• Title/Summary/Keyword: Homogeneous precipitate reaction

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Synthesis of aragonite precipitated calcium carbonate by homogeneous precipitate reaction of $Ca(OH)_2\;and Na_2CO_3$ ($Ca(OH)_2\;및 \;Na_2CO_3$수용액의 균일침전 반응에 의한 아라고나이트 침강성 탄산 칼슘의 합성)

  • Park, Jin-Koo;Park, Hyun-Seo;Ahn, Ji-Whan;Kim, Hwan;Park, Charn-Hoon
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.14 no.3
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    • pp.110-114
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    • 2004
  • Formation behavior of aragonite precipitated calcium carbonate was investigated with changed the concentration of $Na_2CO_3$ solution and addition method which added in the $Ca(OH)_2$ slurry at $75^{\circ}C$. In this reaction, we found that $Na^+$ ions were substituted into $Ca^{2+}$ion site then disturb the growth of calcite, and while proceed the crystal growth in a certain direction and promote the formation of aragonite. Also, a decrease of reaction rate by control the concentration of $CO_3^{2-}$ ion, induce the homogeneous precipitate reaction and increase substitution ability of $Na^+$ ions, consequently it was promote the formation and growth of aragonite.

Synthesis of Yttrium Iron Garnet Powder by Homogeneous Precipitation and its Crystallization (균일침전법에 의한 Yttrium Iron Garnet 분말의 합성 및 결정화)

  • 안영수;한문희;김종오
    • Journal of the Korean Ceramic Society
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    • v.33 no.6
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    • pp.693-699
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    • 1996
  • YIG precursor powder was obtained by homogeneous precipitation in chloride salt solution by thermal decom-position of urea. It was found that ferric ions precipitated prior to yttrium ions. The precipitate was minute and spherical in shape. The precipitate formed consisted of the mixture of amorphous and ferric oxyhydroxide. Crystallization of YIG was proceeded by solid state reaction of intermediate YFeO3 and Fe2O3 in the temperature range of 85$0^{\circ}C$ to 140$0^{\circ}C$. Single phase of YIG was obtained by heat-treatment of the powder at 140$0^{\circ}C$ for 6 hrs in air. The powder calcined was molded into pellets and sintered in air. The maximum density of 4,92 g/cm3(95.1% of theoretical density) was obtainable for the pellet sintered at 145$0^{\circ}C$ using the powder calcined at 90$0^{\circ}C$.

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Preparation of Hydrated Basic Aluminum Salts by Homogeneous Precipitation Method and Their Thermal Decomposition (균일침전법에 의한 수화 염기성 알루미늄염의 합성 및 열분해)

  • 박홍채;김주석;이승호;오기동
    • Journal of the Korean Ceramic Society
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    • v.26 no.1
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    • pp.132-138
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    • 1989
  • High purity(99.99%) spherical particles of hydrated Basic Aluminum Salts(BAS) were prepared by a homogeneous precipitation process utilizing the urea decomposition reaction and characterized by XRD, SEM, TG-DTA, IR and PSA methods. Amorphous hydrated BAS was precipitated in the range of pH 4~6. The molar ratio [Al3+]/[SO42-] for the precipitate particles was about 3.7. With increasing the concentration of aluminum sulfate the precipitation of the hydrated BAS occurred slowly and the precipitate particles with a narrow size distribution were fine(1-2${\mu}{\textrm}{m}$ in diameter). At temperatures in the range 400$^{\circ}$to 95$0^{\circ}C$, desulfurization and dehydroxylization resulted in weight loss with 22%. When the precipitate particles were thermally treated, the crystlline ${\gamma}$-Al2O3 was identifited by XRD at 50$0^{\circ}C$ and ${\gamma}$-Al2O3 particles were transformed into $\alpha$-Al2O3 at 100$0^{\circ}C$. A vermicular network was produced by calcining at 125$0^{\circ}C$ for 30min.

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Preparation of Monodispersed Colloidal Particles of Yttrium Compound by Homogeneous Precipitation. I.Effect of $Y(NO_3)_3$ Concentration (균일침전법에 의한 균일입도 초미분 이트륨화합물의 제조에 관한 연구 I. $Y(NO_3)_3$ 농도의 영향)

  • 권영식;김연식
    • Journal of the Korean Ceramic Society
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    • v.33 no.5
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    • pp.495-506
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    • 1996
  • Monodispersed colloidaly yttria(Y2O3) can be used in a variety of applications such as phosphors. IR transparent materials and fine ceramics. For preparing monodispersed yttria homogeneous precipitation has been regarded as a fovorable method that is monodispersed yttria can be obtained through calcining monodispersed colloidal compound of yttrium (eg:Y(OH)CO3.nH2O)which can be prepared by homogeneous precipitation with urea. It is however still required to find out the quantitative effects of important variables of precipitation such as concentration of yttrium and urea reaction temperature and initial pH of reactant even though homogeneous precipitation of Y3+ with urea has been studied extensively. Among the effects of these variables we investiga-ted 1) the effect of yttrium concentration on the shape and size of precipitate and the reation rate 2) range of yttrium concentration required to make monodispersed colloidal particles 3) the reason for limited concentra-tion range of yttrium and 4) the effect of ultrasonic radiation on the limited concentration.

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Environmental Geochemistry and Heavy Matel Contamination of Ground and Surface Water, Soil and Sediment at the Kongjujuil Mine Creek, Korea (공주제일광산 수계에 분포하는 지하수, 지표수, 토양 및 퇴적물의 환경지구화학적 특성과 중금속 오염)

  • 이찬희
    • Economic and Environmental Geology
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    • v.32 no.6
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    • pp.611-631
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    • 1999
  • Enviromental geochemisty and heary metal contamination at the Kongjueil mine creek were underaken on the basis of physicohemical properties and mineralogy for various kinds of water (surface, mine and ground water),soil, precipitate and sediment collected of April and December in 1998. Hydrgeochemical composition of the water samples are characterized by relatively significant enricant of Ca+Na, alkiali ions $NO_3$ and Cl inground and surfore water, wheras the mine waters are relatively eneripheral water of the mining creek have the characteristics of the (Ca+Mg)-$(HCO_3+SO_4)$type. The pH of the mine water is high acidity (3.24)and high EC (613$\mu$S/cm)compared with those of surface and ground water. The range of $\delta$D and $\delta^{18}O$ values (relative to SMOW) in the waters are shpwn in -50.2 to -61.6% and -7.0 to -8.6$\textperthousand$(d value=5.8 to 8.7). Using computer program, saturation index of albite, calcite, dolomite in mine water are nearly saturated. The gibbiste, kaolinite and smectite are superaturated in the surface and ground water, respectively. Calculated water-mineral reaction and stabilities suggest that weathing of silicate minerals may be stable kaolinite owing to the continuous water-rock reaction. Geochemical modeling showed that mostly toxic heavy metals may exist larfely in the from of metal-sulfate $(MSO_4\;^2)$and free metal $(M^{2+})$ in nmine water. These metals in the ground and surface water could be formed of $CO_3$ and OH complex ions. The average enrichment indices of water samples are 2.72 of the groundwater, 2.26 of the surface water and 14.15 of the acid mine water, normalizing by surface water composition at the non-mining creek, repectively. Characteristics of some major, minor and rate earth elements (Al/Na, K/Na, V/Ni, Cr/V, Ni/Co, La/Ce, Th/Yb, $La_N/Yb_N$, Co/Th, La/Sc and Sc/Th) in soil and sediment are revealed a narrow range and homogeneous compositions may be explained by acidic to intermediate igneous rocks. And these suggested that sediment source of host granitic gneiss colud be due to rocks of high grade metamorphism originated by sedimentary rocks. Maximum concentrations of environmentally toxic elements in sediment and soil are Fe=53.80 wt.% As=660, Cd=4, Cr=175, Cu=158, Mn=1010, Pb=2933, Sb=4 and Zn=3740 ppm, and extremely high concentrations are found are found in the subsurface soil near the ore dump and precipitates. Normalizing by composition of host granitic gneiss, the average enerichment indices are 3.72 of the sediments, 3.48 of the soils, 10.40 of the precipitates of acid mine drainage and 6.25 of the soils near the main adit. The level of enerichment was very severe in mining drainage sediments, while it was not so great in the soils. mineral composition of soil and sediment near the mining area were partly variable being composed of quartz, mica, feldspar, chlorite, vermiculite, bethierin and clay minerals. reddish variable being composed of quartz, mica, feldspar, chlorite, vermiculite, bethierin and clay minerals. Reddish brown precipitation mineral in the acid mine drainage identifies by schwertmanite. From the separated mineralgy, soil and sediment are composed of some pyrite, arsenopyite, chalcopyrite, sphalerite, galena, malachite, goethite and various kinds of hydroxied minerals.

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