Ion exchange is a process in which ions are exchanged between a solution and an ion exchanger, an insoluble solid or gel. Typical ion exchangers are ion exchange resins, zeolite, montmorillonite, clay, and humus. Ion exchangers are either cation exchangers for positively charged cations or anion exchangers for negatively charged anions. Ion exchange is a reversible process and the ion exchanger can be regenerated or loaded by washing with an excess of the ions to be exchanged.

Ion exchange is a method widely used in household and industrial water purifications to produce soft water. This is accomplished by exchanging calcium Ca²⁺ and magnesium Mg²⁺ cations against sodium Na⁺ or hydrogen H⁺ cations.

Ion exchange chromatography is a chromatographical method that is widely used in biochemistry to separate charged molecules such as proteins.

See also

• Water softener