Technology

Membrane cell technology is a reworking of the diaphragm cell method so that the diaphragm is a permselective ion-exchange membrane. This membrane
inhibits the passage of chlorine ions (negatively charged), but allows sodium ions (positively charged) to move through freely.

In this process, sodium or potassium brine is fed to the cell and distributed equally throughout the anode compartments while water flows into the cathode compartments. The electrolysis reactions in this process are the same as they are in the diaphragm cell process.

As the brine is depleted it overflows with chlorine gas into an anolyte header and the caustic soda that is produced overflows with hydrogen gas into a catholyte header.

Today’s membranes are made of a perfluorosulfonate polymer layer, a polytetrafluoroethylene (PTFE) reinforcing fabric, and a perfluorocarboxylate polymer, bonded together This combination allows for low electrical resistivity and for low caustic back migration, which ultimately creates a more efficient and productive system.

Source: Jedidiah Crook & Aliyar Mousavi (2016) The chlor-alkali process: A review of history and pollution, Environmental Forensics, 17:3, 211-217, DOI: 10.1080/15275922.2016.1177755