Coal fly ash (CFA), a significant byproduct of coal-fired power plants, is a rich source of valuable metal ions, such as nickel, cobalt, and iron. These metals are critical for various industrial and technological applications, including energy storage, catalysis, and alloy production. The current study focuses on optimizing the leaching process followed by characterization using UV-Vis spectroscopy for metal ions extraction from CFA. The acid digestion process involved treating CFA with concentrated acids, such as sulfuric acid and hydrochloric acid, under controlled conditions of temperature and reaction time to break down the matrix and release metal ions. Subsequently, the leaching process was performed, with parameters such asControlled temperature, leaching time, solid-to-liquid ratio, and acid concentration using acid-based leaching reagents, which included sulfuric acid and hydrochloric acid. Systematic process parameter optimization aimed to maximize recovery efficiency and minimize environmental as well as economic costs. The leachates were analyzed by UV-Vis spectroscopy, a sensitive and reliable method for identifying and quantifying metal ions through their characteristic absorbance peaks. Standard calibration curves for nickel, cobalt, and iron were established, thus allowing the concentration of each of these species in the extracted solutions to be determined with precision. In addition, the formation of metal-ligand complexes during leaching was examined to understand the chemistry of the extraction process.Recovered metals have good usage opportunities. Nickel and cobalt have a crucial role in making nickel-cadmium rechargeable batteries, widely used lithium ion batteries used in electric vehicles and portable electronic products, and the iron may find its use in steel and precursors to catalytic or magnetic materials. This work thus demonstrates the potential of coal fly ash as a secondary resource for these critical metals, contributing to the sustainability of resources and to reducing the environmental burden associated with the disposal of CFA. The integration of efficient leaching techniques with spectroscopic characterization will provide a pathway toward integrating waste valorization into a circular economy framework that addresses both environmental and industrial challenges while supporting the growth in demand for renewable energy technologies and advanced materials.
December 28, 2025