Chemical desalination refers to the process in which various ions contained in water are removed by ion exchange reaction with ion exchange resin, also known as ion exchange demineralized water treatment. When various cations in the water react with the cation exchange resin, the water contains only hydrogen ions exchanged from the cation resin; After various anions in water react with anion exchange resin, the water only contains hydroxyl ions exchanged from anion resin. Hydrogen ions and hydroxyl ions can combine with each other to produce water, which realizes the chemical desalination of water. Obviously, the cation exchange resin used must be hydrogen type, and the anion exchange resin used must be hydrogen oxygen type. This is the basic principle of chemical desalination.

When various ions in water are exchanged into hydrogen ions and hydroxyl ions, the deep chemical desalination of water is realized. If one or more cations or anions remain in the water, partial chemical desalination of the water is realized.

In order to realize deep chemical desalination, a system with strong acid cation resin and strong alkaline anion resin must be used. As long as partial chemical desalting is realized, various systems composed of cation resin and anion resin can be used, including the system composed of weak acid cation resin and weak alkali anion resin, and amphoteric resin unit equipment containing only weak acid group and weak alkali group.

After deep chemical desalting, many surface water and well water can be made into pure water; After partial chemical desalting, surface water and well water containing more salt can be made into fresh water.