The study on lead desorption from the real-field contaminated soil by circulation-enhanced electrokinetics (CEEK) with EDTA

This study applied a circulation-enhanced electrokinetics (CEEK) technique to remove heavy metal lead from the agricultural land. Soil samples (lead concentration around 4000 mg/kg) were collected in a certain polluted agricultural site in Nantou, Taiwan. Operational parameters of CEEK such as the voltage gradient (1.0 V/cm), the concentration of working solution (EDTA), and pH buffer (0.01 M Na2CO3) were controlled. The CEEK with EDTA can maintain at relatively neutral pH to beneficially remove heavy metals due to appropriate EO flow, electromigration, and EDTA complexation. EDTA served as the chelating agent to react with lead in soils and its concentration plays the key factor for desorbing heavy metals from soils; the 0.1 M EDTA can achieve 79% of Pb depletion (from 3703 mg/kg to 781 mg/kg). The stoichiometric calculation can be roughly used to estimate the Pb removal efficiency based on the 1:1 M ratio of Pb to EDTA and ignores other reactions between EDTA and soil constituents. The CEEK technique with 0.1 M EDTA can remove 63% Pb (from 3430 mg/kg to 1260 mg/kg) within 6-day treatment.