Study of Efficiencies of Selected Extractants: SDS, Iodide, Citric Acid in Soil Remediation from Lead

The effect of anionic surfactant sodium dodecyl sulphate, SDS, utilized individually and also in different combinations with the ligand iodide or citric acid, in leaching of Pb present in contaminated soils was investigated. Remediation studies were carried out at constant pH. Soil samples artificially contaminated by Pb in concentrations between 40-400 mg kg(-1) with volume-to-mass (V/m) ratio of 20 mL g(-1), and between 80-800 mg kg(-1) with V/m of 40 mL g(-1) were first treated with SDS, iodide, and citric acid individually. Remediation power of SDS did not exceed 10% at 6-100 mM concentrations. Leaching process was relatively more successful with ligands iodide (50 to 400 mM) and citric acid (2.5 to 20 mM). Desorption of Pb varied between 5 and 75% when only iodide was present in the medium, whereas the percent of desorption was between 4 and 42% in the presence of citric acid alone. Generally, desorption of Pb increased as V/m ratio increased. SDS was then paired with either one of the ligands. The combination of 400 mM iodide with 50 mM SDS having V/m ratio of 20 mL g(-1) resulted in removal of 65 to 75% Pb from the soil; whereas the percent of removal was 75-82% when V/m ratio was 40 mL g(-1). The same efficiency was not observed with 100 mM SDS, in which case desorption of Pb was 50 to 65%. When citric acid was used in combination with SDS, it was found to be not as effective as iodide with respect to both V/m ratios of SDS. Highest percentage of Pb removed was 48% when 20 mM citric acid was used in combination with 50 mM of SDS with V/m ratio of 40 mL g(-1). The remediation order was: SDS < citric acid < SDS+citric acid < iodide < SDS+iodide.