The ion exchange process removes hardness-causing ions from water by exchanging them for ions on cross-linked polymer resins. There are two main types of resins: cation exchange resins that replace calcium and magnesium ions with hydrogen ions, and anion exchange resins that replace chloride and sulfate ions with hydroxide ions. The process produces deionized water that is free from minerals and hardness ions.

1. ION EXCHANGE PROCESS
or Demineralization or Deionzation
• Hardness causing ions are exchanged with ions of resins
• Water obtained- free from minerals and hardness causing ions
(Known as deionized or demineralized water)
ION-EXCHANGE RESINS
• Cross linked, high mol weight organic polymers
• functional groups attached to the
polymeric chains are responsible for ion-exchange properties
• Natural Resins comes from plants
Ion exchange resin beads
1

2. TYPES OF ION EXCHANGE RESINS
Cation exchange resin Anion exchange resin
• Cation exchange resin
• Anion exchange resin −CH=CH2
2
Styrene divinyl benzene copolymers

3. • Cation exchange resin
Styrene divinyl benzene copolymers,
Have acidic functional groups like –COOH or -SO3H which can
exchange the cations of hard water (Ca2+, Mg2+) by their H+
ions
Styrene divinyl benzene copolymers on sulphonation become
capable of exchanging their H+ ions with the cations of
solution
2 RH + Ca2+ → R2Ca + 2H+
Resin Hard Water
2 RH + Mg2+ → R2Mg + 2H+
Resin Hard WateR
3

4. • Anion exchange resin
Styrene divinyl benzene copolymers having basic functional
groups like –NH2 or –NH4
+
These resins after treatment with NaOH become capable of
exchanging their OH- ions with the anions of water Cl- , SO4
2-
R’OH + Cl- → R' Cl + OH-
Resin Hard Water
2 R’OH + SO4
2- → R2'SO4 + 2OH-
Resin Hard Water
4

5. PROCESS
Ca2+, Mg2+ Cl- , SO4
2-
5
H- + OH- → H2O

6. 6

7. 7
The exhausted cation exchange resin can be
regenerated by passing a solution of dil HCl and
H2SO4.
The exhausted anion exchange resin can be
regenerated by passing a solution of dil NaOH