SYNTHESIS OF FAU AND CHA ZEOLITES FROM CLASS C FLY ASH

Date

2023-11-21

Author

Gölboylu, Selin Cansu

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Fly ash is a by-product generated from coal combustion in thermal power plants, and it consists of fine, powdery particles rich in various oxides, such as silica (SiO2), alumina (Al2O3), hematite (Fe2O3), and lime (CaO). Its widespread production poses significant environmental challenges due to the sheer volume generated and the potential for environmental contamination. However, fly ash also presents a valuable opportunity for resource utilization, as it contains precious components that can be harnessed for beneficial applications. One such application is the synthesis of zeolites, a class of porous materials with exceptional properties, including high surface area, tunable pore sizes, and excellent ion exchange capacity. Due to their unique properties and versatile applications, zeolites have gained immense importance in various industrial sectors, including catalysis, gas separation, and environmental remediation. This study aims to explore the potential of utilizing fly ash as a precursor for zeolite synthesis, thereby converting waste material into a valuable resource and contributing to sustainable materials for a greener future. In this study, Soma fly ash obtained from a Turkish thermal power plant was subjected to several analyses and then categorized as Class C due to its notable silica, alumina, iron, calcium, and sulfur oxide composition. To facilitate the utilization of Soma fly ash in zeolite synthesis, a crucial step, acid leaching, was determined for removing impurity phases and increasing the silicon-to-aluminum ratio (SAR). Consequently, this additional process step allowed the successful synthesis of high silica zeolites. For this purpose, various parameters, such as acid leaching conditions, gel formula, reaction temperature and time, and the type of alkaline agent, were explored to optimize the formation of zeolite frameworks. Under different synthesis conditions, different zeolite structures, including Faujasite (FAU), Chabazite (CHA), Sodalite (SOD), Gismondine (GIS), Merlinoite (MER), and Phillipsite (PHI), were obtained. The optimization of synthesis parameters was done to obtain various zeolite frameworks, each with unique properties and potential applications. Through SEM, EDX, BET, and TGA analyses, optimized zeolite samples revealed distinct structures and improved chemical compositions. SEM analysis exposed well-defined FAU, CHA, GIS, and PHI zeolites morphologies consistent with the literature. Enhanced SAR and reduced impurities upon acid leaching were evident in EDX analysis. N2 adsorption tests demonstrated mesoporous characteristics in FAU zeolite, supported by low-angle XRD results. Water sorption capacity assessments underscored that FAU-type zeolite has a higher water sorption capacity than CHA. In summary, this research contributed to the sustainable utilization of fly ash, a waste product from coal combustion, by converting it into valuable zeolite materials. These zeolites can find applications in environmental remediation, gas separation, and catalysis, offering a promising avenue for waste valorization and resource sustainability. The successful synthesis of zeolites from Soma fly ash holds promise in addressing waste management challenges and contributing to the advancement of sustainable materials for a greener future.

Subject Keywords

Fly ash, Zeolite, Acid leaching, Sustainable synthesis, Solid waste management

URI

https://hdl.handle.net/11511/106395

Collections

Graduate School of Natural and Applied Sciences, Thesis