The internal microstructure and fibrous mineralogy of fly ash from coal-burning power stations

• Published in: Environmental pollution (1987) Vol. 159; no. 12; pp. 3324 - 3333
• Main Authors: Brown, Patrick, Jones, Tim, BéruBé, Kelly
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-12-2011; Elsevier
• Subjects: Air Pollutants - chemistry; Air Pollution; Aluminum Silicates - chemistry; Applied sciences; China; Coal - analysis; Coal Ash - chemistry; Coal fly ash; elemental composition; Environmental Monitoring; Exact sciences and technology; Fibers; Fibres; Fibrous mullite; Fly ash; Geochemistry; Habits; Lungs; microscopy; Microstructure; Mineralogy; minerals; Mullite; Other wastes and particular components of wastes; Particle Size; particle size distribution; Poland; Pollution; Power Plants - standards; Power stations; respiratory tract diseases; United Kingdom; Wastes; X-Ray Diffraction; United Kingdom; British Isles; Coal fly ash; Geochemistry; Microstructure; Mineralogy; Fibrous mullite; Fly ash; Morphology; Coal power plant; Fossil fuel; Solid waste
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2011.08.041

Coal fly ash (CFA) is a significant environmental pollutant that presents a respiratory hazard when airborne. Although previous studies have identified the mineral components of CFA, there is a paucity of information on the structural habits of these minerals. Samples from UK, Polish and Chinese power stations were studied to further our understanding of the factors that affect CFA geochemistry and mineralogy. ICP-MS, FE-SEM/EDX, XRD, and laser diffraction were used to study physicochemical characteristics. Analysis revealed important differences in the elemental compositions and particle size distributions of samples between sites. Microscopy of HF acid-etched CFA revealed the mullite present possesses a fibrous habit; fibres ranged in length between 1 and 10 μm. Respirable particles (<10 μm) were frequently observed to contain fibrous mullite. We propose that the biopersistence of these refractory fibres in the lung environment could be contributing towards chronic lung diseases seen in communities and individuals continually exposed to high levels of CFA.
► Chinese CFA had a greater crystalline mineral content and smaller particle size. ► Mullite and quartz, two hazardous minerals, recrystallise from glass melt particles. ► Mullite revealed a fibrous habit, with fibres 1–10 μm in length and 0.5–1 μm in width.
Chinese CFA possessed a greater crystalline mineral content and smaller particle size than UK and Polish CFA, the fibrous mullite prhiesent displayed a high aspect-ratio and thus is likely to be a respiratory hazard in vivo.