The purpose of extracting or removing certain ions in a solution is to be a unit operation belonging to the mass transfer separation process by exchanging the ions in the dilute solution with the ions in the solid ion exchange agent. Ion exchange is a reversible equivalent exchange reaction.
As early as 1850, the ion exchange phenomenon of the soil absorbed by ammonium salts was found, but the ion exchange as a modern separation method was made after the artificial synthesis of ion exchange resins in in the 1940 of the 20th century. The process and equipment of ion exchange operation are basically identical to adsorption, but the selectivity of ion exchange is higher, which is more suitable for separating and purifying high purity.
Ion exchange is mainly used in water treatment (softening and purification), refining and decolorization of solution (such as sugar), extracting uranium and rare metals from mineral leaching, extracting antibiotics from fermentation broth and recovering precious metals from industrial waste water.