Enhancement of acidic-basic properties of silica by modification with CeO2-Fe2O3 nanoparticles via successive ionic layer deposition

Abstract

α-CeO2 and α-Fe2O3 nanocrystals were successfully synthesized by successive ionic layer deposition (SILD). The size of the prepared nanocrystals of α-CeO2 and α-Fe2O3 is 6–8 nm and 13–14 nm, correspondingly. The developed method was used to modify silica gel. The obtained samples were characterized by EDX, SEM, TEM-ED, PXRD; and N2 adsorption-desorption analysis and analysis of acid-base properties were made. There was established that the silica gel modification with 4.1 mass % of α-CeO2 and α-Fe2O3 nanocrystals lead to increase of acidic/basic sites in 6.6 and 13.6 times, correspondingly, while maintaining the surface area of modified silica about 311 m2/g and almost unchanged pore structure. It was shown that α-CeO2 and α-Fe2O3 nanocrystals forming by SILD modification of silica gel are mainly found in the micropores and mesopores and define the phenomenon of the increase of active sites concentration in the prepared composite. The resulting materials can be used as the basis for promising acid-base catalysts and sorbents of toxic heavy metal cations and oxyanions.