Metal-contaminant leaching from lead smelter fly ash using pH-stat experiments

Fly ash from secondary Pb metallurgy was submitted to the pH-static leaching procedure according to the PrEN 14997 European leaching standard. The 48 It pH-static leaching experiments were performed on (1) fresh untreated fly ash and (2) previously washed fly ash with a Cumulative wash step of 601 kg(-1). Greater release of metallic contaminants (Pb, Cd, Zn) was observed in the acidic pH range for both ashes. Washing significantly reduced the release of Cd and Zn, but greater concentrations of Pb were observed in leachates from washed fly ash due to the more important leaching of anglesite (PbSO(4)). The PHREEQC-2 speciation-solubility calculations showed that anglesite, phosgenite (PbCl(2)center dot PbCO(3)) and laurionite (Pb(OH)Cl) are the most important solubility-controlling phases for Pb, which is the most important contaminant.