The ion-exchange properties of the titanium silicate, M Ti O SiO ? nH O (M 5 H,Na), towards alkali ions has been 2 2 3 4 2 examined. Potentiometric titration of the highly crystalline phase in the proton form, H Ti O (SiO ) ? 1.6H O, showed a 2 2 3 4 2
dependency of the exchange on the size and charge of the ion and the pH of the solution. It was found that the accessability of three different ion-exchange sites in the titanium silicate framework controls the uptake of ions: 100% of the total amount of the ion-exchange sites could be occupied at pH 12.5 by sodium and lithium ions, about 75% by potassium and rubidium ions and only 25% by cesium ion. The ion-exchange isotherms of alkali metal ions were determined and the corrected selectivity coefficients as a function of metal loading were analyzed. Sodium titanium silicate exhibits a high affinity for
heavy alkali metals with the selectivity order Cs . Rb . K . By studying the cesium and strontium uptake in the presence of NaNO , CaCl , NaOH, NaOH 1 KOH, and HNO (in the range of 0.01-6 M) the titanium silicate was found to 3 2 3 1 be an efficient Cs ion exchanger in acid, neutral and alkaline media, which makes it promising for treatment of different types of nuclear waste and contaminated environmental and biological liquors.