Demineralization of Water:
Ion-Exchange Process: Various synthetic ion-exchange resins are nowadays available for softening hard water. They are of two types:
Cation Exchange Resins represented by RH:
Hard water is first passed through cation exchange resins (RH) which removes all the cations like Ca+2, Mg+2, etc. An equivalent amount of H+ ions are released into water.
Anion Exchange Resins represented by NR4OH:
The effluent water contains acids like HCL, H2SO4 etc. Hard water is then passed through a bed of anion exchange resins (NR4OH) which removes all the anions like Cl–, SO42-, etc.
The removal of all the cations and anions of the dissolved electrolyte in water is known as Deionisation or Demineralization of Water.