• Membrane Journal
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• v.28 no.3
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• pp.169-179
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• 2018

The purposes of this paper were to improve both fouling and chlorine resistance by increasing the hydrophilicity of the reverse osmosis membrane. In order to improve chlorine resistance, the surface of RO membrane was activated by ultraviolet irradiation, and then it was modified by the sol-gel method using Octyltriethoxysilane (OcTES) such as the silane coupling agent to low sensitivity to chlorine, thereby the polyamide active layer was protected and chlorine resistance was improved. In addition, polyglycerol polyglycidyl ether (PGPE) and sorbitol polyglycidyl ether (SPE) coating with different number of epoxides, ring opening reaction of epoxide improved the anti-fouling resistance. The surface modification condition was optimized by FT-IR, XPS, and contact angle analysis. As a result, the permeability reduction rate of the silane-epoxy modified membrane after the fouling test was decreased about 1.5 times as compared with that of the commercial membrane. And the salt rejection was maintained over 90% at $20,000ppm{\times}hr$ even after chlorine resistance test.

• Journal of Electrochemical Science and Technology
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• v.12 no.3
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• pp.358-364
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• 2021

In this study, an anion exchange membrane water electrolysis (AEMWE) cell was operated for ~1000 h at a voltage bias of 1.95 V. Impedance spectra were regularly measured every ~ 100 h, and changes in the ohmic and non-ohmic resistance were traced as a function of time. While there was relatively little change in the I-V curves and the total cell resistance during the long-term test, we observed various electrochemical phenomena in the cell: 1) initial activation with a decrease in both ohmic and non-ohmic resistance; 2) momentary and non-permanent bubble resistance (non-ohmic resistance) depending on the voltage bias, and 3) membrane degradation with a slight increase in the ohmic resistance. Thus, the regular test protocol used in this study provided clear insights into the performance degradation (or improvement) mechanism of AEMWE cells.

• Membrane Journal
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• v.13 no.4
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• pp.219-228
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• 2003

This study was carried to investigate the effect of humic acid and kaloin which cause the turbidity and organic substance component for optimization of drinking water treatment process using the membrane separation. Also we were ovserved the optimum operating condition which flux was stabilized, while specific resistance value in membrane was minimized. As the result, the membrane separation was operated at low specific resistance value with the increase of the pressure. And then, cake load decreased by high velocity with the increase of the linear velocity, and the tendency in which specific resistance value and flux increased. Therefore, we confirmed the optimum operating condition as pressure $2.0 kgf/cm^2,$ 0.92 m/sec linear velocity.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.6
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• pp.717-726
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• 2007

Fully-grown flocs in a mixing tank of membrane filtration with dead-end membrane are ruptured while passing through a pump and the ruptured flocs are aggregated again in a Membrane-Feed-Pipe (MFP). To look at more details, this study tries to relate the reaggregation to a parameter of mixing intensity in MFP, i.e., G-value. The G-value is a function of Reynolds number, pipe diameter, friction factor and average velocity in MFP. To deal with polydispersity condition, we develop a representative particle size called in this study EDPD (Effective Diameter for Polydispersity condition in Dead-end filtration). The experimental results show that as the G-value increases, the EDPD decreases and also the cake resistance increases. Through comparison between EDPD and cake resistance, these results show that cake resistances are controlled by reaggregation phenomenon in MFP. The effect of detention time in MFP, however, does not affect the reaggregation of the broken flocs as G-values are increased.

• Membrane Journal
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• v.21 no.2
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• pp.141-147
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• 2011

The cation exchange membrane using TPA (tungstophosphoric acid) and the block co-polymer of polysulfone and polyphenylenesulfidesulfone was prepared for a separator of all-vanadium redox flow battery. The membrane resistance of the prepared cation exchange membrane in 1mol/L $H_2SO_4$ aqueous solution was measured. The membrane resistance of the prepared Psf-PPSS and Psf-TPA-PPSS cation exchange membrane was about $0.94{\Omega}{\cdot}cm^2$. Electrochemical property of all-vanadium redox flow battery using the prepared cation exchange membrane was measured. The measured charge-discharge cell resistance of V-RFB at 4 A decreased in the order; Nafion117 < Psf-TPA-PPSS < Psf-PPSS. The durability of membrane was earried out by soaking it in $VO_2{^+}$ solution and evaluated by measuring the charge-discharge cell resistance of V-RFB with an increase of soaking time. The prepared Psf-PPSS cation exchange membrane had high durability and Psf-TPA-PPSS cation exchange membrane had almost same durability compared with Nafion117.

• Membrane Journal
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• v.8 no.3
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• pp.130-137
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• 1998

Membrane fouling characteristics in the membrane-coupled activated sludge system were investigated. The influence of the floc size variation on the filtration resistance was analyzed using resistance-in-series model and mixed liquor was fractionated into three components to verify which component would give rise to a major contribution to the total resistance. The microbial floc size was rapidly reduced during the initial 4~6 hours of operation, and then decreased slightly but steadily, followed by leveling off at the size of 20 $\mu$m. The specific resistance of activated sludge increased with operation time, and measured values of specific resistance were matched well with the values estimated on the basis of the mean particle size in the mixed liquor. The contribution of soluble organics and cells to the total resistance was relativdy small compared with that of the supematant. Colloidal particles in the supematant showed much higher specific resistance than that of microbial floc, and played the most important role in the cake resistance.

• Membrane Journal
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• v.23 no.6
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• pp.469-474
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• 2013

An anion exchange membrane was prepared for a separator in the alkaline water electrolysis. An anion exchange membrane was prepared by the chloromethylation and amination of polyvinyl chloride (PVC) used as a base polymer. The membrane properties of the prepared anion exchange membrane such as the membrane resistance and ion exchange capacity were measured. The minimum membrane resistance of the prepared anion exchange membrane was $2.9{\Omega}{\cdot}cm^2$ in 1M NaOH aq. solution. This membrane had 2.17 meq./g-dry-membrane and 43.4% for the ion exchange capacity and water content, respectively. The membrane properties of the prepared anion exchange membrane was compared with that of the commercial anion exchange membrane. The membrane resistance decreased in the order; AHT>IOMAC> Homemade membrane> AHA>APS=AFN. The ion exchange capacity decreased in the order; Homemade membrane>AFN>APS>AHT>AHA>IOMAC.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.6
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• pp.645-652
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• 2016

A membrane module including grid was designed and introduced to MBR (membrane bio-reactor) for the purpose of better control of membrane fouling. It could be anticipated that the grid enhances the shear force of fluid-air mixture into the membrane surface by even-distributing the fluid-air to the membrane module. As MLSS concentration, packing density which is expressed in the ratio of the housing and the cross-sectional area of membrane fibers ($A_m/A_t$) and air-flow rate were changed, membrane foulings were checked by monitoring fouling resistances. The total fouling resistance ($R_c+R_f$) without grid installation (i.e., control) was $2.13{\times}10^{12}m^{-1}$, whereas it was reduced to $1.69{\times}10^{12}m^{-1}$ after the grid was installed. Regardless of the grid installation, the $R_c+R_f$ increased as the packing density increased from 0.09 to 0.28, however, the increment of resistance for the grid installation was less than that of the control. Increase in the air flow rate did not always guarantee the reduction of fouling resistance, indicating that the higher air flow rate can partially de-flocculate the activated sludge flocs, which led to severer membrane fouling. Consequently, installation of grids inside the housing have brought a beneficial effect on membrane fouling and optimum air flow rate is important to keep the membrane lowering fouling.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.5
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• pp.453-460
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• 2018

The impact of sodium hydroxide, which is one of chemicals of clean in place (CIP) for removing membrane fouling, on the PVDF membrane is reviewed with respect to physical/chemical structural change, the permeability affected therefrom. Based on the cleaning concentration applied in membrane water treatment facilities, 10% of accumulated defluorination was confirmed up to 166g.hr/L which reflects the exposure time. However, membrane resistance was confirmed to be reduced by about 10%. Through FT-IR and EDS analysis, reduction of F and change of are confirmed as factors that affect the permeability of membrane. Membrane resistance, which affects permeability, is affected by loss of additives for hydrophilicity, rather than defluorination of PVDF material. Therefore, in order to check membrane degradation degree, an accelerated test by NaOH was carried out, loss of additives was confirmed, and then PVDF inherent characteristic was observed.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.4
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• pp.553-559
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• 2013

We make several membranes with multilayer structure and characterize protective performance in various ways. Multilayer membrane is composed of shell fabric, support membrane, functional polymer membrane and liner fabric. In this research, we apply cellulose acetate derivatives as base polymer in functional polymer membrane and characterize water resistance, water vapor permeation, protective performance against DMMP and aerosol. Test results show that cellulose based polymer with polyethyleneimine possess performance with good water vapor permeation and excellent protective capability against DMMP equivalent to Saratoga type's protective suits. Also, these materials possess aerosol protective performance and water resistance.