Radiation-grafted PVDF anion exchange membrane for salt splitting

Poly(vinylidenefluoride) (PVDF) was radiation grafted using vinylbenzyl chloride (VBC) followed by amination with trimethylamine to yield a VBC-grafted PVDF anion-exchange membrane. Evaluation of the electrochemical characteristics of the anionic membrane is obtained from the electrohydrolysis of sodium sulphate in a two-compartment electrolysis cell. The influence of different experimental conditions on the behaviour of the new material is described. The electrochemical performance was characterised in terms of current efficiencies and transport properties. The results revealed that flow-rate had small influence on current efficiency, while higher current densities and salt concentrations significantly affected current utilisation and productivity. The PVDF material showed high selectivity, low electrical resistance and good chemical and mechanical stability, although lower current efficiencies compared to a commercial anion-exchange membrane were obtained. A comparison against salt splitting with cationic PVDF membranes demonstrated, despite the lower energy requirements, an inferior performance of the anion-exchange material, in terms of current utilisation. An empirical model balancing the transport of ions across the anion-exchange membrane gave adequate prediction of the amount of sulphuric acid formed.