Preliminary studies for removal of lead from surrogate and real soils using a water soluble chelator: Adsorption and batch extraction

A technique for removing Pb from contaminated soil is to wash excavated soil with a solution containing a chelating agent specific for the heavy metal contaminant of interest. Parameters needed to demonstrate the plausibility of this remediation method include the amount of chelator adsorption to soil and the rate of Pb extraction. This paper investigates these parameters for a newly developed water-soluble chelator, Metaset-Z, which has a high specificity for Pb. Metaset-Z chelated Pb in aqueous solutions on the time scale of seconds. This chelator has a low affinity for quartz. Its adsorption is independent of ionic strength over the range tested. Mini column experiments demonstrated that Metaset-Z adsorption is also independent of polymer, Ca, and Pb aqueous-phase concentrations. Removal of Pb to below EPA requirements was achieved using both surrogate, quam contaminated soil and a Superfund contaminated soil. A one-site semiempirical, equilibrium reaction model fit the surrogate soil extraction data well; a two-site reaction model fit the contaminated soil data well. Overall, this study shows that Metaset-Z can be used as a batch extractant for Pb-contaminated soil.