Synthesis and structure of analcime and analcime-zirconia composite derived from coal fly ash cenospheres

Abstract Cubic analcime and analcime-zirconia composite with the Si/Al ratio of 2.04 and 2.16, respectively, was synthesized by hydrothermal treatment of coal fly ash cenospheres (Si/Al = 2.7) at 150 °C. The scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), synchronous thermal analysis (STA) methods were used to study the morphology, composition and structure of the products. Two main types of analcime bearing particles were obtained, such as hollow microspheres with attached analcime icositetrahedra of 5–50 μm in size and individual analcime crystals of a narrow particle size distribution (Dm = 41 μm) with incorporated zirconia (4.8 wt% Zr). The high quality of the crystalline fractions allowed an accurate full-profile PXRD analysis of complete analcime crystal structure and composition including anisotropic displacement parameters of all atoms and H-positions of water molecules.