Cation Exchange Membranes for the Chlor-Alkali Membrane Process

2 Cation Exchange Membranes for the Chlor-Alkali Membrane Process 

Hydrophilic treatment of the surfaces of a cation exchange membrane is essential to decrease the voltage drop between electrodes during electrolysis. Such treatments involve coating with inorganic materials, e.g., metal oxides (zirconium 

The concentration of sodium hydroxide at the cathode surface is higher than that of the bulk solution in electrolysis of sodium chloride because 1 mol of water decomposes at the cathode surface per Faraday. When the solution at the cathode surface is separated from the bulk solution with a suitable separator, sodium hydroxide of higher concentration can be obtained from the cathode surface.171 The concentration of caustic soda produced from an electrolyzer is generally about 32-35%, of which 42-54% is directly and economically produced from an electrolyzer by forming a specific, thin membrane layer on the cathode side of the membrane.172 The current efficiency for caustic soda production is more than 95% in commercial production. 

---