Electrolysis membranes
Cells for chlorine-sodium electrolysis

Since the early 1970s, a new type of separator has been used in electrolysis: the membrane.

Unlike the diaphragm, which is porous, the membrane is, in principle, permeable only to those ions that its structure is designed to transfer. It is an ion-selective membrane. For example, for the electrolysis of NaCl solutions, fluorinated polymers grafted with sulfonic or carboxylic end groups are used, which confer cation exchange and transport properties (so-called "cationic" membranes) (see figure ).

The Na⁺ ion thus moves across the membrane under the effect of the electric field, as shown in figure .

The membrane must be chemically stable and resistant under electrolysis conditions, which is generally the case with fluorinated resins.

The membrane...