Soft water treatment

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More than half of ion exchange devices are used for water treatment and desalination, and the main types of resins used in such applications are strongly acidic hydrogen-type cation exchange resins and strongly basic hydroxide-type anion exchange resins. When a hydrogen-type cation exchange resin comes into contact with water, an ion exchange reaction occurs: various cations in the water are adsorbed onto the resin, while the hydrogen ions bound to the resin are displaced. At this point, the water contains only hydrogen ions as the sole type of cation. When the hydroxide-type anion resin comes into contact with water and undergoes an ion exchange reaction, various anions in the water are adsorbed, leaving only hydroxide ions in the water. When water that has passed through such an oxyhydrogen-type cation resin is then passed through an oxyhydrogen-type anion resin, only the two types of ions present in the water—hydrogen ions and hydroxide ions—combine to form water, thus completing the water desalination process.