• 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.

• Membrane Journal
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• v.23 no.3
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• pp.220-225
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• 2013

Hydrophilic monomers were polymerized for lamination on polyvinylidene fluoride (PVDF) membrane surface for hydrophilization of the membranes. Hydrophilization reduced the contact angle from $95^{\circ}$ to $55^{\circ}$ and enhanced the water flux by 10 times while it reduced the bovine serum albumin (BSA) adsorption amount to 1/4 level. Thermal polymerization process was optimized by examining several operation parameters. Dimethyl oxobuthyl acrylamide (DOAA) showed the best effect due to its better hydrophilicity than others. Increase of amount of monomer enhanced the performance until the optimum concentration of 30 wt%, beyond which excess amount of monomer resulted in homopolymerization to deteriorate the performance. Azobis (isobutyronitrile)(AIBN) initiator has greater activation temperature range than benzoyl peroxide (BPO) and it showed better hydrophilation performance. Two stage lamination process, application of initiator followed by monomer addition, was more effective than one stage process, addition of initiator and monomer at once, which still reduced the contact angle but also reduced the water flux by pore blocking phenomena.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.3
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• pp.243-254
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• 2009

Tunnel problems relate to pore water pressure generally occur due to the restriction of groundwater flow into the tunnel which is generally caused by the deterioration of drainage systems. Previous studies have identified the problem as combined mechanical and hydraulic interaction occasions. In this study, detrimental effects of pore water pressure on the lining were investigated using the finite element method considering deterioration of the drainage system. Particularly, double-lined linings with drain-holes are considered. Deterioration of drainage system is represented as blockages of drain-holes. It is identified that the secondary lining ran be influenced by the deterioration of drainage system. It is shown that a tunnel with all drain-holes blocked moved upward, and unbalanced drain-hole blocking may result in torsional behavior of the tunnel which causes significant damages to the secondary linings.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.11
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• pp.815-820
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• 2013

The purpose of this research is to prepare the aluminum electrode coated with activated carbon for removing air pollution dust. The experiments were studied on the selection of optimal polymer for binding aluminum plate with powdered activated carbon, preventing the pore blocking of activated carbon from polymer binder, and the dust treatability for the prepared activated carbon electrode. The optimal adhesive for coating activated carbon on an electric aluminum plate was polyvinyl acetate (PVA) with vinyl functional group. For the opening of the blocked pore with polymer, it was very effective to embed polymer solvent in pore of activated catbon firstly before mixing activated carbon with PVA, and then to devolatilize the embedded solvent of carbon pore at high temperature. The mass of trapped dust on aluminum electrode coated with activated carbon was about double of the trapped one on just aluminum electrode.

• Journal of Korean Society on Water Environment
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• v.22 no.1
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• pp.140-144
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• 2006

This study was performed to investigate the effect of organic characteristics and feed water solution chemistry on membrane fouling index such as Silt Density Index (SDI) and Modified Fouling Index (MFI). Specifically, Aldrich humic acids (AHA) and Suwannee river humic acids (SHA) were used in SDI/MFI experiments. Higher SDI values were observed with increasing organic concentration. AHA with larger molecular weight (MW) and SUVA (${\approx}UV_{254}/TOC$) resulted in higher SDI values, compared to SHA. The feed solution chemistry (i.e, pH, ionic strength, and hardness) also affects SDI values to some degree. In particular, SDI increased with increasing hardness ($Ca^{2+}$) concentration for AHA. Unlike SDI, the MFI developed on the basis of particle cake filtration theory, was not accurately assessed due to internal fouling by organics such as pore adsorption and subsequent pore blocking.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.1
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• pp.11-23
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• 2015

In this study the laboratory test for hydraulic conductivity and the seepage analysis with finite element method on measurement section of sea dike embankment were performed for the purpose of estimating the relative density of embankment from the measured pore water pressures, and both results of the test and the analysis were coupled with the method of estimating seepage blocking state with the hydraulic head loss rate in sea dike embankment. The relationship of void ratio vs hydraulic head loss rate was obtained by setting hydraulic conductivity as common ordinate on the relationships between the void ratio and the hydraulic conductivity and between the hydraulic conductivity and the hydraulic head loss rate. The void ratio on the segment between measuring points was calculated from the coupled relationship of the void ratio vs the hydraulic conductivity. The allowable upper and lower limits of hydraulic head loss rate and those of void ratio on the safety were generated from the coupled relationship between the laboratory compaction test and the sedimentation test. Current hydraulic head loss rate and void ratio were evaluated in the allowable range between upper and lower limits.

• Journal of the Korean Institute of Gas
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• v.8 no.3 s.24
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• pp.43-51
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• 2004

In this study, gas permeation and separation characteristics of $CO_2$ and $N_2$ on nano-porous TPABr(Tetrapropylammoniumbromide) templating silica/alumina composite membrane were studied by using GMS (Generalized Maxwell Stefan) model. Since the transport mechanisms of meso-porous alumina support are Knudsen diffusion and viscous diffusion(or poiseulle flow), they can be identified by DGM (dusty gas model). The transport mechanism of TPABr templating silica layer, which would contribute mainly to the separation of $N_2/CO_2$ mixture, showed surface diffusion rather than pore diffusion. Therefore, the oermeationjseparation mechanisms in multi-component suface diffusion were successfully analyzed by the GMS model. In the separation of $N_2/CO_2$ mixture using the composite membrane, $CO_2$, the strongadsorbate, was permeated through the membrane more than Na due to the pore-blocking phenomena of $CO_2$ by adsorption isotherm and solace diffusion.

• Korean Chemical Engineering Research
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• v.45 no.6
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• pp.669-676
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• 2007

The raw water was fractionated into hydrophobic (HPO), transphilic (TPI), and hydrophilic portions (HPI) using XAD resins. The raw water DOC contains 39% of hydrophilics, 43% of hydrophobics, and 18% of transphilics. When fractionated NOM (natural organic matter) was passed through hydrophilic membrane with 100 kDa, hydrophobic portion (HPO) caused the most fouling and hydrophilic portion (HPI) caused the least fouling. This could be related to size and adsorption capability of organics. Small sized organics would pass through membrane pores, but large sized organics would be attracted to either membrane pores or surface, which led to the fouling. An effect of membrane pore size on membrane fouling is related to the availability of organics at membrane pores. As the pore size became larger, the more organics were transported into the membrane pore. Some organics caused pore blocking, and others caused pore adsorption, which resulted in membrane fouling. Membrane material is also important for membrane fouling. More fouling occurred at hydrophobic membrane than hydrophilic membrane regardless of its pore size. Hydrophobic interaction caused more fouling at hydrophobic membrane.

• Polymer(Korea)
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• v.26 no.2
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• pp.160-167
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• 2002

We synthesized HPP-g-GMA copolymer using pre-irradiation method by E-beam and aminated HPP-g-GMA using amination reaction. Degree of grafting increased with increasing GMA monomer concentration and showed the maximum value of 130% at 1.46 M of GMA. The degree of amination increased with increasing the degree of grafting. When the degree of grafting was 100%, degree of amination showed the maximum value of 37.4%. The ion exchange capacity of aminated HPP-g-GMA was about 3.78 meq/g, and it showed remarkable adsorption ability of hollow fiber ion exchanger. Through the BET analysis, the surface area of aminated HPP-g-GMA was 54.83 $\m^2/g$ and the mean pore size was $26\AA$. These showed the decrease of surface area and the slight increase of the mean pore size. SEM results show that the thickness of fiber increased after the step of reaction and there pore blocking phenomena was not observed. The aminated HPP-g-GMA was synthesized successfully and found to be suitable for the adsorption and separation of anion.

• Membrane and Water Treatment
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• v.9 no.2
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• pp.69-77
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• 2018

The use of membrane as an innovative technology for water treatment process has now widely been accepted and adopted to replace the conventional water treatment process in increasing fresh water production for various domestic and industrial purposes. In this study, ultrafiltration (UF) membranes with different formulation were fabricated via phase inversion method. The membranes were fabricated by varying the polymer concentration (16 wt%, 18 wt%, 20 wt%, and 21 wt%). A series of tests, such as field emission scanning electron microscope (FESEM), pore size and porosity, contact angle, and zeta potential were performed to characterize the membranes. The membrane performance in terms of permeation flux and rejection were evaluated using a laboratory bench-scale test unit with mine water, lake water and tube well as model feed solution. Long hour filtration study of the membranes provides the information on its fouling property. Few pore blocking mechanism models were proposed to examine the behaviour of flux reduction and to estimate the fouling parameters based on different degree of fouling. 21 wt% PVDF membrane with smaller membrane pore size showed an excellent performance for surface water treatment in which the treated water complied with NWQS class II standard.