• Title, Summary, Keyword: pyrolusite

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The Study of Analytical Chemistry of the Modification of Manganese Dioxide (III). Quntitative Determination of Pyrolusite by Differential Heating Curves (변태 이산화망간의 분석 화학적 연구 (제3보) 시차 열곡선에 의한 Pyrolusite의 정량)

  • Kim Chan-Ho
    • Journal of the Korean Chemical Society
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    • v.17 no.2
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    • pp.122-125
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    • 1973
  • A study on the endothermic peak of transformation of the pyrolusite was made by using differential thermal curves for analytical reproducibility, and it was done in quantity on range from 50 mg to 450 mg of pyrolusite species. The separation of ${\alpha}-MnO_2$ peak was impossible due to the overlapping between $\alpha$ and pyrolusite peaks, and the pyrolusite was determined among the species, ${\gamma}-MnO_2$ and ${\delta}-MnO_2$, with an error ranging from $5{\%}$ to $10{\%}$.

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Dechlorination of the Fungicide Chlorothalonil by Zerovalent Iron and Manganese Oxides (Zerovalent Iron 및 Manganese Oxide에 의한 살균제 Chlorothalonil의 탈염소화)

  • Yun, Jong-Kuk;Kim, Tae-Hwa;Kim, Jang-Eok
    • The Korean Journal of Pesticide Science
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    • v.12 no.1
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    • pp.43-49
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    • 2008
  • This study is conducted to determine the potential of zerovalent iron (ZVI), pyrolusite and birnessite to remediate water contaminated with chlorothalonil. The degradation rate of chlorothalonil by treatment of ZVI, pyrolusite and birnessite was much higher in low condition of pH. Mixing an aqueous solution of chlorothalonil with 1.0% (w/v) ZVI, pyrolusite and birnessite resulted in 4.7, 13.46 and 21.38 hours degradation half-life of chlorothalonil, respectively. Dechlorination number of chlorothalonil by treaonent of ZVI, pyrolusite and birnessite exhibited 2.85, 1.12 and 1.09, respectively. Degradation products of chlorothalonil by teartment of pyrolusite and birnessite were confirmed as trichloro-1,3-dicyanobenzene and dichloro-1,3-dicyanobenzene which were dechlorinated one and two chlorine atoms from parent chlorothalonil by GC-mass. Degradation products of chlorothalonil by ZVI were identified not only as those by pyrolusite and birnessite but as further reduced chloro-1,3-dicyanobenzene and chlorocyanobenzene.

Kinetics of Chromium(III) Oxidation by Various Manganess Oxides (망간 산화물에 의한 3가 크롬의 산화)

  • Chung, Jong-Bae;Zasoski, Robert J.;Lim, Sun-Uk
    • Applied Biological Chemistry
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    • v.37 no.5
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    • pp.414-420
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    • 1994
  • Birnessite, pyrolusite and hausmannite were synthesized and tested for the ability to oxidize Cr(III) to Cr(VI). These oxides differed in zero point of charge, surface area, and crystallinity. The kinetic study showed that Cr(III) oxidation on the Mn-oxide surface is a first-order reaction. The reaction rate was various for different oxide at different conditions. Generally the reaction by hausmannite, containing Mn(III), was faster than the others, and oxidation by pyrolusite was much slower. Solution pH and initial Cr(III) concentration had a significant effect on the reaction. Inhibited oxidation at higher pH and initial Cr(III) concentration could be due to the chance of Cr(III) precipitation or complexing on the oxide surface. Oxidations by birnessite and hausmannite were faster at lower pH, but pyrolusite exhibited increased oxidation capacity at higher pH in the range between 3.0 and 5.0. Reactions were also temperature sensitive. Although calculated activation energies for the oxidation reactions at pH 3.0 were higher than the general activation energy for diffusion, there is no experimental evidence to suggest which reaction is the rate limiting step.

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Chromium Speciation in Cr(III) Oxidation by Mn-Oxides: Relation to the Oxidation Mechanism (망간 산화물에 의한 3가 크롬의 산화반응에 미치는 크롬 화학종들의 영향)

  • Chung, Jong-Bae
    • Applied Biological Chemistry
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    • v.41 no.1
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    • pp.89-94
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    • 1998
  • Various Mn-oxides can oxidize Cr(III) to Cr(VI). Behaviors of chromium species in the oxidation system, especially on the oxide surface, are expected to control the reaction. During Cr(III) oxidation by birnessite and pyrolusite, Cr species in the reaction system were determined to elucidate their effects on the oxidation. Capacities of Cr oxidation of the two Mn-oxides were quite different. Solution pH and initial Cr(III) concentration also had significant effects on the Cr(III) oxidation by Mn-oxides. Chromium oxidation by pyrolusite was less than 5% of the oxidation by birnessite. The high crystallinity of pyrolusite could be one of the reasons and the difficulty of Cr (III) diffusion to the positive pyrolusite surface and Cr(VI) and Cr(III) adsorption seems to be other controlling factors. At pH 3, adsorption or precipitation of Cr species on the surface of birnessite were not found. Small amount of Cr(VI) adsorption was found on the surface of pyrolusite, but arty Cr precipitation on the oxide surface was not found. Therefore Cr(III) oxidation at pH 3 seems to be controlled mainly by the characteristics of Mn-oxides. Chromiun oxidation by Mn-oxides is thermodynamically more favorable at higher solution pH. However as solution pH increased Cr oxidation by birnessite was significantly inhibited. For Cr oxidation by pyrolusite, as pH increased the oxidation increased, but as Cr(III) addition increased the reaction was inhibited. Under these conditions some unidentified fraction of Cr species was found and this fraction is considered to be Cr(III) precipitation an the oxide surface. Chromium(III) precipitation on the oxide surface seems to play an important role in limiting Cr(III) oxidation by armoring the reaction surface on Mn-oxides as well as lowering Cr(III) concentration available for the oxidation reaction.

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Reduction of Carbon Tetrachloride at Different pHs in Pyrolusite Catalyzed Fenton-like reduction (Pyrolusite으로 촉매화된 펜톤유사반응에서 pH변화에 따른 사염화탄소(CT)의 환원분해)

  • 김상민;공성호;김용수;허정욱
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • pp.231-234
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    • 2002
  • According to recent investigations regarding Fenton-like reaction, it was reported that there was a key factor to decompose organic materials by not only the hydoroxyl radical but also several reductants which were superoxide anion and hydroperoxide anion. This research was focused on an investigation of the decomposition of carbon tetrachloride(CT) by reductants which were generated by pyrolusite with hydrogen peroxide. Generally, CT decomposition rate increased with raising pH values. Especially,, CT was decomposed over 60 percent by 10,000 ppm of hydrogen peroxide within 10 minutes in neutral condition. In addition, the decomposition of chlorinated compounds would be accelerated in alkaline condition, even with low concentration of hydrogen peroxide.

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The Study of Analytical Chemistry of the Modification of Manganese Dioxide (Report Two). Quantitative Determination of ${\gamma}$-Manganese Dioxide by Differential Heating Curves (變態二酸化 망간의 分析化學的 硏究 (第二報). 示差熱曲線에 依한 ${\gamma}-MnO_2$의 定量法)

  • Chan Ho Kim
    • Journal of the Korean Chemical Society
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    • v.15 no.5
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    • pp.241-245
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    • 1971
  • Endothermic peak of transformation of ${\gamma}-MnO_2$ was obviously shown by differential heating curve in the present study, and the transformation temperature was different from other modification. ${\gamma}-MnO_2$ carried out to analyze exclusively, by means of the half area method in corresponding endothermic peak of differential heating curve. ${\alpha}-\;and\;{$beta}-MnO_2$ (Pyrolusite) containing in sample about 75% is interfered about ${\pm}$10% of the relative error, and while those of below 50% is interfered about ${\pm}$5%.

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Microstructure of Nanocrystalline Electrolytic $MnO_2$ (EMD) (Nanocrystalline Electrolytic $MnO_2$ (EMD)의 미세구조 연구)

  • ;Anqiang He;Arthur H. Heuer
    • Korean Journal of Crystallography
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    • v.14 no.2
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    • pp.79-83
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    • 2003
  • The microstructure of bulk electrolytic MnO₂ (EMD) was studied using x-ray diffraction and transmission electron microscopy (TEM). The bulk sample showed a typical powder x-ray diffraction pattern of EMD materials. TEM study showed that the structure of EMD is present at two length scales;grains, ∼0.2 ㎛ in diameter, and ∼10 nm crystallites within the grain. The electron beam microdiffraction study revealed that each grain is an assemblage of multiphase with a common crystallographic orientation, and_that ∼50% of the crystallites are Ramsdellite, ∼30% are ε-MnO₂, and ∼15% are Pyrolusite. The {1120}peak located at about 67° in powder XRD pattern as well as a high-resolution electron microscope (HREM) image of (0001) plane support the existence of ε-MnO₂ phase.

Mineralogy and Genesis of Manganese Ores from the Eosangcheon Mine, Korea (어상주광산(魚上川鑛山)의 망간광석(鑛石)에 대(對)한 광물학적(鑛物學的) 및 성인적연구(成因的硏究))

  • Kim, Soo Jin;Kim, Seong Hoon
    • Economic and Environmental Geology
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    • v.15 no.4
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    • pp.205-219
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    • 1982
  • The Eosangcheon manganese ore deposits occur as supergene weathering deposits along quartz porphyry dikes developed in the Ordovician Heungweolri dolomite and Samtaesan limestone formations. The manganese ores are composed of manganese oxide minerals and associated other minerals. Rancieite and todorokite are abundantly found, and birnessite, nsutite, pyrolusite and chalcophanite are found in minor quantities. Associated other minerals are calcite, gypsum, goethite, lepidocrosite, quartz, and sericite. Microscopic, chemical, X-ray powder diffraction, infrared absorption spectroscopic and differential thermal analyses have been made for manganese oxide minerals and associated other minerals. The relationship of birnessite and rancieite was studied by means of X-ray powder diffraction and infrared absorption spectroscopic analyses. It is assumed that these minerals are closely related to each other in crystal structure, but separate species. The manganese oxide minerals were formed mainly by replacement, precipitation from solution, and recrystallization in the supergene weathering environment. The trend of formation of manganese oxide minerals is: (Rhodochrosite)-(todorokite)-(birnessite, rancieite)-(nsutite, pyrolusite, chalcophanite).

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Mineralogy and Genesis of Manganese Ores from the Jangseong Manganese Deposits, Korea (장성(長省) 망간 광석(鑛石)에 대(對)한 광물학적(鑛物學的) 및 성인적(成因的) 연구(硏究))

  • Kim, Soo Jin;Yoon, Hyeon
    • Economic and Environmental Geology
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    • v.19 no.4
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    • pp.265-276
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    • 1986
  • The Jangseong manganese deposits are supergene oxidation products of hydrothermal rhodochrosite. The manganese ore veins are developed in the Dongjeom Quartzite, and Dumudong Formation. The deposits consist of primary manganese carbonate ores in the deeper part and manganese oxide ores near the surface. The manganese carbonate ores are composed of rhodochrosite and small amounts of sulfides. The manganese oxide ores are composed of birnessite, nsutite, todorokite, chalcophanite, and pyrolusite. Microscopic, X-ray diffraction, infrared, thermal and EPMA analyses have been made for manganese oxide minerals and other associated minerals. The manganese minerals were formed in the following sequence. Rhodochrosite$\rightarrow$birnessite$\rightarrow$todorokite$\rightarrow$nsutite-pyrolusite. Thermochemical properties of chalcophanite were studied by methods of X-ray powder diffraction, infrared absorption spectroscopic analysis and dehydration experiments. Chalcophanite changes to $4.8{\AA}$ phase at $90{\sim}110^{\circ}C$. Chemical analyses show that the manganese oxide minerals generally have high concentration in Zn.

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Oxidation of Chromium(III) to Chromium (VI) by Manganese Oxides : Variability in Mineralogy

  • Kim, Jae Gon
    • Proceedings of the Petrological Society of Korea Conference
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    • pp.25-29
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    • 1999
  • Manganese (Mn) oxides in soils and sediments differ in structure and composition. The influence of that diversity on the chromium (Cr) oxidation is the subject of this report. Oxidation of Cr(III) to Cr(VI) by coarse clay size Mn oxides (synthetic pyrolusite and natural lithiophorite, todorokite, and bimessite) was studied. Chromium oxidation by Mn oxides was initially fast and followed by a slow reaction. More Cr was oxidized by the Mn oxides at lower pH and higher initial Cr(III) concentration in solution. Birnessite had the highest chromium oxidation capacity per unit external surface area (COCUESA) and lithiophorite had the lowest COCUESA. The kinetics of Cr oxidation and COCUESA of Mn oixdes were apparently controlled by reactivity of surface Mn, mineralogy, and solution properties (pH and Cr(III) concentration).

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