• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.639-645
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• 2008

The objectives of this research are to (1) observe changes in particle size distribution due to formation of microflocs during coagulation process (2) identify the membrane fouling potential on cross flow system (3) investigate the mechanism of membrane fouling. The rate of flux decline for the hydrophobic membrane was significantly greater than for the hydrophilic membrane, regardless of pretreatment conditions. The pretreatment of the raw water significantly reduced the fouling of the UF membrane. Also, the rate of flux decline for the hydrophobic membrane was considerably greater than for the hydrophilic membrane. Applying coagulation process before membrane filtration showed not only reducing membrane fouling, but also improving the removal of dissolved organic materials that might otherwise not be removed by the membrane. That is, during the mixing period, substantial changes in particle size distribution occurred under rapid and slow mixing condition due to the simultaneous formation of microflocs and NOM precipitates. Therefore, combined pretreatment using coagulation not only improved dissolved organics removal efficiency but also flux recovery efficiency.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.1
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• pp.28-38
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• 2014

The organic-inorganic composite membrane in polymer exchange membrane fuel cells (PEMFCs) have several fascinating technological advantages such as a proton conductivity, thermal stability and mechanical properties. As the inorganic filler, silicon carbide (SiC) fiber have been used in various fields due to its unique properties such as thermal stability, conductivity, and tensile strength. In this study, composite membrane was successfully fabricated by modified-silicon carbide fiber. Modified process, as a novel process in SiC, takes reaction by phosphoric acid after oxidation process (generated homogeniusly $SiO_2$ layer on SiC fiber). The mechanical property which was conducted by tensile test of the 5wt% modified-$SiO_2@SiCf$ composite membrane was better than that of Aquivion casting membrane as well as ion cxchange capacity(IEC) and proton conductivity. In addition, the single cell performance was observed that the 5wt% modified-$SiO_2@SiCf$ composite membrane was approximately $0.2A/cm^2$ higher than that of a Aquivion casting electrolyte membrane and electrochemical impedance was improved with the charge transfer resistance and membrane resistance.

• Membrane and Water Treatment
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• v.9 no.4
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• pp.221-231
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• 2018

A new procedure to produce poly(vinylidene fluoride)/boron nitride hybrid membrane is presented for application in membrane distillation (MD) process. The influence of hexagonal boron nitride (h-BN) incorporation on the performance of the polymeric membranes is studied through the present investigation. For this aim, h-BN nanopowders were successfully synthesized using the simple chemical vapor deposition (CVD) route and subsequent solvent treatments. The resulting h-BN nanosheets were blended with poly(vinylidene fluoride) (PVDF) solution. Then, the prepared composite solution was subjected to phase inversion process to obtain PVDF/h-BN hybrid membranes. Various examinations such as scanning electron microscopy (SEM), wettability, permeation flux, mechanical strength and liquid entry pressure (LEP) measurements are performed to evaluate the prepared membrane. Moreover, Air gap membrane distillation (AGMD) experiments were carried out to investigate the salt rejection performance and the durability of membranes. The results show that our hybrid PVDF/h-BN membrane presents higher water permeation flux (${\sim}18kg/m^2h$) compared to pristine PVDF membrane. In addition, the experimental data confirms that the prepared nanocomposite membrane is hydrophobic (water contact angle: ${\sim}103^{\circ}$), has a porous skin layer (>85%), as well competitive fouling resistance and operational durability. Furthermore, the total salt rejection efficiency was obtained for PVDF/h-BN membrane. The results prove that the novel PVDF/h-BN membrane can be easily synthesized and applied in MD process for salt rejection purposes.

• Membrane and Water Treatment
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• v.8 no.4
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• pp.311-321
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• 2017

Hydrophilic and high modulus PPTA molecules were incorporated into PVDF matrix via the in situ polymerization of PPD and TPC in PVDF solution. PPTA/PVDF/NWF blend membrane was prepared through the immersion precipitation phase inversion method and nonwoven coating technique. The membrane integrated technology including PPTA/PVDF/NWF blend membrane and reverse osmosis (RO) membrane was employed to treat the polyester/viscose spunlace nonwoven process wastewater. During the consecutive running of six months, the effects of membrane integrated technology on the COD, ammonia nitrogen, suspended substance and pH value of water were studied. The results showed that the removal rate of COD, ammonia nitrogen and suspended substance filtered by PPTA/PVDF blend membrane was kept above 90%. The pH value of the permeate water was about 7.1 and the relative water flux of blend membrane remained above 90%. After the deep treatment of RO membrane, the permeate water quality can meet the water circulation requirement of spunlace process.

• Elastomers and Composites
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• v.42 no.2
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• pp.86-92
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• 2007

A few of polytetrafluoroethylene(PTFE) membranes and PTFE fine powders were analyzed to chooce an optimum resin. The bi-axial stretching process was developed to set up the foundation of the preparation process and control the pore size and porosity of PTFE membrane. The pretreatment of PTFE fine powder used in the preparation process for PTFE was needed. The mixing of additives, the ripening of mixture, paste extrusion process of ripening powder, calendering process and the bi-axial process were conducted for controlling pore size, porosity and thckness of membrane. The aftertreatment which strengthened the mechanical properties was necessary. The control of pore size and porosity of the membrane were determined. The ratio of PTFE fine powder and additives at the paste extrusion process, the ripening time, the ripening temperature and the parameters of temperature and pressure at the paste extrusion process were optimized.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.12
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• pp.1273-1280
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• 2008

This study sought to establish the optimum operating condition for the recovery of caustic (NaOH) solution from mercerization in textile process. As main factors, the silt density index (SDI) evaluation of ceramic membrane for the application of nanofiltration/reverse osmosis (NF/RO) membrane, the recovery yield measurement of caustic solution for the application of polymeric membrane, the optimum condition of chemical cleaning for the membrane regeneration, the optimum removal condition of total organic carbon (TOC), turbidity, color, and the permeate flux of ceramic membrane/polymeric membrane combined process were investigated. As results, ceramic ultrafiltration (UF) in the first step and nanofiltration (NF) in the second step were found to be suitable for the removal of total suspended solid (TSS), residual organics, turbidity including color, and the recovery of caustic solution from caustic wastewater stream in mercerization process. When only the ceramic UF membrane was used, the rejection efficiency of both of TSS and turbidity was more than 99.0%, and the color and TOC were rejected about 74.7% and 49.2%, respectively. Meanwhile, the combined membrane precess of UF and NF membranes showed even more efficient removal abilities and thus more than 99.9% of TSS and turbidity, 87.7% of color, and 78.2% of TOC were removed. In particular, 91.3% of NaOH was successfully recovered with 83.7% of total volume in the combined membrane process. With this regard, a clean caustic solution was obtained in a high purity, which can be reused for mercerization process, expecting to offer economical benefits.

• Membrane Journal
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• v.32 no.5
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• pp.348-356
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• 2022

With the development of the bio industry, membrane chromatography with a high adsorption efficiency is emerging to replace the existing column chromatography used in the downstream processes of pharmaceuticals, food, etc. In this study, through the deacetylation reaction of two commercial cellulose acetate (CA) membranes with different pore sizes, the porous regenerated cellulose (RC) supports for membrane chromatography were obtained to attach the anion exchange ligands. The adsorptive membranes for anion exchange were prepared by attaching an anion exchange ligand ([3-(methacryloylamino) propyl] trimethylammonium chloride) containing quaternary ammonium groups on the RC supports by grafting and UV polymerization. The protein adsorption capacities of the prepared membranes were obtained through both the static binding capacity (SBC) and the dynamic adsorption capacity (DBC) measurement. As a result, the membrane chromatography with the smaller the pore size, the larger the surface area showed the highest protein adsorption capacity. Membrane chromatography which was prepared by using deacetylated commercial CA support with MAPTAC ligand (i.e., RC 0.8 + MAPTAC: 43.69 mg/ml, RC 3.0 + MAPTAC: 36.33 mg/ml) showed a higher adsorption capacity compared to commercial membrane chromatography (28.38 mg/ml).

• Membrane Journal
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• v.33 no.4
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• pp.191-200
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• 2023

Polyethersulfone (PES) is a widely employed membrane material for water and industrial purification applications owing to its hydrophilicity and ease of phase separation. However, PES membranes and filters prepared using the nonsolvent induced phase separation method often encounter significant flux decline due to pore clogging and cake layer formation on the dense membrane surfaces. Our investigation revealed that tight microfiltration or loose ultrafiltration membranes can be subject to physical fouling due to the formation of a dense skin layer on the bottom side caused by water intrusion to the gap between the shrank membrane and the substrate. To investigate the effect of the bottom surface porosity on membrane fouling, two membranes with the same selective layers but different sub-layer structures were prepared using single and double layer casting methods, respectively. The double layered PES membrane with highly porous bottom surface showed high flux and physical fouling tolerance compared to the pristine single layer membrane. This study highlights the importance of physical optimization of the membrane structure to prevent membrane fouling.

• Membrane and Water Treatment
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• v.1 no.3
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• pp.193-206
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• 2010

Organic fouling and biofouling pose a significant challenge to the membrane filtration process. Photocatalysis-membrane hybrid system is a novel idea for reducing these membranes fouling however, when $TiO_2 photocatalyst nanoparticles are used in suspension, catalyst recovery is not only imposes an extra step on the process but also significantly contributes to increased membrane resistance and reduced permeate flux. In this study, $TiO_2$ photocatalyst has been immobilized by coating on the microfiltration (MF) membrane surface to minimize organic and microbial fouling. Nano-sized $TiO_2$ was first synthesized by a sol-gel method. The synthesized $TiO_2$ was coated on a Poly Vinyl Difluoride (PVDF) membrane (MF) surface using spray coating and dip coating techniques to obtain hybrid functional composite membrane. The characteristics of the synthesized photocatalyst and a functional composite membrane were studied using numerous instruments in terms of physical, chemical and electrical properties. In comparison to the clean PVDF membrane, the $TiO_2$ coated MF membrane was found more effective in removing methylene blue (20%) and E-coli (99%).

• Membrane Journal
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• v.25 no.3
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• pp.216-222
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• 2015

The method measuring LEP (liquid entry pressure) was optimized to evaluate the wettabilities of hydrophobic membranes which might affect long-term durability of membrane in MD (membrane distillation) process. Conductivity of the permeate was monitored to measure the LEPs of PE (polyethylene) and PVDF (polyvinylidene di-fluoride) hollow fiber membranes from highly concentrated synthetic feed water of 20 wt% NaCl. Holding time over 5 min and the ratio of membrane area to the tank volume more than $10m^2/m^3$ were required to ensure LEP value.