Sodium titanium germanate with a semicrystalline framework (STG) of the formula Na3H(TiO)3(GeO)(GeO4)3·7H2O was synthesized under mild hydrothermal conditions and its proton form, H4(TiO)3(GeO)(GeO4)3·8H2O (STG-H), was prepared by acid treatment of the sodium compound. The STG was characterized by elemental analysis, TGA, FT-IR,
and X-ray powder diffraction. A comparative ion exchange examination of the STG-H towards alkali and alkaline earth metals
in a broad pH and concentration range was carried out. It was found that the STG is a moderately weak cation exchanger, possessing
high ion exchange capacity (up to 4.0 meq/g) and showing preference for heavy alkali and alkaline earth metals. The STG selectivity
towards Cs+ and Sr2+ ions in the presence of competitive metal ions and certain organic compounds was also studied. The data obtained suggest
that the sodium titanium germanate is a more selective exchanger for Sr2+ ion than its titanium silicate analogue, K3H(TiO)4(SiO4)3·4H2O.