Selective removal of Cs-137 and Sr-90 from aqueous environments is essential for the volume reduction and ultimate safe storage of nuclear waste. This study introduces a facile one-pot hydrothermal synthesis of Dual-cation form of TitanoSilicate (DTS, M3HTi4O4(SiO4)(3), M = Na+ and K+) for the effective and simultaneous removal of Cs+ and Sr2+. DTS showed enhanced adsorption capacities (469 mg/g for Cs+ and 179 mg/g for Sr2+) and the adsorption kinetics were extremely fast with around 98% and > 99% removal achieved within 1 min from a dilute Cs+ and Sr2+ solution, respectively. Moreover, DTS indicated the superior selectivity for both Cs+ and Sr2+ due to the dual-cation incorporation in the structure. In groundwater, the distribution coefficients (K-d at V/ m = 1000 mL/g) for DTS were high for both Cs+ (1 ppm, 2.9 x 10(5) mL/g) and Sr2+ (1 ppm, 1.0 x 10(5) mL/g), and even in seawater DTS maintained a Cs+ (1 ppm) K-d value as high as 4.9 x 10(4) mL/g. Remarkably, DTS is synthesized as a membrane with graphene oxide for continuous removal of the radionuclides, which is extremely beneficial to purifying a large volume of contaminated water.