• Title, Summary, Keyword: hematite

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Effects of Hydrothermal Conditions on the Morphology of Hematite Particles (Hematite 입자형상에 미치는 수열반응조건의 영향)

  • 변태봉;손진군
    • Journal of the Korean Ceramic Society
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    • v.31 no.2
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    • pp.117-128
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    • 1994
  • Hematite particles were obtained by hydrothermal reaction of ferric hydroxide in the presence of small amount of citric acid which is acted as crystal growth controller. The effects of hydrothermal reaction condition son the morphology and crystal structure of powder were investigated using X-ray, TEM and FT-IR. Ellipsoidal or rectangular hematite particles were formed in the range of pH 10.75~11.75 as initial basicity of reactants and 3$\times$10-5 ~9$\times$10-5 mol as citric acid content. Crystallization of hematite was inhibited in the range of pH9. 0~10.5 and above citric acid content of $1.5\times$10-4 mol. Hematite particle length and aspect ratio were decreased gradually with increasing of citric acid content. Hematite particles formed at 14$0^{\circ}C$ exhibited particle properties with the length of 0.7 ${\mu}{\textrm}{m}$ and aspect ratio of 8. Hematite particles having a good acicular-type were not obtained above 22$0^{\circ}C$.

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Growth of Hematite by Using Ultrasonic Nebulizer Pyrolysis for Use in a Photoelectrochemical Electrode

  • Ha, Jin-Wook;Ryu, Hyukhyun;Lee, Sang-Jin;Lee, Won-Jae
    • Journal of the Korean Physical Society
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    • v.70 no.8
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    • pp.802-808
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    • 2017
  • In this study, a hematite photoelectrode was grown on a fluorine-doped tin-oxide substrate by using the ultrasonic nebulizer pyrolysis method. We analyzed the morphological, structural, optical, electrical, and photoelectrochemical properties of hematite samples grown at different temperatures. Field emission scanning electron microscopy, X-ray diffraction, ultraviolet-visible spectroscopy and electrochemical impedance spectroscopy with a 3-electrode potentiostat, were used to characterize hematite. The hematite sample grown at $300^{\circ}C$ had the highest crystallinity and the largest excited minority carrier density. Consequently, the hematite grown at $300^{\circ}C$ had the highest photocurrent density of $0.39mA/cm^2$ at 0.55 V (vs. saturated calomel electrode (Sat. 3.3 M KCl)).

Reduction of nitrate in groundwater by hematite supported bimetallic catalyst

  • Hamid, Shanawar;Lee, Woojin
    • Advances in environmental research
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    • v.5 no.1
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    • pp.51-59
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    • 2016
  • In this study, nitrate reduction of real groundwater sample by 2.2%Cu-1.6%Pd-hematite catalyst was evaluated at different nitrate concentrations, catalyst concentrations, and recycling. Results show that the nitrate reduction is improved by increasing the catalyst concentration. Specific nitrate removal by 2.2%Cu-1.6%Pd-hematite increased linearly with the increase of nitrate concentration showing that the catalyst possesses significantly higher reduction capacity. More than 95% nitrate reduction was observed over five recycles by 2.2%Cu-1.6%Pd-hematite with ~56% nitrogen selectivity in all recycling batches. The results from this study indicate that stable reduction of nitrate in groundwater can be achieved by 2.2%Cu-1.6%Pd-hematite over the wide range of initial nitrate inputs.

Utilization of Mineral Oxides to Attenuate Mn-EDTA and Fluoride (산화광물을 이용한 수중의 망간-EDTA, 불소 제거)

  • 현재혁;남인영
    • Journal of Korea Soil Environment Society
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    • v.1 no.2
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    • pp.51-60
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    • 1996
  • Removal of Mn-EDTA complex and fluoride by use of hematite and ferrite, which are the by-product to be disposed of as industrial wastes, was investigated. For the comparison of removal rate, Na-bentonite known as excellent absorbent of inorganic contaminants was included in the experiments. As the results of batch mode experiments, for manganese, ferrite-A revealed 48∼65% of removal capacity, ferrite-B 46∼57%, hematite 17∼26%, while Na-bentonite showed 10∼23% of removal, depending on the initial concentration. Meanwhile, in case of fluoride : hematite revealed 53 ∼63% of removal : ferrite-A 54∼63 %, while ferrite-B did 20∼38 %. From the results, it can be postulated that the capacity of hematite and ferrite to attenuate inorganic pollutants, especially when they form complex ions, is superior to that of Na-bentonite. Consequently, the mixing of such oxide minerals with Na-bentonite will reinforce the function of Na-bentonite, especially in the undergroud liner aspect.

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나노 크기 적철석 입자 피복 모래를 이용한 지하수내 비소 3가와 5가의 제거 기술 개발

  • 고일원;이철효;이상우;김주용;김경웅
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • pp.78-82
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    • 2003
  • Development of hematite-coated sand was evaluated for the application of the PRB (permeable reactive barrier) in the arsenic-contaminated subsurface of the metal mining areas. The removal efficiency of As(III) and As(V), the effect of anion competition and the capability of arsenic removal in the flow system were investigated through the experiments of adsorption isotherm, arsenic removal kinetics against anion competition and column removal. Hematite-coated sand followed a linear adsorption isotherm with high adsorption capacity at low level concentrations of arsenic (< 1.0 mg/l). When As(III) and As(V) underwent adsorption reactions in the presence of anions (sulfate, nitrate and bicarbonate), sulfate caused strong inhibition of arsenic removal, and bicarbonate and nitrate caused weak inhibition due to specific and nonspecific adsorption onto hematite, respectively. In the column experiments, high content of hematite-coated sand enhance the arsenic removal, but the amount of the arsenic removal decreased due to the higher affinity of As(V) than As(III) and reduced adsorption kinetics in the flow system, Therefore, the amount of hematite-coated sand, the adsorption affinity of arsenic species and removal kinetics determined the removal efficiency of arsenic in the flow system. arsenic, hematite-coated sand, permeable reactive barrier, anion competition, adsorption.

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Comparative Study of $Cu^{2+}$ Adsorption of Goethite, Hematite and Kaolinite : Mechanistic Modeling Approach

  • 정진호;조영환;한필수
    • Bulletin of the Korean Chemical Society
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    • v.19 no.3
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    • pp.324-327
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    • 1998
  • The mechanisms of Cu2+ adsorption onto goethite, hematite and kaolinite are different. Goethite and hematite showed a similar adsorption behavior (ionic-strength independent), but kaolinite gave somewhat different result (ionic-strength dependent). These experimenal results were successfully simulated using a surface complexation model, TLM, which defines the inner- or outer-sphere complex. The chemical nature of Cu2+ adsorption onto kaolinite was qualitatively identified by EPR spectroscopy.

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Characterization of Hematite Red Pigment for Porcelain Surface Coating (Porcelain의 표면코팅을 위한 Hematite 적색 안료의 특성)

  • Kim, Kyung-Nam;Park, Hyun;Won, Il-An
    • Korean Journal of Materials Research
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    • v.27 no.4
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    • pp.206-210
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    • 2017
  • In this study, an ${\alpha}-Fe_2O_3$ (hematite) coated porcelain plate was sintered in a temperature range from $1100^{\circ}C$ to $1250^{\circ}C$ using ferrous sulfate. The specimens were investigated by X-ray diffractometer (XRD), scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), and UV-visible spectrophotometer. It was confirmed that ${\alpha}-Fe_2O_3$ (hematite) was densely fused to the surface at several tens of ${\mu}m$, the ${\alpha}-Fe_2O_3$ (hematite) was in the form of thin platelet and polyhedra, and no other compounds appeared in the sintering process. In the specimen coated with ${\alpha}-Fe_2O_3$ (hematite), the reflectance spectra show a red absorption band of 560-650 nm. The $L^*$ value decreased from 53.18 to 46.94 with the firing temperature. The values of $a^*$ and $b^*$ were at 19.03 and 15.25 at $1100^{\circ}C$ and gradually decreased with increasing temperature; these values decreased rapidly at $1250^{\circ}C$ to 11.54 and 7.98, respectively. It is considered that the new phases are formed by the phase transition of the porcelain plate (clay), and thus the $a^*$ and $b^*$ values are greatly influenced.

Changes in Physical and Chemical Properties of Sandy Loam Soils by Hematite Addition (적철석 첨가에 의한 사질양토의 물리·화학적 특성변화)

  • Kim, Jae Gon;Dixon, Joe B.;Moon, Hi-Soo
    • Economic and Environmental Geology
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    • v.31 no.4
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    • pp.291-296
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    • 1998
  • Pedogenic hematite is a well known agent for sink of pollutants and nutrients and for aggregation of particles in soils. Changes in physical and chemical properties of two sandy loam soils (Anahuac and Crowley soils) from the Southern Coastal Plain, the United States of America, were tested after adding finely ground crystalline hematite prepared for drilling fluid weighting material. There was an increase in hydraulic conductivity (HC) of the soils with addition of up to 3% by weight of hematite but a decrease in HC with addition of more hematite. The aggregate stability (AS) of the soils was not affected by adding hematite. Anahuac soil with higher content of organic matter and lower sodium adsorption ratio (SAR) had higher values of HC and AS than Crowley soil. Adding hematite also resulted in a slight increase in zinc (Zn) adsorption by the soils, but had no influence on the adsorption of phosphate.

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The Effects on the Traditional Processing Operation of Hematite Medicinal Mineral through Heating and Quenching in Vinegar (전통적 초쉬법에 의한 적철석 약광물의 약재가공 효과)

  • Hwang, Jeong
    • Journal of the Korean earth science society
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    • v.29 no.7
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    • pp.523-530
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    • 2008
  • The phase changes and variations of elemental contents in hematite medicinal mineral were investigated by a traditional processing operation including heating and quenching in vinegar. Hematite was processed at $650^{\circ}C$ and $900^{\circ}C$ through at least 5 processing cycles. Metal extraction tests in water were carried out with the processed hematite. Heating and quenching in vinegar could not change the phase of hematite. The effect of this traditional method was not clear because there were no variational trends between extracted elements and the number of processing cycles at $650^{\circ}C$ and $900^{\circ}C$. However, the traditional processing operation of heating and quenching in vinegar was very effective to change the hematite mineral towards soft and easily crushing medicinal material.

Preparation of Iron Oxide Thin Films by Vacuum Evaporation Method and Its Electrical Properties (진공증착법에 의한 산화철박막의 제조 및 전기적특성)

  • 조경형;오재희
    • Journal of the Korean Ceramic Society
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    • v.22 no.6
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    • pp.87-93
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    • 1985
  • The hematite the magetite and the maghemite thin film were prepared by oxidation and reductino of the vaccum-evaporated iron thin film. Interre;atoms between film preparation process and the electrical properties were investigated. At room temperature the electrical conductivity of the iron the hematite the magnetite and the maghemite thin film were $1{\times}10^4\Omega^{-1}cm^{-1}$, 2{\times}10^{-5}\Omega^{-1}cm^{-1}$, $3{\times}10^{-5}\Omega^{-1}cm^{-1}$, and $4{\times}10^{-5}\Omega^{-1}cm^{-1}$, resp-ectively. The surface of each thin film was dense and homogeneous. At the temperature that the iron thin film was converted into the hematite thin film the electrical conductivity decreased rapidly and the electrical con-ductivity of the hematite thin film increased as temperature increased. The hematite thin film was reduced to the magnetite thin film in H2 atmosphere. The electrical conductivity decreased rapidly at the temperature that the maghemite thin film is formed by oxidation of the magnetite thin film and the electrical conductivity of the maghemite thin film increased as temperature increased.

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