Britannica
Sources used in this answer
How does a column make an ion-exchange reaction proceed nearly to completion?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
ion-exchange reaction
Figure 1: Chemical structure of cation exchanger. The exchangeable ions are marked +. The whole structure is permeated by solvent molecules, usually water (not shown).
An ion-exchange reaction is intrinsically reversible, but packing the exchanger into a column forces the reaction to proceed toward completion.1
This occurs because the solution flowing down the column is continuously exposed to fresh, unreacted exchanger. As the solution moves through the column, the exchange process advances incrementally: a reaction that is only partially completed in the first section of the column progresses further in each subsequent section. Consequently, the exchangeable ions are steadily adsorbed until they become analytically undetectable in the effluent. This process continues until the column becomes completely saturated with the ions.1