An Investigative Study on the Chemical, Morphological and Mineralogical Alterations of Dry Disposed Fly Ash During Sequential Chemical Extraction

S. A. AkinyemiA., A. Akinlua, W. M. Gitari, S. M. Nyale, R. O. Akinyeye, L. F. Petrik


The hazardous elements associated with various physicochemical forms in coal fly ash are of environmental concern due to their leaching potential and subsequent contamination of surface and groundwater in the vicinity of the ash dump. Selective sequential extraction was performed on dry disposed fly ash samples from a coal-fired power station in Mpumalanga province, South Africa. The alteration of the chemical, morphological and mineralogical species of weathered fly ash during the selective sequential extraction was investigated using X-ray fluorescence (XRF), Nano-scan electron microscopy (NANOSEM) and X-ray powder diffraction (XRD). Insoluble residue from the water-soluble fraction is composed of amorphous alumino-silicate. The residues from exchangeable carbonate and Fe and Mn fractions consisted mostly of amorphous alumino-silicate spheres with a lesser quantity of iron-rich spheres. The iron-rich spheres are surrounded by amorphous alumino-silicate spheres.  The leaching behavior of trace metals (such as Ce, Y, Nb, Rb, U, and Tl) in weathered dry disposed fly ash was considered to have a dependency relationship with the components of SiO2, CaO, MgO, P2O5, and amount of unburned carbon. The decrease in the quantities of calcite with successive extraction could be considered as a marker of progress of sequential extraction technique. At the same time, the increase in the quantities of quartz could be also considered as an indicator of progress of the sequential extraction scheme. Trace elements bound to exchangeable or carbonate fraction during sequential chemical extraction were found associated with calcite. The elemental concentrations, as determined by electron dispersive x-ray spectroscopy (EDS), were consistent with XRF and XRD data. Therefore, the chemical extractant used in this study proved efficient for extraction of inorganic metals associated with various physicochemical forms in weathered fly ash.

Key words: Coal fly ash; Selective sequential extraction; Major components; Trace elements; Morphology; Mineralogical composition


Coal fly ash; Selective sequential extraction; Major components; Trace elements; Morphology; Mineralogical composition

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[1] Adriano, D. C., Page, A. L., Elseewi, A. A., Chang, A. C., & Straughan, I. (1980). Utilization and Disposal of Fly Ash and Other Coal Residues in Terrestrial Ecosystems: A Review. J. Environmental Quality, 9(3), 333-344.

[2] Aitken, R. L., & Bell, L. C. (1985). Plant Uptake and Phytotoxicity of Boron in Australian Fly Ashes. Plant and Soil, 84(2), 245–257.

[3] Akinyemi, S. A., Akinlua, A., Gitari, W. M., Akinyeye, R. O., & Petrik, L. F. (2011a). The Leachability of Major Elements at Different Stages of Weathering in Dry Disposed Coal Fly Ash. Coal Combustion and Gasification Products, 3, 28-40. doi: 10.4177/CCGP-D-11-00005.1.

[4] Akinyemi, S. A., Akinlua, A., Gitari, W. M., & Petrik, L. F. (2011b). Mineralogy and Mobility Patterns of Chemical Species in Weathered Coal Fly Ash. Energy Sources, Part A, 33(8), 768–784.

[5] Bern, J. (1976). Residues from Power Generation: Processing, Recycling and Disposal. In: Land Application of Waste Materials (pp. 226–248). Ankeny, Iowa: Soil Conservation Society of America.

[6] Bhanarkar, A. D., Gavane, A. G., Tajne, D. S., Tamhane, S. M., & Nema, P. (2008). Composition and Size Distribution of Particles Emissions from a Coal-Fired Power Plant in India. Fuel, 87(10-11), 2095–2101.

[7] Chen, Y., Shah, N., Huggins, F. E., & Huffman, G. P. (2005a). Characterisation of Fine and Ultrafine Fly Ash by Electron Microscopy Techniques. World of Coal Ash (WOCA), April 11-15, Lexington, Kentucky: USA.

[8] Chen, Y, Shah, N, & Huggins, F. E. et al. (2005b). Characterization of Ultrafine Coal Fly Ash Particles by Energy-Filtered TEM. J. Microsc., 217(3), 225–234.

[9] Cope, F. (1962). The Development of a Soil from an Industrial Waste. Transactions of the International Soil Science Society Conference IV (pp. 859–863).

[10] Davison, R. L., Natusch, D. F. S., Wallace, J. R., & Evans Jr., C. A. (1974). Trace Elements in Fly Ash – Dependence of Concentration on Particle Size. Environ. Sci. Technol., 8(13), 1107–1113.

[11] Gleyzes, C., Tellier, S., & Astruc, M. (2002). Fractionation Studies of Trace Elements in Contaminated Soils and Sediments: A Review of Sequential Extraction Procedures. Trends in Analytical Chemistry, 21(6-7), 451-467.

[12] Go´mez Ariza, J. L., Gira´ldez, I., Sa´nchez-Rodas, D., & E. Morales, E. (2000). Selectivity Assessment of a Sequential Extraction Procedure for Metal Mobility Characterization Using Model Phases. Talanta, 52(3), 545–554.

[13] Hower, J. C., Graham, U. M., Dozier, A., Tseng, M. T., & Khatri, R. A. (2008). Association of the Sites of Heavy Metals with Nanoscale Carbon in a Kentucky Electrostatic Precipitator Fly Ash. Environ. Sci. Technol., 42(22), 8471–7.

[14] IAWG. (1997). Municipal Solid Waste Incinerator Residues. Amsterdam, The Netherlands: Elsevier Science B.V.

[15] Jegadesaan, G., Al-Abed, S. R., Pinto, P. (2008). Influence of Trace Metal Distribution on Its Leachability from Coal Fly Ash. Fuel, 87(10-11), 1887-1893.

[16] Jones, D. G., & Straughan, l. R. (1978). Impact of Solid Discharges from Coal Usage in the Southwest. Environmental Health Perspectives, 27, 275-281.

[17] Junor, R. S. (1978). Control of Wind Erosion on Coal Ash. Journal of the Soil Conservation Service of New South Wales, 34, 8-13.

[18] Kheboian, C, & Bauer, C. F. (1987). Accuracy of Selective Extraction Procedures for Metal Speciation in Model Aquatic Sediments. Analytical Chemistry, 59(10), 1417-1425.

[19] Kutchko, B. G., & Kim, A. G. (2006). Fly Ash Characterization by SEM–EDS. Fuel, 85(17-18), 2537–2544.

[20] Mattigod, S. V., Dhanpat, R., Eary, L. E., & Ainsworth, C. C. (1990). Geochemical Factors Combustion Residues: I. Review of the Major Elements. Journal of Environmental Quality, 19, 188–201.

[21] Mollah, M. Y. A., Promreuk, S., Schennach, R., Cocke, D. L., & Guler, R. (1999). Cristobalite Formation from Thermal Treatment of Texas Lignite Fly Ash. Fuel, 78(11), 1277–1282.

[22] Murarka, I. P., Rai, D., Eary, L. E., & Ainsworth, C. C. (1991). Geochemical Basis for Predicting Leaching of Inorganic Constituents from Coal-Combustion Residues (ASTM STP 1075, Friedman, D. Ed., pp. 279–288). American Society for Testing and materials.

[23] Natusch, D. F. S., Bauer, C. F., Matusiewicz, H., Evans, C. A., Baker, J., Loth, A., Linton, R. W., & Hopke, P.K. (1975). In T. E. Hutchinson (ed.), Proceeding of International.Conference on Heavy Metals in Environment. Part 2 (pp. 553–575). Toronto, Ontario, Canada.

[24] Page, A. L., Elseewi, A. A., & Straughan, I. R. (1979). Physical and Chemical Properties of Fly Ash from Coal-Fired Power Plants with Special Reference to Environmental Impacts. Residue Rev., 71, 83-120.

[25] Petrik, L., Hendricks, N., Ellendt, N., & Burgers, C. (2007). Toxic Element Removal from Water Using Zeolite Adsorbents Made from Solid Waste Residues. Water Research Commission, WRC Report No. 1546/1/07, University of the Western Cape, South Africa.

[26] Quispe, D, Pérez-López, R, Silva,L. F. O., & Nieto, J. M. (2012). Changes in Mobility of Hazardous Elements During Coal Combustion in Santa Catarina Power Plant (Brazil). Fuel, 94, 495-503. doi:10.1016/j.fuel.2011.09.034.

[27] Saikia, N., Kato, S., & Kojima, T. (2006). Compositions and Leaching Behaviours of Combustion Residues. Fuel, 85(2), 264–271.

[28] Schure, M. R., Soitys, P. A., Natusch, D. F. S., & Mauneys, T. (1985). Surface Area and Porosity of Coal Fly Ash. Environ. Sci. Technol., 19(1), 82-86.

[29] Silva, L. F. O., DaBoit K., Serra, C., Mardon, S. M., & Hower, J. C. (2010a). Fullerenes and Metallofullerenes in Coal-Fired Stoker Fly Ash. Coal Combustion and Gasification Products, 2, 66–79.

[30] Silva, L. F. O., Ward, C. R., Hower, J. C., Izquierdo, M., Waanders, F., Oliveira, M. L. O., Li, Z., Hatch, R. S., & Querol, X. (2010b). Mineralogy and Leaching Characteristics of Coal Ash from a Major Brazilian Power Plant. Coal Combustion and Gasification Products, 2, 51–65.

[31] Smeda, A., & Zyrnicki, W. (2002). Application of Sequential Extraction and the ICP-AES Method for Study of the Partitioning of Metals in Fly Ashes. Microchemical, 72(1), 9–16.

[32] Smichowski, P., Polla, G., Gomez, D., Fernandez Espinosa, A. J., & Lopez, A. C. (2008). A Three Step Sequential Metal Fractionation Scheme for Fly Ashes Collected in an Argentine Thermal Power Plant. Fuel, 87(7), 1249–1258.

[33] Takaoka, M., Nakatsuka, D., Takeda, N., & Fujiwara, T. (2000). Application of X-Ray Fluorescence Analysis to Determination of Elements in Fly Ash. J. Jpn. Soc. Waste Manag. Experts, 11, 333–342.

[34] Tomeczek, J., & Palugniok, H. (2002). Kinetics of Mineral Matter Transformation During Coal Combustion. Fuel, 81(10), 1251–1258.

[35] Townsend, W. N., & Hodgson, D. R. (1973). Edaphological Problems Associated with Deposits of Pulverized Fuel Ash (In: Hutnik, R.J., Davis, G. Eds.). Ecology and Reclamation of Devastated Land. Vol. 1. New York: Gordon and Breach.

[36] Vassileva, S. V., Menedez, R., Alvarez, D., Diaz-Somoano, M., & Martinez-Tarazona, M. R. (2003). Phase Mineral and Chemical Composition of Coal Fly Ashes as a Basis for Their Multi-Component Utilization. 1. Characterization of Feed Coals and Fly Ashes. Int. J. Coal Geol., 82, 1793–811.

[37] Vassilev, S. V., Vassileva, C. G., Karayigit, A. I., Bulut, Y., Alsatuey, A., & Querol, X. (2005). Phase Mineral and Chemical Composition of Fractions Separated from Composite Fly Ashes at the Soma Power Station, Turkey. Int J. Coal Geol., 61(1-2), 65–85.

[38] Wan, X., Wang, W., Ye, T., Guo, Y., & Gao, X. (2006). A Study on the Chemical and Mineralogical Characterization of MSWI Fly Ash Using a Sequential Extraction Procedure. Journal of Hazardous Materials, 134(1-3), 197–201.



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