• Membrane Journal
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• v.25 no.3
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• pp.276-286
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• 2015

The effects of relaxation and backwashing on fouling in ultrafiltration were investigated using full-scale membrane bioreactors (MBRs) which operated at a constant flux of 30 LMH. This paper also estimated the feasibility of using intermittent aeration strategies for minimizing the hydraulic resistance to filtration in comparison with the continuous aeration for running MBRs. Multiple cycles of filtration (14.5 min each) and relaxation (0.5 min each) were repeated. Similarly, a backwash was conducted by replacing a relaxation after each filtration cycle for the comparative performance test. The attached cake thickness on the membrane rapidly increased, caused by subsequent no aeration leading to easier combining with gel layer and the formation of heterogeneous layer on the membrane surface. During periodic backwashing, it is expected that gel and thin cake layer might sufficiently be removed by heterogeneous layer. After periodic backwashing, subsequent cake layer formation during time of no aeration was rapid than frequent no aeration, acting as a prefilter and preventing further irreversible fouling. Based on the Pearson correlation analysis, overall period fouling (dTMP/min) and average of all cycles (dTMP/min) were strongly correlated with the on-off period of aeration for operating MBRs.

• Membrane Journal
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• v.33 no.4
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• pp.201-210
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• 2023

Dust filter membranes play a crucial role in human life and various industries, as they contribute to several important aspects of human health, safety, and environmental protection. This study presents the development of a polysulfone@polyphenylene sulfide/polytetrafluoroethylene (PSf@PPS/ePTFE) composite dust filter membrane with excellent thermal stability and adhesion properties for high-temperature conditions. FT-IR analysis confirms successful impregnation of PSf adhesive onto PPS fabric and interaction with ePTFE support. FE-SEM images reveal improved fiber interconnection and adhesion with increased PSf concentration. PSf@PPS/ePTFE-5 exhibits the most suitable porous structure. The composite membrane demonstrates exceptional thermal stability up to 400℃. Peel resistance tests show sufficient adhesion for dust filtration, ensuring reliable performance under tough, high-temperature conditions without compromising air permeability. This membrane offers promising potential for industrial applications. Further optimizations and applications can be explored.

• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.730-738
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• 1992

Filtration characteristics according to membrane materials were studied In the ultrafiltration of anaerobic digestion broth as a post treatment method. A series of resistances for different membranes were quantitatively assessed on the basis of the resistance-in-series model. Flux behavior observed with the digestion broth was irrelevant to initial water permeabilities of each membrane. The fluoro polymer membrane showed the most significant improvement of flux with increase of cross-flow velocity, which suggests that the cake layer formed on this membrane is more weakly attached to the membrane surface than those on the other membranes. Flux reduction during longtime running was attrib-used to the polarization layer resistance ($R_p$) as well as the fouling layer resistance($R_f$). Continuous increase of $R_p$ may reflect the variation in the characteristics of cake layers, which could result from size, shape, and structure changes due to lysis and growth of biomass. Hydrophilic cellulosic membrane had a much lower fouling tendency than hydrophobic polysulfone membrane. The depressurization method induced a small increase in flux of $5-10L/m^2/h$. During washing and cleaning, filtrability of each membrane was rapidly recovered within 15 minutes until a stationary value was reached.

• Membrane Journal
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• v.13 no.2
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• pp.65-72
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• 2003

This study was focused on the investigation of filtration characteristics of membrane-coupled fermentor system for dissolved organics recovery from liquid organic sludge. On the filterability of MF over the range of $0.1{\sim}5 {\mu}m,$ the magnitude of total membrane resistance ($R_t$) is ranged as follows in the order; $0.1 {\mu}m>0.2{\mu}m>0.5 >1{\mu}m>2{\mu}m>5{\mu}m$. The cake layer resistance ($R_c$) occupied about 68~88% of total resistance with fermented sludge. Permeation flux decline was mainly attributed to the $R_c$, which was formed by a strong deposition from physico-chemical interactions of solids on membrane surface. Higher suspended solids (SS) concentration of suspension caused lower permeation flux. However, there was not a proportion relation beyond a certain SS concentration. The cross-flow velocity on the membrane surface was faster, which resulted in the higher permeation flux and also more efficient with low trans membrane pressure (TMP) in viewpoint of energy efficiency. The appropriate pH of suspension was over the range of 5.0~6.0 for dissolved organics recovery as well as the permeation flux. It is possible f3r bacteria to be separated perfectly with $0.1{\mu}m\; and \;0.2{\mu}m$ membrane pore size. Based on experimental results, most appropriate membrane pore size for the recovery is believed to around $1{\mu}m$.

• Membrane Journal
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• v.17 no.1
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• pp.44-53
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• 2007

The primary objective of this study is to increase the extent of water flux and fouling resistance of nano-filtration or reverse osmosis membranes. This study was performed to investigate the effect of surface characteristics of silane coated membranes on modified fouling index. Commercial polyamide composite RO membrane (RE1812-LP) and NF membrane (ESNA4040-LF) were treated with silane coupling agents in ethanol at five different concentrations. The silane coupling reagent, aminopropylmethoxydiethoxysilane, contains one aminoalkyl and three alkoxy groups. The hydrophilic effect of aminoalkyl group of APMDES on the permeability and fouling resistance of the modified membrane was examined. The surfaces of the modified membranes were characterized by FE-SEM, contact angle analyzer, and zeta potentiometer in order to confirm successful sol-gel methods. The modified NF membranes showed significantly enhanced water flux and fouling resistance without a decrease in salt rejection in divalent ionic feed solution.

• Membrane Journal
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• v.13 no.2
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• pp.88-100
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• 2003

A change of filtrate flux in Taylor vortex flow filtration was investigated experimentally by rotating speed of inner cellulose ester membrane cylinder (average pore size: 1.2 ${\mu}m$), slurry concentration, and particle size. The filtrate flux was a direct proportion relation with TMP, but an inverse relation with resistances. A change of cake resistance with time was examined by rotating speed, slurry concentration, and particle size. Initial resistance increased dramatically as raising slurry concentration, and the pseudo-steady state was maintained at high resistance value. However, times to reach the pseudo-steady state did not depend on slurry concentration. The resistance was larger as smaller particle size, because possibility of pore blocking inside membrane could be higher and shear effect should be lower as smaller particle size. A model equation suggested in this study was composed of particle deposition and removal terms, and could confirm well experimental data using average values of experimental coefficients.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.417-417
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• 2009

Although a transparent conductive film (TCF) belongs to essential supporting materials for many device applications such as touch screens, flat panel displays, and sensors, a conventional transparent conductive material, indium-tin oxide (ITO), suffers from considerable drawback because the price of indium has soared since 2001. Despite a recent falloff, a demand of ITO is expected to increase sharply in the future due to the trend of flat panel display technologies toward flexible, paper-like features. There have been recently extensive studies to replace ITO with new materials, in particular, carbon nanotubes (CNTs) since CNTs possess excellent properties such as flexibility, electrical conductivity, optical transparency, mechanical strength, etc., which are prerequisite to TCFs. This study fabricated TCFs with single-walled carbon nanotubes (SWCNTs) produced by arc discharge. The SWCNTs were dispersed in water with a surfactant of sodium dodecyl benzene sulfonate (NaDDBS) under sonication. Carbon black and fullerene nanoparticles were added to the SWCNT-dispersed solution to enhance contact resistance between CNTs. TCFs were manufactured by a filtration and transfer method. TCFs added with carbon black and fullerene nanoparticles were characterized by scanning electron microscopy (SEM), UV-vis spectroscopy (optical transmittance), and four-point probe measurement (sheet resistance).

• Membrane Journal
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• v.6 no.2
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• pp.109-116
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• 1996

This work is a fundamental study for applying hybrid process coupling adsorption with microfiltration to waste-water treatment. Phenol was separated by adsorption on powdered activated carbon, adsorbed phenol with activated carbon was separated by microfiltration. As the particle size in suspension increased, filtration resistance decreased, and effect of particle concentration on resistance was less pronounced. The rate of uptake was greatly dependent on the degree of phenol loading. For a smaller amounts of activated carbon, the change of permeate concentration before break point and phenol loading with time were steeper than in the case of large amounts. Permeate concentration before break point decreased with decreasing particle size, this could be due to the increase of outer surface of particle and film mass transfer coefficient.

• Journal of Environmental Science International
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• v.20 no.1
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• pp.25-34
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• 2011

The new empirical static model was constructed on the basis of dimension analysis to predict the pressure drop according to the operating conditions. The empirical static model consists of the initial pressure drop term (${\Delta}P_{initial}$) and the dust mass number term($N_{dust}=\frac{{\omega}_0{\nu}_f}{P_{pulse}t}$), and two parameters (dust deposit resistance and exponent of dust mass number) have been estimated from experimental data. The optimum injection distance was identified in the 64 experimental data at the fixed filtration velocity and pulse pressure. The dust deposit resistance ($K_d$), one of the empirical static model parameters got the minimum value at d=0.11m, at which the total pressure drop was minimized. The exponent of dust mass number was interpreted as the elasticity of pressure drop to the dust mass number. The elasticity of the unimodal behavior had also a maximum value at d=0.11m, at which the pressure drop increased most rapidly with the dust mass number. Additionally, the correlation coefficient for the new empirical static model was 0.914.

• Membrane and Water Treatment
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• v.2 no.2
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• pp.91-103
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• 2011

The flux behavior in the separation of equimolar bovine serum albumin (BSA) and bovine hemoglobin (HB) in aqueous solutions by cross-flow ultrafiltration (UF) was investigated, in which polyacylonitrile membrane with a molecular weight cut-off (MWCO) of 100 kDa was used. BSA and HB have comparable molar mass (67,000 vs. 68,000) but different isoelectric points (4.7 vs. 7.1). The effects of process variables including solution pH (6.5, 7.1, and 7.5), total protein concentration (1.48 and 7.40 ${\mu}M$), transmembrane pressure (69, 207, and 345 kPa), and solution ionic strength (with or without 0.01 M NaCl) on the separation were examined. It was shown that the ionic strength had a negligible effect on separation performance under the conditions studied. Although BSA and HB are not rigid bodies, the flux decline in the present cross-flow UF did not result from the mechanism of cake filtration with compression. In this regard, the specific cake resistance when pseudo steady-state was reached was evaluated and discussed.