• Applied Chemistry for Engineering
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• v.24 no.1
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• pp.49-54
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• 2013

We fabricated a composite carbon electrode to remove nitrate ions selectively from a mixed solution of anions. The electrode was fabricated by coating the surface of a carbon electrode with the nitrate-selective anion exchange resin (BHP55, Bonlite Co.) powder. We performed capacitive deionization (CDI) experiments on a mixed solution containing chloride, nitrate, and sulfate ions using a BHP55 cell constructed with the fabricated electrode. The removal of nitrate ions in the BHP55 cell was compared to that of a membrane capacitive deionization (MCDI) cell constructed with ion exchange membranes. The total quantity of ions adsorbed in BHP55 cell was $38.3meq/m^2$, which is 31% greater than that of MCDI cell. In addition, the number of nitrate adsorption in the BHP55 cell was $15.9meq/m^2$ (42% of total adsorption), 2.1 times greater than the adsorption in the MCDI cell. The results showed that the fabricated composite carbon electrode is very effective in the selective removal of nitrate ions from a mixed solution of anions.

• Membrane Journal
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• v.33 no.6
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• pp.315-324
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• 2023

Ion-exchange membrane (IEM), is a key component that determines the performance of the electro-membrane processes. In this review, the latest research trends in improving the performance of IEMs used in various electro-membrane processes through modification using carbon-based and metal-based nanomaterials are investigated. The nanomaterials can be introduced into IEMs through various methods. In particular, carbon-based nanomaterials can strengthen their interaction with polymer chains by introducing additional functional groups through chemical modification. Through this, not only can the ion conductivity of IEM be improved, but also the permselectivity can be improved through the sieving effect through the layered structure. Meanwhile, metal-based nanomaterials can improve permselectivity through sieving properties using the difference in hydration radius between target ions and excluded ions within a membrane by using the property of having a layered or porous structure. In addition, depending on the characteristics of the binder used, ion conductivity can be improved through interaction between nanomaterials and binders. From this review, it can be seen that the properties of IEMs can be effectively controlled using carbon-based and metal-based nanomaterials and that research on this is important to greatly improve the performance of the electro-membrane process.

• Membrane Journal
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• v.26 no.3
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• pp.220-228
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• 2016

Carbon molecular sieve (CMS) hollow fiber membranes were prepared by carbonizing a polyimide precursor manufactured by non-solvent induced phase separation process. Gas separation performance of CMS hollow fiber membrane was investigated on the effect of three carbonization conditions. CMS membrane with the highest gas separation performance was obtained at the pyrolysis temperature of $250-450^{\circ}C$: $N_2$, $SF_6$, and $CF_4$ permeance were 20, 0.32, 0.48 GPU, respectively, and $N_2/SF_6$ and $N_2/CF_4$ selectivities were 62 and 42, respectively. In the $SF_6/CF_4/N_2$ mixture gas test, when the stage cut was 0.2, the recovery ratio of $SF_6$ and $CF_4$ was over 99% and 98%. $SF_6$ concentration ratio was 4.5 times higher than the $SF_6$ concentration at the feed side. From the results, it was concluded that CMS membrane was one of the promising membranes for recovery Perfluorocompound gases process.

• Membrane Journal
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• v.11 no.4
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• pp.190-203
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• 2001

In this study the discharged wastewater from a paper plant was filtrated by 4 kinds of tubular carbon ceramic ultrafiltration membranes with periodic water-back-flushing. We could investigate effects of watch-back-flushing period, transmembrane pressure (TMP) and flow rate, and find optimal operating conditions. The back-f1ushing time (BT) was fixed at 3 sec, and fi1tration times (FT) werc changed in 15~60 scc, TMP in 1.00~2.50$kg_{f}$/$cm^2$, and the flow rates in 0.27~1.75 L/min. The optimal conditions were discussed in 7he viewpoints of dimensionless permeate flux (J/J$_{0}$), total permeate volume ($V^T$) and resistance of membrane fouling ($R^f$). Optima1 back-flushing period was BT/FT=0.20, suggesting that the frequent back-flushing should decrease membrane fouling. Optimal TMP in the viewpoint of $V^T$ was 1.00~1.55$kg_{f}$/$cm^2$, suggesting that rising TMP should increase membrane fouling and decrease permeate flux. But, rising f1ow rate should decrease membrane fouling and increase permeate flux. Then, average rejection rates of pollutants filtratedby carbon ceramic membranes were 88~98 % for turbidity, 48~72% fort $COD_{cr}$ and 37~76% for TDS.

• Membrane Journal
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• v.30 no.2
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• pp.97-110
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• 2020

CO₂ capture and storage (CCS) is one of the promising technologies that can mitigate ever-growing emission of anthropogenic carbon dioxide and resultant climate change. Among them, chemical looping combustion (CLC) and calcium looping (CaL) are getting increasing attention recently as the prospective alternatives to the existing amine scrubbing. Both methods use metal oxides in the process and consist of cyclic reactions. Yet, due to their cyclic nature, they both need to resolve sintering-induced cyclic stability deterioration. Moreover, the structure of the metal oxides needs to be optimized to enhance the overall performance of CO₂ capture and storage. Deposition of thin film coating on the metal oxide is another way to get rid of wear and tear during the sintering process. Chemical vapor deposition or atomic layer deposition are the well-known, established methods to form thin film membranes, which will be discussed in this review. Various effective recent developments on structural modification of metal oxide and incorporation of stabilizers for cyclic stability are also discussed.

• Membrane Journal
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• v.31 no.3
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• pp.212-218
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• 2021

It is inevitable to generate incomplete combustion gases when mankind utilizes fossil fuels. From this point of view, gas separation process of combustion gas suggests the possibility of recycling CO gas. In this study, we fabricated a facilitated transport polymeric composite membrane for CO separation using AgBF₄ and HBF₄. The copolymer was synthesized via free-radical polymerization of poly(vinyl alcohol) (PVA) as a main chain and acrylic acid (AA) monomer as a side chain. The polymer synthesis was confirmed by FT-IR and the interactions of graft copolymer with AgBF₄, and HBF₄ were characterized by TEM. PVA-g-PAA graft copolymer membranes showed good channels for facilitated CO transport. In this perspective, we suggest the novel approach in CO separation membrane area via combination of grafting and facilitated transport.

• Membrane Journal
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• v.32 no.5
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• pp.314-324
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• 2022

This study is aimed to design a membrane process that systematically removes contaminants including microplastics in sun-dried salt using a separation membrane. In this study, we selected the separation membrane material, pore size, and module suitable for the sun-dried salt fields, and proceeded with the experiments under the salt fields and laboratory conditions. A pilot plant was constructed and tested in our lab and in the actual saltern with the selected 200 kDa, 4 kDa ultrafiltration membranes, and 3 kDa nanofiltration membranes. Most of the impurities in the sea salt were 0.1 ㎛ in size, and more than 7 types of various microplastics were detected in the impurities. After that, as a result of checking the filtered water through the separation membrane process, no impurities were detected. As a result of comparing the existing sea salt component and the sea salt component prepared with separation membrane filtrate, impurities were effectively removed without change in the sea salt component.

• Membrane Journal
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• v.33 no.6
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• pp.352-361
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• 2023

Steam methane reforming is currently the most widely used technology for producing hydrogen, a clean fuel. Hydrogen produced by steam methane reforming contains impurities such as carbon monoxide, and it is essential to undergo an appropriate post-purification step for commercial usage, such as fuel cells. Recently, membrane separation technology has been gaining great attention as an effective purification method; in this study, we evaluated the feasibility of using commercial polysulfone membranes for biogas upgrading to separate and recover hydrogen from a hydrogen/carbon monoxide gas mixture. Initially, we examined the physicochemical properties of the commercial membrane used. We then conducted performance evaluations of the commercial membrane module under various conditions using mixed gas, considering factors such as stage-cut and operating pressure. Finally, based on the evaluation results, we carried out simulations for process design. The maximum H₂ permeability and H₂/CO separation factor for the commercial membrane process were recorded at 361 GPU and 20.6, respectively. Additionally, the CO removal efficiency reached up to 94%, and the produced hydrogen concentration achieved a maximum of 99.1%.

• Journal of Korean Society of Water and Wastewater
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• v.34 no.2
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• pp.127-137
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• 2020

In this study, a MWCNT(multi-wall carbon nanotube) was added to polysulfone(PSf) support layer to improve flux of TFC(thin film composite) RO(reverse osmosis) membrane. Two different kinds of MWCNT were used. Surfaces of some MWCNTs were modified hydrophilically through acid treatment, while those of other MWCNTs were modified through heat treatment to maintain their hydrophobicity. MWCNT/PSf support layer was prepared by adding PSf to the NMP mixed solvent containing 0.1 wt% MWCNTs using a phase inversion method. The surface porosity of the MWCNT/PSf support increased by 42~46% while its surface pore size being maintained. The TFC RO membrane made of MWCNT/PSf support layer showed a 20% flux increase while its salt rejection characteristics is sustained. In addition, the MWCNT/PSf support layer has better mechanical stability than the PSf support layer, there resulting in an increased resistance of flux reduction due to physical pressure.

• Membrane Journal
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• v.33 no.2
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• pp.70-76
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• 2023

Heavy water (D₂O) can induce various biochemical changes in comparison with light water (H₂O). In order to reduce excessive energy consumption, which is a disadvantage of the existing separation process, we conduct the forward osmosis with electrospun polyamide membranes. NaCl and phosphoric acid were used as draw solutions. FT-IR spectroscopy was used to quantify the concentration of heavy water. It was observed that phosphoric acid could concentrate heavy water through a forward osmosis process and its special interaction with hydrogen/deuterium (H/D) was spectrophotometrically confirmed.