Diaphragm cell process
In the diaphragm cell process, the anode area is separated from the cathode area by a permeable diaphragm. The brine is introduced into the anode compartment and flows through the diaphragm into the cathode compartment.
Diluted caustic brine then leaves the cell. If needed, the caustic soda can be concentrated to 50% and have any salt removed.
This is often by using an evaporative process with about three tonnes of steam per tonne of caustic soda.
The salt separated from the caustic brine can be used to saturate diluted brine. The chlorine contains oxygen and must often be purified by liquefaction and evaporation.