Immobilization of Contaminants in Alkaline Solid Wastes Derived from Fossil Energy Conversion Process

The combustion of fossil fuels (eg coal, oil shale) to generate energy results in the production of alkaline solid wastes @y ash, clean coal technology (CCT) ash, spent shale etc). Reactions involving calcium (Ca) and carbon dioxide (C02) usually control the pH and mobility of inorganic contaminants such as Cd, P b and Se in alkaiine solid wastes. Samples offly ash, spent shale iutd CCT ash were reacted \r*ith CO:! at different pressures, moisture levels and for various reaction times. Treated and untreated samples were subjected to X-ray diffraction (XRD) and ABD TPA (ammonium bicarbonate diethylenetriamine pentaacetic acid) extraction studies. Some C02 treatment conditions efectively precipitated calcite, and therefore lowered the pH and extractable concentrations of inorganic contaminants (eg Cd, Pb, Zn, Mn, As and Se) in alkaline solid wastes. Thus, the risk of these elements contaminating soils and groundwater resources could be reduced when CU2 treated alkaline solid wastes are disposed in landfills.