Membrane performance on electro-electrodialysis of HI-I-HO mixture for IS process

Tanaka, Nobuyuki ; Yamaki, Tetsuya; Asano, Masaharu; Terai, Takayuki*; Onuki, Kaoru

Research and development of a water-splitting hydrogen-production method, called iodine-sulfur (IS) process, has been conducting as one of the heat applications of high temperature gas-cooled reactor. Among the unit operations in this IS process, we have investigated electro-electrodialysis (EED) using an ion-exchange membrane to concentrate HI in an HI-I-HO mixture. Aiming at maximizing EED performance, new membrane materials were prepared by the radiation-induced graft polymerization and were examined in terms of their proton permeability through the membrane, i.e., transport number and conductivity at different iodine (I) concentrations in the HI-I-HO mixture. The transport number increased and the conductivity decreased with an increase in the feed I molality. The EED model derived by the Nernst-Planck theory suggested that this trend could be explained exclusively by the variation of diffusion coefficient of I.