Electrodialysis is now a mature technology, with Ionics remaining the worldwide industry leader except in Japan. Desalting of brackish water and the production of boiler feed water and industrial process water were the main applications until the 1990s, but electrodialysis has since lost market share due to stiff competition from improved reverse osmosis membranes. Beginning in the 1990s,electrodeionization, a combination process using electrodialysis and ion exchange, began to be used to achieve very good salt removal in ultrapure water plants. This is now a major use of electrodialysis. Other important applications are control of ionic impurities from industrial effluent streams, water softening and desalting certain foods, particularly milk whey [10,11]. Over the last 20 years a number of other uses of ion exchange membranes have been found. Perhaps the most important is the development by Asahi, Dow and DuPont of perfluoro-based ion exchange membranes with exceptional chemical stability for membrane chloralkali cells [12]. More than 1 million square meters of these membranes have been installed. Ion exchange membranes are also finding an increasing market in electrolysis processes of all types. One application that has received a great deal of attention is the use of bipolar membranes to produce acids and alkalis by electrolysis of salts. Bipolar membranes are laminates of anionic and cationicmembranes. The first practical bipolar membranes were developed by K.J. Liu and others at Allied Chemicals in about 1977 [13]; they were later employed in Allied’s Aquatech acid/base production process [14]. A final, growing use of ion exchange membranes is in advanced fuel cells and battery systems in which the membranes regulate ion transport from various compartments in the cells [15]. A time line illustrating the major milestones in the development of ion exchangemembranes is shown in Figure 10.3.
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