Microstructural and Mineralogical Properties of Acid and Alkali Activated Coal Fly Ash

Abstract

Fly ash (FA), a coal combustion residue of thermal power plants has been regarded as a problematic solid waste all over the world. In this study FA samples were modified with NaOH and H2SO4. The mineralogical and microstructural characterization were carried out by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS) and Braunauer-Emmett-Tellers multilayer adsorption theory (BET). Experimental data showed that cenospheres were dominated with quartz and mullite glasses with both amorphous and crystalline phases. The acid treatment increased Si/Al ratios by removing impurities and dealuminations but alkali treatment significantly increased total pore volume. The specific surface area of alkali and acid treated samples were found 6.9 m2g-1 and 2.1 m2g-1 respectively, while that of virgin material was 1.5 m2g-1.