• KSBB Journal
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• v.19 no.1
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• pp.62-66
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• 2004

The oxygen permeation characteristics of BOPP, OPP and CPP membranes were studied against various thicknesses and temperatures. The experimental results showed that the present method of using electrochemical oxygen sensor was a convenient method for measurement of membrane permeability of oxygen and its activation energy, while the thickness dependency on permeability has an order of BOPP ＞ CPP ＞ OPP. And the activation energy of oxygen permeability showed different values for each membrane ranging from 13.1 kJ/mol to 28.5 kJ/mol, without depending on membrane thickness, presumably due to its depending upon membrane material itself.

• Journal of Korean Society on Water Environment
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• v.27 no.1
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• pp.44-53
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• 2011

Membrane bio-reactor (MBR) has several advantages over the conventional activated sludge process, including a high biomass, low sludge production, and better permeate quality. Therefore, the MBR have gained popularity for municipal and industrial wastewater treatment. However the MBR usually were used for sewage and low streng th wastewater treatment because of membrane fouling problem and limitation of oxygen transfer into biomass. In this study, the hybrid process combining MBR and pure oxygen was tested for high strength organic wastewater treatment in the COD loading range from 2 to $10kgCOD/m^3{\cdot}day$. The hybrid process, membrane coupled pure oxygen high compact reactor (MPHCR), had been operated for one year and operation parameters, the effect of COD loading, MLSS concentration and the location of membrane module were studied for membrane fouling characteristic. Also membrane resistance test and the component of foulant was analyzed to investigate what is specific foulant in the MBR.

• Proceedings of the Membrane Society of Korea Conference
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• 2002.05a
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• pp.35-41
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• 2002

Dense oxygen ionic conducting materials can be used for oxygen separation membranes at high temperatures. However, they show relatively low permeation flux because of their large resistances. To reduce resistances and improve the oxygen permeation flux, thin dense yttria-stabilized-zirconia (YSZ)/Pd composite dual-phase membranes were fabricated by a new approach that combines the reservoir method and chemical vapor deposition (CVD). A thin porous YSZ layer was coated on a porous alumina support by dip-coating the YSZ suspension. A continuous Pd phase was formed inside pores of the YSZ layer by the reservoir method. The residual pores of the YSZ/Pd layer were plugged with yttria/zirconia by CVD to ensure the gas tightness of the membranes. The oxygen permeation fluxes through these composite membrane were 2.0$\times$10$^{-8}$ mol/cm$^2$.s and 4.8$\times$10$^{-8}$ mol/cm$^2$.s at 105$0^{\circ}C$ when air and oxygen were used as the permeate gases, respectively. These oxygen permeation values are about 1 order of magnitude higher than those of pure YSZ membranes prepared under similar conditions.

• Korean Membrane Journal
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• v.9 no.1
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• pp.34-42
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• 2007

A perovskite-type ($La_{0.6}Sr_{0.4}Ti_{0.2}Fe_{0.8}O_{3-{\delta}}$) dense ceramic membrane was prepared by polymerized complex method, using citric acid as a chelating agent and ethylene glycol as an organic stabilizer. Effect of Ti addition on lanthanum-strontium ferrite mixed conductor was investigated by evaluating the thermal expansion coefficient, the oxygen flux, the electrical conductivity, and the phase stability. The thermal expansion coefficient in air was $21.19\;{\times}\;10^{-6}/K$ at 473 to 1,223 K. At the oxygen partial pressure of 0.21 atm ($20%\;O_2$), the electrical conductivity increased with temperature and then decreased after 973 K. The decrement in electrical conductivity at high temperatures was explained by a loss of the lattice oxygen. The oxygen flux increased with temperature and was $0.17\;mL/cm^2{\cdot}min$ at 1,223 K. From the temperature-dependent oxygen flux data, the activation energy of oxygen ion conduction was calculated and was 80.5 kJ/mol at 1,073 to 1,223 K. Also, the Ti-added lanthanum-strontium ferrite mixed conductor was structurally and chemically stable after 450 hours long-term test at 1,173 K.

• Applied Chemistry for Engineering
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• v.7 no.5
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• pp.877-887
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• 1996

The ideal membranes for membrane-covered oxygen probes system should be selectively permeable for oxygen and chemically inert, and have good mechanical strength. Polysulfone(PSf) was selected to develop the membrane for membrane-covered oxygen electrodes system. PSf membranes have properties such as good reproducibility, good mechanical strength, chemical inertness, and high heat resistance. PSf membranes were cast from polymer solution on the glass plate at constant temperature, and casting solvents used were tetrahydrofuran(THF), methylene chloride, and N-methyl-2-pyrrolidone(NMP). Tricresyl phosphate(TCP) as plasicizer was added to PSf to increase the softness of membrane. The permeation characteristics were observed for pure oxygen and nitrogen through pure PSf membranes by variable volume method and membrane-covered electrode system. The permeability coefficients of oxygen and nitrogen measured by variable volume method were slightly decreased with increasing of upstream pressure. The permeation properties of PSf membrane using methylene choride as casting solvent were not affected by the PSf amount of polymer solution. The permeability coefficients of oxygen and nitrogen for PSf membrane containing TCP were very slightly lower than those for pure PSf membrane, but ideal separation factors were slightly higher. The flexibility of PSf membrane containing 2wt% TCP was better than that of pure PSf membrane. It was expected that this increase in flexibility would solve the difficulty of fixing the membrane to the cathode. The membrane-covered oxygen probes system was composed of anode, cathode and electrolyte. The type of the anode was Ag/AgCl half-cell, that of cathode was Ag, and the electrolyte was 4N KCl solution. The result of sampled current voltametry for PSf membrane showed the plateu region at -0.3V~-1.0V. The correlation coefficient of oxygen partial pressure versus current for PSf membrane was relatively high, 0.99949. It was concluded that PSf membrane was the good candidate for the membrane-covered oxygen probes system.

• Nuclear Engineering and Technology
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• v.31 no.6
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• pp.541-547
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• 1999

Corrosion control, in the end-shield cooling system of Wolsung Nuclear Power Plant, is directly related to the control of dissolved oxygen (DO). The current method, being used to deoxygenate the end-shield cooling water, is a chemical treatment by addition of reducing agent, hydrazine, to react with DO. This method has several limitations including high reaction temperature of hydrazine , unwanted explosive hydrogen gas production, and its intrinsic harmful property. A new approach to remove DO using a membrane-based oxygen removal system (MORS) was tried to overcome limitations of the hydrazine treatment. The DO removal efficiency of the MORS was found to be in the range 87% to 98%: The higher vacuum, the lower water flow rate and the higher water temperature tend to increase the DO removal efficiency.

• Membrane Journal
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• v.21 no.4
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• pp.321-328
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• 2011

$PrBa_{0.9}Sr_{0.1}Co_2O_{5+{\delta}}$ oxide was synthesized by soild state reaction method. Dense ceramic membrane was prepared using as-prepared powder by pressing and sintering at $1250^{\circ}C$. XRD result of membrane showed double perovskite structure. Leakage and oxygen permeation test were conducted on the membrane sealed by pyrex ring as a sealing material. Oxygen permeation was measured in the temperature range from 850 to $950^{\circ}C$. The oxygen flux of $PrBa_{0.9}Sr_{0.1}Co_2O_{5+{\delta}}$ membrane was increased with the temperature from 0.15 to $0.32mL/cm^2{\cdot}min$.

• Korean Membrane Journal
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• v.8 no.1
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• pp.1-12
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• 2006

In semiconductor industries, dissolved oxygen is one of the most undesirable contaminants of ultrapure water. A method for dissolved oxygen removal (DOR) consists in the use of polymeric hollow fibres, loaded with a catalyst and fed with a reducing agent such as hydrogen. In this work, PVDF hollow fibres loaded with Pd were characterized by means of perporometry, scanning electron microscopy (SEM), energy dispersive X-ray (EDX). The hollow fibre analyzed shows a five-layer structure with remarkable morphological differences. An estimation of pore diameters and their distribution was performed giving a mean pore diameter of 100 nm. The permeance and selectivity of the fibres were measured using $H_2,\;N_2,\;O_2$ as single gases, at different operating conditions. An $H_2$ permeance of $37 mmol/m^2s$ was measured and $H_2/O_2$ and $H_2/N_2$ selectivities of ca. 3 were obtained. $H_2$ permeance was 1/3 when a water stream flows in the shell side. Catalytic fibrebehaviour was simulated using a mathematical model for a loop membrane reactor, considering only $O_2$ and $H_2$ diffusive transport inside the membrane and their catalytic reaction. Dimensionless parameters such as the Thiele modulus are employed to describe the system behaviour. The model agrees well with the experimental reaction data.

• Korean Chemical Engineering Research
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• v.44 no.6
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• pp.597-601
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• 2006

The degradation of the Nafion membrane by oxygen radical (OH, $HO_2$) was investigated in Polymer electrolyte membrane fuel cell (PEMFC). Nafion membrane was degraded in Fenton solution consisted with hydrogen peroxide (10-30％) and ferrous ion (1-4 ppm) at $80^{\circ}C$. After degradation in Fenton solution, C-F, S-O and C-O chemical bonds of membrane were broken by oxygen radical attack. Breaking of C-F bond reduced the mechanical strength of Nafion membrane, and hence induced pinholes, resulting in increase of $H_2$ crossover through the membrane. Decomposition of S-O and C-O bonds decreased the ion exchange capacity of the electrolyte membrane. The performance of unit cell composed the membrane, which was degraded in 30％ $H_2O_2$ with 4ppm $Fe^{2+}$ solution for 48 hr, was about half times as low as one with normal membrane.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.208.2-208.2
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• 2016

Many researchers have paid attention to the studies on the interaction between non-thermal plasma and aqueous solutions for biomedical applications. The gas composition in the plasma is very important. Oxygen and nitrogen are the main gases of interest in biological applications. Especially, we focus on the oxygen concentration. In this experiment, we studied the role of oxygen concentration in plasma induced chemical reactions in solution. At first, the amount of ions are measured according to changing the oxygen concentration. And we checked the relationship between these ions and pH value. Secondly, when the oxygen concentration is changed, it identified the type and amount of radical generated by the plasma. In order to confirm the effect of these chemical property change to biological material, hemoglobin and RBCs are chosen. RBCs are one of the common basic biological cells. Thirdly, when plasma treated according to oxygen concentration in nitrogen feeding gas, oxidation of hemoglobin and RBC is checked. Finally, membrane oxidation of RBC is measured to examine the relation between hemoglobin oxidation and membrane damage through relative hemolysis and Young's modulus. Our results suggest that reactive species generated by the plasma differsdepending on the oxygen concentration changes. The pH values are decreased when oxygen concentration increased. OH decrease and NO increase are also observed. These reactive species makes change of chemical properties of solution. We also able to confirm that the difference in these reactive species to affect the oxidation of the Hb and RBCs. The Hb and RBCs are more oxidized with the high oxygen concentration conditions. But membrane is damaged more by plasma treatment with only nitrogen gas. It is shown that red blood cells membrane damage and oxidation of hemoglobin are not directly related.