• Proceedings of the Membrane Society of Korea Conference
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• 2001.10a
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• pp.39-50
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• 2001

The performance of membranes is governed their pore struture. Pore structures of porous materials can be determined by a number of techniques. However, The novel technique, capillary folw porometry has a number of advantages. In this technique, the sample is brought in contact with a liquid that fills the pores in the membrane spontaneously. Gas under pressure is used to force the liquid from the pores and increase gas flow. Gas flow rate measured as a function of gas pressure in wet and dry samples yield data on the largest pore size, the mean flow pore size, flow distribution and permeability. Pore characteristics of a number of membranes were measured using this technique. This technique did not require the use of any toxic material and the pressure employed was low. Capillary flow porometry is a suitable technique for measurement of the pore structure of many membranes.

• Membrane and Water Treatment
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• v.1 no.2
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• pp.121-137
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• 2010

This work presents inexpensive inorganic precursor formulations to yield submicron range symmetric ceramic microfiltration (MF) membranes whose average pore sizes were between 0.1 and $0.4{\mu}m$. Incidentally, the sintering temperature used in this work was about 800 to $950^{\circ}C$ instead of higher sintering temperatures ($1100^{\circ}C$) that are usually deployed for membrane fabrication. Thermogravimetric (TGA) and X-Ray diffraction (XRD) analysis were carried out to evaluate the effect of temperature on various phase transformations during sintering process. The effect of sintering temperature on structural integrity of the membrane as well as pore size distribution and average pore size were evaluated using scanning electron microscopy (SEM) analysis. The average pore sizes of the membranes were increased from 0.185 to $0.332{\mu}m$ with an increase in sintering temperature from 800 to $950^{\circ}C$. However, a subsequent reduction in membrane porosity (from 34.4 to 19.6%) was observed for these membranes. Permeation experiments with both water and air were carried out to evaluate various membrane morphological parameters such as hydraulic pore diameter, hydraulic permeability, air permeance and effective porosity. Later, the membrane prepared with a sintering temperature of $950^{\circ}C$ was tested for the treatment of synthetic oily waste water to verify its real time applicability. The membrane exhibited 98.8% oil rejection efficiency and $5.36{\times}10^{-6}\;m^3/m^2.s$ permeate flux after 60 minutes of experimental run at 68.95 kPa trans-membrane pressure and 250 mg/L oil concentration. Based on retail and bulk prices of the inorganic precursors, the membrane cost was estimated to be $220 /$m^2$ and $1.53 /$m^2$, respectively.

• Korean Membrane Journal
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• v.7 no.1
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• pp.42-50
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• 2005

Among ceramic membranes developed to date, amorphous silica membranes are attractive for gas separation at elevated temperatures. Most of the silica membranes can be formed on a porous support by sol-gel or chemical vapor deposition (CVD) process. To improve gas permselectivity of the membrane, well-controlled pores having desired size and chemical affinity between permeates and membrane become important factors in the preparation of membranes. In this article, we review the literature and introduce our technologies on the microstructure to be solved and pore size control of silica membranes using sol-gel and CVD methods.

• Elastomers and Composites
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• v.30 no.3
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• pp.185-194
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• 1995

Membrane process has been employed to separate a specific substance from gas or liquid mixture, and treat wastewater. This is due to the fact that the substance of mixture can be permeated and separated selectively by membrane. Since Initial equipment and operation costs are not expensive, membrane process has been adopted in various fields such as petroleum Industry, chemistry, polymer, electronics, foods, biochemical industry and wastewater treatment. In this study, $CaCO_3$ particles impregnated in silicone rubber network were extracted by using supercritical carbon dioxide and pore distribution of silicone $rubber-CaCO_3$ was investigated with varying amount of extract. Silicone rubber has excellent mechanical properties such as heat-resistance, cold-resistance etc. and $CaCO_3$ has microporous structure. It is possible to make silicone $rubber-CaCO_3$ composite sheets via work-intensive kneading processes. In so doing $CaCO_3$ particles become distributed and impregnated in silicone rubber network. Supercritical carbon dioxide diffuse through composite sample, then sample is swollen. $CaCO_3$ in silicone rubber network Is dissolved in supercritical carbon dioxide, and its sites become pores. Pore distribution, pore shape and surface area are observed by SEM(scanning electron microscope) micrograph and BET surface area analyzer examination respectively. Pore characteristics of membrane suggest the possibilities that the membrane can be used for process of mixture separation and wastewater treatment.

• Membrane and Water Treatment
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• v.14 no.3
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• pp.115-120
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• 2023

The design theory for nanoporous filtration membranes needs to be established. The present study shows that the performance and technical advancement of nanoporous filtration membranes are determined by the fundamental parameter I (in the unit Watt^1/2) which is formulated as a function of the shear strength of the liquid-pore wall interface, the radius of the filtration pore, the membrane thickness, and the bulk dynamic viscosity of the flowing liquid. This parameter determines the critical power loss on a single filtration pore for initiating the wall slippage, which is important for the flux of the membrane. It also relates the membrane permeability to the power cost by the filtration pore. It is shown that for biological cellular membranes its values are on the scale 1.0E-8Watt^1/2, for mono-layer graphene membranes its values are on the scale 1.0E-9Watt^1/2, and for nanoporous membranes made of silica, silicon nitride or silicon carbonized its values are on the scale 1.0E-5Watt^1/2. The scale of the value of this parameter directly measures the level of the performance of a nanoporous filtration membrane. The carbon nanotube membrane has the similar performance with biological cellular membranes, as it also has the value of I on the scale 1.0E-8Watt^1/2.

• Korean Chemical Engineering Research
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• v.45 no.6
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• pp.669-676
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• 2007

The raw water was fractionated into hydrophobic (HPO), transphilic (TPI), and hydrophilic portions (HPI) using XAD resins. The raw water DOC contains 39% of hydrophilics, 43% of hydrophobics, and 18% of transphilics. When fractionated NOM (natural organic matter) was passed through hydrophilic membrane with 100 kDa, hydrophobic portion (HPO) caused the most fouling and hydrophilic portion (HPI) caused the least fouling. This could be related to size and adsorption capability of organics. Small sized organics would pass through membrane pores, but large sized organics would be attracted to either membrane pores or surface, which led to the fouling. An effect of membrane pore size on membrane fouling is related to the availability of organics at membrane pores. As the pore size became larger, the more organics were transported into the membrane pore. Some organics caused pore blocking, and others caused pore adsorption, which resulted in membrane fouling. Membrane material is also important for membrane fouling. More fouling occurred at hydrophobic membrane than hydrophilic membrane regardless of its pore size. Hydrophobic interaction caused more fouling at hydrophobic membrane.

• Membrane Journal
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• v.15 no.1
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• pp.22-33
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• 2005

Asymmetric PVDF membranes were prepared by the phase inversion from casting solutions containing PVDF, NMP as solvent and 1,4-dioxane, DGDE, acetone, or GBL as additives by immersing them in water. The effects of various additives on the casting solution properties, permeation properties, and membrane structures were investigated. Low miscibility of 1,4-dioxane, DGDE and acetone with the coagulant (water) compared with NMP resulted in reducing the membrane pore size. When DGDE is used as an additive, the pore size was reduced because of its incipient sharp interface formation in the water. GBL increased membrane pore size because of its polarity compared to that of NMP. The PVDF membranes with various pore sizes could be obtained by controlling the amount of additive. The effect of mixed solvent (aqueous and non-aqueous solution) on permeation through membrane was investigated. Not only solution viscosity but surface tension affected solvent permeation.

• Journal of Korean Society for Atmospheric Environment
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• v.12 no.E
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• pp.19-28
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• 1996

A pore concensation-based separation technique was studied experimentally using toluene and xylene in a nitrogen stream. The removal rate of toluene and xylene on a microporous ceramic membrane was enhanced by increasing the partial pressure difference across the membrane, but the selectivity was reduced with increasing flux of nitrogen. This was found both in vacuum and pressure modes of operation. The experimental results from this study suggest that the pores mear the inlet portion of the module were filled with the organic solvent while the pores near the exit section of the module were slightly opened as the solvent concentration was depleted along the module. In the case of xylene, the rate of N$_{2}$ permeation was reduced considerably relative to toluene, resulting in a much higher separation gactor. Condensibility of xylene appeared to be higher than that of toluene, the potential for pore condensation-based separation of xylene was also found to be higher than that for toluene.

• Journal of environmental and Sanitary engineering
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• v.13 no.3
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• pp.72-78
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• 1998

For investigation into gas permeation characteristics, the porous alumina membrane with asymmetrical structure, having upper layer with 10 nanometer under of pore diameter and lower layer with 36 nanometer of pore diameter, was prepared by anodic oxidation using DC power supply of constant current mode in an aqueous solution of sulfuric acid. The aluminium plate was pre-treated with thermal oxidation, chemical polishing and electrochemical polishing before anodic oxidation. Because the pore size depended upon the electrolyte, electrolyte concentration, temperature, current density, and so on, the the membranes were prepared by controling the current density, as a very low current density for upper layer of membrane and a high current density for lower layer of membrane. By control of current quantity, the thicknesses of upper layer of membranes were about $6{\;}{\mu}m$ and the total thicknesses of membranes were about $80-90{\;}{\mu}m$. We found that the mechanism of gas permeation depended on model of the Knudsen flow for the membrane prepared at each condition.

• Korean Membrane Journal
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• v.5 no.1
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• pp.31-35
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• 2003

The permeation characteristics of the wastewater containing Si fine particles were examined by ultrafiltration using the polyolefin tubular membrane module. Flux with time was due to the growth of Si cake deposited on the membrane surface and the pore plugging by fine particles. The rate of flux decline in the initial stage increased with the trans-membrane pressure. The pore blocking resistance was the dominant resistance at the initial period of filtration and the cake resistance began to dominate with the initial pore blocking resistance. The larger pores compared with the fine particles, the more the membrane pores could be blocked by the fine particles. Before and after treatment, the distribution of particle size was shifted toward to the left. Then, the average size of fine particles in the permeate was 20 nm.