Remediation of Clay Soils Contaminated with Potentially Toxic Elements: The Santo Amaro Lead Smelter, Brazil, Case

The remediation of clayey soil contaminated by potentially toxic elements is a challenging task, especially because of the low permeability and strong affinity of such toxic elements, which prevent the effective use of low-cost in situ remediation methods. The clay soil from the region of the former Santo Amaro primary lead smelter has high concentrations of potentially toxic elements, especially Pb, Cd, Sb, and Zn. This study presents a preliminary evaluation of remediation by soil washing and thermal stabilization, which can support clean-up initiatives for this site. The treatment results indicate that soil washing using EDTA can be an effective method to clean up the soil; however, the solid-liquid separation step by filtration is slow. Soil thermal treatment at temperatures higher than 800 degrees C in an oxidant atmosphere results in the formation of ceramic structure because of the high smectite content, which stabilizes the potentially toxic elements. The estimated cost for remediation by soil excavation, replacement, and stabilization, of the critically contaminated site at the Santo Amaro region is estimated at about 20 to 30 million US$.