Ce3+-enriched core–shell ceria nanoparticles for silicate adsorption

Abstract

Ce3+ ions in ceria nanoparticles (NPs) play a role as reactive sites in the adsorption of silicate anions. However, the limited concentration of Ce3+ ions in ceria NPs remains a major challenge in this regard. Herein, we report a simple strategy to synthesize Ce3+-enriched core–shell ceria NPs for enhanced adsorption of silicate anions. To increase the overall Ce3+ concentration, a shell layer is composed of Ce3+-rich ultrasmall ceria NPs approximately 5 nm in size. The Ce3+ concentration of such core–shell ceria NPs is increased by 12.7–17.1% relative to that of the pristine ceria NPs, resulting in increased adsorption of silicate anions. The Freundlich model fits the observed adsorption isotherm well and the constants of adsorption capacity (KF) and adsorption intensity (1/ n) indicate higher adsorption affinity of the core–shell ceria NPs for silicate anions. We attribute these improvements to the increased Ce3+ concentration contributed by the ultrasmall ceria coating. This strategy can be used for enhancing the reactivity of ceria materials.