• Title, Summary, Keyword: $CaCO_3$ 제조

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Preparation and Electrochemical Properties of Pr1-x (Sr, Ca)xCoO3 Cathode Materials for Zinc Air Batteries (아연공기전지용 Pr1-x (Sr, Ca)xCoO3 양극촉매 제조 및 전기화학적 특성)

  • Heo, Sang-Hun;Eom, Seung-Wook;Kim, Hyun-Soo
    • Journal of the Korean Electrochemical Society
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    • v.12 no.4
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    • pp.342-348
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    • 2009
  • Zn/Air secondary batteries are high energy density type and environment-friendly. Also, they have safer properties than batteries of other type by low manufacturing cost and using the electrolyte solution. But, they have a weak concerning large output discharge. Oxygen evolution reaction(OER) and oxgen reduction reaction(ORR) in aqueous solution make a result of a decrease of cell efficiency and life span. Therefore, to minimize the voltage drop from between OCV and charge/discharge voltage is key point. The problem should be solved through developing catalysts of high efficiency. In this study, we synthesized $Pr_{1-x}(Sr,\;Ca)_x\;CoO_3$ powders by citric method and then measured physical characteristics of each powder by XRD, SEM, TGA etc. We examined its electrochemical properties by the cathodic polarization, anodic polarization and cyclic voltammogram. We achieved results that new catalysts showed better performances than existing $La_{1-x}Sr_xCoO_3$, $La_{1-x}Ca_xCoO_3$, ect. catalysts prepared in our lab.

Study on the Interaction of U(VI) Species With Natural Organic Matters in KURT Groundwater (KURT 지하수의 천연 유기물질과 6가 우라늄 화학종의 상호작용에 관한 연구)

  • Jung, Euo Chang;Baik, Min Hoon;Cho, Hye-Ryun;Kim, Hee-Kyung;Cha, Wansik
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.15 no.2
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    • pp.101-116
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    • 2017
  • The interaction of U(VI) (hexavalent uranium) species with natural organic matter (NOM) in KURT (KAERI Underground Research Tunnel) groundwater is investigated using a laser spectroscopic technique. The luminescence spectra of the NOM are observed in the ultraviolet and blue wavelength regions by irradiating a laser beam at 266 nm in groundwater. The luminescence spectra of U(VI) species in groundwater containing uranium concentrations of $0.034-0.788mg{\cdot}L^{-1}$ are measured in the green-colored wavelength region. The luminescence characteristics (peak wavelengths and lifetime) of U(VI) in the groundwater agree well with those of $Ca_2UO_2(CO_3)_3(aq)$ in a standard solution prepared in a laboratory. The luminescence intensities of U(VI) in the groundwater are weaker than those of $Ca_2UO_2(CO_3)_3(aq)$ in the standard solution at the same uranium concentrations. The luminescence intensities of $Ca_2UO_2(CO_3)_3(aq)$ in the standard solution mixed with the groundwater are also weaker than those of $Ca_2UO_2(CO_3)_3(aq)$ in the standard solution at the same uranium concentrations. These results can be ascribed to calcium-U(VI)-carbonate species interacting with NOM and forming non-radiative U(VI) complexes in groundwater.

Crystal growth of gypsum by neutralization reaction of waste sulphuric acid using sludge and dust in Pohang Iron & Steel plant (포항제철(주) 슬러지와 Dust를 이용한 폐황산 중화반응에서 얻어진 석고의 결정성장연구)

  • Ji whan Ahn;Ka yeon Kim;Hwan Kim;Sang bop Lee;Eu dug Hwang
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.7 no.4
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    • pp.673-680
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    • 1997
  • NaOH, $Na_2CO_3, CaO, Ca(OH)_2$ and $CaCO_3$ are widely used counteractives for neoutralizing the waste sulphuric acid produced during the metal surface treatment process and/or the metal refining process. To reduce the tremendous expenses for the neutralization treatment of the waste sulphuric acid, the sludge from calcination plant and the stainless refining dust in POSCO (Pohang Iron & Steel co. Ltd.) was utilized. For the sludge, it will be effective to use calcined and then hydrated sludge in strong acid region (pH<2) and to use the sludge itself in weak acid region (pH>2), The gypsum, the by-product of this treatment, was tested to fit the industrial standard of gypsum, so it is expected that it will solve the lack of gypsum supply. For the stainless refining dust, the phase and the morphology of produced gypsum from waste suiphuric acid neutralization was compared with those from pure sulphuric acid. Because of high reactivity and reaction temperature, $CaSO_4$ non-hydrate was obtained in pure sulphuric acid. But $CaSO_4$ dihydrate was obtained in waste sulphuric acid. It is also judged to be a good material for a counteractive of the waste sulphuric acid.

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Development of a Catalyst/Sorbent for Methane-Steam Reforming (메탄스팀개질반응용 촉매흡착제 개발에 관한 연구)

  • Cho, Yong-Hoon;Na, Jeong-Geol;Kim, Seong-Soo;Kim, Jin-Gul;Chung, Soo-Hyun
    • Korean Chemical Engineering Research
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    • v.44 no.3
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    • pp.307-313
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    • 2006
  • In order to improve the efficiency of methane steam reforming process, a part of the system which produces hydrogen from heavy hydrocarbon resources such as coal, we combined metal catalyst with CaO sorbent and fabricated catalyst/sorbent. To increase the porosity and the compressive strength of sorbent, carbon black and ${\alpha}-alumina$ were mixed with CaO powder during preparation. The effects of sorbent composition on the physical properties were investigated by SEM, TGA, BET, XRD, abrasion strength measuring device and adsorption-desorption instrument. Sorbent with 5 wt% $Al_2O_3$ and 10 wt% carbon black showed the best physical features with $7.61kg_f$ strength and 47% $CO_2$ adsorption capability. Various metal catalysts such as Ni, Co and Fe were supported on the sorbent developed and 10 wt% Ni/sorbent was selected for methane steam reforming process based on the result of reaction experiment. The reaction system using the catalyst/sorbent showed better $H_2$ productivity compared to the detached system with catalyst and sorbent, indicating the effectiveness of the system developed in this study.

라군슬러지 처리 공정 평가 및 개선

  • 황두성;오종혁;김연구;이규일;최윤동;황성태;박진호
    • Proceedings of the Korean Radioactive Waste Society Conference
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    • pp.238-238
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    • 2004
  • 우라늄 변환시설은 중수로용 $UO_2$ 분말 제조 시설로서 2001년도부터 제염 해체를 통한 변환시설 환경복원사업을 시작하였다. 변환 공정의 운전 중 발생하여 라군(lagoon)에 저장되어 있는 방사성 슬러지 폐액의 처리는 시설의 해체과정에서 매우 중요한 업무중의 하나이다. 라군 슬러지의 주성분은 $NH_4NO_3$, $NaNO_3$, $Ca(NO_3)_3$, $CaCO_3$ 및 U 화합물과 소량의 Fe, Mg, Al, Si 및 P 화합물로 구성되어 있다.(중략)

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The Production of Calcium Lactate by Lactobacillus sporogenes II. Production of Calcium Lactate (Lactobacillus sporgenes에 의한 젖산칼슘 생산 II. 젖산 칼슘 제조)

  • Lee, Gye-Geun;Kim, Yeong-Man;Min, Gyeong-Chan
    • The Korean Journal of Food And Nutrition
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    • v.1 no.2
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    • pp.102-107
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    • 1988
  • Production of calcium lactate very useful for medical supplies of Ca-therapy was obtained by lactic acid fermentation of lactobacillus sporogenes, a spore forming lactic acid bacterium. Corn steep liquor 1%, soybean enzyme hydrolysate 3%, yeast extract powder 2% can substitute for yeast extract and peptone as nutrient sort traces in fermentation medium using 10% glucose concentration. In the calcium lactate production medium containing yeast extract powder 2%, glucose 18%, CaCO3 12%, the lactic acid fermentation was carried out at 45$^{\circ}C$ for 4days with continuous agitation of 100 rpm. As results, fermentation yield was 97.5%. The five steps such as protein coagulation, decolorizing evaporating, crystallizing, and drying were carried out to harvest calcium lactate from 10l of supernatant of fermented medium to be removed cell and CaCO3. As results, 2065.0g of white crystal calcium lactate dihyrate was recovered and a yield of 84.9% was obtained.

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Studies on the Preparation of Aragonite (Ⅰ). Formation of Aragonite of Pillar Shape (Aragonite의 제조에 관한 연구 (Ⅰ). 주상형 아라고나이트의 생성)

  • Park, Seoung-Sik;Ha, Ho;Lee, Hee-Cheol
    • Journal of the Korean Chemical Society
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    • v.39 no.7
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    • pp.578-584
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    • 1995
  • An aqueous solution of $Ca(OH)_2$ containing a small amount of dissolved $Sr(OH)_2$ was carbonated with $CO_2$ gas, and the effects of the reaction temperature and $Sr(OH)_2$ on the carbonation were investigated. The higher the reaction temperature and the larger the ratio of $Sr(OH)_2(aq)$ to $Ca(OH)_2(aq)$, which amounts to the larger the ratio of $OH^-$ to $CO_2(aq)$, the better pillar aragonite was formed. $Sr(OH)_2$ played an important role in the formation of pillar aragonite, because it is easily formed itself into rhombic $SrCO_3$ during the initial period of carbonation process and acting as a seed for the pillar aragonite of similar morphology. In addition, due to its substantially higher solubility compared with $Ca(OH)_2$, $OH^-$ concentration in the carbonation mixture and subsequently $CO_3^{2-}$ necessary for the crystal growth are increased.

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Preparation and Characteristics of Hydroxyapatite Power by Wet Method (습식법에 의한 Hydroxyapatite 분말제조와 그 분체특성)

  • Kim, Jong-Moon;Kim, Kyum;Lee, Seo-Woo
    • Journal of the Korean Ceramic Society
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    • v.28 no.1
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    • pp.46-52
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    • 1991
  • The hydroxyapatite powders were prepared by the reaction of Ca(CH3COO)2$.$H2O and H3PO4 in aqueous solution. Effect of Ca/P mole ration and pH value on the powder characteristics were investigated. For phosphoric acid was dissociated to PO43- ion above pH 10, the preparation condition of hydroxyapatite by H3PO4 solution had this value. Dried powders were agglomerated each other. The mean agglomerate particle diameter was minimum when the condition was pH 11, Ca/P=1.75 and its specific surface area was 97㎡/g. All powders had poor crystallinity and small CO2. It prevented CaCO3 from using aspirator in preparation and maturing time. In most cases, hydroxyapatite was decomposed into ${\beta}$-TCP at more than 800$^{\circ}C$, into ${\alpha}$-TCP at 1200$^{\circ}C$. However non-decomposed hydroxyapatite was remained in Ca/P=1.85.

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A Conversion of AFm Phases by Addition of CaCO3, CaCl2 and CaSO4 · 2H2O (CaCO3, CaCl2 및 CaSO4 · 2H2O 첨가에 의한 AFm상의 변화)

  • 이종규;추용식
    • Journal of the Korean Ceramic Society
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    • v.40 no.1
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    • pp.24-30
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    • 2003
  • A formation and conversion of AFm phases decisively play role in the hydration, hardening and corrosion processes of various cement. In this study, the conversion of Alumino-Ferrite Monohydrates(AFm) phases under the addition of $CaCO_3,;CaCl_2;and;CaSO_4{cdot}2H_2O$was investigated by the XRD quantitative analysis. The thypical AFm phases are $M_S(monosulfoaluminate),;M_C(monocarboaluminate);and;M_{Cl}(monochloroaluminate and also Called Friedel's salts)$in this cementitious system, The conversion reaction were not occurred in $M_C-CaCO_3,;M_{Cl}-CaCO_3$ and $M_{Cl}-CaCl_2$system. However, in $M_S-CaCO_3$ system, ettringite and $monocarboaluminate(M_C)$ were formed. In $M_S-CaCl_2;system;M_S$ was transformed to Friedel's $salts(M_{Cl})$ and ettringite was formed. In the case of $CaSO_4{cdot}2H_2O$ addition, all AFm $phases(M_S,;M_C;and;M_{Cl})$ were transformed to ettringite. The order of stabilization of AFm phases under $CaCO_3,;CaCl_2;and;CaSO_4{cdot}2H_2O$ was as follows : $M_S< M_C

Properties of Epoxy Modified PVC-sol Sealants (에폭시가 함유된 PVC졸 실란트의 물성)

  • Lee, Seung-Jin;Kim, Hyun-Kyo;Park, Hwan-Man;Cho, Won-Jei;Ha, Chang-Sik
    • Elastomers and Composites
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    • v.34 no.3
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    • pp.199-211
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    • 1999
  • In this work, the effects of the addition of epoxy on the properties of PVC-sol sealants were investigated. PVC-sol was plasticized with dioctyl phthalates(DOP). Two kinds of epoxy resins having different epoxy equivalent weight (E.E.W.) were used. It was found that the properties of the PVC-sol sealants were significantly affected by the contents and types of the added epoxy resins. The viscosity behaviors of the epoxy-modified sealants, in the case of epoxy A addition, the viscosity was decreased with increasing the epoxy contents, but In the case of $CaCO_3$ addition, the viscosity was increased with increasing the $CaCO_3$ contents. The viscosity of epoxy modified sealants aged at $45^{\circ}C$ waterbath was decreased with increasing epoxy contents, since the epoxy acted on the sealants as a stabilizer. The thermal stability of the PVC-sol sealants was slightly improved by adding epoxy. The tensile strength and elongation of sealants modified with epoxy A(two functionalities of epoxy) were increased with increasing the epoxy contents up to a certain epoxy contents but was decreased with further increasing the epoxy contents. In the case of $CaCO_3$ addition, the tensile strength of sealants were decreased with increasing the $CaCO_3$ contents. In view of the electrical properties, such as tan ${\delta}$($0.1{\pm}0.04$) and ${\epsilon}_r$($0.5{\pm}0.04$), it was found that the epoxy modified sealants were as good as insulators.

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