Recovery of hollow spherical particles with two different densities from coal fly ash and their characterization

Abstract

The extraction of hollow spherical particles i.e., ‘cenosphere’ from coal fly ash and their industrial applications have been extensively increased in the recent years. The unique properties of cenospheres (e.g., light weight, high compressive strength, superior insulation, enhanced flow characteristics, less water absorption, chemical inertness, good thermal resistance, etc.) make them amenable to a wide range of industrial applications. Hollow spherical particles of different density and particle sizes are available in markets for various applications. The analysis of physical, chemical and mineralogical properties of these particles is important as these properties influence the quality of a product. Cenospheres of different densities vary in their physico-chemico-mineralogical properties. In the present study, distilled water is used as the medium for extracting light weight particles from fly ash i.e., floaters or cenosphere of density less than 1.0g/cc; while Lithium Metatungstate (LMT) solution of density 1.5g/cc is used as the medium for extracting floaters or cenosphere of density greater than 1.0g/cc and less than 1.5g/cc. The Scanning Electron Microscope–Energy Dispersive Spectroscopy (SEM–EDS) and X-ray Diffraction (XRD) has been used for the analysis of physical, chemical and mineralogical properties of floaters or cenospheres. The results show that percentage of hollow spherical particles or cenosphere is much more with densities between 1.0 and 1.5g/cc as compared to the cenosphere having densities less than 1.0g/cc. The particle sizes of the cenospheres of two different densities were similar but the average shell thickness of density 1.282g/cc was little higher as compared to density 0.857g/cc.