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

Abstract

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.

Memory and fine motor skill test performance among children living near coal ash storage sites.

“…As the particles rise through the smokestack, the liquid droplets undergo rapid solidification and small, glassy, perfectly spherical particles form (Brown et al, 2011). These small spherical particles are fly ash and often appear as tan or gray in color of fine to medium silt-size depending on the coal source (Brown et al, 2011;el-Mogazi et al, 1988;U.S. Department of Transportation, 2015).…”

“…Fly ash is made up of small, spherical particles with diameters predominately ≤ 10 µm (PM 10 ) (Roy et al, 1981;Patra, Rautray, Tripathy, & Nayak, 2012). During coal combustion, fine liquid droplets are released and carried away by flue glasses (Brown et al, 2011). As the particles rise through the smokestack, the liquid droplets undergo rapid solidification and small, glassy, perfectly spherical particles form (Brown et al, 2011).…”

“…The elemental composition of fly ash depends on the properties of the coal that was burned; however, the five most common elemental components of fly ash include silicon, aluminum, iron, calcium, and oxygen (Brown et al, 2011;Borm, 1997). Commonly found trace elements include nickel, vanadium, arsenic, beryllium, cadmium, copper, zinc, lead, mercury, selenium, radon, and molybdenum (Brown et al, 2011).…”

“…Coal ash frequently contains heavy metals, such as cadmium, lead, mercury, chromium VI, and manganese, all of which are known neurotoxins (Brown et al, 2011;Patra et al, 2012;Nodelman, Pisupati, Miller, & Scaroni, 2000). Fly ash particles are small enough to penetrate deeply into the lungs and access the bloodstream and thus pose a risk for bypassing the blood-brain barrier and coming into contact with cells in the brain (Roy et al, 1981;Oberdörster et al, 2005).…”

“…Commonly found trace elements include nickel, vanadium, arsenic, beryllium, cadmium, copper, zinc, lead, mercury, selenium, radon, and molybdenum (Brown et al, 2011).…”