• Membrane Journal
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• v.32 no.6
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• pp.390-400
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• 2022

Nanofiltration (NF) membranes are more popular than reverse osmosis (RO) membranes as they can be operated at much lower pressures for applications in treatment of wastewater from industries like food processing and pharmaceutical as well as municipal sewage water. The separation mechanism in case of NF membranes is based on solution diffusion as well as sieving, for which the crosslinking density of the thin film of the composite membrane is less then RO membrane. Unlike ceramic membranes, membrane fouling is one of the chronic problems that occur during the nanofiltration process in polymeric membranes. Membrane cleaning is done to get rid of reversible as well as irreversible fouling by treatment with sodium hypochlorite. Compared to polymeric membranes, ceramic membranes show higher stability against these agents. In this review different types of ceramic membrane applied wastewater treatment by NF process are discussed.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.4
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• pp.271-277
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• 2010

$(Ba(Zr_{0.85}Y_{0.15})O_{3-\delta})$ oxide, showing high protonic conductivity at high temperatures and good chemical stability with $CO_2$ are referred to as hydrogen separation membrane. For high efficiency of hydrogen separation ($H_2$ flux and selectivity) and low fabrication cost, ultimate thin and dense BZY-Ni layer has to be coated on a porous substrate such as $ZrO_2$. Aerosol depostion (AD) process is a novel technique to grow ceramic film with high density and nano-crystal structure at room-temperature, and may be applicable to the fabrication process of AD integration ceramic layer effectively. XRD, SEM, X-ray mapping measurements were conducted in order to analyze the characteristics of BZY-Ni membrane fabricated by AD process. it is observed that it is homogeneous distribution for BZY-Ni. The result of $H_2$ permeation rate suggests that BZY-Ni composite is higher than BZY.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.3
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• pp.353-362
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• 2009

A new method and equipment for measuring the zeta potential of the external surface of hollow fiber (HF) membranes is reported. An existing commercial streaming potential analyzer in conjunction with home-made test cells was used to determine the electrokinetic surface characteristics of various HF membranes. It was shown that measurements of the external surface of HF membrane using the home-made test cells designed in this study were easy and reliable. The zeta potential values were quite accurate and reproducible. By varying the physical shape of the test cells to adjust hydrodynamics inside the test cells, several upgrade versions of home-made test cells were obtained. It was shown that the zeta potential of the external surface of HF membranes was most influenced by membrane materials as well as the way of surface modification. However, the overall surface charge of tested HF membranes were much less than that of commercial polyamide thin-film-composite (TFC) reverse osmosis (RO) membranes due to the lack of surface functional groups. For the HF membranes with the same material, the effect of pore size on the zeta potential was not significant, implying the potential of accurate zeta potential measurements for various HF membranes. The results obtained in this study are expected to be useful for better understating of electrokinetic surface characteristics of the external surface of HF membranes.

• Membrane Journal
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• v.27 no.6
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• pp.506-510
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• 2017

The interfacial polymerization method has been applied to various fields as a reaction in which reactive monomers dissolved in two immiscible solutions cause polymerization at the interface. In the case of water treatment membranes, m-phenylene diamine and trimesoyl chloride are used as reactants. The performance of the membrane is affected by various polymerization factors. In this study, we investigated how the spreading rate of the organic solution influences the surface and structure of the membrane. Spreading rate of organic solutions was adjusted to 7.6 and 25 mm/sec. The solution volume of the organic phase was adjusted to 1~3 drops. The observed results showed that cracks were not found in the polyamide membrane when dropping at a drop of 7.6 mm/sec and dropping two drops at 25 mm/sec. On the other hand, cracks occurred in all cases. Therefore, the spreading rate of the initial organic solvent is expected to greatly affect the performance of the polyamide membrane.

• Membrane Journal
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• v.31 no.5
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• pp.293-303
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• 2021

Separation membranes used in water filtration, protein purification or biomedical filtration device frequently undergo membrane fouling for several reasons. The formation of biofilm on the membrane surface by bacteria causes a severe problem for durability of the membrane. For the protein separation, the membrane pores get blocked due to surface hydrophobicity of the membrane. There are several approaches controlling the membrane fouling and one of them is the incorporation of silver nanoparticles. Antibacterial properties of silver nanoparticles are well known and thus widely used in several applications. In this review, we have focused on the membranes where silver nanoparticles or its derivatives are either incorporated in the active layer of thin film composite membranes or uniformly distributed throughout the whole membranes.

• Journal of the Korean institute of surface engineering
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• v.45 no.6
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• pp.248-256
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• 2012

A Pd-based hydrogen membranes for hydrogen purification and separation need high hydrogen perm-selectivity. The surface roughness of the support is important to coat the pinholes free and thin-film membrane over it. Also, The pinholes drastically decreased the hydrogen perm-selectivity of the Pd-based composite membrane. In order to remove the pinholes, we introduced various surface pre-treatment such as alumina powder packing, nickel electro-plating and micro-polishing pre-treatment. Especially, the micro-polishing pretreatment was very effective in roughness leveling off the surface of the porous nickel support, and it almost completely plugged the pores. Fine Ni particles filled surface pinholes with could form open structure at the interface of Pd alloy coating and Ni support by their diffusion to the membrane and resintering. In this study, a $4{\mu}m$ surface pore-free Pd-Cu-Ni ternary alloy membrane on a porous nickel substrate was successfully prepared by micro-polishing, high temperature sputtering and Cu-reflow process. And $H_2$ permeation and $N_2$ leak tests showed that the Pd-Cu-Ni ternary alloy hydrogen membrane achieved both high permeability of $13.2ml{\cdot}cm^{-2}{\cdot}min^{-1}{\cdot}atm^{-1}$ permation flux and infinite selectivity.

• Membrane Journal
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• v.31 no.6
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• pp.417-425
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• 2021

As the demand for high-capacity batteries increases, there has been growing researches on the lithium metal anode with a capacity (3,860 mAh/g) of higher than that of conventional one and a low electrochemical potential (-3.040 V). In this study, using the anatase phased TiO₂ nanoparticles synthesized by hydrothermal synthesis, a PVdF-HFP/TiO₂ organic/inorganic composite material was designed and used as an interfacial protective layer for a Li metal anode. As-formed organic/inorganic-lithium composite thin film was confirmed through the crystalline structure and morphological analyses. In addition, the electrochemical test (cycle stability and voltage profile) confirmed that the protective layer of PVdF-HFP/TiO₂ composite (10 wt% TiO₂ and 1.1 ㎛ film thickness) contributed to the enhanced electrochemical performance of the lithium metal anode (Colombic efficiency retention: 90% for 77 cycles). Based on comparative test with the untreated lithium electrode, it was confirmed that our protective layer plays an important role to stabilize/improve the EC performance of the lithium metal negative electrode.

• Membrane Journal
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• v.12 no.3
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• pp.182-191
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• 2002

Polyamide reverse osmosis (RO) membrane with thin film composite structure was commercialized for seawater desalination process. Recently, it has been reported that some RO processes for high pressure and recovery leads to reducing in energy cost and pretreatment scale compared with earlier process. The development of energy recovery, pumping device and RO elements with high pressure and rejection made high pressure and recovery process possible. In this study, permeation properties of commercialized seawater RO membrane were investigated under the condition of high pressure and recovery. In the RO sheet membrane test 3.5% NaCl of synthetic seawater was used. The synthetic seawater contained only sodium chloride. In the RO module test, natural seawater was used at Happo Bay, Masan city. As the results, RO membrane with high durability of pressure was better than that with high rejection of seawater for high pressure and recovery process. Seawater rejection of high concentrate tends to be improved by high pressure operation.

• Journal of Adhesion and Interface
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• v.20 no.3
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• pp.110-115
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• 2019

Graphene oxide has been gathering interests as a way to exfoliate graphene. Since the oxidation group of graphene oxide can hydrogen bond with various functional groups, tremendous efforts have been actively conducted to apply various applications. However, graphene oxide alone cannot substantially possess the mechanical properties required for the practical application. Therefore, in this study, polydopamine, which is a bio-mimetic mussel protein-inspired material, was combined with graphene oxide to form a large-area composite membrane at the liquid-gas interface. In addition, the morphology of the polydopamine-graphene oxide composite thin film was also controlled to obtain a composite membrane having a nano-wrinkle structure. It can be expected to be used in the next generation seawater desalination membranes or carbon composites because it can form mechanically superior and sophisticated nanostructures.

• Membrane Journal
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• v.24 no.6
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• pp.453-462
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• 2014

Thin film composite (TFC) polyamide (PA) membranes were prepared on polyester (PET) nonwoven reinforced polysulfone supports for forward osmosis (FO) processes. PSF (polysulfone) supports were prepared via the phase inversion process from PSF casting solutions in dimethyl formamide (DMF) solvents (19 wt%) by using a PET nonwoven (thickness of $100{\mu}m$) as a mechanical reinforcing material for reverse osmosis (RO) membrane. The PSF support from 19 wt% of DMF/PSF casting solution showed sponge-like morphology and asymmetric internal structure. To reduce the internal concentration polarization in FO operation, thin ($20{\mu}m$ of thickness) nonwoven-supported PSF supports were prepared by using PSF/DMF casting solution (9~19 wt%). A desirable support structure with a highly porous sponge-like morphology were achieved from the thin nonwoven-supported PSF layer prepared with 9~12 wt% casting solution. A crosslinked aromatic polyamide layer was fabricated on top of each support to form a TFC PA membrane. The tested sample from 12 wt% of DMF/PSF casting solution presented outstanding FO performance, almost 5.5 times higher water flux (24.3 LMH) with low reverse salt flux (RDF, 1.5 GMH) compared to a thick nonwoven rainforced membrane (4.5 LMH of flux and 3.47 GMH of RSF). By reducing the thickness of the nonwoven and optimizing PSF concentration of casting solution, the morphology of the prepared membranes were changed from a dense structure to a porous sponge structure in the boundary area between nonwoven and PET support layer.