• Membrane Journal
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• v.29 no.5
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• pp.263-275
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• 2019

In the present study, thickness of MOR zeolite membranes was controlled by changing seed size, seeding amount, and aging time of hydrothermal solution, and then effect of membrane thickness on pervaporative ethanol dehydration for 90 wt.% ethanol-water mixture was investigated. First, nanosize MOR zeolite seeds with a diameter of 20 to 30 nm was successfully prepared by planetary milling a laboratory synthesized MOR zeolites and the coating amount was controlled by seed concentration and infiltration volume of coating solution during vacuum-assisted seeding. As seeding amount decreased, membrane thickness was reduced up to around $4{\mu}m$. The MOR zeolite membrane having a thickness of $4{\mu}m$ showed a water/ethanol separation factor of 760 and water flux of $1.0kg/m^2h$. The excellent water flux was due to the reduced membrane thickness which was derived from the nanosize seed. Therefore, it could be concluded that membrane thickness control by using nanosize seed can be a crucial factor to improve pervaporative water flux of MOR zeolite membrane.

• Membrane Journal
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• v.13 no.3
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• pp.191-199
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• 2003

Cation exchange polymer electrolyte membrane for the application of direct methanol fuel cell (DMFC) was studied. Poly(vinyl alcohol)(PVA) well known as a methanol barrier in pervaporation separation was used fur the base materials and poly(acrylic acid)(PAA) was used for the crosslinking agent with various concentration. Methanol permeability, ion conductivity, ion exchange capacity, water contents and fixed ion concentration of the membranes were investigated to evaluate the performance of the fuel cell electrolyte membrane. Methanol permeability and ion conductivity of the membranes were decreased with increasing PAA content and were increased over 15% of PAA content. These phenomena would be explained with the introduction of hydrophilic crosslinking agent. The membranes with 15% content of PAA showed methanol permeability of $6.49{\times}10^{-8}/cm^2/s,\; 2.85{\times}10^{-7}CM^2/s$ at $25^{\circ}C,\; 50^{\circ}C$ of operating temperatures, respectively. ion conductivities of the membrane were $2.66{\times}10^{-3}\;S/cm,$ $9.16{\times}10^{-3}\;S/cm$ at $25^{\circ}C,\; 50^{\circ}C$ of operating temperatures, respectively. ion exchange capacity, water content and fixed ion concentration of the membrane were revealed 1.32 meq/g membrane,0.25 g $H_2$O/g membrane and 5.25 meq/g $H_2O$, respectively.

• Membrane Journal
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• v.28 no.5
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• pp.340-350
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• 2018

In the present study, crystallographically b- and c-axis oriented mordenite zeolite membranes were prepared and their pervaporative ethanol dehydration was investigated. The seed layer with a high coverage grew to be c-axis oriented dense layer, while the seed layer with a low coverage grew to be b-axis oriented layer. This phenomenon could be explained by the evolutionary selection growth mechanism. The b-axis grown membrane with 8-membered rings showed a high separation factor of above 1000 and a considerable total flux of around $0.2kg/m^2h$. The c-axis grown, columnar structured membrane with 8- and 12-membered rings showed a low separation factor of less than 200 and a relatively high total flux of around $0.25kg/m^2h$. The high performance of b-axis grown membrane was due to the relatively small opening of 8-membered rings. Water molecules can freely permeate through the openings, but ethanol molecules, difficultly. Therefore, in the present study, we introduced a new method to control crystallographic orientation of mordenite membrane by changing seeding amount of needle-like crystals, and elucidated that b-axis oriented mordenite membrane showed better performance than c-axis grown mordenite membrane.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.256-259
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• 2000

Ethanol fermentration of glucose by a strain of Zymomonas mobilis KCTC 1535 was studied in membrane recycle bioreactor, which was coupled with closs flow hollow fiber membrane. The maximum values of product yields and productivity are 0.4685g total ethanol/ g glucose, 14.05g total ethanol/ L/h, respectively The pervaporation performance of the PDMS menbrane has been investigated for the separation of binary mixtures of EtOH/water at $50^{\circ}C{\sim}70^{\circ}C$. The optimum conditions of feed concentration, temperature, feed solution flow rates is determined to be 8%, $70^{\circ}C$, 492ml/min, respectively. An ethanol permselectivity of 7.5 and flux of $0.04kg/m^2/hr$ were obtained with these membrane

• Membrane Journal
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• v.13 no.2
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• pp.118-124
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• 2003

The ion exchange membranes prepared from the reaction between poly(vinyl alcohol) (PVA) which is known as the good methanol barrier in pervaporation membrane processes and sulfo-succinic acid (SSA) was used as the basic membranes. In order to improve the ion exchange capacity, poly(acrylic acid) (PAA) was added to this ion exchange membranes. The methanol permeabilities, ion conductivities, water contents and ion exchange capacity were measured for the resulting membranes with varying PAA contents. In general, methanol permeability and ion conductivity of PVA/SSA/PAA membranes were less than those of PVA/SSA membranes due to the reduction of free volumes resulted from crosslinking. The vehicle mechanism could be more dominant than jump mechanism for membranes in question.

• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.605-613
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• 1992

NCO-terminated prepolymers were synthesized by reacting carbonate-type polyol(PTMCG)($M_w=1,000$ and 2,000) with MDI and N-methyldiethanolamine, as a chain extender. Carbonate-type polyurethane containg zwitterionic group was prepared by reacting the prepolymer with 1,3-propane sultone. From the IR and NMR spectra of model reactions, it was known that the ionization occurred under the same condition. The structure of zwitterionic carbonate-type polyurethane(ZPU) therefore could be confirmed from the model reactions. Glass transition temperature(Tg) ranged between $-15{\sim}-30^{\circ}C$ from the thermal data. Tg was between $-15{\sim}-18^{\circ}C$ for a series of ZPU10 samples and between $-25{\sim}-26^{\circ}C$ for a series of ZPU20 polymers. Tensile strength increased with mole ratio of ionic content. On the contrary, elongation was rather dropped with mole ratio of ionic content. ZPU10-30 having better tensile strength and less elongation was selected as a membrane for the concentration of ethanol aqueous solution through pervaporation. To obtain the better selectivity, it was crosslinked with HMDI. In the swelling test, it showed the higher swelling degree at around 50wt% ethanol concentration due to the plastization effect of ethanol. To optimize the separation capacity, two operating factors-feed concentration and temperature-were considered. The overall separation capacity was as follows : separation factor, 2~83.2 ; the flux, $25.4{\sim}58.8g/m^2hr$.

• Membrane Journal
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• v.18 no.3
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• pp.198-205
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• 2008

A novel technology for homogeneous deposition of zeolite particles on a porous support was developed so that those particles played a seeding role for the growth of zeolite crystals. After the particles were dispersed in water, the aqueous solution was 134 through the bore of a porous tubular support. By keeping the other side of the support in a vacuum, the aqueous solution passed through the pores of the support, leading the particles to be homogeneously deposited on the support. The amount of the deposited particles was investigated by changing the following operating parameters: a particle concentration in the solution, a time for deposition, and the feeding rate of the solution. The amount of the deposited particles increased from 0.0019 g to 0.0208 g as the concentration of the particles was changed from 0.01 wt% to 0.3 wt%, while the feeding rate and the deposition time were kept to 100 mL/min and 4 min, respectively. As the deposition time was varied from 1 min to 4 min, the deposition amount increased from 0.0004g to 0.0019g at the typical condition of the rest parameters. Also, it was observed that the deposited weight increased from 0.0029 g to 0.01 g as the feeding rate increased from 100 mL/min to 300 mL/min. However, the total permeance of water and ethanol decreased through the zeolite membrane as the deposited weight increased.

• Applied Chemistry for Engineering
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• v.1 no.1
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• pp.52-62
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• 1990

Cationic polycarbonate type polyurethane was prepared from the quaternization reaction of N-methyldiethanolamine(MDEA) in urethane backbone which was obtained from the reaction of polycarbonate polyol, MDI and MDEA(chain exetender). Tensile strength and modulus of the cationic urethane resins were increased sharply with increasing the ionic content in urethane backbone. But hydrolysis resistance was decreased with increasing ionic contents. The selectivity of the cationic polycabonate urethane membrane for water/ethanol separation by pervaporation was about 20. The carrier mediated transport mechanism was considered the most probable separation mechanism for these membranes.

• Applied Chemistry for Engineering
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• v.8 no.1
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• pp.29-38
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• 1997

In the w/o concentrated emulsion, the volume fraction of the dispersed is greater than 0.74 and the hydrophilic liquid is dispersed in the hydrophobic liquid of the continuous phase. The emulsion has the same appearance and behaviour as a gel. The polarity of the hydrophilic liquids and hydrophobic liquids, the pH and the ionic strength of the hydrophilic liquid are found to be important factors in the stability at the polymerization temperature such as $50^{\circ}C$. The lower the polarity of the hydrophobic liquid and the higher the polarity of the hydrophilic liquid, the more stable the emulsion. Electron microscopy studies of the hydrophilic-hydrophobic polymer composites show that the particles of polyacrylamide, the dispersed phase, are separated by he network of the thin film of polystyrene, the continuous phase. This hydrophilic-hydrophobic polymer composites show higher permselectivity to water in the mixture of water-ethanol. The pervaporation experiment shows that the selectivity of the membrane ranges between 4-40 and increases with increasing enthanol concentration in the feed. The rate of permeation decreases with increasing ethanol concentration in the feed.

• Proceedings of the Membrane Society of Korea Conference
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• 1998.10a
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• pp.70-72
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• 1998

1. 서론 : 최근에 폐수나 지하수 및 음용수에 존재하는 휘발성 유기화합물(Volatile Prganic Compound, VOC)는 심각한 환경오염이 주범이 되고 있다. 이러한 문제를 해결하는 방법으로 흡착, 증류, air stripping 등의 여러 가지 분리기술이 제시되어 왔다. 그러나 전통적인 방법들은 분리된 오염물질이 제2의 상으로 전이된다는 점에서 또 다른 분리공정을 필요로 하는 단점을 지니고 있다. 이에 반해 투과증발공정은 추가적인 분리과정이 없이 효율적으로 오염된 물속의 유기용매를 제거한다는 점에서 많은 관심을 모으고 있다. 이미 알려진 이러한 VOC 제거에는 소수성이면서 고무상인 고분자가 우수한 특성을 가지는 것으로 밝혀졌고 그 중에서 실록산계 고분자가 아주 효과적인 것으로 알려져 있다. 그러나 이러한 실록산계 고분자는 기계적 강도가 약하여 필름의 박막형성능력이 떨어지는 것으로 알려져 있어 이러한 단점을 보완하기 위해 가교구조의 도입이나 공중합체의 구조를 도입하는 연구가 많이 수행되어 왔다. 이러한 연구의 한 방법으로 실록산-아미드공중합체를 이용하여 투과증발에 적용한 연구는 수행되어 왔다. 이들의 제막방법으로 주로 실록산다이아민/방향족다이아민의 비를 달리하거나 실록산다이아민의 분자량의 변화를 달리하면서 실록산-이미드 블록 또는 그래프트중합체를 제조하는 방법을 사용하였다. 이 실험에서는 주로 실록산-이미드의 비율이 낮아지면 유기용매의 선택성에서 물의 선택성으로 바뀌는 percolation point가 관찰되며 이것은 실록산-이미드의 비율이 낮을수록 물속의 유기용매의 제거에 유리하다는 것을 보여준다. 이에 따라 실록산다이아민과 다이안하이드라이드만을 사용한 실록산이미드막이 추천되나 여기에 대한 투과특성연구는 전혀 이루어지지 않았다.정육점이었고 백화점과 재래닭 사육장에서 직접구입도 하고 있었다. 구입 동기는 가족들이 좋아하고 영양가를 생각한다가 62%였으며 구입정보는 주위사람의 권유로 구입하고 있었다. $\bigcirc$ 구입할 때 중점적으로 살펴보는 사항은 신선도와 순수재래종 여부, 위생상태였다. 한편 소비자가 언제나 구입할 수 없다는 의견이 85.2%나 되어 원활한 공급과 시장조성이 아직 정착되지 않고 있었다. $\bigcirc$ 현재 유통되고 있는 재래종닭은 소비자 대부분이 잡종으로 인식하고 있었으며, 재래종과 일반육계와의 구별은 깃털색, 피부색, 정강이색등 외관상으로 구별하고 있었다. 체중에 대한 반응은 너무 작다는 의견이었고, 식품으로의 인식도는 비교적 고급식품으로 인식하고 있다. $\bigcirc$ 재래종닭고기의 브랜드화에 대한 견해는 젊고 소득이 높은 계층에서 브랜드화의 필요성을 강조하고 있다. $\bigcirc$ 재래종달걀의 소비형태는 대부분의 소비자가 좋아하였으나 아직 먹어보지 못한 응답자가 많았다. 재래종달걀의 맛에 대해서는 고소하고 독특하여 차별성을 느끼고 있었다. $\bigcirc$ 재래종달걀의 구입장소는 계란판매점(축협.농협), 슈퍼, 백화점, 재래닭 사육 농장등 다양하였으며 포장단위는 10개를 가장 선호하였고, 포장재료는 종이, 플라스틱, 짚의 순으로 좋아하였다. $\bigcirc$ 달걀의 가격은 200원정도를 적정하다고 하였으며, 크기는 (평균 52g)는 가장 적당하다고 인식하고 있으며, 난각색은 대부분의 응답자가 갈색을 선호하였다. $\bigcirc$ 재래종달걀의 구입시 애로사항은 믿을수 없고, 구입장소를 몰라서, 값