Chloralkali process

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A chloralkali process is any which produces chlorine or a related oxidizer, such as bleaching powder and an alkaline salt such as sodium hydroxide or sodium carbonate.

Electrolysis of an aqueous solution of sodium chloride produces chlorine and sodium hydroxide: 2 NaCl_(aq) + 2 H₂O_(l) —→ 2 NaOH_(aq) + Cl_2(g) + 2 H⁺ + 2 e^-; 2 H⁺ + 2 e^- —→ H_{2 (g)}.

In the membrane cell, the anode and cathode are separated by an ion-permeable membrane. Saturated brine is fed to the compartment with the anode (the anolyte). A DC current is passed through the cell and the NaCl splits into its constituent components. The membrane passes Na+ ions to the cathode compartment (catholyte), where it forms sodium hydroxide in solution. The chloride ions are oxidised to chlorine gas at the anode, which is collected, purified and stored. Hydrogen gas and Hydroxide ions are formed at the cathode.