Performance of the Electrochemical Bunsen Reaction Using Two Different Proton Exchange Membranes in the Sulfur-Iodine Cycle

The application of an electrochemical cell to the Bunsen reaction has been proposed as a promising way to reduce the excess of iodine, due to the separation of H2SO4 and HI solution by a proton exchange membrane. Apart from the desired proton transfers from anolyte to catholyte, other unexpected solutes can pass through the membrane as well, leading to the cross-contamination between the two acid solutions. The permeation of HI from catholyte to anolyte and H2SO4 from anolyte to catholyte using Nafion 115 was measured as the current density, temperature, flow rate, H2SO4 concentration, HI concentration, and I-2/HI molar ratio changed. The concentration of contaminants in the anolyte was 2-10 times higher than that in the catholyte. The molality of two acids after electrolysis and the electric energy consumption using Nafion 115 and Nation 117 were compared. Nafion 115 was better for concentration of HI at most conditions, while a higher H2SO4 concentration was obtained using Nafion 117. The energy consumption using Nafion 115 was almost lower than that using Nation 117 excluding some conditions, so a suitable proton exchange membrane should be adopted according to the operating parameters.