Comparable study of vermiculites from four commercial deposits prepared with fixed ceria nanoparticles

Abstract

Four commercial macroscopic vermiculites (Ver) from different exploited deposits were investigated regarding their chemistry and structural transformation stage from mica (phlogopite), and compared with selected raw vermiculites and "hydrobioties" known from literature, in which the chemical analyzes verified the existence of iron as Fe3+ and Fe2+. Subsequently prepared vermiculite/ceria (Ver/CeO2) nanoparticles composites were compared from the point of view of the fixation of ceria nanoparticles by using stability test and regarding their photocatalytic activity in the decomposition of N2O. The experimental methods used for these studies were X-ray fluorescence spectrometry, atomic emission spectrometry, X-ray powder diffraction, infrared (FR-IR) and Raman spectroscopy and transmission electron microscopy with high resolution (HRTEM). Negative layer charge of vermiculites produced by the local charge balance and distribution of Fe3+ in tetrahedral and octahedral sheets were related to the CeO2 nanocrystals fixation and orientation. Among the four Ver/CeO2 nanoparticles composite samples, the vermiculite in sample Ver-C/CeO2 exhibited the highest negative layer charge. The CeO2 crystallites were the smallest among all four samples. HRTEM found separated CeO2 nanocrystallites and CeO2 agglomerates of differently oriented nanocrystallites. Such forms of CeO2 nanocrystals influenced the position of the Raman CeO2 F-28 and suppressed ability for photocatalytic N2O conversion.