Ion and water transport properties of cation exchange membranes prepared by heavy-ion-track grafting technique

Sawada, Shinichi*; Goto, Mitsuaki*; Koshikawa, Hiroshi*; Kitamura, Akane; Higa, Mitsuru*; Yamaki, Tetsuya*

In this study, we prepared ion exchange membranes (CEMs) by our ion-track-grafting technique and investigated their ion and water transport properties. The CEM preparation involved irradiation of ethylene-co-tetrafluoroethylene films with 310 MeV Kr beam, grafting of styrene into the resulting latent tracks, and sulfonation of styrene units. Membrane resistance was measured by an AC impedance method. Osmotic-pressure-driven water flux was measured by using a permeation cell containing two compartments filled with pure water and an aqueous 3 mol/L NaCl solution. At higher IEC, the membrane resistance decreased, while the water flux increased. Interestingly, the water flux of the ion-track-grafted CEMs is significantly lower than that of commercially products and a conventional -ray-grafted CEM. This result demonstrates a great potential for industrial electrodialysis. In conclusion, unique one dimensional ionic channels achieved by the ion-track-grafting can facilitate Na+ transport and hinder water permeation.