Treatment and Recovery of Heavy Metals from Incinerator Ashes

High levels of potentially leachable toxic metals such as Pb, Cd, and Cr, in the ash residues require consideration of treatment technologies prior to disposal or utilization of the ashes in other applications. Extraction studies revealed information on the leaching characteristics of the ashes and on the ability of the extraction solutions to separate these metals from the ash matrix. The kinetics of the Pb, Cd, and Cr extraction were determined through a series of batch extraction studies. The specific incinerator design and the equilibrium conditions strongly influenced the ash matrix and the extraction kinetics. Recovery of the metals from the waste extract solution was accomplished utilizing electrochemical plating techniques. A laboratory scale pilot plant was designed to continuously treat ash residues at a rate of 1 kg/hr through extraction and electrochemical recovery techniques. Initial pilot plant operational study results are presented.