• Membrane Journal
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• v.15 no.2
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• pp.157-164
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• 2005

In this study, composite hollow fiber membranes were developed for the recovery of olefin monomers in polyolefin industry off-gases. Polyetherimide (PEI) hollow fiber support membranes were fabricated from spinning solutions containing PEI, NMP and polyethylene glycol (PEG). The influence of dope solution and inner coagulant composition on the permeation properties and structure of hollow fiber supports was examined. PDMS was used as a selective layer and coated on PEI hollow fiber support. The thickness of active layer was controlled by changing coating solution concentration. The permeation properties of hollow fiber supports and composite membranes were characterized with a pure gas permeation test. The optimized composite hollow fiber membrane has $10\;{\mu}m$ selective layer and shows excellent separation performance; the ideal selectivity of olefins over nitrogen is in the following order: 1-butylene (6.4) > propylene (17) > ethylene (97), which selectivity data are similar to the intrinsic olefin/nitrogen selectivities of PDMS. This confirms that the new composite hollow fiber membranes suitable for olefin off-gas recovery has developed successfully.

• Korean Journal of Environmental Agriculture
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• v.6 no.2
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• pp.94-100
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• 1987

Plant mitochondria, irradiated with blue-colored $sunlight(350{\sim}500nm)$ under aerobic and anaerobic conditions, were assayed as to the electron transfer activity of respiratory enzyme system, and compared with those irradiated with orange-colored light(white sunlight minus blue-colored light). The respiratory activity of mitochondria was most seriousely inhibited by illumination with blue-colored light under aerobic condition. Deaeration of mitochondrial suspension resulted in substantial decrease of the photoinhibition by blue-colored light. Meanwhile, orange-colored light demonstrated much less effectiveness-almost ineffectiveness-in causing the inhibition of mitochondrial respiration system. The results of enzymatic assay revealed a strong possibility that FMN in NDH and heme group at least in cytochrome c oxidase, but not FAD in SDH, are the photodynamic sensitizers in mitochondrial inner membrane. Also worthwhile to note is the significant difference from the others of SDH in its photoinhibitory response to the light quality of visible light; that the inhibition of SDH by irradiation was not affected by atmospheric condition and that orange-colored light gave rise to considerable extents of inhibition to the enzyme. This observation was tentatively interpreted in terms of photosensitized reaction not involving molecular oxygen possibly catalyzed by Fe-S centers in the enzyme. The superoxide production and the membrane peroxidation of mitochondria under various treatments also indicated that there was blue-light photodynamic reaction in mitochondria involving active oxygens.

• Analytical Science and Technology
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• v.10 no.3
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• pp.161-167
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• 1997

This is on hydrogen ion-selective memebrane electrodes which were made of tetrabenzylmethylenediamine (TBMDA), tetrabenzylethylenediamine (TBEDA), tetrabenzylpropylenediamine(TBPDA) and tetrabenzylhexylenediamine(TBHDA) as neutral carriers. Their response potentials to carbon number between amino groups showed linear selectivities to hydrogen ion in the range of pH 1~pH 9, pH 2~pH 9, pH 3~pH 9 and pH 4~pH 9 and slopes were 48mV/pH, 52mV/pH, 64mV/pH, 59mV/pH respectively. The interferences effect on the cations were measured to alkali metal ions($Li^+$, $Na^+$, $K^+$), alkaline earth metal ions ($Mg^{2+}$, $Ca^{2+}$, $Sr^{2+}$, $Ba^{2+}$), transition metals ions($Cu^{2+}$, $Ni^{2+}$, $Co^{2+}$) and anions($I^-$, $Br^-$, ${NO_3}^-$, $SCN^-$), and selectivity coefficients were measured by separate-solution method. The membrane electrode made of TBMDA among the electrodes showed the best selectivity in acidic solution.

• Applied Chemistry for Engineering
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• v.24 no.5
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• pp.456-470
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• 2013

Hollow-fiber membranes, is one of the new technologies that is growing rapidly in the past few decades. In addition, separation membranes using polymer materials, have attracted attentions in various fields including gas separation, fuel cells, water treatment, wastewater treatment, and organic separation. Nanofiltration (NF) membranes having the separation characteristics in the intermediate range between ultrafiltration and reverse osmosis (RO) membranes for liquid separation, with relatively low investment cost and operating pressure lower than that of RO membranes, have high permeance and rejection performance of multivalent ions as well as organic compounds of molecular weight between $200{\sim}1000gmol^{-1}$. In this paper, we would like to review the research trends on the various structure control and characterization of NF hollow fiber membranes with respect to materials and the methods of preparation (phase inversion method and interfacial polymerization method). Currently, most of NF membranes have been manufactured by plate and frame types or spiral wound types. But hollow fiber types have delayed in commercial products, because of the weak strength when to produce on the basis of the existing materials, therefore the development of new materials or improvement of existing materials will be needed. If improving manufacturing technology is available, hollow fiber types will replace spiral wound types and gradually show a higher market share.

• Journal of Applied Biological Chemistry
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• v.61 no.3
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• pp.213-217
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• 2018

Tolaasin secreted by Pseudomonas tolaasii is a peptide toxin and causes brown blotch disease on the cultivated mushrooms by collapsing cellular and fruiting body structure. Toxicity of tolaasin was evaluated by measuring hemolytic activity because tolaasin molecules form membrane pores on the red blood cells and destroy cell membrane structure. In the previous studies, we found that tolaasin cytotoxicity was suppressed by $Zn^{2+}$ and $Ni^{2+}$. $Ni^{2+}$ inhibited the tolaasin-induced hemolysis in a dose-dependent manner and its $K_i$ value was 1.8 mM. The hemolytic activity was completely inhibited at the concentration higher than 10 mM. The inhibitory effect of $Zn^{2+}$ on tolaasin-induced hemolysis was increased in alkaline pH, while that of $Ni^{2+}$was not much dependent on pH. When the pH of buffer solution was increased from pH 7 to pH 9, the time for 50% hemolysis ($T_{50}$) was increased greatly by $100{\mu}M$ $Zn^{2+}$; however, it was slightly increased by 1 mM $Ni^{2+}$ at all pH values. When the synergistic effect of $Zn^{2+}$ and $Ni^{2+}$ on tolaasin-induced hemolysis was measured, it was not dependent on the pH of buffer solution. Molecular elucidation of the difference in pH-dependence of these two metal ions may contribute to understand the mechanism of tolaasin pore formation and cytotoxicity.

• Environmental Engineering Research
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• v.25 no.3
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• pp.299-308
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• 2020

Composting is among the most effective integrated waste management strategies used to recycle sewage sludge (SS) waste and generate a useful product. An encapsulated lifting system is a relatively new industrial-scale composting technology. The objective of this study was to evaluate the effectiveness of composting dewatered stabilized SS mixed with green waste using this new technology. The composting process was monitored by changes in the physico-chemical properties, UV-visible spectra, and fourier transform infrared (FTIR) spectra. The composting temperature was steady in the thermophilic range for 24 and 12 d in the intensive and maturation phases, respectively, which fulfilled the disinfection requirement. Moreover, the temperature increased rapidly to 76.8℃ within three days, and the thermophilic temperatures peaked twice and lasted longer than in traditional composting, which accelerated SS degradation and decreased the composting period necessary to obtain mature compost. FTIR spectroscopic analysis showed a diminished in methyl group derived from methylene C-H aliphatic groups because of organic matter degradation by microorganisms and an increased number of aromatic chains. The new technology may be a viable and sustainable alternative for SS management that converts waste into compost that is useful as a soil amendment.

• Membrane Journal
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• v.25 no.2
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• pp.115-122
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• 2015

$SiO_2{\cdot}B_2O_3$ was prepared by trimethylborate (TMB)/tetraethylorthosilicate (TEOS) mole ratio 0.01 at $800^{\circ}C$. PDMS[poly(dimethysiloxane)]-$SiO_2{\cdot}B_2O_3$ composite membranes were prepared by adding porous $SiO_2{\cdot}B_2O_3$ to PDMS. To investigate the characteristics of PDMS-$SiO_2{\cdot}B_2O_3$ composite membrane, we observed PDMS-$SiO_2{\cdot}B_2O_3$ composite membrane using TG-DTA, FT-IR, BET, X-ray, and SEM. PDMS-$SiO_2{\cdot}B_2O_3$ composite membrane was studied on the permeabilities of $H_2$ and $N_2$ and the selectivity ($H_2/N_2$). Following the results of TG-DTA, BET, X-ray, FT-IR, $SiO_2{\cdot}B_2O_3$ was the amorphous porous $SiO_2{\cdot}B_2O_3$ with $247.6868m^2/g$ surface area and $37.7821{\AA}$ the mean of pore diameter. According to the TGA measurements, the thermal stability of PDMS-$SiO_2{\cdot}B_2O_3$ composite membrane was enhanced by inserting $SiO_2{\cdot}B_2O_3$. SEM observation showed that the size of dispersed $SiO_2{\cdot}B_2O_3$ in the PDMS-$SiO_2{\cdot}B_2O_3$ composite membrane was about $1{\mu}m$. The increasing of $SiO_2{\cdot}B_2O_3$ content in PDMS leaded the following results in the gas permeation experiment: the permeability of both $H_2$ and $N_2$ was increased, and the permeability of $H_2$ was higher than $N_2$, but the selectivity($H_2/N_2$) was decreased.

• Membrane Journal
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• v.21 no.3
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• pp.256-262
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• 2011

This study describes the performance of PSF and PC membranes for separation and recovery of $SF_6$ from gas mixtures (10% $SF_6$/70% $N_2$/19% $O_2$/1% $CF_4$) containing low concentration of $SF_6$. The $SF_6$ concentration in retentate, recovery efficiency and selectivity of mixed gases were measured as a function of retentate flow rate and temperature. The concentration of $SF_6$ in the gas recovered from PSF and PC membrane respectively decreased with increase of retentate flow rate and increased with increase of temperature. The values of $SF_6$ concentration in retentate of PSF membrane were higher than those of PC membrane at constant experimental conditions. The maximum value of recovery efficiency of PSF and PC membranes are 95.9% and 67.8%, respectively, under 298.15 K and 150 cc/min of retentate flow rate. With the exception of $CF_4/SF_6$, the real selectivities of $N_2/SF_6$ and $O_2/SF_6$ at PSF membrane were higher than those of PC membrane.

• Membrane Journal
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• v.6 no.3
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• pp.173-181
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• 1996

Common volatile organic compounds(VOCs) such as toluene and methanol were removed successfully from N$_{2}$ using a novel silicone-coated hollow fiber membrane module. This novel membrane is a thin film composite(TFC) and was highly efficient in removing VOCs selectively from a N$_{2}$ stream. This membrane had some innate advantages over other silicone-based membrane in that the selective barrier was ultrathin(~1 $\mu$m) and the porosity of the polypropylene substrate was high which leads to a low permeation resistance. The substram was very strongly bonded to the coating layer by plasma polymerization and can withstand a very high pressure. A small hollow fiber module having a length of 25cm and 50 fibers could remove 96~99% of toluene as well as methanol vapors when the feed flow rate was up to 60cc/min. The percent removal of VOCs were even higher when the feed inlet concentration was higher. This process is especially suitable for treating streams having a low flow rate and high VOCs concentration. The permeances of VOCs through this membrane was in the range of $4~30 \times 10^{-9}gmol/sec \cdot cm^{2}\cdot cmHg$ for both toluene and methanol, and nitrogen permeance was between $3~9 \times 10^{-10}gmol/sec \cdot cm^{2} \cdot cmHg$. High separation factor between 10~55 for toluene/N$_{2}$ and 15~125 for methanol/N$_{2}$ were obtained depending on the feed flow rate ranges and feed VOCs concentration levels.

• Membrane Journal
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• v.19 no.3
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• pp.252-260
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• 2009

The effects of the treatment of an acidic solution at pH 2 on polyacrylonitrile ultrafiltration (UF) membranes were investigated using a circular cross-flow filtration bench with a membrane module. A substantial reduction in the membrane permeability was observed after 80 hours' treatment of the acidic solution. In addition, the analyses of the sample solutions by ultraviolet/visible absorption spectroscopy and gas chromatography/mass spectrometry (GC/MS), which were taken from the feed tank as a function of the treatment time, showed that a new organic compound was produced in the course of the treatment. From a thorough search of the mass spectral library we presumed the new compound to be 1,6-dioxacyclododecane-7,12-dione (DCD), one of the well-known additives for polyurethane. Based on further experimental results, including the scanning electron microscope (SEM) images and the solid-state NMR spectra of the membranes used for the treatment of the acidic solution, we suggested that the decrease of the permeate flux resulted not from the deformation of the membranes, but from the fouling by DCD eluted from the polyurethane tubes in the filtration bench during the treatment. Those results imply that the reactivity to an acidic solution of the parts comprising the filtration bench is as important as that of the membranes themselves for effective treatments of acidic solutions, for efficient chemical cleaning by strong acids, and also in determining the pH limit of the solutions that can be treated by the membranes.