Morphology and composition of microspheres in fly ash from the luohuang power plant, Chongqing, Southwestern China

Abstract

In order to effectively raise both utilization rate and additional value of fly ash, X-Ray diffraction (XRD), scanning electron microscope (SEM) and energy-dispersive X-Ray spectrometer (EDS) were used to investigate the morphology, and chemical and mineral composition of the microspheres in fly ash from the Luohuang coal-fired power plant, Chongqing, southwestern China. The majority of fly ash particles are various types of microspheres, including porous microsphere, plerospheres (hollow microspheres surrounding sub-microspheres or mineral fragments) and magnetic ferrospheres. Maghemite (γ-Fe2O3) crystals with spinel octahedron structure regularly distribute on the surfaces of ferrospheres, which explained the source of their strong magnetism that would facilitate the separation and classification of these magnetic ferrospheres from the fly ash. Microspheres in Luohuang fly ash generally are characterized by an elemental transition through their cross-section: the inner layer consists of Si and O; the chemical component of the middle layer is Si, Al, Fe, Ti, Ca and O; and the Fe-O mass (maghemite or hematite) composes the outer layer (ferrosphere). Studies on composition and morphological characteristics of microspheres in fly ash would provide important information on the utilization of fly ash, especially in the field of materials.