Leachability of heavy metals in Greek fly ash from coal combustion

A laboratory leaching test was used to determine the potential mobility of Pb, Cd, Cr, Cu, Zn, Ca, and Mn in fly ash samples, originated from four locations in Northern Greece, in order to assess their leachability when these wastes are disposed of. The cascade leaching test was used at liquid to solid ratios (L/S) ranging between 5 and 100. All fly ash samples exhibited strong alkaline reaction, as indicated by pH values > 11.75 at L/S = 10 and contact time of 10 min. In general, Ca showed the highest leachability and Mn the lowest in all samples. The percentage of leached amounts follows the trend Ca > Cd > Cr > Pb > Zn > Cu > Mn for samples from Kardia and Agios Dimitrios, Ca > Pb > Cd > Cr > Cu > Zn > Mn for the sample from Ptolemais, and Ca > Cu > Cd > Pb > Cr > Zn > Cu > Mn for the sample from Amideo. The six metals studied (Cd, Cr, Zn, Mn, and Cu) in fly ash from Amideo exhibited an increase in the leachate concentration as the leachant pH was reduced from 8 to 4. Pb followed by Cd exhibited the maximum extractability at all pH values. The least leachable components were Cu and Mn. (C) 1998 Elsevier Science Ltd.