exchangesite
An exchangesite is a localized region on a solid material where ions or molecules can be reversibly exchanged with a surrounding phase, typically an aqueous solution. In ion-exchange systems, exchange sites carry fixed electrical charges that attract counterions from solution and release previously bound ions in response to changes in composition, concentration, or pH. Cation-exchange sites are negatively charged and exchange positively charged ions; anion-exchange sites are positively charged and exchange anions.
Common materials hosting exchange sites include ion-exchange resins (organic polymers bearing sulfonate groups for cation exchange
Applications span water treatment (removing hardness, recovering heavy metals, purifying process streams), soil science (cation exchange