About 10 years ago, a crystalline silicotitanate (CST) was synthesized using an alkali metal hydroxide and the alkoxides of titanium and silicon. TAM5 is a specific form of the developed CST. Later, TAM5 was modified by replacing about 25% of the titanium with niobium. The modified TAM5 was tested extensively to enable its use as an inorganic ion exchanger for the removal of radioisotopes, especially Cs-137 from highly alkaline nuclear waste solutions. IONSIV IE 911 is a granular form of modified TAM5 that is commercially available from UOP, LLC and was tested successfully at a pilot plant at Oak Ridge National Laboratory. In separate experiments, the degeneration of hydrogen peroxide was used to generate gas in situ to determine the effect of gas production on the column performance. These experiments led to experiments to determine the effect, if any, of hydrogen peroxide on the cesium partition coefficient (Cs K-d) and the CST structure. CST was equilibrated with alkaline nuclear waste simulants containing varying amounts of hydrogen peroxide (from trace to 1 M). The Cs loading on the CST was determined by atomic absorption (AA) spectroscopy. The dissolution of elements from CST to simulant was determined by inductively coupled argon plasma spectrometry. Powder X-ray diffraction spectrometry was used to determine the crystal structures in the CST. At trace levels, hydrogen peroxide does not have a significant effect on the Cs K-d or the CST structure. At higher concentrations (1 M or higher), the Cs Kd drops and the tetragonal phase, the major component of the CST, slowly dissolves into the simulant. Furthermore, the XRD pattern changes, indicating the dissolution of the tetragonal crystal structure, which is the phase in TAM5 that is selective for cesium.