Surface Modification of Fly Ash by Thermal Activation: A DR/FTIR Study

To acquire a deeper understanding of surface chemistry of fly ash along with thermal activation, the states of mineral phases, water and –OH groups on silica are studied in fly ash at different calcination temperatures by DR/FTIR spectroscopic technique. DR/FTIR spectroscopy allows differentiation of various types of bonds in a material on a molecular level. The spectroscopic results are also supported by XRF, XRD and SEM analysis. Studied fly ash was collected from Jamshedpur Thermal Power Station as an extremely fine ash, formed from the inorganic components of the coal, mainly silica and alumina which remain after combustion of the carbonaceous part of the coal. Distinguish changes were observed in fly ash IR bands regarding absorbed water, -OH group and Si-O-Si group with thermal activation. This investigation reveals that as the temperature increases, the physically adsorbed water begins to remove first, then silanol groups on surface is dehydrated. Increased temperature causes formation of different crystalline phases like quartz, mullite and hematite etc. and increased the crystallinity of the calcined samples.