• Membrane Journal
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• v.28 no.6
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• pp.406-413
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• 2018

In OBIGGS, a small amount of ozone in the atmosphere damages the polymer membrane. Therefore, the ozone removal device is installed at the front end to prevent the damage of the membrane by reducing the concentration of ozone in the gas delivered to the membrane. In this study, two hollow fiber membranes, PI and PSf, used to fabrication hollow fiber module with an effective membrane area of $6.37cm^2$ for gas separation in OBIGGS. The ozone concentration in the chamber was maintained at 2-3 ppm. The gas was continuously supplied into the module by using a pump. The gas permeation characteristics and the tensile strength were evaluated as a function of ozone exposure time. The PI-based hollow fiber membrane showed only 20% reduction in the transmittance, and remained its original uniformity without any significant changes. However, when PSf type hollow fiber membranes were used, the permeability decreased by more than 80% and the tensile strength decreased by more than 70%.

• Membrane Journal
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• v.5 no.1
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• pp.35-43
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• 1995

For several years lots of attempts have been made to establish the liquid membrane-based techniques for separations of gas mixtures especially containing carbon dioxide. A more effective system to separate $CO_{2}$ from flue gases, a circulatory hollow-fiber membrane absorber(HFMA) consisting of absorption and desorption modules with vacuum mode, has been considered in this study. Gas-liquid mass transfer has been modeled on a membrane module with non-wetted hollow-fibers in the laminar flow regime. The influence of an absorbent flow rate on the separation performance of the circulatory HFMA can be predicted quantitatively by obtaining the $CO_{2}$ concentration profile in a tube side. The system of $CO_{2}/N_{2}$ binary gas mixture has been studied using pure water as an(inert) absorbent. As the absorbent flow rate is increased, the permeation flux(i.e., defined as permeation rate/membrane contact area) also increases. The enhanced selectivity compared to the previous results, on the other hand, shows the decreasing behavior. It has been found obviously that the permeation flux depends on the variations of pressure in gas phase of desorption module. From an accurate comparison with the results of conventional flat sheet membrane module, the advantageous permeability of this circulatory HFMA can be clearly ascertained as expected. Our efforts to the theoretical model will provide the basic analysis on the circulatory HFMA technique for a better design and process.

• Journal of Korean Society of Water and Wastewater
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• v.17 no.4
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• pp.503-509
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• 2003

COD fractionation of primary settled municipal wastewater was conducted by respirometry. RBCOD (Readily Biodegradable COD) fraction was analyzed to be 21% of influent TCOD. However, SCOD fraction, analyzed by physical separation using $0.45{\mu}m$ membrane filter, was about 31% of TCOD. Therefore, 10% of soluble inert COD was comprised in TCOD. It means that kinetic analysis of activated sludge system was impossible because serious error would be occurred if SCOD was used as a biodegradable soluble component instead of RBCOD estimated from respirometry. In this study, RBCOD fraction of raw wastewater could be analyzed by respirometry within the error range of 57%. In addition, SBCOD (Slowly Biodegradable COD) content could be determined by kinetic simulation of the experimental results. SBCOD showed about 2-fold higher fraction (38% of TCOD) as compared with RBCOD.

• Membrane Journal
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• v.24 no.4
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• pp.292-300
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• 2014

Chlorine-resistant sulfonated poly(arylene ether sulfone) random copolymer (SPAES)-thin film composite (TFC) membranes for desalination are prepared using monoglyme as a selective solvent, which dissolves SPAES, but should be inert to porous polysulfone layer (e.g., Udel$^{(R)}$). Different from formic acid and diethylene glycol used as other selective solvents, monoglyme is environmentally friendly and has much lower boiling temperature. After a pretreatment of Udel$^{(R)}$ support film in isopropyl alcohol-glycerine mixture to minimize pore penetration leading to fairly reduced water flux, coating of SPAES solution in monoglyme onto the support and stepwise drying processes are conducted for defect-free TFC formation. The transport behavior through SPAES-TFC membranes is observed, correlating with the effects of sulfonation level, protonation, and physical and chemical crosslinking of SPAES selective layers.

• 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.

• Journal of the Korean Chemical Society
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• v.51 no.4
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• pp.324-330
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• 2007

A new ion selective PVC membrane electrode is developed as a sensor for mercury(II) ions based on bis(benzoylacetone) propylenediimine (H2(BA)2PD) as an ionophore. The electrode shows good response characteristics and displays, a linear Emf vs. log[Hg2+] response over the concentration range of 1.0×10-6 to 1.0×10-1 M Hg(II) with a Nernstian slope of 29.8±0.75 mV per decade and with a detection limit of 2.2×10-7 M Hg(II) over the pH range of 2.5-11.5. Selectivity concentrations for Hg(II) relative to a number of potential interfering ions were also investigated. The sensor is highly selective for Hg(II) ions over a large number of cations with different charge. The sensor has been found to be chemically inert showing a fast response time of 60 s and was used over a period of 3 months with a good reproducibility (S = 0.27 mV). The electrode was successfully applied to determine mercury(II) in real samples with satisfactory results.

• Membrane and Water Treatment
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• v.11 no.3
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• pp.231-235
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• 2020

Industrialization and modern developments have led to an influx of toxic heavy metals into the aquatic environment, and the accumulation of heavy metals has serious adverse effects on humans. Among the various heavy metal treatment methods, adsorption is very useful and frequently used. Plastic materials, such as polypropylene and polyethylene, have been widely used as filter media due to their mechanical and chemical stability. However, the surface of plastic material is inert and therefore the adsorption capability of heavy metals is very limited. In this study, granular media and fiber media composed of polypropylene and polyethylene are used, and the surface modification was conducted in order to increase adsorption capability toward heavy metals. Oxygen plasma generated hydroxyl groups on the surface of the media to activate the surface, and then acrylic acid was synthesized on the surface. The grafted carboxyl group was confirmed by FT-IR and SEM. Heavy metal adsorption capability of pristine and surface modified adsorbents was also evaluated. Overall, heavy metal adsorption capability was increased by surface modification due to electrostatic interaction between the carboxyl groups and heavy metal ions. Fibrous PP/PE showed lower improvement compared to granular PP media because pore blockage occurred by the surface modification step, thereby inhibiting mass transfer.

• Journal of the Korean Applied Science and Technology
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• v.28 no.1
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• pp.57-63
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• 2011

Polymer electrolyte membrane fuel cell (PEMFC) performance degrades when hydrogen sulfide ($H_2S$) is present in the fuel hydrogen gas; this is referred to as $H_2S$ poisoning. This paper reveals $H_2S$ poisoning on PEMFC by measuring electrical performance of single cell FC under various operating conditions. The severity of $H_2S$ poisoning depended on $H_2S$ concentration under best operating conditions($65^{\circ}C$ of cell temperature and 100% of anode humidification). $H_2S$ adsorption occured on the surface of catalyst layer on MEA, but not on the gas diffusion layer(GDL) by analyzing SEM/EDX data. In addition, MEA poisoning by $H_2S$ was cumulative but reversible. After poisoning for less than 150 min, performance of PEMFC was recovered up to 80% by just inert nitrogen gas purging.

• Journal of environmental and Sanitary engineering
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• v.13 no.2
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• pp.106-114
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• 1998

This study was carried out for the purpose of industrial reuse of effluent released from activated sludge unit by $\gamma $-ray irradiation technique. The dissolved organic carbon in the effluent of an activated sludge unit is mostly refractory or inert material which are difficult to be degraded by micro organism. The effluent generated from activated sludge unit was irradiated with Co$^{60}$ $\gamma $-ray under condition of air bubbling. The effects of irradiation on the pH, COD, TOC, color, molecular weight distribution were investigated by membrane filtration and u.v.-spectrum analysis. With increasing dose, the TOC was decreased smoothly. The COD was increased at lower dose, while the COD was decreased at higher dose. The TOC and COD, however, were decreased smoothly when TiO$_{2}$ was added to the solution. It was thought that the differential decreasing trend of COD and TOC in according to the absence or presence of TiO$_{2}$ was due to the molecular weight distribution shifted from group of higher molecular weight to group of lower one which are more easy to be decomposed. The removal efficiency of color was 71.5% and it was increased to 85.7% when TiO$_{2}$ was added to the solution. The $\gamma $-ray irradiation was effective on the production of chlorine.

• Macromolecular Research
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• v.15 no.6
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• pp.565-574
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• 2007

In this study, five representative, commercially available polymers, Ultem 1000 polyetherimide, Kapton polyimide, phenolic resin, polyacrylonitrile and cellulose acetate, were used to prepare pyrolyzed polymer membranes coated on a porous {\alpha}-alumina$ tube via inert pyrolysis for gas separation. Pyrolysis conditions (i.e., final temperature and thermal dwell time) of each polymer were determined using a thermogravimetric method coupled with real-time mass spectroscopy. The surface area and pore size distribution of the pyrolyzed materials derived from the polymers were estimated from the nitrogen adsorption/desorption isotherms. Pyrolyzed membranes from polymer precursors exhibited type I sorption behavior except cellulose acetate (type IV). The gas permeation of the carbon/{\alpha}-alumina$ tubular membranes was characterized using four gases: helium, carbon dioxide, oxygen and nitrogen. The polyetherimide, polyimide, and phenolic resin pyrolyzed polymer membranes showed typical molecular sieving gas permeation behavior, while membranes from polyacrylonitrile and cellulose acetate exhibited intermediate behavior between Knudsen diffusion and molecular sieving. Pyrolyzed membranes with molecular sieving behavior (e.g., polyetherimide, polyimide, and phenolic resin) had a $CO_2/N_2$ selectivity of greater than 15; however, the membranes from polyacrylonitrile and cellulose acetate with intermediate gas transport behavior had a selectivity slightly greater than unity due to their large pore size.