Remediation of heavy metal contaminated solid wastes using agglomeration techniques

Abstract

A process has been developed for the remediation of heavy metal contaminated, fine textured; solid wastes so that the treated material will meet EPA's TCLP and Total Extractable Metal Limits. The process involves the formation of strong aggregates using dry agglomeration methods. Remediation is achieved either by incorporating metal fixation agents into the agglomerates, or by leaching of heavy metal and other soluble salts by percolation through a packed bed of agglomerated soil. The handling problems encountered during solid liquid separations in conventional soil washing are overcome by agglomerating the fine textured solids. The newly developed process was applied to the remediation of a fine textured soil sample from a Dupont site contaminated with lead and a sediment from the Coeur d'Alene river, contaminated with Pb, Cd, and Zn. Because of low hydraulic flow-rates leaching of metals from unagglomerated solids was slow. The removal of metals from agglomerated feed occurred on the time scale of hours compared to days for the original materials. Batch column extraction studies showed that HCl, EDTA and citric acid were effective extractants for the removal of lead from the agglomerated material. The results of this study demonstrate that NRC's remediation process is suitable for the remediation of contaminated soil or soil like materials and has potential for commercialization.