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An ion-exchange membrane is a semi-permeable membrane that transports certain dissolved ions, while blocking other ions or neutral molecules. [1] Ion-exchange membranes are therefore electrically conductive. They are often used in desalination and chemical recovery applications, moving ions from one solution to another with little passage of ...
By inserting two ion exchange membranes, a modified form of CDI is obtained, namely Membrane Capacitive Deionization. [13] This modification improves the CDI cell in several ways: Co-ions do not leave the electrodes during the adsorption phase, as described above (see Ion adsorption in Electrical Double Layers for explanation).
Selective electrodialysis uses ion selective exchange membranes to concentrate only some ions, whereas other species remain in the diluted channel. Selective electrodialysis is usually done by employing monovalent anion and/or cation exchange membranes, that only allows migration of monovalent anion or cations, respectively.
Compared to RO membranes, ion exchange requires repetitive regeneration when inlet water is hard (has high mineral content). [citation needed] Industrial and analytical ion-exchange chromatography is another area to be mentioned. Ion-exchange chromatography is a chromatographical method that is widely used for chemical analysis and separation ...
Reverse electrodialysis is a technology based on membranes which gets electricity from a mixing of two water streams with different salinities. It commonly uses anion exchange membranes (AEM) and cation exchange membranes (CEM). AEMs are used to allow the pass of anions and obstruct the pass of cations and CEMs are used to do the opposite.
Ion exchange resins, in the form of beads, are a functional component of domestic water softening units. Conventional water-softening appliances intended for household use depend on an ion-exchange resin in which "hardness ions"—mainly Ca 2+ and Mg 2+ —are exchanged for sodium ions. [7]
Poly(fluorenyl-co-aryl piperidinium) (PFAP)-based anion exchange materials (electrolyte membrane and electrode binder) with high ion conductivity and durability under alkaline conditions has been demonstrated for use to extract hydrogen from water. Performance was 7.68 A/cm 2 at 2 V, some 6x the performance of existing materials.
The chemical potential difference between salt and fresh water generates a voltage over each membrane and the total potential of the system is the sum of the potential differences over all membranes. The process works through difference in ion concentration instead of an electric field, which has implications for the type of membrane needed. [2]