Preparation and characterization of nickel hexacyanoferrate films for the removal of cesium ion by electrically switched ion exchange (ESIX)

The method of electrically switched ion exchange (ESIX) involves the sequential application of reduction and oxidation potentials to an ion exchange film to induce the respective loading and unloading of Cs+. In this study, four films of nickel hexacyanoferrate were prepared on nickel electrodes with different preparation procedures. Films were characterized by SEM/EDX. Each film shows a different performance with regard to Cs+ separation. Scanning electron microscopy was used to characterize the modified film surfaces. Cyclic voltammetry was used to investigate the ion exchange capacity and stability. The four films show a better capacity for Cs+ separation compared to previous methods for the deposition of ESIX films. An optimal nickel hexacyanoferrate film was generated when using an applied potential of 0.2 V relative to a saturated calomel electrode (SCE) to generate the nucleation sites, followed by a 1.3 V vs. SCE potential during the growth stage of the film. This film demonstrated the highest film capacity for ion exchange initially (17.3 × 10−3 C cm−2) and again after 1000 cycles (11.1 × 10−3 C cm−2).