• 한국분말재료학회지
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• 제12권4호
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• pp.303-308
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• 2005

Various kinds of Mg-Zn-Ca base alloys were rapidly quenched via melt spinning process. The meltspun ternary and quaternary alloy ribbons were heat-treated, and then the effects of additional elements on age hardening behavior and phase change of precipitates were investigated using Vickers hardness tester, XRD, and TEM equipped with EDS system. In ternary alloys, age hardening was mostly due to the distribution of $Mg_6Ca_2Zn_3$ and $Mg_2Ca$. The stable phases of precipitates were varied according to the aging temperature and the alloy composition. With the increase of Ca content, $Mg_2Ca$ precipitates were detected more than $Mg_6Ca_2Zn_3$ precipitates. In quaternary alloys, the precipitates taken from Mg-Zn-Ca-Co were identified as new quaternary phase, whereas those taken from Mg-Zn-Ca-Zr as MgZnCa containing Zr. In general, the ternary alloy showed higher peak hardness and thermal stability than the quaternary considering the total amounts of the solutes. It implies that the structure of precipitate should be controlled to have the coherent interface with the Mg matrix.

• 분석과학
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• 제12권3호
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• pp.243-247
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• 1999

HCl 산성에서 aconitine류 알칼로이드는 Reineke 시액으로 백색의 침전을, 그리고 TCR 시액으로 청색의 침전을 형성하였다. 백색의 침전은 $NH_4OH$ 알칼리성의 물에 녹아 aconitine류 알칼로이드를 유리시키며, 유리된 aconitine류 알칼로이드는 DCE층으로 쉽게 전용되었다. 전용된 DCE층을 분취하여 UV흡광파장을 측정하고 TLC로 분리하였다. 청색의 침전은 DCE층에 전용되므로 전용된 DCE층을 분취하여 UV/Vis.흡광파장을 측정하였다. 이상의 방법으로 aconitine류 알칼로이드를 검출하여 생약이나 제제에서 aconitine류 알칼로이드를 함유한 부자류 생약을 확인할 수 있었다.

• 한국응용과학기술학회지
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• 제33권2호
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• pp.232-238
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• 2016

본 연구에서는 액-액 반응에 의한 액상탄산화법을 이용하여 탄산칼슘을 제조하였다. MEA를 사용하여 습식화학수법의 셔틀메카니즘을 도입하였다. MEA 30% 수용액에 고농도 이산화탄소(A)와 배기가스(B)를 사용하여 이산화탄소를 포집하였으며, 액상탄산화과정을 통해 슬러지 mg 당 0.35 mg의 이산화탄소를 고정하였다. 최종생성물의 SEM 분석결과 탄산칼슘의 구조는 calcite가 혼합되어 있으나 대부분 구형 vaterite가 생성되었다.

• 펄프종이기술
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• 제31권2호
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• pp.15-24
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• 1999

A new technique for recycling of white water was developed in order to reduce the calcium hardness in a closed OCC recycling system. Calcium ions present in the white water were precipitated as calcium carbonate by reacting with sodium carbonate, and the precipitated $CaCO_3$ was removed from the system using a flotation fractionation method, which has been commonly used in deinking process. In the flotation stage, a mixed gas of $CO_2$-air was purged into the flotation cell because the pH of $Na_2CO_3$-treated white water was reduced to neutral by $CO_2$ gas. Since $CaCO_3$ precipitate tends to stick onto fine fiber surface and then selectively removed from the white water, a proper amount of suspended solid in white water acts as an important factor for deciding the removal efficiency. By the application of $Na_2CO_3$ addition-$CO_2$ flotation to the short circulated white water, the calcium hardness was significantly reduced by 87% and more. Removal of calcium ions with fine fibers led to a drainage improvement, reduction of fresh water consumption, and enhanced efficiency of wet-end chemicals.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 1999년도 Proceedings of Pre-symposium of the 10th ISWPC
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• pp.164-171
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• 1999

A new technique for recycling process water was developed in order to reduce the calcium hardness of the closed OCC recycling system. Calcium ions present in the white water were precipitated as calcium carbonate by a reaction with sodium carbonate and the CaCO$_3$precipitates were easily removed from the system by a dissolved air flotation(DAF) method. After the DAF stage, CO$_2$-gas was purged into the water because the pH of Na$_2$CO$_3$-treated white water was reduced to neutral by CO$_2$gas. Since CaCO$_3$precipitate tends to stick onto the fine fiber surface and then is selectively removed from the water, a proper amount of suspended solid in the process water acts as an important factor in deciding the removal efficiency. By the application of Na$_2$CO$_3$addition - DAF - CO$_2$purging to the short circulated white water the calcium hardness was significantly reduced by 92% and more. The removal of calcium ions with fine fibers led to drainage improvement, reduction of fresh water consumption, and enhanced efficiency of wet-end chemicals.

• Nuclear Engineering and Technology
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• 제34권1호
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• pp.1-8
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• 2002

After kaolin clay was artificially contaminated with Co$^{2+}$ ion, the remediation characteristics were analyzed by the electrokinetic method. Ethanoic buffer was injected in the soil column and $CH_3$COOH was continuously inputted to the cathode reservoir to restrain the pH increase. Since the pH of the cathode side of the soil column was 4.0 initially and increased to only 6.5 after remediation for 43.6 hours, precipitate, Co(OH)$_2$, was not formed in the column. The effluent rate increased with the passage of time and Co$^{2+}$ removal in the column at the initial time were mainly controlled by ion migration. 13.1% of the total amount of Co$^{2+}$ in the soil column was removed in 10 hours, 46.8% of the total Co$^{2+}$ in 20.8 hours, 71.7% of the total Co$^{2+}$ in 30.1 hours, and 94.6% of the total Co$^{2+}$ in 43.6 hours. Meanwhile, residual concentrations in the column calculated by the developed model were similar to those by experiment. experiment.

• 방사성폐기물학회지
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• 제10권2호
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• pp.77-85
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• 2012

본 연구는 우라늄-함유 석회침전물로부터 U을 제거(/회수) 하기위하여 탄산염 산화용해-산성화 침전과 질산용해-과산화수소 침전을 각각 고찰하였다. 석회침전물 내 우라늄을 용해하는 관점에서는 질산용해가 유리하나 (약 98% 이상 용해) 이 경우 U과 Al, Ca, Fe, Mg, Si 등의 공존 불순물이 다량 공용해되고, 또한 과산화수소 침전에서도 상당량의 불순물이 U과 함께 공침전 된다. 한편 탄산염 용해에 의한 산성화 침전은 우라늄의 용해가 90% 이하로 방사성 고체페기물의 부피감용 측면에서는 질산용해 보다 덜 효율적이지만, 우라늄과 불순물의 공용해나 산성화 침전에 의한 우라늄과 불순물의 공침전이 거의 일어나지 않아 보다 순수한 U을 회수하는 측면에서는 매우 효과적이다.

• 상하수도학회지
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• 제31권4호
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• pp.329-338
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• 2017

The problem of disposal of brine due to increased MD/RO desalination plant has recently become a big social issue. The chlor-alkali process through electrolysis of brine has been studied as a method to overcome this problem. In order to increase the electrolysis efficiency, a pretreatment process for removal of hard substances must be preceded. In this study, we investigated the mechanism of removal of hardness through chemical precipitation. As a result, Ca was greatly influenced by addition of $Na_2CO_3$, and Mg was strongly influenced by pH. Also, the addition of NaOH and $Na_2CO_3$ enabled simultaneous removal of Ca and Mg, and showed a removal efficiency of 99.9% or more. Finally, the residual concentrations of Ca and Mg in the brine after the reaction were 0.14 and 0.13 mg/L, respectively. Saturation index was calculated using Visual MINTEQ 3.1, and solid phase analysis of the precipitate was performed by FE-SEM and PXRD analysis. It was confirmed that precipitate formed by the formation of calcite and brucite.

• 대한화학회지
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• 제38권9호
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• pp.667-675
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• 1994

$La(OH)_3$를 공침제로 사용하여 해수중 흔적량 세 가지 원소를 동시에 부선시켜 정량하는 방법에 관하여 연구하였다. 인공해수를 사용하여 효과적인 부선을 위한 용액의 pH, 공침제의 양, 계면활성제의 종류와 양 등의 실험조건을 최적화시켰다. 부선하기 전에 Cr(VI)를 $NaBH_4$에 의하여 Cr(III)으로 환원시켜 크롬이 공침되도록 하였다. 해수시료 1.0 l에 $La^{3+}$를 가하고 용액의 pH를 9.8로 조절하여 $La(OH)_3$로 침전시키면서 흔적량 Co(III), Cu(II) 및 Cr(Ⅲ)이 공침되게 하였다. 부피 1:8의 0.5% sodium oleate와 sodium dodecylsulfate 에탄올 용액을 가하고 질소기체로 bubbling하여 침전들을 띄웠다. 뜬 침전을 분리해 내어 걸르고 씻은 다음 7.0 M $HNO_3$ 용액으로 녹여서 탈염수로 묽혀 25.0 ml가 되게 하였다. 분석원소들을 흑연료 원자흡수 분광광도법으로 정량하는데 인공해수로 표준용액을 만들어 검정곡선을 작성하였다. 이 방법을 동해와 서해의 물시료중 이들 원소분석에 응용하여 좋은 결과를 얻었다. 그리고 해수시료에 이들 원소를 일정량 첨가하여 얻은 회수율은 90.0% 이상으로 본 방법이 정량적임을 확인하였다.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2010년도 추계학술발표논문집 1부
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• pp.495-499
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• 2010

The biocatalytic capture of $CO_2$, and its precipitationas $CaCO_3$, over bovine carbonic anhydrase (BCA) immobilized on a pore-expanded SBA-15 support was investigated. SBA-15 was synthesized using TMB as a pore expander, and the resulting porous silica was characterized by XRD, BET, IR, and FE-SEM analysis. BCA was immobilized on SBA-15 through various approaches, including covalent attachment (BCA-CA), adsorption (BCA-ADS), and cross-linked enzyme aggregation (BCA-CLEA). The immobilization of BCA on SBA-15 was confirmed by the presence of zinc metal in the EDXS analysis. The effects of pH, temperature, storage stability, and reusability on the biocatalytic performance of BCA were characterized by examining para-nitrophenyl acetate (p-NPA) hydrolysis. The $K_{cat}/K_m$ values for p-NPA hydrolysis were 740.05, 660.62, and $680.11M^{-1}s^{-1}$, respectively, where as $K_{cat}/K_m$ for free BCA was $873.76M^{-1}s^{-1}$. The amount of $CaCO_3$ precipitate was measured quantitatively using anion-selective electrode and was found to be 12.41, 11.82, or 11.28 mg $CaCO_3$/mg for BCA-CLEA, BCA-ADS, or BCA-CA, respectively. The present results indicate that the immobilized BCA-CLEA, BCA-ADS, and BCA-CA are green materials, and are tunable, reusable, and promising biocatalysts for $CO_2$ sequestration.