• Membrane Journal
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• v.2 no.1
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• pp.59-66
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• 1992

The experimental studies were carried out on ultrafiltration of PEG #6000 and dextran 70T macromole¬cules. using an asymmetric cellulose acetate membrane in a cross flow plane type cell. Effects of pressure difference. feed concentration were studied on permeate flux and observed rejection for both the macromole¬cules. and the concentration polarization layer resistance $R_{b1}$ on permeate flux was analysed. The concentration polarization layer resistance $R_{b1}$ was correlated with the average macromolecule concen¬tration $C_{b1}$ in polarization layer. The resulting dimensionless correlation was expressed as : $\frac{R_{b1}}{{R_m}}=\alpha[\frac{\rho_{b1}}{C_{b1}}]^\beta$

• BMB Reports
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• v.33 no.6
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• pp.541-547
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• 2000

Fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) was used to evaluate the effects of chlorpromazine HCl on the range of the rotational mobility of bulk bilayer structure of the synaptosomal plasma membrane vesicles (SPMV) isolated from a bovine brain. In a dose-dependent manner, chlorpromazine HCl increased the anisotropy (r), limiting anisotropy ($r_{\infty}$) and order parameter (S) of DPH in the membranes. Cationic 1-[4-(trimethylammonio)-phenyl]-6-phenylhexa-1,3,5-hexatriene (TMA-DPH) and anionic 3-[p-(6-phenyl)-1,3,5-hexatrienyl]-phenylpropionic acid (PRO-DPH) were utilized to examine the range of transbilayer asymmetric rotational mobility of the neuronal membranes. The anisotropy (r) of TMA-DPH in the inner monolayer was 0.034 greater than the value of PRO-DPH in the outer monolayer of the membranes. Both cationic TMA-DPH and anionic PRO-DPH were also used to examine the transbilayer asymmetric effects of chlorpromazine HCl on the range of rotational mobility of the membranes. Chlorpromazine HCl have a decreasing effects on the rotational mobility of the bulk bilayer structures and have a greater decreasing effect on the mobility of the inner monolayer as compared to the outer monolayer of the membranes. It has been proven that chlorpromazine HCl exhibit a selective rather than nonselective fluidizing effect within the transbilayer domains of the SPMV.

• Proceedings of the Membrane Society of Korea Conference
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• 1999.07a
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• pp.39-42
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• 1999

Perfluoropolymers represent the ultimate resistance to hostile chemical environments and high service temperature, attributed to the presence of fluorine in the polymer backbone, i.e. to the high bond energy of C-F and C-C bonds of fluorocarbons. Copolymers of Tetrafluoroethylene (TEE) and 2, 2, 4Trifluoro-5Trifluorometoxy- 1, 3Dioxole (TTD), commercially known as HYFLON AD, are amorphous perfluoropolymers with glass transition temperature (Tg)higher than room temperature, showing a thermal decomposition temperature exceeding 40$0^{\circ}C$. These polymer systems are highly soluble in fluorinated solvents, with low solution viscosities. This property allows the preparation of self-supported and composite membranes with desired membrane thickness. Symmetric and asymmetric perfluoropolymer membranes, made with HYFLON AD, have been prepared and evaluated. Porous and not porous symmetric membranes have been obtained by solvent evaporation with various processing conditions. Asymmetric membranes have been prepared by th wet phase inversion method. Measure of contact angle to distilled water have been carried out. Figure 1 compares experimental results with those of other commercial membranes. Contact angles of about 120$^{\circ}$for our amorphous perfluoropolymer membranes demonstrate that they posses a high hydrophobic character. Measure of contact angles to hexandecane have been also carried out to evaluate the organophobic character. Rsults are reported in Figure 2. The observed strong organophobicity leads to excellent fouling resistance and inertness. Porous membranes with pore size between 30 and 80 nanometers have shown no permeation to water at pressures as high as 10 bars. However high permeation to gases, such as O2, N2 and CO2, and no selectivities were observed. Considering the porous structure of the membrane, this behavior was expected. In consideration of the above properties, possible useful uses in th field of gas- liquid separations are envisaged for these membranes. A particularly promising application is in the field of membrane contactors, equipments in which membranes are used to improve mass transfer coefficients in respect to traditional extraction and absorption processes. Gas permeation properties have been evaluated for asymmetric membranes and composite symmetric ones. Experimental permselectivity values, obtained at different pressure differences, to various single gases are reported in Tab. 1, 2 and 3. Experimental data have been compared with literature data obtained with membranes made with different amorphous perfluoropolymer systems, such as copolymers of Perfluoro2, 2dimethyl dioxole (PDD) and Tetrafluorethylene, commercialized by the Du Pont Company with the trade name of Teflon AF. An interesting linear relationship between permeability and the glass transition temperature of the polymer constituting the membrane has been observed. Results are descussed in terms of polymer chain structure, which affects the presence of voids at molecular scale and their size distribution. Molecular Dyanmics studies are in progress in order to support the understanding of these results. A modified Theodoru- Suter method provided by the Amorphous Cell module of InsightII/Discover was used to determine the chain packing. A completely amorphous polymer box of about 3.5 nm was considered. Last but not least the use of amorphous perfluoropolymer membranes appears to be ideal when separation processes have to be performed in hostile environments, i.e. high temperatures and aggressive non-aqueous media, such as chemicals and solvents. In these cases Hyflon AD membranes can exploit the outstanding resistance of perfluoropolymers.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.521-528
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• 2008

The micro-porous asymmetric PVDF hollow fiber membranes for gas-liquid contactor were prepared by the dry-jet wet phase inversion process and the characteristics of hollow fiber membranes were evaluated by the gas permeation method and scanning electron microscope. The chemical absorbent for removal of $SO_2$ gas was sodium hydroxide at bench scale hollow fiber membrane contactor. The experiments were performed in a counter-current mode of operation with gas in the shell side and liquid in the fiber lumen of the module to examine the effect of various operating variables such as concentration of absorbent, gas flow rate, L/G ratio and concentration of inlet $SO_2$ gas on the $SO_2$ removal efficiency using PVDF hollow fiber membrane contactor. Membrane mass transfer coefficient($k_m$) was calculated by mathematical modeling. The volumetric overall mass transfer coefficient increased with increasing the concentration of absorbent and L/G ratio. The increase of the absorbent concentration and L/G ratio not only provides more sufficient alkalinity but also decreases liquid phase resistance. The volumetric overall mass transfer coefficient increased with increasing gas flow rate due to decreasing the gas phase resistance.

• Membrane Journal
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• v.23 no.1
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• pp.80-91
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• 2013

Metal-templated condensation of cyclohexanedione dioxime and phenylboronic acid in the presence of Fe(II) sulfate heptahydrate proceeds cleanly in methanol to furnish the Fe(II) clathrochelate. An organic/inorganic hybrid membranes composed of Fe(II) clathrochelate and polyethersulfone was prepared by using phase inversion method. For membrane preparation, the Fe(II) clathrochelate was highly soluble (3~5 g/L) in DMF, NMP, and DMAc, which meets the requirements for the solubility of metal complexes in polar aprotic solvent used in membrane preparation. It was stable even in the presence of strong acids, such as trifluorosactic acid (pKa = 0.3). It was characterized by UV-vis spectroscopy, and their stability in solution phase studied in the presence of (i) strong acids or (ii) competing chelates. Organic/inorganic hybrid membranes were prepared with polyethersulfone, polyvinylpyrrolidone, p-toluenesulfonic acid, Fe(II) clathrochelate and DMF by using nonsolvent induced phase inversion method. The addition of Fe(II) clathrochelate leads increase of surface pore density, mean pore size and flux. We can obtain highly asymmetric membranes by addition of Fe(II) clathrochelate.

• Korean Chemical Engineering Research
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• v.49 no.4
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• pp.498-504
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• 2011

In this research, hollow fiber membranes were used in order to investigate to permeation and selectivity of the $CH_4$ and $N_2$. Polyimide and polyethersulfone hollow fiber membrane were prepared by the dry-wet phase inversion method and the module was manufactured by fabricating fibers after surface coating with silicone elastomer. The scanning electron microscopy (SEM) studies showed that the produced fibers typically had an asymmetric structure. The permeance of $CH_4$ and $N_2$ were increased with pressure and temperature. However, the selectivity was decreased with increasing temperature. The permeances of $CH_4$ and $N_2$ were decreased with increasing the air gap and the effect of post-treatment on membrane showed the increase in permeance up to 3.2~7.0 times.

• Membrane Journal
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• v.14 no.2
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• pp.108-116
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• 2004

In this study, the pore-filled ion-exchange membranes were prepared by using the asymmetric PVDF membrane as a nascent membrane. First, the solution of PVBCI having the chlorornethylate aryl ring of 80 percents and DABCO was made with the mixed solvent of THF and DU (8:2). These mixed solution was then, filled in the pores of PVDF membrane, and left for a day to complete the gelation. Finally the pore-filled anion-exchange membrane is obtained fallowed by the amination of the remaining chloromethyl groups with trimethylamine (TMA, 40 wt% in water) forming the positive ammonium ion sites. This 2 step procedure enabled us to produce the pore-filled membranes without change of size, and to control the properties of final membrane with various degree of cross-linking. The results of SEM and AFM showed the polyelectrolyte existed in the pores of nascent membrane as a certain configuration. From the investigation of the solvent affecting much to the permeability and rejection, it was found that the membranes using mixed solvent of THE and DMF (8:2) showed better performances than the membranes produced by THF only. The result of an investigation for the water permeability of the final membrane at low pressure (100 Kpa) showed a typical ultrafiltration membrane's permeability (8 ∼ 10 kg/$m^2$hr) and good values of rejection (55∼60 percent).

• Membrane Journal
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• v.15 no.4
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• pp.310-319
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• 2005

This paper describes the preliminary study on the development of multi-stage membrane demonstration plant for removal of carbon dioxide from flue gas stream being emitted from LNG boiler in thermal power generation plant. The prerequisite requirement is to design and develop the membrane process producing a $99\%\;CO_2$ with $90\%$ recovery from LNG flue gas of 1,000 $Nm^3$/day. Asymmetric polyethersulfone hollow fiber membranes and membrane modules developed in this laboratory[1] were used in this study. Using the permeation data for the hollow fiber membranes, modelling on the membrane module and multi-stage membrane process was done to meet the requirement condition of the process design. The effects of the operating pressure of feed and permeate side and feed concentration on $CO_2$ purity and recovery were investigated experimentally with the developed hollow fiber modules. These experimental results matched well with theoretical modelling results.

• Membrane Journal
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• v.16 no.4
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• pp.303-312
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• 2006

The asymmetric hybrid membranes of polyethersulfone (PES) and $ZrO_2$ nanoparticles were prepared via new one-step procedure combining simultaneously the phase-inversion method and the sol-gel technique. The optimum contents of $Zr(PrO)_4\;and\;HNO_3$ catalyst were determined by the adsorption experiments of phosphate anion onto the resulting hybrid membranes. The maximum adsorption of phosphate anion is obtained at the conditions of 0.15 mL $Zr(PrO)_4$ addition per 1 mL PES and 30 mL $HNO_3$ addition per 1 mL $Zr(PrO)_4$. Variation of morphology, performance and incorporated $ZrO_2$ amount of the resulting hybrid membranes were discussed and determined using SEM, pure water flux, TGA, ICP, XRD and contact angle measurements. Increasing $Zr(PrO)_4$ addition into casting solution, pure water flux is increased and $ZrO_2$ amount in the hybrid membrane is maximized at the conditions 0.15 mL $Zr(PrO)_4$ addition per 1 mL PES. The prephosphatation of PES-$ZrO_2$ hybrid membrane was studied to modify the surface characteristics of membrane. Ultrafiltration of bovine serum albumin (BSA) solution was performed in a dead-end cell using both a bare (non-phosphated) and a phosphated hybrid membrane. It is revealed that both the permeate flux and BSA rejection were increased as about 40% by prephosphatation of hybrid membrane. These results may be explained on the basis of the increase of membrane hydrophilicity, which was determined from contact angle measurements.

• Applied Chemistry for Engineering
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• v.4 no.2
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• pp.393-402
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• 1993

Redox flow secondary battery have been studied actively as one of the most promising electrochemical energy storage devices for a wide range of applications, such as electric vehicles, photovoltaic arrays, and excess power generated by electric power plants. In all-vanadium redox flow battery using solution of vanadium-sulfuric acid as a active material, the difficulty in developing an efficient ion selective membrane can still be identified. The asymmetric cation exchange membrane(M-30) as a separator of all-vanadium redox flow battery which were obtained by the reaction of chlorosulfonation for 30 minutes under the irradiation of UV, showed its superiority in the transport number of 0.94 and electrical resistivity of $0.5{\Omega}{\cdot}cm^2$. The base membrane were prepared by lamination a low density polyethlene film of $10{\mu}m$ thickness on polyolefin membrane(HIPORE 120). The electrical resistivity of M-30 membrane in real solution of vanadium-sulfuric acid was $3.79{\Omega}{\cdot}cm^2$ and it was similar to that of Nafion 117 membrane. Also the cell resistivity was $6.6{\Omega}{\cdot}cm^2$and lower than that of Nafion 117. In considertion of electrochemical properties and costs of membranes, M-30 membrane was better than that of Nafion 117 and CMV of Asahi glass Co. as a separator of all-vanadium redox flow battery.