• Membrane Journal
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• v.33 no.3
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• pp.87-93
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• 2023

Electrodialysis (ED) is essential in separating ions through an ion exchange membrane. The disposal of brine generated from seawater desalination is a primary environmental concern, and its recycling through membrane separation technology is highly efficient. Alkali is produced by several chemical industries such as leather, electroplating, dyeing, and smelting, etc. A high concentration of alkali in the waste needs treatment before releasing into the environment as it is highly corrosive and has a chemical oxygen demand (COD) value. The concentration of calcium and magnesium is almost double in brine and is the perfect candidate for carbon dioxide adsorption, a major environmental pollutant. Sodium hydroxide is essential for the metal carbonation process which, is easily produced by the bipolar membrane electrodialysis process. Various strategies are available for its recovery, like reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), and ED. This review discusses the ED process by ion exchange membrane for alkali recovery are discussed.

• Prospectives of Industrial Chemistry
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• v.14 no.6
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• pp.21-28
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• 2011

이온교환막을 이용한 전기적 탈염기술은 막모듈 내에 양이온교환막과 음이온교환막을 교대로 장착시키고 모듈의 양단 전극에 전압을 적용함으로써 물속에 용존되어 있는 양이온과 음이온들을 전기의 힘을 이용하여 선택적으로 투과시키는 원리를 기반으로 하는 청정공정 기술이다. 이온교환막 공정은 전통적으로 산/알칼리의 생산, 산업폐수의 중금속의 제거, 해수의 담수화, 반도체 산업의 초순수의 제조, 해수에서 식염의 제조, 발효산업의 유기산 및 아미노산의 회수 등 다양한 산업분야에서 응용되어 왔다. 최근에는 이러한 기존의 응용분야에서 벗어나 새롭게 응용분야가 넓어지고 있다. 이온교환막과 다공성 탄소전극을 결합한 막축전식 해수담수화기술, 해수와 담수의 염도차를 이용한 역전기투석식 해수발전 등의 새로운 선택분리기능 및 응용분야를 가진 이온교환막의 개발 및 공정에 관한 연구가 활발히 이루어지고 있다. 그러나 국내에서는 이온교환막이 아직 상용화되지 않고 있어 이온교환막을 이용한 응용연구가 활발하게 진행되지 못하고 있어 그 개발이 시급하다. 본 논문에서는 먼저 이온교환막을 이용한 전기투석식 탈염기술, 물분해 전기투석, 전기탈이온 공정에 관한 동향을 조사하였다. 아울러 미래의 이온교환막의 응용기술인 해수담수화기술로서 역삼투법과 경쟁하여 에너지를 낮게 소모할 것으로 예상되는 분리막을 이용한 막축전식 탈염기술과 무한한 신재생에너지원인 해수와 담수를 이용한 역전기투석 해수발전기술에 대해 기술의 원리들과 최근의 연구동향 등을 정리하였다.

• Membrane Journal
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• v.34 no.1
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• pp.20-29
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• 2024

Membranes are increasingly used in a variety of applications including desalination, gas separation, disposable filters, and healthcare products. Recently, sustainable and green membrane fabrication technology is recognized as one of the decisive initiatives to reach the target of pollution control. Especially, the fabrication of bio-based membranes using such as poly lactic acid (PLA), polybutylene adipate terephthalate (PBAT), and polybutylene succinate (PBS) has attracted considerable attention. The phase inversion method is one of the versatile approaches for preparing PLA membranes. This article reviews the recent advances in PLA membrane preparation via the phase inversion method. Furthermore, it provides a perspective on the potential outlook for future advances. Overall, this review has demonstrated has been conducted in the area of bio-based PLA membranes.

• Journal of Bio-Environment Control
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• v.28 no.4
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• pp.454-460
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• 2019

The purpose of this study is to analyze the distribution characteristics of mist spray particle size by devising a rotary mist spraying device to develop the evaporative salt water desalination system. The rotary mist spraying device was consisted of a BLDC sirocco fan, a spinning fan, a fan fixed shaft and a salt water supply device etc. In this study we analyzed the characteristics of spray particle size and distribution according to the variation of sirocco fan surface roughness(Ra, ${\mu}m$), revolutions(rpm) and salt water flow rate(mL/min). When sirocco fan surface roughness(Ra) was in the range of $0.27{\sim}7.65{\mu}m$, the spray particle size was $0.117{\sim}1.360{\mu}m$. And then more than 90% of spray particles were found to be less than $0.50{\mu}m$. When sirocco fan surface roughness(Ra) was in the range of $12.70{\sim}22.84{\mu}m$, the spray particle size was $2.51{\sim}184.79{\mu}m$ and more than 98% of spray particles were found to be less than $13.59{\mu}m$. To analyze the effect of fan rotation speed on the size and distribution of spray particles, when surface roughness Ra was fixed $0.27{\mu}m$ and fan rotation speed and salt water flow rate was respectively changed at 3,800~5,600 rpm and 2.77~8.28 mL/min, spray particle size was $0.314{\sim}0.541{\mu}m$. And when salt water flow rate was 9.74 mL/min and fan rotation speed was 3,800~5,200 rpm, spray particle size was in the range of $29.29{\sim}341.46{\mu}m$ and in case of 5,600 rpm more than 98.23% of spray particles were in the range of $2.51{\sim}13.59{\mu}m$.

• Korean Journal of Construction Engineering and Management
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• v.9 no.1
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• pp.107-117
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• 2008

In this study, surveys and interviews are used to evaluate technological competitiveness of each product with respect to that of foreign leading firms, for seven leading domestic construction products which have been determined to have competitive edge in offshore markets, Such evaluation provides a more in depth study than previously conducted research, and is meaningful in that corporate level, rather than industry level, perspective is projected. Major findings of such evaluations are the following. First, as expected, it has been evaluated that domestic technological competitiveness in desalination plant and power plant has reached the point where it can compete with foreign leading firms. Moreover, a noteworthy result of the evaluation is that development program sector, including urban development of satellite cities, has reached considerable level of competitiveness in offshore market. In the case of the development market, domestic firms have accumulated sufficient experience in domestic market and engineering technology is not a decisive factor as in plant sector, and these factors lead to such an evaluation. Second, in the cases of gas, oil refinery and petro-chemical plants, domestic products' technological competitiveness that can contest in offshore market is still centered around production and construction. On the other hand, there are still weaknesses in license technology and basic design capabilities, which constitute the "value added" area. Third, skyscrapers, a promising product in offshore construction market and a product group which domestic firms have much performance record and projects in progress both in domestic and offshore markets, are considered. While direct comparison between skyscrapers and plant sector is not feasible, with the exception of production and construction, overall domestic capability in this sector has been assessed to be the lowest amongst those products that were surveyed. Fourth, it has been indicated that competitiveness is relatively higher in common technology than in key technology. In project management capability, it has been assessed that there are weaknesses in procedure document area. Also, a characteristic is the point that low overall assessments have been given across all product groups for corporate and management areas, not technological areas. Especially, financing, contracting/claim, risk management and investment on research and development received low evaluations. Fifth, it has been assessed that overall corporate and governmental supports are weak. This result is especially evident for corporate management and support areas across all product groups surveyed.

• Journal of the Korean GEO-environmental Society
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• v.14 no.8
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• pp.23-27
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• 2013

In this study, efficiency of pre-treatment of turbid seawater was measured where micro-air bubbles were used to remove particles in seawater after input of natural coagulant PGA. Artificial seawater was prepared having the intended trubidity using marine sediments and microalgae. 73.7% of turbidity removal was achieved when 0.5g/L of $AlCl_3{\cdot}6H_2O$ was added in the artificial seawater, but 92.4% of turbidity removal was observed when 0.05g/L of PGA was added in the artificial seawater containing microalgae. In addition, much greater turbidity removal was achieved for microalage than sediments. For both cases, input of 0.1g/L PGA and following additional input of micro-air bubbles for 5 seconds resulted in the maximum removal efficiency where reaction time of coagulation was 1 min and flotation by micro-air bubbles was 10 min. From this study, we concluded that micro-air floation after coagulation could be a possible economical pre-treatment method for highly turbid seawater.

• Corrosion Science and Technology
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• v.13 no.2
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• pp.70-80
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• 2014

Duplex stainless steels with nearly equal fraction of the ferrite(${\alpha}$) phase and austenite(${\gamma}$) phase have been increasingly used for various applications such as power plants, desalination facilities due to their high resistance to corrosion, good weldability, and excellent mechanical properties. Hyper duplex stainless steel (HDSS) is defined as the future duplex stainless steel with a pitting resistance equivalent (PRE=wt.%Cr+3.3(wt.%Mo+0.5wt.%W)+30wt.%N) of above 50. However, when HDSS is welded with gas tungsten arc (GTA), incorporation of nitrogen in the Ar shielding gas are very important because the volume fraction of ${\alpha}$-phase and ${\gamma}$-phase is changed and harmful secondary phases can be formed in the welded zone. In other words, the balance of corrosion resistance between two phases and reduction of $Cr_2N$ are the key points of this study. The primary results of this study are as follows. The addition of $N_2$ to the Ar shielding gas provides phase balance under weld-cooling conditions and increases the transformation temperature of the ${\alpha}$-phase to ${\gamma}$-phase, increasing the fraction of ${\gamma}$-phase as well as decreasing the precipitation of $Cr_2N$. In the anodic polarization test, the addition of nitrogen gas in the Ar shielding gas improved values of the electrochemical parameters, compared to the Pure Ar. Also, in the erosion-corrosion test, the HDSS welded with shielding gas containing $N_2$ decreased the weight loss, compared to HDSS welded with the Ar pure gas. This result showed the resistance of erosion-corrosion was increased due to increasing the fraction of ${\gamma}$-phase and the stability of passive film according to the addition $N_2$ gas to the Ar shielding gas. As a result, the addition of nitrogen gas to the shielding gas improved the resistance of erosion-corrosion.

• Korean Chemical Engineering Research
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• v.55 no.5
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• pp.704-710
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• 2017

Although the desalination technique using gas hydrate formation is at a development stage compared to the commercially well-established reverse osmosis (RO), it still draws attention because of its simplicity and moderate operational conditions especially when using refrigerants for guest gases. In this study, DFT (density functional theory)-based molecular modeling was employed to explain the energetics of the gas hydrate formation using HFC (hydrofluorocarbon) and HCFC (hydrochlorofluorocarbon) refrigerants. For guest gases, R-134a, R-227ea, R-236fa, and R-141b were selected and three cavity structures ($5^{12}$, $5^{12}6^2$, and $5^{12}6^4$) composed of water molecules were constructed. The geometries of guest gas, cavity, and cavity encapsulating guest gas were optimized by molecular modeling respectively and their located energies were then used for the calculation of binding energy between the guest gas and cavity. Finally, the comparison of binding energies was used to propose which refrigerant is more favorable for the gas hydrate formation energetically. In conclusion, R-236fa was the best choice in terms of thermodynamic spontaneity, less toxicity, and low solubility in water.

• Membrane Journal
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• v.28 no.2
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• pp.96-104
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• 2018

With the rapid increase in seawater desalination, the importance of boron rejection is rising. This study was conducted to investigate the effect of hydrophilic compounds on surface modification to maximize water flux and increase boron rejection. First, polyamide active layer was fabricated by interfacial polymerization of polysulfone ultrafiltration membrane with M-phenylenediamine (MPD) and trimesoyl chloride (TMC) to obtain Control polyamide membrane. Next, D-gluconic acid (DGCA) and D-gluconic acid sodium salt (DGCA-Na) were synthesized with glutaraldehyde (GA) and hydrochloric acid (HCl) by modifying the surface of Control polyamide membrane. XPS analysis was carried out for the surface analysis of the synthesized membrane, and it was confirmed that the reaction of surface with DGCA and DGCA-Na compounds was performed. Also, FE-SEM and AFM analysis were performed for morphology measurement, and polyamide active layer formation and surface roughness were confirmed. In the case of water flux, the membrane fabricated by the surface modification had a value of 10 GFD or less. However, the boron rejection of the membranes synthesized with DGCA and DGCA-Na compounds were 94.38% and 94.64%, respectively, which were 12.03 %p and 12.29 %p larger than the Control polyamide membrane, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.721-728
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• 2016

97% of water on earth exists in the form of seawater. Therefore, the use of marine resources is one of the most important research issues at present. The use of seawater is expanding in various fields (seawater desalination, cooling water for nuclear power plants, deep seawater utilization, etc.). Seawater intake systems utilizing sand filters in order to take in clean seawater are being actively employed. For the intake pipe used in this system, assuring equal intake flows through the respective holes is very important to improve the efficiency of the intake and filtering process. In this study, we analyzed the efficiency of the dual structure perforated pipe used in the seawater intake system using 3D numerical simulations and the inflow rate according to the gap of the up holes. In the case of decreasing gaps in the up holes toward the pipe end, the variation of the total inflow rate was small in comparison with the other cases. However, the standard deviation of the inflow rate through the up holes was the lowest in this case. Also, stable flow occurred, which can improve the efficiency of the intake process. In the future, a sensitivity analysis of the various conditions should be performed based on the results of this study, in order to determine the factors influencing the efficiency, which can then be utilized to derive optimal designs suitable for specific environments.