Technology Type

The Chlor-Alkali electrolysis process is used in the manufacture of chlorine, hydrogen, and sodium hydroxide (caustic) solution. Of these 3, the primary product is chlorine. There are 3 types of electrolytic processes used in the production of chlorine:

1. the Diaphragm Cell Process,
2. the Mercury Cell Process, and
3. the Membrane Cell Process.

In each process, a salt solution is electrolyzed by the action of direct electric current that converts chloride ions to elemental chlorine. The overall process reaction is:

In all 3 methods, the chlorine (Cl₂) is produced at the positive electrode (anode) and the caustic soda (NaOH) and hydrogen (H₂) are produced, directly or indirectly, at the negative electrode (cathode). The three processes differ in the method by which the anode products are kept separate from the cathode products.

Source:  EPA, Chlor-Alkali