Cation exchange membrane based on side chain grafted sulfonic acid with poly(vinylidene fluoride-co-hexafluoropropylene) for electro-electrodialysis of HIx mixture

Acid and oxidative resistant sulphonated copolymer cation exchange membrane (CEM) was prepared and electro-electrodialysis experiments were performed to improve HI molality in the HIx (HI + I2) mixture. Reported membrane was prepared by chemical grafting of 2-methyl-2-(N-(3-sulfopropyl)acrylamido)propane-1-sulfonic acid with dehydofluorinated poly(vinylidene fluoride-cohexafluoropropylene) in presence of radical initiator. Different CEMs were assessed by their morphology, physicochemical properties, and stabilities in compare to Nafion117 membrane. Most suitable PVSU-1.72 membrane showed superior proton conductivity (5.15 × 10−2 S/cm) and ion exchange capacity (1.72 m eq./g) values in comparison to other acid resistant membranes reported in the literature. Further, PVSU-1.72 membrane consumes low electrical power (65.5 kJ/mol) in comparison to Nafion 117 membrane (156.0 kJ/mol) during electro-electrodialysis. Also in previous case, close to 100% current efficiency (ηc and ηa) demonstrates membrane suitability. Further, PVSU-1.72 consumes about 290 kJ mol−1-H2 energy to produce 1 mol H2, while Nafion117 membrane consumes 280.80 kJ/mol-H2 energy. These observations is helpful for devising high performance electro-electrodialysis process to develop the HI concentration as H2 source.