Commercial preparation of Sodium hydroxide

This presentation will guide you properly in the understanding of industrial preparation of sodium hydroxide also known as caustic soda.

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

2. 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)

3. Produ ct ion Process of Caustic Soda (NaOH) and Chlorine by EleMrolysis Basically Caustic soda and chlorine are produced as co-products by the electrolysis of brine (Salt water ). In this process there are three types of electrolytic cell s used : Diaphragm Cell Mercury Cell Membrane Cell Production of Caustic Soda (NaOH)

4. Brine Solution ( Conc. NaCl Solution) OR NaCl Water Raw Materials

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

6. 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

7. 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 Hydrogen liberates at the steel cathodes weak brine containing caustic soda is withdrawn from the collecting tank.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

8. Reactions NaCl Na + + Cl ̄ Δ H = + 97.2kcals 2H 2 O + 2e ̄ H 2 + OH ̄ Δ H = + 68.3kcals At cathode 2H 2 O + 2e ̄ H + + 2OH ̄ Na + + OH ̄ NaOH Δ H = + 112.0kcals At Anode Cl ̄ + e ̄ Cl Cl ̄ + Cl ̄ Cl 2 Net Reaction NaCl + H 2 O NaOH + H 2 + Cl 2 Reactions during process

9. Applications