A review on the formation, recovery, and properties of coal fly ash (CFA)-derived microspheres for sustainable technologies and biomedical applications

Coal fly ash (CFA), a by-product of coal combustion in thermal power plant (TPP), is an environmental concern due to its massive production and improper disposal. Among its components, microspheres like cenospheres (CS), plerospheres (PS), and ferrospheres (FS) hold significant industrial value. CS are lightweight, hollow particles with unique properties such as low density, high mechanical strength, and thermal stability, making them suitable for composites, ceramics, and insulation. PS, with their porous structures, are useful in construction and ceramics, while FS, rich in iron, are applied in catalysis and magnetic materials. Additionally, CFA-derived microspheres, such as CS and FS, exhibit promising potential in biomedical applications due to their unique structural and chemical features. Their suitability for drug delivery, tissue engineering, and diagnostic tools highlights their emerging role in sustainable healthcare solutions. This review focuses on the formation, recovery, and properties of these microspheres, highlighting their sustainable applications in lightweight composites, environmental clean-up, and advanced materials. Various recovery methods, including wet and dry techniques, are discussed to optimize extraction processes. The study emphasizes the potential of these microspheres in reducing CFA waste while supporting innovative and eco-friendly technologies. This work contributes to developing sustainable solutions for managing CFA, with the goal of reducing environmental impacts and enhancing industrial utility, particularly in sustainable and biomedical applications.