ion exchange science definition

A reversible chemical reaction between two substances (usually a relatively insoluble solid and a solution) during which ions of equal charge may be interchanged. Ion exchange is used in water softening and purification, chemical analysis, the separation of radioactive isotopes, and kidney dialysis.
♦ cation exchange  is the exchange of positively charged ions.
♦ anion exchange  is the exchange of negatively charged ions.