• Proceedings of the Membrane Society of Korea Conference
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• 2003.07a
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• pp.133-135
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• 2003

The removal of dissolved oxygen(DO) from water was studied using a poly(vinyliene fluoride)(PVDF) hollow fiber membrane contactor(HFMC) with the vacuum degassing process(VDP), Asymmetric porous PVDF hollow fiber membranes (HFM) for membrane contactor were prepared by a wet phase inversion method. In spinning of these PVDF hollow fibers, dimethy lacetamide (DMAc), LiCl and pure water were used as a solvent, a pore-forming additive and internal/external coagulant, respectively. The characteristics of the structure(pore size, porosity etc.) of the prepared PVDF HFMs as a function of concentration of pore-forming additive in polymer dope solution were studied. Also, the removal efficiency of DO from water according to flow rates of water, using PVDF HFMC with VDP, was studied. The performance of the asymmetric porous PVDF HFMC and a symmetric porous PP HFMC commercialized were compared. As a result, the asymmetric porous PVDF HFMC showed higher removal efficiency of DO than that of a symmetric porous PP HFMC.

• Membrane Journal
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• v.24 no.1
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• pp.50-62
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• 2014

An asymmetric microfiltration membranes were prepared with polysulfone by an immersion precipitation phase inversion method. Microfiltration membranes were prepared by polysulfone/N-methyl-2-pyrrolidone/polyvinylpyrrolidone/phosphoric acid casting solution and water coagulant. The vapor induced phase inversion method was used to prepare the membranes. The pore size and the morphology were changed by the phosphoric acid additive, the temperature of casting plate and the exposure time at the relative humidity of 74%. The morphology of membranes was investigated by scanning electron microscopy and microflow permporometer. By the addition of the phosphoric acid additive in the casting solution, the morphology of the prepared membranes were changed from a dense sponge structure to a loose asymmetric sponge structure. Due to the addition of catalytic amount of phosphoric acid to NMP casting solution, the mean pore size increased almost $0.2{\mu}m$ and the water flux increased about 3,000 LMH. The temperature of casting plate and exposure time had a apparent effect on the skin layer structure and the pore size and the porosity of the membrane.

• Membrane and Water Treatment
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• v.13 no.6
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• pp.291-301
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• 2022

In this study, cement/PVDF hollow-fiber hybrid membranes were prepared via a mixed process of diffusion-induced phase separation and hydration. The presence of X-ray diffraction peaks of Ca(OH)₂, an AFt phase, an AFm phase, and C-S-H phase confirmed the hydration reaction. Good hydrophilicity was obtained. The cross-sectional and surface morphologies of the hybrid membranes showed that an asymmetric pore structure was formed. Hydration products comprising parallel plates of Ca(OH)₂, fibrous ettringite AFt, and granulated particles AFm were obtained gradually. For the hybrid membranes cured for different time, the pore-size distribution was similar but the porosity decreased because of blocking of the hydration products. In addition, the water flux decreased with hydration time, and carbon retention was 90% after 5 h of rejection treatment. Almost all the Zn²⁺ ions were adsorbed by the hybrid membrane. The above results proved that the obtained membrane could be alternative as basement membrane for separation application.

• Bulletin of the Korean Chemical Society
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• v.30 no.2
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• pp.389-396
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• 2009

MFI structural zeolite (ZSM-5 or Sililcalite) was treated with HF solution to introduce mesoporous channels in the microporous crystals. Inner mesopore size could be controlled from 2.5 to 3.5 nm by changing the concentration of HF solution. The pore structure of HF-treated MFI zeolite was studied by instrumental analysis. The active Co (III) salen complex monomers were successfully anchored non-covalently on the surfaces of mesoporous MFI-type zeolite. These heterogeneous catalysts could be applied in asymmetric ring opening of terminal epoxides by phenol derivatives. It showed very high enantioselectivity and yield up to 95% in the catalytic synthesis of optically active $\alpha$-aryloxy alcohol compounds.

• Membrane Journal
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• v.26 no.3
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• pp.212-219
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• 2016

The alumina hollow fiber membranes were prepared by spinning and sintering a polymer solution containing suspended alumina powders. For determine pore structure of hollow fiber membranes formed by different solvent-nonsolvent interaction rate, dimethylsulfoxide (DMSO), dimethylacetamide (DMAc), triethylphosphite (TEP) were prepared in dope solution by solvent, polyethersulfone (PESf) and polyvinylpyrrolidone (PVP) were used as a polymer binder and additive. The pore structure of hollow fiber membranes was characterized using scanning electron microscope (SEM). The alumina hollow fiber membranes prepared by DMSO, DMAc were had the asymmetric structure mixed sponge-like and finger-like morphology, while TEP solvent were had single sponge-like structure. The prepared hollow fiber membranes were analyzed gas permeation and mechanical strength experiment also. The hollow fiber membrane having single sponge-like structure was had high gas permeation performance. On the contrary to this, more finger-like morphology was less gas permeation performance.

• Korean Membrane Journal
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• v.9 no.1
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• pp.1-11
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• 2007

To prepare chemically stable asymmetric microporous membranes with a hydrophilic surface, which would be expected to have better antifouling properties, poly(vinylidene fluoride) (PVDF) blend membranes were prepared by the phase inversion process. PVDF mixture solutions in N-methylpyrrolidone (NMP) blended with several polar potential ionic polymers such as polyacrylonitrile (PAN), poly(methylmethacrylate) (PMMA) and poly(N-isopropylacrylamide) (NIPAM) were used for the formation of the PVDF blend membranes. They were then characterized with several analytical methods such as FESEM, FTIR, contact angle measurement, pore size distribution and permeability measurement. Regardless of different polar polymers blended, they all showed a finger-like structure with more hydrophilic surface than the pristine PVDF membrane. For all the PVDF blend membrane, due to the polar potential ionic polymers used, the flux of those was improved. Especially the PVDF blend membrane with NIPAM showed the highest flux among the membranes prepared. Also antifouling property of the PVDF membrane was improved by the use of the polar polymers.

• Korean Membrane Journal
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• v.1 no.1
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• pp.50-58
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• 1999

Symmetric asymmetric and composite perfluoropolymer membranes made with HYFLON AD have been prepared and evaluated. Porous and non porous symmetric membranes have been prepared by solvent evaporation with various processing conditions. Non-contact atomic force microscopy (AFM) was used to investigate the membrane morphology in air. Analysis of the images gave quantitative imformation on the surface pore strcture in particular on the pore size distributin. Possible useful uses of porous membranes are envisaged in the field of gas-liquid separations such as membrane contactors (MSc) Molecular Dynamics(MD) simulations structure of HYFLON AD 60X copolymer supporting these results are also reported. Amorphous perfluoropolymer membranes appears to be ideal other than in MCs when separation processes have to be performed in hostile environments i.e. high temperatures and aggressive non-aqueous media such as chemicals and solvents. In these cases HYFLON AD mem-branes can exploit the outstanding resistance of perfluoropolymers.

• Membrane Journal
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• v.20 no.2
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• pp.135-141
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• 2010

Various asymmetric Polysulfone membranes were prepared for a MBR process. Ether-typed alcohols (co-solvent) were added into a dope solution in order to control the pore size of membrane, whose effect on water permeability were investigated. Pore size of the prepared membranes were more affected by molecular-structure of co-solvent than by boiling point of theirs. With the increasing order of methoxy ($CH_3$-O-) < secondary propanol ($-CH_2$-CH(OH)$-CH_3$) < ethoxy ($CH_3-CH_2$-O-), water permeability of the prepared membrane increased. The phenomenon might attribute to the difference of molecularly steric hinderance of co-solvent (eg, Methoxy propanol, Ethoxy ethanol, Methoxy ethanol) in dope solution during the phase inversion. By the addition of ether typed alcohol into a dope solution, the pore size of MF (microfiltration) could be controlled. Also, Membrane prepared was applied to a MBR process and the system was stably operated for 2 months.

• Membrane Journal
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• v.25 no.1
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• pp.32-41
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• 2015

High performance polysulfone microfiltration membranes with a high were successfully prepared by vapor induced phase separation (VIPS) coupled with non-solvent induced phase separation (NIPS) process. Asymmetric Membranes were prepared with PSF/DMF/PVP/PEG/DMSO/water mixed solutions and water/IPA coagulant. PSF, DMF, PVP, PEG, DMSO, water was used as a membrane polymer, a solvent, a hydrophilic polymer additive, a polar protic liquid polymer, a polar aprotic nonsolvent, and a polar protic nonsolvent in the casting solution, respectively. The addition of polar aprotic nonsolvents, and polar protic nonsolvents is a convenient and effective method to control membrane structure. In order to control the morphology of polymeric membranes, the spontaneous emulsification induced by drawing water vapor into the exposed casting solution surface has been used. Control of the internal morphology of polymeric membranes by using mixed coagulation solution such as water and IPA is discussed in the present work. The pure water permeability, pore size distribution, surface hydrophilicity and membrane morphology were investigated. Due to the addition of DMSO to casting solution, the mean pore size increased almost $0.2{\mu}m$ and the water flux increased about 1000-1800 LMH.

• Membrane Journal
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• v.15 no.1
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• pp.15-21
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• 2005

The integrally skinned asymmetric PAN ultrafiltration membranes were annealed for reducing the pore size. The effect of the chemical structure of two PAN polymers (homo- and copolymer) on annealing was investigated. The annealing of PAN polymer was strongly affected by the chemical structure of the polymer. In other words, the annealing effect of the copolymer was much larger than that of the homopolymer due to its less rigid structure of the main chain. Before annealing, the membranes were usually preheated in water in terms of the complete removal of remained solvents in the membranes. The annealing effect was bigger when no preheating. However, the preheating of the membrane before annealing at high temperatures leads to an increase in the pore size of membranes. The surface of the membranes was slightly negative and the salt rejection of PAN nanofiltration membrane was in the following order: R(Na₂SO₄) > R(NaCl) > R(MgSO₄) > R(CaCl₂). This salt rejection behavior could be explained by the Donnan equilibrium and the electroneutrality.