Hydrogenated ceria nanoparticles for high-efficiency silicate adsorption

Abstract

Ce³⁺ ions from the surface of CeO₂ nanoparticles play a key role as active sites in various chemical reactions including silicate adsorption. However, the insufficient concentration of Ce³⁺ ions at the CeO₂ surface is a limitation in the use of CeO₂ nanoparticles. In the present study, we introduce hydrogenated CeO₂ nanoparticles with plentiful Ce³⁺ concentration for high-efficiency silicate adsorption. Surface-modified CeO₂ nanoparticles were prepared using heat treatment at 800 °C for 10 hours with 10% and 20% hydrogen atmospheres to increase oxygen vacancies. During the modification process, two excess electrons from the increased oxygen vacancy formation localized the 4f-state of cerium ions, leading to a valence change in the Ce ions from Ce⁴⁺ to Ce³⁺. As a result, the concentration of Ce³⁺ ions increased by 45%, from 16.59 to 24.01%, according to hydrogen reduction. The adsorption properties of silicate ions onto hydrogenated CeO₂ surfaces were investigated through adsorption isothermal analysis. Finally, the adsorption isotherm results were fitted using the Langmuir and Freundlich equations to elucidate their improved adsorption behaviors.