Abstract
Characterization of magnetic particulate matter (PM) in coal fly ashes is critical to assessing the health risks associated with industrial coal combustion and for future applications of fine fractions that will minimize solid waste pollution. In this study, magnetic narrow fractions of fine ferrospheres related to environmentally hazardous PM(2.5), PM(2.5-10), and PM(10) were for the first time separated from fly ash produced during combustion of Ekibastuz coal. It was determined that the average diameter of globules in narrow fractions is 1, 2, 3, and 7 μm. The major components of chemical composition are Fe(2)O(3) (57-60) wt %, SiO(2) (25-28 wt %), and Al(2)O(3) (10-12 wt %). The phase composition is represented by crystalline phases, including ferrospinel, α-Fe(2)O(3), ε-Fe(2)O(3), mullite, and quartz, as well as the amorphous glass phase. Mössbauer spectroscopy and magnetic measurements confirmed the formation of nanoscale particles of ε-Fe(2)O(3). Stabilization of the ε-Fe(2)O(3) metastable phase, with quite ideal distribution of iron cations, occurs in the glass matrix due to the rapid cooling of fine globules during their formation from mineral components of coal.