• Membrane Journal
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• v.31 no.1
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• pp.16-34
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• 2021

Water supplies are decreasing in comparison to increasing clean water demands. Using nanofiltration is one of the most effective and economical methods to meet the need for clean water. Common methods for desalination are reverse osmosis and nanofiltration. However, pristine membranes lack the essential features which are, stability, economic efficiency, antibacterial and antifouling performances. To enhance the properties of the pristine membranes, graphene oxide (GO) is a promising and widely researched material for thin film composites (TFC) membrane due to their characteristics that help improve the hydrophilicity and anti-fouling properties. Modification of the membrane can be done on different layers. The thin film composite membranes are composed of three different layers, the top filtering active thin polyamide (PA) layer, supporting porous layer, and supporting fabric. Forward osmosis (FO) process is yet another energy efficient desalination process, but its efficiency is affected due to biofouling. Incorporation of GO enhance antibacterial properties leading to reduction of biofilm formation on the membrane surface. Pressure retarded osmosis (PRO) is an excellent process to generate clean energy from sea water and the biofouling of membrane is reduced by introduction of GO into the active layer of the TFC membrane. Different modifications on the membranes are being researched, each modification with its own advantages and disadvantages. In this review, modifications of nanofiltration membranes and their composites, characterization, and performances are discussed.

• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.240-244
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• 2013

Although forward osmosis desalination technology has drawn substantial attention as a next-generation desalination method, the energy efficiency of its draw solution treatment process should be improved for its commercialization. When ammonium bicarbonate is used as the draw solute, the system consists of forward-osmosis membrane modules, draw solution separation and recovery processes. Mixed gases of ammonia and carbon dioxide generated during the draws solution separation, need to be recovered to re-concentrate ammonium bicarbonate solution, for continuous operation as well as for the economic feasibility. The diluted ammonium bicarbonate solution has been proposed as the absorbent for the draw solution regeneration. In this study, experiments are conducted to investigate performance and features of the absorption corresponding to absorbent concentration. It is concluded that ammonium bicarbonate solution can be used to recover the generated ammonia and carbon dioxide. The results will be applied to design and operation of pilot-scale forward-osmosis desalination system.

• Membrane Journal
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• v.28 no.1
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• pp.75-82
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• 2018

Forward osmosis (FO) desalination system has been highlighted to improve the energy efficiency and drive down the carbon footprint of current reverse osmosis (RO) desalination technology. To improve the trade-off between water flux and salt rejection of thin film composite (TFC) desalination membrane, thin film nanocomposite membranes (TFN), in which nanomaterials as a filler are embeded within a polymeric matrix, are being explored to tailor the separation performance and add new functionality to membranes for water purification applications. The objective of this article is to develop a graphene nanocomposite membrane with high performance of water selective permeability (high water flux, high salt rejection, and low reverse solute diffusion) as a next-generation FO desalination membrane. For advances in fabrication of graphene oxide (GO) membranes, layer-by-layer (LBL) technique was used to control the desirable structure, alignment, and chemical functionality that can lead to ultrahigh-permeability membranes due to highly selective transport of water molecules. In this study, the GO nanocomposite membrane fabricated by LBL dip coating method showed high water flux ($J_w/{\Delta}{\pi}=2.51LMH/bar$), water selectivity ($J_w/J_s=8.3L/g$), and salt rejection (99.5%) as well as high stability in aqueous solution and under FO operation condition.

• Membrane Journal
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• v.17 no.4
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• pp.277-286
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• 2007

The technology of seawater desalination has been received much attentions to solve the problem of water shortage through all over the world. In this study, it attempts to confirm the use-possibility of cellulose triacetate (CTA) for preparation of reverse osmosis membranes which have been highlighted as high efficiency and low energy consumption process for seawater desalination. The effects of casting dope parameters like an acetyl content, solvent, additives on the membrane performance were investigated. It was possible to produce the membranes which have high water flow rate and salt rejection with the increase of acetyl content and dioxane content among various dioxane/acetone ratios. Acetic acid and maleic acid were preferred for additives to produce high performance membranes. It was verified that $HOLLOSEP^{(R)}$ module which is commercialized CTA membrane by TOYOBO Co. can produce stable water production and high-quality water for long-term operation in the practice plants without any chemical treatments.

• Journal of the Korean Geotechnical Society
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• v.35 no.4
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• pp.37-42
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• 2019

Hydrate dissociation is required to produce methane, which generates both water and methane. Thus, multiphase fluid flow and desalination are expected during methane production, which causes the fine migration and clogging in pores. The goal of this study is to explore the effects of both multiphase fluid flow and desalination on the migration and clogging of kaolin particles as typical fines. The results are as follows : (1) the larger the pore size is, the more mounting the critical clogging concentration is, (2) kaolin particles are more easily clustering and clogging in deionized water than salty water, and (3) the critical clogging concentration of kaolin in multiphase fluid flow is lower than in singlephase fluid flow. Therefore, clustering and clogging of kaolin within pore occur easily due to desalination and multiphase fluid flow when methane is produced from hydrates, and the efficiency of methane production is expected to decrease due to the degradation of permeability coefficient.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.482-486
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• 2003

A high-efficiency turbo steam compressor has been successfully developed for the MVR desalination system, first one in Korea. The state-of-the-art design methods using real gas properties were applied to get all the aerodynamic design results. Bull and pinion gear trains, tilting-pad bearings and investment cast impellers were developed also to be integrated into the integral gear-driven turbo steam compressor. System tests show highly efficient performance.

• Membrane Journal
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• v.17 no.2
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• pp.93-98
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• 2007

The reliability of innovative membrane contactors technology (i.e. Gas/Liquid Membrane Contactors, Membrane Distillation/Crystallization) is today increasing for seawater desalination processes, where traditional pressure-driven membrane separation units are routinely operated. Furthermore, conventional membrane operations can be integrated with membrane contactors in order to promote possible improvements in process efficiency, operational stability, environmental impact, water quality and cost. Seawater is the most abundant aqueous solution on the earth: the amount of dissolved salts covers about 3% of its composition, and six elements (Na, Mg, Ca, K, Cl, S) account for more than 90% of ionic species. Recent investigations on Membrane Distillation-Crystallization have shown the possibility to achieve significant overall water recovery factors, to limit the brine disposal problem, and to recover valuable salts (i.e. calcium sulphate, sodium chloride, magnesium sulphate) by combining this technology with conventional RO trains. In this work, the kinetics of $CaSO_4{\cdot}2H_2O,\;NaCl\;and\;MgSO_4{\cdot}7H_2O$ crystallization is experimentally investigated in order to improve the design of the membrane-based crystallization unit.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.2
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• pp.177-184
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• 2011

Membrane fouling is an unavoidable phenomenon in operation of seawater reverse osmosis (SWRO) and major obstacle for economic and efficient operation. When fouling occurs on the membrane surface, the permeate flux is decreased, on the contrary, the trans-membrane pressure (TMP) is increased, therefore operation and maintaining costs and potential damage of membranes are able to the pivotal risks of the process. Chemical cleaning process is essential to prevent interruptions for effective RO membrane filtration process. This study focused on proper chemical cleaning condition for polyamide RO membranes of 4 companies. Several chemical agents were applied for chemical cleaning under numbers of operating conditions. Additionally, a monitoring tool of FEEM as autopsy analysis method is adapted for the prediction of organic bio-fouling.

• Carbon letters
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• v.16 no.2
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• pp.93-100
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• 2015

Surface modified carbon felts were utilized as an electrode for the removal of inorganic ions from seawater. The surfaces of the carbon felts were chemically modified by alkaline and acidic solutions, respectively. The potassium hydroxide (KOH) modified carbon felt exhibited high Brunauer-Emmett-Teller (BET) surface areas and large pore volume, and oxygen-containing functional groups were increased during KOH chemical modification. However, the BET surface area significantly decreased by nitric acid ($HNO_3$) chemical modification due to severe chemical dissolution of the pore structure. The capability of electrosorption by an electrical double-layer and the efficiency of capacitive deionization (CDI) thus showed the greatest enhancement by chemical KOH modification due to the appropriate increase of carboxyl and hydroxyl functional groups and the enlargement of the specific surface area.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.201-201
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• 2019

세계적인 기상이변으로 가뭄발생 빈도 및 영향이 증가하고 있으며, 급속한 산업화로 사용 가능한 수자원이 점차 고갈되어 있어, 국내에서도 해수담수화(Seawater Desalination)는 새로운 대체수자원으로 많은 관심을 받고 있다. 해수담수에 필요한 에너지 약 50~70%는 역삼투(Reverse Osmosis) 공정에서 발생되며, 해수온도 및 염분도에 따라 많이 변동될 수 있으므로 국립해양조사원(KHOA)의 과거 20년 자료를 이용하여 해수담수화 시설물 위치에 따른 영향을 분석하였다. 해수담수화에 필요한 에너지는 막 제조사에서 제공하는 RO Projection Software를 적용하여 에너지 소모량을 평가하고, 이를 고려한 시설물 위치에 대한 평가 모델을 구축하였다. 기존 해수담수화 시설은 대규모 물 공급이 필요한 지역을 우선적으로 고려했기 때문에 시설물 위치에 대한 객관적인 평가기준 마련이 어려웠다. 그러나 해수담수화 플랜트는 한번 설치되면 장기적인 시설물 유지 및 관리가 필요함으로 경제성을 고려한 최적 입지의 선정은 매우 중요하다. 본 연구는 국립해양조사원의 수집된 자료를 바탕으로 해수담수화 시설물 입지선정을 정량적으로 평가함으로서, 시설물 위치에 대한 의사결정시 참고할 수 있는 기초자료로 활용될 것으로 기대한다.