The main function of ion exchange resin is to produce pure water by "ion exchange method". The ions (calcium, magnesium, copper, sodium and other metal ions) and anions (carbonate, nitrate, sulfate and other non-metallic ions) produced by the ionization of various inorganic salts in raw water react with hydrogen ions and hydroxide ions on the resin when passing through the ion exchange resin layer (ion exchanger in the ion exchange column). Adsorbed by resin, hydrogen ion replaced from resin and hydroxide ion combine to form water molecule (hydrogen peroxide), thus achieving the effect of removing inorganic salts in water and achieving the purpose of producing desalinated pure water, as shown in the figure:

Because ion exchange is reversible, the used ion exchange resins are usually washed with inorganic acid or alkali of appropriate concentration, and can be restored to their original state and reused. This process is called regeneration. Cation exchange resin can be eluted by dilute hydrochloric acid and sulfuric acid, and anion exchange resin can be regenerated by sodium hydroxide and other solutions.

For this reason, ion exchange resin can be understood as an ion exchanger of organic monomer particles made of polymer copolymer by chemical synthesis, which is an ion exchange resin for softening water treatment.