• Title, Summary, Keyword: manganese oxide

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Synthesis and Electrochemical Characterization of Reduced Graphene Oxide-Manganese Oxide Nanocomposites

  • Lee, Yu-Ri;Song, Min-Sun;Lee, Kyung-Min;Kim, In-Young;Hwang, Seong-Ju
    • Journal of Electrochemical Science and Technology
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    • v.2 no.1
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    • pp.1-7
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    • 2011
  • Nanocomposites of reduced graphene oxide and manganese (II,III) oxide can be synthesized by the freeze-drying process of the mixed colloidal suspension of graphene oxide and manganese oxide, and the subsequent heat-treatment. The calcined reduced graphene oxide-manganese (II,III) oxide nanocomposites are X-ray amorphous, suggesting the formation of homogeneous and disordered mixture without any phase separation. The reduction of graphene oxide to reduced graphene oxide upon the heat-treatment is evidenced by Fourier-transformed infrared spectroscopy. Field emission-scanning electronic microscopy and energy dispersive spectrometry clearly demonstrate the formation of porous structure by the house-of-cards type stacking of reduced graphene oxide nanosheets and the homogeneous distribution of manganese ions in the nanocomposites. According to Mn K-edge X-ray absorption spectroscopy, manganese ions in the calcined nanocomposites are stabilized in octahedral symmetry with mixed Mn oxidation state of Mn(II)/Mn(III). The present reduced graphene oxide-manganese oxide nanocomposites show characteristic pseudocapacitance behavior superior to the pristine manganese oxide, suggesting their applicability as electrode material for supercapacitors.

Thermal analysis of anodically deposited manganese oxide film (Anodic deposition된 $MnO_2$ 막의 열분석 특성)

  • Kim, Bong-Seo;Lee, Dong-Yoon;Lee, Hee-Woong;Chung, Won-Sub
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.900-903
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    • 2003
  • Using $DV-X{\alpha}$ method, it is calculated that nickel reduces the energy band gap of manganese oxide in 3 additives of titanium, nickel and tin. Therefore, it is estimated that the electrical conductivity of manganese-nickel oxide has the lowest value in 3 kinds of manganese oxide. The manganese oxide and manganese-nickel oxide which were produced by anodic deposition under $30mA/cm^2$ at room temperature in manganese sulfate and manganese-nickel sulfate solution were thermal-analyzed by DTA and TGA. The weight change of manganese oxide continuously decreased below $508^{\circ}C$ and kept constant at $518{\sim}600^{\circ}C$. However, the manganeses-nickel oxide transformed at the temperature range of $510{\sim}537^{\circ}C$. It is observed that the nickel addition to manganese oxide increases transformation temperature and its range.

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Soluble Manganese Removal Using Manganese Oxide Coated Media (MOCM) (산화망간피복여재를 이용한 용존망간 제거)

  • Kim, Jinkeun;Jeong, Sechae;Ko, Suhyun
    • Journal of Korean Society of Water and Wastewater
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    • v.20 no.6
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    • pp.813-822
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    • 2006
  • Soluble manganese removal was analyzed as a function of filter media, filter depth, presence or absence of chlorination, and surface manganese oxide concentration in water treatment processes. Sand, manganese oxide coated sand (MOCS), sand+MOCS, and granular activated carbon(GAC) were used as filter media. Manganese removal, surface manganese oxide concentration, turbidity removal, and regeneration of MOCS in various filter media were investigated. Results indicated that soluble manganese removal in MOCS was rapid and efficient, and most of the removal happened at the top of the filter. When filter influent (residual chlorine 1.0mg/L) with an average manganese concentration of 0.204mg/L was fed through a filter column, the sand+MOCS and MOCS columns can remove 98.9% and 99.2% of manganese respectively on an annual basis. On the other hand, manganese removal in sand and the GAC column was minimal during the initial stage of filtration, but after 8 months of filter run they removed 99% and 35% of manganese, respectively. Sand turned into MOCS after a certain period of filtration, while GAC did not. In MOCS, the manganese adsorption rate on the filter media was inversely proportional to the filter depth, while the density of media was proportional to the filter depth.

Electrical Conductivity Change of Manganese oxide with Addition of Transition Metal (천이금속 첨가에 따른 이산화망간의 전기전도도 변화)

  • Kim, Bong-Seo;Lee, Dong-Yoon;Lee, Hee-Woong;Chung, Won-Sub
    • Proceedings of the KIEE Conference
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    • pp.2028-2030
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    • 2005
  • The electrical conductivity of manganese oxide and complex manganese oxide produced by anodic deposition method was measured. The additive transition metal is Cu, Co and Fe. The transition metals like as Cu, Co and Fe improved electrical conductivity of complex manganese oxide compared with manganese oxide. This is coincide with the results of molecular orbital calculation by DV-Xa.

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Application of Manganese Oxide for the Oxidative Degradation of Bisphenol-A in Aqueous Phase (망간산화물을 이용한 수용액내 Bisphenol-A의 산화 반응성 평가)

  • Jee, Sang-Hyun;Ko, Seok-Oh
    • Journal of Korean Society on Water Environment
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    • v.23 no.5
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    • pp.659-664
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    • 2007
  • The objective of this study is to evaluate the detoxification method for the endocrine disrupting chemicals by manganese oxide. Manganese coated sand and bisphenol-A (BPA) was used as the reactive medium and the contaminant. Results showed that manganese oxide effectively degrades BPA by oxidative coupling reaction. The nonlinear oxidative coupling reaction orders were obtained for BPA and oxide, respectively. The reaction rate of BPA decreased as initial BPA concentration increased, as oxide loading decreased and as pH increased. The higher ionic strength, the higher reaction rate was observed. Divalent cations were adsorbed on the oxide surfaces, resulting in the decreased degradation rate of BPA.

Toluene Catalytic Oxidation by Manganese-Cerium Bimetallic Catalysts (Mn-Ce 복합 산화물에 의한 톨루엔 촉매 산화)

  • Cheon Tae-Jin;Choi Sung-Woo;Lee Chang-Soep
    • Journal of Environmental Science International
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    • v.14 no.4
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    • pp.427-433
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    • 2005
  • Activity of manganese oxide supported on ${\nu}-Al_2O_3$ was increased when cerium was added. Also, cerium-added manganese oxide on ${\nu}-Al_2O_3$ was more effective in oxidation of toluene than that without cerium. XRD result, it was observed that $MnO_2+CeO_2$ crystalline phases were present in the samples. For the used catalyst, a prominent feature has increased by XPS. TPR/TPO profiles of cerium-added manganese oxide on ${\nu}-Al_2O_3$ changed significantly increased at a lower temperature. The activity of $18.2 wt{\%}\;Mn+ 10.0 wt{\%}\;Ce/{\nu}-Al_2O_3$ increased at a lower temperature. The cerium added on the manganese catalysts has effects on the oxidation of toluene.

Synthesis of Alumina-Grafted Manganese Oxide Particles Using Surfactants through Coprecipitation Method and Their Thermal Properties

  • Kwon, Boseong;Park, Jun-Hwan;Jang, Seong-Cheol;Oh, Seong-Geun
    • Bulletin of the Korean Chemical Society
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    • v.34 no.12
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    • pp.3559-3564
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    • 2013
  • Alumina particles were grafted onto the surface of manganese oxide particles via the coprecipitation process using surfactant and cosurfactant. The phase of Mn/Al salts (Phase I) and the phase of precipitation agent (Phase II) were prepared in aqueous surfactant solution, separately. Phase II was added into Phase I and the reaction was performed to form the precursors of composites through hydrogen bonding between $Mn(OH)_2$ and $Al(OH)_3$ prepared by the reaction of Mn/Al salts with the precipitation agent. The alumina-grafted manganese oxide particles were obtained as a final product after calcination. The concentrations of Al salt and surfactant were varied to investigate their effects on the formation and the crystallinity of composites. In addition, the crystal structure of products could be controlled by changing the calcination temperature. Through thermal analyses, it was found that the thermal stability of manganese oxide was improved by the introduction of alumina on its surface.

Mineralogy and Genesis of Manganese Ores from the Buncheon Mine, Korea (분천광산(汾川鑛山)의 망간광석(鑛石)에 대(對)한 광물학적(鑛物學的) 및 성인적(成因的) 연구(硏究))

  • Kim, Soo Jin;Son, Byong Kook
    • Economic and Environmental Geology
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    • v.17 no.4
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    • pp.273-282
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    • 1984
  • The Buncheon manganese ore deposits occur in vein along the fault of $N20^{\circ}E$, cutting the foliation of Yulri Series. The deposits consist of primary manganese silicate ores in the deeper part and superficial manganese oxide ores near the surface. The spatial distribution of manganese oxide ores with respect to the manganese silicate ores suggests that the manganese oxide ores are the supergene oxidation product of the manganese silicate ores. Manganese silicate ores consist mainly of fine-to coarse-grained pyroxmangite with minor rhodochrosite, quartz, sulfides and chlorite. Manganese oxide ores are composed of supergene manganese oxides such as nsutite, birnessite, manganite and todorokite, and other associated minerals. Paragenetic sequence of formation of the manganese minerals are as follows: $\array{{rhodochrosite{_{\rightarrow}^o}todorokite{_{\searro}^o}}\\pyroxmangite{_{\line(10){90}}^o}{\nearro}}birnessite{_{\rightarrow}^o}nsutite{_{\rightarrow}^s}manganite$ In order to elucidate the mineralogy of the manganese minerals, microscopic, X-ray, IR spectroscopic, and thermal studies were made for manganese and associated minerals.

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The study of manganese removal mechanism in aeration-sand filtration process for treating bank filtered water (강변여과수 처리를 위한 포기-모래여과공정에서 망간제거 기작에 관한 연구)

  • Choi, Seung-Chul;Kim, Se-Hwan;Yang, Hae-Jin;Lim, Jae-Lim;Wang, Chang-Keun;Jung, Kwan-Sue
    • Journal of Korean Society of Water and Wastewater
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    • v.24 no.3
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    • pp.341-349
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    • 2010
  • It is well known that manganese is hard to oxidize under neutral pH condition in the atmosphere while iron can be easily oxidized to insoluble iron oxide. The purpose of this study is to identify removal mechanism of manganese in the D water treatment plant where is treating bank filtered water in aeration and rapid sand filtration. Average concentration of iron and manganese in bank filtered water were 5.9 mg/L and 3.6 mg/L in 2008, respectively. However, their concentration in rapid sand filtrate were only 0.11 mg/L and 0.03 mg/L, respectively. Most of the sand was coated with black colored manganese oxide except surface layer. According to EDX analysis of sand which was collected in different depth of sand filter, the content of i ron in the upper part sand was relatively higher than that in the lower part. while manganese content increased with a depth. The presence of iron and manganese oxidizing bacteria have been identified in sand of rapid sand filtration. It is supposed that these bacteria contributed some to remove iron and manganese in rapid sand filter. In conclusion, manganese has been simultaneously removed by physicochemical reaction and biological reaction. However, it is considered that the former reaction is dominant than the latter. That is, Mn(II) ion is rapidly adsorbed on ${\gamma}$-FeOOH which is intermediate iron oxidant and then adsorbed Mn(II) ion is oxidized to insoluble manganese oxide. In addition, manganese oxidation is accelerated by autocatalytic reaction of manganese oxide. The iron and manganese oxides deposited on the surface of the sand and then are aged with coating sand surface.

Applicability Test of Various Stabilizers for Heavy Metals Contaminated Soil from Smelter Area (제련소 주변 오염토양의 중금속 안정화를 위한 다양한 안정화제의 적용성 연구)

  • Jeon, Jonwon;Bae, Bumhan;Kim, Younghun
    • Journal of the Korean Geoenvironmental Society
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    • v.11 no.11
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    • pp.63-75
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    • 2010
  • There are several remediation technologies for heavy metal contaminated soils but increasing cost limits the application of the technology if the contaminated area is large. Therefore, stabilization, which blocks the release of heavy metals or makes slow the release, is one of the applicable technology for the heavy metal contaminated soil. Current study is an applicability test for a smelter area with various stabilizer such as magnetite, hematite, zeolite-A, zeolite-X, zeolite-Y, zinc oxide, calcium oxide, carbon trioxide, manganese oxide, manganese dioxide, fish bone, sodium phosphate. The soil contaminated with arsenic, lead, copper, nickel, and zinc could not be stabilized only one stabilizer which is known to have stability for certain metal. Many of the stabilizer works for a few metal but not all of the heavy metal. In several cases, stabilizers increase the release of the other metals while they stabilize some metals. In general, the stabilizing efficiency was increased with time. For Ni, Pb, calcium oxide, carbon trioxide, manganese oxide had good stabilizing effect in water extractable portion. For Cu, manganese oxide, zeolite showed good results especially in the exchangeable portion of the sequential extraction. For As, magnetite had good ability but most of the metal oxide which showed good result for other heavy metals increased with the release of As. Current study suggest that multiple stabilizers are needed for the contaminated soil and dose of the stabilizer and stabilizing time should be carefully considered for the soil contaminated with various metals.