This document summarizes the commercial production process of sodium hydroxide (NaOH) through electrolysis of brine. It describes how salt is dissolved in water to create a brine solution, which is purified and then sent to diaphragm cells where electrolysis occurs. During electrolysis, sodium ions migrate to the cathode where they react with hydroxyl ions to form NaOH, while chlorine gas forms at the anode. The end products are caustic soda solution extracted from the cathode chamber and chlorine gas collected from the anode chamber.

2. Commercial Production of Sodium Hydroxide
By
Mr. Muhammad Ullah Afridi
Institute of Chemical Sciences, University of Peshawar.

3. Sodium Hydroxide (NaOH)
 Sodium hydroxide (NaOH)
also known as lye and caustic
soda
 Is a highly caustic metallic
base which is a white solid
available in:
• pellets
• flakes
• Granules
• 50% saturated solution.
Introduction to Caustic Soda (NaOH)

4. Production Process of CausticSoda (NaOH)andChlorineby EleMrolysis
 Basically Caustic soda and chlorine are produced as
co-products by the electrolysis of brine (Salt water ).
 Inthis process there are three types of electrolytic cells
used:
 Diaphragm Cell
 Mercury Cell
 Membrane Cell
Production of Caustic Soda (NaOH)

5.  Brine Solution (Conc. NaCl Solution)
OR
 NaCl
 Water
Raw Materials

6.  Salt is first dissolved in the
dissolutiontank.
 The obtained saturated brine (salt
water) is then sent to a purification
tank to remove impurities.
Process of Caustic Soda (NaOH)

7. Diaphragm Cell
 The diaphragm cells contain a porous asbestos diaphragm
which permits a flow of brine from the anode to cathode and
prevents the mixing of anode product and cathode products.
 Graphite is used as an anode.
 Perforated steel is used as cathode
 Electrolysis starts with dry
or
empty cathode compartment.
 E. g. Nelson, Gibbs and Vorce cells

9.  A feed of brine between anode and cathode compartment
maintains the separation of anode products from cathode
products.
 The brine passed into the anode compartment of the cell through
the concrete cover and liberated chlorine gas at the anode escapes
through the cell cover.
 Hydrogen liberates at the steel cathodes
 weak brine containing caustic soda is withdrawn from the
collecting tank.
Working Principles

10. Reactions
NaCl Na+ + Cl ̄ ΔH = + 97.2kcals
2H2O + 2e ̄ H2 + OH ̄ ΔH = + 68.3kcals
At cathode
2H2O + 2e ̄ H+ + 2OH ̄
Na+ + OH ̄ NaOH ΔH = + 112.0kcals
At Anode
Cl ̄ + e ̄ Cl
Cl ̄ + Cl ̄ Cl2
Net Reaction
NaCl + H2O NaOH + H2 + Cl2
Reactions during process

11. Applications