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Ion exchange membranes transport dissolved ions across a conductive polymeric membrane. The membranes are often used in desalination and chemical recovery applications, moving ions from one solution to another while preventing the passage of water. Ion exchange membranes are made of a polymeric material attached to charged ion groups. Anion exchange membranes contain fixed cationic groups with mobile anions; they allow the passage of anions and block cations. Cation exchange membranes contain fixed anionic groups with mobile cations; they allow the passage of cations and block anions. There are two primary classes of membranes: (1) heterogeneous, and (2) homogeneous. Heterogeneous membranes are low cost, have a thicker composition with higher resistance and a rough surface that can be subject to fouling. Homogeneous membranes are more expensive, but have a thinner composition with lower resistance and a smooth surface less susceptible to fouling. Homogeneous membrane surfaces can be modified to alter the membrane permselectivity to protons, monovalent ions, and divalent ions. The permselectivity of ion exchange membranes describes their charge selectivity. This charge selectivity reflects the membrane’s ability to discriminate between ions of opposite charge. A higher selectivity leads to increased recovery and performance of the membrane. == Traditional applications == Ion exchange membranes are traditionally used in electrodialysis or diffusion dialysis by means of an electrical potential or concentration gradient, respectively, to selectivity transport cationic and anionic species. When applied in an electrodialysis desalination process, anion and cation exchange membranes are typically arranged in an alternating pattern between two electrodes (an anode and a cathode) within the electrodialysis stack. A galvanic potential is supplied as a voltage generated at the electrodes. A typical industrial electrodialysis stack consists of two chambers: a product water chamber and a concentrate reject chamber. During stack operation, salts are transferred from the product to the concentrate. As a result, the reject stream is concentrated up while the product stream is desalted. Exemplary applications of ion exchange membranes utilized in electrodialysis and EDR include seawater desalination, industrial wastewater treatment of highly scaling waters, food and beverage production, and other industrial wastewaters. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ion exchange membranes」の詳細全文を読む スポンサード リンク
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