Selective and rapid capture of Sr2+ with LTA zeolites: Effect of crystal sizes and mesoporosity

Abstract

Zeolite LTA (Linde Type A) is a highly aluminous material (Si/Al = 1) that can be utilized for the removal of cationic radioactive element such as Sr2+ (the homologues of 90Sr radionuclide) via the electrostatic interaction. Herein, a series of microporous LTA zeolites with controlled crystal sizes in a high uniformity was prepared for investigation of adsorption kinetics for Sr2+ from seawater. Solely microporous LTA zeolites of various crystal sizes with 100 nm, 500 nm, and 2 µm were prepared by control of various synthetic parameters, and LTA zeolite having mesoporous structure with crystal size of 2 µm was also synthesized with an organosilane surfactant as the mesopore generating agent. The adsorption study for Sr2+ from seawater using the LTA zeolites demonstrated that the different crystal size and mesoporosity gave a prominent influence on the adsorption performances that were compared numerically with the Lagergren 1st- and 2nd-order kinetic models. The resultant kinetic parameters revealed that the Sr2+ adsorption kinetics followed 2nd-order model more preferentially than 1st-order one. Depending on the crystal sizes, the adsorption rate constant can be changed from 0.002 g mg−1 min−1 for the LTA with the largest size to 0.016 g mg−1 min−1 for the mesoporous LTA zeolite at 20 °C.