Alkaline Hydrothermal Synthesis of Zeolite from Class F Coal Fly Ash

Coal Fly ash is an industrial waste produced from coal-based thermal power plants. Of the total amount of fly ash generated, a small fraction is used as a supplement to Portland cement and rest of the fly ash is used as landfill. One of the novel ways of utilizing coal fly ash is through zeolitization, zeolites being hydrated aluminosilicates, and coal fly ash a rich source of alumina and silica. Coal fly ash obtained from the thermal power plant of NTPC Kaniha is subjected to alkaline hydrothermal treatment and the resulted zeolite is characterized for chemical analysis, crystal structure, thermal stability, FTIR studies, ion exchange capacities, etc. After zeolitization surface area of the product increases due to the formation of more pores and channels and also there is an increase in its crystallinity. When subjected to temperature its crystallinity first increases and then decreases and after a particular temperature the crystalline character almost vanishes. The resulted zeolite is found to be NaP1 zeolite with a high ion exchange capacity. High cation exchange (CEC) values ensure the adsorption of heavy metals by zeolites which can be used for the treatment of wastewater and industrial waste material. Thus zeolites can be hydrothermally synthesized from an industrial waste like coal fly ash at a much cheaper cost of production. The synthesized zeolite can be used for cation exchange, adsorption catalysis, and a host of other industrial applications.