Static and dynamic leaching studies on coal gangue

Abstract

In the present study, an attempt has been made to determine the leachability of selected trace metals like As, Cr, Co, Se, Ni, Cu, Zn, Cd, Pb and Mn from coal gangue sourced from an underground and open cast mining area(s) of Bhupalpally Coalfields of Telangana State, India. A standard laboratory leaching test (dynamic in nature) developed for combustion residues has been adopted to study the leachability of these trace elements as a function of liquid to solid ratio and pH. A series of static column leaching tests were also conducted to investigate the leachability of these selected heavy metal ions simulating field conditions. The column tests revealed that heavy metals from coal gangue exhibit greater mobility particularly under acidic conditions. Further, relatively higher concentrations were leached for both static and dynamic leaching conditions at low pH levels and is attributed to the difference in solubility product values of respective metal ion complexes. Among the targeted metal ions, with a metal extraction of 30% and 65%, respectively, As and Se showed highest mobility from both static and dynamic leaching tests.