LEACHING STUDY OF TOXIC TRACE-ELEMENTS FROM FLY-ASH IN BATCH AND COLUMN EXPERIMENT

Leaching of trace elements such as Cr, Fe, Ni, Cu, Zn, Pb, Sb, As and Se generated from flyash of coal based thermal power plant was studied in a batch and column experiments at pH 6.0 with dentention time of 20 hrs. and flow rate of 10 ml/hr respectively. The leaching was carried out at various poring volume of distilled water at pH 5.0. It was found that the metals in the leachate decreases as the number of pore increases. The concentration of these metals in flyash were determined after extracting with water at pH 6.0 in a batch experiment at different interval of shaking time. Average percentage of leachatable toxic metals was found to be 44.7% and 35.0% for batch and column study. Leaching of iron is almost negligeble. The leaching behaviour of these metals described in terms of specific mass transfer function F(t), which gives the net release rate of metals. The metals were analysed by the atomic absorption spectrophotometer.