The use of ethylenediaminetetraacetic acid as enhancing agent for the remediation of a lead polluted soil

Result: for Pb extraction experiments from a contaminated soil performed with citric acid and ethylenediaminetetraacetic acid disodium salt (Na(2)EDTA) indicate that Na(2)EDTA is much more efficient. The Pb removal after 5 successive extractions using 24 mL of 0.1 M Na(2)EDTA solutions and 8 g of soil is close to 100%. Other non-toxic metals such as Ca and Mg, that are present in important concentrations in this soil, are also solubilized, but important differences in the behavior of each metal are observed. A local equilibrium model is used for the interpretation of the results of these batch experiments; the experimental and the model results are in a fairly good agreement. From these results it is concluded that Na(2)EDTA presents almost ideal characteristics for its use as enhancing agent for an electrokinetic remediation of the soil. Therefore, experiments were performed, in which the pH value is controlled at both electrode-compartments using Na(2)EDTA at the cathode and NaOH at the anode, aiming to the recovery of PbEDTA(2-) at the anode. Nevertheless, no significant amounts of lead are recovered. The possible negative effects of the electric current over the performance of Na(2)EDTA are studied using a two-compartment cell for electrodialytic remediation with an important electrical current and comparing the results with those obtained under identical conditions without current. It is concluded that the electric current produce no negative effects. Therefore, the cancelling effects of the electromigration and the electroosmotic movement are considered as the most probable explanation for the experimental results. (C) 2015 Elsevier Ltd. All rights reserved. (Less)