Adsorptionionbytning

Adsorptionionbytning, often referred to as adsorption-based ion exchange or adsorption–ion exchange, describes a class of separation processes in which ions in a liquid phase are removed by adsorption onto a solid that contains exchangeable ionic groups, and the adsorbed ions are simultaneously exchanged with ions from the solution. In practice, the sorbent presents fixed sites with a preference for certain ions; when contact occurs, ions in the solution are captured and a counterion bound to the site is released into the liquid, effectively exchanging ions at the solid–liquid interface. The process is governed by selectivity, ionic strength, pH, and temperature, and may involve both outer-sphere adsorption and inner-sphere complexation.

Common sorbents include ion-exchange resins (divinylbenzene-based polymers bearing sulfonic acid or quaternary ammonium groups), natural clays and zeolites, activated alumina, and modified carbons. While traditional ion exchange targets specific ions, adsorptionionbytning emphasizes the dual role of adsorption to bring ions to the sorbent surface and exchange chemistry to release counterions, enabling high selectivity in multi-ionic streams.

Applications include drinking water softening (removal of Ca2+, Mg2+), deionization, removal of heavy metals and radionuclides, and selective capture of certain oxyanions or cations. It is used in mining, chemical processing, and environmental remediation, where selective ion removal is advantageous.

Regeneration restores the sorbent’s capacity by replacing bound ions with a regenerant solution (e.g., NaCl for cation systems, NaOH or HCl for anion systems). Spent regenerants and sorbent aging raise environmental and economic considerations, and fouling or competing ions can reduce capacity.