• Korean Chemical Engineering Research
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• v.54 no.5
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• pp.653-658
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• 2016

Poly(ether-block-amide)(PEBAX$_{(R)}$) resin is a thermoplastic elastomer combining linear chains of hard-rigid polyamide block interspaced soft-flexible polyether block. It was believed that the hard polyamide block provides the mechanical strength and permselectivity, whereas gas transport occurs primarily through the soft polyether block. The objective of this work was to investigate the gas permeation properties of carbon dioxide and methane for PEBAX$^{(R)}$-1657 membrane, and compare with those obtained for other grade of pure PEBAX$^{(R)}$, PEBAX$^{(R)}$-2533 and PEBAX$^{(R)}$ based hybrid membranes. The hybrid membranes based PEBAX$^{(R)}$ were obtained by a sol-gel process using GPTMS ((3-glycidoxypropyl) trimethoxysilane) as the only inorganic precursor. Molecular structure and morphology of membrane were analyzed by $^{29}Si$-NMR, DSC and SEM. PEBAX$_{(R)}$-2533 membrane exhibited higher gas permeability coefficients than PEBAX$^{(R)}$-1657 membrane. This was explained by the increase of chain mobility. In contrast, ideal separation factor of $CO_2/CH_4$ for PEBAX$^{(R)}$-1657 membrane was higher than PEBAX$^{(R)}$-2533 membrane. It was explained by the decrease of diffusion selectivity caused by increase of chain mobility. For PEBAX$^{(R)}$/GPTMS hybrid membrane, gas permeability coefficients were decreased with reaction time. Gas permeability coefficient of $CH_4$ was more significantly decreased than $CO_2$. It can be explained by the reduction of chain mobility caused by the sol-gel process, and strong affinity of PEO segment with $CO_2$. Comparing with pure PEBAX$^{(R)}$-1657 membrane, ideal separation factor of $CO_2/CH_4$ for PEBAX$^{(R)}$/GPTMS hybrid membrane has decreased to 4.5%, and gas permeability coefficient of $CO_2$ has increased 3.5 times.

• Membrane Journal
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• v.24 no.3
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• pp.240-248
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• 2014

Porous PVDF hollow fiber membranes were prepared by hybrid process of TIPS(thermally induced phase separation) and stretching for membrane distillation. The tests were conducted to investigate that permeability of the membrane could be enhanced by reducing membrane wall thickness. During fiber spinning, dope discharge rate from nozzle was reduced and flow rate of bore fluid increased to make the wall thickness thinner. As dope discharge rate from nozzle was reduced and flow rate of bore fluid increased, the membrane wall thickness was reduced. As a result, air permeability, water permeability and vapor permeability of the membranes increased.

• Membrane and Water Treatment
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• v.13 no.3
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• pp.147-166
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• 2022

Liquid-liquid membrane contactor (LLMC), a device that exchanges dissolved gas molecules between the two sides of a hydrophobic membrane through membrane pores, can be employed to extract ammoniacal nitrogen from a feed solution, which is transported across the membrane and accumulated in a stripping solution. This LLMC process offers the promise of improving the sustainability of the global nitrogen cycle by cost-effectively recovering ammonia from wastewater. Despite recent technological advances in LLMC processes, a comprehensive review of their feasibility for ammonia recovery is rarely found in the literature. Our paper aims to close this knowledge gap, and in addition to analyze the challenges and provide potential solutions for improvement. We begin with discussions on the operational principles of the LLMC process for ammonia recovery and membrane types and membrane configurations commonly used in the process. We then assess the performance of the process by reviewing publications that demonstrate its practical application. Challenges involved in the implementation of the LLMC process, such as membrane fouling, membrane wetting, and chemical requirements, are presented, along with discussions on potential strategies to address each. These strategies, including membrane modification, hybrid process design, and process optimization based on cost-benefit analysis, guide the reader to identify key areas of future research and development.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.4
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• pp.445-448
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• 2008

The application of the membrane filtration process has been increased for the drinking water treatment system because of excellent quality of treated water compared with the sand filtration process. The selection of suitable pre-treatment processes and optimum flux according to the characteristics of raw water are important factors for the design of membrane processes. In this study, the most efficient pre-treatment processes for drinking water was selected by investigating the effects of pre-treatment processes on the operational stability of the membrane filtration process. Both lab-scale and pilot-scale experiments were conducted. In the lab-scale test, the effect of pre-treatment processes on the stability of the membrane filtration process was investigated indirectly by comparing the performance of membrane flux for raw water, pre-treated water, and membrane permeated water. In the pilot-scale test, the usefulness of prefiltration processes was assessed by comparing the performance of single membrane process and hybrid coagulation-membrane process. The results indicated that the coagulation process contributed to the stabilization of trans-membrane pressure (TMP) by removing contaminants on membranes, though the pre-filtration process had little effect on the TMP.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.4
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• pp.429-436
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• 2005

A coagulation/ultrafiltration membrane hybrid system was operated to treat river water with capacity of $0.06m^3/d$. The impact on membrane fouling by flux and linear velocity was investigated. It is known that pressure increase is proportional to flux increase. However, pressure increase was much faster than theoretical value in the pilot plant test. So it was suggested that flux was on important factor in ultrafiltration of continuous operation. Membrane fouling was decreased when linear velocity was increased. This phenomenon was found more obviously without coagulation. With the combination of coagulation and sedimentation, membrane fouling was not reduced conspicuously. Big particles formed during coagulation and sedimentation were destroyed by feed and circulation pumping, which resulted in little effect on membrane fouling reduction. The degree of destruction was similar at various linear velocities. In this study, the hollow fiber membrane was used and the system was operated in pressure type module. In case of the system used in this study, membrane fouling has been affected lightly by linear velocity variation when coagulation pretreatment was applied.

• Membrane Journal
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• v.23 no.3
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• pp.211-219
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• 2013

Effect of water back-flushing period (FT) was investigated in hybrid water treatment process of carbon ultrafiltration and polypropylene (PP) beads coated with photocatalyst, and membrane effect was studied by comparing the previous studies with carbon microfiltration or alumina ultrafiltration, microfiltration membranes. FT 6 min was the most effective to control initial membrane fouling and optimal condition because the membrane fouling resistance was low until initial 60 min and the maximum total permeate volume was acquired at this FT. The turbidity treatment efficiency was high beyond 98.6%, and did not depend on FT, which was same with the previous result of carbon or alumina microfiltration. The organic matters treatment efficiency was the highest value of 98.2% at FT 6 min, which was almost same trend with the previous result of alumina microfiltration. Then the organic matters treatment efficiency of carbon microfiltration was the minimum at no back-flushing (NBF) and increased as decreasing FT, but that of alumina ultrafiltration was the maximum at NBF and also increased as decreasing FT. Therefore it means that water back-flushing effect on the organic matters treatment efficiency had a different mechanism depending on pore size in spite of the same material membranes.

• Membrane Journal
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• v.23 no.2
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• pp.159-169
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• 2013

The effect of humic acid (HA), and the roles of microfiltration (MF), PES (polyethersulfone) beads adsorption, and photo-oxidation were investigated in hybrid process of ceramic MF and PES beads loaded with titanium dioxide ($TiO_2$) photocatalyst for advanced drinking water treatment. The results of water and nitrogen back-flushing were compared in viewpoints of membrane fouling resistance ($R_f$), permeate flux (J), and total permeate volume ($V_T$). Because membrane fouling increased dramatically as increasing HA, Rf increased and J decreased, and finally $V_T$ was the highest at 2 mg/L HA. Average turbidity treatment efficiencies were almost same independent of HA concentration. Average organic matter treatment efficiency was the minimum 71.4% at 10 mg/L HA in water back-flushing, but those were almost constant in nitrogen back-flushing. The hybrid process of MF, PES beads, and UV (MF + $TiO_2$ + UV) have the lowest $R_f$, and the highest J and $V_T$ in both water and nitrogen back-flushing. The turbidity and organic matter treatment efficiencies were the maximum at MF + $TiO_2$ + UV independent of water and nitrogen back-flushing, and decreased sequently as simplifying the process to MF. However, adsorption performed the more important role than photo-oxidation in water back-flushing, and photo- oxidation was the more than adsorption in nitrogen back-flushing.

• Membrane and Water Treatment
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• v.2 no.1
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• pp.1-24
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• 2011

The deficiency of clean water is a major global concern because all the living creatures rely on the drinkable water for survival. On top of this, abundant of clean water supply is also necessary for household, metropolitan inhabitants, industry, and agriculture. Among many purification processes, advances in low-energy membrane separation technology appear to be the most effective solution for water crisis because membranes have been widely recognized as one of the most direct and feasible approaches for clean water production. The aim of this article is to give an overview of (1) two new emerging membrane technologies for water reuse and desalination by forward osmosis (FO) and membrane distillation (MD), and (2) the molecular engineering and development of highly permeable hollow fiber membranes, with polyvinylidene fluoride (PVDF) and polybenzimidazole (PBI) as the main focuses for the aforementioned applications in National University of Singapore (NUS). This article presents the main results of membrane module design, separation performance, membrane characteristics, chemical modification and spinning conditions to produce novel hollow fiber membranes for FO and MD applications. As two potential solutions, MD and FO may be synergistically combined to form a hybrid system as a sustainable alternative technology for fresh water production.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.6
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• pp.633-640
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• 2008

In this research, the $3.6m^3/day$ scale pilot plant consisting preozonation, coagulation, flocculation, and ceramic membrane processes was operated for long term period to evaluate the validity of ceramic membrane filtration process for treating lake water containing high concentration manganese. The higher concentration of dissolved manganese($Mn^{2+}$) was effectively oxidized to the bigger insoluble colloidal manganese ($MnO^2$) by 1~2 mg/L ozone. The colloidal manganese reacted with coagulant (poly aluminium chloride, PAC) and then formed the big floc. Ceramic membrane rejected effectively manganese floc during membrane filtration. Dissolved organic carbon(DOC) removal was dependent upon $Mn^{2+}$ concentration. While average $Mn^{2+}$ concentration was 0.43 and 0.85 mg/L in raw water, DOC removal rate in preozonation was 26.5 and 13.5%, respectively. The decrease rate of membrane permeability was faster without preozonation than with preozonation while membrane fouling decreased with NOM oxidation by ozone. In conclusion, raw water containing high concentration of manganese can be effectively treated in preozonation-coagulation-ceramic membrane filtration system.

• Membrane Journal
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• v.14 no.1
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• pp.53-56
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• 2004

Direct Methanol Fuel Cell (DMFC) is considered as a candidate technology for applications in stationary, transportation as well as electronic power generation purposes. To develop a high performance direct methanol fuel cell(DMFC), a competent electrolyte membrane is needed. The electrolyte membrane should be durable and methanol crossover must be low. One of the approaches to increase the stability of generally used polymer electrolyte membranes such as Nafion against swelling or thermal degradation is to bond it with an inorganic material physically or chemically. In Noritake Company, we have developed a novel method of reinforcing the polymer electrolyte matrix with inorganic fibers. Methanol crossover values measured were significantly lower than the original polymer electrolyte membranes. These fiber reinforced electrolyte membranes (FREM) were used for DMFC study and stable power output values as high 160 mW/$\textrm{cm}^2$ were measured. The details of the characteristics of the membranes as well as I-V data of fuel cell stacks are detailed in the paper.