• Journal of the Korean Chemical Society
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• v.30 no.3
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• pp.265-272
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• 1986

Kinetic studies for the methanolysis of tert-butyl halides (t-BuCl, t-BuBr, t-BuI) were carried out in MeOH-1,1,2,2-tetrachloroethane mixtures. The solvatochromic comparison method was used with six indicators to analyze solvent effects on the ionizations of tert-butyl halides. It was shown that the cooperative effect of solvent polarity-polarizability was the most important factor influenced on the methanolysis rates of tert-butyl halides, but the electrophilic assistance for halide leaving group and the nucleophilic assistance for tert-butylium ion were considerably influential, too. And it was found that the electrophilic assistance caused by hydrogen bonding and the nucleophilic assistance for carbon center were stronger for more basic leaving group ($I^-) and more polarizable leaving group(t-BuCl

• Korean Chemical Engineering Research
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• v.51 no.1
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• pp.53-57
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• 2013

For the purpose of development of the extraction process of lithium ion from concentrated water eliminated from desalination process, an experimental research on the solvent extraction of lithium ion from aqueous solutions was performed. The effects of operating parameters, such as concentration of extractant, ratio of extracting solution/aqueous solution, pH of aqueous solution, were examined. The effect of sodium chloride, the major component of sea water, was also examined. Lithium ion in aqueous solutions of pH=10.2~10.6 adjusted by ammonia solution was most effectively extracted by extracting solution composed of 0.02 M TTA and 0.04 M TOPO in kerosine. The addition of sodium chloride in lithium aqueous solution significantly interfered the extraction of lithium ion.

• KSBB Journal
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• v.14 no.6
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• pp.696-701
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• 1999

The enzymatic hydrolysis of Castor oil for the mass production of ricinoleic acid was studied to find out the optimum conditions such as solvents and the weight ratio of substrate to enzyme. Three different lipases were tested for the hydrolysis of castor oil: lipase from Porcine Pancrease(lipsase PP), lipase from Candida cylindracea(lipase CC), lipase from Candida Rugosa(lipase CR). The poor mass transfer in water caused a low degree of hydrolysis of castor oil. To overcome this problem, organic solvents were used. Among organic solvents tested, hydrophobic solvents gave better results of hydrolysis than hydrophilic solvents. Organic solvents also lowered or changed the effect of pH. Isopropyl ether made complete hydrolysis of castor oil. The ratio of water to isopropyl ether and the ratio of weight ratio of lipase to castor oil were important for the hydrolysis of castor oil. At 30$^{\circ}C$ castor oil was completely hydrolyzed by 4 wt% of lipase in the mixture of isopropyl ether and water(1:1 in volume).

• Journal of the Korean Chemical Society
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• v.46 no.6
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• pp.528-534
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• 2002

We have studied to find the optimum electrolyte that satisfied high ionic conductivity, large elec-trochemical window, etc in Li-ion battery. And also studied were the effect of a passive film on carbon anode surface,which is formed by solvent decomposition during the initial charge process. Electrochemical properties of the passive film formed on carbon anode surface investigated and explained as the volumetric ratio of the mixed solvents. The results of scanning electron microscopy, chronopotentiometry, cyclic voltammetry, impedance spectroscopy revealed that the electrochemical properties of the passive film were varied with the ionic conductivity of the electrolyte including the mixed solvents.

• Clean Technology
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• v.23 no.3
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• pp.279-285
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• 2017

In this study, a new organophosphorus acid-based solvent (KMC-P) from KMC Co., Ltd. was used for the recovery of the iron chloride etching waste solution. In order to increase the extraction efficiency for the new solvent in the solvent extraction process, we selected the process variables and conducted the optimization experiment according to the DOE to investigate the correlation between the variables. Solvent concentration, pH, and O/A ratio were found to be factors affecting extraction and stripping efficiency. The optimum stripping efficiency was 69.7% when the solvent concentration was 29.4 wt%, the HCl addition amount was 0 mL, and the O/A ratio was 7, and the reliability was more than 86%.

• Journal of the Korean Chemical Society
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• v.27 no.3
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• pp.167-177
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• 1983

The kinetics of 2-anthracenesulfonyl chloride in methanol-water, ethanol-water, acetone-water and acetonitrile-water has been studied by electroconductometric method. For media in which water has the same mole fraction, the rate was greater in protic solvent than in dipolar aprotic solvent and it was greater consistently in methanol-water than in ethanol-water over the whole range of solvent composition investigated, while the two rates in acetone-water and acetonitrile-water inverted at about 0.9 of mole fraction of water. Both m value, susceptibility of rate to the ionizing power and n value, solvent participation number in the transition state were much smaller in protic solvent. These values and the activation parameters show that solvolysis of 2-anthracenesulfonyl chloride proceeds by $ S_N2$ mechanism.

• Journal of Navigation and Port Research
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• v.28 no.5
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• pp.463-468
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• 2004

A lab-scale fundamental study to develop the solvent extraction process of ship wash wastewater containing TBT was carried out. For various solvents, including diesels for car and ship, bunker B, thinner, toluene, and ether, the extraction efficiencies of TBT from synthetic ship wash wastewater were compared The effect of extraction conditions, such as solvent amount, time and intensity of agitation, and pH, on the extraction efficiency of TBT was evaluated Diesel for ship showed better extraction efficiency of TBT than those of other tested solvents, and the proper amount of the extraction solvent for 1L of the wastewater was l0mL. When the agitation intensity was increased from 50rpm to 250rpm, the TBT remained in the wastewater after the extraction was decreased from around 120ppb to 2.8ppb. The remaining TBT in the wastewater was sharply decreased from 1hr of the extraction time, but was slightly increased again after 5hrs of the extraction time. The efficiency of TBT extraction was good in the weak acid range of pH, but was not significant as much as the others.

• Journal of the Mineralogical Society of Korea
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• v.31 no.2
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• pp.67-73
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• 2018

The objective of this study was to investigate the application of sulfate solvents for the economic and eco-friendly leaching of valuable metals from Au concentrate using an acid bake-water leaching system (AWS). AWS experiments were performed using an electric furnace with various baking temperatures ($100-500^{\circ}C$) and sulfate solvents ($H_2SO_4$, $K_2SO_4$, $(NH_4)_2SO_4$, $MgSO_4$, and $CaSO_4$). The efficiency of the valuable metal leaching increased as the baking temperature was increased to $400^{\circ}C$. Based on the AWS leaching time experiments, the maximum leaching rate occurred with the aqueous $(NH_4)_2SO_4$ solvent. This study demonstrates that aqueous $(NH_4)_2SO_4$ could be used as an effective solvent for valuable metal leaching using an AWS.

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.967-972
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• 1997

Recovery of aromatics in extract phase which was obtained by batch equilibrium extraction between light cycle oil(LCO) and dimethylsulfoxide(DMSO) solution as solvent was investigated by re-extraction. To select the most suitable re-extraction solvent for recovery of aromatics in extract phase, distribution equilibrium was measured between extract phase and solvents. The solvents used were benzene(B), toluene(T), m-Xylene(mX), n-hexane(Hx) and n-hexane(Hx) and n-Octane(Ot). From the distribution coefficients and yields of aromatics, Hx seemed to be the most suitable. Furthermore, effects of operation parameters for re-extraction of aromatics in the extract phase were studied by batch equilibrium re-extracion with Hx as solvent. Yields of aromatics were found to increase with increasing solvent/feed (extract phase) mass ratio(S/F), while distribution coefficients of aromatics were fixed irrespective of S/F used. Operating temperature did not affect distribution coefficients and yields of aromatics. Distibution coefficients and yields of naphthalene group(carbon numer : 10~12) increased with increasing cabon number. Mass transfer rates of aromatics were also measured with a batch stirred vessel.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.113-113
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• 2018

환경 친화형 전기자동차, 하이브리드 자동차, 전철 등에서는 고내압 및 소형으로 전력손실을 감소시킬 수 있는 파워 디바이스가 필수이다. 최근, 실리콘 카바이드(SiC, silcon carbide)는 기존 실리콘(Si)보다 스위칭 손실의 저감 및 고온환경에서의 동작 특성이 우수하여, 차세대 저 손실 전력반도체 재료로서 기대를 받고 있다. 용액 성장 법에서 고품질 SiC 결정을 만들 수 있다. 그러나 늦은 성장 속도 때문에 SiC의 양산을 어렵게 하고 있다. 현재까지 성장 속도 향상을 위한 Si용매에 Cr을 첨가하여 탄소 용해도를 높이는 방법이 사용되고 안정된 성장을 위한 Si-Cr용매에 Al를 첨가하는 등 다양한 금속을 첨가하는 방법이 이용되고 있다. 선행 연구에서는 다양한 용매인 탄소 용해도를 실측하고 특히 큰 탄소 용해도를 보인 것은 Co이었다. 본 연구에서는 $Si_{0.6}Cr_{0.4}$원료와 Co를 첨가한 $Si_{0.56}Cr_{0.4}Co_{0.04}$의 용매에 의한 SiC용액 성장을 실시하고 결정 성장 속도 및 표면 상태의 변화를 검토했다. on-axis 4H-SiC(000-1)을 사용한 Top-seeded solution growth(TSSG)법과 원자 비율로 $Si_{0.6}Cr_{0.4}$와 $Si_{0.56}Cr_{0.4}Co_{0.04}$의 용매를 이용하여 SiC 용액 성장을 실시했다. Ar가스에서 저항 가열로 내를 치환 후에 $1800^{\circ}C$까지 가열하고 종자화 후에 120분간 유지하고 결정 성장을 실시했다. 냉각 후에 성장의 표면에 남은 용매를 $HF+HNO_3$에서 제거했다. 광학 현미경을 이용하여 결정면과 두께를 관찰 측정했다. Co를 첨가한 $Si_{0.56}Cr_{0.4}Co_{0.04}$의 경우는 $Si_{0.6}Cr_{0.4}$의 경우보다 결정 성장 속도가 향상됐다. 또한 $Si_{0.6}Cr_{0.4}$보다 step-flow의 성장을 나타낸 결정의 표면이 전반적으로 관찰됐으며 안정된 결정성장을 나타냈다. 본 연구에서 실시한 연구 방법과 결과는 고품질 및 고속의 SiC 용액성장을 위한 매우 유용한 자료로 활용 될 수 있을 것으로 판단한다.