• Membrane and Water Treatment
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• 제5권4호
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• pp.235-250
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• 2014

The impacts of membrane degradation due to chlorine attack on the rejection of inorganic salts and trace organic contaminants by nanofiltration (NF) and reverse osmosis (RO) membranes were investigated in this study. The rejection of trace contaminants was examined at environmentally relevant concentrations. Changes in the membrane surface morphology were observed as a result of chlorine exposure. A small increase in rejection was consistently observed with all four membranes selected in this study after being exposed to a low concentration of hypochlorite (100 ppm). In contrast, a higher concentration of hypochlorite (i.e., 2000 ppm) could be detrimental to the membrane separation capacity. Membranes with severe chlorine impact showed a considerable decrease in rejection over filtration time, possibly due to rearrangement of the polyamide chains under the influence of chlorine degradation and filtration pressure. The reported results indicate that loose NF membranes are more sensitive to chlorine exposure than RO membranes. The impact of hypochlorite exposure (both positive and negative) on rejection is dependent on the strength of the hypochlorite solution and is more significant for the neutral carbamazepine compound than the negatively charged sulfamethoxazole.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.421-424
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• 2006

Nafion/Pt/Polypyrrole composite membranes were fabricated by chemical in-situ polymerization of pyrrole monomers with Pt precursors in Nafion matrix for DMFC. We demonstrated that positively charged pyrrolinum groups of polypyrrole particles were co-interacted with sulfonic groups of Nafion as verified by FT-IR results. Mutual interaction between $Nafion-SO_3^-$ (or negatively charged Pt precursors) and Polypyrrole$-NH_2^+$ influenced the physical properties of pristine Nafion. Thermal property proton conductivity, methanol permeability, and cell performance of pristine and modified Nafion were analyzed for an application of DMFC membrane. Thermal stabilities of sulfonic groups and side chains in Nafion/Pt/polypyrrole composite membranes were higher than those of Nafion due to mutual interaction between sulfonic groups of Nafion and pyrrolinum groups of polypyrrole. Methanol permeabilities of Nafion/Pt/Polypyrrole composite were reduced more proton conductivities with the increase in the content of Pt particles. As a result of that, the enhancement of cell performance by Nafion/Pt/Polypyrole O2 relative to Nafion was more pronounced under the specific experimental condition such as high temperature and more concentrated methanol solution.

• Carbon letters
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• 제14권4호
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• pp.247-250
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• 2013

In this study, we present a facile method of fabricating graphene oxide (GO) films on the surface of polyimide (PI) via layer-by-layer (LBL) assembly of charged GO. The positively charged amino-phenyl functionalized GO (APGO) is alternatively complexed with the negatively charged GO through an electrostatic LBL assembly process. Furthermore, we investigated the water vapor transmission rate and oxygen transmission rate of the prepared (reduced GO $[rGO]/rAPGO)_{10}$ deposited PI film (rGO/rAPGO/PI) and pure PI film. The water vapor transmission rate of the GO and APGO-coated PI composite film was increased due to the intrinsically hydrophilic property of the charged composite films. However, the oxygen transmission rate was decreased from 220 to 78 $cm^3/m^2{\cdot}day{\cdot}atm$, due to the barrier effect of the graphene films on the PI surface. Since the proposed method allows for large-scale production of graphene films, it is considered to have potential for utilization in various applications.

• BMB Reports
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• 제40권6호
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• pp.1090-1094
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• 2007

Melittin (ME), a linear 26-residue non-cell-selective antimicrobial peptide, displays strong lytic activity against bacterial and human red blood cells. To design ME analogue with improved cell selectivity, we synthesized a melittin diastereomer (ME-D) with D-amino acid in the leucine zipper sequence (Leu-6, Lue-13 and Ile-20). Compared to ME, ME-D exhibited the same or 2-fold higher antibacterial activity but 8-fold less hemolytic activity. Circular dichroism analysis revealed that ME-D has much less $\alpha$-helical content in $\alpha$-helical content in the presence of zwitterionic EYPC/cholesterol (10 : 1, w/w) liposomes compared to negatively charged EYPE/EYPG (7 : 3, w/w) liposomes. The blue shift of the fluorescence emission maximum of ME-D in zwitterionic EYPC/cholesterol (10 : 1, w/w) liposomes was much smaller than in negatively charged EYPE/EYPG (7 : 3, w/w) liposomes. These results suggested that the improvement in therapeutic index/cell selectivity of ME-D is correlated with its less permeability to zwitterionic membranes.

• Membrane and Water Treatment
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• 제12권2호
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• pp.65-73
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• 2021

Sponge ball cleaning can generate an abrasion effect, which leads to an attractive increasing in both permeate flux and membrane rejection. The aim of this study was to investigate the influence of the daily sponge ball cleaning (SBC) on the performance of different UF cross-flow membrane modules integrated with a bioreactor. Two 1"-membrane modules and one 1/2"-membrane module were tested. The parameters measured and controlled are temperature, pH, viscosity, particle size, dissolved organic carbon (DOC), total suspended solids (TSS), and permeate flux. The permeate flux could be improved by 60%, for some modules, after 11 days of daily sponge ball cleaning at a transmembrane pressure of 350 kPa and a flow velocity of 4 m/s. Rejection values of all tested modules were improved by 10%. The highest permeate flux of 195 L/㎡.h was achieved using a 1"-membrane module with the aid of its negatively charged membrane material and the daily sponge ball cleaning. In addition, the enhancement in the permeate flux caused by daily sponge ball cleaning improved the energy specific demand for all tested modules. The negatively charged membrane showed the lowest energy specific demand of 1.31 kWh/㎥ in combination with the highest flux, which is a very competitive result.

• 폴리머
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• 제35권5호
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• pp.419-423
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• 2011

항균제 대체제로 응용하기 위하여 다양한 저분자량 수용성 키토산(LMWSC; MW1, MW3, MW5, MW10)을 제조하였으며, 이들의 항균제 대체제 사용 가능여부와 그 작용 기작에 대하여 연구하였다. 먼저, 다양한 분자량 형태의 LMWSC를 이용하여 사람에게 유해한 각종 박테리아를 이용하여 항균효과를 확인하였고, 그 중 MW10의 항균효과가 가장 우수한 것으로 확인되었다. 그 반면 사람의 적혈구를 이용한 용혈활성 실험에서 독성을 나타내지 않았다. MW10의 항균 효과가 세균의 어느 부분에서 일어나는지 확인하기 위해 박테리아의 세포막 조건(PE/PG=7/3, w/w)으로 인공리포좀을 만들었고, 여기에 MW10을 처리한 결과 세균 막에서 항균효과를 나타냄을 추론할 수 있었다.

• Environmental Engineering Research
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• 제22권4호
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• pp.356-362
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• 2017

This study investigates the use of methyl-esterified eggshell membranes (MESM) for the harvesting of microalgae species under various conditions. Eggshell membranes were esterified with HCl to impact polycationic characteristics. After methyl esterification, the negative surface charge property of eggshell membrane was changed from negative to positive for all pH values to improve microalgae sorption capacity. The harvesting efficiency of microalgae by MESM reached 78-99% for all pH ranges evaluated. In addition, a 150 mesh particle size and $10mg\;L^{-1}$ MESM dose were found to yield up to 98% microalgae harvesting. These results indicate that the high cationic charge of MESM strongly adsorbs the negatively-charged microalgae. MESM is biocompatible and can be applied to the harvest of microalgae.

• 한국자기공명학회논문지
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• 제15권1호
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• pp.1-13
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• 2011

9Pbw2 is a 9-mer analog of protaetiamycine derived from the larvae of the beetle Protaetia brevitarsis. Previously, we designed four 9-mer peptide analogues to optimize the balance between the hydrophobicity and cationicity of the peptides and to increase bacterial cell selectivity. Among them, 9Pbw2 has high antibacterial activity without cytotoxicity. The results obtained in previous study suggest that the bactericidal action of 9Pbw2 may be attributed to the inhibition of the functions of intracellular components after penetration of the bacterial cell membrane. In order to understand structure-activity relationships, we determined the three-dimensional structure of 9Pbw2 in 200 mM DPC micelle by NMR spectroscopy. 9Pbw2 has one hydrophobic turn helix from $Trp^3$ to $Arg^8$ and positively charged residues at the N- and C-terminus. This result suggested that positively charged residues from position at the C-terminus in 9Pbw2 may be important for the primary binding to the negatively charged phospholipid head groups in bacterial cell membranes and hydrophobic residues in the middle portion face toward the acyl chains of the hydrophobic lipid in the bacterial cell membrane.

• Membrane and Water Treatment
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• 제3권2호
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• pp.123-131
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• 2012

This study investigated the extraction and stripping performance of PIMs consisting of PVC and Aliquat 336. Extraction and stripping of three representative heavy metals - namely $Cd^{2+}$, $Cu^{2+}$, and $Zn^{2+}$ - by the synthesized membranes were evaluated as a function of sodium chloride concentration and under different stripping solutions (0.01 M $HNO_3$, Milli-Q water, 0.01 M HCl and 0.01 M NaOH), respectively. Results reported here indicate that the formation of negatively charged metal chloride complex species was responsible for the extraction of the target metal to PIMs. Experimental results and thermodynamic modeling of the speciation of chloro metal complexes further confirm that the extraction selectivity between $Cd^{2+}$, $Cu^{2+}$ and $Zn^{2+}$ can be controlled by regulating the chloride concentration of the feed solution. An acidic solution without any chloride was the most effective stripping solution, followed by Milli-Q water, and a diluted hydrochloric acid solution. On the other hand, the stripping of metals from PIMs did not occur when a basic stripping solution was used.

• Membrane and Water Treatment
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• 제7권4호
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• pp.277-296
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• 2016

The aim of this research was to investigate the ability of nanofiltration (NF) and ultrafiltration (UF) membranes as a filtration unit for groundwater treatment for drinking water resources. Commercial membranes denoted as TS40, TFC-SR3 and GHSP were used to study the performance based on rejections and fluxes. The investigation has been conducted using natural groundwater obtained from a deep tube well with initial concentration of iron (Fe) and manganese (Mn) at 7.15 mg/L and 0.87 mg/L, respectively. Experimental results showed that NF membranes exhibited higher fluxes than UF membrane with pure water permeability at 4.68, 3.99 and $3.15L.m^{-2}.h^{-1}.bar^{-1}$, respectively. For metal rejection, these membranes have performed higher removal on Fe with TS40, TFC-SR3 and GHSP membranes having more than 82%, 92% and 86% respectively. Whereas, removal on Mn only achieved up to 60%, 80% and 30%, for TS40, TFC-SR3 and GHSP membranes respectively. In order to achieve drinking water standard, the membranes were efficient in removing Fe ion at 1 and 2 bar in contrast with Mn ion at 4 and 5 bar. Higher rejection of Fe and Mn were achieved when pH of feed solution was increased to more than 7 as TFC-SR3 membrane was negatively charged in basic solution. This effect could be attributed to the electrostatic effect interaction between membrane material and rejected ions. In conclusion, this study proved that NF membrane especially the TFC-SR3 membrane successfully treated local groundwater sources for public drinking water supply in line with the WHO standard.