• Journal of Korean Society of Environmental Engineers
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• v.35 no.12
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• pp.877-882
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• 2013

The application of ultrafiltration (UF) and microfiltration (MF) membranes has been increased for drinking water purification. The advantages of UF/MF membrane process compared to conventional treatment processes are stable operation under varying feed water quality, smaller construction area, and automatic operation. Most membrane treatment plants are designed with polymeric membranes. Recently, some studies suggested that the process of treating surface water with ceramic membranes is competitive to the application of polymeric membranes. Higher water flux, less frequent cleaning, and much longer lifetime are the advantages of ceramic membrane comparing to polymeric membrane. Therefore, this research focused on the application of ceramic MF membrane pilot plant at the slow sand filtration plant. The ceramic membrane pilot plant has three trains that used raw water and sand filtered water as a feed water, respectively. For optimizing the pilot plant process, the coagulation with PACl coagulant was used as a pretreatment of ceramic membrane process. In addition, CEB (Chemical Enhanced Backwash) process using $H_2SO_4$ and NaOCl was used for 1.5 days, respectively. The experimental results showed that applying the optimum coagulant dose before membrane filtration showed enhancing membrane fluxes for both raw water and sand filtered water. Also, when using raw water as a feed of membrane, minimum fouling rate was 2.173 kPa/cycle with 25 mg/L of PACl and when using sand filtered water, the minimum fouling rate was 0.301 kPa/cycle with 5 mg/L of PACl.

• Membrane Journal
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• v.23 no.6
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• pp.393-408
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• 2013

Gas separation processes using polymeric membranes have been greatly developed during the last few decades due to high energy efficiency and economic advantages. To achieve optimum economic performance, gas separation membranes required high permeability and selectivity. So, a number of reports examining the various polymeric materials for gas separation membranes have been published. Among the studied materials, polyimide (PI), which exhibit high permselectivity for various gas pairs, high chemical resistance, thermal stability, and mechanical strength, have attracted much attention. This paper focuses on the basic principle of gas separation, preparation procedure of membrane along with the recent developments and research trends of PI based materials for gas separation.

• Membrane Journal
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• v.7 no.3
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• pp.131-135
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• 1997

Polymeric micellar enhanced ultrafiltration method using a new type of polyrmer, $\alpha$-allyl-$\omega$-methoxy polyoxyethlene and maleic anhydride copolymer (AKM-0531, Mw 15, 000), has been proposed to separate 1-naphthylamine as a weak cationic toxic organic solubilizate. Enhancement effect of polymeric micelle was identified by the ultrafiltration runs using polyacryronitrile(PAN) holow fiber membrane with molecular weight cut off 6, 000. The linear dependance of flux on the pressure difference is shown to be valid up to 0.6kg/${cm}^2$ and the rate of flux increase in response to change in the pressure is gradually reduced under the pressure difference. Rejection of 0.96 was observed for f mM of 1-naphthylamine with 2 wt.% polymer solution at the conditions of 0.4kg/${cm}^2$, natural pH. and $25^{\circ}C$ Solubilization of 1-naphthylamine into the polymeric micelle enhanced the separation efficiency.

• Proceedings of the Membrane Society of Korea Conference
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• 1998.10a
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• pp.103-105
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• 1998

Asymmetric polymeric membranes prepared by the phase transition technique usually have either a top layer consisting of closely packed nodules or pores dispersed throughout the membrane surfaces. In this study, we present AFM image of a polysulfone membrane which show a clear evidence for the nodular structure and porous structure resulted from different phase separation mechanisms; spinodal decomposition and nucleation and growth. The surface morphology obtained by SEM and AFM was also compared.

• Membrane Journal
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• v.25 no.5
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• pp.373-384
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• 2015

In the past few decades, polymeric membrane has played an important role in gas separation applications. For the separation of $CO_2$, one of greenhouse gases, high permselectivity, long-term stability and scale-up are needed. However, conventional polymeric membranes have shown a trade-off relation between permeability and selectivity while inorganic materials are highly permeable but expensive. Mixed matrix membranes (MMMs) combining the advantages of both polymeric and inorganic materials have become a possible breakthrough for the next-generation gas separation membranes. The MMMs could be either symmetric or asymmetric but the latter is more preferred to improve the permeance. Important factors influencing the MMM fabrication include homogeneous distribution of inorganic particles and good interfacial contact between inorganic filler and organic matrix. Recently, metal organic frameworks (MOFs) have received much attention as a new class of porous crystalline materials and a potential candidate for $CO_2$ separation. Zeolitic imidazolate frameworks (ZIFs), a sub-branch of MOFs, are the most widely used in MMMs due to small particle size and appropriate pore size for $CO_2$ separation. One of the major issues associated with the incorporation of porous particles in a polymeric membrane is to control the microstructure of the porous particle materials such as particle size, orientation, and boundary conditions etc. In this review, major challenges surrounding MMMs and the strategies to tackle these challenges are given in detail.

• Membrane Journal
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• v.26 no.1
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• pp.55-61
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• 2016

Organic fouling observed in submerged membrane filtration as a pretreatment for seawater desalination increases energy consumption for membrane operation because of requiring frequent chemical cleaning and membrane replacement. In membrane pretreatment for seawater facing with algae blooms, membrane fouling was observed in submerged microfiltration using sodium alginate model compound which is one of the main components of extracellular polymeric substances. Without aeration, aglinate fouling increased with its concentration while aeration reduced the alginate fouling effectively regardless of its concentration tested. In the absence of aeration, alingate fouling tended to be decreased with increasing calcium concentration. However, this effectiveness was reduced by increasing sodium chloride concentration. At high concentration of sodium chloride and calcium similar to the seawater conditions, aeration reduced initial fouling. However, as time progressed, the effect of increased airflow rate on fouling reduction was not significant, implying that optimum airflow rate to control alginate fouling in submerged microfiltration can exist.

• Membrane Journal
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• v.9 no.2
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• pp.114-125
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• 1999

Dense polymer membranes were made from vanous silicone polymers such as poly(1-trimethylsilyl-1-propyneHPTMSP), poly(dimethylsiloxaneHPDMS), PTMSP- g-PDMS. These membranes were evaluated in terms of the removal of chlorinated organic hydrocarbons such as chloroform, trichloroethylene(TCE), perchloroethylene(PCE) from water by pervaporation. It was possible for membranes used in this study to remove PCE selectively which is dissolved small quantity in water among other separable solutes. PTMSP membranes exhibited a remarkable decay in permeability with time because of the free volume decreases. However, PTMSP-g-PDMS membrane underwent no physical aging and showed the stable flux behavior. From the results of the contact angle measurement, polymeric membranes used in this study showed affinity with solutes for separation and no affinity with water. The relative swelling degree was directly related to the selectivity, while it has no influence on the flux.

• Bulletin of the Korean Chemical Society
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• v.26 no.8
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• pp.1219-1224
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• 2005

We prepared lead ion-selective PVC membranes that were based on N,N'-bis-thiophene-2-ylmethylene-ethane-1,2-diamine as a membrane carrier. The membrane electrode has a linear dynamic range between 1.0 ${\times}$ $10^{-5}$ and 1.0 ${\times}$ $10^{-1}$ M with a Nernstian slope of 29.79 mV per decade, and its detection limit was 2.04 ${\times}$ $10^{-6}$ M at room temperature. The potentiometric response is independent of the pH of the solution in the pH range of 5-7. The proposed electrode revealed good selectivity and response for $Pb^{2+}$ over a wide variety of other metal ions in pH 5.0 buffer solutions, and there was good reproducibility of the base line on the subsequent measurements. The membrane electrode has a relatively fast response time, satisfactory reproducibility and a relatively long life time.

• Membrane and Water Treatment
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• v.6 no.6
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• pp.501-512
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• 2015

A laboratory-scale submerged membrane bioreactor (MBR) was continuously operated for 100 d at an infinite sludge retention time (SRT) with the aim of identifying possible relation between the filterability of mixed liquor and sludge properties, such as extracellular polymeric substances (EPS), soluble microbial products (SMP), viscosity of mixed liquor, zeta potential of flocs and particle size distributions (PSD). Research results confirmed that MBR can operate with a complete sludge retention ensuring good treatment performances for COD and $NH_3-N$. However, the long term operation (about 40 d) of MBR with no sludge discharge had a negative influence on sludge filterability, and an increase in membrane fouling rates with the time was observed. There as a strong correlation between the sludge filterability and the fouling rate. Among the different sludge properties parameters, the concentration SMP and EPS had a more closely correlation with the sludge filterability. The concentrations of SMP, especially SMP with MW above 10 kDa, had a strong direct correlation to the filterability of mixed sludge. The protein fractions in EPS were biodegradable and available for microorganism metabolism after about 60 days, and the carbohydrates in EPS had a significantly negative effect on sludge filterability in MBR at an infinite SRT.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.2
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• pp.323-329
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• 2000

The coupling of an activated sludge reactor with a membrane unit, i.e., Membrane Coupled Activated Sludge (MCAS) system offers several advantages over conventional process. But the major hurdle in the extensive use of this process is the continuous reduction of permeation flux caused by membrane fouling. The aim of this study is to investigate membrane fouling characteristics in the MCAS process. During crossflow ultrafiltration(CFUF) of activated sludge, floc size decreased abruptly at the beginning of operation and thereafter decreased continuously and gradually. The floc size changed from 100~200 to $6{\sim}8{\mu}m$ depending on recirculation velocity. This floc breakage played a key role in rapid increase of $R_c$(cake layer resistance), which led to flux decline. The floc breakage stimulated biomass to release EPS(Extracellular Polymeric Substance) which has been known to be one of the major membrane foul-ants. The amounts of EPS before and after CFUF were 266 and 405(VS mg/MLSS g), respectively. The rise up of EPS concentration was another factor affecting flux decline in MCAS system.