• Membrane Journal
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• v.24 no.1
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• pp.50-62
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• 2014

An asymmetric microfiltration membranes were prepared with polysulfone by an immersion precipitation phase inversion method. Microfiltration membranes were prepared by polysulfone/N-methyl-2-pyrrolidone/polyvinylpyrrolidone/phosphoric acid casting solution and water coagulant. The vapor induced phase inversion method was used to prepare the membranes. The pore size and the morphology were changed by the phosphoric acid additive, the temperature of casting plate and the exposure time at the relative humidity of 74%. The morphology of membranes was investigated by scanning electron microscopy and microflow permporometer. By the addition of the phosphoric acid additive in the casting solution, the morphology of the prepared membranes were changed from a dense sponge structure to a loose asymmetric sponge structure. Due to the addition of catalytic amount of phosphoric acid to NMP casting solution, the mean pore size increased almost $0.2{\mu}m$ and the water flux increased about 3,000 LMH. The temperature of casting plate and exposure time had a apparent effect on the skin layer structure and the pore size and the porosity of the membrane.

• Membrane Journal
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• v.31 no.6
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• pp.434-442
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• 2021

Poly(vinylidene fluoride) (PVDF) membrane has a good membrane durability because of its high mechanical resistance, thermal and chemical stability. However, the strong hydrophobic property of PVDF membrane can induce a low water permeability and easy fouling by proteins and organic matters. In order to improve the anti-fouling properties of PVDF membrane, the PVDF mixed matrix asymmetric membranes impregnated with biofunctional material 𝛽-cyclodextrin (𝛽-CD) in the membrane structure were prepared by phase inversion method. The membrane filtration experiments of pure water and BSA solution were performed using the PVDF/𝛽-CD mixed matrix asymmetric membranes prepared according to the 𝛽-CD contents. The experiments showed that the introduction of 𝛽-CD into the PVDF polymer matrix contributed to increase in the hydrophilic property of the PVDF membranes, and this led to the reduction of contact angles and improvement of anti-fouling properties. The PVDF/𝛽-CD membrane which was prepared using the dope solution with a 2 wt% 𝛽-CD content represented 64 L/m²·h of pure water flux, 95% of BSA rejection and maximum 80% of flux enhancements compared to flux results of the pristine PVDF membrane.

• Proceedings of the Membrane Society of Korea Conference
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• 1998.10a
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• pp.103-105
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• 1998

Asymmetric polymeric membranes prepared by the phase transition technique usually have either a top layer consisting of closely packed nodules or pores dispersed throughout the membrane surfaces. In this study, we present AFM image of a polysulfone membrane which show a clear evidence for the nodular structure and porous structure resulted from different phase separation mechanisms; spinodal decomposition and nucleation and growth. The surface morphology obtained by SEM and AFM was also compared.

• Molecules and Cells
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• v.37 no.8
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• pp.592-597
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• 2014

The cell membrane provides critical cellular functions that rely on its elaborate structure and organization. The structure of turtle membranes is an important part of an ongoing study of erythrocyte membranes. Using a combination of atomic force microscopy and single-molecule force spectroscopy, we characterized the turtle erythrocyte membrane structure with molecular resolution in a quasi-native state. High-resolution images both leaflets of turtle erythrocyte membranes revealed a smooth outer membrane leaflet and a protein covered inner membrane leaflet. This asymmetry was verified by single-molecule force spectroscopy, which detects numerous exposed amino groups of membrane proteins in the inner membrane leaflet but much fewer in the outer leaflet. The asymmetric membrane structure of turtle erythrocytes is consistent with the semi-mosaic model of human, chicken and fish erythrocyte membrane structure, making the semi-mosaic model more widely applicable. From the perspective of biological evolution, this result may support the universality of the semi-mosaic model.

• Membrane Journal
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• v.15 no.4
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• pp.272-280
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• 2005

In this study, asymmetric polysulfone membranes were prepared by the phase inversion method and the casting solutions were containing N-methyl-2-pyrrolidone (NMP) as a solvent. Deionized water and various alcohols(methanol, ethanol, and propanol) were used as a coagulation medium in preparing asymmetric polysulfone membranes. This study investigates the effect of alcohol coagulants having different solubility parameters as a pore-former on the construction of porous structures and their pure water permeation properties. Asymmetric polysulfone membranes immersed in the pure alcohol coagulation bath solution showed the typical sponge-like structures and the reduced water permeability as compared with those of polysulfone membranes precipitated in the pure water coagulation bath solution. In the water/alcohol mixtures, asymmetric polysulfone membranes showed the finger-like structures with the sponge-like structures. Therefore, the sponge-like structure of polysulfone membrane was formed under the delayed demixing systems while the porosity of membrane was decreased significantly. The water permeability of polysulfone membrane precipitated in the pure water coagulant showed 164 [$L/m^2hr$] at 14.7 psi. In case of polysulfone membranes prepared in the pure methanol and ethanol coagulant, they showed the water permeability of 56 and 30 [$L/m^2hr$], respectively.

• Membrane Journal
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• v.7 no.1
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• pp.22-30
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• 1997

Porous asymmetric membranes were prepared from polyetherimide polymer by the phase-inversion technique under different conditions. The performance of the membranes was tested for the removal of acetone vapour from nitrogen. A membrane which showed a high acetone permeability and a high selectivity was chosen and tested further for the separation of different organic vapours from nitrogen. The molecular structure of organic vapours and the selectivity were correlated. A strong correlation was also found between the chromatographic retention time of the organic vapour and the selectivity. These experimental results led to the conclusion that the sorption is the factor governing the separation of volatile organic compounds from nitrogen. A membrane was also prepared by coating the surface of a porous polyetherimide membrane with silicone rubber. The performance of membranes with and without silicone rubber coating was compared.

• Proceedings of the Membrane Society of Korea Conference
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• 1994.06a
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• pp.33-43
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• 1994

It is the purpose of this paper to review the recent developments and future trends in various membrane processes, which will result in energy savings. Historically, there was a long period of academic curiosity in membrane research covering from gas separation to reverse osmosis. With advent of asymmetric membrane technology, many membrane processes proved to be energy efficient than the conventional separation methods. Thus, membrane technology has gained wide acceptance from many sectors of industry. The commercial sale of membranes is still modest compared to the major technologies, but it is one of the fastest growing industries. Recently the U.S.Department of Energy conducted a study (1) to evaluate and prioritize research needs in the membrane separation industry in order to foster and better support the deveolpment of energy-efficient new technologies. The National Science Foundation (U.S.A.) did also do a similar investigation. Both agencies have arrived neary at the same conclusion, that is, membrane separations can offer many new and alternative methods of separations that are more energy efficient than existing processes. This paper is largely based on these findings.

• Membrane Journal
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• v.27 no.3
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• pp.273-283
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• 2017

Polysulfone (PSF) is one of an important polymer that has been widely used in the manufacture of asymmetric microfiltration (MF) membranes. PSF membrane is considered as hydrophobic membrane that easily fouled during membrane operation process. The blending method is an effective method for improving the fouling resistance of PSF membranes. sPES (sulfonated polyethersulfone) is one of the useful polymers that can be used in PSF polymer blend method to improve hydrophilicity of PSF membranes. In this study, microfiltration polymer membranes were prepared by using PSF/sPES/PVP/BE/DMF casting solution and water coagulant. The morphology of MF membranes was changed by addition of a small amount of sPES in casting solution. The morphology of the sPES added membranes was changed into a highly asymmetric structure. The active layer grew and mean pore size was decreased by addition of sPES. However, the water flux of PSF/sPES/DMF/PVP/BE membrane was higher than that of PSF/DMF/PVP/BE membrane.

• Korean Membrane Journal
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• v.1 no.1
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• pp.38-42
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• 1999

Membrane technology can be applied in two ways to produce pure enantiomers. In one case a membrane separation process can be cmbined with an enantiospecific reaction to obtain so-called 'en-antiospecific membrane reacto' These systems are useful to carry out asymmetric synthesis or kinetic resolution and simulatneously separate the produced enantiomer. As for general membrane reactors the result is a more compact system with a higher conversion: in fact removal of a product drives equilibrium-limited reactions towards completion. The other way to apply membrane technology to chiral production is the use of intrinsically enantioselective membranes that are able to distinguish between two isomers favouring preferential transport of only one isomer in absence of reaction. In this paper the current development of chiral membrane processes will be discussed.

• Proceedings of the Membrane Society of Korea Conference
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• 1999.07a
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• pp.31-34
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• 1999

Membrane technology can be applied in two ways to produce pure enantiomers. In one case, a membrane separation process can be combined with an enantiospecific reaction to obtain so-called 'enantiospecific membrane reactor'. These systems are useful to carry out asymmetric synthesis or kinetic resolution and simultaneously separate the produced enantiomer. As for general membrane reactors, the result is a were compact system with a higher conversion; in fact, removal of a product drives equilibrium-limited reactions towards completion. The other way to apply membrane technology to chiral production is the use of intrinsically enantioselective membranes that are able to distinguish between two isomers favouring preperential transport of only one isomer in absence of reaction. In This paper, the current development of chiral membrane processes will be discussed.