STUDY OF DIFFERENT LEACHING METHODS OF METALLIC ELEMENTS FROM COAL FLY-ASH

This paper describes the mobility of the present metallic elements in coal fly ash in order to quantify possible environmental problems from the disposal of this waste. Different leaching methods are studied: EPA, INSA and Column. Results suggest that the pH value as well as the surface predominance of trace elements on the particles influence the mobility of metals. Calcium and Mg were the most soluble among studied major elements when fly ash is subjected to leaching condition of the EPA procedure. The trace elements Ni, Cu, Co, V, Mo and Cr enriched on particle surface exhibited mobilities in acid extracts (EPA procedure). On the other hand, in alkaline extract (INSA and Column procedures), Mo, Cr and V are also mobilized. The column procedure in alkaline extracts of fly ash indicate that Ca, Na, K, Mo and Cr show higher mobilities during the early phase of the leachate.