In surface chemistry, if the adsorption of one or several ionic species is accompanied by the simultaneous desorption (displacement) of an equivalent amount of one or more other ionic species, this process is called ion exchange.
Source: PAC, 1972, 31, 577. 'Manual of Symbols and Terminology for Physicochemical Quantities and Units, Appendix II: Definitions, Terminology and Symbols in Colloid and Surface Chemistry' on page 585 (https://doi.org/10.1351/pac197231040577)
The process of exchanging ions between a solution and an ion exchanger.
Source: PAC, 1993, 65, 819. 'Nomenclature for chromatography (IUPAC Recommendations 1993)' on page 854 (https://doi.org/10.1351/pac199365040819)