• KSBB Journal
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• v.11 no.3
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• pp.360-366
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• 1996

Electrodialysis of acetic acid was studied to find out the trend of the transport of organic acids through ultrafiltration and ion exchange membranes. The net transport rate of acetic acid was determined from the electro-migration velocity relative to the electro-osmotic flow rate through the membrane. Electro-osmosis flows through ultrafiltration membranes were from the anodic side to the cathodic side in the presence of electric field. The surface of ultrafiltration membrane was measured by the electro-osmotic flow to be charged negatively. Different transport behaviors of acetic acid were found with the ultrafiltration membranes of different materials. In general, regenerated cellulose membranes (YM series) were more effective than polysulfone membranes (PM series) for the transport of acetic acid. The transport of acetic acid was affected by electric strength, distance between the electrodes, surface area of electrode, temperature, and pore size of membrane. The transport rate through the ion exchange membrane was 1.5 to 3 times of those through the ultrafiltration membranes at the constant current of 150 mA in the experimental ranges. The transport rate of acetic acid through the ion exchange membrane increased by 10% with a pulse electric field of 10 sec/hr.

• Membrane Journal
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• v.34 no.1
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• pp.58-69
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• 2024

Reverse electrodialysis (RED) is an electro-membrane process employing ion-exchange membranes (IEMs) that can harvest electric energy from the concentration difference between seawater and river water. Multivalent ions contained in seawater and river water bind strongly to the fixed charge groups of the IEM, causing high resistance and reducing open-circuit voltage and power density through uphill transport. In this study, a pore-filled anion-exchange membrane (PFAEM) with excellent monovalent ion selectivity and electrochemical properties was fabricated and characterized for RED application. The monovalent ion selectivity of the prepared membrane was 3.65, which was superior to a commercial membrane (ASE, Astom Corp.) with a selectivity of 1.27 under the same conditions. Additionally, the prepared membrane showed excellent electrochemical properties, including low electrical resistance compared to ASE. As a result of evaluating RED performance under seawater of 0.459 M NaCl/0.0510 M Na₂SO₄ and river water of 0.0153 M NaCl/0.0017 M Na₂SO₄, the maximum power density of 1.80 W/m² was obtained by applying the prepared membrane, which is a 40.6% improved output performance compared to the ASE membrane.

• Journal of the Korean Ceramic Society
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• v.51 no.5
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• pp.466-471
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• 2014

Hydrous zirconia particles were prepared from $ZrOCl_2$ aqueous solution using an electro-dialysis [ED] process. For the preparation of $(Zr,Y)(OH)_4$ precipitates, 3 mol% $YCl_3$ was added into $ZrOCl_2$ aqueous solution. During the hydrolysis of 0.5 mol/L $(Zr,Y)OCl_2$ solution at $90^{\circ}C$ a slurry solution was obtained. The ED process was used for the removal of chlorine from the slurry solution. Two kinds of slurry solution were sampled at the beginning and end of the ED process. The morphology of hydrous zirconia particles in the solution was observed using an inverted optical microscope and an FE-SEM. The hydrous zirconia particles were nano-crystalline, and easily coagulated with drying. Yttrium stabilized zirconia [YSZ] powder could be obtained by the calcination of $(Zr,Y)(OH)_4$ precipitates prepared from a $(Zr,Y)OCl_2$ solution by the ED process. The coagulated dry powders were shaped and sintered at $1500^{\circ}C$ for 2 h. The sintered body showed a dense microstructure with uniform grain morphology.

• Journal of the Korean Ceramic Society
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• v.53 no.3
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• pp.325-331
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• 2016

Anatase particles of titanium dioxide were prepared from $TiCl_4$ aqueous solution by using an electro-dialysis [ED] process. For the preparation of an aqueous solution of $TiCl_4$ precipitates, $TiCl_4$ liquid frozen in ice was transferred to a neck flask and then hydrolyzed using deionized [DI] $H_2O$. During the hydrolysis of the $TiCl_4$ solution at $0^{\circ}C$, a slurry solution of $TiOCl_2$ was obtained and the color changed from red to orange. The ED process was applied for the removal of chlorine content in the slurry solution. Two kinds of hydrolyzed slurry solution with lower [$Ti^{4+}$] and higher [$Ti^{4+}$] were sampled and the ED process was applied for the samples according to the removal time of [$Cl^-$]. With de-chlorination, the solution status changed from sol to gel and the color quickly changed to blue. Finally, white crystalline powders were formed and the phase was confirmed by XRD to be anatase crystallites. The morphology of the hydrous titania particles in the solution was observed by FE-SEM. The hydrous titania particles were nano-crystalline, and easily coagulated with drying.

• Membrane and Water Treatment
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• v.4 no.3
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• pp.215-222
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• 2013

The maximum current density that can be achieved in bipolar membrane electrodialysis is limited by the sharp increase in resistance that is experienced when the water content at the membrane interface is not adequately replenished and the membranes dry out. In this paper we show how the water content near the interface depends on the properties of the membranes. A water retaining parameter is introduced, which characterizes the thermodynamic properties of the membrane material and may be used to guide the choice of polymers for mitigation of the dry-out problem.

• Membrane Journal
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• v.30 no.2
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• pp.79-96
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• 2020

Secondary energy conversion systems have been briskly developed owing to environmental issue and problems of fossil fuel. They are basically operated based on electro-chemical systems. In addition, ion exchange membranes are one of the significant factors to determine performance in their systems. Therefore, the ion exchange membranes in suitable conditions must be developed to improve the performance for the electro-chemical systems. These ion exchange membranes can be classified into various types such as cation exchange membrane, anion exchange membrane and bipolar membrane. Their membranes have distinct characteristics according to the chemical, physical and morphological structure. In this review, the types of ion exchange membranes and their fabrication processes are described with main characteristics. Moreover, applications of ion exchange membranes in newly developed energy conversion systems such as reverse electrodialysis, redox flow battery and water electrolysis process are described including their roles and requirements.

• Membrane Journal
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• v.18 no.2
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• pp.138-145
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• 2008

A series of anion exchange composite membranes were prepared and characterized for electro-dialysis process used in the removal of toxic anion and cation polutants in groundwater or wastewater. The membranes were prepared as follows; first, porous poly(ethylene) (PE) substrates were fully impregnated with monomer mixtures with various ratio of vinylbenzylchloride (VBC), divinylbenzene (DVB) and ${\alpha},\;{\alpha}$-azobis(isobutyronitrile) (AIBN). Second, they were thermally polymerized to yield crosslinked poly(VBC-DVB)/PE composite membranes. Finally, the membranes were treated in trimethylamine (TMA)/acetone to give $-N^+(CH_3)_3$-containing poly(VBC-DVB)/PE membranes. The basic membrane properties such as ion exchange capacity (IEC), electric resistance and water content of the resulting membranes were measured as a function of VBC/DVB and TMA/Acetone content. As a result, the composite membranes showed lower electric resistance, lower water content and higher IEC than commercial anion exchange membranes (AMX, Astom) due to thin PE substrates, indicating that the composite membranes could be successfully applied to the electrodialysis for water treatment.

• Korean Chemical Engineering Research
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• v.52 no.6
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• pp.768-774
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• 2014

SI process is a thermochemical process producing hydrogen by decomposing water while recycling sulfur and iodine. Various technologies have been developed to improve the efficiency on Section III of SI process, where iodine is separated and recycled. EED(electro-electrodialysis) could increase the efficiency of Section III without additional chemical compounds but a substantial amount of $I_2$ from a process stream is loaded on EED. In order to reduce the load, a crystallization technology prior to EED is considered as an $I_2$ removal process. In this work, $I_2$ particle sinking behavior was modeled to secure basic data for designing an $I_2$ crystallizer applied to $I_2$-saturated $HI_x$ solutions. The composition of $HI_x$ solution was determined by thermodynamic UVa model and correlation equations and pure properties were used to evaluate the solution properties. A multiphysics computational tool was utilized to calculate particle sinking velocity changes with respect to $I_2$ particle radius and temperature. The terminal velocity of an $I_2$ particle was estimated around 0.5 m/s under considered radius (1.0 to 2.5 mm) and temperature (10 to $50^{\circ}C$) ranges and it was analyzed that the velocity is more dependent on the solution density than the solution viscosity.

• Food Science and Preservation
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• v.22 no.6
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• pp.859-866
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• 2015

The purpose of this study was to develop a supplemental healthy food that can help prevent high blood pressure-related diseases caused due to the excessive consumption of sodium in salt. This was achieved by using ion-displacement techniques to produce mineral salt with lower sodium content by using fermented brown rice by-products rich in minerals. Mineral salt containing 2019.2 mg/100 g of potassium, 678.5 mg/100 g of magnesium, 48.7 mg/100 g of calcium, and 19.5 mg/100 g of sodium was obtained by fermenting brown rice by-products to create a culture medium for the mineral salt. Mineral salt containing 1769.7 mg/100 g of potassium, 573.6 mg/100 g of magnesium, 35.3 mg/100 g of calcium, and 19.5 mg/100 g of sodium was obtained by filtering and refining the by-product extract of fermented brown rice. The results showed that when the stream velocity of the instrument used for electrolysis was 200 mL/min and the current and the concentration of the reactive liquid in the purified water chamber were higher, the effect of electrolysis was greater. Ion hot water extraction of the fermented brown rice by-products improved by up to 95% and was collected as purified water within 90 min of the reaction time. Chloride ions with pH 7.4 were produced by mixing sodium hydroxide in a purified saline water chamber with electro-analyzed water. The salt produced in this study contained low sodium, 5.7~30%, as compared to 40% sodium content of the normal salt.

• Korean Journal of Materials Research
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• v.33 no.1
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• pp.21-28
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• 2023

The electromembrane process, which has advantages such as scalability, sustainability, and eco-friendliness, is used in renewable energy fields such as fuel cells and reverse electrodialysis power generation. Most of the research to visualize the internal flow in the electromembrane process has mainly been conducted on heterogeneous ion exchange membranes, because of the non-uniform swelling characteristics of the homogeneous membrane. In this study, we successfully visualize the electro-convective vortices near the Nafion homogeneous membrane in PDMS-based microfluidic devices. To reinforce the mechanical rigidity and minimize the non-uniform swelling characteristics of the homogeneous membrane, a newly developed swelling supporter was additionally adapted to the Nafion membrane. Thus, a clear image of electroconvective vortices near the Nafion membrane could be obtained and visualized. As a result, we observed that the heterogeneous membrane has relatively stronger electroconvective vortices compared to the Nafion homogeneous membranes. Regarding electrical response, the Nafion membrane has a higher limiting current and less overlimiting current compared to the heterogeneous membrane. Based on our visualization, it is assumed that the heterogeneous membrane has more activated electroconvective vortices, which lower electrical resistance in the overlimiting current regime. We anticipate that this work can contribute to the fundamental understanding of the ion transport characteristics depending on the homogeneity of ion exchange membranes.