Fractional characteristics of coal fly ash for beneficial use

As a primary by-product of coal combustion produced in large quantities, coal fly ash is a material receiving considerable interest for potential large-scale engineering applications. However, the beneficial use of coal fly ash in concrete production and contaminant removal, which have divergent constraints to sorption capacity, requires a more complete understanding of the surface and sorptive characteristics of fly ash. A systematic analysis of fly ash particle size fractions established linkages between particle size, particle morphology, unburned carbon content, surface area, and sorption capacity. Unburned carbon was enriched in fly ash fractions of the largest particle sizes and associated with irregularly shaped particles. Further, most of the surface area and sorption capacity of fly ash could be attributed to unburned carbon. More importantly, unburned carbon content, specific surface area, and methylene blue sorption capacity were shown to strongly correlate to one another, providing a potentially quantitative basis for understanding the surface properties of fly ash and developing more effective process options to enhance the fly ash sorption behavior desirable for specific engineering applications.