• Title/Summary/Keyword: Manganese precipitation

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Precipitation of Manganese in the p-Xylene Oxidation with Oxygen-Enriched Gas in Liquid Phase

  • Jhung, Sung-Hwa;Park, Youn-Seok
    • Bulletin of the Korean Chemical Society
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    • v.23 no.3
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    • pp.369-373
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    • 2002
  • The liquid phase oxidation of p-xylene has been carried out with oxygen-enriched gas, and the manganese component was precipitated probably via over-oxidation to $Mn^{4+}$. The precipitation increased with rising oxygen concentration in the reaction gas and occurred mainly in the later part of the oxidation. The activity of the reaction decreased, and the blackening of the product and side reactions to carbon dioxide increased with the degree of precipitation. Precipitation can be decreased with the addition of metal ions, such as cerium, chromium and iron.

A Study on the critical cooling rate to avoid carbide precipitation in austenitic manganese steels during quenching (고망간 주강품의 열처리시 탄화물 석출방지를 위한 임계 냉각속도에 관한 연구)

  • Kim, Jeong-Tae;Kwahk, Si-Young;Choi, Jeong-Kil;Hong, Chun-Pyo
    • Journal of the Korean Society for Heat Treatment
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    • v.12 no.3
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    • pp.206-214
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    • 1999
  • The effect of cooling rate on carbide precipitation during quenching of austenitic manganese steel was investigated by optical microscopy, image analyzer and numerical analysis. A computer program based on the finite difference method for analyzing heat treatment processes was developed in order to evaluate cooling rates and the possibility of carbide precipitation during quenching. The area ratio of carbide precipitated in the austenite matrix was measured by the image analyzer, and used to determine the critical point of carbide precipitation. Temperature-dependent critical cooling rates at the critical points were calculated using the present simulation program, The calculated results showed a good agreement with the experimental ones.

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Mechanisms of Formation of Manganese Oxide Minerals in the Manganese Deposits of the Taebaeg Mt. Region, Korea (太白山地區 망간鑛床에 있어서 酸化망간鑛物의 生成機構)

  • Kim, Soo-Jin;Cho, Hyen-Goo;Choi, Hun-Soo
    • Journal of the Mineralogical Society of Korea
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    • v.5 no.1
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    • pp.1-5
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    • 1992
  • The manganese oxide ores in the Taebaeg Mt. region have been formed by supergene weathering of the primary hydrothermal or sedimentary manganese ores. The supergenesis is controlled by the physical chemistry of the descending groundwater in the supergene zone. It includes the fundamental geological processes, such as dissolution, oxidation, transportation, precipitation, and crystallization and recrystallization. However, the fundamental mechanisms for the formation of various manganese oxide minerals are 1) replacement, 2) precipitation from solution, and 3) solid state crystallization and recrystallization. Various textures and structures of ores have been formed by these processes. Detailed paragenetic sequence of manganese oxide minerals in each ore deposit is summerized.

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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.

Synthesis of Manganese Hydrogen Phosphate Hydrate by Controlled Double-jet Precipitation (더블제트 침전법에 의한 제이인산망간염 수화물의 새로운 합성 방법)

  • Kim, Won-Seok;Kang, Yong;Kim, Yeong-Cheol
    • Applied Chemistry for Engineering
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    • v.19 no.1
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    • pp.66-72
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    • 2008
  • Manganese hydrogen phosphate hydrate, $MnHPO_4{\cdot}2.25H_2O$, is a major constituent of the pre-conditioning compositions for the manganese phosphate coating treatment over carbon steel substrate. This compound is conventionally produced by the synthesis in the aqueous solution process followed by the filtration and drying processes and a series of size reduction and classification processes in dry state. However, it is evident that the conventional process is neither environment-friendly nor cost-effective. In this work, a new process principle was examined based on the controlled double-jet precipitation technology to produce the manganese chemical product of fairly uniform particle size distribution in an aqueous solution media. The effects of stabilizing agents were comparatively studied by the scanning electron microscope analysis in a uniformity point of view of the resulting particle size. Polyvinylpyrrolidone and Gum Arabic were excellent in controlling the crystal growth step, resulting in fairly uniform size distributions of the particles from the controlled double-jet process.

Effect of Mn and S Contents on Edge Cracking of Low Carbon Steels in Mini-Mill Process (미니밀공정 중 저탄소강의 에지크랙에 미치는 Mn 및 S의 영향)

  • 곽재현;정진환;조경목
    • Transactions of Materials Processing
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    • v.9 no.1
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    • pp.66-71
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    • 2000
  • The present study tackles the metallurgical subjects involving the thin slab-direct hot rolling process, i.e. mini-mill process. In order to clarify the effect of chemical composition of steel and MnS precipitation behaviors on the development of edge cracking during hot rolling, the content of manganese and sulfur in low carbon steel was varied and the isothermal treatment prior to roughing was applied. Edge cracking during roughing in the hot-rolling process of mini-mill was effectively prevented by means of the isothermal treatment at 115$0^{\circ}C$ for 5 minutes in the 0.4% manganese steel containing sulfur lower than 0.013%. With the increase in manganese content in low carbon steel, coarser MnS developed. The edge cracking index which denotes the total length of edge crack per unit edge-length of rolled specimens was proposed in this paper. It was found that the edge cracking index linearly decreased with the increase in the ratio of MnS.

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High Luminance $Zn_2SiO_4$:Mn phosphors Prepared by Homogeneous Precipitation Method

  • Jung, Ha-Kyun;Sohn, Kee-Sun;Sung, Bu-Young;Park, Hee-Dong
    • Journal of Information Display
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    • v.1 no.1
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    • pp.35-41
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    • 2000
  • Manganese-doped $Zn_2SiO_4$ phosphors well known as a green emitter with high luminescence efficiency were prepared by the homogeneous precipitation method, and their photoluminescence properties under vacuum-ultraviolet (VUV) excitation were investigated. $Zn_2SiO_4$:Mn phosphors obtained by this method have exhibited a high luminance of property and a spherical shape of particles. In particular, the green emission intensity of zinc orthosilicate prepared as containing around 2 mole% of manganese was much stronger than that of the commercial $Zn_2SiO_4$:Mn phosphor, while the decay time was longer. However, addition of $Al^{3+}$ and $Li^+$ into $Zn_2SiO_4$:Mn composition has significantly diminished the decay time of the phosphor without much degradation of the emission intensity.

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Synthesis and Electrochemical Characterization of Silica-Manganese Oxide with a Core-shell Structure and Various Oxidation States

  • Ryu, Seong-Hyeon;Hwang, Seung-Gi;Yun, Su-Ryeon;Cho, Kwon-Koo;Kim, Ki-Won;Ryu, Kwang-Sun
    • Bulletin of the Korean Chemical Society
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    • v.32 no.8
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    • pp.2683-2688
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    • 2011
  • Silica-manganese oxides with a core-shell structure were synthesized via precipitation of manganese oxides on the $SiO_2$ core while varying the concentration of a precipitation agent. Elemental analysis, crystalline property investigation, and morphology observations using low- and high-resolution electron microscopes were applied to the synthesized silica-manganese oxides with the core-shell structure. As the concentration of the precipitating agent increased, the manganese oxide shells around the $SiO_2$ core sequentially appeared as $Mn_3O_4$ particles, $Mn_2O_3+Mn_3O_4$ thin layers, and ${\alpha}-MnO_2$ urchin-like phases. The prepared samples were assembled as electrodes in a supercapacitor with 0.1 M $Na_2SO_4$ electrolyte, and their electrochemical properties were examined using cyclic voltammetry and charge-discharge cycling. The maximum specific capacitance obtained was 197 F $g^{-1}$ for the $SiO_2-MnO_2$ electrode due to the higher electronic conductivity of the $MnO_2$ shell compared to those of the $Mn_2O_3$ and $Mn_3O_4$ phases.

Characterization of Pseudomonas sp. MN5 and Purification of Manganese Oxidizing Protein (Pseudomonas sp. MN5의 특성과 망간산화단백질 정제)

  • Lee, Seung-Hui;Park, Kyeong-Ryang
    • Journal of Life Science
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    • v.18 no.1
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    • pp.84-90
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    • 2008
  • Bacterial colonies which were able to oxidize the manganese were isolated from six soil samples in Byungchon area. Among them, one bacterial strain was selected for this study based on its high manganese oxidation activity. This selected bacterial strain was identified as Pseudomonas sp. MN5 through physiological-biochemical test and analysis of its 16s rRNA sequence. This selected bacterial strain was able to utilize fructose and maltose, but they doesn't utilizing various carbohydrates as a sole carbon source. Pseudomonas sp. MN5 showed a very sensitive to antibiotics such as kanamycin, chloramphenicol, streptomycin and tetracycline, but a high resistance up to mg/ml unit to heavy metals such as lithium, manganese and barium. Optimal manganese oxidation condition of Pseudomonas sp. MN5 was pH 7.5 and manganese oxidation activity was inhibited by proteinase K and boiling treatment. The manganese oxidizing protein produced by Pseudomonas sp. MN5 was purified by ammonium sulfate precipitation, HiTrap Q FF anion exchange chromatography and G3000sw $_{XL}$ gel filtration chromatography. By sodium dodecyl sulfate polyacrylamide gel electrophoresis, three manganese oxidizing protein with estimated molecular weights of 15 kDa, 46.7 kDa and 63.5 kDa were detected. Also, it was estimated that manganese oxidizing protein produced by Pseudomonas sp. MN5 were a kind of porin proteins through internal sequence and N-terminal sequence analysis.

Determination of Polonium Nuclides in a Water Sample with Solvent Extraction Method

  • Lee, M.H.;Lee, C.H.;Song, K.;Kim, C.K.;Martin, P.
    • Bulletin of the Korean Chemical Society
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    • v.31 no.9
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    • pp.2488-2492
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    • 2010
  • A method is described for the determination of the Po nuclides in a water sample. After the Po nuclides were purified from interfering elements in a water sample using a manganese dioxide precipitation followed by a solvent extraction method, the Po nuclides were deposited onto the silver plate. A large volume of the water sample was effectively pretreated with manganese dioxide precipitation method. To determine the optimum conditions for plating Po, the effects of the pH, volume, temperature and time on the Po deposition were investigated in hydrochloric acid solution. The investigated determination method of Po nuclides with solvent extraction was applied to a tap water sample.