• Membrane Journal
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• v.22 no.1
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• pp.54-61
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• 2012

To separate and recover of VOCs, supporting membranes using PEI were prepared by phase separation method and it was coated with PDMS to prepare PEI-PDMS hollow composite membrane. To investigate characteristic of prepared membrane, pure gas permeability was measured using oxygen and nitrogen, the stage cut and permeance property with feed concentration were evaluated using xylene, ethyl benzene, toluene and cyclohexane. Also, to check solvent resistance on VOCs, stress-strain property of membrane with immersion time in solvent were measured by DMA. The permeance value of $O_2$ and $N_2$ showed 63 GPU and 30 GPU respectively. Permeated VOCs concentration was decreased with increasing stage cut. But, conversely, recovery efficiency that was increased with increasing stage cut. As a result of DMA test, the stress and strain were 11.93 MPa and 13.52%, respectively.

• Membrane and Water Treatment
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• v.14 no.2
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• pp.85-93
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• 2023

Membrane separation is widely used for several applications such as water treatment, membrane reactors and climate change. Cross-linked organic-inorganic hybrid polyvinylidene fluoride (PVDF) / Tetraethyl orthosilicate (TEOS) was adopted for the preparation of optimized hollow membrane (HFM) for membrane distillation or other low pressure separators for mechanical properties and permeability under varying pretreatment schemes. HFMs were prepared on semi-pilot membrane fabrication system. Novel adopted post-treatment schemes involved soaking in glycerol, magnesium sulphate (MgSO₄), sodium hypochlorite (NaOCl), and isopropanol for different durations. All fibers were characterized for morphology using a scanning electron microscope (SEM), surface roughness using atomic force microscope (AFM), elemental composition by examining Energy Dispersive Spectroscopy (EDS), water contact angle (CA°) and porosity. The performance of the fibers was evaluated for pure water permeation flux (PWF). Post-treatment with MgSO₄ gave the highest both tensile modulus and flux. Assessment of properties and performance revealed comparable results with other organic-inorganic separators, HF or flat. In spite of few reported data on post treatment using MgSO₄ in presence of TEOS, this proves the potential of low cost treatment without negative impact on other membrane properties. The flux is also comparable with hypochlorite which manifests substantial precaution requirements in actual industrial use.The relatively high values of flux/bar for sample treated with TEOS, post treated with MgSO₄ and hypochlorite are 88 and 82 LMH/bar respectively.

• Membrane Journal
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• v.32 no.1
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• pp.74-82
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• 2022

The objective of this work was to investigate the gas permeation properties of CO₂ and CH₄ for PEBAX^®/TS-530 hybrid membranes and compare with pure PEBAX^®-1657 membrane. With FTIR and XRD it was possible to confirm that TS-530 was dispersed well in PEBAX^® matrix. Compared with pure PEBAX^® membrane, ideal separation factor for PEBAX^®/TS-530 (10 wt%) hybrid membrane was enhanced a little. As the amount of TS-530 was increased, the gas permeability coefficients of both CO₂ and CH₄ were increased, while the ideal separation factor was decreased. This results were explained by the reduction of crystallinity of polyamide block and interchain distance caused by introduction of inorganic nanoparticles. And fumed silica might tend to agglomerate, resulting in forming nonselective nanogaps in the hybrid materials, thus the diffusivity would be enhanced at the expense of diffusivity selectivity.

• Membrane Journal
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• v.33 no.5
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• pp.240-247
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• 2023

Even among gas separation methods, CO₂ capture and separation via membranes is an ever-growing field, with many different membrane compositions continually being developed. Ionic liquid (IL) based composite membranes show excellent performance values in separating CO₂. Similarly, various copolymer/IL composite membranes also display improved performance. The addition of fillers such as graphene oxide to these copolymer/IL composite membranes shows a further enhanced version of these fillers, most likely due to the strong interactions that occur between ILs and organic fillers, which consequently improves factors such as the affinity, selectivity, and adsorption of CO₂. Copolymer/IL composite membranes utilizing a metal-organic framework (MOF) showed improved CO₂ permeability. This review discusses the study of various combinations of ionic liquid and copolymer composite membranes for carbon dioxide separation.

• Membrane Journal
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• v.23 no.6
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• pp.450-459
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• 2013

2,3,5,6-Tetramethyl-1,4-phenylenediamine (TMPD) based polyimide (PI) were crosslinked with 1,2-Diaminoethane (DAE) and 1,6-Diaminohexane (DAH) to enhance gas transport properties. Fourier transform infrared (FT-IR) studies show that imide groups were converted into amide groups during crosslinking process. Thermogravimetric analysis (TGA) results indicate that the degradation temperature of crosslinked PI membranes decreased after crosslinking. This is due to degradation of alkyl group in crosslinking agent. The d-space of crosslinked PI membranes decreased with increasing crosslinking time. The ideal permeability for $CH_4$, $N_2$, $O_2$, and $CO_2$ decreased after crosslinking and the ideal permeability of crosslinked PI membranes induced by DAH is larger than that by DAE. In contrast, the permselectivity of $CO_2/CH_4$, $CO_2/N_2$ and $O_2/N_2$ increased during crosslinking. For the gas pair of $CO_2/CH_4$, the maximum increment is about 39.5% after 6 minutes of DAE crosslinking. Also, that of $O_2/N_2$ gas pair is about 20.5% after 6 minutes of DAE crosslinking. According to these result, DAE is more suitable for enhanced permselectivity than DAH. On the contrary, DAE is not useful for $CO_2/N_2$ separation due to reduction in $CO_2/N_2$ permselectivity after 3 minutes DAE crosslinking.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.13 no.1
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• pp.57-68
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• 2010

The purpose of this study is to analyze the characteristics of environment-friendliness of waterproof materials based on comprehensive experiments on waterproofness in terms of coefficients of permeability, harmfulness of waterproof materials and fish toxicity of Oryzias latipes mortality to verify eco-toxicity of each method of construction and waterproof material, which are to be applied by taking eco-toxicity into account when building ecological flows in upper areas on natural and artificial grounds. As a result, the following conclusions have been reached in this study: 1. In regard of the harmfulness analyzed, each material showed a different result of analytical value in each lab tank. Compared to input water, pH, COD, SS, T-P, and T-N values increased a little, but DO value decreased. The value of turbidity analyzed independent of the water quality standard of aquatic ecosystem set forth by the Ministry of Environment increased a little compared to the value in input water. 2. In the experiment of fish toxicity, compacted quicklime, cement fluid waterproof material, cement mortar waterproof material and bentonite powder were found to have 100% of fish mortality, respectively, and membrane waterproof material showed 83.3% of mortality, indicating strong fish toxicity. Improved asphalt sheet (63.3%) and synthetic rubber sheet (53.3%) were analyzed to have medium fish toxicity, while bentonite sheet (6.7%), Hwang-toh (6.7%) and clay (3.3%) showed relatively lower mortality and fish toxicity. 3. Regarding the analysis on waterproofness in terms of the coefficient of permeability of each waterproof material, improved asphalt sheet, synthetic rubber sheet, membrane waterproof material, cement fluid and mortar waterproof material and bentonite sheet were found impervious in case no leakage takes place in construction. Bentonite powder was found practically impervious based on the analytical results from the experiment done in compliance with weight ratios. So were the clay and Hwang-toh from the experimental results. To sum up such results as found in the experiment mentioned so far, the values of harmfulness and waterproofness analyzed were different in each lab tank, but there was absolutely little correlation with the mortality gained from the experiment on fish toxicity. In the experiment of fish toxicity, environment-friendly waterproof materials were analyzed, and it was found that clay, Hwang-toh and bentonite sheet are highly environment-friendly. In contrast, synthetic rubber and improved asphalt sheets were found to have medium-level environment-friendliness. Also, membrane water-proof materials, compacted quicklime, cement fluid and mortar waterproof material and bentonite powder were analyzed to have low environment-friendliness.

• Journal of the Korean Electrochemical Society
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• v.5 no.2
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• pp.68-73
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• 2002

Modified polymer electrolyte membranes were fabricated by the applying dc magnetron sputter-deposited Pd thin layers on the surface of the $Nafion^{TM}$ membranes in argon atmosphere. The Pd thin films were characterized by investigating its morphology, methanol permeability, and protonic conductivity. The performance of a direct methanol fuel cell(DMFC) with the modifed polymer electrolyte membrane was also tested by the measurement of its currents and voltages under flowing methanol. The Pd thin film could be a barrier layer to methanol crossover, but the protonic conductivity of the modified polymer membrane was reduced. By using the modified polymer eletrolyte membranes, both the methanol permeability and the protonic conductivity were decreased with increasing the thickness of Pd thin film. However, the performances of DMFC were almost independent on the thickness of Pd thim films. The efffcts of methanol concentration in a feeding fuels on the protonic conductivity and the cell performance were also investigated.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.3
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• pp.454-458
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• 2014

In this study, we examined the ionization rate and permeability of nanocalcium prepared from oyster shells with various particle sizes. Four particle sizes of the calcium samples were prepared by centrifugation according to their density disparity in alcoholic solution: NC (normal calcium), C-1 (supernatant of 1,000 rpm), C-2 (supernatant of 2,000 rpm), and C-3 (supernatant of 3,000 rpm). Particle sizes of NC, C-1, C-2, and C-3 were $2,280.3{\pm}64.3nm$, $521.3{\pm}83.3nm$, $313.9{\pm}29.5nm$, and $280.0{\pm}3.4nm$, respectively. C-3 showed a slight increase in ionization rate compared with the other calcium samples, but their differences were not significant. Dialysis membrane-employed analysis showed that nanocalcium permeability increased as its particle size smaller; 32% of C-3 nanocalcium was transported to the outside of the membrane, whereas C-1 showed a 25% transport rate. We determined the permeability of the nanocalciums by using rat intestinal sacs, in order to provide different intestinal environments depending on pH level. Nanocalcium generally showed a higher permeability at pH 7, which represents an ileum environments compared to the duodenum and jejunum environments at pH 4.2 and pH 6.2, respectively. However, C-3 calcium showed the highest permeability, followed by C-2, C-1 and NS calciums. This result shows that the size of calcium positively affected its permeability in the intestinal sac. Taken together, nano-sized calcium derived from discarded oyster shell shows improved permeability in intestinal environments.

• Membrane Journal
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• v.17 no.2
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• pp.81-92
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• 2007

Membrane-based separation processes are receiving increasing attention in the scientific community and industry since they provide a desirable alternative to processes that are not easy to achieve by conventional separation technologies. In particular, gas separation using polymeric membranes have annually grown so fast owing to advantages such as easy installation, no moving parts, small footprint and low energy process. The key element is definitely a polymer membrane exhibiting high permeability and high selectivity to compete with other gas separation technologies. Current polymer membranes used for commercial gas separation are a family of hydrocarbon polymers for hydrogen separation, air separation and carbon dioxide separation from natural gas sweetening. Relatively, gas or vapor separation properties of fluoropolymers are not known so much as compared with those of hydrocarbon polymers. Accordingly, in this study, membranes prepared from amorphous perfluoropolymers are of particular interest because of the unique properties of these polymers. The advantages offered by these amorphous perfluoropolymers for use in gas and vapor separation will be discussed. In addition, membrane properties and separation performance will be compared with other membranes available on the market.

• Journal of the Korean Electrochemical Society
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• v.11 no.4
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• pp.256-261
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• 2008

In this study, Nafion membrane was modified to prevent methanol crossover by layer-by-layer self assembly using polyaniline (PANi) as a polycation and sulfonated poly(ether sulfone) (SPES) as a polyanion onto the Nafion surface. Since PANi and SPES possess thermal and chemical stability and rigid backbone, their layer-by-layer self-assembled films on the Nafion are expected to reduce methanol permeability and to increase mechanical stability. UV-Vis absorption spectroscopy verified a linear build-up of the multilayers of PANi and SPES. We found that the thickness per bilayer was about 10 nm by TEM measurement. Although modified Nafion membrane exhibited 15% decrease of proton conductivity, it reduceded 67% of methanol permeability compared to that of the pristine Nafion membrane, resulting in 2.5 times larger selectivity. At the performance test of the fuel cell using 5M methanol as a fuel, the modified Nafion membrane showed 2.4 times higher maximum power density at $30^{\circ}C$ and 1.4 times larger at $60^{\circ}C$ than the pristine Nafion.