Electrodialysis chlor-alkali process

Ion-exchange membranes are currently used not only for more or less conventional separation processes like membrane electrolysis (mainly the chlor-alkali process), electrodialysis, dialysis or electro-ultrafiltration (cf. Table 2.1), but also in various... 

As membranes employed in the chlor-alkali industry are generally of the non-crosslinked type, their properties are influenced significantly by the conditions in which they are utilized. The extreme temperature, concentration and current density to which they are subjected in the chlor-alkali process are not encountered in other applications such as electrodialysis. Clarification of the membrane properties is therefore both practically necessary and theoretically interesting, and application of ion cluster theory has been attempted (42, 43). 

The effect of the cost of the ion exchange membrane on the total cost of electrodialysis or electrolysis is large because the membrane is relatively expensive. The lifetime of the membrane depends on the purpose and conditions of electrodialysis or electrolysis. A membrane for the electrodialytic concentration of seawater to produce sodium chloride has a lifetime of over 10 years, and that in the chlor-alkali membrane process, which is operated at ten times or more higher current density than that of seawater concentration, is over 5 years. However, in applications for food industries, the lifetime of the membrane is relatively short due to periodical sanitary cleaning of the electrodialyzer by acid or alkali solution, and sometimes oxidizing agents. 

Bipolar cell configurations have been examined and are used in various electrochemical operations which include fuel cells [9,10], batteries [11-20], electrochemical capacitors [21], chlorate and chlor-alkali cells [22-27], electrowinning of metals [28-30], fused salt electrolysis of A1 and Mg [31-36], electrodialysis [37], and electroorganic processes [38]. 

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