang [School of Life Science and Medicine, Dalian University of Technology, Panjin 124221 (China); Xu, Weiping; Liu, Lifen [Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Food and Environment, Dalian University of Technology, Panjin 124221 (China)

    2016-03-05

    Highlights: • An efficient Mn(II) oxidation marine sediments microbial community was obtained. • High-throughput sequencing indicated new Mn(II) oxidation associated genus. • Na{sub 3}MnPO{sub 4}CO{sub 3} and MnCO{sub 3} were synthesized by the consortium. • Consortium exhibited Mn(II) oxidation performance over a range of harsh conditions. - Abstract: Sediment contamination with metals is a widespread concern in the marine environment. Manganese oxidizing bacteria (MOB) are extensively distributed in various environments, but a marine microbial community containing MOB is rarely reported. In this study, a consortium of marine metal-contaminated sediments was acclimated using Mn(II). The shift in community structure was determined through high-throughput sequencing. In addition, the consortium resisted several harsh conditions, such as toxic metals (1 mM Cu(II) and Fe(III)), and exhibited high Mn(II) oxidation capacities even the Mn(II) concentration was up to 5 mM. Meanwhile, biogenic Mn containing particles were characterized by scanning electron microscope (SEM), X-ray powder diffraction (XRD), and N{sub 2} adsorption/desorption. Dye removal performance of the Mn containing particles was assayed using methylene blue, and 20.8 mg g{sup −1} adsorption capacity was obtained. Overall, this study revealed several new genera associated with Mn(II) oxidation and rare biogenic Na{sub 3}MnPO{sub 4}CO{sub 3.} Results suggested the complexity of natural microbe-mediated Mn transformation.

  7. A Highly Active and Selective Manganese Oxide Promoted Cobalt-on-Silica Fischer-Tropsch Catalyst

    NARCIS (Netherlands)

    den Breejen, Johan P.|info:eu-repo/dai/nl/304837318; Frey, Anne M.|info:eu-repo/dai/nl/341358851; Yang, Jia; Holmen, Anders; van Schooneveld, Matti M.|info:eu-repo/dai/nl/315032863; de Groot, Frank M. F.|info:eu-repo/dai/nl/08747610X; Stephan, Odile; Bitter, Johannes H.|info:eu-repo/dai/nl/160581435; de Jong, Krijn P.|info:eu-repo/dai/nl/06885580X

    A highly active and selective manganese oxide-promoted silica-supported cobalt catalyst for the Fischer-Tropsch reaction is reported. Co/MnO/SiO2 catalysts were prepared via impregnation of a cobalt nitrate and manganese nitrate precursor, followed by drying and calcination in an NO/He flow. The

  8. Oxidative damage and neurodegeneration in manganese-induced neurotoxicity

    International Nuclear Information System (INIS)

    Milatovic, Dejan; Zaja-Milatovic, Snjezana; Gupta, Ramesh C.; Yu, Yingchun; Aschner, Michael

    2009-01-01

    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 2 -isoprostanes (F 2 -IsoPs) and mitochondrial dysfunction (ATP), as early as 2 h following Mn exposure. Treatment of neurons with 500 μM Mn also resulted in time-dependent increases in the levels of the inflammatory biomarker, prostaglandin E 2 (PGE 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 2 -IsoPs and PGE 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.

  9. Nature of Activated Manganese Oxide for Oxygen Evolution.

    Science.gov (United States)

    Huynh, Michael; Shi, Chenyang; Billinge, Simon J L; Nocera, Daniel G

    2015-12-02

    Electrodeposited manganese oxide films (MnOx) are promising stable oxygen evolution catalysts. They are able to catalyze the oxygen evolution reaction in acidic solutions but with only modest activity when prepared by constant anodic potential deposition. We now show that the performance of these catalysts is improved when they are "activated" by potential cycling protocols, as measured by Tafel analysis (where lower slope is better): upon activation the Tafel slope decreases from ∼120 to ∼70 mV/decade in neutral conditions and from ∼650 to ∼90 mV/decade in acidic solutions. Electrochemical, spectroscopic, and structural methods were employed to study the activation process and support a mechanism where the original birnessite-like MnOx (δ-MnO2) undergoes a phase change, induced by comproportionation with cathodically generated Mn(OH)2, to a hausmannite-like intermediate (α-Mn3O4). Subsequent anodic conditioning from voltage cycling or water oxidation produces a disordered birnessite-like phase, which is highly active for oxygen evolution. At pH 2.5, the current density of activated MnOx (at an overpotential of 600 mV) is 2 orders of magnitude higher than that of the original MnOx and begins to approach that of Ru and Ir oxides in acid.

  10. Synthesis and characterization of cobalt-manganese oxides

    Energy Technology Data Exchange (ETDEWEB)

    Valencia, J. [Laboratorio de Magnetismo y Materiales Avanzados, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia); Department of Aerospace Engineering and Mechanics, University of Minnesota, Minneapolis 55455-0153 (United States); Arias, N.P. [Laboratorio de Materiales Nanoestructurados y Funcionales, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia); Departamento de Ingenieria Electrica, Electronica y Computacion, Facultad de Ingenieria y Arquitectura, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia); Giraldo, O. [Laboratorio de Materiales Nanoestructurados y Funcionales, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia); Rosales-Rivera, A., E-mail: arosalesr@unal.edu.co [Laboratorio de Magnetismo y Materiales Avanzados, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia)

    2012-08-15

    Cobalt doped/un-doped manganese oxides materials were synthesized at various doping rates by soft chemical reactions, oxidation-reduction method, which allows generating a metal-mixed oxide. The synthesized materials were characterized using several techniques including chemical analysis, X-rays diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and vibrating sample magnetometer (VSM). The chemical analysis confirmed the presence of cobalt in the samples. XRD patterns reveal mainly a spinel-like structure and SEM micrographs exhibited morphology with fine aggregate of particles. TGA profiles showed weight loss due to loss of water in a first step, followed by a loss of oxygen from the lattice associated with partial reduction of Mn{sup 4+} to Mn{sup 3+}. VSM was used to measure the magnetization as a function of the applied magnetic field at temperatures T=50 and 300 K. Different magnetic behaviors were observed when cobalt percentage changed in the samples. These behaviors are considered to be related to the size of the particles and composition of the materials. Higher coercive field and lesser magnetization were observed for the sample with higher cobalt content.

  11. Synthesis and characterization of cobalt-manganese oxides

    International Nuclear Information System (INIS)

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

    2012-01-01

    Cobalt doped/un-doped manganese oxides materials were synthesized at various doping rates by soft chemical reactions, oxidation-reduction method, which allows generating a metal-mixed oxide. The synthesized materials were characterized using several techniques including chemical analysis, X-rays diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and vibrating sample magnetometer (VSM). The chemical analysis confirmed the presence of cobalt in the samples. XRD patterns reveal mainly a spinel-like structure and SEM micrographs exhibited morphology with fine aggregate of particles. TGA profiles showed weight loss due to loss of water in a first step, followed by a loss of oxygen from the lattice associated with partial reduction of Mn 4+ to Mn 3+ . VSM was used to measure the magnetization as a function of the applied magnetic field at temperatures T=50 and 300 K. Different magnetic behaviors were observed when cobalt percentage changed in the samples. These behaviors are considered to be related to the size of the particles and composition of the materials. Higher coercive field and lesser magnetization were observed for the sample with higher cobalt content.

  12. Nonaqueous liquid-liquid extraction of manganese from ethylene glycol solution with trioctylphosphine oxide

    International Nuclear Information System (INIS)

    Aoki, Toru

    1981-01-01

    The nonaqueous liquid-liquid extraction of manganese was investigated between the nonpolar solvents (cyclohexane or toluene) containing tri-n-octylphosphine oxide and ethylene glycol containing hydrogen chloride. Manganese was extracted in the two different hydrogen chloride concentration regions in the ethylene glycol phase. One of the manganese extractions was found at the higher hydrogen chloride concentration (above about 10 -2 M), and the extracted from was MnCl 2 .2TOPO. Another was caused at the lower hydrogen chloride concentration (below about 10 -3 M) and the extracted species was presumed to be manganese (deprotonated ethylene glycol) 2 .nTOPO complex. (author)

  13. Bioavailability of manganese from feed grade manganese oxides for broiler chicks.

    Science.gov (United States)

    Wong-Valle, J; Ammerman, C B; Henry, P R; Rao, P V; Miles, R D

    1989-10-01

    An experiment was conducted to study the relative biological availability of Mn from inorganic Mn sources using 288, 1-day-old male Cobb feather-sexed chicks. Chicks were fed a basal corn-soybean meal diet (82.5 ppm Mn, as-fed basis) ad libitum or the basal diet supplemented with 0, 1,000, 2,000, or 3,000 ppm Mn from reagent grade (RG) MnSO4.H2O, MnO RG, or feed grade (FG) Oxide A, B, or C for 21 days. Bone and kidney Mn concentrations were used to estimate bioavailability. Manganese source and level had no effect on chick performance. Uptake of dietary Mn by bone and kidney from all sources was highly linear (P less than .001). Based on multiple linear regression slopes from bone Mn concentrations, the relative bioavailability values of MnO RG and MnO FG A, B, and C were 81.9 +/- 6.0, 93.1 +/- 6.7, 75.0 +/- 3.6, and 70.3 +/- 5.7, respectively, compared with 100% for MnSO4; those based on kidney Mn were 85.7 +/- 7.9, 68.0 +/- 7.5, 52.2 +/- 4.2, and 53.0 +/- 7.3, respectively.

  14. The effects of fire on biogenic soil emissions of nitric oxide and nitrous oxide

    Science.gov (United States)

    Levine, Joel S.; Cofer, Wesley R., III; Sebacher, Daniel I.; Boston, Penelope J.; Winstead, Edward L.; Sebacher, Shirley

    1988-01-01

    Measurements of biogenic soil emissions of nitric oxide (NO) and nitrous oxide (N2O) before and after a controlled burn conducted in a chaparral ecosystem on June 22, 1987, showed significantly enhanced emissions of both gases after the burn. Mean NO emissions from heavily burned and wetted (to simulate rainfall) sites exceeded 40 ng N/sq m s, and increase of 2 to 3 compared to preburn wetted site measurements. N2O emissions from burned and wetted sites ranged from 9 to 22 ng N/sq m s. Preburn N2O emissions from these wetted sites were all below the detection level of the instrumentation, indicating a flux below 2 ng N/sq m s. The flux of NO exceeded the N2O flux from burned wetted sites by factors ranging from 2.7 to 3.4. These measurements, coupled with preburn and postburn measurements of ammonium and nitrate in the soil of this chaparral ecosystem and measurements of NO and N2O emissions obtained under controlled laboratory conditions, suggest that the postfire enhancement of NO and N2O emissions is due to production of these gases by nitrifying bacteria.

  15. Datasets used in the manuscript titled "Nitrate radicals and biogenic volatile organic compounds: oxidation, mechanisms and organic aerosol"

    Data.gov (United States)

    U.S. Environmental Protection Agency — This dataset documents that all of the data used in the manuscript "Nitrate radicals and biogenic volatile organic compounds: oxidation, mechanisms, and organic...

  16. Oxidation of phenolic acids by soil iron and manganese oxides

    Energy Technology Data Exchange (ETDEWEB)

    Lehmann, R.G.; Cheng, H.H.; Harsh, J.B.

    Phenolic acids are intermediary metabolites of many aromatic chemicals and may be involved in humus formation, allelopathy, and nutrient availability. Depending on their structures, six phenolic acids were shown to react at different rates with oxidized forms of Fe and Mn in a Palouse soil (fine-silty, mixed, mesic Pachic Ultic Haploxeroll). Increasing methoxy substitution on the aromatic ring of phenolic acids increased the reaction rate. Reaction rate was also increased for longer carboxyl-containing side chains. After 4 h reaction, little of the applied (10 mg kg/sup -1/ soil) p-hydroxybenzoic or p-coumaric acids had reacted, while 0 to 5, 70, 90, and 100% of the vanillic, ferulic, syringic, and sinapic acids, respectively, had reacted. After 72 h under conditions limiting microbial growth, none of the p-hydroxybenzoic, 30% of the p-coumaric, and 50% of the vanillic acids had reacted. The reaction was shown to be predominantly chemical, and not biological, since phenolic acid extractabilities were similar for Palouse soil and for Palouse soil pretreated with LiOBr to remove organic matter. When the Palouse soil was pretreated with a sodium dithionite-citrate solution to remove Fe and Mn oxides, none of the phenolic acids reacted after 1 h. The reaction of sinapic acid with Palouse soil was shown to produce Fe(II) and soluble Mn as reaction products. The reaction of phenolic acids with soil was thus shown to be an oxidation of the phenolic acids, coupled with a reduction of soil Fe and Mn oxides.

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

    Science.gov (United States)

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

    2013-03-06

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

  18. Interaction of dietary calcium, manganese, and manganese source (Mn oxide or Mn methionine complex) on chick performance and manganese utilization.

    Science.gov (United States)

    Scheideler, S E

    1991-06-01

    Two trials were conducted to determine the utilization of manganese (Mn) as influenced by the level and source of Mn and the level of dietary calcium (Ca) in broiler chickens. Trial One was a 2 x 2 x 3 factorial arrangement of two Mn sources (Mn methionine or manganous oxide), two levels of dietary Ca (1.8 or 1.0), and three levels of supplemental Mn (30, 60, or 200 mg/kg) fed until 4 wk of age. Total phosphorus (available phosphorus) levels were 0.70% (0.48%) during all ages. High levels of dietary Ca caused a slower early rate of growth (0.53 vs. 0.64 kg) for chicks fed 1.8 vs 1.0% Ca, respectively. Chick weight was equivalent for all diets within the Ca-treatment group, except the dietary combination of high Ca and 200 mg/kg Mn as Mn methionine. Bone and liver Mn were significantly increased as the Mn level increased, but were not affected by the Mn source. Chicks fed 1.8% Ca had higher levels of bone Mn (9.28 ppm) than chicks fed 1.0% Ca (7.23 ppm). High levels of dietary Ca and 200 ppm Mn methionine dramatically depressed early growth, feed intake, and bone ash in this trial, raising the question of a diet x environment (heat-stress) effect. Trial Two was a 2 x 2 factorial arrangement of two levels of dietary Ca (1.8 or 1.0%) and two Mn sources (200 mg/kg Mn as Mn methionine or MnO) up to 3 wk of age in a controlled heat-stress environment. No growth depression in the chicks fed high levels of Ca and Mn methionine was observed. In the presence of high levels of dietary Ca, bone Mn was significantly higher when chicks were fed the MnO source. In summary, dietary Ca did not decrease Mn utilization in these trials, and availability of Mn in Mn methionine as a source compared to MnO depended on dietary Ca levels.

  19. Tuning the Synthesis of Manganese Oxides Nanoparticles for Efficient Oxidation of Benzyl Alcohol

    Science.gov (United States)

    Fei, Jingyuan; Sun, Lixian; Zhou, Cuifeng; Ling, Huajuan; Yan, Feng; Zhong, Xia; Lu, Yuxiang; Shi, Jeffrey; Huang, Jun; Liu, Zongwen

    2017-01-01

    The liquid phase oxidation of benzyl alcohol is an important reaction for generating benzaldehyde and benzoic acid that are largely required in the perfumery and pharmaceutical industries. The current production systems suffer from either low conversion or over oxidation. From the viewpoint of economy efficiency and environmental demand, we are aiming to develop new high-performance and cost-effective catalysts based on manganese oxides that can allow the green aerobic oxidation of benzyl alcohol under mild conditions. It was found that the composition of the precursors has significant influence on the structure formation and surface property of the manganese oxide nanoparticles. In addition, the crystallinity of the resulting manganese nanoparticles was gradually improved upon increasing the calcination temperature; however, the specific surface area decreased obviously due to pore structure damage at higher calcination temperature. The sample calcined at the optimal temperature of 600 °C from the precursors without porogen was a Mn3O4-rich material with a small amount of Mn2O3, which could generate a significant amount of {O}_2- species on the surface that contributed to the high catalytic activity in the oxidation. Adding porogen with precursors during the synthesis, the obtained catalysts were mainly Mn2O3 crystalline, which showed relatively low activity in the oxidation. All prepared samples showed high selectivity for benzaldehyde and benzoic acid. The obtained catalysts are comparable to the commercial OMS-2 catalyst. The synthesis-structure-catalysis interaction has been addressed, which will help for the design of new high-performance selective oxidation catalysts.

  20. Structural investigations of biogenic iron oxide samples. Preliminary results

    International Nuclear Information System (INIS)

    Balasoiu, M.; Kuklin, A.I.; Orelovich, O.L.; Kovalev, Yu.S.; Arzumanyan, G.M.; Kurkin, T.S.; Stolyar, S.V.; Iskhakov, R.S.; Rajkher, Yu.L.

    2008-01-01

    Some preliminary results on morphology and structure of iron oxide particles formed inside Klebsiella oxytoca bacteria are presented. In particular, by means of optical microscopy, scanning electron microscopy and small-angle X-ray scattering the effect of the bacteria age (the duration of growth) on the nanoparticles properties is studied

  1. Biogenic iron oxide transformation by hyperthermophiles: spectral and physiological potentials

    Science.gov (United States)

    Kashyap, S.; Sklute, E.; Dyar, M. D.; Holden, J. F.

    2017-12-01

    It is likely that any putative life in our Solar System beyond Earth, extinct or extant, is microbial. However, to detect such life, distinct organic or mineral biosignatures need to be established. Microbe-mineral interactions and mineral transformations deserve further examination in this regard. This study focused on hyperthermophilic iron oxide-reducing archaea and addressed the types of iron-oxide minerals that are favored for growth, the kinetics of such reactions, and the mineral transformations that occur depending upon the electron acceptor. Two hyperthermophilic archaea (Pyrodictium delaneyi and Pyrobaculum islandicum) and six laboratory-synthesized nanophase iron oxide minerals (2-line ferrihydrite, lepidocrocite, akaganéite, goethite, hematite and maghemite) were tested for cell growth and Fe(II) production. The mineral end-products were further characterized by examining the spectral signatures associated with these transformations using reflectance, Raman, and Mössbauer spectroscopies and electron diffraction patterns. Additionally, we critically examined how sample preparation techniques influence the end products of these transformations by comparing freeze-dried samples against those still in solution. Results showed that both organisms utilize all six nanophase iron oxides, although with varying success. The best candidates for microbial reduction were ferrihydrite, akaganéite, and lepidocrocite. The mineral transformation products and the extent of reduction varied and showed subtle differences based on organism and the type of iron oxide used. The subtle spectral differences were best characterized using combined spectroscopy techniques. This research provides new insights into microbe-mineral interactions and the discrimination of potential biosignatures in the search for life beyond Earth.

  2. Stability of a novel synthetic amorphous manganese oxide in contrasting soils

    Czech Academy of Sciences Publication Activity Database

    Ettler, V.; Knytl, V.; Komárek, M.; Della Puppa, L.; Bordas, F.; Mihaljevič, M.; Klementová, Mariana; Šebek, O.

    2014-01-01

    Roč. 214, FEB (2014), s. 2-9 ISSN 0016-7061 Institutional support: RVO:61388980 Keywords : Amorphous manganese oxide * Stability * Soils * Chemical stabilization * Pollution Subject RIV: CA - Inorganic Chemistry Impact factor: 2.772, year: 2014

  3. Ferro-manganese oxide growth on shark teeth from cenral Indian Ocean basin

    Digital Repository Service at National Institute of Oceanography (India)

    Banakar, V.K.; Sudhakar, M.

    Study of ferro-manganese oxide growth on apatitic substrates like shark teeth enamel from siliceous sediment environment (lat. 10 degrees S and long. 75 degrees E) suggests the changes in depositional environments within the sediment layer through...

  4. Synthesis of Magnetic Carbon Supported Manganese Catalysts for Phenol Oxidation by Activation of Peroxymonosulfate

    OpenAIRE

    Yuxian Wang; Yongbing Xie; Chunmao Chen; Xiaoguang Duan; Hongqi Sun; Shaobin Wang

    2016-01-01

    Magnetic core/shell nanospheres (MCS) were synthesized by a novel and facile one-step hydrothermal method. Supported manganese oxide nanoparticles (Fe3O4/C/Mn) were obtained from various methods (including redox, hydrothermal and impregnation) using MCS as the support material and potassium permanganate as the precursor of manganese oxide. The Mn/MCS catalysts were characterized by a variety of characterization techniques and the catalytic performances of Fe3O4/C/Mn nanoparticles were tested ...

  5. Rapid Deposition of Oxidized Biogenic Compounds to a Temperate Forest

    Science.gov (United States)

    Nguyen, Tran B.; Crounse, John D.; Teng, Alex P.; St. Clair, Jason M.; Paulot, Fabien; Wolfe, Glenn M.; Wennberg, Paul O.

    2015-01-01

    We report fluxes and dry deposition velocities for 16 atmospheric compounds above a southeastern United States forest, including: hydrogen peroxide (H2O2), nitric acid (HNO3), hydrogen cyanide (HCN), hydroxymethyl hydroperoxide, peroxyacetic acid, organic hydroxy nitrates, and other multifunctional species derived from the oxidation of isoprene and monoterpenes. The data suggest that dry deposition is the dominant daytime sink for small, saturated oxygenates. Greater than 6 wt %C emitted as isoprene by the forest was returned by dry deposition of its oxidized products. Peroxides account for a large fraction of the oxidant flux, possibly eclipsing ozone in more pristine regions. The measured organic nitrates comprise a sizable portion (15%) of the oxidized nitrogen input into the canopy, with HNO3 making up the balance. We observe that water-soluble compounds (e.g., strong acids and hydroperoxides) deposit with low surface resistance whereas compounds with moderate solubility (e.g., organic nitrates and hydroxycarbonyls) or poor solubility (e.g., HCN) exhibited reduced uptake at the surface of plants. To first order, the relative deposition velocities of water-soluble compounds are constrained by their molecular diffusivity. From resistance modeling, we infer a substantial emission flux of formic acid at the canopy level (approx. 1 nmol m(exp.-2)·s(exp.-1)). GEOS-Chem, awidely used atmospheric chemical transport model, currently underestimates dry deposition for most molecules studied in this work. Reconciling GEOS-Chem deposition velocities with observations resulted in up to a 45% decrease in the simulated surface concentration of trace gases.

  6. Evaluation of biogenic emission flux and its impact on oxidants and inorganic aerosols in East Asia

    Science.gov (United States)

    Han, K. M.; Song, C. H.; Park, R. S.; Woo, J.; Kim, H.

    2010-12-01

    As a major precursor during the summer season, biogenic species are of primary importance in the ozone and SOAs (secondary organic aerosols) formations. Isoprene and mono-terpene also influence the level of inorganic aerosols (i.e. sulfate and nitrate) by controlling OH radicals. However, biogenic emission fluxes are highly uncertain in East Asia. While isoprene emission fluxes from the GEIA (Global Emissions Inventory Activity) and POET (Precursors of Ozone and their Effects in the Troposphere) inventories estimate approximately 20 Tg yr-1 in East Asia, those from the MEGAN (Model of Emissions of Gases and Aerosols from Nature) and MOHYCAN (MOdel for Hydrocarbon emissions by the CANopy) estimate approximately 10 Tg yr-1 and 5 Tg yr-1, respectively. In order to evaluate and/or quantify the magnitude of biogenic emission fluxes over East Asia, the tropospheric HCHO columns obtained from the GOME (Global Ozone Monitoring Experiment) observations were compared with the HCHO columns from the CMAQ (Community Multi-scale Air Quality) simulations over East Asia. In this study, US EPA Models-3/CMAQ v4.5.1 model simulation using the ACE-ASIA (Asia Pacific Regional Aerosol Characterization Experiment) emission inventory for anthropogenic pollutants and GEIA, POET, MEGAN, and MOHYCAN emission inventories for biogenic species was carried out in conjunction with the Meteorological fields generated from the PSU/NCAR MM5 (Pennsylvania state University/National Center for Atmospheric Research Meso-scale Model 5) model for the summer episodes of the year 2002. In addition to an evaluation of the biogenic emission flux, we investigated the impact of the uncertainty in biogenic emission inventory on inorganic aerosol formations and variations of oxidants (OH, O3, and H2O2) in East Asia. In this study, when the GEIA and POET emission inventories are used, the CMAQ-derived HCHO columns are highly overestimated over East Asia, particularly South China compared with GOME-derived HCHO

  7. A microbial-mineralization-inspired approach for synthesis of manganese oxide nanostructures with controlled oxidation states and morphologies

    Energy Technology Data Exchange (ETDEWEB)

    Oba, Manabu; Oaki, Yuya; Imai, Hiroaki [Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan)

    2010-12-21

    Manganese oxide nanostructures are synthesized by a route inspired by microbial mineralization in nature. The combination of organic molecules, which include antioxidizing and chelating agents, facilitates the parallel control of oxidation states and morphologies in an aqueous solution at room temperature. Divalent manganese hydroxide (Mn(OH){sub 2}) is selectively obtained as a stable dried powder by using a combination of ascorbic acid as an antioxidizing agent and other organic molecules with the ability to chelate to manganese ions. The topotactic oxidation of the resultant Mn(OH){sub 2} leads to the selective formation of trivalent manganese oxyhydroxide ({beta}-MnOOH) and trivalent/tetravalent sodium manganese oxide (birnessite, Na{sub 0.55}Mn{sub 2}O{sub 4}.1.5H{sub 2}O). For microbial mineralization in nature, similar synthetic routes via intermediates have been proposed in earlier works. Therefore, these synthetic routes, which include in the present study the parallel control over oxidation states and morphologies of manganese oxides, can be regarded as new biomimetic routes for synthesis of transition metal oxide nanostructures. As a potential application, it is demonstrated that the resultant {beta}-MnOOH nanostructures perform as a cathode material for lithium ion batteries. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Actinomycetes-mediated biogenic synthesis of metal and metal oxide nanoparticles: progress and challenges.

    Science.gov (United States)

    Manimaran, M; Kannabiran, K

    2017-06-01

    Actinomycetes-mediated biogenic synthesis of metal nanoparticles and their antimicrobial activities are well documented. Actinomycetes facilitate both intracellular and extracellular metal nanoparticles synthesis and are efficient candidates for the production of polydispersed, stable and ultra-small size metal nanoparticles. Secondary metabolites and new chemical entities derived from Actinomycetes have not been extensively studied for the synthesis of metal/metal oxide nanoparticles. The present review focuses on biogenic synthesis of metal nanoparticles from Actinomycetes and the scope for exploring Actinomycetes-derived compounds (enzymes, organics acids and bioactive compounds) as metal and metal oxide reducing agents for the synthesis of desired nanoparticles. This review also focuses on challenges faced in the applications of nanoparticles and the methods to synthesize biogenic metal nanoparticles with desired physiochemical properties such as ultra-small size, large surface to mass ratio, high reactivity etc. Methods to evade their toxicity and unique interactions with biological systems to improve their chance as an alternative therapeutic agent in medical and pharmaceutical industry are also discussed. © 2017 The Society for Applied Microbiology.

  9. Extracellular zinc competitively inhibits manganese uptake and compromises oxidative stress management in Streptococcus pneumoniae.

    Directory of Open Access Journals (Sweden)

    Bart A Eijkelkamp

    Full Text Available Streptococcus pneumoniae requires manganese for colonization of the human host, but the underlying molecular basis for this requirement has not been elucidated. Recently, it was shown that zinc could compromise manganese uptake and that zinc levels increased during infection by S. pneumoniae in all the niches that it colonized. Here we show, by quantitative means, that extracellular zinc acts in a dose dependent manner to competitively inhibit manganese uptake by S. pneumoniae, with an EC50 of 30.2 µM for zinc in cation-defined media. By exploiting the ability to directly manipulate S. pneumoniae accumulation of manganese, we analyzed the connection between manganese and superoxide dismutase (SodA, a primary source of protection for S. pneumoniae against oxidative stress. We show that manganese starvation led to a decrease in sodA transcription indicating that expression of sodA was regulated through an unknown manganese responsive pathway. Intriguingly, examination of recombinant SodA revealed that the enzyme was potentially a cambialistic superoxide dismutase with an iron/manganese cofactor. SodA was also shown to provide the majority of protection against oxidative stress as a S. pneumoniae ΔsodA mutant strain was found to be hypersensitive to oxidative stress, despite having wild-type manganese levels, indicating that the metal ion alone was not sufficiently protective. Collectively, these results provide a quantitative assessment of the competitive effect of zinc upon manganese uptake and provide a molecular basis for how extracellular zinc exerts a 'toxic' effect on bacterial pathogens, such as S. pneumoniae.

  10. Nickel mobilization in a groundwater well field: Release by pyrite oxidation and desorption from manganese oxides

    DEFF Research Database (Denmark)

    Postma, Dieke; Larsen, Flemming

    1997-01-01

    Processes controlling the nickel concentration in groundwater have been studied in a well field of a sandy aquifer capped by clayey till. The water table in the aquifer was lowered due to groundwater abstraction, and in association with pyrite oxidation in the unsaturated zone, nickel is released...... to the groundwater in concentrations of up to 4000 nM. The nickel concentration in pyrite was determined to be 40-140 x 10(-5) mol of Ni/mol of pyrite. Groundwater nickel concentrations are particularly high in the unsaturated zone and in the recently resubmerged uppermost saturated zone. The resubmerged zone...... is furthermore characterized by enhanced Mn2+ concentrations. Apparently nickel accumulates on manganese oxides during pyrite oxidation. When the water table rises again, partially oxidized pyritic layers are resubmerged, and due to an insufficient supply of oxygen, the oxidation of Fe2+ released during pyrite...

  11. Contribution to the study of iron-manganese alloy oxidation in oxygen at high temperatures

    International Nuclear Information System (INIS)

    Olivier, Francoise

    1972-01-01

    This research thesis reports a systematic investigation of the oxidation of three relatively pure iron-manganese alloys in oxygen, under atmospheric pressure, and between 400 and 1000 C, these alloys being annealed as well as work-hardened. It also compares their behaviour with that of non-alloyed iron oxidized under the same conditions. The author describes the experimental techniques and installations, discusses the morphology of oxide films formed under the experimental conditions, discusses the film growth kinetics which is studied by thermogravimetry, proposes interpretations of results, and outlines the influence of manganese addition to iron on iron oxidation

  12. Roles of manganese oxides in degradation of phenol under UV-Vis irradiation: adsorption, oxidation, and photocatalysis.

    Science.gov (United States)

    Zhang, Qin; Cheng, Xiaodi; Zheng, Chen; Feng, Xionghan; Qiu, Guohong; Tan, Wenfeng; Liu, Fan

    2011-01-01

    Manganese oxides are known as one type of semiconductors, but their photocatalysis characteristics have not been deeply explored. In this study, photocatalytic degradation of phenol using several synthesized manganese oxides, i.e, acidic birnessite (BIR-H), alkaline birnessite (BIR-OH), cryptomelane (CRY) and todorokite (TOD), were comparatively investigated. To elucidate phenol degradation mechanisms, X-ray diffraction (XRD), ICP-AES (inductively coupled plasma-atomic emission spectroscopy), TEM (transmission electronic microscope), N2 physisorption at 77 K and UV-visible diffuse reflectance spectroscopy (UV-Vis DRS) were employed to characterize the structural, compositional, morphological, specific surface area and optical absorption properties of the manganese oxides. After 12 hr of UV-Vis irradiation, the total organic carbon (TOC) removal rate reached 62.1%, 43.1%, 25.4%, and 22.5% for cryptomelane, acidic birnessite, todorokite and alkaline birnessite, respectively. Compared to the reactions in the dark condition, UV-Vis exposure improved the TOC removal rates by 55.8%, 31.9%, 23.4% and 17.9%. This suggests a weak ability of manganese oxides to degrade phenol in the dark condition, while UV-Vis light irradiation could significantly enhance phenol degradation. The manganese minerals exhibited photocatalytic activities in the order of: CRY > BIR-H > TOD > BIR-OH. There may be three possible mechanisms for photochemical degradation: (1) direct photolysis of phenol; (2) direct oxidation of phenol by manganese oxides; (3) photocatalytic oxidation of phenol by manganese oxides. Photocatalytic oxidation of phenol appeared to be the dominant mechanism.

  13. Role of biogenic sulfide in attenuating zinc oxide and copper nanoparticle toxicity to acetoclastic methanogenesis.

    Science.gov (United States)

    Gonzalez-Estrella, Jorge; Puyol, Daniel; Sierra-Alvarez, Reyes; Field, Jim A

    2015-01-01

    Soluble ions released by zinc oxide (ZnO) and copper (Cu(0)) nanoparticles (NPs) have been associated with toxicity to methanogens. This study evaluated the role of biogenic sulfide in attenuating ZnO and Cu(0) NP toxicity to methanogens. Short- and long-term batch experiments were conducted to explore ZnO and Cu(0) NPs toxicity to acetoclastic methanogens in sulfate-containing (0.4mM) and sulfate-free conditions. ZnO and Cu(0) were respectively 14 and 7-fold less toxic in sulfate-containing than in sulfate-free assays as indicated by inhibitory constants (Ki). The Ki with respect to residual soluble metal indicated that soluble metal was well correlated with toxicity irrespective of the metal ion source or presence of biogenic sulfide. Long-term assays indicated that ZnO and Cu(0) NPs caused different effects on methanogens. ZnO NPs without protection of sulfide caused a chronic effect, whereas Cu(0) NPs caused an acute effect and recovered. This study confirms that biogenic sulfide effectively attenuates ZnO and Cu(0) NPs toxicity to methanogens by the formation of metal sulfides. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Studies on inorganic exchangers : hydrous manganese (II) oxide

    International Nuclear Information System (INIS)

    Mathew, C.; Rao, K.L.N.; Dash, A.; Varma, R.N.; Balasubramanian, K.R.; Murthy, T.S.

    1992-01-01

    The inorganic exchanger hydrous manganese dioxide has been prepared and its characteristics evaluated. A method has been developed for the separation of 144 Ce from fission products solution using this exchanger. (author). 16 refs., 4 figs., 5 tabs

  15. Iron and manganese oxide mineralization in the Pacific

    Science.gov (United States)

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

    1997-01-01

    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. These processes are discussed.

  16. Methyl chavicol: characterization of its biogenic emission rate, abundance, and oxidation products in the atmosphere

    Directory of Open Access Journals (Sweden)

    N. C. Bouvier-Brown

    2009-03-01

    Full Text Available We report measurements of ambient atmospheric mixing ratios for methyl chavicol and determine its biogenic emission rate. Methyl chavicol, a biogenic oxygenated aromatic compound, is abundant within and above Blodgett Forest, a ponderosa pine forest in the Sierra Nevada Mountains of California. Methyl chavicol was detected simultaneously by three in-situ instruments – a gas chromatograph with mass spectrometer detector (GC-MS, a proton transfer reaction mass spectrometer (PTR-MS, and a thermal desorption aerosol GC-MS (TAG – and found to be abundant within and above Blodgett Forest. Methyl chavicol atmospheric mixing ratios are strongly correlated with 2-methyl-3-buten-2-ol (MBO, a light- and temperature-dependent biogenic emission from the ponderosa pine trees at Blodgett Forest. Scaling from this correlation, methyl chavicol emissions account for 4–68% of the carbon mass emitted as MBO in the daytime, depending on the season. From this relationship, we estimate a daytime basal emission rate of 0.72–10.2 μgCg−1 h−1, depending on needle age and seasonality. We also present the first observations of its oxidation products (4-methoxybenzaldehyde and 4-methyoxy benzene acetaldehyde in the ambient atmosphere. Methyl chavicol is a major essential oil component of many plant species. This work suggests that methyl chavicol plays a significant role in the atmospheric chemistry of Blodgett Forest, and potentially other sites, and should be included explicitly in both biogenic volatile organic carbon emission and atmospheric chemistry models.

  17. Biomimetic oxidation of carbamazepine with hydrogen peroxide catalyzed by a manganese porphyrin

    Directory of Open Access Journals (Sweden)

    Cláudia M. B. Neves

    2012-01-01

    Full Text Available This laboratory project is planned for an undergraduate chemistry laboratory in which students prepare a manganese porphyrin able to mimic the oxidative metabolism of carbamazepine, one of the most frequently prescribed drugs in the treatment of epilepsy. The in vitro oxidation of carbamazepine results in the formation of the corresponding 10,11-epoxide, the main in vivo metabolite. The reaction is catalyzed by manganese porphyrin in the presence of H2O2, an environmentally-friendly oxidant. Through this project students will develop their skills in organic synthesis, coordination chemistry, chromatographic techniques such as TLC and HPLC, UV-visible spectrophotometry, and NMR spectroscopy.

  18. Biomimetic oxidation of carbamazepine with hydrogen peroxide catalyzed by a manganese porphyrin

    Energy Technology Data Exchange (ETDEWEB)

    Neves, Claudia M.B.; Simoes, Mario M.Q.; Domingues, Fernando M.J.; Neves, M. Graca P.M.S.; Cavaleiro, Jose A.S., E-mail: msimoes@ua.pt [Dept. de Quimica, QOPNA, Universidade de Aveiro (Portugal)

    2012-07-01

    This laboratory project is planned for an undergraduate chemistry laboratory in which students prepare a manganese porphyrin able to mimic the oxidative metabolism of carbamazepine, one of the most frequently prescribed drugs in the treatment of epilepsy. The in vitro oxidation of carbamazepine results in the formation of the corresponding 10,11-epoxide, the main in vivo metabolite. The reaction is catalyzed by manganese porphyrin in the presence of H{sub 2}O{sub 2}, an environmentally-friendly oxidant. Through this project students will develop their skills in organic synthesis, coordination chemistry, chromatographic techniques such as TLC and HPLC, UV-visible spectrophotometry, and NMR spectroscopy. (author)

  19. Synthesis and redox behaviors of copper oxide and manganese oxide nanoparticles

    Science.gov (United States)

    Pike, Jenna Malia

    Chapter 1. A general introduction to the field of transition metal oxide nanoparticles is presented, highlighting the industrial applications and research interest in copper oxide and manganese oxide nanoparticles in particular. A background of x-ray diffraction and transition electron microscopy used in this research is presented. Chapter 2. An aqueous method for producing 5--18 nm wide copper oxide (CuO) nanoparticles at 36°C to 50°C using copper nitrate and hexamethylenetetramine (HMT) is presented. HMT quality and concentration is used to control CuO nanoparticle size. A decrease in nanoparticle size with increasing HMT concentration indicates that HMT acts as a surfactant in the reaction. Activation energy for formation of CuO is calculated from the reaction rate. Chapter 3. An aqueous method for synthesizing 20--40 nm Mn3O4 nanoparticles from manganese nitrate and HMT at temperatures between 25°C and 80°C is described and results of nanoparticle characterization are presented. The effects of nitrate concentration, synthesis temperature, and reaction time on the Mn3O4 nanoparticle size, size distribution, and morphology are evaluated. The activation energy for the formation of Mn3O4 nanoparticles is calculated from the synthesis yield. Chapter 4. The behavior of copper oxide nanoparticles in reduction experiments is evaluated; synchrotron radiation and in-situ time-resolved x-ray diffraction (TR-XRD) are used to monitor phase changes during reduction. CuO reduction experiments in CO and H 2 gases using ramping temperature and isothermal conditions are presented. Chapter 5. Reduction of Mn3O4 nanoparticles and oxidation of MnO nanoparticles using synchrotron radiation and in-situ TR-XRD is presented. Redox temperature decreases with decreases nanoparticle size. The formation of the intermediate phase Mn5O8 with further oxidation of MnO, observed in MnO nanoparticles, is discussed. Chapter 6. Measurements of lattice parameter in nanoparticles of MnO and Cu2O

  20. Three-dimensional reticular tin-manganese oxide composite anode materials for lithium ion batteries

    International Nuclear Information System (INIS)

    Zhu, X.J.; Guo, Z.P.; Zhang, P.; Du, G.D.; Poh, C.K.; Chen, Z.X.; Li, S.; Liu, H.K.

    2010-01-01

    Tin-manganese oxide film with three-dimensional (3D) reticular structure has been prepared by electrostatic spray deposition (ESD). X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicate that the film is amorphous. X-ray-photoemission spectroscopy (XPS) demonstrates that the 3D grid is composed of tin-manganese oxide. As an anode electrode for the lithium ion battery, the tin-manganese oxide film has 1188.3 mAh g -1 of initial discharge capacity and very good capacity retention of 656.2 mAh g -1 up to the 30th cycle. Such a composite film can be used as an anode for lithium ion batteries with higher energy densities.

  1. Durable rechargeable zinc-air batteries with neutral electrolyte and manganese oxide catalyst

    Science.gov (United States)

    Sumboja, Afriyanti; Ge, Xiaoming; Zheng, Guangyuan; Goh, F. W. Thomas; Hor, T. S. Andy; Zong, Yun; Liu, Zhaolin

    2016-11-01

    Neutral chloride-based electrolyte and directly grown manganese oxide on carbon paper are used as the electrolyte and air cathode respectively for rechargeable Zn-air batteries. Oxygen reduction and oxygen evolution reactions on manganese oxide show dependence of activities on the pH of the electrolyte. Zn-air batteries with chloride-based electrolyte and manganese oxide catalyst exhibit satisfactory voltage profile (discharge and charge voltage of 1 and 2 V at 1 mA cm-2) and excellent cycling stability (≈90 days of continuous cycle test), which is attributed to the reduced carbon corrosion on the air cathode and decreased carbonation in neutral electrolyte. This work describes a robust electrolyte system that improves the cycle life of rechargeable Zn-air batteries.

  2. Deposition of Biogenic Iron Minerals in a Methane Oxidizing Microbial Mat

    Directory of Open Access Journals (Sweden)

    Christoph Wrede

    2013-01-01

    Full Text Available The syntrophic community between anaerobic methanotrophic archaea and sulfate reducing bacteria forms thick, black layers within multi-layered microbial mats in chimney-like carbonate concretions of methane seeps located in the Black Sea Crimean shelf. The microbial consortium conducts anaerobic oxidation of methane, which leads to the formation of mainly two biomineral by-products, calcium carbonates and iron sulfides, building up these chimneys. Iron sulfides are generated by the microbial reduction of oxidized sulfur compounds in the microbial mats. Here we show that sulfate reducing bacteria deposit biogenic iron sulfides extra- and intracellularly, the latter in magnetosome-like chains. These chains appear to be stable after cell lysis and tend to attach to cell debris within the microbial mat. The particles may be important nuclei for larger iron sulfide mineral aggregates.

  3. Deposition of biogenic iron minerals in a methane oxidizing microbial mat.

    Science.gov (United States)

    Wrede, Christoph; Kokoschka, Sebastian; Dreier, Anne; Heller, Christina; Reitner, Joachim; Hoppert, Michael

    2013-01-01

    The syntrophic community between anaerobic methanotrophic archaea and sulfate reducing bacteria forms thick, black layers within multi-layered microbial mats in chimney-like carbonate concretions of methane seeps located in the Black Sea Crimean shelf. The microbial consortium conducts anaerobic oxidation of methane, which leads to the formation of mainly two biomineral by-products, calcium carbonates and iron sulfides, building up these chimneys. Iron sulfides are generated by the microbial reduction of oxidized sulfur compounds in the microbial mats. Here we show that sulfate reducing bacteria deposit biogenic iron sulfides extra- and intracellularly, the latter in magnetosome-like chains. These chains appear to be stable after cell lysis and tend to attach to cell debris within the microbial mat. The particles may be important nuclei for larger iron sulfide mineral aggregates.

  4. Cation Effects on the Layer Structure of Biogenic Mn-Oxides

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, M.; Ginder-Vogel, M; Parikh, S; Feng, X; Sparks, D

    2010-01-01

    Biologically catalyzed Mn(II) oxidation produces biogenic Mn-oxides (BioMnO{sub x}) and may serve as one of the major formation pathways for layered Mn-oxides in soils and sediments. The structure of Mn octahedral layers in layered Mn-oxides controls its metal sequestration properties, photochemistry, oxidizing ability, and topotactic transformation to tunneled structures. This study investigates the impacts of cations (H{sup +}, Ni(II), Na{sup +}, and Ca{sup 2+}) during biotic Mn(II) oxidation on the structure of Mn octahedral layers of BioMnO{sub x} using solution chemistry and synchrotron X-ray techniques. Results demonstrate that Mn octahedral layer symmetry and composition are sensitive to previous cations during BioMnO{sub x} formation. Specifically, H{sup +} and Ni(II) enhance vacant site formation, whereas Na{sup +} and Ca{sup 2+} favor formation of Mn(III) and its ordered distribution in Mn octahedral layers. This study emphasizes the importance of the abiotic reaction between Mn(II) and BioMnO{sub x} and dependence of the crystal structure of BioMnO{sub x} on solution chemistry.

  5. Manganese compounds as catalysts for water oxidation and as CO releasing molecules

    OpenAIRE

    Berends, Hans-Martin

    2011-01-01

    This PhD thesis deals with several aspects of manganese chemistry and is divided into three parts. The first two concern the synthesis and characterization of manganese-based water oxidation catalysts. The four-electron oxidation of water to dioxygen is a key process of oxygenic photosynthesis in which solar energy is captured and stored in the form of carbohydrates. In nature, this reaction is catalyzed by a µ-oxido-Mn4Ca cluster, the oxygen evolving complex (OEC). Mimicking this reacti...

  6. Biomimetic oxidation of piperine and piplartine catalyzed by iron(III) and manganese(III) porphyrins.

    Science.gov (United States)

    Schaab, Estela Hanauer; Crotti, Antonio Eduardo Miller; Iamamoto, Yassuko; Kato, Massuo Jorge; Lotufo, Letícia Veras Costa; Lopes, Norberto Peporine

    2010-01-01

    Synthetic metalloporphyrins, in the presence of monooxygen donors, are known to mimetize various reactions of cytochrome P450 enzymes systems in the oxidation of drugs and natural products. The oxidation of piperine and piplartine by iodosylbenzene using iron(III) and manganese(III) porphyrins yielded mono- and dihydroxylated products, respectively. Piplartine showed to be a more reactive substrate towards the catalysts tested. The structures of the oxidation products were proposed based on electrospray ionization tandem mass spectrometry.

  7. Growth and Dissolution of Iron and Manganese Oxide Films

    Energy Technology Data Exchange (ETDEWEB)

    Scot T. Martin

    2008-12-22

    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

  8. Enhanced methanol electro-oxidation activity of Pt/MWCNTs electro-catalyst using manganese oxide deposited on MWCNTs

    International Nuclear Information System (INIS)

    Nouralishahi, Amideddin; Khodadadi, Abbas Ali; Mortazavi, Yadollah; Rashidi, Alimorad; Choolaei, Mohammadmehdi

    2014-01-01

    Highlights: • Promoting effects of manganese oxide (MnO x ) on methanol electro-oxidation over Pt/MWCNTs are studied. • 3.3 times higher activity and improved stability are observed on Pt/MnO x -MWCNTs in MOR. • Both hydrogen spill over and bi-functional mechanism are facilitated in presence of MnO x . • MnO x significantly enhances electrochemical active surface area and dispersion of Pt nanoparticles. • Proton conductivity of electrocatalyst layer is improved upon MnO x incorporation. - Abstract: Electro-oxidation of methanol on platinum nanoparticles supported on a nanocomposite of manganese oxide (MnO x ) and multi-wall carbon nanotubes (MWCNTs) is investigated. The morphology, structure, and chemical composition of the electro-catalysts are characterized by TEM, XRD, EDS, TGA, and H 2 -TPR. The electro-catalytic properties of electrodes are examined by cyclic voltammetry, CO-stripping, electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV). Compared to Pt/MWCNTs, the Pt/MnO x -MWCNTs electro-catalyst exhibits about 3.3 times higher forward peak current density, during cyclic voltammetry, and 4.6 times higher exchange current density in methanol electro-oxidation reaction. In addition, deposition of manganese oxide onto MWCNTs dramatically increases the electrochemical active surface area from 29.7 for Pt/MWCNTs to 89.4 m 2 g −1 Pt for Pt/MnO x -MWCNTs. The results of long-term cyclic voltammetry show superior stability of Pt nanoparticles upon addition of manganese oxide to the support. Furthermore, the kinetics of formation of the chemisorbed OH groups improves upon manganese oxide incorporation. This leads to a lower onset potential of CO ads oxidation on Pt/MnO x -MWCNTs than on Pt/MWCNTs

  9. The kinetics of iodide oxidation by the manganese oxide mineral birnessite

    Science.gov (United States)

    Fox, P.M.; Davis, J.A.; Luther, G. W.

    2009-01-01

    The kinetics of iodide (I-) and molecular iodine (I2) oxidation by the manganese oxide mineral birnessite (??-MnO2) was investigated over the pH range 4.5-6.25. I- oxidation to iodate (IO3-) proceeded as a two-step reaction through an I2 intermediate. The rate of the reaction varied with both pH and birnessite concentration, with faster oxidation occurring at lower pH and higher birnessite concentration. The disappearance of I- from solution was first order with respect to I- concentration, pH, and birnessite concentration, such that -d[I-]/dt = k[I-][H+][MnO2], where k, the third order rate constant, is equal to 1.08 ?? 0.06 ?? 107 M-2 h-1. The data are consistent with the formation of an inner sphere I- surface complex as the first step of the reaction, and the adsorption of I- exhibited significant pH dependence. Both I2, and to a lesser extent, IO3- sorbed to birnessite. The results indicate that iodine transport in mildly acidic groundwater systems may not be conservative. Because of the higher adsorption of the oxidized I species I2 and IO3-, as well as the biophilic nature of I2, redox transformations of iodine must be taken into account when predicting I transport in aquifers and watersheds.

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

    Science.gov (United States)

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

    2011-10-01

    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.

  11. [Isolation and identification of Mn oxidizing bacterium Aminobacter sp. H1 and its oxidation mechanism].

    Science.gov (United States)

    Yan, Ping; Jiang, Li-Ying; Chen, Jian-Meng; He, Zhi-Min; Xiao, Shao-Dan; Jiang, Yi-Feng

    2014-04-01

    A bacterium with high manganese oxidizing activity was isolated from a biological manganese removal filter and named as H1. Based on its characteristics and the analysis of 16S rDNA sequence, the strain H1 belonged to the genus Aminobacter sp. and its manganese oxidizing ability had never been reported. In this paper, the microbiologic properties of the strain H1, the manganese oxidation mechanisms and characteristics of biogenic manganese oxides were investigated. The results showed that the maximal tolerant Mn concentration of strain H1 was 50 mmol x L(-1), and Mn(II) could be completely removed by strain H1 when the concentration was lower than 10 mmol x L(-1). Strain H1 could oxidize Mn2+ by both the production of manganese oxidizing activity factor and alkaline metabolites during growth, which were synthesized in the cell and then secreted into extracellular culture medium. During the oxidation process, the intermediate of soluble Mn(III) was detected. SEM showed that the biogenic manganese oxides were amorphous and poorly-crystalline, and it closely combined with bacteria. The components of the biogenic manganese oxides produced by strain H1 were identified as MnCO3, MnOOH, Mn3O4 and MnO2 by XRD, XPS and SEM-EDX.

  12. Organ weight changes in mice after long-term inhalation exposure to manganese oxides nanoparticles

    Science.gov (United States)

    Zeman, T.; Buchtová, M.; Dočekal, B.; Míšek, I.; Navrátil, J.; Mikuška, P.; Šerý, O.; Večeřa, Z.

    2015-05-01

    Recently, it has been proven that manganese from inhaled particles of manganese compounds can accumulate in the internal organs of laboratory animals. Nevertheless, there were only a few researches dealing with changes in body morphology induced by inhalation of these particles, even though results of some studies indicate existence of such changes. The aim of our research was to assess the effect of inhaled manganese oxides nanoparticles on weight of internal organs. For this purpose a long-term inhalation experiment on laboratory mice was performed, during which the mice were exposed to MnO.Mn2O3 nanoparticles in concentration 2 × 106 particles/cm3 for 17 weeks, 24 hours a day, 7 days a week. Manganese oxides nanoparticles were synthesized continuously via aerosol route in a hot wall tube flow reactor using thermal decomposition of metal organic precursor manganese(II)acetylacetonate in the flow tube reactor at temperature 750 °C in the presence of 30 vol% of oxygen. It was proven that inhaled nanoparticles can influence the weight of internal organs of mice. Moreover, it was discovered that the resulting change in weight of selected organs is disproportional. The mice from the experimental group had statistically significantly lighter kidneys, liver and spleen and heavier pancreas compared to the mice from the control group.

  13. Fabrication of ultrafine manganese oxide-decorated carbon nanofibers for high-performance electrochemical capacitors

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ying; Lee, Sungsik; Brown, Dennis E.; Zhao, Hairui; Li, Xinsong; Jiang, Daqiang; Hao, Shijie; Zhao, Yongxiang; Cong, Daoyong; Zhang, Xin; Ren, Yang

    2016-09-01

    Ultrafine manganese oxide-decorated carbon nanofibers (MnOn-CNF) as a new type of electrode materials are facilely fabricated by direct conversion of Mn, Zn-trimesic acid (H3BTC) metal organic framework fibers (Mn-ZnBTC). The construction and evolution of Mn-ZnBTC precursors are investigated by SEM and in situ high-energy XRD. The manganese oxides are highly dispersed onto the porous carbon nanofibers formed simultaneously, verified by TEM, X-ray absorption fine structure (XAFS), Raman, ICP-AES and N2 adsorption techniques. As expected, the resulting MnOn-CNF composites are highly stable, and can be cycled up to 5000 times with a high capacitance retention ratio of 98% in electrochemical capacitor measurements. They show a high capacitance of up to 179 F g–1 per mass of the composite electrode, and a remarkable capacitance of up to 18290 F g–1 per active mass of the manganese(IV) oxide, significantly exceeding the theoretical specific capacitance of manganese(IV) oxide (1370 F g–1). The maximum energy density is up to 19.7 Wh kg–1 at the current density of 0.25 A g–1, even orders higher than those of reported electric double-layer capacitors and pseudocapacitors. The excellent capacitive performance can be ascribed to the joint effect of easy accessibility, high porosity, tight contact and superior conductivity integrated in final MnOn-CNF composites.

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

    CSIR Research Space (South Africa)

    Thackeray, MM

    1993-10-01

    Full Text Available Lithium-manganese-oxides prepared at moderate temperatures are under investigation as insertion electrodes for rechargeable lithium batteries. The structures of two defect-spinel compounds synthesized by the reaction of MnCO3 and Li2CO3 at 400°C...

  15. Synthesis and structural characterization of defect spinels in the Lithium-Manganese-Oxide system

    CSIR Research Space (South Africa)

    Thackeray, MM

    1993-10-01

    Full Text Available Lithium-manganese-oxides prepared at moderate temperatures are under investigation as insertion electrodes for rechargeable lithium batteries. The structures of two defect-spinel compounds synthesised by the reaction of MnCO3 and Li2CO3 at 400...

  16. Synthesis of nanostructured manganese oxides based materials and application for supercapacitor

    Science.gov (United States)

    Dung Dang, Trung; Le, Thi Thu Hang; Bich Thuy Hoang, Thi; Mai, Thanh Tung

    2015-01-01

    Manganese oxides are important materials with a variety of applications in different fields such as chemical sensing devices, magnetic devices, field-emission devices, catalysis, ion-sieves, rechargeable batteries, hydrogen storage media and microelectronics. To open up new applications of manganese oxides, novel morphologies or nanostructures are required to be developed. Via sol—gel and anodic electrodeposition methods, M (Co, Fe) doped manganese oxides were prepared. On the other hand, nanostructured (nanoparticles, nanorods and hollow nanotubes) manganese oxides were synthesized via a process including a chemical reaction with carbon nanotubes (CNTs) templates followed by heat treatment. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV) and impedance spectroscopy (EIS) were used for characterization of the prepared materials. The influence of chemical reaction conditions, heat treatment and template present on the morphology, structure, chemical and electrochemical properties of the prepared materials were investigated. Chronopotentiometry (CP) and CV results show high specific capacitance of 186.2 to 298.4 F g-1 and the charge/discharge stability of the prepared materials and the ideal pseudocapacitive behaviors were observed. These results give an opening and promising application of these materials in advanced energy storage applications.

  17. Carbon/manganese oxide based fuel cell electrocatalyst using "Flywheel" principle

    Czech Academy of Sciences Publication Activity Database

    Vondrák, Jiří; Klápště, Břetislav; Velická, Jana; Sedlaříková, M.; Novák, V.; Reiter, Jakub

    2005-01-01

    Roč. 8, č. 1 (2005), s. 1-4 ISSN 1480-2422 Institutional research plan: CEZ:AV0Z40320502 Keywords : manganese oxide * oxygen electrode * bifunctional electrode Subject RIV: CA - Inorganic Chemistry Impact factor: 0.772, year: 2005

  18. Improved capacity retention in rechargeable 4 V lithium/lithium manganese oxide (spinel) cells.

    CSIR Research Space (South Africa)

    Gummow, RJ

    1994-04-01

    Full Text Available if LiMn2O4 is doped with mono- or multivalent cations (e.g. Li+, Mg2+, Zn2+) or, alternatively, with additional oxygen to increase the average manganese-ion oxidation state marginally above 3.5....

  19. Cobalt immobilization by manganese oxidizing bacteria from the Indian ridge system

    Digital Repository Service at National Institute of Oceanography (India)

    Antony, R.; Sujith, P.P.; Fernandes, S.O.; Verma, P.; Khedekar, V.D.; LokaBharathi, P.A.

    Co immobilization by two manganese oxidizing isolates from Carlsberg Ridge waters (CR35 and CR48) was compared with that of Mn at same molar concentrations. At a lower concentration of 10 mu M, CR35 and CR48 immobilized 22 and 23 fM Co cell-1...

  20. Synthesis, characterization and photocatalytic activity of porous manganese oxide doped titania for toluene decomposition

    International Nuclear Information System (INIS)

    Jothiramalingam, R.; Wang, M.K.

    2007-01-01

    The present study describes the photocatalytic degradation of toluene in gas phase on different porous manganese oxide doped titanium dioxide. As synthesized birnessite and cryptomelane type porous manganese oxide were doped with titania and tested for photocatalytic decomposition of toluene in gas phase. The effects of the inlet concentration of toluene, flow rate (retention time) were examined and the relative humidity was maintained constantly. Thermal and textural characterization of manganese oxide doped titania materials were characterized by X-ray diffraction (XRD), thermogravemetry (TG), BET and TEM-EDAX studies. The aim of the present study is to synthesize the porous manganese oxide doped titania and to study its photocatalytic activity for toluene degradation in gas phase. Cryptomelane doped titania catalyst prepared in water medium [K-OMS-2 (W)] is shown the good toluene degradation with lower catalysts loading compared to commercial bulk titania in annular type photo reactor. The higher photocatalytic activity due to various factors such as catalyst preparation method, experimental conditions, catalyst loading, surface area, etc. In the present study manganese oxide OMS doped titania materials prepared by both aqueous and non-aqueous medium, aqueous medium prepared catalyst shows the good efficiency due to the presence of OH bonded groups on the surface of catalyst. The linear forms of different kinetic equations were applied to the adsorption data and their goodness of fit was evaluated based on the R 2 and standard error. The goodness to the linear fit was observed for Elovich model with high R 2 (≥0.9477) value

  1. Synthesis and catalytic activity of Birnessite-Type Manganese Oxide synthesized by solvent-free method

    Science.gov (United States)

    Siregar, S. S.; Awaluddin, A.

    2018-04-01

    Redox reaction between KMnO4 and glucose usingsolvent-free method produces the octahedral layer birnessite-type manganese oxide. The effects of mole ratios, temperatures, and calcinations time on the structures and crystallinity of the oxides were studied throughthe X-ray powder diffraction analysis. The mole ratio of KMnO4/glucose (1:3) produces the purebirnessite with low crystallinity, whereas the mole ratio of KMnO4/glucose (3:1) yields high crystalline birnessite with minor components of hausmannite-type manganese oxide.The increasing of the temperature and calcinations times (300-700 °C and 3-7 h, respectively) willimprove the crystallinity and the purity of the as-synthesized oxide. Further experiments also showed that the as-syntesized octahedral layer birnessite-type manganese oxides have catalytic activity on the degradation of methylene blue (MB) dye with H2O2 as oxidant. The results revealed that the effective degradation could be achieved only in the presence of both the birnessite and H2O2, whereas without the addition of catalyst (H2O2only) or addition of H2O2 (catalyst only), the 3.5% and 15.5% of MB removal were obtained, respectively.

  2. Topotactic oxidative and reductive control of the structures and properties of layered manganese oxychalcogenides.

    Science.gov (United States)

    Hyett, Geoffrey; Barrier, Nicolas; Clarke, Simon J; Hadermann, Joke

    2007-09-12

    Topotactic modification, by both oxidation and reduction, of the composition, structures, and magnetic properties of the layered oxychalcogenides Sr4Mn3O7.5Cu2Ch2 (Ch=S, Se) is described. These Mn3+ compounds are composed of alternating perovskite-type strontium manganese oxide slabs separated by anti-fluorite-type copper chalcogenide layers and are intrinsically oxide deficient in the central layer of the perovskite slabs. The systems are unusual examples of perovskite-related compounds that may topotactically be both oxidized by fluorination and reduced by deintercalation of oxygen from the oxide-deficient part of the structure. The compounds exhibit antiferromagnetic ordering of the manganese magnetic moments in the outer layers of the perovskite slabs, while the other moments, in the central layers, exhibit spin-glass-like behavior. Fluorination has the effect of increasing the antiferromagnetic ordering temperature and the size of the ordered moment, whereas reduction destroys magnetic long-range order by introducing chemical disorder which leads to both further disorder and frustration of the magnetic interactions in the manganese oxide slab.

  3. Electrochemical oxidation of sulfites by DWCNTs, MWCNTs, higher fullerenes and manganese

    Science.gov (United States)

    Uzun, Dzhamal; Pchelarov, George; Dimitrov, Ognian; Vassilev, Sasho; Obretenov, Willi; Petrov, Konstantin

    2018-03-01

    Different electrocatalysts were tested for oxidation of sulfites to sulfates, namely, manganese thin films deposited on fullerenes and carbon nanotubes. The results presented clearly show that electrodes containing HFs (higher fullerenes), DWCNTs (double-wall carbon nanotubes) and manganese acetate are effective catalysts in S/O2 fuel cells. HFs and DWCNTs have high catalytic activity and can be employed as standalone catalysts. Manganese was deposited on DWCNTs, HFs and fullerenes C60/C70 by a thermal process. The electrocatalysts were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical testing was carried out by plotting the E/V polarization curve. The polarization curves of the electrodes composed of pristine DWCNTs showed the lowest overpotentials.

  4. Low temperature self-assembled growth of rutile TiO2/manganese oxide nanocrystalline films

    Science.gov (United States)

    Sun, Zhenya; Zhou, Daokun; Du, Jianhua; Xie, Yuxing

    2017-10-01

    We report formation of rutile TiO2 nanocrystal at low temperature range in the presence of α-MnO2 which self-assembled onto sulfanyl radical activated silicon oxide substrate. SEM, HRTEM, XPS and Raman spectroscopy were used to study the morphology and oxidation state of synthesised crystals. The results showed that when the α-MnO2 was reduced to Mn3O4, it induced the formation of rutile instead of anatase phase in the TiCl4-HCl aqueous system. The finding will promote the understanding of phase transformation mechanism when manganese oxide and titanium oxide co-exist in soil and water environment.

  5. Oxidative Precipitation of Manganese from Acid Mine Drainage by Potassium Permanganate

    Directory of Open Access Journals (Sweden)

    Regeane M. Freitas

    2013-01-01

    Full Text Available Although oxidative precipitation by potassium permanganate is a widely recognised process for manganese removal, research dealing with highly contaminated acid mine drainage (AMD has yet to be performed. The present study investigated the efficiency of KMnO4 in removing manganese from AMD effluents. Samples of AMD that originated from inactive uranium mine in Brazil were chemically characterised and treated by KMnO4 at pH 3.0, 5.0, and 7.0. Analyses by Raman spectroscopy and geochemical modelling using PHREEQC code were employed to assess solid phases. Results indicated that the manganese was rapidly oxidised by KMnO4 in a process enhanced at higher pH. The greatest removal, that is, 99%, occurred at pH 7.0, when treated waters presented manganese levels as low as 1.0 mg/L, the limit established by the Brazilian legislation. Birnessite (MnO2, hausmannite (Mn3O4, and manganite (MnOOH were detected by Raman spectroscopy. These phases were consistently identified by the geochemical model, which also predicted phases containing iron, uranium, manganese, and aluminium during the correction of the pH as well as bixbyite (Mn2O3, nsutite (MnO2, pyrolusite (MnO2, and fluorite (CaF2 following the KMnO4 addition.

  6. Gold & silver nanoparticles supported on manganese oxide: Synthesis, characterization and catalytic studies for selective oxidation of benzyl alcohol

    OpenAIRE

    Alabbad, Saad; Adil, S.F.; Assal, M.E.; Khan, Mujeeb; Alwarthan, Abdulrahman; Siddiqui, M. Rafiq H.

    2014-01-01

    Nano-gold and silver particles supported on manganese oxide were synthesized by the co-precipitation method. The catalytic properties of these materials were investigated for the oxidation of benzyl alcohol using molecular oxygen as a source of oxygen. The catalyst was calcined at 300, 400 and 500 °C. They were characterized by electron microscopy, powder X-ray diffraction (XRD) and surface area. It was observed that the calcination temperature affects the size of the nanoparticle, which play...

  7. Biodegradation and corrosion behavior of manganese oxidizer Bacillus cereus ACE4 in diesel transporting pipeline

    International Nuclear Information System (INIS)

    Rajasekar, A.; Ganesh Babu, T.; Karutha Pandian, S.; Maruthamuthu, S.; Palaniswamy, N.; Rajendran, A.

    2007-01-01

    The degradation problem of petroleum products arises since hydrocarbon acts as an excellent food source for a wide variety of microorganisms. Microbial activity leads to unacceptable level of turbidity, corrosion of pipeline and souring of stored product. The present study emphasizes the role of Bacillus cereus ACE4 on degradation of diesel and its influence on corrosion of API 5LX steel. A demonstrating bacterial strain ACE4 was isolated from corrosion products and 16S rRNA gene sequence analysis showed that it has more than 99% similarity with B. cereus. The biodegradation and corrosion studies revealed that B. cereus degraded the aliphatic protons and aromatic protons in diesel and is capable of oxidizing ferrous/manganese into oxides. This is the first report that discloses the involvement of manganese oxidizer B. cereus ACE4 on biodegradation of diesel and its influence on corrosion in a tropical country pipeline

  8. Manganese oxides supported on gold nanoparticles: new findings and current controversies for the role of gold.

    Science.gov (United States)

    Najafpour, Mohammad Mahdi; Hosseini, Seyedeh Maedeh; Hołyńska, Małgorzata; Tomo, Tatsuya; Allakhverdiev, Suleyman I

    2015-12-01

    We synthesized manganese oxides supported on gold nanoparticles (diameter oxide is deposited on the gold nanoparticles. The compounds were characterized by scanning electron microscopy, energy-dispersive spectrometry, high-resolution transmission electron microscopy, X-ray diffraction, UV-Vis spectroscopy, Fourier transform infrared spectroscopy, and atomic absorption spectroscopy. In the next step, the water-oxidizing activities of these compounds in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant were studied. The results show that these compounds are good catalysts toward water oxidation with a turnover frequency of 1.0 ± 0.1 (mmol O2/(mol Mn·s)). A comparison with other previously reported Mn oxides and important factors influencing the water-oxidizing activities of Mn oxides is also discussed.

  9. Coupled biotic-abiotic oxidation of organic matter by biogenic MnO_{2}

    Science.gov (United States)

    Gonzalez, Julia; Peña, Jasquelin

    2016-04-01

    Some reactive soil minerals are strongly implicated in stabilising organic matter. However, others can play an active role in the oxidation of organic molecules. In natural systems, layer-type manganese oxide minerals (MnO2) typically occur as biomineral assemblages consisting of mineral particles and microbial biomass. Both the mineral and biological fractions of the assemblage can be powerful oxidants of organic C. The biological compartment relies on a set of enzymes to drive oxidative transformations of reduced C-substrates, whereas MnO2 minerals are strong, less specific abiotic oxidants that are assumed to rely on interfacial interactions between C-substrates and the mineral surface. This project aims to understand the coupling between microbial C mineralization and abiotic C oxidation mediated by MnO2 in bacterial-MnO2 assemblages. Specifically, under conditions of high C turnover, microbial respiration can significantly alter local pH, dissolved oxygen and pool of available reductants, which may modify rates and mechanism of C oxidation by biotic and abiotic components. We first investigated changes in the solution chemistry of Pseudomonas putida suspensions exposed to varying concentrations of glucose, chosen to represent readily bioavailable substrates in soils. Glucose concentrations tested ranged between 0 and 5.5mM and changes in pH, dissolved oxygen and dissolved organic and inorganic carbon were tracked over 48h. We then combined literature review and wet-chemical experiments to compile the pH dependence of rates of organic substrate oxidation by MnO2, including glucose. Our results demonstrate a strong pH dependence for these abiotic reactions. In assemblages of P. putida - MnO2, kinetic limitations for abiotic C oxidation by MnO2 are overcome by changes in biogeochemical conditions that result from bacterial C metabolism. When extrapolated to a soil solution confronted to an input of fresh dissolved organic matter, bacterial C metabolism of the

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

    Science.gov (United States)

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

    2013-04-19

    DypB, a dye-decolorizing peroxidase from the lignolytic soil bacterium Rhodococcus jostii RHA1, catalyzes the peroxide-dependent oxidation of divalent manganese (Mn(2+)), albeit less efficiently than fungal manganese peroxidases. Substitution of Asn246, a distal heme residue, with alanine increased the enzyme's apparent k(cat) and k(cat)/K(m) values for Mn(2+) by 80- and 15-fold, respectively. A 2.2 Å resolution X-ray crystal structure of the N246A variant revealed the Mn(2+) 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 from that of another bacterial Mn(2+)-oxidizing peroxidase. The first coordination sphere was entirely composed of solvent, consistent with the variant's high K(m) for Mn(2+) (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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Migliaccio, Oriana; Castellano, Immacolata [Laboratory of Cellular and Developmental Biology, Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Naples (Italy); Romano, Giovanna [Laboratory of Functional and Evolutionary Ecology, Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Naples (Italy); Palumbo, Anna, E-mail: anna.palumbo@szn.it [Laboratory of Cellular and Developmental Biology, Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Naples (Italy)

    2014-11-15

    Highlights: • NO is produced in sea urchin embryos in response to cadmium and manganese. • Cadmium and manganese affect the expression of specific genes. • NO levels regulate directly or indirectly the expression of some metal-induced genes. • NO is proposed as a sensor of different stress agents in sea urchin embryos. - Abstract: 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.

  12. Investigations on thermochemical energy storage based on manganese-iron oxide in a lab-scale reactor

    Science.gov (United States)

    Wokon, Michael; Bauer, Thomas; Linder, Marc

    2017-06-01

    Thermochemical energy storage based on reversible redox reactions of metal oxides constitutes a promising concept to store thermal energy at high temperatures, which renders those storage materials specifically attractive for the implementation in solar tower plants. Only a few experimental studies on lab-scale storage reactors working with metal oxides have been reported. Therefore, an investigation of granular metal oxides in a packed bed storage reactor is presented with regard to thermal storage characteristics and prevalent limitations influencing thermal charging and discharging. Pure manganese oxide and manganese-iron oxide with a Mn/Fe molar ratio of 2:1 are compared as potential storage materials. The main advantages of the binary oxide are derived from the experimental results. Moreover, heat transfer between solid and gas has been identified to be the main limiting factor for the onward reactions of manganese-iron oxide under the applied experimental conditions.

  13. [Age-related changes in biogenic amine content and oxidative stress profile in the rat hypothalamus in hyperhomocysteinemia].

    Science.gov (United States)

    Milyutina, Yu P; Pustygina, A V; Zaloznyaya, I V; Arutjunyan, A V

    2016-01-01

    The article presents a detailed analysis of correlations between the content of a variety of biogenic amines in the hypothalamic structures responsible for the luteinizing hormone releasing hormone synthesis and secretion (the medial preoptic area and median eminence) and such independent factors as total L-homocysteine plasma level elevation induced by L-methionine loading and aging. Both a nature and a pattern of changes in oxidative stress profile were evaluated. It was shown that ageing, when compared to hyperhomocysteinemia, is a determining factor influencing biogenic amine content in the studied hypothalamic structures. Unlike antioxidant defense system profile, considerable changes in macromolecule oxidative modification were not found, which evidences a balanced activity of pro- and antioxidant systems in the hypothalamus.

  14. Electrochemical synthesis of birnessite-type layered manganese oxides for rechargeable lithium batteries

    Science.gov (United States)

    Nakayama, Masaharu; Kanaya, Taku; Lee, Jong-Won; Popov, Branko N.

    Layered manganese dioxide (MnO 2) films intercalated with Li +, Na + or Mg 2+ ions were synthesized by a one-step electrochemical method. The electrodeposition was potentiostatically performed by applying an anodic potential of 1.0 V vs. Ag/AgCl in an aqueous MnSO 4 solution containing a perchlorate salt of the cation. The electrodeposited oxide films have a birnessite-type layered structure with alkali cations and water molecules between manganese oxide layers. The galvanostatic charge-discharge experiments performed in 1 M LiPF 6-DME/PC solution indicated that the Mg 2+-intercalated MnO 2 electrode exhibits an initial discharge capacity as large as 140 mAh g -1 and it shows a better capacity retention during cycling as compared with the Li +- or Na +-intercalated MnO 2 electrode.

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

    Science.gov (United States)

    Harvey, Judson W.; Fuller, Christopher C.

    1998-01-01

    We determined the role of the hyporheic zone (the subsurface zone where stream water and shallow groundwater mix) in enhancing microbially mediated oxidation of dissolved manganese (to form manganese precipitates) in a drainage basin contaminated by copper mining. The fate of manganese is of overall importance to water quality in Pinal Creek Basin, Arizona, because manganese reactions affect the transport of trace metals. The basin-scale role of the hyporheic zone is difficult to quantify because stream-tracer studies do not always reliably characterize the cumulative effects of the hyporheic zone. This study determined cumulative effects of hyporheic reactions in Pinal Creek basin by characterizing manganese uptake at several spatial scales (stream-reach scale, hyporheic-flow-path scale, and sediment-grain scale). At the stream-reach scale a one-dimensional stream-transport model (including storage zones to represent hyporheic flow paths) was used to determine a reach-averaged time constant for manganese uptake in hyporheic zones, 1/λs, of 1.3 hours, which was somewhat faster but still similar to manganese uptake time constants that were measured directly in centimeter-scale hyporheic flow paths (1/λh= 2.6 hours), and in laboratory batch experiments using streambed sediment (1/λ = 2.7 hours). The modeled depths of subsurface storage zones (ds = 4–17 cm) and modeled residence times of water in storage zones (ts = 3–12 min) were both consistent with direct measurements in hyporheic flow paths (dh = 0–15 cm, th = 1–25 min). There was also good agreement between reach-scale modeling and direct measurements of the percentage removal of dissolved manganese in hyporheic flow paths (fs = 8.9%, andfh = 9.3%rpar;. Manganese uptake experiments in the laboratory using sediment from Pinal Creek demonstrated (through comparison of poisoned and unpoisoned treatments) that the manganese removal process was enhanced by microbially mediated oxidation. The

  16. The effects of fire on biogenic emissions of methane and nitric oxide from wetlands

    Science.gov (United States)

    Levine, Joel S.; Cofer, Wesley R., III; Sebacher, Daniel I.; Rhinehart, Robert P.; Winstead, Edward L.; Sebacher, Shirley; Hinkle, C. Ross; Schmalzer, Paul A.; Koller, Albert M., Jr.

    1990-01-01

    Enhanced emissions of methane (CH4) and nitric oxide (NO) were measured following three controlled burns in a Florida wetlands in 1987 and 1988. Wetlands are the major global source of methane resulting from metabolic activity of methanogenic bacteria. Methanogens require carbon dioxide, acetate, or formate for their growth and the metabolic production of methane. All three water-soluble compounds are produced in large concentrations during biomass burning. Postfire methane emissions exceeded 0.15 g CH 4/sq m per day. Preburn and postburn measurements of soil nutrients indicate significant postburn increases in soil ammonium, from 8.35 to 13.49 parts per million (ppm) in the upper 5 cm of the Juncus marsh and from 8.83 to 23.75 ppm in the upper 5 cm of the Spartina marsh. Soil nitrate concentrations were found to decrease in both marshes after the fire. These measurements indicate that the combustion products of biomass burning exert an important 'fertilizing' effect on the biosphere and on the biogenic production of environmentally significant atmospheric gases.

  17. Synthesis and Electrochemical Analyses of Manganese Oxides for Super-Capacitors.

    Science.gov (United States)

    Kim, Taewoo; Hwang, Hyein; Jang, Jaeyong; Park, Inyeong; Shim, Sang Eun; Baeck, Sung-Hyeon

    2015-11-01

    δ-Phase and α-phase manganese oxides were prepared using a hydrothermal method and their electrochemical properties were characterized. The influence of calcination temperature on the properties of manganese oxides was studied. Crystallinities were studied by X-ray diffraction, and scanning and transmission electron microscopy were utilized to examine morphologies. Average pore sizes and specific surface areas of samples were analyzed using the Barret-Joyner-Halenda and Brunauer-Emmett-Teller methods, respectively. After calcination in the range 300 degrees C to 600 degrees C, changes in morphology and crystallinity were observed. The flower-like shape of as synthesized samples became nanorod-like and the δ-phase changed to the α-phase. These changes may have been due to the removal of water during calcination. Furthermore, a transition stage in which the two phases coexisted was observed. Synthesized manganese oxides were mixed with carbon by sonification, to increase electric conductivity and to induce a synergistic effect between pseudo-capacitor and electric double layer capacitor (EDLC). Specific capacitances and rate durability of each composite were investigated by cyclic voltammetry in 1 M Na2SO4 electrolyte at different scan rates. MnO2 calcined at 400 degrees C exhibited the highest capacitance, probably due to its high surface area and more porous structure.

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

    Directory of Open Access Journals (Sweden)

    Andy Banh

    Full Text Available 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.

  19. Nitrate radicals and biogenic volatile organic compounds: oxidation, mechanisms, and organic aerosol

    Energy Technology Data Exchange (ETDEWEB)

    Ng, Nga Lee; Brown, Steven S.; Archibald, Alexander T.; Atlas, Elliot; Cohen, Ronald C.; Crowley, John N.; Day, Douglas A.; Donahue, Neil M.; Fry, Juliane L.; Fuchs, Hendrik; Griffin, Robert J.; Guzman, Marcelo I.; Herrmann, Hartmut; Hodzic, Alma; Iinuma, Yoshiteru; Jimenez, José L.; Kiendler-Scharr, Astrid; Lee, Ben H.; Luecken, Deborah J.; Mao, Jingqiu; McLaren, Robert; Mutzel, Anke; Osthoff, Hans D.; Ouyang, Bin; Picquet-Varrault, Benedicte; Platt, Ulrich; Pye, Havala O. T.; Rudich, Yinon; Schwantes, Rebecca H.; Shiraiwa, Manabu; Stutz, Jochen; Thornton, Joel A.; Tilgner, Andreas; Williams, Brent J.; Zaveri, Rahul A.

    2017-01-01

    Oxidation of biogenic volatile organic compounds (BVOC) by the nitrate radical (NO3) represents one of the important interactions between anthropogenic emissions related to combustion and natural emissions from the biosphere. This interaction has been recognized for more than 3 decades, during which time a large body of research has emerged from laboratory, field, and modeling studies. NO3-BVOC reactions influence air quality, climate and visibility through regional and global budgets for reactive nitrogen (particularly organic nitrates), ozone, and organic aerosol. Despite its long history of research and the significance of this topic in atmospheric chemistry, a number of important uncertainties remain. These include an incomplete understanding of the rates, mechanisms, and organic aerosol yields for NO3-BVOC reactions, lack of constraints on the role of heterogeneous oxidative processes associated with the NO3 radical, the difficulty of characterizing the spatial distributions of BVOC and NO3 within the poorly mixed nocturnal atmosphere, and the challenge of constructing appropriate boundary layer schemes and non-photochemical mechanisms for use in state-of-the-art chemical transport and chemistry–climate models.

    This review is the result of a workshop of the same title held at the Georgia Institute of Technology in June 2015. The first half of the review summarizes the current literature on NO3-BVOC chemistry, with a particular focus on recent advances in instrumentation and models, and in organic nitrate and secondary organic aerosol (SOA) formation chemistry. Building on this current understanding, the second half of the review outlines impacts of NO3-BVOC chemistry on air quality and climate, and suggests critical research needs to better constrain this interaction to improve the predictive capabilities of atmospheric models.

  20. Bio-inspired iron and manganese complexes derived from mixed N,O ligands for the oxidation of olefins

    NARCIS (Netherlands)

    Moelands, M.A.H.

    2014-01-01

    This Thesis describes the synthesis and structural analysis of bio-inspired iron and manganese complexes used for the catalytic oxidation of olefin substrates. The development of catalytic systems for oxidation chemistry that are based on first row transition metals and that apply a green oxidant

  1. Simultaneous stripping recovery of ammonia-nitrogen and precipitation of manganese from electrolytic manganese residue by air under calcium oxide assist.

    Science.gov (United States)

    Chen, Hongliang; Liu, Renlong; Shu, Jiancheng; Li, Wensheng

    2015-01-01

    Leaching tests of electrolytic manganese residue (EMR) indicated that high contents of soluble manganese and ammonia-nitrogen posed a high environmental risk. This work reports the results of simultaneous stripping recovery of ammonia-nitrogen and precipitation of manganese by air under calcium oxide assist. The ammonia-nitrogen stripping rate increased with the dosage of CaO, the air flow rate and the temperature of EMR slurry. Stripped ammonia-nitrogen was absorbed by a solution of sulfuric acid and formed soluble (NH4)2SO4 and (NH4)3H(SO4)3. The major parameters that effected soluble manganese precipitation were the dosage of added CaO and the slurry temperature. Considering these two aspects, the efficient operation conditions should be conducted with 8 wt.% added CaO, 60°C, 800 mL min(-1) air flow rate and 60-min reaction time. Under these conditions 99.99% of the soluble manganese was precipitated as Mn3O4, which was confirmed by XRD and SEM-EDS analyses. In addition, the stripping rate of ammonia-nitrogen was 99.73%. Leaching tests showed the leached toxic substances concentrations of the treated EMR met the integrated wastewater discharge standard of China (GB8978-1996).

  2. Effects of Cobalt on Manganese Oxidation by Pseudomonas putida MnB1

    Science.gov (United States)

    Pena, J.; Bargar, J.; Sposito, G.

    2005-12-01

    The oxidation of Mn(II) in the environment is thought to occur predominantly through biologically mediated pathways. During the stationary phase of growth, the well-characterized freshwater and soil bacterium Pseudomonas putida MnB1 oxidizes soluble Mn(II) to a poorly crystalline layer type Mn(IV) oxide. These Mn oxide particles (2 - 5 nm thickness) are deposited in a matrix of extracellular polymeric substances (EPS) surrounding the cell, creating a multi-component system distinct from commonly studied synthetic Mn oxides. Accurate characterization of the reactivity of these biomineral assemblages is essential to understanding trace metal biogeochemistry in natural waters and sediments. Moreover, these biogenic oxides may potentially be used for the remediation of surface and ground waters impacted by mining, industrial pollution, and other anthropogenic activities. In this study, we consider the interactions between Co, P. putida MnB1, and its biogenic Mn oxide. Cobalt is a redox-active transition metal which exists in the environment as Co(II) and Co(III). While Co is not generally found in the environment at toxic concentrations, it may be released as a byproduct of mining activities (e.g. levels of up to 20 μM are found in Pinal Creek, AZ, a stream affected by copper mining). In addition, the radionuclide 60Co, formed by neutron activation in nuclear reactors, is of concern at Department of Energy sites, such as that at Hanford, and has several industrial applications, including radiotherapy. We address the following questions: Do high levels of Co inhibit enzymatic processes such as Mn(II) oxidation? Can the multicopper oxidase enzyme involved in Mn(II) oxidation facilitate Co(II) oxidation? Lastly, does the organic matter surrounding the oxides affect Co or Mn oxide reactivity? These issues were approached via wet chemical analysis, synchrotron radiation X-ray diffraction (SR-XRD), and extended X-ray absorption fine structure (EXAFS) spectroscopy. In the

  3. Characterization of manganese oxide precipitates from Appalachian coal mine drainage treatment systems

    International Nuclear Information System (INIS)

    Tan Hui; Zhang Gengxin; Heaney, Peter J.; Webb, Samuel M.; Burgos, William D.

    2010-01-01

    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 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 deg. 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 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 MnO x precipitates from all sites was coarse and 'sponge-like' composed of nm-sized lathes and thin sheets. Based on scanning electron microscopy (SEM), MnO 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 MnO x mineral assemblages in CMD treatment systems.

  4. Manganese-oxidizing photosynthesis before the rise of cyanobacteria

    Science.gov (United States)

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

    2012-12-01

    The evolution of oxygenic photosynthesis was a singularity that fundamentally transformed our planet's core biogeochemical cycles and changed the redox structure of Earth's surface, crust, and mantle. To date, understanding the evolution of this molecular machinery has largely been derived from comparative biology. Several biochemical innovations enabled water-splitting, including a central photosynthetic pigment with a higher redox potential and coupled photosystems. However the critical photochemical invention was the water oxidizing complex (WOC) of photosystem II, a cubane cluster of four redox-active Mn atoms and a Ca atom bound by oxo bridges, that couple the single electron photochemistry of the photosystem to the four-electron oxidation of water to O2. Transitional forms of the WOC have been postulated, including an Mn-containing catalase-like peptide using an H2O2 donor, or uptake and integration of environmental Mn-oxides. One attractive hypothesis from the perspective of modern photo-assembly of the WOC posits an initial Mn(II)-oxidizing photosystem as a precursor to the WOC (Zubay, 1996; Allen and Martin, 2007). To test these hypotheses, we studied the behavior of the ancient Mn cycle captured by 2415 ± 6 Ma scientific drill cores retrieved by the Agouron Drilling Project through the Koegas Subgroup in Griqualand West, South Africa. This succession contains substantial Mn-enrichments (up to 17 wt.% in bulk). To better understand the petrogenesis and textural context of these deposits, we employed a novel X-ray absorption spectroscopy microprobe to make redox maps of ultra-thin sample sections at a 2μm scale. Coupled to light and electron microscopy and C isotopic measurements, we observe that all of the Mn is present as Mn(II), contained within carbonate minerals produced from early diagenetic reduction of Mn-oxide phases with organic matter. To assay the environmental oxidant responsible for the production of the Mn-oxides we examined two independent

  5. Catalytic oxidation of cyanides in an aqueous phase over individual and manganese-modified cobalt oxide systems

    International Nuclear Information System (INIS)

    Christoskova, St.; Stoyanova, M.

    2009-01-01

    The possibility for purification of wastewaters containing free cyanides by applying of a new method based on cyanides catalytic oxidation with air to CO 2 and N 2 at low temperature and atmospheric pressure was investigated. On this purpose, individual and modified with manganese Co-oxide systems as active phase of environmental catalysts were synthesized. The applied method of synthesis favours the preparation of oxide catalytic systems with high active oxygen content (total-O* and surface-O* s ) possessing high mobility, and the metal ions being in a high oxidation state and in an octahedral coordination-factors determining high activity in reactions of complete oxidation. The catalysts employed were characterized by powder X-ray diffraction, Infrared spectroscopy, and chemical analysis. The effect of pH of the medium and catalyst loading on the effectiveness of the cyanide oxidation process, expressed by the degree of conversion (α, %), by the rate constant (k, min -1 ), and COD was studied. The results obtained reveal that using catalysts investigated a high cyanide removal efficiency could be achieved even in strong alkaline medium. The higher activity of the manganese promoted catalytic sample could be explained on the basis of higher total active oxygen content and its higher mobility both depending on the conditions, under which the synthesis of catalyst is being carried out.

  6. Antifouling Manganese Oxide Nanoparticles: Synthesis, Characterization, and Applications for Enhanced MR Imaging of Tumors.

    Science.gov (United States)

    Wang, Peng; Yang, Jia; Zhou, Benqing; Hu, Yong; Xing, Lingxi; Xu, Fanli; Shen, Mingwu; Zhang, Guixiang; Shi, Xiangyang

    2017-01-11

    Antifouling manganese oxide (Mn 3 O 4 ) nanoparticles (NPs) were synthesized by solvothermal decomposition of tris(2,4-pentanedionato) manganese(III) in the presence of trisodium citrate, followed by surface modification with polyethylene glycol and l-cysteine. The as-prepared nanoparticles have a uniform size distribution, good colloidal stability and good cytocompatibility. The modification of l-cysteine rendered the particles with much longer blood circulation time (half-decay time of 28.4 h) than those without l-cysteine modification (18.5 h), and decreased macrophage cellular uptake. Thanks to desirable antifouling property and relatively high r 1 relaxivity (3.66 mM -1 s -1 ), the l-cysteine-modified Mn 3 O 4 NPs can be used for enhanced tumor magnetic resonance imaging applications.

  7. Recent advancements in the cobalt oxides, manganese oxides and their composite as an electrode material for supercapacitor: a review

    Science.gov (United States)

    Uke, Santosh J.; Akhare, Vijay P.; Bambole, Devidas R.; Bodade, Anjali B.; Chaudhari, Gajanan N.

    2017-08-01

    In this smart edge, there is an intense demand of portable electronic devices such as mobile phones, laptops, smart watches etc. That demands the use of such components which has light weight, flexible, cheap and environmental friendly. So that needs an evolution in technology. Supercapacitors are energy storage devices emerging as one of the promising energy storage devices in the future energy technology. Electrode material is the important part of supercapacitor. There is much new advancement in types of electrode materials as for supercapacitor. In this review, we focused on the recent advancements in the cobalt oxides, manganese oxides and their composites as an electrodes material for supercapacitor.

  8. Metalloradical complexes of manganese and chromium featuring an oxidatively rearranged ligand.

    Science.gov (United States)

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

    2008-12-01

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

  9. Determination of the point-of-zero, charge of manganese oxides with different methods including an improved salt titration method

    NARCIS (Netherlands)

    Tan, W.F.; Lu, S.J.; Liu, F.; Feng, X.H.; He, J.Z.; Koopal, L.K.

    2008-01-01

    Manganese (Mn) oxides are important components in soils and sediments. Points-of-zero charge (PZC) of three synthetic Mn oxides (birnessite, cryptomelane, and todorokite) were determined by using three classical techniques (potentiometric titration or PT, rapid PT or R-PT, and salt titration or ST)

  10. Development and Applications of Thallium isotopes: a new proxy tracking the extent of manganese oxide burial

    Science.gov (United States)

    Owens, J. D.; Nielsen, S.; Ostrander, C.; Peterson, L. C.; Anbar, A. D.

    2015-12-01

    Thallium (Tl) isotopes are a new and potential powerful paleoredox proxy with the possibility to track bottom water oxygen conditions based on the burial flux of manganese oxides. Thallium has a residence time of ~20 thousand years, which is long enough to render modern oxic seawater conservative with respect to concentration and isotopes. The isotopic signature of Tl in the global ocean is driven mainly by two outputs (1) adsorption onto manganese oxides and (2) low temperature oceanic crust alteration. Importantly, the isotopic inputs of Tl are all nearly the same value; thus, the isotopic composition and flux of the outputs almost exclusively set the seawater signature. For relatively short term redox events it is reasonable to assume that the dominant isotope fractionation process is associated with manganese oxide precipitation because low temperature alteration is controlled by long-term average ocean crust production rates. We present a broad range of modern samples that span several open ocean profiles combined with water column and sediment profiles from the permanently anoxic basins of the Black Sea and Cariaco Basins. The open ocean shows no variation in depth profiles that encompass most of the major water masses in the Atlantic and Southern Oceans. The anoxic basins, however, reveal Tl isotope signatures closer to their inputs, which is likely due to basinal restriction. The authigenic fraction of organic-rich sediments from the Black Sea and Cariaco Basin capture the Tl isotope value of the overlying water column, which shows that Tl isotopes could be applied as a faithful deep time redox proxy. For the first time, we will present new data showing that Tl isotopes is tracking bottom water ocean oxygenation. We are applying this isotope system to ancient samples, testing the spatial and temporal variability of ocean oxygenation coinciding with major biogeochemical events.

  11. Biogenic oxidized organic functional groups in aerosol particles from a mountain forest site and their similarities to laboratory chamber products

    Science.gov (United States)

    Schwartz, R. E.; Russell, L. M.; Sjostedt, S. J.; Vlasenko, A.; Slowik, J. G.; Abbatt, J. P. D.; MacDonald, A. M.; Li, S. M.; Liggio, J.; Toom-Sauntry, D.; Leaitch, W. R.

    2010-06-01

    Submicron particles collected at Whistler, British Columbia, at 1020 m a.s.l. during May and June 2008 on Teflon filters were analyzed by Fourier transform infrared (FTIR) and X-ray fluorescence (XRF) techniques for organic functional groups (OFG) and elemental composition. Organic mass (OM) concentrations ranged from less than 0.5 to 3.1 μg m-3, with a project mean and standard deviation of 1.3±1.0 μg m-3 and 0.21±0.16 μg m-3 for OM and sulfate, respectively. On average, organic hydroxyl, alkane, and carboxylic acid groups represented 34%, 33%, and 23% of OM, respectively. Ketone, amine and organosulfate groups constituted 6%, 5%, and volatile organic compounds (VOC), including isoprene and monoterpenes from biogenic VOC (BVOC) emissions and their oxidation products (methyl-vinylketone / methacrolein, MVK/MACR), were made using co-located proton transfer reaction mass spectrometry (PTR-MS). We present chemically-specific evidence of OFG associated with BVOC emissions. Positive matrix factorization (PMF) analysis attributed 65% of the campaign OM to biogenic sources, based on the correlations of one factor to monoterpenes and MVK/MACR. The remaining fraction was attributed to anthropogenic sources based on a correlation to sulfate. The functional group composition of the biogenic factor (consisting of 32% alkane, 25% carboxylic acid, 21% organic hydroxyl, 16% ketone, and 6% amine groups) was similar to that of secondary organic aerosol (SOA) reported from the oxidation of BVOCs in laboratory chamber studies, providing evidence that the magnitude and chemical composition of biogenic SOA simulated in the laboratory is similar to that found in actual atmospheric conditions. The biogenic factor OM is also correlated to dust elements, indicating that dust may act as a non-acidic SOA sink. This role is supported by the organic functional group composition and morphology of single particles, which were analyzed by scanning transmission X-ray microscopy near edge X

  12. Biogenic oxidized organic functional groups in aerosol particles from a mountain forest site and their similarities to laboratory chamber products

    Directory of Open Access Journals (Sweden)

    R. E. Schwartz

    2010-06-01

    Full Text Available Submicron particles collected at Whistler, British Columbia, at 1020 m a.s.l. during May and June 2008 on Teflon filters were analyzed by Fourier transform infrared (FTIR and X-ray fluorescence (XRF techniques for organic functional groups (OFG and elemental composition. Organic mass (OM concentrations ranged from less than 0.5 to 3.1 μg m−3, with a project mean and standard deviation of 1.3±1.0 μg m−3 and 0.21±0.16 μg m−3 for OM and sulfate, respectively. On average, organic hydroxyl, alkane, and carboxylic acid groups represented 34%, 33%, and 23% of OM, respectively. Ketone, amine and organosulfate groups constituted 6%, 5%, and <1% of the average organic aerosol composition, respectively. Measurements of volatile organic compounds (VOC, including isoprene and monoterpenes from biogenic VOC (BVOC emissions and their oxidation products (methyl-vinylketone / methacrolein, MVK/MACR, were made using co-located proton transfer reaction mass spectrometry (PTR-MS. We present chemically-specific evidence of OFG associated with BVOC emissions. Positive matrix factorization (PMF analysis attributed 65% of the campaign OM to biogenic sources, based on the correlations of one factor to monoterpenes and MVK/MACR. The remaining fraction was attributed to anthropogenic sources based on a correlation to sulfate. The functional group composition of the biogenic factor (consisting of 32% alkane, 25% carboxylic acid, 21% organic hydroxyl, 16% ketone, and 6% amine groups was similar to that of secondary organic aerosol (SOA reported from the oxidation of BVOCs in laboratory chamber studies, providing evidence that the magnitude and chemical composition of biogenic SOA simulated in the laboratory is similar to that found in actual atmospheric conditions. The biogenic factor OM is also correlated to dust elements, indicating that dust may act as a non-acidic SOA sink. This role is supported by the organic functional

  13. Enhancement of arsenite removal using manganese oxide coupled with iron (III) trimesic

    Science.gov (United States)

    Phanthasri, Jakkapop; Khamdahsag, Pummarin; Jutaporn, Panitan; Sorachoti, Kwannapat; Wantala, Kitirote; Tanboonchuy, Visanu

    2018-01-01

    A simultaneous removal of As(III) was investigated on a mixture of manganese oxide based octahedral molecular sieves (K-OMS2) and iron-benzenetricarboxylate (Fe-BTC). As(III) removal was stimulated by an oxidation cooperated with adsorption process. K-OMS2 and Fe-BTC were separately synthesized and characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). K-OMS2 showed characters of pure cryptomelane phase, nanorod structure, and a mixed-valent manganese framework with the coexistence of Mn(IV) and Mn(III). As(III) was successfully oxidized to As(V) by K-OMS2 in a temperature range of 303-333 K. An intermediate adsorption of As(V) was carried out with Fe-BTC in the same batch. A maximum adsorption capacity, described by Langmuir isotherm model, was observed at 76.34 mg/g. With an As(III) initial concentration of 5 mg/L, when K-OMS2 and Fe-BTC were simultaneously introduced into the solution, the As(III) removal process was completed within 60 min. Thus, it shortened the process time compared to the case where K-OMS2 was added first, followed by the addition of Fe-BTC.

  14. High-performance symmetric electrochemical capacitor based on graphene foam and nanostructured manganese oxide

    Directory of Open Access Journals (Sweden)

    Abdulhakeem Bello

    2013-08-01

    Full Text Available We have fabricated a symmetric electrochemical capacitor with high energy and power densities based on a composite of graphene foam (GF with ∼80 wt% of manganese oxide (MnO2 deposited by hydrothermal synthesis. Raman spectroscopy and X-ray diffraction measurements showed the presence of nanocrystalline MnO2 on the GF, while scanning and transmission electron microscopies showed needle-like manganese oxide coated and anchored onto the surface of graphene. Electrochemical measurements of the composite electrode gave a specific capacitance of 240 Fg−1 at a current density of 0.1 Ag−1 for symmetric supercapacitors using a two-electrode configuration. A maximum energy density of 8.3 Whkg−1 was obtained, with power density of 20 kWkg−1 and no capacitance loss after 1000 cycles. GF is an excellent support for pseudo-capacitive oxide materials such as MnO2, and the composite electrode provided a high energy density due to a combination of double-layer and redox capacitance mechanisms.

  15. Pretreatment of algae-laden and manganese-containing waters by oxidation-assisted coagulation: Effects of oxidation on algal cell viability and manganese precipitation.

    Science.gov (United States)

    Lin, Jr-Lin; Hua, Lap-Cuong; Wu, Yuting; Huang, Chihpin

    2016-02-01

    Preoxidation is manipulated to improve performance of algae and soluble manganese (Mn) removal by coagulation-sedimentation for water treatment plants (WTPs) when large amount of soluble Mn presents in algae-laden waters. This study aimed to investigate the effects of preoxidation on the performance of coagulation-sedimentation for the simultaneous removal of algae and soluble Mn, including ionic and complexed Mn. NaOCl, ClO2, and KMnO4 were used to pretreat such algae-laden and Mn containing waters. The variation of algal cell viability, residual cell counts, and concentrations of Mn species prior to and after coagulation-sedimentation step were investigated. Results show that NaOCl dosing was effective in reducing the viability of algae, but precipitated little Mn. ClO2 dosing had a strongest ability to lower algae viability and oxidize ionic and complexed soluble Mn, where KMnO4 dosing oxidized ionic and complexed Mn instead of reducing the viability of cells. Preoxidation by NaOCl only improved the algae removal by sedimentation, whereas most of soluble Mn still remained. On the other hand, ClO2 preoxidation substantially improved the performance of coagulation-sedimentation for simultaneous removal of algae and soluble Mn. Furthermore, KMnO4 preoxidation did improve the removal of algae by sedimentation, but left significant residual Mn in the supernatant. Images from FlowCAM showed changes in aspect ratio (AR) and transparency of algae-Mn flocs during oxidation-assisted coagulation, and indicates that an effective oxidation can improve the removal of most compact algae-Mn flocs by sedimentation. It suggests that an effective preoxidation for reducing algal cell viability and the concentration of soluble Mn is a crucial step for upgrading the performance of coagulation-sedimentation. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Biogenic copper oxide nanoparticles synthesis using Tabernaemontana divaricate leaf extract and its antibacterial activity against urinary tract pathogen.

    Science.gov (United States)

    Sivaraj, Rajeshwari; Rahman, Pattanathu K S M; Rajiv, P; Salam, Hasna Abdul; Venckatesh, R

    2014-12-10

    This investigation explains the biosynthesis and characterization of copper oxide nanoparticles from an Indian medicinal plant by an eco-friendly method. The main objective of this study is to synthesize copper oxide nanoparticles from Tabernaemontana divaricate leaves through a green chemistry approach. Highly stable, spherical copper oxide nanoparticles were synthesized by using 50% concentration of Tabernaemontana leaf extract. Formation of copper oxide nanoparticles have been characterized by UV-Vis absorption spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) and transmission electron microscopy (TEM) analysis. All the analyses revealed that copper oxide nanoparticles were 48±4nm in size. Functional groups and chemical composition of copper oxide were also confirmed. Antimicrobial activity of biogenic copper oxide nanoparticles were investigated and maximum zone of inhibition was found in 50μg/ml copper oxide nanoparticles against urinary tract pathogen (Escherichia coli). Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Subchronic, Low-Level Intraperitoneal Injections of Manganese (IV) Oxide and Manganese (II) Chloride Affect Rat Brain Neurochemistry

    DEFF Research Database (Denmark)

    Nielsen, Brian S.; Larsen, Erik Huusfeldt; Ladefoged, Ole

    2017-01-01

    Manganese (Mn) is neurotoxic and can induce manganism, a Parkinson-like disease categorized as being a serious central nervous system irreversible neurodegenerative disease. An increased risk of developing symptoms of Parkinson disease has been linked to work-related exposure, for example, for wo...

  18. Manganese oxide nanowires wrapped with nitrogen doped carbon layers for high performance supercapacitors.

    Science.gov (United States)

    Li, Ying; Mei, Yuan; Zhang, Lin-Qun; Wang, Jian-Hai; Liu, An-Ran; Zhang, Yuan-Jian; Liu, Song-Qin

    2015-10-01

    In this study, manganese oxide nanowires wrapped by nitrogen-doped carbon layers (MnO(x)@NCs) were prepared by carbonization of poly(o-phenylenediamine) layer coated onto MnO2 nanowires for high performance supercapacitors. The component and structure of the MnO(x)@NCs were controlled through carbonization procedure under different temperatures. Results demonstrated that this composite combined the high conductivity and high specific surface area of nitrogen-doped carbon layers with the high pseudo-capacitance of manganese oxide nanowires. The as-prepared MnO(x)@NCs exhibited superior capacitive properties in 1 M Na2SO4 aqueous solution, such as high conductivity (4.167×10(-3) S cm(-1)), high specific capacitance (269 F g(-1) at 10 mV s(-1)) and long cycle life (134 F g(-1) after 1200 cycles at a scan rate of 50 mV s(-1)). It is reckoned that the present novel hybrid nanowires can serve as a promising electrode material for supercapacitors and other electrochemical devices. Copyright © 2015 Elsevier Inc. All rights reserved.

  19. Synthesis of Magnetic Carbon Supported Manganese Catalysts for Phenol Oxidation by Activation of Peroxymonosulfate

    Directory of Open Access Journals (Sweden)

    Yuxian Wang

    2016-12-01

    Full Text Available Magnetic core/shell nanospheres (MCS were synthesized by a novel and facile one-step hydrothermal method. Supported manganese oxide nanoparticles (Fe3O4/C/Mn were obtained from various methods (including redox, hydrothermal and impregnation using MCS as the support material and potassium permanganate as the precursor of manganese oxide. The Mn/MCS catalysts were characterized by a variety of characterization techniques and the catalytic performances of Fe3O4/C/Mn nanoparticles were tested in activation of peroxymonosulfate to produce reactive radicals for phenol degradation in aqueous solutions. It was found that Fe3O4/C/Mn catalysts can be well dispersed and easily separated from the aqueous solutions by an external magnetic field. Kinetic analysis showed that phenol degradation on Fe3O4/C/Mn catalysts follows the first order kinetics. The peroxymonosulfate activation mechanism by Fe3O4/C/Mn catalysts for phenol degradation was then discussed.

  20. Oxygen reduction reaction catalysts of manganese oxide decorated by silver nanoparticles for aluminum-air batteries

    International Nuclear Information System (INIS)

    Sun, Shanshan; Miao, He; Xue, Yejian; Wang, Qin; Li, Shihua; Liu, Zhaoping

    2016-01-01

    In this paper, the hybrid catalysts of manganese oxide decorated by silver nanoparticles (Ag-MnO x ) are fully investigated and show the excellent oxygen reduction reaction (ORR) activity. The Ag-MnO 2 is synthesized by a facile strategy of the electroless plating of silver on the manganese oxide. The catalysts are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Then, the ORR activities of the catalysts are systematically investigated by the rotating disk electrode (RDE) and aluminum-air battery technologies. The Ag nanoparticles with the diameters at about 10 nm are anchored on the surface of α-MnO 2 and a strong interaction between Ag and MnO 2 components in the hybrid catalyst are confirmed. The electrochemical tests show that the activity and stability of the 50%Ag-MnO 2 composite catalyst (the mass ratio of Ag/MnO 2 is 1:1) toward ORR are greatly enhanced comparing with single Ag or MnO 2 catalyst. Moreover, the peak power density of the aluminum-air battery with 50%Ag-MnO 2 can reach 204 mW cm −2 .

  1. Biogenic uraninite precipitation and its reoxidation by iron(III) (hydr)oxides: A reaction modeling approach

    Science.gov (United States)

    Spycher, Nicolas F.; Issarangkun, Montarat; Stewart, Brandy D.; Sevinç Şengör, S.; Belding, Eileen; Ginn, Tim R.; Peyton, Brent M.; Sani, Rajesh K.

    2011-08-01

    One option for immobilizing uranium present in subsurface contaminated groundwater is in situ bioremediation, whereby dissimilatory metal-reducing bacteria and/or sulfate-reducing bacteria are stimulated to catalyze the reduction of soluble U(VI) and precipitate it as uraninite (UO 2). This is typically accomplished by amending groundwater with an organic electron donor. It has been shown, however, that once the electron donor is entirely consumed, Fe(III) (hydr)oxides can reoxidize biogenically produced UO 2, thus potentially impeding cleanup efforts. On the basis of published experiments showing that such reoxidation takes place even under highly reducing conditions (e.g., sulfate-reducing conditions), thermodynamic and kinetic constraints affecting this reoxidation are examined using multicomponent biogeochemical simulations, with particular focus on the role of sulfide and Fe(II) in solution. The solubility of UO 2 and Fe(III) (hydr)oxides are presented, and the effect of nanoscale particle size on stability is discussed. Thermodynamically, sulfide is preferentially oxidized by Fe(III) (hydr)oxides, compared to biogenic UO 2, and for this reason the relative rates of sulfide and UO 2 oxidation play a key role on whether or not UO 2 reoxidizes. The amount of Fe(II) in solution is another important factor, with the precipitation of Fe(II) minerals lowering the Fe +2 activity in solution and increasing the potential for both sulfide and UO 2 reoxidation. The greater (and unintuitive) UO 2 reoxidation by hematite compared to ferrihydrite previously reported in some experiments can be explained by the exhaustion of this mineral from reaction with sulfide. Simulations also confirm previous studies suggesting that carbonate produced by the degradation of organic electron donors used for bioreduction may significantly increase the potential for UO 2 reoxidation through formation of uranyl carbonate aqueous complexes.

  2. Oxidation of triclosan by permanganate (Mn(VII)): importance of ligands and in situ formed manganese oxides.

    Science.gov (United States)

    Jiang, Jin; Pang, Su-Yan; Ma, Jun

    2009-11-01

    Experiments were conducted to examine permanganate (Mn(VII); KMnO(4)) oxidation of the widely used biocide triclosan (one phenolic derivative) in aqueous solution at pH values of 5-9. Under slightly acidic conditions, the reactions displayed autocatalysis, suggesting the catalytic role of in situ formed MnO(2). This was further supported by the promoting effects of the addition of preformed MnO(2) colloids on Mn(VII) oxidations of triclosan and two other selected phenolics (i.e., phenol and 2,4-dichlorophenol), as well as p-nitrophenol which otherwise showed negligible reactivity toward Mn(VII) and MnO(2) colloids, respectively. Surprisingly, phosphate buffer significantly enhanced Mn(VII) oxidation of triclosan, as well as phenol and 2,4-dichlorophenol over a wide pH range. Further, several other selected ligands (i.e., pyrophosphate, EDTA, and humic acid) also exerted oxidation enhancement, supporting a scenario where highly active aqueous manganese intermediates (Mn(INT)(aq)) formed in situ upon Mn(VII) reduction might be stabilized to a certain extent in the presence of ligands and subsequently involved in further oxidation of target phenolics, whereas without stabilizing agents Mn(INT)(aq) autodecomposes or disproportionates spontaneously. The effectiveness of Mn(VII) for the oxidative removal of triclosan in natural water and wastewater was confirmed. Their background matrices were also found to accelerate Mn(VII) oxidation of phenolics.

  3. Scalable Synthesis of Efficient Water Oxidation Catalysts: Insights into the Activity of Flame-Made Manganese Oxide Nanocrystals.

    Science.gov (United States)

    Liu, Guanyu; Hall, Jeremy; Nasiri, Noushin; Gengenbach, Thomas; Spiccia, Leone; Cheah, Mun Hon; Tricoli, Antonio

    2015-12-21

    Chemical energy storage by water splitting is a promising solution for the utilization of renewable energy in numerous currently impracticable needs, such as transportation and high temperature processing. Here, the synthesis of efficient ultra-fine Mn3O4 water oxidation catalysts with tunable specific surface area is demonstrated by a scalable one-step flame-synthesis process. The water oxidation performance of these flame-made structures is compared with pure Mn2O3 and Mn5O8, obtained by post-calcination of as-prepared Mn3O4 (115 m(2)  g(-1)), and commercial iso-structural polymorphs, probing the effect of the manganese oxidation state and synthetic route. The structural properties of the manganese oxide nanoparticles were investigated by XRD, FTIR, high-resolution TEM, and XPS. It is found that these flame-made nanostructures have substantially higher activity, reaching up to 350 % higher surface-specific turnover frequency (0.07 μmolO2  m(-2)  s(-1)) than commercial nanocrystals (0.02 μmolO2  m(-2)  s(-1)), and production of up to 0.33 mmolO2  molMn (-1)  s(-1). Electrochemical characterization confirmed the high water oxidation activity of these catalysts with an initial current density of 10 mA cm(-2) achieved with overpotentials between 0.35 and 0.50 V in 1 m NaOH electrolyte. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Secretome-based Manganese(II) Oxidation by Filamentous Ascomycete Fungi

    Science.gov (United States)

    Zeiner, C. A.; Purvine, S.; Zink, E.; Paša-Tolić, L.; Chaput, D.; Wu, S.; Santelli, C. M.; Hansel, C. M.

    2017-12-01

    Manganese (Mn) oxides are among the strongest oxidants in the environment, and Mn(II) oxidation to Mn(III/IV) (hydr)oxides includes both abiotic and microbially-mediated processes. While white-rot Basidiomycete fungi oxidize Mn(II) using laccases and Mn peroxidases in association with lignocellulose degradation, the mechanisms by which filamentous Ascomycete fungi oxidize Mn(II) and a physiological role for Mn(II) oxidation in these organisms remain poorly understood. Through a combination of chemical and in-gel assays, bulk mass spectrometry, and iTRAQ proteomics, we demonstrate enzymatic Mn(II) oxidation in the secretomes of three phylogenetically diverse Ascomycetes that were isolated from Mn-laden sediments. Candidate Mn(II)-oxidizing enzymes were species-specific and included bilirubin oxidase and tyrosinase in Stagonospora sp. SRC1lsM3a, GMC oxidoreductase in Paraconiothyrium sporulosum AP3s5-JAC2a, and FAD-binding oxidoreductases in Pyrenochaeta sp. DS3sAY3a. These findings were supported by full proteomic characterization of the secretomes, which revealed a lack of Mn, lignin, and versatile peroxidases in these Ascomycetes but a substantially higher proportion of LMCOs and GMC oxidoreductases compared to wood-rot Basidiomycetes. We also identified the potential for indirect enzymatic Mn(II) oxidation by hydroxyl radical, as the secretomes were rich in diverse lignocellulose-degrading enzymes that could participate in Fenton chemistry. A link between Mn(II) oxidation and carbon oxidation analogous to white-rot Basidiomycetes remains unknown in these Ascomycetes. Interestingly, growth rates on rich medium were unaffected by the presence of Mn(II), and the production of Mn(II)-oxidizing proteins in the secretome was constitutive and not inducible by Mn(II). Thus, no physiological benefit of Mn(II) oxidation in these Ascomycetes has yet been identified, and Mn(II) oxidation appears to be a side reaction. Future work will explore the lignin-degrading capacity of

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

    Science.gov (United States)

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

    2005-12-01

    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 mnx

  6. Manganese-oxide minerals in fractures of the Crater Flat Tuff in drill core USW G-4, Yucca Mountain, Nevada

    International Nuclear Information System (INIS)

    Carlos, B.A.; Bish, D.L.; Chipera, S.J.

    1990-07-01

    The Crater Flat Tuff is almost entirely below the water table in drill hole USW G-4 at Yucca Mountain, Nevada. Manganese-oxide minerals from the Crater Flat Tuff in USW G-4 were studied using optical, scanning electron microscopic, electron microprobe, and x-ray powder diffraction methods to determine their distribution, mineralogy, and chemistry. Manganese-oxide minerals coat fractures in all three members of the Crater Flat Tuff (Prow Pass, Bullfrog, and Tram), but they are most abundant in fractures in the densely welded devitrified intervals of these members. The coatings are mostly of the cryptomelane/hollandite mineral group, but the chemistry of these coatings varies considerably. Some of the chemical variations, particularly the presence of calcium, sodium, and strontium, can be explained by admixture with todorokite, seen in some x-ray powder diffraction patterns. Other chemical variations, particularly between Ba and Pb, demonstrate that considerable substitution of Pb for Ba occurs in hollandite. Manganese-oxide coatings are common in the 10-m interval that produced 75% of the water pumped from USW G-4 in a flow survey in 1983. Their presence in water-producing zones suggests that manganese oxides may exert a significant chemical effect on groundwater beneath Yucca Mountain. In particular, the ability of the manganese oxides found at Yucca Mountain to be easily reduced suggests that they may affect the redox conditions of the groundwater and may oxidize dissolved or suspended species. Although the Mn oxides at Yucca Mountain have low exchange capacities, these minerals may retard the migration of some radionuclides, particularly the actinides, through scavenging and coprecipitation. 23 refs., 21 figs., 2 tabs

  7. Control of arsenic mobilization in paddy soils by manganese and iron oxides.

    Science.gov (United States)

    Xu, Xiaowei; Chen, Chuan; Wang, Peng; Kretzschmar, Ruben; Zhao, Fang-Jie

    2017-12-01

    Reductive mobilization of arsenic (As) in paddy soils under flooded conditions is an important reason for the relatively high accumulation of As in rice, posing a risk to food safety and human health. The extent of As mobilization varies widely among paddy soils, but the reasons are not well understood. In this study, we investigated As mobilization in six As-contaminated paddy soils (total As ranging from 73 to 122 mg kg -1 ) in flooded incubation and pot experiments. Arsenic speciation in the solution and solid phases were determined. The magnitude of As mobilization into the porewater varied by > 100 times among the six soils. Porewater As concentration correlated closely with the concentration of oxalate-extractable As, suggesting that As associated with amorphous iron (oxyhydr)oxides represents the potentially mobilizable pool of As under flooded conditions. Soil containing a high level of manganese oxides showed the lowest As mobilization, likely because Mn oxides retard As mobilization by slowing down the drop of redox potential upon soil flooding and maintaining a higher arsenate to arsenite ratio in the solid and solution phases. Additions of a synthetic Mn oxide (hausmannite) to two paddy soils increased arsenite oxidation, decreased As mobilization into the porewater and decreased As concentrations in rice grain and straw. Consistent with previous studies using simplified model systems or pure mineral phases, the present study shows that Mn oxides and amorphous Fe (oxyhydr)oxides are important factors controlling reductive As mobilization in As-contaminated paddy soils. In addition, this study also suggests a potential mitigation strategy using exogenous Mn oxides to decrease As uptake by rice in paddy soils containing low levels of indigenous Mn oxides, although further work is needed to verify its efficacy and possible secondary effects under field conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. The Adsorption of Cd(II on Manganese Oxide Investigated by Batch and Modeling Techniques

    Directory of Open Access Journals (Sweden)

    Xiaoming Huang

    2017-09-01

    Full Text Available Manganese (Mn oxide is a ubiquitous metal oxide in sub-environments. The adsorption of Cd(II on Mn oxide as function of adsorption time, pH, ionic strength, temperature, and initial Cd(II concentration was investigated by batch techniques. The adsorption kinetics showed that the adsorption of Cd(II on Mn oxide can be satisfactorily simulated by pseudo-second-order kinetic model with high correlation coefficients (R2 > 0.999. The adsorption of Cd(II on Mn oxide significantly decreased with increasing ionic strength at pH < 5.0, whereas Cd(II adsorption was independent of ionic strength at pH > 6.0, which indicated that outer-sphere and inner-sphere surface complexation dominated the adsorption of Cd(II on Mn oxide at pH < 5.0 and pH > 6.0, respectively. The maximum adsorption capacity of Mn oxide for Cd(II calculated from Langmuir model was 104.17 mg/g at pH 6.0 and 298 K. The thermodynamic parameters showed that the adsorption of Cd(II on Mn oxide was an endothermic and spontaneous process. According to the results of surface complexation modeling, the adsorption of Cd(II on Mn oxide can be satisfactorily simulated by ion exchange sites (X2Cd at low pH and inner-sphere surface complexation sites (SOCd+ and (SO2CdOH− species at high pH conditions. The finding presented herein plays an important role in understanding the fate and transport of heavy metals at the water–mineral interface.

  9. The Adsorption of Cd(II) on Manganese Oxide Investigated by Batch and Modeling Techniques.

    Science.gov (United States)

    Huang, Xiaoming; Chen, Tianhu; Zou, Xuehua; Zhu, Mulan; Chen, Dong; Pan, Min

    2017-09-28

    Manganese (Mn) oxide is a ubiquitous metal oxide in sub-environments. The adsorption of Cd(II) on Mn oxide as function of adsorption time, pH, ionic strength, temperature, and initial Cd(II) concentration was investigated by batch techniques. The adsorption kinetics showed that the adsorption of Cd(II) on Mn oxide can be satisfactorily simulated by pseudo-second-order kinetic model with high correlation coefficients (R² > 0.999). The adsorption of Cd(II) on Mn oxide significantly decreased with increasing ionic strength at pH adsorption was independent of ionic strength at pH > 6.0, which indicated that outer-sphere and inner-sphere surface complexation dominated the adsorption of Cd(II) on Mn oxide at pH 6.0, respectively. The maximum adsorption capacity of Mn oxide for Cd(II) calculated from Langmuir model was 104.17 mg/g at pH 6.0 and 298 K. The thermodynamic parameters showed that the adsorption of Cd(II) on Mn oxide was an endothermic and spontaneous process. According to the results of surface complexation modeling, the adsorption of Cd(II) on Mn oxide can be satisfactorily simulated by ion exchange sites (X₂Cd) at low pH and inner-sphere surface complexation sites (SOCd⁺ and (SO)₂CdOH - species) at high pH conditions. The finding presented herein plays an important role in understanding the fate and transport of heavy metals at the water-mineral interface.

  10. Using Iron-Manganese Co-Oxide Filter Film to Remove Ammonium from Surface Water

    Directory of Open Access Journals (Sweden)

    Ruifeng Zhang

    2017-07-01

    Full Text Available An iron-manganese co-oxide filter film (MeOx has been proven to be a good catalyst for the chemical catalytic oxidation of ammonium in groundwater. Compared with groundwater, surface water is generally used more widely and has characteristics that make ammonium removal more difficult. In this study, MeOx was used to remove ammonium from surface water. It indicated that the average ammonium removal efficiency of MeOx was greater than 90%, even though the water quality changed dramatically and the water temperature was reduced to about 6–8 °C. Then, through inactivating microorganisms, it showed that the removal capability of MeOx included both biological (accounted for about 41.05% and chemical catalytic oxidation and chemical catalytic oxidation (accounted for about 58.95%. The investigation of the characterizations suggested that MeOx was formed by abiotic ways and the main elements on the surface of MeOx were distributed homogenously. The analysis of the catalytic oxidation process indicated that ammonia nitrogen may interact with MeOx as both ammonia molecules and ammonium ions and the active species of O2 were possibly •O and O2−.

  11. Gold & silver nanoparticles supported on manganese oxide: Synthesis, characterization and catalytic studies for selective oxidation of benzyl alcohol

    Directory of Open Access Journals (Sweden)

    Saad Alabbad

    2014-12-01

    Full Text Available Nano-gold and silver particles supported on manganese oxide were synthesized by the co-precipitation method. The catalytic properties of these materials were investigated for the oxidation of benzyl alcohol using molecular oxygen as a source of oxygen. The catalyst was calcined at 300, 400 and 500 °C. They were characterized by electron microscopy, powder X-ray diffraction (XRD and surface area. It was observed that the calcination temperature affects the size of the nanoparticle, which plays a significant role in the catalytic process. The catalyst calcined at 400 °C, gave a 100% conversion and >99% selectivity, whereas catalysts calcined at 300 and 500 °C gave a conversion of 69.51% and 19.90% respectively, although the selectivity remains >99%.

  12. Recent Advancements in the Cobalt Oxides, Manganese Oxides, and Their Composite As an Electrode Material for Supercapacitor: A Review

    Directory of Open Access Journals (Sweden)

    Santosh J. Uke

    2017-08-01

    Full Text Available Recently, our modern society demands the portable electronic devices such as mobile phones, laptops, smart watches, etc. Such devices demand light weight, flexible, and low-cost energy storage systems. Among different energy storage systems, supercapacitor has been considered as one of the most potential energy storage systems. This has several significant merits such as high power density, light weight, eco-friendly, etc. The electrode material is the important part of the supercapacitor. Recent studies have shown that there are many new advancement in electrode materials for supercapacitors. In this review, we focused on the recent advancements in the cobalt oxides, manganese oxides, and their composites as an electrode material for supercapacitor.

  13. Synthesis and characterization of carbon black/manganese oxide air cathodes for zinc-air batteries: Effects of the crystalline structure of manganese oxides

    Science.gov (United States)

    Li, Po-Chieh; Hu, Chi-Chang; Noda, Hiroyuki; Habazaki, Hiroki

    2015-12-01

    Manganese oxides (MnOx) in α-, β-, γ-, δ-MnO2 phases, Mn3O4, Mn2O3, and MnOOH are synthesized for systematically comparing their electrocatalytic activity of the oxygen reduction reaction (ORR) in the Zn-air battery application. The optimal MnOx/XC-72 mass ratio for the ORR is equal to 1 and the oxide crystalline structure effect on the ORR is compared. The order of composites with respect to decreasing the ORR activity is: α-MnO2/XC-72 > γ-MnO2/XC-72 > β-MnO2/XC-72 > δ-MnO2/XC-72 > Mn2O3/XC-72 > Mn3O4/XC-72 > MnOOH/XC-72. The textural properties of MnOx are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption/desorption isotherms with Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Electrochemical studies include linear sweep voltammetry (LSV), rotating ring-disk electrode (RRDE) voltammetry, and the full-cell discharge test. The discharge peak power density of Zn-air batteries varies from 61.5 mW cm-2 (α-MnO2/XC-72) to 47.1 mW cm-2 (Mn3O4/XC-72). The maximum peak power density is 102 mW cm-2 for the Zn-air battery with an air cathode containing α-MnO2/XC-72 under an oxygen atmosphere when the carbon paper is 10AA. The specific capacity of all full-cell tests is higher than 750 mAh g-1 at all discharge current densities.

  14. Heterogeneous catalytic ozonation of ciprofloxacin in water with carbon nanotube supported manganese oxides as catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Sui, Minghao, E-mail: suiminghao.sui@gmail.com [State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092 (China); Xing, Sichu; Sheng, Li; Huang, Shuhang; Guo, Hongguang [State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092 (China)

    2012-08-15

    Highlights: Black-Right-Pointing-Pointer Ciprofloxacin in water was degraded by heterogeneous catalytic ozonation. Black-Right-Pointing-Pointer MnOx were supported on MWCNTs to serve as catalyst for ozonation. Black-Right-Pointing-Pointer MnOx/MWCNT exhibited highly catalytic activity on ozonation of ciprofloxacin in water. Black-Right-Pointing-Pointer MnOx/MWCNT resulted in effective antibacterial activity inhibition on ciprofloxacin. Black-Right-Pointing-Pointer MnOx/MWCNT promoted the generation of hydroxyl radicals. - Abstract: Carbon nanotube-supported manganese oxides (MnOx/MWCNT) were used as catalysts to assist ozone in degrading ciprofloxacin in water. Manganese oxides were successfully loaded on multi-walled carbon nanotube surfaces by simply impregnating the carbon nanotube with permanganate solution. The catalytic activities of MnOx/MWCNT in ciprofloxacin ozonation, including degradation, mineralization effectiveness, and antibacterial activity change, were investigated. The presence of MnOx/MWCNT significantly elevated the degradation and mineralization efficiency of ozone on ciprofloxacin. The microbiological assay with a reference Escherichia coli strain indicated that ozonation with MnOx/MWCNT results in more effective antibacterial activity inhibition of ciprofloxacin than that in ozonation alone. The effects of catalyst dose, initial ciprofloxacin concentration, and initial pH conditions on ciprofloxacin ozonation with MnOx/MWCNT were surveyed. Electron spin resonance trapping was applied to assess the role of MnOx/MWCNT in generating hydroxyl radicals (HO{center_dot}) during ozonation. Stronger 5,5-dimethyl-1-pyrroline-N-oxide-OH signals were observed in the ozonation with MnOx/MWCNT compared with those in ozonation alone, indicating that MnOx/MWCNT promoted the generation of hydroxyl radicals. The degradation of ciprofloxacin was studied in drinking water and wastewater process samples to gauge the potential effects of water background matrix on

  15. Improved photoelectrochemical water oxidation by the WO3/CuWO4 composite with a manganese phosphate electrocatalyst.

    Science.gov (United States)

    Nam, Ki Min; Cheon, Eun Ah; Shin, Won Jung; Bard, Allen J

    2015-10-06

    We describe a composite of the n-type semiconductors for the photoelectrochemical oxygen evolution reaction (OER). A simple drop-casting technique of mixed precursors and a one-step annealing process were used in the synthesis of the WO3/CuWO4 composite. The composite showed improved photocurrent for water oxidation compared to either of the two compounds individually. We discuss possible electron-hole separation mechanisms in two semiconductors comprising a primary photon-absorbing semiconductor of CuWO4 with a secondary semiconductor of WO3. When the WO3/CuWO4 composite is simultaneously irradiated, the photogenerated hole from the WO3 valence band transfers to CuWO4, which results in an enhanced charge separation of CuWO4. Furthermore, the OER catalytic activity of manganese phosphate (MnPO) was compared to manganese oxide nanoparticles (Mn2O3) by electrochemical measurements, showing that the manganese phosphate was more efficient for the OER reaction. To investigate the effect of catalysts on semiconductors, manganese phosphate was deposited on the WO3/CuWO4 composite. The result demonstrates the promise of manganese phosphate for improving the photocurrent as well as the stability of the WO3/CuWO4 composite.

  16. Synthesis and characterization of monodispersed orthorhombic manganese oxide nanoparticles produced by Bacillus sp. cells simultaneous to its bioremediation.

    Science.gov (United States)

    Sinha, Arvind; Singh, Vidya Nand; Mehta, Bodh Raj; Khare, Sunil Kumar

    2011-08-30

    A heavy metal resistant strain of Bacillus sp. (MTCC10650) is reported. The strain exhibited the property of bioaccumulating manganese, simultaneous to its remediation. The nanoparticles thus formed were characterized and identified using energy dispersive X-ray analysis (EDAX), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (PXRD) and atomic force microscopy (AFM). When the cells were challenged with manganese, the cells effectively synthesized nanoparticles of average size 4.62±0.14nm. These were mostly spherical and monodispersed. The ex situ enzymatically synthesized nanoparticles exhibited an absorbance maximum at 329nm. These were more discrete, small and uniform, than the manganese oxide nanoparticles recovered after cell sonication. The use of Bacillus sp. cells seems promising and advantageous approach. Since, it serves dual purposes of (i) remediation and (ii) nanoparticle synthesis. Considering the increasing demand of developing environmental friendly and cost effective technologies for nanoparticle synthesis, these cells can be exploited for the remediation of manganese from the environment in conjunction with development of a greener process for the controlled synthesis of manganese oxide nanoparticles. Copyright © 2011 Elsevier B.V. All rights reserved.

  17. Transition metal alloy-modulated lithium manganese oxide nanosystem for energy storage in lithium-ion battery cathodes

    CSIR Research Space (South Africa)

    West, N

    2013-07-01

    Full Text Available . The material crystallite size was 10 nm with clear lattice fringes having a separation value of 0.48 nm which concurrently improved the diffusion rate of Li(sup+). Solid-state NMR results showed the progressive increase in average nominal manganese oxidation...

  18. Arsenic(III) sorption on nanostructured cerium incorporated manganese oxide (NCMO): a physical insight into the mechanistic pathway

    CSIR Research Space (South Africa)

    Gupta, K

    2012-07-01

    Full Text Available Arsenic(III) sorption was investigated with nanostructured cerium incorporated manganese oxide (NCMO). The pH between 6.0 and 8.0 was optimized for the arsenic(III) sorption. Kinetics and equilibrium data (pH = 7.0 ± 0.2, T = 303 ± 1.6 K, and I = 0...

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

    Science.gov (United States)

    Hem, J.D.; Lind, Carol J.

    1991-01-01

    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

  20. Relationship between anti-oxidant capacity and manganese accumulation in the soft tissues of two freshwater molluscs: Unio pictorum mancus (Lamellibranchia, Unionidae and Viviparus ater (Gastropoda, Prosobranchia

    Directory of Open Access Journals (Sweden)

    Oscar RAVERA

    2005-08-01

    Full Text Available Manganese is an element of great importance in the life cycle of plants and animals. For example, it plays an essential role as an activator of various enzymatic systems such as isoenzymes of superoxide dismutase. Freshwater Unionidae concentrate relatively large amounts of manganese in their tissues, but little is known about the physiological role of this metal. The aim of this research is to acquire a better knowledge of the role of manganese in molluscs which accumulate large amounts of this metal and in those with low manganese concentrations. As manganese is one of the metals present in the superoxide molecule, the possible relationship between manganese concentration in the soft tissues of molluscs and the antioxidant capacity of the metal can usefully be tested. To this end two species of molluscs were analysed: Unio pictorum mancus (Lamellibranchia, Unionidae, which is very rich in manganese, and Viviparus ater (Gastropoda, Prosobranchia which has a low manganese content. The adults of both species were analysed for manganese concentration by ICP, and for antioxidant capacity as RAC (Relative Antioxidant Capacity by a superoxide dismutase method. The results clearly demonstrate the active role played by manganese against free radicals and consequently the important role of the metal in protecting Unio against oxidative stress. The low concentration of manganese in Viviparus may be the result of the effective excretion of this metal, as was found for ruthenium.

  1. Synthesis and Characterization of Mixed Iron-Manganese Oxide Nanoparticles and Their Application for Efficient Nickel Ion Removal from Aqueous Samples

    OpenAIRE

    Buccolieri, Alessandro; Serra, Antonio; Maruccio, Giuseppe; Monteduro, Anna Grazia; Padmanabhan, Sanosh Kunjalukkal; Licciulli, Antonio; Bonfrate, Valentina; Salvatore, Luca; Manno, Daniela; Calcagnile, Lucio; Giancane, Gabriele

    2017-01-01

    Mixed iron-manganese oxide nanoparticles, synthesized by a simple procedure, were used to remove nickel ion from aqueous solutions. Nanostructures, prepared by using different weight percents of manganese, were characterized by transmission electron microscopy, selected area diffraction, X-ray diffraction, Raman spectroscopy, and vibrating sample magnetometry. Adsorption/desorption isotherm curves demonstrated that manganese inclusions enhance the specific surface area three times and the por...

  2. Promotion effect of manganese oxide on the electrocatalytic activity of Pt/C for methanol oxidation in acid medium

    Science.gov (United States)

    Abdel Hameed, R. M.; Fetohi, Amani E.; Amin, R. S.; El-Khatib, K. M.

    2015-12-01

    The modification of Pt/C by incorporating metal oxides for electrocatalytic oxidation of methanol has gained major attention because of the efficiency loss during the course of long-time operation. This work describes the preparation of Pt-MnO2/C electrocatalysts through a chemical route using ethylene glycol or a mixture of ethylene glycol and sodium borohydride as a reducing agent. The crystallite structure and particle size of synthesized electrocatalysts are determined using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The addition of MnO2 improves the dispersion of Pt nanoparticles. The electrocatalytic activity of Pt-MnO2/C towards methanol oxidation in H2SO4 solution is investigated using cyclic voltammetry and electrochemical impedance spectroscopy. The onset potential value of methanol oxidation peak is negatively shifted by 169 mV when MnO2 is introduced to Pt/C. Moreover, the charge transfer resistance value at Pt-MnO2/C is about 10 times as low as that at Pt/C. Chronoamperometry and chronopotentiometry show that CO tolerance is greatly improved at Pt-MnO2/C. The increased electrocatalytic activity and enhanced ability to clean platinum surface elect manganese oxide as a suitable promoter for the anode performance in direct methanol fuel cells (DMFCs).

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

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jin-Woo, E-mail: jinwoo@knu.ac.kr [Department of Periodontology, School of Dentistry, Kyungpook National University, 188-1, Samduk 2Ga, Jung-Gu, Daegu 700-412 (Korea, Republic of); Kim, Youn-Jeong; Jang, Je-Hee [Department of Periodontology, School of Dentistry, Kyungpook National University, 188-1, Samduk 2Ga, Jung-Gu, Daegu 700-412 (Korea, Republic of)

    2011-11-01

    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 {mu}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.

  4. Bio-templated synthesis of lithium manganese oxide microtubes and their application in Li+ recovery.

    Science.gov (United States)

    Yu, Qianqian; Sasaki, Keiko; Hirajima, Tsuyoshi

    2013-11-15

    Microbial transformations, a primary pathway for the Mn oxides formation in nature, provide potential for material-oriented researchers to fabricate new materials. Using Mn oxidizing fungus Paraconiothyrium sp. WL-2 as a bio-oxidizer as well as a bio-template, a special lithium ion sieve with microtube morphology was prepared through a solid-state transformation. Varying the calcination temperature from 300 to 700 °C was found to influence sample properties and consequently, the adsorption of Li(+). Lithium manganese oxide microtube (LMO-MTs) calcined at different temperatures as well as their delithiated products (HMO-MTs) were characterized by X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Calcination temperatures affect not only the content but also the crystal structure of LMO spinel, which is important in Li(+) adsorption. The optimized sample was obtained after calcination at 500 °C for 4h, which shows higher Li(+) adsorption capacity than particulate materials. Copyright © 2013 Elsevier B.V. All rights reserved.

  5. Manganese oxide octahedral molecular sieves as insertion electrodes for rechargeable Mg batteries

    KAUST Repository

    Rasul, Shahid

    2013-11-01

    Magnesium has been inserted electrochemically into manganese oxide octahedral molecular sieves (OMS-5 MnO2) at room temperature. Discharge/charge profiles show that a large amount of Mg, i.e., 0.37 Mg/Mn can be inserted electrochemically using 1 M Mg(ClO4)2/AN electrolyte when OMS-5 is prepared in presence of acetylene black. X-ray diffraction analysis and discharge/charge profiles verify that a solid state solution reaction takes place upon Mg insertion into the host lattice with concurrent reduction of Mn4+ to Mn2+. However, upon each reduction of Mn by Mg insertion and resultant dissolution into electrolyte, decrease in the active compound occurs consequently. A low intrinsic electronic conductivity of OMS-5 was suggested to play a vital role in Mg insertion into the host. © 2013 Elsevier Ltd.

  6. On the Oxidation State of Manganese Ions in Li-Ion Battery Electrolyte Solutions.

    Science.gov (United States)

    Banerjee, Anjan; Shilina, Yuliya; Ziv, Baruch; Ziegelbauer, Joseph M; Luski, Shalom; Aurbach, Doron; Halalay, Ion C

    2017-02-08

    We demonstrate herein that Mn 3+ and not Mn 2+ , as commonly accepted, is the dominant dissolved manganese cation in LiPF 6 -based electrolyte solutions of Li-ion batteries with lithium manganate spinel positive and graphite negative electrodes chemistry. The Mn 3+ fractions in solution, derived from a combined analysis of electron paramagnetic resonance and inductively coupled plasma spectroscopy data, are ∼80% for either fully discharged (3.0 V hold) or fully charged (4.2 V hold) cells, and ∼60% for galvanostatically cycled cells. These findings agree with the average oxidation state of dissolved Mn ions determined from X-ray absorption near-edge spectroscopy data, as verified through a speciation diagram analysis. We also show that the fractions of Mn 3+ in the aprotic nonaqueous electrolyte solution are constant over the duration of our experiments and that disproportionation of Mn 3+ occurs at a very slow rate.

  7. Intraparticle diffusion coefficient of lithium on granulated adsorbent of manganese oxide in seawater

    International Nuclear Information System (INIS)

    Miyai, Yoshitaka; Kanoh, Hirofumi; Feng, Qi; Ooi, Kenta

    1995-01-01

    Five kinds of manganese-oxide adsorbent granulated with different particle sizes were prepared using polyvinyl chloride (PVC) as a binder. Rates of lithium adsorption on the adsorbents were measured in lithium-enriched seawater ([Li]=3.1 mg·dm -3 ) by a batch method. The intraparticle diffusivities (D p 's) of lithium were evaluated in terms of the model of pore diffusion with a Freundrich-type adsorption isotherm. The D p values were about 2 x 10 -6 cm·s -1 and slightly dependent on particle size. The D p values were also evaluated using column adsorption data. The calculated values (about 4 x 10 -6 cm·s -1 ) agreed comparatively well with those derived from the batch adsorption data. The agreement suggests that the intraparticle diffusion is a rate-determining step in column adsorption at space velocity above 200 h -1 . (author)

  8. Manganese oxide nanoparticle-assisted laser desorption/ionization mass spectrometry for medical applications

    Directory of Open Access Journals (Sweden)

    Shu Taira, Kenji Kitajima, Hikaru Katayanagi, Eiichiro Ichiishi and Yuko Ichiyanagi

    2009-01-01

    Full Text Available We prepared and characterized manganese oxide magnetic nanoparticles (d =5.6 nm and developed nanoparticle-assited laser desorption/ionization (nano-PALDI mass spectrometry. The nanoparticles had MnO2 and Mn2O3 cores conjugated with hydroxyl and amino groups, and showed paramagnetism at room temperature. The nanoparticles worked as an ionization assisting reagent in mass spectroscopy. The mass spectra showed no background in the low m/z. The nanoparticles could ionize samples of peptide, drug and proteins (approx. 5000 Da without using matrix, i.e., 2,5-dihydroxybenzoic acid (DHB, 4-hydroxy-α-cinnamic acid (CHCA and liquid matrix, as conventional ionization assisting reagents. Post source decay spectra by nano-PALDI mass spectrometry will yield information of the chemical structure of analytes.

  9. Effect of support on the catalytic activity of manganese oxide catalyts for toluene combustion

    Energy Technology Data Exchange (ETDEWEB)

    Pozan, Gulin Selda, E-mail: gpozan@istanbul.edu.tr [Istanbul University, Faculty of Engineering, Chemical Engineering Department, Avcilar 34320, Istanbul (Turkey)

    2012-06-30

    Highlights: Black-Right-Pointing-Pointer {alpha}-Al{sub 2}O{sub 3}, obtained from Bohmite, as a support for enhancing of the activity. Black-Right-Pointing-Pointer The support material for catalytic oxidation. Black-Right-Pointing-Pointer The manganese state and oxygen species effect on the catalytic combustion reaction. - Abstract: The aim of this work was to study combustion of toluene (1000 ppm) over MnO{sub 2} modified with different supports. {alpha}-Al{sub 2}O{sub 3} and {gamma}-Al{sub 2}O{sub 3} obtained from Boehmite, {gamma}-Al{sub 2}O{sub 3} (commercial), SiO{sub 2}, TiO{sub 2} and ZrO{sub 2} were used as commercial support materials. In view of potential interest of this process, the influence of support material on the catalytic performance was discussed. The deposition of 9.5MnO{sub 2} was performed by impregnation over support. The catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction and oxidation (TPR/TPO) and thermogravimetric analysis (TGA). The catalytic tests were carried out at atmospheric pressure in a fixed-bed flow reactor. 9.5MnO{sub 2}/{alpha}-Al{sub 2}O{sub 3}(B) (synthesized from Boehmite) catalyst exhibits the highest catalytic activity, over which the toluene conversion was up to 90% at a temperature of 289 Degree-Sign C. Considering all the characterization and reaction data reported in this study, it was concluded that the manganese state and oxygen species played an important role in the catalytic activity.

  10. Effect of support on the catalytic activity of manganese oxide catalyts for toluene combustion

    International Nuclear Information System (INIS)

    Pozan, Gulin Selda

    2012-01-01

    Highlights: ► α-Al 2 O 3 , obtained from Bohmite, as a support for enhancing of the activity. ► The support material for catalytic oxidation. ► The manganese state and oxygen species effect on the catalytic combustion reaction. - Abstract: The aim of this work was to study combustion of toluene (1000 ppm) over MnO 2 modified with different supports. α-Al 2 O 3 and γ-Al 2 O 3 obtained from Boehmite, γ-Al 2 O 3 (commercial), SiO 2 , TiO 2 and ZrO 2 were used as commercial support materials. In view of potential interest of this process, the influence of support material on the catalytic performance was discussed. The deposition of 9.5MnO 2 was performed by impregnation over support. The catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction and oxidation (TPR/TPO) and thermogravimetric analysis (TGA). The catalytic tests were carried out at atmospheric pressure in a fixed-bed flow reactor. 9.5MnO 2 /α-Al 2 O 3 (B) (synthesized from Boehmite) catalyst exhibits the highest catalytic activity, over which the toluene conversion was up to 90% at a temperature of 289 °C. Considering all the characterization and reaction data reported in this study, it was concluded that the manganese state and oxygen species played an important role in the catalytic activity.

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

    Science.gov (United States)

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

    2013-06-01

    Manganese, in the form of oxide, was recovered from spent alkaline and zinc-carbon batteries employing a biohydrometallurgy process, using a pilot plant consisting in: an air-lift bioreactor (containing an acid-reducing medium produced by an Acidithiobacillus thiooxidans bacteria immobilized on elemental sulfur); a leaching reactor (were battery powder is mixed with the acid-reducing medium) and a recovery reactor. Two different manganese oxides were recovered from the leachate liquor: one of them by electrolysis (EMO) and the other by a chemical precipitation with KMnO4 solution (CMO). The non-leached solid residue was also studied (RMO). The solids were compared with a MnOx synthesized in our laboratory. The characterization by XRD, FTIR and XPS reveal the presence of Mn2O3 in the EMO and the CMO samples, together with some Mn(4+) cations. In the solid not extracted by acidic leaching (RMO) the main phase detected was Mn3O4. The catalytic performance of the oxides was studied in the complete oxidation of ethanol and heptane. Complete conversion of ethanol occurs at 200°C, while heptane requires more than 400°C. The CMO has the highest oxide selectivity to CO2. The results show that manganese oxides obtained using spent alkaline and zinc-carbon batteries as raw materials, have an interesting performance as catalysts for elimination of VOCs. Copyright © 2013 Elsevier Ltd. All rights reserved.

  12. Biogenic Volatile Organic Compounds (BVOCs) and their oxidation products at two Mediterranean background sites

    Science.gov (United States)

    Debevec, Cecile; Sauvage, Stephane; Gros, Valerie; Sciare, Jean; Pikridas, Michael; Dusanter, Sebastien; Leonardis, Thierry; Gaudion, Vincent; Depelchin, Laurence; Fronval, Isabelle; Sarda-Esteve, Roland; Baisnee, Dominique; Vasiliadou, Emily; Savvides, Chrysanthos; Kalogridis, Cerise; Michoud, Vincent; Locoge, Nadine

    2017-04-01

    In the framework of the ChArMEx (Chemistry Aerosol Mediterranean Experiments) program, this work aims at providing a better characterization of the sources and fate of VOCs impacting the Mediterranean region as well as conducting a parallel between organic aerosol and gas phase composition. To reach these objectives, on-line measurements of a large number of VOCs were conducted by flame ionization detection/gas chromatography and proton transfer reaction mass spectrometry at two Mediterranean receptor sites, Cape Corsica in summer 2013 and the Cyprus Atmospheric Observatory (CAO) in March 2015. Additionally, off-line air samples were collected on cartridges. On-line submicron aerosol chemical composition was performed in parallel with an aerosol mass spectrometer. VOCs Sources were identified using positive matrix factorization (PMF) tool and discussed in previous studies (Michoud et al., submitted, Debevec et al., submitted). This work focuses on BVOCs measured at these sampling sites (especially on their levels, speciation, variability and processes). Different speciation of monoterpenes was noticed at these sites. Even if monoterpenes were mainly composed of β-pinene at both sites (34 % - 38 % of the total monoterpenes mass concentration), α-terpinene was observed in higher proportion at Cape Corsica (21 %) than CAO (2 %) while lower proportion of α-pinene was measured (Cape Corsica: 24 %, CAO: 35 %). Biogenic sources were found to be significant contributors to the VOCs concentrations observed at these sampling sites (Cape Corsica: 20%, CAO: 36 %) but have shown different variabilities. At Cape Corsica, a primary and a secondary biogenic factor were identified, both correlating with air temperature and exhibiting a clear diurnal profile. At CAO, two different biogenic factors were identified with distinct diurnal profiles, the first one driven by isoprene was correlated with air temperature and the second one, driven by monoterpenes, showed maxima during

  13. Preliminary characterization and biological reduction of putative biogenic iron oxides (BIOS) from the Tonga-Kermadec Arc, southwest Pacific Ocean.

    Science.gov (United States)

    Langley, S; Igric, P; Takahashi, Y; Sakai, Y; Fortin, D; Hannington, M D; Schwarz-Schampera, U

    2009-01-01

    Sediment samples were obtained from areas of diffuse hydrothermal venting along the seabed in the Tonga sector of the Tonga-Kermadec Arc, southwest Pacific Ocean. Sediments from Volcano 1 and Volcano 19 were analyzed by X-ray diffraction (XRD) and found to be composed primarily of the iron oxyhydroxide mineral, two-line ferrihydrite. XRD also suggested the possible presence of minor amounts of more ordered iron (hydr)oxides (including six-line ferrihydrite, goethite/lepidocrocite and magnetite) in the biogenic iron oxides (BIOS) from Volcano 1; however, Mössbauer spectroscopy failed to detect any mineral phases more crystalline than two-line ferrihydrite. The minerals were precipitated on the surfaces of abundant filamentous microbial structures. Morphologically, some of these structures were similar in appearance to the known iron-oxidizing genus Mariprofundus spp., suggesting that the sediments are composed of biogenic iron oxides. At Volcano 19, an areally extensive, active vent field, the microbial cells appeared to be responsible for the formation of cohesive chimney-like structures of iron oxyhydroxide, 2-3 m in height, whereas at Volcano 1, an older vent field, no chimney-like structures were apparent. Iron reduction of the sediment material (i.e. BIOS) by Shewanella putrefaciens CN32 was measured, in vitro, as the ratio of [total Fe(II)]:[total Fe]. From this parameter, reduction rates were calculated for Volcano 1 BIOS (0.0521 day(-1)), Volcano 19 BIOS (0.0473 day(-1)), and hydrous ferric oxide, a synthetic two-line ferrihydrite (0.0224 day(-1)). Sediments from both BIOS sites were more easily reduced than synthetic ferrihydrite, which suggests that the decrease in effective surface area of the minerals within the sediments (due to the presence of the organic component) does not inhibit subsequent microbial reduction. These results indicate that natural, marine BIOS are easily reduced in the presence of dissimilatory iron-reducing bacteria, and that the

  14. The oxidation of acid azo dye AY 36 by a manganese oxide containing mine waste

    International Nuclear Information System (INIS)

    Clarke, Catherine E.; Kielar, Filip; Johnson, Karen L.

    2013-01-01

    Highlights: ► This study looks at the oxidative breakdown of the amine containing dye acid yellow 36 by a Mn oxide containing mine waste. ► The oxidation proceeds by successive one electron transfers between the dye molecule and the Mn oxide minerals. ► The initial decolorization of the dye is rapid, but does not involve the cleavage of the azo bond. -- Abstract: The oxidative breakdown of acid azo dye acid yellow 36 (AY 36) by a Mn oxide containing mine tailings is demonstrated. The oxidation reaction is pH dependent with the rate of decolorization increasing with decreasing pH. The oxidation reaction mechanism is initiated at the amino moiety and proceeds via successive, one electron transfers from the dye to the Mn oxide minerals. The reaction pathway involves the formation of a number of colorless intermediate products, some of which hydrolyze in a Mn oxide-independent step. Decolorization of the dye is rapid and is observed before the cleavage of the azo-bond, which is a slower process. The terminal oxidation products were observed to be p-benzoquinone and 3-hydroxybenzenesulfonate. The reaction order of the initial decolorization was determined to be pseudo fractional order with respect to pH and pseudo first order with respect to dye concentration and Mn tailings’ surface area

  15. Thallium-isotopic compositions of euxinic sediments as a proxy for global manganese-oxide burial

    Science.gov (United States)

    Owens, Jeremy D.; Nielsen, Sune G.; Horner, Tristan J.; Ostrander, Chadlin M.; Peterson, Larry C.

    2017-09-01

    Thallium (Tl) isotopes are a new and potentially powerful paleoredox proxy that may track bottom water oxygen conditions based on the global burial flux of manganese oxides. Thallium has a residence time of ∼20 thousand years, which is longer than the ocean mixing time, and it has been inferred that modern oxic seawater is conservative with respect to both concentration and isotopes. Marine sources of Tl have nearly identical isotopic values. Therefore, the Tl sinks, adsorption onto manganese oxides and low temperature oceanic crust alteration (the dominant seawater output), are the primary controls of the seawater isotopic composition. For relatively short-term, ∼million years, redox events it is reasonable to assume that the dominant mechanism that alters the Tl isotopic composition of seawater is associated with manganese oxide burial because large variability in low temperature ocean crust alteration is controlled by long-term, multi-million years, average ocean crust production rates. This study presents new Tl isotope data for an open ocean transect in the South Atlantic, and depth transects for two euxinic basins (anoxic and free sulfide in the water column), the Cariaco Basin and Black Sea. The Tl isotopic signature of open ocean seawater in the South Atlantic was found to be homogeneous with ε205Tl = -6.0 ± 0.3 (±2 SD, n = 41) while oxic waters from Cariaco and the Black Sea are -5.6 and -2.2, respectively. Combined with existing data from the Pacific and Arctic Oceans, our Atlantic data establish the conservatism of Tl isotopes in the global ocean. In contrast, partially- and predominantly-restricted basins reveal Tl isotope differences that vary between open-ocean (-6) and continental material (-2) ε205Tl, scaling with the degree of restriction. Regardless of the differences between basins, Tl is quantitatively removed from their euxinic waters below the chemocline. The burial of Tl in euxinic sediments is estimated to be an order of magnitude

  16. Biogenic amine formation and oxidation by Staphylococcus xylosus strains from artisanal fermented sausages.

    Science.gov (United States)

    Martuscelli, M; Crudele, M A; Gardini, F; Suzzi, G

    2000-09-01

    Fifty strains of Staph. xylosus, isolated from artisanal fermented sausages in Southern Italy (Lucania region) were tested to verify their potential to produce or degrade biogenic amines. Twenty-six strains analysed were not able to form amines, but seven had the potential to produce spermine and/or spermidine and, at lower levels, tryptamine and tyramine. By contrast, about 80% of the strains that did not possess amino acid decarboxylase activity, exhibited an ability to degrade histamine. The greatest histamine-oxidase activity was present in the strains S81 (100% degradation), S206 (93%), S79 (68%) and S90 (53%). The strain S142 exhibited a remarkably high potential to oxidase tyramine and histamine, reducing the initial concentrations by 63 and 47%, respectively.

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

    Science.gov (United States)

    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

    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 (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 α-MnO2. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. A manganese oxido complex bearing facially coordinating trispyridyl ligands--is coordination geometry crucial for water oxidation catalysis?

    Science.gov (United States)

    Berends, Hans-Martin; Manke, Anne-Marie; Näther, Christian; Tuczek, Felix; Kurz, Philipp

    2012-05-28

    In this work the synthesis of the novel manganese complex [Mn(2)(III,III)(tpdm)(2)(μ-O)(μ-OAc)(2)](2+) (1) is reported, containing two manganese centres ligated to the unusual, facially coordinating, all-pyridine ligand tpdm (tris(2-pyridyl)methane). The geometric and electronic properties of complex 1 were characterised by X-ray crystallography, vibrational (IR and Raman) and optical spectroscopy (UV/Vis and MCD). Cyclic voltammograms of 1 showed a quasi-reversible oxidation event at 950 mV and an irreversible reduction wave at -250 mV vs. Ag/Ag(+). The redox behaviour of the compound was investigated in detail by UV/Vis- and X-band EPR-spectroelectrochemistry. Both electrochemical (+1200 mV) and chemical (tBuOOH) oxidations transform 1 into the singly oxidized di-μ-oxido species [Mn(2)(III,IV)(tpdm)(2)(μ-O)(2)(μ-OAc)](2+). Further electrochemical oxidation at the same potential results in the removal of a second electron to obtain a Mn(2)(IV,IV)-species. The ability of compound 1 to evolve O(2) was studied using different reaction agents. While reactions with both hydrogen peroxide and peroxomonosulfate yield O(2), homogeneous water-oxidation using Ce(IV) was not observed. Nevertheless, the oxidation reactions of 1 are very interesting model processes for oxidation state (S-state) transitions of the natural manganese water-oxidation catalyst in photosynthesis. However, despite its favourable coordination geometry and multielectron redox chemistry, complex 1 fails to be a catalytically active model for natural water-oxidation.

  19. Nutrient input influences fungal community composition and size and can stimulate manganese (II) oxidation in caves.

    Science.gov (United States)

    Carmichael, Sarah K; Zorn, Bryan T; Santelli, Cara M; Roble, Leigh A; Carmichael, Mary J; Bräuer, Suzanna L

    2015-08-01

    Little is known about the fungal role in biogeochemical cycling in oligotrophic ecosystems. This study compared fungal communities and assessed the role of exogenous carbon on microbial community structure and function in two southern Appalachian caves: an anthropogenically impacted cave and a near-pristine cave. Due to carbon input from shallow soils, the anthropogenically impacted cave had an order of magnitude greater fungal and bacterial quantitative-polymerase chain reaction (qPCR) gene copy numbers, had significantly greater community diversity, and was dominated by ascomycotal phylotypes common in early phase, labile organic matter decomposition. Fungal assemblages in the near-pristine cave samples were dominated by Basidiomycota typically found in deeper soils (and/or in late phase, recalcitrant organic matter decomposition), suggesting more oligotrophic conditions. In situ carbon and manganese (II) [Mn(II)] addition over 10 weeks resulted in growth of fungal mycelia followed by increased Mn(II) oxidation. A before/after comparison of the fungal communities indicated that this enrichment increased the quantity of fungal and bacterial cells, yet decreased overall fungal diversity. Anthropogenic carbon sources can therefore dramatically influence the diversity and quantity of fungi, impact microbial community function, and stimulate Mn(II) oxidation, resulting in a cascade of changes that can strongly influence nutrient and trace element biogeochemical cycles in karst aquifers. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

  20. Sapindus mukorossi mediated green synthesis of some manganese oxide nanoparticles interaction with aromatic amines

    Science.gov (United States)

    Jassal, Vidhisha; Shanker, Uma; Gahlot, Sweta; Kaith, B. S.; Kamaluddin; Iqubal, Md Asif; Samuel, Pankaj

    2016-04-01

    A green route was successfully used to synthesize some manganese oxides (MO) nanoparticles like MnO2, Mn2O3 and Mn3O4 with varied Mn/O ratio. This approach involved utilization of Sapindus mukorossi (raw reetha)-water as a natural surfactant-solvent system. The most important feature of present work was that during the synthesis of nanoparticles, no harmful toxic solvent or chemicals were used in order to follow the principles of green chemistry. The size of nanoparticles was recorded below 100 nm with different shapes and morphologies. MnO2 nanoparticles were found to have needle shape, Mn2O3: spherical and Mn3O4: cubic shape. The synthesized nanoparticles were characterized by powder X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. The synthesized MO nanoparticles were found to act as a solid support cum catalysts for the oxidation and polymerization of some aromatic amines like p-anisidine, p-toluidine, p-chloroaniline and aniline.

  1. MR Tracking of Transplanted Cells With “Positive Contrast” Using Manganese Oxide Nanoparticles

    Science.gov (United States)

    Gilad, Assaf A.; Walczak, Piotr; McMahon, Michael T.; Na, Hyon Bin; Lee, Jung Hee; An, Kwangjin; Hyeon, Taegwhan; van Zijl, Peter C.M.; Bulte, Jeff W.M.

    2008-01-01

    Rat glioma cells were labeled using electroporation with either manganese oxide (MnO) or superparamagnetic iron oxide (SPIO) nanoparticles. The viability and proliferation of SPIO-labeled cells (1.9 mg Fe/ml) or cells electroporated with a low dose of MnO (100 μg Mn/ml) was not significantly different from unlabeled cells; a higher MnO dose (785 μg Mn/ml) was found to be toxic. The cellular ion content was 0.1−0.3 pg Mn/cell and 4.4 pg Fe/cell, respectively, with cellular relaxivities of 2.5−4.8 s−1 (R1) and 45−84 s−1 (R2) for MnO-labeled cells. Labeled cells (SPIO and low-dose MnO) were each transplanted in contralateral brain hemispheres of rats and imaged in vivo at 9.4T. While SPIO-labeled cells produced a strong “negative contrast” due to the increase in R2, MnO-labeled cells produced “positive contrast” with an increased R1. Simultaneous imaging of both transplants with opposite contrast offers a method for MR “double labeling” of different cell populations. PMID:18581402

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

    Science.gov (United States)

    Liu, Ting; Wu, Kun; Zeng, Lihua

    2012-05-30

    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. Copyright © 2012 Elsevier B.V. All rights reserved.

  3. In situ synthesis of manganese oxides on polyester fiber for formaldehyde decomposition at room temperature

    Science.gov (United States)

    Wang, Jinlong; Yunus, Rizwangul; Li, Jinge; Li, Peilin; Zhang, Pengyi; Kim, Jeonghyun

    2015-12-01

    Removal of low-level formaldehyde (HCHO) is of great interest for indoor air quality improvement. Supported materials especially those with low air pressure drop are of necessity for air purification. Manganese oxides (MnOx) was in situ deposited on the surface of fibers of a non-woven fabric made of polyethylene terephthalate (PET). As-synthesized MnOx/PET were characterized by SEM, XRD, TEM, ATR-FTIR and XPS analysis. The growth of MnOx layer on PET is thought to start with partial hydrolysis of PET, followed by surface oxidation by KMnO4 and then surface-deposition of MnOx particles from the bulk phase. The MnOx particles assembled with nanosheets were uniformly coated on the PET fibers. MnOx/PET showed good activity for HCHO decomposition at room temperature which followed the Mars-van Krevelen mechanism. The removal of HCHO was kept over 94% after 10 h continuous reaction under the conditions of inlet HCHO concentration ∼0.6 mg/m3, space velocity ∼17,000 h-1 and relative humidity∼50%. This research provides a facile method to deposit active MnOx onto polymers with low air resistance, and composite MnOx/PET material is promising for indoor air purification.

  4. Enhanced electrochemical performance of amorphous carbon nanotube-manganese-di-oxide-poly-pyrrole ternary nanohybrid

    Science.gov (United States)

    Pahari, D.; Das, N. S.; Das, B.; Howli, P.; Chattopadhyay, K. K.; Banerjee, D.

    2017-12-01

    Amorphous carbon nanotubes (a-CNTs) manganese di oxide (MnO2)-poly pyrrole (PPy) ternary nanocomposites have been synthesized by a simple chemical route. The as prepared samples have been characterized with different characterization tools that include field emission scanning and high resolution transmission electron microscopy, Raman, Fourier transformed infrared as well as UV-Vis spectroscopy. The electrochemical performance of all the as prepared pure and hybrid samples have been studied in detail. It has been seen that the ternary hybrid shows efficient electrochemical performance with high value of specific capacitance with good stability even up to 2000 cycles. The superior performance of the hybrid samples can be attributed to the strong synergistic effect between the components resulting electron shuttling along PPy main chains and inter-chain raising built-in continuous conductive network. The ternary composite approach offers an effective solution to enhance the device performance of metal-oxide based supercapacitors for long cycling applications. These studies can well speculate the existence of another supercapacitor hybrid for the use in environment friendly electrode and thus a pollution free nature.

  5. Thermodynamic analysis of a combined-cycle solar thermal power plant with manganese oxide-based thermochemical energy storage

    Science.gov (United States)

    Lei, Qi; Bader, Roman; Kreider, Peter; Lovegrove, Keith; Lipiński, Wojciech

    2017-11-01

    We explore the thermodynamic efficiency of a solar-driven combined cycle power system with manganese oxide-based thermochemical energy storage system. Manganese oxide particles are reduced during the day in an oxygen-lean atmosphere obtained with a fluidized-bed reactor at temperatures in the range of 750-1600°C using concentrated solar energy. Reduced hot particles are stored and re-oxidized during night-time to achieve continuous power plant operation. The steady-state mass and energy conservation equations are solved for all system components to calculate the thermodynamic properties and mass flow rates at all state points in the system, taking into account component irreversibilities. The net power block and overall solar-to-electric energy conversion efficiencies, and the required storage volumes for solids and gases in the storage system are predicted. Preliminary results for a system with 100 MW nominal solar power input at a solar concentration ratio of 3000, designed for constant round-the-clock operation with 8 hours of on-sun and 16 hours of off-sun operation and with manganese oxide particles cycled between 750 and 1600°C yield a net power block efficiency of 60.0% and an overall energy conversion efficiency of 41.3%. Required storage tank sizes for the solids are estimated to be approx. 5-6 times smaller than those of state-of-the-art molten salt systems.

  6. Thermodynamic analysis of a combined-cycle solar thermal power plant with manganese oxide-based thermochemical energy storage

    Directory of Open Access Journals (Sweden)

    Lei Qi

    2017-01-01

    Full Text Available We explore the thermodynamic efficiency of a solar-driven combined cycle power system with manganese oxide-based thermochemical energy storage system. Manganese oxide particles are reduced during the day in an oxygen-lean atmosphere obtained with a fluidized-bed reactor at temperatures in the range of 750–1600°C using concentrated solar energy. Reduced hot particles are stored and re-oxidized during night-time to achieve continuous power plant operation. The steady-state mass and energy conservation equations are solved for all system components to calculate the thermodynamic properties and mass flow rates at all state points in the system, taking into account component irreversibilities. The net power block and overall solar-to-electric energy conversion efficiencies, and the required storage volumes for solids and gases in the storage system are predicted. Preliminary results for a system with 100 MW nominal solar power input at a solar concentration ratio of 3000, designed for constant round-the-clock operation with 8 hours of on-sun and 16 hours of off-sun operation and with manganese oxide particles cycled between 750 and 1600°C yield a net power block efficiency of 60.0% and an overall energy conversion efficiency of 41.3%. Required storage tank sizes for the solids are estimated to be approx. 5–6 times smaller than those of state-of-the-art molten salt systems.

  7. The Impacts of Graphene Nanosheets and Manganese Valency on Lithium Storage Characteristics in Graphene/Manganese Oxide Hybrid Anode

    Directory of Open Access Journals (Sweden)

    S. L. Cheekati

    2012-01-01

    Full Text Available Graphene nanosheets (GNS with attached MnOx nanoparticles are studied in regard to their structure and morphology. The relationship between the lithium storage performances and GNS contents as well as manganese valency was investigated. Experimental results showed that the specimen with 44 wt% GNS and high content of MnO delivered high reversible capacity (over twice of that in graphitic carbon anode, good cycling stability (0.8% fading per cycle, and high rate capability (67% at the 800 mA/g, which are dramatically better than pure Mn3O4. The improvement is attributed to the presence of GNS which provides continuous networks for fast electronic conduction and mechanical flexibility for accommodating the large volume change. The MnOx/GNS hybrid material has the added advantages over pure GNS, benefiting from its lithium storage potential of around 0.5 V which not only ensures high rate capability but also reduces the risk of metallic lithium formation with its safety hazard.

  8. Influence of modelled soil biogenic NO emissions on related trace gases and the atmospheric oxidizing capacity

    NARCIS (Netherlands)

    Steinkamp, J.; Ganzeveld, L.N.; Wilcke, W.; Lawrence, M.G.

    2009-01-01

    The emission of nitric oxide (NO) by soils (SNOx) is an important source of oxides of nitrogen (NOx=NO+NO2) in the troposphere, with estimates ranging from 4 to 21 Tg of nitrogen per year. Previous studies have examined the influence of SNOx on ozone (O-3) chemistry. We employ the ECHAM5/MESSy

  9. Durability of carbon-supported manganese oxide nanoparticles for the oxygen reduction reaction (ORR) in alkaline medium

    Czech Academy of Sciences Publication Activity Database

    Roche, I.; Chainet, E.; Chatenet, M.; Vondrák, Jiří

    2008-01-01

    Roč. 38, č. 9 (2008), s. 1195-1201 ISSN 0021-891X R&D Projects: GA AV ČR KJB4813302; GA ČR GA104/02/0731 Grant - others:CNRS(FR) 18105 Institutional research plan: CEZ:AV0Z40320502 Keywords : oxygen reduction reaction * rotating ring-disc electrode * carbon-supported manganese oxide Subject RIV: CA - Inorganic Chemistry Impact factor: 1.540, year: 2008

  10. Covalent Hybrid of Spinel Manganese-Cobalt Oxide and Gra-phene as Advanced Oxygen Reduction Electrocatalysts

    OpenAIRE

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

    2012-01-01

    Through direct nanoparticle nucleation and growth on nitrogen doped, reduced graphene oxide sheets and cation substitution of spinel Co3O4 nanoparticles, a manganese-cobalt spinel MnCo2O4/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 hybrid results in covalent coupl...

  11. The role of electronic and ionic conductivities in the rate performance of tunnel structured manganese oxides in Li-ion batteries

    Directory of Open Access Journals (Sweden)

    B. W. Byles

    2016-04-01

    Full Text Available Single nanowires of two manganese oxide polymorphs (α-MnO2 and todorokite manganese oxide, which display a controlled size variation in terms of their square structural tunnels, were isolated onto nanofabricated platforms using dielectrophoresis. This platform allowed for the measurement of the electronic conductivity of these manganese oxides, which was found to be higher in α-MnO2 as compared to that of the todorokite phase by a factor of ∼46. Despite this observation of substantially higher electronic conductivity in α-MnO2, the todorokite manganese oxide exhibited better electrochemical rate performance as a Li-ion battery cathode. The relationship between this electrochemical performance, the electronic conductivities of the manganese oxides, and their reported ionic conductivities is discussed for the first time, clearly revealing that the rate performance of these materials is limited by their Li+ diffusivity, and not by their electronic conductivity. This result reveals important new insights relevant for improving the power density of manganese oxides, which have shown promise as a low-cost, abundant, and safe alternative for next-generation cathode materials. Furthermore, the presented experimental approach is suitable for assessing a broader family of one-dimensional electrode active materials (in terms of their electronic and ionic conductivities for both Li-ion batteries and for electrochemical systems utilizing charge-carrying ions beyond Li+.

  12. Electrical characterization of a laminar manganese oxide type birnessite; Caracterizacion electrica de un oxido de manganeso laminar tipo birnesita

    Energy Technology Data Exchange (ETDEWEB)

    Arias, N. P.; Becerra, M. E.; Giraldo, O., E-mail: ohgiraldoo@unal.edu.co [Universidad Nacional de Colombia, Sede Manizales, Facultad de Ciencias Exactas y Naturales, Laboratorio de Materiales Nanoestructurados y Funcionales, Carrera 27 No. 64-60, 170004 Manizales (Colombia)

    2015-07-01

    This paper records the characterization of a manganese oxide synthesized by solid state routes which is analogous to natural mineral called birnessite. The analysis of X-ray diffraction and average oxidation state of manganese show that the material has a lamellar structure containing manganese in oxidation states (+4) and (+3). The results of electron microscopy along with surface area and pore size measurements reveal the presence of micro and meso pores in the material. Impedance spectroscopy suggests that high frequency electrical conduction occurs in the volume and on the border of the aggregates; in contrast, ionic conductivity at low frequencies was associated with potassium ions located in the interlaminar region. Ac conductivity values at low frequencies were 1.599 x 10{sup -6} Ω{sup -1} cm{sup -1} and 6.416 x 10{sup -5} Ω{sup -1} cm{sup -1} at high frequencies. These values are associated with an increased probability of electron jumping as frequency increases. These findings contribute to the understanding of electrical conduction processes and provides important information about its potential applications. As a result, this research will prove relevant in the field of batteries, super capacitors and heterogeneous catalysis, among others. (Author)

  13. Biogenic Emission Inventory System (BEIS)

    Science.gov (United States)

    Biogenic Emission Inventory System (BEIS) estimates volatile organic compound (VOC) emissions from vegetation and nitric oxide (NO) emission from soils. Recent BEIS development has been restricted to the SMOKE system

  14. Solar-thermal Water Splitting Using the Sodium Manganese Oxide Process & Preliminary H2A Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Francis, Todd M; Lichty, Paul R; Perkins, Christopher; Tucker, Melinda; Kreider, Peter B; Funke, Hans H; Lewandowski, A; Weimer, Alan W

    2012-10-24

    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.

  15. Microwave assisted synthesis of manganese mixed oxide nanostructures using plastic templates

    Science.gov (United States)

    Leyva, A. G.; Stoliar, P.; Rosenbusch, M.; Lorenzo, V.; Levy, P.; Albonetti, C.; Cavallini, M.; Biscarini, F.; Troiani, H. E.; Curiale, J.; Sanchez, R. D.

    2004-11-01

    The synthesis method for obtaining sub-micrometric structures of rare earth manganese-based mixed oxide compounds is described. Pore wetting of porous polycarbonate templates with the liquid precursor was followed by a two-stage thermal treatment to obtain single phase La 0.325Pr 0.300Ca 0.375MnO 3 hollow and solid structures, with external diameter determined by the sacrificial template pore size. The first thermal stage, a microwave assisted denitration process, determines the shape of the structures. The second treatment, performed at 1073 K, allows to obtain the crystallographic structure of the compound. A variety of techniques (scanning and transmission electron microscopy, scanning probe microscopy) allowed to fully characterize the microstructure and morphology of these self-standing manganite nanostructures. For 1 μm pore size templates we obtained tubes, with external diameter around 800 nm and wall thickness around 150 nm; densely packed nanoparticles sized 20-50 nm are the building blocks of the walls. For pore size below 0.1 μm, solid nanowires were obtained, the size of constituent crystallites being around 10 nm. Overall obtained material exhibits ferromagnetic ordering below 200 K.

  16. Novel proximity effect between high-Tc superconductor and magnetic manganese oxide

    International Nuclear Information System (INIS)

    Kozono, Y.; Kasai, M.; Kanke, Y.; Ohno, T.; Hanazono, M.; Sugita, Y.

    1991-01-01

    A novel proximity effect between high-Tc superconductor and magnetic manganese oxide has been found. Supercurrents were observed through La 0.7 Ca 0.3 MnO z (LCMO) magnetic barrier as thick as 500 nm in YBCO/LCMO/YBCO trilayered junctions. We confirmed this proximity effect in coplanar-type junctions with spacing of 200 nm, and presented a possibility that this phenomenon occurs between NbN and LCMO. Furthermore we investigated current-voltage (I-V) characteristics and magnetic properties for Y 1 Ba 2 Cu 3 O y /La 1-x Sr x MnO z (200nm)/Y 1 Ba 2 Cu 3 O y (YBCO/LSMO/YBCO) junctions. I-V characteristics changed systematically with varying the magnetism of the barrier. When x value was 0.2, supercurrents passed through the barrier, and it was found that ferromagnetism (Ms=135emu/cc) and supercurrents coexist in this proximity state. Magnetism of the LSMO is understood as a complicated and fluctuated state of ferromagnetic coupling in a-b plane and antiferromagnetic coupling along c-axis. Considering supercurrents passed through the La 1-x Sr x (Mn 3+ 1-x Mn 4+ x )O z along c-axis, our results suggest a novel proximity effect mechanism, that is antiferromagnetic spin fluctuation and charge fluctuation can transport Cooper-pairs over a long range. (orig.)

  17. Synthesis of manganese oxides and antimony silicates and their applications to take up Thorium-234

    International Nuclear Information System (INIS)

    Al-Attar, L.; Budeir, Y.

    2009-07-01

    Birnessite, a layered manganese oxide, antimonysilicate and their corresponding cation-exchange derivatives were tested for their ability to take up thorium using a batch-type method. Sorption experiments were performed in different concentrations of acid, and sodium, potassium and calcium nitrate solutions in order to evaluate the influence of cations likely to be present in waste effluents. The results were expressed in terms of distribution coefficients. Linear regressions of the logarithmic plots enabled the elucidation of exchange mechanisms. Variation in the magnitude and mechanism of thorium sorption on the exchangers was ascribed to structural differences and the exchange properties of the materials, as well as the aqueous chemistry of the actinide element. The work expanded to included investigation of thorium solution' pH in controlling the sorption process. In nitric acid solutions, H-antimonysilicate proved to be the best sorbent. The hydrated layer structure of birnessite allows for facile mobility of the interlayer cations with fast kinetics and little structural rearrangement, making it of great importance for intercalation and ion exchange uses in salt conditions. Potassium had the most, and calcium the least, effect on thorium selectivity by birnessites, when they are present as macro components. Conversely, calcium ions did greatly inhibit the sorption behaviour of the actinide on Ca-doped antimonysilicate. Studying the effect of thorium solution' pH reflected the microcrystal modifications of birnessites occurred during experiments. (authors)

  18. Solid-phase photocatalytic degradation of polyethylene film with manganese oxide OMS-2

    Science.gov (United States)

    Liu, Guanglong; Liao, Shuijiao; Zhu, Duanwei; Cui, Jingzhen; Zhou, Wenbing

    2011-01-01

    Solid-phase photocatalytic degradation of polyethylene (PE) film with cryptomelane-type manganese oxide (OMS-2) as photocatalyst was investigated in the ambient air under ultraviolet and visible light irradiation. The properties of the composite films were compared with those of the pure PE film through performing weight loss monitoring, IR spectroscopy, scanning electron microscopic (SEM) and X-ray photoelectron spectroscopy (XPS). The photoinduced degradation of PE-OMS-2 composite films was higher than that of the pure films, while there has been little change under the visible light irradiation. The weight loss of PE-OMS-2 (1.0 wt%) composite films steadily decreased and reached 16.5% in 288 h under UV light irradiation. Through SEM observation there were some cavities on the surface of composite films, but few change except some surface chalking phenomenon occurred in pure PE film. The degradation rate with ultraviolet irradiation is controllable by adjusting the content of OMS-2 particles in PE plastic. Finally, the mechanism of photocatalytic degradation of the composite films was briefly discussed.

  19. Large coercivity and unconventional exchange coupling in manganese-oxide-coated manganese—gallium nanoparticles

    International Nuclear Information System (INIS)

    Feng Jun-Ning; Liu Wei; Geng Dian-Yu; Ma Song; Yu Tao; Zhao Xiao-Tian; Dai Zhi-Ming; Zhao Xin-Guo; Zhang Zhi-Dong

    2014-01-01

    The microstructures and magnetic properties of nanoparticles, each composed of an antiferromagnetic (AFM) manganese-oxide shell and a ferromagnetic-like core of manganese—gallium (MnGa) compounds, are studied. The core-shell structure is confirmed by transmission electron microscope (TEM). The ferromagnetic-like core contains three kinds of MnGa binary compounds, i.e., ferrimagnetic (FI) D0 22 -type Mn 3 Ga, ferromagnetic (FM) Mn 8 Ga 5 , and AFM D0 19 -type Mn 3 Ga, of which the first two correspond respectively to a hard magnetic phase and to a soft one. Decoupling effect between these two phases is found at low temperature, which weakens gradually with increasing temperature and disappears above 200 K. The exchange bias (EB) effect is observed simultaneously, which is caused by the exchange coupling between the AFM shell and FM-like core. A large coercivity of 6.96 kOe (1 Oe = 79.5775 A·m −1 ) and a maximum EB value of 0.45 kOe are achieved at 300 K and 200 K respectively. (special topic — international conference on nanoscience and technology, china 2013)

  20. Quantum Femtosecond Magnetism: Phase Transition in Step with Light in a Strongly Correlated Manganese Oxide

    Science.gov (United States)

    Wang, Jigang

    2014-03-01

    Research of non-equilibrium phase transitions of strongly correlated electrons is built around addressing an outstanding challenge: how to achieve ultrafast manipulation of competing magnetic/electronic phases and reveal thermodynamically hidden orders at highly non-thermal, femtosecond timescales? Recently we reveal a new paradigm called quantum femtosecond magnetism-photoinduced femtosecond magnetic phase transitions driven by quantum spin flip fluctuations correlated with laser-excited inter-atomic coherent bonding. We demonstrate an antiferromagnetic (AFM) to ferromagnetic (FM) switching during about 100 fs laser pulses in a colossal magneto-resistive manganese oxide. Our results show a huge photoinduced femtosecond spin generation, measured by magnetic circular dichroism, with photo-excitation threshold behavior absent in the picosecond dynamics. This reveals an initial quantum coherent regime of magnetism, while the optical polarization/coherence still interacts with the spins to initiate local FM correlations that compete with the surrounding AFM matrix. Our results thus provide a framework that explores quantum non-equilibrium kinetics to drive phase transitions between exotic ground states in strongly correlated elecrons, and raise fundamental questions regarding some accepted rules, such as free energy and adiabatic potential surface. This work is in collaboration with Tianqi Li, Aaron Patz, Leonidas Mouchliadis, Jiaqiang Yan, Thomas A. Lograsso, Ilias E. Perakis. This work was supported by the National Science Foundation (contract no. DMR-1055352). Material synthesis at the Ames Laboratory was supported by the US Department of Energy-Basic Energy Sciences (contract no. DE-AC02-7CH11358).

  1. Promotion effect of manganese oxide on the electrocatalytic activity of Pt/C for methanol oxidation in acid medium

    Energy Technology Data Exchange (ETDEWEB)

    Abdel Hameed, R.M., E-mail: randa311eg@yahoo.com [Chemistry Department, Faculty of Science, Cairo University, Giza (Egypt); Fetohi, Amani E.; Amin, R.S.; El-Khatib, K.M. [Chemical Engineering Department, National Research Center, Dokki, Giza (Egypt)

    2015-12-30

    Graphical abstract: Physical and electrochemical properties of Pt/C, Pt–MnO{sub 2}/C-1 and Pt–MnO{sub 2}/C-2 electrocatalysts. - Highlights: • Adding MnO{sub 2} to Pt/C improved the dispersion of Pt nanoparticles. • The existence of MnO{sub 2} improved the kinetics of methanol oxidation reaction. • R{sub ct} value of Pt–MnO{sub 2}/C was about 10 times as low as that at Pt/C. • The removal of CO{sub ads} poisoning species was facilitated at Pt–MnO{sub 2}/C. - Abstract: The modification of Pt/C by incorporating metal oxides for electrocatalytic oxidation of methanol has gained major attention because of the efficiency loss during the course of long-time operation. This work describes the preparation of Pt–MnO{sub 2}/C electrocatalysts through a chemical route using ethylene glycol or a mixture of ethylene glycol and sodium borohydride as a reducing agent. The crystallite structure and particle size of synthesized electrocatalysts are determined using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The addition of MnO{sub 2} improves the dispersion of Pt nanoparticles. The electrocatalytic activity of Pt–MnO{sub 2}/C towards methanol oxidation in H{sub 2}SO{sub 4} solution is investigated using cyclic voltammetry and electrochemical impedance spectroscopy. The onset potential value of methanol oxidation peak is negatively shifted by 169 mV when MnO{sub 2} is introduced to Pt/C. Moreover, the charge transfer resistance value at Pt–MnO{sub 2}/C is about 10 times as low as that at Pt/C. Chronoamperometry and chronopotentiometry show that CO tolerance is greatly improved at Pt–MnO{sub 2}/C. The increased electrocatalytic activity and enhanced ability to clean platinum surface elect manganese oxide as a suitable promoter for the anode performance in direct methanol fuel cells (DMFCs).

  2. In situ synthesis of manganese oxides on polyester fiber for formaldehyde decomposition at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jinlong [State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084 (China); Collaborative Innovation Center for Regional Environmental Quality (China); Yunus, Rizwangul [State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084 (China); Xinjiang Zhongtai Chemical Company, Xinjiang 831511 (China); Li, Jinge; Li, Peilin [State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084 (China); Zhang, Pengyi, E-mail: zpy@tsinghua.edu.cn [State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084 (China); Collaborative Innovation Center for Regional Environmental Quality (China); Kim, Jeonghyun [State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084 (China); Collaborative Innovation Center for Regional Environmental Quality (China)

    2015-12-01

    Graphical abstract: - Highlights: • The MnO{sub x} particles assembled with nanosheets were uniformly coated on PET fibers. • The growth process of MnO{sub x} layer on PET is clearly clarified. • MnO{sub x}/PET showed good activity for HCHO decomposition at room temperature. • MnO{sub x}/PET material is promising for indoor air purification due to its light, flexible and low air-resistant properties. - Abstract: Removal of low-level formaldehyde (HCHO) is of great interest for indoor air quality improvement. Supported materials especially those with low air pressure drop are of necessity for air purification. Manganese oxides (MnO{sub x}) was in situ deposited on the surface of fibers of a non-woven fabric made of polyethylene terephthalate (PET). As-synthesized MnO{sub x}/PET were characterized by SEM, XRD, TEM, ATR-FTIR and XPS analysis. The growth of MnO{sub x} layer on PET is thought to start with partial hydrolysis of PET, followed by surface oxidation by KMnO{sub 4} and then surface-deposition of MnO{sub x} particles from the bulk phase. The MnO{sub x} particles assembled with nanosheets were uniformly coated on the PET fibers. MnO{sub x}/PET showed good activity for HCHO decomposition at room temperature which followed the Mars–van Krevelen mechanism. The removal of HCHO was kept over 94% after 10 h continuous reaction under the conditions of inlet HCHO concentration ∼0.6 mg/m{sup 3}, space velocity ∼17,000 h{sup −1} and relative humidity∼50%. This research provides a facile method to deposit active MnO{sub x} onto polymers with low air resistance, and composite MnO{sub x}/PET material is promising for indoor air purification.

  3. A study on the reaction characteristics of vanadium-impregnated natural manganese oxide in ammonia selective catalytic reduction.

    Science.gov (United States)

    Kim, Sung Su; Lee, Sang Moon; Park, Kwang Hee; Kwon, Dong Wook; Hong, Sung Chang

    2011-05-01

    This study investigated the effect of adding vanadium (V) to natural manganese oxide (NMO) in ammonia (NH3) selective catalytic reduction (SCR). The addition of V to NMO decreased the catalytic activity at low temperatures by blocking the active site. However, the enhancement of catalytic activity was achieved by controlling NH3 oxidation at high temperatures. From the NH3 temperature programmed desorption and oxygen on/off test, it was confirmed that the amount of Lewis acid site and active lattice oxygen of the catalyst affects the catalytic performance at low temperature.

  4. Tailor-made ultrathin manganese oxide nanostripes: ‘magic widths’ on Pd(1 1 N) terraces

    Science.gov (United States)

    Franchini, C.; Li, F.; Surnev, S.; Podloucky, R.; Allegretti, F.; Netzer, F. P.

    2012-02-01

    The growth of ultrathin two-dimensional manganese oxide nanostripes on vicinal Pd(1 1 N) surfaces leads to particular stable configurations for certain combinations of oxide stripe and substrate terrace widths. Scanning tunneling microscopy and high-resolution low-energy electron diffraction measurements reveal highly ordered nanostructured surfaces with excellent local and long-range order. Density functional theory calculations provide the physical origin of the stabilization mechanism of ‘magic width’ stripes in terms of a finite-size effect, caused by the significant relaxations observed at the stripe boundaries.

  5. Revealing biogenic sulfuric acid corrosion in sludge digesters: detection of sulfur-oxidizing bacteria within full-scale digesters.

    Science.gov (United States)

    Huber, B; Drewes, J E; Lin, K C; König, R; Müller, E

    2014-01-01

    Biogenic sulfuric acid corrosion (BSA) is a costly problem affecting both sewerage infrastructure and sludge handling facilities such as digesters. The aim of this study was to verify BSA in full-scale digesters by identifying the microorganisms involved in the concrete corrosion process, that is, sulfate-reducing (SRB) and sulfur-oxidizing bacteria (SOB). To investigate the SRB and SOB communities, digester sludge and biofilm samples were collected. SRB diversity within digester sludge was studied by applying polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) targeting the dsrB-gene (dissimilatory sulfite reductase beta subunit). To reveal SOB diversity, cultivation dependent and independent techniques were applied. The SRB diversity studies revealed different uncultured SRB, confirming SRB activity and H2S production. Comparable DGGE profiles were obtained from the different sludges, demonstrating the presence of similar SRB species. By cultivation, three pure SOB strains from the digester headspace were obtained including Acidithiobacillus thiooxidans, Thiomonas intermedia and Thiomonas perometabolis. These organisms were also detected with PCR-DGGE in addition to two new SOB: Thiobacillus thioparus and Paracoccus solventivorans. The SRB and SOB responsible for BSA were identified within five different digesters, demonstrating that BSA is a problem occurring not only in sewer systems but also in sludge digesters. In addition, the presence of different SOB species was successfully associated with the progression of microbial corrosion.

  6. Ozone reactivity of biogenic volatile organic compound (BVOC) emissions during the Southeast Oxidant and Aerosol Study (SOAS)

    Science.gov (United States)

    Park, J.; Guenther, A. B.; Helmig, D.

    2013-12-01

    Recent studies on atmospheric chemistry in the forest environment showed that the total reactivity by biogenic volatile organic compound (BVOC) emission is still not well understood. During summer 2013, an intensive field campaign (Southeast Oxidant and Aerosol Study - SOAS) took place in Alabama, U.S.A. In this study, an ozone reactivity measurement system (ORMS) was deployed for the direct determination of the reactivity of foliage emissions. The ORMS is a newly developed measurement approach, in which a known amount of ozone is added to the ozone-free air sample stream, with the ORMS measuring ozone concentration difference between before and after a glass flask flow tube reaction vessel (2-3 minutes of residence time). Emissions were also collected onto adsorbent cartridges to investigate the discrepancy between total ozone reactivity observation and reactivity calculated from identified BVOC. Leaf and canopy level experiments were conducted by deploying branch enclosures on the three dominant tree species at the site (i.e. liquidambar, white oak, loblolly pine) and by sampling ambient air above the forest canopy. For the branch enclosure experiments, BVOC emissions were sampled from a 70 L Teflon bag enclosure, purged with air scrubbed for ozone, nitrogen oxides. Each branch experiment was performed for 3-5 days to collect at least two full diurnal cycle data. In addition, BVOCs were sampled using glass tube cartridges for 2 hours during daytime and 3 - 4 hours at night. During the last week of campaign, the inlet for the ORMS was installed on the top of scaffolding tower (~30m height). The ozone loss in the reactor showed distinct diurnal cycle for all three tree species investigated, and ozone reactivity followed patterns of temperature and light intensity.

  7. Oxidation Products of Biogenic Emissions Contribute to Nucleation of Atmospheric Particles

    CERN Document Server

    Riccobono, Francesco; Baltensperger, Urs; Worsnop, Douglas R; Curtius, Joachim; Carslaw, Kenneth S; Wimmer, Daniela; Wex, Heike; Weingartner, Ernest; Wagner, Paul E; Vrtala, Aron; Viisanen, Yrjö; Vaattovaara, Petri; Tsagkogeorgas, Georgios; Tomé, Antonio; Stratmann, Frank; Stozhkov, Yuri; Spracklen, Dominick V; Sipilä, Mikko; Praplan, Arnaud P; Petäjä, Tuukka; Onnela, Antti; Nieminen, Tuomo; Mathot, Serge; Makhmutov, Vladimir; Lehtipalo, Katrianne; Laaksonen, Ari; Kvashin, Alexander N.; Kürten, Andreas; Kupc, Agnieszka; Keskinen, Helmi; Kajos, Maija; Junninen, Heikki; Hansel, Armin; Franchin, Alessandro; Flagan, Richard C; Ehrhart, Sebastian; Duplissy, Jonathan; Dunne, Eimear M; Downard, Andrew; David, André; Breitenlechner, Martin; Bianchi, Federico; Amorim, Antonio; Almeida, João; Rondo, Linda; Ortega, Ismael K; Dommen, Josef; Scott, Catherine E; Vrtala, Aron; Santos, Filipe D; Schallhart, Simon; Seinfeld, John H; Sipila, Mikko; Donahue, Neil M; Kirkby, Jasper; Kulmala, Markku

    2014-01-01

    Atmospheric new-particle formation affects climate and is one of the least understood atmospheric aerosol processes. The complexity and variability of the atmosphere has hindered elucidation of the fundamental mechanism of new-particle formation from gaseous precursors. We show, in experiments performed with the CLOUD (Cosmics Leaving Outdoor Droplets) chamber at CERN, that sulfuric acid and oxidized organic vapors at atmospheric concentrations reproduce particle nucleation rates observed in the lower atmosphere. The experiments reveal a nucleation mechanism involving the formation of clusters containing sulfuric acid and oxidized organic molecules from the very first step. Inclusion of this mechanism in a global aerosol model yields a photochemically and biologically driven seasonal cycle of particle concentrations in the continental boundary layer, in good agreement with observations.

  8. Oxidation products of biogenic emissions contribute to nucleation of atmospheric particles.

    Science.gov (United States)

    Riccobono, Francesco; Schobesberger, Siegfried; Scott, Catherine E; Dommen, Josef; Ortega, Ismael K; Rondo, Linda; Almeida, João; Amorim, Antonio; Bianchi, Federico; Breitenlechner, Martin; David, André; Downard, Andrew; Dunne, Eimear M; Duplissy, Jonathan; Ehrhart, Sebastian; Flagan, Richard C; Franchin, Alessandro; Hansel, Armin; Junninen, Heikki; Kajos, Maija; Keskinen, Helmi; Kupc, Agnieszka; Kürten, Andreas; Kvashin, Alexander N; Laaksonen, Ari; Lehtipalo, Katrianne; Makhmutov, Vladimir; Mathot, Serge; Nieminen, Tuomo; Onnela, Antti; Petäjä, Tuukka; Praplan, Arnaud P; Santos, Filipe D; Schallhart, Simon; Seinfeld, John H; Sipilä, Mikko; Spracklen, Dominick V; Stozhkov, Yuri; Stratmann, Frank; Tomé, Antonio; Tsagkogeorgas, Georgios; Vaattovaara, Petri; Viisanen, Yrjö; Vrtala, Aron; Wagner, Paul E; Weingartner, Ernest; Wex, Heike; Wimmer, Daniela; Carslaw, Kenneth S; Curtius, Joachim; Donahue, Neil M; Kirkby, Jasper; Kulmala, Markku; Worsnop, Douglas R; Baltensperger, Urs

    2014-05-16

    Atmospheric new-particle formation affects climate and is one of the least understood atmospheric aerosol processes. The complexity and variability of the atmosphere has hindered elucidation of the fundamental mechanism of new-particle formation from gaseous precursors. We show, in experiments performed with the CLOUD (Cosmics Leaving Outdoor Droplets) chamber at CERN, that sulfuric acid and oxidized organic vapors at atmospheric concentrations reproduce particle nucleation rates observed in the lower atmosphere. The experiments reveal a nucleation mechanism involving the formation of clusters containing sulfuric acid and oxidized organic molecules from the very first step. Inclusion of this mechanism in a global aerosol model yields a photochemically and biologically driven seasonal cycle of particle concentrations in the continental boundary layer, in good agreement with observations. Copyright © 2014, American Association for the Advancement of Science.

  9. Synthesis of single crystal manganese oxide octahedral molecular sieve (OMS) nanostructures with tunable tunnels and shapes.

    Science.gov (United States)

    Li, Wei-Na; Yuan, Jikang; Gomez-Mower, Sinue; Sithambaram, Shantakumar; Suib, Steven L

    2006-02-23

    A new and facile route is reported to manipulate the self-assembly synthesis of hierarchically ordered Rb-OMS-2 and pyrolusite with an interesting flowerlike morphology by a direct and mild reaction between rubidium chromateand manganese sulfate without any organic templates. The crystal forms, morphologies, and tunnel sizes of the obtained OMS materials can be controlled. A mechanism for the growth of manganese dioxides with flowerlike architectures was proposed. The obtained products exhibit potential for use in catalysis and other applications.

  10. Characterization of the Fe-Doped Mixed-Valent Tunnel Structure 2 Manganese Oxide KOMS-2

    Energy Technology Data Exchange (ETDEWEB)

    Hanson J. C.; Shen X.; Morey A.M.; Liu J.; Ding Y.; Cai J.; Durand J.; Wang Q.; Wen W.; Hines W.A.; Bai J.; Frenkel A.I.; Reiff W.; Aindow M.; Suib S.L.

    2011-11-10

    A sol-gel-assisted combustion method was used to prepare Fe-doped manganese oxide octahedral molecular sieve (Fe-KOMS-2) materials with the cryptomelane structure. Characterization of the nanopowder samples over a wide range of Fe-doping levels (0 {le} Fe/Mn {le} 1/2) was carried out using a variety of experimental techniques. For each sample, Cu K{alpha} XRD and ICP-AES were used to index the cryptomelane structure and determine the elemental composition, respectively. A combination of SEM and TEM images revealed that the morphology changes from nanoneedle to nanorod after Fe doping. Furthermore, TGA scans indicated that the thermal stability is also enhanced with the doping. Anomalous XRD demonstrated that the Fe ions replace the Mn ions in the cryptomelane structure, particularly in the (211) planes, and results in a lattice expansion along the c axis, parallel to the tunnels. Reasonable fits to EXAFS data were obtained using a model based on the cryptomelane structure. Moessbauer spectra for selected Fe-KOMS-2 samples indicated that the Fe is present as Fe{sup 3+} in an octahedral environment similar to Mn in the MnO{sub 6} building blocks of KOMS-2. Magnetization measurements detected a small amount of {gamma}-Fe{sub 2}O{sub 3} second phase (e.g., 0.6 wt % for the Fe/Mn = 1/10 sample), the vast majority of the Fe being in the structure as Fe{sup 3+} in the high-spin state.

  11. Electrospun manganese (III) oxide nanofiber based electrochemical DNA-nanobiosensor for zeptomolar detection of dengue consensus primer.

    Science.gov (United States)

    Tripathy, Suryasnata; Krishna Vanjari, Siva Rama; Singh, Vikrant; Swaminathan, S; Singh, Shiv Govind

    2017-04-15

    Nanoscale biosensors, owing to their high-sensitivity and extremely low limits-of-detection, have enabled the realization of highly complex and sophisticated miniaturized platforms for several important healthcare applications, the most predominant one being disease diagnosis. In particular, nanomaterial facilitated electrochemical detection of DNA hybridization has had an exceptional impact on fields such as genetics and cancerous mutation detection Here we report an ultrasensitive electrochemical platform using electrospun semi-conducting Manganese (III) Oxide (Mn 2 O 3 ) nanofibers for DNA Hybridization detection. The proposed platform coalesces the inherent advantages of metal-oxide nanofibers and electrochemical transduction techniques, resulting in label-free zeptomolar detection of DNA hybridization. As proof of concept, we demonstrate zeptomolar detection of Dengue consensus primer (limit of detection: 120×10 -21 M) both in control as well as spiked serum samples. Our reported detection limit is superior in comparison with previously reported electrochemical DNA hybridization sensors for Dengue virus detection, spanning both labeled and label-free transductions. This ultra-sensitivity, we believe, is a result of synthesizing a low bandgap electrospun metal-oxide nanomaterial corresponding to a specific oxidation state of Manganese. This methodology can be extended for detection of any hybridization of interest by simply adapting an appropriate functionalization protocol and thus is very generic in nature. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Electrochemically active manganese oxides: structural modelling, modifications induced by thermal processing and photon insertion

    International Nuclear Information System (INIS)

    Ripert, Michel

    1990-01-01

    The objective of this research study is to understand the mechanism of proton insertion into manganese dioxide. It comprised the performances of in situ discharges of two commercial samples in an electrochemical cell designed for this purpose. In order to characterise the structure of electrochemically active manganese dioxides, and particularly to elucidate the orthorhombic-hexagonal dilemma, the author proposes a crystalline-chemical approach which comprises the development of a unique structural model which takes the structure of all forms of electrochemically active manganese dioxides into account, and a numerical simulation of diffraction diagrams (X rays and neutrons) of these structures. The development of this modelling results in the development of a method which allows, from experimental diffraction diagrams, characteristic structural parameters of each sample of EMD (electrolytic manganese dioxide) or CMD (chemical manganese dioxide) to be obtained. Moreover, the observation of the structural evolution of the dioxide is possible by using in situ neutron diffraction. Reduction has been studied by using slow potential scanning voltammetry. By using these both techniques (neutron diffraction and voltammetry), it is possible to explain the structural mechanism of reduction of MnO 2 and to show the origin of the non-reversibility of the proton/MnO 2 system, to quantitatively explain the shape voltammetry curves, and to highlight experimentally for the first time the different sites of insertion of the proton

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

    Science.gov (United States)

    Bobay, Keith E.

    1986-01-01

    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

  14. Biogenic concrete protection driven by the formate oxidation by Methylocystis parvus OBBP

    Directory of Open Access Journals (Sweden)

    Giovanni eGanendra

    2015-08-01

    Full Text Available The effectiveness of Microbiologically Induced Carbonate Precipitation (MICP from the formate oxidation by Methylocystis parvus OBBP as an alternative process for concrete protection was investigated. MICP was induced on Autoclaved Aerated Concrete (AAC, the model material, by immersing the material in 109 M. parvus cells mL-1 containing 5 g L-1 of calcium formate. A 2 days immersion of the material gave the maximum weight increase of the specimens (38 ± 19 mg and this was likely due to the deposition of calcium carbonate, biomass, and unconverted calcium formate. The solid deposition mainly occurred in the micropores of the specimen, close to the outer surface. A significantly lower water absorption was observed in the bacterially treated specimens compared to the non-treated ones (up to 2.92 ± 0.91 kg m-2 and this could be attributed to the solid deposition. However, the sonication test demonstrated that the bacterial treatment did not give a consolidating effect to the material. Overall, compared to the currently employed urea hydrolysis process, the formate-based MICP by M. parvus offers a more environmentally friendly approach for the biotechnological application to protect concrete.

  15. Factors that influence the oxidation of the manganese in a growth of mangroves forest, Itacuruca, R J

    International Nuclear Information System (INIS)

    Canesin, F.P.; Bellido, A.V.B.; Lacerda, L.D.

    1999-01-01

    The kinetic behavior of the oxidation of the manganese in the growth of mangroves forest, Itacuruca, Sepetiba Bay, R J, have been studied through the incubation with the radiotracer Mn-54. We have observed the great influence of the factors that interferes in the rate oxidation with the mangrove state in the moment of the sampling. We applied statistical multivariate to verify the correlation with the tide height and the physical-chemical parameters. With the program Statistical Analysis System, SAS, the samples were classified by hierarchical conglomerate methods and Factor Analysis. Water samples were collected in the entrance of the tide channel in five campaigns in the months of August, September, November and December of 98, and January of 99, in several tide heights. As a conclusion, by the multivariate statistical analysis where variables correlations are presented in each group or cluster in a population. Therefore the variables that we are measuring as reflecting the influence the oxidation manganese in the mangroves. Although the variable tide height did not influence in the classification groups. We suppose that will need more sampling in different tide height cycle. (author)

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

    OpenAIRE

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

    2014-01-01

    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 o...

  17. Lithium ion adsorptive properties of spinel-type manganese oxide obtained from MnOOH and Li2CO3

    International Nuclear Information System (INIS)

    Ooi, Kenta; Miyai, Yoshitaka; Katoh, Shunsaku; Abe, Mitsuo.

    1991-01-01

    Spinel-type manganese oxides were prepared by heating a mixture of MnOOH and Li 2 CO 3 (Li/Mn = 0.5) at different temperatures followed by an acid treatment with a HCl solution. Their adsorptive properties for alkali metal ions were investigated by measurement of distribution coefficient (Kd) and by pH titration. The adsorptive properties varied depending on the heating temperature. The sample obtained at 400degC showed the highest Li + adsorptivity from seawater. (author)

  18. Synthesis of waste cooking oil based biodiesel via ferric-manganese promoted molybdenum oxide / zirconia nanoparticle solid acid catalyst: influence of ferric and manganese dopants.

    Science.gov (United States)

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

    2015-01-01

    The utilization of ferric-manganese promoted molybdenum oxide/zirconia (Fe-Mn- MoO3/ZrO2) (FMMZ) solid acid catalyst for production of biodiesel was demonstrated. FMMZ is produced through impregnation reaction followed by calcination at 600°C for 3 h. The characterization of FMMZ had been done using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), temperature programmed desorption of NH3 (TPD-NH3), transmission electron microscopy(TEM) and Brunner-Emmett-Teller (BET) surface area measurement. The effect of waste cooking oil methyl esters (WCOME's) yield on the reactions variables such as reaction temperature, catalyst loading, molar ratio of methanol/oil and reusability were also assessed. The catalyst was used to convert the waste cooking oil into corresponding methyl esters (95.6%±0.15) within 5 h at 200℃ reaction temperature, 600 rpm stirring speed, 1:25 molar ratio of oil to alcohol and 4% w/w catalyst loading. The reported catalyst was successfully recycled in six connective experiments without loss in activity. Moreover, the fuel properties of WCOME's were also reported using ASTM D 6751 methods.

  19. Metal inhibition on the reactivity of manganese dioxide toward organic contaminant oxidation in relation to metal adsorption and ionic potential.

    Science.gov (United States)

    Jiang, Jing; Wang, Zhuopu; Chen, Yang; He, Anfei; Li, Jianliang; Sheng, G Daniel

    2017-03-01

    Coexisting metal ions may significantly inhibit the oxidative reactivity of manganese oxides toward organic contaminants in metal-organic multi-pollutant waters. While the metal inhibition on the oxidation of organic contaminants by manganese oxides has previously been reported, the extent of the inhibition in relation to metal properties has not been established. Six alkali, alkaline, and transition metals, as well as two testing metals were evaluated for their abilities to inhibit the reactivity of birnessite. Regardless of the pathways of phenol and diuron oxidation (polymerization vs. breakdown), the extent of metal inhibition depended mainly on the metal itself and its concentration. The observed metal inhibition efficiency followed the order of Mn 2+  > Co 2+  > Cu 2+  > Al 3+  > Mg 2+  > K + , consistent with metal adsorption on birnessite. The first-order organic oxidation rate constant (k obs ) was linearly negatively correlated with metal adsorption (q e ) on birnessite. These observations demonstrated that the metal inhibition efficiency was determined by metal adsorption on birnessite. The slopes of the k obs -q e varied among metals and followed the order of K +  > Ca 2+  > Mg 2+  > Mn 2+  > Cd 2+  > Co 2+  > Cu 2+  > Al 3+ . These slopes defined intrinsic inhibitory abilities of metals. As metals were adsorbed hydrated on birnessite, the intrinsic inhibitory ability was significantly linearly correlated with ionic potentials of metals, leading to a single straight line. Metals with multiple d electrons in the outermost orbit with polarizing energy that promotes hydrolysis sat slightly below the line, and vice versa. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Bioaccumulation of manganese and its toxicity in feral pigeons (Columba livia) exposed to manganese oxide dust (Mn{sub 3}O{sub 4})

    Energy Technology Data Exchange (ETDEWEB)

    Sierra, P.; Chakrabarti, S.; Tounkara, R.; Loranger, S.; Kennedy, G.; Zayed, J. [Univ. of Montreal (Canada)

    1998-11-01

    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.

  1. Tris(trimethylsilyl)phosphate as electrolyte additive for self-discharge suppression of layered nickel cobalt manganese oxide

    International Nuclear Information System (INIS)

    Liao, Xiaolin; Zheng, Xiongwen; Chen, Jiawei; Huang, Ziyu; Xu, Mengqing; Xing, Lidan; Liao, Youhao; Lu, Qilun; Li, Xiangfeng; Li, Weishan

    2016-01-01

    Highlights: • TMSP is effective for self-discharge suppression of the charged NCM under 4.5 V. • TMSP oxidizes preferentially forming protective cathode interface film on NCM. • The film suppresses electrolyte decomposition and prevents NCM destruction. - Abstract: Application of layered nickel cobalt manganese oxide as cathode under higher potential than conventional 4.2 V yields a significant improvement in energy density of lithium ion battery. However, the cathode fully charged under high potential suffers serious self-discharge, in which the interaction between the cathode and electrolyte proceeds without potential limitation. In this work, we use tris(trimethylsilyl)phosphate (TMSP) as an electrolyte additive to solve this problem. A representative layered nickel cobalt manganese oxide, LiNi 1/3 Co 1/3 Mn 1/3 O 2 , is considered. The effect of TMSP on self-discharge behavior of LiNi 1/3 Co 1/3 Mn 1/3 O 2 is evaluated by physical and electrochemical methods. It is found that the self-discharge of charged LiNi 1/3 Co 1/3 Mn 1/3 O 2 can be suppressed significantly by using TMSP. TMSP is oxidized preferentially in comparison with the standard electrolyte during initial charging process forming a protective cathode interface film, which avoids the interaction between cathode and electrolyte at any potential and thus prevents electrolyte decomposition and protects LiNi 1/3 Co 1/3 Mn 1/3 O 2 from structure destruction.

  2. Dimers and organosulfates derived from biogenic oxidation products in aerosols during the Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX) in California 2007 and 2009 (Invited)

    Science.gov (United States)

    Glasius, M.; Worton, D. R.; Kristensen, K.; Nguyen, Q.; Surratt, J.; Enggrob, K. L.; Bouvier-Brown, N. C.; Farmer, D.; Docherty, K. S.; Platt, S.; Bilde, M.; Nøjgaard, J. K.; Seinfeld, J.; Jimenez, J. L.; Goldstein, A.

    2010-12-01

    Oxidation products of biogenic volatile organic compounds, such as monoterpenes and isoprene, contribute to biogenic secondary organic aerosol (BSOA). The organosulfate derivatives of these compounds are formed through heterogeneous reactions involving sulphur compounds, with a considerable contribution from anthropogenic sources. Organosulfate derivatives of biogenic oxidation products thus belong to a new group of anthropogenic enhanced biogenic SOA (ABSOA). The Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX) during summers of 2007 and 2009 provided an excellent platform at Blodgett Forest, California (a ponderosa pine plantation) for studying ABSOA. Typically, polluted air masses were transported upslope from the California Central Valley during day, while night conditions were influenced by downslope transport of air masses, low local atmospheric mixing and formation of a shallow boundary layer. We collected particle samples (PM2.5) as one nighttime and two daytime samples per day. After extraction of filters in polar organic solvents (i.e. acetonitrile or methanol), organic aerosol constituents were analyzed by HPLC coupled through an electrospray inlet to a quadrupole time-of-flight mass spectrometer (qTOF-MS). Organosulfates and nitrooxy organosulfates derived from oxidation products of α-pinene, β-pinene, limonene and isoprene were identified based on their molecular mass and MS fragmentation patterns. Measurements by High Resolution Time of Flight Aerosol Mass Spectrometry (HR-ToF-AMS) show high mass loadings of nitrate in the night and morning samples with highest levels of the nitrooxy organosulfates with MW 295 and MW 297. This may indicate that elevated levels of nitrate and nitrooxy organosulfates are formed in the same polluted air mass, probably through nitrate radical reactions. Terpenylic acid, diterpenylic acid acetate, and methylbutane tricarboxylic acid were found at concentrations comparable to pinic acid. A dimer of

  3. Bridging-type changes facilitate successive oxidation steps at about 1 V in two binuclear manganese complexes--implications for photosynthetic water-oxidation.

    Science.gov (United States)

    Magnuson, A; Liebisch, P; Högblom, J; Anderlund, M F; Lomoth, R; Meyer-Klaucke, W; Haumann, M; Dau, H

    2006-07-01

    The redox behavior of two synthetic manganese complexes illustrates a mechanistic aspect of importance for light-driven water oxidation in Photosystem II (PSII) and design of biomimetic systems (artificial photosynthesis). The coupling between changes in oxidation state and structural changes was investigated for two binuclear manganese complexes (1 and 2), which differ in the set of first sphere ligands to Mn (N(3)O(3) in 1, N(2)O(4) in 2). Both complexes were studied by electron paramagnetic resonance (EPR) and X-ray absorption spectroscopy (XAS) in three oxidation states which had been previously prepared either electro- or photochemically. The following bridging-type changes are suggested. In 1: Mn(II)-(mu-OR)(mu-OCO)(2)-Mn(II)Mn(II)-(mu-OR)(mu-OCO)(2)-Mn(III)-->Mn(III)-(mu-OR)(mu-OCO)(mu-O)-Mn(III). In 2: Mn(II)-(mu-OR)(mu-OCO)(2)-Mn(III)Mn(III)-(mu-OR)(mu-OCO)(2)-Mn(III)-->Mn(III)-(mu-OR)(mu-OCO)(mu-O)-Mn(IV). In both complexes, the first one-electron oxidation proceeds without bridging-type change, but involves a redox-potential increase by 0.5-1V. The second one-electron oxidation likely is coupled to mu-oxo-bridge (or mu-OH) formation which seems to counteract a further potential increase. In both complexes, mu-O(H) bridge formation is associated with a redox transition proceeding at approximately 1V, but the mu-O(H) bridge is observed at the Mn(2)(III,III) level in 1 and at the Mn(III,IV) level in 2, demonstrating modulation of the redox behavior by the terminal ligands. It is proposed that also in PSII bridging-type changes facilitate successive oxidation steps at approximately the same potential.

  4. Novel synthesis of manganese and vanadium mixed oxide (V2O5/OMS-2) as an efficient and selective catalyst for the oxidation of alcohols in liquid phase

    International Nuclear Information System (INIS)

    Mahdavi, Vahid; Soleimani, Shima

    2014-01-01

    Graphical abstract: Oxidation of various alcohols is studied in the liquid phase over new composite mixed oxide (V 2 O 5 /OMS-2) catalyst using tert-butyl hydroperoxide (TBHP). The activity of V 2 O 5 /OMS-2 samples was considerably increased with respect to OMS-2 catalyst and these samples are found to be suitable for the selective oxidation of alcohols. - Highlights: • V 2 O 5 /K-OMS-2 with different V/Mn molar ratios prepared by the impregnation method. • Oxidation of alcohols was studied in the liquid phase over V 2 O 5 /K-OMS-2 catalyst. • V 2 O 5 /K-OMS-2 catalyst had excellent activity for alcohol oxidation. • Benzyl alcohol oxidation using excess TBHP followed a pseudo-first order kinetic. • The selected catalyst was reused without significant loss of activity. - Abstract: This work reports the synthesis and characterization of mixed oxide vanadium–manganese V 2 O 5 /K-OMS-2 at various V/Mn molar ratios and prepared by the impregnation method. Characterization of these new composite materials was made by elemental analysis, BET, XRD, FT-IR, SEM and TEM techniques. Results of these analyses showed that vanadium impregnated samples contained mixed phases of cryptomelane and crystalline V 2 O 5 species. Oxidation of various alcohols was studied in the liquid phase over the V 2 O 5 /K-OMS-2 catalyst using tert-butyl hydroperoxide (TBHP) and H 2 O 2 as the oxidant. Activity of the V 2 O 5 /K-OMS-2 samples was increased considerably with respect to K-OMS-2 catalyst due to the interaction of manganese oxide and V 2 O 5 . The kinetic of benzyl alcohol oxidation using excess TBHP over V 2 O 5 /K-OMS-2 catalyst was investigated at different temperatures and a pseudo-first order reaction was determined with respect to benzyl alcohol. The effects of reaction time, oxidant/alcohol molar ratio, reaction temperature, solvents, catalyst recycling potential and leaching were investigated

  5. Fabrication of electrochemical theophylline sensor based on manganese oxide nanoparticles/ionic liquid/chitosan nanocomposite modified glassy carbon electrode

    International Nuclear Information System (INIS)

    MansouriMajd, Samira; Teymourian, Hazhir; Salimi, Abdollah; Hallaj, Rahman

    2013-01-01

    In this study, the preparation of a glassy carbon (GC) electrode modified with chitosan/NH 2 -ionic liquid/manganese oxide nanoparticles (Chit/NH 2 -IL/MnO x ) was described for electrocatalytic detection of theophylline (TP). First, chitosan hydrogel (Chit) was electrodeposited on the GC electrode surface at a constant potential (−1.5 V) in acidic solution. Then, the previously synthesized amine-terminated 1-(3-Aminopropyl)-3-methylimidazolium bromide ionic liquid (NH 2 -IL) was covalently attached to the modified electrode via glutaraldehyde (GA) as linking agent. Finally, manganese oxide (MnO x ) nanoparticles were electrodeposited onto the Chit/NH 2 -IL film by potential cycling between −1.0 and 1.7 V in Mn(CH 3 COO) 2 ·4H 2 O neutral aqueous solution. Electrochemical behavior of the modified electrode was evaluated by cyclic voltammetry (CV) technique. The charge transfer coefficient (α) and electron transfer rate constant (k s ) for MnOOH/MnO 2 redox couple were calculated to be 0.35 and 1.62 s −1 , respectively. The resulting system brings new capabilities for electrochemical sensing through combining the advantages of IL and MnO x nanoparticles. The differential pulse voltammetric (DPV) results indicated the high ability of GC/Chit/NH 2 -IL/MnO x modified electrode to catalyze the oxidation of TP. DPV determination of TP in acetate buffer solution (pH 5) gave linear responses over the concentration range up to 120 μM with the detection limit of 50 nM and sensitivity of 804 nA μM −1 . Furthermore, the applicability of the sensor for TP analysis in pharmaceutical samples has been successfully demonstrated

  6. High resolution electron energy loss spectroscopy of manganese oxides: Application to Mn{sub 3}O{sub 4} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Laffont, L., E-mail: Lydia.laffont@ensiacet.fr [Institut Carnot, Laboratoire CIRIMAT (equipe MEMO), CNRS UMR 5085, ENSIACET, 4 allee Emile Monso, BP 74233, 31432 Toulouse cedex 4 (France); Gibot, P. [Laboratoire de Reactivite et Chimie des Solides CNRS UMR 6007, Universite de Picardie Jules Verne, 33 rue Saint Leu, 80039 Amiens cedex 9 (France)

    2010-11-15

    Manganese oxides particularly Mn{sub 3}O{sub 4} Hausmannite are currently used in many industrial applications such as catalysis, magnetism, electrochemistry or air contamination. The downsizing of the particle size of such material permits an improvement of its intrinsic properties and a consequent increase in its performances compared to a classical micron-sized material. Here, we report a novel synthesis of hydrophilic nano-sized Mn{sub 3}O{sub 4}, a bivalent oxide, for which a precise characterization is necessary and for which the determination of the valency proves to be essential. X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and particularly High Resolution Electron Energy Loss Spectroscopy (HREELS) allow us to perform these measurements on the nanometer scale. Well crystallized 10-20 nm sized Mn{sub 3}O{sub 4} particles with sphere-shaped morphology were thus successfully synthesized. Meticulous EELS investigations allowed the determination of a Mn{sup 3+}/Mn{sup 2+} ratio of 1.5, i.e. slightly lower than the theoretical value of 2 for the bulk Hausmannite manganese oxide. This result emphasizes the presence of vacancies on the tetrahedral sites in the structure of the as-synthesized nanomaterial. - Research Highlights: {yields}Mn{sub 3}O{sub 4} bulk and nano were studied by XRD, TEM and EELS. {yields}XRD and TEM determine the degree of crystallinity and the narrow grain size. {yields}HREELS gave access to the Mn{sup 3+}/Mn{sup 2+} ratio. {yields}Mn{sub 3}O{sub 4} nano have vacancies on the tetrahedral sites.

  7. Metal-organic chemical vapour deposition of lithium manganese oxide thin films via single solid source precursor

    Directory of Open Access Journals (Sweden)

    Oyedotun K.O.

    2015-12-01

    Full Text Available Lithium manganese oxide thin films were deposited on sodalime glass substrates by metal organic chemical vapour deposition (MOCVD technique. The films were prepared by pyrolysis of lithium manganese acetylacetonate precursor at a temperature of 420 °C with a flow rate of 2.5 dm3/min for two-hour deposition period. Rutherford backscattering spectroscopy (RBS, UV-Vis spectrophotometry, X-ray diffraction (XRD spectroscopy, atomic force microscopy (AFM and van der Pauw four point probe method were used for characterizations of the film samples. RBS studies of the films revealed fair thickness of 1112.311 (1015 atoms/cm2 and effective stoichiometric relationship of Li0.47Mn0.27O0.26. The films exhibited relatively high transmission (50 % T in the visible and NIR range, with the bandgap energy of 2.55 eV. Broad and diffused X-ray diffraction patterns obtained showed that the film was amorphous in nature, while microstructural studies indicated dense and uniformly distributed layer across the substrate. Resistivity value of 4.9 Ω·cm was obtained for the thin film. Compared with Mn0.2O0.8 thin film, a significant lattice absorption edge shift was observed in the Li0.47Mn0.27O0.26 film.

  8. Origin of the chemical shift in X-ray absorption near-edge spectroscopy at the Mn K-Edge in manganese oxide compounds

    NARCIS (Netherlands)

    de Vries, AH; Hozoi, L.; Broer, R.

    2003-01-01

    The absorption edge in Mn K-edge X-ray absorption spectra of manganese oxide compounds shows a shift of several electronvolts in going from MnO through LaMnO3 to CaMnO3. On the other hand, in X-ray photoelectron spectra much smaller shifts are observed. To identify the mechanisms that cause the

  9. A self-seeded, surfactant-directed hydrothermal growth of single crystalline lithium manganese oxide nanobelts from the commercial bulky particles.

    Science.gov (United States)

    Zhang, Lizhi; Yu, Jimmy C; Xu, An-Wu; Li, Quan; Kwong, Kwan Wai; Wu, Ling

    2003-12-07

    Single crystalline lithium manganese oxide nanobelts were obtained through a self-seeded, surfactant-directed growth process from the commercial bulky particles under hydrothermal treatment. A possible mechanism was proposed to explain the growth of the nanobelts. This new process could be extended to prepare other one-dimensional nanomaterials such as Se nanorods, Te nanotubes, and MnO2 nanowires.

  10. Supported manganese oxide on TiO{sub 2} for total oxidation of toluene and polycyclic aromatic hydrocarbons (PAHs): Characterization and catalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Aboukaïs, Antoine, E-mail: aboukais@univ-littoral.fr [Univ Lille Nord de France, 59000 Lille (France); Equipe Catalyse, UCEIV, EA 4492, MREI, ULCO, 59140 Dunkerque (France); Abi-Aad, Edmond [Univ Lille Nord de France, 59000 Lille (France); Equipe Catalyse, UCEIV, EA 4492, MREI, ULCO, 59140 Dunkerque (France); Taouk, Bechara [Laboratoire de Sécurité des procédés Chimiques (LSPC), EA 4704, INSA Rouen, Avenue de l' Université, 76801 Saint Etienne du Rouvray (France)

    2013-11-01

    Manganese oxide catalysts supported on titania (TiO{sub 2}) were prepared by incipient wetness impregnation method in order to elaborate catalysts for total oxidation of toluene and PAHs. These catalysts have been characterized by means of X-ray diffraction (XRD), electron paramagnetic resonance (EPR), temperature programmed reduction (TPR) and temperature programmed desorption (TPD). It has been shown that for the 5%Mn/TiO{sub 2} catalyst the reducibility and the mobility of oxygen are higher compared, in one side, to other x%Mn/TiO{sub 2} samples and, in another side, to catalysts where TiO{sub 2} support was replaced by γ-Al{sub 2}O{sub 3} or SiO{sub 2}. It has been shown that the content of manganese loading on TiO{sub 2} has an effect on the catalytic activity in the toluene oxidation. A maximum of activity was obtained for the 5%Mn/TiO{sub 2} catalyst where the total conversion of toluene was reached at 340 °C. This activity seems to be correlated to the presence of the Mn{sup 3+}/Mn{sup 4+} redox couple in the catalyst. When the Mn content increases, large particles of Mn{sub 2}O{sub 3} appear leading then to the decrease in the corresponding activity. In addition, compared to both other supports, TiO{sub 2} seems to be the best to give the best catalytic activity for the oxidation of toluene when it is loaded with 5% of manganese. For this reason, the latter catalyst was tested for the abatement of some PAHs. The light off temperature of PAHs compounds increases with increasing of benzene rings number and with decreasing of H/C ratio. All of PAHs are almost completely oxidized and converted at temperatures lower than 500 °C. - Highlights: • Preparation of x%MnO{sub 2}/TiO{sub 2} catalysts. • Catalytic oxidation tests of toluene and PAHs. • EPR, TPR and TPD characterizations of Mn(II) and Mn(IV) ions.

  11. Manganese oxidation and bacterial diversity on different filter media coatings during the start-up of drinking water biofilters

    DEFF Research Database (Denmark)

    Breda, I. L.; Ramsay, L.; Roslev, P.

    2017-01-01

    Manganese removal is a typical concern in drinking water production. Biofiltration may be used when treating groundwater sources but the onset of manganese removal in virgin biofilters can vary considerably. The aim of this study was to investigate the effect of different filter media on manganese...

  12. Manganese Oxide Nanoparticle as a New p-Type Dopant for High-Performance Polymer Field-Effect Transistors.

    Science.gov (United States)

    Long, Dang Xuan; Choi, Eun-Young; Noh, Yong-Young

    2017-07-26

    We report a new p-type dopant, manganese oxide (Mn 3 O 4 ) nanoparticle, to enhance the performance of organic field-effect transistors (OFETs) with conjugated polymers, including poly(3-hexylthiophene-2,5-diyl), poly[[N,N 9-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,59-(2,29-bithiophene)], and poly[[2,5-bis(2-octyldodecyl)-2,3,5,6-tetrahydro-3,6-dioxopyrrolo[3,4-c]pyrrole-1,4-diyl]-alt-[[2,2'-(2,5-thiophene)bis-thieno(3,2b) thiophene]-5,5'-diyl

  13. Water-soluble Manganese and Iron Mesotetrakis(carboxyl)porphyrin: DNA Binding, Oxidative Cleavage, and Cytotoxic Activities.

    Science.gov (United States)

    Shi, Lei; Jiang, Yi-Yu; Jiang, Tao; Yin, Wei; Yang, Jian-Ping; Cao, Man-Li; Fang, Yu-Qi; Liu, Hai-Yang

    2017-06-29

    Two new water-soluble metal carboxyl porphyrins, manganese (III) meso -tetrakis (carboxyl) porphyrin and iron (III) meso -tetrakis (carboxyl) porphyrin, were synthesized and characterized. Their interactions with ct-DNA were investigated by UV-Vis titration, fluorescence spectra, viscosity measurement and CD spectra. The results showed they can strongly bind to ct-DNA via outside binding mode. Electrophoresis experiments revealed that both complexes can cleave pBR322 DNA efficiently in the presence of hydrogen peroxide, albeit 2-Mn exhibited a little higher efficiency. The inhibitor tests suggest the oxidative DNA cleavage by these two complexes may involve hydroxyl radical active intermediates. Notably, 2-Mn exhibited considerable photocytotoxicity against Hep G2 cell via triggering a significant generation of ROS and causing disruption of MMP after irradiation.

  14. Metalloradical Complexes of Manganese and Chromium Featuring an Oxidatively Rearranged Ligand

    OpenAIRE

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

    2008-01-01

    Redox events involving both metal and ligand sites are receiving increased attention since a number of biological processes direct redox equivalents toward functional residues. Metalloradical synthetic analogs remain scarce and require better definition of their mode of formation and subsequent operation. The trisamido-amine ligand [(RNC6H4)3N]3−, where R is the electron-rich 4-t-BuPh, is employed in this study to generate redox active residues in manganese and chromium complexes. Solutions o...

  15. Core chemistry influences the toxicity of multicomponent metal oxide nanomaterials, lithium nickel manganese cobalt oxide, and lithium cobalt oxide to Daphnia magna.

    Science.gov (United States)

    Bozich, Jared; Hang, Mimi; Hamers, Robert; Klaper, Rebecca

    2017-09-01

    Lithium intercalation compounds such as lithium nickel manganese cobalt oxide (NMC) and lithium cobalt oxide (LCO) are used extensively in lithium batteries. Because there is currently little economic incentive for recycling, chances are greater that batteries will end up in landfills or waste in the environment. In addition, the toxicity of these battery materials traditionally has not been part of the design process. Therefore, to determine the environmental impact and the possibility of alternative battery materials, representative complex battery nanomaterials, LCO and NMC, were synthesized, and toxicity was assessed in Daphnia magna. Toxicity was determined by assessing LCO and NMC at concentrations in the range of 0.1 to 25 mg/L. Acute studies (48 h) showed no effect to daphnid survival at 25 mg/L, whereas chronic studies (21 d) show significant impacts to daphnid reproduction and survival at concentrations of 0.25 mg/L for LCO and 1.0 mg/L for NMC. Dissolved metal exposures showed no effect at the amounts measured in suspension, and supernatant controls could not reproduce the effects of the particles, indicating a nanomaterial-specific impact. Genes explored in the present study were actin, glutathione-s-transferase, catalase, 18s, metallothionein, heat shock protein, and vitellogenin. Down-regulation of genes important in metal detoxification, metabolism, and cell maintenance was observed in a dose-dependent manner. The results show that battery material chemical composition can be altered to minimize environmental impacts. Environ Toxicol Chem 2017;36:2493-2502. © 2017 SETAC. © 2017 SETAC.

  16. Biphase Cobalt-Manganese Oxide with High Capacity and Rate Performance for Aqueous Sodium-Ion Electrochemical Energy Storage

    Energy Technology Data Exchange (ETDEWEB)

    Shan, Xiaoqiang [Univ. of New Hampshire, Durham, NH (United States). Dept. of Chemical Engineering; Charles, Daniel S. [Univ. of New Hampshire, Durham, NH (United States). Dept. of Chemical Engineering; Xu, Wenqian [Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS). X-ray Science Division; Feygenson, Mikhail [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical and Engineering Materials Division and Spallation Neutron Source (SNS) outstation Juelich Centre for Neutron Science (JCNS), Forschungszentrum Juelich GmbH; Su, Dong [Brookhaven National Lab. (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN); Teng, Xiaowei [Univ. of New Hampshire, Durham, NH (United States). Dept. of Chemical Engineering

    2017-11-22

    Manganese-based metal oxide electrode materials are of great importance in electrochemical energy storage for their favorable redox behavior, low cost and environmental-friendliness. However, their storage capacity and cycle life in aqueous Na-ion electrolytes is not satisfactory. In this paper, we report the development of a bi-phase cobalt-manganese oxide (Co-Mn-O) nanostructured electrode material, comprised of a layered MnO2.H2O birnessite phase and a (Co0.83Mn0.13Va0.04)tetra(Co0.38Mn1.62)octaO3.72 (Va: vacancy; tetra: tetrahedral sites; octa: octahedral sites) spinel phase, verified by neutron total scattering and pair distribution function analyses. The bi-phase Co-Mn-O material demonstrates an excellent storage capacity towards Na-ions in an aqueous electrolyte (121 mA h g-1 at a scan rate of 1 mV s-1 in the half-cell and 81 mA h g-1 at a current density of 2 A g-1 after 5000 cycles in full-cells), as well as high rate performance (57 mA h g-1 a rate of 360 C). Electro-kinetic analysis and in situ X-ray diffraction measurements further confirm that the synergistic interaction between the spinel and layered phases, as well as the vacancy of the tetrahedral sites of spinel phase, contribute to the improved capacity and rate performance of the Co-Mn-O material by facilitating both diffusion-limited redox and capacitive charge storage processes.

  17. Electrostatic Spray Deposition-Based Manganese Oxide Films—From Pseudocapacitive Charge Storage Materials to Three-Dimensional Microelectrode Integrands

    Directory of Open Access Journals (Sweden)

    Richa Agrawal

    2017-07-01

    Full Text Available In this study, porous manganese oxide (MnOx thin films were synthesized via electrostatic spray deposition (ESD and evaluated as pseudocapacitive electrode materials in neutral aqueous media. Very interestingly, the gravimetric specific capacitance of the ESD-based electrodes underwent a marked enhancement upon electrochemical cycling, from 72 F∙g−1 to 225 F∙g−1, with a concomitant improvement in kinetics and conductivity. The change in capacitance and resistivity is attributed to a partial electrochemical phase transformation from the spinel-type hausmannite Mn3O4 to the conducting layered birnessite MnO2. Furthermore, the films were able to retain 88.4% of the maximal capacitance after 1000 cycles. Upon verifying the viability of the manganese oxide films for pseudocapacitive applications, the thin films were integrated onto carbon micro-pillars created via carbon microelectromechanical systems (C-MEMS for examining their application as potential microelectrode candidates. In a symmetric two-electrode cell setup, the MnOx/C-MEMS microelectrodes were able to deliver specific capacitances as high as 0.055 F∙cm−2 and stack capacitances as high as 7.4 F·cm−3, with maximal stack energy and power densities of 0.51 mWh·cm−3 and 28.3 mW·cm−3, respectively. The excellent areal capacitance of the MnOx-MEs is attributed to the pseudocapacitive MnOx as well as the three-dimensional architectural framework provided by the carbon micro-pillars.

  18. Nanoscale Structural/Chemical Characterization of Manganese Oxide Surface Layers and Nanoparticles, and the Associated Implications for Drinking Water

    Science.gov (United States)

    Michel Eduardo Vargas Vallejo

    Water treatment facilities commonly reduce soluble contaminants, such as soluble manganese (Mn2+), in water by oxidation and subsequent filtration. Previous studies have shown that conventional porous filter system removes Mn2+ from drinking water by developing Mn-oxides (MnO x(s)) bearing coating layers on the surface of filter media. Multiple models have been developed to explain this Mn2+ removal process and the formation mechanism of MnOx(s) coatings. Both, experimental and theoretical studies to date have been largely focused on the micrometer to millimeter scale range; whereas, coating layers are composed of nanoscale particles and films. Hence, understanding the nanoscale particle and film formation mechanisms is essential to comprehend the complexity of soluble contaminant removal processes. The primary objective of this study was to understand the initial MnOx(s) coating formation mechanisms and evaluate the influence of filter media characteristics on these processes. We pursued this objective by characterizing at the micro and nanoscale MnO x(s) coatings developed on different filter media by bench-scale column tests with simulating inorganic aqueous chemistry of a typical coagulation fresh water treatment plant, where free chlorine is present across filter bed. Analytical SEM and TEM, powder and synchrotron-based XRD, XPS, and ICPMS were used for characterization of coatings, filter media and water solution elemental chemistry. A secondary objective was to model how surface coating formation occurred and its correlation with experimentally observed physical characteristics. This modeling exercise indicates that surface roughness and morphology of filtering media are the major contributing factors in surface coating formation process. Contrary to previous models that assumed a uniform distribution and growth of surface coating, the experimental results showed that greater amounts of coating were developed in rougher areas. At the very early stage of

  19. Dietary supplementation of green synthesized manganese-oxide nanoparticles and its effect on growth performance, muscle composition and digestive enzyme activities of the giant freshwater prawn Macrobrachium rosenbergii.

    Science.gov (United States)

    Asaikkutti, Annamalai; Bhavan, Periyakali Saravana; Vimala, Karuppaiya; Karthik, Madhayan; Cheruparambath, Praseeja

    2016-05-01

    The green synthesized Mn3O4 nanoparticles (manganese-oxide nanoparticles) using Ananas comosus (L.) peel extract was characterized by various techniques. HR-SEM photograph showed that manganese-oxide nanoparticles (Mn-oxide NPs) were spherical in shape, with an average size of 40-50 nm. The Zeta potential revealed the surface charge of Mn-oxide NPs to be negative. Further, the Mn-oxide NPs were dietary supplemented for freshwater prawn Macrobrachium rosenbergii. The experimental basal diets were supplemented with Mn-oxide NPs at the rates of 0 (control), 3.0, 6.0, 9.0, 12, 15 and 18 mg/kg dry feed weight. The as-supplemented Mn-oxide NPs were fed in M. rosenbergii for a period of 90 days. The experimental study demonstrated that prawns fed with diet supplemented with 3-18 mg Mn-oxide NPs/kg shows enhanced (P0.05) alterations in prawns fed with 3.0-18 mg/kg of Mn-oxide NPs supplemented diets. Consequently, the present work proposed that 16 mg/kg of Mn-oxide NPs could be supplemented for flexible enhanced survival, growth and production of M. rosenbergii. Therefore, the data of the present study recommend the addition of 16 mg/kg of Mn-oxide NPs diet to developed prawn growth and antioxidant defense system. Copyright © 2016 Elsevier GmbH. All rights reserved.

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

    Science.gov (United States)

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

    2014-12-01

    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.

  1. Novel mode of microbial energy metabolism: organic carbon oxidation coupled to dissimilatory reduction of iron or manganese.

    Science.gov (United States)

    Lovley, D R; Phillips, E J

    1988-06-01

    A dissimilatory Fe(III)- and Mn(IV)-reducing microorganism was isolated from freshwater sediments of the Potomac River, Maryland. The isolate, designated GS-15, grew in defined anaerobic medium with acetate as the sole electron donor and Fe(III), Mn(IV), or nitrate as the sole electron acceptor. GS-15 oxidized acetate to carbon dioxide with the concomitant reduction of amorphic Fe(III) oxide to magnetite (Fe(3)O(4)). When Fe(III) citrate replaced amorphic Fe(III) oxide as the electron acceptor, GS-15 grew faster and reduced all of the added Fe(III) to Fe(II). GS-15 reduced a natural amorphic Fe(III) oxide but did not significantly reduce highly crystalline Fe(III) forms. Fe(III) was reduced optimally at pH 6.7 to 7 and at 30 to 35 degrees C. Ethanol, butyrate, and propionate could also serve as electron donors for Fe(III) reduction. A variety of other organic compounds and hydrogen could not. MnO(2) was completely reduced to Mn(II), which precipitated as rhodochrosite (MnCO(3)). Nitrate was reduced to ammonia. Oxygen could not serve as an electron acceptor, and it inhibited growth with the other electron acceptors. This is the first demonstration that microorganisms can completely oxidize organic compounds with Fe(III) or Mn(IV) as the sole electron acceptor and that oxidation of organic matter coupled to dissimilatory Fe(III) or Mn(IV) reduction can yield energy for microbial growth. GS-15 provides a model for how enzymatically catalyzed reactions can be quantitatively significant mechanisms for the reduction of iron and manganese in anaerobic environments.

  2. Synthesis and Characterization of Mixed Iron-Manganese Oxide Nanoparticles and Their Application for Efficient Nickel Ion Removal from Aqueous Samples

    Science.gov (United States)

    Serra, Antonio; Monteduro, Anna Grazia; Padmanabhan, Sanosh Kunjalukkal; Licciulli, Antonio; Bonfrate, Valentina; Salvatore, Luca; Calcagnile, Lucio

    2017-01-01

    Mixed iron-manganese oxide nanoparticles, synthesized by a simple procedure, were used to remove nickel ion from aqueous solutions. Nanostructures, prepared by using different weight percents of manganese, were characterized by transmission electron microscopy, selected area diffraction, X-ray diffraction, Raman spectroscopy, and vibrating sample magnetometry. Adsorption/desorption isotherm curves demonstrated that manganese inclusions enhance the specific surface area three times and the pores volume ten times. This feature was crucial to decontaminate both aqueous samples and food extracts from nickel ion. Efficient removal of Ni2+ was highlighted by the well-known dimethylglyoxime test and by ICP-MS analysis and the possibility of regenerating the nanostructure was obtained by a washing treatment in disodium ethylenediaminetetraacetate solution. PMID:28804670

  3. Synthesis and Characterization of Mixed Iron-Manganese Oxide Nanoparticles and Their Application for Efficient Nickel Ion Removal from Aqueous Samples.

    Science.gov (United States)

    Buccolieri, Alessandro; Serra, Antonio; Maruccio, Giuseppe; Monteduro, Anna Grazia; Padmanabhan, Sanosh Kunjalukkal; Licciulli, Antonio; Bonfrate, Valentina; Salvatore, Luca; Manno, Daniela; Calcagnile, Lucio; Giancane, Gabriele

    2017-01-01

    Mixed iron-manganese oxide nanoparticles, synthesized by a simple procedure, were used to remove nickel ion from aqueous solutions. Nanostructures, prepared by using different weight percents of manganese, were characterized by transmission electron microscopy, selected area diffraction, X-ray diffraction, Raman spectroscopy, and vibrating sample magnetometry. Adsorption/desorption isotherm curves demonstrated that manganese inclusions enhance the specific surface area three times and the pores volume ten times. This feature was crucial to decontaminate both aqueous samples and food extracts from nickel ion. Efficient removal of Ni 2+ was highlighted by the well-known dimethylglyoxime test and by ICP-MS analysis and the possibility of regenerating the nanostructure was obtained by a washing treatment in disodium ethylenediaminetetraacetate solution.

  4. Synthesis and Characterization of Mixed Iron-Manganese Oxide Nanoparticles and Their Application for Efficient Nickel Ion Removal from Aqueous Samples

    Directory of Open Access Journals (Sweden)

    Alessandro Buccolieri

    2017-01-01

    Full Text Available Mixed iron-manganese oxide nanoparticles, synthesized by a simple procedure, were used to remove nickel ion from aqueous solutions. Nanostructures, prepared by using different weight percents of manganese, were characterized by transmission electron microscopy, selected area diffraction, X-ray diffraction, Raman spectroscopy, and vibrating sample magnetometry. Adsorption/desorption isotherm curves demonstrated that manganese inclusions enhance the specific surface area three times and the pores volume ten times. This feature was crucial to decontaminate both aqueous samples and food extracts from nickel ion. Efficient removal of Ni2+ was highlighted by the well-known dimethylglyoxime test and by ICP-MS analysis and the possibility of regenerating the nanostructure was obtained by a washing treatment in disodium ethylenediaminetetraacetate solution.

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

    International Nuclear Information System (INIS)

    Imamura, N.; Mizoguchi, T.; Yamauchi, H.; Karppinen, M.

    2008-01-01

    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 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

  6. Rational design of coaxial structured carbon nanotube-manganese oxide (CNT-MnO2) for energy storage application.

    Science.gov (United States)

    Salunkhe, Rahul R; Ahn, Heejoon; Kim, Jung Ho; Yamauchi, Yusuke

    2015-05-22

    Recently, there has been great research interest in the development of composites (core-shell structures) of carbon nanotubes (CNTs) with metal oxides for improved electrochemical energy storage, photonics, electronics, catalysis, etc. Currently, the synthetic strategies for metal oxides/hydroxides are well established, but the development of core-shell structures by robust, cost-effective chemical methods is still a challenge. The main drawbacks for obtaining such electrodes are the very complex synthesis methods which ultimately result in high production costs. Alternatively, the solution based method offers the advantages of simple and cost effective synthesis, as well as being easy to scale up. Here, we report on the development of multi-walled carbon nanotube-manganese oxide (CNT-MnO2) core-shell structures. These samples were directly utilized for asymmetric supercapacitor (ASC) applications, where the CNT-MnO2 composite was used as the positive electrode and ZIF-8 (zeolitic imidazolate framework, ZIF) derived nanoporous carbon was used as the negative electrode. This unconventional ASC shows a high energy density of 20.44 W h kg(-1) and high power density of 16 kW kg(-1). The results demonstrate that these are efficient electrodes for supercapacitor application.

  7. Peroxymonosulfate activation and pollutants degradation over highly dispersed CuO in manganese oxide octahedral molecular sieve

    Science.gov (United States)

    Li, Jun; Ye, Peng; Fang, Jia; Wang, Manye; Wu, Deming; Xu, Aihua; Li, Xiaoxia

    2017-11-01

    Manganese oxide octahedral molecular sieves (OMS-2) supported CuO catalysts were synthesized, characterized and used in the removal of Acid Orange 7 (AO7) in aqueous solution by an oxidation process involving peroxymonosulfate (PMS). It was found that the CuO species were highly dispersed in OMS-2 with a high ratio of easily reduced surface oxygen species. The synergetic effect between CuO and OMS-2 significantly improved the dye degradation rate and catalytic stability, compared with CuO, OMS-2 and supported CuO on other materials. About 97% of the dye was removed within 15 min at neutral solution pH by using 0.2 g/L of CuO/OMS-2 and PMS. The effect of initial solution pH, PMS concentration, reaction temperature and CuO content in the composites on AO7 degradation was also investigated. Mechanism study indicated that SO4-rad radicals generated from the interaction between PMS and Mn and Cu species with different oxidation states, mainly accounted for the degradation.

  8. Control of Manganese Dioxide Particles Resulting From In Situ Chemical Oxidation Using Permanganate

    Science.gov (United States)

    2008-09-01

    the autocatalytic permanganate oxidation of formic acid . International Journal of Chemical Kinetics, 22:261-287. Perez-Benito J.F., E. Brillas, and R...particles can allow for improved oxidant injection, oxidant transport , and contact between the oxidant and contaminants of concern. This project’s...incorporate transport phenomena , were conducted to study particle stabilization aids under varied reaction matrix conditions. Variations include particle

  9. Mechanisms in iron, nickel, and manganese, catalysis with small molecule oxidants

    NARCIS (Netherlands)

    Padamati, Sandeep

    2017-01-01

    Oxidation plays a vital role in the metabolism of living organisms, manifested in a finely organized set of enzymes and proteins to selectively oxidize substrates in a controlled fashion. Biochemical oxidation has inspired many scientists to model the processes found in living organisms to synthetic

  10. Nanostructured Iron and Manganese Oxide Electrode Materials for Lithium Batteries: Influence of Chemical and Physical Properties on Electrochemistry

    Science.gov (United States)

    Durham, Jessica L.

    The widespread use of portable electronics and growing interest in electric and hybrid vehicles has generated a mass market for batteries with increased energy densities and enhanced electrochemical performance. In order to address a variety of applications, commercially fabricated secondary lithium-ion batteries employ transition metal oxide based electrodes, the most prominent of which include lithium nickel manganese cobalt oxide (LiNixMn yCo1-x-yO2), lithium iron phosphate (LiFePO4), and lithium manganese oxide (LiMn 2O4). Transition metal oxides are of particular interest as cathode materials due to their robust framework for lithium intercalation, potential for high energy density, and utilization of earth-abundant elements (i.e. iron and manganese) leading to decreased toxicity and cost-effective battery production on industrial scales. Specifically, this research focuses on MgFe2O4, AgxMn8O16, and AgFeO 2 transition metal oxides for use as electrode materials in lithium-based batteries. The electrode materials are prepared via co-precipitation, reflux, and hydrothermal methods and characterized by several techniques (XRD, SEM, BET, TGA, DSC, XPS, Raman, etc.). The low-temperature syntheses allowed for precise manipulation of structural, compositional, and/or functional properties of MgFe2O4, AgxMn8 O16, and AgFeO2 which have been shown to influence electrochemical behavior. In addition, advanced in situ and ex situ characterization techniques are employed to study the lithiation/de-lithiation process and establish valid redox mechanisms. With respect to both chemical and physical properties, the influence of MgFe2O4 particle size and morphology on electrochemical behavior was established using ex situ X-ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM) imaging. Based on composition, tunneled AgxMn8O16 nanorods, prepared with distinct Ag+ contents and crystallite sizes, display dramatic differences in ion-transport kinetics due to

  11. Manganese iron oxide superparamagnetic powder by mechanochemical processing. Nanoparticles functionalization and dispersion in a nanofluid

    Energy Technology Data Exchange (ETDEWEB)

    Bellusci, M., E-mail: mariangela.bellusci@enea.it; Aliotta, C. [ENEA, CR Casaccia, Dipartimento di Chimica e Technologia dei Materiali (Italy); Fiorani, D. [ISM-CNR, Area della Ricerca (Italy); La Barbera, A.; Padella, F. [ENEA, CR Casaccia, Dipartimento di Chimica e Technologia dei Materiali (Italy); Peddis, D. [ISM-CNR, Area della Ricerca (Italy); Pilloni, M. [ENEA, CR Casaccia, Dipartimento di Chimica e Technologia dei Materiali (Italy); Secci, D. [Universita di Roma La Sapienza, Dipartimento di Chimica e Tecnologie del Farmaco (Italy)

    2012-06-15

    Manganese ferrite nanoparticles were synthesized using a High-Energy Ball-Milling mechanochemical method. After 1 h of milling, the process produces a material consisting of single crystalline domain nanoparticles having a diameter of about 8 nm. Chemical properties of the synthesized powders allow an easy functionalization with citric acid. Both as-obtained and functionalized samples show superparamagnetic behaviour at room temperature, and the functionalized powder is stably dispersible in aqueous media at physiological pH. The average hydrodynamic diameter is equal to {approx}60 nm. Nanoparticles obtained by the reported High-Energy Ball-Milling method can be synthesized with high yield and low costs and can be successfully utilized in ferrofluids development for biomedical applications.

  12. Effects of plant polyphenols and a-tocopherol on lipid oxidation, residual nitrites, biogenic amines, and N-nitrosamines formation during ripening and storage of dry-cured bacon

    Science.gov (United States)

    Effects of plant polyphenols (green tea polyphenols (GTP) and grape seed extract (GSE) and a-tocopherol on physicochemical parameters, lipid oxidation, residual nitrite, microbiological counts, biogenic amines, and N-nitrosamines were determined in bacons during dry-curing and storage. Results show ...

  13. Synthesis and electrochemical properties of high performance polyhedron sphere like lithium manganese oxide for lithium ion batteries

    International Nuclear Information System (INIS)

    Guo, Donglei; Wei, Xiuge; Chang, Zhaorong; Tang, Hongwei; Li, Bao; Shangguan, Enbo; Chang, Kun; Yuan, Xiao-Zi; Wang, Haijiang

    2015-01-01

    Graphical abstract: Polyhedron structured sphere-like LiMn 2 O 4 synthesized from β-MnO 2 nanorod precursor via a solid state reaction at a temperature of 800 °C exhibits excellent rate capability and cycling performance at both 25 °C and 55 °C. - Highlights: • Polyhedron sphere-like LiMn 2 O 4 was synthesized from β-MnO 2 nanorod precursor. • The polyhedron sphere-like LiMn 2 O 4 exhibits excellent rate capability and cycling performance. • The polyhedron sphere-like structure spinel LiMn 2 O 4 suppresses the dissolution of manganese ions. • The polyhedron sphere-like LiMn 2 O 4 has high diffusion coefficient of Li + . - Abstract: Polyhedron structured sphere-like lithium manganese oxide (LiMn 2 O 4 ) is successfully synthesized from β-MnO 2 nanorod precursor via a solid state reaction at a temperature of 800 °C. For comparison, LiMn 2 O 4 materials with nanorod and octahedron structures are also obtained from β-MnO 2 nanorod precursor at temperatures of 700 °C and 900 °C, respectively. The galvanostatic charge–discharge result shows that the polyhedron sphere-like LiMn 2 O 4 sample exhibits the best electrochemical performance at high rate and high temperature. After 100 cycles at 5 C, this electrode is able to maintain 94% of its capacity at 25 °C and 81% at 55 °C. This is attributed to that the polyhedron sphere-like spinel LiMn 2 O 4 can suppress the dissolution of manganese ions. Based on Brunauer Emmett Teller (BET), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), the polyhedron sphere-like LiMn 2 O 4 sample has the lowest BET surface area, largest diffusion coefficient of Li + and least charge transfer resistance. This study provides an insight into the capacity fading of LiMn 2 O 4 electrodes and the polyhedron structured sphere-like LiMn 2 O 4 can be a promising material for lithium ion batteries

  14. Iron, copper, and manganese complexes with in vitro superoxide dismutase and/or catalase activities that keep Saccharomyces cerevisiae cells alive under severe oxidative stress.

    Science.gov (United States)

    Ribeiro, Thales P; Fernandes, Christiane; Melo, Karen V; Ferreira, Sarah S; Lessa, Josane A; Franco, Roberto W A; Schenk, Gerhard; Pereira, Marcos D; Horn, Adolfo

    2015-03-01

    Due to their aerobic lifestyle, eukaryotic organisms have evolved different strategies to overcome oxidative stress. The recruitment of some specific metalloenzymes such as superoxide dismutases (SODs) and catalases (CATs) is of great importance for eliminating harmful reactive oxygen species (hydrogen peroxide and superoxide anion). Using the ligand HPClNOL {1-[bis(pyridin-2-ylmethyl)amino]-3-chloropropan-2-ol}, we have synthesized three coordination compounds containing iron(III), copper(II), and manganese(II) ions, which are also present in the active site of the above-noted metalloenzymes. These compounds were evaluated as SOD and CAT mimetics. The manganese and iron compounds showed both SOD and CAT activities, while copper showed only SOD activity. The copper and manganese in vitro SOD activities are very similar (IC50~0.4 μmol dm(-3)) and about 70-fold higher than those of iron. The manganese compound showed CAT activity higher than that of the iron species. Analyzing their capacity to protect Saccharomyces cerevisiae cells against oxidative stress (H2O2 and the O2(•-) radical), we observed that all compounds act as antioxidants, increasing the resistance of yeast cells mainly due to a reduction of lipid oxidation. Especially for the iron compound, the data indicate complete protection when wild-type cells were exposed to H2O2 or O2(•-) species. Interestingly, these compounds also compensate for both superoxide dismutase and catalase deficiencies; their antioxidant activity is metal ion dependent, in the order iron(III)>copper(II)>manganese(II). The protection mechanism employed by the complexes proved to be independent of the activation of transcription factors (such as Yap1, Hsf1, Msn2/Msn4) and protein synthesis. There is no direct relation between the in vitro and the in vivo antioxidant activities. Copyright © 2014 Elsevier Inc. All rights reserved.

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

    Science.gov (United States)

    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

    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. Copyright © 2012 Elsevier Ltd. All rights reserved.

  16. The fate of ammonium in anoxic manganese oxide-rich marine sediment

    Science.gov (United States)

    Thamdrup, Bo; Dalsgaard, Tage

    2000-12-01

    The possibility for anaerobic NH 4+ oxidation and N 2 formation was explored in a Mn oxide-rich continental basin sediment from Skagerrak. The surface sediment contained 2.9 weight-% Mn(IV), and reactive Mn oxide persisted to ≥10 cm depth. Microbial Mn reduction completely dominated anaerobic carbon oxidation, whereas neither Fe reduction nor sulfate reduction were significant. Accumulation rates of soluble NH 4+ during anoxic incubations scaled with Mn reduction rates and did not indicate any substantial oxidation of NH 4+. No sustained production of 15N-labelled N 2 from added 15NH 4+ was detectable during the four-day incubations, which constrains the rate of NH 4+ conversion to N 2 to coupled nitrification/denitrification resulting from sediment handling. Oxidation of NH 4+ to NO 3- was also insignificant as there was no accumulation of NO 3- during the incubations and added 15NO 3- was rapidly consumed with N 2 as a major product. Although the oxidation of NH 4+ with Mn oxide is thermodynamically favorable, our results demonstrate that such oxidation was insignificant and that NH 4+ can be considered the end product of nitrogen mineralization in this anoxic Mn oxide-rich sediment.

  17. Oxidation Of Manganese At Kimberley, Gale Crater: More Free Oxygen In Mars' Past?

    Science.gov (United States)

    Lanza, N. L.; Wiens, R. C.; Arvidson, R. E.; Clark, B. C.; Fischer, W. W.; Gellert, R.; Grotzinger, J. P.; Hurowitz, J. A.; McLennan, S. M.; Morris, R. V.; hide

    2015-01-01

    High Mn concentrations provide unique indicators of water-rich environments and their redox state. Very high-potential oxidants are required to oxidize Mn to insoluble, high-valence oxides that can precipitate and concentrate Mn in rocks and sediments; these redox potentials are much higher than those needed to oxidize Fe or S. Consequently, Mn-rich rocks on Earth closely track the rise of atmospheric oxygen. Given the association between Mn-rich rocks and the redox state of surface environments, observations of anomalous Mn enrichments on Mars raise similar questions about redox history, solubility and aqueous transport, and availability as a metabolic substrate. Our observations suggest that at least some of the high Mn present in Gale crater occurs in the form of Mn-oxides filling veins that crosscut sand-stones, requiring post-depositional precipitation as highly oxidizing fluids moved through the fractured strata after their deposition and lithification.

  18. Daily Manganese Intake Status and Its Relationship with Oxidative Stress Biomarkers under Different Body Mass Index Categories in Korean Adults.

    Science.gov (United States)

    Bu, So-Young; Choi, Mi-Kyeong

    2012-07-01

    Manganese (Mn) is an essential micronutrient for human and plays an important role as a cofactor for several enzymes involving fatty acid synthesis, hepatic gluconeogenesis, and oxidative stresses. Also, Mn intake status has been reported to have beneficial effects in reversing metabolic dysfunction including obesity and nonalcoholic steatosis which is linked to mitochondrial dysfunction and oxidative stresses, however, information on dietary Mn intake in Koreans are limited. Hence we investigated the relationship between dietary Mn intake and antioxidant defense factors in healthy and obese subjects. Total of 333 healthy subjects were recruited in the study and were assigned to one of three study groups: a normal group (18.5-22.9), a overweight group (23-24.9), and a obesity group (>25) according to their body mass index (BMI). We assessed Mn intakes (24-hr recall method) and several indicators for antioxidative defenses such as glutathione (GSH), glutathione peroxidase (GPx) and urinary malonaldehyde (MDA). Results showed that body weight and blood pressure of study subjects were increased in dependent of their BMI (p stress biomarkers (GSH, GPx, and MDA) were not significantly different by groups defined by BMI. In correlation analysis adjusting for age, sex and energy intake, dietary Mn intake of the subjects in different BMI categories were not significantly correlated with GSH, GPx, MDA and showed a weak or no association with these oxidative stress markers. In conclusion dietary Mn intake at least in this study has a little or no influence on markers of oxidative status in both healthy and obese subjects.

  19. Transformation of triclosan to 2,8-dichlorodibenzo-p-dioxin by iron and manganese oxides under near dry conditions.

    Science.gov (United States)

    Ding, Jiafeng; Su, Mian; Wu, Cuiwei; Lin, Kunde

    2015-08-01

    Triclosan (TCS) is a broad-spectrum antibacterial agent widely used in household and personal care products and is frequently detected in the environment. Previous studies have shown that TCS could be converted to the more toxic compound 2,8-dichlorodibenzo-p-dioxins (2,8-DCDD) in photochemical reactions and incineration processes. In this study, we demonstrated the formation of 2,8-DCDD from the oxidation of TCS by α-FeOOH and a natural manganese oxides (MnOx) sand. Experiments at room temperature and under near dry conditions showed that Fe and Mn oxides readily catalyzed the conversion of TCS to 2,8-DCDD and other products. Approximately 5.5% of TCS was transformed to 2,8-DCDD by α-FeOOH in 45 d and a higher conversion percentage (6.7%) was observed for MnOx sand in 16d. However, the presence of water in the samples significantly inhibited the formation of 2,8-DCDD. Besides 2,8-DCDD, 2,4-dichlorphenol (2,4-DCP), 4-chlorobenzene-1,2-diol, 2-chloro-5-(2,4-dichlorophenoxy)benzene-1,4-diol, and 2-chloro-5-(2,4-dichlorophenoxy)-1,4-benzoquinone were identified in the reactions. The possible pathways for the formation of reaction products were proposed. This study suggests that Fe and Mn oxides-mediated transformation of TCS under near dry conditions might be another potential pathway for the formation of 2,8-DCDD in the natural environment. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Synthesis of magnetic core/shell carbon nanosphere supported manganese catalysts for oxidation of organics in water by peroxymonosulfate.

    Science.gov (United States)

    Wang, Yuxian; Sun, Hongqi; Ang, Ha Ming; Tadé, Moses O; Wang, Shaobin

    2014-11-01

    Magnetic separation is more cost-effective than conventional separation processes in heterogeneous catalysis, especially for ultrafine nanoparticles. Magnetic core/shell nanospheres (MCS, Fe3O4/carbon) were synthesized by a hydrothermal method and their supported manganese oxide nanoparticles (Mn/MCS) were obtained by redox reactions between MCS and potassium permanganate at a low temperature. The materials were analyzed by a variety of characterization techniques such as powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectrometer (EDS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and N2 adsorption/desorption. The Mn/MCS catalysts were able to effectively activate Oxone® for phenol degradation in aqueous solutions. Nitrogen treated MCS supported Mn achieved 100% conversion within 120min. Kinetic studies showed that phenol degradation over supported Mn catalysts follows the first order kinetics. It was also found that the catalysts can be easily separated from the aqueous solutions by an external magnetic field. The Oxone® activation mechanism by Mn/MCS catalysts was discussed and sulfate radicals were suggested to be the primary reactive species generated from peroxymonosulfate (PMS) for phenol catalytic oxidation. Copyright © 2014 Elsevier Inc. All rights reserved.

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

    Digital Repository Service at National Institute of Oceanography (India)

    Sujith, P.P.; Mourya, B.S.; Krishnamurthi, S.; Meena, R.M.; LokaBharathi, P.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...

  2. Measurements of Potential Secondary Organic Aerosol Formation from OH, O3, and NO3 oxidation of Ambient Air: a Contrast of Different Anthropogenically-Influenced Biogenic Environments

    Science.gov (United States)

    Jimenez, J. L.

    2016-12-01

    Oxidation flow reactors (OFRs) are useful tools for studying potential secondary organic aerosol (SOA) formation from OH, O3, or NO3 oxidation in both laboratory and field experiments. With a several-minute residence time and a portable design with no inlet, OFRs are particularly well-suited for oxidizing ambient air to investigate in situ SOA formation from real ambient precursors. In recent years, our team has pioneered the use of OFRs to quantify SOA potential from a wide variety of environments, including a rural pine forest in the Rocky Mountains, a regionally polluted deciduous/coniferous forest in the SE US, the Amazon rain forest, air influenced by biomass burning, and urban outflow. We present a comparison of the SOA production from these contrasting sources. In all settings, the amount of SOA formed was larger at night than during the day. In forests, the amount of potential SOA after oxidation of ambient air correlated with biogenic precursors (e.g., monoterpenes). In urban air, potential SOA formation correlated instead with reactive anthropogenic tracers (e.g., trimethylbenzene). Despite these correlations, the SOA predicted to be formed by the oxidation of speciated ambient VOC concentrations could only explain approximately 10-50% of the total SOA formed from the oxidation of ambient air, regardless of location. Evidence suggests that lower-volatility gases (semivolatile and intermediate-volatility organic compounds; S/IVOCs) are present in ambient air and are a likely source of the SOA formation that cannot be explained by VOCs. These measurements show that S/IVOCs likely play an important intermediary role in ambient SOA formation in all of the sampled locations, from rural forests to urban air. Characteristics of the SOA formed from different air masses, e.g., H:C and O:C ratios of newly formed SOA as well as PMF factor analysis, will also be discussed.

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

    Science.gov (United States)

    Babakhani, Banafsheh

    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

  4. Biodiesel synthesis catalyzed by transition metal oxides: ferric-manganese doped tungstated/molybdena nanoparticle catalyst.

    Science.gov (United States)

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

    2015-01-01

    The solid acid Ferric-manganese doped tungstated/molybdena nananoparticle catalyst was prepared via impregnation reaction followed by calcination at 600°C 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°C; 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.

  5. Synthesis and characterization of carbon black/manganese oxide air cathodes for zinc-air batteries

    Science.gov (United States)

    Li, Po-Chieh; Hu, Chi-Chang; Lee, Tai-Chou; Chang, Wen-Sheng; Wang, Tsin Hai

    2014-12-01

    Due to the poor electric conductivity but the excellent catalytic ability for the oxygen reduction reaction (ORR), manganese dioxide in the α phase (denoted as α-MnO2) anchored onto carbon black powders (XC72) has been synthesized by the reflux method. The specific surface area and electric conductivity of the composites are generally enhanced by increasing the XC72 content while the high XC72 content will induce the formation of MnOOH which shows a worse ORR catalytic ability than α-MnO2. The ORR activity of such air cathodes have been optimized at the XC72/α-MnO2 ratio equal to 1 determined by the thermogravimetric analysis. By using this optimized cathode under the air atmosphere, the quasi-steady-state full-cell discharge voltages are equal to 1.353 and 1.178 V at 2 and 20 mA cm-2, respectively. Due to the usage of ambient air rather than pure oxygen, this Zn-air battery shows a modestly high discharge peak power density (67.51 mW cm-2) meanwhile the power density is equal to 47.22 mW cm-2 and the specific capacity is more than 750 mAh g-1 when this cell is operated at 1 V.

  6. Biogenic silica in space and time in sediments of Central Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Pattan, J.N.; Gupta, S.M.; Mudholkar, A.V.; Parthiban, G.

    rate averages 2.25 x 10/5 g.cm/2.y/1 and it is contributed from 33 to 50% of the total silica. Higher biogenic silica content of the surface sediment is well correlated with Mn, Cu and Ni concentration of the overlying manganese nodules. Higher biogenic...

  7. Morphology and phase identification of micron to nanosized manganese oxide (MnO) with variations in sintering time

    Science.gov (United States)

    Sasongko, Muhammad Ilman Nur; Puspitasari, Poppy; Yazirin, Cepi; Tsamroh, Dewi Izzatus; Risdanareni, Puput

    2017-09-01

    Manganese oxide (MnO) occurs in many rock types and may take the form of minerals. MnO has its drawbacks, namely highly reactive oxidizing species classified as dangerous and explosive at temperatures above 55 °C. Despite this,MnO has excellent magnetic, electrochemical, and conductivity properties, which should be reduced to nano-size to maximize their use and improve the properties of MnO. Phase and morphology characterization of powder this research aims to reduce the grain size of the MnO from micro to nano using the sol-gel method with various sintering times. Sol-gel is a simple synthesis method that has been proven capable of synthesizing a wide variety of micro-sized oxide materials into nano. Sintering time is a technique performed in the synthesis process to dry the material to a temperature above the normal temperature. The temperature used for sintering starting from 600 °C to 1000 °C. Characterizations were done using XRD, SEM, EDX, and FTIR machines. The sintering processes in this study used a temperature of 600 °C with different sintering periods of 30, 60 and 90 minutes. The XRD characterization with a 30-minute sintering time resulted in the smallest MnO in the form crystalline powder of 47.3 nm. The highest intensity (degree of crystallinity) found in MnO sintered for 90 minutes. The results of the morphological characterization of SEM showed a morphological change in MnO from micro-sized triangular to nano-sized spherical shape. The EDX characterization results indicated that the 30-minute sintering caused the lowest change in Mn and the highest change in O. The results of FTIR characterization showed a shift in C-H and Mn-O followed by an increase in the group of N-H, C=O and Mn-O.

  8. Integrated removal of NO and mercury from coal combustion flue gas using manganese oxides supported on TiO2.

    Science.gov (United States)

    Zhang, Shibo; Zhao, Yongchun; Wang, Zonghua; Zhang, Junying; Wang, Lulu; Zheng, Chuguang

    2017-03-01

    A catalyst composed of manganese oxides supported on titania (MnO x /TiO 2 ) synthesized by a sol-gel method was selected to remove nitric oxide and mercury jointly at a relatively low temperature in simulated flue gas from coal-fired power plants. The physico-chemical characteristics of catalysts were investigated by X-ray fluorescence (XRF), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses, etc. The effects of Mn loading, reaction temperature and individual flue gas components on denitration and Hg 0 removal were examined. The results indicated that the optimal Mn/Ti molar ratio was 0.8 and the best working temperature was 240°C for NO conversion. O 2 and a proper ratio of [NH 3 ]/[NO] are essential for the denitration reaction. Both NO conversion and Hg 0 removal efficiency could reach more than 80% when NO and Hg 0 were removed simultaneously using Mn0.8Ti at 240°C. Hg 0 removal efficiency slightly declined as the Mn content increased in the catalysts. The reaction temperature had no significant effect on Hg 0 removal efficiency. O 2 and HCl had a promotional effect on Hg 0 removal. SO 2 and NH 3 were observed to weaken Hg 0 removal because of competitive adsorption. NO first facilitated Hg 0 removal and then had an inhibiting effect as NO concentration increased without O 2 , and it exhibited weak inhibition of Hg 0 removal efficiency in the presence of O 2 . The oxidation of Hg 0 on MnO x /TiO 2 follows the Mars-Maessen and Langmuir-Hinshelwood mechanisms. Copyright © 2016. Published by Elsevier B.V.

  9. The effects of iron(II) on the kinetics of arsenic oxidation and sorption on manganese oxides.

    Science.gov (United States)

    Wu, Yun; Li, Wei; Sparks, Donald L

    2015-11-01

    In this study, As(III) oxidation kinetics by a poorly-crystalline phyllomanganate (δ-MnO2) in the presence and absence of dissolved Fe(II) was investigated using stirred-flow and batch experiments. Chemically synthetic δ-MnO2 was reacted with four influent solutions, containing the same As(III) concentration but different Fe(II) concentrations, at pH 6. The results show an initial rapid As(III) oxidation by δ-MnO2, which is followed by an appreciably slow reaction after 8h. In the presence of Fe(II), As(III) oxidation is inhibited due to the competitive oxidation of Fe(II) as well as the formation of Fe(III)-(hydr)oxides on the δ-MnO2 surface. However, the sorption of As(III), As(V) and Mn(II) are increased, for the newly formed Fe(III)-(hydr)oxides provide additional sorption sites. This study suggests that the competitive oxidation of Fe(II) and consequently the precipitation of Fe(III) compounds on the δ-MnO2 surface play an important role in As(III) oxidation and As sequestration. Understanding these processes would be helpful in developing in situ strategies for remediation of As-contaminated waters and soils. Copyright © 2015 Elsevier Inc. All rights reserved.

  10. Biogenic nitrogen oxide emissions from soils ─ impact on NOx and ozone over West Africa during AMMA (African Monsoon Multidisciplinary Experiment: modelling study

    Directory of Open Access Journals (Sweden)

    J.-P. Chaboureau

    2008-05-01

    Full Text Available Nitrogen oxide biogenic emissions from soils are driven by soil and environmental parameters. The relationship between these parameters and NO fluxes is highly non linear. A new algorithm, based on a neural network calculation, is used to reproduce the NO biogenic emissions linked to precipitations in the Sahel on the 6 August 2006 during the AMMA campaign. This algorithm has been coupled in the surface scheme of a coupled chemistry dynamics model (MesoNH Chemistry to estimate the impact of the NO emissions on NOx and O3 formation in the lower troposphere for this particular episode. Four different simulations on the same domain and at the same period are compared: one with anthropogenic emissions only, one with soil NO emissions from a static inventory, at low time and space resolution, one with NO emissions from neural network, and one with NO from neural network plus lightning NOx. The influence of NOx from lightning is limited to the upper troposphere. The NO emission from soils calculated with neural network responds to changes in soil moisture giving enhanced emissions over the wetted soil, as observed by aircraft measurements after the passing of a convective system. The subsequent enhancement of NOx and ozone is limited to the lowest layers of the atmosphere in modelling, whereas measurements show higher concentrations above 1000 m. The neural network algorithm, applied in the Sahel region for one particular day of the wet season, allows an immediate response of fluxes to environmental parameters, unlike static emission inventories. Stewart et al (2008 is a companion paper to this one which looks at NOx and ozone concentrations in the boundary layer as measured on a research aircraft, examines how they vary with respect to the soil moisture, as indicated by surface temperature anomalies, and deduces NOx fluxes. In this current paper the model-derived results are compared to the observations and calculated fluxes presented by Stewart et

  11. Protective effects of antioxidants and anti-inflammatory agents against manganese-induced oxidative damage and neuronal injury

    Energy Technology Data Exchange (ETDEWEB)

    Milatovic, Dejan, E-mail: dejan.milatovic@vanderbilt.edu [Vanderbilt University School of Medicine, Department of Pediatrics, Nashville, TN (United States); Gupta, Ramesh C. [Murray State University, Breathitt Veterinary Center, Hopkinsville, KY (United States); Yu, Yingchun; Zaja-Milatovic, Snjezana [Vanderbilt University School of Medicine, Department of Pediatrics, Nashville, TN (United States); Aschner, Michael [Vanderbilt University School of Medicine, Department of Pediatrics, Nashville, TN (United States); Pharmacology and the Kennedy Center for Research on Human Development, Nashville, TN (United States)

    2011-11-15

    Exposure to excessive manganese (Mn) levels leads to neurotoxicity, referred to as manganism, which resembles Parkinson's disease (PD). Manganism is caused by neuronal injury in both cortical and subcortical regions, particularly in the basal ganglia. The basis for the selective neurotoxicity of Mn is not yet fully understood. However, several studies suggest that oxidative damage and inflammatory processes play prominent roles in the degeneration of dopamine-containing neurons. In the present study, we assessed the effects of Mn on reactive oxygen species (ROS) formation, changes in high-energy phosphates and associated neuronal dysfunctions both in vitro and in vivo. Results from our in vitro study showed a significant (p < 0.01) increase in biomarkers of oxidative damage, F{sub 2}-isoprostanes (F{sub 2}-IsoPs), as well as the depletion of ATP in primary rat cortical neurons following exposure to Mn (500 {mu}M) for 2 h. These effects were protected when neurons were pretreated for 30 min with 100 of an antioxidant, the hydrophilic vitamin E analog, trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), or an anti-inflammatory agent, indomethacin. Results from our in vivo study confirmed a significant increase in F{sub 2}-IsoPs levels in conjunction with the progressive spine degeneration and dendritic damage of the striatal medium spiny neurons (MSNs) of mice exposed to Mn (100 mg/kg, s.c.) 24 h. Additionally, pretreatment with vitamin E (100 mg/kg, i.p.) or ibuprofen (140 {mu}g/ml in the drinking water for two weeks) attenuated the Mn-induced increase in cerebral F{sub 2}-IsoPs? and protected the MSNs from dendritic atrophy and dendritic spine loss. Our findings suggest that the mediation of oxidative stress/mitochondrial dysfunction and the control of alterations in biomarkers of oxidative injury, neuroinflammation and synaptodendritic degeneration may provide an effective, multi-pronged therapeutic strategy for protecting dysfunctional

  12. Morphology–dependent electrochemical sensing properties of manganese dioxide–graphene oxide hybrid for guaiacol and vanillin

    International Nuclear Information System (INIS)

    Gan, Tian; Shi, Zhaoxia; Deng, Yaping; Sun, Junyong; Wang, Haibo

    2014-01-01

    Highlights: • MnO 2 with different morphologies were prepared via facile methods. • MnO 2 are loaded on GO via simply grinding which have high solubility and stability. • MnO 2 –GO exhibit high electrocatalytic activities depending on their shapes. • MnO 2 –GO is first used to the determination of guaiacol and vanillin simultaneously. - Abstract: Various morphologies of manganese dioxide (MnO 2 ) electrocatalysts, including nanoflowers, nanorods, nanotubes, nanoplates, nanowires and microspheres were prepared via facile hydrothermal synthesis and precipitation methods. By simply grinding with graphene oxide (GO), MnO 2 could be readily dissolved in water with high solubility and stability. The structures and electrochemical performances of these as–prepared MnO 2 –GO hybrids were fully characterized by various techniques, and the properties were found to be strongly dependent on morphology. As sensing materials for the simultaneous determination of guaiacol and vanillin for the first time, the nanoflowers–like MnO 2 , coupled with GO, exhibited relatively high sensitivity. The enhanced electrocatalytic activity was ascribed to the high purity, good crystallinity, and unique porous microstructure, which were favorable for transfer of electrons. These results may provide valuable insights for the development of nanostructured modified electrodes for next–generation high–performance electrochemical sensors

  13. Improved electrochemical performances of Li-rich nickel cobalt manganese oxide by partial substitution of Li+ by Mg2+

    Science.gov (United States)

    Sallard, Sébastien; Sheptyakov, Denis; Villevieille, Claire

    2017-08-01

    Li-rich nickel cobalt manganese oxide (NCM) materials with partial substitution of lithium by magnesium is synthesized by the Pechini process. Different synthesized Li100-2xMgx-NCM materials (x = 0, 1, 2.5, 5, and 10) are investigated by X-ray diffraction (XRD), neutron diffraction, and scanning electron microscopy to determine the role of Mg in the structure and its impact on the morphology and electrochemical properties. The chemical composition, crystal structure, and particle morphology are compared with those of the reference (x = 0) material. Mg substitution has a significant impact on the electrochemical properties. In comparison with the reference sample, the x = 1 sample exhibits a mitigation of the voltage drop owing to more stable structure during cycling, leading to a specific discharge of 210 mAh g-1 after 100 cycles at C/10 rate. However, compositions with x ≥ 2.5 exhibit larger voltage drop in discharge, due to the faster formation of a spinel-like structure during cycling.

  14. Impedance change and capacity fade of lithium nickel manganese cobalt oxide-based batteries during calendar aging

    Science.gov (United States)

    Schmitt, Julius; Maheshwari, Arpit; Heck, Michael; Lux, Stephan; Vetter, Matthias

    2017-06-01

    The calendar aging of commercial 18650 lithium-ion batteries with lithium nickel manganese cobalt oxide cathode and graphite anode is studied by regular electrochemical characterization of batteries stored at defined conditions. The cell capacity is found to decrease linearly with time and shows a faster decrease at higher storage temperatures. From current pulse tests, it is determined that both higher temperature and higher state of charge (SOC) cause accelerated resistance increase with storage time. Changes in different battery parameters during storage are also quantified by analyzing electrochemical impedance spectroscopy (EIS) spectra. The cell degradation causes a gradual increase of the ohmic and the total polarization resistance with storage duration, where the latter one is found to be the main contributor to the increased cell impedance. An increase in the mean relaxation time constant and changes in the porous structure for the electrode processes are observed from EIS analysis. Resistance for this cell chemistry is found to be current independent by comparing the cell resistance calculated from the current pulse method after 1s and from the EIS analysis at 1 Hz. Furthermore, it is seen that the additional charge throughput due to the periodic electrochemical characterization induces significant cell degradation effects.

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

    Science.gov (United States)

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

    2015-03-21

    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. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Selective hydrogenation of halogenated arenes using porous manganese oxide (OMS-2) and platinum supported OMS-2 catalysts.

    Science.gov (United States)

    McManus, Iain J; Daly, Helen; Manyar, Haresh G; Taylor, S F Rebecca; Thompson, Jillian M; Hardacre, Christopher

    2016-07-04

    Porous manganese oxide (OMS-2) and platinum supported on OMS-2 catalysts have been shown to facilitate the hydrogenation of the nitro group in chloronitrobenzene to give chloroaniline with no dehalogenation. Complete conversion was obtained within 2 h at 25 °C and, although the rate of reaction increased with increasing temperature up to 100 °C, the selectivity to chloroaniline remained at 99.0%. Use of Pd/OMS-2 or Pt/Al2O3 resulted in significant dechlorination even at 25 °C and 2 bar hydrogen pressure giving a selectivity to chloroaniline of 34.5% and 77.8%, respectively, at complete conversion. This demonstrates the potential of using platinum group metal free catalysts for the selective hydrogenation of halogenated aromatics. Two pathways were observed for the analogous nitrobenzene hydrogenation depending on the catalyst used. The hydrogenation of nitrobenzene was found to follow a direct pathway to aniline and nitrosobenzene over Pd/OMS-2 in contrast to the OMS and Pt/OMS-2 catalysts which resulted in formation of nitrosobenzene, azoxybenzene and azobenzene/hydrazobenzene intermediates before complete conversion to aniline. These results indicate that for Pt/OMS-2 the hydrogenation proceeds predominantly over the support with the metal acting to dissociate hydrogen. In the case of Pd/OMS-2 both the hydrogenation and hydrogen adsorption occur on the metal sites.

  17. Removal of arsenic from water using manganese (III) oxide: Adsorption of As(III) and As(V).

    Science.gov (United States)

    Babaeivelni, Kamel; Khodadoust, Amid P

    2016-01-01

    Removal of arsenic from water was evaluated with manganese (III) oxide (Mn2O3) as adsorbent. Adsorption of As(III) and As(V) onto Mn2O3 was favorable according to the Langmuir and Freundlich adsorption equilibrium equations, while chemisorption of arsenic occurred according to the Dubinin-Radushkevich equation. Adsorption parameters from the Langmuir, Freundlich, and Temkin equations showed a greater adsorption and removal of As(III) than As(V) by Mn2O3. Maximum removal of As(III) and As(V) occurred at pH 3-9 and at pH 2, respectively, while removal of As(V) in the pH range of 6-9 was 93% (pH 6) to 61% (pH 9) of the maximum removal. Zeta potential measurements for Mn2O3 in As(III) was likely converted to As(V) solutions indicated that As(III) was likely converted to As(V) on the Mn2O3 surface at pH 3-9. Overall, the effective Mn2O3 sorbent rapidly removed As(III) and As(V) from water in the pH range of 6-9 for natural waters.

  18. Epitaxial growth of manganese oxide films on MgAl2O4 (001) substrates and the possible mechanism

    Science.gov (United States)

    Ren, Lizhu; Wu, Shuxiang; Zhou, Wenqi; Li, Shuwei

    2014-03-01

    Three types of manganese oxide films were grown on MgAl2O4 (001) substrates by plasma-assisted molecular beam epitaxy (PA-MBE) under different growth rates and substrate temperatures. The structural characteristics and chemical compositions of the films were investigated by using in-situ reflection high-energy electron diffraction (RHEED), ex-situ X-ray diffraction, Raman, and X-ray photoelectron spectra (XPS). At a lower substrate temperature (730 K), the epitaxial film tends to form mixed phases with a coexistence of Mn3O4 and Mn5O8 in order to relieve the mismatch-strain. However, at a higher substrate temperature (750 K), all of the films crystallize into Mn3O4; the critical thickness of the film grown under a lower growth rate (7 Å/min) is much larger than that under a high growth rate (10 Å/min). When the film reaches a certain critical thickness, the surface will become fairly rough, and another oriented phase Mn3O4 would crystallize on such a surface.

  19. Catalytic ozonation of sulfamethoxazole by composite iron-manganese silicate oxide: cooperation mechanism between adsorption and catalytic reaction.

    Science.gov (United States)

    Gao, Guoying; Kang, Jing; Shen, Jimin; Chen, Zhonglin; Chu, Wei

    2016-11-01

    A systematic investigation of the cooperation mechanism between adsorption and catalytic reaction during the catalytic ozonation of sulfamethoxazole (SMX) by composite iron-manganese silicate oxide (FMSO) was carried out in this work. Results showed that the total organic carbon (TOC) removal increased significantly from 27 % (sole-ozonation) to 79.8 % (FMSO catalytic ozonation). The presence of FMSO in the ozonation process effectively enhanced the ozone utilization efficiency and accelerated the transformation of ozone into hydroxyl radicals. The latter result was verified by the indirect method, using NaHSO 3 as the reductor, and the direct electron spin resonance (ESR) determination technology. The adsorption of SMX on FMSO was minimal (1.8 %). However, ozone rapidly converted SMX into various intermediates, which was exhibited by the much higher adsorption affinity on the surface of FMSO than that of SMX. The accumulation of various intermediates on the FMSO surface also increased their contact probability with the ·OH radicals generated by the ozone decomposition. The continuous interaction of intermediates with ·OH radicals could further promote the benign cycling of the release of adsorption sites and the succeeding adsorption/decomposition of ozone and intermediates on FMSO. This could be another reason for the higher and faster TOC removal rate.

  20. Effects of manganese oxide on arsenic reduction and leaching from contaminated floodplain soil

    DEFF Research Database (Denmark)

    Ehlert, Katrin; Mikutta, Christian; Kretzschmar, Ruben

    2016-01-01

    Reductive release of the potentially toxic metalloid As from Fe(III) (oxyhydr)oxides has been identified as an important process leading to elevated As porewater concentrations in soils and sediments. Despite the ubiquitous presence of Mn oxides in soils and their oxidizing power toward As......(III), their impact on interrelated As, Fe, and Mn speciation under microbially reducing conditions remains largely unknown. For this reason, we employed a column setup and X-ray absorption spectroscopy to investigate the influence of increasing birnessite concentrations (molar soil Fe-to-Mn ratios: 4.8, 10.2, and 24.......7) on As speciation and release from an As-contaminated floodplain soil (214 mg As/kg) under anoxic conditions. Our results show that birnessite additions significantly decreased As leaching. The reduction of both As and Fe was delayed, and As(III) accumulated in birnessite-rich column parts, indicating...

  1. Susceptibility of dry-cured tuna to oxidative deterioration and biogenic amines generation: I. Effect of NaCl content, antioxidant type and ageing.

    Science.gov (United States)

    Roseiro, L C; Santos, C; Gonçalves, H; Serrano, C; Aleixo, C; Partidário, A; Lourenço, A R; Dias, M Abreu; da Ponte, D J B

    2017-08-01

    This study aimed to assess lipid oxidation and biogenic amine (BA) development in "muxama", a dry-cured tuna muscle product, as affected by salt content, antioxidant type and ageing time. Overall, BA contents decreased with NaCl level (2785.1mgkg -1 , 1148.1mgkg -1 and 307.7mgkg -1 ) and increased with ageing time (366.2mgkg -1 , 1711.8mgkg -1 and 2959.2mgkg -1 in the final product (T0), and after 1 (T1) and 3 (T3) months of ageing, respectively). Regardless of the test conditions, the most concentrated BA was always tyramine. For the ageing periods considered in the present study, malondialdehyde formation was affected by the NaCl level, with the saltiest samples exhibiting lower content. Rosemary and sage extracts represented promising technological options for preserving muxama from oxidation and to minimize the presence of a fishy flavour and odour, but this treatment may cause the colour to lose some of its redness and become less appealing. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. A chromatographic method to analyze products from photo-oxidation of anthropogenic and biogenic mixtures of volatile organic compounds in smog chambers.

    Science.gov (United States)

    Pindado Jiménez, Oscar; Pérez Pastor, Rosa M; Vivanco, Marta G; Santiago Aladro, Manuel

    2013-03-15

    A method for quantifying secondary organic aerosol compounds (SOA) and water soluble secondary organic aerosol compounds (WSOA) produced from photo-oxidation of complex mixtures of volatile organic compounds (VOCs) in smog chambers by gas chromatography/mass spectrometry (GC/MS) has been developed. This method employs a double extraction with water and methanol jointly to a double derivatization with N,O-bis (trimethylsilil) trifluoroacetamide (BSTFA) and O-(2,3,4,5,6)-pentafluorobenzyl-hydroxylamine hydrochloride (PFBHA) followed by an analysis performed by GC/MS. The analytical procedure complements other methodologies because it can analyze SOA and WSOA compounds simultaneously at trace levels. As application, the methodology was employed to quantify the organic composition of aerosols formed in a smog chamber as a result of photo-oxidation of two different mixtures of volatile organic compounds: an anthropogenic mixture and a biogenic mixture. The analytical method allowed us to quantify up to 17 SOA compounds at levels higher than 20 ng m(-3) with reasonable recovery and a precision below 11%. Values found for applicability, selectivity, linearity, precision, recovery, detection limit, quantification limit and sensitivity demonstrated that the methodology can be satisfactorily applied to quantify SOA and WSOA. Copyright © 2012 Elsevier B.V. All rights reserved.

  3. Comparison of iron and copper doped manganese cobalt spinel oxides as protective coatings for solid oxide fuel cell interconnects

    DEFF Research Database (Denmark)

    Talic, Belma; Molin, Sebastian; Wiik, Kjell

    2017-01-01

    MnCo2O4, MnCo1.7Cu0.3O4 and MnCo1.7Fe0.3O4 are investigated as coatings for corrosion protection of metallic interconnects in solid oxide fuel cell stacks. Electrophoretic deposition is used to deposit the coatings on Crofer 22 APU alloy. All three coating materials reduce the parabolic oxidation...... rate in air at 900 °C and 800 °C. At 700 °C there is no significant difference in oxidation rate between coated samples and uncoated pre-oxidized Crofer 22 APU. The cross-scale area specific resistance (ASR) is measured in air at 800 °C using La0.85Sr0.1Mn1.1O3 (LSM) contact plates to simulate...

  4. Manganese associated nanoparticles agglomerate of iron(III) oxide: synthesis, characterization and arsenic(III) sorption behavior with mechanism.

    Science.gov (United States)

    Gupta, Kaushik; Maity, Arjun; Ghosh, Uday Chand

    2010-12-15

    Three samples of manganese associated hydrous iron(III) oxide (MNHFO), prepared by incinerating metal hydroxide precipitate at T (± 5)=90, 300 and 600°C, showed increase of crystalline nature in XRD patterns with decreasing As(III) removal percentages. TEM images showed the increase of crystallinity from sample-1 (MNHFO-1) to sample-3 (MNHFO-3). Dimensions (nm) of particles estimated were 5.0, 7.0 and 97.5. Optimization of pH indicated that MNHFO-1 could remove aqueous As(III) efficiently at pH between 3.0 and 7.0. Kinetic and equilibrium data of reactions under the experimental conditions described the pseudo-second order and the Langmuir isotherm equations very well, respectively. The Langmuir capacity (q(m)) estimated was 691.04 mmol kg(-1). The values of enthalpy, Gibb's free energy and entropy changes (ΔH(0)=+23.23 kJ mol(-1), ΔG(0)=-3.43 to -7.20 kJ mol(-1) at T=283-323K, ΔS(0)=+0.094 kJ mol(-1)K(-1)) suggested that the reaction was endothermic, spontaneous and took place with increasing entropy. The As(III) sorbed by MNHFO-1 underwent surface oxidation to As(V), and evidences appeared from the XPS and FTIR investigations. MNHFO-1 packed column (internal diameter: 1.0 cm, height: 3.7 cm) filtered 11.5 dm(3) groundwater (105 μg As dm(-3)) with reducing arsenic concentration to ≤ 10 μg dm(-3). Copyright © 2010 Elsevier B.V. All rights reserved.

  5. Electrochemical Modeling and Performance of a Lithium- and Manganese-Rich Layered Transition-Metal Oxide Positive Electrode

    Energy Technology Data Exchange (ETDEWEB)

    Dees, Dennis W.; Abraham, Daniel P; Lu, Wenquan; Gallagher, Kevin G.; Bettge, Martin; Jansen, Andrew N

    2015-01-21

    The impedance of a lithium- and manganese-rich layered transition-metal oxide (MR-NMC) positive electrode, specifically Li1.2Ni0.15Mn0.55Co0.1O2, is compared to two other transition-metal layered oxide materials, specifically LiNi0.8Co0.15Al0.05O2 (NCA) and Li1.05(Ni1/3Co1/3Mn1/3)0.95O2 (NMC). A more detailed electrochemical impedance spectroscopy (EIS) study is conducted on the LMR-NMC electrode, which includes a range of states-of-charge (SOCs) for both current directions (i.e. charge and discharge) and two relaxation times (i.e. hours and one hundred hours) before the EIS sweep. The LMR-NMC electrode EIS studies are supported by half-cell constant current and galvanostatic intermittent titration technique (GITT) studies. Two types of electrochemical models are utilized to examine the results. The first type is a lithium ion cell electrochemical model for intercalation active material electrodes that includes a complex active material/electrolyte interfacial structure. In conclusion, the other is a lithium ion half-cell electrochemical model that focuses on the unique composite structure of the bulk LMR-NMC materials.

  6. Effect of respiration and manganese on oxidative stress resistance of Lactobacillus plantarum WCFS1

    NARCIS (Netherlands)

    Watanabe, M.; Veen, van der S.; Nakajima, H.; Abee, T.

    2012-01-01

    Lactobacillus plantarum is a facultatively anaerobic bacterium that can perform respiration under aerobic conditions in the presence of haem, with vitamin K2 acting as a source of menaquinone. We investigated growth performance and oxidative stress resistance of Lb. plantarum WCFS1 cultures grown in

  7. Cooperative functions of manganese and thiol redox system against oxidative stress in human spermatozoa

    Directory of Open Access Journals (Sweden)

    Amrit Kaur Bansal

    2009-01-01

    Full Text Available Aims: In this study, the effects of 0.1 mM Mn 2+ on thiol components (total thiols [TSH], glutathione reduced [GSH], glutathione oxidized [GSSG] and redox ratio [GSH/ GSSG] have been determined in human spermatozoa. Settings and Design: The subjects of the study were healthy males having more than 75% motility and 80 x 10 6 sperms/mL. Materials and Methods: Fresh semen was suspended in phosphate-buffered saline (PBS (pH 7.2 and this suspension was divided into eight equal fractions. All fractions, control (containing PBS and experimental (treated/untreated with [ferrous ascorbate, FeAA - 200 FeSO 4 μM, 1000 μM ascorbic acid, nicotine (0.5 mM and FeAA + nicotine], supplemented/unsupplemented with Mn 2+ [0.1 mM], were incubated for 2 h at 378C. These fractions were assessed for determining the thiol components. Statistical Analysis: The data were statistically analyzed by Students " t" test. Results and Conclusions: Ferrous ascorbate, nicotine and ferrous ascorbate + nicotine induced oxidative stress and decreased GSH and redox ratio (GSH/GSSG ratio but increased the TSH and GSSG levels. Mn 2+ supplementation improved TSH, GSH and redox ratio (GSH/GSSG but decreased the GSSG level under normal and oxidative stress conditions. Thiol groups serve as defense mechanisms of sperm cells to fight against oxidative stress induced by stress inducers such as ferrous ascorbate, nicotine and their combination (ferrous ascorbate + nicotine. In addition, Mn 2+ supplementation maintains the thiol level by reducing oxidative stress.

  8. Charge storage mechanisms of manganese oxide nanosheets and N-doped reduced graphene oxide aerogel for high-performance asymmetric supercapacitors

    Science.gov (United States)

    Iamprasertkun, Pawin; Krittayavathananon, Atiweena; Seubsai, Anusorn; Chanlek, Narong; Kidkhunthod, Pinit; Sangthong, Winyoo; Maensiri, Santi; Yimnirun, Rattikorn; Nilmoung, Sukanya; Pannopard, Panvika; Ittisanronnachai, Somlak; Kongpatpanich, Kanokwan; Limtrakul, Jumras; Sawangphruk, Montree

    2016-11-01

    Although manganese oxide- and graphene-based supercapacitors have been widely studied, their charge storage mechanisms are not yet fully investigated. In this work, we have studied the charge storage mechanisms of K-birnassite MnO2 nanosheets and N-doped reduced graphene oxide aerogel (N-rGOae) using an in situ X-ray absorption spectroscopy (XAS) and an electrochemical quart crystal microbalance (EQCM). The oxidation number of Mn at the MnO2 electrode is +3.01 at 0 V vs. SCE for the charging process and gets oxidized to +3.12 at +0.8 V vs. SCE and then reduced back to +3.01 at 0 V vs. SCE for the discharging process. The mass change of solvated ions, inserted to the layers of MnO2 during the charging process is 7.4 μg cm-2. Whilst, the mass change of the solvated ions at the N-rGOae electrode is 8.4 μg cm-2. An asymmetric supercapacitor of MnO2//N-rGOae (CR2016) provides a maximum specific capacitance of ca. 467 F g-1 at 1 A g-1, a maximum specific power of 39 kW kg-1 and a specific energy of 40 Wh kg-1 with a wide working potential of 1.6 V and 93.2% capacity retention after 7,500 cycles. The MnO2//N-rGOae supercapacitor may be practically used in high power and energy applications.

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

    Science.gov (United States)

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

    2009-09-01

    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.

  10. Protective effects of antioxidants and anti-inflammatory agents against manganese-induced oxidative damage and neuronal injury

    International Nuclear Information System (INIS)

    Milatovic, Dejan; Gupta, Ramesh C.; Yu, Yingchun; Zaja-Milatovic, Snjezana; Aschner, Michael

    2011-01-01

    Exposure to excessive manganese (Mn) levels leads to neurotoxicity, referred to as manganism, which resembles Parkinson's disease (PD). Manganism is caused by neuronal injury in both cortical and subcortical regions, particularly in the basal ganglia. The basis for the selective neurotoxicity of Mn is not yet fully understood. However, several studies suggest that oxidative damage and inflammatory processes play prominent roles in the degeneration of dopamine-containing neurons. In the present study, we assessed the effects of Mn on reactive oxygen species (ROS) formation, changes in high-energy phosphates and associated neuronal dysfunctions both in vitro and in vivo. Results from our in vitro study showed a significant (p 2 -isoprostanes (F 2 -IsoPs), as well as the depletion of ATP in primary rat cortical neurons following exposure to Mn (500 μM) for 2 h. These effects were protected when neurons were pretreated for 30 min with 100 of an antioxidant, the hydrophilic vitamin E analog, trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), or an anti-inflammatory agent, indomethacin. Results from our in vivo study confirmed a significant increase in F 2 -IsoPs levels in conjunction with the progressive spine degeneration and dendritic damage of the striatal medium spiny neurons (MSNs) of mice exposed to Mn (100 mg/kg, s.c.) 24 h. Additionally, pretreatment with vitamin E (100 mg/kg, i.p.) or ibuprofen (140 μg/ml in the drinking water for two weeks) attenuated the Mn-induced increase in cerebral F 2 -IsoPs? and protected the MSNs from dendritic atrophy and dendritic spine loss. Our findings suggest that the mediation of oxidative stress/mitochondrial dysfunction and the control of alterations in biomarkers of oxidative injury, neuroinflammation and synaptodendritic degeneration may provide an effective, multi-pronged therapeutic strategy for protecting dysfunctional dopaminergic transmission and slowing of the progression of Mn-induced neurodegenerative

  11. Comparative Analysis of Secretome Profiles of Manganese(II)-Oxidizing Ascomycete Fungi.

    Science.gov (United States)

    Zeiner, Carolyn A; Purvine, Samuel O; Zink, Erika M; Paša-Tolić, Ljiljana; Chaput, Dominique L; Haridas, Sajeet; Wu, Si; LaButti, Kurt; Grigoriev, Igor V; Henrissat, Bernard; Santelli, Cara M; Hansel, Colleen M

    2016-01-01

    Fungal secretomes contain a wide range of hydrolytic and oxidative enzymes, including cellulases, hemicellulases, pectinases, and lignin-degrading accessory enzymes, that synergistically drive litter decomposition in the environment. While secretome studies of model organisms such as Phanerochaete chrysosporium and Aspergillus species have greatly expanded our knowledge of these enzymes, few have extended secretome characterization to environmental isolates or conducted side-by-side comparisons of diverse species. Thus, the mechanisms of carbon degradation by many ubiquitous soil fungi remain poorly understood. Here we use a combination of LC-MS/MS, genomic, and bioinformatic analyses to characterize and compare the protein composition of the secretomes of four recently isolated, cosmopolitan, Mn(II)-oxidizing Ascomycetes (Alternaria alternata SRC1lrK2f, Stagonospora sp. SRC1lsM3a, Pyrenochaeta sp. DS3sAY3a, and Paraconiothyrium sporulosum AP3s5-JAC2a). We demonstrate that the organisms produce a rich yet functionally similar suite of extracellular enzymes, with species-specific differences in secretome composition arising from unique amino acid sequences rather than overall protein function. Furthermore, we identify not only a wide range of carbohydrate-active enzymes that can directly oxidize recalcitrant carbon, but also an impressive suite of redox-active accessory enzymes that suggests a role for Fenton-based hydroxyl radical formation in indirect, non-specific lignocellulose attack. Our findings highlight the diverse oxidative capacity of these environmental isolates and enhance our understanding of the role of filamentous Ascomycetes in carbon turnover in the environment.

  12. Comparative Analysis of Secretome Profiles of Manganese(II-Oxidizing Ascomycete Fungi.

    Directory of Open Access Journals (Sweden)

    Carolyn A Zeiner

    Full Text Available Fungal secretomes contain a wide range of hydrolytic and oxidative enzymes, including cellulases, hemicellulases, pectinases, and lignin-degrading accessory enzymes, that synergistically drive litter decomposition in the environment. While secretome studies of model organisms such as Phanerochaete chrysosporium and Aspergillus species have greatly expanded our knowledge of these enzymes, few have extended secretome characterization to environmental isolates or conducted side-by-side comparisons of diverse species. Thus, the mechanisms of carbon degradation by many ubiquitous soil fungi remain poorly understood. Here we use a combination of LC-MS/MS, genomic, and bioinformatic analyses to characterize and compare the protein composition of the secretomes of four recently isolated, cosmopolitan, Mn(II-oxidizing Ascomycetes (Alternaria alternata SRC1lrK2f, Stagonospora sp. SRC1lsM3a, Pyrenochaeta sp. DS3sAY3a, and Paraconiothyrium sporulosum AP3s5-JAC2a. We demonstrate that the organisms produce a rich yet functionally similar suite of extracellular enzymes, with species-specific differences in secretome composition arising from unique amino acid sequences rather than overall protein function. Furthermore, we identify not only a wide range of carbohydrate-active enzymes that can directly oxidize recalcitrant carbon, but also an impressive suite of redox-active accessory enzymes that suggests a role for Fenton-based hydroxyl radical formation in indirect, non-specific lignocellulose attack. Our findings highlight the diverse oxidative capacity of these environmental isolates and enhance our understanding of the role of filamentous Ascomycetes in carbon turnover in the environment.

  13. Comparative Analysis of Secretome Profiles of Manganese(II)-Oxidizing Ascomycete Fungi

    Energy Technology Data Exchange (ETDEWEB)

    Zeiner, Carolyn A.; Purvine, Samuel O.; Zink, Erika M.; Paša-Tolić, Ljiljana; Chaput, Dominique L.; Haridas, Sajeet; Wu, Si; LaButti, Kurt; Grigoriev, Igor V.; Henrissat, Bernard; Santelli, Cara M.; Hansel, Colleen M.; Pöggeler, Stefanie

    2016-07-19

    Fungal secretomes contain a wide range of hydrolytic and oxidative enzymes, including cellulases, hemicellulases, pectinases, and lignin-degrading accessory enzymes, that synergistically drive litter decomposition in the environment. While secretome studies of model organisms such as Phanerochaete chrysosporium and Aspergillus species have greatly expanded our knowledge of these enzymes, few have extended secretome characterization to environmental isolates or conducted side-by-side comparisons of diverse species. Thus, the mechanisms of carbon degradation by many ubiquitous soil fungi remain poorly understood. Here we use a combination of LC-MS/MS, genomic, and bioinformatic analyses to characterize and compare the protein composition of the secretomes of four recently isolated, cosmopolitan, Mn(II)-oxidizing Ascomycetes (Alternaria alternata SRC1lrK2f, Stagonospora sp. SRC1lsM3a, Pyrenochaeta sp. DS3sAY3a, and Paraconiothyrium sporulosum AP3s5-JAC2a). We demonstrate that the organisms produce a rich yet functionally similar suite of extracellular enzymes, with species-specific differences in secretome composition arising from unique amino acid sequences rather than overall protein function. Furthermore, we identify not only a wide range of carbohydrate-active enzymes that can directly oxidize recalcitrant carbon, but also an impressive suite of redox-active accessory enzymes that suggests a role for Fenton-based hydroxyl radical formation in indirect, non-specific lignocellulose attack. Our findings highlight the diverse oxidative capacity of these environmental isolates and enhance our understanding of the role of filamentous Ascomycetes in carbon turnover in the environment.

  14. Thallium isotopes track fluctuations in global manganese oxide burial during the Ediacaran Period

    Science.gov (United States)

    Ostrander, C. M.; Nielsen, S.; Owens, J. D.; Jiang, G.; Planavsky, N.; Sahoo, S. K.; Zhang, F.; Lyons, T. W.; Anbar, A. D.

    2017-12-01

    Complex marine ecosystems appear in the geologic record for the first time during the Ediacaran (635 - 541 Ma), after the Marinoan Glaciation but before the Cambrian Explosion. Much debate surrounds the redox-state of global oceans during this diversification, with some arguing for pervasive anoxic conditions and others for increased oxygenation, including the possibility of episodic oxygen increases. Here, we use thallium (Tl) isotopes preserved in organic-rich shales from a deep-water section at Wuhe, South China, to track large-scale perturbations in Mn oxide burial during the Ediacaran. Changes to the Tl isotope composition of seawater over geologic timescales are driven dominantly by fluctuations in global Mn oxide burial, which require persistent O2 at the sediment-water interface. Importantly, the suite of sedimentary rocks analyzed is thought to have been deposited beneath persistent localized euxinia, which is an environment shown to effectively capture the Tl isotope composition of seawater. Within samples previously suggested to host oceanic oxygenation episodes (OOEs) because of high redox-sensitive element (RSE) enrichments (Sahoo et al. 2016, Geobiology), we find Tl isotope values as light as -5 epsilon units, which are indicative of removal of heavy Tl by Mn oxides elsewhere in the Ediacaran ocean and in-line with the presence of deep-marine O2. Intriguingly, between these events, during periods previously viewed as dominantly anoxic, we find Tl isotope excursions to values that are even lighter than during the OOEs (less than -10 epsilon units). To first order, these results imply that an even larger Mn oxide sink was present between the OOEs, which would require pervasive oceanic oxygenation. This interpretation is in direct conflict with interpretations of low RSE enrichments in these same samples, which invoke reservoir drawdown due to widespread anoxia—as well as many other data that suggest dominantly anoxic deep marine conditions through the

  15. Effects of subchronic manganese chloride exposure on tambaqui (Colossoma macropomum) tissues: oxidative stress and antioxidant defenses.

    Science.gov (United States)

    Gabriel, Diogo; Riffel, Ana Paula K; Finamor, Isabela A; Saccol, Etiane M H; Ourique, Giovana M; Goulart, Luis O; Kochhann, Daiani; Cunha, Mauro A; Garcia, Luciano O; Pavanato, Maria A; Val, Adalberto L; Baldisserotto, Bernardo; Llesuy, Susana F

    2013-05-01

    This study aimed to evaluate oxidative stress parameters in juvenile tambaqui (Colossoma macropomum) exposed to 3.88 mg l(-1) Mn(2+) for 96 hours. Biomarkers of oxidative stress, such as thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), catalase (CAT), and glutathione-S-transferase (GST) activities, as well as content of reduced glutathione (GSH), were analyzed in gill, liver, brain, and kidney. The presence of Mn(2+) in the water corresponded to increased levels of Mn(2+) accumulation according to the following sequence: gill > kidney > brain > liver. There was a significant increase in TBARS levels (40 %) and SOD activity (80 %) in addition to a significant decrease in GSH content (41 %) in gills of fish exposed to waterborne Mn(2+). In hepatic tissue of the exposed animals, TBARS levels decreased significantly (35 %), whereas SOD (82 %) and GST activities (51 %) as well as GSH content (43 %) increased significantly. In brain of exposed juvenile fish, only significant decreases in SOD (32 %) and CAT activities (65 %) were observed. Moreover, the kidney of exposed fish showed a significant increase in TBARS levels (53 %) and a significant decrease in SOD activity (41 %) compared with the control. Thus, the changes in biomarkers of oxidative stress were different in the tissues, showing a specific toxicity of this metal to each organ.

  16. Promoting effects of thoria on the nickel-manganese mixed oxide catalysts for the aerobic oxidation of benzyl alcohol

    Directory of Open Access Journals (Sweden)

    S.S.P. Sultana

    2017-05-01

    Full Text Available Due to the recent advancement in the development of various characterization techniques, mixed metal oxide (MMO based catalysts have gained tremendous attention in the field of catalysis. In this study, we demonstrated the synthesis of a series of novel MMO based catalysts by a facile co-precipitation method. The detailed structure and composition of thoria promoted NiMnO catalysts was investigated using various microscopic and spectroscopic techniques such as, SEM, EDAX, XRD, TGA, BET and TPR. In order to study the effect of the content of thorium oxide on the catalytic activity of the as-prepared material various samples were prepared by the addition of low quantities of thorium oxide with 1%, 3% and 5% on NiMnO. The catalytic performances of the as-prepared catalysts were evaluated towards the aerobic oxidation of benzyl alcohol using molecular oxygen as oxidant. Furthermore, in order to investigate the effect of the calcination temperatures on the catalytic activities of the as-prepared materials, the samples were calcined at three different temperatures at 300 °C, 400 °C and 500 °C. The catalysts displayed significant enhancement in catalytic activity towards the catalytic conversion of benzyl alcohol (C6H5CH2OH to benzaldehyde (C6H5CHO. Detailed kinetic studies of the reactions using gas chromatography have revealed that the variation of calcination temperature and the percentage of thoria had significant effect on the catalytic performances of the materials. Among all synthesized catalysts ThO2-(5%-NiMnO catalyst calcined at 400 °C exhibited the highest catalytic performance and stability for the selective oxidation of alcohols.

  17. Spontaneous and continuous anti-virus disinfection from nonstoichiometric perovskite-type lanthanum manganese oxide

    Directory of Open Access Journals (Sweden)

    Ding Weng

    2015-06-01

    Full Text Available Viral pathogens have threatened human being׳s health for a long time, from periodically breakout flu epidemics to recent rising Ebola virus disease. Herein, we report a new application of nonstoichiometric Perovskite-type LaxMnO3 (x=1, 0.95, and 0.9 compounds in spontaneous and continuous disinfection of viruses. Perovskite-type LaxMnO3 (x=1, 0.95, and 0.9 is well-known for their catalytic properties involving oxidization reactions, which are usually utilized as electrodes in fuel cells. By utilizing superb oxidative ability of LaxMnO3 (x=1, 0.95, and 0.9, amino acid residues in viral envelope proteins are oxidized, thus envelope proteins are denatured and infectivity of the virus is neutralized. It is of great importance that this process does not require external energy sources like light or heat. The A/PR/8/34H1N1 influenza A virus (PR8 was employed as the sample virus in our demonstration, and high-throughput disinfections were observed. The efficiency of disinfection was correlated to oxidative ability of LaxMnO3 (x=1, 0.95, and 0.9 by EPR and H2-TPR results that La0.9MnO3 had the highest oxidative ability and correspondingly gave out the best disinfecting results within three nonstoichiometric compounds. Moreover, denaturation of hemagglutinin and neuraminidase, the two key envelope proteins of influenza A viruses, was demonstrated by HA unit assay with chicken red blood cells and NA fluorescence assay, respectively. This unique disinfecting application of La0.9MnO3 is considered as a great make up to current sterilizing methods especially to photocatalyst based disinfectants and can be widely applied to cut-off spread routes of viruses, either viral aerosol or contaminated fluid, and help in controlling the possibly upcoming epidemics like flus and hemorrhagic fever.

  18. Spatial Distribution of Iron in Soils and Vegetation Cover Close to an Abandoned Manganese Oxide Ore Mine, Botswana

    Science.gov (United States)

    Ekosse, Georges Ivo E.

    This study aimed at establishing the spatial distribution of iron (Fe) in soils and vegetation cover within the periphery of the Kgwakgwe Manganese (Mn) oxides ore abandoned mine in Botswana. Four hundred soil samples and two hundred vegetation samples were obtained from a 4 km2 area close to the mine. Determination of Fe concentrations after acid digestion of samples was performed using an atomic absorption spectrometer equipped with a deuterium background correction. Tests for soil pH and soil colour were complementary to soil chemical analysis. Results were processed using Geographical Information Systems (GIS) and Remote Sensing (RS) techniques with integrated Land and Water Information System (ILWIS), Geosoft Oasis Montaj, ArcGIS and Microsoft Excel software packages. Concentrations of Fe in soils was from 1116.59 to 870766.00 μg g-1 with a mean of 17593.52 μg g-1 and for leaves, levels were from 101.2 to 3758.09 μg g-1 with a mean of 637.07 μg g-1. Soil pH values ranged from 2.92 to 7.26 and soil colour shades ranged from yellowish red to very dark grey. Gridded soils and vegetation maps show Fe anomalies in different parts of the study area. Values were low in areas located at the mine workings and in the Northwestern part of the study area and high in the north and southern part. Where concentrations of Fe were high in soils, correspondingly high figures were obtained for vegetation cover. Similar trends were obtained for soil pH distribution in the study area. Bedrock geology, topography, Mn mineralization, soil acidity and prevailing oxidizing conditions were governing factors that influenced the concentration and spatial distribution of Fe in the soils and vegetation. The findings further confirm that Fe distribution and its chemistry in the soils and environment around the Kgwakgwe abandoned Mn oxides ore mine have affected the vegetation cover.

  19. Dinuclear manganese complexes for water oxidation: evaluation of electronic effects and catalytic activity.

    Science.gov (United States)

    Arafa, Wael A A; Kärkäs, Markus D; Lee, Bao-Lin; Åkermark, Torbjörn; Liao, Rong-Zhen; Berends, Hans-Martin; Messinger, Johannes; Siegbahn, Per E M; Åkermark, Björn

    2014-06-28

    During recent years significant progress has been made towards the realization of a sustainable and carbon-neutral energy economy. One promising approach is photochemical splitting of H2O into O2 and solar fuels, such as H2. However, the bottleneck in such artificial photosynthetic schemes is the H2O oxidation half reaction where more efficient catalysts are required that lower the kinetic barrier for this process. In particular catalysts based on earth-abundant metals are highly attractive compared to catalysts comprised of noble metals. We have now synthesized a library of dinuclear Mn2(II,III) catalysts for H2O oxidation and studied how the incorporation of different substituents affected the electronics and catalytic efficiency. It was found that the incorporation of a distal carboxyl group into the ligand scaffold resulted in a catalyst with increased catalytic activity, most likely because of the fact that the distal group is able to promote proton-coupled electron transfer (PCET) from the high-valent Mn species, thus facilitating O-O bond formation.

  20. Kinetics of oxidation of D-arabinose and D-xylose by vanadium (V in the presence of manganese II as homogeneous catalyst

    Directory of Open Access Journals (Sweden)

    Ezekiel O. Odebunmi

    2010-12-01

    Full Text Available Kinetics of oxidation of D-arabinose and D-xylose by acidic solution of vanadium (V ions in the presence of manganese (II has been reported. First-order dependence of the reaction rate was observed on [sugars] and [H+] at low concentrations throughout the oxidation reaction and a zero-order dependence on [sugar] and [H+] was observed at high concentrations. First-order kinetics with respect to [Mn (II] was also observed throughout the oxidation for both sugars. The results indicate the effect of Cl- concentration is negligible. The reaction rates increase with the ionic strength of the medium. Various activation parameters were evaluated and provide further support to the proposed mechanism. Formic acid was reported as one of the oxidation products of these sugars.

  1. Trace Elements in Manganese Minerals as Potential Biosignatures on Mars

    Science.gov (United States)

    Lanza, N.; Clegg, S. M.; Cousin, A.; Forni, O.; Kirk, M. F.; Lamm, S. N.; Ollila, A.; Wiens, R. C.

    2017-12-01

    Observations from the Curiosity rover in Gale crater, Mars have shown the presence of high abundances of manganese (>3 wt% MnO) within sedimentary rocks throughout the traverse. Such high Mn abundances point to the past presence of abundant liquid water and strongly oxidizing conditions. On Earth, these types of environments are almost always habitable and are frequently inhabited by microbes. Given its close association with life and habitable environments on Earth, manganese has long been considered a potential biosignature for Mars. However, high concentrations of martian Mn have only recently been observed. In addition to the observations in Gale crater, high abundances of Mn have also been observed in Endeavor crater by the Opportunity rover and in the paired martian meteorites NWA 7034 and 7533 (`Black Beauty'), suggesting that Mn deposits may be more widespread on Mars than previously thought. The goal of this work is to determine whether there are unique signatures from rover payload instruments that can distinguish Mn-rich deposits as biogenic in origin (i.e., produced by life) from abiogenic Mn deposits. Importantly, Mn-oxides are known to scavenge trace metals from water because of their surface charge properties. We hypothesize that the presence and abundance of specific trace elements are the critical, distinguishing evidence for identifying the biogenic origin of Mn-bearing materials. A suite of natural rocks containing Mn-rich minerals with a range of Mn redox states was selected for analysis with laser-induced breakdown spectroscopy (LIBS). Samples with a biogenic origin had mixed valence redox states between Mn3+ and Mn4+ as inferred by mineralogy. Trace elements Ba, Li, Sr, and Rb were quantified and the presence or absence of Zn and Cu was ascertained by examining key LIBS peaks. Results show that samples with a known microbial origin had moderate Mn abundances >30 wt% MnO and higher Li and Ba. These results suggest that high Mn abundance alone

  2. Octahedral magnesium manganese oxide molecular sieves as the cathode material of aqueous rechargeable magnesium-ion battery

    International Nuclear Information System (INIS)

    Zhang, Hongyu; Ye, Ke; Shao, Shuangxi; Wang, Xin; Cheng, Kui; Xiao, Xue; Wang, Guiling; Cao, Dianxue

    2017-01-01

    Highlights: • The mico-sheet Mg-OMS-1 is synthesized by a simple hydrothermal method. • The mechanism of Mg 2+ insertion/deinsertion from Mg-OMS-1 is explored. • The electrode exhibits a good electrochemical performance in MgCl 2 electrolyte. - Abstract: Aqueous magnesium-ion batteries have shown the desired properties of high safety characteristics, similar electrochemical properties to lithium and low cost for energy storage applications. The micro-sheet morphology of todorokite-type magnesium manganese oxide molecular sieve (Mg-OMS-1) material, which applies as a novel cathode material for magnesium-ion battery, is obtained by the simple hydrothermal method. The structure and morphology of the particles are confirmed by X-ray power diffraction, X-ray photoelectron spectroscopy, inductively coupled plasma, scanning and transmission electron microscopy. The electrochemical performance of Mg-OMS-1 is researched by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and constant current charge-discharge measurement. Mg-OMS-1 shows a good battery behavior for Mg 2+ insertion and deinsertion in the aqueous electrolyte. When discharging at 10 mA g −1 in 0.2 mol dm −3 MgCl 2 aqueous electrolyte, the initial discharge capacity reaches 300 mAh g −1 . The specific capacity retention rate is 83.7% after cycling 300 times at 100 mA g −1 in 0.5 mol dm −3 MgCl 2 electrolyte with a columbic efficiency of nearly 100%.

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

    Science.gov (United States)

    Stamatatos, Theocharis C; Christou, George

    2009-04-20

    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.

  4. Electrochemical behaviour of manganese & ruthenium mixed oxide@ reduced graphene oxide nanoribbon composite in symmetric and asymmetric supercapacitor

    Science.gov (United States)

    Ahuja, Preety; Ujjain, Sanjeev Kumar; Kanojia, Rajni

    2018-01-01

    This paper reports the interaction of 3d-4d transition metal mixed oxide as simultaneous existence of M(3d) and M(4d) expectedly enhance the electrochemical performance of the resulting composite. Electrochemical performance of MnO2-RuO2 nanoflakes reduced graphene oxide nanoribbon composite (MnO2-RuO2@GNR) is intensively explored in symmetric and asymmetric supercapacitor assembly. In situ incorporation of graphene oxide nanoribbon (GONR) during synthesis provides efficient binding sites for growth of MnO2-RuO2 nanoflakes via their surface functionalities. The interconnected MnO2-RuO2 nanoflakes via GNR form a network with enhanced diffusion kinetics leading to efficient supercapacitor performance. Fabricated asymmetric supercapacitor reveals energy density 60 Wh kg-1 at power density 14 kW kg-1. Based on the analysis of impedance data in terms of complex power, quick response time of supercapacitor reveals excellent power delivery of the device. Improved cycling stability after 7000 charge discharge cycles for symmetric and asymmetric supercapacitor highlights the buffering action of GNR and can be generalized for next generation high performance supercapacitor.

  5. Biogenic synthesis of Zinc oxide nanostructures from Nigella sativa seed: Prospective role as food packaging material inhibiting broad-spectrum quorum sensing and biofilm

    Science.gov (United States)

    Al-Shabib, Nasser A.; Husain, Fohad Mabood; Ahmed, Faheem; Khan, Rais Ahmad; Ahmad, Iqbal; Alsharaeh, Edreese; Khan, Mohd Shahnawaz; Hussain, Afzal; Rehman, Md Tabish; Yusuf, Mohammad; Hassan, Iftekhar; Khan, Javed Masood; Ashraf, Ghulam Md; Alsalme, Ali Mohammed; Al-Ajmi, Mohamed F.; Tarasov, Vadim V.; Aliev, Gjumrakch

    2016-01-01

    Bacterial spoilage of food products is regulated by density dependent communication system called quorum sensing (QS). QS control biofilm formation in numerous food pathogens and Biofilms formed on food surfaces act as carriers of bacterial contamination leading to spoilage of food and health hazards. Agents inhibiting or interfering with bacterial QS and biofilm are gaining importance as a novel class of next-generation food preservatives/packaging material. In the present study, Zinc nanostructures were synthesised using Nigella sativa seed extract (NS-ZnNPs). Synthesized nanostructures were characterized hexagonal wurtzite structure of size ~24 nm by UV-visible, XRD, FTIR and TEM. NS-ZnNPs demonstrated broad-spectrum QS inhibition in C. violaceum and P. aeruginosa biosensor strains. Synthesized nanostructures inhibited QS regulated functions of C. violaceum CVO26 (violacein) and elastase, protease, pyocyanin and alginate production in PAO1 significantly. NS-ZnNPs at sub-inhibitory concentrations inhibited the biofilm formation of four-food pathogens viz. C. violaceum 12472, PAO1, L. monocytogenes, E. coli. Moreover, NS-ZnNPs was found effective in inhibiting pre-formed mature biofilms of the four pathogens. Therefore, the broad-spectrum inhibition of QS and biofilm by biogenic Zinc oxide nanoparticles and it is envisaged that these nontoxic bioactive nanostructures can be used as food packaging material and/or as food preservative. PMID:27917856

  6. Structural oxidation state studies of the manganese cluster in the oxygen evolving complex of photosystem II

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Wenchuan [Univ. of California, Berkeley, CA (United States)

    1994-11-01

    X-ray absorption spectroscopy (XAS) was performed on Photosystem II (PSII)-enriched membranes prepared from spinach to explore: (1) the correlation between structure and magnetic spin state of the Mn cluster in the oxygen evolving complex (OEC) in the S2 state; and (2) the oxidation state changes of the Mn cluster in the flash-induced S-states. The structure of the Mn cluster in the S2 state with the g~4 electron paramagnetic resonance (EPR) signal (S2-g4 state) was compared with that in the S2 state with multiline signal (S2-MLS state) and the S1 state. The S2-g4 state has a higher XAS inflection point energy than that of the S1 state, indicating the oxidation of Mn in the advance from the S1 to the S2-g4 state. Differences in the edge shape and in the extended X-ray absorption fine structure (EXAFS) show that the structure of the Mn cluster in the S2-g4 state is different from that in the S2-MLS or the S1 state. In the S2-g4 state, the second shell of backscatterers from the Mn absorber contains two Mn-Mn distances of 2.73 Å and 2.85 Å. Very little distance disorder exists in the second shell of the S1 or S2-MLS states. The third shell of the S2-g4 state at about 3.3 Å also contains increased heterogeneity relative to that of the S2-MLS or the S1 state. Various S-states were prepared at room-temperature by saturating, single-turnover flashes. The flash-dependent oscillation in the amplitude of the MLS was used to characterize the S-state composition and to construct "pure" S-state Mn K-edge spectra. The edge position shifts to higher energy by 1.8 eV upon the S1 → S2 transition.

  7. High temperature carburization behaviour of Mn-Cr-O spinel oxides with varied concentrations of manganese

    International Nuclear Information System (INIS)

    Li Hao; Chen Weixing

    2011-01-01

    Research highlights: → High temperature carbonaceous attacks of Mn-Cr-O samples with varied Mn contents were examined. → The stoichiometric MnCr 2 O 4 shows the best resistance to carbonaceous attacks. → Formation of (Mn,Cr) 7 C 3 in Mn-Cr-O samples is catalytic to coke formation. → (Mn,Cr) 7 C 3 can be decomposed and react with H 2 O moisture to form volatile Mn(OH) 2 . → High content of Cr stabilizes (Mn,Cr) 7 C 3 phase and prevents it from its further decomposition. - Abstract: Mn-Cr-O spinel often formed on austenitic alloys is an oxide phase that could be protective against high temperature carbonaceous attack. In this research, various Mn-Cr-O samples were tested in carburization environments with controlled oxygen partial pressures. The stoichiometric MnCr 2 O 4 shows better resistance to carburization and coke formation than the Mn-rich Mn-Cr-O and the Cr-rich Mn-Cr-O samples because of its highest thermodynamic stability as compared with MnO and Cr 2 O 3 . (Mn,Cr) 7 C 3 formed after carburization is catalytic to coke formation, and was found instable at higher levels of H 2 O/oxygen and may form volatile phases in the presence of H 2 O, leading to a continuous reduction in sample weight.

  8. Preparation of graphene oxide-manganese dioxide for highly efficient adsorption and separation of Th(IV)/U(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Ning; Li, Long; Ding, Jie [College of Chemistry, Sichuan University, Chengdu 610064 (China); Li, Shengke [State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Taipa, Macau SAR (China); Wang, Ruibing, E-mail: rwang@umac.mo [State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Taipa, Macau SAR (China); Jin, Yongdong, E-mail: jinyongdong@scu.edu.cn [College of Chemistry, Sichuan University, Chengdu 610064 (China); Wang, Xiangke [School of Environment and Chemical Engineering, North China Electric Power University, Beijing 102206 (China); Xia, Chuanqin, E-mail: xiachqin@163.com [College of Chemistry, Sichuan University, Chengdu 610064 (China); Key Laboratory of Radiation Physics and Technology, Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064 (China)

    2016-05-15

    Highlights: • Simultaneous removal of Th(IV)/U(VI) by using MnO{sub 2}/GO was demonstrated. • MnO{sub 2}/GO had the highest adsorption capacity for Th(IV) and/or U(VI) than GO, MnO{sub 2}. • The selective desorption of Th(IV)/U(VI) from MnO{sub 2}/GO was evaluated. • FTIR and XPS analyses indicate the interaction between Th(IV) or U(VI) and MnO{sub 2}/GO. • XRD analysis indicates the adsorption manner of Th(IV) or U(VI) onto MnO{sub 2}/GO. - Abstract: Manganese dioxide decorated graphene oxide (GOM) was prepared via fixation of crystallographic MnO{sub 2} (α, γ) on the surface of graphene oxide (GO) and was explored as an adsorbent material for simultaneous removal of thorium/uranium ions from aqueous solutions. In single component systems (Th(IV) or U(VI)), the α-GOM{sub 2} (the weight ratio of GO/α-MnO{sub 2} of 2) exhibited higher maximum adsorption capacities toward both Th(IV) (497.5 mg/g) and U(VI) (185.2 mg/g) than those of GO. In the binary component system (Th(IV)/U(VI)), the saturated adsorption capacity of Th(IV) (408.8 mg/g)/U(VI) (66.8 mg/g) on α-GOM{sub 2} was also higher than those on GO. Based on the analysis of various data, it was proposed that the adsorption process may involve four types of molecular interactions including coordination, electrostatic interaction, cation-pi interaction, and Lewis acid-base interaction between Th(IV)/U(VI) and α-GOM{sub 2}. Finally, the Th(IV)/U(VI) ions on α-GOM{sub 2} can be separated by a two-stage desorption process with Na{sub 2}CO{sub 3}/EDTA. Those results displayed that the α-GOM{sub 2} may be utilized as an potential adsorbent for removing and separating Th(IV)/U(VI) ions from aqueous solutions.

  9. Evaluation antimicrobial activity of biogenic zinc oxide nanoparticles on two standard gram positive and gram negative strains

    OpenAIRE

    Mohammadreza Aflatoonian; Mehrdad Khatami; Iraj Sharifi; Shahram Pourseyedi; Mansour Khatami; Hajar Yaghobi; Mahin Naderifar

    2017-01-01

    Background: Nanoparticles are particles that have at least one dimension between 1 and 100 nanometers. Nanoparticles are a new generation of antimicrobial agents. Nanoparticles with antimicrobial activity, especially as a new class of biomedical materials for use in increasing the level of public health in daily life have emerged.  Zinc oxide nanoparticles have attracted a great attention due to the variety of their applications in medical science. The aim of this study was to evaluate a...

  10. Cadmium-manganese oxide composite thin films: Synthesis, characterization and photoelectrochemical properties

    Energy Technology Data Exchange (ETDEWEB)

    Mansoor, M.A. [Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Low Dimensional Materials Research Centre, Department of Physics, University of Malaya, Faculty of Science, Kuala Lumpur 50603 (Malaysia); Ebadi, M. [Solar Energy Research Institute, University Kebangsaan Malaysia, Bangi 43600, Selangor (Malaysia); Mazhar, M., E-mail: mazhar42pk@yahoo.com [Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Huang, N.M. [Low Dimensional Materials Research Centre, Department of Physics, University of Malaya, Faculty of Science, Kuala Lumpur 50603 (Malaysia); Mun, L.K.; Misran, M. [Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Basirun, W.J. [Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Institute of Nanotechnology and Catalysis (NanoCat), University Malaya, Kuala Lumpur 50603 (Malaysia)

    2017-01-15

    Ceramic composite CdO–Mn{sub 2}O{sub 3} thin films have been deposited on fluorine doped tin oxide (FTO) coated glass substrates by aerosol assisted chemical vapour deposition (AACVD) using a 1:1 mixture of cadmium complex, [Cd(dmae){sub 2}(OAc){sub 2}]·H{sub 2}O (1) (where dmae = 2-dimethylaminoethanolato and OAc = acetato), and diacetatomanganese (II). The phase purity, stoichiometry and thickness of the films were examined by X-ray diffraction (XRD), Fourier transformed infra-red (FTIR), Raman spectroscopy, field emission gun scanning electron microscopy (FEG-SEM), energy dispersive X-ray spectroscopy (EDX), UV–Vis spectroscopy and profilometer. The FEG-SEM analysis illustrated that the morphology of the fabricated films was influenced by the type of solvent. The optical direct band gap of the film fabricated from THF solution was 1.95 eV. From the current–voltage characteristics it is evident that the CdO–Mn{sub 2}O{sub 3} composite semiconductor electrode exhibits n-type behaviour and the photocurrent density was found to be dependent on the deposition medium. The film deposited from THF solution displayed maximum photocurrent density of 4.80 mA cm{sup −2} at 0.65 V vs. Ag/AgCl/3 M KCl (∼1.23 V vs. RHE) in 0.5 M NaOH electrolyte. - Highlights: • Single crystal X-ray structure of [Cd(dmae){sub 2}(OAc){sub 2}]·H{sub 2}O (1). • CdO-Mn{sub 2}O{sub 3} composite photoanode thin films. • Optical band gap of CdO-Mn{sub 2}O{sub 3} photoanode. • Photoelectrochemical and EIS studies.

  11. Adsorption of Arsenate by Nano Scaled Activated Carbon Modified by Iron and Manganese Oxides

    Directory of Open Access Journals (Sweden)

    George P. Gallios

    2017-09-01

    Full Text Available The presence of arsenic in water supplies is a major problem for public health and still concerns large parts of population in Southeast Asia, Latin America and Europe. Removal of arsenic is usually accomplished either by coagulation with iron salts or by adsorption with iron oxides or activated alumina. However, these materials, although very efficient for arsenic, normally do not remove other undesirable constituents from waters, such as chlorine and organo-chlorine compounds, which are the results of water chlorination. Activated carbon has this affinity for organic compounds, but does not remove arsenic efficiently. Therefore, in the present study, iron modified activated carbons are investigated as alternative sorbents for the removal of arsenic(V from aqueous solutions. In addition, modified activated carbons with magnetic properties can easily be separated from the solutions. In the present study, a simple and efficient method was used for the preparation of magnetic Fe3(Mn2+O4 (M:Fe and/or Mn activated carbons. Activated carbons were impregnated with magnetic precursor solutions and then calcinated at 400 °C. The obtained carbons were characterized by X-ray diffraction (XRD, nitrogen adsorption isotherms, scanning electron microscopy (SEM, vibrating sample magnetometer (VSM, Fourier Transform Infrared Spectrometry (FTIR and X-ray photoelectron spectroscopy (XPS measurements. Their adsorption performance for As(V was evaluated. The iron impregnation presented an increase in As(V maximum adsorption capacity (Qmax from about 4 mg g−1 for the raw carbon to 11.05 mg g−1, while Mn incorporation further increased the adsorption capacity at 19.35 mg g−1.

  12. Self-consistent Hartree energy band calculation for manganese oxide (MnO)

    International Nuclear Information System (INIS)

    Bakhshai, A.

    1982-01-01

    A self-consistent Hartree energy band calculation was done for the MnO crystal using the linear combination of atomic orbitals (LCAO) method. Gaussian type atomic orbitals were used in the LCAO method. This calculation was done for paramagnetic MnO with the NaCl lattice structure. The results show that the energy bands around the Fermi level of MnO are unusually flat, meaning that the electrons in this region are strongly localized. Therefore short range correlation was added to the results of this band calculation. The short range correlation effects were added by calculating atomic type corrections to the original band structure. The results of this correlation calculation show that a large amount of energy is required to excite an electron from the Mn 3d band. Therefore the lowest excitation (the one that requires the least energy) is an excitation from the top of the O 2p band to the Fermi level. This yields a fundamental band gap of 4.8 eV which is in good agreement with optical absorption experiments. This fundamental band gap of 4.8 eV implies that MnO is an insulator, in agreement with conductivity experiments. The Hartree results for the valence bands of MnO agree very well with the results of photoemission experiments. In comparison to the photoemission data, the results of the self-consistent Hartree calculation are an order of magnitude better than the results of the only other band calculation for MnO. Comparison with band calculations for other transition metal oxides (other than MnO) imply that with a good self-consistent Hartree energy band calculation for MnO can be superior

  13. Biogenic emissions modeling for Southeastern Texas

    Energy Technology Data Exchange (ETDEWEB)

    Estes, M.; Jacob, D.; Jarvie, J. [Texas Natural Resource Conservation Commission, Austin, TX (United States)] [and others

    1996-12-31

    The Texas Natural Resource Conservation Commission (TNRCC) modeling staff performed biogenic hydrocarbon emissions modeling in support of gridded photochemical modeling for ozone episodes in 1992 and 1993 for the Coastal Oxidant Assessment for Southeast Texas (COAST) modeling domain. This paper summarizes the results of the biogenic emissions modeling and compares preliminary photochemical modeling results to ambient air monitoring data collected during the 1993 COAST study. Biogenic emissions were estimated using BIOME, a gridded biogenic emissions model that uses region-specific land use and biomass density data, and plant species-specific emission factor data. Ambient air monitoring data were obtained by continuous automated gas chromatography at two sites, one-hour canister samples at 5 sites, and 24-hour canister samples at 13 other sites. The concentrations of Carbon Bond-IV species (as determined from urban airshed modeling) were compared to measured hydrocarbon concentrations. In this paper, we examined diurnal and seasonal variations, as well as spatial variations.

  14. Kinetics and Mechanism of Paracetamol Oxidation by Chromium(VI in Absence and Presence of Manganese(II and Sodiumdodecyl Sulphate

    Directory of Open Access Journals (Sweden)

    Maqsood Ahmad Malik

    2007-11-01

    Full Text Available The kinetics of paracetamol oxidation are first order each in [paracetamol] and [HClO4]. The kinetic study shows that the oxidation proceeds in two steps. The effects of anionic micelles of sodiumdodecyl sulphate (SDS and complexing agents (ethylenediammine tetraacetic acid (EDTA and 2,2′-bipyridyl (bpy were also studied. Fast kinetic spectrophotometric method has been described for the determination of paracetamol. The method is based on the catalytic effect of manganese(II on the oxidation of paracetamol by chromium(VI in the presence of HClO4 (= 0.23 mol dm−3. Optimum reaction time is 4 to 6 minutes at a temperature of 30∘C. The addition of manganese(II ions largely decreased the absorbance of chromium(VI at 350 nm. This reaction can be utilized for the determination of paracetamol in drugs.

  15. Facile one-step template-free synthesis of uniform hollow microstructures of cryptomelane-type manganese oxide K-OMS-2.

    Science.gov (United States)

    Galindo, Hugo M; Carvajal, Yadira; Njagi, Eric; Ristau, Roger A; Suib, Steven L

    2010-08-17

    Hollow microstructures of cryptomelane-type manganese oxide were produced in a template-free one-step process based on the fine-tuning of the oxidation rate of manganese species during the synthesis. The tuning of the reaction rate brought about by a mixture of the oxidants oxone and potassium nitrate becomes apparent from the gradual physical changes taking place in the reaction medium at early times of the synthesis. The successful synthesis of the hollow uniform structures could be performed in the ranges 120-160 degrees C and 8.2-10.7 for temperature and mass ratio oxone/potassium nitrate, respectively. Independent of the conditions of the synthesis, all of the complex microstructures showed the same pattern for the array of very long nanofibers in which some of these elongated around the surface confining the cavity and the other fibers grew normal to the surface created by the previous arrangement. A mechanism based on the heterogeneous nucleation of the cryptomelane phase on the surface of an amorphous precursor and the growth of the nanoscale fibers by processes such as dissolution-crystallization and lateral attachment of primary nanocrystalline fibers is proposed to explain the formation of the hollow structures.

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

    OpenAIRE

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

    2014-01-01

    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 d...

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

    Science.gov (United States)

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

    2014-09-01

    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.

  18. Recovery of 'Nsutite' from Tailings Material of Ghana Manganese ...

    African Journals Online (AJOL)

    GMC) Limited Mine, Nsuta. M Ali, RK Amankwah. Abstract. An investigation was conducted for the enrichment of manganese oxide tailings generated by a spiral concentration plant at Ghana Manganese Company (GMC) Limited, Nsuta. The work ...

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

    Science.gov (United States)

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

    2014-09-28

    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.

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

    Directory of Open Access Journals (Sweden)

    Bellusci M

    2014-04-01

    Full Text Available Mariangela Bellusci,1 Aurelio La Barbera,1 Franco Padella,1 Mariateresa Mancuso,2 Alessandra Pasquo,2 Maria Giuseppa Grollino,2 Giorgio Leter,2 Elisa Nardi,3 Carlo Cremisini,3 Paola Giardullo,4 Francesca Pacchierotti21Technical Unit for Material Technologies, 2Technical Unit for Radiation Biology and Human Health, 3Technical Unit for Environmental Characterization, Prevention and Recovery, Agenzia Nazionale per le Nuove Tecnologie, l'Energia e lo Sviluppo Economico Sostenibile (ENEA, Casaccia Research Centre, Rome, Italy; 4Department of Radiation Physics, Marconi University, Rome, ItalyAbstract: 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 µg

  1. The performance of manganese-based catalysts with Ce0.65Zr0.35O2 as support for catalytic oxidation of toluene

    Science.gov (United States)

    Hou, Zhongyan; Feng, Jie; Lin, Tao; Zhang, Hailong; Zhou, Xiaoying; Chen, Yaoqiang

    2018-03-01

    Mesoporous Ce0.65Zr0.35O2 composites are synthesized by co-precipitation method and a series of novel MnOx/Ce0.65Zr0.35O2 monolithic catalysts with different content of manganese oxides are prepared for toluene catalytic oxidation. The results show that the catalytic activity of Ce0.65Zr0.35O2 is promoted by introduction of manganese and influenced remarkably by the amount of MnOx. In particular, the catalyst with 15 wt.% MnOx loading performs best activity in view of the lowest complete conversion temperature of 250 °C at a GHSV of 12000 h-1. According to the characterizations of N2 adsorption-desorption, XRD, SEM-EDX, H2-TPR, O2-TPD and XPS analyses, the superior catalytic activity could be attributed to the well-dispersed MnOx species, good low-temperature redox property, more Mn4+ species and more available surface and lattice oxygen species. Additionally, the optimized catalyst shows high stability during the thermal aging experiment and long-term testing experiment, and it also shows a good activity under the condition of high gas hourly space velocity, which presents a well application prospect.

  2. The distribution of uranium in some Pacific manganese nodules and crusts

    International Nuclear Information System (INIS)

    Kunzendorf, H.; Glasby, G.P.; Plueger, W.L.; Friedrich, G.H.

    1982-01-01

    A total of 1386 bulk samples of manganese nodules from several areas of the North and South Pacific were analysed for uranium; variations in the U contents of nodules within individual nodules and crusts have been documented on a local scale and on a regional scale. Uranium appears to be one of those elements not associated with the biogenic cycling of elements into nodules in the equatorial high-productivity zone. The principal factor controlling these variations appears to be the clear association of U with Fe in the nodules. Uranium is therefore most probably coprecipitated with Fe from seawater in an iron-rich ferromanganese oxide phase. This explains the higher U contents of nodules containing MnO 2 compared to 10A manganite as the principal manganese oxide phase. Data for a manganese crust from the equatorial North Pacific nodule belt suggest normal seawater deposition for uranium and other metals (Mn, Fe, Ni and Cu) superimposed on possibly basalt alteration as the principal growth mechanisms for the crust. (Auth.)

  3. Electrochemical water splitting by layered and 3D cross-linked manganese oxides: correlating structural motifs and catalytic activity

    OpenAIRE

    Bergmann, Arno; Zaharieva, Ivelina; Dau, Holger; Strasser, Peter

    2013-01-01

    Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich. This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively. Manganese based precious metal-free electrocatalysts for the oxygen evolution reaction (OER) are promising materials for energy storage systems based on dark or photo-couple...

  4. Redox preparation of mixed-valence cobalt manganese oxide nanostructured materials: highly efficient noble metal-free electrocatalysts for sensing hydrogen peroxide

    Science.gov (United States)

    Kuo, Cheng-Chi; Lan, Wen-Jie; Chen, Chun-Hu

    2013-12-01

    High-performance hydrogen peroxide sensors provide valuable signals of biological interactions, disorders, and developing of diseases. Low-cost metal oxides are promising alternatives but suffer from low conductivity and sensing activity. Multi-component metal oxides are excellent candidates to accomplish these challenges, but the composition inhomogeneity is difficult to manage with conventional material preparation. We demonstrated redox preparation strategies to successfully synthesize highly homogeneous, noble metal-free H2O2 sensors of spinel nanostructured cobalt manganese oxides with enhanced conductivity, multiple mixed-valence features, and efficient H2O2 sensing activities. The designed redox reactions accompanied with material nucleation/formation are the key factors for compositional homogeneity. High conductivity (1.5 × 10-2 S cm-1) and H2O2 sensing activity (12 times higher than commercial Co3O4) were achieved due to the homogeneous multiple mixed-valence systems of Co(ii)/(iii) and Mn(iii)/(iv). A wide linear detection range (from 0.1 to 25 mM) with a detection limit of 15 μM was observed. Manganese species assist the formation of large surface area nanostructures, enhancing the H2O2 reduction activities, and inhibit the sensing interference. The material controls of hierarchical nanostructures, elemental compositions, porosity, and electrochemical performances are highly associated with the reaction temperatures. The temperature-dependent properties and nanostructure formation mechanisms based on a reaction rate competition are proposed.High-performance hydrogen peroxide sensors provide valuable signals of biological interactions, disorders, and developing of diseases. Low-cost metal oxides are promising alternatives but suffer from low conductivity and sensing activity. Multi-component metal oxides are excellent candidates to accomplish these challenges, but the composition inhomogeneity is difficult to manage with conventional material

  5. Reagent removal of manganese from ground water

    Science.gov (United States)

    Brayalovsky, G.; Migalaty, E.; Naschetnikova, O.

    2017-06-01

    The study is aimed at the technology development of treating drinking water from ground waters with high manganese content and oxidizability. Current technologies, physical/chemical mechanisms and factors affecting in ground treatment efficiency are reviewed. Research has been conducted on manganese compound removal from ground waters with high manganese content (5 ppm) and oxidizability. The studies were carried out on granular sorbent industrial ODM-2F filters (0.7-1.5 mm fraction). It was determined that conventional reagent oxidization technologies followed by filtration do not allow us to obtain the manganese content below 0.1 ppm when treating ground waters with high oxidizability. The innovative oxidation-based manganese removal technology with continuous introduction of reaction catalytic agent is suggested. This technology is effective in alkalization up to pH 8.8-9. Potassium permanganate was used as a catalytic agent, sodium hypochlorite was an oxidizer and cauistic soda served an alkalifying agent.

  6. Biogenic Emission Sources

    Science.gov (United States)

    Biogenic emissions sources come from natural sources and need to accounted for in photochemical grid models. They are computed using a model which utilizes spatial information on vegetation and land use.

  7. Magnetic iron oxide and manganese-doped iron oxide nanoparticles for the collection of alpha-emitting radionuclides from aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    O' Hara, Matthew J.; Carter, Jennifer C.; Warner, Cynthia L.; Warner, Marvin G.; Addleman, Raymond S.

    2016-10-31

    Magnetic nanoparticles are well known to possess chemically active surfaces and high surface areas that can be employed to extract a range of ions from aqueous solutions. Additionally, their paramagnetic property provides a convenient means for bulk collection of the material from solution after the targeted ions have been adsorbed. Herein, two nanoscale amphoteric metal oxides, each possessing useful magnetic attributes, were evaluated for their ability to collect both naturally occurring radioactive isotopes (polonium (Po), radium (Ra), and uranium (U)) as well as the transuranic element americium (Am) from a suite of naturally occurring aqueous matrices. The nanomaterials include commercially available paramagnetic magnetite (Fe3O4) and magnetite that was modified to incorporate manganese (Mn) into the crystal structure. The chemical stability of these nanomaterials was evaluated in Hanford Site, WA ground water between the natural pH (~8) and pH 1 (acidified with HCl). Whereas the magnetite was observed to have good stability over the pH range, the Mn-doped material was observed to leach Mn at low pH. The materials were evaluated in parallel to characterize their uptake performance of the aforementioned alpha-emitting radionuclide spikes from Hanford Site ground water across a range of pH (from ~8 down to 2). In addition, radiotracer uptake experiments were performed on Columbia River water, seawater, and human urine at their natural pH and at pH 2. Despite the observed leaching of Mn from the Mn-doped nanomaterial in the lower pH range, it exhibited generally superior analyte extraction performance compared to the magnetite, and analyte uptake was observed across a broader pH range. The uptake behavior of the various radiotracers on these two materials at different pH levels can generally be explained by the amphoteric nature of the nanoparticle surfaces. Finally, the rate of sorption of the radiotracers on the two materials in unacidified groundwater was

  8. Effects of plant polyphenols and a-tocopherol on lipid oxidation, microbiological characteristics, and biogenic amines formation in dry-cured bacons

    Science.gov (United States)

    Effects of plant polyphenols (tea polyphenol, grape seed extract, and gingerol) and a-tocopherol on physicochemical parameters, microbiological counts, and biogenic amines were determined in dry-cured bacons at the end of ripening. Results showed that plant polyphenols and a-tocopherol significantly...

  9. Manganese in Marine Microbiology.

    Science.gov (United States)

    Hansel, Colleen M

    2017-01-01

    The importance of manganese in the physiology of marine microbes, the biogeochemistry of the ocean and the health of microbial communities of past and present is emerging. Manganese is distributed widely throughout the global ocean, taking the form of an essential antioxidant (Mn 2+ ), a potent oxidant (Mn 3+ ) and strong adsorbent (Mn oxides) sequestering disproportionately high levels of trace metals and nutrients in comparison to the surrounding seawater. Manganese is, in fact, linked to nearly all other elemental cycles and intricately involved in the health, metabolism and function of the ocean's microbiome. Here, we briefly review the diversity of microbes and pathways responsible for the transformation of Mn within the three Mn pools and their distribution within the marine environment. Despite decades of interrogation, we still have much to learn about the players, mechanisms and consequences of the Mn cycle, and new and exciting discoveries are being made at a rapid rate. What is clear is the dynamic and ever-inspiring complexity of reactions involving Mn, and the acknowledgement that microorganisms are the catalytic engine driving the Mn cycle. © 2017 Elsevier Ltd. All rights reserved.

  10. Effects of sediment resuspension on the oxidation of acid-volatile sulfides and release of metals (iron, manganese, zinc) in Pescadero estuary (CA, USA).

    Science.gov (United States)

    Richards, Chandra M; van Puffelen, Jasper L; Pallud, Céline

    2017-11-23

    Bar-built estuaries are unique ecosystems characterized by the presence of a sandbar barrier, which separates the estuary from the ocean for extended periods and can naturally reopen to the ocean with heavy rainfall and freshwater inflows. The physical effects associated with the transition from closed to open state, specifically water mixing and sediment resuspension, often indirectly worsen water quality conditions and are suspected to drive near-annual fish kills at the Pescadero estuary in northern California. The effects of sediment acid-volatile sulfide (AVS) oxidation, specifically oxygen depletion, acidification, and metal release, are believed to aggravate water conditions for fish but remain poorly understood. We performed slurry incubations containing sediment from 4 sites in the Pescadero estuary, representing a gradient from the Pacific Ocean to freshwater tributaries. We measured near-maximum rates of aqueous hydrogen sulfide oxidation, sediment AVS oxidation, sulfate production, and acidification, as well as near-maximum release rates of iron (Fe), manganese (Mn), and zinc (Zn) to the water column. We estimated AVS oxidation rates of 8 to 21 mmol S kg -1  d -1 , which were 3 orders of magnitude higher than aqueous hydrogen sulfide oxidation rates, 6 to 26 μmol S kg -1  d -1 . We suggest that aqueous hydrogen sulfide cannot be responsible for the observed kills because of low concentrations and minimal oxidative effects on pH and metal concentrations. However, the oxidative effects of AVS are potentially severe, decreasing pH to strongly acidic levels and releasing aqueous Fe, Mn, and Zn concentrations up to 11.2 mM, 0.46 mM, and 88 μM, respectively, indicating a potential role in worsening water conditions for fish in the Pescadero estuary. Environ Toxicol Chem 2018;9999:1-14. © 2017 SETAC. © 2017 SETAC.

  11. Cryptomelane-type manganese oxide (KMn8O16) nanorods cathode materials synthesized by a rheological phase for lithium ion batteries

    Science.gov (United States)

    Zheng, Hao; Wang, Ting; Zhao, Rongfei; Chen, Jinsong; Li, Lin

    2018-01-01

    Cryotolerance-type manganese oxide (KMn8O16) nanorods were prepared for the first time by a rheological phase reaction method. The KMn8O16 samples were characterized by X-ray diffraction, scanning electron microscopy, the effects of different annealed temperatures on the morphologies and electrochemical properties of the final products were systematically investigated. The result that the annealed samples exhibit the superior electrochemical performances compared to the unannealed sample. The KMn8O16 nanorods annealed at 400 °C show the highest reversible discharge capacity (147.9 mAh/g even after 80 cycles) at current density of 50 mA/g and the best cycling stability. These results indicate that the KMn8O16 nanorods could be a promising cathode material for lithium ion batteries.

  12. The ABAG biogenic emissions inventory project

    Science.gov (United States)

    Carson-Henry, C. (Editor)

    1982-01-01

    The ability to identify the role of biogenic hydrocarbon emissions in contributing to overall ozone production in the Bay Area, and to identify the significance of that role, were investigated in a joint project of the Association of Bay Area Governments (ABAG) and NASA/Ames Research Center. Ozone, which is produced when nitrogen oxides and hydrocarbons combine in the presence of sunlight, is a primary factor in air quality planning. In investigating the role of biogenic emissions, this project employed a pre-existing land cover classification to define areal extent of land cover types. Emission factors were then derived for those cover types. The land cover data and emission factors were integrated into an existing geographic information system, where they were combined to form a Biogenic Hydrocarbon Emissions Inventory. The emissions inventory information was then integrated into an existing photochemical dispersion model.

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

    DEFF Research Database (Denmark)

    Su, Hai-Yan; Gorlin, Yelena; Man, Isabela Costinela

    2012-01-01

    reduction reaction (ORR) and the oxygen evolution reaction (OER). First, we electrochemically characterize the nanostructured α-Mn2O3 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...

  14. Size-controlled synthesis and formation mechanism of manganese oxide OMS-2 nanowires under reflux conditions with KMnO4 and inorganic acids

    Science.gov (United States)

    Zhang, Qin; Cheng, Xiaodi; Qiu, Guohong; Liu, Fan; Feng, Xionghan

    2016-05-01

    This study presents a simplified approach for size-controlled synthesis of manganese oxide octahedral molecular sieve (OMS-2) nanowires using potassium permanganate (KMnO4) and different inorganic acids (HCl, HNO3, and H2SO4) under reflux conditions. The morphology and nanostructure of the synthesized products are characterized by X-ray diffraction, Ar adsorption, and electron microscopy analysis, in order to elucidate the controlling effects of acid concentration and type as well as the formation mechanism of OMS-2 nanowires. The concentration of inorganic acid is a crucial factor controlling the phase of the synthesized products. OMS-2 nanowires are obtained with HCl at the concentration ≥0.96 mol/L or with HNO3 and H2SO4 at the concentrations ≥0.72 mol/L. Differently, the type of inorganic acid effectively determines the particle size of OMS-2 nanowires. When the acid is changed from HCl to HNO3 and H2SO4 in the reflux system, the average length of OMS-2 declines significantly by 60-70% (1104-442 and 339 nm), with minor decreased in the average width (43-39 and 34 nm). The formation of OMS-2 nanowires under reflux conditions with KMnO4 and inorganic acids involves a two-step process, i.e., the initial formation of layered manganese oxides, and subsequent transformation to OMS-2 via a dissolution-recrystallization process under acidic conditions. The proposed reflux route provides an alternative approach for synthesizing OMS-2 nanowires as well as other porous nano-crystalline OMS materials.

  15. What the multiline signal (MLS) simulation data with average of weighted computations reveal about the Mn hyperfine interactions and oxidation states of the manganese cluster in OEC?

    Science.gov (United States)

    Baituti, Bernard

    2017-11-01

    Understanding the structure of oxygen evolving complex (OEC) fully still remains a challenge. Lately computational chemistry with the data from more detailed X-ray diffraction (XRD) OEC structure, has been used extensively in exploring the mechanisms of water oxidation in the OEC (Gatt et al., J. Photochem. Photobiol. B 104(1-2), 80-93 2011). Knowledge of the oxidation states is very crucial for understanding the core principles of catalysis by photosystem II (PSII) and catalytic mechanism of OEC. The present study involves simulation studies of the X-band continuous wave electron-magnetic resonance (CW-EPR) generated S 2 state signals, to investigate whether the data is in agreement with the four manganese ions in the OEC, being organised as a `3 + 1' (trimer plus one) model (Gatt et al., Angew. Chem. Int. Ed. 51, 12025-12028 2012; Petrie et al., Chem. A Eur. J. 21, 6780-6792 2015; Terrett et al., Chem. Commun. (Camb.) 50, 8-11 2014) or `dimer of dimers' model (Terrett et al. 2016). The question that still remains is how much does each Mn ion contribute to the " g2multiline" signal through its hyperfine interactions in OEC also to differentiate between the `high oxidation state (HOS)' and `low oxidation state (LOS)' paradigms? This is revealed in part by the structure of multiline (ML) signal studied in this project. Two possibilities have been proposed for the redox levels of the Mn ions within the catalytic cluster, the so called `HOS' and `LOS' paradigms (Gatt et al., J. Photochem. Photobiol. B 104(1-2), 80-93 2011). The method of data analysis involves numerical simulations of the experimental spectra on relevant models of the OEC cluster. The simulations of the X-band CW-EPR multiline spectra, revealed three manganese ions having hyperfine couplings with large anisotropy. These are most likely Mn III centres and these clearly support the `LOS' OEC paradigm model, with a mean oxidation of 3.25 in the S2 state. This is consistent with the earlier data by Jin et

  16. Rates of Cr(VI) Generation from CrxFe1-x(OH)3Solids upon Reaction with Manganese Oxide.

    Science.gov (United States)

    Pan, Chao; Liu, Huan; Catalano, Jeffrey G; Qian, Ao; Wang, Zimeng; Giammar, Daniel E

    2017-11-07

    The reaction of manganese oxides with Cr(III)-bearing solids in soils and sediments can lead to the natural production of Cr(VI) in groundwater. Building on previous knowledge of MnO 2 as an oxidant for Cr(III)-containing solids, this study systematically evaluated the rates and mechanisms of the oxidation of Cr(III) in iron oxides by δ-MnO 2 . The Fe/Cr ratio (x = 0.055-0.23 in Cr x Fe 1-x (OH) 3 ) and pH (5-9) greatly influenced the Cr(VI) production rates by controlling the solubility of Cr(III) in iron oxides. We established a quantitative relationship between Cr(VI) production rates and Cr(III) solubility of Cr x Fe 1-x (OH) 3 , which can help predict Cr(VI) production rates at different conditions. The adsorption of Cr(VI) and Mn(II) on solids shows a typical pH dependence for anions and cations. A multichamber reactor was used to assess the role of solid-solid contact in Cr x Fe 1-x (OH) 3 -MnO 2 interactions, which eliminates the contact of the two solids while still allowing aqueous species transport across a permeable membrane. Cr(VI) production rates were much lower in multichamber than in completely mixed batch experiments, indicating that the redox interaction is accelerated by mixing of the solids. Our results suggest that soluble Cr(III) released from Cr x Fe 1-x (OH) 3 solids to aqueous solution can migrate to MnO 2 surfaces where it is oxidized.

  17. Adsorption and transformation of selected human-used macrolide antibacterial agents with iron(III) and manganese(IV) oxides

    International Nuclear Information System (INIS)

    Feitosa-Felizzola, Juliana; Hanna, Khalil; Chiron, Serge

    2009-01-01

    The adsorption/transformation of two members (clarithromycin and roxithromycin) of the macrolide (ML) antibacterial agents on the surface of three environmental subsurface sorbents (clay, iron(III) and manganese(IV) oxy-hydroxides) was investigated. The adsorption fitted well to the Freundlich model with a high sorption capacity. Adsorption probably occurred through a surface complexation mechanism and was accompanied by slow degradation of the selected MLs. Transformation proceeded through two parallel pathways: a major pathway was the hydrolysis of the cladinose sugar, and to a lesser extent the hydrolysis of the lactone ring. A minor pathway was the N-dealkylation of the amino sugar. This study indicates that Fe(III) and Mn(IV) oxy-hydroxides in aquatic sediments may play an important role in the natural attenuation of MLs. Such an attenuation route yields a range of intermediates that might retain some of their biological activity. - Iron(III) and manganese(IV) oxy-hydroxides in aquatic sediments may play an important role in the natural attenuation of macrolide antibacterial agents

  18. Adsorption and transformation of selected human-used macrolide antibacterial agents with iron(III) and manganese(IV) oxides

    Energy Technology Data Exchange (ETDEWEB)

    Feitosa-Felizzola, Juliana [Laboratoire Chimie Provence, Aix-Marseille Universites-CNRS (UMR 6264), 3 place Victor Hugo, 13331 Marseille Cedex 3 (France); Hanna, Khalil [Laboratoire de Chimie Physique et Microbiologie pour l' Environnement, CNRS-Universite Henri Poincare-Nancy 1 (UMR 7564), 405 rue de Vandoeuvre, 54600 Villers-les-Nancy (France); Chiron, Serge [Laboratoire Chimie Provence, Aix-Marseille Universites-CNRS (UMR 6264), 3 place Victor Hugo, 13331 Marseille Cedex 3 (France)], E-mail: serge.chiron@univ-provence.fr

    2009-04-15

    The adsorption/transformation of two members (clarithromycin and roxithromycin) of the macrolide (ML) antibacterial agents on the surface of three environmental subsurface sorbents (clay, iron(III) and manganese(IV) oxy-hydroxides) was investigated. The adsorption fitted well to the Freundlich model with a high sorption capacity. Adsorption probably occurred through a surface complexation mechanism and was accompanied by slow degradation of the selected MLs. Transformation proceeded through two parallel pathways: a major pathway was the hydrolysis of the cladinose sugar, and to a lesser extent the hydrolysis of the lactone ring. A minor pathway was the N-dealkylation of the amino sugar. This study indicates that Fe(III) and Mn(IV) oxy-hydroxides in aquatic sediments may play an important role in the natural attenuation of MLs. Such an attenuation route yields a range of intermediates that might retain some of their biological activity. - Iron(III) and manganese(IV) oxy-hydroxides in aquatic sediments may play an important role in the natural attenuation of macrolide antibacterial agents.

  19. A photo-oxidation procedure using UV radiation/H{sub 2}O{sub 2} for decomposition of wine samples - Determination of iron and manganese content by flame atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Walter N.L. dos [Departamento de Ciencias Exatas e da Terra, Universidade do Estado da Bahia, Salvador, Bahia (Brazil); Universidade Federal da Bahia, Instituto de Quimica, Campus Ondina, Salvador, Bahia, 40170-290 Brazil (Brazil)], E-mail: wlopes@uneb.br; Brandao, Geovani C.; Portugal, Lindomar A.; David, Jorge M.; Ferreira, Sergio L.C. [Universidade Federal da Bahia, Instituto de Quimica, Campus Ondina, Salvador, Bahia, 40170-290 Brazil (Brazil)

    2009-06-15

    This paper proposes the use of photo-oxidation with UV radiation/H{sub 2}O{sub 2} as sample pretreatment for the determination of iron and manganese in wines by flame atomic absorption spectrometry (FAAS). The optimization involved the study of the following variables: pH and concentration of buffer solution, concentrated hydrogen peroxide volume and irradiation time. The evaluation of sample degradation was monitored by measuring the absorbance at the maximum wavelength of red wine (530 nm). Using the experimental conditions established during the optimization (irradiation time of 30 min, oxidant volume of 2.5 mL, pH 10, and a buffer concentration of 0.15 mol L{sup - 1}), this procedure allows the determination of iron and manganese with limits of detection of 30 and 22 {mu}g L{sup - 1}, respectively, for a 5 mL volume of digested sample. The precision levels, expressed as relative standard deviation (RSD), were 2.8% and 0.65% for iron and 2.7% and 0.54% for manganese for concentrations of 0.5 and 2.0 mg L{sup - 1}, respectively. Addition/recovery tests for evaluation of the accuracy were in the ranges of 90%-111% and 95%-107% for iron and manganese, respectively. This digestion procedure has been applied for the determination of iron and manganese in six wine samples. The concentrations varied from 1.58 to 2.77 mg L{sup - 1} for iron and from 1.30 to 1.91 mg L{sup - 1} for manganese. The results were compared with those obtained by an acid digestion procedure and determination of the elements by FAAS. There was no significant difference between the results obtained by the two methods based on a paired t-test (at 95% confidence level)

  20. Selection of Amine-Oxidizing Dairy Lactic Acid Bacteria and Identification of the Enzyme and Gene Involved in the Decrease of Biogenic Amines

    Science.gov (United States)

    Guarcello, Rosa; De Angelis, Maria; Settanni, Luca; Formiglio, Sabino; Gaglio, Raimondo; Moschetti, Giancarlo; Gobbetti, Marco

    2016-01-01

    ABSTRACT Accumulation of biogenic amines (BAs) in cheese and other foods is a matter of public health concern. The aim of this study was to identify the enzyme activities responsible for BA degradation in lactic acid bacteria which were previously isolated from traditional Sicilian and Apulian cheeses. The selected strains would control the concentration of BAs during cheese manufacture. First, 431 isolates not showing genes encoding the decarboxylases responsible for BA formation were selected using PCR-based methods. Ninety-four out of the 431 isolates degraded BAs (2-phenylethylamine, cadaverine, histamine, putrescine, spermine, spermidine, tyramine, or tryptamine) during cultivation on chemically defined medium. As shown by random amplification of polymorphic DNA-PCR and partial sequencing of the 16S rRNA gene, 78 of the 94 strains were Lactobacillus species (Lactobacillus casei, Lb. fermentum, Lb. parabuchneri, Lb. paracasei, Lb. paraplantarum, and Lb. rhamnosus), Leuconostoc species (Leuconostoc lactis and Ln. mesenteroides), Pediococcus pentosaceus, Lactococcus lactis, Streptococcus species (Streptococcus gallolyticus and S. thermophilus), Enterococcus lactis, and Weissella paramesenteroides. A multicopper oxidase-hydrolyzing BA was purified from the most active strain, Lb. paracasei subsp. paracasei CB9CT. The gene encoding the multicopper oxidase was sequenced and was also detected in other amine-degrading strains of Lb. fermentum, Lb. paraplantarum, and P. pentosaceus. Lb. paracasei subsp. paracasei CB9CT and another strain (CACIO6CT) of the same species that was able to degrade all the BAs were singly used as adjunct starters for decreasing the concentration of histamine and tyramine in industrial Caciocavallo cheese. The results of this study disclose a feasible strategy for increasing the safety of traditional cheeses while maintaining their typical sensorial traits. IMPORTANCE Because high concentrations of the potentially toxic biogenic amines may be

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

    Science.gov (United States)

    Nowlan, G.A.

    1976-01-01

    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.

  2. New insight into the origin of manganese oxide ore deposits in the Appalachian Valley and Ridge of northeastern Tennessee and northern Virginia, USA

    Science.gov (United States)

    Carmichael, Sarah K.; Doctor, Daniel H.; Wilson, Crystal G.; Feierstein, Joshua; McAleer, Ryan J.

    2017-01-01

    Manganese oxide deposits have long been observed in association with carbonates within the Appalachian Mountains, but their origin has remained enigmatic for well over a century. Ore deposits of Mn oxides from several productive sites located in eastern Tennessee and northern Virginia display morphologies that include botryoidal and branching forms, massive nodules, breccia matrix cements, and fracture fills. The primary ore minerals include hollandite, cryptomelane, and romanèchite. Samples of Mn oxides from multiple localities in these regions were analyzed using electron microscopy, X-ray analysis, Fourier transform infrared spectroscopy, and trace and rare earth element (REE) geochemistry. The samples from eastern Tennessee have biological morphologies, contain residual biopolymers, and exhibit REE signatures that suggest the ore formation was due to supergene enrichment (likely coupled with microbial activity). In contrast, several northern Virginia ores hosted within quartz-sandstone breccias exhibit petrographic relations, mineral morphologies, and REE signatures indicating inorganic precipitation, and a likely hydrothermal origin with supergene overprinting. Nodular accumulations of Mn oxides within weathered alluvial deposits that occur close to breccia-hosted Mn deposits in Virginia show geochemical signatures that are distinct from the breccia matrices and appear to reflect remobilization of earlier-emplaced Mn and concentration within supergene traps. Based on the proximity of all of the productive ore deposits to mapped faults or other zones of deformation, we suggest that the primary source of all of the Mn may have been deep seated, and that Mn oxides with supergene and/or biological characteristics resulted from the local remobilization and concentration of this primary Mn.

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

    Science.gov (United States)

    Davis, R.; Tebo, B. M.

    2013-12-01

    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

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

    International Nuclear Information System (INIS)

    Olin, M.; Lehikoinen, J.

    1997-12-01

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

  5. Manganese oxide as a promoter for C2-C4 olefin production in the hydrogenation of carbon dioxide

    International Nuclear Information System (INIS)

    Kim, C.; Chen, K.; Hanson, F.V.; Oblad, A.G.; Tsai, Y.

    1986-01-01

    A number of active research and development programs have been initiated to explore the potential of CO hydrogenation process as a source of low molecular weight (C 2 -C 4 ) olefins. Metal catalysts such as Co-Mn, Ni-zeolite, Rd and Mo have been evaluated for low molecular weight olefin selectivity. The coprecipitated Fe-Mn system (Mn/Fe=9/1) was reported to be highly olefin selective. Recently, many investigators reported supporting evidence for the promotional effect of Mn for precipitated Fe catalysts. In this study, Raney Fe promoted with Mn has been evaluated for C 2 -C 4 olefin selectivity in the hydrogenation of CO relative to coprecipitated Fe-Mn catalysts. Catalyst characterization, including BET surface area, X-ray diffraction, selective chemisorption and ESCA, has been carried to provide insight into the role of manganese in both the Coprecipitated and Raney catalyst systems

  6. Layered lithium manganese(0.4) nickel(0.4) cobalt(0.2) oxide(2) as cathode for lithium batteries

    Science.gov (United States)

    Ma, Miaomiao

    The lithium ion battery occupies a dominant position in the portable battery market today. Intensive research has been carried out on every part of the battery to reduce cost, avoid environmental hazards, and improve battery performance. The commercial cathode material LiCoO2 has been partially replaced by LiNiyCo1- yO2 in the last two years, and mixed metal oxides have been introduced in the last quarter. From a resources point of view, only about 10 million tons of cobalt deposits are available from the world's minerals. However, there is about 500 times more manganese available than cobalt. Moreover, cobalt itself is not environmentally friendly. The purpose of this work is to find a promising alternative cathode material that can maintain good cycling performance, while at the same time reducing the cost and toxicity. When the cost is lowered, it is then possible to consider the larger scale use of lithium ion batteries in application such as hybrid electric vehicles (HEV). The research work presented in this thesis has focused on a specific composition of a layered lithium transition metal oxide, LiMn0.4Ni 0.4Co0.2O2 with the R3¯m structure. The presence of cobalt plays a critical role in minimizing transition metal migration to the lithium layer, and perhaps also in enhancing the electronic conductivity; however, cobalt is in limited supply and it is therefore more costly than nickel or manganese. The performance of LiMn0.4Ni0.4Co 0.2O2 was investigated and characterized utilizing various techniques an its performance compared with cobalt free LiMn0.5N i0.5O2, as well as with LiMn1/3Ni1/3Co 1/3O2, which is the most extensively studied replacement candidate for LiNiyCo1- yO2, and may be in SONY'S new hybrid cells. First, the structure and cation distribution in LiMn0.4Ni 0.4Co0.2O2 was studied by a combination of X-ray and neutron diffraction experiments. This combination study shows that about 3--5% nickel is present in the lithium layer, while manganese and

  7. Manganese dosimetry: species differences and implications for neurotoxicity.

    Science.gov (United States)

    Aschner, Michael; Erikson, Keith M; Dorman, David C

    2005-01-01

    Manganese (Mn) is an essential mineral that is found at low levels in food, water, and the air. Under certain high-dose exposure conditions, elevations in tissue manganese levels can occur. Excessive manganese accumulation can result in adverse neurological, reproductive, and respiratory effects in both laboratory animals and humans. In humans, manganese-induced neurotoxicity (manganism) is the overriding concern since affected individuals develop a motor dysfunction syndrome that is recognized as a form of parkinsonism. This review primarily focuses on the essentiality and toxicity of manganese and considers contemporary studies evaluating manganese dosimetry and its transport across the blood-brain barrier, and its distribution within the central nervous system (CNS). These studies have dramatically improved our understanding of the health risks posed by manganese by determining exposure conditions that lead to increased concentrations of this metal within the CNS and other target organs. Most individuals are exposed to manganese by the oral and inhalation routes of exposure; however, parenteral injection and other routes of exposure are important. Interactions between manganese and iron and other divalent elements occur and impact the toxicokinetics of manganese, especially following oral exposure. The oxidation state and solubility of manganese also influence the absorption, distribution, metabolism, and elimination of manganese. Manganese disposition is influenced by the route of exposure. Rodent inhalation studies have shown that manganese deposited within the nose can undergo direct transport to the brain along the olfactory nerve. Species differences in manganese toxicokinetics and response are recognized with nonhuman primates replicating CNS effects observed in humans while rodents do not. Potentially susceptible populations, such as fetuses, neonates, individuals with compromised hepatic function, individuals with suboptimal manganese or iron intake, and

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

    International Nuclear Information System (INIS)

    Ramachandran, Anup; Lebofsky, Margitta; Weinman, Steven A.; Jaeschke, Hartmut

    2011-01-01

    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.

  9. Dyslipdemia induced by chronic low dose co-exposure to lead, cadmium and manganese in rats: the role of oxidative stress.

    Science.gov (United States)

    Oladipo, Olusola Olalekan; Ayo, Joseph Olusegun; Ambali, Suleiman Folorunsho; Mohammed, Bisalla; Aluwong, Tanang

    2017-07-01

    Lead (Pb), cadmium (Cd) and manganese (Mn) have many potential adverse health effects in vitro and in animal models of clinical toxicity. The current study investigated the dyslipidaemic and oxidative stress effects of chronic low-dose oral exposure to Pb, Cd and Mn and the combination (Pb+Cd+Mn) in rats for 15 weeks. Chronic exposure to the metals did not significantly (P>0.05) alter serum lipid profiles. However, the atherogenic index decreased by 32.2% in the Pb+Cd+Mn group, relative to the control. The triglyceride/high-density lipoprotein cholesterol ratio decreased by 39.4% in the Pb+Cd+Mn group, relative to the control, and elevated by 81.8, 94.8 and 20.8%, relative to the Pb, Cd and Mn groups, respectively. While the serum concentrations of malondialdehyde significantly increased in the Mn and Pb+Cd+Mn groups, that of glutathione peroxidase-1 decreased in the Pb+Cd+Mn group, and metallothionein-1 and zinc concentrations markedly decreased in all the metal treatment groups. The results suggest that long-term exposure of rats to Pb+Cd+Mn may result in hypolipidaemia, mediated via oxidative stress and metal interactions. Individuals who are constantly exposed to environmentally relevant levels of the metals may be at risk of hypolipidaemia. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Anodic Lodes and Scrapings as a Source of Electrolytic Manganese

    Directory of Open Access Journals (Sweden)

    Daniel Fernández-González

    2018-03-01

    Full Text Available Manganese is an element of interest in metallurgy, especially in ironmaking and steel making, but also in copper and aluminum industries. The depletion of manganese high grade sources and the environmental awareness have led to search for new manganese sources, such as wastes/by-products of other metallurgies. In this way, we propose the recovery of manganese from anodic lodes and scrapings of the zinc electrolysis process because of their high Mn content (>30%. The proposed process is based on a mixed leaching: a lixiviation-neutralization at low temperature (50 °C, reached due to the exothermic reactions involved in the process and a lixiviation with sulfuric acid at high temperature (150–200 °C, in heated reactor. The obtained solution after the combined process is mainly composed by manganese sulphate. This solution is then neutralized with CaO (or manganese carbonate as a first purification stage, removing H2SO4 and those impurities that are easily removable by controlling pH. Then, the purification of nobler elements than manganese is performed by their precipitation as sulphides. The purified solution is sent to electrolysis where electrolytic manganese is obtained (99.9% Mn. The versatility of the proposed process allows for obtaining electrolytic manganese, oxide of manganese (IV, oxide of manganese (II, or manganese sulphate.

  11. Selection of Amine-Oxidizing Dairy Lactic Acid Bacteria and Identification of the Enzyme and Gene Involved in the Decrease of Biogenic Amines.

    Science.gov (United States)

    Guarcello, Rosa; De Angelis, Maria; Settanni, Luca; Formiglio, Sabino; Gaglio, Raimondo; Minervini, Fabio; Moschetti, Giancarlo; Gobbetti, Marco

    2016-12-01

    Accumulation of biogenic amines (BAs) in cheese and other foods is a matter of public health concern. The aim of this study was to identify the enzyme activities responsible for BA degradation in lactic acid bacteria which were previously isolated from traditional Sicilian and Apulian cheeses. The selected strains would control the concentration of BAs during cheese manufacture. First, 431 isolates not showing genes encoding the decarboxylases responsible for BA formation were selected using PCR-based methods. Ninety-four out of the 431 isolates degraded BAs (2-phenylethylamine, cadaverine, histamine, putrescine, spermine, spermidine, tyramine, or tryptamine) during cultivation on chemically defined medium. As shown by random amplification of polymorphic DNA-PCR and partial sequencing of the 16S rRNA gene, 78 of the 94 strains were Lactobacillus species (Lactobacillus casei, Lb. fermentum, Lb. parabuchneri, Lb. paracasei, Lb. paraplantarum, and Lb. rhamnosus), Leuconostoc species (Leuconostoc lactis and Ln. mesenteroides), Pediococcus pentosaceus, Lactococcus lactis, Streptococcus species (Streptococcus gallolyticus and S. thermophilus), Enterococcus lactis, and Weissella paramesenteroides A multicopper oxidase-hydrolyzing BA was purified from the most active strain, Lb. paracasei subsp. paracasei CB9CT. The gene encoding the multicopper oxidase was sequenced and was also detected in other amine-degrading strains of Lb. fermentum, Lb. paraplantarum, and P. pentosaceus Lb. paracasei subsp. paracasei CB9CT and another strain (CACIO6CT) of the same species that was able to degrade all the BAs were singly used as adjunct starters for decreasing the concentration of histamine and tyramine in industrial Caciocavallo cheese. The results of this study disclose a feasible strategy for increasing the safety of traditional cheeses while maintaining their typical sensorial traits. Because high concentrations of the potentially toxic biogenic amines may be found in traditional

  12. Asymmetric supercapacitors based on functional electrospun carbon nanofiber/manganese oxide electrodes with high power density and energy density

    Science.gov (United States)

    Lin, Sheng-Chi; Lu, Yi-Ting; Chien, Yu-An; Wang, Jeng-An; You, Ting-Hsuan; Wang, Yu-Sheng; Lin, Chih-Wen; Ma, Chen-Chi M.; Hu, Chi-Chang

    2017-09-01

    Carbon nanofibers modified with carboxyl groups (CNF-COOH) possessing good wettability and high porosity are homogeneously deposited with amorphous manganese dioxide (amorphous MnO2) by potentiodynamic deposition for asymmetric super-capacitors (ASCs). The potential-cycling in 1 M H2SO4 successfully enhances the hydrophilicity of carbonized polymer nanofibers and facilitates the access of electrolytes within the CNF-COOH matrix. This modification favors the deposition of amorphous MnO2 and improves its electrochemical utilization. In this composite, MnO2 homogeneously dispersed onto CNF-COOH provides desirable pseudocapacitance and the CNF-COOH network works as the electron conductor. The composite of CNF-COOH@MnO2-20 shows a high specific capacitance of 415 F g-1 at 5 mV s-1. The capacitance retention of this composite is 94% in a 10,000-cycle test. An ASC cell consisting of this composite and activated carbon as positive and negative electrodes can be reversibly charged/discharged to a cell voltage of 2.0 V in 1 M Na2SO4 and 4 mM NaHCO3 with specific energy and power of 36.7 Wh kg-1 and 354.9 W kg-1, respectively. This ASC also shows excellent cell capacitance retention (8% decay) in the 2V, 10,000-cycle stability test, revealing superior performance.

  13. Identification of a novel Gsp-related pathway required for secretion of the manganese-oxidizing factor of Pseudomonas putida strain GB-1.

    Science.gov (United States)

    De Vrind, Johannes; De Groot, Arjan; Brouwers, Geert Jan; Tommassen, Jan; De Vrind-De Jong, Elisabeth

    2003-02-01

    The manganese-oxidizing factor of Pseudomonas putida strain GB-1 is associated with the outer membrane. One of the systems of protein transport across the outer membrane is the general secretory pathway (Gsp). The gsp genes are called xcp in Pseudomonas species. In a previous study, it was shown that mutation of the prepilin peptidase XcpA and of a homologue of the pseudopilin XcpT inhibited transport of the factor. In the present study, we describe the genomic region flanking the xcpT homologue (designated xcmT1). We show that xcmT1 is part of a two-gene operon that includes an xcpS homologue (designated xcmS). No other xcp-like genes are present in the regions flanking the xcmT1/xcmS cluster. We also characterized the site of transposon insertion of another transport mutant of P. putida GB-1. This insertion appeared to be located in a gene (designated xcmX) possibly encoding another pseudopilin-related protein. This xcmX is clustered with two other xcpT-related genes (designated xcmT2 and xcmT3) on one side and homologues of three csg genes (designated csmE, csmF and csmG) on the other side. The csg genes are involved in production of aggregative fibres in Escherichia coli and Salmonella typhimurium. A search for XcmX homologues revealed that the recently published genome of Ralstonia solanacearum and the unannotated genome of P. putida KT2440 contain comparable gene clusters with xcmX and xcp homologues that are different from the well-described 'regular'xcp/gsp clusters. They do contain xcpR and xcpQ homologues but, for example, homologues of xcpP, Y and Z are lacking. The results suggest a novel Xcp-related system for the transport of manganese-oxidizing enzymes to the cell surface.

  14. Manganese Countries

    Directory of Open Access Journals (Sweden)

    Maria Sousa Galito

    2014-05-01

    Full Text Available Cheickna Bounajim Cissé wrote an article in Mars 2013 in the Journal Les Afriques N. º 237, suggesting a new acronym, MANGANESE, for the nine African countries: Morocco, Angola, Namibia, Ghana, Algeria, Nigeria, Egypt, South Africa and Ethiopia. According to Cissé, this group of African nations will be the fastest growing states in the region over the next few years. The purpose of this article is to test the pertinence of the acronym, discuss the credibility and reliability of the future prospects of these countries by comparing selected socioeconomic and sociopolitical indicators based on the latest global rankings and trends. Likewise, the potential of Cissé's claim will be assessed, especially in relationship to drug trafficking and terrorism that may put their recent sustainability in danger now and in the future.

  15. Biological low pH Mn(II) oxidation in a manganese deposit influenced by metal-rich groundwater

    Science.gov (United States)

    Bohu, Tsing; Akob, Denise M.; Abratis, Michael; Lazar, Cassandre S.; Küsel, Kirsten

    2016-01-01

    The mechanisms, key organisms, and geochemical significance of biological low-pH Mn(II) oxidation are largely unexplored. Here, we investigated the structure of indigenous Mn(II)-oxidizing microbial communities in a secondary subsurface Mn oxide deposit influenced by acidic (pH 4.8) metal-rich groundwater in a former uranium mining area. Microbial diversity was highest in the Mn deposit compared to the adjacent soil layers and included the majority of known Mn(II)-oxidizing bacteria (MOB) and two genera of known Mn(II)-oxidizing fungi (MOF). Electron X-ray microanalysis showed that romanechite [(Ba,H2O)2(Mn4+,Mn3+)5O10] was conspicuously enriched in the deposit. Canonical correspondence analysis revealed that certain fungal, bacterial, and archaeal groups were firmly associated with the autochthonous Mn oxides. Eight MOB within the Proteobacteria, Actinobacteria, and Bacteroidetes and one MOF strain belonging to Ascomycota were isolated at pH 5.5 or 7.2 from the acidic Mn deposit. Soil-groundwater microcosms demonstrated 2.5-fold-faster Mn(II) depletion in the Mn deposit than adjacent soil layers. No depletion was observed in the abiotic controls, suggesting that biological contribution is the main driver for Mn(II) oxidation at low pH. The composition and species specificity of the native low-pH Mn(II) oxidizers were highly adapted to in situ conditions, and these organisms may play a central role in the fundamental biogeochemical processes (e.g., metal natural attenuation) occurring in the acidic, oligotrophic, and metalliferous subsoil ecosystems.

  16. from Tailings Material of Ghana Manganese Company (GMC)

    African Journals Online (AJOL)

    user

    1 Introduction. The name „Nsutite‟ (γ - MnO2); referred to as better- grade manganese oxide mineral type, was named after Nsuta, where extraction from the Nsuta-. Dagwin manganese deposits began almost a century ago. According to Kesse (1985), the deposits mainly contain oxide (chiefly pyrolusite and psilomelane) ...

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

    Directory of Open Access Journals (Sweden)

    Yadollah Abdollahi

    2014-01-01

    Full Text Available 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.

  18. Analysis of a Battery Management System (BMS Control Strategy for Vibration Aged Nickel Manganese Cobalt Oxide (NMC Lithium-Ion 18650 Battery Cells

    Directory of Open Access Journals (Sweden)

    Thomas Bruen

    2016-04-01

    Full Text Available Electric vehicle (EV manufacturers are using cylindrical format cells as part of the vehicle’s rechargeable energy storage system (RESS. In a recent study focused at determining the ageing behavior of 2.2 Ah Nickel Manganese Cobalt Oxide (NMC Lithium-Ion 18650 battery cells, significant increases in the ohmic resistance (RO were observed post vibration testing. Typically a reduction in capacity was also noted. The vibration was representative of an automotive service life of 100,000 miles of European and North American customer operation. This paper presents a study which defines the effect that the change in electrical properties of vibration aged 18650 NMC cells can have on the control strategy employed by the battery management system (BMS of a hybrid electric vehicle (HEV. It also proposes various cell balancing strategies to manage these changes in electrical properties. Subsequently this study recommends that EV manufacturers conduct vibration testing as part of their cell selection and development activities so that electrical ageing characteristics associated with road induced vibration phenomena are incorporated to ensure effective BMS and RESS performance throughout the life of the vehicle.

  19. Combined cycling and calendar capacity fade modeling of a Nickel-Manganese-Cobalt Oxide Cell with real-life profile validation

    DEFF Research Database (Denmark)

    de Hoog, Joris; Timmermans, Jean-Marc; Stroe, Daniel-Ioan

    2017-01-01

    This paper presents the development of a semi-empirical combined lifetime model for a Nickel Manganese Cobalt Oxide (NMC) cathode and a graphite anode based cell, considered as one of the most promising candidates for the automotive industry. The development of this model was based on a thorough...... understanding of the degradation behavior of a 20-A h NMC cell, based on the analysis of the results of an extensive test-matrix using 146 cells. This test-matrix was designed around four impact factors: temperature (25–45 °C), Depth-of-Discharge (100–20% DoD), middle State-of-Charge (80–20% Mid......-SoC) and current rates (C/3 to 2C). Gathering sufficient data for a mathematical model requires a huge time-investment, and the measurements gathered over the course of 2.5 years offer a unique insight in the aging behavior of the NMC cells used in this study. Experimental results for cycling aging indicated...

  20. Manganese doped-iron oxide nanoparticle clusters and their potential as agents for magnetic resonance imaging and hyperthermia

    KAUST Repository

    Casula, Maria F.

    2016-06-10

    A simple, one pot method to synthesize water-dispersible Mn doped iron oxide colloidal clusters constructed of nanoparticles arranged into secondary flower-like structures was developed. This method allows the successful incorporation and homogeneous distribution of Mn within the nanoparticle iron oxide clusters. The formed clusters retain the desired morphological and structural features observed for pure iron oxide clusters, but possess intrinsic magnetic properties that arise from Mn doping. They show distinct performance as imaging contrast agents and excellent characteristics as heating mediators in magnetic fluid hyperthermia. It is expected that the outcomes of this study will open up new avenues for the exploitation of doped magnetic nanoparticle assemblies in biomedicine. © the Owner Societies 2016.

  1. Quantitative iTRAQ-based secretome analysis reveals species-specific and temporal shifts in carbon utilization strategies among manganese(II)-oxidizing Ascomycete fungi

    Energy Technology Data Exchange (ETDEWEB)

    Zeiner, Carolyn A.; Purvine, Samuel O.; Zink, Erika M.; Paša-Tolić, Ljiljana; Chaput, Dominique L.; Wu, Si; Santelli, Cara M.; Hansel, Colleen M.

    2017-09-01

    Fungi generate a wide range of extracellular hydrolytic and oxidative enzymes and reactive metabolites, collectively known as the secretome, that synergistically drive plant litter decomposition in the environment. While secretome studies of model organisms have greatly expanded our knowledge of these enzymes, few have extended secretome characterization to environmental isolates or directly compared temporal patterns of enzyme utilization among diverse species. Thus, the mechanisms of carbon (C) degradation by many ubiquitous soil fungi remain poorly understood. Here we use a combination of iTRAQ proteomics and custom bioinformatic analyses to compare the protein composition of the secretomes of four manganese(II)-oxidizing Ascomycete fungi over a three-week time course. We demonstrate that although the fungi produce a similar suite of extracellular enzymes, they exhibit striking differences in the regulation of these enzymes among species and over time, revealing species-specific and temporal shifts in C utilization strategies as they degrade the same substrate. Specifically, our findings suggest that Paraconiothyrium sporulosum AP3s5-JAC2a and Alternaria alternata SRC1lrK2f employ sequential enzyme secretion patterns concomitant with decreasing resource availability, Stagonospora sp. SRC1lsM3a preferentially degrades proteinaceous substrate before switching to carbohydrates, and Pyrenochaeta sp. DS3sAY3a utilizes primarily peptidases to aggressively attack carbon sources in a concentrated burst. This work highlights the diversity of operative metabolic strategies among cellulose-degrading Ascomycetes and enhances our understanding of their role in C turnover in the environment.

  2. The ground states properties and the spin effect on the cubic and hexagonal perovskite manganese oxide BaMnO3: GGA+U calculation

    International Nuclear Information System (INIS)

    Hamdad, Noura

    2011-01-01

    Particularly interesting as candidates to technological applications are the manganese perovskites with AMnO 3 formula. Their magnetic structure was described as resulting from a particular ordering of the occupied d orbitals which possess. This reflects my understanding of the structural, electronic and magnetic phenomena, which is well established only in the limit where the systems show localized or itinerant electron behavior. In general, the perovskites of ABO 3 -type are well known with their (anti)ferroelectric, piezoelectric and (anti)ferromagnetism properties applied in considerable technological investigations. In my paper, I studied the ground states properties of the BaMnO 3 perovskite oxide. My structural properties are given using LSDA, GGA, LSDA+U and GGA+U in the aim to introduce the exchange correlation potential. In the following paper, I use the GGA+U on the electronic and magnetic properties calculation. I show in my study the density of states, the band structures and also the charge density figures. My results such as lattice parameter, bulk modulus and its pressure derivative agree very well with available theoretical works and experimental data. I discuss the magnetic moment and the U-Hubbard effect introduced by LSDA+U and GGA+U on my results given in this paper. -- Research highlights: → I examine the structural electronic and magnetic properties of the BaMnO 3 perovskite oxide within the GGA+U. → I study different magnetic configurations of BaMnO 3 to indicate that it exhibits the G-AFM behavior. → I conclude that BaMnO 3 is G-AFM. → I confirm that the GGA+U is an accurate approximation than others such as LDA, GGA and LSDA+U. → The introduction of U-Hubbard term has extensively influenced the obtained results.

  3. Mechanistic Links in the in-situ Formation of Dinuclear Manganese Catalysts, H2O2 Disproportionation, and Alkene Oxidation

    NARCIS (Netherlands)

    Angelone, Davide; Abdolahzadeh, Shaghayegh; de Boer, Johannes W.; Browne, Wesley R.

    The oxidation of substrates, such as alkenes, with H2O2 and the catalyst [Mn-2(IV)(mu-O)(3)(tmtacn)(2)](2+) (1; tmtacn = 1,4,7-tri-methyl-1,4,7-triazacyclononane) is promoted by the addition of carboxylic acids through the in situ formation of bis-(carboxylato) complexes of the type

  4. Microbial, algal, and fungal strategies for manganese oxidation at a Shade Township coal mine, Somerset County, Pennsylvania

    International Nuclear Information System (INIS)

    Robbins, E.I.; Brant, D.L.; Ziemkiewicz, P.F.

    1999-01-01

    Successful designs to eliminate Mn from mine discharge are necessary for both restoring abandoned mine lands and permitting the mining of high sulfur coal in the eastern United States. A passive in-line system that meets Mn discharge limits was built at the discharge from the former Shade Township coal mine in south central Pennsylvania. Qualitative research on monthly changes in the microbial and algal community that removes Mn is underway. Epilithic attachment of microorganisms was analyzed on artificial (glass microscope slides) and natural substrates (limestone thin sections) that were immersed in surface water for one month periods over 6 months. Organisms attached to both glass and limestone substrates. Limestone became coated with 34--86% more Mn that did glass surfaces. Light microscopy revealed 12 different strategies are being used by bacteria, cyan bacteria, diatoms, green algae, and fungi to oxidize Mn. the dominant method used by the epilithic community to oxidize Mn is coating of holdfasts by the iron bacterium, Liptothrix discophora, and the green alga, Ulothrix sp. Other methods for Mn removal by oxidation include coating of individual cells, filaments/sheaths/hyphae, extracellular polysaccharides, and biofilms. The unplanned community at the site is multifaceted and extremely efficient in its Mn removal ability. Community interactions or complexity may play roles in the stability of the ecosystem and the efficiency of its Mn oxidizing ability

  5. AMOchar: Amorphous manganese oxide coating of biochar improves its efficiency at removing metal(loid)s from aqueous solutions.

    Science.gov (United States)

    Trakal, Lukáš; Michálková, Zuzana; Beesley, Luke; Vítková, Martina; Ouředníček, Petr; Barceló, Andreu Piqueras; Ettler, Vojtěch; Číhalová, Sylva; Komárek, Michael

    2018-06-01

    A novel sorbent made from biochar modified with an amorphous Mn oxide (AMOchar) was compared with pure biochar, pure AMO, AMO+biochar mixtures and biochar+birnessite composite for the removal of various metal(loid)s from aqueous solutions using adsorption and solid-state analyses. In comparison with the pristine biochar, both Mn oxide-biochar composites were able to remove significantly greater quantities of various metal(loid)s from the aqueous solutions, especially at a ratio 2:1 (AMO:biochar). The AMOchar proved most efficient, removing almost 99, 91 and 51% of Pb, As and Cd, respectively. Additionally, AMOchar and AMO+biochar mixture exhibited reduced Mn leaching, compared to pure AMO. Therefore, it is concluded that the synthesis of AMO and biochar is able to produce a double acting sorbent ('dorbent') of enhanced efficiency, compared with the individual deployment of their component materials. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. The impacts of copper, iron and manganese metal ions on the EPR assessment of beer oxidative stability.

    OpenAIRE

    Jenkins, David; James, Sue; Dehrmann, Frieda; Smart, Katherine; Cook, David

    2018-01-01

    Beer flavour stability is a key quality parameter as brewers seek to maintain the quality of their product throughout the supply chain. The electron paramagnetic resonance (EPR) oxidative stability assay is one method that brewers are utilising to optimise their process with regards to flavour stability without the time requirements of stored aging and sensory testing of beer. There are still gaps in knowledge relating to the EPR measurement and the factors within the assay that affect the me...

  7. Cobalt-manganese-based spinels as multifunctional materials that unify catalytic water oxidation and oxygen reduction reactions.

    Science.gov (United States)

    Menezes, Prashanth W; Indra, Arindam; Sahraie, Nastaran Ranjbar; Bergmann, Arno; Strasser, Peter; Driess, Matthias

    2015-01-01

    Recently, there has been much interest in the design and development of affordable and highly efficient oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalysts that can resolve the pivotal issues that concern solar fuels, fuel cells, and rechargeable metal-air batteries. Here we present the synthesis and application of porous CoMn2 O4 and MnCo2 O4 spinel microspheres as highly efficient multifunctional catalysts that unify the electrochemical OER with oxidant-driven and photocatalytic water oxidation as well as the ORR. The porous materials were prepared by the thermal degradation of the respective carbonate precursors at 400 °C. The as-prepared spinels display excellent performances in electrochemical OER for the cubic MnCo2 O4 phase in comparison to the tetragonal CoMn2 O4 material in an alkaline medium. Moreover, the oxidant-driven and photocatalytic water oxidations were performed and they exhibited a similar trend in activity to that of the electrochemical OER. Remarkably, the situation is reversed in ORR catalysis, that is, the oxygen reduction activity and stability of the tetragonal CoMn2 O4 catalyst outperformed that of cubic MnCo2 O4 and rivals that of benchmark Pt catalysts. The superior catalytic performance and the remarkable stability of the unifying materials are attributed to their unique porous and robust microspherical morphology and the intrinsic structural features of the spinels. Moreover, the facile access to these high-performance materials enables a reliable and cost-effective production on a large scale for industrial applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Layer by Layer Ex-Situ Deposited Cobalt-Manganese Oxide as Composite Electrode Material for Electrochemical Capacitor.

    Directory of Open Access Journals (Sweden)

    Rusi

    Full Text Available The composite metal oxide electrode films were fabricated using ex situ electrodeposition method with further heating treatment at 300°C. The obtained composite metal oxide film had a spherical structure with mass loading from 0.13 to 0.21 mg cm(-2. The structure and elements of the composite was investigated using X-ray diffraction (XRD and energy dispersive X-ray (EDX. The electrochemical performance of different composite metal oxides was studied by cyclic voltammetry (CV and galvanostatic charge-discharge (CD. As an active electrode material for a supercapacitor, the Co-Mn composite electrode exhibits a specific capacitance of 285 Fg(-1 at current density of 1.85 Ag(-1 in 0.5 M Na2SO4 electrolyte. The best composite electrode, Co-Mn electrode was then further studied in various electrolytes (i.e., 0.5 M KOH and 0.5 M KOH/0.04 M K3Fe(CN 6 electrolytes. The pseudocapacitive nature of the material of Co-Mn lead to a high specific capacitance of 2.2 x 10(3 Fg(-1 and an energy density of 309 Whkg(-1 in a 0.5 M KOH/0.04 M K3Fe(CN 6 electrolyte at a current density of 10 Ag(-1. The specific capacitance retention obtained 67% of its initial value after 750 cycles. The results indicate that the ex situ deposited composite metal oxide nanoparticles have promising potential in future practical applications.

  9. Screening of oxygen-carrier particles based on iron-, manganese-, copper- and nickel oxides for use in chemical-looping technologies

    Energy Technology Data Exchange (ETDEWEB)

    Johansson, Marcus

    2007-07-01

    Capture and storage of carbon dioxide from combustion will likely be used in the future as a method of reducing emissions of greenhouse gases and thus be part of the overall strategy to stabilize the atmospheric levels of CO{sub 2}. Chemical-looping combustion is a method of combustion where CO{sub 2} is inherently separated from the non-condensable components in the flue gas without the need for an energy intensive air separation unit. This is because nitrogen from the combustion air is never mixed with the fuel. Instead, oxygen carriers, in the form of metal oxide particles, circulate between two interconnected fluidized reactors and transfer oxygen from the air to the fuel through heterogeneous gas-solid redox reactions. The technology could also be adapted for the production of hydrogen from fossil fuels with CO{sub 2} separation, i.e. chemical-looping reforming. 108 different oxygen-carriers based on iron-, manganese-, copper- and nickel oxides have been investigated. These carriers are prepared with inert material to increase the lifetime and performance of the particles. All particles but one have been produced by a freeze-granulation method. In order to optimize the performance of the particles, the sintering temperature of the particles was varied between 950 deg C and 1600 deg C. Normally particles of the size range of 125-180 squarem have been used for the reactivity investigations. Screening tests were performed in a laboratory fluidized-bed reactor of quartz placed in a furnace. The particles were exposed to an environment simulating a real chemical looping combustor, by alternating between reducing (50% CH{sub 4} - 50 % H{sub 2}O) and oxidizing conditions (5% O{sub 2} in N{sub 2}). The temperature was varied in the range 600 - 950 deg C with most experiments conducted at 950 deg C. In addition the particles were characterized with respect to strength, physical appearance and chemical structure before and after the experiments. Some suitable oxygen

  10. Manganese nodules

    Science.gov (United States)

    Hein, James R.; Harff, Jan; Petersen, Sven; Thiede, Jorn

    2016-01-01

    The existence of manganese (Mn) nodules (Figure 1) has been known since the late 1800s when they were collected during the Challenger expedition of 1873–1876. However, it was not until after WWII that nodules were further studied in detail for their ability to adsorb metals from seawater. Many of the early studies did not distinguish Mn nodules from Mn crusts. Economic interest in Mn nodules began in the late 1950s and early 1960s when John Mero finished his Ph.D. thesis on this subject, which was published in the journal Economic Geology (Mero, 1962) and later as a book (Mero, 1965). By the mid-1970s, large consortia had formed to search for and mine Mn nodules that occur between the Clarion and Clipperton fracture zones (CCZ) in the NE Pacific (Figure 2). This is still the area considered of greatest economic potential in the global ocean because of high nickel (Ni), copper (Cu), and Mn contents and the dense distribution of nodules in the area. While the mining of nodules was fully expected to begin in the late 1970s or early 1980s, this never occurred due to a downturn in the price of metals on the global market. Since then, many research cruises have been undertaken to study the CCZ nodules, and now 15 contracts for exploration sites have been given or are pending by the International Seabed Authority (ISA). Many books and science journal articles have been published summarizing the early work (e.g., Baturin, 1988; Halbach et al., 1988), and research has continued to the present day (e.g., ISA, 1999; ISA, 2010). Although the initial attraction for nodules was their high Ni, Cu, and Mn contents, subsequent work has shown that nodules host large quantities of other critical metals needed for high-tech, green-tech, and energy applications (Hein et al., 2013; Hein and Koschinsky, 2014).

  11. Manganese oxide nanoflakes/multi-walled carbon nanotubes/chitosan nanocomposite modified glassy carbon electrode as a novel electrochemical sensor for chromium (III) detection

    International Nuclear Information System (INIS)

    Salimi, Abdollah; Pourbahram, Bahareh; Mansouri-Majd, Samira; Hallaj, Rahman

    2015-01-01

    Highlights: • CNTs/chitosan/GC electrode used as platform for electrodeposition of MnO x -nanoflakes. • Modified electrode has excellent catalytic activity for oxidation of Cr 3+ at pH 3–7. • Detection limit and sensitivity of sensor for Cr 3+ detection were 0.3 μM and 18.7 nA/μM. • Sensor has good stability and high selectivity in the presence of common interferences. • Sensor applied for the detection of Cr 3+ in real samples with satisfactory results. - Abstract: In this research a nanocomposite containing chitosan (Chit) and maltiwalled carbon nanotubes (MWCNTs) was applied as platform for immobilization of electrodeposited manganese oxide (MnOx) nanostructures. First, glassy carbon (GC) electrode modified with thin film of Chitosan/MWCNTs nanocomposite. Then MnO x nanostructures was electrodeposited onto Chitosan/MWCNTs modified GC electrode using combination of constant potential step (0.6 V) and cyclic voltammetry(0.3–0.6 V) techniques. The XRD patterns and scanning electron microscope images indicated immobilization of uniformly MnOx nanoflakes with high crystallite onto MWCNTs/Chit film. The modified electrode shows a well-defined redox couple for Mn 2+ /MnO 2 system. Charge transfer coefficient (α), electron transfer rate constant (k s ) and surface concentration (Γ) were 0.394, 3.44 s −1 and 3.3 × 10 −11 mol cm −2 , respectively. The modified electrode showed excellent electrocatalytic activity toward oxidation of chromium (III) at natural pH solutions. Cyclic voltammetry and hydrodynamic amperometery were applied as measuring techniques for chromium detection. Detection limit, sensitivity and linear concentration range of the sensor were, 0.3 (μM), 18.7 nAμ M −1 and 3 μM to 200 μM, respectively. Moreover, the sensor retained about 90% of its original response toward Cr(III) after storage three months in ambient condition. Furthermore, the sensor response toward different common interferences was negligible. Finally, the

  12. Novel Non-Stoichiometric Manganese – Cobalt – Nickel – Oxide Composite as Humidity Sensor Through Solid-State Electrical Conductivity Measurements

    Directory of Open Access Journals (Sweden)

    R. Sundaram

    2006-08-01

    Full Text Available Equimolar amounts of manganese(II chloride, cobalt(III nitrate and nickel(II chloride in aqueous solution were reacted with ammonia and the resulting precipitate of hydroxides was heated to 7500 C in 6h to yield a non stoichiometric oxides having a composition of Mn0.06Co0.6Ni0.6O2.5 as analyzed by atomic absorption spectroscopy to a pellet and sintered at 6000 C. Characterization of the material has been made with AAS, Far-IR, TG-DTA, XRD, SEM, VSM and electrical conductance measurement. The far-IR spectra indicated the presence of metal-oxygen bonds and the discrete nature of the oxide was established from power X-ray diffraction pattern recorded at room temperature. The thermogravimetric data indicated the successive loss and gain of fraction of oxygen atoms, a specific feature of non-stoichiometric metal oxides. It was subjected to solid-state DC electrical conductivity measurements at room temperature. The current increases linearly with applied field and exponentially with increase in temperature showing conformance to ohmic law and semiconducting nature. The scanning electron microscopy (SEM studies were carried out to study the surface and pores structure of the sensor materials. The Brunauer-Emmett-Teller (BET surface adsorption studies showed that the radiuses of the pore sizes were found to be distributed from 10-45A with the pore specific volume being 0.01 cm3 g-1. As the composites having micropores are preferred for humidity sensing properties, the material was subjected to water vapour of different humidity achieved by various water buffers at room temperature and the electrical conductivity was measured as a function of relative humidity (RH. The electrical resistivity drastically decreases with increase in humidity, proving the material to be a good water vapour sensor. The sensitivity factor (Sf was 55000 in the range 5–98% RH, meaning the resistivity falls by a factor of 5.5 x 104 when the atmospheric RH increases from 5

  13. Chronic manganese intoxication

    Energy Technology Data Exchange (ETDEWEB)

    Huang, C.C.; Chu, N.S.; Lu, C.S.; Wang, J.D.; Tsai, J.L.; Tzeng, J.L.; Wolters, E.C.; Calne, D.B. (Chang Gung Medical College Hospital, Taipei, Taiwan (China))

    1989-10-01

    We report six cases of chronic manganese intoxication in workers at a ferromanganese factory in Taiwan. Diagnosis was confirmed by assessing increased manganese concentrations in the blood, scalp, and pubic hair. In addition, increased manganese levels in the environmental air were established. The patients showed a bradykinetic-rigid syndrome indistinguishable from Parkinson's disease that responded to treatment with levodopa.

  14. Biological removal of iron and manganese in rapid sand filters - Process understanding of iron and manganese removal

    DEFF Research Database (Denmark)

    Lin, Katie

    -filter, where iron is removed. Step 2: Filtration in an after-filter where e.g. ammonium and manganese is removed. The treatment relies on microbial processes and may present an alternative, greener and more sustainable approach for drinking water production spending less chemicals and energy than chemical (e...... of manganese by simple aeration and precipitation under normal drinking water treatment conditions insignificant. Manganese may also be oxidized autocatalytically. Iron is usually easier to remove. First, iron is rapidly chemically oxidized by oxygen at neutral pH followed by precipitation and filtration...... manganese removal. Iron had a negative effect on manganese removal and even caused an increase in manganese concentration (release). Experiments with filter material from another water works, Astrup, specially designed to remove iron biologically, showed that the biological iron removal increased...

  15. Geothermal Thermoelectric Generation (G-TEG) with Integrated Temperature Driven Membrane Distillation and Novel Manganese Oxide for Lithium Extraction

    Energy Technology Data Exchange (ETDEWEB)

    Renew, Jay [Southern Research Inst., Birmingham, AL (United States); Hansen, Tim [Southern Research Inst., Birmingham, AL (United States)

    2017-06-01

    Southern Research Institute (Southern) teamed with partners Novus Energy Technologies (Novus), Carus Corporation (Carus), and Applied Membrane Technology, Inc. (AMT) to develop an innovative Geothermal ThermoElectric Generation (G-TEG) system specially designed to both generate electricity and extract high-value lithium (Li) from low-temperature geothermal brines. The process combined five modular technologies including – silica removal, nanofiltration (NF), membrane distillation (MD), Mn-oxide sorbent for Li recovery, and TEG. This project provides a proof of concept for each of these technologies. The first step in the process is silica precipitation through metal addition and pH adjustment to prevent downstream scaling in membrane processes. Next, the geothermal brine is concentrated with the first of a two stage MD system. The first stage MD system is made of a high-temperature material to withstand geothermal brine temperatures up to 150C.° The first stage MD is integrated with a G-TEG module for simultaneous energy generation. The release of energy from the MD permeate drives heat transfer across the TE module, producing electricity. The first stage MD concentrate is then treated utilizing an NF system to remove Ca2+ and Mg2+. The NF concentrate will be disposed in the well by reinjection. The NF permeate undergoes concentration in a second stage of MD (polymeric material) to further concentrate Li in the NF permeate and enhance the efficiency of the downstream Li recovery process utilizing a Mn-oxide sorbent. Permeate from both the stages of the MD can be beneficially utilized as the permeates will contain less contaminants than the feed water. The concentrated geothermal brines are then contacted with the Mn-oxide sorbent. After Li from the geothermal brine is adsorbed on the sorbent, HCl is then utilized to regenerate the sorbent and recover the Li. The research and development project showed that the Si removal goal (>80%) could

  16. Insights into the Effects of Zinc Doping on Structural Phase Transition of P2-Type Sodium Nickel Manganese Oxide Cathodes for High-Energy Sodium Ion Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xuehang; Xu, Gui-Liang; Zhong, Guiming; Gong, Zhengliang; McDonald, Matthew J.; Zheng, Shiyao; Fu, Riqiang; Chen, Zonghai; Amine, Khalil; Yang, Yong

    2016-08-31

    P2-type sodium nickel manganese oxide-based cathode materials with higher energy densities are prime candidates for applications in rechargeable sodium ion batteries. A systematic study combining in situ high energy X-ray diffraction (HEXRD), ex situ Xray absorption fine spectroscopy (XAFS), transmission electron microscopy (TEM), and solid-state nuclear magnetic resonance (SSNMR) techniques was carried out to gain a deep insight into the structural evolution of P2-Na0.66Ni0.33-xZnxMn0.67O2 (x = 0, 0.07) during cycling. In situ HEXRD and ex situ TEM measurements indicate that an irreversible phase transition occurs upon sodium insertion-extraction of Na0.66Ni0.33Mn0.67O2. Zinc doping of this system results in a high structural reversibility. XAFS measurements indicate that both materials are almost completely dependent on the Ni4+/Ni3+/ Ni2+ redox couple to provide charge/discharge capacity. SS-NMR measurements indicate that both reversible and irreversible migration of transition metal ions into the sodium layer occurs in the material at the fully charged state. The irreversible migration of transition metal ions triggers a structural distortion, leading to the observed capacity and voltage fading. Our results allow a new understanding of the importance of improving the stability of transition metal layers.

  17. Photogeochemical reactions of manganese under anoxic conditions

    Science.gov (United States)

    Liu, W.; Yee, N.; Piotrowiak, P.; Falkowski, P. G.

    2017-12-01

    Photogeochemistry describes reactions involving light and naturally occurring chemical species. These reactions often involve a photo-induced electron transfer that does not occur in the absence of light. Although photogeochemical reactions have been known for decades, they are often ignored in geochemical models. In particular, reactions caused by UV radiation during an ozone free early Earth could have influenced the available oxidation states of manganese. Manganese is one of the most abundant transition metals in the crust and is important in both biology and geology. For example, the presence of manganese (VI) oxides in the geologic record has been used as a proxy for oxygenic photosynthesis; however, we suggest that the high oxidation state of Mn can be produced abiotically by photochemical reactions. Aqueous solutions of manganese (II) as well as suspensions of rhodochrosite (MnCO3) were irradiated under anoxic condition using a 450 W mercury lamp and custom built quartz reaction vessels. The photoreaction of the homogeneous solution of Mn(II) produced H2 gas and akhtenskite (ɛ-MnO2) as the solid product . This product is different than the previously identified birnessite. The irradiation of rhodochrosite suspensions also produced H2 gas and resulted in both a spectral shift as well as morphology changes of the mineral particles in the SEM images. These reactions offer alternative, abiotic pathways for the formation of manganese oxides.

  18. Application of Multivariate Analysis in Understanding Anions in Soils Close to an Abandoned Manganese Oxide Ore Mine

    Science.gov (United States)

    Ekosse, Georges-Ivo E.

    Multivariate Analysis (MVA) was used in elucidating on the relationships and environmental implications of anions (particularly chloride, sulphate and carbonate which generally affect bioavailability of soil nutrients) in soils within the proximity of an abandoned Mn oxide ore mine in Southeastern Botswana. Four hundred soil samples were obtained from a 4 km2 area close to the abandoned mine and analysed for their anionic contents and pH. The Statistical Package for Social Sciences (SPSS) software was used for data processing. Anion concentrations in the soil samples were: chloride = 0.2 to 11.9 mg kg-1, with a mean of 7.63 mg kg-1, sulphate = 2.1 to 47.5 mg kg-1, with a mean of 19.36 mg kg-1 and carbonate = 5.1 g kg-1 to 59.1 g kg-1, with a mean of 40.98 g kg-1. Correlation coefficients depicted strong positive associations. Two clusters were produced: cluster one had the three anions with SO42¯ being the most important; and cluster two equally had all three anions but with negative t-statistic values. The anions have been continuously displaced as result of their very high mobility as reflected in lower concentrations than those from the control site.

  19. Electrochemical catalysis of styrene epoxidation with films of manganese dioxide nanoparticles, and, Synthesis of mixed metal oxides using ultrasonic nozzle spray and microwaves

    Science.gov (United States)

    Espinal, Laura

    Films of polyions and octahedral layered manganese oxide (OL-1) nanoparticles on carbon electrodes made by layer-by-layer alternate electrostatic adsorption were active for electrochemical catalysis of styrene epoxidation in solution in the presence of hydrogen peroxide and oxygen. The highest catalytic turnover was obtained by using applied voltage -0.6 V vs. SCE, O2, and 100 mM H2O2. 18O isotope labeling experiments suggested oxygen incorporation from three different sources: molecular oxygen, hydrogen peroxide and/or lattice oxygen from OL-1 depending on the potential applied and the oxygen and hydrogen peroxide concentrations. Oxygen and hydrogen peroxide activate the OL-1 catalyst for the epoxidation. The pathway for styrene epoxidation in the highest yields required oxygen, hydrogen peroxide and a reducing voltage, and may involve an activated oxygen species in the OL-1 matrix. Multicomponent metal oxide (MMO) crystallites were prepared by spraying a reactant solution into a receiving solution or air under microwave radiation at atmospheric pressure. The injection of nitric acid solution through an ultrasonic nozzle into a receiving solution of metal precursor and the use of microwave radiation were combined to form a novel preparation technique called the nozzle-spray/microwave (NMW) method. The inclusion of an additional step, the in situ mixing of precursor solutions prior to their injection through the ultrasonic nozzle spray, led to another procedure called the in situ/nozzle-spray/microwave (INM) method. For comparison, MMO materials with the same metal constituents as those prepared by our novel techniques were prepared by conventional hydrothermal (CH) methods. Fresh materials prepared by NMW, INM and CH methods were heat treated to study the effect of calcination. All materials were characterized before and after calcination using XRD, SEM, Bet, and ICP. The NMW method produces particles with rod-like morphologies different from those obtained using

  20. Nanoscale Cobalt-Manganese Oxide Catalyst Supported on Shape-Controlled Cerium Oxide: Effect of Nanointerface Configuration on Structural, Redox, and Catalytic Properties.

    Science.gov (United States)

    Hillary, Brendan; Sudarsanam, Putla; Amin, Mohamad Hassan; Bhargava, Suresh K

    2017-02-28

    Understanding the role of nanointerface structures in supported bimetallic nanoparticles is vital for the rational design of novel high-performance catalysts. This study reports the synthesis, characterization, and the catalytic application of Co-Mn oxide nanoparticles supported on CeO 2 nanocubes with the specific aim of investigating the effect of nanointerfaces in tuning structure-activity properties. High-resolution transmission electron microscopy analysis reveals the formation of different types of Co-Mn nanoalloys with a range of 6 ± 0.5 to 14 ± 0.5 nm on the surface of CeO 2 nanocubes, which are in the range of 15 ± 1.5 to 25 ± 1.5 nm. High concentration of Ce 3+ species are found in Co-Mn/CeO 2 (23.34%) compared with that in Mn/CeO 2 (21.41%), Co/CeO 2 (15.63%), and CeO 2 (11.06%), as evidenced by X-ray photoelectron spectroscopy (XPS) analysis. Nanoscale electron energy loss spectroscopy analysis in combination with XPS studies shows the transformation of Co 2+ to Co 3+ and simultaneously Mn 4+/3+ to Mn 2+ . The Co-Mn/CeO 2 catalyst exhibits the best performance in solvent-free oxidation of benzylamine (89.7% benzylamine conversion) compared with the Co/CeO 2 (29.2% benzylamine conversion) and Mn/CeO 2 (82.6% benzylamine conversion) catalysts for 3 h at 120 °C using air as the oxidant. Irrespective of the catalysts employed, a high selectivity toward the dibenzylimine product (97-98%) was found compared with the benzonitrile product (2-3%). The interplay of redox chemistry of Mn and Co at the nanointerface sites between Co-Mn nanoparticles and CeO 2 nanocubes as well as the abundant structural defects in cerium oxide plays a key role in the efficiency of the Co-Mn/CeO 2 catalyst for the aerobic oxidation of benzylamine.

  1. On the photocatalytic cycle of water splitting with small manganese oxides and the roles of water clusters as direct sources of oxygen molecules.

    Science.gov (United States)

    Yamamoto, Kentaro; Takatsuka, Kazuo

    2018-02-28

    We theoretically studied the chemical principles behind the photodynamics of water splitting: 2H 2 O + 4hν + M → 4H + + 4e - + O 2 + M. To comprehend this simple looking but very complicated reaction, the mechanisms of at least three crucial phenomena, among others, need to be clarified, each of which is supposed to constitute the foundation of chemistry: (i) charge separation (4H + + 4e - ), (ii) the catalytic cycle for essentially the same reactions to be repeated by each of four photon absorptions with a catalyst M, and (iii) the generation of oxygen molecules of spin triplet. We have previously clarified the photodynamical mechanism of charge separation, which we refer to as coupled proton electron-wavepacket transfer (CPEWT), based on the theory of nonadiabatic electron wavepacket dynamics [K. Yamamoto and K. Takatsuka, ChemPhysChem, 2017, 18, 537]. CPEWT gives an idea of how charge separation can be materialized at each single photon absorption. Yet, this mechanism alone cannot address the above crucial items such as (ii) the catalytic cycle and (iii) O 2 formation. In the studies of these fundamental processes, we constructed a possible minimal chemical system and perform semi-quantitative quantum chemical analyses, with which to attain insights about the possible mechanisms of photochemical water splitting. The present study has been inspired by the idea underlying the so-called Kok cycle, although we do not aim to simulate photosystem II in biological systems in nature. For instance, we assume here that a catalyst M (actually simple manganese oxides in this particular study) is pumped up to its excited states leading to charge separation by four-time photon absorption, each excitation of which triggers individual series of chemical reactions including the reorganization of the hydrogen-bonding network (cluster) of water molecules surrounding the photocatalytic center. It is shown that in the successive processes of restructuring of the relevant water

  2. Restoration of growth by manganese in a mutant strain of Escherichia coli lacking most known iron and manganese uptake systems

    DEFF Research Database (Denmark)

    Taudte, Nadine; German, Nadezhda; Zhu, Yong-Guan

    2016-01-01

    The interplay of manganese and iron homeostasis and oxidative stress in Escherichia coli can give important insights into survival of bacteria in the phagosome and under differing iron or manganese bioavailabilities. Here, we characterized a mutant strain devoid of all know iron....../manganese-uptake systems relevant for growth in defined medium. Based on these results an exit strategy enabling the cell to cope with iron depletion and use of manganese as an alternative for iron could be shown. Such a strategy would also explain why E. coli harbors some iron- or manganese-dependent iso......-enzymes such as superoxide dismutases or ribonucleotide reductases. The benefits for gaining a means for survival would be bought with the cost of less efficient metabolism as indicated in our experiments by lower cell densities with manganese than with iron. In addition, this strain was extremely sensitive to the metalloid...

  3. Synthesis, Characterization, and Reactivities of Manganese(V)-Oxo Porphyrin Complexes

    OpenAIRE

    Song, Woon Ju; Seo, Mi Sook; George, Serena DeBeer; Ohta, Takehiro; Song, Rita; Kang, Min-Jung; Tosha, Takehiko; Kitagawa, Teizo; Solomon, Edward I.; Nam, Wonwoo

    2007-01-01

    The reactions of manganese(III) porphyrin complexes with terminal oxidants, such as m-chloroperbenzoic acid, iodosylarenes, and H2O2, produced high-valent manganese(V)-oxo porphyrins in the presence of base in organic solvents at room temperature. The manganese(V)-oxo porphyrins have been characterized with various spectroscopic techniques, including UV-vis, EPR, 1H and 19F NMR, resonance Raman, and X-ray absorption spectroscopy. The combined spectroscopic results indicate that the manganese(...

  4. Orbital Configuration of the Valence Electrons, Ligand Field Symmetry, and Manganese Oxidation States of the Photosynthetic Water Oxidizing Complex: Analysis of the S(2) State Multiline EPR Signals.

    Science.gov (United States)

    Zheng, Ming; Dismukes, G. Charles

    1996-05-22

    A theoretical framework is presented for analysis of all three "multiline" EPR spectra (MLS) arising from the tetramanganese (Mn(4)) cluster in the S(2) oxidation state of the photosynthetic water oxidizing complex (WOC). Accurate simulations are presented which include anisotropy of the g and (four) (55)Mn hyperfine tensors, chosen according to a database of (55)Mn(III) and (55)Mn(IV) hyperfine tensors obtained previously using unbiased least-squares spectral fitting routines. In view of the large (30%) anisotropy common to Mn(III) hyperfine tensors in all complexes, previous MLS simulations which have assumed isotropic hyperfine constants have required physically unrealistic parameters. A simple model is found which offers good simulations of both the native "19-21-line" MLS and the "26-line" NH(3)-bound form of the MLS. Both a dimer-of-dimers and distorted-trigonal magnetic models are examined to describe the symmetry of the Heisenberg exchange interactions within the Mn(4) cluster and thus define the initial electronic basis states of the cluster. The effect of rhombic symmetry distortions is explicitly considered. Both magnetic models correspond to one of several possible structural models for the Mn(4) cluster proposed independently from Mn EXAFS studies. Simulated MLS were constructed for each of the eight (or seven) doublet states of the Mn(4) cluster in the WOC for the two viable oxidation models (3Mn(III)-1Mn(IV) or 3Mn(IV)-1Mn(III)), and using a wide range of axial Mn hyperfine tensors, with either coaxial or orthogonal tensor alignments. We find accurate simulations using the 3Mn(III)-1Mn(IV) oxidation model. In the dimer-of-dimers coupling model, the spin state conversion between two doublet states |S(12),S(34),S(T)|(7)/(2),4,(1)/(2)> and |(7)/(2),3,(1)/(2)> is found to explain the large (25%) contraction in the hyperfine splitting observed upon conversion from the native MLS to the NH(3)-bound MLS. Stabilization of this excited state as the new ground

  5. Aging of biogenic secondary organic aerosol via gas-phase OH radical reactions

    DEFF Research Database (Denmark)

    Donahue, Neil M.; Henry, Kaytlin M.; Mentel, Thomas F.

    2012-01-01

    The Multiple Chamber Aerosol Chemical Aging Study (MUCHACHAS) tested the hypothesis that hydroxyl radical (OH) aging significantly increases the concentration of first-generation biogenic secondary organic aerosol (SOA). OH is the dominant atmospheric oxidant, and MUCHACHAS employed environmental...

  6. Hydropower's Biogenic Carbon Footprint.

    Science.gov (United States)

    Scherer, Laura; Pfister, Stephan

    2016-01-01

    Global warming is accelerating and the world urgently needs a shift to clean and renewable energy. Hydropower is currently the largest renewable source of electricity, but its contribution to climate change mitigation is not yet fully understood. Hydroelectric reservoirs are a source of biogenic greenhouse gases and in individual cases can reach the same emission rates as thermal power plants. Little is known about the severity of their emissions at the global scale. Here we show that the carbon footprint of hydropower is far higher than previously assumed, with a global average of 173 kg CO2 and 2.95 kg CH4 emitted per MWh of electricity produced. This results in a combined average carbon footprint of 273 kg CO2e/MWh when using the global warming potential over a time horizon of 100 years (GWP100). Nonetheless, this is still below that of fossil energy sources without the use of carbon capture and sequestration technologies. We identified the dams most promising for capturing methane for use as alternative energy source. The spread among the ~1500 hydropower plants analysed in this study is large and highlights the importance of case-by-case examinations.

  7. Hydropower's Biogenic Carbon Footprint.

    Directory of Open Access Journals (Sweden)

    Laura Scherer

    Full Text Available Global warming is accelerating and the world urgently needs a shift to clean and renewable energy. Hydropower is currently the largest renewable source of electricity, but its contribution to climate change mitigation is not yet fully understood. Hydroelectric reservoirs are a source of biogenic greenhouse gases and in individual cases can reach the same emission rates as thermal power plants. Little is known about the severity of their emissions at the global scale. Here we show that the carbon footprint of hydropower is far higher than previously assumed, with a global average of 173 kg CO2 and 2.95 kg CH4 emitted per MWh of electricity produced. This results in a combined average carbon footprint of 273 kg CO2e/MWh when using the global warming potential over a time horizon of 100 years (GWP100. Nonetheless, this is still below that of fossil energy sources without the use of carbon capture and sequestration technologies. We identified the dams most promising for capturing methane for use as alternative energy source. The spread among the ~1500 hydropower plants analysed in this study is large and highlights the importance of case-by-case examinations.

  8. Nanostructured manganese oxides in supercapacitors

    CSIR Research Space (South Africa)

    Makgopa, K

    2016-07-01

    Full Text Available The development of energy storage systems (ESSs) comes as a crucial factor when it comes to addressing the problem of energy in the world due to the rapid development of the global economy, the depletion of fossil fuels and the increase...

  9. Sensitivity of modeled ozone concentrations to uncertainties in biogenic emissions

    International Nuclear Information System (INIS)

    Roselle, S.J.

    1992-06-01

    The study examines the sensitivity of regional ozone (O3) modeling to uncertainties in biogenic emissions estimates. The United States Environmental Protection Agency's (EPA) Regional Oxidant Model (ROM) was used to simulate the photochemistry of the northeastern United States for the period July 2-17, 1988. An operational model evaluation showed that ROM had a tendency to underpredict O3 when observed concentrations were above 70-80 ppb and to overpredict O3 when observed values were below this level. On average, the model underpredicted daily maximum O3 by 14 ppb. Spatial patterns of O3, however, were reproduced favorably by the model. Several simulations were performed to analyze the effects of uncertainties in biogenic emissions on predicted O3 and to study the effectiveness of two strategies of controlling anthropogenic emissions for reducing high O3 concentrations. Biogenic hydrocarbon emissions were adjusted by a factor of 3 to account for the existing range of uncertainty in these emissions. The impact of biogenic emission uncertainties on O3 predictions depended upon the availability of NOx. In some extremely NOx-limited areas, increasing the amount of biogenic emissions decreased O3 concentrations. Two control strategies were compared in the simulations: (1) reduced anthropogenic hydrocarbon emissions, and (2) reduced anthropogenic hydrocarbon and NOx emissions. The simulations showed that hydrocarbon emission controls were more beneficial to the New York City area, but that combined NOx and hydrocarbon controls were more beneficial to other areas of the Northeast. Hydrocarbon controls were more effective as biogenic hydrocarbon emissions were reduced, whereas combined NOx and hydrocarbon controls were more effective as biogenic hydrocarbon emissions were increased

  10. Characteristics of manganese-coated sand using SEM and EDAX analysis.

    Science.gov (United States)

    Hu, Po-Yu; Hsieh, Yung-Hsu; Chen, Jen-Ching; Chang, Chen-Yu

    2004-04-15

    "Manganese-coated sand" is a type of silica medium coated with manganese oxides, formed from the sorption of manganese oxides during long-term filtration via the process of rapid sand filtration, followed by aeration in a water treatment plant. Locally available manganese-coated sand, both for packing and as a byproduct of filtration processes for water treatment plants in Taiwan, was found to be a low-cost and promising adsorbent for removal of Mn(2+) from raw water. This study was conducted to build the basic data for coating hydrated manganese oxide on the sand surface to utilize the adsorbent properties of the coating and the filtration properties of the sand. In this study, gas adsorption porosimetry and scanning electron microscopy analyses were used to investigate the surface properties of the coated layer. An energy dispersive X-ray (EDAX) technique of analysis was used to characterize metal adsorption sites on a manganese-coated sand surface. Results indicated that manganese-coated sand had more micropores and higher specific surface area, owing to attachment of manganese sand. Manganese ions penetrated into the micropores and mesopores of manganese oxide on a sandy surface; regeneration of manganese-coated sand could be achieved by soaking with pH packed bed for treatment of heavy metals from water. The results of this study can also benefit plant operational capacity data for engineering design.

  11. From urban municipalities to polar bioremediation: the characterisation and contribution of biogenic minerals for water treatment.

    Science.gov (United States)

    Freidman, Benjamin L; Northcott, Kathy A; Thiel, Peta; Gras, Sally L; Snape, Ian; Stevens, Geoff W; Mumford, Kathryn A

    2017-06-01

    Minerals of biological origin have shown significant potential for the separation of contaminants from water worldwide. This study details the contribution of biologically derived minerals to water treatment operations, with a focus on filtration media from urban municipalities and remote cold regions. The results support biofilm-embedded iron and manganese to be the building blocks of biogenic mineral development on activated carbon and nutrient-amended zeolites. The presence of similar iron and manganese oxidising bacterial species across all filter media supports the analogous morphologies of biogenic minerals between sites and suggests that biological water treatment processes may be feasible across a range of climates. This is the first time the stages of biogenic mineral formation have been aligned with comprehensive imaging of the biofilm community and bacterial identification; especially with respect to cold regions. Where biogenic mineral formation occurs on filter media, the potential exists for enhanced adsorption for a range of organic and inorganic contaminants and improved longevity of filter media beyond the adsorption or exchange capacities of the raw material.

  12. Manganese phosphate-coating

    International Nuclear Information System (INIS)

    Peyre, Y.

    1999-01-01

    Manganese phosphate-coating is one of the numerous chemical surface treatment which is used industrially. Its applications are usual for improving the friction properties of a lot of mechanical parts. Used for the treatment of steels and cast steels, baths (containing phosphoric acid, manganese phosphate and different additives) lead to the formation of nonmetal coatings of a few micrometers. These manganese-iron or manganese phosphates crystals reduce the friction coefficient and retain the lubricant film in contact with the moving parts. The running noises, the wear and the seizure risks are then strongly reduced. Pure manganese phosphate-coating is currently developing because the obtained coatings are thinner and more regular. (O.M.)

  13. Oxidative mobilization of cerium and uranium and enhanced release of "immobile" high field strength elements from igneous rocks in the presence of the biogenic siderophore desferrioxamine B

    Science.gov (United States)

    Kraemer, Dennis; Kopf, Sebastian; Bau, Michael

    2015-09-01

    Polyvalent trace elements such as the high field strength elements (HFSE) are commonly considered rather immobile during low-temperature water-rock interaction. Hence, they have become diagnostic tools that are widely applied in geochemical studies. We present results of batch leaching experiments focused on the mobilization of certain HFSE (Y, Zr, Hf, Th, U and rare earth elements) from mafic, intermediate and felsic igneous rocks in the presence and absence, respectively, of the siderophore desferrioxamine B (DFOB). Our data show that DFOB strongly enhances the mobility of these trace elements during low-temperature water-rock interaction. The presence of DFOB produces two distinct features in the Rare Earths and Yttrium (REY) patterns of leaching solutions, regardless of the mineralogical and chemical composition or the texture of the rock type studied. Bulk rock-normalized REY patterns of leaching solutions with DFOB show (i) a very distinct positive Ce anomaly and (ii) depletion of La and other light REY relative to the middle REY, with a concave downward pattern between La and Sm. These features are not observed in experiments with hydrochloric acid, acetic acid or deionized water. In DFOB-bearing leaching solutions Ce and U are decoupled from and selectively enriched relative to light REY and Th, respectively, due to oxidation to Ce(IV) and U(VI). Oxidation of Ce3+ and U4+ is promoted by the significantly higher stability of the Ce(IV) and U(VI) DFOB complexes as compared to the Ce(III) and U(IV) DFOB complexes. This is similar to the relationship between the Ce(IV)- and Ce(III)-pentacarbonate complexes that cause positive Ce anomalies in alkaline lakes. However, while formation of Ce(IV) carbonate complexes is confined to alkaline environments, Ce(IV) DFOB complexes may produce positive Ce anomalies even in mildly acidic and near-neutral natural waters. Siderophore-promoted dissolution processes also significantly enhance mobility of other 'immobile' HFSE

  14. Manganese phospate physical chemistry and surface properties

    International Nuclear Information System (INIS)

    Najera R, N.; Romero G, E. T.

    2008-01-01

    This paper presents the methodology for the manganese phosphate (III) synthesis (MnP0 4 H 2 0) from manganese chloride. The physicochemical characterization was carried out by: X-ray diffraction, scanning electron microscopy, infrared analysis and thermal gravimetric analysis. The surface characterization is obtained through the determination of surface area, point of zero charge and kinetics of moisture. As a phosphate compound of a metal with low oxidation state is a promising compound for removal pollutants from water and soil, can be used for the potential construction of containment barriers for radioactive wastes. (Author)

  15. Biogenic synthesis of copper oxide nanoparticles using olea europaea leaf extract and evaluation of their toxicity activities: An in vivo and in vitro study.

    Science.gov (United States)

    Sulaiman, Ghassan M; Tawfeeq, Amer T; Jaaffer, Marwa D

    2018-01-01

    Copper oxide nanoparticles (CUNPs) were synthesized using Olea europaea leaf extract as reducing and protecting agent. The formation of nanoparticles was observed through a color change from yellowish to brownish black. The CUNPs were confirmed with UV-Vis spectrophotometer, which revealed a peak absorbance at 289 nm. The synthesized CUNPs were characterized by XRD, FTIR, SEM, and TEM. The XRD pattern revealed that CUNPs were crystalline in nature with a diameter around 20 nm. FTIR spectral analysis showed that CUNPs were capped with plant constituents. From SEM and TEM analyses, the CUNPs were generally found to be spherical in shape, and the size range was 20-50 nm. Free radical scavenging potential of CUNPs against DPPH was confirmed by its stable antioxidant effects. In addition, the toxicity of CUNPs in mice was also assessed by body weight and weights of liver, kidneys, spleen, and thymus. The immune response in mice was signaled through an obvious change in spleen and thymus index, with a decrease of ADA enzyme activity in serum, spleen, and thymus after CUNPs treatment. The CUNPs were found to exert cell growth arrest against AMJ-13 and SKOV-3 cancer cells in a dose-dependent manner and induce cell death by apoptosis. Less significant cytotoxic effect was observed in normal dermal fibroblast cells. These findings suggest that CUNPs may have the potential to be anticancer agents. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:218-230, 2018. © 2017 American Institute of Chemical Engineers.

  16. BOREAS TGB-5 Biogenic Soil Emissions of NO and N2O

    Science.gov (United States)

    Levine, J. S.; Winstead, E. L.; Parsons, D. A. B.; Scholes, M. C.; Cofer, W. R.; Cahoon, D. R.; Sebacher, D. I.; Scholes, R. J.; Hall, Forrest G. (Editor); Conrad, Sara K. (Editor)

    2000-01-01

    The BOReal Ecosystem-Atmosphere Study Trace Gas Biogeochemistry (BOREAS TGB)-5 team made several measurements of trace gas concentrations and fluxes at various NSA sites. This data set contains biogenic soil emissions of nitric oxide and nitrous oxide that were measured over a wide range of spatial and temporal site parameters. Since very little is known about biogenic soil emissions of nitric oxide and nitrous oxide from the boreal forest, the goal of the measurements was to characterize the biogenic soil fluxes of nitric oxide and nitrous oxide from black spruce and jack pine areas in the boreal forest. The diurnal variation and monthly variation of the emissions was examined as well as the impact of wetting through natural or artificial means. Temporally, the data cover mid-August 1993, June to August 1994, and mid-July 1995. The data are provided in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884).

  17. Biogenic Iron-Rich Filaments in the Quartz Veins in the Uppermost Ediacaran Qigebulake Formation, Aksu Area, Northwestern Tarim Basin, China: Implications for Iron Oxidizers in Subseafloor Hydrothermal Systems.

    Science.gov (United States)

    Zhou, Xiqiang; Chen, Daizhao; Tang, Dongjie; Dong, Shaofeng; Guo, Chuan; Guo, Zenghui; Zhang, Yanqiu

    2015-07-01

    Fe-(oxyhydr)oxide-encrusted filamentous microstructures produced by microorganisms have been widely reported in various modern and ancient extreme environments; however, the iron-dependent microorganisms preserved in hydrothermal quartz veins have not been explored in detail because of limited materials available. In this study, abundant well-preserved filamentous microstructures were observed in the hydrothermal quartz veins of the uppermost dolostones of the terminal-Ediacaran Qigebulake Formation in the Aksu area, northwestern Tarim Basin, China. These filamentous microstructures were permineralized by goethite and hematite as revealed by Raman spectroscopy and completely entombed in chalcedony and quartz cements. Microscopically, they are characterized by biogenic filamentous morphologies (commonly 20-200 μm in length and 1-5 μm in diameter) and structures (curved, tubular sheath-like, segmented, and mat-like filaments), similar to the Fe-oxidizing bacteria (FeOB) living in modern and ancient hydrothermal vent fields. A previous study revealed that quartz-barite vein swarms were subseafloor channels of low-temperature, silica-rich, diffusive hydrothermal vents in the earliest Cambrian, which contributed silica to the deposition of the overlying bedded chert of the Yurtus Formation. In this context, this study suggests that the putative filamentous FeOB preserved in the quartz veins might have thrived in the low-temperature, silica- and Fe(II)-rich hydrothermal vent channels in subseafloor mixing zones and were rapidly fossilized by subsequent higher-temperature, silica-rich hydrothermal fluids in response to waning and waxing fluctuations of diffuse hydrothermal venting. In view of the occurrence in a relatively stable passive continental margin shelf environment in Tarim Block, the silica-rich submarine hydrothermal vent system may represent a new and important geological niche favorable for FeOB colonization, which is different from their traditional

  18. Estimation of biogenic volatile organic compounds emissions in subtropical island--Taiwan.

    Science.gov (United States)

    Chang, Ken-Hui; Chen, Tu-Fu; Huang, Ho-Chun

    2005-06-15

    Elevated tropospheric ozone is harmful to human health and plants. It is formed through the photochemical reactions involving volatile organic compounds (VOCs) and nitrogen oxides (NO(x)). The elevated ozone episodes occur mainly in summer months in the United States, while the high-ozone episodes frequently occur during the fall in Taiwan. The unique landscape of Taiwan produces tremendous amounts of biogenic VOCs in the mountain regions that are adjacent to concentrated urban areas. The urban areas, in turn, generate prodigious amounts of anthropogenic emissions. Biogenic VOC emissions have direct influence on tropospheric ozone formation. To explore the air quality problems in Taiwan, this study attempts to develop a biogenic VOC emission model suitable for air quality applications in Taiwan. The emission model is based on the Biogenic Emissions Inventory System Version 2 and coupled with a detailed Taiwan land use database. The 1999 total Taiwan biogenic VOC emissions were estimated at 214,000 metric tons. The emissions of isoprene, monoterpenes, and other VOCs were about 37.2%, 30.4%, and 32.4% of total biogenic VOC emissions, respectively. The annual total biogenic VOC emission per unit area was more than two times the value of that in any European country, implying that detailed emissions estimates in any size of region will benefit the global biogenic emission inventories.

  19. Biogenic emissions of isoprenoids and NO in China and comparison to anthropogenic emissions

    International Nuclear Information System (INIS)

    Tie Xuexi; Li Guohui; Ying, Zhuming; Guenther, Alex; Madronich, Sasha

    2006-01-01

    In this study, a regional dynamical model (WRF) is used to drive biogenic emission models to calculate high resolution (10 x 10 km) biogenic emissions of isoprene (C 5 H 8 ), monoterpenes (C 1 H 16 ), and nitric oxide (NO) in China. This high resolution biogenic inventory will be available for the community to study the effect of biogenic emissions on photochemical oxidants in China. The biogenic emissions are compared to anthropogenic emissions to gain insight on the potential impact of the biogenic emissions on tropospheric chemistry, especially ozone production in this region. The results show that the biogenic emissions in China exhibit strongly diurnal, seasonal, and spatial variations. The isoprenoid (including both isoprene and monoterpenes) emissions are closely correlated to tree density and strongly vary with season and local time. During winter (January), the biogenic isoprenoid emissions are the lowest, resulting from lower temperature and solar radiation, and highest in summer (July) due to higher temperature and solar radiation. The biogenic NO emissions are also higher during summer and lower during winter, but the magnitude of the seasonal variation is smaller than the emissions of isoprene and monoterpenes. The biogenic emissions of NO are widely spread out in the northern, eastern, and southern China regions, where high-density agricultural soil lands are located. Both biogenic NO and isoprenoid emissions are very small in western China. The calculated total biogenic emission budget is smaller than the total anthropogenic VOC emission budget in China. The biogenic isoprenoid and anthropogenic VOC emissions are 10.9 and 15.1 Tg year -1 , respectively. The total biogenic and anthropogenic emissions of NO are 5.9 and 11.5 Tg(NO) year -1 , respectively. The study shows that in central eastern China, the estimated biogenic emissions of isoprenoids are very small, and the anthropogenic emissions of VOCs are dominant in this region. However, in

  20. Biogenic emissions of isoprenoids and NO in China and comparison to anthropogenic emissions.

    Science.gov (United States)

    Tie, Xuexi; Li, Guohui; Ying, Zhuming; Guenther, Alex; Madronich, Sasha

    2006-12-01

    In this study, a regional dynamical model (WRF) is used to drive biogenic emission models to calculate high resolution (10x10 km) biogenic emissions of isoprene (C(5)H(8)), monoterpenes (C(10)H(16)), and nitric oxide (NO) in China. This high resolution biogenic inventory will be available for the community to study the effect of biogenic emissions on photochemical oxidants in China. The biogenic emissions are compared to anthropogenic emissions to gain insight on the potential impact of the biogenic emissions on tropospheric chemistry, especially ozone production in this region. The results show that the biogenic emissions in China exhibit strongly diurnal, seasonal, and spatial variations. The isoprenoid (including both isoprene and monoterpenes) emissions are closely correlated to tree density and strongly vary with season and local time. During winter (January), the biogenic isoprenoid emissions are the lowest, resulting from lower temperature and solar radiation, and highest in summer (July) due to higher temperature and solar radiation. The biogenic NO emissions are also higher during summer and lower during winter, but the magnitude of the seasonal variation is smaller than the emissions of isoprene and monoterpenes. The biogenic emissions of NO are widely spread out in the northern, eastern, and southern China regions, where high-density agricultural soil lands are located. Both biogenic NO and isoprenoid emissions are very small in western China. The calculated total biogenic emission budget is smaller than the total anthropogenic VOC emission budget in China. The biogenic isoprenoid and anthropogenic VOC emissions are 10.9 and 15.1 Tg year(-1), respectively. The total biogenic and anthropogenic emissions of NO are 5.9 and 11.5 Tg(NO) year(-1), respectively. The study shows that in central eastern China, the estimated biogenic emissions of isoprenoids are very small, and the anthropogenic emissions of VOCs are dominant in this region. However, in

  1. USER'S GUIDE TO THE PERSONAL COMPUTER VERSION OF THE BIOGENIC EMISSIONS INVENTORY SYSTEM (PC-BEIS2)

    Science.gov (United States)

    The document is a user's guide for an updated Personal Computer version of the Biogenic Emissions Inventory System (PC-BEIS2), allowing users to estimate hourly emissions of biogenic volatile organic compounds (BVOCs) and soil nitrogen oxide emissions for any county in the contig...

  2. Non-enzymatic U(VI) interactions with biogenic mackinawite

    Science.gov (United States)

    Veeramani, H.; Qafoku, N. P.; Kukkadapu, R. K.; Murayama, M.; Hochella, M. F.

    2011-12-01

    Reductive immobilization of hexavalent uranium [U(VI)] by stimulation of dissimilatory metal and/or sulfate reducing bacteria (DMRB or DSRB) has been extensively researched as a remediation strategy for subsurface U(VI) contamination. These bacteria derive energy by reducing oxidized metals as terminal electron acceptors, often utilizing organic substrates as electron donors. Thus, when evaluating the potential for in-situ uranium remediation in heterogeneous subsurface media, it is important to understand how the presence of alternative electron acceptors such as Fe(III) and sulfate affect U(VI) remediation and the long term behavior and reactivity of reduced uranium. Iron, an abundant subsurface element, represents a substantial sink for electrons from DMRB, and the reduction of Fe(III) leads to the formation of dissolved Fe(II) or to reactive biogenic Fe(II)- and mixed Fe(II)/Fe(III)- mineral phases. Consequently, abiotic U(VI) reduction by reactive forms of biogenic Fe(II) minerals could be a potentially important process for uranium immobilization. In our study, the DMRB Shewanella putrefaciens CN32 was used to synthesize a biogenic Fe(II)-bearing sulfide mineral: mackinawite, that has been characterized by XRD, SEM, HRTEM and Mössbauer spectroscopy. Batch experiments involving treated biogenic mackinawite and uranium (50:1 molar ratio) were carried out at room temperature under strict anoxic conditions. Following complete removal of uranium from solution, the biogenic mackinawite was analyzed by a suite of analytical techniques including XAS, HRTEM and Mössbauer spectroscopy to determine the speciation of uranium and investigate concomitant Fe(II)-phase transformation. Determining the speciation of uranium is critical to success of a remediation strategy. The present work elucidates non-enzymatic/abiotic molecular scale redox interactions between biogenic mackinawite and uranium.

  3. Manganese concentrate usage in steelmaking

    Science.gov (United States)

    Nokhrina, O. I.; Rozhihina, I. D.

    2015-09-01

    The results of the research process of producing metalized products by solid-phase reduction of iron using solid carbonaceous reducing agents. Thermodynamic modeling was carried out on the model of the unit the Fe-C-O and system with iron ore and coal. As a result of modeling the thermodynamic boundary reducing, oxidizing, and transition areas and the value of the ratio of carbon and oxygen in the system. Simulation of real systems carried out with the gas phase obtained in the pyrolys of coal. The simulation results allow to determine the optimal cost of coal required for complete reduction of iron ore from a given composition. The kinetics of the processes of solid-phase reduction of iron using coal of various technological brands. The paper describes experiments on effects of metal deoxidizer composition, component proportion, pelletizing mixture, particle size distribution of basic materials and flux on manganese recovering from oxides under direct melting.

  4. Climate/chemistry feedbacks and biogenic emissions.

    Science.gov (United States)

    Pyle, John A; Warwick, Nicola; Yang, Xin; Young, Paul J; Zeng, Guang

    2007-07-15

    The oxidizing capacity of the atmosphere is affected by anthropogenic emissions and is projected to change in the future. Model calculations indicate that the change in surface ozone at some locations could be large and have significant implications for human health. The calculations depend on the precise scenarios used for the anthropogenic emissions and on the details of the feedback processes included in the model. One important factor is how natural biogenic emissions will change in the future. We carry out a sensitivity calculation to address the possible increase in isoprene emissions consequent on increased surface temperature in a future climate. The changes in ozone are significant but depend crucially on the background chemical regime. In these calculations, we find that increased isoprene will increase ozone in the Northern Hemisphere but decrease ozone in the tropics. We also consider the role of bromine compounds in tropospheric chemistry and consider cases where, in a future climate, the impact of bromine could change.

  5. Sodium Para-aminosalicylic Acid Protected Primary Cultured Basal Ganglia Neurons of Rat from Manganese-Induced Oxidative Impairment and Changes of Amino Acid Neurotransmitters.

    Science.gov (United States)

    Li, Shao-Jun; Li, Yong; Chen, Jing-Wen; Yuan, Zong-Xiang; Mo, Yu-Huan; Lu, Guo-Dong; Jiang, Yue-Ming; Ou, Chao-Yan; Wang, Fang; Huang, Xiao-Wei; Luo, Yi-Ni; Ou, Shi-Yan; Huang, Yan-Ni

    2016-04-01

    Manganese (Mn), an essential trace metal for protein synthesis and particularly neurotransmitter metabolism, preferentially accumulates in basal ganglia. However, excessive Mn accumulation may cause neurotoxicity referred to as manganism. Sodium para-aminosalicylic acid (PAS-Na) has been used to treat manganism with unclear molecular mechanisms. Thus, we aim to explore whether PAS-Na can inhibit Mn-induced neuronal injury in basal ganglia in vitro. We exposed basal ganglia neurons with 50 μM manganese chloride (MnCl2) for 24 h and then replaced with 50, 150, and 450 μM PAS-Na treatment for another 24 h. MnCl2 significantly decreased cell viability but increased leakage rate of lactate dehydrogenase and DNA damage (as shown by increasing percentage of DNA tail and Olive tail moment). Mechanically, Mn reduced glutathione peroxidase and catalase activity and interrupted amino acid neurotransmitter balance. However, PAS-Na treatment reversed the aforementioned Mn-induced toxic effects. Taken together, these results showed that PAS-Na could protect basal ganglia neurons from Mn-induced neurotoxicity.

  6. Concentração foliar de manganês e zinco em laranjeiras adubadas com óxidos e carbonatos via foliar Leaf concentrations of manganese and zinc in the orange fertilized via foliar application with oxides and carbonates

    Directory of Open Access Journals (Sweden)

    Leandro José Grava de Godoy

    2013-09-01

    , corresponding to 250 and and 500g ha-1 of Mn, plus a control sprayed with water only. In the second experiment three sources of Zn were tested for foliar application: zinc oxide A, zinc oxide B and zinc sulphate at two rates per fertilizer, corresponding to 375 and 750g ha-1 of Zn, plus the control. Samples of leaves were collected monthly, beginning 30 days after application of the treatments. The foliar application of manganese carbonate B at a rate of 500g ha-1 Mn, and zinc oxide B at a rate of 750g ha-1, each provided adequate nutritional levels of Mn and Zn in the leaves of the orange. With the absence of rain, the appropriate levels of Mn and Zn in the soil are not enough to supply the Pêra orange grafted onto Rangpur lime.

  7. Manganese (III) meso-tetrakis N-ethylpyridinium-2-yl porphyrin acts as a pro-oxidant to inhibit electron transport chain proteins, modulate bioenergetics, and enhance the response to chemotherapy in lymphoma cells.

    Science.gov (United States)

    Jaramillo, Melba C; Briehl, Margaret M; Batinic-Haberle, Ines; Tome, Margaret E

    2015-06-01

    The manganese porphyrin, manganese (III) meso-tetrakis N-ethylpyridinium-2-yl porphyrin (MnTE-2-PyP(5+)), acts as a pro-oxidant in the presence of intracellular H2O2. Mitochondria are the most prominent source of intracellular ROS and important regulators of the intrinsic apoptotic pathway. Due to the increased oxidants near and within the mitochondria, we hypothesized that the mitochondria are a target of the pro-oxidative activity of MnTE-2-PyP(5+) and that we could exploit this effect to enhance the chemotherapeutic response in lymphoma. In this study, we demonstrate that MnTE-2-PyP(5+) modulates the mitochondrial redox environment and sensitizes lymphoma cells to antilymphoma chemotherapeutics. MnTE-2-PyP(5+) increased dexamethasone-induced mitochondrial ROS and oxidation of the mitochondrial glutathione pool in lymphoma cells. The combination treatment induced glutathionylation of Complexes I, III, and IV in the electron transport chain, and decreased the activity of Complexes I and III, but not the activity of Complex IV. Treatment with the porphyrin and dexamethasone also decreased cellular ATP levels. Rho(0) malignant T-cells with impaired mitochondrial electron transport chain function were less sensitive to the combination treatment than wild-type cells. These findings suggest that mitochondria are important for the porphyrin's ability to enhance cell death. MnTE-2-PyP(5+) also augmented the effects of 2-deoxy-D-glucose (2DG), an antiglycolytic agent. In combination with 2DG, MnTE-2-PyP(5+) increased protein glutathionylation, decreased ATP levels more than 2DG treatment alone, and enhanced 2DG-induced cell death in primary B-ALL cells. MnTE-2-PyP(5+) did not enhance dexamethasone- or 2DG-induced cell death in normal cells. Our findings suggest that MnTE-2-PyP(5+) has potential as an adjuvant for the treatment of hematologic malignancies. Copyright © 2015 Elsevier Inc. All rights reserved.

  8. Coupled anoxic nitrification/manganese reduction in marine sediments

    OpenAIRE

    Hulth, Stefan; Aller, Robert Curwood; Gilbert, Franck

    1999-01-01

    International audience; Pore water and solid phase distributions of oxygen, manganese, and nitrogen from hemipelagic and shelf sediments sometimes indicate a close coupling between the manganese and nitrogen redox cycles. Reaction coupling must be sustained in part by biological reworking of Mn-oxide-rich surface sediments into underlying anoxic zones. Surface sediment from Long Island Sound (USA) was used in laboratory experiments to simulate such intermittent natural mixing processes and su...

  9. Arsenic removal by manganese greensand filters

    Energy Technology Data Exchange (ETDEWEB)

    Phommavong, T. [Saskatchewan Environment, Regina (Canada); Viraraghavan, T. [Univ. of Regina, Saskatchewan (Canada). Faculty of Engineering

    1994-12-31

    Some of the small communities in Saskatchewan are expected to have difficulty complying with the new maximum acceptable concentration (MAC) of 25 {micro}g/L for arsenic. A test column was set up in the laboratory to study the removal of arsenic from the potable water using oxidation with KMnO{sub 4}, followed by manganese greensand filtration. Tests were run using water from the tap having a background arsenic concentration of <0.5 {micro}g/L and iron concentration in the range of 0.02 to 0.77 mg/L. The test water was spiked with arsenic and iron. Results showed that 61 % to 98% of arsenic can be removed from the potable water by oxidation with KMnO{sub 4} followed by manganese greensand filtration.

  10. Biogenic Amines in Insect Antennae

    Directory of Open Access Journals (Sweden)

    Marianna I. Zhukovskaya

    2017-06-01

    Full Text Available Insect antenna is a multisensory organ, each modality of which can be modulated by biogenic amines. Octopamine (OA and its metabolic precursor tyramine (TA affect activity of antennal olfactory receptor neurons. There is some evidence that dopamine (DA modulates gustatory neurons. Serotonin can serve as a neurotransmitter in some afferent mechanosensory neurons and both as a neurotransmitter and neurohormone in efferent fibers targeted at the antennal vessel and mechanosensory organs. As a neurohormone, serotonin affects the generation of the transepithelial potential by sensillar accessory cells. Other possible targets of biogenic amines in insect antennae are hygro- and thermosensory neurons and epithelial cells. We suggest that the insect antenna is partially autonomous in the sense that biologically active substances entering its hemolymph may exert their effects and be cleared from this compartment without affecting other body parts.

  11. Manganese Olivine. Pt. 1. Electrical conductivity

    International Nuclear Information System (INIS)

    Bai, Q.; Wang, Z.C.; Kohlstedt, D.L.

    1995-01-01

    To investigate the point defect chemistry and the kinetic properties of manganese olivine Mn 2 SiO 4 , electrical conductivity (σ) of single crystals was measured along either the [100] or the [010] direction. The experiments were carried out at temperatures T = 850-1200 C and oxygen fugacities f O 2 = 10 -11 - 10 -2 atm under both Mn oxide (MO) buffered and MnSiO 3 (MS) buffered conditions

  12. Manganese in silicon carbide

    International Nuclear Information System (INIS)

    Linnarsson, M.K.; Hallén, A.

    2012-01-01

    Structural disorder and relocation of implanted Mn in semi-insulating 4H–SiC has been studied. Subsequent heat treatment of Mn implanted samples has been performed in the temperature range 1400–2000 °C. The depth distribution of manganese is recorded by secondary ion mass spectrometry. Rutherford backscattering spectrometry has been employed for characterization of crystal disorder. Ocular inspection of color changes of heat-treated samples indicates that a large portion of the damage has been annealed. However, Rutherford backscattering shows that after heat treatment, most disorder from the implantation remains. Less disorder is observed in the [0 0 0 1] channel direction compared to [112 ¯ 3] channel direction. A substantial rearrangement of manganese is observed in the implanted region. No pronounced manganese diffusion deeper into the sample is recorded.

  13. Manganese in silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Linnarsson, M.K., E-mail: marga@kth.se [Royal Institute of Technology, School of Information and Communication Technology, P.O. Box E229, SE-16440 Kista-Stockhom (Sweden); Hallen, A. [Royal Institute of Technology, School of Information and Communication Technology, P.O. Box E229, SE-16440 Kista-Stockhom (Sweden)

    2012-02-15

    Structural disorder and relocation of implanted Mn in semi-insulating 4H-SiC has been studied. Subsequent heat treatment of Mn implanted samples has been performed in the temperature range 1400-2000 Degree-Sign C. The depth distribution of manganese is recorded by secondary ion mass spectrometry. Rutherford backscattering spectrometry has been employed for characterization of crystal disorder. Ocular inspection of color changes of heat-treated samples indicates that a large portion of the damage has been annealed. However, Rutherford backscattering shows that after heat treatment, most disorder from the implantation remains. Less disorder is observed in the [0 0 0 1] channel direction compared to [112{sup Macron }3] channel direction. A substantial rearrangement of manganese is observed in the implanted region. No pronounced manganese diffusion deeper into the sample is recorded.

  14. Biogenic Calcium Phosphate Transformation in Soils over Millennium Time Scales

    Energy Technology Data Exchange (ETDEWEB)

    Sato, S.; Neves, E; Solomon, D; Liang, B; Lehmann, J

    2009-01-01

    Changes in bioavailability of phosphorus (P) during pedogenesis and ecosystem development have been shown for geogenic calcium phosphate (Ca-P). However, very little is known about long-term changes of biogenic Ca-P in soil. Long-term transformation characteristics of biogenic Ca-P were examined using anthropogenic soils along a chronosequence from centennial to millennial time scales. Phosphorus fractionation of Anthrosols resulted in overall consistency with the Walker and Syers model of geogenic Ca-P transformation during pedogenesis. The biogenic Ca-P (e.g., animal and fish bones) disappeared to 3% of total P within the first ca. 2,000 years of soil development. This change concurred with increases in P adsorbed on metal-oxides surfaces, organic P, and occluded P at different pedogenic time. Phosphorus K-edge X-ray absorption near-edge structure (XANES) spectroscopy revealed that the crystalline and therefore thermodynamically most stable biogenic Ca-P was transformed into more soluble forms of Ca-P over time. While crystalline hydroxyapatite (34% of total P) dominated Ca-P species after about 600-1,000 years, {Beta}-tricalcium phosphate increased to 16% of total P after 900-1,100 years, after which both Ca-P species disappeared. Iron-associated P was observable concurrently with Ca-P disappearance. Soluble P and organic P determined by XANES maintained relatively constant (58-65%) across the time scale studied. Conclusions - Disappearance of crystalline biogenic Ca-P on a time scale of a few thousand years appears to be ten times faster than that of geogenic Ca-P.

  15. Unconventional shallow biogenic gas systems

    Science.gov (United States)

    Shurr, G.W.; Ridgley, J.L.

    2002-01-01

    Unconventional shallow biogenic gas falls into two distinct systems that have different attributes. Early-generation systems have blanketlike geometries, and gas generation begins soon after deposition of reservoir and source rocks. Late-generation systems have ringlike geometries, and long time intervals separate deposition of reservoir and source rocks from gas generation. For both types of systems, the gas is dominantly methane and is associated with source rocks that are not thermally mature. Early-generation biogenic gas systems are typified by production from low-permeability Cretaceous rocks in the northern Great Plains of Alberta, Saskatchewan, and Montana. The main area of production is on the southeastern margin of the Alberta basin and the northwestern margin of the Williston basin. The huge volume of Cretaceous rocks has a generalized regional pattern of thick, non-marine, coarse clastics to the west and thinner, finer grained marine lithologies to the east. Reservoir rocks in the lower part tend to be finer grained and have lower porosity and permeability than those in the upper part. Similarly, source beds in the units have higher values of total organic carbon. Patterns of erosion, deposition, deformation, and production in both the upper and lower units are related to the geometry of lineament-bounded basement blocks. Geochemical studies show that gas and coproduced water are in equilibrium and that the fluids are relatively old, namely, as much as 66 Ma. Other examples of early-generation systems include Cretaceous clastic reservoirs on the southwestern margin of Williston basin and chalks on the eastern margin of the Denver basin. Late-generation biogenic gas systems have as an archetype the Devonian Antrim Shale on the northern margin of the Michigan basin. Reservoir rocks are fractured, organic-rich black shales that also serve as source rocks. Although fractures are important for production, the relationships to specific geologic structures are

  16. A comparison between acoustic properties and heat effects in biogenic (magnetosomes) and abiotic magnetite nanoparticle suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Józefczak, A., E-mail: aras@amu.edu.pl [Institute of Acoustics, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Leszczyński, B. [Institute of Acoustics, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Skumiel, A.; Hornowski, T. [Institute of Acoustics, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland)

    2016-06-01

    Magnetic nanoparticles show unique properties and find many applications because of the possibility to control their properties using magnetic field. Magnetic nanoparticles are usually synthesized chemically and modification of the particle surface is necessary. Another source of magnetic nanoparticles are various magnetotactic bacteria. These biogenic nanoparticles (magnetosomes) represent an attractive alternative to chemically synthesized iron oxide particles because of their unique characteristics and a high potential for biotechnological and biomedical applications. This work presents a comparison between acoustic properties of biogenic and abiotic magnetite nanoparticle suspensions. Experimental studies have shown the influence of a biological membrane on the ultrasound properties of magnetosomes suspension. Finally the heat effect in synthetic and biogenic magnetite nanoparticles is also discussed. The experimental study shows that magnetosomes present good heating efficiency. - Highlights: • A biogenic and abiotic magnetite nanoparticle suspensions are investigated. • A comparison between ultrasonic properties and heat effects is presented. • Magnetosomes and abiotic magnetite nanoparticles exhibit good heating efficiency.

  17. A comparison between acoustic properties and heat effects in biogenic (magnetosomes) and abiotic magnetite nanoparticle suspensions

    International Nuclear Information System (INIS)

    Józefczak, A.; Leszczyński, B.; Skumiel, A.; Hornowski, T.

    2016-01-01

    Magnetic nanoparticles show unique properties and find many applications because of the possibility to control their properties using magnetic field. Magnetic nanoparticles are usually synthesized chemically and modification of the particle surface is necessary. Another source of magnetic nanoparticles are various magnetotactic bacteria. These biogenic nanoparticles (magnetosomes) represent an attractive alternative to chemically synthesized iron oxide particles because of their unique characteristics and a high potential for biotechnological and biomedical applications. This work presents a comparison between acoustic properties of biogenic and abiotic magnetite nanoparticle suspensions. Experimental studies have shown the influence of a biological membrane on the ultrasound properties of magnetosomes suspension. Finally the heat effect in synthetic and biogenic magnetite nanoparticles is also discussed. The experimental study shows that magnetosomes present good heating efficiency. - Highlights: • A biogenic and abiotic magnetite nanoparticle suspensions are investigated. • A comparison between ultrasonic properties and heat effects is presented. • Magnetosomes and abiotic magnetite nanoparticles exhibit good heating efficiency.

  18. Impacts of biogenic emissions of VOC and NOx on tropospheric ozone during summertime in eastern China.

    Science.gov (United States)

    Wang, Qin'geng; Han, Zhiwei; Wang, Tijian; Zhang, Renjian

    2008-05-20

    This study is intended to understand and quantify the impacts of biogenic emissions of volatile organic compounds (VOC) and nitrogen oxides (NO(x)) on the formation of tropospheric ozone during summertime in eastern China. The model system consists of the non-hydrostatic mesoscale meteorological model (MM5) and a tropospheric chemical and transport model (TCTM) with the updated carbon-bond chemical reaction mechanism (CBM-IV). The spatial resolution of the system domain is 30 km x 30 km. The impacts of biogenic emissions are investigated by performing simulations (36 h) with and without biogenic emissions, while anthropogenic emissions are constant. The results indicate that biogenic emissions have remarkable impacts on surface ozone in eastern China. In big cities and their surrounding areas, surface ozone formation tends to be VOC-limited. The increase in ozone concentration by biogenic VOC is generally 5 ppbv or less, but could be more than 10 ppbv or even 30 ppbv in some local places. The impacts of biogenic NO(x) are different or even contrary in different regions, depending on the relative availability of NO(x) and VOC. The surface ozone concentrations reduced or increased by the biogenic NO(x) could be as much as 10 ppbv or 20 ppbv, respectively. The impacts of biogenic emissions on ozone aloft are generally restricted to the boundary layer and generally more obvious during the daytime than during the nighttime. This study is useful for understanding the role of biogenic emissions and for planning strategies for surface ozone abatement in eastern China. Due to limitations of the emission inventories used and the highly non-linear nature of zone formation, however, some uncertainties remain in the results.

  19. [Advances in researches of biogenic molluscicides].

    Science.gov (United States)

    Xue, Li; Jian-Rong, Dai; Yun-Tian, Xing

    2017-01-05

    Biogenic molluscicides refer to the use of plants, animals and micro-organisms or their metabolites, and synthesis biomimetic molluscicides to kill Oncomelania hupensis snails. With the rapid development of science and technology, new biogenic molluscicides are continuously emerging and the category also continues to expand. According to the molluscicidal active ingredient and sources, at present, the biogenic molluscicides with in-depth studies include plant-derived molluscicides, micro-organism molluscicides, microbial metabolite molluscicides and animal molluscicides. This paper reviews the advances in the researches of biogenic molluscicides in recent years.

  20. Urchin-like cobalt incorporated manganese oxide OMS-2 hollow spheres: Synthesis, characterization and catalytic degradation of RhB dye

    Science.gov (United States)

    Ahmed, Khalid Abdelazez Mohamed; Li, Buyi; Tan, Bien; Huang, Kaixun

    2013-01-01

    Urchin-like KxCoyMn8-yO16 hollow spheres assembled from nanoplate building blocks were successfully fabricated via a one-pot hydrothermal route using cobalt acetate and potassium permanganate as raw material. The products were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectrometer, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) measurement. The thermal stability and surface areas of cobalt ion in the manganese sites of KMn8O16 structures were clearly evidenced by TGA and N2 adsorption-desorption isotherms curves. Based on time depended experiment results, a possible formation mechanism for this structures was proposed. The catalytic degradation of Rhodamine B (RhB) on KxCoyMn8-yO16 materials has, therefore been dependent for the molar precursor ratio and specific surface area of the as-fabricated products. UV-vis, LC-MS and barium hydroxide methods were utilized to monitor the temporal course of the catalytic reaction.

  1. Synthesis and magnetic structure of the layered manganese oxide selenide Sr{sub 2}MnO{sub 2}Ag{sub 1.5}Se{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Blandy, Jack N. [Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR (United Kingdom); Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom); Boskovic, Jelena C. [Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR (United Kingdom); Clarke, Simon J., E-mail: simon.clarke@chem.ox.ac.uk [Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR (United Kingdom)

    2017-01-15

    The synthesis of a high-purity sample of the layered oxide selenide Sr{sub 2}MnO{sub 2}Ag{sub 1.5}Se{sub 2} is reported. At ambient temperature it crystallises in the space group I4/mmm with two formula units in the unit cell and lattice parameters a=4.08771(1) Å, c=19.13087(8) Å. The compound displays mixed-valent manganese in a formal oxidation state close to +2.5 and powder neutron diffraction measurements reveal that below the Néel temperature of 63(1) K this results in an antiferromagnetic structure which may be described as A-type, modelled in the magnetic space group P{sub I}4/mnc (128.410 in the Belov, Neronova and Smirnova (BNS) scheme) in which localised Mn moments of 3.99(2) μ{sub B} are arranged in ferromagnetic layers which are coupled antiferromagnetically. In contrast to the isostructural compound Sr{sub 2}MnO{sub 2}Cu{sub 1.5}S{sub 2}, Sr{sub 2}MnO{sub 2}Ag{sub 1.5}Se{sub 2} does not display long range ordering of coinage metal ions and vacancies, nor may significant amounts of the coinage metal readily be deintercalated using soft chemical methods. - Graphical abstract: Sr{sub 2}MnO{sub 2}Ag{sub 1.5}Se{sub 2} containing mixed valent Mn ions undergoes magnetic ordering with ferromagnetic coupling within MnO{sub 2} sheets and antiferromagnetic coupling between MnO{sub 2} sheets. - Highlights: • High purity sample of Sr{sub 2}MnO{sub 2}Ag{sub 1.5}Se{sub 2} obtained. • Magnetic structure determined. • Compared with related mixed-valent manganite oxide chalcogenides.

  2. Framework for Assessing Biogenic CO2 Emissions from Stationary Sources

    Science.gov (United States)

    This revision of the 2011 report, Accounting Framework for Biogenic CO2 Emissions from Stationary Sources, evaluates biogenic CO2 emissions from stationary sources, including a detailed study of the scientific and technical issues associated with assessing biogenic carbon dioxide...

  3. Manganese deposition in drinking water distribution systems.

    Science.gov (United States)

    Gerke, Tammie L; Little, Brenda J; Barry Maynard, J

    2016-01-15

    This study provides a physicochemical assessment of manganese deposits on brass and lead components from two fully operational drinking water distributions systems. One of the systems was maintained with chlorine; the other, with secondary chloramine disinfection. Synchrotron-based in-situ micro X-ray adsorption near edge structure was used to assess the mineralogy. In-situ micro X-ray fluorescence mapping was used to demonstrate the spatial relationships between manganese and potentially toxic adsorbed metal ions. The Mn deposits ranged in thickness from 0.01 to 400 μm. They were composed primarily of Mn oxides/oxhydroxides, birnessite (Mn(3+) and Mn(4+)) and hollandite (Mn(2+) and Mn(4+)), and a Mn silicate, braunite (Mn(2+) and Mn(4+)), in varying proportions. Iron, chromium, and strontium, in addition to the alloying elements lead and copper, were co-located within manganese deposits. With the exception of iron, all are related to specific health issues and are of concern to the U.S. Environmental Protection Agency (U.S. EPA). The specific properties of Mn deposits, i.e., adsorption of metals ions, oxidation of metal ions and resuspension are discussed with respect to their influence on drinking water quality. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Kinetic spectrophotometric determination of trace manganese (II) with dahlia violet in nonionic microemulsion medium.

    Science.gov (United States)

    Wei, Qin; Yan, Liangguo; Chang, Guohua; Ou, Qingyu

    2003-02-06

    A new catalytic kinetic spectrophotometric method has been developed for the determination of trace amount of manganese (II) in nonionic microemulsion medium. The method is based on the catalytic effect of manganese (II) on the oxidation of dahlia violet by potassium periodate with nitrilotriacetic acid as an activitor in the presence of nonionic microemulsion. Under the optimum conditions, the calibration graph is linear in the range of 0.0004-0.0056 mug ml(-1) of manganese (II) at 580 nm. The detection limit achieved is 3.75x10(-5) mug ml(-1). Manganese (II) in foodstuff samples was determined with satisfactory results.

  5. A biokinetic model for manganese

    Energy Technology Data Exchange (ETDEWEB)

    Leggett, R.W., E-mail: rwl@ornl.gov

    2011-09-15

    The International Commission on Radiological Protection (ICRP) is updating its biokinetic models used to derive dose coefficients and assess bioassay data for intake of radionuclides. This paper reviews biokinetic data for manganese and proposes a biokinetic model for systemic manganese in adult humans. The proposed model provides a more detailed and physiologically meaningful description of the behavior of absorbed manganese in the body than the current ICRP model. The proposed model and current ICRP model yield broadly similar estimates of dose per unit activity of inhaled or ingested radio-manganese but differ substantially with regard to interpretation of bioassay data. The model is intended primarily for use in radiation protection but can also serve as a baseline model for evaluation of potentially excessive intakes of stable manganese in occupational settings. - Highlights: {yields} Manganese is an essential trace element but a neurotoxin when inhaled excessively. {yields} Manganese-54 is an important radiation hazard in and around nuclear reactors. {yields} Biokinetic data for manganese are reviewed and a new biokinetic model is developed. {yields} The main purpose is to update the manganese model used in radiation protection. {yields} The model can also be applied in evaluations of manganese as a chemical hazard.

  6. A biokinetic model for manganese

    International Nuclear Information System (INIS)

    Leggett, R.W.

    2011-01-01

    The International Commission on Radiological Protection (ICRP) is updating its biokinetic models used to derive dose coefficients and assess bioassay data for intake of radionuclides. This paper reviews biokinetic data for manganese and proposes a biokinetic model for systemic manganese in adult humans. The proposed model provides a more detailed and physiologically meaningful description of the behavior of absorbed manganese in the body than the current ICRP model. The proposed model and current ICRP model yield broadly similar estimates of dose per unit activity of inhaled or ingested radio-manganese but differ substantially with regard to interpretation of bioassay data. The model is intended primarily for use in radiation protection but can also serve as a baseline model for evaluation of potentially excessive intakes of stable manganese in occupational settings. - Highlights: → Manganese is an essential trace element but a neurotoxin when inhaled excessively. → Manganese-54 is an important radiation hazard in and around nuclear reactors. → Biokinetic data for manganese are reviewed and a new biokinetic model is developed. → The main purpose is to update the manganese model used in radiation protection. → The model can also be applied in evaluations of manganese as a chemical hazard.

  7. Intolerance to dietary biogenic amines : a review

    NARCIS (Netherlands)

    Jansen, SC; van Dusseldorp, M; Bottema, KC; Dubois, AEJ

    Objective: To evaluate the scientific evidence for purported intolerance to dietary biogenic amines. Data Sources: MEDLINE was searched for articles in the English language published between January 1966 and August 2001. The keyword biogenic amin* was combined with hypersens*, allergen intoler*, and

  8. Intolerance to dietary biogenic amines: A review

    NARCIS (Netherlands)

    Jansen, S.C.; Dusseldorp, M. van; Bottema, K.C.; Dubois, A.E.J.

    2003-01-01

    Objective: To evaluate the scientific evidence for purported intolerance to dietary biogenic amines. Data Sources: MEDLINE was searched for articles in the English language published between January 1966 and August 2001. The keyword biogenic amin* was combined with hypersens*, allerg*, intoler*, and

  9. Checkerboard deposition of lithium manganese oxide spinel (LiMn2O4) by RF magnetron sputtering on a stainless steel in all-solid-state thin film battery

    Science.gov (United States)

    Hsueh, T. H.; Yu, Y. Q.; Jan, D. J.; Su, C. H.; Chang, S. M.

    2018-03-01

    All-solid-state thin film lithium batteries (TFLBs) are the most competitive low-power sources to be applied in various kinds of micro-electro-mechanical systems and have been draw a lot of attention in academic research. In this paper, the checkerboard deposition of all-solid-state TFLB was composed of thin film lithium metal anode, lithium phosphorus oxynitride (LiPON) solid electrolyte, and checkerboard deposition of lithium manganese oxide spinel (LiMn2O4) cathode. The LiPON and LiMn2O4 were deposited by a radio frequency magnetron sputtering system, and the lithium metal was deposited by a thermal evaporation coater. The electrochemical characterization of this lithium battery showed the first discharge capacity of 107.8 μAh and the capacity retention was achieved 95.5% after 150 charge-discharge cycles between 4.3V and 3V at a current density of 11 μA/cm2 (0.5C). Obviously, the checkerboard of thin film increased the charge exchange rate; also this lithium battery exhibited high C-rate performance, with better capacity retention of 82% at 220 μA/cm2 (10C).

  10. Use of bovine catalase and manganese dioxide for elimination of hydrogen peroxide from partly oxidized aqueous solutions of aromatic molecules - Unexpected complications

    Science.gov (United States)

    Kovács, Krisztina; Sági, Gyuri; Takács, Erzsébet; Wojnárovits, László

    2017-10-01

    Being a toxic substance, hydrogen peroxide (H2O2) formed during application of advanced oxidation processes disturbs the biological assessment of the treated solutions. Therefore, its removal is necessary when the concentration exceeds the critical level relevant to the biological tests. In this study, H2O2 removal was tested using catalase enzyme or MnO2 as catalysts and the concentration changes were measured by the Cu(II)/phenanthroline method. MnO2 and Cu(II) were found to react not only with H2O2 but also with the partly oxidized intermediates formed in the hydroxyl radical induced degradation of aromatic antibiotic and pesticide compounds. Catalase proved to be a milder oxidant, it did not show significant effects on the composition of organic molecules. The Cu(II)/phenanthroline method gives the correct H2O2 concentration only in the absence of easily oxidizable compounds, e.g. certain phenol type molecules.

  11. Manganese and related elements in the interstitial water of marine sediments.

    Science.gov (United States)

    Presley, B J; Brooks, R R; Kaplan, I R

    1967-11-17

    Analyses for manganese, nickel, iron, cobalt, sodium, and lithium in the interstitial water of cores from the southern California borderland and six deep-sea cores in the area of the East Pacific Rise show great variation in concentration of trace elements. Oxidizing near-shore sediments showed a 50-fold enrichment in manganese in contrast to sulfide-rich reducing sediments, which showed no enrichment. Deep-sea sediments were variable in their concentration of the trace metals. All but one core showed a high enrichment in dissolved manganese, with a maximum of 6.6 parts per million. Two cores showed a 100-fold enrichment in nickel and cobalt. The manganese appears to be in solution either as Mn(2+) or as a complex. The results appear to support manganese nodule formation in deep-sea sediments through a diffusion of manganese from depth to the surface.

  12. Solvent-free, improved synthesis of pure bixbyite phase of iron and manganese mixed oxides as low-cost, potential oxygen carrier for chemical looping with oxygen uncoupling

    Czech Academy of Sciences Publication Activity Database

    Mungse, P.B.; Saravanan, G.; Nishibori, M.; Šubrt, Jan; Labhsetwar, N.K.

    2017-01-01

    Roč. 89, č. 4 (2017), s. 511-521 ISSN 0033-4545. [International Conference Solid State Chemistry 2016 /12./. Prague, 18.09.2016-23.09.2016] Institutional support: RVO:61388980 Keywords : CO capture and sequestration * Lattice * Mixed metal oxides * Reactive oxygen * Thermal power plants Subject RIV: CA - Inorganic Chemistry OBOR OECD: Inorganic and nuclear chemistry Impact factor: 2.626, year: 2016

  13. Exploiting a Simple Method for the Determination of Manganese in Polyethylene Lined Tubing for Petroleum and Natural Gas Industries

    Directory of Open Access Journals (Sweden)

    Shao Xiaodong

    2018-01-01

    Full Text Available The polyethylene lined tubing is the key to enabling the industry to meet some of the energy security challenges that nations face today. It is well known that manganese is an important element in polyethylene lined tubing. In this paper, a simple spectrophotometric method was described for the determination of manganese in polyethylene lined tubing. The method was based on the oxidation-reduction reaction between ammonium persulfate and manganese(II producing manganese(VII in the presence of silver nitrate as a catalyst. The characteristic wavelength of maximum absorption of manganese(VII was obtained locating at 530 nm. Under the optimum reaction conditions the absorption value was proportional to the concentration of manganese in the range of 0.2%~1.9% (R2 = 0.9997, and the relative standard deviation was less than 3.0% (n=5. The proposed method was applied successfully to determine manganese in polyethylene lined tubing real samples.

  14. Hydrogen peroxide oxidation of mustard-model sulfides catalyzed by iron and manganese tetraarylporphyrines. Oxygen transfer to sulfides versus H(2)O(2) dismutation and catalyst breakdown.

    Science.gov (United States)

    Marques, A; Marin, M; Ruasse, M F

    2001-11-16

    Fe(III)- and Mn(III)-meso-tetraarylporphyrin catalysis of H(2)O(2) oxidation of dibenzyl and phenyl-2-chloroethyl sulfides, 1, is investigated in ethanol with the aim of designing catalytic systems for mustard decontamination. The sulfide conversion, the sulfoxide and sulfone yields, the oxygen transfer from H(2)O(2) to the sulfide, and the catalyst stability depend markedly on the metal, on the substituents of its ligand, and on the presence or the absence of a cocatalyst, imidazole or ammonium acetate. With Fe, sulfones, the only oxidation products, are readily obtained whatever the ligand (TPP, F(20)TPP, or TDCPP) and the cocatalyst; the oxygen transfer is fairly good, up to 95% when the catalyst concentration is small ([1]/[Cat] = 420); the catalyst breakdown is insignificant only in the absence of any cocatalyst. With Mn, the sulfide conversion is achieved completely when the ligand is TDCPP or TSO(3)PP, but not F(20)TPP or TPP; a mixture of sulfoxide, 2, and sulfone, 3, is always obtained with [2]/[3] = 3.5-0.85 depending on the ligand and the cocatalyst (electron withdrawing substituents favor 3 and NH(4)OAc, 2). The catalyst stability is very good, but the oxygen transfer is poor whatever the ligand and the cocatalyst. These results are discussed in terms of a scheme in which sulfide oxygenation, H(2)O(2) dismutation, and oxidative ligand breaking compete. It is shown that the efficiency of the oxygen transfer is related not only to the rate constant of the dismutation route but also to the concentration of the active metal-oxo intermediate, most likely a perferryl or permanganyl species, i.e., to the rate of its formation.

  15. Pilot study points way to iron/manganese removal

    Energy Technology Data Exchange (ETDEWEB)

    Qureshi, N.; Barnes, A. [Progressive Consulting Engineers Inc., Minneapolis, MN (United States)

    1994-12-31

    The use of coal, greensand and sand in filters for removing iron and manganese from the Brooklyn Park, Minnesota, water supply was investigated. The most effective and economic treatment involved using a dual media filtration and potassium permanganate as the oxidant.

  16. Habit plane-driven P2-type manganese-based layered oxide as long cycling cathode for Na-ion batteries

    Science.gov (United States)

    Luo, Rui; Wu, Feng; Xie, Man; Ying, Yao; Zhou, Jiahui; Huang, Yongxin; Ye, Yusheng; Li, Li; Chen, RenJie

    2018-04-01

    Layered transition metal oxides are considered to be promising candidates as cathode materials for sodium-ion batteries. Herein, a facile solid-state reaction is developed to synthesize hexagons plate-like Na0.67Ni0.25Mn0.75O2+δ (denoted as P2-NNM) material with habit plane formed. The structure of this layered oxide is characterized by XRD, HR-TEM and SAED. The layered material delivers a high reversible capacity of 91.8 mAh g-1 at 0.2 C with a capacity retention of 94.4 % after 280 cycles, superior rate capability and long cycle life (84.2 % capacity retention after 1000 cycle). Ni2+ is an active ion and Ni doping alleviates the Jahn-Teller distortion, and Mn3+/Mn4+ coexist as Mn4+ is desired from the stability perspective. Particularly, CV and XPS results confirm these results. Moreover, the electrode exhibits a quasi-solid-solution reaction during the sodium extraction and insertion. This contribution demonstrates that P2-NNM is a promising cathode electrode for rechargeable long-life sodium-ion batteries.

  17. Manganese oxide octahedral molecular sieve K-OMS-2 as catalyst in post plasma-catalysis for trichloroethylene degradation in humid air

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen Dinh, M.T. [Université Lille, Sciences et Technologies, Unité de Catalyse et Chimie du Solide UMR CNRS UCCS 8181, 59655 Villeneuve d’Ascq (France); The University of Da-Nang, University of Science and Technology, 54, Nguyen Luong Bang, Da-Nang (Viet Nam); Giraudon, J.-M., E-mail: jean-marc.giraudon@univ-lille1.fr [Université Lille, Sciences et Technologies, Unité de Catalyse et Chimie du Solide UMR CNRS UCCS 8181, 59655 Villeneuve d’Ascq (France); Vandenbroucke, A.M.; Morent, R.; De Geyter, N. [Ghent University, Faculty of Engineering and Architecture, Department of Applied Physics, Research Unit Plasma Technology, Sint-Pietersnieuwstraat 41, 9000 Ghent (Belgium); Lamonier, J.-F. [Université Lille, Sciences et Technologies, Unité de Catalyse et Chimie du Solide UMR CNRS UCCS 8181, 59655 Villeneuve d’Ascq (France)

    2016-08-15

    Highlights: • Post plasma catalysis: negative DC glow discharge combined with a cryptomelane. • The α-MnO{sub 2} catalyst totally decomposes the NTP generated ozone. • Active oxygen oxidizes the end-up plasma VOC by-products. - Abstract: The total oxidation of trichloroethylene (TCE) in air at low relative humidity (RH = 10%) in the presence of CO{sub 2} (520 ppmv) was investigated in function of energy density using an atmospheric pressure negative DC luminescent glow discharge combined with a cryptomelane catalyst positioned downstream of the plasma reactor at a temperature of 150 °C. When using Non-Thermal Plasma (NTP) alone, it is found a low COx (x = 1–2) yield in agreement with the detection of gaseous polychlorinated by-products in the outlet stream as well as ozone which is an harmful pollutant. Introduction of cryptomelane enhanced trichloroethylene removal, totally inhibited plasma ozone formation and increased significantly the COx yield. The improved performances of the hybrid system were mainly ascribed to the total destruction of plasma generated ozone on cryptomelane surface to produce active oxygen species. Consequently these active oxygen species greatly enhanced the abatement of the plasma non-reacted TCE and completely destroyed the hazardous plasma generated polychlorinated intermediates. The facile redox of Mn species associated with oxygen vacancies and mobility as well as the textural properties of the catalyst might also contribute as a whole to the efficiency of the process.

  18. Physicochemical properties of manganese dioxide synthesized using C2–C5 alcohols as reducing agents and their catalytic activities for CO oxidation

    KAUST Repository

    Lee, Young-Ho

    2015-09-26

    MnO2 catalysts were synthesized in an aqueous solution of KMnO4 and C2–C5 alcohols using a simple redox method at room temperature. The crystalline structure of all samples was δ-MnO2 after being calcined at 300 °C. However, other physicochemical properties of the samples varied depending on the symmetry of the alcohols used. For the catalytic oxidation of CO, MnO2 catalysts prepared with 1° alcohols performed better than the samples prepared in 2° alcohols. Catalytic activities were correlated to the quantity of labile oxygen species of the catalysts. In CO-TPD analysis, the relative area of desorbed radical dotCO2, which is the product of the reaction between adsorbed CO and lattice oxygen species, becomes larger for MnO2 prepared with 1° alcohols than with 2° alcohols. These results were primarily resulted from the innate hydrogen dissociation behavior of alcohol in solution. The pKa was found to be an important factor in determining the physicochemical properties and catalytic activity toward CO oxidation of MnO2.

  19. Future changes in biogenic isoprene emissions: how might they affect regional and global atmospheric chemistry?

    Science.gov (United States)

    Christine Wiedinmyer; Xuexi Tie; Alex Guenther; Ron Neilson; Claire. Granier

    2006-01-01

    Isoprene is emitted from vegetation to the atmosphere in significant quantities, and it plays an important role in the reactions that control tropospheric oxidant concentrations. As future climatic and land-cover changes occur, the spatial and temporal variations, as well as the magnitude of these biogenic isoprene emissions, are expected to change. This paper presents...

  20. Manganese oxide octahedral molecular sieve K-OMS-2 as catalyst in post plasma-catalysis for trichloroethylene degradation in humid air.

    Science.gov (United States)

    Nguyen Dinh, M T; Giraudon, J-M; Vandenbroucke, A M; Morent, R; De Geyter, N; Lamonier, J-F

    2016-08-15

    The total oxidation of trichloroethylene (TCE) in air at low relative humidity (RH=10%) in the presence of CO2 (520ppmv) was investigated in function of energy density using an atmospheric pressure negative DC luminescent glow discharge combined with a cryptomelane catalyst positioned downstream of the plasma reactor at a temperature of 150°C. When using Non-Thermal Plasma (NTP) alone, it is found a low COx (x=1-2) yield in agreement with the detection of gaseous polychlorinated by-products in the outlet stream as well as ozone which is an harmful pollutant. Introduction of cryptomelane enhanced trichloroethylene removal, totally inhibited plasma ozone formation and increased significantly the COx yield. The improved performances of the hybrid system were mainly ascribed to the total destruction of plasma generated ozone on cryptomelane surface to produce active oxygen species. Consequently these active oxygen species greatly enhanced the abatement of the plasma non-reacted TCE and completely destroyed the hazardous plasma generated polychlorinated intermediates. The facile redox of Mn species associated with oxygen vacancies and mobility as well as the textural properties of the catalyst might also contribute as a whole to the efficiency of the process. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Comparative study of biogenic and abiotic iron-containing materials

    Energy Technology Data Exchange (ETDEWEB)

    Cherkezova-Zheleva, Z., E-mail: zzhel@ic.bas.bg; Shopska, M., E-mail: shopska@ic.bas.bg; Paneva, D. [Bulgarian Academy of Sciences, Institute of Catalysis (Bulgaria); Kovacheva, D. [Bulgarian Academy of Sciences, Institute of General and Inorganic Chemistry (Bulgaria); Kadinov, G.; Mitov, I. [Bulgarian Academy of Sciences, Institute of Catalysis (Bulgaria)

    2016-12-15

    Series of iron-based biogenic materials prepared by cultivation of Leptothrix group of bacteria in different feeding media (Sphaerotilus-Leptothrix group of bacteria isolation medium, Adler, Lieske and silicon-iron-glucose-peptone) were studied. Control samples were obtained in the same conditions and procedures but the nutrition media were not infected with bacteria, i.e. they were sterile. Room and low temperature Mössbauer spectroscopy, powder X-ray diffraction (XRD), and infrared spectroscopy (IRS) were used to reveal the composition and physicochemical properties of biomass and respective control samples. Comparative analysis showed differences in their composition and dispersity of present phases. Sample composition included different ratio of nanodimensional iron oxyhydroxide and oxide phases. Relaxation phenomena such as superparamagnetism or collective magnetic excitation behaviour were registered for some of them. The experimental data showed that the biogenic materials were enriched in oxyhydroxides of high dispersion. Catalytic behaviour of a selected biomass and abiotic material were studied in the reaction of CO oxidation. In situ diffuse-reflectance (DR) IRS was used to monitor the phase transformations in the biomass and CO conversion.

  2. Measurements of atmospheric hydrocarbons and biogenic emission fluxes in the Amazon boundary layer

    Science.gov (United States)

    Zimmerman, P. R.; Greenberg, J. P.; Westberg, C. E.

    1988-01-01

    Tropospheric mixing ratios of methane, C2-C10 hydrocarbons, and carbon monoxide were measured over the Amazon tropical forest near Manaus, Amazonas, Brazil, i