• Bulletin of the Korean Chemical Society
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• v.12 no.3
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• pp.265-270
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• 1991

Theoretical calculations on the stabilization energies of framework atoms in hydrolyses Co(Ⅱ )-exchanged zeolite A were made using some potential energy functions and optimization program. The protons which are produced by hydrolysis of $[Co(H_2O)_n]^{2+}$ ion in large cavity showed a tendency to attack the framework oxygen atom O(1) preferentially, and the oxygen atom O(4) within OH- ion was coordinated at Al atom. The weakness of bonds between T(Si, Al) and oxygen by attack of proton and too large coordination number around small aluminum atom will make the framework of Co(Ⅱ)-exchanged zeolite A more unstable. The stabilization energy of $Co_4Na_4$-A framework (- 361.57 kcal/mol) was less than that of thermally stable zeolite A($Na_{12-}$A: - 419.68 kcal/mol) and greater than that of extremely unstable Ba(Ⅱ)-exchanged zeolite A($Ba_{6-}$A: - 324.01 kcal/mol). All the data of powder X-ray diffraction, infrared and Raman spectroscopy of Co(Ⅱ)-exchanged zeolite A showed the evidence of instability of its framework in agreement with the theoretical calculation. Three different groups of water molecules are found in hydrated Co(Ⅱ )-exchanged zeolite A; W(Ⅰ) group of water molecules having only hydrogen-bonds, W(Ⅱ) group water coordinated to $Na^+$ ion, ans W(Ⅲ) group water coordinated to Co(Ⅱ) ion. The averaged interaction energy of each water group shows the decreasing order of W(Ⅲ)>W(Ⅱ)>W(Ⅰ).

• Environmental Engineering Research
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• v.25 no.1
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• pp.88-95
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• 2020

An investigation of rare metals recovery from LiNi_xCo_yMn_zO₂ cathode material of the end-of-life lithium-ion batteries is presented. To determine the influence of reductant on the leach process, the cathode material (containing Li 7.6%, Co 20.4%, Mn 19.4%, and Ni 19.3%) was leached in H₂SO₄ solutions either with or without H₂O₂. The optimal process parameters with respect to acid concentration, addition dosage of H₂O₂, temperature, and the leaching time were found to be 2.0 M H₂SO₄, 4 vol.% H₂O₂, 70℃, and 150 min, respectively. The yield of metal values in the leach liquor was > 99%. The leach liquor was subsequently treated by precipitation techniques to recover nickel as Ni(C₄H₇N₂O₂)₂ and lithium as Li₂CO₃ with stoichiometric ratios of 2:1 and 1.2:1 of dimethylglyoxime:Ni and Na₂CO₃:Li, respectively. Cobalt was recovered by solvent extraction following a 3-stage process using Na-Cyanex 272 at pH_eq ~5.0 with an organic-to-aqueous phase ratio (O/A) of 2/3. The loaded organic phase was stripped with 2.0 M H₂SO₄ at an O/A ratio of 8/1 to yield a solution of 114 g/L CoSO₄; finally recovered CoSO₄.xH₂O by crystallization. The process economics were analyzed and found to be viable with a margin of $476 per ton of the cathode material.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.7
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• pp.293-297
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• 2003

Silicon dioxide (SiO$_2$) layers were fabricated on Si$_3$N$_4$/SiO$_2$/Si layer structures by low pressure chemical vapor deposition (LPCVD). Potassium and aluminum were then coimplanted by implanting potassium ions with the energy of 100 ［keY］ and dose of 5x10$^{16}$ [cm￣$^2$］ and 1x10$^{17}$ [cm￣$^2$］ into an aluminum buffer layer on the SiO$_2$Si$_3$N4/SiO$_2$/Si structure. The pH, pNa, and pK ion sensitivities of the resulting layers were investigated and compared to those of as-deposited silicon dioxide layer. The pK-sensitivity of the silicon dioxide was enhanced by the K and Al coimplantation. On the contrary, the pH and pNa-sensitivities of the coimplanted silicon dioxides were quite lower than that of the as-deposited silicon dioxide.

• Resources Recycling
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• v.3 no.1
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• pp.9-16
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• 1994

Fine cobalt metal powders was produced from domestic Stellite scrap by decomposing it with molten sodium hydroxide. Complete decomposition of the scrap could be obtained with the weigth ratio of sodium hydroxide to Stellite being about 2 at the temperature ranges of $750~800^{\circ}C$ for an hour. The cobalt-bearing compound was identified as $Co_2O_3{\dot}H_2O$ by X-ray analysis and D.T.-T.G.a.. The compound was then digested in HCI to form cobalt chloride, and after iron removal by adjusting the pH of the solution, cobaltous or cobaltic hydroxide was precipitated at the pH of about 13 or 4, respectively. The precipitates were reduced by hydrogen in the temperatures of $400~500^{\circ}C$ to fine cobalt powders of high purity with the size of 1.0 to $1.5\mu\textrm{m}$. The recovery of cobalt from Stellite scrap was about 75~86% by weight.

• Journal of the Korean Ceramic Society
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• v.20 no.4
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• pp.340-346
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• 1983

The effect of aging coprecipitate obtained by the reaction of mixed solution 1.1 mol FeCl-0.1 mol $BaCl_2$ and 4.0 mol. NaOH-1.0 mol $K _2 CO_3$ on the synthesis process of Baferrite $(BaFe_{12}O_{19})$ was investigated by means of DTA, TGA, XRD and electron microscope. The no-aged coprecipitate seems to be the aggregate of amorphosus $Fe_3$ .$nH_2O$ and (1-X) $BaCO_3$.$xBa(OH)_2$, but the 30 days-aged to be composed of crystalline $Fe_2O_3H_2O$ and $BaCO_3$. The decomposition temperature of $BaCO_3$ in the coprecipitate increases from 400-$700^{\circ}C$ to 700-90$0^{\circ}C$ with increment of aging-time. In the no-aged coprecipitate Ba-ferrite is synthesized through the surface reaction of amorphous Fe_2O_3$ and skeleton crystal BaO at 800-90$0^{\circ}C$ with more compact crystalization. During calcination of the 30 days-aged coprecibitate the intermediate phase BaFe_2O_4$ is formed at 600-$700^{\circ}C$ and completely transformed to Ba-ferrite at 800-90$0^{\circ}C$.

• Journal of the Korean Chemical Society
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• v.13 no.2
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• pp.149-156
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• 1969

$NaAl(OH)_2CO_3$was synthesized using colloidal earth (Allophane) as the starting material and some of its were studied in detail. It was found that Dawsonite was formed in the pH range (pH 12.5~12.0) that the concentration of $HCO_3^-$ was just begun to increase and the presence of $HCO_3^-$ in the product was clarified from the infrared absorption spectrum. The chemical formular of Dawsonite was therefore presumed as $NaAlO (OH) HCO_3$. From toahhe results of X-ray powder diffraction, both peaks at 5.7 $\AA$ and 2.8 $\AA$ were observed, and fibrous crystalline structure was observed from electron micrograph and also found from the microscopic electron diffraction at 5.7 $\AA.$ Therefore the fibrous axis was considered as =Al=O2=Al=O2=Al=(*image) direction. True specific gravity of Dawsonite was 2.44 and its porosity was 91.4%. It was practically insoluble in water, but decomposed in the boiling water to form Pseudo Boehmite. Stable pH range of Dawsonite was about 4.5~11.5. From the results of D.T.A. and T.G.A., it was observed that $CO_2$was liberated at $350^{\circ}C$, and $H_2O$ at $650^{\circ}C$, and converted into strongly hygroscopic $NaAlO_2$, which was easily decomposed in water into $\beta-Al(OH)_3(Bayerite)$ and NaOH.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.6
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• pp.639-647
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• 2005

A single particle analytical technique, named low-Z particle electron probe X-ray microanalysis (EPMA), was applied to characterize samples collected at a subway station and ambient samples in Seoul. According to their chemical composition, many distinctive particle types were identified. For samples collected at the subway station platform, the major chemical species are carbon-rich, organic, aluminosilicates (AlSi), AlSi/C, AlSi/$CaCO_{3},\;CaCO_{3},\;SiO_{2},\;and\;Fe_{2}O_{3}$. For outdoor samples, carbon-rich, organic, AlSi, $CaCO_{3},\;SiO_{2},\;NaNO_{3},\;(Na,Mg)NO_{3},\;Na(CO_{3},NO_{3},SO_{4}),\;and\;(NH_{4})_2SO_4$, are abundantly encountered. Samples collected at the subway station show very high contents of $Fe_{2}O_{3}$, both in coarse and fine fractions, which come from brake block, subway train wheel, electric contact materials, etc. It is demonstrated that the single-particle characterization using this low-Z particle EPMA technique provided detailed information on various types of chemical species in indoor and outdoor samples.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.134-137
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• 2004

새로운 리튬 2차전지용 양극활물질인 Li[NiMnCo]O2를 간단히 합성할 수 있는 방법과 Si의 doping에 의해 그 특성을 향상하였다. 원하는 당량비의 Li, Ni, Co, Mn의 nitrate를 고순도의 에탄올에 용해하고 여기에 Si의 원료물질로서 poly(methyl phenyl siloxane)을 원하는 양(전체 전이금속 이온의 $2{\sim}10\;mol%$)만큼 첨가한 후 약 30분 정도 교반하였다. 이 용액을 약 $70{\sim}80^{\circ}C$ 정도의 온도에서 고점도의 진흙 상태가 될 정도로 가열하고 $450{\sim}500^{\circ}C$의 온도에서 약 5시간 정도 열처리 하여 유기물이 없는 상태의 전구체를 제조하였다. 이 전구체를 분말형태로 분쇄하고 $600{\sim}650^{\circ}C$ 정도의 온도에서 3시간, $900{\sim}950^{\circ}C$ 정도의 온도에서 5시간 연속적으로 열처리 하여 최종 활물질을 제조하였다. 이렇게 제조된 활물질은 175mAh/g 정도의 높은 비용량을 나타내었으며 4.5V 충전 조건에도 우수한 수명특성을 나타내었다. Si이 doping되지 않은 활물질에 비해 Si이 doping된 물질은 율특성, 수명특성에서 보다 우수한 특성을 나타내었는데 이것은 층상구조 활물질의 격자상수 증가와 impedance 증가 억제에 기인한 것으로 분석되었다.

• Journal of the Mineralogical Society of Korea
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• v.22 no.4
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• pp.307-312
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• 2009

Motukoreaite and quintinite-3T, Mg-Al layered double hydroxides, were found in the Sinyangri Formation of Jeju Island. They fill the pores of basaltic volcaniclastic sediments in globular and botryoidal aggregates of fine platy particles. Globular aggregates of quintinite-3T were crusted with the parallel overgrowth of motukoreaite plates. X-ray diffraction data and chemical composition are consistent with those reported in literature, while the Mg/Al ratio of motukoreaite is higher. Structural formula of motukoreaite and quintinite-3T derived from electron microprobe analysis are $Na_{1.6}Ca_{0.1}Mg_{40.7}Al_{20.7}Si_{0.9}(CO_3)_{13.6}(SO_4)_{7.4}(OH)_{108}56H_2O$, and $Mg_{3.7}Al_{1.9}Si_{0.2}(OH)_{12}(CO_3)_{0.8}(SO_4)_{0.2}3H_2O$, respectively. Motukoreaite and quintinite-3T were formed by reaction between seawater and basaltic glass, and contributed to the cementation and lithification of the volcaniclastic sediments.

• Journal of the Korean Chemical Society
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• v.13 no.2
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• pp.157-164
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• 1969

Aoolphane was treated with 30% Hydrochloric acid at $18^{\circ}C$ for two hows with stirring in order to obtain the insoluble form of SiO2 gel and to extract quantitatively both $Al_2O_3$as and $Fe_2O_3AlCl_3{\cdot}6H_2O Fe$ and $Cl_3{\cdot}6H_2O$ forms, respectively, at the same time. $SiO_2$ gel was filtered and to the filterate Ammonia was added to precipitate $Al(OH)_3[Fe(OH)_3 Contaminated ]$ The precipitate was separated by filteration and the filterate was recovered as the form of $NH_4Cl$. The precipitate was treated with 200g (NaOH)/l Concentration of NaOH a little excessively to the equivalent at $65~70^{\circ}C$ as $Fe(OH)_3$ formed was insoluble, it was filtered of and to the filterate containing $NaAl(OH)_4(OH_2)_2$Carbon dioxide gas was bubbled at $50^{\circ}C~90^{\circ}C$ to obtain the precipitate with excellent filterability and crystallinity. The product was certified to be Dawsonite $(NaAl(OH)_2CO_3)$ by X-Ray diffraction analysis at below $40^{\circ}C$, when $CO_2$ gas was bubbled into the relatively lower concentration of $NaAl(OH)_4(OH_2)_2$ solution, the precipitate of very fine particles was formed, which was hard to filter and with the Composition of $\alpha-Al_2O_3-H_2O$ (Boehmite).