Ion exchange selectivities of crystalline antimonic acid

Crystalline antimonic acid (C-SbA) showed an unique selectivity for microamounts of metal ions in nitric acid media. The ion-exchange isotherms of the systems of various metal ions/hydrogen ions have been studied on C-SbA. S-shaped isotherms were observed for most of the metal ions, indicating selectivity reversal. Kielland plots were close to straight lines with slopes correlated to the crystal ionic radii of the metal ions exchanged. In order to interpret the selectivities a hypothetical equilibrium constant was determined by extrapolating to zero loading of metal ions in C-SbA. From these values, thermodynamic data was calculated and evaluated. (author)