Effect of Lead Extraction by EDTA on the Physico-Mechanical Behavior of Bentonite Soil

Abstract: Lead contamination of soils is a common problem throughout the world. The application of ethylenediaminetetraacetic acid (EDTA) as an extraction material has been exhibited to be an effective method of removal of Pb from many contaminated soils. The extraction of heavy metal from contaminated soils will alter the properties of soil-water system, resulting in changes in the physico-mechanical behavior of soil, specifically soils with relatively high surface area such as bentonite. This study investigates the influence of lead removal from contaminated bentonite by the use of EDTA on its physic-mechanical behaviour. A set of experiment including precipitation testing, Atterberg limits, and consolidation were performed on contaminated bentonite before and after EDTA treatment. The achieved results were compared with bentonite behaviour. The results of this research indicate that in contaminated bentonite with medium concentration of lead nitrate (up to 10 cmol/kg soil) after soil remediation with EDTA, the mechanical behavior of soil is changed. After contamination removal, this mechanical behavior is relatively similar to the mechanical behavior of uncontaminated soil. In other words, the soil properties are almost reversible. However, in highly contaminated bentonite (i.e. 50 to 100 cmol/kg soil lead nitrate), there is not much difference between the mechanical properties of contaminated and remediated soil. In other words, in this case the soil properties after contaminant removal are mainly irreversible. [Vahidreza Ouhadi, Amirhoushang Omidi. Consideration of the effects of extraction of lead (Pb) by EDTA on th