Two different microporous Na-titanosilicates with high cation exchange capacities were synthesized and characterized by X-ray diffraction, scanning electron microscopy (SEM) and solid-state Si-29 and Al-27 magic-angle spinning nuclear magnetic resonance (MASNMR) spectroscopy. The ion exchange properties of Na-ETS-4 (ETS = Engelhard TitanoSilicate) and Na-titanosilicate were investigated for Sr2+ and Ba2+ using isotherms and Kielland plots in order to check the potential for the decontamination of Sr-90 and Ba-133 from nuclear waste solutions. Na-ETS-4 and Na-titanosilicate show high affinity for Sr2+ to high equivalent fraction of Sr2+ on solid phase. In case of Ba2+ the selectivity coefficient of both titanosilicate exchangers rapidly decreased due to the steric hindrance at exchange sites at (X) over bar (Ba) > similar to 0.5. However, Na-ETS-4 was still selective for Ba2+ even after the above rapid decrease in selectivity, unlike Na-titanosilicate. Therefore, Na-ETS-4 is one of the best candidates for the removal of both Sr2+ and Ba2+ from nuclear waste solutions. (C) 2012 Elsevier B.V. All rights reserved.