ABSTRACT
Electrodialysis (ED) is a membrane process in which ionic species present in aqueous solutions can be separated or concentrated by application of electrical potential across charged polymeric membranes. Compounds that can be separated are inorganic and organic salts, mineral and organic acids, alkalis, and even hazardous chemicals such as sodium azide, which can ionize in aqueous medium. There are two different types of ion-exchange membranes: cation exchange membrane (CEM) where the polymer matrix carries negatively charged groups and anion exchange membrane (AEM) that contain positively charged groups. This process is widely used for desalination of brackish water, production of potable water, and table salt. In general, AEMs and CEMs are placed alternatively in the ED stack whereas in certain specific cases only one type of membrane is used. Bipolar membranes are advanced versions that have a CEM laminated on one side and an AEM on the other side of the supporting fabric. Bipolar membranes possess the unique water splitting ability that results in the production of acids and bases during the desalination process, enhancing overall economy.
