Preparation of nanostructured hydrated antimony oxide using a sol-gel process. Characterization and applications for sorption of La³⁺ and Sm³⁺ from aqueous solutions

Abstract

The study focused mainly on the synthesis of nanosized hydrated antimony oxide as an ion exchange material via sol-gel process using water as a reagent to control the pH and to obtain a pure and dense hydrated antimony oxide. The obtained antimony oxide was characterized using X-ray diffractometer, scanning electron microscope, TG-DTA, and fourier transform infrared spectroscopy. The result showed the formation of stibiconite with a cubic crystal structure in nanometric range (9.54 nm). FTIR study confirmed the formation of antimony oxide with characteristic bands at about 766 and 552 cm^–1 attributed to Sb–O streatching modes of Sb–O–Sb and Sb–OH, respectively. The synthesized hydrated antimony oxide demonstrated monofunctional ion-exchange characteristic and reasonably good chemical stability in acidic and basic media. The synthesized ion exchanger was then used for the removal of lanthanum(III) and samarium(III) from aqueous solutions. As can be seen from distribution studies the distribution coefficient K _d increased with increasing the reaction temperatures of the solution. Adsorption experiments were carried out using both batch and column systems. The Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) equilibrium models were used and a value q _max was 41.10 and 48.42 mg g^–1 for La(III) and Sm(III), respectively. Thermodynamic parameters, ΔH°, ΔG°, and ΔS° were calculated and indicated an endothermic and spontaneous process.