Electro-electrodialysis of hydriodic acid in the presence of iodine at elevated temperature

Electrolysis of hydriodic acid with HI molality of ca. 10 mol/kg was examined in the presence of iodine using a commercial cation-exchange membrane, CMH, as the separator. Redox reaction of iodine–iodide ions that occurred at the glassy carbon electrodes, the selective proton permeation and the relatively low water permeation through the membrane enabled the increase of HI molality in the catholyte by sacrifice of HI in the anolyte even at the temperature of 80°C. Effects of temperature and iodine molality on the membrane properties such as proton transport number and electroosmosis coefficient were clarified in the ranges of 15–80°C and 4–15 mol/kg, respectively. The effects on the electric resistance of test cell were also determined. Carbon cloth was effective in reducing the cell resistance.