• Membrane Journal
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• v.34 no.5
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• pp.293-303
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• 2024

In this study, we studied the fabrication of a cation-exchange membrane (CEM) with high permselectivity for monovalent ions that can be applied to an electrodialysis (ED) process for efficient separation of acid-metal ions from acid wastewater. The pore-filled cation-exchange membranes (PFCEMs) were fabricated by filling a porous substrate with sodium 4-vinylbenzenesulfonate (NaSS) monomers having sulfonic acid groups and vinylphosphonic acid (VPA) monomers having phosphonic acid groups together with a crosslinker into an asymmetric structure and in-situ photopolymerization. The fabricated PFCEMs had a slightly lower ion-exchange capacity than that of a commercial membrane, but they exhibited electrical resistance and mechanical properties suitable for practical applications. The permselectivity of the PFCEMs fabricated with various NaSS:VPA molar ratios and a commercial membrane (CSE, Astom, Japan) in H⁺/Fe²⁺ mixed solutions was measured. The best permselectivity was confirmed at the condition of NaSS:VPA = 25:75, which was more than 10 higher than that of the commercial membrane. In addition, the ED results of H⁺/Fe²⁺ mixed solution using the optimally fabricated membrane showed excellent acid-metal ion separation performance compared to the commercial membrane. The CEM including both sulfonic acid groups with excellent ion conductivity and phosphonic acid groups with strong binding affinity for metal ions is expected to be effective in separating various valuable metal ions in addition to Fe²⁺ from acid waste solutions.

• Applied Chemistry for Engineering
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• v.9 no.4
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• pp.579-584
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• 1998

Polymer dispersed liquid crystal(PDLC) composite films were made by polymerization induced phase separation method using UV-curing to investigate the effect of fabrication conditions, such as photoinitiator concentration, film thickness, polymerization temperature, and electric field during polymerization, etc., on the electro-optic properties. As the amount of photoinitiator increased, the driving voltage of PDLC device increased due to the increase of small-size liquid crystal phases. This was considered as the results from the increased interfacial area between liquid crystal (LC) and polymer matrix, since LC molecules at the interfacial regions were relatively difficult to response for the applied electric field. When the higher molecular weight oligomer (PTDA-1000) was used as matrix, the initial transmittance was observed to be relatively higher than that for the lower molecular weight oligomer (PTDA-250). Saturation transmittance for PTDA-1000 was observed at relatively lower voltage than that for PTDA-250, of which transmittance was not saturated even at 60 V. As polymerization temperature increased, the initial transmittance of resulting PDLC film increased due to the larger LC droplets formation and the more matched refractive index between LC and matrix than those cases for the lower polymerization temperature. Though driving voltage decreased for the thinner film, it was considered that optimum thickness of the film should be maintained to get some practical contrast, which is the ratio of off- and on-state transmittance. Furthermore, electro-optic properties such as initial transmittance, driving voltage, and response time were observed to be considerably affected by application of external field during polymerization.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.05b
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• pp.98-101
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• 2004

최근에 이루어지고 있는 생명공학의 성장에 따라 단백질을 대량으로 정제할 수 있는 공정 개발에 대한 필요성이 부각되고 있다. 이러한 목적으로 기존에 이루어지고 있는 침전법, 결정화법 그리고 원심분리법과 같은 방법은 선택도가 매우 떨어지는 단점이 있으며, 반면 크로마토그래피 및 전기영동과 같은 방법은 탁월한 선택도에 비해 그 규모가 매우 작은 경우 에 알맞은 방법으로서 대량생산 체계에서는 적합하지 못하다는 것이 그 단점이다.(중략)

• Membrane Journal
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• v.31 no.6
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• pp.426-433
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• 2021

In this study, a novel material polyketone (PK) was chosen and PK micro/nano fiber membranes were fabricated via electrospinning method under various conditions. After that, the potential application in oil-water separation was thoroughly investigated. The surface of microfiber membrane formed under high humidity especially became much rougher than that formed under low humidity. When salt was added to the spinning solution, the diameter of fibers was reduced up to 90% and the nanofiber membranes could be formed. The oil/water emulsions were prepared and separated under gravity condition using the manufactured rPK-LNC and PK-H membranes. The separation characteristics was evaluated by measuring total organic carbon (TOC) and turbidity. Meanwhile, the changes in the physical properties of fiber membranes under various conditions and with or without salt, as well as the changes in oil water separation characteristics were also studied.

• Korean Chemical Engineering Research
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• v.51 no.3
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• pp.330-334
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• 2013

Mixtures of poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) and silica nanoparticles are coated on the surface of a silk fabrics separator. The coated separators are finally prepared by injecting an electrolyte solution and then characterized for use of lithium-ion battery separator/electrolyte. In the preparation, various contents of dibutylphthalate (DBP) as a plasticizer are used to enhance the formation of micropores within the coated membrane. The coated silk fabrics separators are characterized in terms of ionic conductivity, drenching rate, and electrochemical stability, and the charge-discharge profiles of lithium-ion batteries adopting the coated separators are also examined. As a result, the coated silk fabrics separator prepared using DBP 40~50 wt% and silica shows the superior separator properties and high-rate capability. This is due to (i) high sustainability of silk fabrics, (ii) the formation of micropores with the coated layer membrane by DBP, (iii) increase in drenching rate by silica nanoparticles to involve great enhancements in specific surface area and ionic conductivity.

• Resources Recycling
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• v.33 no.5
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• pp.14-27
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• 2024

Citric acid is an organic acid used in various industries, and its demand is steadily increasing. Citric acid is primarily obtained via recovery processes, such as the separation and purification of the fermentation broth obtained from microbial fermentation. Various technologies have been developed for the recovery processes, such as solvent extraction, ion exchange resins, and electromembrane separation, with a primary focus on precipitation methods. This study examines citric acid recovery technologies that are both commercially available and are being developed and suggests directions for the development of more efficient and eco-friendly recovery technologies, particularly for recycling waste citric acid solutions.

• Korean Chemical Engineering Research
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• v.54 no.3
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• pp.293-298
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• 2016

A hydrogel electrolyte consisting of 6 M KOH aqueous solution, potassium polyacrylate (PAAK, 3 wt.%), and a hydrophilic silica OX50 (1 wt.%) was prepared to use as an electrolyte medium coated on a Scimat separator of activated carbon supercapacitor. The silica particle distributed homogeneously on surface pores of the separator to increase ionic conductivity and electrochemical stability of the hydrogel electrolyte. The silica addition also involved superior specific capacitance even at higher scan rates due to decrease in interfacial resistance between hydrogel electrolyte and activated carbon electrode.

• Membrane Journal
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• v.4 no.2
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• pp.96-105
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• 1994

Theoretical model for membrane transport of large polye!ectroiyte is presented. When the electric field is applied, the molecular conformation quickly orients in the field direction showing overshooting orientation. the predicted dependence of overshoot time and orientation upon field intensity and molecular size aids to understand the dynamic motion of molecules in membrane transport. The dynamics of the overshoot is associated with self-trapping conformations of molecule. The understanding of these effects supports evidences for the electrophoretic filtration of polydectrolyte in the polymeric membrane. This paper shows one example for molecular study in the theoretical review paper of membrane transport.

• Membrane Journal
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• v.24 no.2
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• pp.151-157
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• 2014

In this study, the nanofiber composite membrane was prepared by electrospinning method with poly (ancrylonitrile) (PAN) and a dispersed solution of graphene oxide (GO) and $Fe_3O_4$ functionalized graphene oxide (M-GO) in dimethyl formamide (DMF). The pore-diameter of prepared membranes was controlled by change of those layers. It was confirmed with SEM that the nanofiber composite membranes having fiber size of 500 nm were prepared. It was found with Raman spectroscopy and EDS that GO and M-GO were well dispersed on those membranes. Final nanofiber composite membrane showed the similar pore properties ($0.21{\sim}0.24{\mu}m$/pore-size, 40% porosity) with the commercial membrane ($0.27{\mu}m$/pore-size, 55% porosity) and their water-flux results also showed the 200% higher flux than its PAN membrane. From these results, it was expected that the nanofiber composite membrane prepared by electrospinning method could be utilized as a water-treatment membrane.

• Journal of the Korean Electrochemical Society
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• v.12 no.4
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• pp.324-328
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• 2009

The internal short-circuit between cathodes and anodes has been known to be a critical concern for the safety failures of lithium-ion batteries, which is strongly influenced by the thermal stability of separators. In this study, to effectively suppress the internal short-circuit failures, we developed a new composite separator with the improved thermal stability compared to conventional polyolefin-based separators. The composite separators were prepared by introducing a ceramic coating layer ($Al_2O_3$/PVdF-HFP) onto both sides of a polyethylene (PE) separator. The microporous structure of ceramic coating layers is determined by controlling the phase inversion of coating solutions and becomes more developed with the increase of nonsolvent (water) content. This structural change of ceramic coating layers was observed to greatly affect the thermal stability as well as the electrochemical performance of composite separators, which was systematically discussed in terms of phase inversion.