• Membrane and Water Treatment
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• v.9 no.4
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• pp.221-231
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• 2018

A new procedure to produce poly(vinylidene fluoride)/boron nitride hybrid membrane is presented for application in membrane distillation (MD) process. The influence of hexagonal boron nitride (h-BN) incorporation on the performance of the polymeric membranes is studied through the present investigation. For this aim, h-BN nanopowders were successfully synthesized using the simple chemical vapor deposition (CVD) route and subsequent solvent treatments. The resulting h-BN nanosheets were blended with poly(vinylidene fluoride) (PVDF) solution. Then, the prepared composite solution was subjected to phase inversion process to obtain PVDF/h-BN hybrid membranes. Various examinations such as scanning electron microscopy (SEM), wettability, permeation flux, mechanical strength and liquid entry pressure (LEP) measurements are performed to evaluate the prepared membrane. Moreover, Air gap membrane distillation (AGMD) experiments were carried out to investigate the salt rejection performance and the durability of membranes. The results show that our hybrid PVDF/h-BN membrane presents higher water permeation flux (${\sim}18kg/m^2h$) compared to pristine PVDF membrane. In addition, the experimental data confirms that the prepared nanocomposite membrane is hydrophobic (water contact angle: ${\sim}103^{\circ}$), has a porous skin layer (>85%), as well competitive fouling resistance and operational durability. Furthermore, the total salt rejection efficiency was obtained for PVDF/h-BN membrane. The results prove that the novel PVDF/h-BN membrane can be easily synthesized and applied in MD process for salt rejection purposes.

• Membrane Journal
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• v.13 no.2
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• pp.65-72
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• 2003

This study was focused on the investigation of filtration characteristics of membrane-coupled fermentor system for dissolved organics recovery from liquid organic sludge. On the filterability of MF over the range of $0.1{\sim}5 {\mu}m,$ the magnitude of total membrane resistance ($R_t$) is ranged as follows in the order; $0.1 {\mu}m>0.2{\mu}m>0.5 >1{\mu}m>2{\mu}m>5{\mu}m$. The cake layer resistance ($R_c$) occupied about 68~88% of total resistance with fermented sludge. Permeation flux decline was mainly attributed to the $R_c$, which was formed by a strong deposition from physico-chemical interactions of solids on membrane surface. Higher suspended solids (SS) concentration of suspension caused lower permeation flux. However, there was not a proportion relation beyond a certain SS concentration. The cross-flow velocity on the membrane surface was faster, which resulted in the higher permeation flux and also more efficient with low trans membrane pressure (TMP) in viewpoint of energy efficiency. The appropriate pH of suspension was over the range of 5.0~6.0 for dissolved organics recovery as well as the permeation flux. It is possible f3r bacteria to be separated perfectly with $0.1{\mu}m\; and \;0.2{\mu}m$ membrane pore size. Based on experimental results, most appropriate membrane pore size for the recovery is believed to around $1{\mu}m$.

• Journal of Hydrogen and New Energy
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• v.22 no.2
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• pp.161-167
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• 2011

Proton conductors have attracted considerable attention for solid oxide fuel cell (SOFC), hydrogen pump, gas sensor, and membrane separators. Doped $SrCeO_3$ exhibits appreciable proton conductivity in hydrogen-containing atmosphere at high temperature. However commercial realization has been hampered due to the reactivity of $SrCeO_3$ with $CO_2$. The chemical stability and proton conductivity are dependent on dopant type. The purpose of this work is to investigate chemical stability of $SrCe_{0.95}Gd_{0.05}O_{3-\alpha}-Ce_{0.9}Gd_{0.1}O_{2-\beta}$ composites in $CO_2$ and $H_2$ gases. Thermogravimetric analysis (TGA) was performed in gaseous $CO_2$ and electrical conductivity of the composites were also measured between 500 and $900^{\circ}C$ in air and $H_2$ atmosphere. $SrCe_{0.95}Gd_{0.05}O_{3-\alpha}-Ce_{0.9}Gd_{0.1}O_{2-\beta}$ composite membranes showed good chemical stability of in $CO_2$ atmosphere and high conductivity at hydrogen condition. The hydrogen permeation of $SrCe_{0.95}Gd_{0.05}O_{3-\alpha}-Ce_{0.9}Gd_{0.1}O_{2-\beta}$ composite membranes was investigated as a function of volumetric content of $SrCe_{0.95}Gd_{0.05}O_{3-\alpha}$. The $SrCe_{0.95}Gd_{0.05}O_{3-\alpha}-Ce_{0.9}Gd_{0.1}O_{2-\beta}$(6:4) membrane with a thickness of 1.0 mm showed the highest hydrogen permeability with the flux reaching of 0.12 $ml/min{\cdot}cm^2$ at $800^{\circ}C$ in 100%$H_2/N_2$ as feed gas.

• Membrane Journal
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• v.28 no.4
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• pp.233-242
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• 2018

To study gas membrane using GO (graphene oxide), the PEBAX [poly(ether-block-amide)]-GO polymer composite membrane was prepared by adding GO to PEBAX. Through this composite membrane, gas permeation characteristics for $H_2$, $N_2$, $CH_4$, and $CO_2$ were studied. As a result of the gas permeation test, the permeability of $N_2$, $CH_4$, and $CO_2$ to PEBAX-GO composite membranes gradually decreased as the GO content increased. On the other hand, the gas permeability of $H_2$ increased with the increase of GO content, and it was 21.43 barrer at the GO content of 30 wt%, which was about 5 times higher than that of PEBAX membrane. This is because the GO was easier to operate with a fast and selective gas transport channel for $H_2$ than other gases. The increased selectivity ($H_2/N_2$) and selectivity ($H_2/CH_4$) were influenced by the diffusion selectivity by the permeate gas size. The increased selectivity ($CO_2/N_2$) and selectivity ($CO_2/CH_4$) were more influenced by the solubility selectivity due to the affinity of $CO_2$ and GO for -COOH.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.5
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• pp.502-508
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• 2001

The extracellualr hemolysin produced by pathogenic Vibrio furnissii was isolated and purified by ammonium sulfate precipitation and followed by DEAE-Sephadex A-50 (1st and 2nd) ion-exchange and Sephadex G-100 gel permeation chromatography. The molecular weight of the purified hemolysin was 61 kDa. The enzyme activity was inactivated by heating at 60 for 5 min, and inhibited by additions of $Cu^{2+},\;Zn^{2+}$ and a high concentration of cholesterol. Lysis of human erythrocytes by the enzyme was temperature dependent, and optimal temperature of the enzyme was $37^{\circ}C$. The purified hemolysin was unstable at pH 6.0, 6.5 and 10.0. The optimal concentration of human erythrocytes on hemolysins was about $1.5\%$. The purified hemolysin was active for erythrocytes from three animal species including mouse, rabbit and rat, and was the most active against rabbit erythrocytes. B blood group of human erythrocytes also showed a high sensitivity to the enzyme.

• Membrane Journal
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• v.30 no.6
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• pp.450-459
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• 2020

Membrane-based separations have the potential to reduce energy consumption and environmental impact associated with conventional processes. However, many researches have been done to develop new membrane materials with greater selectivity and permeability. Here, we report highly selective membranes by introducing bulky ethyl substituents into the polyimide. The ethyl group in the ortho position to the imide nitrogen interferes the chain packing and increases chain stiffness and the distance between the polymer chains. The polyimide membranes were synthesized from various aromatic dianhydrides and 4,4'-methylenebis(2,6-diethylaniline) (MDEA). The synthesized membranes with increased gas diffusion length due to bulky substituents showed improved propylene/propane (C3H6/C3H8) selectivity. Single gas permeation showed high C3H6/C3H8 selectivity of 14.5, and C3H6 permeability of 7.0 barrer was found in MDEA-polyimide. Mixed-gas permeation results also demonstrate that MDEA-polyimide can achieve high selectivity in mixed-gas environment. Furthermore, this approach could significantly increase the feasibility of economic propylene separation compared to conventional polymer materials.

• Korean Membrane Journal
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• v.6 no.1
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• pp.30-36
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• 2004

The gas permeation performance of commercially available polyetherimide (Ultem$\^$/) is simulated by means of molecular dynamics methods. By the observation of trajectory, long distance hopping of gas molecules is needed to transverse from top to bottom of membrane. Two possibilities mechanism of diffusion phenomena through glassy polymers can be issued. Diffusion coefficients were calculated by Einstein relation equation. In solubility simulation, the value of the constants C'$\_$H/ and b for O$_2$ at 300 K were calculated. The diffusion and solubility coefficient of He for PEI were simulated in this simulation work. the permeability coefficient is 9.88 Barrer. This value is closed to experimental value of 9.4 Barrer.

• Applied Chemistry for Engineering
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• v.19 no.5
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• pp.477-483
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• 2008

$La_{0.7}Sr_{0.3}Co_{0.2}Fe_{0.8}O_{3-{\delta}$ oxide was synthesized by a citrate method and a typical dense membrane of perovskite oxide has been prepared using as-prepared powder by pressing and sintering at $1300^{\circ}C$. Precursor of $La_{0.7}Sr_{0.3}Co_{0.2}Fe_{0.8}O_{3-{\delta}$ prepared by citrate method was investigated by TGA and XRD. Metal-citrate complex in precursor was decomposed into perovskite oxide in the temperature range of $260{\sim}410^{\circ}C$ but XRD results showed $SrCO_3$ existed as impurity at less than $900^{\circ}C$. Electrical conductivity of membrane increased with increasing temperature but then decreased over $700^{\circ}C$ in air atmosphere ($Po_2=0.2atm$) and $600^{\circ}C$ in He atmosphere ($Po_2=0.01atm$) respectively due to oxygen loss from the crystal lattice. The oxygen permeation flux increased with increasing temperature and maximum oxygen permeation flux of $La_{0.7}Sr_{0.3}Co_{0.2}Fe_{0.8}O_{3-{\delta}$ membrane with 1.6 mm thickness was about $0.31cm^3/cm^2{\cdot}min$ at $950^{\circ}C$. The activation energy for oxygen permeation was 88.4 kJ/mol in the temperature range of $750{\sim}950^{\circ}C$. Perovskite structure of membrane was not changed after permeation test of 40 h and the membrane was stable without secondary phase change with 0.3 mol Sr addition.

• Archives of Pharmacal Research
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• v.24 no.6
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• pp.572-577
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• 2001

The feasibility of skin penetration was studied for aspalatone (AM, acetylsalicylic acid maltol ester), a novel antithrombotic agent. In this studys hairless mouse dorsal skins were used as a model to select composition of vehicle and AM. Based on measurements of solubility and partition coefficient, the concentration of PC that showed the highest flux for AM across the hairless mouse skin was found to be 40%. The cumulative amount permeated at 48 h, however, appear inadequate, even when the PC concentration was employed. To identify a suitable absorption enhancer and its optimal concentration for AM, a number of absorption enhancers and a variety of concentration were screened for the increase in transdermal flux of AM. Amongst these, linoleic acid (LOA) at the concentration of 5% was found to have the largest enhancement factor (i.e., 132). However, a further increase in AM flux was not found in the fatty acid concentration greater than 5%, indicating the enhancement effect is in a bell-shaped currie. In a study of the effect of AM concentration on the permeation, there was no difference in the permeation rate between 0.5 and 1% for AM, below its saturated concentration. At the donor concentration of 2%, over the saturated condition, the flux of AM was markedly increased. A considerable degradation of AM was found during permeation studies, and the extent was correlated with protein concentrations in the epidermal and serosal extracts, and skin homogenates. In rat dorsal skins, the protein concentration decreased in the rank order of skin homogenate > serosal extract > epidermal extract. Estimated first order degradation rate constants were $6.15{\pm}0.14,{\;}0.57{\pm}0.02{\;}and{\;}0.011{\pm}{\;}0.004{\;}h^{-1}$ for skin homogenate, serosal extract and epidermal extract, respectively. Therefore, it appeared that AM was hydrolyzed to some extent into salicylmaltol by esterases in the dermal and subcutaneous tissues of skin. taken together, our data indicated that transdermal delivery of AM is feasible when the combination of PC and LOA is used as a vehicle. However, since AM is not metabolically stable, acceptable degradation inhibitors may be nervessary to fully realize the transdermal delivery of the drug.

• Journal of the Korean Geotechnical Society
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• v.19 no.2
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• pp.159-170
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• 2003

In this study, the mixed design of grout with hish strength.high permeation.high durability and environmental stability as the state of the art in material field was performed. Also, the subjects of grouting, grouting effects for ground conditions, and environmental effects were analyzed. According to these results, the fundamental data will be suggested as a design of grouting in the field application. The physical, mechanical and chemical characteristics with particle shape of the grouts were analyzed. Then, the gel-time of grouts, which is essential for workability and permeation range, were controlled. Also, the laboratory model grouting tests were performed to find the characteristics of solidification, permeation and durability with grouts. The ordinary portland, slag and microcement which have been used in the construction field were evaluated fur the environmental effects. To find the leaching of $Cr^{6+}$characteristics in cement grouts, $Cr^{6+}$ leaching tests were performed for the raw materials. Also, the results of leaching test were shorn by surrounding environment. Then, the unconfined compression strength tests were performed with the homo-gel samples, and the amount of changed $Cr^{6+}$ was measured by curing solution.