Sol-gel hydrothermal synthesis of nano crystalline silicotitanate and its strontium and cesium adsorption.

Crystalline silicotitanate (CST) was synthesized via a sol-gel hydrothermal method using NaSiO·9HO and TiCl as silicon and titanium sources. The effects of pH, silicon concentration, hydrothermal temperature, and time on the CST synthesis were studied at a fixed molar ratio of silicon:titanium (0.98:1). Pure nano-CST crystals were synthesized at pH = 12.5, silicon concentration of 5 g L, 170 °C for 7 days. The average CST particle size was < 100 nm, with a Sr/Cs distribution coefficient up to 1.9 × 10 mL g/9.4 × 10 mL g under the optimum conditions. In addition, nano-CST absorbed Sr/Cs over a wide pH range. The nano-CST also displayed a much faster equilibrium time, 4 h, as compared with previous studies. Furthermore, nano-CST adsorption of Sr/Cs followed a Langmuir adsorption model and was consistent with pseudo-second-order kinetics.