Effect of different treatments on electrokinetic remediation of Zn, Pb and Cd from a contaminated calcareous soil

Abstract

Electrokinetic remediation is a promising method to decontamination of the heavy metals from soils. In this paper, the remediation of a contaminated calcareous soil with Zn, Cd and Pb sampled from around Zanjan province of Iran, was investigated using electrokinetic method. In this paper, the soil contain a high concentration of Zn (1400 mg·kg−1), Cd (15 mg·kg−1) and Pb (250 mg·kg−1). Electrokinetic decontamination consists of two series of experiments as follows: (1) the effect of five treatments including the use of distilled water, acetic acid and EDTA electrolyte solutions, and approaching anodes systems, and the circulation flow of electrolyte at two different voltage gradient (i.e. 1.33 and 2.66 V·cm−1), and (2) the effect of moisture content (saturated, FC and 0.7FC, FC indicated soil moisture at “Field Capacity”) with a voltage gradient of 1.33 V·cm−1. After applying electric current for 5 days, the results of experiments indicated that the removal efficiency of heavy metals can be increased by raising the voltage gradient. In this matter, the highest remediation can be observed among different treatments in EDTA (Ethylene diamine tetra acetic acid) treatment (40.11%, 43.10% and 24.7% for Zn, Cd and Pb, respectively). Moreover, the heavy metals removal at the saturated moisture was at the highest level so that 32.62% cadmium, 31.33% zinc and 18.82% lead being removed after 120 h of electric current application. By decreasing moisture to 0.7FC, the removal percentage for the three heavy metals obtained 20.97%, 18.44% and 12.25%, respectively. Furthermore, Cd had the highest removal, and Zn and Pb were next among the three heavy metals in question.