Synthesis and thermoanalytical study of SiO2–TiO2 composites modified with macrocyclic endoreceptors

Abstract

We have developed processes for the fabrication of SiO₂–TiO₂ composites containing crown ethers (CEs) with composite: CE weight ratios from 1: 0.06 to 1: 1. As oxide sources, we used titania and silica sols. The composites were characterized by differential thermal analysis, X-ray diffraction, and adsorption gravimetry. The results demonstrate that most of the water and the solvent are bound into a complex with the CE, which decomposes at temperatures from 170 to 230°C. The temperature range of CE removal depends on the SiO₂: TiO₂ and oxide: CE ratios in the composite. Our results demonstrate effectiveness of strontium cation imprint formation in an adsorbent in the sol–gel processing step, which ensures an increase in the amount of strontium cation adsorption by 20%. We have identified conditions for quantitative lanthanum, strontium, and barium adsorption on the synthesized composites.