The immobilization of crown ethers (dibenzo-18-crown-6, dibenzo-21-crown-7, dibenzo-24-crown-8) during the sol-gel synthesis of mixed oxides SiO-TiO enabled the preparation of composites that strongly retain the organic molecule within the inorganic matrix, as confirmed by IR spectroscopy and elemental analysis. The sorption properties toward rare earth element (REE) cations were studied under acidic and neutral conditions. Transitioning from the original oxides and crown ethers to their composites significantly increased both the sorption efficiency (S, %) and the sorption capacity (Q, mg/g). For the dibenzo-18-crown-6-SiO-TiO composite, the sorption efficiency of REE cations from dilute solutions (2×10 mol/dm) reached 89.1–95.1%, and the sorption capacity from concentrated REE solutions (0.1 mol/dm) was 6.1–34.5 mg/g. The sorption process of lanthanum cations by the dibenzo-18-crown-6-SiO-TiO composite was analyzed using Langmuir (R = 0.9915), Freundlich (R = 0.8745), Temkin (R = 0.9506), and Dubinin-Radushkevich (R = 0.9754) isotherm models.
Yu.V. Rekh (Wed,) studied this question.