Abstract
This review article presents trends and prospects of membrane separation processed using ion–exchange membranes in water treatment and energy conversion processes. Cation–exchange membranes (CEMs) and anion–exchange membranes (AEMs) have permselectivity for counter–ions; hence, electrodialysis (ED) process using the membranes has been applied to desalination/concentration processes of salty water. A bipolar membrane composed of a cation– and an anion–exchange layer generates protons and hydroxyl ions in a case of applying voltage across the membrane, and has applied to acid regeneration etc. A charged mosaic membrane consisting of cation– and anion–exchange domains passing through the membrane has permselectivity for electrolytes; hence, it can be applied to desalination process using a piezo–dialysis system. A reverse electrodialysis system having the same structure as ED converts salinity gradient energy between two salt solutions to electric power, and is expected as a renewable energy with a high operating rate and a small footprint.
