Particle Size Distribution and Elemental Composition of Fine Magnetic Microspheres from Lignite-Derived Fly Ash

Coal combustion in thermal power plants generates large quantities of fly ash (CFA), whose utilization remains limited because of considerable variability in particle size, chemical composition, and phase distribution. Since the size and composition of CFA particles largely determine their application potential, a promising strategy involves recovering microspherical fractions within a defined size range, whose compositional stabilization is achieved during high-temperature combustion. Special attention must be directed toward environmentally hazardous fine particles smaller than 10 µm, including PM10 magnetic microspheres, which pose a significant risk to human health. This study focuses primarily on the particle size distribution and elemental composition of fine magnetic microspheres isolated from CFA generated by lignite combustion. A total of 596 microspheres in the magnetic fraction, with an average diameter of 6.7 µm, were analyzed. The majority of the microspheres fell within the 2.5–5.0 µm range, accounting for 37% of the total. Their morphological diversity—including smooth spheres, porous particles, globules with surface features, and smoothed polyhedral forms—was accompanied by substantial compositional variability. Regression analysis revealed strong correlations between the FeO and CaO content, which are specific to this lignite ash sample and may serve as a preliminary reference for the development of functional magnetic materials made from CFA.