Katioonivahetus

Katioonivahetus is a process used to remove dissolved cations from a solution by exchanging them for other cations held on a solid ion-exchange resin. This technique is widely employed in water treatment, purification, and chemical analysis. The ion-exchange resin, typically a porous polymer material, contains charged functional groups. These groups are bonded to mobile counter-ions, which are usually cations like sodium (Na+) or hydrogen (H+). When a solution containing unwanted cations, such as calcium (Ca2+) or magnesium (Mg2+), passes through the resin bed, the unwanted cations have a stronger affinity for the functional groups on the resin than the counter-ions. Consequently, the unwanted cations are adsorbed onto the resin, and the counter-ions are released into the solution.

The capacity of the ion-exchange resin to exchange ions is a crucial parameter, indicating the total amount of ions it can hold. Once the resin is saturated with the unwanted cations, it needs to be regenerated. Regeneration typically involves passing a concentrated solution of the original counter-ions (e.g., a strong acid for H+ resin or a brine solution for Na+ resin) through the bed. This reverses the exchange process, removing the adsorbed cations and restoring the resin to its original ionic form, ready for further use. Katioonivahetus finds applications in softening hard water, demineralizing water for industrial processes, purifying pharmaceuticals, and separating ions in analytical chemistry.