Analysis of the leaching behavior of elements from coal combustion residues for better management

摘要

In this study, fly ash, pond ash, bottom ash, slurry ash, raw water, pond water, and slurry samples were collected from Bokaro Thermal Power Plant, Bokaro, Jharkhand, India, and studied for the leachability of different elements by acid digestion and shake test at different liquid to solid (L/S) ratios. The raw water, pond water, slurry water, and leachates of acid digestion and shake tests were analyzed for the elements sodium (Na), potassium (K), calcium (Ca), iron (Fe), copper (Cu), cobalt (Co), manganese (Mn), cadmium (Cd), zinc (Zn), lead (Pb), nickel (Ni), and chromium (Cr). Shake test results confirmed that the water got saturated when the L/S ratio was equal to or above 10, indicating no further increase in concentration of elements at the L/S ratio of 10. Leaching behavior of Na from pond ash was not understood in the present study. In the study, the chemical composition showed that all the four types of ashes contain a small fraction of CaO (about 0.37 to 0.90 % by weight) and very high contents of SiO2 (about 55.14 to 58.34 % by weight) and Al2O3 (about 29.44 to 32.81 % by weight) that are the major composition of Portland cement. The study will help to understand the leachability potential of harmful elements present in fly ash, pond ash, bottom ash, and slurry ash under natural conditions and to take regulatory measures to protect the surface water, groundwater, and soil environment.