• Membrane and Water Treatment
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• v.4 no.3
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• pp.215-222
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• 2013

The maximum current density that can be achieved in bipolar membrane electrodialysis is limited by the sharp increase in resistance that is experienced when the water content at the membrane interface is not adequately replenished and the membranes dry out. In this paper we show how the water content near the interface depends on the properties of the membranes. A water retaining parameter is introduced, which characterizes the thermodynamic properties of the membrane material and may be used to guide the choice of polymers for mitigation of the dry-out problem.

• Proceedings of the Membrane Society of Korea Conference
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• 1996.10a
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• pp.8-11
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• 1996

전기투석은 역삼투압, 한외여과와 함께 가장 많이 이용되고 막공정 중의 하나이다. 전기투석은 다른 막공정과 같이 막의 선택성에 의한 분리조작이며 병렬식 배열에 의한 막의 이용이 가능하고 막오염 현상이 있으며 따라서 막-유체간의 접촉에 대한 제어가 필요하다. 전기투석은 운전목적에 따라 desalting electrodialysis(ED)와 water-splitting electrodiaiysis(WSED)로 구분할 수 있다. Desalting electrodialysis는 고전적 의미의 탈염을 위한 전기투석공정이며 WSED는 bipolar membrane을 이용하여 염을 산과 염기로 분리시키는 기능을 갖는 전기투석 공정을 말한다. WSED는 전기적으로 물을 분리한다는 의미로서 Electrohydrolysis로 불리기도 한다. WSED의 기본원리는 bipolar membrane의 양쪽면에서 수소이옹과 수산이온을 발생시켜 산 또는 염기용액으로 전달하고 bipolar membrane에 접하고 있는 양이온 또는 음이온 교환막에서는 각 용액의 전기적 중성을 유지하기 위해 대응하는 이온을 투과시키는 것이다. WSED는 염으로부터 산 염기제조 뿐만아니라 염의 형태로 생성되는 유기산, 아미노산 등 발효생성물의 회수 또는 acidification에 이용되고 있다.

• Membrane Journal
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• v.13 no.3
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• pp.143-153
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• 2003

The effects of bipolar interface formed on the surface of cation-exchange membrane on water splitting phenomena were investigated. Results showed that the formation of immobilized bipolar interface resulted in significant water splitting during electrodialysis. In particular, the immobilized bipolar interface was easily created on the cation-exchange membrane surface in the electrodialytic systems where multivalent cations served as an electrolyte. Multivalent cations with low solubility product resulted in violent water splitting because they were easily precipitated on the membrane surface in hydroxide form. Therefore, the bipolar interface consisting of H- and OH-affinity groups were formed on the membrane-solution interface. Apparently, water splitting was largely activated with the help of strong electric fields generated between the metal hydroxide layer and fixed charge groups on the membrane surface. Likewise, the accumulation of large molecular counter ions on the membrane surface led to the formation of a fixed bipolar structure that could cause significant water splitting in the over-limiting current region. Therefore, the prevention of the immobilization of bipolar interface on the membrane surface is very essential in improving the process efficiency in a high-current operation.

• Membrane Journal
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• v.30 no.2
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• pp.79-96
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• 2020

Secondary energy conversion systems have been briskly developed owing to environmental issue and problems of fossil fuel. They are basically operated based on electro-chemical systems. In addition, ion exchange membranes are one of the significant factors to determine performance in their systems. Therefore, the ion exchange membranes in suitable conditions must be developed to improve the performance for the electro-chemical systems. These ion exchange membranes can be classified into various types such as cation exchange membrane, anion exchange membrane and bipolar membrane. Their membranes have distinct characteristics according to the chemical, physical and morphological structure. In this review, the types of ion exchange membranes and their fabrication processes are described with main characteristics. Moreover, applications of ion exchange membranes in newly developed energy conversion systems such as reverse electrodialysis, redox flow battery and water electrolysis process are described including their roles and requirements.