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 Na2Si2O3·9H2O and TiCl4 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−1, 170 °C for 7 days. The average CST particle size was < 100 nm, with a Sr2+/Cs+ distribution coefficient up to 1.9 × 106 mL g−1/9.4 × 103 mL g−1 under the optimum conditions. In addition, nano-CST absorbed Sr2+/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 Sr2+/Cs+ followed a Langmuir adsorption model and was consistent with pseudo-second-order kinetics.