Adsorption of caesium (Cs⁺) from aqueous solution by porous titanosilicate xerogels

Two types of titanosilicate (TiSi) materials were synthesized by the sol–gel method using pure and technical precursors. All samples obtained were characterized using X-ray diffraction, FTIR in the mid-region and the low-temperature nitrogen adsorption/desorption technique. The synthesized xerogels were found to be amorphous with a developed porous structure. Solution pH, sample mass, initial Cs⁺ concentration, competitive ions, contact time and temperature were studied for their influence on TiSi sorption ability. Both samples demonstrated a high capacity for caesium across a broad pH range of 2–12, and the adsorption isotherms were fitted to the Langmuir, Freundlich, Sips, Toth and Redlich–Peterson models, while the kinetic data were described using pseudo-first and pseudo-second models. All the TiSi samples were characterized by X-ray photoelectron spectroscopy and scanning electron microscopy with energy dispersive X-ray spectroscopy before and after the adsorption tests. Activated adsorption was proposed as a stage in the adsorption mechanism.