The role of organic acids in the mobilization of heavy metals from soil

Batch laboratory experiments were performed to determine the effectiveness of organic acids in mobilizing heavy metals (Cu, Pb, Zn) from contaminated soils. Because the direct measurement of all of the species that are extracted by an organic acid is not possible, we calculated the speciation of Cu, Pb, and Zn in the presence of oxalate with regard to the primary distribution of metals and oxalate in solution using GEOCHEM-PC. Significant amounts of copper and zinc were removed from contaminated soil at higher initial concentrations of oxalic and succinic acids in solution. For the viewpoint of lead immobilization in soil, citric acid was the most effective among organic acids. Our speciation calculations by GEOCHEM-PC for metal-oxalate complex imply that significant amounts of the Cu, Pb and Zn that was extracted from the soil existed as oxalate complexes and free metal ionic form.