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Ion-exchange membranes are traditionally used in electrodialysis or diffusion dialysis by means of an electrical potential or concentration gradient, respectively, to selectively transport cationic and anionic species. When applied in an electrodialysis desalination process, anion- and cation-exchange membranes are typically arranged in an ...
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 ...
Electrodialysis is a process of separation which uses ion-exchange membranes and an electrical potential as a driving force. It is mainly used to remove ions from aqueous solutions. There are three electrodialysis processes which are commonly used - Donnan dialysis, reverse electrodialysis, and electro-electrodialysis.
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.
In the case of dialysis, the driving concentration gradient in the membrane is reduced. [6] In the case of electromembrane processes, the potential drop in the diffusion boundary layers reduces the gradient of electric potential in the membrane. Lower rate of separation under the same external driving force means increased power consumption.
Membrane distillation (MD) is a thermally driven separation process in which separation is driven by phase change.A hydrophobic membrane presents a barrier for the liquid phase, allowing the vapour phase (e.g. water vapour) to pass through the membrane's pores. [1]
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).
Electrodialysis reversal (EDR) is an electrodialysis reversal water desalination membrane process that has been commercially used since the early 1960s. [1] An electric current migrates dissolved salt ions, including fluorides, nitrates and sulfates, through an electrodialysis stack consisting of alternating layers of cationic and anionic ion exchange membranes.