The purpose of this study was to explore the influence of organic matter in soils while removing heavy metals by sodium metabisulfite and EDTA solutions. The results obtained show that both sodium metabisulfite and sodium EDTA solutions have good removal efficiencies of zinc and lead. However, sodium metabisulfite was effective in extracting lead from a low organic content silty clay soil, and 0.05 M EDTA solution was a better extraction agent for soils with high organic matter content. These preliminary experimental results indicate that it might be worthwhile to consider the use of a chelating agent like sodium EDTA in the treatment of heavy-metal contaminated soils.

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The effect of ethylenediaminetetraacetic acid (EDTA) during electrokinetic decontamination (EKD) was investigated in this research. EDTA is a ligand that can form soluble complexes with precipitated heavy metals inside soil pores. Millpond sludge, primarily contaminated with lead (Pb) and zinc (Zn), was subjected to EKD with and without the presence of EDTA. Dilute EDTA solutions with strengths of 0.05 M and 0.125 M were injected into the millpond sludge by electroosmosis. Several beneficial effects of using EDTA were observed in this research. One was that the presence of EDTA substantially increased the electroosmotic (EO) flow in the millpond sludge indicating that it could significantly reduce the duration of EKD. Another advantage was that a significantly higher percentage of Pb and Zn removal was achieved from the solid phase due to the complexation of EDTA with these heavy metals. Also, EDTA was able to prevent the precipitation of metals at the cathode electrode, typically observed in EKD process.