• Korean Chemical Engineering Research
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• v.51 no.1
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• pp.98-105
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• 2013

The NaA zeolite particles were dispersed in a poly(vinyl alcohol) (PVA) matrix to prepare a composite membrane. The nano sized zeolite particles of NaA were synthesized in the laboratory and the mean size was approximately 60 nm. Pervaporation characteristics such as a permeation flux and a separation factor were investigated using the membrane as a function of the feed concentration from 0.01 to 0.05 mole fraction and the weight % of NaA particles between 0 wt% and 5 wt% in the membrane. Also, the micro sized particles of $5{\mu}m$ were dispersed in the membrane for a comparison purpose. When the ethanol concentration in the feed solution was 0.01 mole fraction, the flux of water significantly increased from $600g/m^2/hr$ to $2000g/m^2/hr$ as the content of the nano NaA particles in the membrane increased from 0 wt% to 5 wt%, while the NaA particles improved the separation factor from 1.5 to 7.9. When the flux of water through the membrane containing nano sized particles was roughly 15% increased compared to the micro sized particles, whereas the separation factor of water was found to be approximately 5% increased. It can be said that the role of the nano sized NaA particles is quite important since both the flux and the separation factor are strongly affected.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.3
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• pp.162-166
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• 2011

Phosphorous contaminated in the effluent from sewage treatment plants can cause the eutrophication in surface water bodies. In this study, a powder of titanium oxysulfate-sulfuric acid made of ion-exchange materials was immobilized in an alginate gel and this material was examined to evaluate its phosphorous removal efficiency. Equilibrium and kinetic studies were carried out to quantify the adsorption capacity and time dependent removal rate of phosphorous. Adsorption isotherms and kinetic parameters were obtained for the entrapped titanium beads with three different methods. Equilibrium data were analyzed using Langmuir adsorption isotherm model and found to be well fitted to the model. The maximum adsorption capacity for phosphorous by the titanium bead synthesized with the solution method was 92.26 mg/g. Kinetic data followed a pseudo-second-order kinetic model. Due to the low production cost and high adsorption capacity, the titanium bead synthesized by the solution method has a potential to be utilized for the cost-effective removal of phosphorous from wastewater.

• Clean Technology
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• v.23 no.3
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• pp.270-278
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• 2017

This study introduces a method to easily fabricate highly monodisperse pectin hydrogel microfibers in a microfluidic device by using partial gelation. The hydrodynamic parameters between the pectin aqueous solution and the calcium ions containing oil solution are precisely controlled to form a stable elongation flow of the pectin aqueous solution, and partial gelation of the pectin aqueous solution is performed by the chelating of the calcium ions at the interface between the two phases. The partially gelled pectin aqueous solution is phase-separated from the oil solution in an aqueous calcium chloride solution outside the microfluidic device and is completely gelled to produce monodisperse pectin hydrogel microfibers. The thickness of the pectin hydrogel microfiber is controlled in a reproducible manner by controlling the volumetric flow rate of the initially injected pectin aqueous solution. The pectin hydrogel microfibers were 200 to 500 micrometers in diameter and had a coefficient of variation below 5% under all thickness conditions, indicating that the pectin hydrogel microfibers produced by partial gelation are highly monodisperse. In addition, biomaterials can be immobilized to the pectin hydrogel microfibers produced by a single process, demonstrating the possibility that our pectin hydrogel microfiber can be used as carriers for biomaterials or tissue engineering.

• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.1-5
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• 1999

The dispersing performance of oligomer-type anionic surfactants ($C_mD-Na$), cooligomers of diethylester maleate and alkylvinylether of different alkyl chain lengths or polymerization degree were studied on the aqueous suspension of iron dxide or titanium dioxide particles which are hydrophilic pigments. The dispersion behavior of oligomer-type surfactants for these dispersoids, although anion charges on the surface of pigments particles showed different dispersing properties, was dependent upon the side alkyl chain length. Oligomer-type surfactants having more than $C_8$ side alkyl chain exhibited large dispersing action for relatively hydrophobic ${\alpha}-Fe_2O_3$ and Anatase $TiO_2$ in the concentration range of more than 0.1% oligomer-type surfactant solutions.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.61-62
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• 2022

Carbon nanotubes were used to secure high strength, high durability, and fracture toughness of cementitous composites.In this study, carbon nanotube dispersion solutions were prepared using commercial superplasticizers, such as polycarboxylate-ester and sodium naphthalene sulfonate with tip sonication. The solutions were used to prepare cement paste with MWCNT and The mechanical properties of the cement paste composite with MWCNT solutions were evaluated.

• Applied Chemistry for Engineering
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• v.24 no.6
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• pp.656-662
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• 2013

The iron oxide ($Fe_3O_4$) particles in the coolant of the secondary system of a nuclear power plant reduce the heat transfer performance or induce corrosion on the surface of the heat transfer tube. To prevent these problems, we conducted a study to improve the dispersion stability of iron oxide using polymeric dispersant injection in simulated secondary system water. The three kinds of anionic polymers containing carboxyl groups were selected. The dispersion characteristics of the iron oxide particles with the polymeric dispersants were evaluated by performing a settling test and measuring the transmission, the zeta potential, and the hydrodynamic particle size of the colloid solutions. Polymeric dispersants had a significant impact on the iron oxide dispersion stability in an aqueous solution. While the dispersant injection tended to improve the dispersion stability, the dispersion stability of iron oxide did not increase linearly with an increase in the dispersant concentration. This non-linearity is due to the agglomerations between the iron oxide particles above a critical dispersant concentration. The effect of the dispersant on the dispersion stability improvement was significant when the dispersant concentration ratio (ppm, dispersant/magnetite) was in the range of 0.1 to 0.01. This suggests that the optimization of dispersant concentration is required to maximize the iron oxide removal effect with the dispersant injection considering the applied environments, the iron oxide concentration and the concentration ratio of dispersant to iron oxide.

• Applied Chemistry for Engineering
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• v.9 no.1
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• pp.1-5
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• 1998

The dispersing behaviors of oligomer-type anionic surfactants, cooligomers of diethyl maleate(CmD-Na) or maleic anhydride (CmM-Na) and $C_4{\sim}C_{16}$ alkyl vinylether, which have a different alkyl chain length of the hydrophobic group or degree of polymerization, were studied on the aqueous suspension of ${\alpha}-$ and ${\beta}-$ copper phthalocyanine and carbon black particles. In case of the side alkyl chain length of $C_4{\sim}C_{10}$ of CmD-Na, the dispersing actions were good in the concentration range of 0.01 to 0.1%. Especially, side alkyl groups played an important role in the orientation adsorption on the surface of pigment particles, and oligomers having smaller degrees of polymerization were more effective in the dispersing action, but did not affect the dispersability of carbon black.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.50-50
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• 2012

투습방수필름으로 많이 사용되고 있는 폴리우레탄(PU)에 광촉매 기능성을 가지고 있는 나노-$TiO_2$(Degussa P25)를 1~10wt% 복합시킨 후, 은(Ag)이온 수용액에서 자외선 조사에 의한 광증착시키는 과정을 거쳐 은이 도핑된 PU/$TiO_2$/Ag 하이브리드 멤브레인 필름을 제조하였다. (주)비에스지에서 제공받은 PU/DMF/MEK 용액에 $TiO_2$를 초음파로 균일하게 분산배합한 후, 필름캐스팅하여 만든 필름을 AgNO3 수용액에 침지시키고 254nm의 자외선을 30~120초 동안 조사하는 광증착법으로 은을 환원시켜 도핑시켰다. 은 도핑된 하이브리드 필름을 Shaking flask method에서 폐렴간균, 황색포도상구균에 대한 항균성을 측정하고, Clear zone method에서 대장균에 대한 항균성을 측정한 결과, $TiO_2$ 함량이 3wt% 이상이고 UV조사시간이 60초 이상인 경우 99.9% 이상의 항균성을 나타내는 것을 확인하였다.

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.53-61
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• 2014

온실가스 증가로 인한 지구온난화 문제가 범세계적인 문제로 대두되고 있는 가운데, 특히 온실가스 중 약 76%이상을 차지하는 이산화탄소를 흡수하기 위한 흡수제 개발에 여러 국가들이 심혈을 기울이고 있다. 그 중 이산화탄소 흡수제로 가장 상용화 되어 있는 모노에탄올아민(monoethanolamine, MEA)은 분자량이 작아 몰 농도비에 따른 이산화탄소의 흡수에 유리하고 반응속도가 빠르다는 장점이 있으나, 재생에 필요한 에너지가 높다는 단점이 존재한다. 수용액중에서 MEA가 $CO_2$를 흡수하는 반응의 반응자유에너지는 반응메카니즘을 이해하는데 가장 기본적인 도구이다. 본 연구에서는 B3LYP, M06-2X의 밀도범함수를 이용하여 MEA의 $CO_2$ 흡수반응의 반응자유에너지를 계산하는 계산모델을 선정하였다. 수용액에서 MEA가 $CO_2$를 흡수하는 반응의 반응자유에너지를 밀도범함수를 이용하여 계산할 때는, 수용액상태에서 화학종의 분자구조를 최적화하는 것이 필요하였다. 또한 M06-2X 밀도범함수가 B3LYP 밀도범함수보다 좋은 결과를 주었으며, 분산보정을 하는 것이 보다 좋은 결과를 주었다.

• Analytical Science and Technology
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• v.8 no.3
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• pp.293-298
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• 1995

The stability of brass coated on steel cords with pH and applied constant potential changes in aqueous solution has been investigated by AC impedance measurements. In solutions of the constant pH, as a applied constant potential is shifted to positive potential, the coating pore resistance is reduced. The fact indicates that as a applied constant potential is shifted to positive potential, the brass coated is dissolved more in solution. The stability of brass coated on steel cords decrease in the order pH=7.1 > pH=4.0 > pH=10.0. The above results are demonstrated by the data of scanning of electronic microscopy(SEM)/energy dispersive spectrometer(EDS).