• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.684-689
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• 2012

Poly(acrylic acid) (PAA) microspheres is one of the widely-used polymeric materials for the bio-field application and the electric materials. For the synthesis of PAA microspheres, the polymerization technique using surfactants is applied. After the synthesis, the purification and separation processes are required for the removal of surfactant. When general organic solvents were used, many problems, such as huge amount of waste solvent, additional separation processes, and the possibility of residual media, were occurred. Thus, High-pressure Soxhlet extraction using liquid $CO_2$ was developed to solve these problems. In this study, High-pressure Soxhlet extraction of the synthesized PAA microspheres using liquid $CO_2$ was conducted for the removal of Monasil PCA which is used for the dispersion polymerization of acrylic acid in compressed liquid Dimethyl ether (DME). The morphology of the extracted PAA particles was checked by field emission scanning electron microscopy (FE-SEM) and the residual concentration of Monasil PCA was analyzed by inductively coupled plasma - Optical Emission Spectrometer (ICP-OES). For studying the effect of the solvent effect, Soxhlet extraction was conducted using n-hexane, liquid DME, and liquid $CO_2$. In case of n-hexane, some extracted PAA microspheres were produced. However, deformation was also occurred due to the high thermal energy of n-hexane vapor. Liquid DME could not remove Monasil PCA. When using liquid $CO_2$, the extracted PAA microspheres which were free for the residual solvent were produced without deformation. For finding the optimum operating condition, high-pressure Soxhlet extraction was conducted for 8 hours with changing the temperature of reboiler and condenser. When the extractor temperature is $19.6{\pm}0.2^{\circ}C$ and the pressure is $51.5{\pm}0.5$ bar, the best removal efficiency was obtained.

• Resources Recycling
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• v.31 no.2
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• pp.20-32
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• 2022

This study implemented a chelating agent (Ethylenediaminetetraacetic acid, EDTA) in purification to obtain high-purity vanadium pentoxide (V₂O₅) for use in VRFB (Vanadium Redox Flow Battery). V₂O₅ (powder) was produced through the precipitation recovery of ammonium metavanadate (NH₄VO₃) from a vanadium solution, which was prepared using a low-purity vanadium raw material. The initial purity of the powder was estimated to be 99.7%. However, the use of a chelating agent improved its purity up to 99.9% or higher. It was conjectured that the added chelating agent reacted with the impurity ions to form a complex, stabilizing them. This improved the selectivity for vanadium in the recovery process. However, the prepared V₂O₅ powder exhibited higher contents of K, Mn, Fe, Na, and Al than those in the standard counterparts, thus necessitating additional research on its impurity separation. Furthermore, the vanadium electrolyte was prepared using the high-purity V₂O₅ powder in a newly developed direct electrolytic process. Its analytical properties were compared with those of commercial electrolytes. Owing to the high concentration of the K, Ca, Na, Al, Mg, and Si impurities in the produced vanadium electrolyte, the purity was analyzed to be 99.97%, lower than those (99.98%) of its commercial counterparts. Thus, further research on optimizing the high-purity V₂O₅ powder and electrolyte manufacturing processes may yield a process capable of commercialization.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.298-298
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• 2008

제지산업은 다량의 용수를 사용하면서 또한 많은 양의 폐수를 배출하고 있다. 기존의 폐수처리 공정에서는 침전처리를 위한 큰 공간과 오랜 시간이 요구되어 처리비용이 비교적 많이 드는 단점이 있다. 이러한 기존 기술의 문제점을 보완할 수 있는 새로운 고도처리가 가능한 초전도 마그네트를 이용한 자기분리 기술을 적용하고자 하였다. 자기분리의 기본 원리는 강력한 자기력에 의하여 액체에 포함된 자성입자를 분리해내는 것으로 자성입자들이 자계의 힘에 의하여 잡아당겨지고 포획될으로서 제거되는 것이다. 자기분리용 전자석으로서는 아주 이상적으로 이러한 초전도마그네트와 체(sieve) 형 자기필터를 결합시키면 아주 높은 고구배의 자장(HGMS; High Gradient Magnetic Separation)을 발생 시킬 수 있다. 초전도마그네트를 이용하면 대공간에 전력손실 없이 고자장을 발생시킬수 있기 때문에 미립자를 효과적으로 고속으로 분리하는 것이 가능해지며 또한 상자성 미세입자까지도 처리할 수 있다. 본 연구에서는 주로 유기물로 구성된 제지며|수의 부유물을 자성체와의 응집반응에 의해 플록을 형성하여 자성플록의 자기분리 효과를 연구하였다. 응집제의 종류와 응집반응 공정에 따른 자성플록의 형성 정도를 조사하였으며 자기분리 후 폐수의 탁도, COD 등의 특성을 분석하였다.

• Clean Technology
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• v.11 no.3
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• pp.123-128
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• 2005

Among various metal oxides semiconductors, $TiO_2$ is the most studied semiconductor for environmental clean-up applications due to its unique ability in photocatalyzing various organic contaminants, its chemical inertness, and nontoxicity. $TiO_2$, however, has a few drawbacks to be solved such as reactivity mainly working under ultraviolet irradiation (${\lambda}$ < 387 nm) and electron - hole recombination on $TiO_2$. In this study, to extend the absorption range of $TiO_2$ into the visible range and enhance electron - hole separation, we synthesized platinum (Pt) deposited $C-TiO_2$. The presence of Pt as an electron sink has been known to snhance the separation of photogenerated electron-hole pairs and induce the thermal decomposition. The characterization of as-synthesized $Pt-C-TiO_2$ was performed by Transmission Electron Microscopic (TEM), the Brunuer-Emmett-Teller (BET) method, X-ray Diffractometer (XRD), UV-vis spectrometer (UV-DRS), and X-ray Photoelectron Spectroscopy (XPS). In order to estimate the photocatalytic activity of the synthesized materials, the photoelectron Spectroscopy (XPS). In order to estimate the photocatalytic activity of the synthesized materials, the photodegradation experiment of an azo dye (Acid Red 44; $C_{10}H_7N=NC_{10}H_3(SO_3Na)_2OH$)was carried out by using an Xe arc lamp (300 W, Oriel). A 420 nm cut-off filter was used for visible light irradiation. From the results, Pt-deposited $C-TiO_2$ showed a far superior phothdegradation activity to Degussa P25, the commercial product under the irradiation of visible light and enhanced photocatalytic activity of visible-working $C-TiO_2$. This is a useful result into the application for the purification system of dye wastewater using visible energy of sun light.

• Journal of the Korean Society of Food Science and Nutrition
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• v.19 no.6
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• pp.625-635
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• 1990

The purpose of this study was focused on investigation of biochemical properties of amylases in germinating corn(Zea mays L.) the amylase(I), (II) and (III) from germinating corn seeds were partially purified by ammonium sulfate precipitation, DEAE-Sephadex A-50 ion exchange column chromatography and Sephadex G-100 gel filtration. The last step was effective for separation of the corn amylases to a homogeneous slate. the purified amylase(I) was identified as a kind of $\alpha$-amylase from the fact that 5％ starch solution was hydrolysed into mainly maltose and maltotetrose by it, and amylase(II) and amylase(III) were enzymes producing maltotetrose as main product. The molecular weight and specific activity of the amylase(I), (II) and (III) were determined to be 54,000 and 70.47 unit/mg, 39,000 and 62.98 unit/mg, and 51,000 and 80.39 unit/mg, respectively. It showed a tendency to increase the amylases activities in presence of Ba, Ca, Co and Fe groups, but inhibits in that of Ag, Sn, Hg and Zn groups, and amylase(I), (II) and (III) remained stable at pH 5-6 and 2$0^{\circ}C$ for 40 days in containing of 1 mM CaCl$_2$. The optimum pH and optimum temperatures were pH 6, pH 5 and pH 6 and 35$^{\circ}C$, 55$^{\circ}C$ and 55$^{\circ}C$, respectively. These results suggest that the amylase(I), (II) and (III) were different amylases.

• Korean Journal of Environmental Agriculture
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• v.35 no.3
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• pp.166-174
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• 2016

BACKGROUND: The current study developed a monitoring method of 6 veterinary antibiotics (amoxicillin, ampicillin, enrofloxacin, tetracycline, chlortetracycline, oxytetracycline) in agricultural soils using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in positive electrospray ionization mode.METHODS AND RESULTS: Sample preparation was carried out using acidic acetonitrile and citrate salts followed by purification with dispersive solid phase extraction (d-SPE). Separation on Eclipse Plus C₁₈ column was conducted in gradient of the mobile phase, 0.1% formic acid and 5 mM ammonium formate in methanol (A) and 0.1% formic acid and 5 mM ammonium formate in distilled water (B). The linearity of the matrix-matched calibrations expressed as the coefficient of determination was good with R²≥0.9900. The limit of quantifications (LOQs) ranged from 0.5 to 10 μg/kg for all analytes. Analysis of 51 agricultural soil samples taken in the Republic of Korea revealed concentrations less than 1.9 μg/kg for enrofloxacin, 75.5 μg/kg for chlortetracycline.CONCLUSION: The method was successfully applied to monitor 6 veterinary antibiotics from 51 field incurred agricultural soil samples in 17 provincial areas throughout the Republic of Korea. The developed method was simple, easy, and versatile and can be used for monitoring various veterinary antibiotics in soil.

• Journal of the Korean association of regional geographers
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• v.10 no.4
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• pp.757-774
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• 2004

This paper is to reclassify systematically the functions of urban river: that is, water supply, land management, transportation and energy source as social and economic function; formation of geomorphic surface, water-side landscape, community constitution and boundary and separation between regions as spatial function; and drainage of waste water, purification, habitation, and weather regulation as ecological function. On the basis of this reclassification, it can be argued that the socio-economic functions (eg. water supply) of the river among the functions of the river have been strongly mobilized in the process of modernization, while the spatial function and ecological function of urban river have been ignored. The Kumho river which flows through Daegu and the adjacent area has made a great contribution to the modem development process of the river basin area, but as a result of a selective development of a specific function of the river, that is the social and economic function, it now suffers from the lack of instream flow and is deprived of its original functions with the water pollution and degradation. Moreover the Daegu region seems no longer possible to develop on the dependence of the river. In order to overcome this kind of social and environmental crisis, this paper is to suggest both some principles and main evaluating indicators to restore the original and comprehensive functions of the river, and important measures to make the co-evolution of the city and the river possible.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.52 no.5
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• pp.461-467
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• 2019

Several studies investigating the prevention and treatment of external parasites in farmed olive flounder Paralichthys olivaceus have found that the anticoccidial agent toltrazuril sulfone is an effective antiparasitic. Prior to undertaking a full-scale study, we developed analytical methods to detect the levels of toltrazuril and toltrazuril sulfone in farmed flounder samples using liquid chromatography-electrospray ionization tandem mass spectrometry (LC-MS/MS). This analysis showed that LC-MS/MS changed the mobile phase and collision energy of toltrazuril and toltrazuril sulfone. This was validated using established conditions. Sample pre-treatment for this process involved extraction with dichloromethane and purification by liquid-liquid extraction in formic acid, acetonitrile, and h-hexane, followed by determination of all compounds by LC-MS/MS. Separation was achieved within 10 min by gradient elution using a Capcell Pak C18 ($3.0{\mu}m$, $100{\times}2.0mm$) analytical column (Shiseido UG 120V) with a mixture of 0.1% (v/v) formic acid and acetonitrile. Multiple reaction monitoring was used for selective detection of toltrazuril and toltrazuril sulfone. This method yields satisfactory results for linearity, precision, and limits of quantification. Therefore, the method established in our study will serve as a basis for further research on parasite control by toltrazuril and toltrazuril sulfone.

• Economic and Environmental Geology
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• v.11 no.3
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• pp.89-98
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• 1978

Mineralogy, beneficiation, and processes of titanium ores are reviewed from petrographic viewpoints. The most important titanium minerals are ilmenite ($FeTiO_3$) and rutile ($TiO_2$). Ilmenite will play major role :for raw material, because rutile are rapidly diminishing. Thus, there is a need to develope a successful process for producing high grade Ti02 from ilmenite. Commercial, as well as R and D processes to treat more abundant ilmenite ores fall in three general classess: 1. Iron in ilmenite is partially or completely reduced and separated either physically or chemically. 2. Iron is reduced to ferrous state and chemically leached away from the titanium. 3. Ore is treated to make chlorides either selectively or with subsequent separation and purification of $TiC_4$. Routes and efficiencies of these process technologies are primarily influenced by the particular ore deposit to be mined and secondly by environmental considerations. One deposit parameters which influence ilmenite process technologies are: 1. Complexity of microtextures of ilmenite intergrown with Fe-oxide minerals. 2. Composition of concentrates; ilmenites contain minor amounts of substituted Mg, Mn, and V. These elements plus iron and gangue minerals can cause difficulties to complete reactions, substantial acid consumption, difficulties of removing waste solids, and waste disposal problems. Major contributions to be made by petrologists for process optimization are: characterization and interpretation of compositional and physical changes of raw materials and solids derived from process streams. These informations can play significant role in selecting and improving process steps for titania production.

• Membrane Journal
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• v.28 no.1
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• pp.75-82
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• 2018

Forward osmosis (FO) desalination system has been highlighted to improve the energy efficiency and drive down the carbon footprint of current reverse osmosis (RO) desalination technology. To improve the trade-off between water flux and salt rejection of thin film composite (TFC) desalination membrane, thin film nanocomposite membranes (TFN), in which nanomaterials as a filler are embeded within a polymeric matrix, are being explored to tailor the separation performance and add new functionality to membranes for water purification applications. The objective of this article is to develop a graphene nanocomposite membrane with high performance of water selective permeability (high water flux, high salt rejection, and low reverse solute diffusion) as a next-generation FO desalination membrane. For advances in fabrication of graphene oxide (GO) membranes, layer-by-layer (LBL) technique was used to control the desirable structure, alignment, and chemical functionality that can lead to ultrahigh-permeability membranes due to highly selective transport of water molecules. In this study, the GO nanocomposite membrane fabricated by LBL dip coating method showed high water flux ($J_w/{\Delta}{\pi}=2.51LMH/bar$), water selectivity ($J_w/J_s=8.3L/g$), and salt rejection (99.5%) as well as high stability in aqueous solution and under FO operation condition.