2 - Functionalization of fly ash

Abstract

Fly ash, an inexpensive and abundant residue, generated from the combustion of coals in coal-fired thermal power plants, is a recognized environmental pollutant owing to its entourage of constituents, which apart from comprising oxides of iron, silicon, aluminum, and many more vital components, also consist of heavy metal compounds such as mercury, arsenic, lead. etc., posing a serious threat to human health as well as proving to be equally dangerous to land and aquatic animals when these ashes are dumped in ash ponds and landfills covering a large area of land. Large amounts of coal fly ash are produced globally and with this increasing amount, the threat to the environment also increases. So, its effective utilization is a necessity to curb its wastage. Apart from using fly ash in construction applications, its use as a filler in composites is growing day by day. Surface modification of fly ash is a necessity in order to develop a synergy between matrix and filler to achieve high performance for desired applications. Various methods of functionalization, such as isothermal heating, surface modification by planetary ball milling, mechanochemical activation of fly ash, and surface functionalization by chemical treatment have been explored in this chapter. Surface functionalization by ball milling leads to a reduction of the particle size from micro to nano and thus increases the surface area and bonding affinity with the matrix material. Fly ash has also proved its utility as an adsorbent for the removal of organic pollutants from wastewater as well as in coating applications.