TABLE OF CONTENTS Ion exchange membranes have been used in various industrial fields, and have great potential for use in new fields due to their adaptable polymer membrane. As mentioned in the Introduction, membranes are characterized mainly by ion conductivity, hydrophilicity and the existence of carriers, which originate from the ion exchange groups of the membrane. Table 6.1 shows reported examples of applications of ion exchange membranes and the membrane species used in various fields. Various driving forces are usable for separation: electrochemical potential, chemical potential, hydraulic pressure such as piezodialysis and pervaporation, temperature difference (thermo-osmosis), etc. Of these, the main applications of the membrane are to electrodialysis, diffusion dialysis, as a separator for electrolysis and a solid polymer electrolyte such as in fuel cells.
| Process | Purpose | Membrane to be used |
|---|---|---|
| Electrodialysis | Concentration or desalination of electrolyte solution, separation of non-electrolyte from electrolyte, recovery of valuable materials, continuous fermentation, electrodialytic denitration of well water, etc. | Cation and (or) anion membrane |
| Continuous electrodialytic ion exchange across the membrane | Bipolar ion exchange membrane and cation and (or) anion exchange membrane | |
| Double decomposition (AX + BY = AY + BX) | Cation and anion exchange membrane | |
| Water splitting (H 2O ? H + + OH ?) | Bipolar ion exchange membrane, and cation and (or) anion exchange membrane | |
| Electrolysis | Electro-synthesis of inorganic and organic chemicals (chlor-alkali process, organic synthesis, synthesis of developer of photo-resist, etc.) | Cation exchange membrane,... |
