ION EXCHANGE PROCESSor 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

TYPES OF ION EXCHANGE RESINS

Cation exchange resin Anion exchange resin

• Cation exchange resin• Anion exchange resin −CH=CH2

2

Styrene divinyl benzene copolymers

• Cation exchange resinStyrene 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 becomecapable of exchanging their H+ ions with the cations ofsolution

2 RH + Ca2+ → R2Ca + 2H+Resin Hard Water

2 RH + Mg2+ → R2Mg + 2H+

Resin Hard WateR

3

• Anion exchange resinStyrene 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 + SO42- → R2'SO4 + 2OH-

Resin Hard Water

4

PROCESS

Ca2+, Mg2+ Cl- , SO42-

5

H- + OH- → H2O

6

7

The exhausted cation exchange resin can beregenerated by passing a solution of dil HCl andH2SO4.

The exhausted anion exchange resin can beregenerated by passing a solution of dil NaOH