Almost all of the flakes are produced by electrolysis of sodium chloride solution using one of three elements: mercury, diaphragm, and membrane cells.
Caustic Soda Production Methods: Mercury Method
In the mercury method, sodium is discharged as amalgam ions of sodium mercury and chloride as chlorine. The amalgam is transferred to a completely separate chamber, where it reacts with water. Finally, a solution of sodium hydroxide and hydrogen gas is produced. In the diaphragm flake production method, which is usually produced with asbestos flakes, the water stream transports the salt from the anode to the cathode and separates the chlorine and hydrogen gas space. By depleting the hydrogen ions, the hydroxide ions are collected in the cathode chamber with aqueous sodium ions and sodium hydroxide is produced. The velocity of the liquid flowing from one part to another prevents the return of hydroxide ions from the cathode to the anode. The chlorine formed in the anodes increases through the brine to the space created by the cell lining.
Caustic Soda Production Methods: Membrane Method
In the membrane production process, the ion exchange of the membrane acts as a barrier to liquid and gas flows, allowing only sodium ions to pass through the components. Sodium ions are hydrated to release sodium hydroxide at the cathode and release chlorine gas at the anode. This membrane is a complex of tetrafluoride and ethylene or fluorinated monomer. Mercury cells are cheaper to use than diaphragm cells when electricity costs are low and production of a product with a specific concentration and high purity is required, but Mercury must be separated from its waste diffuser.
Caustic Soda Production Methods: Cell Diaphragm Method
The diaphragm cell method produces flake soda, a salt-soaked in a chamber containing a titanium anode coated with ruthenium particles and other metals. In the anode process, the heat and chlorine gas of the liquid produced is absorbed through the plastic cap and the chlorine is sucked in by the compressor. Finally, the unreacted water and salt are transferred to the cathode chamber through the diaphragm separating holes, where the water reacts with the steel cathode. As a result, lye soda (caustic soda) and hydrogen are produced. Not to mention the diaphragm retains the chlorine produced by the anode and the hydrogen produced by the cathode.