Heterogeneous ion-exchange membranes

Abstract

The field of heterogeneous ion exchange membranes is reviewed briefly. Specific advantages and disadvantages of heterogeneous ion exchange membranes are discussed compared with those of homogeneous ion exchange membranes. p]The development of heterogeneous ion exchange membranes is presented in historical perspective. The electrochemistry of ion-selective membranes began with Ostwald in 1890. After the classical work of Michaelis (1925) with collodion membranes, the first fully synthetic ion exchange membranes were prepared by Zhukov (1933) and Wassenegger (1940), based on sulfonated phenol—formaldehyde resins. These initial membranes, which were of the homogeneous type found no practical uses. The era of commercially useful ion exchange membranes began with the work of Wyllie (1948), Juda (1950), Bodamer (1953) and their collaborators who prepared heterogeneous ion exchange membranes by embedding ion exchange particles into polymer matrices. p]Methods for making heterogeneous ion exchange membranes include compression-molding of polymer powders, compounding on hot rolls, latex or solvent blending in situ generation of either the matrix or the ion exchange material. Microheterogeneous ion exchange membranes can be made from block and graft copolymers, interpolymers snake-cage resins, similar techniques and materials. p]Even though the first commercial ion exchange membranes were heterogeneous, the interest in this type of membranes subsided later. As polymer science progressed, speciality monomers and polymers were being made which opened the way to the preparation of quite sophisticated homogeneous ion exchange membranes of satisfactory mechanical strength. However, the possibilities of heterogeneous ion exchange membranes are by no means exhausted and this field may warrant further exploration, applying modern methods and materials and thus progressing beyond the relatively crude heterogeneous ion exchange membranes of the pioneer times.