Ion exchange
Ion exchange is an exchange of ions between two electrolytes or between an electrolyte solution and a complex. In most cases the term is used to denote the processes of purification, separation, and decontamination of aqueous and other ion-containing solutions with solid polymeric or mineralic 'ion exchangers'. Typical ion exchangers are ion exchange resins, zeolites, montmorillonite, clay, and soil humus. Ion exchangers are either
cation exchangers that exchange positively charged ions or
anion exchangers that exchange negatively charged ions. There are also
amphoteric exchangers that are able to exchange both cations and anions simultaneously. However, the simultaneous exchange of cations and anions can be more efficiently performed in
mixed beds that contain a mixture of anion and cation exchange resins, or passing the treated solution through several different ion exchange materials. Ion exchangers can be unselective or have binding preferences for certain ions or classes of ions, depending on their chemical structure. This can be dependent on the size of the ions, their charge, or their structure.